Design, fabrication and characterization of spatial mode selector in silicon

We demonstrate the design, fabrication and experimental characterization of the spatial mode selector that transmit only the second silicon waveguide mode. Nanofabrication results and near field measurements are presented. © 2009 Optical Society of America.

Design, fabrication and characterization of spatial mode selector in silicon

We demonstrate the design, fabrication and experimental characterization of the spatial mode selector that transmit only the second silicon waveguide mode. Nanofabrication results and near field measurements are presented. © 2009 Optical Society of America.

Age, growth, and reproduction of the bitterling (Paracheilognathus imberbis) in a shallow Chinese Lake

Age, growth, and reproduction of the bitterling, Paracheilognathus imberbis (Gunther), in Niushan Lake were studied between 1998 and 1999. Annuli on the scales were clear and could be used as valid indicators of age. The population of the fish comprised only one age group. The growth rate of males was markedly greater than that of females. The fish were multiple spawners, reaching maturity in the second year. Minimum size for males at maturity was 32.9 mm in total length and 0.30 g in weight; for females, the minima were 41.0 mm and 0.73 g. During the breeding season, both sexes exhibited secondary sex characteristics, and the ratio of males to females was 1: 1.04 (n = 104). The size of mature eggs averaged 3.12 mm in length by 1.03 mm. in width. Fecundity per female for one age group ranged from 38 to 189 eggs, with an average of 93 eggs (n = 80).

Survival, growth, sex ratio, and maturity of the Chinese mitten crab (Eriocheir sinensis) reared in a Chinese pond

Aspects of the biology of pond-cultured Chinese mitten crab (Eriocheir sinensis H. Milne-Edwards) were studied from June to November 1993. The survival rate of the population was estimated at 18.6%, and there was no significant difference between sexes in growth (t-test, P > 0.05). As the crabs grew from 7.3 to 33.8 mm in mean carapace length, seven molts were observed for the population. The intermolt period ranged from seven to 22 days and lengthened with increased size. Sex ratio at each sampling time did not differ significantly from 1:1 (Chi-square test, P > 0.05). Female crabs presumably required about eleven postlarval molts to reach sexually mature size, which was 34.1 +/- 3.9 (SD) mm. in carapace length in this study.

An investigation of the mode characteristics of SOI submicron rib waveguides using the film mode matching method

The mode characteristics of SOI (silicon-on-insulator) submicron rib waveguides are very different from those of micrometer-sized ones. Using the full-vector film mode matching method, we propose a simple criterion to determine whether a waveguide mode is guided or not. The single-mode condition for deep-etched waveguides is obtained using this criterion. We also obtain the inherent TM mode leakage and sharp cancelation effects due to TE-TM mode coupling in shallow-etched rib waveguides from numerical simulations, which agree well with the analytical results based on total internal reflection and interference theories.

Measurement of the optical transmission modes and losses of the poled guest-host polymer NAEC/PEK-c planar waveguides

The polyetherketone (PEK-c) guest-host polymer planar waveguides doped with (4'-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The waveguide films were poled by corona-onset poling at elevated temperature (COPET), and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. By using the prism-in coupling method, the dark-line spectrum given by the reflected intensity versus the angle of incidence have been obtained, and the optical transmission losses of mth modes have been measured for the poled polymer waveguides at lambda = 632.8 nm. The measurement result showed that the optical loss of the fundamental mode is less than 0.7 dB cm(-1) for the TE polarization. (C) 2000 Elsevier Science Ltd. All rights reserved.

MEASUREMENT AND SIMULATION OF THE TURN-ON DELAY TIME JITTER IN GAIN-SWITCHED SEMICONDUCTOR-LASERS

The turn-on delay time jitter of four different unbiased gain-switched laser types is determined by measuring the temporal probability distribution of the leading edge of the emitted optical pulse. One single-mode 1.5-mu-m distributed feed-back laser and three multimode Fabry-Perot lasers emitting at 750 nm and 1.3-mu-m are investigated. The jitter is found to decrease for all lasers with increasing injection current. For multimode lasers it decreases from 8 ps excited slightly above threshold down to below 2 ps at three times the threshold current. The jitter of the distributed feedback (DFB) laser is a factor of 3-5 larger than the jitter of the three multimode lasers. A new model to predict the turn-on delay time jitter is presented and explains the experiments quantitatively.

Absorption and luminescence of the surface states in ZnS nanoparticles

A broad absorption band around 500 nm is observed in ZnS nanoparticles. The absorption becomes more intensive and shifts to the blue as the particle size is decreased. The absorption energy is lower than the band gap of the particles and is considered to be caused by the surface states. This assignment is supported by the results of the fluorescence and of the thermoluminescence of the surface states. Both the absorption and the fluorescence reveal that the surface states are size dependent. The glow peak of the semiconductor particles is not varied as much upon decreasing size, indicating the trap depth of the surface states is not sensitive to the particle size. Considering these results, a new model on the size dependence of the surface states is proposed, which may explain our observations reasonably. (C) 1997 American Institute of Physics.

