8,593 research outputs found
Computer program determines thermal environment and temperature history of lunar orbiting space vehicles
Program computes the thermal environment of a spacecraft in a lunar orbit. The quantities determined include the incident flux /solar and lunar emitted radiation/, total radiation absorbed by a surface, and the resulting surface temperature as a function of time and orbital position
Left lateralization in autobiographical memory: An fMRI study using the expert archival paradigm
In brain-imaging and behavioural research, studies of autobiographical memory have higher ecological validity than controlled laboratory memory studies. However, they also have less controllability over the variables investigated. Here we present a novel techniqueâthe expert archival paradigmâthat increases controllability while maintaining ecological validity. Stimuli were created from games played by two international-level chess masters. We then asked these two players to perform a memory task with stimuli generated from their own games and stimuli generated from other playersâ games while they were scanned using fMRI. We found a left lateralised pattern of brain activity which was very similar in both masters. The brain areas activated were the left temporo-parietal junction and left frontal areas. The expert archival paradigm has the advantage of not requiring an interview to assess the participantsâ autobiographical memories, and affords the possibility of measuring their accuracy of remembering as well as their brain activity related to remote and recent memories. It can also be used in any field of expertise, including arts, sciences and sports, in which archival data are available
Development of an Advanced Force Field for Water using Variational Energy Decomposition Analysis
Given the piecewise approach to modeling intermolecular interactions for
force fields, they can be difficult to parameterize since they are fit to data
like total energies that only indirectly connect to their separable functional
forms. Furthermore, by neglecting certain types of molecular interactions such
as charge penetration and charge transfer, most classical force fields must
rely on, but do not always demonstrate, how cancellation of errors occurs among
the remaining molecular interactions accounted for such as exchange repulsion,
electrostatics, and polarization. In this work we present the first generation
of the (many-body) MB-UCB force field that explicitly accounts for the
decomposed molecular interactions commensurate with a variational energy
decomposition analysis, including charge transfer, with force field design
choices that reduce the computational expense of the MB-UCB potential while
remaining accurate. We optimize parameters using only single water molecule and
water cluster data up through pentamers, with no fitting to condensed phase
data, and we demonstrate that high accuracy is maintained when the force field
is subsequently validated against conformational energies of larger water
cluster data sets, radial distribution functions of the liquid phase, and the
temperature dependence of thermodynamic and transport water properties. We
conclude that MB-UCB is comparable in performance to MB-Pol, but is less
expensive and more transferable by eliminating the need to represent
short-ranged interactions through large parameter fits to high order
polynomials
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Brain Localisation of Memory Chunks in Chessplayers
Chess experts store domain-specific representations in their long-term memory; due to the activation of such representations, they perform with high accuracy in tasks that require the maintenance of previously seen information. Chunk-based theories of expertise (chunking theory: Chase & Simon, 1973; template theory: Gobet & Simon, 1996) state that expertise is acquired mainly by the acquisition and storage in long-term memory of familiar chunks that allow quick recognition. We tested some predictions of these theories by using fMRI while chessplayers performed a recognition memory task. These theories predict that chessplayers access long-term memory chunks of domain-specific information, which are presumably stored in the temporal lobes. We also predicted that the recognition memory tasks would activate working memory areas in the frontal and parietal lobes. These predictions were supported by the data
Urinary Excretion of (1-3)-Beta-D-Glucans.
(1â3)-ÎČ-D-Glucans are carbohydrate polymers that are present in the cell wall of various fungi and bacteria; they are pathogen associated molecular patterns that circulate during infection and modulate immunity. Our laboratory has previously established the pharmacokinetics of intravenously and orally administered glucans; the present studies investigated the renal excretion of (1â3)-ÎČ-D-glucans following intravenous and oral administration. Three fluorescently-labeled glucans were administered to adult male rats in the presence or absence of toxic challenge. Urine specimens were collected and analyzed by fluorescence spectroscopy, size-exclusion chromatography and GPC/MALLS. 71 ± 3% of fluorescence remained in the \u3e5K MWCO fraction; this fraction showed a minor peak with a molecular mass (171 ± 11K) corresponding to injected glucan (~150K). Most excreted glucans were of lower molecular mass (13 ± 8.5K), indicating most (1â3)-ÎČ-D-glucans are excreted by the kidneys as smaller polysaccharides. The presence of urinary glucans may be an important indicator of fungal infection
Generalized Unitary Coupled Cluster Wavefunctions for Quantum Computation
We introduce a unitary coupled-cluster (UCC) ansatz termed -UpCCGSD that
is based on a family of sparse generalized doubles (D) operators which provides
an affordable and systematically improvable unitary coupled-cluster
wavefunction suitable for implementation on a near-term quantum computer.
