52 research outputs found
Quantum three-body system in D dimensions
The independent eigenstates of the total orbital angular momentum operators
for a three-body system in an arbitrary D-dimensional space are presented by
the method of group theory. The Schr\"{o}dinger equation is reduced to the
generalized radial equations satisfied by the generalized radial functions with
a given total orbital angular momentum denoted by a Young diagram
for the SO(D) group. Only three internal variables are
involved in the functions and equations. The number of both the functions and
the equations for the given angular momentum is finite and equal to
.Comment: 16 pages, no figure, RevTex, Accepted by J. Math. Phy
Calculation of the photoionization with de-excitation cross sections of He and helium-like ions
We discuss the results of the calculation of the photoionization with
de-excitation of excited He and helium-like ions Li and B at high
but non-relativistic photon energies . Several lower and
states are considered. We present and analyze the ratios
of the cross sections of photoionization with de-excitation,
, and of the photo-ionization with excitation,
. The dependence of on the excitation
of the target object and the charge of its nucleus is presented. Apart to
theoretical interest, results obtained can be verified using such long living
excited state as of He.Comment: 10 pages, 6 table
Low-lying spectrum of the Y-string three-quark potential using hyper-spherical coordinates
We calculate the energies of three-quark states with definite permutation
symmetry (i.e. of SU(6) multiplets) in the N=0,1,2 shells, confined by the
Y-string three-quark potential. The exact Y-string potential consists of one,
so-called three-string term, and three angle-dependent two-string terms. Due to
this technical complication we treat the problem at three increasingly accurate
levels of approximation: 1) the (approximate) three-string potential expanded
to first order in trigonometric functions of hyper-spherical angles; 2) the
(approximate) three-string potential to all orders in the power expansion in
hyper-spherical harmonics, but without taking into account the transition(s) to
two-string potentials; 3) the exact minimal-length string potential to all
orders in power expansion in hyper-spherical harmonics, and taking into account
the transition(s) to two-string potentials. We show the general trend of
improvement %convergence of these approximations: The exact non-perturbative
corrections to the total energy are of the order of one per cent, as compared
with approximation 2), yet the exact energy differences between the
-plets are shifted to 2:2:0.9,
from the Bowler and Tynemouth separation rule 2:2:1, which is obeyed by
approximation 2) at the one per cent level. The precise value of the energy
separation of the first radial excitation ("Roper") -plet
from the -plet depends on the approximation, but does not become
negative, i.e. the "Roper" remains heavier than the odd-parity
-plet in all of our approximations.Comment: 19 pages, 6 figure
State Dependent Effective Interaction for the Hyperspherical Formalism
The method of effective interaction, traditionally used in the framework of
an harmonic oscillator basis, is applied to the hyperspherical formalism of
few-body nuclei (A=3-6). The separation of the hyperradial part leads to a
state dependent effective potential. Undesirable features of the harmonic
oscillator approach associated with the introduction of a spurious confining
potential are avoided. It is shown that with the present method one obtains an
enormous improvement of the convergence of the hyperspherical harmonics series
in calculating ground state properties, excitation energies and transitions to
continuum states.Comment: LaTeX, 16 pages, 8 ps figure
Benchmark Test Calculation of a Four-Nucleon Bound State
In the past, several efficient methods have been developed to solve the
Schroedinger equation for four-nucleon bound states accurately. These are the
Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis
variational, the stochastic variational, the hyperspherical variational, the
Green's function Monte Carlo, the no-core shell model and the effective
interaction hyperspherical harmonic methods. In this article we compare the
energy eigenvalue results and some wave function properties using the realistic
AV8' NN interaction. The results of all schemes agree very well showing the
high accuracy of our present ability to calculate the four-nucleon bound state.Comment: 17 pages, 1 figure
Faecal immunochemical tests (FIT) can help to rule out colorectal cancer in patients presenting in primary care with lower abdominal symptoms:a systematic review conducted to inform new NICE DG30 diagnostic guidance
__Background:__ This study has attempted to assess the effectiveness of quantitative faecal immunochemical tests (FIT) for triage of people presenting with lower abdominal symptoms, where a referral to secondary care for investigation of suspected colorectal cancer (CRC) is being considered, particularly when the 2-week criteria are not met.
__Methods:__ We conducted a systematic review following published guidelines for systematic reviews of diagnostic tests. Twenty-one resources were searched up until March 2016. Summary estimates were calculated using a bivariate model or a random-effects logistic regression model.
__Results:__ Nine studies are included in this review. One additional study, included in our systematic review, was provided as 'academic in confidence' and cannot be described herein. When FIT was based on a single faecal sample and a cut-off of 10 ÎŒg Hb/g faeces, sensitivity estimates indicated that a negative result using either the OC-Sensor or HM-JACKarc may be adequate to rule out nearly all CRC; the summary estimate of sensitivity for the OC-Sensor was 92.1%, based on four studies, and the only study of HM-JACKarc to assess the 10 ÎŒg Hb/g faeces cut-off reported a sensitivity of 100%. The corresponding specificity estimates were 85.8% (95% CI 78.3-91.0%) and 76.6%, respectively. When the diagnostic criterion was changed to include lower grades of neoplasia, i.e. the target condition included higher risk adenoma (HRA) as well as CRC, the rule-out performance of both FIT assays was reduced.
