The crystal structure of the sevenfold mutant of barley beta-amylase with increased thermostability at 2.5 A resolution

The three-dimensional structure of the sevenfold mutant of barley beta-amylase (BBA-7s) with increased thermostability was determined by X-ray crystallography. The enzyme was purified as a single component and crystallized by a hanging drop method in the presence of 14 % PEG 6000. The crystals belong to space group P43212 with cell dimensions a=b=72.11 A, c=250.51 A. The diffraction data up to 2.5 A were collected after soaking the crystal in 100 mM maltose with Rsym of 8.6 %. The structure was determined by a molecular replacement method using soybean beta-amylase (SBA) as a search model and refined to an R-factor of 18.7 %. The final model included 500 amino acid residues, 141 water molecules and three glucose residues, which were located at subsites 1-2 and 4 in the active site. The r.m.s. distance of 485 Calpha atoms between BBA-7s and SBA was 0.62 A. Out of the seven mutated amino acids, four (Ser295Ala, Ile297Val, Ser351Pro and Ala376Ser) were substitutions from the common residues with SBA to the thermostable forms. A comparison of the structures of BBA-7s and SBA indicated that the side-chain of Ser376 makes new hydrogen bonds to the main-chain of an adjacent beta-strand, and that the side-chains of Val297 reduce an unfavorable interaction between the side-chains of Ala314. The mutation of Ser295Ala breaks the hydrogen bond between Ser295 OG and Tyr195 OH, which seems to be the reason for the unoccupied glucose residue at subsite 3. The tandem mutations at 350-352 including substitutions to two Pro residues suggested the reduction of main-chain entropy in the unfolded structure of this solvent-exposed protruded loop.     

Behavior of oxides in the liquid stainless steel

For a super clean steel, the oxygen content should be restricted to a very low level, and controlled during the melt state. The oxide behavior in an Al killed stainless steel melt were observed by analysing the forces exerted. New parameter, homogenization number (H number), was introduced to generalize the forces. Quantitative analysis of the removal of oxides was conducted, and a homogenization number was used to predict whether the oxides would be separated from the melt or mixed with the melt. It was also shown that the H number could possibly be used to estimate the capacity of oxide-absorption at the top slag.     

A multicarrier CDMA system with adaptive subchannel allocation forforward links

Multicarrier transmission schemes have been introduced into code-division multiple access (CDMA) systems to gain advantages for high data rate transmission. One of the methods is to transmit identical narrowband direct-sequence (DS) waveforms in parallel over a number of subchannels using frequency diversity. In this paper, we propose a multicarrier CDMA system with an adaptive subchannel allocation method for forward links. In the proposed system, instead of identical DS waveforms being transmitted over a number of subchannels in parallel, each user's DS waveform is transmitted over the user's favourite subchannel which has the largest fading amplitude among all the subchannels. We analyze the performance characteristics of the system when orthogonal and random signature sequences are used. The proposed system is shown to have performance gain over the conventional multicarrier CDMA system. We also investigate how the performance is influenced when the signal is not perfectly allocated into the best subchannel     

Resistivity variation of semi-insulating Cd1−xZnx Te in relationship to alloy composition

We investigated the resistivity variation of semi-insulating Cd_1−xZn_xTe used as room temperature nuclear radiation detectors, in relationship to the alloy composition. The resistivity and the zinc composition were determined using leakage current measurements and triple axis x-ray diffraction lattice parameter measurements, respectively. While the zinc content of the nominally x_Zn∼0.1 ingot varied monotonically according to the normal freezing behavior with an effective segregation coefficient of k_eff=1.15, the resistivity was found to vary non-systematically throughout the ingot. Furthermore, the “expected” relationship of higher zinc content with higher resistivity was not always observed. For example, wafer regions of x_Zn∼0.12 and x_Zn∼0.08 exhibited resistivity values of ∼10¹⁰ and ∼10¹¹ Ω·cm, respectively. In general, the experimental resistivity values can be explained by calculated values which take into account a compensating deep level defect and various electron and hole mobility values. The relative influence of the parameters that govern the resistivity (n,p, μ_e, and μ_h) are quantitatively investigated.     

