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InGaN/GaN multi-quantum well (MQW) laser diodes (LDs) were grown on c-plane sapphire substrates using a multi-wafer MOCVD system. The threshold current for pulsed lasing was 1.6 A for a gain-guided laser diode with a stripe of 10 × 800 μm2. The threshold current density was 20.3 kA cm−2 and the threshold voltage was 16.5 V. The optical power ratio of transverse electric mode to transverse magnetic mode was found to be greater than 50. The characteristic temperature measured from the plot of threshold current versus measurement temperature was between 130 and 150K.

The Ultra-Fast Flash Observatory (UFFO) is a space observatory for optical follow-ups of gamma ray bursts (GRBs), aiming to explore the first 60 seconds of GRBs optical emission. UFFO is utilized to catch early optical emissions from GRBs within few sec after trigger using a Gimbal mirror which redirects the optical path rather than slewing entire spacecraft. We have developed a 15 cm two-axis Gimbal mirror stage for the UFFO-Pathfinder which is going to be on board the Lomonosov satellite which is to be launched in 2013. The stage is designed for fast and accurate motion with given budgets of 3 kg of mass and 3 Watt of power. By employing stepping motors, the slewing mirror can rotate faster than 15 deg/sec so that objects in the UFFO coverage (60 deg × 60 deg) can be targeted in ~1 sec. The obtained targeting resolution is better 2 arcmin using a close-loop control with high precision rotary encoder. In this presentation, we will discuss details of design, manufacturing, space qualification tests, as well as performance tests.

The Slewing Mirror Telescope (SMT) is the UV/optical telescope of UFFO-pathfinder. The SMT optical system is a Ritchey-Chrétien (RC) telescope of 100 mm diameter pointed by means of a gimbal-mounted flat mirror in front of the telescope. The RC telescope has a 17 × 17arcmin2 in Field of View and 4.3 arcsec resolution (full width half maximum of the point spread function) The beam-steering mirror enables the SMT to access a 35 × 35degree region and point and settle within 1 sec. All mirrors were fabricated to about 0.02 wavelengths RMS in wave front error (WFE) and 84.7% average reflectivity over 200 nm ~ 650 nm. The RC telescope was aligned to 0.05 wavelengths RMS in WFE (test wavelength 632.8 nm). In this paper, the technical details of the RC telescope and slewing mirror system assembly, integration, and testing are given shortly, and performance tests of the full SMT optical system are reported.

The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector, called UBAT (UFFO Burst Alarm & Trigger Telescope), which detects X-rays from the GRB and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes. This report details the calibration of the two components: the MAPMTs and the YSO crystals and simulations of the UBAT. The results shows that this design can observe a GRB within a field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s after the appearance of a GRB X-ray spike.

The Ultra-Fast Flash Observatory (UFFO) aims to detect the earliest moment of Gamma-Ray Bursts (GRBs) which is not well known, resulting into the enhancement of GRB mechanism understanding. The pathfinder mission was proposed to be a scaled-down version of UFFO, and only contains the UFFO Burst Alert & Trigger Telescope (UBAT) measuring the X-ray/gamma-ray with the wide-field of view and the Slewing Mirror Telescope (SMT) with a rapid-response for the UV/optical photons. Once the UBAT detects a GRB candidate with the position accuracy of 10 arcmin, the SMT steers the UV/optical photons from the candidate to the telescope by the fast rotatable mirror and provides the early UV/optical photons measurements with 4 arcsec accuracy. The SMT has a modified Ritchey-Chrètien telescope with the aperture size of 10 cm diameter including the rotatable mirror and the image readout by the intensified charge-coupled device. There is a key board called the UFFO Data Acquisition system (UDAQ) that manages the communication of each telescope and also of the satellite and the UFFO overall operation. This pathfinder is designed and built within the limited size and weight of  ~20 kg and the low power consumption up to  ~30 W. We will discuss the design and performance of the UFFO-pathfinder, and its integration to the Lomonosov satellite.