__Conclusions:__ There is evidence to suggest that triage using FIT at a cut-off around 10 ÎŒg Hb/g faeces has the potential to correctly rule out CRC and avoid colonoscopy in 75-80% of symptomatic patients. Systematic review registration: PROSPERO 4201603772
Impaired Structural Connectivity of Socio-Emotional Circuits in Autism Spectrum Disorders: A Diffusion Tensor Imaging Study
Abnormal white matter development may disrupt integration within neural circuits, causing particular impairments in higher-order behaviours. In autism spectrum disorders (ASDs), white matter alterations may contribute to characteristic deficits in complex socio-emotional and communication domains. Here, we used diffusion tensor imaging (DTI) and tract based spatial statistics (TBSS) to evaluate white matter microstructure in ASD.DTI scans were acquired for 19 children and adolescents with ASD (âŒ8-18 years; mean 12.4±3.1) and 16 age and IQ matched controls (âŒ8-18 years; mean 12.3±3.6) on a 3T MRI system. DTI values for fractional anisotropy, mean diffusivity, radial diffusivity and axial diffusivity, were measured. Age by group interactions for global and voxel-wise white matter indices were examined. Voxel-wise analyses comparing ASD with controls in: (i) the full cohort (ii), children only (â€12 yrs.), and (iii) adolescents only (>12 yrs.) were performed, followed by tract-specific comparisons. Significant age-by-group interactions on global DTI indices were found for all three diffusivity measures, but not for fractional anisotropy. Voxel-wise analyses revealed prominent diffusion measure differences in ASD children but not adolescents, when compared to healthy controls. Widespread increases in mean and radial diffusivity in ASD children were prominent in frontal white matter voxels. Follow-up tract-specific analyses highlighted disruption to pathways integrating frontal, temporal, and occipital structures involved in socio-emotional processing.Our findings highlight disruption of neural circuitry in ASD, particularly in those white matter tracts that integrate the complex socio-emotional processing that is impaired in this disorder
Co@NH 2
We present a synthetic strategy for the efficient encapsulation of a deriv. of a well-âdefined cobaloxime proton redn. catalyst within a photoresponsive metal-âorg. framework (NH2- MIL-â125(Ti)â)â. The resulting hybrid system Co@MOF is demonstrated to be a robust heterogeneous composite material. Furthermore, Co@MOF is an efficient and fully recyclable noble metal-âfree catalyst system for light-âdriven hydrogen evolution from water under visible light illumination
COVID-19 in children and adolescents in Europe: a multinational, multicentre cohort study
Background
To date, few data on paediatric COVID-19 have been published, and most reports originate from China. This study aimed to capture key data on children and adolescents with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across Europe to inform physicians and health-care service planning during the ongoing pandemic.
Methods
This multicentre cohort study involved 82 participating health-care institutions across 25 European countries, using a well established research networkâthe Paediatric Tuberculosis Network European Trials Group (ptbnet)âthat mainly comprises paediatric infectious diseases specialists and paediatric pulmonologists. We included all individuals aged 18 years or younger with confirmed SARS-CoV-2 infection, detected at any anatomical site by RT-PCR, between April 1 and April 24, 2020, during the initial peak of the European COVID-19 pandemic. We explored factors associated with need for intensive care unit (ICU) admission and initiation of drug treatment for COVID-19 using univariable analysis, and applied multivariable logistic regression with backwards stepwise analysis to further explore those factors significantly associated with ICU admission.
Findings
582 individuals with PCR-confirmed SARS-CoV-2 infection were included, with a median age of 5·0 years (IQR 0·5â12·0) and a sex ratio of 1·15 males per female. 145 (25%) had pre-existing medical conditions. 363 (62%) individuals were admitted to hospital. 48 (8%) individuals required ICU admission, 25 (4%) mechanical ventilation (median duration 7 days, IQR 2â11, range 1â34), 19 (3%) inotropic support, and one (<1%) extracorporeal membrane oxygenation. Significant risk factors for requiring ICU admission in multivariable analyses were being younger than 1 month (odds ratio 5·06, 95% CI 1·72â14·87; p=0·0035), male sex (2·12, 1·06â4·21; p=0·033), pre-existing medical conditions (3·27, 1·67â6·42; p=0·0015), and presence of lower respiratory tract infection signs or symptoms at presentation (10·46, 5·16â21·23; p<0·0001). The most frequently used drug with antiviral activity was hydroxychloroquine (40 [7%] patients), followed by remdesivir (17 [3%] patients), lopinavirâritonavir (six [1%] patients), and oseltamivir (three [1%] patients). Immunomodulatory medication used included corticosteroids (22 [4%] patients), intravenous immunoglobulin (seven [1%] patients), tocilizumab (four [1%] patients), anakinra (three [1%] patients), and siltuximab (one [<1%] patient). Four children died (case-fatality rate 0·69%, 95% CI 0·20â1·82); at study end, the remaining 578 were alive and only 25 (4%) were still symptomatic or requiring respiratory support.
Interpretation
COVID-19 is generally a mild disease in children, including infants. However, a small proportion develop severe disease requiring ICU admission and prolonged ventilation, although fatal outcome is overall rare. The data also reflect the current uncertainties regarding specific treatment options, highlighting that additional data on antiviral and immunomodulatory drugs are urgently needed.
Funding
ptbnet is supported by Deutsche Gesellschaft fĂŒr Internationale Zusammenarbeit
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