6,873 research outputs found
On Dirac-like Monopoles in a Lorentz- and CPT-violating Electrodynamics
We study magnetic monopoles in a Lorentz- and CPT-odd electrodynamical
framework in (3+1) dimensions. This is the standard Maxwell model extended by
means of a Chern-Simons-like term, (
constant), which respects gauge invariance but violates both Lorentz and CPT
symmetries (as a consequence, duality is also lost). Our main interest concerns
the analysis of the model in the presence of Dirac monopoles, so that the
Bianchi identity no longer holds, which naively yields the non-conservation of
electric charge. Since gauge symmetry is respected, the issue of charge
conservation is more involved. Actually, the inconsistency may be circumvented,
if we assume that the appearance of a monopole induces an extra electric
current. The reduction of the model to (2+1) dimensions in the presence of both
the magnetic sources and Lorentz-violating terms is presented. There, a
quantization condition involving the scalar remnant of , say, the mass
parameter, is obtained. We also point out that the breaking of duality may be
associated with an asymmetry between electric and magnetic sources in this
background, so that the electromagnetic force experienced by a magnetic pole is
supplemented by an extra term proportional to , whenever compared to the
one acting on an electric charge.Comment: 10 pages, no figures, typed in te
COMPARATIVE ANALYSIS OF THE IAPWS-IF97 FORMULATION PERFORMANCE FOR THERMODYNAMIC PROPERTIES OF WATER ON A RANKINE CYCLE
The present paper presents the computational implementation of the industrial
formulation of the thermodynamic properties of water at liquid and
steam phases, proposed by the International Association for the Properties
of Water and Steam, known as IAPWS-IF97. The validity field extends over
to temperatures T between 0ºC and 800°C, for pressures p up to 100 MPa.
Temperature T, specific volume v, specific enthalpy h, specific entropy s,
specific heat at constant pressure cp and constant volume cv, besides saturation
pressure ps, are calculated having a pair of known input values (p,T),
(p,h) or (p,s). A comparative analysis between the IAPWS-IF97 routines
and others, based on foregoing propositions, from an application on Rankine
cycle, is made. IAPWS-IF97 has proved to be more precise, mainly because
it accounts for the region of compressed liquid, besides requiring less processing
time. The development is carried out as FORTRAN90 subroutines
and functions and is available for public use according to a General Public
License
Benthic macro-invertebrates as indicators of ecological fragility of small rivers ('igarapés') in a bauxite mining region of Brazilian Amazonia
Benthic macroinvertebrate communities were studied in the igarapés Saracá, Caranã and Água Fria near Porto Trombetas, Municipality of Oriximiná, State of Pará, Brazil (1°25' to 1°35'S and 56°15' to 56°W). The main objective was to investigate the potential use of the benthic macroinvertebrates community as indicators of the ecological fragility of the igarapés located in an area of the Amazon basin influenced by bauxite mining. These aquatic ecosystems have low pH (< 4.5); low electrical conductivity (< 90 µS cm-1); low or undetectable total alkalinity; low nutrient concentrations in the sediment, which implies low primary productivity; low species richness; low secondary productivity; and low rates of organic matter decomposition. The benthic macroinvertebrates utilize mainly allochthonous organic matter. Some areas of the ecosystems investigated have been modified by bauxite tailings (especially in their sediment granulometry), by a dam formed by railroad construction (which altered the hydrodynamics and eliminated the terra firma vegetation), and by accidental discharges of various minerals from the railroad traffic and bauxite mining. These factors have drastically modified the local benthic macroinvertebrate communities. The value of benthic macroinvertebrates as indicators of ecological fragility, the health of the ecosystem investigated, and water quality is evaluated
Postpartum psychiatric disorders
OBJETIVO: O pós-parto é um período de alterações biológicas, psicológicas e sociais. Essa é considerada a época mais vulnerável para a ocorrência de transtornos psiquiátricos. A disforia puerperal, a depressão pós-parto e a psicose pós-parto têm sido classicamente relacionadas ao pós-parto. Atualmente, tem sido observado que os transtornos ansiosos também estão associados a esse período. MÉTODO: Neste artigo é feita uma revisão da bibliografia acerca de transtornos psiquiátricos no pós-parto a partir de artigos encontrados no PubMed e no SciELO entre os anos de 2000 e 2009. Livros, teses e outros artigos considerados relevantes citados no material consultado também foram incluídos. RESULTADOS: A disforia puerperal ocorre em 50% a 85% das mulheres, o quadro é leve e transitório e não requer tratamento. A depressão pós-parto tem prevalência em torno de 13%, pode causar repercussões negativas na interação mãe-bebê e em outros aspectos da vida da mulher e deve ser tratada. A psicose pós-parto é rara, aparecendo em cerca de 0,2% das puérperas. Tem quadro grave que envolve sintomas psicóticos e afetivos, havendo risco de suicídio e infanticídio e geralmente requerendo internação hospitalar. Os transtornos ansiosos podem ser exacerbados ou