Coupling of Two Motor Proteins: a New Motor Can Move Faster

We study the effect of a coupling between two motor domains in highly-processive motor protein complexes. A simple stochastic discrete model, in which the two parts of the protein molecule interact through some energy potential, is presented. The exact analytical solutions for the dynamic properties of the combined motor species, such as the velocity and dispersion, are derived in terms of the properties of free individual motor domains and the interaction potential. It is shown that the coupling between the motor domains can create a more efficient motor protein that can move faster than individual particles. The results are applied to analyze the motion of helicase RecBCD molecules

Anatomy of a catchment: the relation of physical attributes of the Plynlimon catchments to variations in hydrology and water status

International audienceThe Plynlimon headwater catchments in mid-Wales have been a landmark study of water resources in the UK uplands for over 30 years. The main physical features of the catchments have been digitised as the basis for linking new model developments and process understanding. Examples are given of how the main physical attributes are related to land management, hydrology and water quality. These data are also being used to provide insights into catchment processes that may underpin the development of new research. This work is particularly relevant given the need for the assessment of water status under the Water Framework Directive. The paper presents hypothetical management scenarios for the catchments, to show how ecological status may be improved, for example, by selectively restructuring areas of commercial forest. Keywords: Plynlimon, GIS, catchment study, forestry, hydrology, WF

Identification of qPCR reference genes suitable for normalizing gene expression in the mdx mouse model of Duchenne muscular dystrophy

The mdx mouse is the most widely-used animal model of the human disease Duchenne muscular dystrophy, and quantitative PCR analysis of gene expression in the muscles of this animal plays a key role in the study of pathogenesis and disease progression and in evaluation of potential therapeutic interventions. Normalization to appropriate stably-expressed reference genes is essential for accurate quantitative measurement, but determination of such genes is challenging: healthy and dystrophic muscles present very different transcriptional environments, further altering with disease progression and muscle use, raising the possibility that no single gene or combination of genes may be stable under all experimental comparative scenarios. Despite the pedigree of this animal model, this problem remains unaddressed. The aim of this work was therefore to comprehensively assess reference gene suitability in the muscles of healthy and dystrophic mice, identifying reference genes appropriate for specific experimental comparisons, and determining whether an essentially universally-applicable set of genes exists. Using a large sample collection comprising multiple muscles (including the tibialis anterior, diaphragm and heart muscles) taken from healthy and mdx mice at three disease-relevant ages, and a panel of sixteen candidate reference genes (FBXO38, FBXW2, MON2, ZFP91, HTATSF1, GAPDH, ACTB, 18S, CDC40, SDHA, RPL13a, CSNK2A2, AP3D1, PAK1IP1, B2M and HPRT1), we used the geNorm, BestKeeper and Normfinder algorithms to identify genes that were stable under multiple possible comparative scenarios. We reveal that no single gene is stable under all conditions, but a normalization factor derived from multiple genes (RPL13a, CSNK2A2, AP3D1 and the widely-used ACTB) appears suitable for normalizing gene expression in both healthy and dystrophic mouse muscle regardless of muscle type or animal age. We further show that other popular reference genes, including GAPDH, are markedly disease- or muscle-type correlated. This study demonstrates the importance of empirical reference gene identification, and should serve as a valuable resource for investigators wishing to study gene expression in mdx mice

Impact of Compliance to Oral Hypoglycemic Agents on Short-Term Disability Costs in an Employer Population

This study evaluated the relationships between compliance with oral hypoglycemic agents and health care/short-term disability costs in a large manufacturing company. The retrospective analysis used an observational cohort drawn from active employees of Ford Motor Company. The study population consisted of 4978 individuals who were continuously eligible for 3 years (between 2001?2007) and who received a prescription for an oral hypoglycemic agent during that time. Medical, pharmacy, and short-term disability claims data were obtained from the University of Michigan Health Management Research Center data warehouse. Pharmacy claims/refill data were used to calculate the proportion of days covered (PDC); an individual was classified as compliant if his/her PDC was ≥80%. Model covariates included age, sex, work type, and Charlson comorbidity scores. The impact of compliance on disability and health care costs was measured by comparing the costs of the compliant with those of the noncompliant during a 1-year follow-up. Among these employees, compliant patients had lower medical, higher pharmacy, and lower short-term disability costs than did the noncompliant. After adjusting for demographics and comorbidity, noncompliance was associated with statistically higher short-term disability costs ($1840 vs.$1161, P<0.0001), longer short-term disability duration, and an increase in short-term disability incidence (21.5% of the noncompliant had a claim compared to 16.0% of the compliant, P<0.0001). These results suggest that medication compliance may be important in curtailing the rise of health care/disability costs in the workplace. Employers concerned with the total costs associated with diabetes should not overlook the impact of compliance on short-term disability. (Population Health Management 2014;17:35-41)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140180/1/pop.2013.0009.pd

Statistical Properties of the Final State in One-dimensional Ballistic Aggregation

We investigate the long time behaviour of the one-dimensional ballistic aggregation model that represents a sticky gas of N particles with random initial positions and velocities, moving deterministically, and forming aggregates when they collide. We obtain a closed formula for the stationary measure of the system which allows us to analyze some remarkable features of the final `fan' state. In particular, we identify universal properties which are independent of the initial position and velocity distributions of the particles. We study cluster distributions and derive exact results for extreme value statistics (because of correlations these distributions do not belong to the Gumbel-Frechet-Weibull universality classes). We also derive the energy distribution in the final state. This model generates dynamically many different scales and can be viewed as one of the simplest exactly solvable model of N-body dissipative dynamics.Comment: 19 pages, 5 figures include

RESEARCH NOTE<br>A comparison between reference transpiration and measurements of evaporation for a riparian grassland site

International audienceThis paper compares direct measurements of evaporation with the values predicted for reference transpiration. The measurements of actual evaporation were made using an eddy correlation device on a grass field adjacent to the river Thames. Measurements of soil moisture and the driving meteorological variables were also made. The results showed that, during a period with minimal rainfall but no water stress, the cumulative values of reference transpiration compared very well with the cumulative measured evaporation and changes in soil moisture content. However, the values on specific days did not compare well. Following significant rainfall, the measured evaporation increased for a few days, probably due to evaporation of free water from the canopy or soil. Reference transpiration fell consistently below the measured evaporation once the soil moisture deficits exceeded 140 to 150 mm

Strangelets: Who is Looking, and How?

It has been over 30 years since the first suggestion that the true ground state of cold hadronic matter might be not nuclear matter but rather strange quark matter (SQM). Ever since, searches for stable SQM have been proceeding in various forms and have observed a handful of interesting events but have neither been able to find compelling evidence for stable strangelets nor to rule out their existence. I will survey the current status and near future of such searches with particular emphasis on the idea of SQM from strange star collisions as part of the cosmic ray flux.Comment: Talk given at International Conference on Strangeness in Quark Matter, 2006. 8 pages. 1 figur

Universality of finite-size corrections to the number of critical percolation clusters

Monte-Carlo simulations on a variety of 2d percolating systems at criticality suggest that the excess number of clusters in finite systems over the bulk value of nc is a universal quantity, dependent upon the system shape but independent of the lattice and percolation type. Values of nc are found to high accuracy, and for bond percolation confirm the theoretical predictions of Temperley and Lieb, and Baxter, Temperley, and Ashley, which we have evaluated explicitly in terms of simple algebraic numbers. Predictions for the fluctuations are also verified for the first time.Comment: 13 pages, 2 figs., Latex, submitted to Phys. Rev. Let