Effect of Processing Parameters on the Mechanical and Microstructural Behavior of Ultra-Fine Al2O3– (ZrO2+8%Mol Y2O3) Bioceramic, Densified By High-Frequency Induction Heat Sintering

High-frequency induction heat sintering (HFIHS) is a comparatively new technique that consolidates metals and ceramics very rapidly to full density. In this work, superfast densification behavior and the attendant microstructural features of Al₂O₃–(ZrO₂+8% mol Y₂O₃) composites processed by HFIHS were investigated. The effects of processing parameters such as sintering temperatures, pressures, and heating rate, on the mechanical and microstructural properties were studied. The results indicated that HFIHS was effective in the preparation of fine-grained, nearly fully dense Al₂O₃–8YSZ ceramics from the powder with a smaller particle size by optimizing the overall processing parameters.     

Chemical Factors Affecting Preparation of Carboxymethyl Starch

Preparation of carboxymethyl starch using chloroacetic acid and sodium hydroxide was investigated under different conditions. The carboxymethylation reaction was studied with respect to the degree of substitution (D. S.) of the carboxymethyl starch and the reaction efficiency (R. E.) of carboxymethylation variables studied included concentration of reactants and liquor ratio as well as reaction time and temperature. D. S. and R. E. were greatly enhanced by decreasing the liquor ratio. D. S. and R. E. increased also by increasing the reaction time. On the other hand, increasing the monochloroacetic acid concentration was accompanied by enhancement in the D. S. and decrement in the R. E., while both the D. S. and R. E. exhibited maximum values at 4N sodium hydroxide. The combined effect of increasing both monochloroacetic acid and sodium hydroxide concentrations was to bring about increased D. S. and decreased R. E. irrespective of the reaction temperature. Of particular interest were the results obtained at 100°C for 1 h; carboxymethyl starch of D. S. 0.436 with R. E. of ca. 79% could be achieved using solid reactants/liquor ratio of 1: 1.     

Anti‐Oxygen Leaking LiCoO2

LiCoO₂ is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from Li_xCoO₂ particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of Li_xCoO₂. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O₂ formation more effectively due to the strong C? O_cathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.     

On the reliability of a number of s-p reducible graphs

Let G=(V,E) be a graph whose edges may fail with known probabilities and let K a subset of V be specified. The overall reliability of G, denoted by R(G), is the probability that all vertices in K=V communicate with each other. We have two types of graphs, s-p reducible and s-p complex, depending on whether after series-arallel reductions the result is a single edge or not. A number of s-p reducible graphs are presented and expressions that evaluate their overall reliability are introduced.     

SRAM dynamic stability estimation using MPFP and its applications

In this paper, an accurate approach for estimating the dynamic stability of static random access memory (SRAM) is proposed. The conventional methods of SRAM stability estimation suffer from two major drawbacks: (1) using static failure criteria, such as SNM, which does not capture the transient and dynamic behavior of SRAM operation, and (2) using quasi-Monte-Carlo simulation, which approximates the failure distribution, resulting in large errors at the tails where the desired failure probabilities exist. These drawbacks are eliminated by employing accurate simulation-based dynamic failure criteria along with a new distribution-independent, Most-probable-failure-point search technique for accurate probability calculation. Compared to previously published techniques, the proposed dynamic stability technique offers orders of magnitude improvement in accuracy. Furthermore, the proposed dynamic stability technique enables the correct evaluation of stability in real operation conditions and for different dynamic circuit techniques, such as dynamic write back, where the conventional methods are not applicable.     

Isolation and analysis of macromolecular fractions responsible for the surface properties in native Champagne wines

Macromolecules present in Champagne wines from the three grape varieties Pinot Noir, Meunier and Chardonnay, were isolated by ultra-concentration on 10 K molecular weight cut-off (MWCO) membranes, then purified by dia-filtration and freeze-dried. Measurements of the surface activity of reconstituted wines from the resulting dry ultra-concentrates by ellipsometry showed the formation of adsorption layers analogous to those observed at the surface of native wines, and responsible for their foam stability. Sequential fractionation of Pinot Noir at decreasing MWCO within the 10–30 K and 30–100 K molecular weight range showed the formation of adsorption layers with both fractions. NMR and chemical analysis indicated that all fractions were mainly composed of polysaccharides and proteins. Monosaccharide analysis gave mannose, galactose, arabinose and glucose as the prominent constituting sugars. Careful bottle rinsing was found to enable thorough macromolecule recovery.     

Fused ring and linking groups effect on overcharge protection for lithium-ion batteries

The derivatives of 1,3-benzodioxan (DBBD1) and 1,4-benzodioxan (DBBD2) bearing two tert-butyl groups have been synthesized as new redox shuttle additives for overcharge protection of lithium-ion batteries. Both compounds exhibit a reversible redox wave over 4 V vs Li/Li⁺ with better solubility in a commercial electrolyte (1.2 M LiPF₆ dissolved in ethylene carbonate/ethyl methyl carbonate (EC/EMC 3/7) than the di-tert-butyl-substituted 1,4-dimethoxybenzene (DDB). The electrochemical stability of DBBD1 and DBBD2 was tested under charge/discharge cycles with 100% overcharge at each cycle in MCMB/LiFePO₄ and Li₄Ti₅O₁₂/LiFePO₄ cells. DBBD2 shows significantly better performance than DBBD1 for both cell chemistries. The structural difference and reaction energies for decomposition have been studied by density functional calculations.     

Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.     

Dissolution Rates of Commercial Phenylbutazone Tablets: Inter-And Intra-Brand Effects

A study has been carried out to investigate the dissolution rate profiles of twelve batches of sugar-coated phenylbutazone tablets belonging to four commercial brands. Using the rotating basket method, significant inter-brand and inter-batch variations in dissolution rates were found. Only two batches of one brand passed the B.P. dissolution limit whilst other batches had percentages dissolution between 0.3 and 58 after 45 min. Batches with poor dissolution characteristics exhibited significant tablet-to-tablet variations in dissolution rates; a finding which was not observed in the relatively fast-dissolving batches. When the paddle method was substituted for the B.P. basket method, the dissolution rates were relatively faster but similar dissolution failure was found. However, the tablet-to-tablet dissolution variability was decreased in some of the batches. The observed differences in dissolution rates of the batches examined were unrelated to their disintegration times. Inspite of the poor dissolution characteristics of most of the batches studied, no apparent chemical degradation was found. It is recommended that when evaluating the dissolution rates of brands of phenylbutazone tablets, a number of batches from each brand should be tested.