1,736 research outputs found

    Primordial black hole detection through diffractive microlensing

    Full text link
    Recent observations of gravitational waves motivate investigations for the existence of Primordial Black Holes (PBHs). We propose the observation of gravitational microlensing of distant quasars for the range of infrared to the submillimeter wavelengths by sub-lunar PBHs as lenses. The advantage of observations in the longer wavelengths, comparable to the Schwarzschild radius of the lens (i.e. RschλR_{\rm sch}\simeq \lambda) is the detection of the wave optics features of the gravitational microlensing. The observation of diffraction pattern in the microlensing light curve of a quasar can break the degeneracy between the lens parameters and determine directly the lens mass as well as the distance of the lens from the observer. We estimate the wave optics optical-depth, also calculate the rate of 0.1\sim 0.1 to 0.3\sim 0.3 event per year per a quasar, assuming that hundred percent of dark matter is made of sub-lunar PBHs. Also, we propose a long-term survey of quasars with the cadence of almost one hour to few days to resolve the wave optics features of the light curves to discover PBHs and determine the fraction of dark matter made of sub-lunar PBHs as well as their mass function.Comment: Accepted for publication in PR

    Analysis of Technical Efficiency and Varietal Differences in Pistachio Production in Iran Using a Meta-Frontier Analysis

    Get PDF
    This paper reports on an analysis of technical efficiency and varietal differences in pistachio production in Iran. A random sample of 475 farmers was selected from the province of Kerman in 2003 and 2004. In this study, farmers are classified into three groups according to the variety of tree they planted. The three main varieties of pistachio trees planted are Kalleh- Ghuchi, Fandoghi and Akbari. The technical efficiency indices are computed using three approaches. First, a standard stochastic production frontier was employed using pooled data. Secondly, stochastic frontier production functions were estimated for each variety (separately). Lastly, the meta-frontier approach was used because production varieties and technologies are expected to differ between the three varieties. Use of this method enabled technical efficiency scores to be corrected by the coefficient of the variety-technology gap ratio (VTGR). Estimates of the frontier were obtained assuming a translog functional form. Results indicate that the mean values of technical efficiency in 2003 and 2004 for the pooled frontier, variety group frontiers and meta-frontier across all data are 54 per cent, 55 per cent and 62 per cent, respectively. The mean value of VTGR in 2003 and 2004 varies from 0.58 for the Kalleh-Ghuchi variety to 0.68 for the Fandoghi variety. These results show the importance of taking into account the differences in frontiers imposed by different tree varieties.pistachio, stochastic meta-frontier, production function, technical efficiency, Iranian agriculture, Productivity Analysis, C21, Q12, Q16, Q55, R58,

    Ga and Gß Proteins Regulate the Cyclic AMP Pathway That Is Required for Development and Pathogenicity of the Phytopathogen Mycosphaerella graminicola

    Get PDF
    We identified and functionally characterized genes encoding three G alpha proteins and one G beta protein in the dimorphic fungal wheat pathogen Mycosphaerella graminicola, which we designated MgGpa1, MgGpa2, MgGpa3, and MgGpb1, respectively. Sequence comparisons and phylogenetic analyses showed that MgGPA1 and MgGPA3 are most related to the mammalian G alpha(i) and G alpha(s) families, respectively, whereas MgGPA2 is not related to either of these families. On potato dextrose agar (PDA) and in yeast glucose broth (YGB), MgGpa1 mutants produced significantly longer spores than those of the wild type (WT), and these developed into unique fluffy mycelia in the latter medium, indicating that this gene negatively controls filamentation. MgGpa3 mutants showed more pronounced yeast-like growth accompanied with hampered filamentation and secreted a dark-brown pigment into YGB. Germ tubes emerging from spores of MgGpb1 mutants were wavy on water agar and showed a nested type of growth on PDA that was due to hampered filamentation, numerous cell fusions, and increased anastomosis. Intracellular cyclic AMP (cAMP) levels of MgGpb1 and MgGpa3 mutants were decreased, indicating that both genes positively regulate the cAMP pathway, which was confirmed because the WT phenotype was restored by adding cAMP to these mutant cultures. The cAMP levels in MgGpa1 mutants and the WT were not significantly different, suggesting that this gene might be dispensable for cAMP regulation. In planta assays showed that mutants of MgGpa1, MgGpa3, and MgGpb1 are strongly reduced in pathogenicity. We concluded that the heterotrimeric G proteins encoded by MgGpa3 and MgGpb1 regulate the cAMP pathway that is required for development and pathogenicity in M. graminicola

