Numerical calculation of energy release rates by virtual crack closure technique

A seamless analysis of material behavior incorporating complex geometry and crack- tip modeling is one of greatly interesting topics in engineering and computational fracture mechanics fields. However, there are still large gaps between the industrial applications and fundamental academic studies due to a time consuming detailed modeling. In order to resolve this problem, a numerical method to calculate an energy release rate by virtual crack closure technique was proposed in this paper. Both free mesh method and finite element method have been utilized and, thereafter, robust local and global elements for various geometries and boundary conditions were generated. A validity of the proposed method has been demonstrated through a series of fracture mechanics analyses without tedious crack-tip meshing.     

Comparative study on organic constituents in polluted and unpolluted inland aquatic environments-I features of hydrocarbons for polluted and unpolluted waters

The constituents of hydrocarbons between highly polluted river waters collected from the Tokyo area and unpolluted river, brook, reservoir and pond waters obtained from the Ogasawara (Bonin) Islands were compared to characterize their features for polluted and unpolluted waters. n-Alkanes between the carbon chain length of C₁₂ and C₃₆, squalane and unresolved complex mixture of hydrocarbons (UCMH) were found in most of the river waters of the Tokyo area at the contents ranging from 0.026 to 14 μg 1⁻¹, from 0.004 to 1.7 μg 1⁻¹ and from less than 5 to 290 μg 1⁻¹, respectively, whereas in the waters of the Ogasawara Islands, only n-alkanes ranging from C₁₃ to C₃₇ were found with the great predominance of odd-carbon numbers at the contents varying from 0.042 to 4.0 μg 1⁻¹.It was indicated that the presence of squalane, UCMH and even-carbon numbered n-alkanes as the major constituents are intimately correlated with artificial hydrocarbon sources (fossil fuels and their products and both combustion products, and industrial products), while the great predominance of odd-carbon numbered n-alkanes for the unpolluted areas are mainly due to algae and higher plants. Besides, the major portion of n-alkanes, squalane and UCMH are thought to be present in polluted and unpolluted waters associated with particulate materials.     

Electronic structure analyses of BN network materials using high energy-resolution spectroscopy methods based on transmission electron microscopy

Electronic structures of boron-nitride (BN) nanotubes and a BN cone-structure material were studied by using a high energy-resolution electron energy-loss spectroscopy (EELS) microscope. A trial of the whole electronic structure study of hexagonal BN (h-BN), which consists of flat BN honeycomb layers, was conducted by a combination of EELS and X-ray emission spectroscopy (XES) based on transmission electron microscopy (TEM) (TEM-EELS/XES). The pi and pi+sigma plasmon energies of BN nanotubes (BNT) were smaller than those of h-BN. The pi+sigma energy was explained by the surface plasmon excitation. The spectrum of a two-wall BNT of 2.7 nm in diameter showed a new spectral onset at 4 eV. The valence electron excitation spectra obtained from the tip region of the BN cone with an apex angle of 20 degrees showed similar intensity distribution with those of BNTs. The B K-shell electron excitation spectra obtained from the bottom edge region of the BN cone showed additional peak intensity when compared with those of h-BN and BNT. The B K-shell electron excitation spectra and B K-emission spectra of h-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appear as peak and/or shoulder structures in the EELS and XES spectra. Interband transitions appeared in the imaginary part of the dielectric function of h-BN experimentally obtained were assigned in the band diagram. The analysis also presented that the LDA calculation estimated the bandgap energy smaller than the real material by an amount of 2 eV. Those results of TEM-EELS/XES analysis presented that high energy-resolution spectroscopy methods combined with TEM is a promising method to analyze whole electronic structures of nanometer scale materials.     

Soft-X-ray emission spectroscopy based on TEM-Toward a total electronic structure analysis

The construction and basic performances of wavelength-dispersive soft-X-ray emission spectroscopy (SXES) devices attached to a transmission electron microscope were presented. An energy resolution of 0.23 eV was obtained at the aluminum L-emission energy. A Cu L-emission spectrum obtained showed four L-emission lines of Lalpha, Lbeta, Ll and Leta. Angle-resolved measurements of boron K-emission spectra of hexagonal-BN (h-BN) were presented. It clearly showed anisotropic emission intensity of the transition from pi-bonding state to 1s core hole. B K-emission spectra of h- and cubic-BNs showed a difference in energy positions of sigma-bonding peaks. An electron energy-loss spectrum of B K-edge and a B K-emission spectrum of cubic-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appeared as peak and/or shoulder structures in those spectra. Interband transitions appeared in the imaginary part of the dielectric function of cubic-BN experimentally obtained were assigned in the band diagram. These results demonstrated a method to analyze the entire electronic structure of materials in the nanoscale using high energy-resolution spectroscopy methods based on transmission electron microscopy.     

