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Search Results: 1 - 10 of 261344 matches for " V. F. Correa "
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Vortex Softening: Origin of the second peak effect in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$
V. F. Correa,G. Nieva,F. de la Cruz
Physics , 2000, DOI: 10.1103/PhysRevLett.87.057003
Abstract: Transverse ac permeability measurements in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta }$ single crystals at low fields and temperatures in a vortex configuration free of external forces show that the decrease of the critical current as measured by magnetization loops at the second peak effect is an artifact due to creep. On the other hand, the increase of critical current at the second peak is due to a genuine softening of the tilting elastic properties of vortices in the individual pinning regime that precedes the transition to a disorder state.
Calculation of Dose in Healthy Organs, during Radiotherapy 4-Field Box 3D Conformal for Prostate Cancer, Simulation of the Linac 2300, Radiotherapy Room and MAX Phantom  [PDF]
Jardel L. Thalhofer, Wilson F. Rebello, Samanda A. Correa, Ademir X. Silva, Edmilson M. Souza, Delano V. Batista
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2013, DOI: 10.4236/ijmpcero.2013.22009

In men, prostate cancer is one of the most frequent types, and radiotherapy is adopted as a form of treatment. Although there are efforts to minimize the dose in the healthy organ and tissues adjacent to the tumor during radiotherapy, these organs are affected by the secondary scattered and leakage radiation originating from the therapeutic beam and these doses deposited in the healthy organs, can induce the appearance of new focal points of cancer. The aim of this study is to calculate the equivalent and effective doses, due to photons and neutrons, in healthy organs of a patient submitted to radiotherapy treatment for prostate cancer. Computed simulation of radiotherapy treatment for prostate cancer was used to perform the dose calculations, adopting the treatment protocol used at INCA (Brazilian National Cancer Institute). The MCNPX code was employed in the simulation radiation transport while the male voxel MAX phantom was used to represent the patient's human anatomy. The results obtained in this study indicate that the organs close to the irradiated region are predominantly affected by the dose due to photons, with an impact on organs from different systems of the body, such as the bladder, colon, and testicles, besides bone structures such as the femur, pelvis and spinal column. The results obtained from the doses deposited due to neutrons suggest that tibia and fibula, mandible, cranium, brain and thyroid, had the highest dose deposited due to neutrons in relation to photons. The result obtained from the effective dose was 31.47 mSv due to photons, while the dose due to neutrons was 0.42 mSv. Note that the effective dose due to photons is significantly higher than the effective dose due to neutrons. The values calculated in this study were compared with the experimental values obtained in the literature, presenting reasonable concordance. Additionally, as described in the literature, it was verified that the dose due to photons decreases considerably with the increase in the distance of the target organ, while the dose due to neutrons is distributed homogeneously in the organs. It is concluded that the contribution of neutrons to the appearance of secondary cancers is more relevant in the organs furthest from the tar

Heritability Estimates of Stillbirth and Preweaning Mortality in a Zebu Population of Southeastern, Mexico
J.C. Segura-Correa,V.M. Segura-Correa,F. Centurion-Castro
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2012.214.217
Abstract: The objective of this study was to estimate the heritabilities of stillbirth and preweaning mortality in a Zebu herd in the tropics of Mexico. The data collected were for cows calving over a 21 years period (1989-2009). The base population was commercial Zebu cattle. The model included the fixed effects of period of year, season of birth, parity number, breed of sire and the random effects of sire within sire breed and the error term. Mean heritability estimates and standard deviations for stillbirth and preweaning mortality from posterior distributions were 0.030±0.020 and 0.031±0.025, respectively. The low heritability here found also suggested that environmental factors are more important than genetic effects on those traits. Therefore, the potential for selective improvement of stillbirth and preweaning mortality appears to be limited to long-term programs and that the control of various management and risk factors would have more immediate effect.
Efecto de la suplementación fosforada sobre la ganancia de peso de bovinos en pastoreo en Yucatán, México.