One of the key aspects of the upcoming Ultra-Fast Flash Observatory (UFFO) pathfinder for Gamma Ray Bursts (GRBs) identification is the UFFO Burst Alert & Trigger Telescope (UBAT). The scientific propose of UBAT is to detect and locate as fast as possible the GRBs in the sky. This is achieved by using a coded mask aperture camera scheme with a wide field of view (FOV) and selecting a X-ray detector of high quantum efficiency and large detection area. This X-ray detector of high quantum efficiency and large detection area is called the UBAT detector. The UBAT detector consists of 48 × 48 Yttrium Oxyorthosilicate (YSO) scintillator crystal arrays and Multi Anode Photomultiplier Tubes (MAPMTs), analog electronics equipped with ASIC chips, digital electronics equipped with Field Programmable Gate Array (FPGA) chips, and a mechanical structure that supports all components of the UBAT detector. The total number of the pixels in the UBAT detector is 2304, and the total effective detection area is 191 cm2. We will present the design and construction, and performance of the UBAT detector including the responses of the UBAT detector to X-ray sources.

The Ultra-Fast Flash Observatory (UFFO), which will be launched onboard the Lomonosov spacecraft, contains two crucial instruments: UFFO Burst Alert & Trigger Telescope (UBAT) for detection and localization of Gamma-Ray Bursts (GRBs) and the fast-response Slewing Mirror Telescope (SMT) designed for the observation of the prompt optical/UV counterparts. Here we discuss the in-space calibrations of the UBAT detector and SMT telescope. After the launch, the observations of the standard X-ray sources such as pulsar in Crab nebula will provide data for necessary calibrations of UBAT. Several standard stars will be used for the photometric calibration of SMT. The celestial X-ray sources, e.g. X-ray binaries with bright optical sources in their close angular vicinity will serve for the cross-calibration of UBAT and SMT.

The Ultra-Fast Flash Observatory (UFFO) Pathfinder for Gamma-Ray Bursts (GRBs) consists of two telescopes. The UFFO Burst Alert & Trigger Telescope (UBAT) handles the detection and localization of GRBs, and the Slewing Mirror Telescope (SMT) conducts the measurement of the UV/optical afterglow. UBAT is equipped with an X-ray detector, analog and digital signal readout electronics that detects X-rays from GRBs and determines the location. SMT is equipped with a stepping motor and the associated electronics to rotate the slewing mirror targeting the GRBs identified by UBAT. First the slewing mirror points to a GRB, then SMT obtains the optical image of the GRB using the intensified CCD and its readout electronics. The UFFO Data Acquisition system (UDAQ) is responsible for the overall function and operation of the observatory and the communication with the satellite main processor. In this paper we present the design and implementation of the electronics of UBAT and SMT as well as the architecture and implementation of UDAQ.

One of the unexplored domains in the study of gamma-ray bursts (GRBs) is the early time phase of the optical light curve. We have proposed Ultra-Fast Flash Observatory (UFFO) to address this question through extraordinary opportunities presented by a series of small space missions. The UFFO is equipped with a fast-response Slewing Mirror Telescope that uses a rapidly moving mirror or mirror array to redirect the optical beam rather than slewing the entire spacecraft or telescope to aim the optical instrument at the GRB position. The UFFO will probe the early optical rise of GRBs with sub-second response, for the first time, opening a completely new frontier in GRB and transient studies. Its fast response measurements of the optical emission of dozens of GRB each year will provide unique probes of the burst mechanism and test the prospect of GRB as a new standard candle, potentially opening up the z > 10 universe. We describe the current limit in early photon measurements, the aspects of early photon physics, our soon-to-be-launched UFFO-pathfinder mission, and our next planned mission, the UFFO-100.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The Ultra-Fast Flash Observatory (UFFO) is a space mission to detect the early moments of an explosion from Gamma-ray bursts (GRBs), thus enhancing our understanding of the GRB mechanism. It consists of the UFFO Burst & Trigger telescope (UBAT) for the recognition of GRB positions using hard X-ray from GRBs. It also contains the Slewing Mirror Telescope (SMT) for the fast detection of UV-optical photons from GRBs. It is designed to begin the UV-optical observations in less than a few seconds after the trigger. The UBAT is based on a coded-mask X-ray camera with a wide field of view (FOV) and is composed of the coded mask, a hopper and a detector module. The SMT has a fast rotatable mirror which allows a fast UV-optical detection after the trigger. The telescope is a modified Ritchey-Chrétien telescope with the aperture size of 10 cm diameter, and an image intensifier readout by CCD. The UFFO pathfinder is scheduled to launch into orbit on 2012 June by the Lomonosov spacecraft. It is a scaled-down version of UFFO in order to make the first systematic study of early UV/optical light curves, including the rise phase of GRBs. We expect UBAT to trigger ~44 GRBs/yr and expect SMT to detect ~10 GRBs/yr.

