2,585 research outputs found
A characterization of quadric constant mean curvature hypersurfaces of spheres
Let be an immersion of a
complete -dimensional oriented manifold. For any , let
us denote by the function given by
and by , the function given by
, where is a Gauss map. We will prove
that if has constant mean curvature, and, for some and some
real number , we have that , then, is
either a totally umbilical sphere or a Clifford hypersurface. As an
application, we will use this result to prove that the weak stability index of
any compact constant mean curvature hypersurface in
which is neither totally umbilical nor a Clifford hypersurface and has constant
scalar curvature is greater than or equal to .Comment: Final version (February 2008). To appear in the Journal of Geometric
Analysi
EVALUATION OF ACCIDENTS WITH DOMINO EFFECT IN LPG STORAGE AREAS
The term domino effect denotes a chain of accidents, or situations, in which a fire/explosion
load generated by an accident in one unit in an industry causes secondary and higher order
accidents in other units. Such chains of accidents have a greater propensity to cause damage
than stand-alone accidents. Most of the past risk assessment studies deal with accident in
a single industry, more so in one of the units of an industry. But, often, accident in one unit
causes a secondary accident in a nearby unit, which in turn may trigger a tertiary accident,
and so on. The probability of occurrence and adverse impacts of such domino or
cascading effects are increasing due to increasing congestion in industrial complexes
and increasing density of human population around such complexes. Accidents with domino
effect are seldom studied. LPG storage areas could produce the worst possible consequences
in the event of an unforeseen incident. This work illustrates the application of models to
evaluate the impacts of events with fire and explosion in LPG tanks on other similar units
in the park and the possibility of occurrence of a domino effect. The criteria for occurrence
of accidents with domino effect adopted in this work were 37.5 kW/m2 in case of fire
radiation and an overpressure of 0.7 atm in explosion cases in a receptor body. The spacing
between LPG tanks was evaluated. The results show that such spacing is minimal and
does not represent, as it should, a parameter indicating a safe distance able to prevent the
propagation of an accident with domino effect
Reference concentrations for trace elements in urine for the Brazilian population based on q-ICP-MS with a simple dilute-and-shoot procedure
Biomonitoring of trace elements is of critical importance in human health assessment. However, trace element concentrations in biological fluids are affected by environmental and physiological parameters, and therefore considerable variations can occur between specific population subgroups. Brazil is a large country with large environmental diversity and with a limited knowledge of the reference values (baseline data) for trace elements in biological fluids. Atomic absorption spectrometry (AAS) and inductively coupled plasma emission spectrometry (ICP-OES) are still the dominant analytical techniques used for biomonitoring trace element analysis in clinical specimens. However, the use of ICP-MS is becoming more usual in clinical laboratory analysis. Then, we evaluated here a simple dilute-and-shoot method for sequential determination of Al, Ba, Be, Cd, Co, Cu, Cs, Mn, Ni, Pb, Pt, Sb, Se, Sn, Tl and U in urine by quadrupole inductively coupled plasma mass spectrometry (q-ICP-MS). Urine samples (500 µL) were accurately pipetted into conical tubes (15 mL) and diluted to 10 mL with a solution containing 0.5 % (v/v) HNO3 + 0.005% (v/v) Triton X-100. Diluted urine samples also contain rhodium, iridium and yttrium added as internal standards. After that, samples were directly analyzed by ICP-MS against matrix-matching calibration. Method detection limit (3s, n = 20) were in the ng L-1 range for all analytes. The method was applied to the analysis of 412 ordinary urine samples from Brazilian healthy and non-exposed subjects to establish reference values. Data validation was provided by the analysis of the standard reference material (SRM) 2670a toxic elements in urine (freeze-dried) (high and low levels) from the National Institute of Standards and Technology (NIST) and reference urine samples from the trace elements intercomparison program operated by the Institut National de Sante' Publique du Quebec, Canada.O biomonitoramento de elementos quÃmicos é de extrema importância na avaliação da saúde humana. Entretanto, as concentrações dos elementos quÃmicos nos fluidos biológicos são afetadas por parâmetros ambientais e fisiológicos e, consequentemente, consideráveis variações podem ocorrer entre subgrupos de populações especÃficas. O Brasil é um paÃs com ampla diversidade ambiental e existe limitado conhecimento de valores de referência para elementos quÃmicos em