980 research outputs found
Growth mechanism of nanocrystals in solution: ZnO, a case study
We investigate the mechanism of growth of nanocrystals from solution using
the case of ZnO. Spanning a wide range of values of the parameters, such as the
temperature and the reactant concentration, that control the growth, our
results establish a qualitative departure from the widely accepted diffusion
controlled coarsening (Ostwald ripening) process quantified in terms of the
Lifshitz-Slyozov-Wagner theory. Further, we show that these experimental
observations can be qualitatively and quantitatively understood within a growth
mechanism that is intermediate between the two well-defined limits of diffusion
control and kinetic control.Comment: 10 pages, 4 figure
Oscillating magnetoresistance due to fragile spin structure in metallic GdPd
Studies on the phenomenon of magnetoresistance (MR) have produced intriguing
and application-oriented outcomes for decades--colossal MR, giant MR and
recently discovered extremely large MR of millions of percents in semimetals
can be taken as examples. We report here the investigation of oscillating MR in
a cubic intermetallic compound GdPd, which is the only compound that
exhibits MR oscillations between positive and negative values. Our study shows
that a very strong correlation between magnetic, electrical and
magnetotransport properties is present in this compound. The magnetic structure
in GdPd is highly fragile since applied magnetic fields of moderate
strength significantly alter the spin arrangement within the system--a behavior
that manifests itself in the oscillating MR. Intriguing magnetotransport
characteristics of GdPd are appealing for field-sensitive device
applications, especially if the MR oscillation could materialize at higher
temperature by manipulating the magnetic interaction through perturbations
caused by chemical substitutions.Comment: 10 pages, 7 figures. A slightly modified version is published in
Scientific Report
Relating transverse structure of various parton distributions
We present the results of T-even TMDs in a light front quark-diquark model of
nucleons with the wave functions constructed from the soft-wall AdS/QCD
prediction. The relations amongst TMDs are discussed. The dependence
of the TMDs are compared with the -dependence of the GPDs. AdS/QCD wave
function provides an explanation behind the approximate and
factorization observed in lattice TMD calculations.Comment: 11 pages, 8 figures, modified extensively, added new results and
discusssion
Phase diagram of vortex matter in layered superconductors with random point pinning
We study the phase diagram of the superconducting vortex system in layered
high-temperature superconductors in the presence of a magnetic field
perpendicular to the layers and of random atomic scale point pinning centers.
We consider the highly anisotropic limit where the pancake vortices on
different layer are coupled only by their electromagnetic interaction. The free
energy of the vortex system is then represented as a Ramakrishnan-Yussouff free
energy functional of the time averaged vortex density. We numerically minimize
this functional and examine the properties of the resulting phases. We find
that, in the temperature () -- pinning strength () plane at constant
magnetic induction, the equilibrium phase at low and is a Bragg glass.
