The formation of a p-n junction in a polymer electrolyte top-gated bilayer graphene transistor

We show simultaneous p- and n-type carrier injection in a bilayer graphene channel by varying the longitudinal bias across the channel and the top-gate voltage. The top gate is applied electrochemically using solid polymer electrolyte and the gate capacitance is measured to be 1.5 microF cm(-2), a value about 125 times higher than the conventional SiO(2) back-gate capacitance. Unlike the single-layer graphene, the drain-source current does not saturate on varying the drain-source bias voltage. The energy gap opened between the valence and conduction bands using top- and back-gate geometry is estimated.

Hydrophobic channels in crystals of an alpha-aminoisobutyric acid pentapeptide

The crystal structure of the pentapeptide p-toluene-sulfonyl-(α-aminoisobutyryl)5-methyl ester (Tosyl-(Aib)5-OMe) has been determined in the space group PImage . Pentapeptide molecules are folded in the 310 helical conformation and packed together, so as to yield a hydrophobic channel with a minimim diameter of 5.2 �. The channel contains crystallographically disordered material. This structure provides a model for channel formation by hydrophobic peptide aggregates and should prove useful in studies of alamethicin, suzukacillin and related Aib containing membrane channels. Triclinic (PImage ) crystals of the pentapeptide are obtained in the presence of LiClO4 in aqueous methanol, whereas crystallization from methanol alone yields crystals in the space group Pbca. The conformations of the peptide in the two crystal forms are very similar and only the molecular packing is dramatically different.

Combustion and Thermal Decomposition of a Binary Oxidiser System: Ammonium Perchlorate-Potassium Perchlorate

Combustion behaviour of ammonium perchlorate-potassium perchlorate pellets is studied using Crawford strand burners. At low concentrations of potassium perchlorate (up to 30 percent potassium perchlorate) the burning rate of ammonium perchlorate-potassium perchlorate condensed mixtures increases with potassium perchlorate content. Above 40 percent potassium perchlorate content, combustion sustenance becomes difficult. Decomposition products of ammonium perchlorate sensitize the melting and subsequent decomposition of potassium perchlorate. The results are explained in terms of the melt layer thickness, flame temperature and the resultant surface temperature, and heat wave penetration into the solid. The study suggests the importance of melt layer on the burning surface in the deflagration behaviour of ammonium perchlorate-potassium perchlorate condensed mixtures

Chlorination of silver dosed with potassium and barium in presence of oxygen: An X-ray photoelectron spectroscopy study

XPS studies show that the presence of chemisorbed chlorine stabilizes and also enhances molecular dioxygen species on Ag surfaces dosed with either K or Ba. The surface atomic oxygen is found to become depleted on chlorination. The variation in the nature of surface species with respect to temperature shows chlorine-induced diffusion of atomic oxygen into the subsurface region at 300 K. For coverages of potassium up to 8 × 1014 atoms/cm2, preferential chloridation of Ag occurs while at higher potassium coverages, KCl formation is distinctly observed on the surface. In the case of barium, two types of adsorbed chlorine species, Cl(α) and Cl(β), associated with Ag and Ba, respectively, are clearly seen even at low barium coverages. This is believed to be due to the higher valence occupation of barium compared to potassium. The Cl(α) species associated with Ag is found to occupy a preferred site on both K- and Ba-dosed surfaces, involving chemisorptive replacement of O(α) to the subsurface region.

Food and Indoor Air Isolated Bacillus Non-Protein Toxins: : Structures, Physico-Chemical Properties and Mechanisms of Effects on Eukaryotic Cells

