Simultaneous electronphoton excitation of helium in a CO2 laser field

International audienceThe R-matrix Floquet method is used to study electron-impact excitation of helium in the presence of a CO 2 laser field, for collision energies between 19 and 21.5 eV and laser intensities of 10 7 and 10 8 W cm −2. Collision geometries with the electron incident at various angles to the laser polarization axis are considered. The signal for production of metastable states is in good agreement with the results of a low-frequency approximation and a semi-classical approach, while agreement with experiment is reasonable

Bis(guanidinium) tetra­iodidomercurate(II)

The Hg atom in the crystal structure of the title compound, (CH6N3)2[HgI4], is tetra­hedrally coordinated by four I atoms. The [HgI4]2− ions are inter­connected to the [C(NH2)3]+ ions by N—H⋯I hydrogen bonds, forming a three-dimensional network. The four different observed Hg—I distances [2.760 (2), 2.7762 (15), 2.8098 (14) and 2.833 (2) Å] are consistent with four different 127I NQR frequencies observed, showing the existence of four unique I atoms in the tetra­iodidomercurate unit

Duality cascade of softly broken supersymmetric theories

We study the duality cascade of softly broken supersymmetric theories. We investigate the renormalization group (RG) flow of SUSY breaking terms as well as supersymmetric couplings. It is found that the magnitudes of SUSY breaking terms are suppressed in most regimes of the RG flow through the duality cascade. At one stage of cascading, the gaugino mass of the strongly coupled sector and scalar masses converge to certain values, which are determined by the gauge coupling and the gaugino mass of the weakly coupled sector. At the next stage, the strongly and weakly coupled sectors are interchanged with each other. We also show the possibility that cascading would be terminated by the gauge symmetry breaking, which is induced by the so-called B-term.Comment: 25 pages, 5 figure

Estudo de mecanismos usados por leveduras no biocontrole de fitopatógenos causadores de doenças pós-colheita de frutas.

Muitos produtores ainda utilizam agrotóxicos no tratamento pós-colheita, provocando a contaminação química da fruta e colocando em risco a saúde da população. O controle biológico é um método alternativo que não deixa resíduos tóxicos. O presente trabalho teve como objetivo estudar os mecanismos de ação envolvidos no biocontrole das leveduras: Sporodiobolus pararoseus, Pichia spp, Pichia membranifaciens, Pichia guilliermondii, Sporobolomyces roseus, Debaryomyces hansenii e Rhodotorula mucilagenosa, sobre o crescimento micelial de Penicillium digitatum de citros e de Fusarium pallidoroseum de melão. Nos estudos de voláteis foram usadas placas bipartidas contendo BDA e colocado em um dos lados a suspensão de levedura e no outro, disco de micélio do fungo. Para avaliação da capacidade de inibição ao crescimento foram realizados dois experimentos. No primeiro, espalhou-se em placas contendo o meio BDA a suspensão com um fungo e após a superfície seca foram adicionados discos estéreis de papel de filtro, previamente imersos em suspensão de leveduras. No segundo experimento, depositou-se em uma extremidade da placa um disco de micélio e no outro lado fizeram-se riscos paralelos com a suspensão da levedura, da borda da placa até o centro. Em ambos os testes as placas foram fechadas e mantidas em BOD a 25 ± 2 oC sob fotoperíodo de 12 h, avaliando-se, diariamente, o crescimento da colônia. Observou-se que, para todas as combinações de fungos e leveduras avaliadas, compostos voláteis não estão envolvidos no biocontrole. Nos estudos sobre antibiose e competição, observou-se que, ao invés do halo de inibição, formou-se, ao redor dos discos embebidos com as leveduras, uma zona de crescimento, que impedia o desenvolvimento dos fungos, diferindo significativamente da testemunha. De maneira similar, os fungos não conseguiram crescer entre os riscos de leveduras e nas proximidades deles, destacando-se a levedura S. roseus. Sugere-se que os principais mecanismos envolvidos no biocontrole das espécies de leveduras avaliadas são: a antibiose e a competição por nutrientes. Abstract: Many producers still use pesticides on post-harvest treatment, causing chemical contamination of fruit and endangering the health of the population. Biological control is an alternative method that leaves no toxic residues. The present work aimed to study the mechanisms of action involved in biocontrol of yeasts: Sporodiobolus pararoseus, Pichia membranifaciens Pichia spp, Pichia guilliermondii, Debaryomyces hansenii and Rhodotorula mucilagenosa, against mycelial growth of Penicillium digitatum of citrus and Fusarium pallidoroseum of melon. On the study of volatile, split Petri dishes containing PDA medium were used, placing on one side the suspension of yeast and fungus mycelium disc on the other side. About antibiosis and competition were carried out two experiments. In the first one, it was spread on Petri dishes, containing the PDA medium, the suspension of the fungus and after the surface was dried, sterile filter paper disks, previously immersed in the suspension of yeast were added. In the second experiment, it was placed on one side of the Petri dishes a mycelium disk and on the other side, parallel risks with the yeast suspension were done, from the edge of the dish to the center. In both tests, the Petri dishes were sealed and kept in BOD to 25 ± 2° C under photoperiod of 12h, evaluating daily the mycelium growth. It was observed that, for all combinations of fungi and yeasts evaluated, the emission of gases probably was not the mechanism involved in biocontrol. About the studies of antibiosis and competition, it was observed that instead of inhibition halo there was a growing zone of yeasts around the disks soaked with them where the fungi did not developed, differing significantly from the control. Similarly, fungi failed to grow between the risks of yeast and near them, especially the yeast S. roseus. It can be suggested that the main mechanisms involved in biocontrol species of evaluated yeasts are antibiosis and competition for nutrients

Aplicação de tratamento hidrotérmico por aspersão, sobre escovas rolantes, no controle do bolor verde em laranja.

