Application of prepared waterborne polyurethane extended with chitosan to impart antibacterial properties to acrylic fabrics

In this study, isophorone diisocyanate (IPDI), 2,2-bis (hydroxylmethyl)-propionic acid and polyethylene glycol (PEG) were employed to polymerize waterborne polyurethane. The polyurethane prepolymer was extended with chitosan of two different molecular weight (100,000 and 150,000), and used as finishing agent for acrylic fabrics. The antibacterial activity of the acrylic fabric treated with the polyurethane-chitosan solution was improved even after 15 washing times. Pretreatment of acrylic fabrics with hydrazine hydrate was found to improve the uptake of the polymer by the fabric. The effects of hydrazine and polyurethane treatments on some of the inherent properties of acrylic were assessed. The functional groups of polyurethane prepolymer as well as polyurethane extended with chitosan were confirmed with the analysis of the spectra of Fourier transform infrared spectroscopy (FT-IR).     

Lipid Metabolism and Cardiovascular Morbidity and Mortality in Hemodialysis Patients: Role of Factors Modulating Cytosolic Calcium

Animal studies indicate that insulin resistance and glucose intolerance leading to dyslipidemia in uremic rats are associated with increased cytosolic calcium ([Ca⁺⁺ i]). The resistance and intolerance are reversed with verapamil, but recur after its discontinuation. This finding suggests that hyperparathyroid‐induced [Ca ⁺⁺ i] increase is responsible for the metabolic derangement. We retrospectively examined, over a 12‐year period, the effects of factors that lower [Ca ⁺⁺i] on total serum cholesterol and triglycerides in 332 hemodialysis (HD) patients. Because the study was retrospective, detailed lipid profiles were not available. We therefore relied on morbidity and mortality outcomes related to atherosclerotic vascular disease. Patients with diabetes mellitus were excluded, because their dyslipidemia and vascular disease are mediated via a different mechanism. Four groups emerged: group I [high parathormone (PTH) in the absence of calcium channel blockers (CCBs), n = 107], representing the highest [Ca⁺⁺ i]; group II (high PTH in the presence of CCBs, n = 76) and group III (lower PTH in the absence of CCBs, n = 66), representing intermediate [Ca ⁺⁺ i]; and group IV (lower PTH in the presence of CCBs, n = 83) representing the lowest [Ca ⁺⁺i]. The theoretically lower [Ca ⁺⁺ i] was achieved via CCB therapy or lower PTH, or both. The mean serum cholesterol in group I was 322 ± 24 mg/dL and the level of triglycerides was 398 ± 34 mg/dL. Group II had mean serum cholesterol of 196 ± 16 mg/dL and triglycerides of 157 ± 17 mg/dL. Group III had a mean serum cholesterol of 202 ± 19 mg/dL and triglycerides of 160 ± 15 mg/dL. Group IV had a mean serum cholesterol of 183 ± 9 mg/dL and triglycerides of 94 ± 6 mg/dL. The differences in cholesterol and triglyceride levels among four groups were significant (p < 0.001) by one‐way analysis of variance (ANOVA). The incidence of cardiovascular morbidity and mortality events was 61% in group I, 24% in group II, 28% in group III, and 18% in group IV (χ ² = 47.7, p < 0.001). We conclude that, in non diabetic HD patients, hyperparathyroidism, especially in the absence of CCBs, is associated with severe dyslipidemia and increased risk of cardiovascular morbidity and mortality. Dyslipidemia may be related to a hyperparathyroid‐induced increase in cytosolic calcium [Ca⁺⁺i]. Lowering [Ca⁺⁺i] by decreasing PTH or by blocking calcium entry into cells (via CCBs), or both, is associated with less dyslipidemia and improved long‐term cardiovascular morbidity and mortality. Prospective randomized studies, with actual measurement of [Ca ⁺⁺i], are needed to verify the results of this study.     

Phosphate recovery through struvite precipitation by CO2 removal: effect of magnesium, phosphate and ammonium concentrations

In the present study, the precipitation of struvite (MgNH(4)PO(4)·6H(2)O) using the CO(2) degasification technique is investigated. The precipitation of struvite was done from supersaturated solutions in which precipitation was induced by the increase of the solution supersaturation concomitant with the removal of dissolved carbon dioxide. The effect of magnesium, phosphate and ammonium concentrations on the kinetics and the efficiency of struvite precipitation was measured monitoring the respective concentrations in solution. In all cases struvite precipitated exclusively and the solid was characterized by powder XRD and FTIR. The morphology of the precipitated crystals was examined by scanning electronic microscopy and it was found that it exhibited the typical prismatic pattern of the struvite crystals with sizes in the range between 100 and 300 μm. The increase of magnesium concentration in the supersaturated solutions, resulted for all phosphate concentration tested, in significantly higher phosphate removal efficiency. Moreover, it is interesting to note that in this case the adhesion of the suspended struvite crystals to the reactor walls was reduced suggesting changes in the particle characteristics. The increase of phosphate concentration in the supersaturated solutions, for the magnesium concentrations tested resulted to the reduction of struvite suppression which reached complete suppression of the precipitate formation. Excess of ammonium in solution was found favour struvite precipitation. Contrary to the results found with increasing the magnesium concentration in solution, higher ammonium concentrations resulted to higher adhesion of the precipitated crystallites to the reactor walls. The results of the present work showed that it is possible to recover phosphorus in the form of struvite from wastewater reducing water pollution and at the same time saving valuable resources.     