We report here the structures and properties of heat-stable, non-protein, and mammalian cell-toxic compounds produced by spore-forming bacilli isolated from indoor air of buildings and from food. Little information is available on the effects and occurrence of heat-stable non-protein toxins produced by bacilli in moisture-damaged buildings. Bacilli emit spores that move in the air and can serve as the carriers of toxins, in a manner similar to that of the spores of toxic fungi found in contaminated indoor air. Bacillus spores in food cause problems because they tolerate the temperatures applied in food manufacture and the spores later initiate growth when food storage conditions are more favorable. Detection of the toxic compounds in Bacillus is based on using the change in mobility of boar spermatozoa as an indicator of toxic exposure. GC, LC, MS, and nuclear magnetic resonance NMR spectroscopy were used for purification, detection, quantitation, and analysis of the properties and structures of the compounds. Toxicity and the mechanisms of toxicity of the compounds were studied using boar spermatozoa, feline lung cells, human neural cells, and mitochondria isolated from rat liver. The ionophoric properties were studied using the BLM (black-lipid membrane) method. One novel toxin, forming ion channels permeant to K+ > Na+ > Ca2+, was found and named amylosin. It is produced by B. amyloliquefaciens isolated from indoor air of moisture-damaged buildings. Amylosin was purified with an RP-HPLC and a monoisotopic mass of 1197 Da was determined with ESI-IT-MS. Furthermore, acid hydrolysis of amylosin followed by analysis of the amino acids with the GS-MS showed that it was a peptide. The presence of a chromophoric polyene group was found using a NMR spectroscopy. The quantification method developed for amylosin based on RP-HPLC-UV, using the macrolactone polyene, amphotericin B (MW 924), as a reference compound. The B. licheniformis strains isolated from a food poisoning case produced a lipopeptide, lichenysin A, that ruptured mammalian cell membranes and was purified with a LC. Lichenysin A was identified by its protonated molecules and sodium- and potassium- cationized molecules with MALDI-TOF-MS. Its protonated forms were observed at m/z 1007, 1021 and 1035. The amino acids of lichenysin A were analyzed with ESI-TQ-MS/MS and, after acid hydrolysis, the stereoisomeric forms of the amino acids with RP-HPLC. The indoor air isolates of the strain of B. amyloliquefaciens produced not only amylosin but also lipopeptides: the cell membrane-damaging surfactin and the fungicidal fengycin. They were identified with ESI-IT-MS observing their protonated molecules, the sodium- and potassium-cationized molecules and analysing the MS/MS spectra. The protonated molecules of surfactin and fengycin showed m/z values of 1009, 1023, and 1037 and 1450, 1463, 1493, and 1506, respectively. Cereulide (MW 1152) was purified with RP-HPLC from a food poisoning strain of B. cereus. Cereulide was identified with ESI-TQ-MS according to the protonated molecule observed at m/z 1154 and the ammonium-, sodium- and potassium-cationized molecules observed at m/z 1171, 1176, and 1192, respectively. The fragment ions of the MS/MS spectrum obtained from the protonated molecule of cereulide at m/z 1154 were also interpreted. We developed a quantification method for cereulide, using RP-HPLC-UV and valinomycin (MW 1110, which structurally resembles cereulide) as the reference compound. Furthermore, we showed empirically, using the BLM method, that the emetic toxin cereulide is a specific and effective potassium ionophore of whose toxicity target is especially the mitochondria.

Mechanoformation of ammonium perchlorate-potassium perchlorate solid solutions

Ammonium perchlorate-potassium perchlorate mixtures, upon pelletization, form a series of homogeneous solid solutions as manifested by X-ray powder diffractograms. Scanning electron microscopic studies throw light on the mechanism of the solid-solution formation. Solid solutions of ammonium perchlorate-potassium perchlorate have also been obtained by a modified cocrystallization technique. The thermal and combustion behavior of the solid solutions have also been studied, using the DTA technique and the Crawford strand burner.

Performance of slotted ALOHA satellite channels with finite buffer

The behaviour of the slotted ALOHA satellite channel with a finite buffer at each of the user terminals is studied. Approximate relationships between the queuing delay, overflow probabilities and buffer size are derived as functions of the system input parameters (i.e. the number of users, the traffic intensity, the transmission and the retransmission probabilities) for two cases found in the literature: the symmetric case (same transmission and retransmission probabilities), and the asymmetric case (transmission probability far greater than the retransmission probability). For comparison, the channel performance with an infinite buffer is also derived. Additionally, the stability condition for the system is defined in the latter case. The analysis carried out in the paper reveals that the queuing delays are quite significant, especially under high traffic conditions.

Ferroelectricity in lithium potassium sulphate

. Measurement of the relation between polarisation P and electric field E for lithium potassium sulphate (LiKSO4) was made in the low temperature range below room temperature. The P-E hysteresis loops along the c axis of LiKSO4 were observed in the low-temperature phase below the lower transition point Ttl of about -70 degrees C, and in the intermediate phase below the upper transition point Ttu of about -25 degrees C. These phases were found to be ferroelectric. The temperature dependence of the spontaneous polarisation Ps and the electric coercive field Ec were obtained.

Velocity Distribution in Smooth Rectangular Open Channels-Closure

Abstract is not available.

