Lower DS Research Articles

The Effect of the Molecular Architecture on the Antioxidant Properties of Chitosan Gallate.

To elucidate the structure–antioxidant activity relationships of chitosan gallate (CG), a series of CG derivatives with different degrees of substitution (DS’s) and molecular weights (MWs) were synthesized from chitosan (CS) and gallic acid (GA) via a free radical graft reaction. A higher MW led to a lower DS of CG. The structures of CG were characterized by FT-IR and 1H NMR, and results showed that GA was mainly conjugated to the C-2 and C-6 positions of the CS chain. The antioxidant activity (the DPPH radical scavenging activity and reducing power) were enhanced with an increased DS and a decreased MW of CG. A correlation between antioxidant activities and the DS and MW of CG was also established. In addition, a suitable concentration (0~250 μg/mL) of CG with different MWs (32.78~489.32 kDa) and DS’s (0~92.89 mg·GAE/g CG) has no cytotoxicity. These results should provide a guideline to the application of CG derivatives in food or pharmacology industries.

Synthesis and enzymatic degradation of randomly substituted 2,3,6-O-cellulose acetate and regioselectively substituted 2,3-O-cellulose acetate

To investigate the effect of substitution site on enzymatic degradation property of cellulose acetate (CA), randomly substituted 2,3,6-O-CA (DS = 0.4, 1.2, and 2.1) and regioselectively substituted 2,3-O-CA (DS = 0.4, 1.3, and 2.0) were synthesized without or with using trytyl group for C6 protection process. Both 2,3,6-O-CA and 2,3-O-CA were submitted to enzymatic degradation test using cellulase from Toricoderma reesei. The concentration of hydrolytic products was analyzed by the reducing sugar analyses using glucose standards. CAs with lower DS (0.4) were more hydrolyzed compared to CAs with higher DS (1.2 or 1.3) and CAs with DS over 2 were not hydrolyzed regardless of substitution site. The degradability of 2,3-O-CAs (DS = 0.4 and 1.3) turned out to be higher than that of 2,3,6-O-CAs (DS = 0.4 and 1.2). The hydrolytic products of 2,3,6-O-CA and 2,3-O-CA were analyzed by HPLC and the relationship between their substitution site and the enzymatic degradation behavior was discussed in detail.

The Same Angiographic Factors Predict Venous and Arterial Graft Patency: A Retrospective Study.

To evaluate the value of angiographic factors in predicting failure of both venous and arterial coronary artery bypass graft.We retrieved from our angiographic database 148 patients who underwent venous and/or arterial CABG and for whom a control coronary angiography at more than 1 month after surgery was available. Pre-CABG and follow-up angiographies were analyzed in order to evaluate diameter stenosis (DS,%), stenosis length (mm), Bogaty score (extent index), Sullivan score, and Gensini score for the extent of coronary artery disease, and Jeopardy Duke score for the extent of myocardial area supplied by an artery.Thirty-nine patients (26%) experienced graft failure at follow-up (mean follow-up 11.3 ± 4.6 months). Patients with venous graft failure [26 (20%)] had significantly smaller DS (P = 0.013), shorter stenosis length (P = 0.01), and lower extent index (P = 0.015), Sullivan score (P = 0.013), Gensini score (P = 0.04) as compared with those without venous graft failure. Patients with arterial graft failure [13 (11%)] had significantly lower DS (P = 0.008), shorter stenosis length (P = 0.001), and lower extent index (P = 0.03) and Sullivan score (P = 0.023) as compared with those without arterial graft failure.Venous and arterial graft failure are associated with less severe stenosis and less extensive atherosclerosis of the grafted vessel.

Synthesis of carboxymethyl chitin in aqueous solution and its thermo- and pH-sensitive behaviors

Homogenous modification of natural chitin offers the advantage of fair structure control. In this work, novel carboxymethyl chitins (CMCHs) with broad range of degree of substitution (DS: 0.035 to 0.74), high degree of acetylation (DA) and little de-polymerization were synthesized homogeneously in aqueous NaOH/urea solution. The simultaneous determination of DA, DS and carboxymethylation fraction at C3 and C6 for these CMCHs was achieved by proton NMR in acidic deuterated aqueous solution for the first time. Due to the good homogeneity, the prepared CMCH-4 with lower DS of carboxymethylation exhibited, for the first time to our knowledge, dual thermo- and pH-sensitive properties. The nontoxic thermo-sensitive polymer systems gel at body temperature (37°C) in physiological condition, which is very useful as injectable hydrogels for drug delivery and tissue engineering.

