Quasi-periodic pulsations in the gamma-ray emission of a solar flare

Quasi-periodic pulsations (QPPs) of gamma-ray emission with a period of about 40 s are found in a single loop X-class solar flare on 2005 January 1 at photon energies up to 2-6 MeV with the SOlar Neutrons and Gamma-rays (SONG) experiment aboard the CORONAS-F mission. The oscillations are also found to be present in the microwave emission detected with the Nobeyama Radioheliograph, and in the hard X-ray and low energy gamma-ray channels of RHESSI. Periodogram and correlation analysis shows that the 40 s QPPs of microwave, hard X-ray, and gamma-ray emission are almost synchronous in all observation bands. Analysis of the spatial structure of hard X-ray and low energy (80-225 keV) gamma-ray QPP with RHESSI reveals synchronous while asymmetric QPP at both footpoints of the flaring loop. The difference between the averaged hard X-ray fluxes coming from the two footpoint sources is found to oscillate with a period of about 13 s for five cycles in the highest emission stage of the flare. The proposed mechanism generating the 40 s QPP is a triggering of magnetic reconnection by a kink oscillation in a nearby loop. The 13 s periodicity could be produced by the second harmonics of the sausage mode of the flaring loop

Earth resources evaluation for New Mexico by LANDSAT-2

The author has identified the following significant results. The Middle Rio Grande project has not yet progressed to the point where mineral exploration sites can be chosen; however, there does appear to be some correlation between the known structure and mineral deposits and the LANDSAT lineament map. A circular feature identified in the southern Magdalena Mountains on LANDSAT-1 imagery agrees well with the location of a newly proposed caldron complex. Several recognized and unrecognized circular features were identified on imagery of the Mogollon-Datil volcanic field. A check of aeromagnetic maps for New Mexico found that the circular features on the LANDSAT imagery showed up as areas of generally high magnetic intensity

Monomorphic subtelomeric DNA in the filamentous fungus, Metarhizium anisopliae, contains a RecQ helicase-like gene.

In most filamentous fungi, telomere-associated sequences (TASs) are polymorphic, and the presence of restriction fragment length polymorphisms (RFLPs) may permit the number of chromosome ends to be estimated from the number of telomeric bands obtained by restriction digestion. Here, we describe strains of Metarhizium, Gliocladium and Paecilomyces species in which only one or a few telomeric bands of unequal intensity are detectable by Southern hybridization, indicating that interchromosomal TAS exchange occurs. We also studied an anomalous strain of Metarhizium anisopliae, which produces polymorphic telomeric bands larger than 8 kb upon digestion of genomic DNA with XhoI. In this case, the first XhoI site in from the chromosome end must lie beyond the presumed monomorphic region. Cloned telomeres from this strain comprise 18?26 TTAGGG repeats, followed at the internal end of the telomere tract by five repeats of the telomere-like sequence TAAACGCTGG. An 8.1-kb TAS clone also contains a gene for a RecQ-like helicase, designated TAH1, suggesting that this TAS is analogous to the Y elements in yeast and the subtelomeric helicase ORFs of Ustilago maydis (UTASRecQ) and Magnaporthe grisea (TLH1). The TAS in the anomalous strain of M. anisopliae, however, appears distinct from these in that it is found at most telomeres and its predicted protein product possesses a significantly longer N-terminal region in comparison to the M. grisea and U. maydis helicases. Hybridization analyses showed that TAH1 homologues are present in all other anomalous M. anisopliae strains studied, as well as in some other polymorphic strains, where the recQ-like gene also appears to be telomere-associated.Published online: 2 June 2005

Quasi-periodic pulsations in the gamma-ray emission of a solar flare

Copyright © 2010 American Astronomical Society / IOP PublishingQuasi-periodic pulsations (QPPs) of gamma-ray emission with a period of about 40 s are found in a single loop X-class solar flare on 2005 January 1 at photon energies up to 2-6 MeV with the SOlar Neutrons and Gamma-rays (SONG) experiment aboard the CORONAS-F mission. The oscillations are also found to be present in the microwave emission detected with the Nobeyama Radioheliograph, and in the hard X-ray and low energy gamma-ray channels of RHESSI. Periodogram and correlation analysis shows that the 40 s QPPs of microwave, hard X-ray, and gamma-ray emission are almost synchronous in all observation bands. Analysis of the spatial structure of hard X-ray and low energy (80-225 keV) gamma-ray QPP with RHESSI reveals synchronous while asymmetric QPP at both footpoints of the flaring loop. The difference between the averaged hard X-ray fluxes coming from the two footpoint sources is found to oscillate with a period of about 13 s for five cycles in the highest emission stage of the flare. The proposed mechanism generating the 40 s QPP is a triggering of magnetic reconnection by a kink oscillation in a nearby loop. The 13 s periodicity could be produced by the second harmonics of the sausage mode of the flaring loop

Efeito de compostos orgânicos voláteis de Trichoderma spp. no crescimento de Sclerotinia sclerotiorum (Lib.) de Bary.

