1,848 research outputs found

    Disturbing Extremal Behavior of Spot Rate Dynamics

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    This paper presents a study of extreme interest rate movements in the U.S. Federal Funds market over almost a half century of daily observations from the mid 1950s through the end of 2000. We analyze the fluctuations of the maximal and minimal changes in short term interest rates and test the significance of time-varying paths followed by the mean and volatility of extremes. We formally determine the relevance of introducing trend and serial correlation in the mean, and of incorporating the level and GARCH effects in the volatility of extreme changes in the federal funds rate. The empirical findings indicate the existence of volatility clustering in the standard deviation of extremes, and a significantly positive relationship between the level and the volatility of extremes. The results point to the presence of an autoregressive process in the means of both local maxima and local minima values. The paper proposes a conditional extreme value approach to calculating value at risk by specifying the location and scale parameters of the generalized Pareto distribution as a function of past information. Based on the estimated VaR thresholds, the statistical theory of extremes is found to provide more accurate estimates of the rate of occurrence and the size of extreme observations.extreme value theory, volatility, interest rates, value at risk

    Effects of the loading direction on high strain rate behavior of woven graphite/epoxy composites

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    Effects of the loading direction on high strain rate behavior of cylindrical woven graphite/epoxy composites are presented. Compressive split Hopkinson pressure bar (SHPB) was used for high strain rate experiments. Cylindrical specimens were loaded diametrically and transversely at the impact energies of 67 J, 163 J, and 263 J. Micro Laser Raman spectroscopy and scanning electron microscopy (SEM) were used for surface characterization. It is observed that diametrically loaded specimens show permanent plastic deformation with high ductility resulting in a catastrophic failure while transversely loaded specimens exhibit viscoplastic deformation with some recoverable damage. As a result of this, Raman peak shifted to higher values for the diametrically loaded fibers whereas almost no change was observed in the Raman shift of transversely loaded fibers

    Effects of chills on the solidification pattern of an axial steel cast impeller

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    This paper presents three-dimensional simulation of transient conduction heat transfer within an axial impeller (AISI 1016), two different sizes of chills (AISI 1016), core (green sand) and mold (green sand) by using Ansys CFX. Specific heat, density and thermal conductivity of AISI 1016 steel, mold and Core materials are considered as functions of temperature

    Effect of the contact geometry on high strain rate behavior of woven graphite/epoxy composites

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    Effects of the loading direction on high strain rate behavior of cylindrical woven graphite/epoxy composites are presented. Compressive split Hopkinson pressure bar (SHPB) was used for high strain rate experiments. Cylindrical specimens were loaded diametrically and transversely at the impact energies of 67 J, 163 J, and 263 J. Micro Laser Raman spectroscopy and scanning electron microscopy (SEM) were used for surface characterization. It is observed that diametrically loaded specimens show permanent plastic deformation with high ductility resulting in a catastrophic failure while transversely loaded specimens exhibit viscoplastic deformation with some recoverable damage. As a result of this, Raman peak shifted to higher values for the diametrically loaded fibers whereas almost no change was observed in the Raman shift of transversely loaded fibers

    Effects of rhizobium inoculation, sulfur and phosphorus applications on yield, yield components and nutrient uptakes in chickpea ( Cicer arietinum L.)

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    This study was carried out to determine the effects of sulfur and phosphorus application and rhizobium inoculation for a chickpea variety, Aziziye-94, under Eastern Turkey conditions in 2004 and 2005. Thetrial was laid out in split-split block design with three replications. Chickpea variety was applied on three different sulfur levels (0, 50 and 100 kg ha-1), phosphorus levels (0, 40 and 80 kg ha-1) andinoculation (inoculated and uninoculated). Whereas the highest grain yield were obtained from 80 kg ha-1 P with 819 kg ha-1 from 100 kg ha-1 S with 758 and from inoculation with 723 kg ha-1. In the first year, they were obtained from 80 kg ha-1 P with 879 kg ha-1 from 100 kg ha-1 S with 818 and from inoculation with 784 kg ha-1 in the second year. Nutrient uptake by grain of chickpea significantly increased due tosulfur doses, except for P uptake in grain at the year of 2004 and S uptake in grain at the year of 2005. Sulfur application significantly increased the uptake of Fe, Mn, Zn and Cu in grain in the both years. The effects of different doses of phosphorus application on nutrient uptakes by grain were found to be statistically significant in both years

    The Protective Effect of L-carnitine on Ionizing Radiation-induced Free Oxygen Radicals

