Optimization of thin-film design for multi-layer dielectric grating

Thin-film design used to fabricate multi-layer dielectric (MLD) gratings should provide high transmittance during holography exposure, high reflectance at use wavelength and sufficient manufacturing latitude of the grating design making the MLD grating achieve both high diffraction efficiency and low electric field enhancement. Based on a (HLL)H-9 design comprising of quarter-waves of high-index material and half-waves of low-index material, we obtain an optimum MLD coating meeting these requirements by inserting a matching layer being half a quarter-wave of Al2O3 between the initial design and an optimized HfO2 top layer. The optimized MLD coatings exhibits a low reflectance of 0.017% under photoresist at the exposure angle of 17.8 degrees for 413 nm light and a high reflectance of 99.61% under air at the use angle of 51.2 degrees for 1053 nm light. Numerical calculation of intensity distribution in the photoresist coated on the MLD film during exposure shows that standing-wave patterns are greatly minimized and thus simulation profile of photoresist gratings after development demonstrates smoother shapes with lower roughness. Furthermore, a MLD gratings with grooves etched into the top layer of this MLD coating provides a high diffraction efficiency of 99.5% and a low electric field enhancement ratio of 1.53. This thin-film design shows perfect performances and can be easily fabricated by e-beam evaporation. (c) 2006 Elsevier B.V. All rights reserved.

8.0nm反射式偏振膜的设计和制备

讨论了软X射线反射式偏振膜的设计原理和方法,利用设计软件模拟设计了8.0nm处的Mo/B4C偏振膜.对影响多层膜性能的参量进行了详细的误差分析.利用磁控溅射镀膜机进行了偏振膜的制备研究,X射线小角衍射测量了多层膜的周期厚度,测量数据的拟合结果与设计值吻合很好.

Characterization of LaF3 coatings prepared at different temperatures and rates

LaF3 thin films were prepared by thermal boat evaporation at different substrate temperatures and various deposition rates. X-ray diffraction (XRD), Lambda 900 spectrophotometer and X-ray photoelectron spectroscopy (XPS) were employed to study crystal structure, transmittance and chemical composition of the coatings, respectively. Laser-induce damage threshold (LIDT) was determined by a tripled Nd:YAG laser system with a pulse width of 8 ns. It is found that the crystal structure became more perfect and the refractive index increased gradually with the temperature rising. The LIDT was comparatively high at high temperature. In the other hand, the crystallization status also became better and the refractive index increased when the deposition rate enhanced at a low level. If the rate was super rapid, the crystallization worsened instead and the refractive index would lessen greatly. On the whole, the LIDT decreased with increasing rate. (C) 2007 Elsevier B.V. All rights reserved.

A miniature insertion element transposable in Microcystis sp FACHB 854

A 186-bp sequence with imperfect terminal inverted repeats and target direct repeats but without any transposase-encoding capacity was found to be transposable in an isolate derived from Microcystis sp. FACHB 854. This miniature insertion element, designated as ISM854-1, and with its homologues present at least 10 copies in the genome of Microcystis FACHB 854, is inserted into the 8-bp long and AT-rich target sequences, but none or few in other Microcystis strains. A variant of ISM854-1, denoted ISM854-1A, has perfect inverted repeat sequences and may transpose in pairs in a structure like a composite transposon. This is the first report of non-autonomous transposition of a mini-IS in a cyanobacterium.

Measurement of 5-day biochemical oxygen demand without sample dilution or bacterial and nutrient enhancement

A direct method for measuring the 5-day biochemical oxygen demand (BODS) of aquaculture samples that does not require sample dilution or bacterial and nutrient enrichment was evaluated. The regression coefficient (R-2) between the direct method and the standard method for the analyses of 32 samples from catfish ponds was 0.996. The slope of the regression line did not differ from 1.0 or the Y-intercept from 0.0 at P = 0.05. Thus, there was almost perfect agreement between the two methods. The control limits (three standard deviations of the mean) for a standard solution containing 15 mg/L each of glutamic acid and glucose were 17.4 and 20.4 mg/L. The precision of the two methods, based on eight replicate analyses of four pond water samples did not differ at P = 0.05. (c) 2005 Elsevier B.V All rights reserved.

Complex mutation at a microsatellite locus in sturgeons: Acipenser sinensis, A-schrenckii, A-gueldenstaedtii and A-baerii

Cross-species amplifications of microsatellite locus Spl-106, which was originally screened from the genome of shovelnose sturgeon (Scaphirhynchus platorynchus) with a perfect TAGA repeat motif, were carried out in four other species of the genera Acipenser. A total of 34 polymerase chain reaction (PCR) products representing 16 different alleles of this locus was sequenced. Sequence analysis results showed that besides the number changes of repeat units, many mutational events, such as single-base substitutions and various insertion/deletion (indels) occurred not only at species level but also at individual level, even among the different alleles within the same individual. The repeat motifs varied from perfect (TAGA)n array to perfect compound (TAAA)m (GAAA)n and perfect or imperfect compound (TAAA)m (TAGA)n (TAAA)x arrays in different species and different individuals. The evolution dynamics of this locus in sturgeons was inferred in that it may evolve from a single perfect to different perfect or imperfect compounds.

