1,234 research outputs found

    WAS FAIR FAIR TO U.S. CORN GROWERS? AN ANALYSIS OF THE PAYMENTS OFFERED TO CORN GROWERS UNDER THE 1996 FEDERAL AGRICULTURAL IMPROVEMENT AND REFORM ACT

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    The 1996 Farm Bill (FAIR) dramatically changed agricultural policy for producers of many commodities. A series of 7 annual decoupled payments replaced the deficiency-payment program. Option-pricing techniques are used to determine whether program benefits to corn producers are smaller or larger under the new program than the old.Agricultural and Food Policy,

    Quasi-bound states of Schrodinger and Dirac electrons in magnetic quantum dot

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    The properties of a two-dimensional electron are investigated in the presence of a circular step magnetic field profile. Both electrons with parabolic dispersion as well as Dirac electrons with linear dispersion are studied. We found that in such a magnetic quantum dot no electrons can be confined. Nevertheless close to the Landau levels quasi-bound states can exist with a rather long life time.Comment: 9 pages, 10 figure

    High order discontinuous finite-volume/finite-element method for CFD applications

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    The proposed method naturally merges the desirable conservative properties and intuitive physical formulation of the widely used finite-volume (FV) technique, with the capability of local arbitrary high-order accuracy and high-resolution which is distinctive in the discontinuous finite-element (FE) framework. This relatively novel scheme, the discontinuous hybrid control-volume/finite-element method (DCVFEM), has been already applied to the solution of advection-diffusion problems and shallow-water equations, and is in this paper extended to the Euler equations in the one-dimensional case. The main features are summarized and the scheme is compared to the well established FV and discontinuous Galerkin (DG) methods

    Roles of gibberellic acid and zinc sulphate in increasing size and weight of olive fruit

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    Olive trees (Olea europaea L. cv. Shengeh) were treated with gibberellic acid (GA3) at 0, 15, 30 and 45 ppm and zinc sulphate at 0, 0.25, 0.5 and 0.75% when fruit were at 70% of their final size in experiments carried out in 2007 season. The effect of GA3 and ZnSO4 treatments on yield and some variables related to fruit characteristics (fruit, pit and pulp weight, pulp/pit weight ratio, fruit length and diameter, pit length and diameter, fruit L/D ratio, pit L/D ratio fruit volume) was analyzed. Fruit weight was significantly increased most by concentrations of GA3 and ZnSO4 treatments with respect to control trees, due to an increase in fruit size. GA3 spray at the 30 ppm concentration was more effective in improving yield than spraying GA3 at other concentrations and control. Thus, these treatments accelerated fruit growth of olive, and also increased both fruit size and total yield per tree, allowing for an increase in its economic value. Use of 0.5% ZnSO4 + 30 ppm GA3 treatments was optimum for improvement of olive fruit yield

    Appropriateness of referrals for single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) in a developing community: A comparison between 2005 and 2009 versions of ACCF/ASNC appropriateness criteria

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    Appropriateness of referrals for myocardial perfusion imaging (MPI) in developing countries has not been extensively studied. Our study was conducted to describe the ordering practices of physicians and appropriateness of MPI referrals in Iran. We prospectively applied 2005 and 2009 versions of the Appropriateness Use Criteria published by the American College of Cardiology Foundation (ACCF) and the American Society of Nuclear Cardiology (ASNC) to 291 consecutive patients (age 55.3 ± 10.3 years) who underwent SPECT-MPI. For this purpose, we convened a panel, consisting of two academic cardiologists, one academic clinician in internal medicine, and one academic clinician in nuclear medicine. The panelists were invited for a face-to-face meeting to judge appropriateness of SPECT-MPI and independently assign a specific indication (scenario), whenever possible, for each case in accordance with ACCF/ASNC appropriateness scenarios. Based on the 2005 ACCF/ASNC criteria, SPECT-MPI studies were judged appropriate for 211 (72.5%), uncertain for 36 (12.4%), inappropriate for 32 (11.0%), and unclassifiable for 12 (4.1%) referrals. The same figures based on the 2009 version were 219 (75.3%), 15 (5.2%), 49 (16.8%), and 8 (2.7%) patients, respectively. Overall agreement between the 2005 and 2009 versions was good (κ 0.63). Lack of chest pain and age below 60 years were significant indicators increasing the likelihood of inappropriate referrals by 2.9-3.4 fold. Absence of diabetes mellitus and hypertension, a normal lipid profile, lack of a past history of myocardial infarction or cardiovascular interventions (CABGs or PCI), as well as lack of application and exercise ECG stress test as the gate keeper (keeping abnormal ETT or inability of the patient to perform exercise as the appropriate indication for SPECT-MPI referral) were significant indicators, decreasing the odds of appropriate referrals. Generally a higher percentage of referrals with inappropriate indications had normal MPI. Our study provides an evidence for the fact that SPECT-MPI ordering practices in our developing community largely parallel the ACCF/ASNC recommendations. The implementation of appropriateness criteria is feasible in clinical settings and might provide an alternative to utilization management. © 2011 American Society of Nuclear Cardiology

