Fibrillation tendency of cellulosic fibers—Part 4. Effects of alkali pretreatment of various cellulosic fibers

The effects of alkali type and the concentration in the alkali treatments on the weight loss in six cellulosic fibers and their influences on the fibrillation tendency were investigated. The fibril number of the cellulosic fibers pretreated with alkalis (FN_pre) increased with increasing the alkali concentrations as well as the weight loss of the fiber except in the lyocell fiber treated in NaOH and KOH solutions. The FN_pre in lyocell was reduced as the fibers were treated in 5 mol/l NaOH and KOH solutions. This result and the fact that the fibers were split in organic alkali such as tetramethylammonium hydroxide even at the low weight loss suggested that not only the loss of cellulose component but also reorganization of microfibril structure, inhomogeneous swelling of the fibers and other influences control the fibrillation tendency of cellulosic fibers.     

Modification of cellulosic fiber with polyurethane acrylate copolymers. Part I: Physicochemical properties

Polyurethane (PU) prepolymers were prepared by using two different diisocyanates i.e., toluene-2,4-diisocyanate (TDI) and or isophorone diisocyanate (IPDI), and poly (2-methyl-1,3-propylene glutarate), hydroxyl terminated group. PU prepolymer was reacted with 2-hydroxyethylacrylate (HEA) to form vinyl terminated PU prepolymer. Vinyl terminated PU prepolymers were further copolymerized with butyl acrylates (BuA) by emulsion process. The structure of proposed PUACs samples was confirmed by FT-IR, and their physicochemical properties were studied determining solid contents (%), emulsion stability and its appearance, tackiness and film appearance. Their acids and base chemical resistance was also studied and discussed. The synthesized PUACs samples were applied using dip-padding techniques on mill un-desized poly-cotton plain weave fabrics. The results emphasis that PUACs based on toluene-2,4-diisocyanate (TDI) have shown excellent performance against physical and chemical resistance as compared to isophorone diisocyanate (IPDI) based PUACs, however vice versa results were found in some studies.     

Modification and characterization of cellulosic cotton fibers for efficient immobilization of urease

Cotton fibers were first grafted by polyacrylonitril in the presence of KMnO(4) and oxalic acid as a combined redox initiator. Moreover, modification of the grafted cotton fibers was done by changing the nitrile group (-CN) into hydrazidine group through the reaction with hydrazine hydrate, then the fibers were activated by glutaraldehyde to introduce free aldehyde groups which were able to react with amino groups of urease to form Schiff's base, and result in cotton fibers immobilized urease. The efficiency of the immobilization was evaluated by examining the relative enzymatic activity of enzyme before and after the immobilization of urease. The results showed that the optimum temperature of immobilized urease was 35°C, which was higher than that of the free enzyme (30°C), and the immobilized urease exhibited a higher relative activity than that of free urease over 35°C. The optimal pH for immobilized urease was 6.5, which was lower than that of the free urease (pH 7.0), and the immobilization resulted in stabilization of enzyme over a wider pH range. The kinetic constant value (K(m)) of immobilized urease was higher than that of the free urease. However, the thermal and operational stabilities of immobilized urease have been improved greatly.     

Chemical force microscopy of cellulosic fibers

Atomic force microscopy with chemically modified cantilever tips (chemical force microscopy) was used to study the pull-off forces (adhesion forces) on cellulose model surfaces and bleached softwood kraft pulp fibers in aqueous media. It was found that for the –COOH terminated tips, the adhesion forces are dependent on pH, whereas for the –CH₃ and –OH terminated tips adhesion is not strongly affected by pH. Comparison between the cellulose model surfaces and cellulosic fibers under our experimental conditions reveal that surface roughness does not affect adhesion strongly. X-ray photoelectron spectroscopy (XPS) and Fourier Transformed Infrared (FTIR) spectroscopy reveal that both substrate surfaces have homogeneous chemical composition. The results show that chemical force microscopy can be used for the chemical characterization of cellulose surfaces at a nano-level.     

Characterization of cellulosic fibers and fabrics by sorption/desorption

Three cellulosic substrates: lyocell (CLY), viscose (CV), and modal (CMD) in the form of fibers and fabrics were subjected to wet/dry or wash/dry treatments. The accessibility of untreated and treated substrates to water and iodine was investigated using dynamic water-vapor sorption, moisture retention, and iodine sorption methods, to study the influence of treatments on sorption-desorption hysteresis, fraction of moisture sorbed as a monomolecular layer, water retention, and iodine sorption. It was found that the sorption properties of untreated and treated substrates differed with sorbate type as well as substrate type and form.     