fluidos biológicos. A espectrometria de absorção atômica (AAS) e a espectrometria de emissão ótica com plasma acoplado indutivamente (ICP-OES) ainda são as técnicas analÃticas mais comumente empregadas no biomonitoramento de elementos quÃmicos em amostras clÃnicas. Entretanto, o uso da espectrometria de massas com plasma acoplado indutivamente (ICP-MS) está se tornando a cada dia mais comum nos laboratórios clÃnicos. Neste estudo, foi avaliado um método rápido envolvendo simples diluição da amostra para determinação de Al, Ba, Be, Cd, Co, Cu, Cs, Mn, Ni, Pb, Pt, Sb, Se, Sn, Tl e U em urina por ICP-MS. Amostras de urina (500 μL) foram pipetadas em frascos cônicos de 15 mL e diluÃdas para 10 mL com uma solução contendo 0,5 % (v/v) HNO3 + 0,005% (v/v) Triton X-100. Ródio, irÃdio e Ãtrio foram adicionados como padrões internos. Em seguida, as amostras foram diretamente analisadas por ICP-MS com calibração por ajuste de matriz. Os limites de detecção do método (3s, n = 20) foram da ordem de ng L-1 para todos os analitos em estudo. O método foi aplicado para a análise de 412 amostras de urina de brasileiros saudáveis e não expostos ambientalmente ou ocupacionalmente a metais para o estabelecimento de valores de referência na população brasileira. A validação dos resultados foi acompanhada pela análise de material de referência certificada de urina (SRM) 2670a proveniente do National Institute of Standards and Technology (NIST) e de materiais de referência provenientes do Institut National de Sante' Publique Du Quebec, no Canadá.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq
Drug Hypersensitivity Quality of Life Questionnaire: validation procedures and first results of the Portuguese version
Background: Hypersensitivity reactions to drugs are unpredictable and can be very complex and severe, even life threatening. Assess its impact on patient’s health related quality of life (HRQoL) is crucial. The Drug Hypersensitivity Quality of Life Questionnaire (DrHy-Q) is the only validated disease-specific HRQoL questionnaire. We aimed to translate and cross-cultural validate the DrHy-Q to the Portuguese population. It was also our purpose to determine the impact of drug hypersensitivity on patients’ HRQoL. Methods: The translation and cross-cultural adaptation of the DrHy-Q to Portuguese was performed according to standards. Reliability of the DrHy-Q Portuguese version was assessed in terms of internal consistency and test–retest reliability. Structural validity, divergent validity (with a generic health related QoLQ-PGWBI) and discriminant validity were also evaluated. Forty patients accepted to participate in the validation phase. The Portuguese version of the DrHy-Q was applied to 260 consecutively adult patients, studied in our Department for suspected drug hypersensitivity. Results: The Portuguese DrHy-Q showed adequate internal consistency (Cronbach’s ¿ = 0.938), good test–retest reliability [ICC = 0.713 (95% CI 0.488–0.850] and one-dimensional structure. No significant correlation was found between the DrHy-Q and the PGWBI total scores (r = - 0.010, p = 0.957). Two hundred of patients completed the study: 78.5% female; mean age = 44 ± 15 years. Mean DrHy-Q score was 36.8 ± 12.6. Two clinical factors significantly predict DrHy-Q total score: clinical manifestations and number of suspected drugs. Patients with anaphylaxis (ß = 11.005; 95% CI 5.523; 16.487), urticaria/angioedema (ß = 7.770; 95% CI 2.600; 12.940) and other manifestations (ß = 7.948; 95% CI 1.933; 13.962) are more likely to have higher DrHy-Q total score than patients with maculopapular exanthema. Patients with = 2 suspected drugs are also more likely to have worse QoL (ß = 7.927; 95% CI 3.687; 12.166). Conclusion: The Portuguese version of DrHy-Q revealed adequate validity and reliability, indicating that it is appropriate to assess the impact of drug hypersensitivity on patients’ HRQoL, providing data for a better comprehension and management of our patients. Moreover, our results highlight that the severity of the drug hypersensitivity reaction and the number of suspected drugs have impact on patient’s DrHy-QoL
On the consistency of a repulsive gravity phase in the early Universe
We exploit the possibility of existence of a repulsive gravity phase in the
evolution of the Universe. A toy model with a free scalar field minimally
coupled to gravity, but with the "wrong sign" for the energy and negative
curvature for the spatial section, is studied in detail. The background
solutions display a bouncing, non-singular Universe. The model is well-behaved
with respect to tensor perturbations. But, it exhibits growing models with
respect to scalar perturbations whose maximum occurs in the bouncing. Hence,
large inhomogeneties are produced. At least for this case, a repulsive phase
may destroy homogeneity, and in this sense it may be unstable. A newtonian
analogous model is worked out; it displays qualitatively the same behaviour.
