Propagation of two longitudinal waves in a cancellous bone with the closed pore boundary

Ultrasound propagation in cancellous bone (porous media) under the condition of closed pore boundaries was investigated. A cancellous bone and two plate-like cortical bones obtained from a racehorse were prepared. A water-immersion ultrasound technique in the MHz range and a three-dimensional elastic finite-difference time-domain (FDTD) method were used to investigate the waves. The experiments and simulations showed a clear separation of the incident longitudinal wave into fast and slow waves. The findings advance the evaluation of bones based on the two-wave phenomenon for in vivo assessment.     

The investigation of short-range 3He, 3H and deuteron spin structure via the measurement of the angular distributions of the analyzing power in the \vec dd \to {}^3Hen and \vec dd \to Hp reactions at 140, 200 and 270 MeV

The results on the vector A _y and tensor A _yy , A _xx and A _xz analyzing powers of the $\vec dd \to {}^3Hen$ and $\vec dd \to {}^3Hp$ reactions obtained at intermediate energies at RARF(RIKEN, Japan) are presented. The high precision experimental data are compared with the theoretical calculation within the one nucleon exchange model by using standard ³He, ³H and deuteron wave functions. The data demonstrate the sensitivity to the short-range ³He, ³H and deuteron spin structure.     

Morphological phase behaviour under pressure of polycatenar mesogens with a perfluorinated moiety

Two polycatenar materials composed of a four-aromatic-ring core with a perfluorinated moiety attached in one terminal position through either butylene- or pentylene spacer groups, and three tetradecyloxy chains at the other end (abbreviated as 14PC₄F and 14PC₅F), were investigated to study the effect of pressure on the phase transition behaviour. A polarizing optical microscope equipped with a high pressure optical hot stage, was used for the purpose. The T vs. P phase diagrams of 14PC₄F and 14PC₅F were constructed in the pressure region up to 100 MPa. 14PC₄F showed the stable crystal (Cr₁)-columnar tetragonal (Col_tet)-smectic A (SmA)-columnar hexagonal (Col_h)-isoropic liquid (I) phase transition sequence under all pressures. 14PC₅F exhibited the phase sequence metastable crystal (Cr₂)-cubic (Cub)-Col_tet-SmA-I in a melt-cooled sample on heating under pressure. But when the melt-cooled Cr₂ sample was annealed at 52-54°C for 2-3 h, the stable crystal (Cr₁) was formed slowly, giving a stable Cr₁-Cub-Col_tet-SmA-I phase sequence. The temperature region of the stable cubic phase broadened with increasing pressure. Furthermore a new mesophase of 14PC₅F was pressure-induced between the I and SmA phases on cooling at pressures above about 16 MPa. Since the monotropic mesophase exhibited a texture very similar to that of the high temperature Col_h phase of 14PC₄F with planar orientation, the new phase was assigned at a high temperature columnar hexagonal phase of 14PC₅F.     

Fundamental Study of Reflection Pulse Oximetry

For the purpose of developing reflection pulse oximetry, we have analyzed the light propagation in tissue to calculate the photon-visit depth for reflected light and to estimate the measured intensities of transmitted and reflected light using the analytical solutions of the photon diffusion equation. The effects of the reflectance of the probe surface have been studied, and a low reflecting surface has been found to provide deeper photon-visit depth than a high reflecting surface for reflection pulse oximetry. Based on analytical estimation, we made reflection type probes, and conducted preliminary experiments to confirm the feasibility of this type of pulse oximetry.     

An improved method for the capillary gas chromatographic derivatization of polyhydroxylated steroids having tert-hydroxyl groups.

An improved method for a suitable derivatization of polyhydroxylated steroids having one or two tert-hydroxyl groups at the 5beta-, 14alpha-, 17alpha-, 24-, and/or 25-positions by capillary gas chromatography (CGC) is described. By using trimethylsilyl triflate as a silylating reagent and 2,6-lutidine as a catalyst, each of 5beta-cholane and 5alpha-cholestane series of steroids was successfully transformed into trimethylsilyl (TMS) ether derivatives to give a single CGC peak under mild conditions. More bulky triethylsilyl (TES) etherification of 14alpha- and 17alpha-hydroxy compounds provided multiple CGC peaks arising from completely- and/or incompletely-derivatized TES ethers accompanied by their thermal elimination products.     

Complex networks: Dynamics and security

This paper presents a perspective in the study of complex networks by focusing on how dynamics may affect network security under attacks. In particular, we review two related problems: attack-induced cascading breakdown and range-based attacks on links. A cascade in a network means the failure of a substantial fraction of the entire network in a cascading manner, which can be induced by the failure of or attacks on only a few nodes. These have been reported for the internet and for the power grid (e.g., the August 10, 1996 failure of the western United States power grid). We study a mechanism for cascades in complex networks by constructing a model incorporating the flows of information and physical quantities in the network. Using this model we can also show that the cascading phenomenon can be understood as a phase transition in terms of the key parameter characterizing the node capacity. For a parameter value below the phase-transition point, cascading failures can cause the network to disintegrate almost entirely. We will show how to obtain a theoretical estimate for the phase-transition point. The second problem is motivated by the fact that most existing works on the security of complex networks consider attacks on nodes rather than on links. We address attacks on links. Our investigation leads to the finding that many scale-free networks are more sensitive to attacks on short-range than on long-range links. Considering that the small-world phenomenon in complex networks has been identified as being due to the presence of long-range links, i.e., links connecting nodes that would otherwise be separated by a long node-to-node distance, our result, besides its importance concerning network efficiency and security, has the striking implication that the small-world property of scale-free networks is mainly due to short-range links.     

Porous layer effects on soft X-ray radiation emitted from a plasma generated by 130-fs laser pulses irradiating a porous silicon target

Received: 2 May 1997/Revised version: 17 October 1997     

Optimization of a Long-Short Portfolio under Nonconvex Transaction Cost

The purpose of this paper is to propose a practical branch and bound algorithm for solving a class of long-short portfolio optimization problem with concave and d.c. transaction cost and complementarity conditions on the variables.We will show that this algorithm can solve a problem of practical size and that the long-short strategy leads to a portfolio with significantly better risk-return structure compared with standard purchase only portfolio both in terms of ex-ante and ex-post performance.     

Preparation of platinum complexes containing a thioamide-based SCS pincer ligand and their light emitting properties

Reaction of 1,3-bis(1-pyrrolidinothiocarbonyl)benzene with PtCl₂(PhCN)₂ afforded a platinum complex with η³-S,C,S type coordination. The molecular structure of the SCS-pincer platinum(II) complex was determined by X-ray analysis. Substitution of chloro ligand with anionic ligands such as iodo and acetylide was carried out. The complexes exhibit strong emission in a glassy frozen state as well as in the solid state. Light-emitting diodes based on the complexes displayed red electroluminescence.