A comparison of the insoluble residues produced by the Klason lignin and acid detergent lignin procedures

Two methods—Klason lignin (KL) and acid detergent lignin (ADL)— for determining lignin concentration in plants were compared using stem material from lucerne (Medicago sativa L), cocksfoot (Dactylis glomerata L) and switchgrass (Panicum virgatum L), at three stages of maturity, and leaf samples from lucerne and cocksfoot. For all forages, KL values were higher than ADL values. Lucerne samples, which had crude protein levels twice that of the grass species, had KL values that were only 30–40% higher than ADL values; in grasses, KL values were 200–300% greater than ADL values. The addition of nitrogenous materials (bovine serum albumin, lysine, and ammonium sulfate) to commercial xylan and cellulose did not result in additional KL residue. Pyrolysis-GC-MS revealed that both residues appeared to be similar to the orginal plant lignin and did not appear to be contaminated with carbohydrate or protein. The higher values for grass KL residues were not due to protein con- tamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment. KL values may give a more accurate quantification of the total lignin within forage plants.     

Degradability of phenolic acid-hemicellulose esters: A model system

A synthetic model system containing p-coumaric and ferulic acids esterified to hemicellulose was used to study polysaccharide degradability. Oatspelts xylan was fractionated into A_linear, B_linear and B_ranched fractions prior to synthetic esterification with phenolic acids at treatment concentrations of 0, 25, 50, 75 and 100 g phenolic acid per kg hemicellulose. Concentrations of phenolic acids esterified to the hemicellulose fractions were determined by alkaline hydrolysis. In-vitro dry matter disappearance (IVDMD) and degradability of hemicellulose neutral sugars were measured after 48 h ruminal fermentations. Esterification efficiency of the phenolic acids to the hemicellulose fractions was low (0.3 to 13.9%) and greater for p-coumaric than ferulic acid (4.7 vs 3.1%, respectively). Concentration of esterified phenolic acids was negatively correlated with IVDMD for the A_linear and B_branched fractions. Ferulic acid appeared to be more inhibitory to IVDMD than p-coumaric acid. Generally the degradability of the side chain sugars of the hemicellulose fractions was negatively correlated with esterified phenolic acid concentrations. Xylose degradation was only correlated with esterified ferulic acid level in the A_linear fraction. The in-vitro ruminal fermentations resulted in the degradation of the majority of the phenolic acid esters. Analysis of the synthetic phenolic acid-hemicellulose esters by ¹³C NMR and FTIR was unable to prove the presence of monomeric phenolic acid esters. The presence of phenolic acid polyesters was unlikely because of the solubility of the synthetic phenolic acid-hemicellulose esters. The neutral sugar degradation data suggest that esterification of the phenolic acids was limited to sugars with primary hydroxyl groups. While this model system was useful for studying cell wall degradation, future studies must employ model systems in which the chemical constituents being tested accurately model those found in nature.     

Permeability of ergot alkaloids across the blood-brain barrier in vitro and influence on the barrier integrity

Scope Ergot alkaloids are secondary metabolites of Claviceps spp. and they have been in the focus of research for many years. Experiments focusing on ergotamine as a former migraine drug referring to the ability to reach the brain revealed controversial results. The question to which extent ergot alkaloids are able to cross the blood‐brain barrier is still not answered. Methods and results In order to answer this question we have studied the ability of ergot alkaloids to penetrate the blood‐brain barrier in a well established in vitro model system using primary porcine brain endothelial cells. It could clearly be demonstrated that ergot alkaloids are able to cross the blood‐brain barrier in high quantities in only a few hours. We could further identify an active transport for ergometrine as a substrate for the BCRP/ABCG2 transporter. Investigations concerning barrier integrity properties have identified ergocristinine as a potent substance to accumulate in these cells ultimately leading to a weakened barrier function. Conclusion For the first time we could show that the so far as biologically inactive described 8‐(S) isomers of ergot alkaloids seem to have an influence on barrier integrity underlining the necessity for a risk assessment of ergot alkaloids in food and feed.     

