Isolation and structure of rebeccamycin - a new antitumor antibiotic from nocardia aerocoligenes

The isolation and structure elucidation of rebeccamycin 1, a new antitumor agent from $\text{Nocardia}$$\text{Aerocoligenes}$, is described. The NMR spectra of 1 and its peracetate 2 are discussed.     

FMR studies in compositionally modulated Co-Nb and Co films

Compositionally modulated (CM) films of Co-Nb have been prepared by sequential evaporation onto Si substrates using two E-guns fitted in an UHV system. The thickness of the Co sublayer was varied in the range 50 to 105 Å and that of Nb in the range 18 to 90 Å. A single layer Co film of about 850 Å was also prepared and studied. Magnetization was measured using a VSM at 290 K. FMR was observed at about 9.8 GHz in the range 3 to 290 K. For Co a layer thickness of 50 Å the magnetization in CM film is about 12% lower at 4.2 K, as compared to the bulk value. The FMR spectrum of single layer Co film shows a single absorption in the perpendicular configuration with a narrow line width of 40 Oe. Other properties of this film agree with those published in the literature. In CM films, multiple absorption modes are observed. A small perpendicular anisoropy is also measured. The magnetization in all the samples varies at T^3/2. The Curie temperature of CM films is lower than that of bulk Co. The resonance line width in CM films at lower temperatures, increases much faster than in Co film.     

Processability characteristics of chlorinated poly(vinyl chloride)

Chlorinated poly(vinyl chloride) (CPVC) is known to have a higher softening temperature than conventional poly(vinyl chloride) (PVC). Its processability characteristics are, however, different; it has been reported that CPVC is more difficult to process. However, only limited information on the processability characteristics is available. This paper describes some studies of the flow behavior of CPVC melts in a capillary rheometer. The true melt viscosity and activation energy were determined between 190° and 210°C for a number of samples, and they appear to be related to the cohesive energy density of the samples. It was observed that melt fracture, i.e., gross distortion of the extrudate, occurs even at low shear rates in samples having a high chlorine content. This has been attributed to the relatively high pressures that have to be used, the pronounced non-Newtonian nature of the melt, and melt elasticity. It is postulated that melt elasticity could result from crosslinking at the site of the double bond which is known to be formed by dehydrochlorination.     

A spreadsheet program for modeling quantitative structure-pharmacokinetic relationships for inhaled volatile organics in humans

The extent and profile of target tissue exposure to toxicants depend upon the pharmacokinetic processes, namely, absorption, distribution, metabolism and excretion. The present study developed a spreadsheet program to simulate the pharmacokinetics of inhaled volatile organic chemicals (VOCs) in humans based on information from molecular structure. The approach involved the construction of a human physiologically-based pharmacokinetic (PBPK) model, and the estimation of its parameters based on quantitative structure-property relationships (QSPRs) in an Excel spreadsheet. The compartments of the PBPK model consisted of liver, adipose tissue, poorly perfused tissues and richly perfused tissues connected by circulating blood. The parameters required were: human physiological parameters such as cardiac output, breathing rate, tissue volumes and tissue blood flow rates (obtained from the biomedical literature), tissue/air partition coefficients (obtained using QSPRs developed with rat data), blood/air partition coefficients (Pb) and hepatic clearance (CL). Using literature data on human Pb and CL for several VOCs (alkanes, alkenes, haloalkanes and aromatic hydrocarbons), multi-linear additive QSPR models were developed. The numerical contributions to human Pb and CL were obtained for eleven structural fragments (CH3, CH2, CH, C, C [double bond] C, H, Cl, Br, F, benzene ring, and H in the benzene ring structure). Using these data as input, the PBPK model written in an Excel spreadsheet simulated the inhalation pharmacokinetics of ethylbenzene (33 ppm, 7 h) and dichloromethane (100 ppm, 6 h) in humans exposed to these chemicals. The QSPRs developed in this study should be useful for predicting the inhalation pharmacokinetics of VOCs in humans, prior to testing and experimentation.     

Amide catalysed facile isomerization of 5,6-dihydroisoquinolines: synthesis of stable 1,2-dihydroisoquinolines.

Stable 1,2-dihydroisoquinolines have been synthesized by an amide catalysed novel isomerization reaction of 5,6-dihydroisoquinolines.     

Attenuation of shock parameters in air and water

This paper describes the results of shock pressure measurements in the range of 1–25 MPa in water and in the range of 60–500 kPa in air. Pressure pulses were generated by exploding wire technique and measured with a quartz piezo-electric transducer. The attenuation with distance of shock overpressure, impulse and energy in shock front has been studied. Experimental data on shock attenuation in air is scarce and the results presented here confirm the attenuation behaviour derived from theoretical considerations.