Al0.24Ga0.76N/GaN heterostructures treated by CF4 plasma at various gas pressures have been electrically investigated using capacitance-voltage and steady-state photo-capacitance spectroscopy ...techniques. The plasma treatments at gas pressures between 1.3 and 6.7 Pa induced a large positive shift in pinch-off voltage VP from -3.05 V. Additionally, three deep-level defects were newly introduced at ∼2.1, ∼2.8, and ∼3.25 eV below the conduction band. Among them, the ∼2.1 eV level is considered to be attributable to Ga vacancy-F complexes in the AlGaN layer and to be strongly responsible for the positive shift in VP due to their negatively fixed charges.
Cyclooxygenase
(COX) is a key enzyme in the synthesis of prostaglandins from
arachidonic acid. Much evidence, including that from epidemiological
and experimental studies, suggests that the inducible ...form of COX,
COX-2, is increased in colon tumor tissues and is involved in colon
cancer tumorigenesis. To determine the significance of COX-2 in
tumorigenesis in the urinary bladder, the expression of COX-2 in
transitional cell carcinoma and preneoplastic lesions of the bladder
was examined. Tumor specificity of COX-2 immunoblotting was 100% in 12
of 35 (34%) tumors, but in 0 of the 10 normal urothelia
samples. COX-2 expression was significantly correlated with
tumor stage in 9 of 20 (45%) muscle-invasive (pT2â4) tumors and in 3
of 15 (20%) superficially invasive (pT1) tumors (P < 0.05). Immunohistochemical examination revealed that 13 of 14 (93%)
samples of carcinoma in situ (CIS), which may be the precursor of muscle-invasive-type tumors, expressed COX-2,
whereas 10 of 21 (48%) samples of dysplasia, which may be the
precursor of both superficially invasive and muscle-invasive tumors,
expressed COX-2. From the expression profile of COX-2 in these various
urothelia, it is suggested that COX-2 is involved in the development of
transitional cell carcinoma of the urinary bladder, especially that of
muscle-invasive tumors via CIS. Furthermore, COX-2 may be a therapeutic
target for CIS because of the high expression rate of COX-2 in CIS
lesions.
The effects of negatively-charged air conditions were analyzed as one of the approaches to improve health and quality of life. We previously reported that the use of a charcoal coating and ...application of an electric voltage yielded predominantly negatively-charged particles in an experimental room, and that 2.5 hours of living in these conditions caused a slight activation of the immune system (slight elevation of serum interleukin (IL)-2), regulated blood flow, and stabilized the autonomic nervous system when compared with control conditions (no dominance of negatively-charged particles). In this study, we expanded the previous study and placed 15 subjects in negatively-charged air conditions for two weeks during the night and analyzed various biological parameters. Although individual biological reactions differed from subject to subject, natural killer (NK) cell activity increased significantly following living in negatively-charged air conditions. Taken together, the results of the previous investigation and those of this study show that repeated elevation of IL-2 (although it immediately returned to the baseline level) causes chronic and recurrent stimulation to NK cells and results in the steady activation of NK cells. Negatively-charged air particles may be a good tool to improve health and quality of life.
The surface detector array of the Telescope Array experiment Abu-Zayyad, T.; Aida, R.; Anderson, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2012, Letnik:
689
Journal Article
Recenzirano
Odprti dostop
The Telescope Array (TA) experiment, located in the western desert of Utah, USA, is designed for the observation of extensive air showers from extremely high energy cosmic rays. The experiment has a ...surface detector array surrounded by three fluorescence detectors to enable simultaneous detection of shower particles at ground level and fluorescence photons along the shower track. The TA surface detectors and fluorescence detectors started full hybrid observation in March, 2008. In this article we describe the design and technical features of the TA surface detector.