Untersuchungen zur stereoselektiven elektrophilen Cyanierung

Studies on Stereoselective Electrophiic Cyanation The enantioselective, electrophilic cyanation of the enolates of 2-substituted 1-tetralones 3 is described. Enantiomerically pure 2-cyanato-1,1′-binaphthyl derivatives 2, 6a and b are used as cyanating agents. The influence of solvent, temperature, additives and the method of enolate formation are investigated. Best results are obtained with 48% ee in the case of compound 2 and 60% ee in the case of compound 6b if the enolate is prepared from the corresponding silyl enol ether 7 and Toluene is used as solvent.     

Minimized Power Consumption for Scan-Based BIST

Power consumption of digital systems may increase significantly during testing. In this paper, systems equipped with a scan-based built-in self-test like the STUMPS architecture are analyzed, the modules and modes with the highest power consumption are identified, and design modifications to reduce power consumption are proposed. The design modifications include some gating logic for masking the scan path activity during shifting, and the synthesis of additional logic for suppressing random patterns which do not contribute to increase the fault coverage. These design changes reduce power consumption during BIST by several orders of magnitude, at very low cost in terms of area and performance.     

Deterministic BIST with Partial Scan

An efficient deterministic BIST scheme based on partial scan chains together with a scan selection algorithm tailored for BIST is presented. The algorithm determines a minimum number of flipflops to be scannable so that the remaining circuit has a pipeline-like structure. Experiments show that scanning less flipflops may even decrease the hardware overhead for the on-chip pattern generator besides the classical advantages of partial scan such as less impact on the system performance and less hardware overhead.     

Instruction Set Extensions for MPEG-4 Video

This paper describes instruction set extensions for the acceleration of MPEG-4 algorithms on programmable (RISC-) CPUs. MPEG-4 standardizes audio and video compression schemes for a variety of bit rates and scenarios. As MPEG-4 targets a much broader range of different applications than previously defined hybrid video coding standards like H.263 or MPEG-2, it employs a much higher number of different algorithms and coding modes. Therefore, MPEG-4 implementations will require a more software-oriented approach to be efficient. However, the total computational load for an optimized implementation of an MPEG-4 video codec is expected to exceed the performance levels of today's multimedia signal processors, making further hardware acceleration a necessity. For that purpose, we propose a number of instruction set extensions that add function-specific blocks to the data path of a CPU. These dedicated modules are highly adapted to the most computation-intensive processing schemes of MPEG-4, such as DCT, motion compensation, padding, shape coding, or bitstream parsing. The increased functionality of basic instructions results in a significant speed-up over standard RISC instruction sets, thus making MPEG-4 implementations feasible on programmable processor platforms. Possible target architectures include VLIW multimedia processors, MIMD-style multiprocessors, or coprocessor architectures     

悬浮聚合的转化率和粒子尺寸分布

基于自由基悬浮聚合反应动力学和群体平衡模型,以苯乙烯为体系,建立了在循环反应器中间歇悬浮聚合过程转化率和成粒机理的数学模型。模型引入了凝胶效应模型和子粒相对分配函数, 由此联用动力学模型和粒径分布模型解出苯乙烯聚合时的转化率和液滴尺寸分布,所得结果与实验值相当一致。     

Synthese,Struktur und photophysikalische Eigenschaften von polyarylierten Imidazolen und Oxazolen

Synthesis, Structure, and Photophysical Properties of Polyarylated Imidazoles and Oxazoles 23 tetraphenylimidazoles 1,2 and 11 triphenyloxazoles 4,5 with amino, nitro, methoxy, hydroxy, or halogeno substituents chiefly in the para position were prepared. The absorption and fluorescence emission properties were investigated in ethanolic solution. The effects of the substituents in 1,2 on the spectral shifts show that the arrangement of the phenyl rings in 1 position is not coplanar in relation to the heterocycle whereas the phenyl rings in 2 position are more coplanar. The spectral changes of compound 2a in solvents of various polarity (dielectric constants 2,02–47,24) are almost negligible. The Stokes shift is moderately increased. A remarkable increase in the fluorescence quantum yield is observed by chlorine substitution in phenyl ring 2.