365 research outputs found
Photosynthetic responses of Amygdalus arabica Olivier and Atriplex canescens (Pursh) Nutt. to drought stress under field conditions
The central Anatolian region of Turkey is exposed to increasing temperatures and severe drought stress. Due to aridity and desertification brought about by global warming, climate change and overutilization, plant species in these regions are under the risk of extinction. Thus, plant species have to adapt to these harsh environmental conditions of extremely high temperatures and low precipitation. In this study, gas exchange and water potentials of the Arabian almond tree Amygdalus arabica Olivier (C3-photosynthesis) and four-winged saltbush Atriplex canescens (Pursh) Nutt. (C4-photosynthesis), two drought-tolerant woody species planted previously in an effort to reduce desertification at Karapınar, Konya, and Central Anatolian Region, were periodically measured from May until September under field conditions. Net photosynthesis and transpiration rates, mid-day water potential and water use efficiency were determined throughout the vegetation period in 2015. Maximum net photosynthetic rates were 12.4 μmol m–2 s–1 in the Arabian almond tree and 29.7 μmol m–2 s–1 in four-winged saltbush, measured in July and September, respectively. Also, the highest transpiration rates were 4.8 mmol m–2 s–1 in the Arabian almond tree and 7.1 mmol m–2 s–1 in four-winged saltbush. Maximum water use efficiency values were measured in June in both species, which made up 5.7 and 7.7 mmol CO2 mol–1 H2O for the Arabian almond tree and four-winged saltbush, respectively. Lowest midday water potentials for both species were recorded in August. The results indicate that both species have the ability to tolerate drought stress in the region, though due to its C4 nature of photosynthesis, the four-winged saltbush might overcome those stresses more efficiently than the Arabian almond tree in arid and barren areas
Risk based facility location by using fault tree analysis in disaster management
Determining the locations of facilities for prepositioning supplies to be used during a disaster is a strategic decision that directly affects the success of disaster response operations. Locating such facilities close to the disaster-prone areas is of utmost importance to minimize response time. However, this is also risky because the facility may be disrupted and hence may not support the demand point(s). In this study, we develop an optimization model that minimizes the risk that a demand point may be exposed to because it is not supported by the located facilities. The purpose is to choose the locations such that a reliable facility network to support the demand points is constructed. The risk for a demand point is calculated as the multiplication of the (probability of the) threat (e.g., earthquake), the vulnerability of the demand point (the probability that it is not supported by the facilities), and consequence (value or possible loss at the demand point due to threat). The vulnerability of a demand point is computed by using fault tree analysis and incorporated into the optimization model innovatively. To our knowledge, this paper is the first to use such an approach. The resulting non-linear integer program is linearized and solved as a linear integer program. The locations produced by the proposed model are compared to those produced by the p-center model with respect to risk value, coverage distance, and covered population by using several test problems. The model is also applied in a real problem. The results indicate that taking the risk into account explicitly may create significant differences in the risk levels. © 2014 Elsevier Ltd
Does Gender Impact Intensity of Care Provided to Older Medical Intensive Care Unit Patients?
Introduction. Women receive less aggressive critical care than men based on prior studies. No documented studies evaluate whether men and women are treated equally in the medical intensive care unit (MICU). The Therapeutic Intervention Scoring System-28 (TISS-28) has been used to examine gender differences in mixed ICU studies. However, it has not been used to evaluate equivalence of care in older MICU patients. We hypothesize that given nonsignificant, baseline health differences between genders at MICU admission, the level of care provided would be equivalent.
Methods. Prospective cohort of 309 patients ≥60 years old in the MICU of an urban university teaching hospital. Explanatory variables were demographic data and baseline measures. Primary outcomes were TISS-28 scores and MICU interventions. We compare TISS-28 scores by gender using a statistical test of equivalence.
Results. Women were older and had more chronic respiratory failure at MICU admission. Using equivalence limits of ±15% on gender-based scores of TISS-28, MICU interventions were equivalent. Supplementary analysis showed no statistically significant association between gender and mortality.
Conclusions. In contrast with other reports from the cardiac critical care literature, as measured by the TISS-28, gender-based care delivered to older MICU patients in this cohort was equivalent
Incompatibility of long-period neutron star precession with creeping neutron vortices
Aims: To determine whether ``vortex creep'' in neutron stars, the slow motion
of neutron vortices with respect to pinning sites in the core or inner crust,
is consistent with observations of long-period precession. Methods: Using the
concept of vortex drag, I discuss the precession dynamics of a star with
imperfectly-pinned (i.e., "creeping'') vortices. Results: The precession
frequency is far too high to be consistent with observations, indicating that
the standard picture of the outer core (superfluid neutrons in co-existence
with type II, superconducting protons) should be reconsidered. There is a slow
precession mode, but it is highly over-damped and cannot complete even a single
cycle. Moreover, the vortices of the inner crust must be able to move with
little dissipation with respect to the solid.Comment: 4 pages, v3. Missing reference adde
Tkachenko waves, glitches and precession in neutron star
Here I discuss possible relations between free precession of neutron stars,
Tkachenko waves inside them and glitches. I note that the proposed precession
period of the isolated neutron star RX J0720.4-3125 (Haberl et al. 2006) is
consistent with the period of Tkachenko waves for the spin period 8.4s. Based
on a possible observation of a glitch in RX J0720.4-3125 (van Kerkwijk et al.
