1,452 research outputs found
Lunar surface mining for automated acquisition of helium-3: Methods, processes, and equipment
In this paper, several techniques considered for mining and processing the regolith on the lunar surface are presented. These techniques have been proposed and evaluated based primarily on the following criteria: (1) mining operations should be relatively simple; (2) procedures of mineral processing should be few and relatively easy; (3) transferring tonnages of regolith on the Moon should be minimized; (4) operations outside the lunar base should be readily automated; (5) all equipment should be maintainable; and (6) economic benefit should be sufficient for commercial exploitation. The economic benefits are not addressed in this paper; however, the energy benefits have been estimated to be between 250 and 350 times the mining energy. A mobile mining scheme is proposed that meets most of the mining objectives. This concept uses a bucket-wheel excavator for excavating the regolith, several mechanical electrostatic separators for beneficiation of the regolith, a fast-moving fluidized bed reactor to heat the particles, and a palladium diffuser to separate H2 from the other solar wind gases. At the final stage of the miner, the regolith 'tailings' are deposited directly into the ditch behind the miner and cylinders of the valuable solar wind gases are transported to a central gas processing facility. During the production of He-3, large quantities of valuable H2, H2O, CO, CO2, and N2 are produced for utilization at the lunar base. For larger production of He-3 the utilization of multiple-miners is recommended rather than increasing their size. Multiple miners permit operations at more sites and provide redundancy in case of equipment failure
Potential of derived lunar volatiles for life support
The lunar regolith contains small quantities of solar wind implanted volatile compounds that have vital, basic uses for maintaining life support systems of lunar or space settlements. Recent proposals to utilize the helium-3 isotope (He-3) derived from the lunar regolith as a fuel for fusion reactors would result in the availability of large quantities of other lunar volatile compounds. The quantities obtained would provide the annual life support replacement requirements of 1150 to 23,000 inhabitants per ton of He-3 recovered, depending on the volatile compound. Utilization of the lunar volatile compounds for life support depends on the costs, in terms of materials and energy, associated with their extraction from the lunar regolith as compared to the delivery costs of these compounds from Earth resources. Considering today's conservative estimated transportation costs (5 dollars per ton), the life support replacement requirements could be more economically supplied by recovering the lunar volatile compounds than transporting these materials from Earth resources, even before He-3 will be utilized as a fusion fuel. In addition, availability of lunar volatile compounds could have a significant cost impact on maintaining the life support systems of the space station and a Mars base
Template-Stripped Multifunctional Wedge and Pyramid Arrays for Magnetic Nanofocusing and Optical Sensing
We present large-scale reproducible
fabrication of multifunctional ultrasharp metallic structures on planar
substrates with capabilities including magnetic field nanofocusing
and plasmonic sensing. Objects with sharp tips such as wedges and
pyramids made with noble metals have been extensively used for enhancing
local electric fields via the lightning-rod effect or plasmonic nanofocusing.
However, analogous nanofocusing of magnetic fields using sharp tips
made with magnetic materials has not been widely realized. Reproducible
fabrication of sharp tips with magnetic as well as noble metal layers
on planar substrates can enable straightforward application of their
material and shape-derived functionalities. We use a template-stripping
method to produce plasmonic-shell-coated nickel wedge and pyramid
arrays at the wafer-scale with tip radius of curvature close to 10
nm. We further explore the magnetic nanofocusing capabilities of these
ultrasharp substrates, deriving analytical formulas and comparing
the results with computer simulations. These structures exhibit nanoscale
spatial control over the trapping of magnetic microbeads and nanoparticles
in solution. Additionally, enhanced optical sensing of analytes by
these plasmonic-shell-coated substrates is demonstrated using surface-enhanced
Raman spectroscopy. These methods can guide the design and fabrication
of novel devices with applications including nanoparticle manipulation,
biosensing, and magnetoplasmonics
Perceived health and quality of life: the effect of exposure to atmospheric pollution
International audienc
Screening for childhood anaemia using copper sulphate densitometry
Objective. To evaluate copper sulphate densitometry to screen for childhood anaemia in a primary care setting, with a view to identifying children requiring definitive diagnostic testing and treatment.
