Emissions drives interest in ceramic engine components: higher engine pressures and stresses cause designers to look at material alternatives
Ceradyne Inc., Costa Mesa, Calif., has built its business around a variety of advanced ceramics, mostly silicon nitride materials. A highly vertically integrated manufacturer, Ceradyne’s most visible application of its materials may be the military body armor it provides various branches of the U.S. military, as well as other ceramic composite armor systems for military vehicle, watercraft, helicopter and aircraft applications.
Outside of military uses, Ceradyne also manufactures a range of ceramic materials for the automotive, engine, industrial wear, medical and electronic markets. It was Ceradyne’s experience with automotive engines that has led it to the diesel engine industry.
Now, with challenges presented by diesel emissions regulations, standards that have caused designers to look into every nook and cranny of industrial engines, some of these investigations have led engine designers to consider different materials than have been used on earlier generations of diesels, especially for internal engine components.
As a result, Ceradyne has found a growing diesel market driven by increasing fuel injection pressures and cylinder operating pressures and other component modifications designed to improve emissions and fuel economy. According to Andy MacQueen, sales manager, Ceradyne has seen these higher pressures exacerbate the warranty problems with metal components, which has led manufacturers to consider ceramic materials.
For the diesel engine market, Ceradyne has centered its efforts around Ceralloy 147 silicon nitrides that MacQueen indicated exhibit mechanical, thermal and electrical properties not found with other materials. “Ceradyne’s unique grade of silicon nitride offers engine designers a new material that is proven to solve these warranty problems,” MacQueen said.
He listed light weight, high-strength fatigue resistance, superior thermal shock behavior, wear resistance, a low coefficient of friction against steel, excellent high temperature oxidation and high chemical corrosion resistance as key features.
As a result of that, MacQueen noted that Ceradyne has developed silicon nitride to a level where valvetrains of heavy-duty diesel engines, high-pressure common rail fuel pumps and unit fuel injection systems can operate with these ceramic components in conditions where more conventional metal components might fail.
Specifically, he noted that Ceradyne silicon nitride cam rollers operate at contact stresses of 150,000 to 350,000 psi with no measurable wear to the silicon nitride or the companion metallic components, MacQueen said. This, he said, eliminates the primary mode of failure of metallic cam rollers, i.e., galling between the mating metallic components.
Ceramic cam rollers, which the company has been manufacturing since the early 1990s, have been a major point of entry to the diesel markets for Ceradyne. MacQueen said the rollers have found acceptance because of the increasing stress levels these and other valvetrain components have encountered with the overall internal pressure increases in diesel engines.
MacQueen said silicon nitride was selected as the material choice for its contact fatigue resistance, as well as a coefficient of friction that is significantly lower. Plus, he said, the weight was 40% less, which reduced the rotating moment of inertia of the rollers.
Ceradyne has developed high-volume machining techniques that allow precise formation of crowned profiles on the outer diameters of cam rollers that result in minimum contact stress distributions on the ceramic and the mating metallic component, further increasing reliability of the system, he noted.
Rollers for high-pressure fuel pumps for heavy- and light-duty diesel engines are another product for these markets. The Ceralloy 147-31N silicon nitride rollers have been used where warranty problems have occurred due primarily to excessive wear, scuffing and galling rollers in common rail fuel pumps. All, again, because of the higher pressures needed to achieve current and future emission standards.
While not used in the diesel markets, Ceradyne also manufactures silicon nitride rolling elements for hybrid bearings. Ceradyne supplies both cylindrical rollers for use in Formula One bearings and balls for use in bearings for the electric motors.
Again, the high compressive strength, contact fatigue resistance, electrical resistivity and low coefficient of friction are key properties, MacQueen said. He added that these properties allow bearings to operate with reduced or no lubrication, at higher stress levels or higher speeds and under conditions that are not favorable to other materials.
MacQueen said hybrid bearings using silicon nitride rolling elements can operate at much higher efficiencies and with reduced audible noise levels.
As diesel emissions move into Tier 3 and Tier 4, MacQueen said there were other component areas starting to look at ceramic components. He specifically mentioned piston pins, EGR valves and possibly turbocharger components as future application possibilities.
Wet end chemical control methods combine to manage paper machine contaminants
A method combining three different chemical approaches is shown in commercial trials to improve treatment and control of paper machine contaminants, such as stickies and wood resins
THREE QUITE DIFFERENT WET end chemical control methods are commonly used to treat paper machine contaminants: stabilization, detackification, and fixation/removal. However, these methods are not commonly used together, since they may conflict with one another. A new approach combining these methods has been developed, and results based on commercial trials have shown that it is considerably more effective on commercial paper machines than conventional methods.
Paper machine contaminants come in many forms, and the first step in effectively managing them is to optimize mechanical screening and cleaning systems to remove them before they are a problem. This also minimizes contaminant particle size, making them more easily passed through the system or addressed by chemical means. However, problematic contaminants, such as stickies from secondary fiber and coated broke and natural wood pitch and resins, are not completely removed.These materials can cause paper quality defects, as well as machine deposits and foul machine clothing. If not managed well, they can lead to poor runnability and less production.
Traditionally, once passed through screening and cleaning, these materials are managed chemically. In order to understand how these methods perform, a review of the parameters affecting deposition and fouling is helpful.
PARAMETERS AFFECTING DEPOSITION. Numerous factors affect the extent to which contaminant deposition and fouling occur. They include temperature, pH, system closure, fiber source, and the nature of the surface the deposit forms on.These factors can be encompassed by four parameters: (1) content or amount of contaminant in the system; (2) depositability; (3) colloidal stability; and (4) surface affinity for deposition.
Content. If the amount of contaminant is reduced, it is obvious there will be less available for deposition.The converse is true as well. Managing the fiber source to limit contaminants coming into the system, as well as screening and cleaning, are commonly used to manage content. Colloidal contaminants may be increased and concentrated by recycling and reusing white water for system closure. Purging contaminants from wastewater streams or through clarification can reduce content. Additionally, retaining and binding colloidal materials during sheet formation and then removing them with the sheet reduces content.
Depositability. Depositability may be thought of as the tackiness or adhesive property of the contaminants, which is influenced by chemical composition, viscosity, temperature, and its surface. For example, wood is aged to increase the oxidation of extractives and decrease the depositability of the pitch. Hot melt adhesives and latex binders flow more easily and gain tack as temperature is increased. Therefore, wet end operating and dryer temperature control may reduce deposition. Applying a chemical barrier (coating) to the contaminant will also lower tackiness and reduce depositability
Colloidal stability. Maximizing contaminant colloidal stability allows it to pass through the process without agglomerating or depositing. Stability is maintained by limiting mechanical shear, thermal agitation, repulsive electrostatic forces, and repulsive surface properties of suspended particles. Changes in concentration due to introduction of fresh water or destabilizing cations may lead to deposition.Temperature shock ought to also be guarded against, as this will influence stability as well.
Factors contributing to stability include small particle size, dissolved organic materials released during pulping, and stability-enhancing surfactants or dispersants. Smaller particles are more easily stabilized than larger particles. High-temperature mechanical dispersion and solvent chemical treatments, for example, can minimize particle size and maximize stability.
Surface affinity. The more receptive a paper machine surface is to the contaminant, the more likely deposits will form. Special Uhle box covers and Teflon coatings for dryer cans can limit deposits. Forming fabrics, felts, and rolls can be sprayed with cationic polymers that form a coating to reduce deposition.
COMMON CHEMICAL APPROACHES. Paper mills commonly use three chemical methods to manage contaminants such as pitch and stickies. These methods are stabilization, detackification, and fixation and removal.
Stabilization. Surfactants and dispersants may be applied to chemically enhance colloidal stability. Surfactants are generally nonionic or anionic, and the dispersants are strongly anionic. Unfortunately, this approach may reduce the effectiveness of an additive used to retain the colloidal material in the sheet.
Detackification. In detackification, a chemical is used to build a boundary layer of water around the contaminant. Mineral absorbents may also function by detackification, creating a physical boundary around the deposit. Both rely on surface attraction to a hydrophobic contaminant and function to decrease depositability. Stability may be enhanced with chemical treatment, but particle size will be increased by mineral treatments, which, in theory, would decrease the colloidal stability of the contaminants.
