23,358 research outputs found
Large anisotropy in the optical conductivity of YNi2B2C
The optical properties of YNiBC are studied by using the
first-principles full-potential linearized augmented plane wave (FLAPW) method
within the local density approximation. Anisotropic behavior is obtained in the
optical conductivity, even though the electronic structure shows 3D character.
A large peak in is obtained at 2.4 eV. The anisotropic optical
properties are analyzed in terms of interband transitions between energy levels
and found that the Ni site plays an important role. The electronic energy loss
spectroscopy (EELS) spectra are also calculated to help elucidate the
anisotropic properties in this system.Comment: revtex4, 4 pages, 5 figures, to appear in PR
Project for the analysis of technology transfer Annual report, 1969
Technology utilization of NASA programs and other research and development programs in Federal Government - project analysis results of technology transfe
Multiple cooperating manipulators: The case of kinematically redundant arms
Existing work concerning two or more manipulators simultaneously grasping and transferring a common load is continued and extended. Specifically considered is the case of one or more arms being kinematically redundant. Some existing results in the modeling and control of single redundant arms and multiple manipulators are reviewed. The cooperating situation is modeled in terms of a set of coordinates representing object motion and internal object squeezing. Nominal trajectories in these coordinates are produced via actuator load distribution algorithms introduced previously. A controller is developed to track these desired object trajectories while making use of the kinematic redundancy to additionally aid the cooperation and coordination of the system. It is shown how the existence of kinematic redundancy within the system may be used to enhance the degree of cooperation achievable
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Nasal-temporal asymmetries in suprathreshold facial expressions of emotion
In this study, we investigated nasal-temporal asymmetries resulting from exposure to visible facial expressions of emotion. The literature has so far reported attentional asymmetries on spatial perception, and nasal-temporal asymmetries resulting from backward masked visual stimuli activated through non-conscious perception. To our knowledge however, no attempt has been made to test such asymmetries with un-masked, consciously visible emotional stimuli. Here, we report on response differences in binocular and monocular viewing on the perception of visible facial expressions of affect. In Study 1, 24 right-handed adults completed a speeded forced-choice paradigm, in which they binocularly viewed bilateral displays of a neutral face in one hemifield, simultaneously paired either with a happy or angry face of variable emotional salience in the opposite hemifield, for 50ms; the task was to indicate the left-right location of the emotional face. In Study 2 (N=23, right-handed), participants completed the same paradigm mononocularly while alternately patching either left and right eye in successive blocks. Under binocular viewing, we found an overall advantage for localising happy faces, further intensified when displayed in the right visual hemifield, and evident even when the emotional expression was extremely subtle. For monocularly viewed stimuli, we observed a response latency asymmetry with faster responses to temporally viewed happy faces. However there was higher overall accuracy for nasal stimuli regardless of emotion, further intensified when the emotional face appeared on the left. Our findings show that the nasal-temporal asymmetries previously associated exclusively with the non-conscious perception of emotional stimuli, manifest as ‘trigger-happy’ responses when emotional stimuli become visible. This asymmetrical reduction in response latency for nasal stimuli could be attributed an overall attentional bias towards the temporal area ipsilateral to the open eye. This however does not appear to increase our detection accuracy, suggesting that a subcortically driven increase in vigilance does not necessarily make for more efficient responses
Dark matter in the inner parts of barred galaxies: The data
This paper presents surface photometry (B,V, I, J, H, K) and H_alpha rotation
curves of 27 isolated spiral galaxies. The final goal is to obtain the mass
distribution of a sample of isolated spiral galaxies in order to model their
gas kinematics. This is then compared to the observed rotation curve, to
determine the necessity of a dark halo in the inner parts (Perez et al. 2004).
