Temperature measurement in a solid body heated by laser beam

A new technique, call the PVD film method, was developed for measuring the temperature inside a solid body. This technique involves physically depositing thin films on the specimen’s surface to act as thermal sensors. The solid body was quickly heated with laser irradiation and the proposed technique was used to measure the internal temperature. The experimentally determined isotherm configurations were then compared with those calculated using FEM analysis, and the analytical and experimental results coincided well. This suggests that the proposed method could prove useful in measuring the temperature of a solid body in a quasi-steady state, such as the tool and workpiece in machining processes.     

Site-directed mutagenesis of active site contact residues in a hydrolytic abzyme: evidence for an essential histidine involved in transition state stabilization

Specific molecular interactions involved in catalysis by antibody 6D9 were investigated by site-directed mutagenesis. The catalytic antibody 6D9, which was generated against a transition state analog (III), hydrolyzes a non-bioactive chloramphenicol monoester derivative (I) to produce chloramphenicol (II). Construction of a three-dimensional molecular model of 6D9 and sequence comparison within a panel of related antibodies suggested candidates for catalytic residues, His (L27d), Tyr (L32), Tyr (H58) and Arg (H100b); these were targeted for the site-directed mutagenesis study. The Y-H58-F and R-H100b-A mutants possessed catalytic activities comparable to that of the wild-type, and the Y-H58-H and Y-L32-F mutant displayed an approximately fivefold decrease in k(cat)/Km. In the transition state analysis, the plots of logK(TSA) versus log(k(cat)/Km) for the mutants are linear, with a slope of approximately 1.0, indicating that the entire hapten-binding energy in the mutants is also utilized to bind the transition state and to accelerate the catalysis. In addition, a dramatic change in the catalytic activity was observed when the histidine residue (27d) in the CDR1 light chain was replaced with alanine. The H-L27d-A mutant had no detectable catalytic activity. This mutation led to a large, 40-fold reduction in transition state binding, with no change in substrate binding. Coupled with the previous kinetic studies and chemical modifications of the intact 6D9 antibody, this mutagenesis study has demonstrated that His L27d plays an essential role in stabilization of the transition state, the mechanism of catalysis by the 6D9 antibody.     

Permeation of solutes through chemically modified chitosan membranes

Chemically and mechanically stable chitosan and N-acylchitosan were prepared. N-Octanoylchitosan gives the pronounced decrease of water content, whereas N-benzoylchitosan keeps a higher content of water. The equilibrium sorption of various sodium salts was determined and is explained by a dual mechanism, consisting of partition and Langmuir sorption. The characteristics of the membrances and the size of the salt anions clearly influence permeability as well as sorption. Permeation behavior was interpreted by the Teorell-Meyer-Sievers (TMS) theorem. The mobility of anions decreases with Stokes radius, decreasing in the order chitosan > N-benzoylchitosan > N-octanoylchitosan, indicating the effect of the polymer chain molecules, especially a steric obstruction effect on the ion transportation through the membranes. The introduction of the N-acylated hydrophobic group to the charged chitosan membranes appears to enhance permselectivity. © 1995 John Wiley & Sons, Inc.     

Modal refractive index of 1.3 μm InGaAsP, AlGaInAs and GaInNAssemiconductor lasers under high hydrostatic pressure

The accurate experimental determination of the modal refractive index of 1.3 μm InGaAsP, AlGaInAs and GaInNAs multiple quantum-well lasers by measuring the longitudinal mode separation up to a pressure of 15 kbar is reported for the first time. A small increase of the indices is observed for the three materials with increasing pressure, which causes a decrease of lasing wavelength     

Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus

The modes of Mg2+ binding to SMase from Bacillus cereus were studied on the basis of the changes in the tryptophyl fluorescence intensity. This enzyme was shown to possess at least two binding sites for Mg2+ with low and high affinities. The effects of Mg2+ binding on the enzymatic activity and structural stability of the enzyme molecule were also studied. The results indicated that the binding of Mg2+ to the low-affinity site was essential for the catalysis, but was independent of the substrate binding to the enzyme. It was also indicated that the alkaline denaturation of the enzyme was partly prevented by the Mg2+ binding, whereas no significant protective effect was observed against the denaturation by urea. The pH dependence of the kinetic parameters for the hydrolysis of micellar HNP and mixed micellar SM with Triton X-100 (1:10), catalyzed by SMase from B. cereus, was studied in the presence of a large amount of Mg2+ to saturate both the low- and high-affinity sites. The pH dependence curves of the logarithm of 1/Km for these two kinds of substrates were similar in shape to each other, and showed a single transition. On the other hand, the shapes of the pH dependence curves of the logarithm of kcat for these two kinds of substrates were different from each other. The pH dependence curve for micellar HNP showed three transitions and, counting from the acidic end of the pH region, the first and third transitions having tangent lines with slopes of +1 and -1, respectively. On the other hand, the curve for mixed micellar SM with Triton X-100 showed one large transition with a slope of +1 (the first transition) and a very small transition (the third transition). On the basis of the present results and the three-dimensional structure of bovine pancreatic DNase I, which has a primary structure similar to that of B. cereus SMase, we proposed a catalytic mechanism for B. cereus SMase based on general-base catalysis.     

Donor passivation in n-AllnAs layers by fluorine

The mechanism of thermal degradation of both the carrier concentration and mobility in AlInAs layers due to thermally diffused fluorine is discussed. The thermal degradation occurs only in n-type AlInAs layers at temperatures as low as 350°C. In contrast, a similar thermal degradation was never observed for AlInAs containing only acceptor impurities. This phenomenon is explained by the reaction of fluorine atoms with exclusive donor impurities, which forms an ionized fluorine (anion: F⁻) and results in a reduction in carrier concentration. The created F⁻ ions form a scattering center which leads to a reduction in carrier mobility. Experimental data support that fluorine atoms are of environmental origin and not incorporated during the growth of layers. From further compre-hensive annealing studies for several kinds of (AlGaIn)As material systems, it is found that this donor passivation behavior is peculiar to those compounds which contain both AlAs and InAs.     

Oligo-2',5'-adenylate synthetase in pulmonary sarcoidosis and idiopathic pulmonary fibrosis

Oligo-2',5'-adenylate synthetase (2,5AS) is an enzyme induced by all types of interferon (IFN). We measured the levels of 2,5AS activity in peripheral blood mononuclear leukocytes (PBML) and bronchoalveolar lavage fluid (BALF) cells of patients with pulmonary sarcoidosis (SAR), idiopathic pulmonary fibrosis (IPF), and normal controls (NC). In NC, the levels of BALF cell 2,5AS activity were approximately seven times as high as the levels of PBML 2,5AS activity. The measurement 2,5AS activity from isolated cells showed that the levels of 2,5AS activity are independent of cell differential from PBML and BALF cells. The levels of PBML and BALF cell 2,5AS activity in SAR were both significantly high in comparison with those in NC. In patients with IPF, the levels of PBML 2,5AS activity were significantly increased as compared with those in NC, whereas there was no significant difference regarding the levels of BALF cell 2,5AS activity between patients with IPF and NC. These results suggest the following: (1) in patients with SAR, IFN production is enhanced both in the alveolar space and peripheral circulation; (2) in patients with IPF, IFN production is greatly enhanced in the circulation, whereas IFN production is not enhanced in the alveolar space; and (3) IFN may contribute to the pathogenesis of SAR and IPF.     

Pial arteriovenous malformation with massive perinidal edema

The dental, clinical, radiological, pedigree and dermatoglyphic findings of a patient showing hypoplasia of enamel and intrinsic staining of the teeth from erythroblastosis fetalis are presented.