Fixation and removal. Cationic polymers are used to combine with and retain, or “fix,” contaminants onto the fiber, thus removing them from the system. This approach relies on anionic contaminants reacting with the cationic polymer. This method also often removes anionic trash, which can lead to improved chemical additive efficiency. However, if the characteristics of the polymer are not matched to the papermaking system, deposition may be aggravated rather than reduced.
Fixation combines the cationic polymer with the contaminant, which is fixed to the fiber, thus destroying colloidal stability. If the complexes are not fixed, they will concentrate in the system, which can lead to deposition.Alum, starches, and some low molecular weight coagulants can neutralize anionic trash and detrimental substances or form complexes. However, they may not carry sufficient cationic charge and/or molecular weight to fix to the fiber. Further, the contaminant particle size must be small enough to strongly affix stickies to the fibers or fines, or they can be pulled from the sheet or redeposited.
COMBINING CHEMICAL METHODS. A new approach has been developed that combines an amphoteric, surface-active, structured protein with a highly-charged cationic polymer The structured protein is able to both increase contaminant stability and reduce tackiness. The real key, however, is the effect achieved when the structured protein is used together with a cationic polymer to retain the contaminants with the web.
The structured protein performs its function through adsorption onto colloidal material, thereby enhancing colloidal stability and modifying the contaminant surface to reduce adhesion.
The protein’s adsorption onto the surface of hydrophobic materials can be measured as a reduction of the zeta potential of a colloidal suspension. Test results show the reduction in zeta potential of colloidally dispersed polystyrene as addition of the structured protein is increased. This indicates the adhesion of the structured protein onto the hydrophobic polystyrene and its attraction to hydrophobic surfaces.
Preferably, this adsorption is strong enough so as to not to be easily washed off or displaced from the surface. This would also prevent the structured protein from being removed by the effects of dilution, refiners, or pumps. Test data comparing a commercial detackifier to the structured protein indicate the protein has a greater tenacity to adhere to the hydrophobic surface.
Colloidal stability is a function of the dispersive forces between contaminant particles. Since charge is reduced by adsorption of the protein, the stability between contaminant particles is more a function of interfacial or steric stabilization.Test data illustrate that if contaminants are treated with the structured protein, greater colloidal stability can be expected. This reduces the tendency of treated contaminants to agglomerate and deposit.
A key to the functionality of the structured protein is surface modification to reduce tack and depositability. Its adsorption onto the surface allows for the building of physical and water layers around the contaminant. These layers interfere with the adhesion of the contaminants to other surfaces. This can be demonstrated by measuring the force required to separate adhesive surfaces with and without the presence of a “detackifier.” The percentage reduction in the required tack, or force, is termed the percent detackification. The relative effectiveness of detackification versus a commercial detackifier was studied. Data confirmed that addition of small amounts of structured protein almost eliminated the tack of the adhesives.
role of AMP kinase in diabetes
Type 2 diabetes is characterized by abnormal metabolism of glucose and fat, due in part to resistance to the actions of insulin in peripheral tissues. If untreated it leads to several complications such as blindness, kidney failure, neuropathy and amputations. The benefit of exercise in diabetic patients is well known and recent research indicates that AMP activated protein kinase (AMPK) plays a major role in this exercise related effect. AMPK is considered as a master switch regulating glucose and lipid metabolism. The AMPK is an enzyme that works as a fuel gauge, being activated in conditions of high energy phosphate depletion. AMPK is also activated robustly by skeletal muscle contraction and myocardial ischaemia, and is involved in the stimulation of glucose transport and fatty acid oxidation produced by these stimuli. In liver, activation of AMPK results in enhanced fatty acid oxidation and decreased production of glucose, cholesterol, and triglycerides. The two leading diabetic drugs namely, metformin and rosiglitazone, show their metabolic effects partially through AMPK. These data, along with evidence from studies showing that chemical activation of AMPK in vivo with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) improves blood glucose concentrations and lipid profiles, make this enzyme an attractive pharmacological target for the treatment of type 2 diabetes and other metabolic disorders.
Type 2 diabetes is characterized by the abnormal metabolism of glucose and fat, due in part to resistance to the actions of insulin in skeletal muscle, liver and fat. In the natural history of type 2 diabetes, pancreatic ?-cells initially compensate for insulin resistance by secreting excess insulin. However with time, progressive ?-cell failure leads to insulin deficiency and overt hyperglycaemia. Progression in diabetes leads to the development of chronic complications such as retinopathy, neuropathy and nephropathy, etc. At present, oral therapy for type 2 diabetes relies on several approaches targeted to reduce hyperglycaemia namely sulphonyl ureas, which increase insulin release from pancreatic islets; ?-glucosidase inhibitors, which inhibit gut glucose absorption; metformin, which acts to reduce hepatic glucose output through inhibition of gluconeogenesis, peroxisome proliferators-activated receptor-ã activator thiazolidinediones (TZDs), which promote insulin sensitization. These therapies have either limited efficacy or significant mechanism based side effects like hypoglycaemia, flatulence, body weight gain or enhancement of gastrointestinal problems. Recently launched glucagon like peptide-1 (GLP-I) mimetic peptides cannot be used for oral treatment and there are concerns of its undesirable effects such as nausea, vomiting, etc1. In such a scenario, there is an acute unmet need for an oral anti-diabetic drug without side effects. Pharma companies across the world are exploring several novel targets for this purpose. Evidence accumulated over the past few years indicates that the AMP activated protein kinase (AMPK) may be a good target for the pharmacologie treatment of type 2 diabetes. Current concepts of the mechanisms by which AMPK influences glucose and fat metabolism are discussed in this review.
AMP activated protein kinase (AMPK)
The AMPK belongs to the family of energy sensing enzymes that are activated by cellular stresses resulting in ATP depletion, thus acting like a ‘fuel gauge’2. Upon activation, AMPK functions to restore cellular ATP by both inhibiting ATP consumption processes as well as accelerating ATP generation processes (Fig. l).The cascade is activated by stresses such as prolonged exercise3, electrical stimulation in skeletal muscle4, ischaemia in heart muscle5, heat shock6 as well as through inhibition of tricarboxylic acid cycle or oxidative phosphorylation7. AMPK is activated by an increase in AMP/ATP and creatine/ phosphocreatine (pCr) ratios, resulting allosteric modification or/and through mechanism involving phosphorylation of the á subunit by upstream kinases (AMPKKs)2-8.
AMPK is a heterotrimeric protein consists of three subunits namely á, â and ã. The regulatory subunit plays an important role in maintaining stability of the heterotrimer complex2·8. Both the á and â subunits have two isoforms each, namely áú & á2 and ßl & ß2, while the ã subunit exists in three isomeric forms, i.e., ãÀ, ã2 and ã3. AMPK áú is widely expressed, whereas the a2 subunit isoform is mainly found in the heart, skeletal muscle, and liver9. AMPKa consists of 548 amino acids (aa)and it contains catalytic domain (1-312 aa), an autoinhibitory domain (312-392 aa) and a subunit binding domain (392-548 aa). The catalytic domain has a site of phosphorylation at Thr172 which is required to be phosphorylated for its activation by AMPKK. Removal of both autoinhibitory domain and subunit binding domains leads to constitutive active AMPK retaining one third of activity compared to full AMPK complex whereas removal of subunit binding domain leads to complete loss of activity10·11. The subunit domain contains PEST sequences which are masked by â and á subunits resulting in slow turnover of this enzyme in native state”. The â subunit contains the glycogen binding domain whereas each ã subunit contains four Bateman domain or cysthatione ß-synthase (CBS) domains and each pair of CBS domain functions as prospective AMP-binding sites10.
