We report the measurement of the emission time profile of scintillation from gamma-ray induced events in the XMASS-I 832 kg liquid xenon scintillation detector. Decay time constant was derived from a ...comparison of scintillation photon timing distributions between the observed data and simulated samples in order to take into account optical processes such as absorption and scattering in liquid xenon. Calibration data of radioactive sources, \(^{55}\)Fe, \(^{241}\)Am, and \(^{57}\)Co were used to obtain the decay time constant. Assuming two decay components, \(\tau_1\) and \(\tau_2\), the decay time constant \(\tau_2\) increased from 27.9 ns to 37.0 ns as the gamma-ray energy increased from 5.9 keV to 122 keV. The accuracy of the measurement was better than 1.5 ns at all energy levels. A fast decay component with \(\tau_1 \sim 2\) ns was necessary to reproduce data. Energy dependencies of \(\tau_2\) and the fraction of the fast decay component were studied as a function of the kinetic energy of electrons induced by gamma-rays. The obtained data almost reproduced previously reported results and extended them to the lower energy region relevant to direct dark matter searches.
A search for dark matter was conducted by looking for an annual modulation signal due to the Earth's rotation around the Sun using XMASS, a single phase liquid xenon detector. The data used for this ...analysis was 359.2 live days times 832 kg of exposure accumulated between November 2013 and March 2015. When we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically scattering on the target nuclei, the exclusion upper limit of the WIMP-nucleon cross section 4.3\(\times\)10\(^{-41}\)cm\(^2\) at 8 GeV/c\(^2\) was obtained and we exclude almost all the DAMA/LIBRA allowed region in the 6 to 16 GeV/c\(^2\) range at \(\sim\)10\(^{-40}\)cm\(^2\). The result of a simple modulation analysis, without assuming any specific dark matter model but including electron/\(\gamma\) events, showed a slight negative amplitude. The \(p\)-values obtained with two independent analyses are 0.014 and 0.068 for null hypothesis, respectively. we obtained 90\% C.L. upper bounds that can be used to test various models. This is the first extensive annual modulation search probing this region with an exposure comparable to DAMA/LIBRA.
Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new ...reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on \(^{124}\)Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as \(4.7 \times 10^{21}\) years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the \(^{126}\)Xe two-neutrino double electron capture half-life of \(4.3 \times 10^{21}\) years at 90% confidence level as well.
Shannon’s information theory states that there is a maximum rate for transmitting data reliably, implying that data almost always inevitably leak. Although there has been advancement in data ...protection technologies, a lack of understanding about data leaks and human error persists.
The capability of a company to survive in business is highly related with its own performance. In order to preserve company's life cycle, management team must be able to maintain, even improve its ...performance. A company that cannot compete to maintain its performance eventually will get kicked out from its industrial environment and will suffer from financial distress. If a company cannot escape from that condition, it will encounter a bankruptcy threat. Bankruptcy is a form of company's failure in carrying out its performance to achieve profit. Bankruptcy occurs when debt value is over its asset market value. The purpose of this research is to find out Nokia Corp financial condition in 2010-2014, whether this company has some serious problem or still in a good condition. Besides, this research would like to know which financial ratio is troublesome that can causes the company trapped in financial distress zone or even creates bankruptcy potential. The methods that used to predict company's bankruptcy in this research are Altman Method, Springate Method and Zmijewski Method. This research shows that using Altman Method, Nokia is in financial distress zone for four years, starting from 2011-2014 while Nokia is in the grey/ ignorance zone in 2010. Using Springate Method, Nokia is in a distress zone for three consecutive years starting from 2011-2013, while Nokia is in a safe zone in 2010 and 2014. In the opposite, using Zmijewski Method, Nokia is in the distress zone only in 2012, while in the other four year period, it is in a safe zone.
Abstract
The soft X-ray excess in the spectra of active galactic nuclei is characterized by similar electron temperatures of 0.1–0.3 keV and similar photon indices around 2.2–3, if fitted with ...inverse Comptonization. It remains a puzzle why both values are not sensitive to the black hole mass nor the accretion rate. Supposing that the scattering-dominated surface layer of an accretion disk can act as a warm corona, we construct a vertical one-zone model to understand what determines its temperature. By solving the equations of (1) the condition for the effective optical depth, (2) the energy balance, and (3) the dominance of the Compton cooling over the bound–free cooling, we could reproduce the basic observational features of the soft excess, provided that anomalous heating (excess heating other than what is expected by local energy dissipation) takes place in the warm corona in agreement with similar studies done so far. The similar temperatures can be understood, since both the anomalous heating and Compton cooling rates are proportional to the dissipation rate of the accretion energy, while similar photon indices are a natural consequence of the fact that observed photons are finally emitted from the layer of Compton y ∼ 1. The soft excess is not observed in black hole binaries, since disk temperatures are too high for the Compton scattering to work as cooling. The derived temperatures are somewhat of an underestimation, however. This may indicate a necessity of multi-zone corona structure. The stability of the warm corona and its consequences are briefly discussed.
Green and Sustainable Computing Ahmad, Norita; Williams, Joseph
Computer,
2023-June, 2023-6-00, Letnik:
56, Številka:
6
Journal Article
Recenzirano
Odprti dostop
This special issue highlights the urgent need for green and sustainable computing practices. Three critical topics, human-centered artificial intelligence, the computing continuum, and green machine ...learning, are discussed as important for creating environmentally friendly and efficient computing systems.
Women politicians in Africa often find themselves in precarious positions as they negotiate their place in men-dominated environments. Their positions are further complicated because political power ...remains weakly institutionalised in most parts of Africa and highly dependent on informal links between individuals/groups and their respective networks. Given this, this paper looks at both formal and informal networks and relationships, as shaped by local political culture and contexts, to advance the search for a way to provide a more reliable picture of the realities of women politicians within the African context. It advances the elite theory by demonstrating how a feminist approach helps provide a way of understanding political elites that accounts for contextualised gendered power dynamics and experiences. It does so using Zimbabwe’s Joice Mujuru as a case study. The paper combines an African feminist approach and discourse analysis to trace the various debates and discourses around Joice Mujuru’s power to influence policies and decisions, her reputation, and her precarious position in Zimbabwe’s men-dominated political spaces. The paper concludes that a feminist perspective in considerations of political elites helps to better comprehend how various political cultures and contexts shape the understanding of women’s roles and positions in political groups and networks and their relationship to power centres. Such comprehension can shed light on contextual factors to take into account when considering effective ways of promoting women’s political leadership. Ultimately, the paper proposes an African feminist method to help create a path to further explorations of African elite groups and networks in gender-sensitive and context-based ways.
Abstract
We investigate the effect of conductive heating of the gas surrounding a geometrically thick accretion disk on the growth of a black hole (BH) at high redshift. If a BH is accreting the ...surrounding gas at a super-Eddington rate, the X-ray radiation from the vicinity of the BH would be highly anisotropic due to the self-shielding of a geometrically thick accretion disk, and then the radiative feedback on the surrounding medium would be suppressed in the equatorial region, within which super-Eddington accretion can continue. However, if this region is sufficiently heated via thermal conduction from the adjacent region that is not shielded and heated by the X-ray irradiation, the surrounding gas becomes isotropically hot, and the Bondi accretion rate would be suppressed and become sub-Eddington. We evaluate the condition under which such isotropic heating is realized and derive new criteria required for super-Eddington accretion.
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