High-density formation of Ge quantum dots on SiO2

We formed high-density Ge quantum dots (QDs) on an ultrathin SiO₂ layer by controlling the early stages of low-pressure chemical vapor deposition (LPCVD) with a germane gas (GeH₄) assisted by a remote plasma of pure H₂. We then characterized the electronic charged states of the QDs by an AFM/Kelvin probe technique. The formation of single crystalline Ge-QDs with an areal dot density of ∼2.0 × 10¹¹ cm⁻² was confirmed after examining the surface morphology and lattice by atomic force microscopy and transmission electron microscopy, respectively. It has been suggested that an increase in the flux of deposition precursors due to efficient decomposition of GeH₄ by a supply of hydrogen radicals and the dehydration reaction of surface OH bonds plays a role in nucleation of Ge-QDs on SiO₂. Surface passivation with hydrogen may also promote the surface migration of deposition precursors during LPCVD. The surface potential of the dots changed in a stepwise manner with respect to the tip bias due to multistep electron injection into and extraction from the Ge-QDs.     

Flowability measurement of pulverized and granulated materials using vibrating tube method

To develop a method for measuring the flowability of MOX (mixed oxide of uranium and plutonium) particles used in the simplified MOX pellet fabrication process, the flowability of model particles has been investigated by the vibrating tube method. As model particles, pulverized ZrO₂ and granulated WO₃ were used. To prepare a variety of samples, coarse particles of 106–250 μm in diameter were mixed with fine particles smaller than 45 μm in diameter in different concentrations. The prepared particles were put into the vibrating tube and the amplitude of vibration was increased at a constant rate for a period of time and then decreased. The mass of particles discharged from the tube was measured at constant time intervals. From the experimental data, the relationships between the mass flow rate and the vibration acceleration (i.e. flowability profiles) were obtained. Two factors (i.e. ‘critical vibration acceleration’ to make the particles flow and ‘characteristic mass flow rate’) were selected to analyze the flowability profiles. The hysteresis of the flowability between increasing and decreasing vibration accelerations was also evaluated.     

Development of a database of low energy homes around the world and analyses of their trends

This study aims to develop a database of low energy techniques for homes around the world, for use in systematically evaluating the low energy home in each region, where climate, culture and policy differ. First, a database was made for the purpose of the systemizing passive and active techniques. Data were input according to seven chapters and 155 items, and 66 homes in 17 nations have been recorded. Homes adopting super insulation, high airtightness and solar energy utilization are common in the each country. The thermal insulation performance of wall and window of the housing in Japan is somewhat inferior to that overseas. It was shown that exhaust heat recovery is rarely adopted in Japan and that the underground thermal energy utilization was seen in less than 10% of recorded homes. Second, recorded homes were categorized according to characteristics of adopted strategies, and the reduction rate of purchased energy versus the purchased energy for a typical home was calculated. This revealed the purchased energy reduction rate of homes with both solar heat utilization and photovoltaic power generation to be very high.     

Chr4, a Schizosaccharomyces pombe homologue of the Saccharomyces cerevisiae Chs4p/Skt5p protein, is related to septum formation and is required for the proper localization of Chs2

In Saccharomyces cerevisiae, Chs4p directly interacts with chitin synthase III (Chs3p) to act as a post-translational regulator of the Chs3p complex. We identified four Chs4p homologous proteins in Schizosaccharomyces pombe which we named Chr1, Chr2, Chr3 and Chr4 (putative chitin synthase regulatory factor). We assessed the functions of these proteins and found that while overproduction of Chr1, Chr2 or Chr3 did not affect the cellular morphology of wild-type Sz. pombe cells, overproduction of Chr4 caused the cells to form multi-septa and delayed their growth. All multiple disruptants of chr1, chr2, chr3 and chr4 grew normally under a variety of growth conditions. However, while chitin synthase II (Chs2) normally localizes exclusively at the septum, in many chr4-disrupted cells it was found in the cytoplasm and the septa. Chs2 did localize at the abnormal septa caused by the overproduction of chr4+. Chr4-13Myc expression was unaffected by the different media or growth conditions in both wild-type and the chs2 disruptant. Chs2 expression was also unaltered by the absence of Chr4. Moreover, Chr4-13Myc localized mostly at the tips and the septum during vegetative growth in chs2, chr1, chr2 and chr3 disruptants as well as in wild-type. Thus, chr4+ is involved in septum formation and is required for the proper localization of Chs2 at the septum in Sz. pombe.     

