Detection of Cherenkov light from air showers with Geiger-APDs

We have detected Cherenkov light from air showers with Geiger-mode APDs (G-APDs). G-APDs are novel semiconductor photon-detectors, which offer several advantages compared to conventional photomultiplier tubes in the field of ground-based gamma-ray astronomy. In a field test with the MAGIC telescope we have tested the efficiency of a G-APD / light catcher setup to detect Cherenkov light from air showers. We estimate a detection efficiency, which is 60% higher than the efficiency of a MAGIC camera pixel. Ambient temperature dark count rates of the tested G-APDs are below the rates of the night sky light background. According to these recent tests G-APDs promise a major progress in ground-based gamma-ray astronomy.Comment: 4 pages, 5 figures, to appear in the proceedings of the 30th International Cosmic Ray Conference, Merida, July 200

Gross Properties and Isotopic Phenomena in Spectator Fragmentation

A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory. Searching for signals of criticality in the fragment production we have applied the model independent universal fluctuations theory already proposed to track criticality signals in multifragmentation to our data. The fluctuation of the largest fragment charge and of the asymmetry of the two and three largest fragments and their bimodal distribution have also been analysed.Comment: 6 pages, 4 figures, IX International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, Brazil, August 28 - September 1, 200

Discriminant Analysis and Secondary-Beam Charge Recognition

The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around 124La and 107Sn were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable 124Sn projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods.Comment: 6 pages, 7 eps figures, elsart, submitted to Nucl. Instr. and Meth.

Gamma-ray Observations Under Bright Moonlight with VERITAS

Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727+502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations

Mass and Isospin Effects in Multifragmentation

A systematic study of isospin effects in the breakup of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory (Darmstadt). Four different projectiles 197Au, 124La, 124Sn and 107Sn, all with an incident energy of 600 AMeV, have been used, thus allowing a study of various combinations of masses and N/Z ratios in the entrance channel. The measurement of the momentum vector and of the charge of all projectile fragments with Z>1 entering the acceptance of the ALADiN magnet has been performed with the high efficiency and resolution achieved with the TP-MUSIC IV detector. The Rise and Fall behavior of the mean multiplicity of IMFs as a function of Zbound and its dependence on the isotopic composition has been determined for the studied systems. Other observables investigated so far include mean N/Z values of the emitted light fragments and neutron multiplicities. Qualitative agreement has been obtained between the observed gross properties and the predictions of the Statistical Multifragmentation Model.Comment: 10 pages,7 figure, 18th Nuclear Physics Division Conference of the EPS, Prague, submitted to Nucl. Phys.

Upper limits from five years of blazar observations with the VERITAS Cherenkov telescopes

Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E > 100 GeV) γ-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ~570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4σ excess

Pengaruh Pemberian Ketotifen terhadap Jumlah Sel Fibroblas dan Kepadatan Sel Kolagen pada Luka Insisi Tikus Wistar

