1,718 research outputs found
Plankton studies in a mangrove environment II: the standing stock and some ecological factors
This work was undertaken to obtain information on seasonal variation of the plankton communities of the Cananéia mangrove system. The results provide a background for further investigations on primary and secondary productivity and the study of the interrelationships of ecological factors that affect the distribution and abundance of plankton. The correlation of data obtained shows that in the mangrove system under study there are different environments with distinct species.Durante 1962, em janeiro, abril, julho e outubro, foram feitas coletas em quatro estações oceanográficas, três na região lagunar de Cananéia e uma na região costeira. O objetivo foi o de efetuar um primeiro levantamento do bacterio, fito e zooplâncton, assim como estudar os fatores ecológicos atuantes nos diferentes locais, em diferentes épocas do ano. Amostras foram tomadas durante os períodos de maré alta e baixa, em superfície e profundidade, para determinação do plancton, material em suspensão, salinidade e oxigênio. Pelos resultados obtidos, verificou-se que o "standing stock" diminuiu gradualmente da estação I para a estação IV, mostrando uma correlação inversa com a salinidade. As condições extremamente variáveis da região lagunar constituem um fator seletivo para as diferentes espécies planctônicas. No fitoplâncton foram encontrados: Diatomáceas, Dinoflagelados, Silicoflagelados, Fitoflagelados e Cianofíceas. As Diatomáceas sempre predominaram, exceto na estação I, no mês de abril, quando apareceram os Fitoflagelados em proporções superiores. O máximo de organismos do fitoplâncton foi na estação I, em janeiro, havendo um decréscimo durante os meses de abril e julho e um novo aumento em outubro. O zooplâncton, constituído, predominantemente, por copépodos e estágios larvares, apresentou também Moluscos, Tintinoideos e em pequenas proporções Medusas, Chaetognatos e Cladoceros. O máximo de zooplâncton ocorreu em abril em todas as estações. A quantidade de matéria orgânica em suspensão, apresentou altos índices, nas estações lagunares em comparação com a costeira, isto devido a detritos levados pelos rios que circundam a região, ao plancton e à decomposição in situ da vegetação do mangue. Por outro lado, a matéria em suspensão, a concentração do plancton e as substâncias coloridas provenientes da vegetação do mangue, mostraram bastante influência sobre a transparência e coloração da água, diminuindo a extensão da camada eufótica
Mean Exit Time and Survival Probability within the CTRW Formalism
An intense research on financial market microstructure is presently in
progress. Continuous time random walks (CTRWs) are general models capable to
capture the small-scale properties that high frequency data series show. The
use of CTRW models in the analysis of financial problems is quite recent and
their potentials have not been fully developed. Here we present two (closely
related) applications of great interest in risk control. In the first place, we
will review the problem of modelling the behaviour of the mean exit time (MET)
of a process out of a given region of fixed size. The surveyed stochastic
processes are the cumulative returns of asset prices. The link between the
value of the MET and the timescale of the market fluctuations of a certain
degree is crystal clear. In this sense, MET value may help, for instance, in
deciding the optimal time horizon for the investment. The MET is, however, one
among the statistics of a distribution of bigger interest: the survival
probability (SP), the likelihood that after some lapse of time a process
remains inside the given region without having crossed its boundaries. The
final part of the article is devoted to the study of this quantity. Note that
the use of SPs may outperform the standard "Value at Risk" (VaR) method for two
reasons: we can consider other market dynamics than the limited Wiener process
and, even in this case, a risk level derived from the SP will ensure (within
the desired quintile) that the quoted value of the portfolio will not leave the
safety zone. We present some preliminary theoretical and applied results
concerning this topic.Comment: 10 pages, 2 figures, revtex4; corrected typos, to appear in the APFA5
proceeding
A SWOT analysis of health service access by men who have sex with men in South Africa: lessons for higher education institutions
n.a
Palliative care and Parkinson's disease : meeting summary and recommendations for clinical research
