Composite Si-Ni nanoparticles produced by plasma spraying physical vapor deposition for negative electrode in Li-ion batteries.

Si-Ni composite nanoparticles have been produced by a single and continuous plasma spray physical vapor deposition (PS-PVD) from Si and Ni powder feedstocks and their electrochemical performances as anode in lithium-ion batteries (LiB) are investigated. Si nanoparticles with 20-40 nm on which Ni is directly attached with Si/NiSi2epitaxial interface are formed spontaneously through co-condensation of high temperature elemental gas mixtures during PS-PVD. When only a little amount of Ni is added to Si, the effect of the epitaxial Ni attachment on the Si nanoparticles becomes evident; the cycle capacity is appreciably improved to reach a 1.6 times higher capacity than that of the Si only cell after 50 cycles, due to reduced charge-transfer resistance and nanosized Si particle. In contrast, excessive Ni addition to Si feedstock leads to formation of various silicides as a result of the accelerated silicidation during PS-PVD, which results in a significant decrease in the cycle capacity due to reduction of the active Si phase amount despite reduced charge-transfer resistance.

Novel preventive treatment options.

A number of novel preventive treatment options which, as with traditional methods, can be differentiated into 3 categories of prevention (primary, secondary and tertiary), have been and are being currently investigated. Those reviewed are either commercially available or appear relatively close to that point. These include: approximal sealants; fluoride applications, including slow-release devices; measures to help remineralize demineralized tissue, including 3 different methods of delivering amorphous calcium phosphate; measures to help modify the biofilm to reduce the cariogenic challenge, including ozone therapy and probiotics; measures to increase enamel resistance to demineralization, including laser treatment of enamel, and a novel 'hybrid' technique for the treatment of primary molar caries which involves 'overlapping' of secondary and tertiary prevention--the Hall technique. Although many of these techniques show considerable promise and dentists should be aware of these developments and follow their progress, the evidence for each of these novel preventive treatment options is currently insufficient to make widespread recommendations. Changes in dental practice should be explored to see how oral health can be best supported through novel preventive systems. Further research is also required involving double-blind randomized controlled trials in order to bring further benefits of more effective caries control to patients. Implementation in practice should follow promptly as new techniques are shown to be clinically valuable for individual patients.

Protein adsorption at polymer-grafted surfaces: comparison between a mixture of saliva proteins and some well-defined model proteins.

Grafting a dense layer of soluble polymers onto a surface is a well-established method for controlling protein adsorption. In the present study, polyethylene oxide (PEO) layers of three different grafting densities were prepared, i.e. 10-15 nm2, 5.5 nm2 and 4 nm2 per polymer chain, respectively. The adsorption of different proteins on the PEO grafted surfaces was measured in real time by reflectometry. Furthermore, the change of the zeta-potential of such surfaces resulting from adsorption of the proteins was determined using the streaming potential method. Both the protein adsorption and the zeta-potential were monitored for 1 h after exposure of the protein solution to the surface. The adsorption pattern for a mixture of saliva proteins was compared to those observed for a number of well-defined model-proteins (lysozyme, human serum albumin, beta-lactoglobulin and ovalbumin). The results of the adsorption kinetics and streaming potential measurements indicate that the effect of the PEO layer on protein adsorption primarily depends on the size and the charge of the protein molecules. The saliva proteins are strongly blocked for adsorption, whereas the change in the zeta-potential is larger than for the other proteins (except lysozyme). It is concluded that positively charged protein molecules, having dimensions larger than those of lysozyme, are involved in the initial stage of adsorption from saliva onto a negatively charged surface.

Effects of Dissipation on Contact Angle Measurements Using a Dynamic Method.

