Detecting submarine groundwater discharge with synoptic surveys of sediment resistivity, radium, and salinity

A synoptic geophysical and geochemical survey was used to investigate the occurrence and spatial distribution of submarine discharges of water to upper Nueces Bay, Texas. The 17 km survey incorporated continuous resistivity profiling; measurements of surface water salinity, temperature, and dissolved oxygen; and point measurements of dissolved Ra isotopes. The survey revealed areas of interleaving, vertical fingers of high and low conductivity extending up through 7 m of bay bottom sediments into the surface water, located within 100 m of surface salinity and dissolved Ra maxima along with peaks in water temperature and lows in dissolved oxygen. These results indicate either brackish submarine groundwater discharge or the leakage of oil field brine from submerged petroleum pipelines

Changing gender profile of medical schools in South Africa

Background. Since 1994, higher education policy has been committed to equity of access for all, irrespective of race and gender. Objectives. We investigated progress towards these goals in the education of medical doctors, with an emphasis on gender. Methods. Databases from the Department of Education (DoE), Health Professions Council of South Africa (HPCSA) and University of Cape Town (UCT) Faculty of Health Sciences were used to explore undergraduate (MB ChB) trends at all eight medical schools and postgraduate (MMed) trends at UCT. Results. Nationally women have outnumbered men in MBChB enrolments since 2000, figures ranging between 52% and 63% at seven of the eight medical schools in 2005. However, the rate of change in the medical profession lags behind and it will take more than two decades for female doctors to outnumber male doctors. A study of UCT postgraduate enrolments shows that females had increased to 42% of MMed enrolments in 2005. However, female postgraduate students were concentrated in disciplines such as paediatrics and psychiatry and comprised no more than 11% of enrolments in the surgical disciplines between 1999 and 2005. Conclusions. The study provides a basic quantitative overview of the changing profile of medical enrolments and raises questions about the career choices of women after they graduate and the social factors influencing these choices. South African Medical Journal Vol. 98 (7) 2008: pp. 557-56

Stress adapted embroidered meshes with a graded pattern design for abdominal wall hernia repair

Abdominal wall hernias are one of the most relevant injuries of the digestive system with 25 million patients in 2013. Surgery is recommended primarily using allogenic non-absorbable wrap-knitted meshes. These meshes have in common that their stress-strain behaviour is not adapted to the anisotropic behaviour of native abdominal wall tissue. The ideal mesh should possess an adequate mechanical behaviour and a suitable porosity at the same time. An alternative fabrication method to wrap-knitting is the embroidery technology with a high flexibility in pattern design and adaption of mechanical properties. In this study, a pattern generator was created for pattern designs consisting of a base and a reinforcement pattern. The embroidered mesh structures demonstrated different structural and mechanical characteristics. Additionally, the investigation of the mechanical properties exhibited an anisotropic mechanical behaviour for the embroidered meshes. As a result, the investigated pattern generator and the embroidery technology allow the production of stress adapted mesh structures that are a promising approach for hernia reconstruction

Evaluation of optical data gained by ARAMIS-measurement of abdominal wall movements for an anisotropic pattern design of stress-adapted hernia meshes produced by embroidery technology

For the sustainable repair of abdominal wall hernia the application of hernia meshes is required. One reason for the relapse of hernia after surgery is seen in an inadequate adaption of the mechanical properties of the mesh to the movements of the abdominal wall. Differences in the stiffness of the mesh and the abdominal tissue cause tension, friction and stress resulting in a deficient tissue response and subsequently in a recurrence of a hernia, preferentially in the marginal area of the mesh. Embroidery technology enables a targeted influence on the mechanical properties of the generated textile structure by a directed thread deposition. Textile parameters like stitch density, alignment and angle can be changed easily and locally in the embroidery pattern to generate a space-resolved mesh with mechanical properties adapted to the requirement of the surrounding tissue. To determine those requirements the movements of the abdominal wall and the resulting distortions need to be known. This study was conducted to gain optical data of the abdominal wall movements by non-invasive ARAMIS-measurement on 39 test persons to estimate direction and value of the major strains

