On arc reversal in balanced digraphs

AbstractIn this note we consider closed walks, which are cycles that are not necessarily elementary. We prove that any arc reversal in a balanced multidigraph without loops decreases the number of closed walks. This also proves that arc reversal in a simple balanced digraph decreases the number of closed walks

Properties of optimal survivable paths in a graph

AbstractWe introduce the concept of a survivable path in an undirected graph G. A survivable path between a pair of vertices in G is a pair of edge-disjoint paths consisting of a working path and a redundant protection path. Protection paths share edges in such a manner as to provide guaranteed recovery upon the failure of any single edge. Survivable paths play an important role in the design of survivable communication networks. We demonstrate several results on the properties of the optimal set of survivable paths

Designing the Stem Cell Microenvironment for Guided Connective Tissue Regeneration

Injuries to connective tissues such as ligaments and tendons are common, and rather than healing, repair typically results in fibrosis, or the formation of mechanically inferior and disorganized scar tissue. This fibrotic repair response is due in part to inflammation, during which the injury site is invaded by a number of cell types, including macrophages, neighboring fibroblasts, and homed stem cells or progenitor cells. Activation of macrophages is believed to be modulated by communications with fibroblasts and stem cells, prompting either a pro-fibrotic or a pro-regenerative response. Beyond changes to the cellular microenvironment, fibrosis also results in changes to the organization and mechanical properties of the matrix microenvironment. For healthy fibrous connective tissues, the matrix is comprised of aligned collagen fibers, while scar tissue is disorganized and exhibits weaker mechanical properties than healthy tissue. To date, the nature of the cell-cell and cell-matrix interactions and their relevance in tissue healing or repair remain understudied. To better understand the cellular and matrix-based cues that direct scar formation versus tissue regeneration, and using anterior cruciate ligament (ACL) injuries as a model, Aim 1 of this thesis tests the hypothesis that in vitro models of cellular communications between fibroblasts, macrophages, and mesenchymal stem cells (MSC) can be used to determine the effects of cellular interactions on macrophage activation and fibrosis. In Aim 2, the contribution of matrix-based cues (alignment and mechanical properties) to the inflammatory and fibrotic response, as well as their modulation of cellular interactions, were examined. Findings from these two aims reveal that 1) communications between native tissue fibroblasts and macrophages drive inflammation and fibrosis, while stem cells modulate the repair process through a combination of trophic signaling and immunomodulatory roles, and 2) matrix alignment and mechanical properties exert combined regulation on cell response during inflammation. From a clinical application perspective, stem cells delivered in conjunction with an engineered matrix that provides the critical cues for driving stem cell immunomodulation and trophic signaling will be essential for promoting tissue regeneration and minimizing fibrosis. In particular, an aligned matrix with an elastic modulus similar to that of developing connective tissue may serve to further minimize inflammation and scar formation, and activate stem cell-guided regeneration of mechanically functional connective tissue

The LRL electron and proton spectrometer on NASA's Orbiting Geophysical Observatory 5/E/ /instrumentation and calibration/

Systems analysis of electron and proton spectrometer on OGO-

Assembling the Tree of Life in Europe (AToLE)

A network of scientists under the umbrella of 'Assembling the Tree of Life in Europe (AToLE)' seeks funding under the FP7-Theme: Cooperation - Environment (including Climate Change and Biodiversity Conservation) programme of the European Commission.
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Hidden evidence of non-exponential nuclear decay

The framework to describe natural phenomena at their basics being quantum mechanics, there exist a large number of common global phenomena occurring in different branches of natural sciences. One such global phenomenon is spontaneous quantum decay. However, its long time behaviour is experimentally poorly known. Here we show, that by combining two genuine quantum mechanical results, it is possible to infer on this large time behaviour, directly from data. Specifically, we find evidence for non-exponential behaviour of alpha decay of 8Be at large times from experiments.Comment: 12 pages LaTex, 3 figure

A European Concern? Genetic Structure and Expansion of Golden Jackals (Canis aureus) in Europe and the Caucasus

In the first continent-wide study of the golden jackal (Canis aureus), we characterised its population genetic structure and attempted to identify the origin of European populations. This provided a unique insight into genetic characteristics of a native carnivore population with rapid large-scale expansion. We analysed 15 microsatellite markers and a 406 basepair fragment of the mitochondrial control region. Bayesian-based and principal components methods were applied to evaluate whether the geographical grouping of samples corresponded with genetic groups. Our analysis revealed low levels of genetic diversity, reflecting the unique history of the golden jackal among Europe’s native carnivores. The results suggest ongoing gene flow between south-eastern Europe and the Caucasus, with both contributing to the Baltic population, which appeared only recently. The population from the Peloponnese Peninsula in southern Greece forms a common genetic cluster with samples from south-eastern Europe (ΔK approach in STRUCTURE, Principal Components Analysis [PCA]), although the results based on BAPS and the estimated likelihood in STRUCTURE indicate that Peloponnesian jackals may represent a distinct population. Moreover, analyses of population structure also suggest either genetic distinctiveness of the island population from Samos near the coast of Asia Minor (BAPS, most STRUCTURE, PCA), or possibly its connection with the Caucasus population (one analysis in STRUCTURE). We speculate from our results that ancient Mediterranean jackal populations have persisted to the present day, and have merged with jackals colonising from Asia. These data also suggest that new populations of the golden jackal may be founded by long-distance dispersal, and thus should not be treated as an invasive alien species, i.e. an organism that is “non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health”. These insights into the genetic structure and ancestry of Baltic jackals have important implications for management and conservation of jackals in Europe. The golden jackal is listed as an Annex V species in the EU Habitats Directive and as such, considering also the results presented here, should be legally protected in all EU member states

Identifying mortality risks in patients with opioid use disorder using brief screening assessment: Secondary mental health clinical records analysis

BACKGROUND: Risk assessments are widely used, but their ability to predict outcomes in opioid use disorder (OUD) treatment remains unclear. Therefore, the aim was to investigate if addiction-specific brief risk screening is effective in identifying high mortality risk groups and if subsequent clinical actions following risk assessment impacts on mortality levels. METHODS: Opioid use disorder (OUD) patients were identified in the South London and Maudsley Case Register. Deaths were identified through database linkage to the national mortality dataset. Cox and competing-risk regression were used to model associations between brief risk assessment domains and all-cause and overdose mortality in 4488 OUD patients, with up-to 6-year follow-up time where 227 deaths were registered. Data were stratified by admission to general mental health services. RESULTS: All-cause mortality was significantly associated with unsafe injecting (HR 1.53, 95% CI 1.10-2.11) and clinically appraised likelihood of accidental overdose (HR 1.48, 95% CI 1.00-2.19). Overdose-mortality was significantly associated with unsafe injecting (SHR 2.52, 95% CI 1.11-5.70) and clinically appraised suicidality (SHR 2.89, 95% CI 1.38-6.03). Suicidality was associated with a twofold increase in mortality risk among OUD patients who were not admitted to mental health services within 2 months of their risk assessment (HR 2.03, 95% CI 1.67-3.24). CONCLUSIONS: Diagnosis-specific brief risk screening can identify OUD patient subgroups at increased risk of all-cause and overdose mortality. OUD patients, where suicidality is evident, who are not admitted into services are particularly vulnerable