InP based semiconductor structures for radiation detection

We report the preparation of semi-insulating InP single crystals of p-type conductivity and intentionally undoped p-type epitaxial layers for radiation detection. We focus on (i) the growth of InP single crystals doped with copper by the Czochralski technique and their subsequent temperature annealing to convert them to a semi-insulating (SI) state of p-type conductivity, and (ii) the growth of thick (>10 μm) p-type InP layers by liquid phase epitaxy with an admixture of Pr and Dy. Grown layers and single crystals were examined by low-temperature photoluminescence spectroscopy, capacitance-voltage and temperature dependent Hall measurements. An efficient purification due to rare earth (RE) admixture has been observed and layers grown with the addition of Pr and Dy exhibit the change of electrical conductivity from n to p at certain RE concentration in the melt. Dominant acceptors responsible for conductivity conversion have been identified. Three types of detection structures exploiting the Schottky or Schottky like contacts on pure and SI p-type InP or exploiting the p–n junction were designed.     

The expression of B-50/GAP-43 and GFAP after bilateral olfactory bulbectomy in rats

In the present study we investigated the effect of a two-stage bilateral lesion of the olfactory bulb (OB) in rats on the regeneration ability of peripheral olfactory neurons and their reinnervation capacity in the spared OB. The outgrowth of newly-generated olfactory axons as well as the maturation of their terminal synaptic field was detected by immunohistochemistry of the growth-associated phosphoprotein B-50/GAP-43. In addition, the glial response to the surgery was monitored by an immunohistochemical marker for astrocytes, glial fibrillary acidic protein (GFAP). In neonatal rats (P3-P5), the right OB was removed, then three months later the contralateral side was ablated. Six days after the second operation the animals were transcardially perfused. Their brains were embedded in paraplast, serially sectioned and processed for histological and immunohistochemical observations. After neonatal OB ablation, homogeneous B-50-immunoreactivity (BIR) was found in the forebrain, olfactory axons and ectopic glomeruli localized in the small OB remnant-like structures and in the regenerated neuroepithelium. A strong GFAP response was revealed in the brain cortex as well as in the newly-formed olfactory axons and glomeruli-like structures of the OB remnants. After adult OB ablation strong BIR was observed in olfactory axons, while remaining glomerular structures were only faintly stained. The neuroepithelium revealed signs of massive degenerative processes with a substantial decrease in BIR. The GFAP-positive astrocytes were scattered throughout the entire OB remnant and were prominent in the glomeruli-like structures and adjacent frontal cortex. In the present study, we applied GAP-43 and GFAP immunohistochemistry to characterize the responses of individual olfactory components after two-stage olfactory bulbectomy. Furthermore, this model of OB ablation characterized by two immunohistochemical markers could elucidate certain molecular mechanisms involved in the regeneration and/or plasticity of the olfactory system.     

Cerebrospinal fluid proteins in the diagnosis of disorders of the blood-cerebrospinal fluid barrier in central nervous system diseases

BACKGROUND: Many neurological diseases are connected with the dysfunction of blood-CSF barrier. The quantitative determination of CSF proteins has already been used in the diagnosis of barrier impairments and inflammatory diseases of the central nervous system. PATIENTS: Serum and CSF, totaling 264 samples, were obtained from 15 controls and 117 patients with various diseases of the nervous system. Laurell's electroimmunoassay was used for estimation of albumin and IgG levels in serum and CSF. CSF-protein profile was evaluated according to Reiber's graph for the evaluation of the CSF-protein profile. RESULTS: The graph for the protein profile can be divided into 5 functionally different parts (1--normal range, 2, 3, 4--different types of barrier dysfunctions and 5--local humoral response in CNS without any barrier impairment). There was a good correlation of CSF-protein profiles and neurological diseases in our group of patients. CONCLUSIONS: According to our results, Reiber's graph was helpful for the diagnosis of blood-CSF-barrier dysfunctions. The graph has the following advantages: a) possibility of simultaneous assessment of the functional state of blood-CSF-barrier and the inflammatory response of the CNS, b)sensitivity for the determination of pathological local IgG-production in CNS and c) minimal number of protein assays necessary.     

