Effective practices of international volunteering for health : perspectives from partner organizations

Abstract: The demand for international volunteer experiences to promote global health and nutrition is increasing and numerous studies have documented the experiences of the international volunteers who travel abroad; however, little is known about effective practices from the perspective of partner organizations. This study aims to understand how variables such as the skill-level of volunteers, the duration of service, cultural and language training, and other key variables affect partner organizations’ perceptions of volunteer effectiveness at promoting healthcare and nutrition..

Assessing amino acid racemization variability in coral intra-crystalline protein for geochronological applications.

Over 500 Free Amino Acid (FAA) and corresponding Total Hydrolysed Amino Acid (THAA) analyses were completed from eight independently-dated, multi-century coral cores of massive Porites sp. colonies. This dataset allows us to re-evaluate the application of amino acid racemization (AAR) for dating late Holocene coral material, 20 years after Goodfriend et al. (GCA56 (1992), 3847) first showed AAR had promise for developing chronologies in coral cores. This re-assessment incorporates recent method improvements, including measurement by RP-HPLC, new quality control approaches (e.g. sampling and sub-sampling protocols, statistically-based data screening criteria), and cleaning steps to isolate the intra-crystalline skeletal protein. We show that the removal of the extra-crystalline contaminants and matrix protein is the most critical step for reproducible results and recommend a protocol of bleaching samples in NaOCl for 48 h to maximise removal of open system proteins while minimising the induced racemization. We demonstrate that AAR follows closed system behaviour in the intra-crystalline fraction of the coral skeletal proteins. Our study is the first to assess the natural variability in intra-crystalline AAR between colonies, and we use coral cores taken from the Great Barrier Reef, Australia, and Jarvis Island in the equatorial Pacific to explore variability associated with different environmental conditions and thermal histories. Chronologies were developed from THAA Asx D/L, Ala D/L, Glx D/L and FAA Asx D/L for each core and least squares Monte Carlo modelling applied in order to quantify uncertainty of AAR age determinations and assess the level of dating resolution possible over the last 5 centuries. AAR within colonies follow consistent stratigraphic aging. However, there are systematic differences in rates between the colonies, which would preclude direct comparison from one colony to another for accurate age estimation. When AAR age models are developed from a combined dataset to include this natural inter-colony variability THAA Asx D/L, Glx D/L and Ala D/L give a 2σ age uncertainty of ±19, ±38 and ±29 year, for the 20th C respectively; in comparison 2σ age uncertainties from a single colony are ±12, ±12 and ±14 year. This is the first demonstration of FAA D/L for dating coral and following strict protocols 2σ precisions of ±24 years can be achieved across different colonies in samples from the last 150 years, and can be ±10 years within a core from a single colony. Despite these relatively large error estimates, AAR would be a valuable tool in situations where a large number of samples need to be screened rapidly and cheaply (e.g. identifying material from mixed populations in beach or uplift deposits), prior to and complementing the more time-consuming geochronological tools of U/Th or seasonal isotopic timeseries

Wind-induced, cross-frontal exchange on Georges Bank : a mechanism for early summer on-bank biological particle transport

Author Posting. © American Geophysical Union, 2003. 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 108, C11 (2003): 8011, doi:10.1029/2002JC001358.Water exchange across the tidal-mixing front on the southern flank of Georges Bank (GB) is examined using a two-dimensional (2D) primitive equation ocean model. The model domain features a cross-frontal transect including a June 1999 hydrographic (CTD)/ADCP study made as part of the U.S. GLOBEC Northwest Atlantic/Georges Bank program. The model was initialized with temperature and salinity fields taken on the 15 June 1999 CTD section and run prognostically with tidal forcing, measured winds, and representative surface heat flux. The results show that fluctuations of wind plus tidal mixing can play the following essential role in the short-term transport of water and particles from the stratified region to the mixed region on GB in early summer, when stratification is just developing with a weak thermocline at a depth of about 10 m. First, a passing weather front drives a wind-induced on-bank Ekman transport of the upper part of the water column at the tidal-mixing front and associated particles in the surface mixed layer. Then, when the wind relaxes or changes direction, the water in the on-bank extension of the front (above the thermocline) mixes quickly through enhanced tidal motion in shallower depths of water. As a result, particles that are advected along the extended front stay in the previously well-mixed region of the bank. Surface heating tends to increase the strength of the thermocline and reduce the thickness of the surface mixed layer. This in turn accelerates the on-bank movement of the front under an easterly wind favorable for Ekman transport and thus enhances the on-bank, cross-frontal transport of particles. Since the wind-induced, cross-frontal on-bank transport of water can occur episodically during passages of meteorological fronts, these could produce a larger net cross-frontal flux than that produced by just tidal forcing on equivalent timescales. Therefore wind-induced processes can be important in the on-bank cross-frontal flux of copepods and other zooplankton species that exhibit shallow maxima in their vertical distributions over the southern flank of GB in early summer.This research was supported by the U.S. GLOBEC Northwest Atlantic/Georges Bank program through NOAA grants NA56RG0487, NA960P003, and NA960P005 to C. Chen, NOAA support to R. Schlitz, G. R. Lough, K. Smith, and J. Manning, and NSF grants OCE 96-32357, OCE 98-06379, and OCE 02-27679 to R. Beardsley