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    Ionizing radiation is known to generate reactive oxygen species (ROS) that can be removed by antioxidants.  L-carnitine, a natural component of mammalian tissue, is a necessary factor in the utilization of long-chain  fatty acids to produce energy. Furthermore it has been shown that L-carnitine is an antioxidant which has  a scavenger effect on ROS and a stabilizing effect on damaged cell membranes. The aim of the study was  to evaluate the potential protective effect of L-carnitine on radiation-induced free radicals in hamsters. Lcarnitine  was given by gavage at a dose of 50 mg/kg for 15 consecutive days before irradiation with a single  dose of 8 Gy. 24 h after radiation exposure, the hamsters were sacrificed and samples were taken from  blood and tissues, and the biochemical and histopatological determinations were carried out. In the irradiated  group, there were significant increases in plasma and liver malondialdehyde (MDA) with marked  reduction in glutathione (GSH) levels in the liver, compared with controls. In red blood cells, superoxide  dismutase (SOD) and catalase activities were also reduced. All these effects were reversed by L-carnitine.  In conclusion, L-carnitine with its antioxidant and free radical scavenging properties could play a modulatory  role against the cellular damage produced by free radicals induced by ionizing radiation.

    Effects of dietary probiotic and prebiotic supplementation on growth performance and serum IgG concentration of broilers

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    This study was conducted to investigate the effects of probiotic and/or prebiotic supplementation on growth performance and serum IgG concentrations in broilers. One thousand two hundred one-day old Ross-308 broiler chicks of mixed sex were randomly divided into four treatment groups of 300 birds each. The treatments were: Starter diets: 1) Unsupplemented control diet; 2) Probiotic (Bio-Plus 2B® 0.05%); 3) Prebiotic (Bio-Mos® 0.2%); 4) Probiotic and Prebiotic mixture (Bio-Plus 2B® 0.05% and Bio-Mos® 0.2%). The grower diets were: 1) Control with no supplements; 2) Probiotic (Bio-Plus 2B® 0.05%); 3) Prebiotic (Bio-Mos® 0.1%); 4) Probiotic and Prebiotic mixture (Bio-Plus 2B® 0.05% and Bio-Mos® 0.1%). Each treatment group was further sub-divided into five replicates of 60 birds per replicate. The chicks were fed the broiler starter diet for the first 21 d and the broiler grower diet between days 22 and 42. Dietary probiotic and/or prebiotic supplementation did not significantly affect body weight, body weight gain, feed intake, carcass weight, carcass yield or concentration of immunoglobulin (IgG) in the serum. However, feed conversion ratio was improved significantly in the supplemented treatments compared to the unsupplemented control. Probiotic and/or prebiotic supplementation did not significantly affect any of the examined parameters except for an improved feed conversion ratio. Keywords: Probiotic, prebiotic, broilers, performanceSouth African Journal of Animal Science Vol. 38 (1) 2008: pp. 21-2

    Mechanisms linking intimate partner violence and prevention of mother-to-child transmission of HIV: A qualitative study in South Africa.

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    : Prevention of mother-to-child transmission (PMTCT) can virtually eliminate HIV infection among infants, yet up to one-third of women miss PMTCT steps. Little is known about how partner dynamics such as intimate partner violence (IPV) influence pregnant and postpartum women's adherence to PMTCT. We conducted 32 qualitative interviews with HIV-positive pregnant and postpartum women in Johannesburg who experienced IPV. Trained researchers conducted in-depth interviews over the period of May 2014-Nov 2015 using narrative and social constructionist approaches. Interviews were transcribed verbatim and analyzed thematically and inductively using Dedoose qualitative software. Twenty-six women experienced recent IPV and one-third had poor adherence to PMTCT. Women's experience of partner violence influenced PMTCT behaviors through four pathways. First, fear of partner disclosure led some women to hide their HIV status to avoid a violent reaction. Despite strategic non-disclosure, several maintained good adherence by hiding medication or moving out from their partner's home. Second, IPV caused feelings of depression and anxiety that led to intentionally or accidentally missing medication. Five women stopped treatment altogether, in a type of passive suicidality, hoping to end the distress of IPV. Third, men's controlling behaviors reduced access to friends and family, limiting social support needed for good adherence. Fourth, in a protective pathway, women reported good adherence partly due to their mothering role. The identity around motherhood was used as a coping technique, reminding women that their infant's wellbeing depended on their own health. PMTCT is essential to prevent vertical HIV transmission, but women living with IPV face multiple pathways to non-adherence. Addressing IPV in antenatal care can support the health of women and infants and may enhance PMTCT coverage.<br/

    Geometric Morphometric Study and Cluster Analysis of Late Byzantine and Modern Human Crania

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    Inter-population variation of cranial morphology, which plays an important role in human evolution studies and biological research, can be studied morphologically and metrically. Geometric morphometry compares body forms using specific landmarks determined by anatomical prominences. The aim of this study was to identify cranial shape differences between the crania of Byzantium period humans and modern humans. Variability in cranial shape was examined using the geometric morphometric technique based on landmark coordinates. Landmark coordinate data were collected from two-dimensional digital photogrammetry and were analyzed using generalized Procrustes analysis, hierarchical clustering and thin-plate spline analysis
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