As one increases or a first order phase transition occurs to another
phase that we characterize as a pinned vortex liquid. The weakly pinned vortex
liquid obtained for high and small smoothly crosses over to the
strongly pinned vortex liquid as is decreased or increased -- we do not
find evidence for the existence, in thermodynamic equilibrium, of a distinct
vortex glass phase in the range of pinning parameters considered here. %cdr We
present results for the density correlation functions, the density and defect
distributions, and the local field distribution accessible via SR
experiments. These results are compared with those of existing theoretical,
numerical and experimental studies.Comment: 15 pages, including figures. Higher resolution files for Figs 3a and
11 available from author
Approximation of Rupture Directivity in Regional Phases Using Upgoing and Downgoing Wave Fields
Recent broadband modeling of regional events suggests that vertical directivity is particularly important at high frequency. Conventionally, such directivity is obtained by summing a grid of point sources. This relatively time-consuming procedure can be greatly reduced by introducing directivity time histories appropriate for the various crustal phases in terms of upgoing and downgoing paths that are calculated at only one depth. To achieve this, we formulated frequency-wavenumber solutions for a simultaneous computation of surface displacement for three wave fields, upgoing, downgoing, and the total from a seismic source buried in a layered medium (Appendix A). The concept of upgoing and downgoing wave field is introduced in the source layer matrix explicitly before allowing the source coefficients to interact with the propagation of the stress-displacement vector. Using this new algorithm, we generated a set of upgoing and downgoing wave fields at a fixed depth for different crustal models. We also simulated the effects of rupture propagation using distributed point-source summations and predicted the same effect by summing the upgoing and downgoing wave fields calculated at a single depth, each convolved with a separate analytical boxcar function representing the far-field rupture. A library of these new Green's functions should prove much more effective in modeling recorded motions than using point-source Green's functions alone
Evaluation of rice–legume–rice cropping system on grain yield, nutrient uptake, nitrogen fixation, and chemical, physical, and biological properties of soil
To achieve higher yields and better soil quality under rice–legume–rice (RLR) rotation in a rainfed production system, we formulated integrated nutrient management (INM) comprised of Azospirillum (Azo), Rhizobium (Rh), and phosphate-solubilizing bacteria (PSB) with phosphate rock (PR), compost, and muriate of potash (MOP). Performance of bacterial bioinoculants was evaluated by determining grain yield, nitrogenase activity, uptake and balance of N, P, and Zn, changes in water stability and distribution of soil aggregates, soil organic C and pH, fungal/bacterial biomass C ratio, casting activities of earthworms, and bacterial community composition using denaturing gradient gel electrophoresis (DGGE) fingerprinting. The performance comparison was made against the prevailing farmers’ nutrient management practices [N/P2O5/K2O at 40:20:20 kg ha−1 for rice and 20:30:20 kg ha−1 for legume as urea/single super-phosphate/MOP (urea/SSP/MOP)]. Cumulative grain yields of crops increased by 7–16% per RLR rotation and removal of N and P by six crops of 2 years rotation increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots over that in compost alone or urea/SSP/MOP plots. Apparent loss of soil total N and P at 0–15 cm soil depth was minimum and apparent N gain at 15–30 cm depth was maximum in Azo/Rh plus PSB dual INM plots. Zinc uptake by rice crop and diethylenetriaminepentaacetate-extractable Zn content in soil increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Total organic C content in soil declined at 0–15 cm depth and increased at 15–30 cm depth in all nutrient management plots after a 2-year crop cycle; however, bacterial bioinoculants-based INM plots showed minimum loss and maximum gain of total organic C content in the corresponding soil depths. Water-stable aggregation and distribution of soil aggregates in 53–250- and 250–2,000 μm classes increased significantly (P < 0.05) in bacterial bioinoculants-based INM plots compared to other nutrient management plots. Fungal/bacterial biomass C ratio seems to be a more reliable indicator of C and N dynamics in acidic soils than total microbial biomass C. Compost alone or Azo/Rh plus PSB dual INM plots showed significantly (P < 0.05) higher numbers of earthworms’ casts compared to urea/SSP/MOP alone and bacterial bioinoculants with urea or SSP-applied plots. Hierarchical cluster analysis based on similarity matrix of DGGE profiles revealed changes in bacterial community composition in soils due to differences in nutrient management, and these changes were seen to occur according to the states of C and N dynamics in acidic soil under RLR rotation
Innovative Technologies for Enhanced Availability of Bajra-Napier Hybrid Rooted Slips
Livestock occupies a crucial position in Indian agriculture and directly contributing 4.1% of total GDP of the country. India, with 2.29% of the world land area, is maintaining about 10.71% of the world’s livestock population. To sustain the present milk growth rate of 4.04% and for further expansion to meet the demands of ever growing human population, livestock needs sustainable supply of feed material. The area under fodder cultivation is estimated to be about 4% of the gross cropped area which remained static for the last four decades.The traditional grazing lands are gradually diminishing because of urbanization, expansion of cultivable area, grazing pressure and industrialization etc. These factors resulted in severe shortage of feed and fodder to the extent of 26% in dry-crop residues, 35.6% in green fodder and 41% of concentrates (Anon, 2013). To reduce the demand and supply gap, the production and productivity of fodder crops needs to be enhanced. The utilization of non-cultivable space viz., field bunds, common grazing lands, backyards apart from regular cultivation of high biomass species like Bajra-Napier hybrid (BN hybrid), guinea grass, Trispecific hybrid helps in enhanced production of green fodder.
