The influence of D-branes' backreaction upon gravitational interactions between open strings

We argue that gravitational interactions between open strings ending on D3-branes are largely shaped by the D3-branes' backreaction. To this end we consider classical open strings coupled to general relativity in Poincare AdS5 backgrounds. We compute the linear gravitational backreaction of a static string extending up to the Poincare horizon, and deduce the potential energy between two such strings. If spacetime is non-compact, we find that the gravitational potential energy between parallel open strings is independent of the strings' inertial masses and goes like 1/r at large distance r. If the space transverse to the D3-branes is suitably compactified, a collective mode of the graviton propagates usual four-dimensional gravity. In that case the backreaction of the D3-branes induces a correction to the Newtonian potential energy that violates the equivalence principle. The observed enhancement of the gravitational attraction is specific to string theory; there is no similar effect for point-particles.Comment: 28 pages, 7 figures. Typos corrected, minor addition

Associations between Organochlorine Contaminant Concentrations and Clinical Health Parameters in Loggerhead Sea Turtles from North Carolina, USA

Widespread and persistent organochlorine (OC) contaminants, such as polychlorinated biphenyls (PCBs) and pesticides, are known to have broad-ranging toxicities in wildlife. In this study we investigated, for the first time, their possible health effects on loggerhead sea turtles (Caretta caretta). Nonlethal fat biopsies and blood samples were collected from live turtles for OC contaminant analysis, and concentrations were compared with clinical health assessment data, including hematology, plasma chemistry, and body condition. Concentrations of total PCBs (∑PCBs), ∑DDTs, ∑chlordanes, dieldrin, and mirex were determined in 44 fat biopsies and 48 blood samples. Blood concentrations of ∑chlordanes were negatively correlated with red blood cell counts, hemoglobin, and hematocrit, indicative of anemia. Positive correlations were observed between most classes of OC contaminants and white blood cell counts and between mirex and ∑TCDD-like PCB concentrations and the heterophil:lymphocyte ratio, suggesting modulation of the immune system. All classes of OCs in the blood except dieldrin were correlated positively with aspartate aminotransferase (AST) activity, indicating possible hepatocellular damage. Mirex and ∑TCDD-like PCB blood concentrations were negatively correlated with alkaline phosphatase (ALP) activity. Significant correlations to levels of certain OC contaminant classes also suggested possible alteration of protein (↑blood urea nitrogen, ↓albumin:globulin ratio), carbohydrate (↓glucose), and ion (↑sodium, ↓magnesium) regulation. These correlations suggest that OC contaminants may be affecting the health of loggerhead sea turtles even though sea turtles accumulate lower concentrations of OCs compared with other wildlife

Self-Organization, Layered Structure, and Aggregation Enhance Persistence of a Synthetic Biofilm Consortium

Microbial consortia constitute a majority of the earth’s biomass, but little is known about how these cooperating communities persist despite competition among community members. Theory suggests that non-random spatial structures contribute to the persistence of mixed communities; when particular structures form, they may provide associated community members with a growth advantage over unassociated members. If true, this has implications for the rise and persistence of multi-cellular organisms. However, this theory is difficult to study because we rarely observe initial instances of non-random physical structure in natural populations. Using two engineered strains of Escherichia coli that constitute a synthetic symbiotic microbial consortium, we fortuitously observed such spatial self-organization. This consortium forms a biofilm and, after several days, adopts a defined layered structure that is associated with two unexpected, measurable growth advantages. First, the consortium cannot successfully colonize a new, downstream environment until it selforganizes in the initial environment; in other words, the structure enhances the ability of the consortium to survive environmental disruptions. Second, when the layered structure forms in downstream environments the consortium accumulates significantly more biomass than it did in the initial environment; in other words, the structure enhances the global productivity of the consortium. We also observed that the layered structure only assembles in downstream environments that are colonized by aggregates from a previous, structured community. These results demonstrate roles for self-organization and aggregation in persistence of multi-cellular communities, and also illustrate a role for the techniques of synthetic biology in elucidating fundamental biological principles

A Highly Conserved Poc1 Protein Characterized in Embryos of the Hydrozoan Clytia hemisphaerica: Localization and Functional Studies