The contribution of viscous friction, slippage, the Marangoni effect, and three-phase contact line resistance is considered in the explanation of contact angle measurements using a dynamic method. It is shown that the viscous friction of the liquid and the specific resistance of the three-phase contact line are the basic dissipative forces governing the rheology, while the slip on the solid-liquid interface is not important for this kind of experiment. Since the method is applied to protein solutions, it is demonstrated that the Marangoni effect of the proteins on the liquid-air surface plays an important role in the right juxtaposition of the theoretical and experimental results. Proper application of the theory allows calculation of both receding and equilibrium contact angles from the dropping time measurements as well as their dependence on the concentration of the protein solutions. Copyright 2001 Academic Press.

Measurements of the wettability of protein-covered hydroxyapatite surfaces.

We developed a new method (dropping time method, DTM) to investigate the wettability of a surface of a protein layer adsorbed on glass plates in aqueous solution. However, the previous setup of DTM can only be utilized for optically transparent materials. In this study, we have extended the method to optically nontransparent materials such as hydroxyapatite plates. DTM is based on measuring the dropping time of a liquid film along a protein-covered surface when this surface is instantaneously vertically removed from the protein solution. The intensity of the reflected light beam depends on the presence of a liquid film on the surface. This allows to estimate the movement of the liquid film along the sorbent surface. Thus, the extended DTM can be used for determining the wettability of optically nontransparent solid plates. The adsorption behavior of four proteins (albumin, lysozyme, beta-lactoglobulin, ovalbumin) on a hydrophobic hydroxyapatite plate in water was studied by this method. When adsorbed from a protein solution of high concentration, the surfaces of adsorbed proteins, except ovalbumin, were fairly hydrophilic; this hydrophilicity was already attained at the initial stage of the adsorption process. The surface of ovalbumin on hydroxyapatite was more hydrophobic than those of the other proteins, and the hydrophilicity increased with the protein adsorption process. At low protein concentration, the hydrophilicity increased in the course of the adsorption process. The change in hydrophilicity with time depends on the kind of protein. Hen's egg lysozyme is more hydrophilic and the time to reach saturation is shorter than for the other proteins. The processes of increasing hydrophilicity of the surface of human serum albumin, beta-lactoglobulin and ovalbumin are similar. However, for beta-lactoglobulin hydrophobicity at adsorption saturation is stronger than for human serum albumin and ovalbumin. Thus, using DTM it is shown that the hydrophilicity of the surface of adsorbed protein on hydroxyapatite depends strongly on the kind of protein.

Factor structures of the Zung Self-Rating Depression Scale (SDS) for undergraduates.

In order to categorize the items of the Zung Self-Rating Depression Scale (SDS) so as to allow the construction of subscales, the Japanese version of the SDS was administered to a total of 2,258 undergraduates. Principal-component analyses of the SDS extracted three factors interpretable as cognitive, affective, and somatic symptoms. The SDS was then administered to 597 undergraduates in order to cross-validate the factor structures. The coefficient of congruence and the goodness-of-fitness index generated by a confirmatory factor analysis showed good cross-validity of the factor structures.

A longitudinal study of the relationship between attributional style, life events, and depression in Japanese undergraduates.

A longitudinal design was used to investigate the relationship between attributional style, life events, and depression in Japanese undergraduates. The 1st hypothesis tested was that among those experiencing negative events, the students with a depressogenic attributional style would be more depressed than those with a nondepressogenic attributional style. The 2nd hypothesis tested was that among those experiencing positive events, the students with an enhancing attributional style would be less depressed than those with a nonenhancing attributional style. A total of 143 undergraduates responded to a depression scale, a life event questionnaire, and an attributional style questionnaire. The results, which generally supported the hypotheses, may reflect cultural differences between Japan and the United States.

Compatibility and stability of ranitidine hydrochloride with six cephalosporins during simulated y-site administration.