Generation of human induced pluripotent stem cells by simple transient transfection of plasmid DNA encoding reprogramming factors

<p>Abstract</p> <p>Background</p> <p>The use of lentiviruses to reprogram human somatic cells into induced pluripotent stem (iPS) cells could limit their therapeutic usefulness due to the integration of viral DNA sequences into the genome of the recipient cell. Recent work has demonstrated that human iPS cells can be generated using episomal plasmids, excisable transposons, adeno or sendai viruses, mRNA, or recombinant proteins. While these approaches offer an advance, the protocols have some drawbacks. Commonly the procedures require either subcloning to identify human iPS cells that are free of exogenous DNA, a knowledge of virology and safe handling procedures, or a detailed understanding of protein biochemistry.</p> <p>Results</p> <p>Here we report a simple approach that facilitates the reprogramming of human somatic cells using standard techniques to transfect expression plasmids that encode OCT4, NANOG, SOX2, and LIN28 without the need for episomal stability or selection. The resulting human iPS cells are free of DNA integration, express pluripotent markers, and form teratomas in immunodeficient animals. These iPS cells were also able to undergo directed differentiation into hepatocyte-like and cardiac myocyte-like cells in culture.</p> <p>Conclusions</p> <p>Simple transient transfection of plasmid DNA encoding reprogramming factors is sufficient to generate human iPS cells from primary fibroblasts that are free of exogenous DNA integrations. This approach is highly accessible and could expand the use of iPS cells in the study of human disease and development.</p

Seismicity and Pn Velocity Structure of Central West Antarctica

We have located 117 previously undetected seismic events mainly occurring between 2015 and 2017 that originated from glacial, tectonic, and volcanic processes in central West Antarctica using data recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations. The seismic events, with local magnitudes (ML) ranging from 1.1 to 3.5, are predominantly clustered in four geographic regions; the Ellsworth Mountains, Thwaites Glacier, Pine Island Glacier, and Mount Takahe. Eighteen of the events are in the Ellsworth Mountains and can be attributed to a mixture of glacial and tectonic processes. The largest event noted in this study was a mid‐crustal (∼19 km focal depth; ML 3.5) normal mechanism earthquake beneath Thwaites Glacier. We also located 91 glacial events near the grounding zones of Thwaites Glacier and Pine Island Glacier that are predominantly associated with time periods of significant calving activity. Eight events, likely arising from volcano‐tectonic processes, occurred beneath Mount Takahe. Using Pn travel times from the seismic events, we find laterally variable uppermost mantle structure in central West Antarctica. On average, the Ellsworth Mountains are underlain by a faster mantle lid (VPn = ∼8.4 km/s) compared to the Amundsen Sea Embayment region (VPn = ∼8.1 km/s). Within the Amundsen Sea Embayment itself, we find mantle lid velocities ranging from ∼8.05 to 8.18 km/s. Laterally heterogeneous uppermost mantle structure, indicative of variable thermal and rheological structure, likely influences both geothermal heat flux and glacial isostatic adjustment spatial patterns and rates within central West Antarctica

(E)-2-(2-Methyl­cyclo­hexyl­idene)hydrazinecarbothio­amide

In the crystal of the title compound, C8H15N3S, mol­ecules are linked by N—H⋯S hydrogen bonds, forming chains along [10]. An intra­molecular N—H⋯N hydrogen bond is also present

Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES-Era Data

Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth\u27s climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES-era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth\u27s climate history

Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES-Era Data

Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth\u27s climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES-era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth\u27s climate history

Dealing with Climate Change: Paleoclimate research in Australia

Palaeoclimate research relevant to marine systems in Australia includes the collection and analysis of: (a) shallow-water and deep-sea corals, which provide highresolution archives, (b) deep-sea sediment and ice cores, which span longer time scales, and (c) palaeoclimate modelling, which gives us insights into mechanisms, dynamics and thresholds underlying past climate states. Palaeoclimate research in Australia is mature and well recognised internationally. To further advance Australian palaeoclimate research, we must address major challenges that include insufficient research vessel access, insufficient targeted research funding, as well as the lack of a well funded national centre to coordinate research efforts (e.g. academic institution or ARC Centre of Excellence for Palaeoclimate Research)

Discriminatory optical force for chiral molecules

We suggest that the force F exerted upon a chiral molecule by light assumes the form F = a∇w + b∇h under appropriate circumstances, where a and b pertain to the molecule whilst w and h are the local densities of electric energy and helicity in the optical field; the gradients ∇ of these quantities thus governing the molecule’s centre-of-mass motion. Whereas a is identical for the mirror- image forms or enantiomers of the molecule, b has opposite signs; the associated contribution to F therefore pointing in opposite directions. A simple optical field is presented for which ∇w vanishes but ∇h does not, so that F is absolutely discriminatory. We then present two potential applications: a Stern–Gerlach-type deflector capable of spatially separating the enantiomers of a chiral molecule and a diffraction grating to which chiral molecules alone are sensitive; the resulting diffraction patterns thus encoding information about their chiral geometry