Skeletal muscle is the main site for glucose disposal in the body and there are two ways to stimulate glucose uptake in skeletal muscle: insulin dependent and insulin independent12. Insulin resistance is one of the early defects detected in the muscle of diabetic patients and insulin resistance is caused mainly due to defect in insulin signaling pathways. Decrease in insulin-stimulated tyrosine phosphorylation of the insulin receptor and insulin receptor-1 substrate (IRS-I) and in 1RS-!-associated phosphatidylinositol -3 kinase (PI-3 kinase) activity leading to the problem in translocation of glucose transporter (GLUT4) from microvesicle to membrane13′17. Currently no pharmacological approach is being persued to correct these defects in insulin signaling pathway. Therefore, targeting insulin independent pathway to restore glucose disposal can be explored as an alternative approach. There are sufficient data available to support the hypothesis that exercise enhances muscle glucose disposal in diabetic patients through an insulin independent mechanism. For example, acute exercise does not increase insulin receptor and IRS1 tyrosine phosphorylation or PI3- kinase activity14·18. Moreover, blockade of the insulin signaling pathway does not alter exercise-stimulated muscle glucose transport19′21. Efforts are ongoing to unravel the molecular mechanism by which exercise functions. Mimicking exercise like effect through drug could be an attractive approach to improve blood glucose level.
Muscle contraction leads to increase in AMP/ ATP and Cr/ pCr levels leading to robust increase in AMPK activity which is well correlated with contraction mediated glucose uptake in muscle22. A similar effect has been observed with AICAR, an AMP analogue and known AMPK activator suggesting that AMPK plays an important role in contraction mediated glucose disposal23. Activation of AMPK by AICAR in rat or muscle cells overexpressing constitutively active AMPK increases glucose uptake and causes translocation of the glucose transporters GLUTl and GLUT4 from microvesicle to plasma membrane establishing the link between AMPK activation, glucose transport and the translocation of glucose transporters24.
Systematic studies using AMPK knockout and transgenic animals helped to clarify the molecular mechanisms of regulation of glucose transport in muscle by AMPK. In AMPK?2 knockout mice (whole body deletion), AICAR stimulated glucose transport is blocked in muscles but insulin stimulated glucose transport is normal in the contracting muscles isolated from these animals25. There is overexpression of the AMPKaI subunit in these animals indicating that though AICAR mediated glucose transport is mainly through AMPKoc2 but it is not indispensable as there is a compensatory mechanism provided by AMPKaI25. On the other hand, in transgenic mice overexpressing muscle specific domain negativeAMPKa2, which blocks the activities of both ?1 and a2 endogenous subunits, AICAR failed to show any stimulation of glucose uptake. Contraction mediated glucose uptake is partially although not completely affected in the isolated muscles of these animals indicating that apart from AMPK mediated mechanism some other unknown mechanisms may be involved in this process26.
The above reports proved the role of non insulin mediated glucose disposal in muscle. A series of in vivo and ex vivo experiments also showed that AMPK is involved in insulin dependent direct glucose transport in muscle. Soleus muscle isolated from AICAR-treated rat shows insulin mediated glucose uptake through translocation of glucose transporter GLUT427. Soleus muscle isolated from normal rats followed by incubation with AICAR and insulin leads to additive increase in glucose uptake through glucose transporter28. In insulin resistant Zucker fa/fa rats, a single dose of AICAR injection improves insulin sensitivity measured using an insulin clamp study29. Taken together these in vivo and ex vivo data prove that AMPK mediated glucose uptake is an additive effect of both insulin dependent and independent mechanisms.
Apart from increasing glucose transport in muscle, AMPK also plays an important role in muscle fat metabolism. Upon activation either by exercise or contraction, AMPK decreases the activity of acetyl CoA carboxylase (ACC) by inhibiting its transcription and also through phosphorylation4·30′32. This leads to a decrease in muscle malonyl CoA content and thus relieving its inhibitory activity on carnitine palmitoyl tranferase 1 (CPT-I)33. Higher CPT-I activity enhances the entry of fatty acids into the mitochondria for oxidation. So, in summary, activated AMPK decreases free fatty acid synthesis (pACCl) and increases mitochondrial ß-oxidation (pACC2), thereby reduces elevated free fatty acid level and thus ameliorates insulin resistance .
In the liver, activated AMPK inactivates ACC at transcriptional and post translational level and also inhibits HMG CoA reductase, the rate limiting enzyme in cholesterol synthesis by phosphorylation34·35. Like skeletal muscle, in liver also, activated AMPK decreases malonyl CoA synthesis resulting in increased ß-oxidation through enhanced CPT-I activity36. Type 2 diabetic patients are often associated with hypertriglyceridaemia and high cholesterol, the potential risk factors for cardiovascular problems. Activated AMPK could reduce this risk by controlling elevated level of free fatty acid, TG and cholesterol37.
The elevation of fasting plasma glucose is associated with type 2 diabetes and it is regulated by gluconeogenesis, a process which makes glucose from non-carbohydrate source in liver. Gluconeogenic enzymes like phosphoenol pyruvate carboxy kinase (PEPCK) and glucose-6phosphate dehydrogenase are the major players in this process38·39. In HepG2 cells and primary rat hepatocytes, AICAR inhibits the transcription of PEPCK indicating the role of AMPK in inhibition of gluconeogenesis38·39. AICAR inhibits hepatic glucose output in rat liver when perfused in vivo2*. Thus, AMPK, by inhibiting hepatic glucose output and increasing muscle glucose uptake, could control elevated blood glucose level in the body.
Role of AMPK in adipocytokine signaling
Adiponectin and leptin, the two adipocytokines produced and secreted from adipose tissues play an important role in the pathogenesis of type 2 diabetes. Adiponectin increases free fatty oxidation through ACC, an AMPK target gene and also enhances insulin sensitivity both in skeletal muscle and liver40·42. There is an inverse relationship with the level of blood plasma adiponectin and insulin resistance. These results indicate that adiponectin behaves like an ideal AMPK activator.
Photophysics and Photochemistry of Horseradish Peroxidase A2 upon Ultraviolet Illumination
Detailed analysis of the effects of ultraviolet (UV) and blue light illumination of horseradish peroxidase A2, a heme-containing enzyme that reduces H^sub 2^O^sub 2^ to oxidize organic and inorganic compounds, is presented. The effects of increasing illumination time on the protein’s enzymatic activity, Reinheitzahl value, fluorescence emission, fluorescence lifetime distribution, fluorescence mean lifetime, and heme absorption are reported. UV illumination leads to an exponential decay of the enzyme activity followed by changes in heme group absorption. Longer UV illumination time leads to lower T^sub m^ values as well as helical content loss. Prolonged UV illumination and heme irradiation at 403 nm has a pronounced effect on the fluorescence quantum yield correlated with changes in the prosthetic group pocket, leading to a pronounced decrease in the heme’s Soret absorbance band. Analysis of the picosecond-resolved fluorescence emission of horseradish peroxidase A2 with streak camera shows that UV illumination induces an exponential change in the preexponential factors distribution associated to the protein’s fluorescence lifetimes, leading to an exponential increase of the mean fluorescence lifetime. Illumination of aromatic residues and of the heme group leads to changes indicative of heme leaving the molecule and/or that photoinduced chemical changes occur in the heme moiety. Our studies bring new insight into light-induced reactions in proteins. We show how streak camera technology can be of outstanding value to follow such ultrafast processes and how streak camera data can be correlated with protein structural changes.
Peroxidases are heme-containing enzymes that reduce H^sub 2^O^sub 2^ to oxidize a wide variety of organic and inorganic compounds. The heme prosthetic group, appointed “ferriprotoporphyrin IX”, allows electron transfer between reductant and oxidant substrates (1). During catalysis in plant peroxidases a porphyrin cation ? radical is formed (2), and in yeast cytochrome c peroxidase a trypiophan radical plays the equivalent role (3,4). In both cases in the first reaction step the iron ion becomes hexacoordinated to an oxygen atom (Fe^sup IV^=O). In classical plant peroxidases tryptophan is uniquely represented and is highly conserved, located in a surface loop connecting two helices. The indole ring is directed toward the core of the protein lying above the plane defined by the heme group at an average distance of 16-18 [Angstrom] (5-8) (Fig. 1 A). Trp fluorescence in classical plant peroxidases is highly quenched in the native state due to energy transfer from the excited state of tryptophan to the heme group (5,9,10). Quantum yields are 100 orders of magnitude lower than that of tryptophan free in solution. Ferriprotoporphyrin also displays a visible absorption spectrum.
