1,371 research outputs found
N=2 Super-Born-Infeld from Partially Broken N=3 Supersymmetry in d=4
We employ the non-linear realization techniques to relate the N=1 chiral, and
the N=2 vector multiplets to the Goldstone spin 1/2 superfield arising from
partial supersymmetry breaking of N=2 and N=3 respectively. In both cases, we
obtain a family of non-linear transformation laws realizing an extra
supersymmetry. In the N=2 case, we find an invariant action which is the low
energy limit of the supersymmetric Born-Infeld theory expected to describe a
D3-brane in six dimensions.Comment: 15 pages, no figures, RevTeX4, new comments and references added,
some equations corrected, discussion at end of sec. 3 change
Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy
Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% YâOâ alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.the FP6 Euratom
Research and Training Programme on Nuclear Energy
(VdC), The Engineering and Physical Sciences
Research Council (SLP) and The Royal Society (EAM).
The Comunidad de Madrid, through the ESTRUMATCM
(MAT-77) programme, and the use of the Chemical
Database Service at DaresburyPublicad
Soil organisms in organic and conventional cropping systems.
Apesar do crescente interesse pela agricultura orgĂąnica, sĂŁo poucas as informaçÔes de pesquisa disponĂveis sobre o assunto. Assim, num Argissolo Vermelho-Amarelo distrĂłfico foram comparados os efeitos de sistemas de cultivo orgĂąnico e convencional, para as culturas do tomate (Lycopersicum esculentum) e do milho (Zea mays), sobre a comunidade de organismos do solo e suas atividades. As populaçÔes de fungos,bactĂ©rias e actinomicetos, determinadas pela contagem de colĂŽnias em meio de cultura, foram semelhantes para os dois sistemas de produção. A atividade microbiana, avaliada pela evolução de CO2, manteve-se superior no sistema orgĂąnico, sendo que em determinadas avaliaçÔes foi o dobro da evolução verificada no sistema convencional. O nĂșmero de espĂ©cimes de minhoca foi praticamente dez vezes maior no sistema orgĂąnico. NĂŁo foi observada diferença na taxa de decomposição de matĂ©ria orgĂąnica entre os dois sistemas. De modo geral, o nĂșmero de indivĂduos de microartrĂłpodos foi superior no sistema orgĂąnico do que no sistema convencional, refletindo no maior Ăndice de diversidade de Shannon. As maiores populaçÔes de insetos foram as da ordem Collembola, enquanto para os ĂĄcaros a maior população foi a da superfamĂlia Oribatuloidea. IndivĂduos dos grupos Aranae, Chilopoda, Dyplopoda, Pauropoda, Protura e Symphyla foram ocasionalmente coletados e de forma similar entre os sistemas
Analytical characterisation of oxide dispersion strengthened steels for fusion reactors
Special issue articleReduced activation ferritic/martensitic and ferritic steels strengthened by a dispersion of oxide nanoparticles have been considered viable structural materials for fusion applications above 550°C. However, the microstructural stability and mechanical behaviour of these steels subjected
to the aggressive operating conditions of these reactors are not well known. An accelerated development of these materials is crucial if they are going to be used in future power reactors.
