1,016 research outputs found
Translational use of homing peptides: Tumor and placental targeting
HypothesisTissue-specific homing peptides have been shown to improve chemotherapeutic efficacy due to their trophism for tumor cells. Other sequences that selectively home to the placenta are providing new and safer therapeutics to treat complications in pregnancy. Our hypothesis is that the placental homing peptide RSGVAKS (RSG) may have binding affinity to cancer cells, and that insight can be gained into the binding mechanisms of RSG and the tumor homing peptide CGKRK to model membranes that mimic the primary lipid compositions of the respective cells.ExperimentsFollowing cell culture studies on the binding efficacy of the peptides on a breast cancer cell line, a systematic translational characterization is delivered using ellipsometry, Brewster angle microscopy and neutron reflectometry of the extents, structures, and dynamics of the interactions of the peptides with the model membranes on a Langmuir trough.FindingsWe start by revealing that RSG does indeed have binding affinity to breast cancer cells. The peptide is then shown to exhibit stronger interactions and greater penetration than CGKRK into both model membranes, combined with greater disruption to the lipid component. RSG also forms aggregates bound to the model membranes, yet both peptides bind to a greater extent to the placental than cancer model membranes. The results demonstrate the potential for varying local reservoirs of peptide within cell membranes that may influence receptor binding. The innovative nature of our findings motivates the urgent need for more studies involving multifaceted experimental platforms to explore the use of specific peptide sequences to home to different cellular targets
Levinson's Theorem for Dirac Particles
Levinson's theorem for Dirac particles constraints the sum of the phase
shifts at threshold by the total number of bound states of the Dirac equation.
Recently, a stronger version of Levinson's theorem has been proven in which the
value of the positive- and negative-energy phase shifts are separately
constrained by the number of bound states of an appropriate set of
Schr\"odinger-like equations. In this work we elaborate on these ideas and show
that the stronger form of Levinson's theorem relates the individual phase
shifts directly to the number of bound states of the Dirac equation having an
even or odd number of nodes. We use a mean-field approximation to Walecka's
scalar-vector model to illustrate this stronger form of Levinson's theorem. We
show that the assignment of bound states to a particular phase shift should be
done, not on the basis of the sign of the bound-state energy, but rather, in
terms of the nodal structure (even/odd number of nodes) of the bound state.Comment: Latex with Revtex, 7 postscript figures (available from the author),
SCRI-06109
Constraints on the Variation of the Fine Structure Constant from Big Bang Nucleosynthesis
We put bounds on the variation of the value of the fine structure constant
, at the time of Big Bang nucleosynthesis. We study carefully all light
elements up to Li. We correct a previous upper limit on estimated from He primordial abundance and we find interesting new
potential limits (depending on the value of the baryon-to-photon ratio) from
Li, whose production is governed to a large extent by Coulomb barriers. The
presently unclear observational situation concerning the primordial abundances
preclude a better limit than |\Delta \alpha/\alpha| \lsim 2\cdot 10^{-2}, two
orders of magnitude less restrictive than previous bounds. In fact, each of the
(mutually exclusive) scenarios of standard Big Bang nucleosynthesis proposed,
one based on a high value of the measured deuterium primordial abundance and
one based on a low value, may describe some aspects of data better if a change
in of this magnitude is assumed.Comment: 21 pages, eps figures embedded using epsfig macr
Anomalies of ac driven solitary waves with internal modes: Nonparametric resonances induced by parametric forces
We study the dynamics of kinks in the model subjected to a
parametric ac force, both with and without damping, as a paradigm of solitary
waves with internal modes. By using a collective coordinate approach, we find
that the parametric force has a non-parametric effect on the kink motion.
Specifically, we find that the internal mode leads to a resonance for
frequencies of the parametric driving close to its own frequency, in which case
the energy of the system grows as well as the width of the kink. These
predictions of the collective coordinate theory are verified by numerical
simulations of the full partial differential equation. We finally compare this
kind of resonance with that obtained for non-parametric ac forces and conclude
that the effect of ac drivings on solitary waves with internal modes is exactly
the opposite of their character in the partial differential equation.Comment: To appear in Phys Rev
Tracking the reflexivity of the (dis)engaged citizen: some methodological reflections
The relationship between governments and citizens in many contemporary democracies is haunted by uncertainty and sociologists face the task of listening effectively to citizensâ own reflections on this uncertain relationship. This article reflects on the qualitative methodology of a recently completed UK project which used a combination of diary and multiple interviews/ focus groups to track over a fieldwork period of up to a year citizensâ reflections on their relationship to a public world and the contribution to this of their media consumption. In particular, the article considers how the projectâs multiple methods enabled multiple angles on the inevitable artificiality and performative dimension of the diary process, resulting in rich data on peopleâs complex reflections on the uncertain position of the contemporary citizen
Citizen Desires, Policy Outcomes, and Community Control
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68810/2/10.1177_107808747200800107.pd
Light Gluinos and the Parton Structure of the Nucleon
We study the effects of light gluinos with mass below about 1 GeV on the
nucleon parton densities and the running of alpha_(S). It is shown that from
the available high-statistics DIS data no lower bound on the gluino mass can be
derived. Also in the new kinematical region accessible at HERA the influence of
such light gluinos on structure f unctions is found to be very small and
difficult to detect. For use in more direct searches involving final state
signatures we present a radiative estimate of the gluino distribution in the
nucleon.Comment: 23 pages, LateX, 8 figures, MPI-PhT/94-22, LMU-3/9
Organic film thickness influence on the bias stress instability in Sexithiophene Field Effect Transistors
In this paper, the dynamics of bias stress phenomenon in Sexithiophene (T6)
Field Effect Transistors (FETs) has been investigated. T6 FETs have been
fabricated by vacuum depositing films with thickness from 10 nm to 130 nm on
Si/SiO2 substrates. After the T6 film structural analysis by X-Ray diffraction
and the FET electrical investigation focused on carrier mobility evaluation,
bias stress instability parameters have been estimated and discussed in the
context of existing models. By increasing the film thickness, a clear
correlation between the stress parameters and the structural properties of the
organic layer has been highlighted. Conversely, the mobility values result
almost thickness independent
Domain Wall Spacetimes: Instability of Cosmological Event and Cauchy Horizons
The stability of cosmological event and Cauchy horizons of spacetimes
associated with plane symmetric domain walls are studied. It is found that both
horizons are not stable against perturbations of null fluids and massless
scalar fields; they are turned into curvature singularities. These
singularities are light-like and strong in the sense that both the tidal forces
and distortions acting on test particles become unbounded when theses
singularities are approached.Comment: Latex, 3 figures not included in the text but available upon reques
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