Alternative Model Selection Using Forecast Error Variance Decompositions in Wholesale Chicken Markets

Although Vector Autoregressive models are commonly used to forecast prices, specification of these models remains an issue. Questions that arise include choice of variables and lag length. This article examines the use of Forecast Error Variance Decompositions to guide the econometrician’s model specification. Forecasting performance of Variance Autoregressive models, generated from Forecast Error Variance Decompositions, is analyzed within wholesale chicken markets. Results show that the Forecast Error Variance Decomposition approach has the potential to provide superior model selections to traditional Granger Causality tests.broiler markets, DAGs, forecasting, market structure, VAR, Agribusiness, Demand and Price Analysis, Livestock Production/Industries, Risk and Uncertainty, C53, D4, L1, Q00,

Prepared for Bioterrorism Events? A Study of the Grain and Oilseed Sector

One of the most crucial problems facing the U.S. economy is the possibility of a terrorist attack on its food sector. The implications can be profound for its stakeholders, who are highly dependent on this sector for their economic livelihood as well as their food supplies. The U.S. Bioterrorism Act of 2002 was enacted to improve the ability of the United States to prevent, prepare for and respond to bioterrorism and other public health emergencies. One of the important features of the U.S. Bioterrorism Act of 2002 is its emphasis on prevention, a change from prior legislation that focused on punishments after an incidence had occurred. The U.S. Bioterrorism Act does not address food safety issues in general; its focus is to prevent intentional contamination. The objective of this study was to assess the preparedness to potential bioterrorism in the grain and oilseed sector based on facility security expenditures and history of security breaches. The study was conducted as a research activity under the multistate project NC-1016 “Economic Assessment of Changes in Trade Arrangements, Bio-terrorism Threats and Renewable Fuels Requirements on the U.S. Grain and Oilseed Sector.” In addition to assessing preparedness, the study investigated the relationship between adoption of security measures and breaches in facility security. Finally the study documents, for a small sample, the extent to which grain and oilseed facilities appear to be following regulations that implement the U.S. Bioterrorism Act.bioterrorism, grain and oilseed sector, Bioterrorism Act of 2002, NC-1016, Agribusiness, Agricultural and Food Policy, Marketing, Political Economy, I18, K23, Q13, Q18,

Attitudes of College Students towards Agriculture, Food and the Role of Government

In 2002 and 2007 we surveyed Agribusiness students’ attitudes about agriculture, farming, food and agricultural policies. Responses were analyzed by year and student characteristics including farm background, citizenship and gender. Citizenship was a significant variable explaining differences in agreement with statements. Year and interactions with year were not significant.agricultural policy, farming, logistic regression, student attitudes, Agricultural and Food Policy, Teaching/Communication/Extension/Profession, A13, A22, C42, Q18,

Uncovering the metabolic capacities of H. pylori 26695 using 13C labeling experiments

The determination of nutritional requirements of pathogenic organisms is of great significance for understanding host-pathogen interactions. Despite the knowledge obtained so far concerning amino acid requirements in H. pylori, it is still unclear which are the metabolic pathways used for biosynthesis and catabolism. Thus, information on the carbon flow in this organism is required. Glutamate is a very important metabolite in bacterial metabolism that can be used as a carbon and nitrogen source. 13C flux analysis has been largely applied to characterize phenotypes by quantifying in vivo the carbon fluxes. One of the most important applications of this approach is the identification of active pathways in less-studied organisms. Thus, in order to clarify the metabolic pathways used by H. pylori 26695, 13C labeling experiments with 13C-glutamate were conducted and labeled amino acids in biomass hydrolysates were analyzed by GC-MS. The obtained results confirmed L-glutamate as a potential sole and effective carbon source for H. pylori. Overall, all non-essential amino acids, except proline, presented a 13C labeling pattern. We hypothesized that L-proline is produced from L-arginine, while L-alanine is probably produced from pyruvate by alanine dehydrogenase. Additionally, the full usage of complete TCA cycle, under the conditions used, was also demonstrated

Flexible and user friendly tools for the incorporation of fluxomics data into metabolic models