Assessment of dietary and genetic factors influencing serum and adipose fatty acid composition in obese female identical twins

Fourteen pairs of obese female monozygotic twins were recruited for a study of genetic influences on serum and adipose fatty acid (FA) composition. Following 1 wk of inpatient stabilization, fasting serum and adipose tissue obtained by surgical excision were analyzed by thin-layer and gas chromatography. Intrapair resemblances (IPR) for individual FA were assessed by Spearman rank correlation and by analysis of variance and were found in serum cholesteryl esters (CE), triglycerides (TG), and adipose TG. With two exceptions (CE linoleate and adipose eicosapentaenoate), these IPR were limited to the nonessential FA. Palmitate had significant IPR in four lipid fractions; in serum CE and adipose TG palmitate was strongly correlated with multiple measures of adiposity. In contrast to other lipid fractions, serum phosphatidylcholine (PC) FA had 12 IPR, of which 6 were essential FA including arachidonate (r=0.76, P<0.0005), eicosapentaenoate (r=0.78, P<0.0005), and docosahexaenoate (r=0.86, P<0.0001). The PC IPR could not be explained by analysis of preadmission 7-d food records. After dividing the pairs into two groups differing and nondiffering according to fat intake of individuals in the pair, there was no evidence of a gene-environment interaction between fat intake and FA composition. The IPR for nonessential FA indicate that there is active genetic control of either food choices or postabsorptive metabolic processing. The high level of IPR in the PC fraction in contrast to the other lipid fractions suggests strong genetic influence over selection of specific FA for this membrane fraction independent of diet.     

Acylation of Ferrocene with Adamantoyl Chloride and Cinnamoyl Chloride

Liquid phase acylation of ferrocene with adamantoyl and cinnamoyl chloride was studied over different structural types of zeolites. The effect of the zeolite structure and acidity, and the influence of the reaction conditions on the ferrocene conversion and selectivity was investigated. The highest ferrocene conversions were achieved over zeolite Beta with Si/Al ratio 12.5 (cinnamoyl chloride 63.5%, adamantoyl chloride 45.9%). It was observed that with decreasing concentration of active sites in zeolite Beta the ferrocene conversion decreases. In addition, it was found that there is an optimum molar ratio of ferrocene to acylating agent, the ferrocene conversion increased with increasing temperature and amount of catalyst. The most important finding is that acylation of ferrocene with adamantoyl and cinnamoyl chloride leads exclusively to monoacylated products, most probably due to a deactivation of the cyclopentadiene rings after the attachment of the first acyl group.     

Synthesis and Evaluation of Novel Acyclic Nucleoside Phosphonates as Inhibitors of Plasmodium falciparum and Human 6‐Oxopurine Phosphoribosyltransferases

Acyclic nucleoside phosphonates (ANPs) are a promising class of antimalarial therapeutic drug leads that exhibit a wide variety of K_i values for Plasmodium falciparum (Pf) and human hypoxanthine‐guanine‐(xanthine) phosphoribosyltransferases [HG(X)PRTs]. A novel series of ANPs, analogues of previously reported 2‐(phosphonoethoxy)ethyl (PEE) and (R,S)‐3‐hydroxy‐2‐(phosphonomethoxy)propyl (HPMP) derivatives, were designed and synthesized to evaluate their ability to act as inhibitors of these enzymes and to extend our ongoing antimalarial structure–activity relationship studies. In this series, (S)‐3‐hydroxy‐2‐(phosphonoethoxy)propyl (HPEP), (S)‐2‐(phosphonomethoxy)propanoic acid (CPME), or (S)‐2‐(phosphonoethoxy)propanoic acid (CPEE) are the acyclic moieties. Of this group, (S)‐3‐hydroxy‐2‐(phosphonoethoxy)propylguanine (HPEPG) exhibits the highest potency for PfHGXPRT, with a K_i value of 0.1 μM and a K_i value for human HGPRT of 0.6 μM . The crystal structures of HPEPG and HPEPHx (where Hx=hypoxanthine) in complex with human HGPRT were obtained, showing specific interactions with active site residues. Prodrugs for the HPEP and CPEE analogues were synthesized and tested for in vitro antimalarial activity. The lowest IC₅₀ value (22 μM ) in a chloroquine‐resistant strain was observed for the bis‐amidate prodrug of HPEPG.     

Acylations with Long-Chain Acid Anhydrides and Acyl Chlorides over Zeolite Beta

Acylation of ferrocene and toluene with linear, branched and aromatic anhydrides and chlorides of different chain length was investigated over zeolite Beta with Si/Al ratio 12.5. It was found that the conversion of ferrocene increased from acetic to butyric anhydride/chloride and then decreased with further increasing of chain length. The selectivity to 1-acylferrocene was in all cases 100%. In the case of toluene acylation, the conversions of acylating agent increased with the chain length of acylating agent up to hexanoic derivatives then the conversion of acylating agent was almost constant. The selectivity to p-isomer in toluene acylation increased with the chain length. The lowest conversions in both cases were achieved with benzoic anhydride and benzoyl chloride.     

Quantitative fractographic analysis of impact fracture surfaces of steel R73

Macroscopic images of fracture surfaces of Charpy test specimens of steel R73 were studied, where bright spots in images represent cleavage facets or ductile dimples, respectively, both in special orientations. Within image analysis, they may be taken for the most significant textural element. Being the brightest patches in the image, they can be extracted by thresholding. Their counts and area distribution are closely related to temperature and impact energy. __________ Translated from Problemy Prochnosti, No. 1, pp. 77–80, January–February, 2008.