353 research outputs found
Bianchi Type-II String Cosmological Models in Normal Gauge for Lyra's Manifold with Constant Deceleration Parameter
The present study deals with a spatially homogeneous and anisotropic
Bianchi-II cosmological models representing massive strings in normal gauge for
Lyra's manifold by applying the variation law for generalized Hubble's
parameter that yields a constant value of deceleration parameter. The variation
law for Hubble's parameter generates two types of solutions for the average
scale factor, one is of power-law type and other is of the exponential form.
Using these two forms, Einstein's modified field equations are solved
separately that correspond to expanding singular and non-singular models of the
universe respectively. The energy-momentum tensor for such string as formulated
by Letelier (1983) is used to construct massive string cosmological models for
which we assume that the expansion () in the model is proportional to
the component of the shear tensor . This
condition leads to , where A, B and C are the metric coefficients
and m is proportionality constant. Our models are in accelerating phase which
is consistent to the recent observations. It has been found that the
displacement vector behaves like cosmological term in the
normal gauge treatment and the solutions are consistent with recent
observations of SNe Ia. It has been found that massive strings dominate in the
decelerating universe whereas strings dominate in the accelerating universe.
Some physical and geometric behaviour of these models are also discussed.Comment: 24 pages, 10 figure
Thermoplastic Composites reinforced with Multi-layer Woven Jute Fabric: A Comparative Analysis
Three commonly available thermoplastic matrices - High-density polyethylene (HDPE), polypropylene (PP) and nylon 6 – are reinforced with hessian jute fabric in multi-layer sequence to prepare composite laminates by compression moulding technique. The composite had a nominal fibre content of 18% in terms of weight and a nominal thickness of 6.5 mm. The mechanical and fracture behaviours of the resultant laminates are tested and compared. It was found that the Nylon-Jute composite exhibited the highest values of tensile strength, Young’s modulus, flexural strength, flexural modulus and hardness. On the other hand, HDPE-Jute composite showed relatively poor performance. Interestingly, the HDPE-Jute composite exhibited the highest impact strength and the Nylon-Jute composite was the poorest in this regard. The amount of water absorption by the composites from highest to the lowest was found in the following order: Nylon-Jute > HDPE-Jute > PP-Jute
Assessing the effectiveness and observing fidelity of a psychosocial support program for Rohingya refugee mothers and their children in Cox’s Bazar, Bangladesh
Introduction: Despite the well-recognized risk poor maternal mental health poses to early child development, it is still rarely addressed in global health programming, especially in humanitarian settings where access to health and mental health infrastructures may be limited. Recognizing the critical role of maternal psychosocial wellness in addressing the health and development of children in conflict, Action contre La Faim/Action Against Hunger (ACF) developed the Baby Friendly Spaces (BFS) program. BFS is a holistic, evidenced-based psychosocial support program that aims to enhance mothers’ wellbeing, internal resources, and child caring skills in order to create a buffer against the deleterious health and developmental impacts of conflict on children. Objectives: In Bangladesh, we sought to evaluate the effectiveness of a psychosocial support program for Rohingya refugee mothers and their malnourished children under two years old living in Cox’s Bazar’s camps. Methods: For this study, we used a matched pair randomization, where ten BFS program sites were allocated to either continue providing services “as usual” or to an “enhanced BFS program” after re-training and providing continuous supportive supervision of the BFS staff throughout the trial period. 600 mothers and their children were enrolled in the study and attended psychosocial stimulation activities related to child care practices and care for women. Data were collected at baseline and 8-week follow-up. Primary outcomes included maternal distress and wellbeing, functioning, and coping. For implementation purpose, a survey was administered on confidence at work for all BFS staff and a fidelity observation assessment was conducted. Results: Relative to “as usual” sites, mothers in enhanced implementation sites reported greater reductions in distress (B=-.30) and improvement in wellbeing (B=.58). These differences were small, but marginally significant (p=.058; p=.038) with standard estimation; There was no significant difference between the two groups for daily functioning and coping. BFS providers in “enhanced BFS program” reported higher confidence in service delivery than their colleagues (p=.01). Fidelity varied widely across different components, with some very high and some very low adherence. There tended to be better adherence to procedures in group versus individual sessions and for some specific activities across domains, for enhanced versus standard BFS. Conclusions: Findings highlight the value of innovative study approaches for real-world evidence generation. Small but feasible adjustments to implementation can both improve program delivery for maximizing impact. Consequently, low-intensity psychosocial support activities holds potential for reducing distress and improving subjective well-being of conflict affected mothers
Wormhole supported by dark energy admitting conformal motion
In this article, we study the possibility of sustaining a static and
spherically symmetric traversable wormhole geometries admitting conformal
motion in Einstein gravity, which presents a more systematic approach to search
a relation between matter and geometry. In wormhole physics, the presence of
exotic matter is a fundamental ingredient and we show that this exotic source
can be dark energy type which support the existence of wormhole spacetimes. In
this work we model a wormhole supported by dark energy which admits conformal
motion. We also discuss the possibility of detection of wormholes in the outer
regions of galactic halos by means of gravitational lensing. The studies of the
total gravitational energy for the exotic matter inside a static wormhole
configuration are also done.Comment: 9 pages, 2 tables and 4 figures, Accepted for Publication in European
Physical Journal
Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron
We study the underlying event in proton-antiproton collisions by examining
the behavior of charged particles (transverse momentum pT > 0.5 GeV/c,
pseudorapidity |\eta| < 1) produced in association with large transverse
momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the
Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV
center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan
production) or the leading jet (in high-pT jet production) in each event to
define three regions of \eta-\phi space; toward, away, and transverse, where
\phi is the azimuthal scattering angle. For Drell-Yan production (excluding the
leptons) both the toward and transverse regions are very sensitive to the
underlying event. In high-pT jet production the transverse region is very
sensitive to the underlying event and is separated into a MAX and MIN
transverse region, which helps separate the hard component (initial and
final-state radiation) from the beam-beam remnant and multiple parton
interaction components of the scattering. The data are corrected to the
particle level to remove detector effects and are then compared with several
QCD Monte-Carlo models. The goal of this analysis is to provide data that can
be used to test and improve the QCD Monte-Carlo models of the underlying event
that are used to simulate hadron-hadron collisions.Comment: Submitted to Phys.Rev.