-UpCCGSD employs products of the exponential of pair coupled-cluster
double excitation operators (pCCD), together with generalized single (S)
excitation operators. We compare its performance in both efficiency of
implementation and accuracy with that of the generalized UCC ansatz employing
the full generalized SD excitation operators (UCCGSD), as well as with the
standard ansatz employing only SD excitations (UCCSD). -UpCCGSD is found to
show the best scaling for quantum computing applications, requiring a circuit
depth of , compared with for UCCGSD and
for UCCSD where is the number of spin
orbitals and is the number of electrons. We analyzed the accuracy of
these three ans\"atze by making classical benchmark calculations on the ground
state and the first excited state of H (STO-3G, 6-31G), HO (STO-3G),
and N (STO-3G), making additional comparisons to conventional coupled
cluster methods. The results for ground states show that -UpCCGSD offers a
good tradeoff between accuracy and cost, achieving chemical accuracy for lower
cost of implementation on quantum computers than both UCCGSD and UCCSD. Excited
states are calculated with an orthogonally constrained variational quantum
eigensolver approach. This is seen to generally yield less accurate energies
than for the corresponding ground states. We demonstrate that using a
specialized multi-determinantal reference state constructed from classical
linear response calculations allows these excited state energetics to be
improved
Eating Right For A Healthy Smile!
This printable handout discusses easy-to-follow tips for mothers and their children to observe for healthy eating and drinking habits (aka âhealthy defaultsâ) for good oral hygiene. The tri-fold also addresses the benefits good oral health has on whole-body wellness and the risks that are associated with poor diet on oral health. The handout is intended to provide mothers with quick and easy tips that feel effortless that will improve her own health, and her children.https://dune.une.edu/an_studedres/1033/thumbnail.jp
Universal persistence exponents in an extremally driven system
The local persistence R(t), defined as the proportion of the system still in
its initial state at time t, is measured for the Bak--Sneppen model. For 1 and
2 dimensions, it is found that the decay of R(t) depends on one of two classes
of initial configuration. For a subcritical initial state, R(t)\sim
t^{-\theta}, where the persistence exponent \theta can be expressed in terms of
a known universal exponent. Hence \theta is universal. Conversely, starting
from a supercritical state, R(t) decays by the anomalous form 1-R(t)\sim
t^{\tau_{\rm ALL}} until a finite time t_{0}, where \tau_{\rm ALL} is also a
known exponent. Finally, for the high dimensional model R(t) decays
exponentially with a non--universal decay constant.Comment: 4 pages, 6 figures. To appear in Phys. Rev.
Geology of Hadley Rille
The regional setting, external and internal shape, and materials of Hadley Rille near the Apollo 15 landing site are described. The petrography presented includes lithologies, regolith, talus, and outcrops. The stratigraphy exposed on the rille wall is also considered
Cluster decomposition of full configuration interaction wave functions: a tool for chemical interpretation of systems with strong correlation
Approximate full configuration interaction (FCI) calculations have recently
become tractable for systems of unforeseen size thanks to stochastic and
adaptive approximations to the exponentially scaling FCI problem. The result of
an FCI calculation is a weighted set of electronic configurations, which can
also be expressed in terms of excitations from a reference configuration. The
excitation amplitudes contain information on the complexity of the electronic
wave function, but this information is contaminated by contributions from
disconnected excitations, i.e. those excitations that are just products of
independent lower-level excitations. The unwanted contributions can be removed
via a cluster decomposition procedure, making it possible to examine the
importance of connected excitations in complicated multireference molecules
which are outside the reach of conventional algorithms. We present an
implementation of the cluster decomposition analysis and apply it to both true
FCI wave functions, as well as wave functions generated from the adaptive
sampling CI (ASCI) algorithm. The cluster decomposition is useful for
interpreting calculations in chemical studies, as a diagnostic for the
convergence of various excitation manifolds, as well as as a guidepost for
polynomially scaling electronic structure models. Applications are presented
for (i) the double dissociation of water, (ii) the carbon dimer, (iii) the
{\pi} space of polyacenes, as well as (iv) the chromium dimer. While the
cluster amplitudes exhibit rapid decay with increasing rank for the first three
systems, even connected octuple excitations still appear important in Cr,
suggesting that spin-restricted single-reference coupled-cluster approaches may
not be tractable for some problems in transition metal chemistry.Comment: 15 pages, 5 figure
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