11,364 research outputs found
Balanced data assimilation for highly-oscillatory mechanical systems
Data assimilation algorithms are used to estimate the states of a dynamical
system using partial and noisy observations. The ensemble Kalman filter has
become a popular data assimilation scheme due to its simplicity and robustness
for a wide range of application areas. Nevertheless, the ensemble Kalman filter
also has limitations due to its inherent Gaussian and linearity assumptions.
These limitations can manifest themselves in dynamically inconsistent state
estimates. We investigate this issue in this paper for highly oscillatory
Hamiltonian systems with a dynamical behavior which satisfies certain balance
relations. We first demonstrate that the standard ensemble Kalman filter can
lead to estimates which do not satisfy those balance relations, ultimately
leading to filter divergence. We also propose two remedies for this phenomenon
in terms of blended time-stepping schemes and ensemble-based penalty methods.
The effect of these modifications to the standard ensemble Kalman filter are
discussed and demonstrated numerically for two model scenarios. First, we
consider balanced motion for highly oscillatory Hamiltonian systems and,
second, we investigate thermally embedded highly oscillatory Hamiltonian
systems. The first scenario is relevant for applications from meteorology while
the second scenario is relevant for applications of data assimilation to
molecular dynamics
Mainstreaming climate adaptation into development assistance in Mozambique: Institutional barriers and opportunities
Based on a literature review and expert interviews, this paper analyzes the most important climate impacts on development goals and explores relevant institutions in the context of mainstreaming climate adaptation into development assistance in Mozambique. Climate variability and change can significantly hinder progress toward attaining the Millennium Development Goals and poverty aggravates the country's climate vulnerability. Because Mozambique is one of the major recipients of official development assistance in the world, there is a clear interest in ensuring that the risks of climate impacts are incorporated into the country's development investments. A screening of donor activities at the sub-national level shows that a high share of development assistance is invested in climate-sensitive sectors, partly in areas that are particularly exposed to droughts, floods, and cyclones. The authors find that Mozambique has a supportive legislative environment and donors have a high awareness of climate risks. However, limited individual, organizational, networking, and financial capacity constrain mainstreaming initiatives. Given strong limitations at the national level, bilateral and multilateral donors can play a key role in fostering institutional capacity in Mozambique.Climate Change,Environmental Economics&Policies,Population Policies,Common Property Resource Development,Global Environment Facility
Ethanol and Biodiesel in Canada: Can They Help Meet Canada's Kyoto Commitment?
The Canadian government ratified the Kyoto Protocol in December 2002. The protocol calls for greenhouse gas emissions to be reduced by 6 percent below the 1990 level (approximately 35 percent below what they are expected to be in a business-as-usual situation) by 2008–2012. To help meet this target, both federal and provincial governments in Canada have developed programs (in some cases mandates) for ethanol and biodiesel production and use in fuel blends. Various subsidy schemes have been designed to stimulate development of a biofuels industry in Canada. While the programs have been promoted on the basis of environmental concerns, a major driver has been the search for new markets for Canadian agricultural commodities that face chronically depressed prices. The purposes of this article are to review the current state of policies, programs and production of ethanol and biodiesel in Canada and to assess the prospect of these biofuels to significantly reduce production of greenhouse gases in Canada.Agricultural and Food Policy,
The effect of quantum fields on black-hole interiors
Charged or rotating black holes possess an inner horizon beyond which determinism is
lost. However, the strong cosmic censorship conjecture claims that even small perturbations
will turn the horizon into a singularity beyond which the spacetime is inextendible,
preventing the loss of determinism. Motivated by this conjecture, this dissertation studies
free scalar quantum fields on various black-hole spacetimes to test whether quantum
effects can lead to the formation of a singularity at the inner horizon in cases where
classical perturbations cannot. The starting point is the investigation of the behaviour
of real-scalar-field observables near the inner horizon of Reissner-Nordström-de Sitter
spacetimes. Using semi-analytical methods, we find that quantum effects can indeed uphold
the censorship conjecture. Subsequently, we consider charged scalar fields on the
same spacetime and observe that a first-principle calculation is essential to accurately describe
the quantum effects at the inner horizon. As a first step towards an extension of
these results to rotating black holes, we rigorously construct the Unruh state for the real
scalar field on slowly rotating Kerr-de Sitter spacetimes. We show that it is a well-defined
Hadamard state and can therefore be used to compute expectation values of the stressenergy
tensor and other non-linear observables.:1 Introduction 7
2 An introduction to quantum fields and black holes 13
