Nonlinear dynamic intertwining of rods with self-contact

Twisted marine cables on the sea floor can form highly contorted three-dimensional loops that resemble tangles. Such tangles or hockles are topologically equivalent to the plectomenes that form in supercoiled DNA molecules. The dynamic evolution of these intertwined loops is studied herein using a computational rod model that explicitly accounts for dynamic self-contact. Numerical solutions are presented for an illustrative example of a long rod subjected to increasing twist at one end. The solutions reveal the dynamic evolution of the rod from an initially straight state, through a buckled state in the approximate form of a helix, through the dynamic collapse of this helix into a near-planar loop with one site of self-contact, and the subsequent intertwining of this loop with multiple sites of self-contact. This evolution is controlled by the dynamic conversion of torsional strain energy to bending strain energy or, alternatively by the dynamic conversion of twist (Tw) to writhe (Wr). KEY WORDS Rod Dynamics, Self-contact, Intertwining, DNA Supercoiling, Cable HocklingComment: 35 pages, 9 figures, submitted to Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science

Gender & Collaboration

The fraction of women in economics has grown significantly over the last forty years. In spite of this, the differences in research output between men and women are large and persistent. These output differences are related to differences in the co-authorship networks of men and women: women have fewer collaborators, collaborate more often with the same co-authors, and a higher fraction of their co-authors are co-authors of each other. Moreover, women collaborate more and do so with more senior co-authors. Standard models of homophily and discrimination cannot account for these differences. We discuss how differences in risk aversion and an adverse environment for women can explain them

Parsing demographic effects of canine parvovirus on a Minnesota wolf population

We examined 35 years of relationships among wolf (Canis lupus) pup survival, population change and canine parvovirus (CPV) seroprevalence in northeastern Minnesota to determine when CPV exerted its strongest effects. Using correlation analysis of data from five periods of 7-years each from 1973 through 2007, we learned that the strongest effect of CPV on pup survival (r = -0.73) and on wolf population change (r = -0.92) was during 1987 to 1993. After that, little effect was documented despite a mean CPV seroprevalence from 1994 of 2007 of 70.8% compared with 52.6% during 1987 to 1993. We conclude that after CPV became endemic and produced its peak effect on the study population, that population developed enough immunity to withstand the disease

Mulch Types on Soil Temperature at Varying Depths in Drip Irrigated Summer and Winter Peppers

Mulch Types on Soil Temperature at Varying Depths in Drip Irrigated Summer and Winter Pepper

Information processing and signal integration in bacterial quorum sensing

Bacteria communicate using secreted chemical signaling molecules called autoinducers in a process known as quorum sensing. The quorum-sensing network of the marine bacterium {\it Vibrio harveyi} employs three autoinducers, each known to encode distinct ecological information. Yet how cells integrate and interpret the information contained within the three autoinducer signals remains a mystery. Here, we develop a new framework for analyzing signal integration based on Information Theory and use it to analyze quorum sensing in {\it V. harveyi}. We quantify how much the cells can learn about individual autoinducers and explain the experimentally observed input-output relation of the {\it V. harveyi} quorum-sensing circuit. Our results suggest that the need to limit interference between input signals places strong constraints on the architecture of bacterial signal-integration networks, and that bacteria likely have evolved active strategies for minimizing this interference. Here we analyze two such strategies: manipulation of autoinducer production and feedback on receptor number ratios.Comment: Supporting information is in appendi

Effect of L- Arginine On Electrocardiographic Changes Induced By Hypercholesterolemia And Isoproterenol In Rabbits

Hypercholesterolemia, a well-known cardiovascular risk factor, is associated with prolonged action potential duration, longer QTc intervals (rate controlled QT interval), suggested that Hypercholesterolemia may have a direct effect on ventricular repolarization. Hypercholesterolemia was induced in rabbits and L-arginine was given orally to animals for sixteen weeks. The isoproterenol was injected in all the animals to produce electrocardiographic changes. ECG was recorded in lead II at start of study, after hypercholesterolemic diet and/ or L-arginine supplementation

Targeting FGFR inhibition in cholangiocarcinoma

Cholangiocarcinomas (CCAs) are rare but aggressive tumours of the bile ducts, which are often diagnosed at an advanced stage and have poor outcomes on systemic therapy. Somatic alterations with therapeutic implications have been identified in almost half of CCAs, in particular in intrahepatic CCA (iCCA), the subtype arising from bile ducts within the liver. Among patients with CCA, fibroblast growth factor receptor 2 (FGFR2) fusions or rearrangements occur almost exclusively in iCCA, where they are estimated to be found in up to 10–15% of patients. Clinical trials for selective FGFR kinase inhibitors have shown consistent activity of these agents in previously treated patients with iCCA harbouring FGFR alterations. Current FGFR kinase inhibitors show differences in their structure, mechanisms of target engagement, and specificities for FGFR1, 2, 3 and 4 and other related kinases. These agents offer the potential to improve outcomes in FGFR-driven CCA, and the impact of variations in the molecular profiles of the FGFR inhibitors on efficacy, safety, acquired resistance mechanisms, and patients’ health-related quality of life remains to be fully characterized. The most common adverse event associated with FGFR inhibitors is hyperphosphatemia, an on-target off-tumour effect of FGFR1 inhibition, and strategies to manage this include dose adjustment, chelators, and the use of a low phosphate diet. As FGFR inhibitors and other targeted agents enter the clinic for use in FGFR-driven CCA, molecular testing for actionable mutations and monitoring for the emergence of acquired resistance will be essential