386 research outputs found

    Nuclear currents based on the integral form of the continuity equation

    Full text link
    We present an approach to obtain new forms of the nuclear electromagnetic current, which is based on an integral form of the continuity equation. The procedure can be used to restore current conservation in model calculations in which the continuity equation is not verified. Besides, it provides, as a particular result, the so-called Siegert's form of the nuclear current, first obtained by Friar and Fallieros by extending Siegert's theorem to arbitrary values of the momentum transfer. The new currents are explicitly conserved and permit a straightforward analysis of their behavior at both low and high momentum transfers. The results are illustrated with a simple nuclear model which includes a harmonic oscillator mean potential.Comment: 19 pages, revtex, plus 2 PS figure

    Self-similar Radiation from Numerical Rosenau-Hyman Compactons

    Full text link
    The numerical simulation of compactons, solitary waves with compact support, is characterized by the presence of spurious phenomena, as numerically-induced radiation, which is illustrated here using four numerical methods applied to the Rosenau-Hyman K(p,p) equation. Both forward and backward radiations are emitted from the compacton presenting a self-similar shape which has been illustrated graphically by the proper scaling. A grid refinement study shows that the amplitude of the radiations decreases as the grid size does, confirming its numerical origin. The front velocity and the amplitude of both radiations have been studied as a function of both the compacton and the numerical parameters. The amplitude of the radiations decreases exponentially in time, being characterized by a nearly constant scaling exponent. An ansatz for both the backward and forward radiations corresponding to a self-similar function characterized by the scaling exponent is suggested by the present numerical results.Comment: To be published in Journal of Computational Physic

    Nuclear vorticity and the low-energy nuclear response - Towards the neutron drip line

    Full text link
    The transition density and current provide valuable insight into the nature of nuclear vibrations. Nuclear vorticity is a quantity related to the transverse transition current. In this work, we study the evolution of the strength distribution, related to density fluctuations, and the vorticity strength distribution, as the neutron drip line is approached. Our results on the isoscalar, natural-parity multipole response of Ni isotopes, obtained by using a self-consistent Skyrme-Hartree-Fock + Continuum RPA model, indicate that, close to the drip line, the low-energy response is dominated by L>1 vortical transitions.Comment: 8 pages, incl. 4 figures; to appear in Phys.Lett.

    The glucagon-like peptide-1 receptor as a potential treatment target in alcohol use disorder: evidence from human genetic association studies and a mouse model of alcohol dependence

    Get PDF
    The hormone glucagon-like peptide-1 (GLP-1) regulates appetite and food intake. GLP-1 receptor (GLP-1R) activation also attenuates the reinforcing properties of alcohol in rodents. The present translational study is based on four human genetic association studies and one preclinical study providing data that support the hypothesis that GLP-1R may have a role in the pathophysiology of alcohol use disorder (AUD). Case–control analysis (N=908) was performed on a sample of individuals enrolled in the National Institute on Alcohol Abuse and Alcoholism (NIAAA) intramural research program. The Study of Addiction: Genetics and Environment (SAGE) sample (N=3803) was used for confirmation purposes. Post hoc analyses were carried out on data from a human laboratory study of intravenous alcohol self-administration (IV-ASA;N=81) in social drinkers and from a functional magnetic resonance imaging study in alcohol-dependent individuals (N=22) subjected to a Monetary Incentive Delay task. In the preclinical study, a GLP-1R agonist was evaluated in a mouse model of alcohol dependence to demonstrate the role of GLP-1R for alcohol consumption. The previously reported functional allele 168Ser (rs6923761) was nominally associated with AUD (P=0.004) in the NIAAA sample, which was partially replicated in males of the SAGE sample (P=0.033). The 168Ser/Ser genotype was further associated with increased alcohol administration and breath alcohol measures in the IV-ASA experiment and with higher BOLD response in the right globus pallidus when receiving notification of outcome for high monetary reward. Finally, GLP-1R agonism significantly reduced alcohol consumption in a mouse model of alcohol dependence. These convergent findings suggest that the GLP-1R may be an attractive target for personalized pharmacotherapy treatment of AUD

    School Leadership and School Mental Health: An Exploratory Study of SMH Content in the Preparation of Principals

