A viscoelastic approach from α-Al2O3 suspensions with high solids content

The flow properties of high solids concentration suspensions has been extensively studied and established, however, the rheological behavior for ceramics suspensions with very high solids loading, up to 60 vol.% is poorly known. This is due to both difficulties of preparation and behavior measurement. The theory shows ceramics suspensions with very high solids loading may present viscoelastic properties attributed to interparticle forces active. The oscillatory and creep-recovery rheological measurements can provide this knowledge when discretion used. Thus, rheological behavior of alumina suspensions with high solids loading (>43 vol.%), properly stabilized and the characterization of slip casting shaped samples has been analyzed. High solids loading suspensions, over 43 vol.%, present adequate flow and suspensions with solid content since 60 vol.% present viscoelastic properties attributed to interparticle forces active. The rheological parameters can provide subsidies to obtain after shaping process, such as extrusion, injection and plastic pressing, suitable products for the desired application.     

Linear ion trap MS(n) of enzymatically synthesized 13C-labeled fructans revealing differentiating fragmentation patterns of β (1-2) and β (1-6) fructans and providing a tool for oligosaccharide identification in complex mixtures

Fructans are polymeric carbohydrates, which play important roles as plant reserve carbohydrates and stress protectants, and are beneficial for human health and animal production. Fructans are formed by the addition of β-d-fructofuranosyl units to sucrose, leading to very complex mixtures of 1-kestose based inulins, 6-kestose linked levans, and 6G-kestose derived neoseries inulins and levans in cool season grasses such as Lolium perenne. The identification of isomeric fructan oligomers in chromatographic analysis of crude plant extracts is often hampered by the lack of authentic standards, and unambiguous peak assignment usually requires time-consuming analyses of purified fructan oligomers. We have developed a LC-MS(n) method for the separation and detection of fructan isomers and present here evidence for specific MS(n) fragmentation patterns associated with β 1-2 (inulins) and β 2-6 (levans) fructans. LC-MS(n) analysis of (13)C labeled fructan oligomers produced by L. perenne fructosyltransferases expressed in yeast has enabled us to account for the observed fragmentation patterns in terms of preferential cleavage of the glycosidic bond between O- and fructose C2 in both inulins and levans and to differentiate reducing-end from nonreducing end cross ring cleavages in levans. We propose that higher order MS fragmentation patterns can be used to distinguish between the two major classes of fructan, i.e., inulins and levans, without the need for authentic standards.     

Molecular Structure of Binary Chromium(III)–DNA Adducts

Chromium(VI) is a carcinogen and mutagen, and its mechanisms of action are proposed to involve binding of its reduction product, chromium(III), to DNA. The manner in which chromium(III) binds DNA has not been established, particularly at a molecular level. Analysis of oligonucleotide duplex DNAs by NMR, EPR, and IR spectroscopies in the presence of chromium(III) allows the elucidation of the Cr binding site. The metal centers were found to interact exclusively with guanine N7 positions. No evidence of chromium interactions with other bases or backbone phosphates nor of Cr forming intra-strand crosslinks between neighboring guanine residues was observed.     

Stress and unaided smoking cessation: A prospective investigation.

A prospective design was used to determine the outcomes associated with unaided smoking cessation and the influence of stress on cessation. Heavy smokers (N?=?308) completed stress-related measures and were then recontacted at 1, 6, and 12 mo. At each follow-up, they indicated their smoking status (which was confirmed by collateral report and biochemical tests) and completed several stress-related questionnaires. Results indicate that 33% of Ss smoked continuously throughout the year, 39% quit briefly but subsequently relapsed, and 15% quit (confirmed biochemically). An additional 7% reported they had quit, but this could not be confirmed, and 6% were lost to follow-up. Compared with nonquitters, quitters reported less perceived stress, greater self-efficacy, greater use of problem solving and cognitive restructuring, and less reliance on wishful thinking, self-criticism, and social withdrawal. A model to forecast quitting was built and cross-validated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of Phase Separation Behavior, Emulsion Stability, Rheology, and Microstructure of Egg White–Polysaccharide Mixtures

ABSTRACT:  Phase separation behavior of egg white-pectin/guar gum mixtures was investigated. These systems led to phase separation arisen by either depletion flocculation or thermodynamic incompatibility. The influence of polysaccharides on the emulsifying activity index (EAI), emulsifying stability index (ESI), creaming stability, microstructure, and rheological properties was also studied at different polysaccharide concentrations (0% to 0.5%, [w/v]). Increasing pectin and guar gum concentration from 0.01% to 0.5% significantly improved EAI by 51% and 25%, respectively. The highest ESI and EAI values were obtained in the presence of 0.5% (w/v) pectin/guar gum. Microscopic images showed that emulsions containing polysaccharides had small droplets as compared to that of emulsions without polysaccharides. The addition of polysaccharides improved emulsion stability against creaming. Egg white-stabilized emulsions with and without polysaccharides reflect the pseudoplastic behavior with  n  < 1.0. Polysaccharides, especially at high concentrations, affected the viscoelastic behavior of the emulsions; storage ( G ') and loss modulus ( G ") crossed-over at lower frequency values as compared to that of emulsions containing no polysaccharide.     

