Wavelet analysis of atmospheric turbulence over a coral reef flat

The world’s tropical coral reefs are at risk of severe bleaching episodes and species decline in response to global climate variability. The ecological and economic value of reef ecosystems is enormous, yet very little is known of the physical interactions that take place at the coral–ocean–atmosphere interfaces. This paper introduces and validates a novel technique for the acquisition of surface energy balance measurements over Heron Reef, part of the Capricorn Bunker Group of the southern Great Barrier Reef, Australia. Measurements of surface energy and radiation exchanges were made using a Campbell Scientific eddy covariance (EC) measurement system mounted on a floating pontoon anchored to the reef flat. A Nortek Vector velocimeter was positioned next to the pontoon to record wave motion. Wavelet analysis techniques were used to decompose the turbulent exchange of sensible heat measured by the EC unit and to compare vertical velocity measurements with wave-induced motion recorded by the velocimeter. The results indicate that although the EC system and the velocimeter share intermittent periods of high common power in their respective wavelet variance spectra, these regions are not coherent and differ in strength by more than an order of magnitude. It was concluded that over a standard averaging period of 30 min the wave-induced motion of the pontoon would not significantly interfere with the acquisition and calculation of turbulent fluxes of sensible and latent heat, thereby confirming the robustness of this method of obtaining surface energy balance measurements over coral reefs

Optical Follow-up of New SMC Wing Be/X-ray Binaries

We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based telescopes have been utilised in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution becoming the latest spectral type known. Monitoring of the Halpha emission line suggests that all the sources bar SXP700 have highly variable circumstellar disks, possibly a result of their comparatively short orbital periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight.Comment: 9 pages, 9 figures, 2 tables, accepted for publication in MNRA

Foehn winds in the McMurdo Dry Valleys, Antarctic: The origin of extreme warming events

Foehn winds resulting from topographic modification of airflow in the lee of mountain barriers are frequently experienced in the McMurdo Dry Valleys (MDVs) of Antarctica. Strong foehn winds in the MDVs cause dramatic warming at onset and have significant effects on landscape forming processes; however, no detailed scientific investigation of foehn in the MDVs has been conducted. As a result, they are often misinterpreted as adiabatically warmed katabatic winds draining from the polar plateau. Herein observations from surface weather stations and numerical model output from the Antarctic Mesoscale Prediction System (AMPS) during foehn events in the MDVs are presented. Results show that foehn winds in the MDVs are caused by topographic modification of south-southwesterly airflow, which is channeled into the valleys from higher levels. Modeling of a winter foehn event identifies mountain wave activity similar to that associated with midlatitude foehn winds. These events are found to be caused by strong pressure gradients over the mountain ranges of the MDVs related to synoptic-scale cyclones positioned off the coast of Marie Byrd Land. Analysis of meteorological records for 2006 and 2007 finds an increase of 10% in the frequency of foehn events in 2007 compared to 2006, which corresponds to stronger pressure gradients in the Ross Sea region. It is postulated that the intra- and interannual frequency and intensity of foehn events in the MDVs may therefore vary in response to the position and frequency of cyclones in the Ross Sea region

Helium Nova on a Very Massive White Dwarf -- A Light Curve Model of V445 Puppis (2000) Revised

V445 Pup (2000) is a unique object identified as a helium nova. Color indexes during the outburst are consistent with those of free-free emission. We present a free-free emission dominated light curve model of V445 Pup on the basis of the optically thick wind theory. Our light curve fitting shows that (1) the white dwarf (WD) mass is very massive (M_WD \gtrsim 1.35 M_\sun), and (2) a half of the accreted matter remains on the WD, both of which suggest that the increasing WD mass. Therefore, V445 Pup is a strong candidate of Type Ia supernova progenitor. The estimated distance to V445 Pup is now consistent with the recent observational suggestions, 3.5 < d < 6.5 kpc. A helium star companion is consistent with the brightness of m_v=14.5 mag just before the outburst, if it is a little bit evolved hot (\log T (K) \gtrsim 4.5) star with the mass of M_He \gtrsim 0.8 M_\sun. We then emphasize importance of observations in the near future quiescent phase after the thick circumstellar dust dissipates away, especially its color and magnitude to specify the nature of the companion star. We have also calculated helium ignition masses for helium shell flashes against various helium accretion rates and discussed the recurrence period of helium novae.Comment: 8 pages including 12 figures, to appear in Ap

INTEGRAL observations of the Small Magellanic Cloud

The first INTEGRAL observations of the Small Magellanic Cloud (carried out in 2003) are reported in which two sources are clearly detected. The first source, SMC X-1, shows a hard X-ray eclipse and measurements of its pulse period indicate a continuation of the long-term spin-up now covering ~30 years. The second source is likely to be a high mass X-ray binary, and shows a potential periodicity of 6.8s in the IBIS lightcurve. An exact X-ray or optical counterpart cannot be designated, but a number of proposed counterparts are discussed. One of these possible counterparts shows a strong coherent optical modulation at ~2.7d, which, together with the measured hard X-ray pulse period, would lead to this INTEGRAL source being classified as the fourth known high mass Roche lobe overflow system.Comment: Accepted for publication in MNRA