Acute bouts of upper and lower body static and dynamic stretching increase non-local joint range of motion.

There are conflicts in the literature concerning the crossover or non-local effects of stretching. The objective of this study was to evaluate whether static (SS) and dynamic (DS) stretching of the shoulders would affect hip flexor range of motion (ROM) and performance and reciprocally whether SS and DS of the lower body would affect shoulder extension ROM and performance. A randomized crossover study design examined the acute effects of upper and lower body SS and DS on lower and upper body performance measures, respectively. Experimental sessions included upper and lower body control tests, upper body (shoulder horizontal abduction) SS and lower body (hip abduction) SS, upper body (shoulder horizontal abduction and adduction) DS and lower body DS (hip abduction and adduction). Passive static and dynamic ROM (hip flexion, shoulder extension), leg flexor and elbow flexor maximal voluntary contraction isometric force, fatigue endurance and electromyography were measured. There were significant shoulder ROM increases following lower body SS (P < 0.010, ∆% = 8.2%) and DS (P < 0.019, ∆% = 9%). There was a significant hip flexor ROM (P < 0.016, ∆% = 5.2%) increase following upper body SS. There were no significant main effects or interactions for dynamic ROM or muscle force and activation variables. The lack of stretch-induced force and fatigue changes suggests that rather than a mechanical or neural drive mechanism, an enhanced stretch tolerance was likely the significant factor in the improved ROM.

Ti adatom diffusion on TiN(001): Ab initio and classical molecular dynamics simulations

Ab initio and classical molecular dynamics (AIMD and CMD) simulations reveal that Ti adatoms on TiN(001) surfaces migrate between neighboring fourfold hollow sites primarily along in-plane <100> channels. <100> and <110> single jumps, as well as <100> double jump rates, obtained directly from MD runs as a function of temperature, are used to determine diffusion activation energies Ea, and attempt frequencies A, for the three preferred Ti adatom migration pathways on TiN(001). From transition rates Aexp[−Ea/(kBT)], we determine adatom surface distribution probabilities as a function of time, which are used to calculate adatom diffusion coefficients Ds(T). AIMD and CMD predictions are consistent and complementary. Using CMD, we investigate the effect on the adatom jump rate of varying the phonon wavelength degrees of freedom by progressively increasing the supercell size. We find that long-wavelength phonons significantly contribute to increasing adatom mobilities at temperatures ≤600K, but not at higher temperatures. Finally, by directly tracking the Ti adatom mean-square displacement during CMD runs, we find that Ti adatom jumps are highly correlated on TiN(001), an effect that yields lower Ds values (Dscorr) than those estimated from uncorrelated transition probabilities. The temperature-dependent diffusion coefficient is Dscorr (T)=(4.5×10−4cm2s−1) exp[−0.55eV/(kBT)].

Effects of ultrasonic pre-treatment on sludge characteristics and anaerobic digestion

In this work, the influence of an ultrasonic pre-treatment on anaerobic digestion of waste activated sludge is studied. Attention is paid to the solubilisation of the main organic (proteins, carbohydrates) and inorganic (heavy metals) sludge components during ultrasonic treatment and the influence of the dry solids content (DS) on the degree of solubilisation. The second part of the paper focuses on the relationship between the applied specific energy of the ultrasonic treatment and methane production. In general, a higher specific energy and a higher DS content are beneficial for the release of organic matter, resulting in an increased methane production. The efficiency of the subsequent anaerobic digestion is similar for both sludge types (2.1 and 3.2% DS). However, at lower DS contents (2.1%), the methane production increase was more significant.

