149 research outputs found
Method for Efficiency and Time Response Measurement on Diverse Target Ion Sources with Stable Alkali
International audienceDevelopments of new setups for radioactive ion beam production by the isotope-separator-on-line (ISOL) method are underway at GANIL in the frame of the SPIRAL (SystÚme de Production d'Ions Radioactifs Accélérés en Ligne) and SPIRAL-II projects. The measurement of total efficiency and time behaviour of these new target/ion-source systems (TISSs) is a crucial step for these devices which aims to produce short-lived isotopes with high intensity. The overall atom-to-ion transformation efficiency depends on several processes: diffusion of the atoms out of the production target, effusion towards the ion source and ionization. The efficiency can be extracted using the ratio between the emerging yield and implanted flux in the TISS. Several methods have already been developed to achieve these measurements: the use of stable or radioactive beams, gas injection, or the introduction of solid material into the TISS. This paper focuses primarily on a method that uses stable alkali. A pulsed/CW alkali ion gun has been built and will be used to optimise diverse TISSs
Explorando as relaçÔes entre estrutura da paisagem e atributos de qualidade de fragmentos em região de mata atlùntica no estado do Rio de Janeiro.
Fenologia de cultivares de trigo para fins de refinamento do zoneamento agrĂcola da cultura na regiĂŁo homogĂȘnea de adaptação de cultivares 4.
Arachnida at "Reserva Ducke", Central Amazonia/Brazil
The class Arachnida contains 11 recent orders: Acari, Amblypygi, Araneae, Opiliones, Palpigradi, Pseudoscorpiones, Ricinulei, Schizomida, Scorpiones, Solifugae and Uropygi (Thelyphonida). In total, >570 families, >9165 genera and >93455 species are known world-wide. More than 136 families, >482 genera and >1547 described species occur in Amazonia. Data show, that almost one-fourth of the families presently known in the Arachnida and about 2% of the worlds described species are represented in Amazonia. In the forest reserve 'Reserva Ducke' near Manaus, the Acari-Oribatida represent 45 families, 72 genera and 35 described species, the Aranea 30 families, 143 genera and 295 described species, the Opiliones 5 families, 7 genera and 8 decribed species, the Scorpiones 2 families, 4 genera and 5 described species, the Pseudoscorpiones 6 families, 11 genera, and 15 described species, the Schizomida, 1 family, 2 genera and 2 described species, and the Amblypygi, Palpigradi, Solifugae and Uropygi (Thelyphonida) one species each. Most names are liste
EficiĂȘncia da utilização de potĂĄssio, cĂĄlcio e magnĂ©sio em 16 hĂbridos de sorgo.
O presente trabalho foi conduzido em casa de vegetação do Departamento de Fototecnia, da Universidade Federal de Viçosa, entre os meses de maio a setembro de 1977, para avaliar a eficiĂȘncia de utilização de potĂĄssio, cĂĄlcio e magnĂ©sio, em dezesseis hĂbridos de sorgo (Sorghum bico/ar (L.) Moench) e teve a finalidade de se verificar a aplicabilidade do conceito de "eficiĂȘncia nutricional"
Permanent magnets under irradiation and radiocative alkali ion beam development for SPIRAL1
International audienceUp to now, eighteen Target Ion Source Systems (TISSs) have been built and used for the production of radioactive ion beams on SPIRAL 1 facility, based on the Isotope- Separator-On-Line (ISOL) method. The TISSs are composed of thick carbon targets and of fully permanentmagnet Electron Cyclotron Resonance Ion Sources (ECRISs) of the Nanogan III type. After irradiation and a decay period of two years, the irradiated TISSs are dismounted and if their magnetic fields are still suitable, the ECRIS are used with a new target. Thereby thirty-two runs have been performed using new or renewed TISSs. , After irradiation, the measured magnetic field sometimes reveals magnet damage. Our experience is reported here. In the second section, we present the progress on the NanoNaKE setup, which aims to extend the radioactive ion beams in SPIRAL 1 to the alkali elements, by connecting a surface-ionization source to the Nanogan III ECRIS via a compact 1+ ion beam line. The main issues and difficulties are discussed and the preliminary solutions are described
The role of C-terminal amidation in the membrane interactions of the anionic antimicrobial peptide, maximin H5
Maximin H5 is an anionic antimicrobial peptide from amphibians, which carries a C-terminal amide moiety, and was found to be moderately haemolytic (20%). The α-helicity of the peptide was 42% in the presence of lipid mimics of erythrocyte membranes and was found able to penetrate (10.8mNm(-1)) and lyse these model membranes (64 %). In contrast, the deaminated peptide exhibited lower levels of haemolysis (12%) and α-helicity (16%) along with a reduced ability to penetrate (7.8mNm(-1)) and lyse (55%) lipid mimics of erythrocyte membranes. Taken with molecular dynamic simulations and theoretical analysis, these data suggest that native maximin H5 primarily exerts its haemolytic action via the formation of an oblique orientated α-helical structure and tilted membrane insertion. However, the C-terminal deamination of maximin H5 induces a loss of tilted α-helical structure, which abolishes the ability of the peptide's N-terminal and C-terminal regions to H-bond and leads to a loss in haemolytic ability. Taken in combination, these observations strongly suggest that the C-terminal amide moiety carried by maximin H5 is required to stabilise the adoption of membrane interactive tilted structure by the peptide. Consistent with previous reports, these data show that the efficacy of interaction and specificity of maximin H5 for membranes can be attenuated by sequence modification and may assist in the development of variants of the peptide with the potential to serve as anti-infective
Determinação de atributos fĂsicos do solo em solos arenosos por meio de Georadar.