Rare-earth metal complexes stabilized by amino-phosphine ligand. Reaction with mesityl azide and catalysis of the cycloaddition of organic azides and aromatic alkynes

Stoichiometric reactions between mesityl azide (MesN(3), Mes = 2,4,6-C6H2Me3) and amino-phosphine ligated rare-earth metal alkyl, LLn(CH2SiMe3) (2)(THF) (L = (2,6-C6H3Me2)NCH2C6H4P(C6H5)(2); Ln = Lu (1a), Sc (1b)), amide, LLu(NH(2,6-(C6H3Pr2)-Pr-i))(2)(THF) (2) and acetylide at room temperature gave the amino-phosphazide ligated rare-earth metal bis(triazenyl) complexes, [L(MesN(3))]Ln[(MesN(3))-(CH2SiMe3)](2) (Ln = Lu (3a); Sc (3b)), bis(amido) complex [L(MesN3)] Lu[NH(2,6-C6H3 Pr-i(2))](2) (4), and bis(alkynyl) complex (5) (L(MesN(3))Lu (C CPh)(2))(2), respectively. The triazenyl group in 3 coordinates to the metal ion in a rare eta(2)-mode via N-beta and N-gamma atoms, generating a triangular metallocycle. The amino-phosphazide ligand, L(MesN(3)), in 3, 4 and 5 chelates to the metal ion in a eta(3)-mode via N-alpha and N-gamma atoms. In the presence of excess phenylacetylene, complex 3a isomerized to 3', where the triazenyl group coordinates to the metal ion in a eta(3) mode via Na and Ng atoms.

Identification of archaeon-producing hyperthermophilic alpha-amylase and characterization of the alpha-amylase

The extremely thermophilic anaerobic archaeon strain, HJ21, was isolated from a deep-sea hydrothermal vent, could produce hyperthermophilic alpha-amylase, and later was identified as Thermococcus from morphological, biochemical, and physiological characteristics and the 16S ribosomal RNA gene sequence. The extracellular thermostable alpha-amylase produced by strain HJ21 exhibited maximal activity at pH 5.0. The enzyme was stable in a broad pH range from pH 5.0 to 9.0. The optimal temperature of alpha-amylase was observed at 95 degrees C. The half-life of the enzyme was 5 h at 90 degrees C. Over 40% and 30% of the enzyme activity remained after incubation at 100 degrees C for 2 and 3 h, respectively. The enzyme did not require Ca2+ for thermostability. This alpha-amylase gene was cloned, and its nucleotide sequence displayed an open reading frame of 1,374 bp, which encodes a protein of 457 amino acids. Analysis of the deduced amino acid sequence revealed that four homologous regions common in amylases were conserved in the HJ21 alpha-amylase. The molecular weight of the mature enzyme was calculated to be 51.4 kDa, which correlated well with the size of the purified enzyme as shown by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Mesoporous spinel MgAl2O4 prepared by in situ modification of boehmite sol particle surface: I Synthesis and characterization of the unsupported membranes

Mesoporous spinel membranes as ultrafiltration membranes were prepared through a novel sol-gel technique. By in situ modification of the sol particle surface during the sol-gel process, control of the material structure on a nanometer scale from the earliest stages of processing was realized. Nano-particles with a chocolate-nut-like morphology, i.e. spinel MgAl2O4 as a shell and gamma -Al2O3 as a core, were first revealed by HRTEM results. The formation of the spinel phase was confirmed by X-ray diffraction (XRD). N-2 adsorption-desorption results showed that the mesoporous membranes had a narrow pore size distribution. (C) 2001 Elsevier Science B.V. All rights reserved.

Characterizations and activities of the nano-sized Ni/Al2O3 and Ni/La-Al2O3 catalysts for NH3 decomposition

A series of nano-sized Ni/Al2O3 and Ni/La-Al2O3 catalysts that possess high activities for NH3 decomposition have been successfully synthesized by a coprecipitation method. The catalytic performance was investigated under the atmospheric conditions and a significant enhancement in the activity after the introduction of La was observed. Aiming to study the influence of La promoter on the physicochemical properties, we characterized the catalysts by N-2 adsorption/desorption, XRD, H-2-TPR, chemisorption and TEM techniques. Physisorption results suggested a high specific surface area and XRD spectra showed that nickel particles are in a highly dispersed state. A combination of XRD, TEM and chemisorption showed that Ni-0 particles with the average size lower, than 5.0 nm are always obtained even though the Ni loading ranged widely from 4 to 63 %. Compared with the Ni/Al2O3 catalysts, the Ni/La-Al2O3 ones with an appropriate amount of promoter enjoy a more open mesoporous structure and higher dispersion of Ni. Reduction kinetic studies of prepared catalysts were investigated by temperature-programmed reduction (TPR) method and the fact that La additive partially destroyed the metastable Ni-Al mixed oxide phase was detailed. (c) 2005 Elsevier B.V. All rights reserved.