Poc1 (Protein of Centriole 1) proteins are highly conserved WD40 domain-containing centriole components, well characterized in the alga Chlamydomonas, the ciliated protazoan Tetrahymena, the insect Drosophila and in vertebrate cells including Xenopus and zebrafish embryos. Functions and localizations related to the centriole and ciliary axoneme have been demonstrated for Poc1 in a range of species. The vertebrate Poc1 protein has also been reported to show an additional association with mitochondria, including enrichment in the specialized “germ plasm” region of Xenopus oocytes. We have identified and characterized a highly conserved Poc1 protein in the cnidarian Clytia hemisphaerica. Clytia Poc1 mRNA was found to be strongly expressed in eggs and early embryos, showing a punctate perinuclear localization in young oocytes. Fluorescence-tagged Poc1 proteins expressed in developing embryos showed strong localization to centrioles, including basal bodies. Anti-human Poc1 antibodies decorated mitochondria in Clytia, as reported in human cells, but failed to recognise endogenous or fluorescent-tagged Clytia Poc1. Injection of specific morpholino oligonucleotides into Clytia eggs prior to fertilization to repress Poc1 mRNA translation interfered with cell division from the blastula stage, likely corresponding to when neosynthesis normally takes over from maternally supplied protein. Cell cycle lengthening and arrest were observed, phenotypes consistent with an impaired centriolar biogenesis or function. The specificity of the defects could be demonstrated by injection of synthetic Poc1 mRNA, which restored normal development. We conclude that in Clytia embryos, Poc1 has an essentially centriolar localization and function

Natural polymorphisms in mycobacterium tuberculosis conferring resistance to delamanid in drug-naïve patients.

Mutations in the genes of the F420 signaling pathway, including dnn, fgd1, fbiA, fbiB, fbiC, and fbiD, of Mycobacterium tuberculosis (Mtb) complex can lead to delamanid resistance. We searched for such mutations among 129 Mtb strains from Asia, South-America, and Africa using whole-genome sequencing; 70 (54%) strains had at least one mutation in one of the genes. For ten strains with mutations, we determined the minimum inhibitory concentration (MIC) of delamanid. We found one strain from a delamanid-naïve patient carrying the natural polymorphism Tyr29del (ddn) that was associated with a critical MIC to delamanid

Saccade Generation by the Frontal Eye Fields in Rhesus Monkeys Is Separable from Visual Detection and Bottom-Up Attention Shift

The frontal eye fields (FEF), originally identified as an oculomotor cortex, have also been implicated in perceptual functions, such as constructing a visual saliency map and shifting visual attention. Further dissecting the area’s role in the transformation from visual input to oculomotor command has been difficult because of spatial confounding between stimuli and responses and consequently between intermediate cognitive processes, such as attention shift and saccade preparation. Here we developed two tasks in which the visual stimulus and the saccade response were dissociated in space (the extended memory-guided saccade task), and bottom-up attention shift and saccade target selection were independent (the four-alternative delayed saccade task). Reversible inactivation of the FEF in rhesus monkeys disrupted, as expected, contralateral memory-guided saccades, but visual detection was demonstrated to be intact at the same field. Moreover, saccade behavior was impaired when a bottom-up shift of attention was not a prerequisite for saccade target selection, indicating that the inactivation effect was independent of the previously reported dysfunctions in bottom-up attention control. These findings underscore the motor aspect of the area’s functions, especially in situations where saccades are generated by internal cognitive processes, including visual short-term memory and long-term associative memory

A specification-based QoS-aware design framework for service-based applications

Effective and accurate service discovery and composition rely on complete specifications of service behaviour, containing inputs and preconditions that are required before service execution, outputs, effects and ramifications of a successful execution and explanations for unsuccessful executions. The previously defined Web Service Specification Language (WSSL) relies on the fluent calculus formalism to produce such rich specifications for atomic and composite services. In this work, we propose further extensions that focus on the specification of QoS profiles, as well as partially observable service states. Additionally, a design framework for service-based applications is implemented based on WSSL, advancing state of the art by being the first service framework to simultaneously provide several desirable capabilities, such as supporting ramifications and partial observability, as well as non-determinism in composition schemas using heuristic encodings; providing explanations for unexpected behaviour; and QoS-awareness through goal-based techniques. These capabilities are illustrated through a comparative evaluation against prominent state-of-the-art approaches based on a typical SBA design scenario

Blood transfusion in the critically ill: does storage age matter?

Morphologic and biochemical changes occur during red cell storage prior to product expiry, and these changes may hinder erythrocyte viability and function following transfusion. Despite a relatively large body of literature detailing the metabolic and structural deterioration that occurs during red cell storage, evidence for a significant detrimental clinical effect related to the transfusion of older blood is relatively less conclusive, limited primarily to observations in retrospective studies. Nonetheless, the implication that the transfusion of old, but not outdated blood may have negative clinical consequences demands attention. In this report, the current understanding of the biochemical and structural changes that occur during storage, known collectively as the storage lesion, is described, and the clinical evidence concerning the detrimental consequences associated with the transfusion of relatively older red cells is critically reviewed. Although the growing body of literature demonstrating the deleterious effects of relatively old blood is compelling, it is notable that all of these reports have been retrospective, and most of these studies have evaluated patients who received a mixture of red cell units of varying storage age. Until prospective studies have been completed and produce confirmative results, it would be premature to recommend any modification of current transfusion practice regarding storage age