The Telescope Array (TA) collaboration has measured the energy spectrum of ultra-high energy cosmic rays (UHECRs) with primary energies above 1.6 x 10 super(18) eV. This measurement is based upon ...four years of observation by the surface detector component of TA. The spectrum shows a dip at an energy of 4.6 x 10 super(18) eV and a steepening at 5.4 x 10 super(19) eV which is consistent with the expectation from the GZK cutoff. We present the results of a technique, new to the analysis of UHECR surface detector data, that involves generating a complete simulation of UHECRs striking the TA surface detector. The procedure starts with shower simulations using the CORSIKA Monte Carlo program where we have solved the problems caused by use of the "thinning" approximation. This simulation method allows us to make an accurate calculation of the acceptance of the detector for the energies concerned.
Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment includes a surface detector (SD) ...array and three fluorescence detector (FD) stations. The FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye (HiRes) experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tube pixels. To obtain the EAS parameters with high accuracy, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of the new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.
We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Observatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a ...mission to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth’s nighttime atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based observation and we compute the annual exposure in nadir observation. The results are based on studies of the expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of clouds and different types of background light. We show that the annual exposure is about one order of magnitude higher than those of the presently operating ground-based observatories.
The JEM-EUSO (Joint Experiment Missions for the Extreme Universe Space Observatory) program aims at developing Ultra-Violet (UV) fluorescence telescopes for efficient detections of Extensive Air ...Showers (EASs) induced by Ultra-High Energy Cosmic Rays (UHECRs) from satellite orbit. In order to demonstrate key technologies for JEM-EUSO, we constructed the EUSO-Balloon instrument that consists of a ∼1 m2 refractive telescope with two Fresnel lenses and an array of multi-anode photo-multiplier tubes at the focus. Distinguishing it from the former balloon-borne experiments, EUSO-Balloon has the capabilities of single photon counting with a gate time of 2.3 µs and of imaging with a total of 2304 pixels. As a pathfinder mission, the instrument was launched for an 8 h stratospheric flight on a moonless night in August 2014 over Timmins, Canada. In this work, we analyze the count rates over ∼2.5 h intervals. The measurements are of diffuse light, e.g. of airglow emission, back-scattered from the Earth’s atmosphere as well as artificial light sources. Count rates from such diffuse light are a background for EAS detections in future missions and relevant factor for the analysis of EAS events. We also obtain the geographical distribution of the count rates over a ∼780 km2 area along the balloon trajectory. In developed areas, light sources such as the airport, mines, and factories are clearly identified. This demonstrates the correct location of signals that will be required for the EAS analysis in future missions. Although a precise determination of count rates is relevant for the existing instruments, the absolute intensity of diffuse light is deduced for the limited conditions by assuming spectra models and considering simulations of the instrument response. Based on the study of diffuse light by EUSO-Balloon, we also discuss the implications for coming pathfinders and future space-based UHECR observation missions.
EUSO-TA is a ground-based telescope, installed at the Telescope Array (TA) site in Black Rock Mesa, Utah, USA. This is the first detector to successfully use a Fresnel lens based optical system and ...multi-anode photomultipliers (64 channels per tube, 2304 channels encompassing a 10.6° × 10.6° field of view) for detection of Ultra High Energy Cosmic Rays (UHECR). The telescope is located in front of one of the fluorescence detectors of the TA experiment. Since its installation in 2013, the detector has observed several ultra-high energy cosmic ray events and, in addition, meteors. The limiting magnitude of 5.5 on summed frames ( ∼ 3 ms) has been established. Measurements of the UV night sky emission in different conditions and moon phases and positions have been completed. The performed observations serve as a proof of concept for the future application of this detector technology.
The electrical properties of a semi-insulating GaN (SI-GaN) epitaxial layer have been investigated and regimes of space charge and Ohmic currents found. Microwave and dc current modes were used for ...temporal measurements of the photocurrent. Transient behaviour was observed in the injection current and photo-response, with a wide range of time constants. The role of the space charge has been analysed and a previous columnar model of the epitaxial layer is shown to require modification. The nature of traps and recombination centres is discussed. Some promising data demonstrating the application of this SI-GaN for the detection of ionising particles, specifically α particles, is presented.
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