bluuebunny/crossref_metadata_2025 huggingface dataset:
Fitness consequences of Anopheles gambiae population hybridization
Authors: Menge David M , Guda Tom , Zhong Daibin , Pai Aditi , Zhou Goufa , Beier John C , Gouagna Louis , Yan Guiyun
Published: September 2005

Background

The use of transgenic mosquitoes with parasite inhibiting genes has been proposed as an integral strategy to control malaria transmission. However, release of exotic transgenic mosquitoes will bring in novel alleles along with parasite-inhibiting genes that may have unknown effects on native populations. Thus it is necessary to study the effects and dynamics of fitness traits in native mosquito populations in response to the introduction of novel genes. This study was designed to evaluate the dynamics of fitness traits in a simulation of introduction of novel alleles under laboratory conditions using two strains of Anopheles gambiae: Mbita strain from western Kenya and Ifakara strain from Tanzania.

Methods

The dynamics of fitness traits were evaluated under laboratory conditions using the two An. gambiae strains. These two geographically different strains were cross-bred and monitored for 20 generations to score fecundity, body size, blood-meal size, larval survival, and adult longevity, all of which are important determinants of the vector's potential in malaria transmission. Traits were analysed using pair-wise analysis of variance (ANOVA) for fecundity, body size, and blood-meal size while survival analysis was performed for larval survival and adult longevity.

Results

Fecundity and body size were significantly higher in the progeny up to the 20th generation compared to founder strains. Adult longevity had a significantly higher mean up to the 10th generation and average blood-meal size was significantly larger up to the 5th generation, indicating that hybrids fitness is enhanced over that of the founder strains.

Conclusion

Hybridization of the two mosquito populations used in this study led to increased performance in the fitness traits studied. Given that the studied traits are important determinants of the vector's potential to transmit malaria, these results suggest the need to release genetically modified mosquitoes that have the same or very similar backgrounds to the native populations.
Eustachian valve endocarditis: a rare localization of right side endocarditis. A case report and review of the literature
Authors: Pellicelli Adriano M , Pino Paolo , Terranova Antonio , D'Ambrosio Cecilia , Soccorsi Fabrizio
Published: September 2005

Background

Right-sided endocarditis occurs predominantly in intravenous drug users, in patients with pacemaker or central venous lines and in patients with congenital heart disease. The vast majority of cases involve the tricuspid valve. Eustachian valve endocarditis is an uncommon disease with similar signs and symptoms of the tricuspid valve endocarditis. A series of only 16 cases of eustachian valve endocarditis are reported in the literature.

Case Presentation

We present a case of a 25-year old woman with intravenous drug abuse who had a staphylococcus aureus tricuspid valve endocarditis associated to eustachian valve endocarditis. Transthoracic echocardiography, as first line examination, showed the vegetations on tricuspid and eustachian valve.

Conclusion

Our case describe an unusual location of right side endocarditis in a intravenous drug abuser. In our case, in accord with other cases described in the literature, transthoracic echocardiography disclosed eustachian valve endocarditis.

Antimicrobial management is not altered by the recognition of eustachian valve endocarditis. Antibiotic treatment and duration of eustachian endocarditis depends on the isolated organism and is similar to antibiotic therapy used in native valve endocarditis.
Valproic acid and HIV-1 latency: beyond the sound bite
Authors: Smith Stephen M
Published: September 2005

A recent publication in Lancet by Dr. David Margolis and colleagues raised the prospect that HIV infection may be curable. In this pilot study, which received much attention from the press, Dr. Margolis'group found that valproic acid plus enfuvirtide reduces the pool of CD4+ T-cells, which are latently infected with HIV-1, the so-called viral reservoir. This commentary critically addresses current data on this topic.
Transcriptional profiles discriminate bone marrow-derived and synovium-derived mesenchymal stem cells
Authors: Djouad Farida , Bony Claire , Häupl Thomas , Uzé Gilles , Lahlou Najiba , Louis-Plence Pascale , Apparailly Florence , Canovas François , Rème Thierry , Sany Jacques , Jorgensen Christian , Noël Danièle
Published: September 2005

Previous studies have reported that mesenchymal stem cells (MSC) may be isolated from the synovial membrane by the same protocol as that used for synovial fibroblast cultivation, suggesting that MSC correspond to a subset of the adherent cell population, as MSC from the stromal compartment of the bone marrow (BM). The aims of the present study were, first, to better characterize the MSC derived from the synovial membrane and, second, to compare systematically, in parallel, the MSC-containing cell populations isolated from BM and those derived from the synovium, using quantitative assays. Fluorescent-activated cell sorting analysis revealed that both populations were negative for CD14, CD34 and CD45 expression and that both displayed equal levels of CD44, CD73, CD90 and CD105, a phenotype currently known to be characteristic of BM-MSC. Comparable with BM-MSC, such MSC-like cells isolated from the synovial membrane were shown for the first time to suppress the T-cell response in a mixed lymphocyte reaction, and to express the enzyme indoleamine 2,3-dioxygenase activity to the same extent as BM-MSC, which is a possible mediator of this suppressive activity. Using quantitative RT-PCR these data show that MSC-like cells from the synovium and BM may be induced to chondrogenic differentiation and, to a lesser extent, to osteogenic differentiation, but the osteogenic capacities of the synovium-derived MSC were significantly reduced based on the expression of the markers tested (collagen type II and aggrecan or alkaline phosphatase and osteocalcin, respectively). Transcription profiles, determined with the Atlas Human Cytokine/Receptor Array, revealed discrimination between the MSC-like cells from the synovial membrane and the BM-MSC by 46 of 268 genes. In particular, activin A was shown to be one major upregulated factor, highly secreted by BM-MSC. Whether this reflects a different cellular phenotype, a different amount of MSC in the synovium-derived population compared with BM-MSC adherent cell populations or the impact of a different microenvironment remains to be determined. In conclusion, although the BM-derived and synovium-derived MSC shared similar phenotypic and functional properties, both their differentiation capacities and transcriptional profiles permit one to discriminate the cell populations according to their tissue origin.
Reduction of D-dimer levels after therapeutic administration of antithrombin in acquired antithrombin deficiency of severe sepsis
Authors: Kountchev Jordan , Bijuklic Klaudija , Bellmann Romuald , Wiedermann Christian J , Joannidis Michael
Published: September 2005

