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Experimental evidence convincingly shows that the combination of XPS and TGA/FTIR enables the provision of significantly more information on degradation and charring of polymers upon heating, which are central to flame retardance and smoke emission of polymers. PVC and PVC/Cu 2 O were chosen as systems to be investigated. Qualitative and quantitative information concerning these two processes in the condensed phase indicates that early crosslinking plays a most important role, in particular, in the presence of catalyst Cu 2 O during degradation and charring processes. The interaction between PVC and Cu 2 O has been experimentally confirmed with the help of the shake-up satellites and Auger parameter α∗, showing that the redox cycle of the catalyst itself works quite well: Cu 2 1 O → Cu 1 Cl → Cu 0 → Cu 1 2 O as the temperature rises from ambient to 500 °C, which is in complete agreement with the reductive-coupling mechanism. The valence band structures also turn out to be quite informative in the elucidation of both processes.

Crosslinking and charring in the condensed phase of polymers during heating, processing, and/or burning are of central importance in their flame retardance and smoke suppression and in formulating polymeric compos ites. Combining with thermal analysis techniques (TGA, DSC), ethylene-vinyl acetate (EVA) copolymers and polyethylenes (HDPE, LDPE) with/without inor ganic phosphorus-containing additives, were selected as model systems for XPS studies of the charring process. A new parameter, Tgr, the transition tempera ture from mesophase to graphitic structure (graphite-like structure, GLS) of the char has been well-defined and determined by combination of core levels and valence bands in XPS. The reason for Tgr to be selected as a likely supplemen tary parameter for characterizing polymer charring in condensed phase is two fold : 1) a clear-cut phase transition; 2) at which temperature a highly cross linked network results. A special emphasis in the paper has been given to the roles of the oxygen atoms either introduced from an adventitious atmosphere or inherent Ac group itself. Along this line some features in both thermal degradation and flame retardance of polymers have been rationalized in terms of transition temperature Tgr.

In tissue engineering research, there has recently been considerable interest in using electrospun biomimetic nanofibers of hybrids, in particular, from natural and synthetic polymers for engineering different tissues. However, phase separation between a pair of much dissimilar polymers might give rise to detrimental influences on both the electrospinning process and the resultant fiber performance. A representative natural-synthetic hybrid of gelatin (GT) and polycaprolactone (PCL) (50:50) was employed to study the phase separation behavior in electrospinning of the GT/PCL composite fibers. Using trifluoroethanol (TFE) as the cosolvent of the two polymers, observation of visible sedimentation and flocculation from dynamic light scattering analysis of the GT/PCL/TFE mixture both showed that phase separation does occur in just a few hours. This consequently led to gradually deteriorated fiber morphologies (e.g., splash, fiber bonding, and varied fiber size) over time during electrospinning GT/PCL. Quantitative analysis also indicated that the ratio of GT to PCL in the resultant GT/PCL fibers was altered over time. To address the phase separation related issues, a tiny amount (

Thermogravimetric analysis and differential scanning calorimetry in combination with X-ray photoelectron spectroscopy, have been applied to the study of degradation of wool and its flame retardation after treatment with Zirpro. ZrOF 2 is of importance in flame retardation and smoke suppression, the latter depending mainly on the contribution of covalent linkages in Zirpro flame retardant.

Although vitamin C (ascorbate) is present in whole blood, measurements in red blood cells (RBCs) are problematic because of interference, instability, limited sensitivity, and sample volume requirements. We describe a new technique using HPLC with coulometric electrochemical detection for ascorbate measurement in RBCs of humans, wild-type mice, and mice unable to synthesize ascorbate. Exogenously added ascorbate was fully recovered even when endogenous RBC ascorbate was below the detection threshold (25 nM). Twenty microliters of whole blood or 10 μl of packed RBCs was sufficient for assay. RBC ascorbate was stable for 24 h from whole-blood samples at 4 °C. Processed, stored samples were stable for >1 month at −80 °C. Unlike other tissues, ascorbate concentrations in human and mouse RBCs were linear in relation to plasma concentrations (R = 0.8 and 0.9, respectively). In healthy humans, RBC ascorbate concentrations were 9–57 μM, corresponding to ascorbate plasma concentrations of 15–90 μM. Mouse data were similar. In human blood stored as if for transfusion, initial RBC ascorbate concentrations varied approximately sevenfold and decreased 50% after 6 weeks of storage under clinical conditions. With this assay, it becomes possible for the first time to characterize ascorbate function in relation to endogenous concentrations in RBCs.