Víctor M. Segura Correa,Arturo F. Castellanos Ruelas
Veterinaria México , 1999,
Abstract: El objetivo del trabajo fue estimar el mín imo de fósforo (P) que deben consumir toretes en pastoreo en la zona oriente de Yucatán, México, para mejorar su velocidad de crecimiento. Se utilizaron 40 bovinos machos, enteros, con un peso inicial promedio de 240.8 ± 63.2 kg (± D.E.), los cuales fueron distribuidos en 4 tipos de suplemento mineral fosforado que propiciaron consumos decrecientes de P. Los tratamientos fueron: alto (A), mediano (M), bajo (B) y un testigo (T) que recibió un suplemento mineral libre de P. Los suplementos fosforados contenían 4.5% de P a partir de un ortofosfato de calcio (21% P). El estudio tuvo una duración de un a o y se dividió en 3 partes, según la época: sequía (marzo-mayo), lluvia (junio-octubre) y nortes -sequía (diciembre-abril). El resultado de la ganancia de peso de cada individuo durante cada época del a o se analizó mediante el método de mínimos cuadrados, en un modelo lineal que incluyó el efecto fijo del tratamiento y utilizó como covariable el peso inicial. El contenido de P en el zacate Guinea (Panicum maximum) pastoreado por los animales, osciló entre 0.09% y 0.07%. Sólo durante la época de lluvias se encontró efecto (P<.05) del tipo de suplemento mineral consumido sobre la ganancia de peso; el tratamiento M incrementó la ganancia de peso sobre el T en 31.8%, al mantener un consumo de P de 3.3 g/animal/día. Un consumo mayor de P no mejoró la respuesta animal.
Brachiaria spp. poisoning of ruminants in Brazil
Riet-Correa, B.;Castro, M.B.;Lemos, R.A.;Riet-Correa, G.;Mustafa, V.;Riet-Correa, F.;
Pesquisa Veterinária Brasileira , 2011, DOI: 10.1590/S0100-736X2011000300001
Abstract: brachiaria species are the most important grasses for cattle production in brazil. however, a limiting factor for the use of brachiaria spp. is their toxicity. most outbreaks of hepatogenous photosensitization are caused by b. decumbens; however b. brizantha, b. humidicola and b. ruziziensis can also cause poisoning. the poisoning affects cattle, sheep, goats and buffalo. sheep are more susceptible than other animal species and the young are more susceptible than adults. there are differences in susceptibility among animals of the same species and it has been suggested that this resistance is genetic. also has been suggested that buffalo and probably some sheep are resilient, i.e. when poisoned these animals have histologic lesions and high ggt serum concentrations, but do not show clinical signs. in general, saponin concentrations are higher in growing plants, but outbreaks occur all over the year, probably due to unexplained rise in saponin concentration in the plant. a clinical syndrome of progressive weight loss and death, without photosensitization, has been reported in cattle poisoned by b. decumbens. main preventive measures are based on the selection of resistant or resilient animals and on the development of brachiaria species or varieties with low saponin concentration.
Epidermal Inclusion Cyst Presenting as a Palpable Scrotal Mass
Andres F. Correa,Bishoy A. Gayed,Mitchell E. Tublin,Anil V. Parwani,Jeffrey R. Gingrich
Case Reports in Urology , 2012, DOI: 10.1155/2012/498324
Abstract: We report a scrotal epidermal inclusion cyst located outside the median raphe which a rare entity in the absence of trauma and few cases have been reported. 47 year old male presents with a complaint of right sided testicular swelling and discomfort. On examination a 3 cm mass was palpated between the scrotum and the medial thigh on the subcutaneous tissue with a positive slip sign. Complete surgical excision of the cyst was performed. Histopathology confirmed epidermal inclusion cyst with no evidence of malignancy.
DYNA , 2012,
Abstract: En diversos escenarios de la vida cotidiana existe la necesidad de comunicarse oralmente con otras personas. Sin embargo, diversas soluciones tecnológicas como la telefonía móvil no pueden ser utilizadas en lugares como reuniones, salones de clase, conferencias, entre otras, sin interrumpir las actividades de las personas alrededor del hablante. Este trabajo de investigación desarrolla una herramienta que permite entablar una conversación de voz en un recinto público sin interrumpir las actividades del medio circundante. Para ello se implementa un sintetizador de voz en una computadora personal comunicada de forma alámbrica con un teléfono móvil, lo cual permite establecer una llamada sin utilizar la voz humana. El sintetizador de voz utiliza la técnica de concatenación de difonemas y es desarrollado específicamente para el idioma espa ol de Colombia. Una descripción matemática del sintetizador muestra su descomposición en diversos procesos independientes entre sí. Se realizaron diversas pruebas de aceptación de usuarios y de calidad de la se al obtenida para evaluar el desempe o de la herramienta. Los resultados muestran una alta relación se al a ruido de las se ales generadas y una alta inteligibilidad de la herramienta.
Clinical and molecular analysis of human reproductive disorders in Brazilian patients
Latronico A.C.,Costa E.M.F.,Domenice S.,Correa R.V.