The Electrochemical Performance of Carboxymethyl Cellulose Lithium as a Binding Material for Anthraquinone Cathodes in Lithium Batteries

The water-soluble binder carboxymethyl cellulose lithium (CMC-Li) is synthesized by acidification and neutralization reactions. The prepared CMC-Li binders are characterized using Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), thermogravimetic analysis (TGA) and scanning electron microscopy (SEM). The electrochemical performance of the 9, 10-anthracenedione (AQ) electrodes with different binders are investigated by galvanostatic discharge/charge, cyclic voltammetry and electrochemical impedance spectroscopy techniques. Tested as the binding material in a lithium cell at room temperature, the CMC-Li electrode shows better electrochemical performance compared to a PVDF electrode. It exhibits a specific capacity of up to 214 mAh·g−1 at the initial discharge, and its specific capacity is maintained at 62 mAh·g−1 after 50 cycles. In addition, it has better stability during the charge and discharge processes. Furthermore, the electrochemical performance of the CMC-Li-1, which has a higher DS (DS = 1.0), is superior to CMC-Li-2, which has a lower DS (DS = 0.62). (DS is the degree of substitution of –OH groups of the cellulose molecules by –CH2COOR groups, when R = Na, H, Li, the products are CMC-Na, CMC-H, CMC-Li, respectively)

New Facile Method for the Hetergeneous Synthesis of Cyanoethyl Cellulose- Solvent Method，and Comparing with Traditional Method

Cyanoethyl cellulose (CEC) with high degree of substitution and uniform distribution was synthesized by solvent method. The choice of solvent, control of base volume, feeding methods and other factors were optimized , toluene/isopropanol (85/15) is the best solvent . Using FT-IR, elemental analysis, TG, DMA, X-ray and other means, we compared the structure, degree of substitution, the crystallinity, thermal stability, dynamic mechanical properties, dielectric properties and acid and alkali resistance between the CECs by solvent method and traditional method. The CEC products by solvent method showed lower crystallinity due to its more uniform distribution, better thermal stable, similar high dielectric with a lower DS , and higher Tg and better resistance to the acid and/or alkaline than CEC by traditional method.Those findings demonstrated solvent method was a new facile and industrial method to synthesize high substituted and uniform distributed cyanoethyl celluloses with good performances.

DMAP-catalyzed phthalylation of cellulose with with phthalic anhydride in [bmim]Cl

It has been generally accepted that some ionic liquids are good media for homogeneous functionalization of cellulose. However, phthalylated cellulosic derivatives prepared in ionic liquids without any catalyst have lower DS as compared to the acetylated ones. In order to prepare the phthalylated cellulosic derivatives with higher DS, chemical modification of sugarcane bagasse cellulose with phthalic anhydride using ionic liquid 1-butyl-3-methylimidazolium chloride ([bmim]Cl) as a solvent and 4-dimethylaminopyridine (DMAP) as a catalyst has been examined. The results indicated that DMAP could enhance the reaction efficiency. The native cellulose and cellulose phthalates were characterized by FT-IR, solid-state CP/MAS 13C NMR, and thermogravimetric analysis. The results from FT-IR and solid-state CP/MAS 13C NMR analyses indicated that the phthalylation between cellulose and phthalic anhydride was successfully achieved. In addition, it was found that the thermal stability of the cellulose phthalates decreased upon chemical modification.

Influence of age, gender and weight on spinal osteoarthritis in the elderly: An analysis of morphometric changes using X-ray images

Various factors in addition to normal aging are reported to be associated with spinal osteoarthritis. The links between the risk factors and osteoarthritis are unclear. This study proposes an analysis of factors associated with spinal osteoarthritis using a collection of cervical and lumbar X-ray images, maintained by the US National Library of Medicine. Five hundred and forty-eight images of adults (60–74 years old, 242 males, 306 females) are analyzed. Six to nine anatomical points are selected by an experienced radiologist on each vertebra. Four dimensionless indexes are calculated: the anterior-to-posterior height ratio (APR), the disc space relative to posterior height of vertebra (DS) and the number of osteophytes. Correlations of these parameters are estimated with three anthropometric indexes: age, gender and body mass index. The univariate relationships are evaluated using one-way analysis of variance and Kruskal-Wallis test. Osteophytes are more frequent for men than for women. Men have lower APR from the levels L1 to L4 and lower DS at the levels C4 and C5. The lumbar levels L2 and L4 are more affected with age by changes in APR. Obese group has a higher DS at the level C3-C4 and a higher APR at the level L1. The analysis of images shows the predominant effect of osteoarthritis at the lower levels of the cervical and lumbar spine.