Then, it is indispensable to understand their atomic scale evolution under high temperature and irradiation conditions. The present paper reviews how the combination of transmission electron microscopy and atom probe tomography has been successfully applied for the characterisation of these steels at the near atomic scale, to reveal the nanoparticle structure, grain boundary
chemistry and void distribution.The present research has been supported by the FP6
Euratom Research and Training Programme on Nuclear
Energy, the Fusion Energy Materials Science (FEMaS)
FP7 coordination action, the IP3 FP6 ESTEEM project
under contract no. 026019 and the ConsejerĂa de
EducaciĂłn de la Comunidad de Madrid, through the
program ESTRUMAT-CM S2009MAT-1585. EAM
thanks the Royal Society for the financial support (RS
Dorothy Hodgkin fellowship)
Microstructural characterization of YâOâ ODS-Fe-Cr model alloys
Proceedings of the: Thirteenth International Conference on Fusion Reactor Materials. Nice (France), 10-14/12/2007.Two Fe-12 wt% Cr alloys, one containing 0.4 wt% YâOâ and the other YâOâ free, have been produced by mechanical alloying followed by hot isostatic pressing. These oxide dispersion strengthened and reference alloys were characterized both in the as-HIPed state and after tempering by transmission electron microscopy and atom-probe tomography. The as-HIPed alloys exhibited the characteristic microstructure of lath martensite and contained a high density of dislocations. Small voids with sizes <10 nm were also observed. Both alloys also contained MâC and MââCâ carbides (M = Cr, Fe) probably as a result of C ingress during milling. After tempering at 1023 K for 4 h the microstructures had partially recovered. In the recovered regions, martensite laths were replaced by equiaxed grains in which MââCâ carbides decorated the grain boundaries. In the ODS alloy nanoparticles containing Y were commonly observed within grains, although they were also present at grain boundaries and adjacent to large carbides.This research has been supported by FP6 Euratom Research and Training Programme on Nuclear Energy. The financial support from the Comunidad de Madrid, through the program ESTRUMAT CM,Grant S 0505/MAT/0077.Publicad
EFICĂCIA DE DOIS SISTEMAS DE TRATAMENTO ANTI-HELMĂNTICO EM FILHOTES DE CĂES COM INFECĂĂO NATURAL
O objetivo do presente trabalho foi testar dois esquemas de tratamento para o
combate da parasitose gastrintestinal em filhotes de cães recém-desmamados. Foram
estabelecidos dois grupos de tratamento, ambos tratados com uma suspensĂŁo pamoato de
pirantel e oxantel: grupo 1 - quatro desverminaçÔes com intervalos de 15 dias e grupo 2 -trĂȘs
desverminaçÔes, nos dias 0, 5 e 25 pós desmame. O primeiro tratamento apresentou redução
de 98,2 % no nĂșmero de ovos por grama de fezes (opg) de Toxocara canis, apĂłs a primeira
desverminação. Cem por cento de redução de opg foi obtido após o segundo tratamento. No
tratamento 2, foi obtido um resultado semelhante apĂłs trĂȘs tratamentos. Para ovos de
Ancylostoma sp. a formulação mostrou eficåcia após a primeira dose para ambos os tratamentos
preconizados. Estes resultados indicam que os esquemas de tratamento propostos poderiam
ser adotados para combate das infecçÔes por estes parasitas em animais recém-desmamados.
Comparison of the efficacy of two systems of antihelminthic treatment in puppies
with natural infection
Abstract
This work was developed to test two treatment outlines for gastrointestinal parasitosis
control in weaned puppies. Two treatment groups were established, both treated with oxantel and
pyrantel pamoate suspension: group 1 (four doses with 15-days intervals) and group 2 (three doses,
at zero, 5th and 25th days). The first treatment presented reduction of 98.2 % on the number of eggs
of Toxocara canis per gram of feces (epg) after the first dose. Complete epg reduction was observed
after the second treatment, 15 days later. Similar result was obtained after the third dose for the
treatment 2. Both treatment protocols showed effectiveness for eggs of Ancylostoma sp. after the
first dose. These results indicate that both treatment outlines could be applied for the roundworm and
the hookworm control in recently-weaned puppies
Electromagnetic properties of graphene junctions
A resonant chiral tunneling (CT) across a graphene junction (GJ) induced by
an external electromagnetic field (EF) is studied. Modulation of the electron
and hole wavefunction phases by the external EF during the CT
processes strongly impacts the CT directional diagram. Therefore the a.c.
transport characteristics of GJs depend on the EF polarization and frequency
considerably. The GJ shows great promises for various nanoelectronic
applications working in the THz diapason.Comment: 4 pages 3 figure
Twist Deformations of the Supersymmetric Quantum Mechanics
The N-extended Supersymmetric Quantum Mechanics is deformed via an abelian
twist which preserves the super-Hopf algebra structure of its Universal
Enveloping Superalgebra. Two constructions are possible. For even N one can
identify the 1D N-extended superalgebra with the fermionic Heisenberg algebra.
Alternatively, supersymmetry generators can be realized as operators belonging
to the Universal Enveloping Superalgebra of one bosonic and several fermionic
oscillators. The deformed system is described in terms of twisted operators
satisfying twist-deformed (anti)commutators. The main differences between an
abelian twist defined in terms of fermionic operators and an abelian twist
defined in terms of bosonic operators are discussed.Comment: 18 pages; two references adde
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