The purpose of this project was to determine the visual compatibility and stability of ranitidine hydrochloride in admixtures during simulated Y-site administration with six individual cephalosporins: ceftizoxime sodium, cefuzonam sodium, cefoperazone sodium, cefmenoxime hydrochloride, moxalactam disodium and flomoxef sodium. Dilutions of ranitidine hydrochloride 1 mg (as the free base)/mL were prepared in 0.9% sodium chloride injection. Two milliliters of the ranitidine solution (1mg/mL) was mixed with 2mL of each cephalosporin (20 mg/ml) in 10 mL glass test tubes. Concentrations of each drug were determined by stability-indicationg high-performance liquid chromatographic assay methods following zero, one, two, and four hours after mixing. All six cephalosporins retained greater than 95% of their original concentrations for four hours in the admixture with ranitidine. Ranitidine retained greater than 95% of its original concentration for four hours in the admixture with four of the tested cephalosporins and apporximately 90% with moxalactam and flomoxef. Solutions containing ranitidine may be coadministered with solutions either ceftizoxime, cefuzonam, cefoperazone or cefmenoxime via Y-injection site over four hours. While the ranitidine concentration may be reduced to near 90% after four hours with moxalactam and flomoxef, the tested antibiotics were not affected in the presence of ranitidine over four hours.

The crystal structure of the nucleotide-free alpha 3 beta 3 subcomplex of F1-ATPase from the thermophilic Bacillus PS3 is a symmetric trimer.

BACKGROUND: F1-ATPase, an oligomeric assembly with subunit stoichiometry alpha 3 beta 3 gamma delta epsilon, is the catalytic component of the ATP synthase complex, which plays a central role in energy transduction in bacteria, chloroplasts and mitochondria. The crystal structure of bovine mitochondrial F1-ATPase displays a marked asymmetry in the conformation and nucleotide content of the catalytic beta subunits. The alpha 3 beta 3 subcomplex of F1-ATPase has been assembled from subunits of the moderately thermophilic Bacillus PS3 made in Escherichia coli, and the subcomplex is active but does not show the catalytic cooperativity of intact F1-ATPase. The structure of this subcomplex should provide new information on the conformational variability of F1-ATPase and may provide insights into the unusual catalytic mechanism employed by this enzyme. RESULTS: The crystal structure of the nucleotide-free bacterial alpha 3 beta 3 subcomplex of F1-ATPase, determined at 3.2 A resolution, shows that the oligomer has exact threefold symmetry. The bacterial beta subunits adopt a conformation essentially identical to that of the nucleotide-free beta subunit in mitochondrial F1-ATPase; the alpha subunits have similar conformations in both structures. CONCLUSIONS: The structures of the bacterial F1-ATPase alpha and beta subunits are very similar to their counterparts in the mitochondrial enzyme, suggesting a common catalytic mechanism. The study presented here allows an analysis of the different conformations adopted by the alpha and beta subunits and may ultimately further our understanding of this mechanism.

Influence of fluoride applications on some physicochemical surface properties of synthetic hydroxyapatite and human dental enamel and its consequences for protein adsorption.

Synthetic hydroxyapatite and human dental enamel (polished and non-polished) were subjected to various fluoride applications, i.e., using solutions of sodium fluoride (NaF), acidulated phosphate fluoride (APF), and stannous fluoride (SnF2). Treatment with APF has a strong influence on the morphology of the apatite. All fluorides, in particular SnF2, make the enamel surfaces more hydrophobic. NaF and APF applications slightly alter the electrokinetic potentials of the surfaces, but SnF2 renders them much more negatively charged. The adsorption of the proteins lysozyme and alpha-lactalbumin on these surfaces can be explained in terms of electrostatic and hydrophobic interactions between the proteins and the sorbent surfaces.

Ca(2+)- and Sr(2+)-sensitive ATPase activity of slow skeletal myofibrils in comparison with fast skeletal and cardiac myofibrils.

