A Stochastic Approach to Shortcut Bridging in Programmable Matter

In a self-organizing particle system, an abstraction of programmable matter, simple computational elements called particles with limited memory and communication self-organize to solve system-wide problems of movement, coordination, and configuration. In this paper, we consider a stochastic, distributed, local, asynchronous algorithm for "shortcut bridging", in which particles self-assemble bridges over gaps that simultaneously balance minimizing the length and cost of the bridge. Army ants of the genus Eciton have been observed exhibiting a similar behavior in their foraging trails, dynamically adjusting their bridges to satisfy an efficiency trade-off using local interactions. Using techniques from Markov chain analysis, we rigorously analyze our algorithm, show it achieves a near-optimal balance between the competing factors of path length and bridge cost, and prove that it exhibits a dependence on the angle of the gap being "shortcut" similar to that of the ant bridges. We also present simulation results that qualitatively compare our algorithm with the army ant bridging behavior. Our work gives a plausible explanation of how convergence to globally optimal configurations can be achieved via local interactions by simple organisms (e.g., ants) with some limited computational power and access to random bits. The proposed algorithm also demonstrates the robustness of the stochastic approach to algorithms for programmable matter, as it is a surprisingly simple extension of our previous stochastic algorithm for compression.Comment: Published in Proc. of DNA23: DNA Computing and Molecular Programming - 23rd International Conference, 2017. An updated journal version will appear in the DNA23 Special Issue of Natural Computin

Bound exciton and free exciton states in GaSe thin slab

The photoluminescence (PL) and absorption experiments have been performed in GaSe slab with incident light polarized perpendicular to c-axis of sample at 10K. An obvious energy difference of about 34meV between exciton absorption peak and PL peak (the highest energy peak) is observed. By studying the temperature dependence of PL spectra, we attribute it to energy difference between free exciton and bound exciton states, where main exciton absorption peak comes from free exciton absorption, and PL peak are attributed to recombination of bound exciton at 10K. This strong bound exciton effect is stable up to 50K. Moreover, the temperature dependence of integrated PL intensity and PL lifetime reveals that a non-radiative process, with active energy extracted as 0.5meV, dominates PL emission.Comment: 10 pages, 4 figure

One-loop SYM-supergravity relation for five-point amplitudes

We derive a linear relation between the one-loop five-point amplitude of N=8 supergravity and the one-loop five-point subleading-color amplitudes of N=4 supersymmetric Yang-Mills theory.Comment: 17 pages, 2 figures; v2: very minor correction

Novel Information on the Epitope of an Inverse Agonist Monoclonal Antibody Provides Insight into the Structure of the TSH Receptor

The TSH receptor (TSHR) comprises an extracellular leucine-rich domain (LRD) linked by a hinge region to the transmembrane domain (TMD). Insight into the orientation of these components to each other is required for understanding how ligands activate the receptor. We previously identified residue E251 at the LRD-hinge junction as contributing to coupling TSH binding with receptor activation. However, a single residue cannot stabilize the LRD-hinge unit. Therefore, based on the LRD crystal structure we selected for study four other potential LRD-hinge interface charged residues. Alanine substitutions of individual residues K244, E247, K250 and R255 (as well as previously known E251A) did not affect TSH binding or function. However, the cumulative mutation of these residues in varying permutations, primarily K250A and R255A when associated with E251A, partially uncoupled TSH binding and function. These data suggest that these three residues, spatially very close to each other at the LRD base, interact with the hinge region. Unexpectedly and most important, monoclonal antibody CS-17, a TSHR inverse agonist whose epitope straddles the LRD-hinge, was found to interact with residues K244 and E247 at the base of the convex LRD surface. These observations, together with the functional data, exclude residues K244 and E247 from the TSHR LRD-hinge interface. Further, for CS-17 accessibility to K244 and E247, the concave surface of the TSHR LRD must be tilted forwards towards the hinge region and plasma membrane. Overall, these data provide insight into the mechanism by which ligands either activate the TSHR or suppress its constitutive activity

The Phylogeography of MERS-CoV in Hospital Outbreak-Associated Cases Compared to Sporadic Cases in Saudi Arabia.

This study compared the phylogeography of MERS-CoV between hospital outbreak-associated cases and sporadic cases in Saudi Arabia. We collected complete genome sequences from human samples in Saudi Arabia and data on the multiple risk factors of human MERS-CoV in Saudi Arabia reported from 2012 to 2018. By matching each sequence to human cases, we identified isolates as hospital outbreak-associated cases or sporadic cases. We used Bayesian phylogenetic methods including temporal, discrete trait analysis and phylogeography to uncover transmission routes of MERS-CoV isolates between hospital outbreaks and sporadic cases. Of the 120 sequences collected between 19 June 2012 and 23 January 2017, there were 64 isolates from hospital outbreak-associated cases and 56 from sporadic cases. Overall, MERS-CoV is fast evolving at 7.43 × 10-4 substitutions per site per year. Isolates from hospital outbreaks showed unusually fast evolutionary speed in a shorter time-frame than sporadic cases. Multiple introductions of different MERS-CoV strains occurred in three separate hospital outbreaks. MERS-CoV appears to be mutating in humans. The impact of mutations on viruses transmissibility in humans is unknown