2.1 Notations and conventions . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 A brief introduction to AQFT . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 An introduction to microlocal analysis . . . . . . . . . . . . . . . . . . . 24
2.4 An introduction to black-hole spacetimes . . . . . . . . . . . . . . . . . 28
2.4.1 The Reissner-Nordström-de Sitter spacetime . . . . . . . . . . . 28
2.4.2 The Kerr-de Sitter spacetime . . . . . . . . . . . . . . . . . . . . 32
2.5 Free scalar fields in black-hole spacetimes . . . . . . . . . . . . . . . . . 37
3 Computing the energy flux of the real scalar field 43
3.1 Strong cosmic censorship on RNdS . . . . . . . . . . . . . . . . . . . . 43
3.2 The Klein-Gordon equation on RNdS . . . . . . . . . . . . . . . . . . . 45
3.3 Extension to the charged scalar field on RNdS . . . . . . . . . . . . . . . 52
3.4 The energy flux at the Cauchy horizon . . . . . . . . . . . . . . . . . . . 53
4 The charged scalar field in Reissner-Nordström-de Sitter 63
4.1 The Unruh state for the charged scalar field . . . . . . . . . . . . . . . . 65
4.2 The renormalized current . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.3 The current in the Unruh state - numerical results . . . . . . . . . . . . . 80
4.4 The charged scalar field at the inner horizon . . . . . . . . . . . . . . . . 86
5 The Unruh state on Kerr-de Sitter 97
5.1 Null geodesics in the Kerr-de Sitter spacetime . . . . . . . . . . . . . . . 98
5.2 The Unruh state on Kerr-de Sitter . . . . . . . . . . . . . . . . . . . . . . 107
5.3 The Hadamard property of the Unruh state . . . . . . . . . . . . . . . . . 120
5.3.1 The Hadamard condition in O . . . . . . . . . . . . . . . . . . . 123
5.3.2 The Hadamard condition on M\O . . . . . . . . . . . . . . . . . 128
6 Summary and discussion 139
A Bibliography 14
Human Sexuality Programs in Catholic Secondary Schools in the 80\u27s
Human sexuality programs, or sex education programs, have been a controversial issue for many years. The purpose of this study was to assess the effectiveness of human sexuality programs within Catholic secondary schools. This study investigated the effect of comprehensive or non-comprehensive sexuality programs upon students\u27 Positive Sexual Attitudes, awareness of Catholic Church Teachings, integration of Catholic Church Values, integration of current Social Values, and Biological Knowledge. Comprehensive human sexuality programs were defined as those containing three or more full semesters of classes related to sex and sexuality. Non-comprehensive human sexuality programs were defined as those containing less than two full semesters of such courses. The research study took place in four Roman Catholic dioceses in the State of California. Twelfth grade female and male students participated in the study and the sample population was established at 1,555. Several survey instruments were developed to test six hypotheses. A quantitative methodology was used in order to present the survey instrument data in a clear and concise manner. The demographic profile supplied independent variables, such as sex and religious influence upon behavior, for additional data analysis. Analytical results showed that only in the areas of Positive Sexual Attitudes and Biological Knowledge were comprehensive human sexuality programs significantly different from non-comprehensive sexuality programs. Higher scores for females over males were seen in five of the hypotheses. In the hypothesis concerning Social Values, males scored higher. Significant differences were noted in religious influence upon behavior in Catholic Church Teachings, Catholic Church Values, and current Social Values
Mechanical magnetometry of Cobalt nanospheres deposited by focused electron beam at the tip of ultra-soft cantilevers
Using focused-electron-beam-induced deposition, Cobalt magnetic nanospheres
with diameter ranging between 100 nm and 300 nm are grown at the tip of
ultra-soft cantilevers. By monitoring the mechanical resonance frequency of the
cantilever as a function of the applied magnetic field, the hysteresis curve of
these individual nanospheres are measured. This enables to evaluate their
saturation magnetization, found to be around 430 emu/cm^3 independently of the
size of the particle, and to infer that the magnetic vortex state is the
equilibrium configuration of these nanospheres at remanence
Impact of Weak Lensing Mass Calibration on eROSITA Galaxy Cluster Cosmological Studies -- a Forecast
We forecast the impact of weak lensing (WL) cluster mass calibration on the
cosmological constraints from the X-ray selected galaxy cluster counts in the
upcoming eROSITA survey. We employ a prototype cosmology pipeline to analyze
mock cluster catalogs. Each cluster is sampled from the mass function in a
fiducial cosmology and given an eROSITA count rate and redshift, where count
rates are modeled using the eROSITA effective area, a typical exposure time,
Poisson noise and the scatter and form of the observed X-ray luminosity-- and
temperature--mass--redshift relations. A subset of clusters have mock shear
profiles to mimic either those from DES and HSC or from the future Euclid and
LSST surveys. Using a count rate selection, we generate a baseline cluster
cosmology catalog that contains 13k clusters over 14,892~deg of
extragalactic sky. Low mass groups are excluded using raised count rate
thresholds at low redshift. Forecast parameter uncertainties for
, and are 0.023 (0.016; 0.014), 0.017 (0.012;
0.010), and 0.085 (0.074; 0.071), respectively, when adopting DES+HSC WL
(Euclid; LSST), while marginalizing over the sum of the neutrino masses. A
degeneracy between the distance--redshift relation and the parameters of the
observable--mass scaling relation limits the impact of the WL calibration on
