368 research outputs found
Rotational symmetry and degeneracy: a cotangent-perturbed rigid rotator of unperturbed level multiplicity
We predict level degeneracy of the rotational type in diatomic molecules
described by means of a cotangent-hindered rigid rotator. The problem is shown
to be exactly solvable in terms of non-classical Romanovski polynomials. The
energies of such a system are linear combinations of t(t+1) and 1/[t(t+1)+1/4]
terms with the non-negative integer principal quantum number t=n+|/bar{m}|
being the sum of the degree n of the polynomials and the absolute value,
|/bar{m}|, of the square root of the separation constant between the polar and
azimuthal motions. The latter obeys, with respect to t, the same branching
rule, |/bar{m}|=0,1,..., t, as does the magnetic quantum number with respect to
the angular momentum, l, and, in this fashion, the t quantum number presents
itself indistinguishable from l. In effect, the spectrum of the hindered
rotator has the same (2t+1)-fold level multiplicity as the unperturbed one. For
small t values, the wave functions and excitation energies of the perturbed
rotator differ from the ordinary spherical harmonics, and the l(l+1) law,
respectively, while approaching them asymptotically with increasing t. In this
fashion the breaking of the rotational symmetry at the level of the
representation functions is opaqued by the level degeneracy. The model provides
a tool for the description of rotational bands with anomalously large gaps
between the ground state and its first excitation.Comment: 10 pages, 6 figures; Molecular Physics 201
Non-nutritive sucking evaluation in preterm newborns and the start of oral feeding: a multicenter study
OBJECTIVES: The assessment of early sucking by preterm infants provides information on the ability of these infants to efficiently and safely receive nutrients via an oral route (oral feeding). To analyze the application and reliability of an instrument in assessing non-nutritive sucking that indicates a capacity for oral feeding in the routine care of different neonatal units. METHODS: A multicenter, prospective cohort study was conducted in seven neonatal units. A non-nutritive sucking assessment with a formulary validated by Neiva et al (2008) (variables evaluated: rooting reaction; easy initiation of sucking; labial sealing; tongue central groove; peristaltic tongue movements; jaw raising and lowering movements; labial, tongue and jaw coordination; sucking strength; sucking rhythm; bites; excessive jaw excursion; stress signals) was applied to 199 pre-term newborns, who had a chronological age â„ 2 days and were clinically stable. These infants were divided into two groups based on their corrected gestational age at the first assessment, as follows: Group I-infants with a gestational age †33 weeks and Group II-infants with a gestational age between 34 and 36 6/7 weeks. RESULTS: The mean gestational age was 31.66±2 weeks, and the mean birth weight was 1494 ± 373 g. The mean scores on the non-nutritive sucking assessment were 46 ± 25 in Group I and 49 ± 24 in Group II. The beginning of oral feeding was successful in 43 (67.2%) infants in Group I and 64 (81%) infants in Group II (pâ=â0.089). CONCLUSION: The method identified preterm infants who were able to feed orally based on 33 points in the non-nutritive sucking assessment and a corrected gestational age of 32 weeks or more. The corrected gestational age was the most important factor in predicting the success of oral feeding
The powerful in vitro bioactivity of Euterpe oleracea Mart. seeds and related phenolic compounds
The Euterpe oleracea Mart. (açaĂ) is a plant from the Amazon region, classified as
"super fruit" because of its various functional properties. However, limited investigation
has been performed on açaà by-products, such as seeds. Therefore, the aim of this work
was to characterized the phenolic compounds of the aqueous extract of açaà seeds and
further evaluate its bioactivity (antioxidant and cytotoxic activities. Only
proanthocyanidins were detected, being a B-type (epi)catechin tetramer the most
abundant; however, procyanidin trimmers were the most predominant form. Açaà seeds
extract revealed a high antioxidant (EC50 ranging from 3.6 to 19.4 ÎŒg/mL) and cytotoxic
activity, being more effective in the cervical carcinoma cell line (HeLa; GI50 = 18
ÎŒg/mL); it did not show toxicity for non-tumor cells. AçaĂ seeds are considered a waste
and could have an added economic benefit, through the extraction of natural
antioxidants, particularly proanthocyanidins, that could find applications in food and
pharmaceutical industries.The authors are grateful to Foundation for Science and Technology (FCT, Portugal) for
financial support to the research centre CIMO (strategic project PEst
OE/AGR/UI0690/2011) and L. Barros researcher contract under âPrograma
Compromisso com CiĂȘncia - 2008â. The authors are also grateful to Jamil S. Oliveira by
the initial discussions on the preparation of samples
Generic thin-shell gravastars
We construct generic spherically symmetric thin-shell gravastars by using the
cut-and-paste procedure. We take considerable effort to make the analysis as
general and unified as practicable; investigating both the internal physics of
the transition layer and its interaction with "external forces" arising due to
interactions between the transition layer and the bulk spacetime. Furthermore,
we discuss both the dynamic and static situations. In particular, we consider
"bounded excursion" dynamical configurations, and probe the stability of static
configurations. For gravastars there is always a particularly compelling
configuration in which the surface energy density is zero, while surface
tension is nonzero.Comment: V1: 39 pages, 9 figures; V2: 40 pages, 9 figures. References added,
some discussion added, some typos fixed. Identical to published version.
arXiv admin note: text overlap with arXiv:1112.205
Green function techniques in the treatment of quantum transport at the molecular scale
The theoretical investigation of charge (and spin) transport at nanometer
length scales requires the use of advanced and powerful techniques able to deal
with the dynamical properties of the relevant physical systems, to explicitly
include out-of-equilibrium situations typical for electrical/heat transport as
well as to take into account interaction effects in a systematic way.
Equilibrium Green function techniques and their extension to non-equilibrium
situations via the Keldysh formalism build one of the pillars of current
state-of-the-art approaches to quantum transport which have been implemented in
both model Hamiltonian formulations and first-principle methodologies. We offer
a tutorial overview of the applications of Green functions to deal with some
fundamental aspects of charge transport at the nanoscale, mainly focusing on
applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references,
submitted to Springer series "Lecture Notes in Physics
Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources
We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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