High-speed organic single-crystal transistors gated with short-channel air gaps: Efficient hole and electron injection in organic semiconductor crystals

Short-channel, high-mobility organic filed-effect transistors (OFETs) are developed based on single crystals gated with short-channel air gaps. The high hole mobility of 10 cm²/Vs for rubrene, and high electron mobility of 4 cm²/Vs for PDIF-CN₂ crystals are demonstrated even with a short channel length of 6 μm. Such performance is due to low contact resistance in these devices estimated to be as low as ～0.5 kΩ cm at gate voltage of ?4 V for rubrene. With the benefit of the short channel length of 4.5 μm in a new device architecture with less parasitic capacitance, the cutoff frequency of the rubrene air–gap device was estimated to be as high as 25 MHz for drain voltage of ?15 V, which is the fastest reported for p-type OFETs, operating in ambient conditions.     

Expression of active and inactive recombinant soluble trehalase using baculovirus–silkworm expression system and their glycan structures

Silkworm soluble trehalase was expressed as a fusion protein with an N-terminal or C-terminal hexahistidine tag in a baculovirus–silkworm expression system and assayed for enzymatic activity. Only N-terminally tagged trehalase showed a high activity. This study is the first to report in vitro functional expression of recombinant insect soluble trehalase.     

Hepatitis C virus variants from Vietnam are classifiable into the seventh, eighth, and ninth major genetic groups

Thirty-four (41%) of 83 hepatitis C virus (HCV) isolates from commercial blood donors in Vietnam were not classifiable into genotype I/1a, II/1b, III/2a, IV/2b, or V/3a; for 15 of them, the sequence was determined for 1.6 kb in the 5'-terminal region and 1.1 kb in the 3'-terminal region. Comparison of the 15 Vietnamese isolates among themselves and with reported full or partial HCV genomic sequences indicated that they were classifiable into four major groups (groups 6-9) divided into six genotypes (6a, 7a, 7b, 8a, 8b, and 9a). Vietnamese HCV isolates of genotypes 7a, 7b, 8a, 8b, and 9a were significantly different from those classified into groups 4, 5, and 6 based on divergence within partial sequences; those of genotype 6a were homologous to a Hong Kong isolate (HK2) of genotype 6a. Phylogenetic trees based on the envelope 1 (E1) gene (576 bp) of 55 isolates and a part of the nonstructural 5 (NS5) region (1093 bp) of 43 isolates revealed at least nine major groups, three of which (groups 7, 8, and 9) were identified only in Vietnamese blood donors. With a prospect that many more HCV isolates with significant sequence divergence will be reported from all over the world, the domain of the HCV genome to be compared and criteria for grouping/typing and genotyping/subtyping will have to be determined, so that they may be correlated with virological, epidemiological, and clinical characteristics.     

Durability of Zeolite Against Repeated Activation Treatments with Microwave Heating

The durability of zeolite X against repeated treatments with microwave heating was studied, and properties of the zeolite as desiccant were compared and assessed with those of the most popular commercial desiccants (calcium chloride) for home use. Mixed cationic forms of zeolite with a ratio of Na-X/Ca-X = 5 g/45 g in a full hydration was used to achieve desirable properties. The mixture was activated by microwave (2.45 GHz) radiation for 15 min with 500 W, and after full hydration it was reactivated under the same conditions. The treatment was repeated up to twenty-five times. The adsorption capacity of the zeolite for water decreased with increasing number of treatments. Analyzing the curve of decreasing water capacity, the degradation degree at every treatment was determined to be 0.013. From this value, the number of treatments at which the adsorption capacity becomes one half of its original capacity was calculated to be 54 (defined as lifetime) and it was estimated that the zeolite could adsorb 10.7 times of its own dry weight of water by its lifetime. The rates of uptake of commercial desiccants for water were followed for two months and the uptake curves were analyzed. The desiccants reached their lifetimes in ca. 120 days and absorbed 0.8–0.9 times of their own weights of water by their lifetime. The total amount of adsorption by the zeolite is 10 times greater when compared to the commercial desiccants. Since the zeolite desiccant by using the microwave activation method exhibits higher water adsorption abilities, it is promising as a repeatedly usable desiccant for home use and other areas.     

Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media

A novel method for the removal of inorganic arsenic(III) (As(III)), monomethylarsonate (MMA), and dimethylarsinate (DMA) from aqueous media, was proposed and investigated. This method involves the combined use of TiO₂-photocatalyst and an adsorbent, which has a high ability of As(V) adsorption, under photo-irradiation. When an aqueous solution of As(III) was stirred and irradiated by sunlight or xenon lamp in the presence of TiO₂ suspension, the oxidation of As(III) into As(V) was effectively attained. By use of the same photocatalytic reaction, MMA and DMA were also degraded into As(V), while the total organic carbon (TOC) in the aqueous phase was decreased. When an aqueous solution of As(III) was stirred with a mixed suspension of TiO₂ and an adsorbent for As(V) (activated alumina) under sunlight irradiation, the arsenic removal reached 89% after 24 h. By use of the same photocatalyst–adsorbent system, 98% of MMA and 97% of DMA were removed. The mechanism of the removal of arsenic species by the photocatalyst–adsorbent system was discussed.     