Fungos do gênero Trichoderma apresentam potencial relevante para o controle de doenças de plantas devido aos seus diversos mecanismos de ação, como a produção de compostos orgânicos voláteis (COVs). O fungo fitopatogênico Sclerotinia sclerotiorum (Lib.) de Bary causa a doença denominada mofo-branco, podridão-de-esclerotinia ou murcha-deesclerotinia, em diversas espécies vegetais. O objetivo deste trabalho foi avaliar os efeitos de COVs produzidos por diferentes linhagens de Trichoderma no crescimento e na morfologia do micélio de S. sclerotiorum. Os ensaios foram realizados em laboratório por meio de testes de placa invertida com avaliação da inibição do crescimento micelial e análises microscópicas das hifas de S. sclerotiorum. Os melhores resultados foram obtidos a partir da linhagem de Trichoderma sp. CEN 1241, com até 35% de inibição do crescimento micelial de S. sclerotiorum. Todas as linhagens de Trichoderma testadas diminuíram a espessura do micélio do patógeno. A diversidade de espécies de Trichoderma e de COVs produzidos por linhagens desse fungo podem possibilitar o desenvolvimento de estratégias de uso de tais compostos no controle de doenças de plantas.bitstream/item/197397/1/Boletim-Trichoderma-3466.pd

Seleção in vitro de linhagens de Trichoderma para controle da podridão-branca do alho e da cebola.

A podridão-branca é uma doença causada pelo fungo Sclerotium cepivorum que ataca as aliáceas, em todas as regiões de cultivo. O fungo Trichoderma vem sendo utilizado no controle de várias doenças de plantas de importância agrícola e apresenta-se como uma das melhores alternativas para o controle da podridão-branca, em cultivos de alho e cebola. Doze linhagens pertencentes a seis espécies de Trichoderma previamente identificadas, isoladas de solos de cultivo de alho e cebola foram utilizadas neste estudo. As linhagens foram analisadas quanto ao potencial de proteção de plantas, pela promoção de crescimento ou supressão do patógeno, sendo também analisadas quanto à sensibilidade ao extrato de alho. Experimentos in vitro mostraram que a linhagem CEN1416 de T. harzianum destacou-se, apresentando efeito positivo nas plantas cultivadas in vitro e inoculadas com o patógeno, as quais diferiram significativamente no crescimento de raiz e parte aérea. Esta linhagem também apresentou bom crescimento em meio contendo extrato de alho, enquanto algumas outras foram totalmente inibidas, como no caso da linhagem CEN1418 de T. asperellum. Estes resultados são importantes, pois trazem novos parâmetros para seleção de linhagens de Trichoderma ativos contra S. cepivorum. Estudos complementares estão sendo desenvolvidos, envolvendo o isolado CEN1416, para confirmar seu potencial de biocontrole da podridão-branca do alho e da cebola.bitstream/item/176100/1/Trichodermafinal.pd

Effects of crack tip geometry on dislocation emission and cleavage: A possible path to enhanced ductility

We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughness of the material by several orders of magnitude. We thus propose an atomic-scale mechanism at the crack tip, that ultimately may lead to a high fracture toughness in some materials where a sharp crack would seem to be able to propagate in a brittle manner. Results for blunt cracks loaded in mode II are also presented.Comment: 12 pages, REVTeX using epsfig.sty. 13 PostScript figures. Final version to appear in Phys. Rev. B. Main changes: Discussion slightly shortened, one figure remove

Quasi-Periodic Pulsations in Solar Flares: new clues from the Fermi Gamma-Ray Burst Monitor

In the last four decades it has been observed that solar flares show quasi-periodic pulsations (QPPs) from the lowest, i.e. radio, to the highest, i.e. gamma-ray, part of the electromagnetic spectrum. To this day, it is still unclear which mechanism creates such QPPs. In this paper, we analyze four bright solar flares which show compelling signatures of quasi-periodic behavior and were observed with the Gamma-Ray Burst Monitor (\gbm) onboard the Fermi satellite. Because GBM covers over 3 decades in energy (8 keV to 40 MeV) it can be a key instrument to understand the physical processes which drive solar flares. We tested for periodicity in the time series of the solar flares observed by GBM by applying a classical periodogram analysis. However, contrary to previous authors, we did not detrend the raw light curve before creating the power spectral density spectrum (PSD). To assess the significance of the frequencies we made use of a method which is commonly applied for X-ray binaries and Seyfert galaxies. This technique takes into account the underlying continuum of the PSD which for all of these sources has a P(f) ~ f^{-\alpha} dependence and is typically labeled red-noise. We checked the reliability of this technique by applying it to a solar flare which was observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) which contains, besides any potential periodicity from the Sun, a 4 s rotational period due to the rotation of the spacecraft around its axis. While we do not find an intrinsic solar quasi-periodic pulsation we do reproduce the instrumental periodicity. Moreover, with the method adopted here, we do not detect significant QPPs in the four bright solar flares observed by GBM. We stress that for the purpose of such kind of analyses it is of uttermost importance to appropriately account for the red-noise component in the PSD of these astrophysical sources.Comment: accepted by A&