Particle Dynamics in the Rising Plume at Piccard Hydrothermal Field, Mid-Cayman Rise

Processes active in rising hydrothermal plumes, such as precipitation, particle aggregation, and biological growth, affect particle size distributions and can exert important influences on the biogeochemical impact of submarine venting of iron to the oceans and their sediments. However, observations to date of particle size distribution within these systems are both limited and conflicting. In a novel buoyant hydrothermal plume study at the recently discovered high-temperature (398°C) Piccard Hydrothermal Field, Mid-Cayman Rise, we report optical measurements of particle size distributions (PSDs). We describe the plume PSD in terms of a simple, power-law model commonly used in studies of upper and coastal ocean particle dynamics. Observed PSD slopes, derived from spectral beam attenuation and laser diffraction measurements, are among the highest found to date anywhere in the ocean and ranged from 2.9 to 8.5. Beam attenuation at 650 nm ranged from near zero to a rarely observed maximum of 192 m-1 at 3.5 m above the vent. We did not find large (\u3e100 µm) particles that would settle rapidly to the sediments. Instead, beam attenuation was well-correlated to total iron, suggesting the first-order importance of particle dilution, rather than precipitation or dissolution, in the rising plume at Piccard. Our observations at Piccard caution against the assumption of rapid deposition of hydrothermal, particulate metal fluxes, and illustrate the need for more particle size and composition measurements across a broader range of sites, globally

Particle dynamics in the rising plume at Piccard Hydrothermal Field, Mid-Cayman Rise

Processes active in rising hydrothermal plumes, such as precipitation, particle aggregation, and biological growth, affect particle size distributions and can exert important influences on the biogeochemical impact of submarine venting of iron to the oceans and their sediments. However, observations to date of particle size distribution within these systems are both limited and conflicting. In a novel buoyant hydrothermal plume study at the recently discovered high-temperature (3988C) Piccard Hydrothermal Field, Mid- Cayman Rise, we report optical measurements of particle size distributions (PSDs). We describe the plume PSD in terms of a simple, power-law model commonly used in studies of upper and coastal ocean particle dynamics. Observed PSD slopes, derived from spectral beam attenuation and laser diffraction measurements, are among the highest found to date anywhere in the ocean and ranged from 2.9 to 8.5. Beam attenuation at 650 nm ranged from near zero to a rarely observed maximum of 192 m21 at 3.5 m above the vent. We did not find large (\u3e100 lm) particles that would settle rapidly to the sediments. Instead, beam attenuation was well-correlated to total iron, suggesting the first-order importance of particle dilution, rather than precipitation or dissolution, in the rising plume at Piccard. Our observations at Piccard caution against the assumption of rapid deposition of hydrothermal, particulate metal fluxes, and illustrate the need for more particle size and composition measurements across a broader range of sites, globally

FIRST DETECTION OF THE RADIOACTIVE MOLECULE 26AlF AND ITS SPECTROSCOPIC ASPECTS

The observation of radioactive isotopes, like $^{26}$Al, gives insights in the earlier nucleosynthesis processes of stellar cores. Until now, the characteristic $\gamma$-photons released during radioactive decay have been used to record their spatial distribution on a large scale, but this method generally fails to identify individual stellar objects due to the limited detection sensitivity.\\ An alternative approach is the observation of molecules containing radioactive isotopes, like $^{26}$AlF. The stable $^{27}$Al-bearing molecule is known to condensate in the outer atmosphere of late-type stars. Radio-telescope facilities, like \textit{ALMA}, can identify these species via their rotational fingerprint. To enable an unambiguous identification the rotational transition frequencies of $^{26}$AlF need to be known with high accuracy.\\ In this work, the first detection of $^{26}$AlF in the merger object \textit{CK Vulpeculae} is reported. The mass-independent molecular parameterization of AlF using a Dunham approach is shown in detail. Further candidate stellar sources of $^{26}$Al will be discussed.\

