The Trojan horse method in nuclear astrophysics: recent results

Difficulties in cross-section measurements at very low energies, when charged particles are involved, led to the development of some indirect methods. The Trojan horse method (THM) allows us to bypass the Coulomb effects and has been successfully applied to several reactions of astrophysical interest. A brief review of the THM applications is reported together with some of the most recent results.

Indirect study of (11)B(p,alpha(0))(8)Be and (10)B(p,alpha)(7)Be reactions at astrophysical energies by means of the Trojan Horse Method: recent results

Nuclear (p,alpha) reactions destroying the so-called ""light-elements"" lithium, beryllium and boron have been largely studied in the past mainly because their role in understanding some astrophysical phenomena, i.e. mixing-phenomena occurring in young F-G stars [1]. Such mechanisms transport the surface material down to the region close to the nuclear destruction zone, where typical temperatures of the order of similar to 10(6) K are reached. The corresponding Gamow energy E(0)=1.22 (Z(x)(2)Z(X)(2)T(6)(2))(1/3) [2] is about similar to 10 keV if one considers the ""boron-case"" and replaces in the previous formula Z(x) = 1, Z(X) = 5 and T(6) = 5. Direct measurements of the two (11)B(p,alpha(0))(8)Be and (10)B(p,alpha)(7)Be reactions in correspondence of this energy region are difficult to perform mainly because the combined effects of Coulomb barrier penetrability and electron screening [3]. The indirect method of the Trojan Horse (THM) [4-6] allows one to extract the two-body reaction cross section of interest for astrophysics without the extrapolation-procedures. Due to the THM formalism, the extracted indirect data have to be normalized to the available direct ones at higher energies thus implying that the method is a complementary tool in solving some still open questions for both nuclear and astrophysical issues [7-12].

Trojan Horse Method: a useful tool for electron screening effect investigation

Direct measurements in the last decades have highlighted a new problem related to the lowering of the Coulomb barrier between the interacting nuclei due to the presence of the ""electron screening"" in the laboratory measurements. It was systematically observed that the presence of the electronic cloud around the interacting ions in measurements of nuclear reactions cross sections at astrophysical energies gives rise to an enhancement of the astrophysical S(E)-factor as lower and lower energies are explored [1]. Moreover, at present Such an effect is not well understood as the value of the potential for screening extracted from these measurements is higher than the tipper limit of theoretical predictions (adiabatic limit). On the other hand, the electron screening potential in laboratory measurement is different from that occurring in stellar plasmas thus the quantity of interest in astrophysics is the so-called ""bare nucleus cross section"". This quantity can only be extrapolated in direct measurements. These are the reasons that led to a considerable growth on interest in indirect measurement techniques and in particular the Trojan Horse Method (THM) [2,3]. Results concerning the bare nucleus cross sections measurements will be shown in several cases of astrophysical interest. In those cases the screening potential evaluated by means of the THM will be compared with the adiabatic limit and results arising from extrapolation in direct measurements.

Indirect Study of the (2)H(d,p)(3)H and (2)H(d,n)(3)He Reactions at Astrophysical Energies via the Trojan Horse Method

The (2)H(d,p)(3)H and (2)H(d,n)(3)He reactions have been indirectly studied by means of the Trojan Horse Method applied to the quasi-free (2)H((3)He, p(3)H)(1)H (2)H((3)He, n(3)He)(1)H reaction at 18 MeV of beam energy. This is the first experiment where the spectator (here (1)H) has been detected in coincidence with the charged participant, avoiding the limitations of standard neutron detectors. The d - d relative energy has been measured from 1.5 MeV down to 2 keV, at center of mass angles from 40A degrees to 170A degrees. Indirect angular distributions are compared with the direct behaviour in the overlapping regions.

Low-energy d plus d fusion reactions via the Trojan Horse Method

The bare nucleus S(E) factors for the (2)H(d, p)(3)H and (2)H(d.n)(3)He reactions have been measured for the first time via the Trojan Horse Method off the proton in (3)He from 1.5 MeV down to 2 key. This range overlaps with the relevant region for Standard Big Bang Nucleosynthesis as well as with the thermal energies of future fusion reactors and deuterium burning in the Pre-Main-Sequence phase of stellar evolution. This is the first pioneering experiment in quasi free regime where the charged spectator is detected. Both the energy dependence and the absolute value of the S(E) factors deviate by more than 15% from available direct data with new S(0) values of 57.4 +/- 1.8 MeVb for (3)H + p and 60.1 +/- 1.9 MeV b for (3)He + n. None of the existing fitting curves is able to provide the correct slope of the new data in the full range, thus calling for a revision of the theoretical description. This has consequences in the calculation of the reaction rates with more than a 25% increase at the temperatures of future fusion reactors. (C) 2011 Elsevier By. All rights reserved.

Exploration of the idea of the horse in graphics and sculpture

The exploration of the idea of the horse is a very complex and open quest. Primarily it entails some conception of what the idea of the horse is. In choosing to title the project as such, I was attempting to indicate that what was of major interest to me was the representation of those qualities of the horse which are abstract and intangible as well as the physical qualities of the horse. Because of this interest, much of my work is concerned with movement, gesture, and the effects of structure, or lack thereof, on movement and gesture.

Kicking a Gift Horse in the Mouth

Yes, of course I know the expression is “Don’t look,” not kicking, but our collective professional behavior makes “kicking” the more operative and appropriate verbal. More about this in due course. As an expression, “don’t look a gift horse in the mouth” comes to us from the Lain, Noli equi dentes inspicere donate. Some argue Jerome said it first in 400 A.D., in which his words, very nearly our Latin literally translated, ran, “Never inspect the teeth of a gift horse.”