Batch cooling crystallization of xylitol produced by biotechnological route

BACKGROUND: This work deals with the xylitol production by biotechnological routes emphasizing the purification process using crystallization. RESULTS: Xylitol volumetric productivity of 0.665 g L^?1 h^?1 and yield of 0.7024 g g^?1 were obtained after 92 h fermentation. The fermented broth (61.3 g L^?1 xylitol) was centrifuged, treated and concentrated obtain a syrup (745.3 g L^?1 xylitol) which was crystallized twice, xylitol crystals with 98.5–99.2% purity being obtained. CONCLUSION: The hypothetical distribution obtained permits the determination of modeling parameters, which make possible the estimation of crystal dominant size from different initial experimental conditions. Copyright © 2008 Society of Chemical Industry     

Algal pigments in Lake Erie dreissenids,pseudofeces and sediments,as tracers of diet,selective feeding and bioaccumulation

Algal class biomarkers revealed the importance of diatoms and chlorophytes in the diet of dreissenids (n 18) collected from eastern Lake Erie (2–20 m depths; hard and soft substrate), during summer and fall, from 2003 to 2005. The most prominent biomarkers in dreissenids, typical of August, were fatty acid esters of carotenoids derived from diatoms (monoesters of fucoxanthinol, average 61%) and chlorophytes (diesters of mactraxanthin, average 30%), while non-esterified biomarkers from diatoms, chlorophytes, cryptophytes and cyanobacteria were below 4% of the total. At cool temperatures (June 2003, 13 °C), dreissenids had 84%:12% diatom:chlorophyte biomarkers, but with unseasonably warm temperatures (June 2004, 18 °C) and a nearshore chlorophyte bloom, dreissenids had a biomarker distribution similar to August. Bioconcentration factors in dreissenids relative to phytoplankton from Lake Erie were largest for the biomarkers from diatoms (21 L/g ww) and chlorophytes (29 L/g ww), compared to those from cryptophytes (2 L/g ww) and cyanobacteria (3 L/g ww). Unlike dreissenids (2003), matching pseudofeces (n 6) and sediments (n 16) contained a relatively large percentage of biomarkers for cryptophytes (20% June, 27% August) and cyanobacteria (31% August), suggesting that their low levels in dreissenids represent ingested feces, which are being rejected. Increased shell size (12–27 mm; surrogate for age; 3 sets) corresponded to an increase in diatom biomarkers (from 60 to 73%) but a decrease in chlorophyte biomarkers (from 31 to 17%); biomarker concentrations also decreased significantly (−3000 pmol/g ww/mm) in the most offshore collection, near Buffalo (Oct. 2005).     

MRI correlates of disease course and activity in multiple sclerosis

We have carried out a comparative cross-sectional study of patients with relapsing and remitting MS (multiple sclerosis) (RRMS) (n=9), primary progressive MS (PPMS) (n=7), and secondary progressive MS (SPMS) (n=10) using image analysis techniques to determine the number and volume of Gd-DTPA-enhancing lesions. RRMS patients had more lesions than either PPMS or SPMS (ns), and the mean volume of the lesions (p=0.006) and the total volume of enhancing lesions (p<0.03) were significantly larger in patients with RRMS compared with PPMS. The prevalence of blood-brain barrier (BBB) breakdown appears to be similar in PPMS and SPMS, with the higher rate in RRMS suggesting a suppressive effect of disease duration (and/or age). Similarly, the volume of the lesion load overall was negatively correlated with disease duration (p –0.56,p<0.003). Differences between PPMS and RRMS/SPMS patients in the volume of the enhancing lesions may reflect differences in the ability of these patients to suppress the immune-mediated damage to axons which may follow episodic BBB breakdown and which is not visualized on conventional magnetic resonance imaging.     

Edge effects determine the direction of bilayer bending

We elucidate the reason for preferential bending along the long edge in thin rectangular bilayers in which one of the layers is isotropically strained. While this preference has been observed previously, the physical basis for this preference has not been understood. We find that the bending direction is determined by the existence of doubly curved regions at the curled edges, which lower the energy. This energy difference between "spiral" and "cigar" shapes increases with aspect ratio.