Bajra-Napier hybrid is one of the high biomass grasses with fodder potential of 300 tons/ha/year. However, this grass can be propagated only through rooted slips as it does not form any viable seed. Several varieties suitable to different agro-climatic zones were released for the successful cultivation of this grass throughout India. Due to increasing demand both from small and marginal farmers as well as well-structured large scale diary industry, there is severe shortage of rooted slips of this grass. The traditional uprooting of tussocks not only destructs the mother tussock but also highly labour intensive and difficult to transport to long distances. Keeping in view of all these constraints, two novel technologies were developed for the large scale multiplication of BN hybrid rooted slips
Hydrodynamics of superfluids confined in blocked rings and wedges
Motivated by many recent experimental studies of non-classical rotational
inertia (NCRI) in superfluid and supersolid samples, we present a study of the
hydrodynamics of a superfluid confined in the two-dimensional region
(equivalent to a long cylinder) between two concentric arcs of radii and
() subtending an angle , with . The case
corresponds to a blocked ring. We discuss the methodology to
compute the NCRI effects, and calculate these effects both for small angular
velocities, when no vortices are present, and in the presence of a vortex. We
find that, for a blocked ring, the NCRI effect is small, and that therefore
there will be a large discontinuity in the moment of inertia associated with
blocking or unblocking circular paths. For blocked wedges () with , we find an unexpected divergence of the velocity at the origin, which
implies the presence of either a region of normal fluid or a vortex for {\it
any} nonzero value of the angular velocity. Implications of our results for
experiments on "supersolid" behavior in solid are discussed. A
number of mathematical issues are pointed out and resolved.Comment: 15 pages, including figures. To appear in Phys. Rev.
Biometric Personal Identification based on Iris Patterns
This paper discusses an analysis of human iris patterns for recognition of biometric system which consists of a segmentation system that is based on the Hough transform, and is able to localize the circular iris and pupil region, occluding eyelids and eyelashes, and reflections. The extracted iris region is then normalized into a rectangular block with constant dimensions to account for imaging inconsistencies. To encode the unique pattern of the iris into a bit-wise biometric template, 1D Log-Gabor filter is used.Finally to match two iris templates hamming distance is used as matching metric. The system performance is analyzed on 312 iris images taken from standard CASIA Iris Interval database version 4. To establish the verification accuracy of iris representation and matching approach, each iris image in the database is matched with all the other iris images in the database and genuine and imposter distribution is found .The performance of the system is implemented by evaluating the Decidability Index (DI), False match rate (FMR), False Non-match rate (FNMR), Genuine Accept Rate (GAR) and Equal error rate (EER)
Role of Vertex Index in Substructure Identification and Activity Prediction: A Study on Antitubercular Activity of a Series of Acid Alkyl Ester Derivatives
Tuberculosis (TB) is a life threatening disease caused due to infection from Mycobacterium tu¬berculosis (Mtb). That most of the TB strains have become resistant to various existing drugs, develop¬ment of effective novel drug candidates to combat this disease is a need of the day. In spite of intensive research world-wide, the success rate of discovering a new anti-TB drug is very poor. Therefore, novel drug discovery methods have to be tried. We have used a rule based computational method that utilizes a vertex index, named ‘distance exponent index (Dx)’ (taken x = –4 here) for predicting anti-TB activity of a series of acid alkyl ester derivatives. The method is meant to identify activity related substructures from a series a compounds and predict activity of a compound on that basis. The high degree of successful pre¬diction in the present study suggests that the said method may be useful in discovering effective anti-TB compound. It is also apparent that substructural approaches may be leveraged for wide purposes in com¬puter-aided drug design. (doi: 10.5562/cca2306
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