523 research outputs found
The Effects of Disease Contamination on Memory for Touched Objects in Older Adults
Recently it has been shown that individuals have better memory for objects that have been touched by an individual with a contagious disease relative to an individual with a non-contagious disease or who is healthy (Gretz & Huff, 2019). This pattern has been suggested to occur due to the activation of the Behavioral Immune System (BIS)—an avoidance-based system designed to thwart sources of potential pathogens. The BIS has been suggested to operate through an evolutionary-based mechanism in which avoidance of pathogens increases the likelihood of survival, increasing reproductive success. Given this approach, an important question is how the activation of the BIS operates in older adults (60 + years of age), since older adults are past their reproductive prime, with many no longer having the physical capacity for reproduction. To evaluate the evolutionary BIS account, older adults watched a series of videos depicting an actor walking through a household scene and interacting with several objects. Prior to watching the videos, older adults were informed that the actor was either diagnosed with Influenza, a highly contagious disease, Cancer, a non-contagious disease, or was Healthy and not afflicted with any ailments. Following the videos, participants then completed a free-recall test where they were to retrieve the objects from the videos regardless if they were touched and a source-recognition test where they had to identify if a specific object was touched, not touched, or not in the videos at all. Recall of touched objects was greatest in the Influenza group, followed by the Cancer and Healthy groups, and source recognition for touched objects was only greater in the Influenza group relative to the Cancer and Healthy groups. Since touched-object recall was greater in the disease groups over the Healthy group, we instead argue for a health-preservation account over an evolutionary account of the BIS, in which BIS activation operates to promote longevity rather than promoting reproductive success
History of Sanbornton, New Hampshire, in two volumes, Vol. I. annals.
Includes bibliographical references and indexes.; I. Annals -- II. Genealogies
Glassy states in lattice models with many coexisting crystalline phases
We study the emergence of glassy states after a sudden cooling in lattice
models with short range interactions and without any a priori quenched
disorder. The glassy state emerges whenever the equilibrium model possesses a
sufficient number of coexisting crystalline phases at low temperatures,
provided the thermodynamic limit be taken before the infinite time limit. This
result is obtained through simulations of the time relaxation of the standard
Potts model and some exclusion models equipped with a local stochastic dynamics
on a square lattice.Comment: 12 pages, 4 figure
Lattice Glass Models
Motivated by the concept of geometrical frustration, we introduce a class of
statistical mechanics lattice models for the glass transition. Monte Carlo
simulations in three dimensions show that they display a dynamical glass
transition which is very similar to that observed in other off-lattice systems
and which does not depend on a specific dynamical rule. Whereas their analytic
solution within the Bethe approximation shows that they do have a discontinuous
glass transition compatible with the numerical observations.Comment: 4 pages, 2 figures; minor change
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Imaging leukocyte trafficking in vivo with two-photon-excited endogenous tryptophan fluorescence
We describe a new method for imaging leukocytes in vivo by exciting the endogenous protein fluorescence in the ultraviolet (UV) spectral region where tryptophan is the major fluorophore. Two-photon excitation near 590 nm allows noninvasive optical sectioning through the epidermal cell layers into the dermis of mouse skin, where leukocytes can be observed by video-rate microscopy to interact dynamically with the dermal vascular endothelium. Inflammation significantly enhances leukocyte rolling, adhesion, and tissue infiltration. After exiting the vasculature, leukocytes continue to move actively in tissue as observed by time-lapse microscopy, and are distinguishable from resident autofluorescent cells that are not motile. Because the new method alleviates the need to introduce exogenous labels, it is potentially applicable for tracking leukocytes and monitoring inflammatory cellular reactions in humans
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Improved diffuse fluorescence flow cytometer prototype for high sensitivity detection of rare circulating cells in vivo
Abstract. Detection and enumeration of rare circulating cells in mice are important problems in many areas of preclinical biomedical research. Recently, we developed a new method termed “diffuse fluorescence flow cytometry” (DFFC) that uses diffuse photons to increase the blood sampling volume and sensitivity versus existing in vivo flow cytometry methods. In this work, we describe a new DFFC prototype with approximately an order-of-magnitude improvement in sensitivity compared to our previous work. This sensitivity improvement is enabled by a number of technical innovations, which include a method for the removal of motion artifacts (allowing interrogation of mouse hindlegs that was less optically attenuating versus the tail) and improved collection optics and signal preamplification. We validated our system first in limb mimicking optical flow phantoms with fluorescent microspheres and then in nude mice with fluorescently labeled mesenchymal stem cells at injected concentrations of 5×103 cells/mL. In combination, these improvements resulted in an overall cell counting sensitivity of about 1 cell/mL or better in vivo