Ca(2+)- and Sr(2+)-sensitive ATPase of myofibrillar preparations from slow skeletal (chicken anterior latissimus dorsi), fast skeletal (chicken breast) and porcine cardiac ventricular muscles was investigated. Sr2+ at concentrations about 6 times higher than Ca2+ was required for activating the ATPase of slow skeletal or cardiac myofibrils, while Sr2+ about 30 times higher than Ca2+ was required for activating fast skeletal myofibrils. The cooperativity of activation of slow skeletal myofibrils was almost the same as that of cardiac myofibrils, but lower than that of fast skeletal myofibrils. Sr2+/Ca2+ sensitivity ratio of the desensitized (troponin-tropomyosin-depleted) fast skeletal myofibrils reconstituted with troponin-tropomyosin from slow skeletal, fast skeletal, and cardiac muscles were 13, 34, and 5, respectively. The troponin C-depleted fast skeletal myofibrils showed the same Sr2+/Ca2+ sensitivity ratio and the same cooperativity of activation as those of the intact fast skeletal myofibrils when reconstituted with fast skeletal troponin C, and as those of the intact slow skeletal myofibrils when reconstituted with slow skeletal troponin C.

Replacement of troponin components in myofibrils.

The Ca(2+)-sensitive ATPase activity of rabbit skeletal myofibrils was desensitized by treatment with excess troponin T and was found to be activated irrespective of the Ca2+ concentrations. A SDS-gel electrophoretic study showed that both troponin C and troponin I were removed from the myofibrils on treatment with troponin T. The Ca(2+)- and Sr(2+)- sensitivities of the ATPase of troponin T-treated myofibrils reconstituted with troponin C. I were the same as in the intact myofibrils. The Ca(2+)-activated ATPase of rabbit skeletal myofibrils was also desensitized on treatment with chicken breast troponin T or its 26K fragment. The SDS-gel electrophoretic study revealed that troponin T, in addition to troponin C and troponin I, was also removed from the myofibrils and, instead, chicken breast troponin T or its 26K fragment was incorporated into the myofibrils. The Ca(2+)- sensitivity of myofibrils treated with chicken breast troponin T or its 26K fragment was then regained on reconstitution with troponin C.I. These findings indicate that the change in composition of myofibrils on treatment with troponin T or its 26K fragment is due to the selective replacement of the troponin C.I.T complex in the myofibrils as a whole with troponin T or its 26K fragment.

Zeta potential of oral bacteria (Streptococci).

This study was carried out to examine whether oral bacteria can be treated electrochemically in the same manner as colloid particles. The zeta potentials for 13 Streptococcus strains incubated in trypticase soy broth (TSBY) and heart infusion broth (HIB) were determined in 1/30 M phosphate buffer solution of pH 7.0 by standard microelectrophoresis. The zeta potentials for the Streptococci showed a wide range of values from -28.7 mV to -2.1 mV in TSBY and from -28.5 mV +2.0 mV in HIB. The zeta potential was useful in determining the potential structure of the bacterial cell as living colloid, especially Streptococcus.

Increased remineralization of subsurface enamel lesions with molybdenum treatment.

The present study was conducted to determine the effect of high molybdenum (Mo) concentration on fluoride (F) uptake and remineralization of subsurface lesions utilizing acid cyclic methods in vitro. Bovine enamel with artificial subsurface lesions were treated with test solutions containing 1,000 ppm F (NaF) with and without 1,000 ppm Mo at pH 7.0. F uptake was analyzed using a microdrilling technique and remineralization was evaluated by polarized light microscopy. The results indicate that addition of 1,000 ppm Mo in a 1,000 ppm F solution modestly increases F uptake and promotes remineralization of subsurface lesions compared with 1,000 ppm F alone. These findings suggest that a high level of Mo may enhance the remineralizing activity of F in subsurface bovine enamel lesions in vitro.

An electrochemical study on the human dental enamel with special reference to isoelectric point.

In an attempt to make a dynamic study of the isoelectric point and the chargeability of human dental enamel, an electrochemical approach was utilized. Zeta potential of three kinds of the enamel was measured by a streaming potential method. As a result, these isoelectric points could be decided.