Anisotropic carbon nanotube papers fabricated from multiwalled carbon nanotube webs

We fabricated large-scale anisotropic carbon nanotube (CNT) paper sheets by stacking long-lasting multiwalled CNT (MWCNT) webs without using binder materials. The MWCNTs are highly aligned in the webs and they retain their alignment in the fabricated paper. Although MWCNTs are just connected by van der Waals force, tensile strength is as strong as 75.6 MPa. In addition, resistivity and thermal conductivity is as good as 2.5 × 10⁻³ Ω cm and 70 W/m K, respectively. The present high anisotropy ratios of 7.3 in resistivity and of 8.1 in thermal conductivity are due to the high alignment of the ultra-long MWCNTs which have lengths of millimeters. High-speed web drawing with a draw speed of over 10 m/s enables very rapid fabrication. The material properties of CNT structures can be measured by conventional methods for macroscopic samples rather than methods designed for nanomaterials. CNT web technology will enable CNTs to be used in new applications.     

Theasaponin E1 destroys the salt tolerance of yeasts

Cells of Zygosaccharomyces rouxii in a medium containing a high concentration of NaCl were killed during incubation for 2–4 h with a low concentration of a mixture of saponins from tea seeds (TSS). The higher the concentration of NaCl in the medium, the higher the inhibitory effect of TSS on the growth of the yeast. The above inhibitory effect of TSS on the growth of the yeast was not observed when cells were incubated in hypertonic media composed of nonionic substances such as sugars. The ATPase activity of plasma membrane preparations from the yeast cells was slightly affected by the addition of TSS. It is shown that TSS facilitates leakage of glycerol from the yeast cells under NaCl-hypertonic conditions. The major inhibitor in the mixture of saponins was isolated and identified as theasaponin E₁. Its isomer, theasaponin E₂, did not have any effect on the salt tolerance of Z. rouxii or Saccharomyces cerevisiae.     

Understanding the mechanism of heat stress tolerance caused by high trehalose accumulation in Saccharomyces cerevisiae using DNA microarray

DNA microarray analysis was performed to examine the stress tolerance mechanism of a Saccharomyces cerevisiae recombinant strain exhibiting high trehalose accumulation and heat stress tolerance. Results suggest that the upregulation of sugar transporter genes is one of the key events for heat stress tolerance of the recombinant strain.     

Activation of serotonergic neurotransmission during the performance of aggressive behavior in rats.

High aggression is often linked to lowered serotonin (5-HT) neurotransmission. Although this may hold for high aggression as a trait characteristic of an individual, serotonergic activity is probably increased during performance of aggressive behavior. To test this hypothesis, first, the 5-HT1A agonist alnespirone and gamma aminobutyric acid-A agonist muscimol were administered into the dorsal raphe nucleus. These treatments which inhibit 5-HT neuronal activity, were shown to decrease performance of aggressive behavior. Second, after a resident-intruder test, the activation of 5-HT neurons (measured by c-fos expression) was increased in high-aggressive rats, compared with low-aggressive rats or control rats that were not subjected to a social confrontation. Results show that performance of aggressive behavior increases 5-HT neuronal activity and that preventing this activation inhibits expression of aggressive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental study on a monovalent inverter-driven water-to-water heat pump with a desuperheater for low energy houses

In this study, a novel monovalent inverter-driven water-to-water heat pump with a desuperheater was developed. In this unique system, domestic hot water is produced at a constant temperature controlled by a variable flow rate and stored in a tank. The heat demand is constantly matched by the system through the use of an inverter-driven compressor, which eliminates the need for a buffer tank. Three heating configurations of the system were examined with respect to variable climate conditions and two space heating target temperatures: space heating (mode 1), domestic hot water production (mode 2) and a combination of both (mode 3). Mappings of the performance variables per frequency were constructed for mode 3. For the other modes, the highest COP was identified for each examined climate condition. The difference between modes 1 and 3 was less than 5% for every variable. The space heating target temperature had a strong influence on both modes, showing an average difference of 29% in the COP between 35 °C and 45 °C. Mode 2 exhibited a considerably reduced COP compared to the other modes, as well as the lowest refrigerant mass flow rate and highest compression ratio among the three modes. From the previous results and the examination of the compressor, the compression ratio presents itself as a key parameter that can help to increase the COP if maintained at low values. The results of this research could be applied to the design of a control methodology for monovalent heat pumps.