Effect of gender on P-wave dispersion in asymptomatic populations

Background: Exercise testing is a diagnostic tool for evaluating the induction of stress-induced paroxysmal atrial fibrillation (PAF). Resting P-wave dispersion has been suggested to be greater in males versus females but if used by clinicians, gender difference in response to exercise must be determined. Methods: Sixteen healthy subjects (n=8 male, age: 21±0.3; n=8 female, age: 23±1.4) performed an incremental exercise test using the Bruce protocol. Electrocardiograms were recorded at rest, end-exercise, 1, 3, and 5 mins recovery. P-waves were measured in each lead with the maximum (P-max) and minimum (P-min) P-wave durations and dispersion calculated. Results: There was a significant decrease in P-max from rest to end-exercise in males and females [males, 118.3±7.4 (95%CI: 109.7 to 126.8ms) vs. 97.9±6.2 (89.3 to 106.4ms); females, 109.4±4.5 (100.8 to 117.9ms) vs. 94.3±4.6 (85.7 to 102.8ms); p=0.001 (5.7 to 29.8ms)]. Similarly, for P-min [males, 65.6±5.6 (57.4 to 73.9ms) vs. 50.8±2.7 (42.5 to 59.0ms); females, 58.4±3.3 (50.1 to 66.6ms) vs. 45.6±2.7 (37.4 to 53.9ms); p=0.01 (2.2 to 25.4ms)]. Irrespective of gender there was limited change in P-wave dispersion in response to exercise. Males had a longer P-max versus females during the protocol [109.6±2.3 (105.8 to 113.4ms) vs. 103.6±1.8 (99.8 to 107.4ms); p=0.03] but this was not stage-specific. There was no gender differences in either P-min (p=0.12) or P-wave dispersion (p=0.64) across the protocol or stage-specific. Conclusions: Results from this study indicate that in contrast to P-max and P-min, the P-wave dispersion may not be significantly influenced by the sympathetic nervous system in males and females. Therefore, this study suggests males and females should be evaluated in the same way using the P-wave dispersion for predicting the development of stress-induced PAF at rest and during exercise testing protocols

All-sky Radio SETI

Over the last decade, Aperture Arrays (AA) have successfully replaced parabolic dishes as the technology of choice at low radio frequencies - good examples are the MWA, LWA and LOFAR. Aperture Array based telescopes present several advantages, including sensitivity to the sky over a very wide field-of-view. As digital and data processing systems continue to advance, an all-sky capability is set to emerge, even at GHz frequencies. We argue that assuming SETI events are both rare and transitory in nature, an instrument with a large field-of-view, operating around the so-called water-hole (1-2 GHz), might offer several advantages over contemporary searches. Sir Arthur C. Clarke was the first to recognise the potential importance of an all-sky radio SETI capability, as presented in his book, Imperial Earth. As part of the global SKA (Square Kilometre Array) project, a Mid-Frequency Aperture Array (MFAA) prototype known as MANTIS (Mid- Frequency Aperture Array Transient and Intensity-Mapping System) is now being considered as a precursor for SKA-2. MANTIS can be seen as a first step towards an all-sky radio SETI capability at GHz frequencies. This development has the potential to transform the field of SETI research, in addition to several other scientific programmes.Comment: 7 pages, 4 figures, accepted for publication, Proceedings of Science, workshop on "MeerKAT Science: On the Pathway to the SKA", held in Stellenbosch 25-27 May 2016. Comments welcom

The role of subgroups and sub-populations in drug development and drug regulation

This thesis addresses the role of subgroups and sub-populations in drug development and regulation and includes the critical appraisal of regulatory guidance.Chapter One introduces clinical trial methodology and describes the current regulatory environment.In Chapter Two, randomisation is reviewed in relation to unbiased estimation of treatment differences and the impact of data exclusion to form subsets is described.Simpson's paradox (SP) is considered in Chapter Three. Randomisation is shown to protect against SP, while a treatment by factor interaction is not required. Balance is redefined for the odds formulation leading to identical unconditional and conditional parameters. The chances of SP (and less extreme inconsistencies) occurring are quantified using simulation, with varying sample size.Chapter Four considers treatment by subgroup interactions. Suggestions regarding the magnitude of a clinically relevant interaction are presented while a simple Bayesian approach to evaluate interactions using margins for the interaction parameter is applied to published data.Chapter Five considers non-inferiority in relation to sub-populations and covariate adjustment for binary outcomes. It is shown that the Per Protocol population is not necessarily conservative and simulation is used to demonstrate the impact on the type I and II errors. Using simulations it is shown that an increase in the type I error occurs if an important covariate is excluded from the logistic model when testing for non-inferiority.Chapter Six is directed towards the sub-population of children. The impact of off-label treatment is discussed in relation to the ethics of placebo-controlled trials, together with the importance of randomisation in evaluating long-term safety.In Chapter Seven, a therapeutic area is selected to ilJustrate the challenges raised during the previous chapters and wording changes to current regulatory guidelines are proposed.The thesis closes with personal thoughts regarding the future potential for individualised treatment

