2,108 research outputs found
Derivation of coarse-grained potentials via multistate iterative Boltzmann inversion
In this work, an extension to the standard iterative Boltzmann inversion
(IBI) method to derive coarse-grained potentials is proposed. It is shown that
the inclusion of target data from multiple states yields a less state-dependent
potential, and is thus better suited to simulate systems over a range of
thermodynamic states than the standard IBI method. The inclusion of target data
from multiple states forces the algorithm to sample regions of potential phase
space that match the radial distribution function at multiple state points,
thus producing a derived potential that is more representative of the
underlying potential interactions. It is shown that the algorithm is able to
converge to the true potential for a system where the underlying potential is
known. It is also shown that potentials derived via the proposed method better
predict the behavior of n-alkane chains than those derived via the standard
method. Additionally, through the examination of alkane monolayers, it is shown
that the relative weight given to each state in the fitting procedure can
impact bulk system properties, allowing the potentials to be further tuned in
order to match the properties of reference atomistic and/or experimental
systems
When we Grade Studentsâ Proofs, Do They Understand our Feedback?
Instructors often write feedback on studentsâ proofs even if there is no expectation for the students to revise and resubmit the work. It is not known, however, what students do with that feedback or if they understand the professorâs intentions. To this end, we asked eight advanced mathematics undergraduates to respond to professor comments on four written proofs by interpreting and implementing the comments. We analyzed the studentâs responses using the categories of corrective feedback for language acquisition, viewing the language of mathematical proof as a register of academic English
Gas Rich Dwarf Spheroidals
We present evidence that nearly half of the dwarf spheroidal galaxies (dSph
and dSph/dIrr) in the Local Group are associated with large reservoirs of
atomic gas, in some cases larger than the stellar mass. The gas is sometimes
found at large distance (~10 kpc) from the center of a galaxy and is not
necessarily centered on it. Similarly large quantities of ionized gas could be
hidden in these systems as well. The properties of some of the gas reservoirs
are similar to the median properties of the High-Velocity Clouds (HVCs); two of
the HI reservoirs are catalogued HVCs. The association of the HI with the dwarf
spheroidals might thus provide a link between the HVCs and stars. We show that
the HI content of the Local Group dSphs and dIrrs exhibits a sharp decline if
the galaxy is within 250 kpc of either the Milky Way or M31. This can be
explained if both galaxies have a sufficiently massive x-ray emitting halo that
produces ram-pressure stripping if a dwarf ventures too close to either giant
spiral. We also investigate tidal stripping of the dwarf galaxies and find that
although it may play a role, it cannot explain the apparent total absence of
neutral gas in most dSph galaxies at distances less than 250 kpc. For the
derived mean density of the hot gas, n_0 = 2.5e-5 cm^-2, ram-pressure stripping
is found to be more than an order of magnitude more effective in removing the
gas from the dSph galaxies. The hot halo, with an inferred mass of 1e10 solar
masses, may represent a reservoir of ~1000 destroyed dwarf systems, either HVCs
or true dwarf galaxies similar to those we observe now.Comment: AASTex preprint style, 27 pages including 12 figures. Submitted to
ApJ. See also http://astro.berkeley.edu/~robisha
Tuberculosis from Mycobacterium bovis in Binational Communities, United States
The incidence in San Diego is increasing and is concentrated mostly in persons of Mexican origin
History of the Innovation of Damage Control for Management of Trauma Patients: 1902-2016
Objective: To review the history of the innovation of damage control (DC) for management of trauma patients. Background: DC is an important development in trauma care that provides a valuable case study in surgical innovation. Methods: We searched bibliographic databases (1950-2015), conference abstracts (2009-2013), Web sites, textbooks, and bibliographies for articles relating to trauma DC. The innovation of DC was then classified according to the Innovation, Development, Exploration, Assessment, and Long-term study model of surgical innovation. Results: The innovation\u27\u27 of DC originated from the use of therapeutic liver packing, a practice that had previously been abandoned after World War II because of adverse events. It then developed\u27\u27 into abbreviated laparotomy using rapid conservative operative techniques.\u27\u27 Subsequent exploration\u27\u27 resulted in the application of DC to increasingly complex abdominal injuries and thoracic, peripheral vascular, and orthopedic injuries. Increasing use of DC laparotomy was followed by growing reports of postinjury abdominal compartment syndrome and prophylactic use of the open abdomen to prevent intra-abdominal hypertension after DC laparotomy. By the year 2000, DC surgery had been widely adopted and was recommended for use in surgical journals, textbooks, and teaching courses ( assessment\u27\u27 stage of innovation). Long-term study\u27\u27 of DC is raising questions about whether the procedure should be used more selectively in the context of improving resuscitation practices. Conclusions: The history of the innovation of DC illustrates how a previously abandoned surgical technique was adapted and readopted in response to an increased understanding of trauma patient physiology and changing injury patterns and trauma resuscitation practices