Nanofibrous membranes from aqueous electrospinning of carboxymethyl chitosan

Carboxymethyl chitosan (CMCS) with varying molecular weights(Mv = 40–405 kDa) and degreesof substitution (DS = 0.25–1.19) has been synthesized by alkalization of chitosan, followed bycarboxymethylation with monochloroacetic acid. At DS up to 1.19, the locationswhere carboxymethylation took place were influenced by the alkalizationtemperature, i.e., both C2 and C6 substitution at ambient temperature(N,O-carboxymethylated) and mainly C6 substitution at the lower temperature,−15 °C (O-carboxymethylated). Generally, carboxymethylation was more favorable at the primary C6 hydroxylthan the C2 position with increasing DS. CMCS synthesized from 405 kDa CS was soluble in waterat DS≥0.73 whereas those from 40 and 89 kDa became water-soluble at lower DS of 0.25 and0.36, respectively. Electrospinning of aqueous solutions of CMCS was facilitatedwith the addition of water-soluble polymers, including PEO, PAA, PAAm andPVA. The optimal fiber formation was observed at equal mass composition ofO-CMCS (89 kDa at 0.36 DS) and PVA, producing nanofibers withan average diameter of 130 nm. Heat-induced esterification (at140 °C for 30 min) produced inter-molecular covalent cross-links within and among fibers, renderingthe fibrous membrane water-insoluble. Membranes containing higher CMCS carboxyl toPVA hydroxyl ratio retained better fiber morphology upon extended water exposure,indicating more favorable inter-molecular cross-links. The fibrous membranes generatedwith less substituted CMCS were more hydrophilic and retained a greater extent of thedesirable amine functionality.

Synthesis of methacrylated hyaluronic acid with tailored degree of substitution

The aim of this work was to develop a new method to derivatize hyaluronic acid (HyA) with polymerizable methacrylate residues with precise control over the substitution degree. The synthesis of methacrylated HyA (HyA-MA) was performed in dimethyl sulfoxide (DMSO) using glycidyl methacrylate (GMA) and 4-(N,N-dimethylamino)pyridine as a catalyst. HyA was rendered soluble in DMSO by exchanging the Na+ ions by the more lipophilic tetrabutylammonium ions. HyA-MA with a fully controlled degree of substitution (DS, defined as the number of methacrylate groups per 100 disaccharide units), ranging from 5 to 30, was obtained at 50°C after 48h. Hydrogels were obtained upon radical polymerization of aqueous solutions of HyA-MA using potassium peroxodisulfate (KPS) as initiator and N,N,N′,N′-tetramethylethylenediamine (TEMED) as catalyst. Almost complete methacrylate conversion (95%) was achieved for hydrogels obtained by polymerization of HyA-MA with a degree of substitution of 15. At lower DS (DS 8.5 and 5) the methacrylate conversion was 82% and 68%, respectively. Rheological characterization showed that with increasing DS the storage modulus of these HyA-MA hydrogels increased. Swelling experiments showed that HyA-MA gels with a DS of 15 or above were dimensionally stable, whereas HyA-MA gels with DS 5 and DS 8.5 swelled 1.6 and 1.4 times their initial weight, respectively. In conclusion, this paper shows that the DS of HyA-MA can be tailored by the reaction conditions and that consequently HyA-MA hydrogels with different characteristics can be prepared.

