Polarography of disodium pentacyanonitrosylferrate(II): Part 2. Determination at Therapeutic Levels in Serum,Plasma, and Whole Blood

Disodium pentacyanonitrosylferrat(II) (sodium nitroprusside) is determined at therapeutic (ng ml^?1) levels in plasma, serum and blood with conventional and high-performance differential pulse polarography (d.p.p. and h.p.d.p.p.) at a dropping mercury electrode or a static mercury drop electrode. Serum or plasma (3 ml) is treated with perchloric acid containing 1 mg ml^?1 potassium hexacyanoferrate(II), centrifuged for 10 min and subjected to polarography. For spiked serum, calibration graphs are linear over the range 30–1000 ng ml^?1 sodium nitroprusside, regardless of the polarographic technique; the estimated detection limit is 15 ng ml^?1 (5 × 10^?8 M). Calculated therapeutic levels range from 100 to 1000 ng ml^?1. Similar results were obtained for spiked plasma. A similar procedure is suitable for whole blood and was used to study the in-vitro degradation of sodium nitroprusside (200 ng ml^?1) on incubation at 37°C. The in-vitro loss is rapid (t_{$\text{1}\text{2}$} ≈ 6 min) but meaningful in-vivo levels can be obtained when the blood is collected in a 0.9% sodium chloride solution at 0°C. Thiocyanate, the main metabolite of nitroprusside, and thiosulphate, which is a potential antidote for cyanide, do not interfere.     

Untersuchung der Ausscheidungsverhältnisse von schmelzgegossenen hochaluminiumoxidhaltigen feuerfesten Materialien

The relation between the conditions of crystallisation and grain texture of fused refractory bricks with high contents of aluminium oxide ist investigated. The results make clear that bricks with small contents of a glass phase have to becooled down slowly, thus avoiding a strongly disturbed growth of the corundum crystals in larger areas of the brick. A fast solidification process caused by rapid cooling does not result in a defined growth of dendrites and in the formation of a stable equilibrium state.     

Selective reflection in the cholesteric and blue phases of a chiral-racemic mixture of CE6

Abstract

The reflection spectrum for visible light is examined for the cholesteric and blue phases of chiral CE6. Pronounced side band oscillations are observed. The Bragg wavelength for total reflection diverges towards the smectic phase with an exponent v = 0·71±0·05. Going from the cholesteric phase to BPI, the lattice parameter increases by (2)^1/2. Evidence is given for the existence of a long-lived supercooled blue phase (BPS).     

Investigation of the chirality dependence of thermal properties in chiral-racemic mixtures of the cholesteric ester CE6

Abstract

A scanning adiabatic calorimetric technique has been used to study the thermal properties of the chiral and racemic liquid crystal CE6 and the phase diagram covering the cholesteric phase, the three blue phases and the isotropic phase. The purpose of this investigation is to study thermal properties of liquid crystals as a function of chirality, while all other parameters remain constant. Results for the temperature and the chirality dependence of the enthalpy and of the heat capacity are reported. The latent heats between the cholesteric phase and BPI and between the different blue phases change slightly as a function of the chirality. The total heat of transition at the isotropic phase boundary is independent of the chirality, but with decreasing chirality, we observe a large increase in the latent heat and, correspondingly, a decrease in the pretransitional contribution. These experimental facts are in qualitative agreement with the predictions of a Landau–de Gennes theory for blue phases.     

Electron energy-loss spectroscopy at incommensurately modulated crystalline and glassy Ba2TiGe2O8

Based on cluster molecular orbital calculations, high-energy resolution (ΔE?～ 0.4?eV) Ti–L_2,3 electron energy loss near-edge structures of single-crystalline and glassy Ba₂TiGe₂O₈ are interpreted. The finding that the Ti–L_2,3 near-edge structure of the Ba₂TiGe₂O₈ single crystal possesses less pronounced peaks than the glass under identical experimental conditions can be attributed to distinct distortions of the titanium environment caused by the very strong one-dimensional structural modulation hosted by the Ba₂TiGe₂O₈ crystal lattice. As lattice periodicity is absent in the glass, the titanium environment is more regular in the vitreous surroundings. Moreover, the modulation in crystalline Ba₂TiGe₂O₈ is responsible for the virtually indiscernible O–K near-edge structures of the glassy and crystalline samples.     

Talopyranose Derivatives Suitable for the Planned Synthesis of Teichoic Acids Containing Di-Glycosylated Ribitol Units

ABSTRACT

Easily accessible 1,6-anhydro-2,3-O-(S)-benzylidene-β-D-mannopyranose was converted in four steps to 1,6-anhydro-3,4-di-O-benzyl-β-D-talopyranose. Glycosylation of the latter with ethyl 2,3,4-tri-O-acetyl-1-thio-α-L-rhamnopyranoside gave, after further processing, 1-O-allyl-3,4-di-O-benzyl-2-O-(2,3,4-tri-O-benzyl-α-L-rhamnopyranosyl)-L-ribitol.     

Transmission of HIV in sexual networks in sub-Saharan Africa and Europe

We are reviewing the literature regarding sexual networks and HIV transmission in sub-Saharan Africa and Europe. On Likoma Island in Malawi, a sexual network was reconstructed using a sociometric survey in which individuals named their sexual partners. The sexual network identified one giant component including half of all sexually active individuals. More than 25% of respondents were linked through independent chains of sexual relations. HIV was more common in the sparser regions of the network due to over-representation of groups with higher HIV prevalence. A study from KwaZulu-Natal in South-Africa collected egocentric data about sexual partners and found that new infections in women in a particular area was associated with the number of life-time partners in men. Data about sexual networks and HIV transmission are not reported in Europe. It is, however, found that the annual number of sexual partners follows a scale-free network. Phylogenetic studies that determine genetic relatedness between HIV isolates obtained from infected individuals, found that patients in the early stages of infections explain a high number of new infections. In conclusion, the limited information that is available suggest that sexual networks play a role in spread of HIV. Obtaining more information about sexual networks can be of benefit for modeling studies on HIV transmission and prevention.