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Search Results: 1 - 10 of 464363 matches for " Deborah A. Schaefer "
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Cathelicidin-like Helminth Defence Molecules (HDMs): Absence of Cytotoxic, Anti-microbial and Anti-protozoan Activities Imply a Specific Adaptation to Immune Modulation
Karine Thivierge equal contributor,Sophie Cotton equal contributor,Deborah A. Schaefer,Michael W. Riggs,Joyce To,Maria E. Lund,Mark W. Robinson,John P. Dalton,Sheila M. Donnelly
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0002307
Abstract: Host defence peptides (HDPs) are expressed throughout the animal and plant kingdoms. They have multifunctional roles in the defence against infectious agents of mammals, possessing both bactericidal and immune-modulatory activities. We have identified a novel family of molecules secreted by helminth parasites (helminth defence molecules; HDMs) that exhibit similar structural and biochemical characteristics to the HDPs. Here, we have analyzed the functional activities of four HDMs derived from Schistosoma mansoni and Fasciola hepatica and compared them to human, mouse, bovine and sheep HDPs. Unlike the mammalian HDPs the helminth-derived HDMs show no antimicrobial activity and are non-cytotoxic to mammalian cells (macrophages and red blood cells). However, both the mammalian- and helminth-derived peptides suppress the activation of macrophages by microbial stimuli and alter the response of B cells to cytokine stimulation. Therefore, we hypothesise that HDMs represent a novel family of HDPs that evolved to regulate the immune responses of their mammalian hosts by retaining potent immune modulatory properties without causing deleterious cytotoxic effects.
QED in strong fields
A. Schaefer
Physics , 1995, DOI: 10.1016/0168-583X(96)00276-5
Abstract: We discuss the status of atomic physics in strong field. We focus on the problem of electron-positron lines observed in heavy-ion collisions and on QED effects, calculated in strong Coulomb fields, especially Delbr\"uck-scattering. We discuss the similarities and differences between these effects and channeling respectively beamstrahlung. We investigated the prospects for photon-channeling, calculated channeling from first principles on the basis of the Dirac equation, and determined the rate for electron-positron pair production in the collision of two high-energy particle pulses.
Using Place as Provocation: In Situ Collaborative Narrative Construction
Matthew Schaefer,Deborah Tatar,Steve Harrison,Alli Crandell
Journal of the Research Center for Educational Technology , 2008,
Abstract: This paper describes a unique model for mobile, collaborative learning embodied in the use of a new software tool called PlaceMark . The model is overtly intended to help learners reflect on their relationship to particular places, and the relationship between their own experience and other people’s experiences of those spaces. PlaceMark does this not by telling people what a place is, but by instead asking them, as they reflect and write about their own experiences of place. This paper describes how PlaceMark facilitates distributed control in coordinated classroom activities. We believe that the stance to knowledge embodied in the system encourages student responsibility within the learning process and helps teach about multiplicity of perspective in a visceral way. Additionally, as cell phones and other technologies become part of ordinary life, it is increasingly important that children (and all of us) come to have a deeper consciousness of place. This work reports on a pilot study of the software conducted with middle school students, and provides an analysis of the study activity.
Canopy, snow, and lichens on woodland caribou range in southeastern Manitoba
James A. Schaefer
Rangifer , 1996,
Abstract: I examined the relationships among snow cover (api), lichen abundance, and canopy composition on the range of the Aikens Lake population of woodland caribou (Rangifer tarandus caribou) in southeastern Manitoba. Percent cover of forage lichens (Cladina spp.) was positively correlated with maximum total thickness and with maximum vertical hardness of api. Mixed communities of trembling aspen (Populus tremuloides), spruce (Picea spp.), and balsam fir (Abies balsamea) showed the most favourable nival conditions for caribou but had low lichen abundance; those dominated by jack pine (Pinus banksiana) were the converse. The results suggest an energetic compromise for woodland caribou when foraging for terrestrial lichens. During winter, caribou exhibited significant selection for jack pine communities whereas mixed communities were avoided.
Incorporating spatial scale into ecological studies of Rangifer
James A. Schaefer
Rangifer , 1998,
Near field computation of the extinction of electromagnetic waves in multiparticle systems
J. Schaefer,A. Kienle
Atti della Accademia Peloritana dei Pericolanti : Classe di Scienze Fisiche, Matematiche e Naturali , 2011, DOI: 10.1478/c1v89s1p083
Abstract: In this contribution extinction of electromagnetic waves inside a medium consisting of cylindrical absorbing particles is considered. Near fields are calculated using a numerical solution of Maxwell’s equations and compared to results given by Lambert- Beer’s law.
Wavelets as a variational basis of the XY model
C. Best,A. Schaefer
Physics , 1993, DOI: 10.1016/0920-5632(94)90512-6
Abstract: We use Daubechies' orthonormal compact wavelets as a variational basis for the $XY$ model in two and three dimensions. Assuming that the fluctuations of the wavelet coefficients are Gaussian and uncorrelated, minimization of the free energy yields the fluctuation strength of wavelet coefficients at different scales, from which observables can be computed. This model is able to describe the low-temperature phase and makes a prediction about the phase transition temperature.
QCD at high baryon density in a random matrix model
S. Pepin,A. Schaefer
Physics , 2000, DOI: 10.1007/s100500170116
Abstract: A high density diquark phase seems to be a generic feature of QCD. If so it should also be reproduced by random matrix models. We discuss a specific one in which the random matrix elements of the Dirac operator are supplemented by a finite chemical potential and by non-random elements which model the formation of instanton-anti-instanton molecules. Comparing our results to those found in a previous investigation by Vanderheyden and Jackson we find additional support for our starting assumption, namely that the existence of a high density diquark phase is common to all QCD-like models.
Evolution Equations for Higher Moments of Angular Momentum Distributions
P. Haegler,A. Schaefer
Physics , 1998, DOI: 10.1016/S0370-2693(98)00414-6
Abstract: Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix we find a complete set of spin and orbital angular momentum evolution equations.
Higher orders and IR renormalon phenomenology in DVCS
A. V. Belitsky,A. Schaefer
Physics , 1998, DOI: 10.1016/S0550-3213(98)00308-3
Abstract: We present results for higher order perturbative corrections to Compton scattering in the generalized Bjorken kinematics. The approach we have used is based on the combination of two techniques: conformal operator product expansion on the one side, and resummation of the fermion vacuum insertions with consequent restoration of the full QCD beta-function via the naive nonabelianization assumption, on the other. These are terms which are lost in the former approach. Due to the presence of the infrared renormalon poles in the Borel transform of the resummed amplitude the latter suffers from ambiguities which reflect the asymptotic character of perturbation series. The residues of these IR renormalon poles give an estimate for the size of power corrections in deeply virtual Compton scattering.
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