The most important UV light absorbers in proteins are the aromatic residues, Trp, Tyr, and Phe along with cystine and His (11). It is known that tryptophan and tyrosine radicals can be induced by ultraviolet (UV) illumination (12-14). Heme groups are also excellent UV absorbers. UV illumination might in some cases induce enzyme inactivation ( 15-18). The mechanisms of inactivation are believed to be due to ionization of aromatic residues associated with an electron transfer mechanism and radical formation together with disruption of disulphide bridges (19-23). Earlier studies confirm that the major reaction after UV excitation of enzymes is phototonization (24). The excited tryplophan after photoionization gives TrpH^sup +^, and electron is ejected from the molecule. In heme proteins, the TrpH^sup +^ might reduce the ferrous heme (25). Porphyrins are a major source of free radicals and singlet oxygen and can induce photobleaching in fluorescent molecules (26). Several studies are reported on photoinactivation of catalase, a tetrameric heme-containing enzyme. Catalase degrades H^sub 2^O^sub 2^ to oxygen and water and represents an important part of the antioxidative system in cells. Blue light (380-500 nm) illumination of sunflower catalase causes partial heme destruction, and oxidation of histidine, present in the catalytic center of catalase, perhaps is an early event in photoinactivation (27). UV irradiation (365 nm) of bovine liver catalase leads to the formation of calalytically inactive compounds III (oxyferrous catalase) and II (catalase FeIV) (28). UV C irradiation of flavocytochrome b^sub 2^, which houses a heme prosthetic group, results in enzyme inactivation, where Tip and Tyr residues as well as the heme group are modified (25). Oxygen presence offers protection of tryptophan against UV-induced damage due to quenching (11), whereas the heme group can act as a photosensitizer thus generating harmful singlet oxygen (29).
This work presents a detailed spectroscopic analysis of UV-induced changes in secondary structure, enzymatic activity, fluorescence emission, fluorescence lifetime distribution, fluorescence mean lifetime, and heme absorption of horseradish peroxidase A2 (HRPA2). The catalytic activity, conformational changes at the secondary structure level, protein fluorescence, and heme absorption were monitored after Trp 296-nm UV illumination. A streak camera study on the effects of UV illumination time on the distribution of the two shortest fluorescence lifetimes of the single endogenous aromatic residue Trp in HRPA2, at pH 4, is presented. We also highlight the outstanding value of streak camera technology in following ultrafast processes and show how streak camera data can be correlated with protein structural changes. Also, we hereby present the effects of continuous illumination of the heme group at 403 nm on Trp fluorescence emission and on heme absorption bands.
Chemicals and sample preparation
Horseradish peroxidase was obtained from Biozyme Laboratories (Blaenavon. UK) (labeled HRP-5) as lyophilized salt-free powder and used without further purification. HRP-S corresponds to HRPA2 according to the nomenclature of Shannon et al. (30) and data reported by Hiner et al. (31). The degree of purity was checked by sodium dodecylsulfaie-polyacrylamide gel electrophoresis, and a single band was observed when stained with Coomassie. HRPA2 concentrations were determined considering the molar extinction coefficient ?^sub 4030n^, = 100 mM^sup -1^cm^sup -1^ (32). Protein solutions used for spectroscopic studies were dissolved in buffer made with Milli-Q water. All salts were of analytical grade. Acetate buffer was used for pH 4. Buffer concentration was always 25 mM.
Extinction coefficient as a function of wavelength of HRPA2 and hematin
The absorbance from 250 nm to 700 nm of a horseradish peroxidase solution prepared as mentioned above was measured on a Thermo Electron (Waltham, MA) UV1 spectrophotometer and compared with a study performed by Du et al. (33) on the absorption of hematin in acetic acid.
Tryptophan irradiation-steady-state fluorescence
The enzyme solution (3 mL of a 5 µM protein solution) was continuously irradiated for different time periods at 296 nm using a 75 W Xenon are lamp from an RTC 2000 PTI (Photon Technology International. Birmingham, NJ) spectrometer provided with a monochromator. Excitation and emission slit widths were set to 6 nm. Tryptophan fluorescence was monitored at 350 nm (excitation spectra) and excited at 296 nm (emission spectra). Temperature in the cell, a quartz cuvette ( 1 -cm path length) was controlled using a Peltier element. The sample was continuously slined at 650 rpm to maintain the homogeneity of the solution, and the temperature was kept constant at 20°C. Line voltage was controlled and maintained at 4 V. thus avoiding fluctuations deriving from the power coming from the electrical outlet.
Activity measurements, steady-state fluorescence spectra, far-UV circular dichroism (CD) spectra, and denaturation curves after ellipticity at 223 nm were determined for samples irradiated for different time periods. Control samples, without irradiation, underwent the same treatment as the exposed ones.
Activity measurements
HRPA2 activity was measured at room temperature using 50 mM guaiacol in 25 mM acetate buffer (pH 4) and 4.4 mM H^sub 2^O^sub 2^. The reaction was followed for 1 min by reading the increase in absorbance at 470 nm. The extinction coefficient of the oxidation product, ?^sub 470nm^ = 26.6 mM^sup -1^cm^sup -1^, was used to calculate initial velocities.
Far-UV CD measurements
CD measurements were carried out using a Jasco (Tokyo, Japan) spectropolarimeter, model J-715. The ellipticity values were obtained in mdegrees directly from the instrument and converted to the mean residue ellipticity ?^sub MRW^ as previously stated (8). The far-UV CD spectra were measured using a rectangular quartz cell of 1-mm path length. Each spectrum was an average of six scans between 300 and 200 nm. The resultant ellipticities of the HRPA2 solutions were calculated by subtracting the elliplicity of the buffer solution. The wavelength of 223 nm was used to monitor thermal denaluration in the far-UV CD range. Temperature scans were carried out in the temperature range 293-358 K using a Pettier element (irradiated samples] or a thermostaled cuvette by means of u circulating water bath, and a temperature probe was immersed in the protein (dark control samples). The experimental parameters were as follows: 1-nm bandwidth, 0.2-K step resolution, 2-s response time, and scanning rates 1.5 (irradiated samples) and 2.6 K min^sup -1^ (control).
HRPA2 home irradiation studies
Irradiation and steady-state fluorescence
A total of 3 mL of a 4 µM protein solution was continuously irradiated for 30 h at 403 nm using a 75-W Xenon are lamp from a RTC 2000 PTI (Photon Technology International) spectrometer provided with a monochromaior (slits width 6 nm). Temperature in the cell, a quartz cuvette (1-cm path length) was controlled using a Peltier element and was kepi constant at 298 K. The sample was continuously stirred at 650 rpm to maintain the homogeneity of the solution. Line voltage was controlled and maintained at 4 V, thus avoiding fluctuations deriving from the power coming from the electrical outlet. Before 403 nm irradiation and at specified times during the irradiation, tryptophan fluorescence emission intensity at 350 nm upon 296-nm excitation was acquired.
Irradiation and absorption measurements
In another experiment, absorption by the protein solution was monitored before and after irradiation with 403-nm light for 26 h. The sample was irradiated using the same conditions as above. Measurements were performed on a Thermo Electron UV1 spectrophoiometer.
To model excited state processes or to unravel heterogeneity in the distribution of fluorophores, experiments under a variety of conditions can be performed. One tun change experimental parameters such as excitation and emission wavelengths, pH, quencher concentration, timescale, temperature, orientation of excitation, and emission polarizers. Finally, a multi-dimensional fluorescence decay surface is obtained. From the separate analyses of the individual decay traces, a model can be deduced. The appropriateness of the model is checked by verifying the consistency of the parameter values obtained from each decay curve analysis. However, the parameter estimates resulting from the various single decay curve analyses may suffer from u large uncertainty so that the model building becomes difficult. It has to be realized that many parameters appear in a nonlinear way in the model function and that in most cases the functions within the model are nonorthogonal. It has been suggested Io perform a simultaneous analysts of related decay traces, i.e., of the fluorescence decay surface, by linking the common parameters. The merits of this global analysis approach have been emphasized and used broadly within the scientific community (34). Global analysis of fluorescence lifetime data can be used to obtain an accurate lit of multi-exponential fluorescence decays. Global analysis algorithms simultaneously tit multiple measurements acquired under different experimental conditions to achieve higher accuracy.