    Effects of Laminaria digitata and Aschophylum nodossum in controlling white spot disease (WSD) in white leg shrimp (Litopenaeus vannamei)

    Get PDF
    Complementary feedstuff extract from Laminaria digitata and Ascophylum nodossum containing 1% alginic acids as stimulator of immune system in Litopenaeus vannamei for controlling WSSV was used in this study. The test shrimps, Litopenaeus vannamei, in larvae stage (Z1-131,1), post larvae stage (PL1-PLO and juvenile (from day 30 to 40) were fed by complimentary feed stuff as the other test conditions in the test and control group were the same. Both groups were exposed to WSSV after 40 days by oral inoculation. The clinical signs and mortality were recorded for 10 days. The results showed the survival rate of the test group was higher than the control group and it was significant (P<0.05). The results also showed that the mortality in the test group occurred 48 hours later than the control group. This study can lead us to new methods for controlling White Spot Disease

    Simulation model for a nomadic animal production system in Southern Iran.

    Get PDF
    The first motive for the determination and evaluation of an energy production system is the need to change. Such system is dynamic in nature and is influenced by many factors such as age and physiological status of individual sheep or goat, quantity and quality of available feed and environment including the management systems. Traditional pastoral resource assessments do not always account for the complex, interrelated nature of land, forage and livestock. Modeling may overcome the limitations of traditional methods by improving the understanding of complex pastoral systems, and makes fast repetitive analyses, spanning time, incorporating variability and representing more realistically complex interactions possible within the system. The estimated values of metabolisable energy for maintenance and production in this study are based on the results of two feeding systems linked together by grazing the energy intake in the Nomadic Production System (NPS) and the dynamic system modeling used to study the assessment of these complex systems. In this study, validation of model relied on the observations of Torki Ghashghaii (TG) sheep (like those in Bakkan) under pen-fed and integrated rangeland-cropland feeding systems, and was carried out mainly by studying the body weight gain of growing animals and also body weight changes of ewes due to pregnancy and lactation. After validation, the study indicated that the mean value of actual data of male and female lambs (weaners) and ewes were in close agreement with the simulated data. These results validate the generalized structure of energy utilization models of grazing sheep under production sub- systems of NPS. These results will enable the prediction of carrying capacities in any given situation under conditions similar to those in Bakkan

    Specific Resistance Genes in Wheat Chinese Landrace ‘Wangshuibai’ against Two Iranian Mycosphaerella Graminicola Isolates

    Get PDF
    Abstract Septoria tritici blotch, caused by the fungus Mycosphaerella graminicola, is currently the major foliar disease of wheat world-wide, and new sources of resistance and knowledge about the genetics of resistance are needed to improve breeding for resistance against this disease. An F10 recombinant inbred population from a cross between ‘Wangshuibai’ (Chinese landrace) and the susceptible cultivar ‘Seri82’ was tested at seedling stage under controlled greenhouse conditions. Two isolate-specific genes for resistance to Iranian M.graminicola isolates IPO08002 and IPO08003 were detected on Chromosomes 2BL and 7DS, respectively. For both genes the resistance was derived from ‘Wangshuibai’ at positions where Stb9 (on 2BL) and Stb4 (on 7DS) have been reported previously. These two genes are closely linked to microsatellite markers, which can be used for marker-assisted selection. ‘Wangshuibai’ may therefore be a valuable source of resistance to STB for wheat breeding, especially in Mediterranean environments

    Effects of temperature on hematological and histopathological changes and survival rate of juvenile Fenneropenaeus vannamei experimentally challenged to White Spot Virus

    Get PDF
    Many shrimp farmers were suffering from White Spot Disease (WSD) onset in last decades. Oscillation of environmental factors could lead mortality in susceptible hosts. Our study was aimed to investigate the effect of different temperatures on juvenile Fenneropenaeus vannamei experimentally exposed to White Spot Virus (WSV). Five hundred and forty juveniles were distributed among 3 treatments in triplicates, 22, 25 and 30°C and experimentally WSV were injected in the shrimps. Our results showed mortality started at 36 h post inoculation (hpi) in the treatment at 25°C (T25), meanwhile the mean value of mortality percent at 54 hpi in T25 (71.10±17.35) showed the significant difference (p=.045) with T22 (3.33±3.33) and T30 (Not Observed, NO.). Our results suggest that in site selection, in primary stage of farm designing, water temperature at more than 29°C, should be considered as key environmental factor. This finding can lead us that why the White Spot Disease occurred with high mortality in some area when the days of shrimp culture were prolonged until mid autumn
    corecore