6,463 research outputs found
On the Hojman conservation quantities in Cosmology
We discuss the application of the Hojman's Symmetry Approach for the
determination of conservation laws in Cosmology, which has been recently
applied by various authors in different cosmological models. We show that
Hojman's method for regular Hamiltonian systems, where the Hamiltonian function
is one of the involved equations of the system, is equivalent to the
application of Noether's Theorem for generalized transformations. That means
that for minimally-coupled scalar field cosmology or other modified theories
which are conformally related with scalar-field cosmology, like gravity,
the application of Hojman's method provide us with the same results with that
of Noether's theorem. Moreover we study the special Ansatz. , which has been introduced for
a minimally-coupled scalar field, and we study the Lie and Noether point
symmetries for the reduced equation. We show that under this Ansatz, the
unknown function of the model cannot be constrained by the requirement of the
existence of a conservation law and that the Hojman conservation quantity which
arises for the reduced equation is nothing more than the functional form of
Noetherian conservation laws for the free particle. On the other hand, for
teleparallel gravity, it is not the existence of Hojman's conservation
laws which provide us with the special function form of functions, but
the requirement that the reduced second-order differential equation admits a
Jacobi Last multiplier, while the new conservation law is nothing else that the
Hamiltonian function of the reduced equation.Comment: 6 pages; minor corrections; accepted for publication by Physics
Letters B. arXiv admin note: substantial text overlap with arXiv:1503.0846
Infertility problems and mental health symptoms in a community-based sample: depressive symptoms among infertile men, but not women
Most researchers agree that men’s and women’s experiences of infertility are
fundamentally different, and impacts upon the nature of psychological distress
encountered. However, design flaws, including non-random samples
unrepresentative of the general population, compromise many existing studies. Data
derived from a random general community sample provides prevalence of current
infertility, and permits examination of longitudinal associations between mental
health symptoms and infertility among 1,978 participants aged 28-32 years. In the
previous 12-months, infertility was experienced by 2.1% and 5.4% partnered men
and women. Infertility independently predicted depressive symptomatology in men,
and anxiety symptoms among women. Gender differences were sustained, even
controlling for prior depression and anxiety. Health professionals are encouraged
to proactively enquire about affective symptoms experienced by both women and
men with infertility problems
Analytic Behaviour of Competition among Three Species
We analyse the classical model of competition between three species studied
by May and Leonard ({\it SIAM J Appl Math} \textbf{29} (1975) 243-256) with the
approaches of singularity analysis and symmetry analysis to identify values of
the parameters for which the system is integrable. We observe some striking
relations between critical values arising from the approach of dynamical
systems and the singularity and symmetry analyses.Comment: 14 pages, to appear in Journal of Nonlinear Mathematical Physic
Aberration corrections for free-space optical communications in atmosphere turbulence using orbital angular momentum states
Age differences in mental health literacy
BACKGROUND: The community's knowledge and beliefs about mental health problems, their risk
factors, treatments and sources of help may vary as a function of age.
METHODS: Data were taken from an epidemiological survey conducted during 2003–2004 with a
national clustered sample of Australian adults aged 18 years and over. Following the presentation
of a vignette describing depression (n = 1001) or schizophrenia (n = 997), respondents were asked
a series of questions relating to their knowledge and recognition of the disorder, beliefs about the
helpfulness of treating professionals and medical, psychological and lifestyle treatments, and likely
causes.
RESULTS: Participant age was coded into five categories and cross-tabulated with mental health
literacy variables. Comparisons between age groups revealed that although older adults (70+ years)
were poorer than younger age groups at correctly recognising depression and schizophrenia, young
adults (18–24 years) were more likely to misidentify schizophrenia as depression. Differences were
also observed between younger and older age groups in terms of beliefs about the helpfulness of
certain treating professionals and medical and lifestyle treatments for depression and
schizophrenia, and older respondents were more likely to believe that schizophrenia could be
caused by character weakness.
CONCLUSION: Differences in mental health literacy across the adult lifespan suggest that more
specific, age appropriate messages about mental health are required for younger and older age
groups. The tendency for young adults to 'over-identify' depression signals the need for awareness
campaigns to focus on differentiation between mental disorders
‘We kind of try to merge our own experience with the objectivity of the criteria’: The role of connoisseurship and tacit practice in undergraduate fine art assessment
This article explores connoisseurship in the context of fine art undergraduate assessment practice. I interviewed twelve fine art lecturers in order to explore and unpack
the concept of connoisseurship in relation to subjectivity, objectivity and tacit practice.
Building on the work of Bourdieu (1973, 1977, 1986) and Shay (2003, 2005), both of whom problematize the view that subjectivity and objectivity are binary opposites, my
research illustrates the ways that connoisseurship is underpinned by informed professional judgements located in communities of practice. Within this particular conception
of connoisseurship, the lecturers’ expertise is co-constituted in communities of assessors through participation and engagement. Standards reside in communities of practice
Pregnancy and levels of depression and anxiety: a prospective cohort study of Australian women
OBJECTIVES:The effects of pregnancy on depression and anxiety remain unclear. Previous research is predominantly cross-sectional, not representative of the general community, and does not include data on mental health prior to pregnancy. This study used longitudinal Australian population-based data to examine whether pregnancy is associated with increases in women's anxiety and depression levels (from pre-pregnancy).METHOD:
A community sample of Australian women aged 20-24 years were recruited prospectively and assessed in 1999, 2003 and 2007. At the follow-up assessments 76 women were pregnant (with no prior children) and 542 remained nulliparous. Mixed models repeated measures analyses of variance were undertaken to compare change in levels of anxiety and depression (Goldberg Anxiety and Depression scales) between those who became pregnant and those who remained non-pregnant.
RESULTS:
Pregnancy was not associated with increased symptoms of depression or anxiety. No association was found with depression, while pregnancy was associated with a decrease in anxiety. Including somatic items in the measures of depression and anxiety resulted in higher symptom levels in pregnancy, suggesting possible item bias.
CONCLUSIONS:
This study is one of the first to follow a community sample of women from pre-pregnancy to pregnancy. The findings suggest that pregnancy is not typically detrimental to women's mental health. The current study offers a starting point for future prospective studies to follow women from pre-pregnancy to postpartum. Study limitations to be improved upon in follow-up research include expanding the sample size, and including both pregnancy-specific measures and trimester-specific data. Future research should continue to identify those women who are most (and least) at risk during pregnancy in order to target resources and assistance most effectively.This research was funded through a grant from the National Health and Medical Research Council nhmrc ID:1035803
Novel duplex vapor electrochemical method for silicon solar cells
Progress in the development of low-cost solar arrays is reported. Topics covered include: (1) development of a simplified feed system for the Na used in the Na-SiF4 reactor; (2) production of high purity silicon through the reduction of sodium fluosilicate with sodium metal; (3) the leaching process for recovering silicon from the reaction products of the SiF4-Na reaction; and (4) silicon separation by the melting of the reaction product
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