Work-related eye injuries and illnesses
More than 65,000 work-related eye injuries and illnesses, causing significant morbidity and disability, are reported in the United States annually. A well-equipped eye tray includes fluorescein dye, materials for irrigation and foreign body removal, a short-acting mydriatic agent, and topical anesthetics and antibiotics. The tray should be prepared in advance in case of an eye injury. Eye patching does not improve cornea reepithelialization or discomfort from corneal abrasions. Blunt trauma to the eye from a heavy object can cause a blow-out fracture. Sudden eye pain after working with a chisel, hammer, grinding wheel, or saw suggests a penetrating globe injury. Chemical eye burns require immediate copious irrigation. Nontraumatic causes of ocular illness are underreported; work-related allergic conjunctivitis increasingly has been recognized among food handlers and agriculture workers who are exposed to common spices, fruits, and vegetables. The patient’s history of eye injury guides the diagnosis. Primary prevention and patient counseling on proper eye protection is essential because over 90 percent of injuries can be avoided with the use of eye protection. As laser use increases in industry and medical settings, adequate personal protection is needed to prevent cataracts. Outdoor workers exposed to significant ultraviolet rays need sun protection and safety counseling to prevent age-related macular degeneration. Contact lenses do not provide eye protection, and physicians should be familiar with guidelines for the use of contacts in the workplace.
More than 65,000 work-related eye injuries and illnesses cause job absenteeism in the United States every year. (1) Workers who have the highest risk of eye injuries include fabricators, laborers, equipment operators, repair workers, and production and precision workers. More than one half of work-related eye injuries occur in the manufacturing, service, and construction industries. Most chemical and thermal eye injuries occur when persons are at work. (2) Eighty-one percent of work-related eye injuries occur in men, and most occur in workers 25 to 44 years of age. (1)
Eye Examination
The visual acuity of a patient with an eye injury should always be tested because vision changes provide objective tools to monitor clinical improvement or deterioration. Prepare an eye tray (Table 1) in advance, and perform irrigation in the event of a chemical burn. Use fluorescein dye and a cobalt-blue filtered light to detect corneal abrasions. After the assessment, gently irrigate the eye to diminish the risk of an adverse reaction to the dye, such as burning. (3)
Only a short-acting mydriatic agent (e.g., tropicamide [Mydriacyl]) should be used to dilate the pupil. The effects of longer-duration agents (e.g., atropine, homatropine hydrobromide [Isopto Homatropine]) may last for days, impairing vision and preventing patients from driving. To reduce injury and discomfort, instill a topical anesthetic (e.g., tetracaine [Pontocaine], proparacaine [Ophthetic]) before using fluorescein or removing a foreign body. Only use anesthetics in the office; if a patient uses the medication at home, it can delay healing and mask complications.
Check the expiration dates of all medications and the batteries of handheld ophthalmoscopes. A slit lamp is useful, but a thorough examination with a handheld ophthalmoscope is adequate for most patients. Evert the eyelids by placing a cotton-tipped swab on top of the upper eyelid and rolling the lid over the swab; carefully inspect the eye for foreign bodies.
Diagnosis and Management
CORNEAL ABRASIONS
Eye pain after a trauma caused by a foreign body, rubbing, or a scratch suggests a corneal abrasion. Associated symptoms may include blinking, tearing, pain with eye movement, headache, blurry vision, and foreign body sensation. Some physicians treat noninfected corneal abrasions prophylactically with topical antibiotics, although the evidence supporting this practice is limited. Ointments are more soothing and persist on the cornea longer than eyedrops. Erythromycin and bacitracin (AK-tracin) are preferred over gentamicin (which may be toxic to corneal epithelium) and Neosporin (which has a relatively high allergic reaction rate). (4)
Studies have shown that eye patching does not improve corneal reepithelialization or discomfort and increases pain in one half of patients. (5-7) The addition of a topical nonsteroidal anti-inf lammatory drug (NSAID; e.g., ketorolac [Acular], diclofenac [Voltaren]) has been shown to be somewhat beneficial for symptom relief (7) and for decreasing narcotic use and time off work; however, NSAIDs may delay healing. (8) Mydriatic agents are no longer recommended to treat corneal abrasions because they offer no additional benefit. (9) Regardless of the ocular agents used, always offer oral analgesics because pain may be severe. Advise the patient to avoid wearing contact lenses until the abrasion is healed and symptoms are resolved.
Interfacial transfer between copper and polyurethane in chemical-mechanical polishing
The interactions between a copper and urethane polishing pads were characterized to investigate the effects of friction on removal mechanisms of a polishing system of copper interconnect wafers in water. In-situ characterization of polished copper and urethane were conducted using Auger and x-ray photoelectron spectroscopy (XPS) analysis techniques. These techniques pinpointed the chemical interactions immediately during polishing. Results indicated that, because of the stimulation of friction, the molecules from the pad transferred to the copper surface, and the oxidized copper surface was transferred to the urethane surface. Without friction, however, such a transformation did not occur and passivation of the copper surface took place. This evidence proves a possible new chemical-mechanical polishing (CMP) mechanism. In addition to the formation and removal of a passivation layer, a transformation layer is formed during CMP because of friction stimulation. This layer is found on both copper and pad surfaces with different chemical bonds. Understanding the transformation layer helps to understand the formation of defects, pad conditioning, and pad life.
Key words: Cu CMP, electrochemistry of Cu, tribology, nanoabrasive particles, Cu passivation, Cu oxidation, friction-stimulated chemical wear Chemical-mechanical polishing (CMP) is a synergetic-planarization process that undergoes kinetic combination of three different components: wafer, slurry, and pad. It is a complicated system that involves more than one mechanism. It has been well accepted that the tungsten-metal CMP is based on the formation and following abrasion of a passivation layer.1 This mechanism is extended to other metal CMP, such as copper and aluminum. There are reports found indicating that this might not be the only case.2 A previous study extrapolating and estimating existing data concluded that abrasive particles abraded a soft surface layer from wafer surfaces.3 Copper oxides exist during CMP,4 and the friction depends on the type of oxides.5 In the past, we have proven that copper CMP does not reach the hydraudynamic regime during polishing.6-9 This means that the polishing pad always contacts the copper through asperities.
The motivation for this study is to pinpoint the chemical interactions caused by mechanical stimulation during polishing. We focus on the interactions between copper and urethane to investigate the effects of friction. This can only be done in a system that includes a friction test and surface analysis instantaneously. At surfaces against one another, different chemical interactions take place.10-12 A tremendous amount of work has been done on lubricating additives in studying the tribochemical wear.13 To distinguish the chemical reactions from the friction-stimulated reactions, a polishing experiment was performed in a vacuum with a controlled amount of water-vapor pressure. Under a vacuum, the sensitivity of the surface analysis is as high as a few nanometers in depth. We evaluate the friction value and surface-bonding nature. Such a study shall bring insights of removal mechanisms of copper and pad behavior in conditioning and polishing.
EXPERIMENTAL
Polishing experiments were conducted on a pinon-disk tribometer located in a vacuum chamber, as shown in Fig. 1, with well-controlled environments and surface analysis tools attached. This system was designed to conduct in-situ surface analysis that cannot be otherwise obtained. As shown in Fig. 1, the system includes two chambers in which a pressure as low as 10^sup -8^ mbar can be achieved. The tribometer is located at the center of the chamber and the surface analytical tools are at the top. Partial pressures of pure gases, water vapor in this study, can be introduced into the main chamber using a leak valve. The pressure can be controlled in the range from 10^sup -7^-10^sup 4^ mbar. The gas concentration is monitored using a residual-gas analyzer.
Surface-analysis equipment was attached to the vacuum chamber for Auger electron spectroscopy (AES) and the x-ray photoelectron spectroscopy (XPS). The AES has an electron probe sizing down to 0.5 (mu)m in diameter. The XPS is performed with a nonmonochromatized source and has a dual anode for MgK(alpha) or AlK(alpha) irradiation. The area of the x-ray is around 1 cm^sup 2^. The electron spectrometer (VS 220i) includes a set of inlet and outlet lenses and an energy analyzer. The electrons emitted by the surface of the sample during AES or XPS analysis are collected by the inlet lenses, energy-filtered by the analyzer, and detected by six-channel electron multipliers.
