A simple model for DNA denaturation

Following Poland and Scheraga, we consider a simplified model for the denaturation transition of DNA. The two strands are modeled as interacting polymer chains. The attractive interactions, which mimic the pairing between the four bases, are reduced to a single short range binding term. Furthermore, base-pair misalignments are forbidden, implying that this binding term exists only for corresponding (same curvilinear abscissae) monomers of the two chains. We take into account the excluded volume repulsion between monomers of the two chains, but neglect intra-chain repulsion. We find that the excluded volume term generates an effective repulsive interaction between the chains, which decays as $1/r^{d-2}$. Due to this long-range repulsion between the chains, the denaturation transition is first order in any dimension, in agreement with previous studies.Comment: 10 page

Heat transfer measurement of turbulent spots in a hypersonic blunt-body boundary layer

This paper presents data on turbulent-spot propagation in the hypersonic boundary-layer flow over a blunted cylindrical body. Data are based on the measurement of time-dependent surface heat transfer rates using gauges positioned as arrays in either th

Correlated Quantum Transport of Density Wave Electrons

Recently observed Aharonov-Bohm quantum interference of period h/2e in charge density wave rings strongly suggest that correlated density wave electron transport is a cooperative quantum phenomenon. The picture discussed here posits that quantum solitons nucleate and transport current above a Coulomb blockade threshold field. We propose a field-dependent tunneling matrix element and use the Schrodinger equation, viewed as an emergent classical equation as in Feynman's treatment of Josephson tunneling, to compute the evolving macrostate amplitudes, finding excellent quantitative agreement with voltage oscillations and current-voltage characteristics in NbSe3. A proposed phase diagram shows the conditions favoring soliton nucleation versus classical depinning. (Published in Phys. Rev. Lett. 108, 036404 (2012).)Comment: 9 pages, 4 figures, (5 pages & 3 figures for main article), includes Supplemental Material with 1 figure. Published version: Physical Review Letters, vol. 108, p. 036404 (2012

‘Some glimpses of an Asian PhD journey in tourism’ – An ethnodrama

By combining three different genres – academic writing, theatrical playwriting and performing – this article presents different ways of knowing and representing realities for tourism scholars. More specifically, drawing upon social scientists\u27 influential work on performance texts and an ethnodramatic script written by the authors based on dramatized ethnographic and autoethnographic fieldwork, it portrays a tourism PhD journey in an Asian institution. As an attempt of representing the power structures underpinning academia (and tourism academia), namely postcolonial, gendered, global, regional, institutional, and socio-cultural forces, among others, the 8 scenes constituting the script (one of which is enacted and presented in a video) discuss how Asian PhD journeys are shaped by specific approaches to supervision, issues of authorship, gendered dynamics and postcolonial legacies. The main rationale behind this work lies in the recognition of the powerful/performative role of embodied texts and performances in producing, shaping and re-presenting realities. More specifically, the ethnodrama presented in this paper and its embodied representation act as vehicles that are both political and entertaining in producing meanings

Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity

Magnetic fields generated by human and animal organs, such as the heart, brain and nervous system carry information useful for biological and medical purposes. These magnetic fields are most commonly detected using cryogenically-cooled superconducting magnetometers. Here we present the frst detection of action potentials from an animal nerve using an optical atomic magnetometer. Using an optimal design we are able to achieve the sensitivity dominated by the quantum shot noise of light and quantum projection noise of atomic spins. Such sensitivity allows us to measure the nerve impulse with a miniature room-temperature sensor which is a critical advantage for biomedical applications. Positioning the sensor at a distance of a few millimeters from the nerve, corresponding to the distance between the skin and nerves in biological studies, we detect the magnetic field generated by an action potential of a frog sciatic nerve. From the magnetic field measurements we determine the activity of the nerve and the temporal shape of the nerve impulse. This work opens new ways towards implementing optical magnetometers as practical devices for medical diagnostics.Comment: Main text with figures, and methods and supplementary informatio

A Preliminary Investigation towards the Risk Stratification of Allogeneic Stem Cell Recipients with Respect to the Potential for Development of GVHD via Their Pre-Transplant Plasma Lipid and Metabolic Signature

The clinical outcome of allogeneic hematopoietic stem cell transplantation (SCT) may be influenced by the metabolic status of the recipient following conditioning, which in turn may enable risk stratification with respect to the development of transplant-associated complications such as graft vs. host disease (GVHD). To better understand the impact of the metabolic profile of transplant recipients on post-transplant alloreactivity, we investigated the metabolic signature of 14 patients undergoing myeloablative conditioning followed by either human leukocyte antigen (HLA)-matched related or unrelated donor SCT, or autologous SCT. Blood samples were taken following conditioning and prior to transplant on day 0 and the plasma was comprehensively characterized with respect to its lipidome and metabolome via liquid chromatography/mass spectrometry (LCMS) and gas chromatography/mass spectrometry (GCMS). A pro-inflammatory metabolic profile was observed in patients who eventually developed GVHD. Five potential pre-transplant biomarkers, 2-aminobutyric acid, 1-monopalmitin, diacylglycerols (DG 38:5, DG 38:6), and fatty acid FA 20:1 demonstrated high sensitivity and specificity towards predicting post-transplant GVHD. The resulting predictive model demonstrated an estimated predictive accuracy of risk stratification of 100%, with area under the curve of the ROC of 0.995. The likelihood ratio of 1-monopalmitin (infinity), DG 38:5 (6.0), and DG 38:6 (6.0) also demonstrated that a patient with a positive test result for these biomarkers following conditioning and prior to transplant will be at risk of developing GVHD. Collectively, the data suggest the possibility that pre-transplant metabolic signature may be used for risk stratification of SCT recipients with respect to development of alloreactivity

DEVELOPMENT OF A PROTOTYPE IN-SITU FATIGUE SENSOR FOR STRUCTURAL HEALTH MONITORING OF HIGHWAY BRIDGES

Fatigue damage to bridges has been identified as a threat to bridge safety. Fatigue cracks usually occur at stresses lower than the anticipated design stress levels. Unlike yielding or corrosion, fatigue cracks are seldom visible enough to be detected by visual inspection and therefore can be easily overlooked. Since a larger portion of the life of a structure is spent on crack initiation (as opposed to crack propagation), it is vital to develop methods to detect fatigue crack initiation.Unfortunately, most of the methods that are developed to detect fatigue cracks do not accommodate crack initiation and are not sensitive enough to detect fatigue nucleation. A prototype in-situ fatigue senor has been developed to detect nucleation of fatigue damage in steel highway bridges.The in-situ fatigue sensor is designed to be bonded to the base structure and is based on the strain-life fatigue analysis method. Sensors are constructed of electrically conductive material with notched sensor arms producing varying stress concentration factors. The sensor operates on the principle of predictable progressive failure of the parallel arms as fatigue damage is accumulated in the base structure. Experimental results of the behavior of the fatigue sensor under constant amplitude loading and variable amplitude loading of a base structure-mimicking carrier specimen are compared with the simulation results obtained by the finite element analysis method and show reasonable agreement