Of peppers and preparedness

What can a chili pepper teach us about disaster preparedness? In June, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) began issuing advisories about a foodborne salmonella outbreak that was detected in the United States. At the end of August, the agencies announced with little fanfare that the outbreak was over. According to the CDC, there were 1,442 cases in 43 states and at least 286 hospitalizations. An incident of biological terrorism has great potential to pose even greater challenges than the summer’s salmonella outbreak. The substance involved may sound familiar, such as salmonella, E. coli, or botulism, but a carefully orchestrated attack at one or more points high up in the food distribution chain or in a public venue such as a major vacation destination would likely present a true investigative nightmare that would challenge currently available resources

Paleoclimate Implications from Stable Isotope Analysis of Sedimentary Organic Carbon and Vertebrate Fossils from the Cedar Mountain Formation, UT, U.S.A.

Oxygen and carbon isotopic compositions of fossilized vertebrate teeth and bone were analyzed to determine isotopic values of vertebrate faunal diet from the early Cretaceous Cedar Mountain Formation of Utah. Results for δ18O of PO4 (δ18Op) (Suarez et al., 2014) from the same data set have been compared to the δ18O of CO3 (δ18Oc) portion of teeth and turtle shell to determine if diagenetic alteration of the isotopes has occurred by plotting the line of best fit equation that models the relationship between unaltered δ18OP and δ18OC of modern mammals from Iacumin et al., 1996. Results indicate slight diagenesis of some specimens has occurred. Mean annual precipitation (MAP) estimates, using the equations from Kohn (2010) and Diefendorf et al., (2010), were determined for each sampled stratigraphic member using carbon isotopic values derived from vertebrate faunal diet estimations from bioapatite, based on the observation that δ13C of modern C3 plants increases with decreasing MAP (Kohn, 2010; and others). Values indicate a prolonged period of semi-arid to arid climate in the Ruby Ranch and Yellow Cat members of the CMF likely caused by a rain-shadow (Suarez et al., 2014) on the eastern, leeward side of the uplifting Sevier Fold and Thrust belt (SFTB). The upper Mussentuchit Member becomes much more humid as the Western Interior foreland basin, continues to subside, eventually becoming inundated by the Western Interior Seaway. The basal Cretaceous CMF sits unconformably atop the Late Jurassic Morrison Formation, with a hiatus of ~20 Ma (Kirkland and Madsen, 2006). Chemostratigraphic curves of the basal Yellow Cat member (YCM) were constructed using δ13C of bulk organics of sediment, and δ13C and δ18O of inorganic carbonate of sediment in an attempt to correlate with the early Cretaceous chemostratigraphic record. Correlating positive and negative carbon isotope excursions (PCIEs and NCIEs) from the YCM to stratigraphically well-constrained marine sections lends evidence for an age determination of the basal CMF. Correlations indicate the YCM to be Barremian to Aptian (~130-120 Ma) in age and detect several distinct CIEs of this period, specifically the B5-B8 excursions of the Barremian and the A1-C5 excursions of the Aptian

Development Of A High Strength Laminate Repair System

Composite manufacturing often requires repairs at some point during the life of the part. Working with LM Wind Power, the Chemical and Mechanical Engineering Departments at the University of North Dakota worked to develop a new laminate repair system to be used in composite repairs. Both chemical and mechanical test methods were explored to analyze various resins in an attempt to increase the interface toughness between the parent laminate and repair laminate. A total of six resins from four suppliers were tested. Differential scanning calorimetry and dynamic mechanical rheological testing were performed to analyze the curing kinetics of each resin tested. Static double cantilever beam and tension-tension fatigue tests were performed to measure the mechanical performance of each resin. All specimens were prepared to mimic that of a large-scale wind turbine blade. Each resin tested was compared to the current repair resin system to determine which choice was best to meet the requirements set for by LM Wind Power for repair laminate improvement. The results indicated that toughened resin performance is superior to that of the current resin system. Along with the analysis of new repair resins, an initiator study was performed. The initiator study was done on the blade resin used for vacuum assisted resin transfer molding (VARTM). Four initiators were tested and compared to the current initiator. Methods included differential scanning calorimetry and rheology. The goal with testing these initiators was to see if changing the initiator would increase the working time while decreasing the overall curing time. To achieve this, the initial viscosity of the resin needed to remain low to ensure a full wet out of the part and once wet out was complete a sharp increase in viscosity would indicate a fast cure. Of the initiators tested, Pulcat from Syrgis Performance Initiators performed better than the others. However, without testing it in production, it is unclear whether or not it is superior to the current initiator MCP-75