Mandated data archiving greatly improves access to research data
The data underlying scientific papers should be accessible to researchers
both now and in the future, but how best can we ensure that these data are
available? Here we examine the effectiveness of four approaches to data
archiving: no stated archiving policy, recommending (but not requiring)
archiving, and two versions of mandating data deposition at acceptance. We
control for differences between data types by trying to obtain data from papers
that use a single, widespread population genetic analysis, STRUCTURE. At one
extreme, we found that mandated data archiving policies that require the
inclusion of a data availability statement in the manuscript improve the odds
of finding the data online almost a thousand-fold compared to having no policy.
However, archiving rates at journals with less stringent policies were only
very slightly higher than those with no policy at all. At one extreme, we found
that mandated data archiving policies that require the inclusion of a data
availability statement in the manuscript improve the odds of finding the data
online almost a thousand fold compared to having no policy. However, archiving
rates at journals with less stringent policies were only very slightly higher
than those with no policy at all. We also assessed the effectiveness of asking
for data directly from authors and obtained over half of the requested
datasets, albeit with about 8 days delay and some disagreement with authors.
Given the long term benefits of data accessibility to the academic community,
we believe that journal based mandatory data archiving policies and mandatory
data availability statements should be more widely adopted
Passengers from India and the United States Have Differential Opinions about Autonomous Auto-Pilots for Commercial Flights
There has been much previous research on cultural differences between the United States and India, as well as some research on consumer attitudes towards auto-pilots in commercial airlines. However, to date, there has been no research that examines how passengers from different countries feel about auto-pilots and remote-controlled (RC) pilots in commercial aircraft, or how they feel about their co-workers or children flying in these situations. The current study manipulates both the type of pilot (human pilot, auto-pilot, and RC pilot) and the passenger (participant, child of participant, or work colleague) and examines three different dependent variables (comfort level, trust and willingness to fly). The results are straightforward. All participants were more negative about the auto-pilot and RC pilot compared to the human pilot. All participants were more negative about themselves or their children flying compared to their colleagues. Indians were less extreme in their views compared to Americans. Finally, the implications of this research are discussed
Vergence eye movements in patients with schizophrenia
AbstractPrevious studies have shown that smooth pursuit eye movements are impaired in patients with schizophrenia. However, under normal viewing conditions, targets move not only in the frontoparallel plane but also in depth, and tracking them requires both smooth pursuit and vergence eye movements. Although previous studies in humans and non-human primates suggest that these two eye movement subsystems are relatively independent of one another, to our knowledge, there have been no prior studies of vergence tracking behavior in patients with schizophrenia. Therefore, we have investigated these eye movements in patients with schizophrenia and in healthy controls. We found that patients with schizophrenia exhibited substantially lower gains compared to healthy controls during vergence tracking at all tested speeds (e.g. 0.25Hz vergence tracking mean gain of 0.59 vs. 0.86). Further, consistent with previous reports, patients with schizophrenia exhibited significantly lower gains than healthy controls during smooth pursuit at higher target speeds (e.g. 0.5Hz smooth pursuit mean gain of 0.64 vs. 0.73). In addition, there was a modest (râ0.5), but significant, correlation between smooth pursuit and vergence tracking performance in patients with schizophrenia. Our observations clearly demonstrate substantial vergence tracking deficits in patients with schizophrenia. In these patients, deficits for smooth pursuit and vergence tracking are partially correlated suggesting overlap in the central control of smooth pursuit and vergence eye movements
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