Epoxidized polyurethaneamide and polyesteramide as petroleum pipeline coatings

Linseed oil fatty acids were epoxidized by peracetic acid, then reacted with diethanolamine to give epoxidized hydroxy ethyl linseed oil fatty acid amide ( I ). This amide was rejected with toluene diisocyanate to produce epoxidized polyurethane-amide ( II ). Component I was also reacted with phthalic anhydride to give epoxidized polyesteramide ( III ). Resins II and III were evaluated as coating materials. The results obtained were compared with commercial epoxy resin, and show that resins II and III may be suitable to use as petroleum pipeline coatings.     

Studies on Sulfamethazine - Lysozyme Interactions by Fluorescence Quenching

The binding of sulfamethazine to lysozyme was investigated in relation to certain physicochemical parameters by a fluorescence quenching technique. The parameters considered are ionization of the drug, hydrogen-ion concentration and alteration in protein conformation induced by urea at different pH-levels. The binding constant of the drug was found to be pH-dependent, increasing as the pH is reduced from 9 to 5. On the other hand, denaturation of lysozyme with urea favors the binding process. The interaction being again more pronounced at the lower pH's, when the drug is in the unionized form, and depends also upon the extent of denaturation of the enzyme.

Graphic representation, as well as, computer analysis of the different corrected binding data, at high drug to protein ratios are strongly indicative of a 1:1 interactions. The nature of the binding forces, and changes in the binding constants associated with alteration in the ionization of sulfamethazine at various pH-points were further interpreted in terms of hydrogen-ion dissociation equilibrium of the drug     

Lower-bound time-complexity greening mechanism for duplication-based scheduling on large-scale computing platforms

The Journal of Supercomputing - Large-scale computing platforms become essential in nowadays business and scientific activities. The electrical energy consumed by such platforms increases...     

Modified fully utilized design (MFUD) method for stress and displacement constraints

The traditional fully stressed method performs satisfactorily for stress-limited structural design. When this method is extended to include displacement limitations in addition to stress constraints, it is known as the Fully Utilized Design (FUD). Typically, the FUD produces an overdesign, which is the primary limitation of this otherwise elegant method. We have modified FUD in an attempt to alleviate the limitation. This new method, called the Modified Fully Utilized Design (MFUD) method, has been tested successfully on a number of problems that were subjected to multiple loads and had both stress and displacement constraints. The solutions obtained with MFUD compare favourably with the optimum results that can be generated by using non-linear mathematical programming techniques. The MFUD method appears to have alleviated the overdesign condition and offers the simplicity of a direct, fully stressed type of design method that is distinctly different from optimization and optimality criteria formulations. The MFUD method is being developed for practicing engineers who favour traditional design methods rather than methods based on advanced calculus and non-linear mathematical programming techniques. The Integrated Force Method (IFM) was found to be the appropriate analysis tool in the development of the MFUD method. In this paper, the MFUD method and its optimality are examined along with a number of illustrative examples. © 1998 This paper was produced under the auspices of the U.S. Government and it is therefore not subject to copyright in the U.S.     

Review: the latest advances in biomedical applications of chitosan hydrogel as a powerful natural structure with eye-catching biological properties

Journal of Materials Science - Chitosan is one of the natural cationic polymers with unique properties such as non-toxicity, biodegradability, biocompatibility, environmentally friendly that has...     

Inhibition of the corrosion of steel by acid dihydrazides

The corrosion inhibitory properties of homologous series of acid dihydrazides were studied. Gasometry, potentiodynamic polarization and impedance measurements were recorded for mild steel specimens immersed in 1.0 M H₂SO₄ or a mixture of 1.0 M H₂SO₄ + 1.0 M Na₂SO₄ having the same ionic strength with a pH range from zero to 7. Effect of presence of different concentrations of oxalic, malonic, succinic or pimelic dihydrazide on the corrosion rate of steel in the above solutions were investigated. The results indicated that the protection efficiency of the acid dihydrazides increased with the increase of the number of the methylene groups in the acid dihydrazide molecule. The results are discussed on the basis of the change of each, of the electron density of the donating atoms, of the inhibitor molecules, and the orientation of the inhibitor at the metal surface with the molecular structure of the inhibitor.