Searching for allosteric effects via QSAR. Part II

Allosteric interactions have in the past been established by means of X-ray crystallography or careful study of a single molecule at a variety of concentrations. Here we report a method for using QSAR to establish a change in reaction mechanism by establishing an inversion point. That is, as polarizability of a member of a congeneric set of compounds is increased (as measured by CMR), activity at first decreases until, at the inversion, activity turns around and increases. Out of 23 examples, 14 have inversion points of 10+/-1. This includes a wide variety of receptors such as thrombin, 5-HT, dopamine, and tyrosine kinase acting with a variety of ligands.     

Cardiovascular effects of nerve growth factor: An analytical review. Part II

The features of NGF’s influence on the functional activity of the cardiovascular system and the signaling pathways by which activated NGF TrkA and p75 ^ntr receptors regulate the functional state of endothelial and vascular smooth muscle cells and cardiomyocytes are discussed. In addition, the theoretical prospects of agonists and antagonists of TrkA and p75 ^ntr receptors for the treatment of heart and vascular disorders are considered.     

Modification of ultraviolet radiation effects on the membrane of myelinated nerve fibers by sulfhydryl compounds

Summary The modification of the ultraviolet blocking of sodium channels and of the ultraviolet-induced potential shift of the gating parameters by means of the sulfhydryl compoundsl-cysteine and 2-mercaptoethanol was investigated in the node of Ranvier under voltage-clamp conditions. The UV wavelength was 280 nm. The radiation-induced potential shift of the voltage-dependent gating parameters was prevented or even reversed by the action of the sulfhydryl compounds (internal application), while the blocking effect was not affected. It is concluded that the two radiation effects are caused by two separate photoreactions. Internally applied N-ethylmaleimide, binding specifically to protein-SH groups, exhibits an effect similar to the ultraviolet-induced potential shift, without affecting the maximum sodium permeability. Therefore, the ultraviolet-induced potential shift might be caused by a photocatalyzed oxidation of —SH groups of membrane proteins changing the surface charge density at the inner side of the nodal membrane.     

Controlled lysis ofE. coli double-lysogen by UV-irradiation

Summary Sequential protein production and cell disruption was studied usingE. coli double-lysogen, P90c/(HL1,434). The induction of the first prophage HL1 to produce -galactosidase by the temperature increase was followed by the induction of the second prophage 434 by the UV-irradiation to lyze the cell. The optimum operating conditions for the UV-irradiation were sought to yield the maximum cell lysis.     

Fluidized-bed denitrification for mine waters. Part II: effects of Ni and Co

The dispersion of nitrogenous compounds and heavy metals into the environment is frequent during mining activities. The effects of nickel (Ni) and cobalt (Co) on denitrification of simulated mine waters were investigated in batch bioassays and fluidized-bed reactors (FBRs). At pH 7, batch tests revealed that Co did not exhibit inhibition on denitrification even at 86.6 mg/L. Ni showed to be inhibitory at 50 and 100 mg/L by decreasing nitrate removal efficiencies of 18 and 65 %, respectively. In two FBRs, operated at 7–8 and 22 °C, 5.5 mg/L Ni did not affect nitrate and nitrite removals because of FBR potential of diluting soluble Ni feed concentration. On the contrary, the effluent pH clearly decreased in both FBR1 and FBR2 because of nickel sulfide precipitation and Ni inhibition of the last two steps of denitrification. When Ni injection was stopped, the process recovered more slowly at 22 than 7–8 °C. This is the first study reporting the effect of Ni on denitrification in biological FBRs.     

Modification of cellulosic fabric using polyvinyl alcohol, part-II: Colorfastness properties

A series of aqueous solutions of poly(vinyl alcohol) of various commercial products were prepared and applied onto the surfaces of cotton and blends of cotton/polyester fabrics. Fourier transform infrared spectrophotometer was used to confirm the molecular structure of the polyvinyl alcohol used. Performance tests such as colorfastness to rubbing (dry and wet) and colorfastness to washing were determined. The controlling variables affecting the performance properties of the finished substrate such as post-treatment with poly(vinyl alcohol) of various commercial trades, concentration and dilutions were studied. Crocking, washing and hue change of the treated dyed and printed fabrics is accompanied by the formation of semi-inter-penetrated network structure due to the presence of the hydroxyl (-OH) groups which make feasible to a number of grafting and physical cross linking reactions of polymer backbone.     

Modification of cellulosic fabric using polyvinyl alcohol—Part-I: Physicochemical properties

A series of poly(vinyl alcohol) of different commercial grades were prepared and applied onto the surfaces of cotton and blends of cotton/polyester fibers. The molecular structure was confirmed using Fourier Transform Infrared spectroscopy. Physicochemical properties such as viscosity and solid contents (%) were determined and discussed. Factors affecting the performance properties of the finished substrate such as post-treatment with poly(vinyl alcohol) of different grades, concentration and dilutions were studied. Fixation of the poly(vinyl alcohol) onto/or within the cellulose structure is accompanied by the formation of semi-inter-penetrated network structure thereby enhancing the association as well as providing very high stiffness. The results revealed that applications of poly(vinyl alcohol) on the textile fabrics in the finishing processes enables to enhance the stiffness as well as helps to improve its pilling resistance.     

