9,368 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
Objectives of sustainable development and youth employment in Colombia
The sustainable development goals (SDGs) aim to raise quality employment, gender
equity in access to employment and increase coverage in education. However, in Colombia, high
unemployment rates and the informality of young people are risks of achieving these goals. The
purpose of this research is to estimate the determinants of youth unemployment and its relationship
with SDGs Objective 8, and linking it to the objectives of quality education and gender equity. Using
the microdata of the Colombian household survey, DANE, this relationship is estimated with a
methodology of age, period, and cohort, through a Probit/Logit Multinomial model. As a novel
result for the Colombian case, it is shown that, although new generations of young people are more
educated, education per se is not enough to guarantee them a quality insertion into the labor market,
penalizing, above all, young women. Lack of work experience and segmentation of the labor market
would help explain this outcome. Employment policies, therefore, to achieve the SDGs must not only
invest in education, but also expand dual education programs, considering gende
The influence of topic and systemic administration of copaiba oil on the alveolar wound healing after tooth extraction in rats
The Copaiba oil has been used as an auxiliary treatment of inflammations, skin disorders and stomach ulcers,
however, in dentistry, this alternative medicine has not been investigated yet. The purpose of this study was to
evaluate the influence of topic and systemic administration of copaiba oil on the alveolar wound healing after tooth
extraction. Twenty-eight wistar male rats had their lower first molar teeth extracted. Subsequently, they were divided in four groups, according to the treatment performed: (a) alveolar socket irrigation with copaiba oil; (b) alveolar
socket irrigation with physiological serum; (c) daily gavage with copaiba oil or (d) daily gavage with physiological
serum. After the sacrifice, the mandibles were removed and processed in order to obtain decalcified histological
sections. The results demonstrated high level of epithelial migration, small number of inflammatory cells and vascular enhancement in the animals which received systemic administration of copaiba oil. The rats treated with topic
administration of copaiba oil presented ulcerations and large number of inflammatory cells. An increased bone
neoformation was observed in both groups treated with copaiba oil when compared with placebo group. It could be
concluded that topic or systemic administration of copaiba oil leads to a better alveolar bone healing, however the
topic application on connective tissue should be carefully considered, regarding the whole socket wound healing
Toxic and Metabolic Myelopathies
Myelopathy describes any neurologic deficit related to the spinal cord. It is most commonly caused by its compression by neoplasms, degenerative disc disease, trauma, or infection. Less common causes of myelopathy include spinal cord tumors, infection, inflammatory, neurodegenerative, vascular, toxic, and metabolic disorders. Conditions affecting the spinal cord must be recognized as early as possible to prevent progression that may lead to permanent disability. Biopsy is rarely performed, thus the diagnosis and management rely on patient׳s history, physical examination, laboratory results, and imaging findings. Here we review the clinical presentations, pathophysiological mechanisms, and magnetic resonance imaging findings of myelopathies related to metabolic or toxic etiologies.info:eu-repo/semantics/publishedVersio
Molecular identification and VOMs characterization of Saccharomyces cerevisiae strains isolated from Madeira region winery environments
The quality and typical characteristic of wines depends, among other factors, on the
volatile organic metabolites (VOMs) that are biosynthesized by yeasts, mainly Saccharomyces cerevisiae
species. The yeast strain influences the diversity and proportions of the VOMs produced during the
fermentation process, as the genetic predisposition of the strains is a by-product of selective adaptation
to the ecosystem. The present work reports the characterization of S. cerevisiae strains isolated from
grape must, used in the Demarcated Region of Madeira (DRM) for winemaking. Yeast species
were identified by amplification and by restriction fragment length polymorphism (RFLP) analysis
of the region 5.8S-internal transcribed spacers (PCR-RFLP of 5.8S-ITS) of ribosomal DNA (rDNA).
The strains identification was performed by analyzing the RFLP pattern of mitochondrial DNA
(RFLP-mtDNA). The representative strains were selected for the characterization of the volatile profile
through headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass
spectrometry (GC-MS) analysis. A total of 77 VOMs were identified. Higher alcohols, esters, and fatty
acids were the major chemical families representing 63%, 16%, and 9%, respectively, in strain A and
54%, 23%, and 15% in strain B. The results indicate the influence of the strain metabolism in the
production of VOMs, many of which probably participate in the aroma of the corresponding wines.info:eu-repo/semantics/publishedVersio
Evaluating brain parcellations using the distance-controlled boundary coefficient
One important approach to human brain mapping is to define a set of distinct regions that can be linked to unique functions. Numerous brain parcellations have been proposed, using cytoarchitectonic, structural, or functional magnetic resonance imaging (fMRI) data. The intrinsic smoothness of brain data, however, poses a problem for current methods seeking to compare different parcellations. For example, criteria that simply compare within-parcel to between-parcel similarity provide even random parcellations with a high value. Furthermore, the evaluation is biased by the spatial scale of the parcellation. To address this problem, we propose the distance-controlled boundary coefficient (DCBC), an unbiased criterion to evaluate discrete parcellations. We employ this new criterion to evaluate existing parcellations of the human neocortex in their power to predict functional boundaries for an fMRI data set with many different tasks, as well as for resting-state data. We find that common anatomical parcellations do not perform better than chance, suggesting that task-based functional boundaries do not align well with sulcal landmarks. Parcellations based on resting-state fMRI data perform well; in some cases, as well as a parcellation defined on the evaluation data itself. Finally, multi-modal parcellations that combine functional and anatomical criteria perform substantially worse than those based on functional data alone, indicating that functionally homogeneous regions often span major anatomical landmarks. Overall, the DCBC advances the field of functional brain mapping by providing an unbiased metric that compares the predictive ability of different brain parcellations to define brain regions that are functionally maximally distinct
The role of MatP, ZapA and ZapB in chromosomal organization and dynamics in Escherichia coli
Despite extensive research over several decades, a comprehensive view of how the Escherichia coli chromosome is organized within the nucleoid, and how two daughter chromosomes segregate has yet to emerge. Here we investigate the role of the MatP, ZapA and ZapB proteins in organizing the replication terminus (Ter) region and in the chromosomal segregation process. Quantitative image analysis of the fluorescently labeled Ter region shows that the replication terminus attaches to the divisome in a single segment along the perimeter of the cell in a MatP, ZapA and ZapB-dependent manner. The attachment does not significantly affect the bulk chromosome segregation in slow growth conditions. With or without the attachment, two chromosomal masses separate from each other at a speed comparable to the cell growth. The separation starts even before the replication terminus region positions itself at the center of the nucleoid. Modeling of the segregation based on conformational entropy correctly predicts the positioning of the replication terminus region within the nucleoid. However, the model produces a distinctly different chromosomal density distribution than the experiment, indicating that the conformational entropy plays a limited role in segregating the chromosomes in the late stages of replication
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