Comparison of yellow poplar pretreatment between NREL digester and sunds hydrolyzer

Single-stage cocurrent dilute acid pretreatments were carried out on yellow poplar (Liriodendron tulipifera) sawdust using an as-installed and short residence time modified pilot-scale Sunds hydrolyzer and a 4-L bench-scale NREL digester (steam explosion reactor). Pretreatment conditions for the Sunds hydrolyzer, installed in the NREL process development unit (PDU), which operates at 1 t/d (bone-dry t) feed rate, spanned the temperature range of 160 – 210°C, 0.1 – 1.0% (w/w) sulfuric acid, and 4-10-min residence times. The batch pretreatments of yellow poplar sawdust in the bench-scale digester were carried out at 210 and 230°C, 0.26% (w/w) sulfuric acid, and 1-, 3-, and 4-min residence times. The dilute acid prehydrolysis solubilized more than 90% of the hemicellulose, and increased the enzymatic digestibility of the cellulose that remained in the solids. Compositional analysis of the pretreated solids and liquors and mass balance data show that the two pretreatment devices had similar pretreatment performance.     

High-resolution electron microscopy of montmorillonite and montmorillonite/epoxy nanocomposites

With the use of high-resolution transmission electron microscopy the structure and morphology of montmorillonite (MMT), a material of current interest for use in polymer nanocomposites, was characterized. Using both imaging theory and experiment, the procedures needed to generate lattice images from MMT were established. These procedures involve careful control of the microscope's objective lens defocus to maximize contrast from features of a certain size, as well as limiting the total dose of electrons received by the sample. Direct images of the MMT lattice were obtained from neat Na+ MMT, organically modified MMT, and organically modified MMT/epoxy nanocomposites. The degree of crystallinity and turbostratic disorder were characterized using electron diffraction and high-resolution electron microscopy (HREM). Also, the extent of the MMT sheets to bend when processed into an epoxy matrix was directly visualized. A minimum radius of curvature tolerable for a single MMT sheet during bending deformation was estimated to be 15 nm, and from this value a critical failure strain of 0.033 was calculated. HREM can be used to improve the understanding of the structure of polymer nanocomposites at the nanometer-length scale.     

Efficient trapping of HNO by deoxymyoglobin

Nitrosyl hydride, HNO, also commonly termed nitroxyl, is a transient species that has been implicated in the biological activity of nitric oxide, NO. Herein, we report the first generation of a stable HNO-metal complex by direct trapping of free HNO. Deoxymyoglobin (Mb-Fe(II)) rapidly reacts with HNO produced from the decomposition of methylsulfonylhydroxylamine (MSHA) or Angeli's salt (AS) in aqueous solutions from pH 7 to pH 10, forming an adduct, Mb-HNO. The unique 1H NMR signal of the Fe-bound HNO at 14.8 ppm allows definitive proof of its formation. The generation of Mb-HNO and quantification of various myoglobin byproducts were accomplished by correlation of 1H NMR, UV-vis, and EPR spectroscopies. Typically, the maximum Mb-HNO yield obtained is 60-80%; competitive side reactions with byproducts as well as the further reactivity of the Mb-HNO decrease the overall yield. At pH 10, the observed rate of Mb-HNO generation by trapping HNO from MSHA is close to that for MSHA decomposition; kinetic simulations give a lower limit to the bimolecular rate of trapping as 1.4 x 10(4) M(-1) s(-1). The binding of HNO to deoxymyoglobin is rapid and essentially irreversible, which suggests that the biological activity of nitroxyl may be mediated by its reactivity with ferrous heme proteins such as myoglobin and hemoglobin.     

脱色阴离子交换剂的再生研究

提出一种新的离子交换剂再生理论，即吸附物的脱附依靠离子交换和络合的协同效应完成．以二价钙离子为再生剂，对糖液脱色用的阴离子交换树脂和阴离子交换纤维进行再生，并与传统的碱性钠盐相比较，研究证明钙离子为再生剂的工艺，具有低成本、无污染的特点．     

In vivo 31P-NMR SPECTROSCOPY OF MAMMARY CARCINOMA SUBJECTED TO SUB CURATIVE PHOTODYNAMIC THERAPY

Abstract In vivo ³¹P-NMR spectroscopy was applied to the investigation of the time course of metabolic response of MCA mammary carcinoma in the C,H mouse subjected to a subcurative treatment with photodynamic therapy. Eleven animals were injected with 12.5 mg kg^_1 Photofrin II and after 24 h were photoactivated with 25 J cm⁻² of light between 630 ± 5 nm. In vivo NMR spectroscopy was performed 1-4, 24 and 72 h after treatment. The ratio of (J-ATP intensity to inorganic phosphate (Pi) intensity changed over the time course of the study. At the 1-4 and 24 h time points the ratio of fi-ATP to Pi decreased from control values. At 72 h there was a significant increase in the ratio above the post treatment values to levels equal to or exceeding that of control pretreatment ratios.     

Formation enthalpies of rare earth titanate pyrochlores

High-temperature oxide melt solution calorimetry and Rietveld refinements of powder X-ray diffraction data were used to investigate the structure (Fd3m; Z=8) and energetics of a series of RE₂Ti₂O₇ (RE=Sm-Lu) compounds with the pyrochlore structure as well as La₂Ti₂O₇ with a layered perovskite-type structure. All of the RE-titanates were found to be stable in enthalpy with respect to their oxides. In the pyrochlore series, Lu₂Ti₂O₇ was least stable in enthalpy (ΔHf-ox at 298 K=−56.0±4.0 kJ/mol); the most stable materials were Gd-, Eu-, and Sm₂Ti₂O₇ with ΔHf-ox at 298 K=−113.4±2.7, −106.1±4.2, −115.4±4.2 kJ/mol, respectively. In general, as the radius ratio of the A- to B-site cations, R_A/R_B, decreases, the pyrochlore structure becomes less stable. The trend of ionic radius of the RE³⁺ cation vs. ΔHf-ox at 298 K is non-linear and approximately parallels the increasing “resistance” to ion-beam-induced amorphization as R_A/R_B decreases.     

The assessment of risk in relation to major hazards,with particular reference to nuclear reactors

The article concentrates mainly on the developing pattern of safety thinking and safety practices which have been brought about by, and in turn have influenced, the growth of modern industrial technology, particularly in the nuclear field.

The need to minimize the chance of accidents with serious consequences led to pursuit of safety by siting, by containment and by automatic built-in safety mechanisms; these are discussed.

Codes of practice and safety guidelines are becoming linked with more quantitative goals to achieve desired objectives in safety and reliability. This is particularly important in the assessment of major hazards.