Design and implementation of the embedded capacitance layers for decoupling of wireless sensor nodes

In this paper, the embedded capacitance material (ECM) is fabricated between the power and ground layers of the wireless sensor nodes, forming an integrated capacitance to replace the large amount of decoupling capacitors on the board. The ECM material, whose dielectric constant is 16, has the same size of the wireless sensor nodes of 3cm*3cm, with a thickness of only 14μm. Though the capacitance of a single ECM layer being only around 8nF, there are two reasons the ECM layers can still replace the high frequency decoupling capacitors (100nF in our case) on the board. The first reason is: the parasitic inductance of the ECM layer is much lower than the surface mount capacitors'. A smaller capacitance value of the ECM layer could achieve the same resonant frequency of the surface mount decoupling capacitors. Simulation and measurement fit this assumption well. The second reason is: more than one layer of ECM material are utilized during the design step to get a parallel connection of the several ECM capacitance layers, finally leading to a larger value of the capacitance and smaller value of parasitic. Characterization of the ECM is carried out by the LCR meter. To evaluate the behaviors of the ECM layer, time and frequency domain measurements are performed on the power-bus decoupling of the wireless sensor nodes. Comparison with the measurements of bare PCB board and decoupling capacitors solution are provided to show the improvement of the ECM layer. Measurements show that the implementation of the ECM layer can not only save the space of the surface mount decoupling capacitors, but also provide better power-bus decoupling to the nodes.

The effects of osmotic stress on the structure and function of the cell nucleus.

Osmotic stress is a potent regulator of the normal function of cells that are exposed to osmotically active environments under physiologic or pathologic conditions. The ability of cells to alter gene expression and metabolic activity in response to changes in the osmotic environment provides an additional regulatory mechanism for a diverse array of tissues and organs in the human body. In addition to the activation of various osmotically- or volume-activated ion channels, osmotic stress may also act on the genome via a direct biophysical pathway. Changes in extracellular osmolality alter cell volume, and therefore, the concentration of intracellular macromolecules. In turn, intracellular macromolecule concentration is a key physical parameter affecting the spatial organization and pressurization of the nucleus. Hyper-osmotic stress shrinks the nucleus and causes it to assume a convoluted shape, whereas hypo-osmotic stress swells the nucleus to a size that is limited by stretch of the nuclear lamina and induces a smooth, round shape of the nucleus. These behaviors are consistent with a model of the nucleus as a charged core/shell structure pressurized by uneven partition of macromolecules between the nucleoplasm and the cytoplasm. These osmotically-induced alterations in the internal structure and arrangement of chromatin, as well as potential changes in the nuclear membrane and pores are hypothesized to influence gene transcription and/or nucleocytoplasmic transport. A further understanding of the biophysical and biochemical mechanisms involved in these processes would have important ramifications for a range of fields including differentiation, migration, mechanotransduction, DNA repair, and tumorigenesis.

Physiological levels of PTEN control the size of the cellular Ins(1,3,4,5,6)P5 pool

To understand how a signaling molecule's activities are regulated, we need insight into the processes controlling the dynamic balance between its synthesis and degradation. For the Ins(1,3,4,5,6)P5 signal, this information is woefully inadequate. For example, the only known cytosolic enzyme with the capacity to degrade Ins(1,3,4,5,6)P5 is the tumour-suppressor PTEN [J.J. Caffrey, T. Darden, M.R. Wenk, S.B. Shears, FEBS Lett. 499 (2001) 6 ], but the biological relevance has been questioned by others [E.A. Orchiston, D. Bennett, N.R. Leslie, R.G. Clarke, L. Winward, C.P. Downes, S.T. Safrany, J. Biol. Chem. 279 (2004) 1116 ]. The current study emphasizes the role of physiological levels of PTEN in Ins(1,3,4,5,6)P5 homeostasis. We employed two cell models. First, we used a human U87MG glioblastoma PTEN-null cell line that hosts an ecdysone-inducible PTEN expression system. Second, the human H1299 bronchial cell line, in which PTEN is hypomorphic due to promoter methylation, has been stably transfected with physiologically relevant levels of PTEN. In both models, a novel consequence of PTEN expression was to increase Ins(1,3,4,5,6)P5 pool size by 30-40% (p<0.01); this response was wortmannin-insensitive and, therefore, independent of the PtdIns 3-kinase pathway. In U87MG cells, induction of the G129R catalytically inactive PTEN mutant did not affect Ins(1,3,4,5,6)P(5) levels. PTEN induction did not alter the expression of enzymes participating in Ins(1,3,4,5,6)P5 synthesis. Another effect of PTEN expression in U87MG cells was to decrease InsP6 levels by 13% (p<0.02). The InsP6-phosphatase, MIPP, may be responsible for the latter effect; we show that recombinant human MIPP dephosphorylates InsP6 to D/L-Ins(1,2,4,5,6)P5, levels of which increased 60% (p<0.05) following PTEN expression in U87MG cells. Overall, our data add higher inositol phosphates to the list of important cellular regulators [Y. Huang, R.P. Wernyj, D.D. Norton, P. Precht, M.C. Seminario, R.L. Wange, Oncogene, 24 (2005) 3819 ] the levels of which are modulated by expression of the highly pleiotropic PTEN protein.