206 research outputs found
Remarks on Duffin-Kemmer-Petiau theory and gauge invariance
Two problems relative to the electromagnetic coupling of Duffin-Kemmer-Petiau
(DKP) theory are discussed: the presence of an anomalous term in the
Hamiltonian form of the theory and the apparent difference between the
Interaction terms in DKP and Klein-Gordon (KG) Lagrangians. For this, we first
discuss the behavior of DKP field and its physical components under gauge
transformations. From this analysis, we can show that these problems simply do
not exist if one correctly analyses the physical components of DKP field.Comment: 19 pages, no figure
Electromagnetic field at Finite Temperature: A first order approach
In this work we study the electromagnetic field at Finite Temperature via the
massless DKP formalism. The constraint analysis is performed and the partition
function for the theory is constructed and computed. When it is specialized to
the spin 1 sector we obtain the well-known result for the thermodynamic
equilibrium of the electromagnetic field.Comment: 6 pages, Latex2e, title changed and minimal modification
The causal approach to scalar QED via Duffin-Kemmer-Petiau equation
In this work we consider the scalar QED via Duffin-Kemmer-Petiau equation in the framework of Bogoliubov-Epstein-Glaser causal perturbation theory. We calculate the lowest order distributions for Compton scattering, vacuum polarization, the self energy and, by using a Ward identity, the vertex correction. The causal method provides a mathematically well defined and noneffective theory which determines, in a natural way, the propagator and the vertex of the usual effective theory
Bose-Einstein Condensation and Free DKP field
The thermodynamical partition function of the Duffin-Kemmer-Petiau theory is
evaluated using the imaginary-time formalism of quantum field theory at finite
temperature and path integral methods. The DKP partition function displays two
features: (i) full equivalence with the partition function for charged scalar
particles and charged massive spin 1 particles; and (ii) the zero mode sector
which is essential to reproduce the well-known relativistic Bose-Einstein
condensation for both theories.Comment: 12 pages, 2 eps figures. To be published in Physics Letter
Decreased ATP production and myocardial contractile reserve in metabolic heart disease
Available online 01 February 2018Metabolic syndrome is a cluster of obesity-related metabolic abnormalities that lead to metabolic heart disease (MHD) with left ventricular pump dysfunction. Although MHD is thought to be associated with myocardial energetic deficiency, two key questions have not been answered. First, it is not known whether there is a sufficient energy deficit to contribute to pump dysfunction. Second, the basis for the energy deficit is not clear. To address these questions, mice were fed a high fat, high sucrose (HFHS) 'Western' diet to recapitulate the MHD phenotype. In isolated beating hearts, we used 31P NMR spectroscopy with magnetization transfer to determine a) the concentrations of high energy phosphates ([ATP], [ADP], [PCr]), b) the free energy of ATP hydrolysis (∆G~ATP), c) the rate of ATP production and d) flux through the creatine kinase (CK) reaction. At the lowest workload, the diastolic pressure-volume relationship was shifted upward in HFHS hearts, indicative of diastolic dysfunction, whereas systolic function was preserved. At this workload, the rate of ATP synthesis was decreased in HFHS hearts, and was associated with decreases in both [PCr] and ∆G~ATP. Higher work demands unmasked the inability of HFHS hearts to increase systolic function and led to a further decrease in ∆G~ATP to a level that is not sufficient to maintain normal function of sarcoplasmic Ca2+-ATPase (SERCA). While [ATP] was preserved at all work demands in HFHS hearts, the progressive increase in [ADP] led to a decrease in ∆G~ATP with increased work demands. Surprisingly, CK flux, CK activity and total creatine were normal in HFHS hearts. These findings differ from dilated cardiomyopathy, in which the energetic deficiency is associated with decreases in CK flux, CK activity and total creatine. Thus, in HFHS-fed mice with MHD there is a distinct metabolic phenotype of the heart characterized by a decrease in ATP production that leads to a functionally-important energetic deficiency and an elevation of [ADP], with preservation of CK flux.Ivan Luptak, Aaron L. Sverdlov, Marcello Panagia, Fuzhong Qin, David R. Pimentel, Dominique Croteau, Deborah A. Siwik, Joanne S. Ingwall, Markus M. Bachschmid, James A. Balschi, Wilson S. Colucc
Reply to the discussion and comments of Azerêdo et al. (2023) and Schneider et al. (2023) on the paper by Magalhães et al. ‘Middle Jurassic multi-scale transgressive–regressive cycles: An example from the Lusitanian Basin’, The Depositional Record, 9, 174–202
cently published paper. The exchange of ideas, data and interpretation improves our knowledge and is the right way to discuss science\u27s advances. This reply considers the points raised by Azerêdo et al. (2023) and Schneider et al. (2023). In both manuscripts, these authors raised many issues about sedimentological and stratigraphic aspects that can be separated into two groups: (a) those related to the age of the studied succession; and (b) those assigning the studied succession to the Candeeiros Formation
Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models
Both community ecology and conservation biology seek further understanding of
factors governing the advance of an invasive species. We model biological
invasion as an individual-based, stochastic process on a two-dimensional
landscape. An ecologically superior invader and a resident species compete for
space preemptively. Our general model includes the basic contact process and a
variant of the Eden model as special cases. We employ the concept of a
"roughened" front to quantify effects of discreteness and stochasticity on
invasion; we emphasize the probability distribution of the front-runner's
relative position. That is, we analyze the location of the most advanced
invader as the extreme deviation about the front's mean position. We find that
a class of models with different assumptions about neighborhood interactions
exhibit universal characteristics. That is, key features of the invasion
dynamics span a class of models, independently of locally detailed demographic
rules. Our results integrate theories of invasive spatial growth and generate
novel hypotheses linking habitat or landscape size (length of the invading
front) to invasion velocity, and to the relative position of the most advanced
invader.Comment: The original publication is available at
www.springerlink.com/content/8528v8563r7u2742
Desempenho reprodutivo de vacas de corte em lactação e solteiras submetidas à indução/sincronização de estro
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