Brazilian Journal of Medical and Biological Research , 2004,
Abstract: Several genes that influence the development and function of the hypothalamic-pituitary-gonadal-axis (HPG) have been identified. These genes encode an array of transcription factors, matrix proteins, hormones, receptors, and enzymes that are expressed at multiple levels of the HPG. We report the experience of a single Endocrinology Unit in the identification and characterization of naturally occurring mutations in families affected by HPG disorders, including forms of precocious puberty, hypogonadism and abnormal sexual development due to impaired gonadotropin function. Eight distinct genes implicated in HPG function were studied: KAL, SF1, DAX1, GnRH, GnRHR, FSH , FSHR, and LHR. Most mutations identified in our cohort are described for the first time in literature. New mutations in SF1, DAX1 and GnRHR genes were identified in three Brazilian patients with hypogonadism. Eight boys with luteinizing hormone- (LH) independent precocious puberty due to testotoxicosis were studied, and all have their LH receptor (LHR) defects elucidated. Among the identified LHR molecular defects, three were new activating mutations. In addition, these mutations were frequently associated with new clinical and hormonal aspects, contributing significantly to the knowledge of the molecular basis of reproductive disorders. In conclusion, the naturally occurring genetic mutations described in the Brazilian families studied provide important insights into the regulation of the HPG.
Epidermal Inclusion Cyst Presenting as a Palpable Scrotal Mass
Andres F. Correa,Bishoy A. Gayed,Mitchell E. Tublin,Anil V. Parwani,Jeffrey R. Gingrich
Case Reports in Urology , 2012, DOI: 10.1155/2012/498324
Abstract: We report a scrotal epidermal inclusion cyst located outside the median raphe which a rare entity in the absence of trauma and few cases have been reported. 47 year old male presents with a complaint of right sided testicular swelling and discomfort. On examination a 3?cm mass was palpated between the scrotum and the medial thigh on the subcutaneous tissue with a positive slip sign. Complete surgical excision of the cyst was performed. Histopathology confirmed epidermal inclusion cyst with no evidence of malignancy. 1. Introduction Epidermoid inclusion cysts (EIC) are rare, benign cysts which occur from implantation of epidermal tissue into the dermis or subcutaneous tissues or in the testicle [1]. This abnormal localization can occur from developmental closure of the median raphe to include the epidermal tissue or through traumatic implantation [1]. These EIC are usually located along the midline and have been reported from the distal penis to the anus [1]. The presentation in the scrotum is usually an asymptomatic, firm, freely moveable extra-testicular mass developing between the second and forth decade of life [2]. We report a case of an extra-testicular epidermoid inclusion cyst with an atypical presentation away from the midline as well as a review of the diagnosis, evaluation and management of these unique scrotal anomalies. 2. Case Report A healthy, 47-year-old male presented with testicular discomfort and a palpable nodule in the upper scrotum just medial to the thigh. He reported that the nodule had been present for nearly seven years and had been slowly enlarging over the last few years. The mass had been initially asymptomatic, until recently when he began to experience some discomfort during exercise along with other activities. He denied any history of trauma or any prior surgeries to the area. On physical exam, a palpable 3?cm soft structure was present in the right scrotum as shown in Figure 1. It was minimally tender and mobile within the subcutaneous tissue, not adherent to the skin or spermatic cord. A scrotal ultrasound revealed a uniform, hypoechoic right extra-testicular lesion. The lesion appeared to be avascular. The mass did not originate from the scrotal wall, but was abutted by the lateral aspect of the right testis as shown in Figure 2. Figure 1: Physical appearance of right extra-testicular mass on 47 year old male. Figure 2: Coronal oblique sonogram shows an oval solid hypoechoic mass (arrow) separate from the right and left testes (T). Given the low malignant potential, we did not send testicular markers and proceeded with
Unusual giant magnetostriction in the ferrimagnet Gd$_{2/3}$Ca$_{1/3}$MnO$_3$
V. F. Correa,N. Haberkorn,G. Nieva,D. J. Garcia,B. Alascio
Physics , 2011, DOI: 10.1209/0295-5075/98/37003
Abstract: We report an unusual giant linear magnetostrictive effect in the ferrimagnet Gd$_{2/3}$Ca$_{1/3}$MnO$_3$ ($T_{c} \approx$80 K). Remarkably, the magnetostriction, negative at high temperature ($T \approx T_{c}$), becomes positive below 15 K when the magnetization of the Gd sublattice overcomes the magnetization of the Mn sublattice. A rather simple model where the magnetic energy competes against the elastic energy gives a good account of the observed results and confirms that Gd plays a crucial role in this unusual observation. Unlike previous works in manganites where only striction associated with 3$d$ Mn orbitals is considered, our results show that the lanthanide 4$f$ orbitals related striction can be very important too and it cannot be disregarded.
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