81 research outputs found
A Unified Algebraic Approach to Few and Many-Body Correlated Systems
The present article is an extended version of the paper {\it Phys. Rev.} {\bf
B 59}, R2490 (1999), where, we have established the equivalence of the
Calogero-Sutherland model to decoupled oscillators. Here, we first employ the
same approach for finding the eigenstates of a large class of Hamiltonians,
dealing with correlated systems. A number of few and many-body interacting
models are studied and the relationship between their respective Hilbert
spaces, with that of oscillators, is found. This connection is then used to
obtain the spectrum generating algebras for these systems and make an algebraic
statement about correlated systems. The procedure to generate new solvable
interacting models is outlined. We then point out the inadequacies of the
present technique and make use of a novel method for solving linear
differential equations to diagonalize the Sutherland model and establish a
precise connection between this correlated system's wave functions, with those
of the free particles on a circle. In the process, we obtain a new expression
for the Jack polynomials. In two dimensions, we analyze the Hamiltonian having
Laughlin wave function as the ground-state and point out the natural emergence
of the underlying linear symmetry in this approach.Comment: 18 pages, Revtex format, To appear in Physical Review
Status of Groundnut Research and Production in South Asia
South Asia, comprising Bangladesh, Bhutan, India, Myanmar, Nepal, Pakistan, and Sri Lanka,
accounts for about 43.4% of the world groundnut (Arachis hypogaea) area (8.6 million ha) and
35.7% of production (8.1 million t). The period coinciding with the Southwest monsoon is the main
growing season in the region although the crop is grown in more than one season in India,
Myanmar, and Sri Lanka. The low average yields of groundnut in the region result from: raising the
crop mostly under rainfed conditions on marginal and submarginal lands with low levels of inputs,
use of varieties with long maturity periods, susceptibility of the crop to a plethora of insect pests and
diseases, and nonavailability of efficient farm machinery and quality seed. All countries in the
region made sustained efforts in the development of improved technology, including development of
high-yielding varieties, improved agronomic practices, new and efficient strains of Bradyrhizobium,
and efficient and economical plant protection schedules for the control of major insect pests and
diseases. When tested in the farmers' fields, the technology indicated much unrealized yield poten-
tial. The future crop improvement research in the region aims to concentrate on the areas of crop
duration. fresh seed dormancy, resistance/tolerance to major biotic stresses, seed quality and
production. and design and development of efficient farm implements and machinery. To realizefull
impact of research on groundnut production in the region, it is important to ensure adequate
support price and market to the crop. The International Crops Research Institute for the Semi-Arid
Tropics (ICRISAT) has contributed substantially towards the development of improved cultivars as
well as offering training facilities to accomplish better human resource development in the region
Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy
Background
A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets.
Methods
Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis.
Results
A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001).
Conclusion
We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty
Comparison of dissolved and particulate arsenic distributions in shallow aquifers of Chakdaha, India, and Araihazar, Bangladesh
International audienceBackground The origin of the spatial variability of dissolved As concentrations in shallow aquifers of the Bengal Basin remains poorly understood. To address this, we compare here transects of simultaneously-collected groundwater and aquifer solids perpendicular to the banks of the Hooghly River in Chakdaha, India, and the Old Brahmaputra River in Araihazar, Bangladesh. Results Variations in surface geomorphology mapped by electromagnetic conductivity indicate that permeable sandy soils are associated with underlying aquifers that are moderately reducing to a depth of 10–30 m, as indicated by acid-leachable Fe(II)/Fe ratios 5 mg L-1. More reducing aquifers are typically capped with finer-grained soils. The patterns suggest that vertical recharge through permeable soils is associated with a flux of oxidants on the banks of the Hooghly River and, further inland, in both Chakdaha and Araihazar. Moderately reducing conditions maintained by local recharge are generally associated with low As concentrations in Araihazar, but not systematically so in Chakdaha. Unlike Araihazar, there is also little correspondence in Chakdaha between dissolved As concentrations in groundwater and the P-extractable As content of aquifer particles, averaging 191 ± 122 ug As/L, 1.1 ± 1.5 mg As kg-1 (n = 43) and 108 ± 31 ug As/L, 3.1 ± 6.5 mg As kg-1 (n = 60), respectively. We tentatively attribute these differences to a combination of younger floodplain sediments, and therefore possibly more than one mechanism of As release, as well as less reducing conditions in Chakdaha compared to Araihazar. Conclusion Systematic dating of groundwater and sediment, combined with detailed mapping of the composition of aquifer solids and groundwater, will be needed to identify the various mechanisms underlying the complex distribution of As in aquifers of the Bengal Basin
A search for time-dependent astrophysical neutrino emission with IceCube data from 2012 to 2017
High-energy neutrinos are unique messengers of the high-energy universe,
tracing the processes of cosmic-ray acceleration. This paper presents analyses
focusing on time-dependent neutrino point-source searches. A scan of the whole
sky, making no prior assumption about source candidates, is performed, looking
for a space and time clustering of high-energy neutrinos in data collected by
the IceCube Neutrino Observatory between 2012 and 2017. No statistically
significant evidence for a time-dependent neutrino signal is found with this
search during this period since all results are consistent with the background
expectation. Within this study period, the blazar 3C 279, showed strong
variability, inducing a very prominent gamma-ray flare observed in 2015 June.