Precision measurement of the top quark mass from dilepton events at CDF II
We report a measurement of the top quark mass, M_t, in the dilepton decay
channel of
using an integrated luminosity of 1.0 fb^{-1} of p\bar{p} collisions collected
with the CDF II detector. We apply a method that convolutes a leading-order
matrix element with detector resolution functions to form event-by-event
likelihoods; we have enhanced the leading-order description to describe the
effects of initial-state radiation. The joint likelihood is the product of the
likelihoods from 78 candidate events in this sample, which yields a measurement
of M_{t} = 164.5 \pm 3.9(\textrm{stat.}) \pm 3.9(\textrm{syst.})
\mathrm{GeV}/c^2, the most precise measurement of M_t in the dilepton channel.Comment: 7 pages, 2 figures, version includes changes made prior to
publication by journa
Measurement of the Ratios of Branching Fractions B(Bs -> Ds pi pi pi) / B(Bd -> Dd pi pi pi) and B(Bs -> Ds pi) / B(Bd -> Dd pi)
Using 355 pb^-1 of data collected by the CDF II detector in \ppbar collisions
at sqrt{s} = 1.96 TeV at the Fermilab Tevatron, we study the fully
reconstructed hadronic decays B -> D pi and B -> D pi pi pi. We present the
first measurement of the ratio of branching fractions B(Bs -> Ds pi pi pi) /
B(Bd -> Dd pi pi pi) = 1.05 pm 0.10 (stat) pm 0.22 (syst). We also update our
measurement of B(Bs -> Ds pi) / B(Bd -> Dd pi) to 1.13 pm 0.08 (stat) pm 0.23
(syst) improving the statistical uncertainty by more than a factor of two. We
find B(Bs -> Ds pi) = [3.8 pm 0.3 (stat) pm 1.3 (syst)] \times 10^{-3} and B(Bs
-> Ds pi pi pi) = [8.4 pm 0.8 (stat) pm 3.2 (syst)] \times 10^{-3}.Comment: 7 pages, 2 figure
Cross Section Measurements of High- Dilepton Final-State Processes Using a Global Fitting Method
We present a new method for studying high- dilepton events
(, , ) and simultaneously
extracting the production cross sections of , , and p\bar{p} \to \ztt at a center-of-mass energy of TeV. We perform a likelihood fit to the dilepton data in a parameter
space defined by the missing transverse energy and the number of jets in the
event. Our results, which use of data recorded with the CDF
II detector at the Fermilab Tevatron Collider, are pb, pb, and
\sigma(\ztt) =291^{+50}_{-46} pb.Comment: 20 pages, 2 figures, to be submitted to PRD-R
Measurement of the Dipion Mass Spectrum in X(3872) -> J/Psi Pi+ Pi- Decays
We measure the dipion mass spectrum in X(3872)--> J/Psi Pi+ Pi- decays using
360 pb-1 of pbar-p collisions at 1.96 TeV collected with the CDF II detector.
The spectrum is fit with predictions for odd C-parity (3S1, 1P1, and 3DJ)
charmonia decaying to J/Psi Pi+ Pi-, as well as even C-parity states in which
the pions are from Rho0 decay. The latter case also encompasses exotic
interpretations, such as a D0-D*0Bar molecule. Only the 3S1 and J/Psi Rho
hypotheses are compatible with our data. Since 3S1 is untenable on other
grounds, decay via J/Psi Rho is favored, which implies C=+1 for the X(3872).
Models for different J/Psi-Rho angular momenta L are considered. Flexibility in
the models, especially the introduction of Rho-Omega interference, enable good
descriptions of our data for both L=0 and 1.Comment: 7 pages, 4 figures -- Submitted to Phys. Rev. Let
Top Quark Mass Measurement from Dilepton Events at CDF II with the Matrix-Element Method
We describe a measurement of the top quark mass using events with two charged
leptons collected by the CDF II detector from collisions with TeV at the Fermilab Tevatron. The likelihood in top mass is
calculated for each event by convoluting the leading order matrix element
describing
with detector resolution functions. The presence of background events in the
data sample is modeled using similar calculations involving the matrix elements
for major background processes. In a data sample with integrated luminosity of
340 pb, we observe 33 candidate events and measure This
measurement represents the first application of this method to events with two
charged leptons and is the most precise single measurement of the top quark
mass in this channel.Comment: 21 pages, 14 figure
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