Levels of the necessary nutrient vitamin C (ascorbate) are tightly regulated by intestinal absorption, tissue accumulation, and renal reabsorption and excretion. Ascorbate levels are controlled in part by regulation of transport through at least 2 sodium-dependent transporters: Slc23a1 and Slc23a2 (also known as Svct1 and Svct2, respectively). Previous work indicates that Slc23a2 is essential for viability in mice, but the roles of Slc23a1 for viability and in adult physiology have not been determined. To investigate the contributions of Slc23a1 to plasma and tissue ascorbate concentrations in vivo, we generated Slc23a1-/- mice. Compared with wild-type mice, Slc23a1-/- mice increased ascorbate fractional excretion up to 18-fold. Hepatic portal ascorbate accumulation was nearly abolished, whereas intestinal absorption was marginally affected. Both heterozygous and knockout pups born to Slc23a1-/- dams exhibited approximately 45% perinatal mortality, and this was associated with lower plasma ascorbate concentrations in dams and pups. Perinatal mortality of Slc23a1-/- pups born to Slc23a1-/- dams was prevented by ascorbate supplementation during pregnancy. Taken together, these data indicate that ascorbate provided by the dam influenced perinatal survival. Although Slc23a1-/- mice lost as much as 70% of their ascorbate body stores in urine daily, we observed an unanticipated compensatory increase in ascorbate synthesis. These findings indicate a key role for Slc23a1 in renal ascorbate absorption and perinatal survival and reveal regulation of vitamin C biosynthesis in mice.

Metallothioneins (MT) are potential candidates for medicine development and application. For the purpose of expressing recombinant MT in E. coli, a crab MT cDNA cloned into pGEM-T was subcloned into pET-GST and then transformed into Escherichia Coli BL21. The fusion protein was proved to be expressed in both soluble and insoluble form by SDS-PAGE and western blot. Since metallothionein chelate metal ions, which may effects the physiological process of E. coli, caused the production of recombinant protein was lower than expected. Optimization of the ions content in the culture medium improved expression. The protein was purified by Zn2+ affinity chromatography, and rinsed off with high imidazole (1.5 M) which was the result of MT chelating instead of His-tag. This fusion protein laid a foundation of further study on the structural and functional biology of metallothionein.

3-Substituted imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[1,2-c]pyrimidine were obtained regiospecifically in yields of 35-92% in one pot by reaction of 2-aminopyridines or 2-(or 4-)aminopyrimidines, respectively, with 1,2-bis(benzotriazolyl)-1,2-(dialkylamino)ethanes.

Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibers in micro-/nano-scale fineness. However, it is still a huge technological challenge in achieving aligned fibers and arrays due to the inherent chaotic motion of an electrospinning jet. We report herein a novel spinning approach termed stable jet electrospinning to offer a facile solution to the noted issue. It involves judiciously using an ultrahigh molecular weight poly(ethylene oxide) to formulate the viscoelasticity of a spinning dope such that a very long and stable jet can be formed during electrospinning. This consequently allows for readily collecting and fabricating individual fibers, multi-filament yarns, well-aligned unidirectional fiber arrays in a large area, and ordered fiber patterns by controlling fiber placement. Our approach could thus open up the possibility of achieving continuous aligned ultrafine fibers and structures in a straightforward and scalable fashion, suitable for a variety of practical applications.