Molecular Beam Epitaxy of Ga(In)AsN/GaAs Quantum Wells towards 1.3µm and 1.55µm

In this article, we report an attempt of extending the InGaAsN materials towards 1.3µm and 1.55µm wavelength. All these InGaAsN samples are grown in a plasma-assisted solid-source molecular-beam epitaxy (SS-MBE) system. Our experiments revealed that the nitrides could be grown with both direct nitrogen beam and dispersive nitrogen. The nitrogen incorporation rate could be reduced by the presence of indium flux. The interaction between nitrogen and indium might lead to 3D growth mode and growth dynamics. It is proved that the increasing growth rate reduces the nitrogen incorporation efficiency. The data for nitrogen sticking coefficient are somewhat contradictive. The growth with dispersive nitrogen source causes the improvement of material quality. Fixed indium flux is a better way for the wavelength control. Also, we report some growth optimization work for better PL property and the annealing effect on the samples. Literature is sometimes reviewed for comparison.Singapore-MIT Alliance (SMA

Design and fabrication of indium phosphide air-bridge waveguides with MEMS functionality

We present the design and fabrication of a dual air-bridge waveguide structure integrated with MEMS functionality. The structure is designed to function as a tunable optical buffer for telecommunication application. The optical buffer structure is based on two parallel waveguides made of high refractive index material with subwavelength dimensions. They are suspended in air, and are separated by a sub-micron air gap. Due to the fact that the size of the waveguides is much smaller than the wavelength of light that propagates in the structure, a significant fraction of the optical mode is in the air gap between the waveguides. By changing the size of the air gap using MEMS techniques, we can vary this fraction and hence the effective refractive index of the waveguide structure, thus generating tunable optical delay.The optical buffer structure was grown on an InP substrate by molecular beam epitaxy, and the device layer was made of InGaP. An InGaAs layer was sandwiched between the device layer and the substrate to serve as a sacrificial layer. The sub-micron waveguides, their supports in the form of side pillars with tapered shapes in order to minimize optical losses, and the MEMS structures were patterned using electron beam lithography and plasma etching. Electrodes were integrated into the structure to provide electrostatic actuation. After the sample patterning, the waveguide structure was released using HF etch. Our simulations predict that by varying the waveguide separation from 50 nm to 500 nm, we could achieve a change in propagation delay by a factor of two

Phenomenological Consequences of Singlet Neutrinos

In this paper, we study the phenomenology of right-handed neutrino isosinglets. We consider the general situation where the neutrino masses are not necessarily given by $m_D^2/M$, where $m_D$ and $M$ are the Dirac and Majorana mass terms respectively. The consequent mixing between the light and heavy neutrinos is then not suppressed, and we treat it as an independent parameter in the analysis. It turns out that $\mu-e$ conversion is an important experiment in placing limits on the heavy mass scale ($M$) and the mixing. Mixings among light neutrinos are constrained by neutrinoless double beta decay, as well as by solar and atmospheric neutrino experiments. Detailed one-loop calculations for lepton number violating vertices are provided.Comment: Revtex file,TRI-PP-94-1,VPI-IHEP-94-1, 23 pages, a compressed for 8 figures is appende

Reasons behind family refusal to organ donation in Sabah, Malaysia

Despite increased public awareness and the increase in the number of pledged organ donors, the actual number of organ donation in Sabah remains low due to the high rejection rate to donation by family members. This retrospective study aims to discover the main reasons of family refusal to organ donation in Sabah, besides attempting to determine whether the reasons of family refusal were significantly associated to the background of the next-of-kin. Descriptive statistics were used to describe the demography of the deceased and the next-of kin, as well as the reason of refusal. Meanwhile, Chisquare test and Kruskal-Wallis test were implemented to identify the significant associations. Not knowing the wish of deceased, unwilling to let the deceased to suffer, and concern over funeral delay stand out to be the most predominant reasons of family refusal. However, none of the background factors are significantly associated with reasons of family refusal to organ donation

ZZ--Z′Z' mixing and oblique corrections in an SU(3)×U(1){\rm SU(3) \times U(1)} model

A global fit for experiments is included in this revised version.Comment: IFP-460-UNC, TRI-PP-93-11, 20 pages, 2 figures are appende

Flavon exchange effects in models with abelian flavor symmetry

In models with abelian flavor symmetry the small mixing angles and mass ratios of quarks and leptons are typically given by powers of small parameters characterizing the spontaneous breaking of flavor symmetry by "flavon" fields. If the scale of the breaking of flavor symmetry is near the weak scale, flavon exchange can lead to interesting flavor-violating and CP violating effects. These are studied. It is found that d_e, mu -> e + gamma, and mu-e conversion on nuclei can be near present limits. For significant range of parameters mu-e conversion can be the most sensitive way to look for such effects.Comment: 19 pages, 5 Postscript figures, LATE