Decontamination of sludge by the METIX-AC process. Part II: effects on maize growth and bioaccumulation of metals

Given the fact that, according to our knowledge, no study has compared the agro-environmental use of decontaminated with non-decontaminated sludge, a greenhouse experiment was carried out to test the growth of maize (Zea mays L., G-4011 Hybrid) and bioaccumulation of metals in the presence of four different sludges (MUC, QUC, BEC and DAI), before and after their decontamination by a novel process (METIX-AC). Data showed that decontaminated sludge ameliorated plant growth and biomass production, and decreased bioaccumulation of metals, more than control soil, inorganic chemical fertilization, or conventional non-decontaminated sludge. Since chemicals used by the METIX-AC process contained S and Fe, decontaminated sludge introduced large amounts of these elements, while the overall presence of metals was reduced. Often, sludge dose also affected maize growth and bioaccumulation of metals. Overall, no toxicity to plants was noticed and bioaccumulation and transfer of many metals remained below the limits reported in the literature.     

Precision rhinoplasty. Part II: Prediction

This retrospective study was undertaken to investigate the soft-tissue response rate to the skeletal and soft-tissue alterations following a rhinoplasty. Ninety-eight patients, 80 females and 18 males, with a mean follow-up of 13 months, were included in this study. The tracings of the outline of preoperative cephaloxerograms and life-size photographs were superimposed on the postoperative ones, and the differences were measured and confirmed with measurements of intraoperative resected segments. The soft-tissue response to skeletal alterations was measured in seven different zones. Zone 1 (nasion) and zone 7 (nasal spine area) had the lowest mean response rate of approximately 25 percent. Zone 2 (proximal bridge) and zone 3 (midbridge) had a 60 percent response rate. Zone 4 (supratip area) had a 43 percent response, zone 5 had a 41 percent response, and zone 6 had a 40 percent response rate. There were statistically significant differences among the response rates of thick, medium, and thin noses. Age was an important factor in zones 1, 4, 5, 6, and 7. The patient's sex did not influence the soft-tissue response rate to skeletal alterations. The soft-tissue response in relation to the alar base narrowing was about 52 percent. This study reveals a predictable soft-tissue response to skeletal alterations on all zones except zone 7 (nasal spine area).     

Ammonium regulation inSaccharopolyspora erythraea. Part II: Regulatory effects under different nutritional conditions

Summary Non-limiting nutritional conditions revealed a growth-associated erythromycin production with ammonium sulfate while the relation was growth-dissociated for ammonium nitrate. Feeding experiments suggested that the residual nitrate level might be the key regulatory element. A nitrate-induced glutamine synthetase pathway was postulated according to the nature and initial concentration of the ammonium salt.     

Acetylcholinesterase inhibition by eserine: rate constants of reaction. Part II

The inhibition of eel acetylcholinesterase by physostigmine at 20 degrees and 25 degrees C have been investigated. In our evaluation the unimolecular reactivation rate constant, k3, the carbamylation rate constant, k2, and the binding constant, Ka, are the first simultaneously determined. The mechanism of this reaction is discussed.     

Saccharification of cellulose by the cellulolytic enzyme system of Thermomonospora sp. II. Hydrolysis of cellulosic substrates

A saccharification of cellulosic material using culture filtrate from the stationary phase of a culture of Thermomonospora sp. produced primarily cellobiose up to levels inhibitory to further saccharification, while the use of whole broth resulted in the production of glucose as well. Glucose production was enhanced and continued throughout the saccharification (24–36 hr) by several additions of cellobiase activity in the form of culture solids. Using Solka-Floc as substrate, the “difference sugar” level (total soluble sugar minus glucose) rapidly rose to the same relatively stable concentration under various hydrolysis conditions, which was independent of the total sugar and glucose concentrations. A rapid hydrolusis rate was observed initially during saccharification, followed by a much slower rate of sugar production. Repeated centrifugation of the reaction mixture and replacement of the supernatant with fresh enzyme solution resulted each time in the reinitiation of a rapid hydrolysis rate. Saccharifications using A vicel microcrystalline cellulose, acid-swollen cellulose, and cotton as substrates were also studied. A modified method of making phosphoric-acid swollen cellulose is described. Saccharification of this substrate by culture filtrate and sequential additions of culture solids resulted in an inverse relationship between the attained glucose concentration and cellobiose-cellotriose concentrations.