Treatment of the Open Abdomen with the Commercially Available Vacuum-Assisted Closure System in Patients with Abdominal Sepsis: Low Primary Closure Rate

Background: Abdominal Vacuum-Assisted Closure (V.A.C.) systems for treatment of open abdomens have been predominantly used for trauma patients with a high primary fascial closure rate. Use of the V.A.C. technique in abdominal sepsis is less well established. Methods: All patients with abdominal sepsis and treatment with the abdominal V.A.C. system between 2004 and 2007 were prospectively assessed. End points were fascial closure, V.A.C.-related morbidity, and quality of life score (SF-36) at follow-up. Results: Thirty patients with abdominal sepsis were included in the study. Primary fascial closure was feasible in 10, partial closure in 4, and no closure in 16 patients. Median number of V.A.C. changes was 3 (range, 1-10). Nine patients died. V.A.C.-related morbidity was as follows: two fistulas, three fascial edge necroses, one skin blister, and four prolapses of small bowel between the fascia and foam. Univariate analysis showed no variables influencing primary closure rate or V.A.C.-related morbidity. Mortality was significantly influenced by age (P<0.001), respiratory failure (P=0.01), and pneumonia (P=0.03). At follow-up, V.A.C. patients scored lower in the physical health scores and similar in the mental health scores compared with the normal population. Conclusions: Treatment of the open abdomen in patients with abdominal sepsis with the abdominal V.A.C. system is safe with good long-term quality of life. Primary closure rate in these patients is substantially lower than in trauma patients. Stepwise closure of the fascia during V.A.C. changes should be attempted to avoid additional lateral retraction of fascial edges. V.A.C.-related complications may be avoided with careful surgical techniqu

Holographic Superconductors with Lifshitz Scaling

Black holes in asymptotically Lifshitz spacetime provide a window onto finite temperature effects in strongly coupled Lifshitz models. We add a Maxwell gauge field and charged matter to a recently proposed gravity dual of 2+1 dimensional Lifshitz theory. This gives rise to charged black holes with scalar hair, which correspond to the superconducting phase of holographic superconductors with z > 1 Lifshitz scaling. Along the way we analyze the global geometry of static, asymptotically Lifshitz black holes at arbitrary critical exponent z > 1. In all known exact solutions there is a null curvature singularity in the black hole region, and, by a general argument, the same applies to generic Lifshitz black holes.Comment: 23 pages, 4 figures; v2: added references; v3: matches published versio

Methods for Determining the Statistical Significance of Enrichment or Depletion of Gene Ontology Classifications under Weighted Membership

High-throughput molecular biology studies, such as microarray assays of gene expression, two-hybrid experiments for detecting protein interactions, or ChIP-Seq experiments for transcription factor binding, often result in an “interesting” set of genes – say, genes that are co-expressed or bound by the same factor. One way of understanding the biological meaning of such a set is to consider what processes or functions, as defined in an ontology, are over-represented (enriched) or under-represented (depleted) among genes in the set. Usually, the significance of enrichment or depletion scores is based on simple statistical models and on the membership of genes in different classifications. We consider the more general problem of computing p-values for arbitrary integer additive statistics, or weighted membership functions. Such membership functions can be used to represent, for example, prior knowledge on the role of certain genes or classifications, differential importance of different classifications or genes to the experimenter, hierarchical relationships between classifications, or different degrees of interestingness or evidence for specific genes. We describe a generic dynamic programming algorithm that can compute exact p-values for arbitrary integer additive statistics. We also describe several optimizations for important special cases, which can provide orders-of-magnitude speed up in the computations. We apply our methods to datasets describing oxidative phosphorylation and parturition and compare p-values based on computations of several different statistics for measuring enrichment. We find major differences between p-values resulting from these statistics, and that some statistics recover “gold standard” annotations of the data better than others. Our work establishes a theoretical and algorithmic basis for far richer notions of enrichment or depletion of gene sets with respect to gene ontologies than has previously been available

A promising new device for the prevention of parastomal hernia.

Parastomal hernia (PSH) is the most frequent long-term stoma complication with serious negative effects on quality of life. Surgical revision is often required and has a substantial morbidity and recurrence rate. The development of PSH requires revisional surgery with a substantial perioperative morbidity and high failure rate in the long-term follow-up. Prophylactic parastomal mesh insertion during stoma creation has the potential to reduce the rate of PSH, but carries the risk of early and late mesh-related complications such as infection, fibrosis, mesh shrinkage, and/or bowel erosion. We developed a new stomaplasty ring (KORING), which is easy to implant, avoids potential mesh-related complications, and has a high potential of long-term prevention of PSH. Here we describe the technique and the first use

The evolution of pebble size and shape in space and time

We propose a mathematical model which suggests that the two main geological observations about shingle beaches, i.e. the emergence of predominant pebble size ratios and strong segregation by size are interrelated. Our model is a based on a system of ODEs called the box equations, describing the evolution of pebble ratios. We derive these ODEs as a heuristic approximation of Bloore's PDE describing collisional abrasion. While representing a radical simplification of the latter, our system admits the inclusion of additional terms related to frictional abrasion. We show that nontrivial attractors (corresponding to predominant pebble size ratios) only exist in the presence of friction. By interpreting our equations as a Markov process, we illustrate by direct simulation that these attractors may only stabilized by the ongoing segregation process.Comment: 22 pages, 8 figure