The azimuthally averaged radial surface brightness profiles and the integrated
magnitudes obtained from ellipse fitting are given for each of the sample
galaxies. The ellipse fitting technique applied to the light distribution also
allowed us to obtain the size of the bar, and the inclination and position
angle of the outer isophotes that allow the galaxy deprojection. Using these
profiles, 1-D disk-bulge decomposition was performed to obtain the disk
scale-length and the bulge effective radius for the different bands. Through
the fitting of a parametric function to the observed rotation curve, the
maximum rotational velocity and the corresponding radius was obtained. The
correlation between the bulge and disk parameters is in agreement with previous
studies (de Jong 1996a; Marquez & Moles 1999; Baggett et al. 1998). Regarding
the Kormendy relation (Kormendy 1977), in agreement with de Jong, no
correlation between the bulge effective radius and its surface brightness is
found, possibly due to the small range of bulge magnitudes covered. We find a
smaller scatter in the structural relations when compared to non-isolated
samples in agreement with Marquez & Moles (1999). Finally, a correlation
between the disk scale-length and the bar size is observed, possibly reflecting
the rapid growth of a bar.Comment: A&A accepted. Fig. 11 and Tables 3-8 can be downloaded at:
http://www.astro.rug.nl/~isa (they will also be available at
http://www.edpsciences.org
Reciprocal Recommender System for Learners in Massive Open Online Courses (MOOCs)
Massive open online courses (MOOC) describe platforms where users with
completely different backgrounds subscribe to various courses on offer. MOOC
forums and discussion boards offer learners a medium to communicate with each
other and maximize their learning outcomes. However, oftentimes learners are
hesitant to approach each other for different reasons (being shy, don't know
the right match, etc.). In this paper, we propose a reciprocal recommender
system which matches learners who are mutually interested in, and likely to
communicate with each other based on their profile attributes like age,
location, gender, qualification, interests, etc. We test our algorithm on data
sampled using the publicly available MITx-Harvardx dataset and demonstrate that
both attribute importance and reciprocity play an important role in forming the
final recommendation list of learners. Our approach provides promising results
for such a system to be implemented within an actual MOOC.Comment: 10 pages, accepted as full paper @ ICWL 201
Role of Coulomb correlation on magnetic and transport properties of doped manganites: La0.5Sr0.5MnO3 and LaSr2Mn2O7
Results of LSDA and LSDA+U calculations of the electronic structure and
magnetic configurations of the 50% hole-doped pseudocubic perovskite
La0.5Sr0.5MnO3 and double layered LaSr2Mn2O7 are presented. We demonstrate that
the on-site Coulomb correlation (U) of Mn d electrons has a very different
influence on the (i) band formations, (ii) magnetic ground states, (iii)
interlayer exchange interactions, and (iv) anisotropy of the electrical
transport in these two manganites. A possible reason why the LSDA failures in
predicting observed magnetic and transport properties of the double layered
compound - in contrast to the doped perovskite manganite - is considered on the
basis of a p-d hybridization analysis.Comment: 11 pages, 3 figure
In vivo imaging of cellular proliferation in colorectal cancer using positron emission tomography
Background and aims: Positron emission tomography (PET) using 18F labelled 2-fluoro-2-deoxy-D-glucose (18FDG) is an established imaging tool, although the recent development of a biologically stable thymidine analogue [18F] 3'-deoxy-3-fluorothymidine (18FLT) has allowed PET to image cellular proliferation by utilising the salvage pathway of DNA synthesis. In this study, we have compared uptake of 18FLT and 18FDG with MIB-1 immunohistochemistry to evaluate the role of PET in quantifying in vivo cellular proliferation in colorectal cancer (CRC).
Patients and methods: Patients with resectable, primary, or recurrent CRC were prospectively studied. Thirteen lesions from 10 patients (five males, five females), median age 68 years (range 54–87), were evaluated. Patients underwent 18FDG and 18FLT PET scanning. Tracer uptake within lesions was quantified using standardised uptake values (SUVs). Histopathological examination and MIB-1 immunohistochemistry were performed on all lesions, and proliferation quantified by calculating a labelling index (% of MIB-1 positively stained nuclei within 1500 tumour cells).
Results: Histology confirmed adenocarcinoma in 12 of 13 lesions; the remaining lesion was reactive. All eight extrahepatic lesions were visualised using both 18FLT and 18FDG. Three of the five resected liver metastases were also avid for 18FLT and showed high proliferation, while the remaining two lesions which demonstrated no uptake of 18FLT had correspondingly very low proliferation. There was a statistically significant positive correlation (r =0.8, p<0.01) between SUVs of the tumours visualised with 18FLT and the corresponding MIB-1 labelling indices. No such correlation was demonstrated with 18FDG avid lesions (r =0.4).
Conclusions: 18FLT PET correlates with cellular proliferation markers in both primary and metastatic CRC. This technique could provide a mechanism for in vivo grading of malignancy and early prediction of response to adjuvant chemotherapy
Ethics and spirituality in the workplace: the growing role of the business case in reforms
This paper amalgamates three inter-related presentations at the conference entitled “Diversity: a Practitioner’s Journey”. Papers addressed issues of employee well-being in the context of political and ethical concerns in the workplace and society at large. Dr Tim Freeman, who chaired the session, has edited a summary of these papers informed by his own research into leadership and the workplace. We start with spirituality and religion in the workplace (Dr Aylin Kunter), followed by workplace diversity (Dr Carlis Douglas) and finally, the ethics of employment deregulation (Dr Ian Roper).
We all have a desire to understand how we can make the workplace better for those who engage with – and rely on – it for their livelihoods and, increasingly, as a source of identity
Radial Mixing due to Spiral-Bar Resonance Overlap: Implications to the Milky Way
We have recently identified a previously unknown radial migration mechanism
resulting from the overlap of spiral and bar resonances in galactic discs
(Minchev & Famaey 2010, Minchev et al. 2010). This new mechanism is much more
efficient than mixing by transient spirals and its presence is unavoidable in
all barred galaxies, such as our own Milky Way. The consequences of this are a
strong flattening in the metallicity gradient in the disc, an extended disc
profile, and the formation of a thick disc component, all taking place in only
a couple of Gyr. This timescale is drastically shorter than previously expected
and thus can put strong constraints on the longevity, strength and pattern
speeds of the Galactic bar and Spiral Structure.Comment: 4 pages, 2 figures, presented at ELSA 2010: Gaia, at the frontiers of
astrometry, 7-11 June 2010, S\`evres, Paris; To published in EAS Series;
Proceedings editors: C. Turon, F. Arenou & F. Meynadie
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