Introduction: Palliative care is an approach to caring for patients and families affected by serious illnesses that focuses on the relief of suffering through the management of medical symptoms, psychosocial issues, advance care planning and spiritual wellbeing. Over the past decade there has been an emerging clinical and research interest in the application of palliative care approaches to Parkinson’s disease (PD) and outpatient palliative care services are now offered by several movement disorders centers. Methods: An International Working Group Meeting on PD and Palliative Care supported by the Parkinson’s Disease Foundation was held in October 2015 to review the current state of the evidence and to make recommendations for clinical research and practice. Results: Topics included: 1) Defining palliative care for PD; 2) Lessons from palliative care for heart failure and other chronic illnesses; 3) Patient and caregiver Needs; 4) Needs assessment tools; 5) Intervention strategies; 6) Predicting prognosis and hospice referrals; 7) Choice of appropriate outcome measures; 8) Implementation, dissemination and education research; and 9) Need for research collaborations. We provide an overview of these discussions, summarize current evidence and practices, highlight gaps in our knowledge and make recommendations for future research. Conclusions: Palliative Care for PD is a rapidly growing area which holds great promise for improving outcomes for PD patients and their caregivers. While clinical research in this area can build from lessons learned in other diseases, there is a need for observational, methodological and interventional research to address the unique needs of PD patients and caregivers
Surface reconstruction of wear in carpets by using a wavelet edge detector
Carpet manufacturers have wear labels assigned to their products by human experts who evaluate carpet samples subjected to accelerated wear in a test device. There is considerable industrial and academic interest in going from human to automated evaluation, which should be less cumbersome and more objective. In this paper, we present image analysis research on videos of carpet surfaces scanned with a 3D laser. The purpose is obtaining good depth Images for an automated system that should have a high percentage of correct assessments for a wide variety of carpets. The innovation is the use of a wavelet edge detector to obtain a more continuously defined surface shape. The evaluation is based on how well the algorithms allow a good linear ranking and a good discriminance of consecutive wear labels. The results show an improved linear ranking for most carpet types, for two carpet types the results are quite significant
A continuous time random walk model for financial distributions
We apply the formalism of the continuous time random walk to the study of
financial data. The entire distribution of prices can be obtained once two
auxiliary densities are known. These are the probability densities for the
pausing time between successive jumps and the corresponding probability density
for the magnitude of a jump. We have applied the formalism to data on the US
dollar/Deutsche Mark future exchange, finding good agreement between theory and
the observed data.Comment: 14 pages, 5 figures, revtex4, submitted for publicatio
Results of the ESO-SEST Key Programme on CO in the Magellanic Clouds. IX. The giant LMC HII region complex N11
We present maps and a catalogue containing the J=1-0 12CO parameters of 29
individual molecular clouds in the second-brightest LMC star formation complex,
N11. In the southwestern part of N11, molecular clouds occur in a ring or shell
surrounding the major OB star association LH9. In the northeastern part, a
chain of molecular clouds delineates the rim of one of the so-called supergiant
shells in the LMC. The well-defined clouds have dimensions close to those of
the survey beam (diameters of 25 pc or less). Some of the clouds were also
observed in J=2-1 12CO, and in the lower two transitions of 13CO. Clouds mapped
with a twice higher angular resolution in J=2-1 12CO show substructure with
dimensions once again comparable to those of the mapping beam. The few clouds
for which we could model physical parameters have fairly warm (T(kin) = 60 -
150 K) and moderately dense (n(H2) = 3000 cm-3) gas. The northeastern chain of
CO clouds, although lacking in diffuse intercloud emission, is characteristic
of the more quiescent regions of the LMC and appears to have been subject to
relatively little photo-processing. The clouds forming part of the southwestern
shell or ring, however, are almost devoid of diffuse intercloud emission and
also exhibit other characteristics of an extreme photon-dominated region (PDR).Comment: 14 pages; accepted for publication in A&
Fine structure in the gamma-ray sky
The EGRET results for gamma-ray intensities in and near the Galactic Plane
have been analysed in some detail. Attention has been concentrated on energies
above 1 GeV and the individual intensities in a longitude bin have
been determined and compared with the large scale mean found from a nine-degree
polynomial fit.