Associated Higgs production with top quarks at the Large Hadron Collider: NLO QCD corrections

We present in detail the calculation of the O(alpha_s^3) inclusive total cross section for the process pp -> t-tbar-h, in the Standard Model, at the CERN Large Hadron Collider with center-of-mass energy sqrt(s_H)=14 TeV. The calculation is based on the complete set of virtual and real O(alpha_s) corrections to the parton level processes q-qbar -> t-tbar-h and gg -> t-tbar-h, as well as the tree level processes (q,qbar)g -> t-tbar-h-(q,qbar). The virtual corrections involve the computation of pentagon diagrams with several internal and external massive particles, first encountered in this process. The real corrections are computed using both the single and the two cutoff phase space slicing method. The next-to-leading order QCD corrections significantly reduce the renormalization and factorization scale dependence of the Born cross section and moderately increase the Born cross section for values of the renormalization and factorization scales above m_t.Comment: 70 pages, 12 figures, RevTeX4: one word changed in the abstract, one sentence reworded in the introduction. To appear in Phys. Rev.

Previously unpublished Odonata records from Sarawak, Borneo, part VI: Miri Division including checklists for Niah, Lambir Hills, Loagan Bunut and Pulong Tau National Parks

Recods of Odonata made from 2005 to 2020 in Miri Division in Sarawak are presented, including records from Lambir Hills, Loagan Bunut, Niah and Pulong Tau National Parks. Primary types of Odonata originating from Miri Division are listed. Surveys of more than one day duration in Miri Division and covered here are tabulated with the funding source where appropriate; four of the surveys covered here were funded by the International Dragonfly Fund. One hundred and eighty-eight species are listed based on surveys made by the authors, of which Macromia jucunda Lieftinck, 1955, had not been recorded from Borneo before, Burmagomphus arthuri Lieftinck, 1953 is a new record for Miri Division and Camacinia gigantea (Brauer, 1867) has only been recorded from the Division re-cently with the only published record in a difficult to access publication (Choong (2020)). At least 48 more of the species listed were recorded from Miri Division for the first time in surveys covered in this report, although the records have been published (in most cases with no details beyond division and district in Dow (2021)) before. Two forms of Xiphi-agrion cyanomelas Selys, 1876 are recorded and the likelihood that they represent different species is discussed. A possibly new, large sized, species of Macromia allied to M. westwoodii Selys, 1874 is recorded and discussed. Other notable records not published with details before include Rhinocypha stygia Förster, 1897, Rhinoneura caerulea Kimmins, 1936, Dysphaea lugens (Selys, 1873), Euphaea ameeka van Tol & Norma-Rashid, 1995, Euphaea basalis (Laidlaw, 1915), Amphicnemis new sp. cf mariae Lieftinck, 1940 (previously recorded from Usun Apau National Park), Anaciaeschna jaspidea (Burmeister, 1839), Heliaeschna uninervulata Martin, 1909, Borneogomphus sp., Heliogomphus borneensis Lieftinck, 1964, Ictinogomphus acutus (Laidlaw, 1914), Chlorogomphus sp., Macromia corycia Laidlaw, 1922, Idionyx montana Karsch, 1891, Hylaeothemis clementia Ris, 1909, Orchithemis xanthosoma Laidlaw, 1911, Rhyothemis fulgens Kirby, 1889, Rhyothemis regia (Brauer, 1867), Tetrathemis sp. cf platyptera Selys, 1878, Tramea phaeoneura Lieftinck, 1953 and Tramea sp. cf virginia (Rambur, 1842). The habitat preferences of Dysphaea lugens are discussed. A male-male tandem of Coeliccia nigrohamata Laidlaw, 1918 is reported. The somewhat peculiar distribution of Argiocnemis rubescens rubeola Selys, 1877 and Pseudothemis jorina Förster, 1904 in Sarawak is discussed. Activity of the apparently normally crepuscular Heliaeschna uninervulata in the middle of the day is reported. An interesting morphological detail of some female Chlorogomphus from Sarawak is discussed. The likelihood that Macromia corycia is a junior synonym of M. gerstaeckeri Krüger, 1899 is discussed. The possibility that the range of Rhyothemis regia is expanding in Sarawak is remarked upon. The identity of Tramea sp. cf virginia is discussed. With the records presented here at least 222 species of Odonata are known from Miri Division and with the addition of Macromia jucunda to the known fauna, 309 species have now been recorded from Sarawak. More detailed specimen records are given in Appendix 1 and a revised checklist of Odonata from Lambir Hills National Park and the first checklis from Loagan Bunut, Niah and Pulong Tau National Parks are given in Appendix 2

Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry A_LL and the differential cross section for inclusive Pi0 production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV. The cross section was measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be in good agreement with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T < 11 GeV/c and excludes a maximal positive gluon polarization in the proton. The mean transverse momentum fraction of Pi0's in their parent jets was found to be around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC