Enhanced roughness of lipid membranes caused by external electric fields

The behavior of lipid membranes in the presence of an external electric field is studied and used to examine the influence of such fields on membrane parameters such as roughness and show that for a micro sized membrane, roughness grows as the field increases. The dependence of bending rigidity on the electric field is also studied and an estimation of thickness of the accumulated charges around lipid membranes in a free-salt solution is presented.Comment: 9 pages, 6 figures, to appear in Computational Materials Scienc

N-player quantum games in an EPR setting

The $N$-player quantum game is analyzed in the context of an Einstein-Podolsky-Rosen (EPR) experiment. In this setting, a player's strategies are not unitary transformations as in alternate quantum game-theoretic frameworks, but a classical choice between two directions along which spin or polarization measurements are made. The players' strategies thus remain identical to their strategies in the mixed-strategy version of the classical game. In the EPR setting the quantum game reduces itself to the corresponding classical game when the shared quantum state reaches zero entanglement. We find the relations for the probability distribution for $N$-qubit GHZ and W-type states, subject to general measurement directions, from which the expressions for the mixed Nash equilibrium and the payoffs are determined. Players' payoffs are then defined with linear functions so that common two-player games can be easily extended to the $N$-player case and permit analytic expressions for the Nash equilibrium. As a specific example, we solve the Prisoners' Dilemma game for general $N \ge 2$. We find a new property for the game that for an even number of players the payoffs at the Nash equilibrium are equal, whereas for an odd number of players the cooperating players receive higher payoffs.Comment: 26 pages, 2 figure

RPPAML/RIMS: A metadata format and an information management system for reverse phase protein arrays

<p>Abstract</p> <p>Background</p> <p>Reverse Phase Protein Arrays (RPPA) are convenient assay platforms to investigate the presence of biomarkers in tissue lysates. As with other high-throughput technologies, substantial amounts of analytical data are generated. Over 1000 samples may be printed on a single nitrocellulose slide. Up to 100 different proteins may be assessed using immunoperoxidase or immunoflorescence techniques in order to determine relative amounts of protein expression in the samples of interest.</p> <p>Results</p> <p>In this report an RPPA Information Management System (RIMS) is described and made available with open source software. In order to implement the proposed system, we propose a metadata format known as reverse phase protein array markup language (RPPAML). RPPAML would enable researchers to describe, document and disseminate RPPA data. The complexity of the data structure needed to describe the results and the graphic tools necessary to visualize them require a software deployment distributed between a client and a server application. This was achieved without sacrificing interoperability between individual deployments through the use of an open source semantic database, S3DB. This data service backbone is available to multiple client side applications that can also access other server side deployments. The RIMS platform was designed to interoperate with other data analysis and data visualization tools such as Cytoscape.</p> <p>Conclusion</p> <p>The proposed RPPAML data format hopes to standardize RPPA data. Standardization of data would result in diverse client applications being able to operate on the same set of data. Additionally, having data in a standard format would enable data dissemination and data analysis.</p

Air ambulance services in the Arctic 1999-2009 : a Norwegian study.

Air ambulance services in the Arctic have to deal with remote locations, long distances, rough weather conditions and seasonable darkness. Despite these challenges, the people living in the area expect a high quality of specialist health care. The objective of this study was to analyse the air ambulance operations performed in the Norwegian Arctic and study variations in diagnoses and flight patterns around the year. A retrospective analysis. All air ambulance operations performed during the time 1999 – 2009 period were analysed. The subjects were patients transported and flights performed. The primary outcome measures were patients’ diagnoses and task patterns around the year. A total of 345 patients were transported and 321 flights performed. Coronary heart and vascular disease, bone fractures and infections were the most common diagnoses. Most patients (85%) had NACA score 3 or 4. Half of all fractures occurred in April and August. Most patients were males (66%), and one fourth was not Norwegian. The median flying time (one way) was 3 h 33 m. Ten percent of the flights were delayed, and only 14% were performed between midnight and 8.00 AM. The period April to August was the busiest one (58% of operations). Norway has run a safe air ambulance service in the Arctic for the last 11 years. In the future more shipping and polar adventure operations may influence the need for air ambulances, especially during summer and autumn