The measurement of fluxes and the understanding of their control are at the core of Metabolic Engineering (ME). In this context, this work presents two integrated open- source software tools that allow to perform tasks of metabolic flux analysis (MFA). Both are platform independent, written in Java, and interact with the OptFlux framework [1], which also facilitates their communication (Figure 1). OptFlux is a modular open-source software that incorporates tools for strain optimization, i.e., the identification of ME targets. It also provides tools to use stoichiometric metabolic models for phenotype simulation of both wild-type and mutant organisms, using methods such as the well known Flux Balance Analysis (FBA). Graphical user interfaces are made available for every operation and to check the results that are obtained. Moreover, a network visualization system is offered, where simulation results can be added to overlap the network graph. The developed tools exploit OptFluxâ??s capabilities in terms of model interaction, simulation methods and visualization features. The first proposed software, named MetabolIc NEtwork Ratio AnaLysis (MiNeRAl) (Figure 1, bottom), aims at analyzing labeling experiments to infer flux constraints that for stoichiometric models. From a set of measurements of a 13C-labelling experiment, mass isotopomer distribution vectors (MDV) are calculated. If aminoacids are measured, the measured fragments, coupled with a carbon transition map provided by the user, are used to determine their precursors, and the corresponding MDVs are calculated. Based on the set of MDVs, the software uses the carbon transitions to determine the flux ratios that produce a given metabolite through the different pathways. These ratios are probabilistic equations that translate how the 13C-labeling pattern is distributed throughout the metabolic network [2]. Since the calculation of the flux ratios is independent of the flux distribution, this software can be used independently of other flux calculation processes, and the ratios can be further exploited to reduce the degrees of freedom of systems obtained in other MFA approaches [3,4]. The main differentiating characteristics of this tool are, besides being usr-friendly, the fact that it is generic for any type of metabolite fragmentation originating from GC-MS techniques and metabolic network topology. Furthermore, the software is also able to investigate what flux ratio constraints are possible to be inferred for a certain experiment beforehand. On the other hand, the second software application here described, jMFA (Figure 1, top), is focused on using different types of experimental flux data to constrain metabolic models and improve their predictions with a variety of tools. It allows users to define constraints associated with measured fluxes and/ or flux ratios, together with environmental conditions (e.g. media) and reaction/ gene knockouts. The application identifies the set of applicable methods based on the constraints defined from user inputs, allowing to select the desired approach, encompassing algebraic and constraint- based simulation methods (such as Flux Balance Analysis and its variants). Anytime a set of constraints is selected, the software calculates the degrees of freedom of the configured system, and updates the admissible methods depending on whether the system is underdetermined, determined or overdetermined, as shown in Figure 1. A method to perform robustness analysis is also implemented. The integration of jMFA within the OptFlux framework allows the use of different model formats and the integration with complementary methods for phenotype simulation and visualization of the results. Moreover, the flux ratio constraints can be obtained from previous calculations in MiNeRAl, or manually defined by the user. The first option provides a straightforward way to integrate both applications in a ME workflow

Mitochondrial DNA Variants in a Portuguese Population of Patients with Alzheimer’s Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder associated with dementia in late adulthood. Mitochondrial respiratory chain impairment has been detected in the brain, muscle, fibroblasts and platelets of AD patients, indicating a possible involvement of mitochondrial DNA (mtDNA) in the etiology of the disease. Several reports have identified mtDNA mutations in AD patients, but there is no consensual opinion regarding the cause of the impairment. We have studied mtDNA NADH dehydrogenase subunit 1 nucleotides 3337-3340, searching for mutations. Our study group included 129 AD patients and 125 healthy age-matched controls. We have found alterations in two AD patients: one had two already known mtDNA modifications (3197 T-C and 3338 T-C) and the other a novel transition (3199 T-C) which, to our knowledge, has not been described before

Two new cases of de novo small supernumerary marker chromosomes (sSMC) detected at prenatal diagnosis

No Abstract

Le médecin, son patient et ses pairs:Une nouvelle approche de la relation thérapeutique

Les travaux relatifs à la relation thérapeutique ont jusqu'alors négligé un élément décisif: les relations entre médecins. Le cas de la cancérologie révèle que l'attention portée à ces relations est susceptible d'apporter un nouvel éclairage à la compréhension de la relation thérapeutique. En particulier, la concurrence entre médecins sur l'activité et sur la définition du bon traitement représente une incertitude supplémentaire majeure pour chaque médecin dans sa tentative de maîtriser la relation avec son patient. Dès lors, les stratégies médicales d'organisation et de réorganisation locale de la prise en charge peuvent s'analyser comme des tentatives de réduction de cette incertitude. Réciproquement, la relation au patient n'a pas pour seule fin la guérison mais constitue aussi un autre moyen de maîtriser cette incertitude et, consécutivement, d'améliorer les relations thérapeutiques futures : le patient est pour le médecin un moyen d'obtenir de l'information sur les comportements de ses pairs et un moyen d'échange pour entretenir des relations privilégiées avec certains d'entre eux