Propensities, Chance, Causation, And Contrastive Explanation

A pragmatic account of scientific understanding is used both to examine and to unify fundamental questions concerning the propensity interpretation of probability and theories of chance, causation, and explanation. One of the most important problems to be addressed is the problem of defining homogeneous reference classes in theories of chance, causation, and explanation. The consistency of the propensity interpretation is defended against traditional criticisms such as Humphreys\u27s paradox. It is demonstrated that the application of this interpretation to theories of chance and probabilistic causation provides insights into problems common to both theories. Various approaches to causation are examined, including those based on identifying sufficient causal factors, necessary causal factors, and contrastive causes. These insights are applied to quantum mechanics and are presented in terms of a set of controlled experiments. The study of quantum mechanics focuses on the paradox of the two slit experiment and quantum logical and quantum probabilistic attempts to resolve this paradox. Finally, the analysis of chance and causation provides the basis for a version of the contrastive theory of explanation. This theory of explanation provides a unique understanding of the nature of explanation, and lessens the impact of the problems of homogeneity and of explanatory ambiguity

Solving the Coulomb scattering problem using the complex scaling method

Based on the work of Nuttall and Cohen [Phys. Rev. {\bf 188} (1969) 1542] and Resigno et al{} [Phys. Rev. A {\bf 55} (1997) 4253] we present a rigorous formalism for solving the scattering problem for long-range interactions without using exact asymptotic boundary conditions. The long-range interaction may contain both Coulomb and short-range potentials. The exterior complex scaling method, applied to a specially constructed inhomogeneous Schr\"odinger equation, transforms the scattering problem into a boundary problem with zero boundary conditions. The local and integral representations for the scattering amplitudes have been derived. The formalism is illustrated with numerical examples.Comment: 3 pages, 3 figure

De novo assembly of a genome-wide transcriptome map of Vicia faba (L.) for transfer cell research

Vicia faba (L.) is an important cool-season grain legume species used widely in agriculture but also in plant physiology research, particularly as an experimental model to study transfer cell (TC) development. TCs are specialized nutrient transport cells in plants, characterized by invaginated wall ingrowths with amplified plasma membrane surface area enriched with transporter proteins that facilitate nutrient transfer. Many TCs are formed by trans-differentiation from differentiated cells at apoplasmic/symplasmic boundaries in nutrient transport. Adaxial epidermal cells of isolated cotyledons can be induced to form functional TCs, thus providing a valuable experimental system to investigate genetic regulation of TC trans-differentiation. The genome of V. faba is exceedingly large (ca. 13 Gb), however, and limited genomic information is available for this species. To provide a resource for future transcript profiling of epidermal TC differentiation, we have undertaken de novo assembly of a genome-wide transcriptome map for V. faba. Illumina paired-end sequencing of total RNA pooled from different tissues and different stages, including isolated cotyledons induced to form epidermal TCs, generated 69.5 M reads, of which 65.8 M were used for assembly following trimming and quality control. Assembly using a De-Bruijn graph-based approach generated 21,297 contigs, of which 80.6% were successfully annotated against GO terms. The assembly was validated against known V. faba cDNAs held in GenBank, including transcripts previously identified as being specifically expressed in epidermal cells across TC trans-differentiation. This genome-wide transcriptome map therefore provides a valuable tool for future transcript profiling of epidermal TC trans-differentiation, and also enriches the genetic resources available for this important legume crop species

Identification of candidate transcriptional regulators of epidermal transfer cell development in Vicia faba cotyledons

Transfer cells (TCs) are anatomically-specialized cells formed at apoplasmic-symplasmic bottlenecks in nutrient transport pathways in plants. TCs form invaginated wall ingrowths which provide a scaffold to amplify plasma membrane surface area and thus increase the density of nutrient transporters required to achieve enhanced nutrient flow across these bottlenecks. Despite their importance to nutrient transport in plants, little is known of the transcriptional regulation of wall ingrowth formation. Here, we used RNA-Seq to identify transcription factors putatively involved in regulating epidermal TC development in cotyledons of Vicia faba. Comparing cotyledons cultured for 0, 3, 9, and 24 h to induce trans-differentiation of epidermal TCs identified 43 transcription factors that showed either epidermal-specific or epidermal–enhanced expression, and 10 that showed epidermal-specific down regulation. Members of the WRKY and ethylene-responsive families were prominent in the cohort of transcription factors showing epidermal-specific or epidermal–enhanced expression, consistent with the initiation of TC development often representing a response to stress. Members of the MYB family were also prominent in these categories, including orthologs of MYB genes involved in localized secondary wall deposition in Arabidopsis thaliana. Among the group of transcription factors showing down regulation were various homeobox genes and members of the MADs-box and zinc-finger families of poorly defined functions. Collectively, this study identified several transcription factors showing expression characteristics and orthologous functions that indicate likely participation in transcriptional regulation of epidermal TC development in V. faba cotyledons

Gauge field theories with covariant star-product

A noncommutative gauge theory is developed using a covariant star-product between differential forms defined on a symplectic manifold, considered as the space-time. It is proven that the field strength two-form is gauge covariant and satisfies a deformed Bianchi identity. The noncommutative Yang-Mills action is defined using a gauge covariant metric on the space-time and its gauge invariance is proven up to the second order in the noncommutativity parameter.Comment: Dedicated to Ioan Gottlieb on the occasion of his 80th birthday anniversary. 12 page

