Quantum renormalization group and excitonic phase transition in a strong magnetic field

The critical behavior of excitonic fluctuations is investigated at low temperatures. The Wilson renormalization group is applied to a generalized free-energy functional of the Landau-Ginzburg-Wilson type, which is derived by coarse-graining a microscopic functional. The quantum mechanical effects give rise to an increase of the effective dimensionality at zero temperature. The values of this increase z are z = 1 for a semiconductor and z = 2 for a semimetal, depending on whether the electronic density of states is zero at the Fermi energy or not, respectively. Quantum-classical crossover phenomena appear at a finite but low temperature. As the phase transition point is approached in a semimetal the critical fluctuations in real space first grow two-dimensionally in the plane perpendicular to the magnetic field and then develop three-dimensionally. It is explicitly shown that the mean field theory breaks down in a semiconductor.Correspondence and reprint requests should be addressed to Tatsuzo Nagai.     

Aquacultural approaches to recycling of dissolved nutrients in secondarily treated domestic wastewaters-II biological productivity of artificial food chains

We have studied the biological productivity, measured as biomass yields, of laboratory scale artificial food chains composed of sequential monocultures of suspended unicellular green algae (Scenedesmus), herbivorous cladoceran crustaceans (Daphnia magna), and herbivorous teleost fish (Hypophthalmichthys). These food chains were grown in minimally modified secondarily treated, chlorinated then dechlorinated, domestic waste waters. Successive stages in the chains were fed the organisms grown in the just preceding stages.Additions of 1 ppm ferrous sulfate and aeration with mixtures of air plus 5% carbon dioxide (buffered cultures) increased yields of Scenedesmus cultures by 52% above yields of air aerated, unsupplemented cultures (unbuffered cultures). Buffered cultures remained stable for long periods (1–2 weeks) and maintained good cell quality (no chlorosis; 90+% of cells present were Scenedesmus). Unbuffered, unsupplemented cultures soon became chlorotic, cells autoflocculated (which greatly reduced yields), and changes occurred in species composition. These latter cultures were unsuitable as food for cladocerans.Three production indices (conversion coefficients, specific production, and production/biomass ratios) showed that better growth occurred in cladoceran cultures fed buffered algal cultures as compared with unbuffered cultures. When fed unbuffered cultures cladocerans showed higher production indices when flocculated but unsettled cultures were used, as compared with supernates from flocculated, settled cultures.Attempts to grow the primarily herbivorous silver carp (Hypophthalmichthys molitrix) in a two-stage (buffered algae-fish) food chain failed. Ammonia toxicity may have been the cause of fish deaths.     

Human late-receptor potential and its clinical use in dyschromatopsia

The off response of the P III component isolated by aspartate in the human eyecup in vitro showed an initial rapid decay followed by a slow decay. The rapid decay in the human ERG originates mainly in cones. The rapid decay was also observed in human subjects. The spectral sensitivity curve of the rapid decay was found to be shifted toward short wavelengths in all nine protanopes tested. In these cases of protanopia, anomalous cone functions were indicated.     

Delayed failure in silica glass

Stable crack-propagation behaviour in silica glass as a raw material for optical fibres is studied under static tensile stress in various environments such as distilled water, NaCl aqueous solution, air and dry nitrogen gas, and the influence of these environments is discussed. The crack-growth rate in distilled water is obtained qualitatively as a function of the stress intensity factor and temperature, and the activation energy of the cracking process is determined as 97.6 kcal mol^–1. The growth rate seems to be unaffected by Na⁺ and Cl^– ions in an NaCl acqueous solution, but is influenced significantly by the humidity in the atmosphere. In a dry atmosphere, the growth rate in Region II cannot be expressed as a single function of the stress intensity factor. A plot of the log of time to failure against the initial stress intensity factor reveals a linear relationship in the environments tested. The critical fracture stress of an optical fibre is evaluated taking account of the crack size on the basis of fracture mechanics concept.     