    Get PDF
    The increasing prevalence of K-12 students with mental health disorders is of great concern because research has shown that these children are at increased risk for academic failure. Accordingly, this study explored two intersecting fields of study – school mental health (SMH) and education administration, first examining the literature on the definition and prevalence of children’s mental health disorders, the history of the SMH movement, and SMH competencies for school leaders. What follows is an exploratory, multiple case study to determine the extent of SMH content within five nationally ranked U.S. principal preparation programs. A mixed methods analysis used text data derived from program mission statements, syllabi, faculty curriculum vitae documents and one program director interview. More than 94 documents were analyzed for SMH text evidence, resulting in 161 text units. These units then were coded by SMH dimension as well as by syllabi context (e.g., assignments, readings, and course objectives). Further inductive analysis revealed 14 SMH topics. Some text units reflected concepts that might be related to SMH (e.g., collaboration, community, and school culture). However, the terms “school mental health” and “children’s mental health” never appeared in any documents, suggesting a lack of attention to the critical importance of children’s mental health disorders and their contribution to poor school performance. Implications of the results as well as recommendations for improving national policy, state standards, local collaborations and higher education preparation programs for school leaders are discussed. These recommendations include promoting better collaboration of national SMH and educational administration leaders in policy forums, incorporating student mental health as a priority in national guidelines for the preparation of school and district leaders, and rethinking preparation programs to improve the capacity of school leaders for developing and sustaining SMH partnerships

    Esforço reprodutivo de Mussismilia braziliensis (Verrill, 1868) (Cnidaria, Scleractinia, Mussidae) no complexo recifal dos Abrolhos, BA, Brasil

    Get PDF
    Mussismilia braziliensis is endemic to Bahia State. lt plays an important role as one of the major reef builders in the area. Ten fragments of colonies were collected at three sites in the Abrolhos Reef Complex, located at different distances from the coast. Reproductive effort was estimated through fecundity (number of eggs per: polyp, cm 2, mesenteries and colony). A new staining method was used to ease identifying and counting eggs in the dissected polyps. The accuracy of the fecundity per gonad obtained through dissection was compared with histological analyses, and showed no significant difference. Mean fecundity per polyp was 338,7 (73,5 s.d.) and the higher number of eggs per polyp was 987. Fecundity per polyp increases as its area, volume, height and number of fertile mesenteries increases. Percentages of fertile mesenteries per polyp were similar among sites. However, the fecundity per mesenteries varied among colonies and sites. Our data showed that the fecundity is variable. The area closest to the coast (Pedra de Leste) presents the highest mean fecundity per polyp and cm 2 (410 [159,29 s.d.] and 233,47 [219,44 s.d.], respectively). This area presents the highest contribution of siliciclastics to the sediment depositing on the reefs and has also the highest cover of Palythoa caribaeorum. We suggested that M braziliensis invest a lot of energy in egg production to increases its chance of survival of the species in more disturb habitats. The study shows data that can be used as a tool if environment threat occur in the area.CAPESFAPERJMussismilia braziliensis é endêmica da Bahia, sendo uma das principais espécies formadoras de recife da região. Dez fragmentos de colônias foram coletados em três áreas do Complexo Recifal dos Abrolhos, as quais se encontram a diferentes distâncias da costa. O esforço reprodutivo foi estimado pela fecundidade (número de ovócitos por: pólipo, cm 2, mesentérios e colônias). Foi desenvolvido um novo método de coloração para observação dos ovócitos nos pólipos dissecados. Não foi observada diferença significativa na acurácia da fecundidade por gônada obtida pela dissecção e a histologia. A fecundidade média encontrada por pólipo foi 338,7 (73,5 d.p.) e o número máximo de ovócitos observado foi 987. A fecundidade por pólipo apresentou correlação significativa com sua área, volume, altura e o número de mesentérios férteis do pólipo. A porcentagem de mesentérios férteis por pólipo foi similar entre os locais. Entretanto, a fecundidade por mesentério variou entre colônias e locais. Os dados mostraram que a fecundidade é um parâmetro variável. A área mais próxima da costa (Pedra de Leste) apresentou a maior fecundidade média por pólipo e cm 2 (410 [159,29 d.p.] e 233,47 [219,44 d.p.], respectivamente). Essa área apresenta a maior contribuição de siliciclásticos nos sedimentos depositados nos recifes, e também tem a maior cobertura de Palythoa caribaeorum. Sugerimos que M. braziliensis aumenta a chance de sobrevivência da espécie em ambientes com mais distúrbios ao investir maior energia na produção de gametas. O trabalho fornece dados que podem ser usados como uma ferramenta caso haja impactos ambientais na área
    corecore