537 research outputs found
Recommended from our members
Four-wave mixing using polarization grating induced thermal grating in liquids exhibiting circular dichroism
A novel four-wave mixing technique for the detection of circular dichroism in optically active liquid samples is demonstrated. When two cross-polarized laser beams are crossed at a small angle in a circular dichroic liquid a weak thermal grating is produced with a phase depending on the sign of the circular dichroism. The authors show that the polarization of one of the beams can be modified to allow coherent interference with an intensity-grating induced thermal grating. A probe beam scattering from the composite grating results in a signal that reveals the sign and magnitude of the circular dichroism. The use of this technique to optimize the signal-to-noise ratio in the presence of scattered light and laser intensity noise is discussed
Projected shell model study for the yrast-band structure of the proton-rich mass-80 nuclei
A systematic study of the yrast-band structure for the proton-rich, even-even
mass-80 nuclei is carried out using projected shell model approach. We describe
the the energy spectra, transition quadrupole moments and gyromagnetic factors.
The observed variations in energy spectra and transition quadrupole moments in
this mass region are discussed in terms of the configuration mixing of the
projected deformed Nilsson states as a function of shell filling.Comment: 22 pages, 7 figure
Probability Distribution Function of the Order Parameter: Mixing Fields and Universality
We briefly review the use of the order parameter probability distribution
function as a useful tool to obtain the critical properties of statistical
mechanical models using computer Monte Carlo simulations. Some simple discrete
spin magnetic systems on a lattice, such as Ising, general spin- Blume-Capel
and Baxter-Wu, -state Potts, among other models, will be considered as
examples. The importance and the necessity of the role of mixing fields in
asymmetric magnetic models will be discussed in more detail, as well as the
corresponding distributions of the extensive conjugate variables.Comment: 14 pages, 13 figures, accepted for publication (Computer Physics
Communications
Self-assembly mechanism in colloids: perspectives from Statistical Physics
Motivated by recent experimental findings in chemical synthesis of colloidal
particles, we draw an analogy between self-assembly processes occurring in
biological systems (e.g. protein folding) and a new exciting possibility in the
field of material science. We consider a self-assembly process whose elementary
building blocks are decorated patchy colloids of various types, that
spontaneously drive the system toward a unique and predetermined targeted
macroscopic structure.
To this aim, we discuss a simple theoretical model -- the Kern-Frenkel model
-- describing a fluid of colloidal spherical particles with a pre-defined
number and distribution of solvophobic and solvophilic regions on their
surface. The solvophobic and solvophilic regions are described via a
short-range square-well and a hard-sphere potentials, respectively.
Integral equation and perturbation theories are presented to discuss
structural and thermodynamical properties, with particular emphasis on the
computation of the fluid-fluid (or gas-liquid) transition in the
temperature-density plane.
The model allows the description of both one and two attractive caps, as a
function of the fraction of covered attractive surface, thus interpolating
between a square-well and a hard-sphere fluid, upon changing the coverage.
By comparison with Monte Carlo simulations, we assess the pros and the cons
of both integral equation and perturbation theories in the present context of
patchy colloids, where the computational effort for numerical simulations is
rather demanding.Comment: 14 pages, 7 figures, Special issue for the SigmaPhi2011 conferenc
Recommended from our members
Electron transport in radiotherapy using local-to-global Monte Carlo
Local-to-Global (L-G) Monte Carlo methods are a way to make three-dimensional electron transport both fast and accurate relative to other Monte Carlo methods. This is achieved by breaking the simulation into two stages: a local calculation done over small geometries having the size and shape of the ``steps`` to be taken through the mesh; and a global calculation which relies on a stepping code that samples the stored results of the local calculation. The increase in speed results from taking fewer steps in the global calculation than required by ordinary Monte Carlo codes and by speeding up the calculation per step. The potential for accuracy comes from the ability to use long runs of detailed codes to compile probability distribution functions (PDFs) in the local calculation. Specific examples of successful Local-to-Global algorithms are given
PDGF-B gene therapy accelerates bone engineering and oral implant osseointegration
Platelet-derived growth factor-BB (PDGF-BB) stimulates repair of healing-impaired chronic wounds such as diabetic ulcers and periodontal lesions. However, limitations in predictability of tissue regeneration occur due, in part, to transient growth factor bioavailability in vivo. Here, we report that gene delivery of PDGF-B stimulates repair of oral implant extraction socket defects. Alveolar ridge defects were created in rats and were treated at the time of titanium implant installation with a collagen matrix containing an adenoviral (Ad) vector encoding PDGF-B (5.5 x 10(8) or 5.5 x 10(9) pfu ml(-1)), Ad encoding luciferase (Ad-Luc; 5.5 x 10(9) pfu ml(-1); control) or recombinant human PDGF-BB protein (rhPDGF-BB, 0.3 mg ml(-1)). Bone repair and osseointegration were measured through backscattered scanning electron microscopy, histomorphometry, micro-computed tomography and biomechanical assessments. Furthermore, a panel of local and systemic safety assessments was performed. Results indicated that bone repair was accelerated by Ad-PDGF-B and rhPDGF-BB delivery compared with Ad-Luc, with the high dose of Ad-PDGF-B more effective than the low dose. No significant dissemination of the vector construct or alteration of systemic parameters was noted. In summary, gene delivery of Ad-PDGF-B shows regenerative and safety capabilities for bone tissue engineering and osseointegration in alveolar bone defects comparable with rhPDGF-BB protein delivery in vivo
A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship
Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship
Interpreting Quantum Particles as Conceptual Entities
We elaborate an interpretation of quantum physics founded on the hypothesis
that quantum particles are conceptual entities playing the role of
communication vehicles between material entities composed of ordinary matter
which function as memory structures for these quantum particles. We show in
which way this new interpretation gives rise to a natural explanation for the
quantum effects of interference and entanglement by analyzing how interference
and entanglement emerge for the case of human concepts. We put forward a scheme
to derive a metric based on similarity as a predecessor for the structure of
'space, time, momentum, energy' and 'quantum particles interacting with
ordinary matter' underlying standard quantum physics, within the new
interpretation, and making use of aspects of traditional quantum axiomatics.
More specifically, we analyze how the effect of non-locality arises as a
consequence of the confrontation of such an emerging metric type of structure
and the remaining presence of the basic conceptual structure on the fundamental
level, with the potential of being revealed in specific situations.Comment: 19 pages, 1 figur
Observational diagnostics of gas in protoplanetary disks
Protoplanetary disks are composed primarily of gas (99% of the mass).
Nevertheless, relatively few observational constraints exist for the gas in
disks. In this review, I discuss several observational diagnostics in the UV,
optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to
study the gas in the disks of young stellar objects. I concentrate in
diagnostics that probe the inner 20 AU of the disk, the region where planets
are expected to form. I discuss the potential and limitations of each gas
tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and
Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date
manuscript: October 2008. 17 Pages, 6 graphics, 134 reference
- …