Properties and interaction of cement with polymer in the hardened cement pastes added absorbent polymer

Ordinary Portland cement mixed with various amounts of absorbent polymer in the form of sodium acrylate ((–CH–)_nCOONa) have been studied. As the content of absorbent polymer increased, heat evolution of samples decreased up to 1.15 wt % of absorbent polymer addition and conversely increased over 1.75 wt %. Flexural strength of cement paste with absorbent polymer was improved more than 20%. As the content of absorbent polymer increased, the porosity values decreased and mean pore diameter shifted to small pore diameter region. Flexural strength of ordinary Portland cement paste had a linear correlation with non-evaporable water content but, that of cement paste with absorbent polymer deviated from a linear correlation with non-evaporable water content. The chemical difference between cement pastes with and without absorbent polymer was found by the inductively coupled plasma-atomic emission spectroscopy and the infrared spectroscopy. For the infrared spectra of absorbent polymer, bands at 1416 and 1560 cm^{– 1} were assigned to C–O single bond and C=O double bond respectively, namely, unidentate complex. As the curing time increased, the absorption bands near 1416 cm^{– 1} shifted to longer wave number and the absorption bands near 1560 cm^{– 1} to shorter wave number and finally bidentate complex was formed. Absorbent polymer released sodium ions to pore solution under the basic condition of pH 12.5–13.5 and became polyacrylic acid. Then some of these polyacrylic acid were crosslinked with others by calcium ions leached from cement grains. Calcium ion was regarded as a central charge connecting the negative parts in carbon-oxygen polarization of absorbent polymer' functional groups.     

An iteration method for directly determining J-Resistance curves of nuclear structural steels

An iteration method has been developed for determining crack growth and fracture resistance curves (J-R curves) of nuclear structural steels from the load versus load-line displacement record only. In this method, the hardening curve, the load versus displacement curve at a given crack length, is assumed to be a power-law function, where the exponent varies with the crack length. The exponent is determined by an iterative calculation method with the assumption that the exponent varies linearly with the load-line displacement. The proposed method was applied to the static J-R tests using compact tension (CT) specimens, a three-point bend (TPB) specimen, and a cracked round bar (CRB) specimen as well as it was applied to the quasi-dynamic J-R tests using CT specimens. The J-R curves determined by the proposed method were compared with those obtained by the conventional testing methodologies. The results showed that the J-R curves could be determined directly by the proposed iteration method with sufficient accuracy in the specimens from SA508 and SA516 pressure vessel steels and their welds and SA312 stainless steel.     

Electrical properties of silane crosslinked polyethylene incomparison with DCP crosslinked polyethylene

The electrical properties such as water tree length, electrical conduction, ac breakdown strength and space charge of silane crosslinked polyethylene (SXLPE) were investigated, with a purpose to compare this material with ordinary dicumyl peroxide (DCP) crosslinked polyethylene (XLPE). Experimental results show that SXLPE has a smaller water tree length, much lower conduction current density, a little bit higher ac breakdown strength than XLPE, and on SXLPE only a very small homocharge is seen. The better behaviour of SXLPE under electric stress is attributed to the absence of residual curing byproducts present in XLPE and the change of chemical structure by grafting and curing reactions     

A short-term,hydroponic-culture of ginseng results in a significant increase in the anti-oxidative activity and bioactive components

Food Science and Biotechnology - Panax ginseng CA Meyer has a variety of biological effects, including antioxidant and antidiabetic activities. Ginseng requires long-term cultivation, but this can...     

Anti-inflammatory and in vitro bone formation effects of Garcinia mangostana L. and propolis extracts

Food Science and Biotechnology - The purpose of this study was to determine the anti-inflammatory and in vitro bone formation effects of Garcinia mangostana L. (mangosteen) and propolis extracts....