the constraints, but with BAO measurements from DESI an improved
determination of to 0.043 becomes possible. With Planck CMB priors,
() can be determined to (), and the
summed neutrino mass limited to eV (at 95\%). If
systematics on the group mass scale can be controlled, the eROSITA group and
cluster sample with 43k objects and LSST WL could constrain
and to 0.007 and to 0.050.Comment: 28 pages, 13 figur
B7/CD28 in Central Tolerance: Costimulation Promotes Maturation of Regulatory T Cell Precursors and Prevents Their Clonal Deletion
According to the “two-step model,” the intrathymic generation of CD4+ regulatory T (Treg) cells segregates into a first, T cell receptor (TCR)-driven phase and a second, cytokine-dependent phase. The initial TCR stimulus gives rise to a CD25+Foxp3− developmental intermediate. These precursors subsequently require cytokine signaling to establish the mature CD25+Foxp3+ Treg cell phenotype. In addition, costimulation via CD28/B7 (CD80/86) axis is important for the generation of a Treg cell repertoire of normal size. Recent data suggest that CD28 or B7 deficient mice lack CD25+Foxp3− Treg cell progenitors. However, these data leave open whether costimulation is also required at subsequent stages of Treg differentiation. Also, the fate of “presumptive” Treg cells carrying a permissive TCR specificity in the absence of costimulation remains to be established. Here, we have used a previously described TCR transgenic model of agonist-driven Treg differentiation in order to address these issues. Intrathymic adoptive transfer of Treg precursors indicated that costimulation is dispensable once the intermediate CD25+Foxp3− stage has been reached. Furthermore, lack of costimulation led to the physical loss of presumptive Treg cells rather than their escape from central tolerance and differentiation into the conventional CD4+ T cell lineage. Our findings suggest that CD28 signaling does not primarily operate through enhancing the TCR signal strength in order to pass the threshold intensity required to initiate Treg cell specification. Instead, costimulation seems to deliver unique and qualitatively distinct signals that coordinately foster the developmental progression of Treg precursors and prevent their negative selection
Pain, self-regulation and temperament in high risk preterm newborns
Os recém-nascidos pré-termo são expostos a experiências dolorosas inevitáveis na Unidade de Terapia Intensiva Neonatal. Apesar de sua imaturidade biológica, esses podem tanto perceber quanto reagir à dor. A exposição repetida à dor exerce impacto negativo no desenvolvimento e pode aumentar a vulnerabilidade dos bebês, dificultando os processos autorregulatórios. A reatividade biocomportamental à dor é um indicador de autorregulação e associa-se ao temperamento da criança. Esses bebês necessitam de estratégias farmacológicas e não farmacológicas para alívio da dor. Além disso, devem ter um contexto de interações sincrônicas com os pais, adaptadas às suas características de temperamento. Os profissionais de saúde podem atuar como suporte de regulação externa para esses bebês promovendo alívio da dor e prevenindo problemas de desenvolvimento.High risk preterm newborns are exposed to unavoidable painful experiences in Neonatal Intensive Care Units. In spite of their biological immaturity, they are able to perceive and react to pain stimuli. Repetitive exposure to pain has a negative impact on the development and may increase the infant's vulnerability, affecting self-regulatory processes. Biobehavioral reactivity to pain is an indicator of self-regulation and it is associated to the child's temperament. Preterm infants need pharmacological and non-pharmacological strategies for pain relieving. Moreover, they need a context of synchronic interaction with their parents which must be adapted to their temperament characteristics. Health professionals may play an important role in supporting external regulation for those infants, promoting pain relief and preventing development problems.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Effect of Progressive Weight Loss on Lactate Metabolism: A Randomized Controlled Trial.
OBJECTIVE:Lactate is an intermediate of glucose metabolism that has been implicated in the pathogenesis of insulin resistance. This study evaluated the relationship between glucose kinetics and plasma lactate concentration ([LAC]) before and after manipulating insulin sensitivity by progressive weight loss. METHODS:Forty people with obesity (BMI = 37.9 ± 4.3 kg/m2 ) were randomized to weight maintenance (n = 14) or weight loss (n = 19). Subjects were studied before and after 6 months of weight maintenance and before and after 5%, 11%, and 16% weight loss. A hyperinsulinemic-euglycemic clamp procedure in conjunction with [6,6-2 H2 ]glucose tracer infusion was used to assess glucose kinetics. RESULTS:At baseline, fasting [LAC] correlated positively with endogenous glucose production rate (r = 0.532; P = 0.001) and negatively with insulin sensitivity, assessed as the insulin-stimulated glucose disposal (r = -0.361; P = 0.04). Progressive (5% through 16%) weight loss caused a progressive decrease in fasting [LAC], and the decrease in fasting [LAC] after 5% weight loss was correlated with the decrease in endogenous glucose production (r = 0.654; P = 0.002) and the increase in insulin sensitivity (r = -0.595; P = 0.007). CONCLUSIONS:This study demonstrates the interrelationships among weight loss, hepatic and muscle glucose kinetics, insulin sensitivity, and [LAC], and it suggests that [LAC] can serve as an additional biomarker of glucose-related insulin resistance
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