Taxotere in various solid tumors]

One of the delicate problems in a cancer treatment is the acquisition of a tolerance for a medicine. Antiandrogen treatment is valid in treatment of prostate cancer, but the disease develops into hormone-refractory prostate cancer after a uniformity period. The molecular mechanisms of recurrence and endocrine therapy failure in prostate cancer have remained unclear. In this paper we discuss the hormone-refractory prostate cancer that has been reported by many investigators.     

Thermal stability and cross-linking studies of diisocyanate cured solar absorptance low-emittance paint coatings prepared via coil-coating process

Thickness-sensitive spectrally-selective (TSSS) paint coatings were prepared by using FeMnCuO_x pigment in combinations with phenoxy and silicone resins. The spectral selectivity expressed as a ratio between solar absorptance (a_s) and thermal emittance (e_T) was 0.92/0.14 for the first and 0.87/0.18 for the second type of the paint. The surface of phenoxy resin based coatings is characterized by pigment particles protruding from the surface, while silicone based paints exhibit a much smoother surface. Abrasion resistance and adhesion of both types of coatings were enhanced by cross linking the resin binder with diisocyanate hardener. Cured coatings withstand temperatures up to 135°C. Cross-linking and degradation mechanisms of both types of coatings were studied by using FT-IR spectroscopy and thermogravimetric measurements, cycling and ageing tests.     

Commercial production of rare earth metals by fused salt electrolysis

The commercial production of rare earth metals by fused salt electrolytic methods is described. These methods are used to make mischmetal, cerium, lanthanum, and didymium (Nd + Pr). The feed materials consist essentially of anhydrous chlorides of the metal to be produced, augmented by additions of nonrare earth salts to yield an electrolyte with satisfactory properties for reduction. The rare earths are derived either from monazite or from bastnasite ores. The anhydrous chlorides are manufactured from the hydrated chlorides by methods which minimize oxidation or hydrolysis. Alternatively, anhydrous chlorides may be used which result from the direct chlorination of rare earth ores by the Gold-schmidt process. These are particularly suitable for electrolysis due to their very low oxychloride content. Fluorides and oxides of the rare earths are produced by wet chemical methods to provide the relatively small quantities of these compounds now used for commercial fused salt electrolysis. Reduction cells in use today are constructed mainly from a) ceramics, b) graphite, or c) iron. The advantages and disadvantages of these types of cells are described together with the typical products which result from their use. Primary attention is given to production of mischmetal (mixed rare earth metal), which is the rare earth metal produced on the largest scale today. Brief reference is made also to production of cerium, lanthanum, and didymium (Nd + Pr) metal. Finally, a resume of the current uses of these metals is presented with reference to recent trends in the industrial applications of the rare earth metals.     

Investigation of a KcsA Cytoplasmic pH Gate in Lipoprotein Nanodiscs

The bacterial potassium channel KcsA is gated by pH, opening for conduction under acidic conditions. Molecular determinants responsible for this effect have been identified at the extracellular selectivity filter, at the membrane–cytoplasm interface (TM2 gate), and in the cytoplasmic C-terminal domain (CTD), an amphiphilic four-helix bundle mediated by hydrophobic and electrostatic interactions. Here we have employed NMR and EPR to provide a structural view of the pH-induced open-to-closed CTD transition. KcsA was embedded in lipoprotein nanodiscs (LPNs), selectively methyl-protonated at Leu/Val residues to allow observation of both states by NMR, and spin-labeled for the purposes of EPR studies. We observed a pHinduced structural change between an associated structured CTD at neutral pH and a dissociated flexible CTD at acidic pH, with a transition in the 5.0–5.5 range, consistent with a stabilization of the CTD by channel architecture. A double mutant constitutively open at the TM2 gate exhibited reduced stability of associated CTD, as indicated by weaker spin–spin interactions, a shift to higher transition pH values, and a tenfold reduction in the population of the associated “closed” channels. We extended these findings for isolated CTD-derived peptides to full-length KcsA and have established a contribution of the CTD to KcsA pH-controlled gating, which exhibits a strong correlation with the state of the proximal TM2 gate.     

An alternating magnetic field in a conducting composite with magnetic fibers

The distribution of an ac magnetic field in a conducting fiber composite of a finite length with components differing in their magnetic and electrical properties has been found. The geometry of the skin layer has been determined, and the degree of homogeneity of the magnetic field in samples representing a system of fibers regularly arranged in the matrix has been evaluated. The specific features of the distribution of the magnetic field and eddy currents caused by the presence of interfaces between unlike materials, magnetic properties, dimensions, and the mutual location of inclusions have been analyzed.     