Design. A cross-sectional screening study. Results of densitometry with a copper sulphate solution of specific gravity (SG) 1.048, corresponding to a haemoglobin (Hb) concentration of 10 g/dl, were compared with laboratory Hb determination.
Setting. Outpatient department of Pretoria Academic Hospital (73 children) and a local cr_che (27 children).
Subjects. One hundred consecutive children, aged between 6 months and 6 years, with informed written consent by parents.
Outcome measure(s). Accuracy of copper sulphate densitometry in screening for Hb concentration below 10 g/dl in terms of sensitivity, specificity, positive and negative predictive values, as well as likelihood ratio.
Results. The prevalence of anaemia (Hb < 10 g/dl) was 17% (95% confidence interval (CI) 10.2; 25.8). Copper sulphate densitometry had a sensitivity of 88.2% (95% CI 62.3; 97.9), a specificity of 89.2% (95% CI 79.9; 94.6), a positive predictive value of 62.5% (95% CI 40.8; 80.5) and a negative predictive value of 97.4% (95%CI 90.0; 99.5) in screening for anaemia. The likelihood ratio of a positive screening test was 8.17.
Conclusions. Copper sulphate densitometry was accurate in screening for childhood anaemia.
(South African Medical Journal: 2002 92(12): 978-981
Immune targets for therapeutic development in depression: towards precision medicine.
Over the past two decades, compelling evidence has emerged indicating that immune mechanisms can contribute to the pathogenesis of major depressive disorder (MDD) and that drugs with primary immune targets can improve depressive symptoms. Patients with MDD are heterogeneous with respect to symptoms, treatment responses and biological correlates. Defining a narrower patient group based on biology could increase the treatment response rates in certain subgroups: a major advance in clinical psychiatry. For example, patients with MDD and elevated pro-inflammatory biomarkers are less likely to respond to conventional antidepressant drugs, but novel immune-based therapeutics could potentially address their unmet clinical needs. This article outlines a framework for developing drugs targeting a novel patient subtype within MDD and reviews the current state of neuroimmune drug development for mood disorders. We discuss evidence for a causal role of immune mechanisms in the pathogenesis of depression, together with targets under investigation in randomized controlled trials, biomarker evidence elucidating the link to neural mechanisms, biological and phenotypic patient selection strategies, and the unmet clinical need among patients with MDD.Johnson and Johnso
Inferred changes in El Niño–Southern Oscillation variance over the past six centuries
It is vital to understand how the El Niño–Southern Oscillation (ENSO) has responded to past changes in natural and anthropogenic forcings, in order to better understand and predict its response to future greenhouse warming. To date, however, the instrumental record is too brief to fully characterize natural ENSO variability, while large discrepancies exist amongst paleo-proxy reconstructions of ENSO. These paleo-proxy reconstructions have typically attempted to reconstruct ENSO's temporal evolution, rather than the variance of these temporal changes. Here a new approach is developed that synthesizes the variance changes from various proxy data sets to provide a unified and updated estimate of past ENSO variance. The method is tested using surrogate data from two coupled general circulation model (CGCM) simulations. It is shown that in the presence of dating uncertainties, synthesizing variance information provides a more robust estimate of ENSO variance than synthesizing the raw data and then identifying its running variance. We also examine whether good temporal correspondence between proxy data and instrumental ENSO records implies a good representation of ENSO variance. In the climate modeling framework we show that a significant improvement in reconstructing ENSO variance changes is found when combining information from diverse ENSO-teleconnected source regions, rather than by relying on a single well-correlated location. This suggests that ENSO variance estimates derived from a single site should be viewed with caution. Finally, synthesizing existing ENSO reconstructions to arrive at a better estimate of past ENSO variance changes, we find robust evidence that the ENSO variance for any 30 yr period during the interval 1590–1880 was considerably lower than that observed during 1979–2009
Atopy in HIV-infected children in Pretoria
