Covariance estimation via Fourier method in the presence of asynchronous trading and microstructure noise

We analyze the effects of market microstructure noise on the Fourier estimator of multivariate volatilities. We prove that the estimator is consistent in the case of asynchronous data and robust in the presence of microstructure noise. This result is obtained through an analytical computation of the bias and the mean squared error of the Fourier estimator and con¯rmed by Monte Carlo experiments.

A Quarterly Food-at-Home Price Database for the U.S.

This report provides a detailed description of the methodology used to construct ERS’s Quarterly Food-at-Home Price Database (Q-FAHPD). As the name suggest, these data provide quarterly observations on the mean price of 52 food categories for specific U.S. markets. We provide a description of the Nielsen Homescan data that was used to create this database, the methodology used to classify foods into food groups, how we determined the appropriate the level of aggregation (sub-regional markets) and our calculation of average prices for each food group. This report also contains an overview and summary of the resulting data.Nielsen Homescan, food prices, diet quality, market prices, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Health Economics and Policy,

On the polytropic Bondi accretion in two-component galaxy models with a central massive BH

In many investigations involving accretion on a central point mass, ranging from observational studies to cosmological simulations, including semi-analytical modelling, the classical Bondi accretion theory is the standard tool widely adopted. Previous works generalized the theory to include the effects of the gravitational field of the galaxy hosting a central black hole and of electron scattering in the optically thin limit. Here, we apply this extended Bondi problem, in the general polytropic case, to a class of new two-component galaxy models recently presented. In these models, a Jaffe stellar density profile is embedded in a dark matter halo such that the total density distribution follows a r−3 profile at large radii; the stellar dynamical quantities can be expressed in a fully analytical way. The hydrodynamical properties of the flow are set by imposing that the gas temperature at infinity is proportional to the virial temperature of the stellar component. The isothermal and adiabatic (monoatomic) cases can be solved analytically; in the other cases, we explore the accretion solution numerically. As non-adiabatic accretion inevitably leads to an exchange of heat with the ambient, we also discuss some important thermodynamical properties of the polytropic Bondi accretion and provide the expressions needed to compute the amount of heat exchanged with the environment as a function of radius. The results can be useful for the subgrid treatment of accretion in numerical simulations, as well as for the interpretation of observational dat

Can Food Stamps Do More to Improve Food Choices? An Economic Perspective

Food stamp recipients, like other Americans, struggle with nutrition problems associated with choice of foods, as well as amounts. This series of Economic Information Bulletins compiles evidence to help answer the question of whether the Food Stamp Program can do more to improve the food choices of participants. It examines the role of affordability and price of healthful foods in influencing food choices and the likely success of any policy targeted at changing food choices through food stamp bonuses or restrictions. It also examines other approaches to changing food choices, including nutrition education and potential strategies drawn from behavioral economics literature. Meaningful improvements in the diets of food stamp recipients will likely depend on a combination of many tactics. Measuring the effect of any policy change on food choices and health outcomes remains a challenge.Food Stamp Program, food consumption, food prices, food expenditures, nutrition education, behavioral economics, food choices, diet, health, fruits and vegetables, Food Assistance and Nutrition Research Program, FANRP, ERS, USDA, Agricultural and Food Policy, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics,

Role of microRNAs in translation regulation and cancer

MicroRNAs (miRNAs) are pervasively expressed and regulate most biological functions. They function by modulating transcriptional and translational programs and therefore they orchestrate both physiological and pathological processes, such as development, cell differentiation, proliferation, apoptosis and tumor growth. miRNAs work as small guide molecules in RNA silencing, by negatively regulating the expression of several genes both at mRNA and protein level, by degrading their mRNA target and/or by silencing translation. One of the most recent advances in the field is the comprehension of their role in oncogenesis. The number of miRNA genes is increasing and an alteration in the level of miRNAs is involved in the initiation, progression and metastases formation of several tumors. Some tumor types show a distinct miRNA signature that distinguishes them from normal tissues and from other cancer types. Genetic and biochemical evidence supports the essential role of miRNAs in tumor development. Although the abnormal expression of miRNAs in cancer cells is a widely accepted phenomenon, the cause of this dysregulation is still unknown. Here, we discuss the biogenesis of miRNAs, focusing on the mechanisms by which they regulate protein synthesis. In addition we debate on their role in cancer, highlighting their potential to become therapeutic targets

Diffusion tensor magnetic resonance imaging of prostate cancer

Purpose: To explore the feasibility of 3 T magnetic resonance (MR) diffusion tensor imaging (DTI) and fiber tracking (FT) in patients with prostate cancer. Materials and methods: Thirty consecutive patients (mean age, 62.5 years) with biopsy proven prostate cancer underwent 3 T-MR imaging (MRI) and DTI using a 6-channel external phased-array coil before radical prostatectomy. Regions of interest of 14 pixels were defined in tumors and nonaffected areas in the peripheral zone (PZ) and central gland (CG), according to histopatology after radical prostatectomy. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were determined. Differences in mean ADC and FA values among prostate cancer, normal PZ and CG were compared by 2-sided Student t test. The predominant diffusion direction of the prostate anisotropy was color coded on a directionally encoded color (DEC) map. A 3D reconstruction of fiber tract orientations of the whole prostate was determined using the continuous tracking method. The overall image quality for tumor localization and local staging was assessed in retrospective matching with whole-mount section histopathology images. Nodules detected at MRI were classified as matched lesions if tumor presence and extension were evidenced at histopathology. Results: For all the patients, the DTI sequence images were suitable for the evaluation of the zonal anatomy of the prostate gland and the tumor localization. Quantitative evaluation of the regions of interest (ROIs) showed a mean ADC value significantly lower in the peripheral neoplastic area (1.06 0.37 10 3 mm2/s) than in the normal peripheral portion (1.95 0.38 10 3 mm2/s) (P 0.05). The mean FA values calculated in the normal peripheral (0.47 0.04) and central area (0.41 0.08) were very similar (P 0.05). The mean FA values in the neoplastic lesion (0.27 0.05) were significantly lower (P 0.05) than in the normal peripheral area and in the normal central and adenomyomatous area. DEC showed a top-bottom type preferential direction in the peripheral but not in the central area, with the tumor lesions reducing the diffusion coding direction represented as color zones tending toward gray. Tractographic analysis permitted good delineation of the prostate anatomy (capsule outline, peripheral and central area borders) and neoplastic lesion extension and capsule infiltration compared with histopathology. Conclusions: Three tesla DTI of the prostate gland is feasible and has the potential for providing improved diagnostic information

Carbon-enhanced stars with short orbital and spin periods

Many characteristics of dwarf carbon stars are broadly consistent with a binary origin, including mass transfer from an evolved companion. While the population overall appears to have old-disc or halo kinematics, roughly 2 per cent of these stars exhibit Hα emission, which in low-mass main-sequence stars is generally associated with rotation and relative youth. Its presence in an older population therefore suggests either irradiation or spin-up. This study presents time-series analyses of photometric and radial-velocity data for seven dwarf carbon stars with Hα emission. All are shown to have photometric periods in the range 0.2–5.2 d, and orbital periods of similar length, consistent with tidal synchronisation. It is hypothesised that dwarf carbon stars with emission lines are the result of close-binary evolution, indicating that low-mass, metal-weak or metal-poor stars can accrete substantial material prior to entering a common-envelope phase