10,006 research outputs found
Photoionization models for extreme Ly 1216 and HeII 1640 ratios in quasar halos, and PopIII vs AGN diagnostics
We explore mechanisms to produce extremely high Ly-alpha/HeII flux ratios, or
to enhance the observed number of Ly-alpha photons per incident ionizing
photon, in extended AGN-photoionized nebulae at high-redshift. Using
photoionization models, we explore the impact of ionization parameter, gas
metallicity, ionizing spectrum, electron energy distribution, and cloud viewing
angle on the relative fluxes of Ly-alpha, HeII and other lines, and on the
observed number of Ly-alpha photons per incident ionizing photon. We find that
low ionization parameter, a relatively soft or filtered ionizing spectrum, low
gas metallicity, kappa-distributed electron energies, or reflection of Ly-alpha
photons by HI can all result in significantly enhanced Ly-alpha relative to
other lines (>10%), with log Ly-alpha/HeII reaching values up to 4.6. In the
cases of low gas metallicity, reflection by HI, or a hard or filtered ionizing
spectrum, the observed number of Ly-alpha photons per incident ionizing photon
is itself significantly enhanced above the nominal Case B value of 0.66 due to
collisional excitation, reaching values up to 5.3 in our 'extreme case' model.
At low gas metallicity (e.g. 0.1 x Solar), the production of Ly-alpha is
predominantly via collisional excitation rather than recombination. In
addition, we find that collisional excitation of Ly-alpha becomes more
efficient if the ionizing continuum is pre-filtered through an optically thin
screen of gas closer to the AGN. We also show that Ly-alpha / HeII ratios of
the z~3.5 quasars studied by Borisova et al. (2016) are consistent with
AGN-photoionization of gas with moderate to low metallicity and/or low
ionization parameter, without requiring exotic ionization/excitation mechanisms
such as strong line-transfer effects. We also present UV-optical diagnostic
diagrams to distinguish between photoionization by Pop III stars and AGN
photoionization.Comment: Accepted for publication in A&A. 14 pages, 9 figures. Abstract
slightly shortened to meet arxiv character limi
Kinetics of hydroformylation of 1-octene in ionic liquid-organic biphasic media using rhodium sulfoxantphos catalyst
Biphasic hydroformylation of 1-octene was performed using rhodium sulfoxantphos catalyst dissolved in [BuPy][BF4] ionic liquid. Preliminary experiments proved this system to retain the catalytic complex within the ionic liquid phase and to maintain a high selectivity towards the linear aldehyde (n:iso ratio of 30) over several cycles. Process parameter investigation showed a first order dependence of the initial rate with respect to the catalyst and 1-octene concentrations, but a more complex behavior with respect to hydrogen (fractional order) and carbon monoxide partial pressures (inhibition at high pressures). Different mathematical models were selected based on the trends observed and evaluated for data fitting. Also, rate models were derived from a proposed mechanism, using Christiansen matrix approach. To calculate concentrations of substrates in the catalytic phase as required by this kinetic modeling, solubility measurements were preformed for the gases (pressure drop technique), as well as for 1-octene and n-nonanal (thermogravimetry analysis)
Integrated Approach to Design and Manufacture of Gas Turbine Components Based on Group Theory
This paper deals with a new method that provides an integrated approach to design and manufacture of gas turbine components by using the group theory and customising standard computer aided design and manufacturing system. With this approach time consuming and iterative design procedure and process planning are automated and become more efficient. Due to the intricate and diverse nature of gas turbine components, grouping them is not easy as in other industries. A possible way of grouping the gas turbine components based on design and manufacturing attributes on a broad basis is presented. A case study of high pressure turbine disc is included with illustrations for design and process planning of this component. The proposed system is implemented on a personal computer and offers an alternate solution to sophisticated and expensive main frame based systems
Investigation Into the Humaneness of Slaughter Methods for Guinea Pigs (Cavia porcelus) in the Andean Region
Guinea pigs (Cavia porcelus) are an important source of nonhuman animal protein in the Andean region of South America. Specific guidelines regarding the welfare of guinea pigs before and during slaughter have yet to be developed. This study critically assessed the humaneness of 4 different stunning/slaughter methods for guinea pigs: cervical neck dislocation (n = 60), electrical head-only stunning (n = 83), carbon dioxide (CO(2)) stunning (n = 21), and penetrating captive bolt (n = 10). Following cervical neck dislocation, 97% of guinea pigs had at least 1 behavioral or cranial/spinal response. Six percent of guinea pigs were classified as mis-stunned after electrical stunning, and 1% were classified as mis-stunned after captive bolt. Increased respiratory effort was observed during CO(2) stunning. Apart from this finding, there were no other obvious behavioral responses that could be associated with suffering. Of the methods assessed, captive bolt was deemed the most humane, effective, and practical method of stunning guinea pigs. Cervical neck dislocation should not be recommended as a slaughter method for guinea pigs
E-Learning
Abstract E-learning presents an entirely new learning environment for students, thus requiring a different skill set to be successful (Romiszowski, 2004). Critical thinking, research, and evaluation skills are growing in importance as students have increasing volumes of information from a variety of sources to sort through (New Media Consortium, 2007). Also, particularly in courses that are entirely electronic, students are much more independent than in the traditional setting. This requires that they be highly motivated and committed to teach (Huynh et al., 2003), with less social interaction with peers or an instructor. Students in online courses tend to do as well as those in classrooms, but there is higher incidence of withdrawal or incomplete grades (Zhang, Zhou and Briggs, 2006). E- Learning can be viewed as computer assisted learning, and as pedagogy for studentcentered and collaborative learning. Early developments in e-learning focused on computer assisted learning, where part or all of the learning content is delivered digitally. More recently the pedagogical dimension of e-learning has become prominent. E-learning comprises all forms of electronically supported learning and teaching. The information and communication systems, whether networked learning or not, serve as specific media to implement the learning process.