Modifiable factors associated with depression and anxiety in multiple sclerosis

Objectives: Modifiable lifestyle factors are implicated in multiple sclerosis (MS) symptoms but their role in mood is unclear. This study aimed to investigate associations between lifestyle and depression and anxiety in Australian participants with MS.Materials and Methods: Self-reported data from the Australian Multiple Sclerosis Longitudinal Study included the Hospital Anxiety and Depression Scale (HADS) and lifestyle measurements from 1500 participants. SNAP score (range 0-5) was the sum of non-smoking, sufficient fruit/vegetable intake, non-hazardous alcohol consumption, sufficient physical activity and healthy BMI. Analyses by log-binomial and linear regression were adjusted for confounding.Results: Symptoms of depression and anxiety were prevalent in 27% and 40%, respectively; 20% had both. Mean SNAP score was 2.7/5; only 3% met all healthy lifestyle recommendations. Only 10% reported adequate fruit/vegetable intake, and 22% reported a combination of unhealthy BMI, inadequate physical activity and inadequate nutrition. A healthier SNAP score was associated with lower depression prevalence (adjusted prevalence ratio 0.83 [95% CI 0.75, 0.92] per unit increase) and depression severity (adjusted β-0.44 [95% CI -0.64, -0.24]), but not with anxiety.Conclusions: Modifiable lifestyle factors are associated with lower frequency and severity of depression, but not anxiety, in Australian people with multiple sclerosis. The associations between a healthier SNAP score and lower depression are likely bi-directional. SNAP risk factor prevalence and co-occurrence, especially inadequate nutrition and low physical activity, were high among Australians with MS

Integrin-mediated interactions with extracellular matrix proteins for nucleus pulposus cells of the human intervertebral disc.

The extracellular matrix (ECM) of the human intervertebral disc is rich in molecules that interact with cells through integrin-mediated attachments. Porcine nucleus pulposus (NP) cells have been shown to interact with laminin (LM) isoforms LM-111 and LM-511 through select integrins that regulate biosynthesis and cell attachment. Since human NP cells lose many phenotypic characteristics with age, attachment and interaction with the ECM may be altered. Expression of LM-binding integrins was quantified for human NP cells using flow cytometry. The cell-ECM attachment mechanism was determined by quantifying cell attachment to LM-111, LM-511, or type II collagen after functionally blocking specific integrin subunits. Human NP cells express integrins β1, α3, and α5, with over 70% of cells positive for each subunit. Blocking subunit β1 inhibited NP cell attachment to all substrates. Blocking subunits α1, α2, α3, and α5 simultaneously, but not individually, inhibits NP cell attachment to laminins. While integrin α6β1 mediated porcine NP cell attachment to LM-111, we found integrins α3, α5, and β1 instead contributed to human NP cell attachment. These findings identify integrin subunits that may mediate interactions with the ECM for human NP cells and could be used to promote cell attachment, survival, and biosynthesis in cell-based therapeutics

The central image of a gravitationally lensed quasar

A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts there should be an odd number of images but, paradoxically, almost all observed lenses have 2 or 4 images. The missing image should be faint and appear near the galaxy's center. These ``central images'' have long been sought as probes of galactic cores too distant to resolve with ordinary observations. There are five candidates, but in one case the third image is not necessarily a central image, and in the others, the central component might be a foreground source rather than a lensed image. Here we report the most secure identification of a central image, based on radio observations of PMN J1632-0033, one of the latter candidates. Lens models incorporating the central image show that the mass of the lens galaxy's central black hole is less than 2 x 10^8 M_sun, and the galaxy's surface density at the location of the central image is more than 20,000 M_sun per square parsec, in agreement with expectations based on observations of galaxies hundreds of times closer to the Earth.Comment: Nature, in press [7 pp, 2 figs]. Standard media embargo applies before publicatio

Motivations Behind Sustainable Purchasing

Sustainability issues in purchasing are receiving greater attention. Literature is rapidly growing, with several research programs being initiated to investigate the topic. This study presents the results of a research project which aims to reveal and structure the motivating forces leading companies to make efforts in sustainability purchasing and the means used to attain achievements in some fields of sustainability. Results presented in the literature are scattered in terms of the fields of sustainability: most of the studies focus only on green or corporate social responsibility issues and there is a lack of exploratory models. Sustainability in purchasing is addressed in a comprehensive way including green, social responsibility and corporate growth issues. After presenting the results of a literature review, theoretical development was undertaken to create a framework in which it is possible to describe the means of sustainability applied and the motivating forces behind them. This framework serves as the basis for an empirical investigation among Hungarian companies. Empirical results confirm the usefulness of the theoretical framework: the number and the characteristics of sustainability activities were determined by the particular types of motivation – to avoid negative effects, to achieve compliance with expectations and to attain positive effects

P21^WAF1/CIP1 RNA expression in highly HIV-1 exposed, uninfected individuals

Some individuals remain HIV-1 antibody and PCR negative after repeated exposures to the virus, and are referred to as HIV-exposed seronegatives (HESN). However, the causes of resistance to HIV-1 infection in cases other than those with a homozygous CCR5Δ32 deletion are unclear. We hypothesized that human p21WAF1/CIP1 (a cyclin-dependent kinase inhibitor) could play a role in resistance to HIV-1 infection in HESN, as p21 expression has been associated with suppression of HIV-1 in elite controllers and reported to block HIV-1 integration in cell culture. We measured p21 RNA expression in PBMC from 40 HESN and 40 low exposure HIV-1 seroconverters (LESC) prior to their infection using a real-time PCR assay. Comparing the 20 HESN with the highest exposure risk (median = 111 partners/2.5 years prior to the 20 LESC with the lowest exposure risk (median = 1 partner/2.5 years prior), p21 expression trended higher in HESN in only one of two experiments (P = 0.11 vs. P = 0.80). Additionally, comparison of p21 expression in the top 40 HESN (median = 73 partners/year) and lowest 40 LESC (median = 2 partners/year) showed no difference between the groups (P = 0.84). There was a weak linear trend between risk of infection after exposure and increasing p21 gene expression (R2 = 0.02, P = 0.12), but again only in one experiment. Hence, if p21 expression contributes to the resistance to viral infection in HESN, it likely plays a minor role evident only in those with extremely high levels of exposure to HIV-1