MID-IR OBSERVATIONS OF THE LATE-TYPE STARS VY CMa AND o-CETI USING IRTF-TEXES AROUND 8 AND 10μm

Late-type stars eject large amounts of material into outer space. At the very beginning of this process, i.e. close to the star, atoms form small molecules which finally react further to form larger species like nanoparticles. This very first step of chemical evolution is still not well understood. How do the first molecules form? What is the chemical inventory of the stellar atmosphere? To investigate these processes in the vicinity of stars requires both, high spatial and high frequency resolution. We have performed mid-infrared observations towards the stars VY Canis Majoris and Mira (o-ceti) using the high resolution TEXES instrument at the IRTF observatory. As the identification of molecular species requires high confidence in the transition frequency positions accompanying laboratory measurements have been performed, e.g for Si$_2$C, Al$_2$O and TiO around 8 and 10 $\mu m$

Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 2203–2230, doi:10.1002/2015JC011452.This paper reports the results of quantitative imaging using a stereoscopic, high-speed camera system at two natural gas seep sites in the northern Gulf of Mexico during the Gulf Integrated Spill Research G07 cruise in July 2014. The cruise was conducted on the E/V Nautilus using the ROV Hercules for in situ observation of the seeps as surrogates for the behavior of hydrocarbon bubbles in subsea blowouts. The seeps originated between 890 and 1190 m depth in Mississippi Canyon block 118 and Green Canyon block 600. The imaging system provided qualitative assessment of bubble behavior (e.g., breakup and coalescence) and verified the formation of clathrate hydrate skins on all bubbles above 1.3 m altitude. Quantitative image analysis yielded the bubble size distributions, rise velocity, total gas flux, and void fraction, with most measurements conducted from the seafloor to an altitude of 200 m. Bubble size distributions fit well to lognormal distributions, with median bubble sizes between 3 and 4.5 mm. Measurements of rise velocity fluctuated between two ranges: fast-rising bubbles following helical-type trajectories and bubbles rising about 40% slower following a zig-zag pattern. Rise speed was uncorrelated with hydrate formation, and bubbles following both speeds were observed at both sites. Ship-mounted multibeam sonar provided the flare rise heights, which corresponded closely with the boundary of the hydrate stability zone for the measured gas compositions. The evolution of bubble size with height agreed well with mass transfer rates predicted by equations for dirty bubbles.Gulf of Mexico Research Initiativ

King-plot analysis of isotope shifts in simple diatomic molecules

We demonstrate that the isotope shift in isotopomers of diatomic molecules, where the nucleus of one of its constituent atoms is replaced by another isotope, can be expressed as the sum of a field shift and a mass shift, similar to the atomic case. We show that a linear relation holds between atomic and molecular isotopes shifts, thus extending the King-plot analysis to molecular isotope shifts. Optical isotope shifts in YbF and ZrO and infrared isotope shifts in SnH are analyzed with a molecular King-plot approach, utilizing Yb$^{+}$ and Zr$^{+}$ ionic isotope shifts and charge radii of Sn obtained with non-optical methods. The changes in the mean-squared nuclear charge radii $\delta \langle r^2 \rangle$ of $^{170-174,176}$Yb and $^{90-92,94,96}$Zr extracted from the molecular transitions are found to be in excellent agreement with the values from the spectroscopy of Yb$^{+}$ and Zr$^{+}$, respectively. On the contrary, in the case of the vibrational-rotational transition in SnH, no sensitivity to the nuclear volume could be deduced within the experimental resolution, which makes it unsuitable for the extraction of nuclear charge radii but provides insights into the molecular electronic wave function not accessible via other methods. The new opportunities offered by the molecular King-plot analysis for research in nuclear structure and molecular physics are discussed.Comment: Accepted at Physical Review X. Link to abstract: https://journals.aps.org/prx/accepted/be075Kf7E0c16505459d9fa833408356a593fd90