Teaching Courses Online: A Review of the Research
This literature review summarizes research on online teaching and learning. It is organized into four topics: course environment, learners’ outcomes, learners’ characteristics, and institutional and administrative factors. The authors found little consistency of terminology, discovered some conclusive guidelines, and identified developing lines of inquiry. The conclusions overall suggest that most of the studies reviewed were descriptive and exploratory, that most online students are nontraditional and Anglo American, and that few universities have written policies, guidelines, or technical support for faculty members or students. Asynchronous communication seemed to facilitate in-depth communication (but not more than in traditional classes), students liked to move at their own pace, learning outcomes appeared to be the same as in traditional courses, and students with prior training in computers were more satisfied with online courses. Continued research is needed to inform learner outcomes, learner characteristics, course environment, and institutional factors related to delivery system variables in order to test learning theories and teaching models inherent in course design
Ordering and Demixing Transitions in Multicomponent Widom-Rowlinson Models
We use Monte Carlo techniques and analytical methods to study the phase
diagram of multicomponent Widom-Rowlinson models on a square lattice: there are
M species all with the same fugacity z and a nearest neighbor hard core
exclusion between unlike particles. Simulations show that for M between two and
six there is a direct transition from the gas phase at z < z_d (M) to a demixed
phase consisting mostly of one species at z > z_d (M) while for M \geq 7 there
is an intermediate ``crystal phase'' for z lying between z_c(M) and z_d(M). In
this phase, which is driven by entropy, particles, independent of species,
preferentially occupy one of the sublattices, i.e. spatial symmetry but not
particle symmetry is broken. The transition at z_d(M) appears to be first order
for M \geq 5 putting it in the Potts model universality class. For large M the
transition between the crystalline and demixed phase at z_d(M) can be proven to
be first order with z_d(M) \sim M-2 + 1/M + ..., while z_c(M) is argued to
behave as \mu_{cr}/M, with \mu_{cr} the value of the fugacity at which the one
component hard square lattice gas has a transition, and to be always of the
Ising type. Explicit calculations for the Bethe lattice with the coordination
number q=4 give results similar to those for the square lattice except that the
transition at z_d(M) becomes first order at M>2. This happens for all q,
consistent with the model being in the Potts universality class.Comment: 26 pages, 15 postscript figure
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Tracking Single Cells in Live Animals Using a Photoconvertible Near-Infrared Cell Membrane Label
We describe a novel photoconversion technique to track individual cells in vivo using a commercial lipophilic membrane dye, DiR. We show that DiR exhibits a permanent fluorescence emission shift (photoconversion) after light exposure and does not reacquire the original color over time. Ratiometric imaging can be used to distinguish photoconverted from non-converted cells with high sensitivity. Combining the use of this photoconvertible dye with intravital microscopy, we tracked the division of individual hematopoietic stem/progenitor cells within the calvarium bone marrow of live mice. We also studied the peripheral differentiation of individual T cells by tracking the gain or loss of FoxP3-GFP expression, a marker of the immune suppressive function of CD4+ T cells. With the near-infrared photoconvertible membrane dye, the entire visible spectral range is available for simultaneous use with other fluorescent proteins to monitor gene expression or to trace cell lineage commitment in vivo with high spatial and temporal resolution
Density functional theory for nearest-neighbor exclusion lattice gasses in two and three dimensions
To speak about fundamental measure theory obliges to mention dimensional
crossover. This feature, inherent to the systems themselves, was incorporated
in the theory almost from the beginning. Although at first it was thought to be
a consistency check for the theory, it rapidly became its fundamental pillar,
thus becoming the only density functional theory which possesses such a
property. It is straightforward that dimensional crossover connects, for
instance, the parallel hard cube system (three-dimensional) with that of
squares (two-dimensional) and rods (one-dimensional). We show here that there
are many more connections which can be established in this way. Through them we
deduce from the functional for parallel hard (hyper)cubes in the simple
(hyper)cubic lattice the corresponding functionals for the nearest-neighbor
exclusion lattice gases in the square, triangular, simple cubic, face-centered
cubic, and body-centered cubic lattices. As an application, the bulk phase
diagram for all these systems is obtained.Comment: 13 pages, 13 figures; needs revtex
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