Simple training tricks for mastering and taming bypass procedures in neurosurgery
Background: Neurosurgeons devoted to bypass neurosurgery or revascularization neurosurgery are becoming scarcer. From a practical point of view, 'bypass neurosurgeons' are anastomosis makers, vessels technicians, and time-racing repairers of vessel walls. This requires understanding the key features and hidden tricks of bypass surgery. The goal of this paper is to provide simple and inexpensive tricks for taming the art of bypass neurosurgery. Most of these tricks and materials described can be borrowed, donated, or purchased inexpensively. Methods: We performed a review of relevant training materials and recorded videos for training bypass procedures for 3 years between June 2014 and July 2017. In total, 1,300 training bypass procedures were performed, of which 200 procedures were chosen for this paper. Results : A training laboratory bypass procedures is required to enable a neurosurgeon to develop the necessary skills. The important skills for training bypass procedures gained through meticulous practice to be as reflexes are coordination, speed, agility, flexibility, and reaction time. Bypassing requires synchronization between the surgeon's gross movements, fine motoric skills, and mental strength. The suturing rhythm must be timed in a brain-body-hand fashion. Conclusion: Bypass-Training is a critical part of neurosurgical training and not for a selected few. Diligent and meticulous training can enable every neurosurgeon to tame the art of bypass neurosurgery. This requires understanding the key features and hidden tricks of bypass surgery, as well as uncountable hours of training. In bypass neurosurgery, quality and time goes hand in hand. © 2017 Surgical Neurology International | Published by Wolters Kluwer - Medknow.Peer reviewe
Relativistic mean field study of the properties of Z=117 nucleus and the decay chains of 117 isotopes
We have calculated the binding energy, root-mean-square radius and quadrupole
deformation parameter for the recently synthesized superheavy element Z=117,
using the axially deformed relativistic mean field (RMF) model. The calculation
is extended to various isotopes of Z=117 element, strarting from A=286 till
A=310. We predict almost spherical structures in the ground state for almost
all the isotopes. A shape transition appears at about A=292 from prolate to a
oblate shape structures of Z=117 nucleus in our mean field approach. The most
stable isotope (largest binding energy per nucleon) is found to be the
117 nucleus. Also, the Q-value of -decay and the
half-lives are calculated for the -decay chains of
117 and 117, supporting the magic numbers at N=172 and/ or 184.Comment: 6 Pages and 8 Figure
Design and Evaluation of Submersible 11/0.415kV Distribution Substation for Flood Prone Areas
Flood levels exceeding 2 metres above ground level has been observed causing electrical equipment in the 11/0.415kV substation to be fully submerged. This caused widespread supply disruption as the equipment need to be switched off due to safety reasons and prevention of further equipment damage. The use of submersible equipment and accessories has been identified as one of the mitigation methods to ensure continuous electrical supply during flood events. A research project was undertaken to develop the design criteria of the selection of submersible equipment and accessories as well as to develop the test method and evaluate the selected submersible equipment and accessories in a substation configuration. All the equipment could continuously operate in ON condition during the wet test. However, design improvements are suggested for the submersible switchgear and feeder pillar for better performance during and after flood events
Anxious medico with nicotine patch: a case report
We often suffer more in our imaginations than in reality. Anxiety is a terrible experience, you could even have an attack and no one would even know most of the times because it is an inward thing. People do get anxious and experience this feeling most of the times in life. Up to an extent its normal as much as it can be controlled if not this unpleasant feeling overrules. We learn to combat this feeling as the age passes but it also depends on different environmental, social occupational factors and the level of stress to overcome can be difficult. Many non-pharmacological and pharmacological methods are available to combat anxiety disorder. Self-medications can be occupational hazard and is strongly entrenched within the culture of both physicians and medical students as an accepted way to buffer their work performance. We are reporting a case of an anxious medico self-medicated to combat anxiety.
Near-IR studies of recurrent nova V745 Scorpii during its 2014 outburst
The recurrent nova (RN) V745 Scorpii underwent its third known outburst on
2014 February 6. Infrared monitoring of the eruption on an almost daily basis,
starting from 1.3d after discovery, shows the emergence of a powerful blast
wave generated by the high velocity nova ejecta exceeding 4000 kms
plowing into its surrounding environment. The temperature of the shocked gas is
raised to a high value exceeding 10K immediately after outburst
commencement. The energetics of the outburst clearly surpass those of similar
symbiotic systems like RS Oph and V407 Cyg which have giant secondaries. The
shock does not show a free-expansion stage but rather shows a decelerative
Sedov-Taylor phase from the beginning. Such strong shockfronts are known to be
sites for ray generation. V745 Sco is the latest nova, apart from five
other known novae, to show ray emission. It may be an important
testbed to resolve the crucial question whether all novae are generically
ray emitters by virtue of having a circumbinary reservoir of material
that is shocked by the ejecta rather than ray generation being
restricted to only symbiotic systems with a shocked red giant (RG) wind. The
lack of a free-expansion stage favors V745 Sco to have a density enhancement
around the white dwarf (WD), above that contributed by a RG wind. Our analysis
also suggests that the WD in V745 Sco is very massive and a potential
progenitor for a future SN Ia explosion.Comment: To appear in ApJ (Letters
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