Ion etching was conducted for cleaning before each test. The Ar ion beam was scanned with 100 tim in diameter. A scanning electron microscope (SEM) was generated using an electron gun and the secondary electron detector, with a lateral resolution near 0.5 (mu)m. The analysis is conducted inside and outside the tested area to study the effects of friction.
The initial vacuum of the chamber was 10-8 mbar (10^sup -6^ Pa). At the beginning of the test, the copper was ion etched to remove the existing oxide layer. This was confirmed with the Auger analysis. Water vapor was then introduced into the chamber so that the vacuum reached 10^sup -6^ mbar (10^sup -4^ Pa). Under a vacuum environment, water molecules were introduced into the chamber as a vapor phase. A couple layers of water molecules were estimated to have formed on the copper and urethane surfaces uniformly.
The copper material has a purity of 99.999 wt.%. It is cut into a 5-mm-diameter pin with a sphere head. The pin is fixed on a holder and moves back and forth on a polyurethane polishing pad. The size of this disk is 8 mm x 12 mm x 3 mm. The pad was not conditioned before it was put into the chamber in order to observe the surface-change reflecting friction. The disk was cleaned and soaked with deionized water and dried in air. It continuously dries under vacuum. The polishing pad was fixed on a vertical shaft attached to an XYZ manipulator. The pad moves in a linear-reciprocating motion. The pad speed was fixed at a slow speed of 0.5 mm/sec to avoid frictional heating. The applied force was 1 N, which is relevant to the pressure of 542 Pa . The speed was 500 jim/sec; the travel length for reciprocal motion was 2 mm. The total number of cycles for the tests was 600. During testing, the frictional force was recorded. The AES and XPS were performed on and off tested areas for chemical analysis.
The friction coefficient as a function of time estimated in dry and in water-vaporized (wet and in vacuum) environments is shown in Fig. 2. This figure shows that the friction-coefficient value changes during sliding in two different conditions: dry vacuum at a pressure of 10^sup -5^ MPa and wet vacuum at pressures of 10^sup -2^ MPa. The open circles are data points recorded when tested in the dry vacuum and filled symbols are that in the wet environment. The frictional behavior depends on the materials and surface properties, and it is generally shown as the change at the beginning of tests and the stabilization after. According to Fig. 2, the wet surfaces produce increased friction at a low rate. The friction increases in the first 40 cycles before it reaches a maximum. The friction in dry conditions increases immediately after the test starts and after eight cycles reaches a maximum. In three tests, the friction coefficient lies in the range of 0.6-0.75. As shown in Fig. 2, the friction is relatively stable for the dry environment, and a few water molecules were introduced. The large variation of friction is in the middle of three potential causes: the softening of the urethane pad surface, the change of the pad surface roughness, and the change of the copper surface. It is known that urethane is sensitive to water.14 When water changes the bonding structure of the urethane surface, the urethane’s shear stress reduces. This change will affect the change in friction.
DOE’s R&D Efforts Offer Means to Boost Pulp Mill Performance, Yield
DOE has developed a number of new technologies for pulping, as well as steam and power generation, that improve energy and environmental performance
The rapid rise and increasing volatility in energy prices since 2001 has caused many pulp and paper mills to reevaluate their energy strategy. Whereas, mills have traditionally focused on managing raw material and labor costs, improving a mill’s energy efficiency is becoming a key competitive advantage for achieving profitability in an increasingly difficult business environment.
The US Department of Energy (DOE) is interested in improving the energy efficiency of the pulp and paper industry because the industry consumes 10% of all energy used in US manufacturing and 3% of the US’s overall energy consumption.1 Large increases in the industry’s energy efficiency will help reduce the nation’s consumption of natural gas, reduce the growing reliance on foreign energy sources, help the industry lower its energy costs and increase its international competitiveness.
Mills can lower their energy consumption through deploying new energy savings technologies or by implementing operational practices that lower energy use. The main purpose of this article is to make mills aware of energy savings technologies that were developed with DOE sponsorship. Mills can also learn about best practices that lower their energy consumption by applying for an Energy Savings Assessment through the Save Energy Now Program.
DOE’s R&D efforts over more than a decade have produced a number of energy savings technologies that are now commercially available. This article from DOE discusses the emerging technologies that decrease energy use and also improve environmental parameters such as lowering VOCs and improving fiber yield. Most all of these technologies have registered trademarks.
Pulping
Chemical for increasing wood pulp yield: ChemStone OAE-Il thoroughly penetrates dense wood chips andprotects fine fibers from overprocessing. This novel pulping additive’s unique chemistry increases alkali penetration by 30% within 15 min, but halts acid hydrolysis upon alkali availability to prevent overcooking. Unwanted compounds are prevented from re-precipitating, and byproducts are effectively eliminated from the fiber mixture. This cooking aid is effective for both hardwood and softwood pulps and is applicable to all pulping processes. The technology:
* Increases pulp yield by 4-5%
* Reduces rejects and reprocessing of second-rate fibers
* Reduces cooking time to save 125,000 Btu/ton of processed wood chips
* Decreases use of bleaching chemicals
* Prevents formation of ethylene glycol residues
* Reduces sulfur-based emissions
ChemStone RBS400: ChemStone RBS400 increases circulation flow in pulping equipment by reducing scale buildup and plugging. This digester additive controls the metals that interfere with bleaching and with the sulfur chemistry of a kraft cook. The chemical also reduces dichloromethane (DCM) extractives by controlling calcium before it can react with fatty and resin acids. The technology:
* Increases southern hardwood yield by 3%
* Minimizes downtime needed for cleaning calcium scales
* Controls calcium levels and reduces DCM extractives
Borate autocaustlcizlng: Pulp mills can use partial borate autocausticizing to increase their causticizing capacity and reduce the amount of natural gas required to fire the lime kiln. Adding sodium metaborate to the liquor cycle drives autocausticizing reactions in the recovery boiler and thereby helps debottleneck a lime kiln-limited mill. The technology:
* Increases causticizing capacity and pulp production
* Reduces lime purchase and recausticizing load
* Reduces lime kiln load and energy requirement
Dynamic simulation model for continuous digesters: This model predicts the dynamic behavior of the continuous digester, including internal operating characteristics throughout the column. The model runs about 300 times faster than real time and includes a graphical user interface. The simulation software is suitable for designing control systems, improving operating policies and training operators. The technology:
* Improves product quality
* Increases wood yield 4-5% per ton
* Saves 125,000 Btu/ton of processed wood chips
* Reduces use of bleaching chemicals
* Prevents formation of ethylene glycol residues
* Reduces sulfur-based emissions
* Reduces alkali requirements by 7%
* Reduces CO emissions in lime kiln
* Reduces effluent color and biological oxygen demand (BOD)
Steam and Power Generation
Methane de-NOx reburn process: Methane de-NOx is a retrofit reburning process that improves solid waste fuel combustion while controlling NOx and CO emissions. The process injects natural gas above the stoker boiler grate and uses flue gas recirculation to enhance mixing and creates an oxygen-deficient atmosphere that retards NOx formation. The technology:
* Reduces NOx emissions by 50-70% without postcombustion control
* Increases thermal efficiency
* Reduces CO2, SOx, H-Cs and particulates
* Increases waste fuel firing capacity
* Improves combustion of hard-to-burn fuels
* Reduces natural gas usage
PyrOptlx detection and control of deposition on pendant tubes In kraft recovery boilers: The PyrOptix infrared camera system enables on-line detection of deposits, blockages, hot spots and fixture damage in kraft recovery boilers. Without shutting down the boiler, the camera produces clear, thermal images and video of boiler depths up to 100 ft. The technology:
* Reduces soot-blowing steam use by up to 20%
* Reduces equipment downtime and shutdowns
* Reduces tube maintenance costs
* Improves heat transfer and reduces fuel use
* Reduces NOx emissions
* Improves boiler safety
Paper Recycling
XTREME Cleaner: Removal of light sticky contaminants: The XTREME Cleaner is a centrifugal cleaning technology that effectively removes stickies, wax, polyethylene, binding glue, and other contaminants from post-consumer fiber sources. This long residence time, small diameter cleaner’s improved kneading and vortex separation technology separates tiny contaminants that are close to the specific gravity of the fiber itself.
