Fibre raman amplifier properties for applications to long-distance optical communications

This paper reviews recent theoretical and experimental studies on optical amplification by stimulated Raman scattering (Raman amplification) in single-mode optical fibres, and discusses its possible applications to long-distance optical communications. The fibre Raman amplifier can be used as an in-line optical amplifier in both repeaterless and non-regenerative all-optical repeater configurations. In the former application, signal transmission of over 400 km has been predicted theoretically, although high-power pump sources are considered to be required. In the latter configuration, in which optical fibre losses are compensated for by Raman gains, it has been shown that extremely long-distance transmission over more than 1000 km is feasible in terms of signal-to-noise ratio, where the distance achievable is mainly limited by the accumulation of Raman noise. Recent experimental demonstrations including bit-error rate measurements on the Raman amplified signal, and laser-diode pumped amplification, etc., are also reviewed. The results confirm the effectiveness of fibre Raman amplifiers in future long-haul systems.     

Status of heavy element research using a gas-filled recoil separator at RIKEN

A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element ²⁷¹[110] have been performed using the ²⁰⁸Pb(⁶⁴Ni,1n)²⁷¹[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope ²⁷¹[110] of element 110.     

A new luciferase reporter gene assay for the detection of androgenic and antiandrogenic effects based on a human prostate specific antigen promoter and PC3/AR human prostate cancer cells.

We developed a new mammalian cell-based luciferase reporter gene assay for androgenic and antiandrogenic activities of chemicals and environmental samples. Environmental samples usually have a complex matrix that may contain the constituents acting as androgen receptor (AR) agonists, AR antagonists or aryl hydrocarbon receptor (AhR) agonists. AhR agonists are known to elicit the antiandrogenic effect through cross-talk between AR and AhR signal transduction pathways. In this study, PC3/AR human prostate carcinoma cells were transiently transfected with a prostate-specific antigen (PSA) promoter-driven luciferase expression plasmid. The cells were treated with a test compound or an environmental sample for 24 h at 37 degrees C and then measured for luciferase activity. The luciferase activity was induced by dihydrotestosterone (DHT) in a concentration-dependent manner in a concentration range from 10 fM to 1 nM. R1881, a synthetic androgen receptor agonist, induced luciferase activity and its inductive effects was additive to that of DHT. The luciferase activity was not induced by cortisol, a glucocorticoid, progesterone, a progestin, and 17beta-estradiol, an estrogen in a concentration range of up to 1 microM. DHT-induced luciferase activity was reduced by bicalutamide and cyproterone acetate, AR antagonists, and also by benzo[a]pyrene, an aryl hydrocarbon receptor agonist, through AhR-mediated pathways. All of these findings indicate that the present assay system correctly responds to AR agonists, AR antagonists and AhR agonist and, therefore, it is a powerful tool for the sensitive and selective screening of chemicals and environmental samples for their androgenic and antiandrogenic activities. We developed the first assay system, in which the expression of luciferase was driven by the promoter of a prostate-specific antigen gene, a typical human androgen-regulated gene.     

Cerasome as an Organic-Inorganic Vesicular Nanohybrid: Characterization of Cerasome-Forming Lipids having a Single or a Dual Trialkoxysilyl Head

Morphological characterization of the organic-inorganic vesicular nanohybrids, Cerasomes, was performed in aqueous media from two aspects. Firstly, a novel Cerasome-forming lipid having two triethoxysilyl groups in the head moiety was synthesized and the physical property of the Cerasome was investigated. While the morphological stability of the Cerasomes, as evaluated from the vesicular collapse behavior against a micelle-forming nonionic surfactant, Triton-X 100, was extremely higher than that of the conventional phospholipid liposome, the stabilities were comparable to each other for the Cerasomes derived from the dual- and single-head lipids. On the other hand, the surface property of the Cerasome formed with the dual-head lipid more closely resembled the colloidal silica particles rather than that derived from the single-head lipid, as suggested by zeta-potential measurements. Secondly, the effect of the media pH on the morphological stability of the Cerasome formed with the single-head lipid was evaluated and appeared as a time difference in obtaining the morphological stability of the Cerasome. These morphological characteristics of the Cerasomes could be mainly owing to the development of the siloxane network on the vesicular surface.     

A system for measuring absolute frequencies of up to 4.25 THz using a Josephson point contact

A system for measuring the absolute frequency of a far-infrared (FIR) laser is described. Josephson point contacts have been utilized in the system as a frequency harmonic mixer connecting microwaves and optically pumped CH₃OH laser lines. The Josephson point contacts are capable of generating beat signals of 90 GHz microwaves and FIR waves of up to 4.25 THz. To measure the frequency of the beat signals from the Josephson junction with a frequency counter, tracking oscillators have been developed, which tracks the beat signals by phase locking and regenerate clean signals for frequency counting. It is shown that the absolute frequency can be measured to an accuracy of about 100 Hz by using the tracking oscillators.     

Fabrication and transport properties of multiwall carbon nanotube crossroads

A multiwall carbon nanotube crossroads has been fabricated by a manipulation technique using a glass microcapillary, and the low temperature transport properties investigated. The two-terminal conductance of an individual tube shows Tomonaga–Luttinger liquid behavior G∝T^α at high temperature and dI/dV ∝V ^α at low temperature. However, no evidence of such a power-law behavior is obtained in the four-terminal conductance at the junction, where the conductance shows an almost metallic behavior ‘corrected’ by weak localization. Weak localization would essentially appear in electron states at the junctions of MWNTs.     

Degree Sums and Covering Cycles

It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc.     

Altered protein synthesis in rat kidney cells exposed to semiconductor materials

It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III–V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [³⁵S]methionine. A protein with a molecular weight (M_r) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with M_r values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins.     

Approximation of transient temperatures in complex geometries using fractional derivatives

It is shown that time-dependent temperatures in a transient, conductive system can be approximately modeled by a fractional-order differential equation, the order of which depends on the Biot number. This approximation is particularly suitable for complex shapes for which a first-principles approach is too difficult or computationally time-consuming. Analytical solutions of these equations can be written in terms of the Mittag-Leffler function. The approximation is especially useful if a suitable fractional-order controller is to be designed for the system.