Effective phase correction function for high-resolution exit wave reconstruction by a three-dimensional Fourier filtering method

The phase correction function used in the three-dimensional Fourier filtering method (3D-FFM) for compensating lens aberrations was investigated to reconstruct a high-resolution exit wave of a sample. An appropriate function, which hardly suffered from imperfect illumination conditions, was determined by comparing two types of phase correction functions with numerical calculations and experiments using through-focus images of an amorphous thin film and a [110]-oriented Si single crystal taken under tilted illumination or partially coherent illumination. Theoretical calculations indicated that a function in terms of w (an axial Fourier component), available uniquely in the 3D Fourier space, compensated for the phase shift due to the spherical aberration more precisely than did a conventional function in terms of g (the two-dimensional (2D) planar Fourier components). Experimentally, exit waves reconstructed using the w-function showed sample structures at approximately 20% higher resolution than those reconstructed using the g-function. Image contrast simulations proved that the w-function had a significant advantage over the g-function: the former canceled out the effect of illumination divergence, resulting in a high-resolution exit wave. These results demonstrated that exit waves, which are uniquely realized in the 3D-FFM, should be reconstructed using the w-type phase correction function.     

Formation of refractory ring-expanded triazine intermediates during the photocatalyzed mineralization of the endocrine disruptor amitrole and related triazole derivatives at UV-irradiated TiO2/H2O interfaces

Amitrole (ATz, 3-amino-1H-1,2,4-triazole) is a widely employed herbicide with strong estrogenic activity that can lead to abnormalities of the thyroid gland and can cause mutations. The photocatalytic transformation of ATz was carried out at the UV-irradiated TiO2/H2O interface, along with the triazole derivatives Tz (1H-1,2,4-triazole) and DaTz (3,5-diamino-1H-1,2,4-triazole) to assess the decomposition of these herbicides, to identify intermediates, and to elucidate some mechanistic details of the ATz degradation. Conversion of the nitrogens of these triazoles to NH4+ and/ or NO3- ions occurs competitively and depends on the number of amine functions on the five-membered triazole rings. Photomineralization of the substrates in terms of loss of nitrogen to NH4+/NO3- was rather low (ca. 25-40%) for each of the triazoles, whereas evolution of CO2 (loss of TOC) was more significant (60-70%), indicating considerable retention of nitrogen in the intermediate products. UV-Vis spectroscopy, TOC assays, FT-IR spectroscopy, proton NMR spectrometry, electrospray LC-MS, and molecular orbital calculations were brought to bear in assessing the temporal course of the photocatalyzed process(es). Results show that after cleavage of the triazole ring, the various intermediate fragments recombine to yield ring-expanded six-membered triazine intermediates, which slowly degrade to give the refractory cyanuric acid under the conditions used.     

The effect of cold working on creep rupture properties for helium-injected austenitic stainless steel

In order to study the effect of helium on the high temperature embrittlement of stainless steel, helium $\text{(7.5 × 10}{}^{\mathrm{?6}}\text{atomic fraction)}$ was injected into cold-worked stainless steels by using a cyclotron. At 650°C, it appeared that the reduction in creep-rupture strength due to helium was larger as cold-working was increased, but a loss of rupture elongation was less for a particular degree of cold-working. The 10% cold-worked material showed particularly good creep-rupture properties in the presence of helium. The loss of ductility was more pronounced in the creep test than in the tensile test.     

High pressure differential thermal analysis (HPDTA) of fatty acid methyl esters and triglycerides

When using high pressure differential thermal analysis to study the stability of a fatty methyl ester or triglyceride in an atmosphere of air, a departure from the base line in the exothermic curve is observed. The point where an extension line from the base line intersects a tangent line to the departure curve was selected as the transition point in the exothermic curve. For each sample studied, temperature at this transition point showed good reproducibility. The influence of sample container and air pressure upon the temperature of the transition point in the exothermic curve (TTE) was examined. A linear correlation between the number of double bonds in the sample and TTE was observed.     

Threshold voltage of ion implanted GaAs MESFET

Threshold voltages for ion implanted GaAs MESFETs are measured and shown to have good coincidence with calculated results. The effect of implantation energy on threshold voltage is discussed. The optimum implantation energy is about 45 ~ 60 keV.     

Primary adenocarcinoma of the renal pelvis in a young male: a case report

The patient was a 16-year-old male who visited our hospital with the chief complaint of microhematuria. Computed tomography revealed left hydronephrosis, renal stones and left renal tumor. Needle biopsy was performed under ultrasonography. The histological diagnosis was adenocarcinoma and left radical nephrectomy was performed. The histological diagnosis was mucinous adenocarcinoma of the renal pelvis. Postoperative chemotherapy was not given. The patient has had neither recurrence nor metastasis for 1 year following surgery. This is the 92nd reported case in the literature.