Adalimumab reduces hand bone loss in rheumatoid arthritis independent of clinical response: Subanalysis of the PREMIER study

<p>Abstract</p> <p>Background</p> <p>Anti-TNF therapy has been shown to reduce radiographic joint damage in rheumatoid arthritis (RA) independent of clinical response. This has previously not been examined for periarticular bone loss, the other characteristic feature of bone involvement in RA.</p> <p>The objective of this study was to examine if treatment with the TNF-α inhibitor adalimumab also could reduce periarticular bone loss in RA patients independent of disease activity.</p> <p>Methods</p> <p>RA patients were recruited from the PREMIER study and included 214 patients treated with methotrexate (MTX) plus adalimumab and 188 patients treated with MTX monotherapy. Periarticular bone loss was assessed by digital X-ray radiogrammetry metacarpal cortical index (DXR-MCI). Change in DXR-MCI was evaluated in patients with different levels of clinical response, as assessed by changes in DAS28 score at 52 weeks and in mean C-reactive protein (CRP) levels during follow-up.</p> <p>Results</p> <p>In the MTX group, there was a greater median DXR-MCI loss among patients with moderate and high disease activity compared to those in remission or with low disease activity (-3.3% vs. -2.2%, p = 0.01). In contrast, periarticular bone loss was independent of disease activity (-1.9% vs. -2.4%, p = 0.99) in the combination group. In the MTX group patients with a mean CRP of ≥ 10 mg/l lost significantly more DXR-MCI than patients with low CRP (-3.1% vs. -1.9%, p <0.01) whereas in the combination group no significant differences between the two CRP groups was seen (-2.4% vs. -2.0%, p = 0.48).</p> <p>Conclusion</p> <p>Adalimumab in combination with MTX reduces periarticular bone loss independently of clinical response. These results support the hypothesis that TNF-α stimulates the osteoclast not only by the inflammatory pathway but do also have a direct effect on the osteoclast.</p> <p>Trial Registration</p> <p>ClinicalTrials (NCT): <a href="http://www.clinicaltrials.gov/ct2/show/NCT001195663">NCT001195663</a></p

Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Née) in two California oak savanna-woodlands

Landscape characteristics and social behavior can affect the foraging patterns of seed-dependent animals. We examine the movement of acorns from valley oak (Quercus lobata) trees to granaries maintained by acorn woodpeckers (Melanerpes formicivorus) in two California oak savanna-woodlands differing in the distribution of Q. lobata within each site. In 2004, we sampled Q. lobata acorns from 16 granaries at Sedgwick Reserve in Santa Barbara County and 18 granaries at Hastings Reserve in Monterey County. Sedgwick has lower site-wide density of Q. lobata than Hastings as well as different frequencies of other Quercus species common to both sites. We found acorn woodpeckers foraged from fewer Q. lobata seed source trees (Kg = 4.1 ± 0.5) at Sedgwick than at Hastings (Kg = 7.6 ± 0.6) and from fewer effective seed sources (Nem* = 2.00 and 5.78, respectively). The differences between sites are due to a greater number of incidental seed sources used per granary at Hastings than at Sedgwick. We also found very low levels of seed source sharing between adjacent granaries, indicating that territoriality is strong at both sites and that each social group forages on its own subset of trees. We discovered an interesting spatial pattern in the location of granaries. At Sedgwick, acorn woodpeckers situated their granaries within areas of higher-than-average tree density, while at Hastings, they placed them within areas of lower-than-average tree density, with the outcome that granaries at the two sites were located in areas of similar valley oak density. Our results illustrate that landscape characteristics might influence the number of trees visited by acorn woodpeckers and the locations of territories, while woodpecker social behavior, such as territoriality, shapes which trees are visited and whether they are shared with other social groups