Atualmente o mercado vem exigindo alimentos sem a presença de resíduos químicos, mas a incerteza quanto à sanidade das frutas tem levado os produtores a utilizar agrotóxicos, no tratamento pós-colheita, provocando a contaminação química da fruta, colocando em risco a saúde do consumidor. Assim o presente trabalho teve como objetivo determinar os binômios de tempo e temperatura para o controle do bolor verde, para subsidiar a pesquisa sobre o uso do tratamento térmico, visando disponibilizar uma técnica limpa no tratamento pós-colheita de laranja que não deixe resíduo tóxico. Os frutos passaram pelos tratamento hidrotérmicos: de aspersão de água quente a 52oC durante 60 s e nas temperaturas: 55, 60, 65 e 70oC, durante 30 s e imersão em água à temperatura de 52oC durante 2 min e em seguida, aspersão de água a 20oC, durante dois minutos, para encerrar o efeito do tratamento térmico. Os tratamentos foram comparados ao fungicida thiabendazole e a testemunha que foi tratada com aspersão de água a 20oC durante 30 s. Analisando-se os resultados, observou-se que, logo na primeira avaliação aos 8 dias de armazenamento, em ambiente refrigerado, o tratamento testemunha já apresentava ao redor de 90% de frutas com sintoma da doença, que evoluiu rapidamente para 100%, enquanto que frutos que receberam o tratamento hidrotérmico iniciaram com níveis baixos de incidência, que evoluíram gradativamente ao longo do período de armazenamento. Observou-se resultados similares na avaliação da severidade da doença, destacando-se os tratamentos por imersão a 52 oC durante 2 min e na mesma temperatura por aspersão durante 60 s. Abstract: Currently the market is demanding food without the presence of chemical residues, but uncertainty as to the sanity of the fruit has led producers to use pesticides in post-harvest treatments, causing chemical contamination of fruit placing at risk the health of the consumer. Thus, the present work had as objective to determine the binomials of time and temperature for the control of green mold, to subsidize research on use of heat treatment, aiming to provide a clean technique in the post-harvest treatment of orange that does not leave toxic residue. The fruits have passed by hydrothermal treatment: hot water sprinkler at 52° C during 60 s and at temperatures: 55, 60, 65 and 70°C for 30 s and immersion in water at temperature of 52° C for two minutes and then sprinkling water at 20°C for two minutes, to finish the effect of heat treatment. The treatments were compared to the fungicide thiabendazole and control, by sprinkling water at 20oC for 30 s. Analyzing the results, it was observed that at the first assessment 8 days of storage in refrigerated environment, while control has presented around 90% of fruit with the symptom of the disease, which evolved quickly to 100%. Fruit treated with hydrothermal treatment started with low levels of incidence, which evolved gradually over the period of storage. Similar results were obtained for severity evaluation, highlighting the immersion treatment at 52°C water during two minutes and at the same temperature by sprinkling during 60 s

Guanidinium tetra­bromidomercurate(II)

The Hg atoms in the crystal structure of the title compound, (CH6N3)2[HgBr4], are tetra­hedrally coordinated by four Br atoms and the resulting [HgBr4]2− tetra­hedral ions are linked to the [C(NH2)3]+ ions by bromine–hydrogen bonds, forming a three-dimensional network. In the structure, the anions are located on special positions. The two different Hg⋯Br distances of 2.664 (1) and 2.559 (1) Å observed in the tetra­bromidomercurate unit are due to the connection of Br atoms to different number of H atoms

Critical points and resonance of hyperplane arrangements

If F is a master function corresponding to a hyperplane arrangement A and a collection of weights y, we investigate the relationship between the critical set of F, the variety defined by the vanishing of the one-form w = d log F, and the resonance of y. For arrangements satisfying certain conditions, we show that if y is resonant in dimension p, then the critical set of F has codimension at most p. These include all free arrangements and all rank 3 arrangements.Comment: revised version, Canadian Journal of Mathematics, to appea

Suppressed supersymmetry breaking terms in the Higgs sector

We study the little hierarchy between mass parameters in the Higgs sector and other SUSY breaking masses. This type of spectrum can relieve the fine-tuning problem in the MSSM Higgs sector. Our scenario can be realized by superconformal dynamics. The spectrum in our scenario has significant implications in other phenomenological aspects like the relic abundance of the lightest neutralino and relaxation of the unbounded-from-below constraints.Comment: 14 pages, late