13,050 research outputs found

    Identification and control of structures in space

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    The derivation of the equations of motion for the Spacecraft Control Laboratory Experiment (SCOLE) is reported and the equations of motion of a similar structure orbiting the earth are also derived. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. A perturbation approach is proposed whereby the quantities defining the rigid-body maneuver are assumed to be relatively large, with the elastic deformations and deviations from the rigid-body maneuver being relatively small. The perturbation equations have the form of linear equations with time-dependent coefficients. An active control technique can then be formulated to permit maneuvering of the spacecraft and simultaneously suppressing the elastic vibration

    Comment on "Self-Purification in Semiconductor Nanocrystals"

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    In a recent Letter [PRL 96, 226802 (2006)], Dalpian and Chelikowsky claimed that formation energies of Mn impurities in CdSe nanocrystals increase as the size of the nanocrystal decreases, and argued that this size dependence leads to "self-purification" of small nanocrystals. They presented density-functional-theory (DFT) calculations showing a strong size dependence for Mn impurity formation energies, and proposed a general explanation. In this Comment we show that several different DFT codes, pseudopotentials, and exchange-correlation functionals give a markedly different result: We find no such size dependence. More generally, we argue that formation energies are not relevant to substitutional doping in most colloidally grown nanocrystals.Comment: 1 page, 1 figur

    The ATLAS-SPT Radio Survey of Cluster Galaxies

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    Using a high-performance computing cluster to mosaic 4,787 pointings, we have imaged the 100 sq. deg. South Pole Telescope (SPT) deep-field at 2.1 GHz using the Australian Telescope Compact Array to an rms of 80 Ī¼\muJy and a resolution of 8". Our goal is to generate an independent sample of radio-selected galaxy clusters to study how the radio properties compare with cluster properties at other wavelengths, over a wide range of redshifts in order to construct a timeline of their evolution out to zāˆ¼1.3z \sim 1.3. A preliminary analysis of the source catalogue suggests there is no spatial correlation between the clusters identified in the SPT-SZ catalogue and our wide-angle tail galaxies.Comment: 9 pages, 4 figures. Submitted to Proceedings of Science for "The many facets of extragalactic radio surveys: towards new scientific challenges", Bologna, Italy 20-23 October 2015 (EXTRA-RADSUR2015

    Effect of dietary vitamin D3 supplementation on meat quality of naked neck chickens

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    Consumersā€™ interest of indigenous chicken meat is increasing. An experiment was conducted to determine the effect of vitamin D3 supplementation on meat quality of indigenous male naked neck chickens. Different supplementation levels of 0, 2000, 4000, 6000 and 8000 IU of vitamin D3 per kg DM of feed were used. 13 weeks old male naked neck chickens with a mean live weight of 1200 Ā± 3 g were supplemented with vitaminĀ  D3 for a period of seven days before slaughter. A 2 (cooking or not) x 2 (postmortem agings of 0 or 24 hs) x 5 (vitamin D3 levels) factorial arrangement in a complete randomized design was used for shear force analysis of raw or cooked naked neck chicken meat. A 2 (postmortem agings of 0 or 24 hs) x 5 (vitamin D3 levels) factorial arrangement in a complete randomized design was used for sensory evaluation of the meat. A quadratic equation was used to determine vitamin D3 supplementation levels for optimum shear force value and sensory attributes. Vitamin D3 supplementation did not improve (P>0.05) shear force values of unaged or aged raw and cooked naked neck chicken meat. Shear force values of unaged raw or cooked meat were optimized at different levels of 3735 (r2=0.832) and 2512 (r2=0.669) IU of vitamin D3 per kg DM feed, respectively. Shear force values of aged raw or cooked meat were optimized at different levels of 6728 (r2 =0.274) and 4249 (r2=0.873) IU of vitamin D3 per kg DM feed, respectively. Vitamin D3 supplementation had no effect (P>0.05) on unaged meat tenderness, juiciness and flavour. However, vitamin D3 supplementation improved (P<0.05) aged meat tenderness and flavour. Tenderness, juiciness and flavour of aged naked neck chicken meat were optimized at supplementation level of 6830 (r2=0.839), 6894 (r2=0.683) and 9795 (r2=0.657) IU of vitaminĀ  D3 per kg DM. It was concluded that vitamin D3 supplementation improved tenderness and flavour of aged naked neck chicken meat. However, shear force values of unaged or aged raw or cooked naked neck chicken meat were not improved by vitamin D3 supplementation.Keywords: Shear force, postmortem aging, calpains, connective tissue, tenderness, juiciness, flavorAfrican Journal of Biotechnology Vol. 12(22), pp. 3576-358

    Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum

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    Many genera of modern planktic foraminifera are adapted to nutrient-poor (oligotrophic) surface waters by hosting photosynthetic symbionts, but it is unknown how they will respond to future changes in ocean temperature and acidity. Here we show that ca. 40 Ma, some fossil photosymbiont-bearing planktic foraminifera were temporarily 'bleached' of their symbionts coincident with transient global warming during the Middle Eocene Climatic Optimum (MECO). At Ocean Drilling Program (ODP) Sites 748 and 1051 (Southern Ocean and mid-latitude North Atlantic, respectively), the typically positive relationship between the size of photosymbiont-bearing planktic foraminifer tests and their carbon isotope ratios (Ī“13C) was temporarily reduced for āˆ¼100 k.y. during the peak of the MECO. At the same time, the typically photosymbiont-bearing planktic foraminifera Acarinina suffered transient reductions in test size and relative abundance, indicating ecological stress. The coincidence of minimum Ī“18O values and reduction in test sizeā€“Ī“13C gradients suggests a link between increased sea-surface temperatures and bleaching during the MECO, although changes in pH and nutrient availability may also have played a role. Our findings show that host-photosymbiont interactions are not constant through geological time, with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont-bearing planktic foraminifera

    Comparison of outcomes of active surveillance in intermediate-risk versus low-risk localised prostate cancer patients: A systematic review and meta-analysis

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    Currently, there is no clear consensus regarding the role of active surveillance (AS) in the management of intermediate-risk prostate cancer (IRPC) patients. We aim to analyse data from the available literature on the outcomes of AS in the management of IRPC patients and compare them with low-risk prostate cancer (LRPC) patients. A comprehensive literature search was performed, and relevant data were extracted. Our primary outcome was treatment-free survival, and secondary outcomes were metastasis-free survival, cancer-specific survival, and overall survival. The DerSimonianā€“Laird random-effects method was used for the meta-analysis. Out of 712 studies identified following an initial search, 25 studies were included in the systematic review. We found that both IRPC and LRPC patients had nearly similar 5, 10, and 15 year treatment-free survival rate, 5 and 10 year metastasis-free survival rate, and 5 year overall survival rate. However, cancer-specific survival rates at 5, 10, and 15 years were significantly lower in IRPC compared to LRPC group. Furthermore, IRPC patients had significantly inferior long-term overall survival rate (10 and 15 year) and metastasis-free survival rate (15 year) compared to LRPC patients. Both the clinicians and the patients can consider this information during the informed decision-making process before choosing AS
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