    Electron Microprobe Chemical Dating of Uraninite as a Reconnaissance Tool for Leucogranite Geochronology

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    We suggest that electron microprobe techniques may be employed to date Tertiary samples of uraninite (UO~2~), which can contain very high concentrations of radiogenic Pb after only a few million of years of U and Th decay. Although uraninite is regarded as a rare accessory mineral, it is relatively abundant in leucogranitic rocks such as those found in the Himalayan orogen. We apply the U-Th-total Pb electron microprobe chemical dating method to a uraninite crystal from a ca. 18.3 Ma dike of the Mugu granite from the Upper Mustang region of central Nepal. With this technique, we calculate a mean chemical date that is consistent with isotope-dilution thermal ionization mass spectrometry (ID-TIMS) U-Pb dates obtained from seven other uraninite grains and a monazite crystal from the same sample. Electron microprobe chemical dating yields results that typically will be an order of magnitude less precise than conventional dates: in the specific case of the Mugu granite, single point chemical dates each have ca. 1.5 Ma 2[sigma] (95%) confidence level uncertainties. However, the mean chemical date of 15 point analyses of the crystal we study has a 2SE (2 standard error) uncertainty of ca. 400 ka, comparable to uncertainties obtained with ID-TIMS. These results show that electron microprobe chemical dating of uraninite has substantial promise as a reconnaissance tool for the geochronology of young granitic rocks. The electron microprobe work also reveals substantial chemical complexity within uraninite that must be taken into account. The analyzed crystal displays a texturally and chemically distinctive core and rim that suggests episodic growth. Concentration gradients in U, Th, and Y across the boundary imply diffusive modification. We estimate the diffusivity of U, Th, and Y in uraninite at ca. 700 °C to be > 10-7 cm2 s-1. In contrast, Pb shows no distinctive concentration gradient across the core-rim boundary, implying that Pb has a much higher diffusivity in uraninite than U, Th, or Y. We estimate that Pb loss of as much as ca. 8.9% has occurred in the uraninite grains we analyzed by ID-TIMS

    Scattering of Dirac electrons by circular mass barriers: valley filter and resonant scattering

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    The scattering of two-dimensional (2D) massless Dirac electrons is investigated in the presence of a random array of circular mass barriers. The inverse momentum relaxation time and the Hall factor are calculated and used to obtain parallel and perpendicular resistivity components within linear transport theory. We found a non zero perpendicular resistivity component which has opposite sign for electrons in the different K and K' valleys. This property can be used for valley filter purposes. The total cross-section for scattering on penetrable barriers exhibit resonances due to the presence of quasi-bound states in the barriers that show up as sharp gaps in the cross-section while for Schr\"{o}dinger electrons they appear as peaks.Comment: 10 pages, 11 figure

    Compare the effect of Consumption CoQ10 Supplement on aerobic power, anaerobic and Muscle soreness in athletes and non athletes