Comparison has been made of the observed standard deviation for the ratio of
these intensities with that expected from variants of our model. The basic
model adopts cosmic ray origin from supernova remnants, the particles then
diffusing through the Galaxy with our usual 'anomalous diffusion'. The variants
involve the clustering of SN, a frequency distribution for supernova explosion
energies, and 'normal', rather than 'anomalous' diffusion.
It is found that for supernovae of unique energy, and our usual anomalous
diffusion, clustering is necessary, particularly in the Inner Galaxy. An
alternative, and preferred, situation is to adopt the model with a frequency
distribution of supernova energies. The results for the Outer Galaxy are such
that no clustering is required.Comment: 10 pages, 4 figures, 1 table, accepted for publication in J.Phys.G:
Nucl.Part.Phy
Clumpy outer Galaxy molecular clouds and the steepening of the IMF
We report the results of high-resolution (~0.2 pc) CO(1-0) and CS(2-1)
observations of the central regions of three star-forming molecular clouds in
the far-outer Galaxy (~16 kpc from the Galactic Center): WB89 85 (Sh 2-127),
WB89 380, and WB89 437. We used the BIMA array in combination with IRAM 30-m
and NRAO 12-m observations. The GMC's in which the regions are embedded were
studied by means of KOSMA 3-m CO(2-1) observations. The properties the CO and
CS clumps are analyzed and compared with newly derived results of previously
published single-dish measurements of local clouds (OrionB South and Rosette).
We find that the slopes of the clump mass distributions (-1.28 and -1.49, for
WB89 85 and WB89 380, respectively) are somewhat less steep than found for most
local clouds, but similar to those of clouds which have been analyzed with the
same clumpfind program. We investigate the clump stability by using the virial
theorem, including all possible contributions (gravity, turbulence, magnetic
fields, and pressure due to the interclump gas). It appears that under
reasonable assumptions a combination of these forces would render most clumps
stable. Comparing only gravity and turbulence, we find that in the far-outer
Galaxy clouds, these forces are in equilibium (virial parameter alpha~1) for
clumps down to the lowest masses found (a few Msol). For clumps in the local
clouds alpha~1 only for clumps with masses larger than a few tens of Msol. Thus
it appears that in these outer Galaxy clumps gravity is the dominant force down
to a much lower mass than in local clouds, implying that gravitational collapse
and star formation may occur more readily even in the smallest clumps. Although
there are some caveats, due to the inhomogeneity of the data used, this might
explain the apparently steeper IMF found in the outer Galaxy.Comment: 29 pages, including 9 tables, 21 figures. Accepted for Astron.
Astrop
Circular polarization measurement in millimeter-wavelength spectral-line VLBI observations
This paper considers the problem of accurate measurement of circular
polarization in imaging spectral-line VLBI observations in the lambda=7 mm and
lambda=3 mm wavelength bands. This capability is especially valuable for the
full observational study of compact, polarized SiO maser components in the
near-circumstellar environment of late-type, evolved stars. Circular VLBI
polarimetry provides important constraints on SiO maser astrophysics, including
the theory of polarized maser emission transport, and on the strength and
distribution of the stellar magnetic field and its dynamical role in this
critical circumstellar region. We perform an analysis here of the data model
containing the instrumental factors that limit the accuracy of circular
polarization measurements in such observations, and present a corresponding
data reduction algorithm for their correction. The algorithm is an enhancement
of existing spectral line VLBI polarimetry methods using autocorrelation data
for calibration, but with innovations in bandpass determination,
autocorrelation polarization self-calibration, and general optimizations for
the case of low SNR, as applicable at these wavelengths. We present an example
data reduction at mm and derive an estimate of the predicted
accuracy of the method of m_c < 0.5% or better at lambda=7 mm and m_c < 0.5-1%
or better at lambda=3 mm. Both the strengths and weaknesses of the proposed
algorithm are discussed, along with suggestions for future work.Comment: 23 pages, 13 figure
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