Tensile and compressive mechanical behavior of twinned silicon carbide nanowires

Molecular dynamics simulations with the Tersoff potential were used to study the response of twinned SiC nanowires under tensile and compressive strain. The critical strain of the twinned nanowires can be enhanced by twin stacking faults, and their critical strains are larger than those of perfect nanowires with the same diameters. Under axial tensile strain, the bonds of the nanowires are stretched just before failure. The failure behavior is found to depend on the twin segment thickness and the diameter of the nanowires. An atomic chain is observed for thin nanowires with small twin segment thickness under tension strain. Under axial compressive strain, the collapse of twinned SiC nanowires exhibits two different failure modes, depending on the length and diameter of the nanowires, i.e., shell buckling for short nanowires and columnar buckling for longer nanowires.

Quantum tunneling through planar p-n junctions in HgTe quantum wells

We demonstrate that a p-n junction created electrically in HgTe quantum wells with inverted band structure exhibits interesting intraband and interband tunneling processes. We find a perfect intraband transmission for electrons injected perpendicularly to the interface of the p-n junction. The opacity and transparency of electrons through the p-n junction can be tuned by changing the incidence angle, the Fermi energy and the strength of the Rashba spin-orbit interaction (RSOI). The occurrence of a conductance plateau due to the formation of topological edge states in a quasi-one-dimensional (Q1D) p-n junction can be switched on and off by tuning the gate voltage. The spin orientation can be substantially rotated when the samples exhibit a moderately strong RSOI.

Role of Bi3+ ions for Er3+ ions efficient 1.54 mu m light emission in Er/Bi codoped SiO2 thin film prepared by sol-gel method

Er/Bi codoped SiO2 thin films were prepared by sol-gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 degrees C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 mu m light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 gm reached maximum at 800 degrees C and decreased dramatically at 1000 degrees C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol-gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er-Bi-Si-O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED

Growth of (10(1)over-bar(3)over-bar) semipolar GaN on m-plane sapphire by hydride vapor phase epitaxy

The crystalline, surface, and optical properties of the (10 (1) over bar(3) over bar) semipolar GaN directly grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) were investigated. It was found that the increase of V/III ratio led to high quality (10 (1) over bar(3) over bar) oriented GaN epilayers with a morphology that may have been produced by step-flow growth and with minor evidence of anisotropic crystalline structure. After etching in the mixed acids, the inclined pyramids dominated the GaN surface with a density of 2 X 10(5) cm(-2), revealing the N-polarity characteristic. In the low-temperature PL spectra, weak BSF-related emission at 3.44eV could be observed as a shoulder of donor-bound exciton lines for the epilayer at high V/III ratio, which was indicative of obvious reduction of BSFs density. In comparison with other defect related emissions, a different quenching behavior was found for the 3.29 eV emission, characterized by the temperature-dependent PL measurement. (C) 2009 Elsevier B.V. All rights reserved.

A Cancer Recognition Method Based on DNA Microarray

The accurate cancer classification is of great importance in clinical treatment. Recently, the DNA microarray technology provides a promising approach to the diagnosis and prognosis of cancer types. However, it has no perfect method for the multiclass classification problem. The difficulty lies in the fact that the data are of high dimensionality with small sample size. This paper proposed an automatic classification method of multiclass cancers based on Biomimetic pattern recognition (BPR). To the public GCM data set, the average correct classification rate reaches 80% under the condition that the correct rejection rate is 81%.

Fabry-Perot microcavity modes observed in the micro-photoluminescence spectra of the single nanowire with InGaAs/GaAs heterostructure

We report on the fabrication of the nanowires with InGaAs/GaAs heterostructures on the GaAs(111) B substrate using selective-area metal organic vapor phase epitaxy. Fabry-Perot microcavity modes were observed in the nanowires with perfect end facets dispersed onto the silicon substrate and not observed in the free-standing nanowires. We find that the calculated group refractive indices only considering the material dispersion do not agree with the experimentally determined values although this method was used by some researchers. The calculated group refractive indices considering both the material dispersion and the waveguide dispersion agree with the experimentally determined values well. We also find that Fabry-Perot microcavity modes are not observable in the nanowires with the width less than about 180 nm, which is mainly caused by their poor reflectivity at the end facets due to their weak confinement to the optical field. (C) 2009 Optical Society of America

An Automatic Classification Method of Metabolic Cycle Based on Biomimetic Pattern Recognition

Correct classification of different metabolic cycle stages to identification cell cycle is significant in both human development and clinical diagnostics. However, it has no perfect method has been reached in classification of metabolic cycle yet. This paper exploringly puts forward an automatic classification method of metabolic cycle based on Biomimetic pattern recognition (BPR). As to the three phases of yeast metabolic cycle, the correct classification rate reaches 90%, 100% and 100% respectively.

Dislocation core effect scattering in a quasitriangle potential well

A theory of scattering by charged dislocation lines in a quasitriangle potential well of AlxGa1-xN/GaN heterostructures is developed. The dependence of mobility on carrier sheet density and dislocation density is obtained. The results are compared with those obtained from a perfect two-dimensional electron gas and the reason for discrepancy is given.

Single-photon source in strong photon-atom interaction regime in quasiperiodic photonic crystals

The antibunching properties of the fluorescence from a two-level ideal system in a 12-fold quasiperiodic photonic crystal are investigated based on the calculated local density of states. We found that the antibunching phenomenon of the fluorescence from two-level ideal systems could be significantly changed by varying their positions, i.e., perfect antibunching and antibunching with damped Rabi oscillation phenomenon occurred in different positions and at different frequencies in photonic crystals as a result of the large differences in the local density of states. This study revealed that the multi-level coherence of fluorescence from a two-level ideal system could be manipulated by controlling the position of the two-level ideal system in photonic crystals and the emission frequency in the photonic band structure. Copyright (C) EPLA, 2008