A regiĂŁo central do Brasil Ă© a sua atual fronteira agrĂcola, com rĂĄpida expansĂŁo das culturas de soja, cafĂ© e algodĂŁo sob solos arenosos. Entre os grandes desafios de manejo desse tipo de solo , destaca-se evitar a redução da sua baixa fertilidade natural e manter ou aumentar a umidade. Esse trabalho teve o objetivo de avaliar a aplicabilidade do uso de Radar de Penetração do Solo (GPR) na determinação de atributos de solos arenosos da parte central do Brasil. O estudo foi realizado no Oeste do estado da Bahia, numa ĂĄrea de topografia plana e sob pastagem. Foram amostrados dois perfis completos, cujas amostras foram analisadas quĂmica e fisicamente. A leitura foi realizada em transectos com comprimento acima de 500m. Foi utilizado GPR equipado com antena de 400 MHz. Foram aplicadas as equaçÔes de Topp, Ledieu e CondĂ© para determinação da umidade gravimĂ©trica a partir de valores de constante dielĂ©trica obtidas dos radargramas. Foi observado tratar-se de solos profundos, sem impedimentos fĂsicos e que apresenta aumento da umidade em profundidad
Scale relativity and fractal space-time: theory and applications
In the first part of this contribution, we review the development of the
theory of scale relativity and its geometric framework constructed in terms of
a fractal and nondifferentiable continuous space-time. This theory leads (i) to
a generalization of possible physically relevant fractal laws, written as
partial differential equation acting in the space of scales, and (ii) to a new
geometric foundation of quantum mechanics and gauge field theories and their
possible generalisations. In the second part, we discuss some examples of
application of the theory to various sciences, in particular in cases when the
theoretical predictions have been validated by new or updated observational and
experimental data. This includes predictions in physics and cosmology (value of
the QCD coupling and of the cosmological constant), to astrophysics and
gravitational structure formation (distances of extrasolar planets to their
stars, of Kuiper belt objects, value of solar and solar-like star cycles), to
sciences of life (log-periodic law for species punctuated evolution, human
development and society evolution), to Earth sciences (log-periodic
deceleration of the rate of California earthquakes and of Sichuan earthquake
replicas, critical law for the arctic sea ice extent) and tentative
applications to system biology.Comment: 63 pages, 14 figures. In : First International Conference on the
Evolution and Development of the Universe,8th - 9th October 2008, Paris,
Franc
Nuclear charge radius of He
The root-mean-square (rms) nuclear charge radius of ^8He, the most
neutron-rich of all particle-stable nuclei, has been determined for the first
time to be 1.93(3) fm. In addition, the rms charge radius of ^6He was measured
to be 2.068(11) fm, in excellent agreement with a previous result. The
significant reduction in charge radius from ^6He to ^8He is an indication of
the change in the correlations of the excess neutrons and is consistent with
the ^8He neutron halo structure. The experiment was based on laser spectroscopy
of individual helium atoms cooled and confined in a magneto-optical trap.
Charge radii were extracted from the measured isotope shifts with the help of
precision atomic theory calculations
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