This event motivated a dedicated study of the blazar, which consists of
searching for a time-dependent neutrino signal correlated with the gamma-ray
emission. No evidence for a time-dependent signal is found. Hence, an upper
limit on the neutrino fluence is derived, allowing us to constrain a hadronic
emission model
LeptonInjector and LeptonWeighter: A neutrino event generator and weighter for neutrino observatories
We present a high-energy neutrino event generator, called LeptonInjector,
alongside an event weighter, called LeptonWeighter. Both are designed for
large-volume Cherenkov neutrino telescopes such as IceCube. The neutrino event
generator allows for quick and flexible simulation of neutrino events within
and around the detector volume, and implements the leading Standard Model
neutrino interaction processes relevant for neutrino observatories:
neutrino-nucleon deep-inelastic scattering and neutrino-electron annihilation.
In this paper, we discuss the event generation algorithm, the weighting
algorithm, and the main functions of the publicly available code, with
examples.Comment: 28 pages, 10 figures, 3 table
Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube Neutrino Telescope
We report in detail on searches for eV-scale sterile neutrinos, in the context of a 3+1 model, using eight years of data from the IceCube Neutrino Telescope. By analyzing the reconstructed energies and zenith angles of 305,735 atmospheric νμ and ¯νμ events we construct confidence intervals in two analysis spaces: sin2(2θ) vs Δm2¦41 under the conservative assumption θ=0; and sin (2θ) vs sin (2θ) given sufficiently large Δm2¦41 that fast oscillation features are unresolvable. Detailed discussions of the event selection, systematic uncertainties, and fitting procedures are presented. No strong evidence for sterile neutrinos is found, and the best-fit likelihood is consistent with the no sterile neutrino hypothesis with a p value of 8% in the first analysis space and 19% in the second
Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube neutrino telescope
We report in detail on searches for eV-scale sterile neutrinos, in the
context of a 3+1 model, using eight years of data from the IceCube neutrino
telescope. By analyzing the reconstructed energies and zenith angles of 305,735
atmospheric and events we construct confidence
intervals in two analysis spaces: vs.
under the conservative assumption ; and
vs. given sufficiently large that
fast oscillation features are unresolvable. Detailed discussions of the event
selection, systematic uncertainties, and fitting procedures are presented. No
strong evidence for sterile neutrinos is found, and the best-fit likelihood is
consistent with the no sterile neutrino hypothesis with a p-value of 8\% in the
first analysis space and 19\% in the second.Comment: This long-form paper is a companion to the letter "An eV-scale
sterile neutrino search using eight years of atmospheric muon neutrino data
from the IceCube Neutrino Observatory". v2: update other experiments contours
on results plo
An eV-scale sterile neutrino search using eight years of atmospheric muon neutrino data from the IceCube Neutrino Observatory
The results of a 3+1 sterile neutrino search using eight years of data from
the IceCube Neutrino Observatory are presented. A total of 305,735 muon
neutrino events are analyzed in reconstructed energy-zenith space to test for
signatures of a matter-enhanced oscillation that would occur given a sterile
neutrino state with a mass-squared differences between 0.01\,eV and
100\,eV. The best-fit point is found to be at
and , which is consistent with the no sterile
neutrino hypothesis with a p-value of 8.0\%.Comment: 11 pages, 5 figures. This letter is supported by the long-form paper
"Searching for eV-scale sterile neutrinos with eight years of atmospheric
neutrinos at the IceCube neutrino telescope," also appearing on arXiv.
Digital data release available at:
https://github.com/icecube/HE-Sterile-8year-data-releas
eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory
The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100 eV. The best-fit point is found to be at sin (2θ)=0.10 and Δm2/41 =4.5 eV, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%
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