Utilization of the Building-Block Approach in Structural Mechanics Research

In the last 20 years NASA has worked in collaboration with industry to develop enabling technologies needed to make aircraft safer and more affordable, extend their lifetime, improve their reliability, better understand their behavior, and reduce their weight. To support these efforts, research programs starting with ideas and culminating in full-scale structural testing were conducted at the NASA Langley Research Center. Each program contained development efforts that (a) started with selecting the material system and manufacturing approach; (b) moved on to experimentation and analysis of small samples to characterize the system and quantify behavior in the presence of defects like damage and imperfections; (c) progressed on to examining larger structures to examine buckling behavior, combined loadings, and built-up structures; and (d) finally moved to complicated subcomponents and full-scale components. Each step along the way was supported by detailed analysis, including tool development, to prove that the behavior of these structures was well-understood and predictable. This approach for developing technology became known as the "building-block" approach. In the Advanced Composites Technology Program and the High Speed Research Program the building-block approach was used to develop a true understanding of the response of the structures involved through experimentation and analysis. The philosophy that if the structural response couldn't be accurately predicted, it wasn't really understood, was critical to the progression of these programs. To this end, analytical techniques including closed-form and finite elements were employed and experimentation used to verify assumptions at each step along the way. This paper presents a discussion of the utilization of the building-block approach described previously in structural mechanics research and development programs at NASA Langley Research Center. Specific examples that illustrate the use of this approach are included from recent research and development programs for both subsonic and supersonic transports

A Mouse Keratin 1 Mutation Causes Dark Skin and Epidermolytic Hyperkeratosis

Chemical mutagenesis in the mouse has increased the utility of phenotype-driven genetics as a means for studying different organ systems, developmental pathways, and pathologic processes. From a large-scale screen for dominant phenotypes in mice, a novel class of pigmentation mutants was identified by dark skin (Dsk). We describe a Dsk mutant, Dsk12, which models the human disease, epidermolytic hyperkeratosis (EHK). At 2 days of age, mutant animals exhibit intraepidermal blisters and erosions at sites of trauma, and by 2 weeks of age develop significant hyperkeratosis. We identified a missense mutation in mutant animals that predicts an S194P amino acid substitution in the 1A domain of Keratin 1, a known target for human mutations that cause EHK. Dsk12 recapitulates the gross pathologic, histologic, and genetic aspects of the human disorder, EHK

Investigation of glucagon-like peptide-1 response to six oral carbohydrates in ponies

Glucagon-like peptide-1 (GLP-1), the principal incretin in horses, may play a role in the pathophysiology of insulin dysregulation (ID). This study aimed to describe its concentration in response to three preserved forages and four dynamic tests for ID in ponies. Twelve adult ponies of mixed ID status were given a meal of hay, soaked hay or haylage, an in-feed oral glucose test (OGT), oral sugar test (OST), an oral test using a proprietary breakfast cereal (WEET) or a combined glucose-insulin tolerance test (CGIT) weekly in a randomised cross-over study. Glucose, insulin and GLP-1 concentrations were measured before and following each intervention. Ponies were designated ID or non-ID and insulin resistant (IR) or non-IR according to OGT and CGIT results, respectively. All interventions apart from the CGIT provoked a GLP-1 response within 30 min. The OGT and WEET interventions, (containing the greatest dose of non-structural carbohydrate, 1.06 and 1 g/kg BW, respectively), resulted in a greater area under the curve (AUC) for GLP-1 compared to all other interventions (P &lt; 0.001). No difference in GLP-1 response was detected according to ID or IR status, despite there being strong positive correlations (rs [95 % CI]) between GLP-1 and insulin concentrations measured at individual time points (0.67 [0.62 – 0.71]; P &lt; 0.001) and as AUC (0.66 [0.49–0.79], P &lt; 0.001). These data do not support of the use of GLP-1 as an adjunctive diagnostic test for ID or IR, as defined by conventional intravenous or oral dynamic tests.</p

Comparison of bulk milk antibody and youngstock serology screens for determining herd status for Bovine Viral Diarrhoea Virus

BACKGROUND: This paper examines the use of Bulk Milk antibody (BM Ab), Youngstock (YS) serology (Check Tests) and Bulk Milk PCR (BM PCR) for determining the presence or absence of animals persistently infected (PI) with Bovine Viral Diarrhoea Virus (BVDV) within a herd. Data is presented from 26 herds where average herd sizes were 343 and 98 animals for dairy and beef units respectively. Seventeen herds had sufficient data to analyse using Receiver Operating Characteristic (ROC) and probability curves enabling calculation of the sensitivity and specificity of BM Ab and YS Check tests for determining the presence of PI animals within herds in this dataset. RESULTS: Using BM Ab to screen a herd for the presence of PI animals, achieved a herd level sensitivity and specificity of 80.00 % (44.39–97.48 %) and 85.71 % (42.13–99.64 %) respectively (95 % confidence intervals quoted). Sensitivity and specificity of YS Check Tests at a cut off of 3/10 Ab positive YS were 81.82 % (48.22–97.72 %) and 66.67 % (22.28–95.67 %) respectively (95 % confidence interval). These results were achieved by comparing the screening tests to whole herd PI searches that took place 1–19 months after the initial screen with a mean interval of 8 months. Removal of this delay by taking BM samples on the day of a whole herd test and simulating a YS Check Test from the herd test data produced improvements in the reliability of the Check Tests. BM Ab sensitivity and specificity remained unchanged. However, the Check Test sensitivity and specificity improved to 90.9 % (58.72–99.77 %) and 100 % (54.07–100 %) respectively (95 % confidence interval) at a cut of off 2.5/10 Ab positive animals. Our limited BM PCR results identified 5/23 dairy farms with a positive BM PCR result; two contained milking PIs, two had non-milking PIs and another had no PIs identified. CONCLUSIONS: Delaying a PI search following an initial herd screen decreased the diagnostic accuracy and relevance of our results. With careful interpretation, longitudinal surveillance using a combination of the techniques discussed can successfully determine farm status and therefore allow changes in BVDV status to be detected early, thus enabling prompt action in the event of a BVDV incursion