Introduction. The development or aggravation of a pre-existingatopic state in patients with human immunodeficiency virus(HIV) has not been thoroughly investigated in South Africa.HIV-infected adults have been shown to have a higherprevalence of atopy in some international studies, but this hasnot been documented in children.Methods. A prospective convenience sample of 50 childrenaged between 3 months and 12 years attending the TshwaneDistrict Hospital Paediatric HIV clinic in Pretoria wasrecruited. Their personal and family histories of atopy, WorldHealth Organization (WHO) HIV clinical staging and Centersfor Disease Control (CDC) immunological staging with CD4counts were documented. An age- and sex-matched controlgroup of 50 HIV-negative children was included. Skin pricktests (SPTs) to identify common aeroallergens were conductedon all patients.Results. One hundred children were enrolled, with 50 in eachgroup. Ten per cent of the HIV-infected patients comparedwith 16% of controls had positive SPTs to aeroallergens. Ahigher percentage of the HIV-infected patients had chronicrhinitis and eczema (60% and 68%, respectively). Therewas no relationship between CD4 count and positive SPTs(p=0.61), mean log CD4 count and presence of reportedasthma (p=0.71), and CD4 count and presence of reporteddermatitis (p=0.84). The CD4 count was not statisticallydifferent between children with and without a family historyof atopy (p=0.68).Conclusion. It appears that the stage of HIV disease does notinfluence the development or expression of allergy. There is a high prevalence of dermatitis and chronic rhinitis in HIVinfectedchildren, probably not atopic in origin
ENSO in a changing climate
The El Niño–Southern Oscillation (ENSO) phenomenon is a naturally occurring climate fluctuation, which originates in the tropical Pacific region and affects ecosystems, agriculture, freshwater supplies, hurricanes and other severe weather events worldwide (Goddard and Dilley 2005; McPhaden et al. 2006). Despite considerable progress in our understanding of the impact of climate change on many of the processes that contribute to ENSO variability (e.g., Collins et al. 2010), it is not yet possible to say whether ENSO activity will be enhanced or damped, or if the frequency or character of events will change in the coming decades (Vecchi and Wittenberg 2010). As changes in ENSO have the potential to be one of the largest manifestations of anthropogenic climate change, this status has profound impacts on the reliability of regional attribution of climate variability and change. Two main reasons can be invoked for these shortcomings. First there is a lack of long and comprehensive enough observations of the various ENSO processes to be able to detect past changes. It may be that we need to observe ENSO for another several decades to detect and attribute significant ENSO changes (Wittenberg 2009; Stevenson et al. 2012). Second, as ENSO involves a complex interplay of numerous ocean and atmospheric processes, accurately modeling this climate phenomenon with CGCMs, an
CLT forbindelse i høybygg
Styrken i CLT er lavere vinkelrett på fibrene i treet, noe som gjør forbindelser sårbare for høye påkjenninger i denne retningen. I større bygninger laget av det nevnte materialet, må vi være forsiktige med utformingen av vegg-gulv-vegg-forbindelser der disse kreftene er store nok til å overgå denne kapasiteten.
Vår gruppe har gjennom tilgjengelig informasjon om emnet skapt et design som bruker treets naturlige egenskaper til vår fordel. I tillegg til dette undersøker vi hvilke innflytelser som er betydelige, og alle faktorene som bidrar til å skape den mest praktiske løsningen. Dette gir oss den oppnådde forbindelsen.
Kapasitetstester, strukturanalyse og annen relevant forskning gir oss nok informasjon til å bekrefte at designet er bedre enn andre alternativer. Til tross for at vi ikke beregner vindkreftene og seismiske handlinger på strukturen, bruker vi sunn fornuft og teknisk bakgrunn til å nå denne konklusjonen.The fibers in CLT have lower strength perpendicular to the grain, which makes connections vulnerable to high stresses in this direction. In larger buildings made of the material mentioned, we must be careful in design of wall-floor-wall connections where these forces are large enough to cover the capacity of this strength.
Our group have through available information about the subject created a design that use the natural properties of the wood in our advantage. As well as this we contemplate about what makes a great joint, and all the factors contributing to create the most practical one. This gives us the achieved connection.
Capacity tests, structure analysis and other relevant research provide us with enough information to confirm that the design is superior to other alternatives. Despite the fact that we do not calculate the wind forces and seismic actions on the structure, we use common sense and engineering reason to reach this conclusion
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