Structural studies of sol–gel urea/polydimethylsiloxane barrier coatings and improvement of their corrosion inhibition by addition of various alkoxysilanes

A sol–gel organic–inorganic hybrid precursor, bis[(ureapropyl)triethoxysilane]bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU, for short), was tested as a corrosion barrier coating for AA 2024 aluminium alloy. The PDMSU coatings were prepared in either ethanol (PDMSU/EtOH) or propanol (PDMSU/PrOH) solvents. XRD measurements of xerogels showed the diffraction peak of amorphous silica domains at 21.5° and a broad peak at approximately 12.2°, which could be associated with the presence of the polyhedral silsesquioxane structural units (T² and T³) determined in our previous investigations from the ²⁹Si NMR spectra. The structure of thin coatings on AA 2024 prepared by heat-treatment at 140 °C was studied with the surface-sensitive IR reflection–absorption (IR RA) spectroscopic technique. Results revealed that in both coatings the poly(dimethylsiloxane) (PDMS) chain segments were projecting from the metal surface, however, this effect was more pronounced for the PDMSU/PrOH than for the PDMSU/EtOH coatings. Information gathered from the structural studies (IR, IR RA, ²⁹Si NMR and XRD) enabled some correlations to be drawn between the coatings’ structure and the effectiveness of the corrosion inhibition, which was assessed from the potentiodynamic and salt-spray measurements. Results showed the improved corrosion inhibition of PDMSU/PrOH coatings attributed to their denser and more compact sol–gel network and also to their higher hydrophobicity, i.e. lower surface energy determined from the contact angle measurements. Addition of various tetraalkoxysilanes and alkyltriethoxysilanes further improved the corrosion inhibition of PDMSU coatings due to more extensive cross-linking. The salt-spray tests showed that tetraethoxysilane and phenyltriethoxysilane were the most effective additives.     

Characterisation of high-temperature-resistant spectrally selective paints for solar absorbers

The spectrally selective paint coatings were prepared from organically modified siloxane resin and inorganic pigment (FeMnCuO_x-P320). To optimise the low-emittance properties, different thicknesses of paints were applied on high-reflecting Al foil by a draw bar coater. For all paints, optical and thermal properties were determined as well as their adhesion resistance. Pigment to volume concentration ratio was 20% and for thicknesses of about 1.7–2.0 g/m², the solar absorptance for these samples were a_s=0.90–0.92 with corresponding thermal emittance of e_T=0.20–0.25. Temperature stability of these samples was followed by FT-IR spectroscopy at 300°C. The obtained results indicated good temperature stability of prepared paint coatings.     

An adenosine deaminase (ADA) allele contains two newly identified deleterious mutations (Y97C and L106V) that interact to abolish enzyme activity

Genetic deficiency of the purine salvage enzyme adenosine deaminase (ADA) results in varying degrees of immunodeficiency, ranging from neonatal onset Severe Combined Immunodeficiency (SCID) to an adult onset immunodeficiency disorder. Multiple different mutations have now been identified in these immunodeficient patients. Additional mutations, initially identified in healthy individuals, abolish ADA in erythrocytes but retain 10-80% of activity in non-erythroid cells ('partial deficiency mutations'). In general, severity of disease correlates inversely with the amount of residual ADA expressed by the mutant enzymes and directly with the accumulation of the toxic metabolites deoxyATP and deoxyadenosine. We report two newly identified mutations (Y97C and L106V), both carried on the same allele of an immunodeficient patient who was diagnosed prenatally and successfully transplanted with haploidentical bone marrow. Based on the ability of mutant cDNAs to express ADA in vitro , the L106V mutation resulted in activity similar to 'partial' mutations (30% of normal) while the Y97C mutation resulted in detectable but markedly reduced activity (1.5% of normal). However, the presence of both mutations on the same allele virtually abolished detectable enzyme activity. Analysis of the crystallographic structure of ADA to understand the marked deleterious effect of the Y97C mutation suggested a previously unappreciated role of salt bridges in the catalytic mechanism of ADA. The patient was also heteroallelic for a previously described deletion of the promoter and exon 1. Testing of additional patients in whom we had not identified a mutation on the second allele revealed presence of this deletion in three of four patients tested. This deletion is therefore relatively common, accounting for 10% of almost 100 chromosomes studied by this and other laboratories, but is easily missed by currently used methods of mutation detection. Lastly, the finding of two mutations on the same allele that interact to reduce residual enzyme function emphasizes hazards in evaluating potential genotype-phenotype correlations in individuals analyzed only for the presence of single specific mutations.     

Spectrally selective solar absorbers in different non-black colours

Silicon paints were prepared from yellow, ochre, dark ochre, green and blue pigments. To improve the solar absorptance, a_s, of these coatings, an existing black paint was admixed in different ratios. The optical properties of the mixed paints thus formed are expressed in terms of the Kubelka–Munk absorption and scattering coefficients in the spectral region 400–17000 nm. The scattering coefficient obtained for all paints was essentially equal. In the visible region the absorption coefficient follows the spectral characteristics of each respective colour. In the infrared absorption at 9000 nm and above 12000 nm are seen in all cases which result in a thickness-dependent increase of the thermal emittance, e_T, of the coating. The metric chroma (C_ab^*) and lightness (L^*) in CIELAB colour space were calculated for wide-angle observer in average daylight conditions. A range of non-black spectrally selective solar absorber surfaces with a_s>0.8 and e_T<0.3 have been prepared with L^*<45 and C_ab^*<10.