precipitados no pós-parto, especialmente o transtorno de ansiedade generalizada, o transtorno de estresse pós-traumático e o transtorno obsessivo-compulsivo. CONCLUSÃO: Apesar de não serem reconhecidos como entidades diagnósticas pelos sistemas classificatórios atuais, os transtornos mentais no puerpério apresentam peculiaridades clínicas que merecem atenção por parte de clínicos e pesquisadores.OBJECTIVE: The postpartum period is marked by biological, psychological and social changes. Women are considered most susceptible to psychiatric disorders during the postpartum period. Puerperal blues, postpartum depression and postpartum psychosis have been classically associated to the postpartum. Anxiety disorders have also recently been associated to this period. METHOD: The present article reports a review of the literature on postpartum psychiatric disorders based on articles found on the PubMed and SciELO databases, published between 2000 and 2009. Relevant books, theses and other articles cited in the articles found were also included in this review. RESULTS: Puerperal dysphoria occurs in 50% to 85% of women following childbirth and is typically mild and transient in nature and requires no treatment. Postpartum depression has a prevalence rate of around 13% and can have negative repercussions on mother-infant interaction and other life events and must therefore be treated. Postpartum psychosis is rare, occurring in approximately 0.2% of puerperium cases. This condition is severe with psychotic and affective symptoms as well as risk of suicide and infanticide. Postpartum psychosis patients generally require hospital treatment. Anxiety disorders may be exacerbated or precipitated during the postpartum, particularly generalized anxiety disorder, post-traumatic stress disorder and compulsive-obsessive disorder. DISCUSSION: Although not recognized as distinct diagnostic entities under current classification systems, mental disorders during the puerperium present clinical features which warrant the attention of clinicians and researchers
Trinucleon photonuclear reactions with Δ-isobar excitation: Processes below pion-production threshold
Radiative nucleon-deuteron capture and two- and three-body photodisintegration of the three-nucleon bound state are described. The description uses the purely nucleonic charge-dependent CD-Bonn potential and its coupled-channel extension CD Bonn +Δ. The Δ-isobar excitation yields an effective three-nucleon force and effective two- and three-nucleon currents beside other Δ-isobar effects; they are mutually consistent. Exact solutions of three-particle equations are employed for the initial and final states of the reactions. The current has one-baryon and two-baryon contributions and couples nucleonic with Δ-isobar channels. Δ-isobar effects on the observables are isolated. Shortcomings of the theoretical description are discussed and their consequence for the calculation of observables is estimated
Ewing's Sarcoma Of The Head And Neck.
CONTEXT: Ewing's sarcoma is a rare neoplasm, which usually arises in long bones of the limbs and in flat bones of the pelvis, with the involvement of head and neck bones being very unusual. CASE REPORT: a case of Ewing's sarcoma occurring in the mandible of a 35-year-old female. Pain and swelling of the tumor were the main complaints. The early hypothesis was an undifferentiated malignant neoplasm, possibly a sarcoma. The CT scan depicted an expansive lesion, encapsulated, with septa and characteristics of soft tissue, involving the left side of the mandible and extending to the surrounding tissues. The patient underwent surgical excision of the lesion, the definitive diagnosis of Ewing's sarcoma was established, and the patient commenced on radiotherapy.118619820
Research Notes : United States : Seed yield on field-grown ms2 ms2 male-sterile plants
Seed set on male-sterile plants is of general interest to geneticists. For the quantitative geneticist, high seed set allows greater flexibility in the design of basic genetic experiments, including selection and variance com-ponent estimation studies. For the plant breeder, high seed set raises a hope of hybrid soybean production. Hybrid production, to be economical, requires adequate seed yield on male-sterile plants grown in the field
One-to-one full scale simulations of laser wakefield acceleration using QuickPIC
We use the quasi-static particle-in-cell code QuickPIC to perform full-scale,
one-to-one LWFA numerical experiments, with parameters that closely follow
current experimental conditions. The propagation of state-of-the-art laser
pulses in both preformed and uniform plasma channels is examined. We show that
the presence of the channel is important whenever the laser self-modulations do
not dominate the propagation. We examine the acceleration of an externally
injected electron beam in the wake generated by 10 J laser pulses, showing that
by using ten-centimeter-scale plasma channels it is possible to accelerate
electrons to more than 4 GeV. A comparison between QuickPIC and 2D OSIRIS is
provided. Good qualitative agreement between the two codes is found, but the 2D
full PIC simulations fail to predict the correct laser and wakefield
amplitudes.Comment: 5 pages, 5 figures, accepted for publication IEEE TPS, Special Issue
- Laser & Plasma Accelerators - 8/200
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