The technology:
* Reduces energy use by 50%
* Maintains product quality and saves $3,500-11,000 per day by using lower-grade furnish
* Improves productivity by reducing machine and paper breaks by 40-60%
* Reduces downtime for cleaning sticky buildup off machinery
MultiWave automated sorting system for efficient recycling: The MultiWave sensor is a paper and plastic sorting system that incorporates an innovative lignin sensor. This sensor detects the presence of paper in a waste stream conveyed at high speeds by measuring the lignin’s fluorescence under green light. Based on the sensor data, the master computer fires compressed air jets to eliminate rejected materials. The technology:
* Increases throughput rates
* Enhances sorting and ejection accuracy
* Improves quality of recycled paper fibers
* Eliminates manual sorting
* Conveys up to 15 tons/hr
* Reduces solid waste
Process Water
Pressurized ozone/ultraflltratlon membrane system for removing total dissolved solids (TDS): This technology combines pressurized ozone injection and ultraflltration to remove dissolved solids from paper mill process water, enabling cost-effective and efficient closed-loop operation. Ozone injection increases the oxidation of organic and inorganic TDS. These solids precipitate out of the process water as large particles and are removed by ultrafiltration or nanofiltration membranes. The technology:
* Removes up to 50% of TDS in one pass
* Provides potential to increase productivity by 5-15%
* Improves performance of chemical additives
* Removes 97.5% total suspended solids (TSS)
Pulping Technologies for Tomorrow
DOE and its commercial partners are currently developing technologies that will soon be ready for commercialization. Many of these have completed or are completing pilot-scale testing and will move towards a full commercial-scale demonstration. The following sections describe a few technologies that the pulp and paper industry can look for in the near future.
Chemical analysis of 1,2,3,4-butanetetracarboxylic acid
Chemical Analysis of 1,2,3,4-Butanetetracarboxylic Acid1
Polycarboxylic acids have been the most promising durable press finishing agents for cotton to replace traditional formaldehyde-based reagents. Among the various polycarboxylic acids investigated in recent years, 1,2,3,4-butanetetracarboxylic acid (BTCA) has been the most effective crosslinking agent. Cottons treated with BTcA have shown superior durable press performance with high levels of laundering durability. In this research, we analyze a reagent grade and an industrial grade BTCA using elemental analysis and acid-base titration. The titration data indicate that the industrial grade product contains approximately 95% BTcA. The two BTCA products are studied by Fm and Fr-Raman spectroscopy, proton magnetic resonance spectroscopy , mass spectroscopy (MS), and liquid chromatography/mass spectroscopy . All the instrumental analysis data indicate the low level of impurities in the industrial BTCA. Cotton fabrics treated with the two products show similar durable press performance, indicating that the differences in effectiveness for crosslinking cotton between these two BTCA products are insignificant. The data also show that the impurity in the industrial grade BTCA does not cause fabric yellowing.
Since the late 1980s, extensive efforts have been made to use multifunctional carboxylic acids to replace the traditional dimethyloldihydroxylethyleneurea (DMDHEU) due to increasing concern with the toxicity of formaldehyde [9]. Polycarboxylic acids have shown high levels of effectiveness for crosslinking cotton when sodium hypophosphite (NaH^sub 2^P0^sub 2^) is used as a catalyst [ 12-14, 17]. A new finishing system consisting of citric acid and a polymer of maleic acid has been commercialized [18]. Polycarboxylic acids have also been used as crosslinking agents for wood pulp cellulose to improve paper wet strength [4, 16, 17, 19]. Among the various effective polycarboxylic acids investigated, BTCA has proved to be the most efficient crosslinking agent for cotton fabrics [12-13].
BTCA can be synthesized by two different methods. The first is to subject the Diels-Alder reaction product of maleic anhydride and 1,3-butadiene to hydrolysis followed by oxidative cleavage [1, 8, 10]. The Diels-Alder reaction takes place in the temperature range of 100140(deg)C with 1,3-butadiene as the solvent [8]. The reaction forms cis-1,2,3,6-tetrahydrophthalic anhydride, which is hydrolyzed to become cis-1,2,3,6-tetrahydrophthalic acid. Finally, cis-1,2,3,6-tetrahydrophthalic acid is subjected to oxidative cleavage by hydrogen peroxide in water in the presence of a catalyst, such as tungstic acid, to form BTCA. The second method is electrolytic hydrodimerization of dialkyl maleate followed by hydrolysis of the hydrodimerization product [2, 3, 6].
Even though BTCA is the most efficient nonformaldehyde crosslinking agent for cotton, it has not been used as a durable press finishing agent by the textile industry because of its high cost and unavailability on a commercial scale. A Chinese producer recently succeeded in manufacturing an industrial grade BTCA at a very competitive price, thus making commercial applications of BTCA likely [11]. In this research, we use both chemical and instrumental analytical techniques to investigate industrial grade BTCA (BTCA-I) and compare it with a reagent grade BTCA (BTCA-R). We also evaluate the performance of these two BTCA products as durable press finishes for cotton fabrics.
Experimental
Measuring moisture content: A BTCA sample was weighed and heated in a vacuum oven at 100(deg)C for 30 minutes, transferred into a desiccator to cool to room temperature, then weighed again. This procedure was repeated until the sample reached a constant weight. The moisture content (%) was calculated using the following formula:
{[Initial weight (g) - dry weight (g)]
/ [initial weight (g)]} X 100%
Elemental analysis: The concentrations of carbon, hydrogen, and oxygen (C, H, 0) of the BTCA samples were analyzed with a PE 240C C, H, N analyzer. Approximately 2 mg of a sample was first combusted, then separated by chemical chromatography, and measured by a thermal conductivity detector to determine the C, H, N concentrations.
Acid/base titration: Approximately 4 g of BTCA was accurately weighed and dissolved in CO^sub 2^-free distilled water in a 1000 ml volumetric flask; 20 ml of the BTCA solution were then titrated with a standard sodium hydroxide solution (0.0540M). The equivalent point (pH = 8.5) was determined by a pH meter. Carboxylic acid concentration (mmol/g) was calculated using the following formula:
[Volume of NaOH (ml)
x concentration of NaOH (mmol/ml)]
X [1000 (ml)/20 (ml)] / [the weight of sample (g)]
The purity of the BTCA sample was calculated using the following formula:
{[Carboxylic acid concentration of the sample (mmol/g)]
/ [theoretical value of the carboxylic
acid concentration of BTCA (mmol/g)]} X 100%
FTIR spectroscopy: A Nicolet Magna 760 FTIR spectrometer was used to collect the transmission spectra of a BTCA powder. Resolution for all the infrared spectra was 4 cm^sup -1^ , and there were 100 scans for each spectrum. No smoothing functions and baseline correction were used.
FT-Raman spectroscopy: A Nicolet 950 FT-Raman spectrometer with a powder sample accessory and an InGaAs detector was used to collect all the Raman spectra of BTCA powders. The resolution was 4 cm^sup -1^, and there were 300 scans for each spectrum.
1H–NMR spectroscopy: NMR data were acquired at 20(deg)C on a Varian Inova 500 spectrometer (500 MHz) using a 10 mg sample dissolved in 0.5 ml D^sub 2^0. The ^sup 1^H chemical shift at 20(deg)C (4.81 ppm) was referenced to DSS (2,2dimethyl-2-silapentane-5-sulfonate) by means of HDo resonance. The coupling constant was computed by multiplying the difference in chemical shift by 500 (Hz).
Mass spectroscopy: The mass analysis was conducted with a Perkin Elmer Sciex API I plus quadrupole mass spectrometer, which scanned negative ions from 100– 600 m/z using a 0.2 m/z step and a 2.0 millisecond dwell time. The samples were dissolved in a mixed solvent of H^sub 2^O/CH^sub 3^CN (50:50) and infused at a rate of 0.2 ml/min.
