1,347 research outputs found
X- and gamma-ray observations of the 15 November 1991 Solar Flare
This work expands the current understanding of the 15 November 1991 Solar Flare. The flare was a well observed event in radio to gamma-rays and is the first flare to be extensively studied with the benefit of detailed soft and hard X-ray images. In this work, we add data from all four instruments on the Compton Gamma Ray Observatory. Using these data we determined that the accelerated electron spectrum above 170 keV is best fit with a power law with a spectral index of â4.6, while the accelerated proton spectrum above 0.6 MeV is fit with a power law of spectral index â4.5. From this we computed lower limits for the energy content of these particles ofâŒ1023âergs (electrons) and âŒ1027âergs (ions above 0.6 MeV). These particles do not have enough energy to produce the white-light emission observed from this event. We computed a time constant of 26+20â15âs for the 2.223 MeV neutron capture line, which is consistent at the 2Ï level with the lowest values of âŒ70 s found for other flares. The mechanism for this short capture time may be better understood after analyses of high energy EGRET data that show potential evidence for pion emission near âŒ100 MeV
COMPTEL observations of gammaâray flares in October 1991
The COMPTEL experiment on GRO images 0.75â30 MeV celestial gammaâradiation that falls within its 1 steradian field of view. During observation 12 (primary target Cen A) in October 1991 the sun had been in the fov and several solar flares associated with the active region 6891 had been observed. Time profile and energy spectra had been produced, using COMPTELâs primary mode of operation (the telescope mode). Additionally the number of counts received in the D2âsingle burst detector (the secondary mode of operation) are given. We summarize the preliminary results on all of these flares
COMPTEL gamma ray and neutron measurements of solar flares
COMPTEL on the Compton Gamma Ray Observatory has measured the flux of xârays and neutrons from several solar flares. These data have also been used to image the Sun in both forms of radiation. Unusually intense flares occurred during June 1991 yielding data sets that offer some new insight into of how energetic protons and electrons are accelerated and behave in the solar environment. We summarize here some of the essential features in the solar flare data as obtained by COMPTEL during June 1991
Neutron and gammaâray measurements of the solar flare of 1991 June 9
The COMPTEL Imaging Compton Telescope onâboard the Compton Gamma Ray Observatory measured significant neutron and Îłâray fluxes from the solar flare of 9 June 1991. The Îłâray flux had an integrated intensity (âł1 MeV) of âŒ30 cmâ2, extending in time from 0136 UT to 0143 UT, while the time of energetic neutron emission extended approximately 10 minutes longer, indicating either extended proton acceleration to high energies or trapping and precipitation of energetic protons. The production of neutrons without accompanying Îłârays in the proper proportion indicates a significant hardening of the precipitating proton spectrum through either the trapping or extended acceleration process
COMPTELâs solar flare catalog
COMPTEL, the imaging gammaâray telescope, capable of detecting gamma rays in the range of 0.1â30 MeV, is one of four instruments aboard NASAâs Compton GammaâRay Observatory. The Comptel burst detectors (single Defector Mode) have a field of view of âŒ2.5 Ï sr. These detectors of COMPTEL permit measurements of energy spectra and time histories of solar flare gammaâray emission. A search through the Single Detector Modeâs data is being conducted. We summarize the preliminary results of this search
Universality of the 1/3 shot-noise suppression factor in nondegenerate diffusive conductors
Shot-noise suppression is investigated in nondegenerate diffusive conductors
by means of an ensemble Monte Carlo simulator. The universal 1/3 suppression
value is obtained when transport occurs under elastic collision regime provided
the following conditions are satisfied: (i) The applied voltage is much larger
than the thermal value; (ii) the length of the device is much longer than both
the elastic mean free path and the Debye length. By fully suppressing
carrier-number fluctuations, long range Coulomb interaction is essential to
obtain the 1/3 value in the low-frequency limit.Comment: RevTex, 4 pages, 4 figure
The two states of Sgr A* in the near-infrared: bright episodic flares on top of low-level continuous variability
In this paper we examine properties of the variable source Sgr A* in the
near-infrared (NIR) using a very extensive Ks-band data set from NACO/VLT
observations taken 2004 to 2009. We investigate the variability of Sgr A* with
two different photometric methods and analyze its flux distribution. We find
Sgr A* is continuously emitting and continuously variable in the near-infrared,
with some variability occurring on timescales as long as weeks. The flux
distribution can be described by a lognormal distribution at low intrinsic
