Trimethylsilylcyclooctadiene-​transition metal complexes: metal-​catalyzed protodesilylation of cyclic vinylsilanes, and transfer hydrogenation promoted by the displaced silyl group

Complexes of 1-​trimethylsilyl-​1,​5-​cyclooctadiene (TMS-​COD) with AgI, RhI, PdII and PtII have been prepd. and characterized. The distortion in their structures in comparison with the near sym. structures of the corresponding, 1,​5-​cyclooctadiene (COD) complexes, which is obviously attributable to the presence of vinylic SiMe3 group, is clearly indicated by their 1H and 13C NMR spectral characteristics. The silver complex is somewhat unstable, but the other complexes are quite stable. An unstable CuI complex that could not be satisfactorily characterized was also obtained. If appropriate conditions for the prepn. of Rh and Pd complexes are not maintained, desilylation occurs, accompanied by redn. of COD to cyclooctene by transfer of hydrogen from the solvent alc. The displaced silicon-​contg. moiety seems to enhance the transfer hydrogenation. Attempts to prep. a RuII complex resulted in the formation of a complex of desilylated diene (RuII-​COD)​

Conditional rifampicin sensitivity of a rif mutant of Escherichia coli: rifampicin induced changes in transcription specificity

Arif mutantof Escherichia coli that exhibits medium and temperature-dependent sensitivity to rifampicin is described. In the absence of rifampicin, this strain grows in minimal and rich media at 30° C and 42°C. In its presence it is viable in rich medium at both temperatures, but in minimal medium only at 30°C. In minimal-rifampicin medium at the higher temperature, RNA synthesis is decreased. The addition of certain divalent salts (MgSO4, CaCl2, BaCl2) in excess, or chelators (EDTA, EGTA, o-phenanthrolein) greatly increase viability in minimal-rifampicin medium at 42°C. Excess MgSO4 (10 mM) also increases the rate of RNA synthesis in the same medium. A model is proposed wherein therif mutation is suggested to cause a structural change in RNA polymerase that allows the binding of rifampicin and other ligands at 42° C. Rifampicin-binding is suggested to alter the conformation of RNA polymerase, impairing its ability to express genes required for growth in minimal medium. Implicit in this view is the assumption that these genes are structurally different from those expressed in rich medium in respect of certain template features recognized by RNA polymerase

Study of nonlinear convection in a sparsely packed porous medium using spectral analysis

Nonlinear study cellular convection in a sparsely packed fluid saturated porous medium is investigated, considering the Brinkman model, using the technique of spectral analysis. It is established how the Brinkman model with free-free boundaries generalizes the study of convection in a porous medium in the sense that it yields the results tending to those of viscous and Darcy flows respectively for very small and very large values of the permeability parameter �2. It also provides results for the transition zone (i.e. 102<�2<103). The cross-interaction of the linear modes caused by non-linear effects are considered through the modal Rayleigh number Rγ. The possibility of the existence of steady solution with two self-excited modes in certain regions is predicted. The similarities of present analysis with and advantages over that of the power integral technique are brought out. A detailed discussion of the heat transport, with the effect of permeability thereon, is made. The theoretical values of the Nusselt number are found to be in good agreement with experimental results. © 1983 Martinus Nijhoff Publishers

Synthesis and Humidity Sensing Properties of Sn-Doped Nano- T

Nanostructured Sn-doped TiO2 have been prepared by ball milling using SnO2 and TiO2 as raw materials. The as-prepared powders are characterized by XRD, SEMs and EDAX to identify the structural phases, surface morphology, and composition of the materials. The materials are prepared with the addition of tin of different molar ratios (0, 0.05, 0.10, 0.15, 0.20, 0.25, and 1.0) to TiO2 and sintered at 800°C for 3 h. They are subjected to dc resistance measurements as a function of relative humidity (RH) in the range of 30%–97% in a self-designed humidity chamber, and the results revealed that the sensitivity factor increased with an increase in tin molar ratio. Among them, TiO2—20 wt% of SnO2 possessed the highest humidity sensitivity, while the pure TiO2 and SnO2 composite possessed a low sensitivity

Identification of Beryllium Hydride Isotopomer Lines in Sunspot Umbral Spectra

A high resolution spectrum of FTS sunspot umbra of NSO/Kitt Peak was used to conduct a search for the molecular absorption lines due to BeH, BeD and BeT isotopomers. Analysis led to estimates of identification of the molecular lines of bands A - X (0,0), (1,1) and (2,2) for BeH, A - X (0,0), (1,1), (2,2) and (3,3) for BeD and of A - X (0,0), (1,1) and (2,2) for BeT. Among the identified lines, those which are well resolved were selected for measurements to calculate equivalent widths. The values of effective rotational temperature T were estimated for bands A - X(1,1) and (2,2) of BeH, A - X(1,1) of BeD and A - X(2,2) of BeT to be 4228K, 4057K, 3941K and 3243K respectively

The performance of organ dysfunction scores for the early prediction and management of severity in acute pancreatitis: an exploratory phase diagnostic study

Objective: To evaluate contemporary organ dysfunction scoring systems for early prediction of severity in acute pancreatitis (AP). Methods: In a consecutive cohort of 181 patients with AP, organ dysfunction scores (logistic organ dysfunction system [LODS] score, Marshall organ dysfunction score, and sequential organ failure assessment score) were collected at 24 and 48 hours. Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were calculated on admission and 24 and 48 hours and C-reactive protein level measured at 48 hours. Patients who died or used critical care facilities (level 2/3) during admission were classed as severe. Results: Area under curve for APACHE II score at admission was 0.78 (95% confidence interval, 0.69-0.86). At 24 hours, area under curve for LODS, Marshall organ dysfunction system, sequential organ failure assessment, and APACHE II scores were 0.82, 0.80, 0.80, and 0.82, respectively. The LODS score at cutoff of 1 achieved 90% sensitivity and 69% specificity, corresponding to a positive predictive value of 38%. Acute Physiology and Chronic Health Evaluation II score as a rule-out for selection of mild cases at a test threshold of 9 (scores <= 8 being selected) gives homogeneity of 91% and efficiency of 79%. Conclusions: Contemporary organ dysfunction scoring systems provides an objective guide to stratification of management, but there is no perfect score. All scores evaluated here perform equivalently at 24 hours. Acute Physiology and Chronic Health Evaluation II may have practical clinical value as a rule-out test

Astrophysical molecule CN : vibronic transition probability parameters

Abstract. Astrophysical applications are broadened by the emerging consensus on the vibration-electronic (vibronic) transition probability parameters such as Franck -Condon (FC) factors &amp; r -centroids of some molecular species like CN , which could be useful in the identification of molecular lines and in the estimation of relative abundance of the species in various celestial bodies especially in the interstellar medium. Such important parameters, that is FC factors and r -centroids, have been computed by a reliable numerical integration procedure for the bands of E i systems of astrophysical molecule CN , using a suitable potential. For E − X system, the improved values of FC factors from the revised molecular constants are given along with the already reported values