Enantioselective copper-catalysed propargylic substitution: synthetic scope study and application in formal total syntheses of (+)-anisomycin and (-)-cytoxazone

A copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic esters with different side chains (R=Ar, Bn, alkyl) into their amine counterparts in very high yields and with good enantioselectivities (up to 90% enantiomeric excess (ee)). Different amine nucleophiles were applied in the reactions and the highest enantioselectivities were obtained for aniline and its analogues. Interestingly, some carbon nucleophiles could also be used and with indoles excellent ee values were obtained (up to 98% ee). The versatility of the propargylic amines obtained was demonstrated by their further elaboration to formal total syntheses of the antibiotic (+)-anisomycin and the cytokine modulator (-)-cytoxazone.     

Reduction of base-transit time of InP-GaInAs HBTs due to electron injection from an energy ramp and base-composition grading

The dc current gain of InP-GaInAs heterojunction bipolar transistors with varying base thickness and composition was measured. Much larger composition grade values than previously reported were achieved using strain compensation. A simple two-parameter Monte Carlo simulation was developed to interpret the results. The simulation yields an accurate plot of the base transit time versus base thickness. Clear evidence for the reduction of base transit time due to hot electron injection was observed in devices with thin uniform bases. The current gain of 45-nm-thick graded base devices saturated as the grading was increased beyond standard values. Grading did not increase the gain of devices with a 20-nm-thick base.     

用低温金属电镀技术制造与封装的惯性微型电学开关

运用光刻胶为注模的多次互不干扰金属电镀技术实现了惯性微型电学开关的低温制造与封装．电镀技术的低温过程可使微型开关直接成形于预先制作好的含有电子信号处理电路的基底上，加上同样借助于低温金属电镀技术的基于整个硅晶片的倒装封装，直接形成环绕各个器件的密封腔体．这一技术最终将使得模块化生产成为现实．微型开关的高度和它的密封腔的高度可以分别控制．电子信号可以通过金属互连线进入密封腔体．为了便于设计，建立了一个既简单又相对准确的“弹簧质量块”模型．以此设计的惯性开关，即使在未封装的常温、常压条件下，均可工作1e９次以上．本文对密封腔体的强度和密封性，以及金属互连线的可靠性，都作了详细的检测，各项指标均达到其各自的标准．     

Problems in parameter identification of the passive response in human arteries

Identification of unique material parameters for the media and adventitia in the case of arteries involves many challenges. Tension-inflation experiments were performed on the internal mammary artery and the axial force and the radial displacements were used to identify the material parameters. It will be shown that these experimental data are not sufficient to uniquely identify the material parameters of the passive response in human arteries. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Polymer-Bromine Interactions. I. Interactions with Polyacrylonitrile

The present paper deals with the interactions of bromine with poly-acrylonitrile (PAN). Kinetics and equilibria of the sorption of Br₂ on PAN were studied at a concentration range of 0.01–0.1 mol/L and a temperature range of 25–40°C. Two kinds of sorption were found: a “reversible” sorption removable by water and an “irreversible” sorption removable by aqueous ammonia solutions. The irreversibly sorbed bromine is presumably linked by charge transfer to the nitrile groups of the PAN, as evidenced by UV spectra. The irreversible sorption follows the reversible sorption and is slower. Partition coefficients obtained from the linear Freundlich isotherms increased with temperature and, at 40°C, the values obtained were 97, 65, and 32 L/kg for the total, irreversible, and reversible sorptions, respectively. At 25°C the chemical potential, enthalpy, and change in entropy for the irreversible sorption were ?2.0 kcal/mol, 9.4 kcal/mol, and 38 cal·mol^?1·K^?1. Effects of a 6-day Br₂ treatment and ammonia rinse were: decrease in dry T _g from 74.5 to 61°C and in water from 38 to 35°C; no significant decrease in M _W ; decrease in tensile strength measured after the bromine stage, and improvement after ammonia stage; increased swollen dimensions from 57% in water to 75%; and stabilization of swollen dimensions upon drying. The results support the existence of two phases in the less ordered regions of PAN.     

Homoleptic Ti[ONO]2 type complexes of amino-acid-tethered phenolato Schiff-base ligands: Synthesis,characterization, time-resolved fluorescence spectroscopy,and cytotoxicity against ovarian and colon cancer cells

Six homoleptic Ti (IV) compounds of dianionic tridentate ONO Schiff base ligands with various substitutions were prepared from chiral amino acids, 2-hydroxybenzaldehyde, which were generated in situ, and Ti (OⁱPr)₄. The compounds were spectroscopically characterized and the molecular geometries of five complexes were established by X-ray crystallography; for two structures, two independent molecules compose the asymmetric units. The di-anionic, tridentate ligands coordinate the titanium centers via the carboxylate-O-, imine-N- and phenoxide-O atoms to form five- and six-membered chelate rings. The molecules are based on a trans-N₂O₄ donor with each carboxylate-O atom trans to a phenoxide-O atom. For the smallest derivative with Me substitution, racemization occurs during repeated recrystallization. Photophysical profiles of the titanium compounds in the solid phase and in solution are discussed. Marked cytotoxicities were recorded toward human ovarian A2780 and colon HT-29 cancer cells with IC₅₀ values ranging between 23 ± 2 and 103 ± 3 μM. Comparative hydrolytic stability of the complexes were studied by NMR in 10% D₂O solutions which provided t_1/2 values of up to 15 ± 2 hr.     

Foliar Delivery of siRNA Particles for Treating Viral Infections in Agricultural Grapevines

Grapevine leafroll disease (GLD) is a globally spreading viral infection that causes major economic losses by reducing crop yield, plant longevity, and berry quality, with no effective treatment. Grapevine leafroll associated virus-3 (GLRaV-3) is the most severe, prevalent GLD strain affecting wine production. Here, the ability of RNA interference (RNAi), a non-GMO gene-silencing pathway, to treat GLRaV-3 in infected Cabernet Sauvignon grapevines is evaluated. Lipid-modified polyethylenimine (lmPEI) is synthesized as the carrier for long double-stranded RNA (dsRNA, 250-bp-long) that targets RNA polymerase and coat protein is a gene target that are conserved in the GLRaV-3 genome. Self-assembled dsRNA–lmPEI particles, 220 nm in diameter, display inner ordered domains spaced 7.3 ± 2 nm from one another, correlating to lmPEI wrapping spirally around the dsRNA. The particles effectively protect RNA from degradation by ribonucleases and show to increase uptake rate into plant cells as a result of the lipid component comprising the RNA carrier. In three field experiments, a single dose of foliar sprayed treatment of the RNA-particles knocks down GLRaV-3 titer, and multiple doses of the treatment keep the viral titer at baseline and trigger recovery of the vine and berries. This study demonstrates RNAi as a promising platform for treating viral diseases in agriculture.     

Minimizing task completion time with the execution set method

We consider a partial ordered set (POSET) of assembling operations, with known execution durations, that must be accomplished. The assembling operations can be executed on an acyclic network with an identical set of robots on each conveyer (arc). The number of depots (nodes) is a known integer. Between each pair of depots we can locate only one conveyer. We seek an arrangement of the network and a plan that divides the task operations among the conveyers, minimizing the overall task completion time. We use linear programming optimization, subject to reasonably general rules for distributing the operation-fragments among the conveyers.