3,943 research outputs found
Effects of rainwater harvesting and afforestation on soil properties and growth of Emblica officinalis while restoring degraded hills in western India
Effect of rainwater harvesting (RWH) structures like Contour trench (CT), gradonie (GD), box trench (BT), V-ditch (VD) and afforestation with Emblica officinalis Gaertn (planted in August, 2005) were studied in <10%, 10-20% and >20% slopes with a view to improve soil status, plant growth, sequester carbon and rehabilitate hills for local benefits. Soil pH and EC decreased and percent soil, SOC, NO3-N and PO4-P increased in June 2010 over 2005. Enhanced soil water and nutrients in <10% slopefacilitated height and collar diameter growth of E. officinalis. Soil water was 14.0 and 51.4% greater in >20% and <10% slopes, respectively than in 10-20% slope, whereas it was 17.8, 16.1, 24.2 and 14.0% greater in CT, GD, BT and VD treatments, respectively over control. The highest plant growth was in CT plots in all slopes. Second best treatment was BT in <10% slope and VD in other slopes. Conclusively, RWH and afforestation facilitated soil improvement but CT/BT treatments were more efficient inconserving soil and water facilitating plant growth and helped restore the degraded hill. However, further research is required on soil water use and its partitioning in different vegetation component and the benefits accrued from it for the local people
The effect of magnetic field and disorders on the electronic transport in graphene nanoribbons
We developed a unified mesoscopic transport model for graphene nanoribbons,
which combines the non-equilibrium Green's function (NEGF) formalism with the
real-space {\pi}-orbital model. Based on this model, we probe the spatial
distributions of electrons under a magnetic field, in order to obtain insights
into the various signature Hall effects in disordered armchair graphene
nanoribbons (AGNR). In the presence of a uniform perpendicular magnetic field
(B\perp-field), a perfect AGNR shows three distinct spatial current profiles at
equilibrium, depending on its width. Under non-equilibrium conditions (i.e. in
the presence of an applied bias), the net electron flow is restricted to the
edges and occurs in opposite directions depending on whether the Fermi level
lies within the valence or conduction band. For electrons at energy level below
the conduction window, the B\perp-field gives rise to local electron flux
circulation, although the global flux is zero. Our study also reveals the
suppression of electron backscattering as a result of the edge transport which
is induced by the B\perp-field. This phenomenon can potentially mitigate the
undesired effects of disorders, such as the bulk and edge vacancies, on the
transport properties of AGNR. Lastly, we show that the effect of B\perp-field
on electronic transport is less significant in the multimode compared to the
single mode electron transport.Comment: 21 pages, 4 figure
Spectral functions of the Falicov-Kimball model with electronic ferroelectricity
We calculate the angular resolved photoemission spectrum of the
Falicov-Kimball model with electronic ferroelectricity where - and
-electrons have different hoppings. In mix-valence regimes, the presence of
strong scattering processes between - excitons and a hole, created by
emission of an electron, leads to the formation of pseudospin polarons and
novel electronic structures with bandwidth scaling with that of -
excitons. Especially, in the two-dimensional case, we find that flat regions
exist near the bottom of the quasiparticle band in a wide range of the - and
-level energy difference.Comment: 5 pages, 5 figure
Complete adiabatic waveform templates for a test-mass in the Schwarzschild spacetime: VIRGO and Advanced LIGO studies
Post-Newtonian expansions of the binding energy and gravitational wave flux
truncated at the {\it same relative} post-Newtonian order form the basis of the
{\it standard adiabatic} approximation to the phasing of gravitational waves
from inspiralling compact binaries. Viewed in terms of the dynamics of the
binary, the standard approximation is equivalent to neglecting certain
conservative post-Newtonian terms in the acceleration. In an earlier work, we
had proposed a new {\it complete adiabatic} approximant constructed from the
energy and flux functions. At the leading order it employs the 2PN energy
function rather than the 0PN one in the standard approximation, so that,
effectively the approximation corresponds to the dynamics where there are no
missing post-Newtonian terms in the acceleration. In this paper, we compare the
overlaps of the standard and complete adiabatic templates with the exact
waveform in the adiabatic approximation of a test-mass motion in the
Schwarzschild spacetime, for the VIRGO and the Advanced LIGO noise spectra. It
is found that the complete adiabatic approximants lead to a remarkable
improvement in the {\it effectualness} at lower PN ( 3PN) orders, while
standard approximants of order 3PN provide a good lower-bound to the
complete approximants for the construction of effectual templates. {\it
Faithfulness} of complete approximants is better than that of standard
approximants except for a few post-Newtonian orders. Standard and complete
approximants beyond the adiabatic approximation are also studied using the
Lagrangian templates of Buonanno, Chen and Vallisneri.Comment: Proceedings of the GWDAW-9, Accepted for publication in Class. Quant.
