A vertical monolithic combination of an InGaAsP/InP laser and a heterojunction bipolar transistor

A DH InGaAsP/InP mesa laser and a DH InGaAsP/InP mass-transport laser were successfully put together with an InGaAsP/InP heterojunction bipolar transistor in a vertical configuration. A laser threshold current as low as 17 mA and an output laser power of over 30 mW were achieved. Base injection current-controlled optical bistability and optical switching were demonstrated

(2-Hy­droxy­acetato-κO 1)bis­(1,10-phenan­throline-κ2 N,N′)copper(II) nitrate

In the title compound, [Cu(C2H3O3)(C12H8N2)2]NO3, the CuII atom is coordinated by two phenanthroline (phen) ligands and one carboxyl-O atom of a hy­droxy­acetate anion in a distorted square-pyramidal geometry. The hy­droxy group of the hy­droxy­acetate ligand links with the counter NO3 − anion via a pair of bifurcated O—H⋯O hydrogen bonds. The centroid–centroid distance of 3.5676 (14) Å between benzene rings of parallel phen ligands of adjacent mol­ecules suggests the existence of π–π stacking. Weak inter­molecular C—H⋯O hydrogen bonding is also present in the crystal structure

Study on the Simulation and Evolution Model of Unexpected Emergencies’ spreading Network

AbstractThe cycle characteristic of unexpected emergencies’ spreading is quantitatively characterized by Gaussian distribution, and Systemic Science is combined with complex network theory to constructs the evolution model of unexpected emergencies’ spreading from the two dimensions of spreading object and event subject so as to study the evolution of unexpected emergencies’ spreading network. By comparing the resolving results with the simulating results, the feature of unexpected emergencies’ spreading network which is in accordance with scale-free network's characteristics of γ=3 is founded which reflects the objective characteristic of unexpected emergencies’ spreading network, so that it means a lot for the emergency department to make “Scene-In response to” control strategy

N,N′-[(2,3,5,6-Tetra­methyl-p-phenyl­ene)dimethyl­ene]bis­[2-chloro-N-(2-chloro­ethyl)ethanamine]

The title mol­ecule, C20H32Cl4N2, lies on an inversion center. A weak intra­molecular C—H⋯N hydrogen bond may, in part, influence the conformation of the mol­ecule

Standards-based mathematics reforms and mathematics achievement of American Indian/Alaska Native eighth graders.

Using the NAEP nationally-representative data collected from eighth-graders, we investigated the relative exposure of American Indian/Alaska Native (AIAN) students to mathematics teachers who are knowledgeable about standards, participate in standards-based professional development, and practice standards-based instruction; American Indian/Alaska Native student reports of standards-based classroom activities; and how student reports of classroom activities and teacher reports of their knowledge, professional development, and practices are associated with mathematics achievement of American Indian/Alaska Native students. We found that AIAN students had among the lowest exposure to teachers who reported they were knowledgeable about standards, who participated in standards-based professional development, and who practiced standards-based instruction. In addition, AIAN students were less likely than African American and Latino students to report that they experienced standards-based classroom activities. Our data showed that teacher reports of standards-based knowledge and practice of standards-based instruction were not significantly associated with mathematics achievement of AIAN students. However, student reports of classroom activities characterizing standards-based instruction was associated with higher mathematics achievement of AIAN students

Compact Metamaterials Induced Circuits and Functional Devices

In recent years, we have witnessed a rapid expansion of using metamaterials to manipulate light or electromagnetic (EM) wave in a subwavelength scale. Specially, metamaterials have a strict limitation on element dimension from effective medium theory with respect to photonic crystals and other planar structures such as frequency selective surface (FSS). In this chapter, we review our effort in exploring physics and working mechanisms for element miniaturization along with the resulting effects on element EM response. Based on these results, we afford some guidelines on how to design and employ these compact meta-atoms in engineering functional devices with high performances. We found that some specific types of planar fractal or meandered structures are particularly suitable to achieve element miniaturization. In what follows, we review our effort in Section 1 to explore novel theory and hybrid method in designing broadband and dual band planar devices. By using single or double such compact composite right-/left-handed (CRLH) atom, we show that many microwave/RF circuits, i.e., balun, rat-race coupler, power divider and diplexer, can be further reduced while without inducing much transmission loss from two perspectives of lumped and distributed CRLH TLs. In Section 2, we show that a more compact LH atom can be engineered by combining a fractal ring and a meandered thin line. Numerical and experimental results demonstrate that a subwavelength focusing is achieved in terms of smooth outgoing field and higher imaging resolution. Section 3 is devoted to a clocking device from the new concept of superscatterer illusions. To realize the required material parameters, we propose a new mechanism by combining both electric and magnetic particles in a composite meta-atom. Such deep subwavelength particles enable exact manipulation of material parameters and thus facilitate desirable illusion performances of a proof-of-concept sample constructed by 6408 gradually varying meta-atoms. Finally, we summarize our results in the last section