2007), I propose a simple model, in which long period precession is powered by
Tkachenko waves generated by a glitch. The period of free precession,
determined by a NS oblateness, should be equal to the standing Tkachenko wave
period for effective energy transfer from the standing wave to the precession
motion. A similar scenario can be applicable also in the case of the PSR
B1828-11.Comment: 6 pages, no figures, accepted to Ap&S
Structure, Deformations and Gravitational Wave Emission of Magnetars
Neutron stars can have, in some phases of their life, extremely strong
magnetic fields, up to 10^15-10^16 G. These objects, named magnetars, could be
powerful sources of gravitational waves, since their magnetic field could
determine large deformations. We discuss the structure of the magnetic field of
magnetars, and the deformation induced by this field. Finally, we discuss the
perspective of detection of the gravitational waves emitted by these stars.Comment: 11 pages, 2 figures, prepared for 19th International Conference on
General Relativity and Gravitation (GR19), Mexico City, Mexico, July 5-9,
201
Experimental analysis of a paraffin-based cold storage tank
[EN] The aim of this study is to characterize a paraffin-based cold storage tank. Novel experimental results are presented for this system which combines a significant amount of paraffin (1450 kg) immersed around 18 spiral-shaped coils disposed in counter-current flow. The paraffin has a phase-change temperature in the range 4 8 °C as measured by a 3-layer calorimeter. Different tests have been carried out with a constant mass flow rate and supply temperature. Around 31% of the paraffin has hardly any contact with the coils and hereby acts as a dead mass. The results show the importance of natural convection within the phase-change-material, particularly during the melting process. The highest efficiency has been achieved for the lowest supply temperatures and mass flow rates of the heat transfer fluid.The authors gratefully acknowledge the fundings from ACCIONA Infraestructuras.Torregrosa-Jaime, B.; López-Navarro, A.; Corberán, JM.; Esteban-Matías, JC.; Klinkner, L.; Payá-Herrero, J. (2013). Experimental analysis of a paraffin-based cold storage tank. International Journal of Refrigeration. 36(6):1632-1640. doi:10.1016/j.ijrefrig.2013.05.001S1632164036
Revising the WHO verbal autopsy instrument to facilitate routine cause-of-death monitoring.
OBJECTIVE: Verbal autopsy (VA) is a systematic approach for determining causes of death (CoD) in populations without routine medical certification. It has mainly been used in research contexts and involved relatively lengthy interviews. Our objective here is to describe the process used to shorten, simplify, and standardise the VA process to make it feasible for application on a larger scale such as in routine civil registration and vital statistics (CRVS) systems. METHODS: A literature review of existing VA instruments was undertaken. The World Health Organization (WHO) then facilitated an international consultation process to review experiences with existing VA instruments, including those from WHO, the Demographic Evaluation of Populations and their Health in Developing Countries (INDEPTH) Network, InterVA, and the Population Health Metrics Research Consortium (PHMRC). In an expert meeting, consideration was given to formulating a workable VA CoD list [with mapping to the International Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) CoD] and to the viability and utility of existing VA interview questions, with a view to undertaking systematic simplification. FINDINGS: A revised VA CoD list was compiled enabling mapping of all ICD-10 CoD onto 62 VA cause categories, chosen on the grounds of public health significance as well as potential for ascertainment from VA. A set of 221 indicators for inclusion in the revised VA instrument was developed on the basis of accumulated experience, with appropriate skip patterns for various population sub-groups. The duration of a VA interview was reduced by about 40% with this new approach. CONCLUSIONS: The revised VA instrument resulting from this consultation process is presented here as a means of making it available for widespread use and evaluation. It is envisaged that this will be used in conjunction with automated models for assigning CoD from VA data, rather than involving physicians
Strongly magnetized pulsars: explosive events and evolution
Well before the radio discovery of pulsars offered the first observational
confirmation for their existence (Hewish et al., 1968), it had been suggested
that neutron stars might be endowed with very strong magnetic fields of
-G (Hoyle et al., 1964; Pacini, 1967). It is because of their
magnetic fields that these otherwise small ed inert, cooling dead stars emit
radio pulses and shine in various part of the electromagnetic spectrum. But the
presence of a strong magnetic field has more subtle and sometimes dramatic
consequences: In the last decades of observations indeed, evidence mounted that
it is likely the magnetic field that makes of an isolated neutron star what it
is among the different observational manifestations in which they come. The
contribution of the magnetic field to the energy budget of the neutron star can
be comparable or even exceed the available kinetic energy. The most magnetised
neutron stars in particular, the magnetars, exhibit an amazing assortment of
explosive events, underlining the importance of their magnetic field in their
lives. In this chapter we review the recent observational and theoretical
achievements, which not only confirmed the importance of the magnetic field in
the evolution of neutron stars, but also provide a promising unification scheme
for the different observational manifestations in which they appear. We focus
on the role of their magnetic field as an energy source behind their persistent
emission, but also its critical role in explosive events.Comment: Review commissioned for publication in the White Book of
"NewCompStar" European COST Action MP1304, 43 pages, 8 figure
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
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