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Notes: Time delays, dwell times, resonant state lifetimes, and electron sheet densities associated with tunneling through quantum well structures are analyzed from a scattering theory (S-matrix) viewpoint. Some of the results differ from intuitively motivated expressions which have appeared in the resonant tunneling literature. It is shown that the sheet density is given by a formula similar to the Tsu–Esaki formula [Appl. Phys. Lett. 22, 562 (1973)] for current density. Sheet density and dwell time are related to Hermitian matrices which are expressed in terms of the S-matrix and in terms of partial widths associated with resonant states.

Notes: A gap junction is composed of two hemichannels and possesses a relatively large pore size (∼ 10–15 Å), allowing passage of ions and molecules up to 1 kDa. Here, we report that connexin hemichannels and gap junctions in the guinea pig cochlea had significant charge selectivity among permeating molecules. In coincubation with anionic and cationic fluorescent dyes, hemichannel permeability in isolated cochlear supporting cells showed significant charge selectivity; 31% of cells had only cationic dye influx and 6% of cells had only anionic dye influx. Charge-selective influx contrary to dye size was also found, indicating charge as a dominant determinant in permeability. The cell–cell gap junctional permeability was consistent with hemichannel permeability and also showed strong charge selectivity; the permeation of anionic dyes was slower than that of cationic probes in the cochlear sensory epithelium. With a combination of immunofluorescent staining for connexin26 (Cx26) and Cx30, which are the predominant connexin isoforms in the cochlea, Cx26 was demonstrated to correlate with anionic permeability. The data indicated that cochlear gap junctions have strong charge selectivity in molecular permeability and metabolic communication. Cx26 mutation may induce specific, irreparable impairment in intercellular signalling and energy and nutrient supplies in the cochlea, causing cell degeneration and hearing loss, given that many important cell-signalling and nutrient and energy molecules (e.g. IP3, ATP, cAMP and cGMP) are anions.

Notes: Encainide was evaluated in 26 patients undergoing programmed electrical stimulation (PES) for ventricular arrhythmias. These patients had inducible symptomatic ventricular tachyarrhythmias during baseline PES and had previously failed a mean of 3.2 antiarrhythmic agents. Encainide was discontinued in six patients prior to PES because of spontaneous ventricular tachycardia (VT) (five patients) and adverse effect (one patient). Encainide increased, the PR, QRS, QTc intervals, and right ventricular effective refractory period (RVERP) significantly from baseline (P 〈 0.05) in 16 patients who were extensive metabolizers. Encainide, at a mean dose of 110 ± 28 mg/day increased the ventricular tachycardia cycle length (VTCL) from 278 ± 77.1 msec to 334 ± 68.8 msec (P 〈 0.05). Encainide alone was effective (〈 15 beats induced) or partially effective (converting inducible sustained VT to 〈 15 beats asymptomatic nonsustained VT or increasing the VTCL 〈 100 msec with no symptoms) in two and seven patients respectively. In seven patients, encainide was also reevaluated at a higher dose (mean dose 148 ± 22 mg/day), but this dose did not significantly alter the overall response or measured parameters. Seven patients were subsequently evaluated on combination of encainide and another antiarrhythmic agent. The combination was effective in three patients and partially effective in three patients. Serum concentrations were measured during each testing period; a moderate correlation was observed between the PR and RR intervals and total concentrations in patients who were extensive metabolizers. Eleven patients who were effective or partially effective during acute testing were placed on long-term encainide therapy (three patients alone and eight patients on combination therapy). In a mean follow-up of 8.9 months (1–25 months) encainide was discontinued in five patients (two patients due to nonsudden cardiac death, one patient due to recurrent nonfatal VT, and two patients due to side effects of combination therapy.) Conclusion: Encainide alone is minimally effective (7.7%) for preventing inducible ventricular tachycardia, but partially effective in 38.9%. Retesting at a higher dose does not offer any additional benefit. However, encainide in combination with another antiarrhythmic agent may improve the response in patients who remain inducible on encainide alone. Further studies are needed to verify this observation.

Notes: The molecular genetics of indole-3-acetic (IAA) synthesis and regulation in Azospirillum brasilense was investigated in this study. Tn5 mutagenesis was performed and five mutants with decreased IAA production were isolated. Five Tn5-inserted genes from these mutants were cloned and sequenced. Four genes were reported for the first time to be involved in IAA production, namely, atrA, ftsA, omaA and aldA that code for GntR-family transcriptional regulator, iron-binding protein component of ABC-type Fe3+ transport system, outer membrane protein, and aldehyde dehydrogenase, respectively. In addition, two genes atrB and atrC, with predicted proteins that showed high homology to aminotransferases, were cloned from the downstream of atrA in this bacterium. Studies also showed that complementation of atrA, ftsA and omaA were able to restore the IAA production of the corresponding IAA− mutants. Comparison of Fe3+ concentrations in culture supernatants of the wild-type strain, the ftsA mutant and the complemented strain revealed that the iron-uptake ability of the ftsA mutant was highly reduced. This result also points to the necessity of iron as a metal ion in IAA synthesis. Statistical analysis showed no significant difference in the IAA accumulated in cells between the omaA mutant and the wild-type strain, suggesting the omaA might not affect IAA secretion but be involved in IAA production in other unknown ways.