LC/MS: The HPLC used a Kromasil C-18 column (1 mm X 250 mm with a 5 (mu)m particle size and 100 Angstrom pore size) made by Keystone Scientific and an Applied Biosystems (ABi) solvent delivery system. Solvent A was H^sub 2^O and solvent B was acetonitrile (CH^sub 3^CN). A sample was injected with 100% A. A was held at 100% for 7 minutes, and B was ramped to 70% in 30 minutes and then to 100% in 5 minutes. 100% B was held for the remainder of the run. The HPLC flow rate was 30 (mu)L per minute. The uv at 220 nm was measured using an ABt 759A absorbance detector. After flowing through the detector, the effluent was split so that it went at a rate of 16 (mu)L per minute into the PE Sciex API I plus quadrupole mass spectrometer equipped with an electrospray source. The mass spectrometer scanned from 100 to 600 m/z with a 2.0 millisecond dwell time and a 0.2 u step size.
Material: The cotton fabrics were desized and bleached print cloth (Testfabrics style 400). Sodium hypophosphite, sodium hydroxide, and BTCA were reagent grade chemicals supplied by Aldrich. Industrial grade BTCA was supplied by Hangzhou Green Additives Institute, Hangzhou, China (green@public 1.hz.zj.cn). The fabric softener was a high-density polyethylene (Mikon HD) supplied by Omnova Solution, South Carolina.
Cotton fabric treatment. The cotton was first impregnated in a solution containing the reagents, padded through two dips and two nips to reach an average wet pickup of 98-103%, dried at 80(deg)C for 3 minutes, and finally cured in a Mathis curing oven at a specified temperature. All the BTCA solutions contained sodium hypophosphite (NaH^sub 2^PO^sub 2^) as a catalyst with a 3:2 (w/w) acid-to-catalyst ratio.
Evaluation of cotton fabric performance: The conditional wrinkle recovery angle (WRA) and durable press (DP) rating of the treated cotton fabric were measured according to AATCC Standard Methods 66-1990 and 124-1992, respectively. Fabric tensile strength was measured according to ASTM Method D5035-90. The fabric ciE whiteness index was measured before washing with a Macbeth Color-Eye 7000A spectrometer according to AATCC Standard Method 110-1995. Initial fabric WRA, DP rating, and tensile strength were evaluated after one home laundering washing/drying (HLWD) cycle without a detergent. Fabric wRA and Dr rating were also evaluated after different numbers of HLWD cycles.
If It Smells Like a Duck, It Might Be an Asthma Subphenotype
Now beginning to be heard above the constant din of powerful marketing efforts to the converse, a growing wave of physicians have been shouting “asthma is not a diagnosis.” Indeed, asthma is but a symptom, categorically on par with diarrhea. Imagine determining the optimum treatment strategy for diarrhea based almost entirely on whether it was “mild,” “moderate,” or “severe,” and “intermittent” or “persistent.” Imagine striving to control excessive stooling while neglecting to consider the cause. Imagine trying to study the genetics of diarrhea. Imagine attempting to examine the efficacy of a new drug by enrolling everyone with diarrhea, regardless of mechanism, in one giant study and expecting the results to be applicable to an individual patient. Now, what applies to diarrhea applies equally well, or equally poorly, to that symptom complex we still refer to as “asthma.”
Variable airway narrowing leading to wheeze can be caused by bronchospasm, inflammatory cell accumulation, mucous plugging, surfactant dysfunction, airway edema, airway vascular congestion, or abnormal structure and function of the airways. Each of these mechanisms of wheeze and air trapping has multiple underlying potential causes. It is no wonder that a one-size-fits-all strategy for managing asthma leaves many insufficiently diagnosed and wrongly treated, for many of the underlying mechanisms are left undiscovered or unaddressed.
To optimize our therapeutic strategies, we are making increasing strides to seek the underlying causes for each individual patient’s asthma using various tests. These efforts to subphenotype the patient’s asthma are in effect efforts to make a true diagnosis. We determine whether or not inhalant allergies might be driving an inflammatory process. We try to guess if gastroesophageal reflux is a contributor to a patient’s symptoms. We are starting to measure exhaled nitric oxide and induced sputum characteristics, thereby quantifying at least a small proportion of the myriad components of the nebulous entity known as inflammation, at which we otherwise blindly direct our therapies. These efforts are noteworthy.
In this issue of AJRCCM(pp. 986-990), Carraro and colleagues (1) continue the efforts of an expanding contingent of researchers to develop means for acquiring biochemical information about the narrow and difficult-to-access passages that lead to our alveoli. They studied exhaled breath condensate-a body fluid easy to obtain (easy on patients), but difficult to assay (hard on scientists) (2). Using nuclear magnetic resonance (NMR) signals derived from concentrated exhaled breath condensate, Carraro and colleagues have identified NMR spectroscopy patterns that, at least post hoc, well differentiate patients with clinically identified asthma from control subjects. Although the human nose cannot sense these patterns, the magnetic nose can. Of course, how such high-tech testing as NMR spectroscopy of breath condensate compares to the gold-standard asthma diagnostic method can never be determined, for there is no gold-standard asthma diagnostic method-quite simply because asthma is not a diagnosis.
These NMR signal patterns in exhaled breath condensate may not only serve as phenotypic discriminators but may also open a window on airway biochemical disturbances underlying airway cellular dysfunction. In other words, they may help us find the disease in each patient that leads to his or her asthma symptoms. We are moving down a path from DNA genomics, through RNA expression , through proteomics, and now on to metabolomics. Each step down this path takes us closer to the direct cause of the physiologic disturbance .
In this preliminary, but novel, methodologic study, Carraro and colleagues speculate that the particular NMR chemical patterns they identify in patients with asthma symptoms may be attributable to abnormal acetylation and oxidation biochemistry of the asthmatic airway. Such chemical pathways are known to exist in humans
(3), although their pathologic relevance in the lungs is completely unknown. As with many breath assays, dilution effects and oral contribution have not yet been well controlled, and prospective analysis based on the post hoc NMR patterns has not yet been done. But this study will be the first of many, and it may be that abnormal acetylation chemistry joins redox disturbance, airway acidification, and abnormal nitrosothiol chemistry as targets for new pharmacologic therapies aimed at addressing the metabolic disturbances of the airway. Noninvasive assays, such as NMR spectroscopic patterning of breath condensate, when validated sufficiently, can be anticipated to assist in identifying which patients are most likely to benefit from any such new therapies. Instead of testing oral antioxidants, inhaled alkaline buffers, and nitrosothiol supplementation as therapies for asthma, we can instead more appropriately test these compounds as specific treatments for “airway redox disturbance,” “airway acidity,” and “nitrosothiol deficiency,” using the asthma symptoms as but one important outcome variable. In such a fashion, testing new therapeutic compounds can be performed in those patients having the relevant metabolic disturbance as identified with objective testing, as opposed to just seeing if the drug works in asthma.
Environmental Municipality Agencies Want Carwash Fundraisers to Use Waterless Products?
A few cities in California are asking non-profit groups to use waterless car wash products, instead of the old fashioned bucket of water and a sponge. Why? Because many municipalities are trying to find additional ways to save water and prevent storm drain pollution, which leads to the environment.
In Santa Monica there is a big push to do this by the city, yet amazingly enough the Santa Monica Bay is polluted because the sewer treatment plant overflows about twice per year. Worse, surfers are warned not to go in and no one dares eat the fish. But this has nothing to do with car wash fundraisers.
Well we must all realize that Dry Wash-n-Guard Waterless Carwash is sold as a Multi-Level Marketing Product right? It is very expensive per bottle. It takes 15 minutes to do a car with it as opposed to 5-minutes with a pressure washer. So the kids groups doing the “apple pie” traditional car wash fundraisers cannot possibly make the money they need using it.
In one online book adopted by the Storm Water Control district for the City of Los Angeles, you will find accepted BMPs or best management practices approved by the RWQD Regional Water Quality Control District, which fully comply with 13.262 of the California Water Code.
It is unfortunate that we attack non-profit groups with environmental laws and rules, which really do not apply, after all the Federal Clean Water Act of 1972 was for things like oil spills and strip-mining, not fundraiser car washes. So, who is pushing these new plans? Well, waterless car wash product companies, fresh out of environmental college municipal workers and carwash owners, who would like to see all that business come to their carwashes instead.