3,841 research outputs found
STM Studies of Synthetic Peptide Monolayers
We have used scanning probe microscopy to investigate self-assembled
monolayers of chemically synthesized peptides. We find that the peptides form a
dense uniform monolayer, above which is found a sparse additional layer. Using
scanning tunneling microscopy, submolecular resolution can be obtained,
revealing the alpha helices which constitute the peptide. The nature of the
images is not significantly affected by the incorporation of redox cofactors
(hemes) in the peptides.Comment: 4 pages, 3 figures (4 gifs); to appear in the Proceedings of the
XIIth Int. Winterschool on Electronic Properties of Novel Materials
"Molecular Nanostructures", Kirchberg/Tyrol, Febr. 199
Experimental resolution of the free energies of aqueous solvation contributions to ligand-protein binding: quinone-QA site interactions in the photosynthetic reaction center protein.
Magnetically-controlled velocity selection in a cold atom sample using stimulated Raman transitions
We observe velocity-selective two-photon resonances in a cold atom cloud in
the presence of a magnetic field. We use these resonances to demonstrate a
simple magnetometer with sub-mG resolution. The technique is particularly
useful for zeroing the magnetic field and does not require any additional laser
frequencies than are already used for standard magneto-optical traps. We verify
the effects using Faraday rotation spectroscopy.Comment: 5 pages, 6 figure
Evaluating the Chinese Revised Controlling Behaviors Scale (C-CBS-R)
The present study evaluated the utility of the Chinese version of the Revised Controlling Behaviors Scale (C-CBS-R) as a measure of controlling behaviors in violent Chinese intimate relationships. Using a mixed-methods approach, in-depth, individual interviews were conducted with 200 Chinese women survivors to elicit qualitative data about their personal experiences of control in intimate relationships. The use of controlling behaviors was also assessed using the C-CBS-R. Interview accounts suggested that the experiences of 91 of the women were consistent with the description of coercive control according to Dutton and Goodmanâs (2005) conceptualization of coercion. Using the split-half validation procedure, a receiver operating characteristics (ROC) curve analysis was conducted with the first half of the sample. The area under the curve (AUC) for using the C-CBS-R to identify high control was .99, and the cutoff score of 1.145 maximized both sensitivity and specificity. Applying the cutoff score to the second half gave a sensitivity of 96% and a specificity of 95%. Overall, the C-CBS-R has demonstrated utility as a measure of controlling behaviors with a cutoff score for distinguishing high from low levels of control in violent Chinese intimate relationships
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Application of Advanced Reservoir Characterization, Simulation and Production Optimization Strategies to Maximize Recovery in Slope and Basin Clastic Reservoirs, West Texas (Delaware Basin)
The objective of this Class III project is to demonstrate that detailed reservoir characterization of slope and basin elastic reservoirs in sandstones of the Delaware Mountain Group in the Delaware Basin of West Texas and New Mexico is a cost-effective way to recover oil more economically through geologically based field development. The project is focused on East Ford, a Delaware Mountain Group field that produces from the upper Bell Canyon Formation (Ramsey sandstone). The field, discovered in 1960, is operated by Orla Petco, Inc., as the East Ford unit. A CO2 flood is being conducted in the unit, and this flood is the Phase 2 demonstration for the project. Reservoir characterization was conducted using logs and pressure and production information from the East Ford unit, supplemented by Bell Canyon outcrop data and information from the nearby Geraldine Ford field. Characterization was enhanced this year by recovery of a core from the Ramsey reservoir interval in the EFU 41R well. Ramsey sandstones are interpreted as having been deposited in a basin-floor setting in a channel-levee system with attached lobes. Overbank splays are interpreted as being the main area of sand storage outside of the channels. Porosity and permeability of the reservoir sandstones are controlled by calcite cement that can be concentrated in layers ranging from 5 to 40 cm in thickness. These laterally extensive calcite-cemented layers form significant vertical permeability baffles in some areas of the reservoir.Bureau of Economic Geolog
Determining the Locations of Dust Sources in FeLoBAL Quasars
We conduct a spectroscopic search of quasars observed by the Sloan Digital