QCD Approach to B->D \pi Decays and CP Violation

The branching ratios and CP violations of the $B\to D\pi$ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass $\mu_g$ is regarded as a universal scale, it is extracted to be around $\mu_g = 440$ MeV from one of the well-measured $B\to D\pi$ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct $CP$ asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the $B\to D^{\pm}\pi^{\mp}$ decays to be consistent with the experimental data at 1-$\sigma$ level. More precise measurements will be helpful to extract weak angle $2\beta+\gamma$.Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for one of decay channels is improve

Numerical Analysis of Cold Injury of Skin in Cryogen Spray Cooling for Laser Dermatologic Surgery

In laser dermatologic surgery, cryogen spray cooling (CSC) is used to avoid unwanted thermal damage such as scars from skin burning due to the melanin absorption of the laser beam. As the cryogen is fully atomized from the nozzle, temperature of the droplets can quickly drop below -60 oC because of evaporation. Such low temperature may lead to cold injury of skin. Therefore, spray cooling process should be accurately controlled during clinical practice to achieve sufficient protection and avoid cold injury. This study presents a numerical analysis for cold injury of skin in cryogen spray cooling for dermatologic laser surgery by a newly developed hest transfer model. For the freezing of skin cells, heat conduction equation was used to describe frozen and unfrozen zones, and heat capacity method was utilized for mushy zone to consider the phase change of tissue. A realistic boundary condition was implemented to simulate the cooling effect during cryogen spray cooling by a generalized correlation for the dynamic heat transfer coefficient. By tracking the front of the tissue phase change, the model can be used to predict the movement of the harmful isothermals. With this model, the severity of cold injury is quantified under various clinical conditions and the effects of initial temperature as well as the spurt duration on possible cold injury of skin are investigated. The results show that 100~150ms spray cooling duration is appropriate to avoid non-uniform cooling along the radial direction and also prevent potential cold injury. Lower room temperature (10~20oC) is recommended to achieve a deep penetration protection. Further development of new candidate cryogens with lower boiling point (e.g. R407C or R404a) are highly recommended to achieved a better cooling effect

Interferences effects in polarized nonlinear Breit-Wheeler process

The creation of polarized electron-positron pairs by the nonlinear Breit-Wheeler process in short laser pulses is investigated using the Baier-Katkov semiclassical method beyond local-constant-field approximation (LCFA), which allows for identifying the interferences effects in the positron polarization. When the laser intensity is in the intermediate %multiphoton regime, the interferences of pair production in different formation lengths induce an enhancement of pair production probability for spin-down positrons, which significantly affects the polarization of created positrons. The polarization features are distinct from that obtained with LCFA, revealing the invalidity of LCFA in this regime. Meanwhile, the angular distribution for different spin states varies, resulting in an angular-dependent polarization of positrons. The average polarization of positrons at beam center is highly sensitive to the laser's carrier-envelope phase (CEP), which provides a potential alternative way of determining the CEP of strong lasers. The verification of the observed interference phenomenon is possible for the upcoming experiments

Inversionless gain in a three-level system driven by a strong field and collisions

Inversionless gain in a three-level system driven by a strong external field and by collisions with a buffer gas is investigated. The mechanism of populating of the upper laser level contributed by the collision transfer as well as by relaxation caused by a buffer gas is discussed in detail. Explicit formulae for analysis of optimal conditions are derived. The mechanism developed here for the incoherent pump could be generalized to other systems.Comment: RevTeX, 9 pages, 4 eps figure