Notes: In this paper the microstructure evolution of AZ91HP magnesium alloy casts producedunder different disturbing treatment conditions such as non-disturbing, argon blowing andmechanical stirring in semi-solid state after holding a short time was studied. The results show thatthe grains of AZ91HP alloy casts refined, the secondary dendritic arms grown and the dendrites tendto rosette shape with the decrease of holding temperature. External disturbance can accelerate theevolution process, and the spherical primary α phase formed easily under mechanical stirringtreatment condition. The formation of non-dendritic structure is owing to ripening of the dendriticarms, refinement of the grains and movement of the primary formed solid phases. Disturbingtreatments in semi-solid state induce more equilibrium solidification and decrease the amount ofbrittle β-Mg17Al12 phase. Blowing argon into the refined and modified magnesium alloy in semi-solidstate can obtain homogeneous non-dendritic structure and the net shaped β phase distributed on α-Mgphase boundaries become fine and thin, this may be have a good effect on the mechanical propertiesof the magnesium alloy casts. Due to the low disturbing strength, argon blowing can maintain themetallurgy quality of the semi-solid slurry well, and also have high efficiency to make it. Thistechnology need not new complex equipments and can be practiced in conventional castingconditions, so it may be used in industrialize manufacture

Notes: In this paper, SiC nanoparticles reinforced AM60 alloys were fabricated by semisolidprocess with pretreatment of SiC nanoparticles. The microstructure, hardness and mechanicalproperties of the alloys have been investigated. The X-ray photoelectron spectroscopy (XPS) was alsoused for analyzing elements chemical status of the nanoparticles and the alloys. The microstructure,hardness and mechanical properties of SiC nanoparticles reinforced magnesium alloys are better thanthose of AM60 alloys without SiC nanoparticles addition. The results show that semisolid processwas suitable for fabricating SiC nanoparticles reinforced magnesium alloys

Notes: Nanocomposites of nanosized-CaCO3/polypropylene-ethylene copolymer (PPE) and nanosizedCaCO3/ PPE/ styrene-butadiene-styrene (SBS) were prepared by using two-roll mill and singlescrew extruder. The average particle size of nanosized CaCO3 was determined to be about 30 nm.By adding nanosized CaCO3 into PPE matrix, the toughness of the matrix improves significantly. Atnanosized CaCO3 content of 12 phr (parts per hundred PPE resin by weight), the impact strength ofCaCO3/PPE at room temperature reaches 61.6 KJ/m2, which is 3.02 times that of unfilled PPEmatrix. In addition, the synergistic toughening effect of nanosized CaCO3 and SBS particles on PPEmatrix was investigated

Notes: Using the coat mix process, porous SiC ceramics are fabricated using commercially availablesilicon powders and phenolic resin as the starting materials. The phase composition, morphology, poresize and pore size distribution of the obtained products are characterized by X-ray diffraction, scanningelectron microscopy and mercury intrusion porosimeter. The results show that high porosity SiC ceramicswith a narrow pore size distribution can be fabricated at 1500°C in vacuum by the coat mix process. Theopen pore porosity can reach up to 60%. The pore size varies in the range of 1-6 'm

Notes: Rolling contact fatigue (RCF) cracks initiated from surface and subsurface defects aretypical failure modes of bearing systems. In this paper, the effects of surface defects on RCFbehavior of M50NiL and M50 steels were studied experimentally. Artificial dents were introducedon the rolling surface by using Rockwell hardness tester. The influences of dent shape and dentshoulders were examined by thrust-type RCF tests. Surface cracks initiation, propagation andspalling were monitored by scanning electron microscope (SEM) observation. The results showedthat artificial dents reduce RCF lives of M50NiL and M50 steels with mineral oil lubrication. Thefatigue failure initiates at the surface defect with the effects of dent shape and dent shoulder.M50NiL steel has higher contact fatigue resistance than M50. The features of surface andsub-surface cracks propagation during RCF tests were also observed

Notes: A TiC coating was fabricated on a carbon steel surface by SHS/PHIP (combustionsynthesis/pseudo heat isostatic pressing) process. Phases in the coating were determined by XRD. Weemploy SEM-EDS to analyze the microstructure of the coating and bonding interface between thesubstrate and the coating, and the distribution of elements adjacent to the interface. The microhardness ofthe coating was also measured. Our results showed that the coating was composed of TiC and Fe phases,with dense and pure microstructure. Metallurgical bonding was formed between the substrate andcoating. The result of thermal shock resistance test showed that the coating has good bonding strength andhardness of the coating was four times higher than that of the substrate