Experimental studies on web crippling strength of hollow flange channels under EOF and IOF load cases

LiteSteel beam (LSB) is a hollow flange channel made from cold-formed steel using a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. LSBs are currently used as floor joists and bearers in buildings. However, there are no appropriate design standards available due to its unique hollow flange geometry, residual stress characteristics and initial geometric imperfections arising from manufacturing processes. Recent research studies have focused on investigating the structural behaviour of LSBs under pure bending, predominant shear and combined actions. However, web crippling behaviour and strengths of LSBs still need to be examined. Therefore, an experimental study was undertaken to investigate the web crippling behaviour and strengths of LSBs under EOF (End One Flange) and IOF (Interior One Flange) load cases. A total of 23 web crippling tests were performed and the results were compared with the current AS/NZS 4600 and AISI S100 design standards, which showed that the cold-formed steel design rules predicted the web crippling capacity of LSB sections very conservatively under EOF and IOF load cases. Therefore, suitably improved design equations were proposed to determine the web crippling capacity of LSBs based on experimental results. In addition, new design equations were also developed under the Direct Strength Method format. This paper presents the details of this experimental study on the web crippling behaviour and strengths of LiteSteel beams under EOF and IOF load cases and the results.

Thermal Decomposition and Combustion Studies on Potassium Perchlorat e/Polystyrene Propellant Systems

STUDIES on potassium perchlorate/polystyrene (KP/PS) propellant systems have been carried out by using such techniques as thermogravimetry (TG), differential thermal analysis (DTA), and mass spectrometry (MS). It has been found that the thermal decomposition (TD) behavior of the KP/PS propellant is similar to that of the AP/PS propellant studied earlier.! It has also been observed that the TD of KP in the melt has a correlation with the burning rate (r) of KP/PS propellant at atmospheric pressure.

Correlated Gaussian Sources over Orthogonal Gaussian Channels

We consider the transmission of correlated Gaussian sources over orthogonal Gaussian channels. It is shown that the Amplify and Forward (AF) scheme which simplifies the design of encoders and the decoder, performs close to the optimal scheme even at high SNR. Also, it outperforms a recently proposed scalar quantizer scheme both in performance and complexity. We also study AF when there is side information at the encoders and decoder.

Genotype-Phenotype Relationships in Long QT Syndrome: Role of Mental Stress, Adrenergic Activity and a Common KCNH2 Polymorphism

Long QT syndrome is a congenital or acquired arrhythmic disorder which manifests as a prolonged QT-interval on the electrocardiogram and as a tendency to develop ventricular arrhythmias which can lead to sudden death. Arrhythmias often occur during intense exercise and/or emotional stress. The two most common subtypes of LQTS are LQT1, caused by mutations in the KCNQ1 gene and LQT2, caused by mutations in the KCNH2 gene. LQT1 and LQT2 patients exhibit arrhythmias in different types of situations: in LQT1 the trigger is usually vigorous exercise whereas in LQT2 arrhythmia results from the patient being startled from rest. It is not clear why trigger factors and clinical outcome differ from each other in the different LQTS subtypes. It is possible that stress hormones such as catecholamines may show different effects depending on the exact nature of the genetic defect, or sensitivity to catecholamines varies from subject to subject. Furthermore, it is possible that subtle genetic variants of putative modifier genes, including those coding for ion channels and hormone receptors, play a role as determinants of individual sensitivity to life-threatening arrhythmias. The present study was designed to identify some of these risk modifiers. It was found that LQT1 and LQT2 patients show an abnormal QT-adaptation to both mental and physical stress. Furthermore, as studied with epinephrine infusion experiments while the heart was paced and action potentials were measured from the right ventricular septum, LQT1 patients showed repolarization abnormalities which were related to their propensity to develop arrhythmia during intense, prolonged sympathetic tone, such as exercise. In LQT2 patients, this repolarization abnormality was noted already at rest corresponding to their arrhythmic episodes as a result of intense, sudden surges in adrenergic tone, such as fright or rage. A common KCNH2 polymorphism was found to affect KCNH2 channel function as demonstrated by in vitro experiments utilizing mammalian cells transfected with the KCNH2 potassium channel as well as QT-dynamics in vivo. Finally, the present study identified a common β-1-adrenergic receptor genotype that is related a shorter QT-interval in LQT1 patients. Also, it was discovered that compound homozygosity for two common β-adrenergic polymorphisms was related to the occurrence of symptoms in the LQT1 type of long QT syndrome. The studies demonstrate important genotype-phenotype differences between different LQTS subtypes and suggest that common modifier gene polymorphisms may affect cardiac repolarization in LQTS. It will be important in the future to prospectively study whether variant gene polymorphisms will assist in clinical risk profiling of LQTS patients.