Sky Survey (SDSS) with broad absorption line (BAL) troughs due to Mg II and
troughs due to Fe II that simultaneously exhibit strong Balmer narrow emission
lines (NELs). We find that in a redshift range of 0.4 less than or equal to z
less than or equal to 0.9 approximately 23 of the 70 Mg II BALs and 4 of a
subset of 15 Fe II BALs exhibit strong Balmer emission. We also find
significant fractions of Mg II BALs (approximately 23%) and those Mg II BALs
with Fe II troughs (approximately 27%) have strong continuum reddening, E(B -
V) greater than or equal to 0.1. From measurements of the Balmer decrement in
three objects, we find similarly significant reddening of the NEL region in
three of the four objects; the NELs in the fourth object are not measurable. We
also include one object in this study not taken from the SDSS sample that shows
Fe II absorption and strong narrow emission, but due to measurement uncertainty
and low continuum reddening the comparison is consistent but inconclusive. We
find a trend in both the Mg II and Fe II BAL samples between the NEL reddening
and continuum reddening. Because the narrow line reddening is consistent with
the continuum reddening in every object in the two SDSS samples, it suggests
that the reddening sources in these objects likely exist at larger radial
distances than the narrow line regions from the central nucleus.Comment: 40 manuscript pages, accepted in ApJ (July
Robust Chauvenet Outlier Rejection
Sigma clipping is commonly used in astronomy for outlier rejection, but the
number of standard deviations beyond which one should clip data from a sample
ultimately depends on the size of the sample. Chauvenet rejection is one of the
oldest, and simplest, ways to account for this, but, like sigma clipping,
depends on the sample's mean and standard deviation, neither of which are
robust quantities: Both are easily contaminated by the very outliers they are
being used to reject. Many, more robust measures of central tendency, and of
sample deviation, exist, but each has a tradeoff with precision. Here, we
demonstrate that outlier rejection can be both very robust and very precise if
decreasingly robust but increasingly precise techniques are applied in
sequence. To this end, we present a variation on Chauvenet rejection that we
call "robust" Chauvenet rejection (RCR), which uses three decreasingly
robust/increasingly precise measures of central tendency, and four decreasingly
robust/increasingly precise measures of sample deviation. We show this
sequential approach to be very effective for a wide variety of contaminant
types, even when a significant -- even dominant -- fraction of the sample is
contaminated, and especially when the contaminants are strong. Furthermore, we
have developed a bulk-rejection variant, to significantly decrease computing
times, and RCR can be applied both to weighted data, and when fitting
parameterized models to data. We present aperture photometry in a contaminated,
crowded field as an example. RCR may be used by anyone at
https://skynet.unc.edu/rcr, and source code is available there as well.Comment: 62 pages, 48 figures, 7 tables, accepted for publication in ApJ
Shock waves in ultracold Fermi (Tonks) gases
It is shown that a broad density perturbation in a Fermi (Tonks) cloud takes
a shock wave form in the course of time evolution. A very accurate analytical
description of shock formation is provided. A simple experimental setup for the
observation of shocks is discussed.Comment: approx. 4 pages&figures, minor corrections^2, to be published as a
Letter in Journal of Physics
Displaced but not replaced: the impact of e-learning on academic identities in higher education.
Challenges facing universities are leading many to implement institutional strategies to incorporate e-learning rather than leaving its adoption up to enthusiastic individuals. Although there is growing understanding about the impact of e-learning on the student experience, there is less understanding of academicsâ perceptions of e-learning and its impact on their identities. This paper explores the changing nature of academic identities revealed through case study research into the implementation of e-learning at one UK university. By providing insight into the lived experiences of academics in a university in which technology is not only transforming access to knowledge but also influencing the balance of power between academic and student in knowledge production and use, it is suggested that academics may experience a jolt to their âtrajectory of selfâ when engaging with e-learning. The potential for e-learning to prompt loss of teacher presence and displacement as knowledge expert may appear to undermine the ontological security of their academic identity
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