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    زمینه و هدف: کوآنزیم Q10 یک ماده شبه ویتامین محلول در چربی است که حامل ضروری الکترون در میتوکندری می باشد و در تولید انرژی و فعالیت ضد اکسیدانی، نقش مهمی بر عهده دارد. هدف این مطالعه پژوهشی نیمه تجربی، مقایسه اثر مکمل کوآنزیم Q10 بر توان هوازی، بی هوازی و برخی از شاخص های منتخب کوفتگی عضلانی تأخیری پسران ورزشکار و غیر ورزشکار بود. روش بررسی: 60 پسر دانش آموز داوطلب، به روش نمونه در دسترس انتخاب که از بین آن ها و به طور تصادفی 20 نفر با میانگین سن، قد و وزن به ترتیب (80/0±30/16 سال، 6±172 سانتی متر، 55/7±76/62 کیلوگرم) انتخاب که در دو گروه ورزشکار (10 =n) و غیر ورزشکار (10 =n) طبقه بندی شدند. از هر دو گروه 4 مرتبه خونگیری (هر بار 5 سی سی مایع از ورید پیش آرنجی) طی دو مرحله (قبل و بعد از مکمل دهی) به عمل آمد که سطح پایه و تغییرات شاخص های کوفتگی تأخیری (LDH و CK)، با کیت آزمایشگاهی پارس آزمون و با دستگاه اتوآنالایزر AT- آلفا کلاستیک مورد ارزیابی قرار گرفت. قراردادهای ورزشی پژوهش، بروس (با استفاده از نوارگردان، جهت ارزیابی VO2max) و فالکنر (با استفاده از نوارگردان- 9/12 V= کیلومتر بر ساعت و 20 g=، جهت ارزیابی توان بی هوازی) بود. ضریب پایایی آزمون بروس و فالکنر به ترتیب در حدود 95/0 تا 99/0 و 76/0 تا 91/0 است. جهت بررسی تفاوت در مراحل مختلف نمونه گیری، تفاوت های درون گروهی و برون گروهی، از آزمون های آنالیز تحلیل واریانس (ANOVA)، SPSS، تی وابسته و تی مستقل در سطح معنی داری 05/0≥P استفاده شد. یافته ها: یافته های پژوهش نشان داد که مصرف کوتاه مدت مکمل CoQ10 منجر به عدم تغییر معنی دار CK (19/0P=)، LDH (12/0P=)، توان بی هوازی (17/0P=) و توان هوازی (43/0P=) هر دو گروه ورزشکار و غیر ورزشکار شد. نتیجه گیری: به طور کلی نتایج بیانگر این بودند که سطح آمادگی بدنی (مقایسه ورزشکار یا غیر ورزشکار بودن)، تأثیری در اثر مکمل کوآنزیم Q10 بر توان هوازی، بی هوازی و کوفتگی عضلانی نداشت و هر دو گروه به یک اندازه از مکمل بهره بردند

    Bayesian Estimation of Asymmetric Jump-Diffusion Processes

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    The hypothesis that asset returns are normally distributed has been widely rejected. The literature has shown that empirical a\u3c\u3eset returns are highly skewed and Ieptokurtic. The affine jump-diffusion (AJD) model improves upon the normal specification by adding a jump component to the price process. Two important extensions proposed by Ramezani and Zeng (1998) and Kou (2002) further improve the AJD specification by having two jump components in the price process, resulting in the asymmetric affine jump-diffusion (AAJD) specification. The AAJD specification allows the probability distribution of the returns to be asymmetrical. That is, the tails of the distribution are allowed to have dilferent shapes and densities. The empirical literature on the leverage effect shows that the impact of innovations in prices on volatility is asymmetric: declines in stock prices are accompanied by larger increases in volatility than the reverse. The asymmetry in AAJD specification indirectly accounts for the leverage effect and is therefore more consistent with the empirical distributions of asset returns. As a result, the AAJD specification has been widely adopted in the portfolio choice, option pricing, and other branches of the literature. However, because of their complexity, empirical estimation of the AAJD models has received little attention to date. The primary objective of this paper is to contribute to the econometric methods for estimating the parameters of the AAJD models. Specifically, we develop a Bayesian estimation technique. We provide a comparison of the estimated parameters under the Bayesian and maximum likelihood estimation (MLE) methodologies using the S&P 500, the NASDAQ, and selected individual stocks. Focusing on the most recent spectacular market bust (2007-2009) and boom (2009-2010) periods, we examine how the parameter estimates differ under distinctly different economic conditions
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