1,606 research outputs found
Stability of bubbles in wax-based oleofoams: decoupling the effects of bulk oleogel rheology and interfacial rheology
Oleofoams are dispersions of gas bubbles in a continuous oil phase and can be stabilized by crystals of fatty acids or waxes adsorbing at the oil-air interface. Because excess crystals in the continuous phase form an oleogel, an effect of the bulk rheology of the continuous phase is also expected. Here, we evaluate the contributions of bulk and interfacial rheology below and above the melting point of a wax forming an oleogel in sunflower oil. We study the dissolution behaviour of single bubbles using microscopy on a temperature-controlled stage. We compare the behaviour of a bubble embedded in an oleofoam, which owes its stability to both bulk and interfacial rheology, to that of a bubble extracted from the oleofoam and resuspended in oil, for which the interfacial dilatational rheology alone provides stability. We find that below the melting point of the wax, bubbles in the oleofoam are stable whereas bubbles that are only coated with wax crystals dissolve. Both systems dissolve when heated above the melting point of the wax. These findings are rationalized through independent bulk rheological measurements of the oleogel at different temperatures, as well as measurements of the dilatational rheological properties of a wax-coated oil-air interface
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
Cold gas accretion in galaxies
Evidence for the accretion of cold gas in galaxies has been rapidly
accumulating in the past years. HI observations of galaxies and their
environment have brought to light new facts and phenomena which are evidence of
ongoing or recent accretion:
1) A large number of galaxies are accompanied by gas-rich dwarfs or are
surrounded by HI cloud complexes, tails and filaments. It may be regarded as
direct evidence of cold gas accretion in the local universe. It is probably the
same kind of phenomenon of material infall as the stellar streams observed in
the halos of our galaxy and M31. 2) Considerable amounts of extra-planar HI
have been found in nearby spiral galaxies. While a large fraction of this gas
is produced by galactic fountains, it is likely that a part of it is of
extragalactic origin. 3) Spirals are known to have extended and warped outer
layers of HI. It is not clear how these have formed, and how and for how long
the warps can be sustained. Gas infall has been proposed as the origin. 4) The
majority of galactic disks are lopsided in their morphology as well as in their
kinematics. Also here recent accretion has been advocated as a possible cause.
In our view, accretion takes place both through the arrival and merging of
gas-rich satellites and through gas infall from the intergalactic medium (IGM).
The infall may have observable effects on the disk such as bursts of star
formation and lopsidedness. We infer a mean ``visible'' accretion rate of cold
gas in galaxies of at least 0.2 Msol/yr. In order to reach the accretion rates
needed to sustain the observed star formation (~1 Msol/yr), additional infall
of large amounts of gas from the IGM seems to be required.Comment: To appear in Astronomy & Astrophysics Reviews. 34 pages.
Full-resolution version available at
http://www.astron.nl/~oosterlo/accretionRevie
Use of traditional cooking fuels and the risk of young adult cataract in rural Bangladesh: a hospital-based case-control study
<p>Abstract</p> <p>Background</p> <p>This study aimed to investigate the independent relationship between the use of various traditional biomass cooking fuels and the occurrence of cataract in young adults in rural Bangladesh.</p> <p>Methods</p> <p>A hospital-based age- and sex-matched case-control study incorporating two control groups was conducted. Cases were cataract patients aged 18 and 49 years diagnosed on the basis of any opacity of the crystalline lens or its capsule and visual acuity poorer than 6/18 on the Log Mar Visual Acuity Chart in either eye, or who had a pseudophakic lens as a result of cataract surgery within the previous 5 years. Non-eye-disease (NE) controls were selected from patients from ENT or Orthopaedics departments and non-cataract eye-disease (NC) controls from the Ophthalmology department. Data pertaining to history of exposure to various cooking fuels and to established risk factors for cataract were obtained by face-to-face interview and analyzed using conditional logistic regression.</p> <p>Results</p> <p>Clean fuels were used by only 4% of subjects. A majority of males (64-80% depending on group) had never cooked, while the rest had used biomass cooking fuels, mainly wood/dry leaves, with only 6 having used rice straw and/or cow dung. All females of each group had used wood/dry leaves for cooking. Close to half had also used rice straw and/or cow dung. Among females, after controlling for family history of cataract and education and combining the two control groups, case status was shown to be significantly related to lifetime exposure to rice straw, fitted as a trend variable coded as never, ⤠median of all exposed, > median of all exposed (OR = 1.52, 95%CI 1.04-2.22), but not to lifetime exposure to wood/dry leaves. Case status among females showed an inverse association with ever use of cow dung as a cooking fuel (OR 0.43, 95%CI 0.22-0.81).</p> <p>Conclusions</p> <p>In this population, where cooking is almost exclusively done using biomass fuels, cases of young adult cataract among females were more likely to have had an increased lifetime exposure to cooking with rice straw fuel and not to have cooked using cow dung fuel. There is a possibility that these apparent associations could have been the result of uncontrolled founding, for instance by wealth. The nature of the associations, therefore, needs to be further investigated.</p
Recommended from our members
Seasonal forecasts of North Atlantic tropical cyclone activity in the North American Multi-Model Ensemble
The North American Multi-Model Ensemble (NMME)-Phase II models are evaluated in terms of their retrospective seasonal forecast skill of the North Atlantic (NA) tropical cyclone (TC) activity, with a focus on TC frequency. The TC identification and tracking algorithm is modified to accommodate model data at daily resolution. It is also applied to three reanalysis products at the spatial and temporal resolution of the NMME-Phase II ensemble to allow for a more objective estimation of forecast skill. When used with the reanalysis data, the TC tracking generates realistic climatological distributions of the NA TC formation and tracks, and represents the interannual variability of the NA TC frequency quite well. Forecasts with the multi-model ensemble (MME) when initialized in April and later tend to have skill in predicting the NA seasonal TC counts (and TC days). At longer leads, the skill is low or marginal, although one of the models produces skillful forecasts when initialized as early as January and February. At short lead times, while demonstrating the highest skill levels the MME also tends to significantly outperform the individual models and attain skill comparable to the reanalysis. In addition, the short-lead MME forecasts are quite reliable. At regional scales, the skill is rather limited and mostly present in the western tropical NA and the Caribbean Sea. It is found that the overall MME forecast skill is limited by poor representation of the low-frequency variability in the predicted TC frequency, and large fluctuations in skill on decadal time scales. Addressing these deficiencies is thought to increase the value of the NMME ensemble in providing operational guidance
Quinoline Group Modified Carbon Nanotubes for the Detection of Zinc Ions
Carbon nanotubes (CNTs) were covalently modified by fluorescence ligand (glycine-N-8-quinolylamide) and formed a hybrid material which could be used as a selective probe for metal ions detection. The anchoring to the surface of the CNTs was carried out by the reaction between the precursor and the carboxyl groups available on the surface of the support. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA) unambiguously proved the existence of covalent bonds between CNTs and functional ligands. Fluorescence characterization shows that the obtained organicâinorganic hybrid composite is highly selective and sensitive (0.2 ÎźM) to Zn(II) detection
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at â s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fbâ1 of â s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
Epidemiology of acute respiratory infections in children - preliminary results of a cohort in a rural north Indian community
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
- âŚ