Extraction of thiamylal in serum using hydrophilic acetonitrile with subzero-temperature and salting-out methods

For high-performance liquid chromatography (HPLC) of thiamylal, one of the barbiturates, the drug in serum samples was extracted by two alternative liquid-liquid extraction techniques using hydrophilic acetonitrile as a solvent and subzero-temperature and salting-out methods. Acetonitrile was mixed with the sample, separated by cooling at -20 degrees C or addition of sodium chloride, and injected directly into the HPLC apparatus. In both the methods, thiamylal was extracted effectively in the acetonitrile phase and pH adjustment of the sample was not required. The salting-out extraction method is rapid and would be suitable for quantitation of drugs in many samples. To avoid coextraction of added salt, the subzero-temperature extraction method was applied to identification of thiamylal by gas chromatography/mass spectrometry and liquid chromatography-tandem mass spectrometry.     

A kinetic study on oxygen transfer between solid oxide phase of ZrO2·CaO and liquid metal phase of silver with the aid of electromotive force decay curves

An experimental method was developed to compare the rate of the metal-oxide interface reaction, O^2?=O+2e, with the rate of oxygen transfer in liquid metal. A direct current was supplied to cause the polarization of the galvanic cell, Air: Liquid Ag?O÷ZrO₂·CaO÷Liquid Ag?O: Air. The electromotive force decay curves were obtained at 1100°C immediately after the supply of the current was cut off. The degree of the polarization was increased by increasing the current and its duration time and by decreasing the area of metal-oxide interface. The absolute value of the electromotive forces was affected by the direction of oxygen transfer. The depolarization was accelerated by stirring the liquid silver. The shapes of decay curves were estimated with the rate controlling step at the first order interface reaction and at the nonsteady state diffusion of oxygen in liquid metal. From the shape of the measured decay curves and the stirring effect, it was concluded that the rate of the interface reaction is much more rapid than the rate of oxygen transfer in the liquid metal under the present experimental condition.     

Renal water channel expression in newborns: measurement of urinary excretion of aquaporin-2

Aquaporin-2 (AQP-2) encodes the vasopressin-regulated "water channels" of the renal collecting duct and is excreted in human urine. We measured urinary excretion of AQP-2 by radioimmunoassay in 15 term and 10 preterm infants on day 1 and day 4 of life to determine the molecular basis of water balance during the newborn period. AQP-2 was detectable in the urine of term and preterm newborns, but AQP-2 excretion was severalfold less than the reported level in normal adults. Urinary excretion of AQP-2 significantly decreased postnatally, in parallel with a reduction in urine osmolality and arginine vasopressin (AVP) excretion. Urinary AQP-2 correlated positively and significantly with urine osmolality on days 1 and 4 and with AVP on day 1 in both groups. No significant differences were detected in AQP-2 levels between term and preterm newborns. Our findings suggest that vasopressin-regulated water channels are expressed in the renal collecting duct of both term and preterm newborns, although to a lesser extent as compared with adults, and these channels encoded by AQP-2 contribute to the urine concentrating power of the newborn kidney.     

Lobe variation effects of experimental diabetes and insulin replacement on rat prostate

We investigated the impact of diabetes with simultaneous and late insulin replacement on rat prostate growth during puberty, paying special attention to different prostatic lobes. Diabetes was induced by administration of streptozotocin (STZ) in 40-day-old male Wistar rats. A subset of diabetic rats underwent simultaneous insulin replacement (3 days after STZ administration), and another subset underwent a late insulin replacement (20 days after STZ administration). The ventral, dorsolateral, and anterior prostatic lobes were weighed and processed for histological, immunohistochemical, and morphometric analyses. Both diabetic and insulin-treated animals maintained low plasma testosterone (T) concentrations, whereas dihydrotestostenore (DHT) levels were normal. Diabetic animals had a decreased gain in absolute prostatic weight when compared to age-matched controls and insulin replacement animals. However, prostatic lobe weight in the diabetic animals was ～100% higher, even at the beginning of the experiment. Among the lobes, the anterior lobe showed the highest weight gain in diabetic and insulin replacement conditions. Epithelial cell proliferation in all lobes was significantly reduced in diabetic animals and significantly increased in insulin replacement animals, although apoptosis was unaltered. In conclusion, diabetes diminishes, but does not abolish, prostate growth during puberty. Even late insulin administration reduces the adverse effects of this disease on the prostate. In a scenario with both low insulin and T levels, DHT and other factors may play an important role in pubertal prostate growth. The adverse effects of diabetes on the rat prostate show a variation in lobe response, suggesting that diabetes may affect human prostate zones differently.