1,067 research outputs found
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
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
Nuclear structure study of Na isotopes with ab initio no-core shell-model
We have done a systematic no-core shell-model study of Na isotopes.
The low-energy spectra of these sodium isotopes consisting of natural and
un-natural parity states were reported, considering three realistic
interactions: inside nonlocal outside Yukawa (INOY), charge-dependent Bonn 2000
(CDB2K), and the chiral next-to-next-to-next-to-leading order (NLO). We
also present the mirror energy differences in the low-energy spectra of
= 1/2 mirror pair (Na - Ne). Apart from the energy spectra, we
have also reported the electromagnetic transition strengths and moments.
Finally, considering all three realistic interactions, we report the
point-proton radii and neutron skin thicknesses.Comment: 17 pages, 17 figures. arXiv admin note: text overlap with
arXiv:2208.0081
Ferromagnetically correlated clusters in semi-metallic Ru2NbAl Heusler alloy
In this work, we report the structural, magnetic and electrical and thermal
transport properties of the Heusler-type alloy Ru2NbAl. From the detailed
analysis of magnetization data, we infer the presence of superparamagnetically
interacting clusters with a Pauli paramagnetic background, while short-range
ferromagnetic interaction is developed among the clusters below 5 K. The
presence of this ferromagnetic interaction is confirmed through heat capacity
measurements. The relatively small value of electronic contribution to specific
heat, gamma (~2.7 mJ/mol-K2), as well as the linear nature of temperature
dependence of Seebeck coefficient indicate a semi-metallic ground state with a
pseudo-gap that is also supported by our electronic structure calculations. The
activated nature of resistivity is reflected in the observed negative
temperature coefficient and has its origin in the charge carrier localization
due to antisite defects, inferred from magnetic measurements as well as
structural analysis. Although the absolute value of thermoelectric figure of
merit is rather low (ZT = 5.2*10-3) in Ru2NbAl, it is the largest among all the
reported non-doped full Heusler alloys.Comment: 25 pages, 14 figure
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.
Large Scale Image Segmentation with Structured Loss based Deep Learning for Connectome Reconstruction
We present a method combining affinity prediction with region agglomeration,
which improves significantly upon the state of the art of neuron segmentation
from electron microscopy (EM) in accuracy and scalability. Our method consists
of a 3D U-NET, trained to predict affinities between voxels, followed by
iterative region agglomeration. We train using a structured loss based on
MALIS, encouraging topologically correct segmentations obtained from affinity
thresholding. Our extension consists of two parts: First, we present a
quasi-linear method to compute the loss gradient, improving over the original
quadratic algorithm. Second, we compute the gradient in two separate passes to
avoid spurious gradient contributions in early training stages. Our predictions
are accurate enough that simple learning-free percentile-based agglomeration
outperforms more involved methods used earlier on inferior predictions. We
present results on three diverse EM datasets, achieving relative improvements
over previous results of 27%, 15%, and 250%. Our findings suggest that a single
method can be applied to both nearly isotropic block-face EM data and
anisotropic serial sectioned EM data. The runtime of our method scales linearly
with the size of the volume and achieves a throughput of about 2.6 seconds per
megavoxel, qualifying our method for the processing of very large datasets
Melting and structure of the vortex solid in strongly anisotropic layered superconductors with random columnar pins
We study the melting transition of the low-temperature vortex solid in
strongly anisotropic layered superconductors with a concentration of random
columnar pinning centers small enough so that the areal density of the pins is
much less than that of the vortex lines. Both the external magnetic field and
the columnar pins are assumed to be oriented perpendicular to the layers Our
method, involving numerical minimization of a model free energy functional,
yields not only the free energy values at the local minima of the functional
but also the detailed density distribution of the system at each minimum: this
allows us to study in detail the structure of the different phases. We find
that at these pin concentrations and low temperatures, the thermodynamically
stable state is a topologically ordered Bragg glass. This nearly crystalline
state melts into an interstitial liquid (a liquid in which a small fraction of
vortex lines remain localized at the pinning centers) in two steps, so that the
Bragg glass and the liquid are separated by a narrow phase that we identify
from analysis of its density structure as a polycrystalline Bose glass. Both
the Bragg glass to Bose glass and the Bose glass to interstitial liquid
transitions are first-order. We also find that a local melting temperature
defined using a criterion based on the degree of localization of the vortex
lines exhibits spatial variations similar to those observed in recent
experiments.Comment: 17 page
Renormalization-Group Treatment of the Random Resistor Network in 6−ε Dimensions
We consider a hypercubic lattice in which neighboring points are connected by resistances which assume independently the random values σ\u3e−1 and σ\u3c−1 with respective probabilities p and 1−p. For σ\u3c=0 the lattice is viewed as consisting of irreducible nodes connected by chains of path length L. This geometrical length is distinct from the characteristic length Lr which sets a scale of resistance in the random network or Lm which sets a scale of effective exchange in a dilute magnet. Near the percolation concentration pc one sets L~|p−pc|−ζ, Lr~|p−pc|−ζr and Lm~|p−pc|−ζm. Stephen and Grest (SG) have already shown that ζm=1+o(ε2) for spatial dimensionality d=6−ε. Here we show in a way similar to SG that ζr=1+o(ε2). Thus it is possible that ζm=ζr=1 for a continuous range of d below 6. However, increasing evidence suggests that this equality does not hold for d\u3c4, and in particular a calculation in 1+ε dimensions analogous to that of SG for ζm does not seem possible
Experimental study of torsional strengthening on thin walled tubular reinforced concrete structures using NSM-CFRP laminates
Although the use of near surface mounted (NSM) reinforcement for shear and flexural strengthening of reinforced concrete (RC) structures has been examined extensively in the past twenty years, its performance as torsional strengthening solution has never been assessed. This paper presents an experimental program on the use of NSM carbon fibre reinforced polymer (CFRP) laminates to enhance the torsional behaviour of RC thin walled tubular elements. Six specimens were tested as part of this work, including two reference specimens and the remaining four strengthened with different configurations of longitudinal and transverse CFRP laminates. The research shows that the addition of NSM CFRP laminates is very effective in increasing the torsional moment carrying capacity, stiffness and torsional deformability, and arresting the crack propagation, with imperceptible alteration of the geometry of the strengthened element.European Network for Durable Reinforcement and
Rehabilitation Solutions, for the grant received to perform the research. Also, to the
industries CASAIS and CiviTest in helping to execute the experimental work. The
support provided by FCT through the PTDC/ECM-EST/1882/201
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