An Unsupervised Adaptive Method to Eigenstructure Analysis of Lower SNR DS Signals

An unsupervised adaptive signal processing method of principal components analysis (PCA) neural networks (NN) based on signal eigen-analysis is proposed to permit the eigenstructure analysis of lower signal to noise ratios (SNR) direct sequence spread spectrum (DS) signals. The objective of eigenstructure analysis is to estimate the pseudo noise (PN) of DS signals blindly. The received signal is firstly sampled and divided into non-overlapping signal vectors according to a temporal window, which duration is two periods of PN sequence. Then an autocorrelation matrix is computed and accumulated by these signal vectors one by one. Lastly, the PN sequence can be estimated by the principal eigenvector of autocorrelation matrix. Since the duration of temporal window is two periods of PN sequence, the PN sequence can be reconstructed by the first principal eigenvector only. Additionally, the eigen-analysis method becomes inefficient when the estimated PN sequence is long. We can use an unsupervised adaptive method of PCA NN to realize the PN sequence estimation from lower SNR input DS-SS signals effectively.

Long chain cellulose esters with very low DS obtained with non-acidic catalysts

Long-chain cellulose esters with very low degree of substitution (DS<0.3), useful for specialty applications, were obtained by reaction with fatty acids (FAs) without solvent for cellulose. Non-acidic catalysts such as FA salts were used to limit the cellulose degradation when subjected to reaction at high temperatures. The surfactant character of this type of molecules was employed to create an emulsion with FA and water to favor the contact of hydrophobic FA and hydrophilic cellulose. Response surface methodology was used as a statistical optimization method to find the best proportions of octanoic acid, potassium laurate and water. A highly hydrophobic product with retention of fibrous structure was thus obtained. The reactions with higher saturated FAs (C10–C18) yielded lower DS values but still comparable hydrophobicity.

Effect of Carboxymethyl Cellulose on Aqueous Processing of Natural Graphite Negative Electrodes and their Electrochemical Performance for Lithium Batteries

Suspensions of natural graphite particles were prepared in an aqueous medium using carboxymethyl cellulose (CMC) and emulsified styrene-butadiene copolymer latex as part of an environmentally friendly fabrication process for graphite anodes (negative electrodes) intended for application in Li-ion batteries. Suspensions were characterized by adsorption isotherms, electroacoustic measurements, rheology and sedimentation tests, at two different degrees of carboxymethyl substitution (DS) on CMC. A lower DS value (0.7) resulted in greater uptake of CMC on graphite compared with a higher DS value (1.28). This was attributed to attractive hydrophobic interactions associated with the lower carboxymethyl substitution. The greater adsorption for correlates with lower relative viscosity in concentrated graphite suspensions, a higher adhesion strength with a copper substrate, and a greater retention of discharge capacity after cycling. The effect of DS is attributed to differences in the aqueous dispersion properties and stability of graphite suspensions. Based on these results, we fabricated high-capacity graphite negative electrodes characterized by gravimetric and volumetric energy densities of greater than and , respectively. This formulation also led to improved adhesion strength, giving the as-fabricated cell an attractive cycle life greater than 90% of initial discharge capacity after .

CreA-mediated carbon catabolite repression of β-galactosidase formation inAspergillus nidulansis growth rate dependent

Carbon catabolite repression by the CreA-transcriptional repressor is widespread in filamentous fungi, but the mechanism by which glucose triggers carbon catabolite repression is still poorly understood. We investigated the hypothesis that the growth rate on glucose may control CreA-dependent carbon catabolite repression by using glucose-limited chemostat cultures and the intracellular β-galactosidase activity of Aspergillus nidulans, which is repressed by glucose, as a model system. Chemostat cultures at four different dilution rates (D=0.095, 0.068, 0.045 and 0.015 h−1) showed that formation of β-galactosidase activity is repressed at the two highest Ds, but increasingly derepressed at the lower Ds, the activity at 0.015 h−1 equalling that in derepressed batch cultures. Chemostat cultures with the carbon catabolite derepressed A. nidulans mutant strain creAΔ4 revealed a dilution-rate independent constant β-galactosidase activity of the same range as that found in the wild-type strain at D=0.015 h−1. Two other enzymes – isocitrate lyase, which is almost absent on glucose due to a CreA-independent mechanism; and galactokinase, which is formed constitutively and independent of CreA – were measured as controls. They were formed at constant activity at each dilution rate, both in the wild-type strain as well as in the carbon catabolite derepressed mutant strain. We conclude that the growth rate on glucose is a determinant of carbon catabolite repression in A. nidulans, and that below a certain growth rate carbon catabolite derepression occurs.

