9,918 research outputs found
Anisotropic Assembly of Colloidal Nanoparticles: Exploiting Substrate Crystallinity
We show that the crystal structure of a substrate can be exploited to drive the anisotropic assembly of colloidal nanoparticles. Pentanethiol-passivated Au particles of approximately 2 nm diameter deposited from toluene onto hydrogen-passivated Si(111) surfaces form linear assemblies (rods) with a narrow width distribution. The rod orientations mirror the substrate symmetry, with a high degree of alignment along principal crystallographic axes of the Si(111) surface. There is a strong preference for
anisotropic growth with rod widths substantially more tightly distributed than lengths. Entropic trapping of nanoparticles provides a plausible explanation for the formation of the anisotropic assemblies we observe
Religious Relationships with the Environment in a Tibetan Rural Community : Interactions and Contrasts with Popular Notions of Indigenous Environmentalism
Acknowledgments: We thank Beijing Forestry University, our field assistants Tashi Rabden, Pema Dechin, Tsewang Chomtso and Gele Chopel for their invaluable help, the Forest Bureau of Daocheng county for permission and support, and the people of Samdo for their hospitality and participation. The research was funded by the ESRC and the World Pheasant Association. This paper is a contribution to Imperial Collegeās Grand Challenges in Ecosystems and the Environment initiative. Two anonymous reviewers gave valuable comments on the manuscript.Peer reviewedPublisher PD
Instructional Alignment of Workplace Readiness Skills in Marketing Education
This study examined high school marketing education teachersā knowledge of workplace readiness skills and whether that knowledge had an impact on student workplace readiness skill achievement. Further, this study examined the usage of Virginiaās 13 Workplace Readiness Skills curriculum and identified the teaching methods and instructional strategies used to disseminate the skills to students. Three sets of data were used for this study: teacher workplace readiness skills data, teacher survey data, and student workplace readiness skills post-test data. Pearsonās correlation was used to determine whether teacher knowledge of workplace readiness skills had an impact on student attainment of the same. The results showed that while overall teacher scores did not show a statistical significance on overall student scores, there were four individual skill areas in which there was a relationship between teacher and student scores
The Anomalous Trajectories of the Pioneer Spacecraft
Because of their unique designs, the Pioneer 10 and 11 spacecraft have
provided the cleanest Doppler, deep-space navigation data. Analysis of this
data can be interpreted as showing an anomalous acceleration of these craft
directed towards the Sun of . The
background of this discovery and the significance of the result are discussed.Comment: 5 pages, 2 figures, to be published in the Proceedings of the Second
Meeting on CPT and Lorentz Symmetr
Disc precession in Be/X-ray binaries drives superorbital variations of outbursts and colour
Superorbital periods that are observed in the brightness of Be/X-ray binaries
may be driven by a misaligned and precessing Be star disc. We examine how the
precessing disc model explains the superorbital variation of (i) the magnitude
of the observed X-ray outbursts and (ii) the observed colour. With
hydrodynamical simulations we show that the magnitude of the average accretion
rate on to the neutron star, and therefore the X-ray outbursts, can vary by
over an order of magnitude over the superorbital period for Be star spin-orbit
misalignments as a result of weak tidal truncation. Most
Be/X-ray binaries are redder at optical maximum when the disc is viewed closest
to face-on since the disc adds a large red component to the emission. However,
A0538-66 is redder at optical minimum. This opposite behaviour requires an
edge-on disc at optical minimum and a radially narrow disc such that it does
not add a large red signature when viewed face-on. For A0538-66, the
misalignment of the disc to the binary orbit must be about and
the inclination of the binary orbit to the line of sight must be similarly
high, although restricted to by the absence of X-ray eclipses.Comment: Accepted for publication in MNRA
cDNA-RNA subtractive hybridization reveals increased expression of mycocerosic acid synthase in intracellular Mycobacterium bovis BCG.
Identifying genes that are differentially expressed by Mycobacterium bovis BCG after phagocytosis by macrophages will facilitate the understanding of the molecular mechanisms of host cell-intracellular pathogen interactions. To identify such genes a cDNA-total RNA subtractive hybridization strategy has been used that circumvents the problems both of limited availability of bacterial RNA from models of infection and the high rRNA backgrounds in total bacterial RNA. The subtraction products were used to screen a high-density gridded Mycobacterium tuberculosis genomic library. Sequence data were obtained from 19 differential clones, five of which contained overlapping sequences for the gene encoding mycocerosic acid synthase (mas). Mas is an enzyme involved in the synthesis of multi-methylated long-chain fatty acids that are part of phthiocerol dimycocerosate, a major component of the complex mycobacterial cell wall. Northern blotting and primer extension data confirmed up-regulation of mas in intracellular mycobacteria and also revealed a putative extended -10 promoter structure and a long untranslated upstream region 5' of the mas transcripts, containing predicted double-stranded structures. Furthermore, clones containing overlapping sequences for furB, groEL-2, rplE and fadD28 were identified and the up-regulation of these genes was confirmed by Northern blot analysis. The cDNA-RNA subtractive hybridization enrichment and high density gridded library screening, combined with selective extraction of bacterial mRNA represents a valuable approach to the identification of genes expressed during intra-macrophage residence for bacteria such as M. bovis BCG and the pathogenic mycobacterium, M. tuberculosis
Search for a Standard Explanation of the Pioneer Anomaly
The data from Pioneer 10 and 11 shows an anomalous, constant, Doppler
frequency drift that can be interpreted as an acceleration directed towards the
Sun of a_P = (8.74 \pm 1.33) x 10^{-8} cm/s^2. Although one can consider a new
physical origin for the anomaly, one first must investigate the contributions
of the prime candidates, which are systematics generated on board. Here we
expand upon previous analyses of thermal systematics. We demonstrate that
thermal models put forth so far are not supported by the analyzed data.
Possible ways to further investigate the nature of the anomaly are proposed.Comment: Changes made for publicatio
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