Ingga Hadian, S-501202027. PENGARUH PEMBERIAN KETOTIFEN TERHADAP JUMLAH SEL FIBROBLAS DAN KEPADATAN SEL KOLAGEN PADA LUKA INSISI TIKUS WISTAR. Pembimbing I : DR. Untung Alfianto, dr, Sp.Bs, Pembimbing II : dr. Ardana Tri Arianto. Msi. Med. Sp.An-KNA. Program studi Magister Kedokteran Keluarga, Minat Utama Ilmu Biomedik, Fakultas Kedokteran Universitas Sebelas Maret, Surakarta, 2016. Latar Belakang : Sel mast merupakan salah satu yang berperan dalam proses inflamasi pada penyembuhan luka. Sel mast dikaitkan dengan kejadian luka kronis, sehingga sel mast diduga ikut memelihara proses inflamasi secara berlebihan. Hambatan pada degranulasi sel mast diharapkan akan mempercepat penyembuhan luka yang ditandai dengan meningkatnya jumlah sel fibroblas dan kepadatan sel kolagen. Ketotifen mampu mengurangi dreganulasi sel Mast dan mengurangi pelepasan Histamin, protease sel Mast, myeloperoxidase, leukotriens, PAF dan bermacam-macam Prostaglandin. Ketotifen juga menghambat agregasi polimorfonuklear serta mengurangi respon inflamasi dan mempercepat migrasi fibroblas di fase proliferasi. Tujuan :Mengetahui perbedaan jumlah sel fibroblas dan kepadatan sel kolagen pada tikus wistar yang diberikan Ketotifen oral dosis 0.3 mg/kg dibandingkan plasebo pada penyembuhan luka insisi tikus wistar. Metode : Penelitian ini termasuk true eksperimental laboratorik dengan desain Randomized Controlled Trial yang menggunakan tikus wistar sebagai obyek penelitian. 14 tikus Wistar dibagi dalam 2 kelompok, masing masing kelompok terdiri atas 7 tikus Wistar. Kelompok 1 merupakan kelompok kontrol yang dilakukan insisi sepanjang 2cm pada kulit punggung tikus dan diberikan plasebo per oral selama 6 hari. Kelompok 2 merupakan kelompok perlakuan yang dilakukan insisi sepanjang 2cm pada kulit punggung tikus dan diberikan Ketotifen 0,3 mg/kgBB per oral setiap 12 jam selama 6 hari. Analisis data untuk membandingkan rerata antar kedua kelompok yaitu kelompok perlakuan dan kelompok kontrol menggunakan uji independent samples t-test, dengan tingkat kemaknaan p < 0,05 (dikatakan bermakna secara statistik). Hasil : Pada kelompok kontrol didapatkan rerata persentase kepadatan sel kolagen sebesar 26,05 %, sedangkan pada kelompok Ketotifen didapatkan rerata persentase kepadatan sel kolagen sebesar 36,13 %. Untuk jumlah sel fibroblas pada kelompok kontrol didapatkan rerata sebesar 423 per lapang pandang, sedangkan pada kelompok Ketotifen didapatkan rerata sebesar 555,43 per lapang pandang. Kesimpulan : Ketotifen mempercepat penyembuhan luka ditandai dengan peningkatan sel fibroblas dan sel kolagen. Kata Kunci : Sel Mast, Ketotifen, Sel fibroblas, Serabut Kolagen. ABSTRACT Ingga Hadian, S-501202027. EFFECTS OF KETOTIFEN ON FIBROBLAST CELL COUNT AND COLLAGEN DENSITY ON INCISED WISTAR RATS. DR. Untung Alfianto, dr., Sp.BS, dr. Ardana Tri Arianto, Msi, Med, Sp.An-KNA. Background: Mast cells have a pivotal role in every healing process that involves inflammation of the cells, usually in wounds of chronic nature. If the degranulation process of the mast cells are inhibited, the healing process of the wound will accelerate, indicated by a raise in fibroblast cells and collagen density. Ketotifen are shown to inhibit the degranulation process and decreasing the release of histamin, mast cells proteases, myeloperoxidases, leukotriens, PAF, and various prostaglandins. Ketotifen can also inhibit the aggregation of polymorphonuclear cells, increasing the rate of fibroblast migration in the proliferation phase. This study was aimed to identify the effects of ketotifen on fibroblast cell count and collagen density tested on a wistar rats model. Methods: This study was a true laboratoric experimental study with randomized controlled trial using wistar rats model as objects. 14 rats were divided into two groups, each group contained seven rats. The first group was the control group, where the rats were incised 2 cm above the back skin, and were given per oral placebo for 6 days. The second group were given the same treatment, only the rats were given ketotifen 0.3 mg/kg per oral, every 12 hours lasting 6 days. The data were then collected and tested with independent sample t-test, with p value less than 0,05 is statistically significant. Results: In the control group, the mean percentage of the thickest collagen density were marked at 26.05%, whereas in the treatment group collagen density were marked at 36.13%. The mean fibroblast cell count were marked at 423 and 555.43 each viewing field, on the control group and the treatment group respectively. Conclusion: Ketotifen can accelerate the healing process, marked by the significant increase in collagen density and fibroblast cell count. Keywords: mast cells, ketotifen, fibroblast cells, collagen fibers

Multiwavelength observations of a TeV-Flare from W comae

We report results from an intensive multiwavelength campaign on the intermediate-frequency-peaked BL Lacertae object W Com (z = 0.102) during a strong outburst of very high energy gamma-ray emission in 2008 June. The very high energy gamma-ray signal was detected by VERITAS on 2008 June 7-8 with a flux F(>200 GeV) =(5.7 0.6) × 10-11 cm-2 s -1, about three times brighter than during the discovery of gamma-ray emission from W Com by VERITAS in 2008 March. The initial detection of this flare by VERITAS at energies above 200 GeV was followed by observations in high-energy gamma rays (AGILE; E γ≥ 100 MeV), X-rays (Swift and XMM-Newton), and at UV, and ground-based optical and radio monitoring through the GASP-WEBT consortium and other observatories. Here we describe the multiwavelength data and derive the spectral energy distribution of the source from contemporaneous data taken throughout the flare. © 2009. The American Astronomical Society. All rights reserved

The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsahovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ⪆ 33) and the size of the emission region (δ-1RB≲ 3.8 × 1013cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.</p

Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era

We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society