CreA-mediated carbon catabolite repression of β-galactosidase formation in Aspergillus nidulans is growth rate dependent

Carbon catabolite repression by the CreA-transcriptional repressor is widespread in filamentous fungi, but the mechanism by which glucose triggers carbon catabolite repression is still poorly understood. We investigated the hypothesis that the growth rate on glucose may control CreA-dependent carbon catabolite repression by using glucose-limited chemostat cultures and the intracellular β-galactosidase activity of Aspergillus nidulans, which is repressed by glucose, as a model system. Chemostat cultures at four different dilution rates (D=0.095, 0.068, 0.045 and 0.015 h−1) showed that formation of β-galactosidase activity is repressed at the two highest Ds, but increasingly derepressed at the lower Ds, the activity at 0.015 h−1 equalling that in derepressed batch cultures. Chemostat cultures with the carbon catabolite derepressed A. nidulans mutant strain creAΔ4 revealed a dilution-rate independent constant β-galactosidase activity of the same range as that found in the wild-type strain at D=0.015 h−1. Two other enzymes – isocitrate lyase, which is almost absent on glucose due to a CreA-independent mechanism; and galactokinase, which is formed constitutively and independent of CreA – were measured as controls. They were formed at constant activity at each dilution rate, both in the wild-type strain as well as in the carbon catabolite derepressed mutant strain. We conclude that the growth rate on glucose is a determinant of carbon catabolite repression in A. nidulans, and that below a certain growth rate carbon catabolite derepression occurs.

Antioxidative activities of water-soluble disaccharide chitosan derivatives

Water-soluble chitosan derivatives, having various degrees of substitution with disaccharide (DS 20–30%, 40–50%, 60–70%), were prepared by reductive alkylation of α-chitosan with lactose, maltose or cellobiose. Antioxidative activities were determined in the present study, including radical scavenging effect for α,α-diphenyl-β-picryl-hydrazyl (DPPH) radicals, superoxide anion radicals, hydrogen peroxide and copper ion chelating ability of these chitosan derivatives. It was found that the tested chitosan derivatives exhibited multiple antioxidative activities that varied with the concentration, DS with disaccharides and the kind of disaccharide present in the derivative molecule. In general, the antioxidative activities increased as the concentration of these chitosan derivatives increased up to a certain extent. A stronger scavenging effects for superoxide anion radicals, DPPH radicals and H 2O 2 was noted with the chitosan derivatives having lower DS with disaccharide than those with higher DS. Among the various antioxidative activities tested, the disaccharide chitosan derivatives were found to show the highest excellent hydrogen peroxide scavenging activity. At a concentration of 400 μg/ml, all the chitosan derivatives tested exhibited 60% or greater scavenging activity for hydrogen peroxide.

MOLDBOARD PLOW PERFORMANCE IN A CLAY SOIL: SIMULATIONS AND EXPERIMENT

The effects of moldboard plow components and adjustments on its performance when used on a clay soil wereanalyzed using both modeling (Finite element method, FEM) and experimental results. With the FEM simulations, theaverage longitudinal force (Fx) was 1.4 and 2.7 times the average vertical (Fz) and lateral (Fy) forces, respectively. Thespecific vertical force (Fzs) was found to decline with width because of both the share edge effect and the greater soil-toolsurface in contact which increased friction. The effects of the sharepoint seemed only predominant at very shallow depthsto initiate penetration. A decrease in friction reduced specific longitudinal force (Fxs) but increased Fzs to promote plowpenetration. From simulations with the same plow bottom Fy, a longer landside is required to prevent lateral movement ofthe plow bottom. During the field experiment, only the specific draft force (Ds) and fuel consumption showed a statisticaldifference between plowing depths with reductions of 16% and 8%, respectively, with the shallowest setting. Knife coulterand short landside had a lower Ds of 8% and 3%, respectively. Depth SD and distance to obtain average depth wereconsidered as a measure of plow stability throughout the plot. The long landside and the knife coulter had both anincreased in distance of 74 and 293 mm, respectively over the short landside and disc coulter.