The generality of this result is discussed. In particular, it is shown that the
addition of an attractive radiative fluid does not change essentially the
results. We discuss also a quantum version of the classical repulsive phase,
through the Wheeler-de Witt equation in mini-superspace, and we show that it
displays essentially the same scenario as the corresponding attractive phase.Comment: Latex file, 15 pages, 7 figures. There is a new figure, a new section
and some other minor correction
Optimization of supply diversity for the self-assembly of simple objects in two and three dimensions
The field of algorithmic self-assembly is concerned with the design and
analysis of self-assembly systems from a computational perspective, that is,
from the perspective of mathematical problems whose study may give insight into
the natural processes through which elementary objects self-assemble into more
complex ones. One of the main problems of algorithmic self-assembly is the
minimum tile set problem (MTSP), which asks for a collection of types of
elementary objects (called tiles) to be found for the self-assembly of an
object having a pre-established shape. Such a collection is to be as concise as
possible, thus minimizing supply diversity, while satisfying a set of stringent
constraints having to do with the termination and other properties of the
self-assembly process from its tile types. We present a study of what we think
is the first practical approach to MTSP. Our study starts with the introduction
of an evolutionary heuristic to tackle MTSP and includes results from extensive
experimentation with the heuristic on the self-assembly of simple objects in
two and three dimensions. The heuristic we introduce combines classic elements
from the field of evolutionary computation with a problem-specific variant of
Pareto dominance into a multi-objective approach to MTSP.Comment: Minor typos correcte
BioWorkbench: A High-Performance Framework for Managing and Analyzing Bioinformatics Experiments
Advances in sequencing techniques have led to exponential growth in
biological data, demanding the development of large-scale bioinformatics
experiments. Because these experiments are computation- and data-intensive,
they require high-performance computing (HPC) techniques and can benefit from
specialized technologies such as Scientific Workflow Management Systems (SWfMS)
and databases. In this work, we present BioWorkbench, a framework for managing
and analyzing bioinformatics experiments. This framework automatically collects
provenance data, including both performance data from workflow execution and
data from the scientific domain of the workflow application. Provenance data
can be analyzed through a web application that abstracts a set of queries to
the provenance database, simplifying access to provenance information. We
evaluate BioWorkbench using three case studies: SwiftPhylo, a phylogenetic tree
assembly workflow; SwiftGECKO, a comparative genomics workflow; and RASflow, a
RASopathy analysis workflow. We analyze each workflow from both computational
and scientific domain perspectives, by using queries to a provenance and
annotation database. Some of these queries are available as a pre-built feature
of the BioWorkbench web application. Through the provenance data, we show that
the framework is scalable and achieves high-performance, reducing up to 98% of
the case studies execution time. We also show how the application of machine
learning techniques can enrich the analysis process
Tillering Dynamics of \u3ci\u3ePanicum maximum\u3c/i\u3e Jacq. cv. Tanzania-1 After Grazing
Tillering dynamics and tiller dry matter weight from Tanzania grass (Panicum maximum cv. Tanzania-1) were evaluated in two post-grazing stubbles (High Post-grazing Stubble – HPS-3.6 t of DM/ha and Low Post-grazing Stubble – LPS-2.3 t of DM/ha). There was no difference between post-grazing stubbles for decapitated axillary and basal remainder and new axillary tillers. The LPS presented greater number of new basal tillers. The rate of appearance of new basal and axillary tillers decreased with time after grazing. There were differences between the treatments on tiller dry matter weight, and greater values were found in the high post-graze stubble
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