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Outcomes of Aortic Surgery for Abdominal Aortic Graft Infections
Background: Literature on postoperative outcomes following aortic surgery for aortic graft infection (AGI) is limited by relatively small sample sizes, resulting in lack of national benchmarks for quality of care. We report in-hospital outcomes following abdominal aortic surgery for AGI and identify factors associated with postoperative complications using the Nationwide Inpatient Sample (NIS) database. Methods: Patients who underwent aortic graft resection for AGI were identified from the 2002 to 2008 NIS database, a multicenter database capturing 20% of all US admissions. Multivariable logistic regression analyses were performed. Results: Among 394 patients (men: 73.4%) who underwent abdominal aortic surgery for AGI, 53% of the admissions were emergent/urgent. A significant trend for decreasing number of abdominal aortic surgery for AGIs per year was observed (Pearson r correlation: -.96; P = .0006). Over the same time span, a significant correlation was also seen with decrease in open and increase in endovascular aortic aneurysm repairs in the NIS database. In-hospital rates of overall postoperative morbidity and mortality were 68.3% and 19.8%, respectively. In-hospital rates of postoperative respiratory failure, renal failure, and cardiac arrest were 35.5%, 14.2%, and 8.9%, respectively. Median length of stay was 26 days, with median hospital charges being US$184 162. On multivariable analysis, increase in age per year (odds ratio [OR] 1.07; 95% confidence interval [CI]: 1.03-1.12) was independently associated with postoperative morbidity, while higher hospital volume for this procedure was protective (OR: 0.71; 95% CI: 0.56-0.89). No preoperative factors were independently associated with postoperative mortality. Conclusion: Incidence of abdominal aortic surgery for AGI has progressively declined over the span of our study in association with decreased open and increased endovascular aortic aneurysm repairs. Aortic surgery for AGI is associated with very high morbidity and mortality rates along with prolonged lengths of stay and elevated hospital charges. The outcomes of operations for AGI are better in younger patients and higher volume hospitals
Phoretic Motion of Spheroidal Particles Due To Self-Generated Solute Gradients
We study theoretically the phoretic motion of a spheroidal particle, which
generates solute gradients in the surrounding unbounded solvent via chemical
reactions active on its surface in a cap-like region centered at one of the
poles of the particle. We derive, within the constraints of the mapping to
classical diffusio-phoresis, an analytical expression for the phoretic velocity
of such an object. This allows us to analyze in detail the dependence of the
velocity on the aspect ratio of the polar and the equatorial diameters of the
particle and on the fraction of the particle surface contributing to the
chemical reaction. The particular cases of a sphere and of an approximation for
a needle-like particle, which are the most common shapes employed in
experimental realizations of such self-propelled objects, are obtained from the
general solution in the limits that the aspect ratio approaches one or becomes
very large, respectively.Comment: 18 pages, 5 figures, to appear in European Physical Journal
A multi-wavelength polarimetric study of the blazar CTA 102 during a Gamma-ray flare in 2012
We perform a multi-wavelength polarimetric study of the quasar CTA 102 during
an extraordinarily bright -ray outburst detected by the {\it Fermi}
Large Area Telescope in September-October 2012 when the source reached a flux
of F photons cm s.
At the same time the source displayed an unprecedented optical and NIR
outburst. We study the evolution of the parsec scale jet with ultra-high
angular resolution through a sequence of 80 total and polarized intensity Very
Long Baseline Array images at 43 GHz, covering the observing period from June
2007 to June 2014. We find that the -ray outburst is coincident with
flares at all the other frequencies and is related to the passage of a new
superluminal knot through the radio core. The powerful -ray emission is
associated with a change in direction of the jet, which became oriented more
closely to our line of sight (1.2) during the ejection of
the knot and the -ray outburst. During the flare, the optical polarized
emission displays intra-day variability and a clear clockwise rotation of
EVPAs, which we associate with the path followed by the knot as it moves along
helical magnetic field lines, although a random walk of the EVPA caused by a
turbulent magnetic field cannot be ruled out. We locate the -ray
outburst a short distance downstream of the radio core, parsecs from the black
hole. This suggests that synchrotron self-Compton scattering of near-infrared
to ultraviolet photons is the probable mechanism for the -ray
production.Comment: Accepted for publication in The Astrophysical Journa
Quantum Size Effects on the Chemical Sensing Performance of Two-Dimensional Semiconductors
We investigate the role of quantum confinement on the performance of gas
sensors based on two-dimensional InAs membranes. Pd-decorated InAs membranes
configured as H2 sensors are shown to exhibit strong thickness dependence, with
~100x enhancement in the sensor response as the thickness is reduced from 48 to
8 nm. Through detailed experiments and modeling, the thickness scaling trend is
attributed to the quantization of electrons which favorably alters both the
position and the transport properties of charge carriers; thus making them more
susceptible to surface phenomena
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