ISRU Reactant, Fuel Cell Based Power Plant for Robotic and Human Mobile Exploration Applications

Three basic power generation system concepts are generally considered for lander, rover, and Extra-Vehicular Activity (EVA) assistant applications for robotic and human Moon and Mars exploration missions. The most common power system considered is the solar array and battery system. While relatively simple and successful, solar array/battery systems have some serious limitations for mobile applications. For typical rover applications, these limitations include relatively low total energy storage capabilities, daylight only operating times (6 to 8 hours on Mars), relatively short operating lives depending on the operating environment, and rover/lander size and surface use constraints. Radioisotope power systems are being reconsidered for long-range science missions. Unfortunately, the high cost, political controversy, and launch difficulties that are associated with nuclear-based power systems suggests that the use of radioisotope powered landers, rovers, and EVA assistants will be limited. The third power system concept now being considered are fuel cell based systems. Fuel cell power systems overcome many of the performance and surface exploration limitations of solar array/battery power systems and the prohibitive cost and other difficulties associated with nuclear power systems for mobile applications. In an effort to better understand the capabilities and limitations of fuel cell power systems for Moon and Mars exploration applications, NASA is investigating the use of in-Situ Resource Utilization (ISRU) produced reactant, fuel cell based power plants to power robotic outpost rovers, science equipment, and future human spacecraft, surface-excursion rovers, and EVA assistant rovers. This paper will briefly compare the capabilities and limitations of fuel cell power systems relative to solar array/battery and nuclear systems, discuss the unique and enhanced missions that fuel cell power systems enable, and discuss the common technology and system attributes possible for robotic and human exploration to maximize scientific return and minimize cost and risk to both. Progress made to date at the Johnson Space Center on an ISRU producible reactant, Proton Exchange Membrane (PEM) fuel cell based power plant project to demonstrate the concept in conjunction with rover applications will be presented in detail

Food- and Health-Related Correlates of Self-Reported Body Mass Index Among Low-Income Mothers of Young Children

Objective: To examine how income-related challenges regarding food and health are associated with variation in self-reported maternal body weight among low-income mothers. Design: Cross-sectional design. Setting: Two Northeastern cities. Seven day care centers and a Supplemental Nutrition Assistance Program outreach project. Participants: Sample of 166 mothers; 67% were overweight or obese, 55% were Hispanic, and 42% reported household food insecurity (HFI). Main Outcome Measures: Maternal self-reported height and weight to calculate body mass index (BMI). Independent variables were food program participation, supermarket use, 8-item food shopping practices scale, HFI, maternal depressive symptoms, and self-rated health. Analysis: Hierarchical multiple regression analysis tested relationships between maternal BMI with the independent variables of interest, adjusting for demographic confounds. Results: Shopping practices to stretch food dollars (P = .04), using community food assistance programs (P \u3c .05), and HFI (P \u3c .04) correlated with heavier maternal BMIs; higher self-rated health corresponded to lower BMIs (P = .004). Conclusions and Implications: Some strategies low-income mothers use to manage food resources are associated with heavier BMIs. Nutrition educators, public health practitioners, and researchers need to collaboratively address the associations between these strategies, food insecurity, poor health, and unhealthy weight

Associations between family food behaviors, maternal depression, and child weight among low-income children

Although low-income children are at greater risk for overweight and obesity than their higher income counterparts, the majority of poor children are not overweight. The current study examined why such variation exists among diverse young children in poor families. Cross-sectional data were collected on 164 low-income, preschool aged children and their mothers living in two Rhode Island cities. Over half of the sample was Hispanic (55%). Mothers completed measures of family food behaviors and depression while trained assistants collected anthropometric data from children at seven day care centers and a Supplemental Nutrition Assistance Program outreach project. Multivariate analysis of covariance revealed that higher maternal depression scores were associated with lower scores on maternal presence when child eats (P \u3c .05), maternal control of child\u27s eating routines (P \u3c .03), and food resource management skills (P \u3c .01), and with higher scores on child control of snacking (P \u3c .03) and negative mealtime practices (P \u3c .05). Multiple regression results revealed that greater maternal presence whenever the child ate was significantly associated with lower child BMI z scores (β = .166, P \u3c .05). Logistic regression analyses indicated that higher scores on food resource management skills reduced the odds of child overweight (odds ratios = .72–.95, P \u3c .01). Maternal depression did not modify the relationship between family food behaviors and child weight. Overall, caregiver presence whenever a child eats, not just at meals, and better parental food resource management skills may promote healthier weights in low-income preschoolers. Further research is needed to identify the mechanisms that connect caregiver presence and food resource management skills to healthier weights for this age group

HIV risk behaviours, perceived severity of drug use problems, and prior treatment experience in a sample of young heroin injectors in Dar es Salaam, Tanzania.

Interviews were conducted with 203 male and 95 female heroin injectors aged 17 to 25 in Dar es Salaam, Tanzania. Nearly one-quarter of participants reported injecting with needles used by someone else. Few reported cleaning needles with bleach. Multiple sexual partnerships, unprotected sex, and trading sex for money were especially present among women, the majority (55%) of whom was HIV seropositive. Self reports suggest the presence of heroin dependence among users. While most participants expressed a desire to quit their use, only 14 (5%) had been in treatment. There appears to be a large unmet need for heroin use treatment. These findings need to be considered in light of a potential forthcoming wave of heroin injection in sub-Saharan Africa.Key Words: HIV, injection drug use, Africa, heroin, drug dependence treatmen