Phenotypic Variation and Bistable Switching in Bacteria

Microbial research generally focuses on clonal populations. However, bacterial cells with identical genotypes frequently display different phenotypes under identical conditions. This microbial cell individuality is receiving increasing attention in the literature because of its impact on cellular differentiation, survival under selective conditions, and the interaction of pathogens with their hosts. It is becoming clear that stochasticity in gene expression in conjunction with the architecture of the gene network that underlies the cellular processes can generate phenotypic variation. An important regulatory mechanism is the so-called positive feedback, in which a system reinforces its own response, for instance by stimulating the production of an activator. Bistability is an interesting and relevant phenomenon, in which two distinct subpopulations of cells showing discrete levels of gene expression coexist in a single culture. In this chapter, we address techniques and approaches used to establish phenotypic variation, and relate three well-characterized examples of bistability to the molecular mechanisms that govern these processes, with a focus on positive feedback.

Nucleoside diphosphate kinase A as a controller of AMP-kinase in airway epithelia

This review integrates recent understanding of a novel role for NDPK-A in two related directions: Firstly, its role in an airway epithelial cell when bound to the luminal (apical) membrane and secondly in the cytosol of many different cells (epithelial and non-epithelial) where an isoform-specific interaction occurs with a regulatory partner, AMPKα1. Thus NDPK-A is present in both a membrane and cytosolic environment but in the apical membrane, its roles are not understood in detail; preliminary data suggest that it co-localises with the cystic fibrosis protein (CFTR). In cytosol, we find that NDPK-A is coupled to the catalytic alpha1 isoform of the AMP-activated protein kinase (AMPKα subunit), which is part of a heterotrimeric protein complex that responds to cellular energy status by switching off ATP-consuming pathways and switching on ATP-generating pathways when ATP is limiting. We find that ATP is located within this complex and ‘fed’ from NDPK to AMPK without ever ‘seeing’ bulk solution. Importantly, the reverse can also happen such that AMPK activity can be made to decline when NDPK-A ‘steals’ ATP from AMPK. Thus we propose a novel paradigm in NDPK-A function by suggesting that AMP-kinase can be regulated by NDPK-A, independently of AMP

A Parsimonious Approach to Modeling Animal Movement Data

Animal tracking is a growing field in ecology and previous work has shown that simple speed filtering of tracking data is not sufficient and that improvement of tracking location estimates are possible. To date, this has required methods that are complicated and often time-consuming (state-space models), resulting in limited application of this technique and the potential for analysis errors due to poor understanding of the fundamental framework behind the approach. We describe and test an alternative and intuitive approach consisting of bootstrapping random walks biased by forward particles. The model uses recorded data accuracy estimates, and can assimilate other sources of data such as sea-surface temperature, bathymetry and/or physical boundaries. We tested our model using ARGOS and geolocation tracks of elephant seals that also carried GPS tags in addition to PTTs, enabling true validation. Among pinnipeds, elephant seals are extreme divers that spend little time at the surface, which considerably impact the quality of both ARGOS and light-based geolocation tracks. Despite such low overall quality tracks, our model provided location estimates within 4.0, 5.5 and 12.0 km of true location 50% of the time, and within 9, 10.5 and 20.0 km 90% of the time, for above, equal or below average elephant seal ARGOS track qualities, respectively. With geolocation data, 50% of errors were less than 104.8 km (<0.94°), and 90% were less than 199.8 km (<1.80°). Larger errors were due to lack of sea-surface temperature gradients. In addition we show that our model is flexible enough to solve the obstacle avoidance problem by assimilating high resolution coastline data. This reduced the number of invalid on-land location by almost an order of magnitude. The method is intuitive, flexible and efficient, promising extensive utilization in future research