Metal contamination in Si and SiO2 films deposited by plasma-enhanced chemical vapor deposition (PECVD) in the fabrication of low-temperature poly Si thin-film transitor was investigated. Aluminum was the major metal impurity to have the highest concentration. Segregation of Al was always observed in the films deposited at temperatures above 400 °C. The impurity level in the segregated region was 1018 ∼ 1020 atoms/cm3 for Al, while the concentration in matrix was about 1016 atoms/cm3. From the transmission electron microscopy image, the Al segregated region contains small-size Al precipitates. Although the Al impurity level of 1016 atoms/cm3 did not cause any serious degradation of device performance, the level of 1018 atom/cm3 and higher can induce a fatal degradation of the threshold voltage. This study revealed that the Al originated from the PECVD chamber, carbon precipitates provided the preferred sites for Al precipitates, and the solubility and diffusivity of Al in Si accelerated the segregation of Al.

Polycrystalline samples of HgBa2(Ca0.86Sr0.14)2Cu3O8+δ (denoted as Hg-1223) were prepared by a precursor route, which involves the reaction between HgO and two precursors: Ba2CuO3+x and Ca0.14CuO2. X-ray powder diffraction analysis revealed that the Hg-1223 is isostructural with pristine HgBa2Ca2Cu3O8−δ and TlBa2Ca2Cu3O9−δ. The Hg-1223 has tetragonal symmetry with space group P4/mmm, and lattice parameters a = 3.8648(2) Å and c = 16.0319(2) Å. The as-synthesized Hg-1223 sample has a Tc of about 126 K. After annealing in an oxygen atmosphere at 280 °C for 10 h, the Tc increased to 132 K. Using this precursor pathway, Hg-1223 samples can be reproducibly synthesized.

History, legend and memory have long pointed to Co Loa, an earthwork enclosure outside Hanoi, as the seat of an indigenous power that gave identity to the people of the Bac Bo region, north Vietnam. Survey, excavation and a set of radiocarbon dates now put this site on the historical map. The main rampart of the middle circuit was built in the later centuries BC, before the coming of Han Imperial China. Nor was this rampart the first defence. The authors show the potential of archaeology for revealing the creation and development of a polity among the prosperous people of the Dongson culture.

Pronuclear formation and intracellular content of glutathione, containing reduced and oxidised forms, in porcine oocytes matured in vitro were determined following insemination and/or electrical stimulation. After insemination, sperm penetration had occurred as early as 3 h and female pronuclei had formed by 6 h with complete development by 12 h. Male pronuclear formation occurred, primarily, between 9 and 12 h after insemination. Glutathione content of the oocytes decreased following sperm penetration and remained at a depressed level until 12 h. After electrical stimulation, oocyte activation had occurred and female pronuclei had formed by 3 and 6 h, respectively. Oocyte glutathione content did not change as a result of oocyte activation. When oocytes were exposed to an electrical pulse and then spermatozoa, female pronuclear formation was observed by 3 h after stimulation/insemination. Sperm penetration was observed between 3 and 9 h. However, the incidence of male pronuclear formation observed at 12 h was extremely low, although sperm decondensation had occurred in some oocytes. Oocyte glutathione content had not decreased by 6 h following electrical activation. These results demonstrate that the changes in glutathione content in porcine oocytes following fertilisation in vitro differ from those due to electrical activation. Further, the decreased intracellular glutathione content in oocytes activated by sperm penetration appears to be due to the presence of a sperm factor.