Postsynthesis of h‐BN/Graphene Heterostructures Inside a STEM

Combinations of 2D materials with different physical properties can form heterostructures with modified electrical, mechanical, magnetic, and optical properties. The direct observation of a lateral heterostructure synthesis is reported by epitaxial in‐plane graphene growth from the step‐edge of hexagonal BN (h‐BN) within a scanning transmission electron microscope chamber. Residual hydrocarbon in the chamber is the carbon source. The growth interface between h‐BN and graphene is atomically identified as largely N–C bonds. This postgrowth method can form graphene nanoribbons connecting two h‐BN domains with different twisting angles, as well as isolated carbon islands with arbitrary shapes embedded in the h‐BN layer. The electronic properties of the vertically stacked h‐BN/graphene heterostructures are investigated by electron energy‐loss spectroscopy (EELS). Low‐loss EELS analysis of the dielectric response suggests a robust coupling effect between the graphene and h‐BN layers.     

Involvement of p85 in p53-dependent apoptotic response to oxidative stress

Reactive oxygen species have damaging effects on cellular components and so trigger defensive responses by the cell and even programmed cell death, although the mechanisms by which mammalian cells transmit signals in response to oxidative damage are unknown. We report here that the protein p85, a regulator of the signalling protein phosphatidyl-3-OH kinase (PI(3)K), participates in the cell death process that is induced in response to oxidative stress and that this role of p85 in apoptosis does not involve PI(3)K. We show that disruption of p85 by homologous recombination impairs the cellular apoptotic response to oxidative stress. Because the protein p53 is required for cell death induced by oxidative damage, we examined the relation between p85 and p53. Using a chimaeric p53 fusion protein with the oestrogen receptor (p53ER) to supply p53 (p53 is induced upon binding of p53ER to oestradiol) in a p53-deficient cell line, we found that p85 is upregulated by p53 and that its involvement in p53-mediated apoptosis is independent of PI(3)K. We propose that p85 acts as a signal transducer in the cellular response to oxidative stress, mediating cell death regulated by p53.     

Distributed power adjustment based on control theory for cognitive radio networks

In this paper, we propose two power adjustment methods for cognitive radio networks. In the first algorithm, the transmitter derives the transmission power with PID control in order to satisfy the QoS constraints in secondary networks. The derived transmission power is compared with a constraint condition in order to avoid the interference with primary networks, and then the actual transmission power is decided. Because the constraint condition affects the performance of our proposed method significantly, we propose an effective update algorithm. On the other hand, the second algorithm is based on model predictive control (MPC). In this method, the decision of transmission power is formulated as quadratic programming (QP) problem and the transmission power is derived directly with the constraint condition. We evaluate the performances of our proposed methods with simulation and compare the proposed methods with the distributed power control (DPC) method. In numerical examples, we show that our proposed methods are more effective than the existing method in some situations. We also prove analytically that the interference with primary networks can be avoided with probability one by using our proposed method if each transmitter has the information about every channel gain.     

Xid-like immunodeficiency in mice with disruption of the p85alpha subunit of phosphoinositide 3-kinase

Mice with a targeted gene disruption of p85alpha, a regulatory subunit of phosphoinositide 3-kinase, had impaired B cell development at the pro-B cell stage, reduced numbers of mature B cells and peritoneal CD5+ Ly-1 B cells, reduced B cell proliferative responses, and no T cell-independent antibody production. These phenotypes are nearly identical to those of Btk-/- or xid (X-linked immunodeficiency) mice. These results provide evidence that p85alpha is functionally linked to the Btk pathway in antigen receptor-mediated signal transduction and is pivotal in B cell development and functions.     

Probabilistic fracture mechanics of nuclear structural components: consideration of transition from embedded crack to surface crack

This paper describes a probabilistic fracture mechanics (PFM) analysis of aged nuclear reactor pressure vessel (RPV) material. New interpolation formulas of three-dimensional stress intensity factors are presented for both embedded elliptical surface cracks and semi-elliptical surface cracks. To investigate effects of transition from embedded crack to surface crack in PFM analyses, one of the PFM round-robin problems set by JSME-RC111 committee (i.e. aged RPV under normal and upset operating conditions) is solved, employing the interpolation formulas.