fluxes (<~5 mJy, dereddened with A_{Ks}=2.5). The lognormal distribution has a
median flux of approximately 1.1 mJy, but above 5 mJy the flux distribution is
significantly flatter (high flux events are more common) than expected for the
extrapolation of the lognormal distribution to high fluxes. We make a general
identification of the low level emission above 5 mJy as flaring emission and of
the low level emission as the quiescent state. We also report here the
brightest Ks-band flare ever observed (from August 5th, 2008) which reached an
intrinsic Ks-band flux of 27.5 mJy (m_{Ks}=13.5). This flare was a factor 27
increase over the median flux of Sgr A*, close to double the brightness of the
star S2, and 40% brighter than the next brightest flare ever observed from
Sgr~A*.Comment: 14 pages, 6 figures, accepted for publication in Ap
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PROGRESS ON INSERTION DEVICE RELATED ACTIVITIES AT THE NSLS-II AND ITS FUTURE PLANS
National Synchrotron Light Source-II (NSLS-II) project is now in the construction stage. A new insertion device (ID) magnetic measurement facility (MMF) is being set up at Brookhaven National Laboratory in order to satisfy the stringent requirement on the magnetic field measurement of IDs. ISO-Class7 temperature stabilized clean room is being constructed for this purpose. A state-of-the-art Hall probe bench and integrated field measurement system will be installed therein. IDs in the project baseline scope include six damping wigglers, two elliptically polarizing undulators (EPUs), three 3.0m long in-vacuum undulators (IVUs) and one 1.5m long IVU. Three-pole wigglers with peak field over 1 Tesla will be utilized to accommodate the users of bending magnet radiation at the NSLS. Future plans includes: (1) an in-vacuum magnetic measurement system, (2) use of PrFeB magnet for improved cryo undulator, (3) development of advanced optimization program for sorting and shimming of IDs, (4) development of a closed loop He gas refrigerator, (5) switchable quasi-periodic EPU. Design features of the baseline devices, IDMMF and the future plans for NSLS-II ID activities are described
Making things happen : a model of proactive motivation
Being proactive is about making things happen, anticipating and preventing problems, and seizing opportunities. It involves self-initiated efforts to bring about change in the work environment and/or oneself to achieve a different future. The authors develop existing perspectives on this topic by identifying proactivity as a goal-driven process involving both the setting of a proactive goal (proactive goal generation) and striving to achieve that proactive goal (proactive goal striving). The authors identify a range of proactive goals that individuals can pursue in organizations. These vary on two dimensions: the future they aim to bring about (achieving a better personal fit within oneâs work environment, improving the organizationâs internal functioning, or enhancing the organizationâs strategic fit with its environment) and whether the self or situation is being changed. The authors then identify âcan do,â âreason to,â and âenergized toâ motivational states that prompt proactive goal generation and sustain goal striving. Can do motivation arises from perceptions of self-efficacy, control, and (low) cost. Reason to motivation relates to why someone is proactive, including reasons flowing from intrinsic, integrated, and identified motivation. Energized to motivation refers to activated positive affective states that prompt proactive goal processes. The authors suggest more distal antecedents, including individual differences (e.g., personality, values, knowledge and ability) as well as contextual variations in leadership, work design, and interpersonal climate, that influence the proactive motivational states and thereby boost or inhibit proactive goal processes. Finally, the authors summarize priorities for future researc
COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy.
BACKGROUND: Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3). OBJECTIVE: To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response. METHODS: The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (paediatric cases/controls: n=134/n=35; adult cases/controls: n=149/n=31). Exacerbation of allergic airway disease in mice was induced by sensitising to ovalbumin (OVA), challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor; Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (n=14) and cystic fibrosis with allergic bronchopulmonary aspergillosis (ABPA; n=9) as well as patients with severe allergic uncontrolled asthma (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed using the Asthma Control Test. RESULTS: Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in cystic fibrosis plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic OR 31.5). CONCLUSION: C4Ma3 levels depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response
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