Effects of diclofenac and dexamethasone on horse experimental endotoxemia

Quinze eqüinos machos, da raça Mangalarga, com idades entre dois e três anos, foram utilizados para se avaliar os possíveis efeitos clínicos benéficos da administração de dexametasona ou diclofenaco sódico durante a endotoxemia experimental em eqüinos. Os animais foram divididos em três grupos de cinco animais cada: controle (C), diclofenaco sódico (SD) e dexametasona (DM). Todos os grupos receberam 0,1µg/kg de lipopolissarídeo de Escherichia coli 055:B5, durante 15 minutos, por via intravenosa mais: grupo SD - 2,2mg/kg de SD, por via oral, 60 minutos antes da infusão da endotoxina; grupo DM - 1,1mg/kg, por via intravenosa, 30 minutos antes da endotoxina; grupo C - 20ml de NaCl 0,9%, por via intravenosa, 30 minutos antes da endotoxina. O SD não preveniu a leucopenia, neutropenia e linfopenia ocorridas três horas após a indução da endotoxemia, porém a DM atenuou essas alterações. As taxas de proteínas plasmática e peritoneal, a concentração de glicose e de fósforo inorgânico e a contagem de células nucleadas totais peritoneais mantiveram-se inalteradas. O diclofenaco foi eficaz na prevenção da febre e alterações nos borborigmos intestinais enquanto que a dexametasona bloqueou as alterações no número de células inflamatórias em relação ao grupo controle.

Evaluation of the Integrity of Horse Hoof Dermal and Epidermal Tissues Collected by Dorsal Transmural Access

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Gastric Torsion from an Intestinal Hernia Through a Rent in the Gastrosplenic Ligament in a Horse

The present report describes an 8-year-old gelding presenting with signs of severe abdominal pain. After performing a thorough physical examination, including rectal palpation and additional diagnostic tests, an exploratory laparotomy was recommended. The jejunum was found herniated through the gastrosplenic ligament, and the stomach was severely distended with gas. Given a poor prognosis, the horse was euthanized on the table. At necropsy, the stomach appeared dilated, with an 180 horizontal gastric torsion, from left (lateral) to right (medial), dividing the organ into dorsal and ventral compartments. We believe that the chronic traction exerted by an incarcerated and distended loop of jejunum, in the dorsal aspect of the gastrosplenic ligament, associated with trauma during episodes of intense rolling, enlarged the rent until it ruptured. Because of this rupture, the lateral dorsal aspect of the stomach became unattached, predisposing it to the torsion. (C) 2012 Elsevier B.V. All rights reserved.

Prevalence of gastric lesions (ulcers and/or erosions) and their relationship to possible stressfull factors in asymptomatic Quarter Horse foals: endoscopic survey

A úlcera gástrica constitui-se numa das mais importantes causas de desconforto abdominal em eqüinos jovens. Com o objetivo de se verificar a prevalência de lesões gástricas (úlceras e/ou erosões) e sua relação com fatores como estresse, idade, e sexo, sessenta potros da raça Quarto de Milha não portadores de sinais clínicos compatíveis com lesões gástricas foram submetidos à gastroscopia. Os potros foram divididos em quatro faixas etárias de 15 animais cada uma, sendo: 1 a 30 dias, 31 a 60 dias, 61 a 90 dias e 91 a 120 dias de idade. A prevalência de lesões gástricas foi de 43,3%. Animais com idade entre 61 a noventa dias foram os mais acometidos. Não houve diferença significativa entre as faixas etárias. Descamações do epitélio aglandular ocorreram em nove potros (60%) entre um e trinta dias, em seis (40%) entre 31 e sessenta dias e em apenas dois (6,6%) com idade superior a sessenta dias. Fatores considerados estressantes, como infestação intensa por carrapatos (29), problemas respiratórios (3), dermatopatias (3), babesiose (2), onfaloflebite (1), diarréia (1), problemas ortopédicos (1) e ferida lacerante com presença de miíase (1) não influenciaram a ocorrência das lesões. Machos e fêmeas foram igualmente acometidos.

Lesions (ulcers and/or erosions) and desquamations location in the gastric mucosa from asymptomatic Quarter Horse foals: endoscopic survey

A úlcera gástrica figura como uma importante causa de desconforto abdominal em eqüinos jovens. de acordo com a localização das lesões na mucosa gástrica, a presença ou ausência de sinais clínicos e possíveis complicações resultantes de sua ocorrência, quatro síndromes clínicas são freqüentemente descritas em potros: 1) Úlceras assintomáticas ou silenciosas; 2) Úlceras sintomáticas ou ativas; 3) Úlceras perfuradas; e 4) Obstruções gástrica ou duodenal. Com o objetivo de se verificar a distribuição de lesões gástricas (úlceras e/ou erosões) e descamações do epitélio aglandular no estômago de eqüinos jovens assim como uma possível relação entre as alterações mencionadas (lesão/descamação) sessenta potros da raça Quarto de Milha não-portadores de sinais clínicos compatíveis com úlceras gástricas foram submetidos à gastroscopia. Os potros foram divididos em quatro faixas etárias de 15 animais cada uma, sendo: 1 a 30 dias, 31 a 60 dias, 61 a 90 dias e 91 a 120 dias de idade. As lesões ocorreram em ordem decrescente de freqüência nas regiões aglandular próximo ao margo plicatus ao longo da curvatura maior, aglandular próximo à cárdia ao longo da curvatura menor, fundo glandular e aglandular e antro. As descamações do epitélio aglandular ocorreram de forma similar nas regiões de fundo e margo plicatus. Não houve associação entre a ocorrência de lesões e descamações.

Guttural Pouch Diseases Causing Neurologic Dysfunction in the Horse

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)