Introduction

In acute disseminated intravascular coagulation, the effect of antithrombin (AT) administration on elevated levels of D-dimer is not well established. In the present study, we report on changes in circulating levels of D-dimer in response to administration of AT in a series of patients with acquired AT deficiency due to severe sepsis.

Methods

Eight consecutive critically ill medical patients presenting with acute disseminated intravascular coagulation associated with severe sepsis/septic shock received a single bolus infusion of AT over 30 minutes, aiming to achieve physiological AT levels. Haemostatic parameters including D-dimer were assessed prior to, 6 and 24 h after AT administration. An average of 42 ± 9 U/kg body weight was infused.

Results

Following AT substitution, elevated levels of D-dimer fell whereas AT levels rose.

Conclusion

These observations support the notion that AT can favourably affect fibrin degradation accompanying disseminated intravascular coagulation of severe sepsis.
Inferring protein domain interactions from databases of interacting proteins
Authors: Riley Robert , Lee Christopher , Sabatti Chiara , Eisenberg David
Published: September 2005

We describe domain pair exclusion analysis (DPEA), a method for inferring domain interactions from databases of interacting proteins. DPEA features a log odds score, E
ij
, reflecting confidence that domains i and j interact. We analyzed 177,233 potential domain interactions underlying 26,032 protein interactions. In total, 3,005 high-confidence domain interactions were inferred, and were evaluated using known domain interactions in the Protein Data Bank. DPEA may prove useful in guiding experiment-based discovery of previously unrecognized domain interactions.
The TP53 Colorectal Cancer International Collaborative Study on the Prognostic and Predictive Significance of p53 Mutation: Influence of Tumor Site, Type of Mutation, and Adjuvant Treatment
Authors: Russo Antonio , Bazan Viviana , Iacopetta Barry , Kerr David , Soussi Thierry , Gebbia Nicola
Published: September 2005

Purpose

The aims of the TP53 Colorectal Cancer (CRC) International Collaborative Study were to evaluate the possible associations between specific TP53 mutations and tumor site, and to evaluate the prognostic and predictive significance of these mutations in different site, stage, and treatment subgroups.

Patients and Methods

A total of 3,583 CRC patients from 25 different research groups in 17 countries were recruited to the study. Patients were divided into three groups according to site of the primary tumor. TP53 mutational analyses spanned exons 4 to 8.

Results

TP53 mutations were found in 34% of the proximal colon tumors and in 45% of the distal colon and rectal tumors. They were associated with lymphatic invasion in proximal tumors. In distal colon tumors, deletions causing loss of amino acids were associated with worse survival. In proximal colon tumors, mutations in exon 5 showed a trend toward statistical significance (P < .05) when overall survival was considered. Dukes' C tumors with wild-type TP53 and those with mutated TP53 (proximal tumors) showed significantly better prognosis when treated with adjuvant chemotherapy.

Conclusion

Analysis of TP53 mutations from a large cohort of CRC patients has identified tumor site, type of mutation, and adjuvant treatment as important factors in determining the prognostic significance of this genetic alteration.
Phase III Trial of Nanoparticle Albumin-Bound Paclitaxel Compared With Polyethylated Castor Oil–Based Paclitaxel in Women With Breast Cancer
Authors: Gradishar William J. , Tjulandin Sergei , Davidson Neville , Shaw Heather , Desai Neil , Bhar Paul , Hawkins Michael , O'Shaughnessy Joyce
Published: September 2005

Purpose

ABI-007, the first biologically interactive albumin-bound paclitaxel in a nanameter particle, free of solvents, was compared with polyethylated castor oil–based standard paclitaxel in patients with metastatic breast cancer (MBC). This phase III study was performed to confirm preclinical studies demonstrating superior efficacy and reduced toxicity of ABI-007 compared with standard paclitaxel.

Patients and Methods

Patients were randomly assigned to 3-week cycles of either ABI-007 260 mg/m2 intravenously without premedication (n = 229) or standard paclitaxel 175 mg/m2 intravenously with premedication (n = 225).

Results

ABI-007 demonstrated significantly higher response rates compared with standard paclitaxel (33% v 19%, respectively; P = .001) and significantly longer time to tumor progression (23.0 v 16.9 weeks, respectively; hazard ratio = 0.75; P = .006). The incidence of grade 4 neutropenia was significantly lower for ABI-007 compared with standard paclitaxel (9% v 22%, respectively; P < .001) despite a 49% higher paclitaxel dose. Febrile neutropenia was uncommon (< 2%), and the incidence did not differ between the two study arms. Grade 3 sensory neuropathy was more common in the ABI-007 arm than in the standard paclitaxel arm (10% v 2%, respectively; P < .001) but was easily managed and improved rapidly (median, 22 days). No hypersensitivity reactions occurred with ABI-007 despite the absence of premedication and shorter administration time.

Conclusion

ABI-007 demonstrated greater efficacy and a favorable safety profile compared with standard paclitaxel in this patient population. The improved therapeutic index and elimination of corticosteroid premedication required for solvent-based taxanes make the novel albumin-bound paclitaxel ABI-007 an important advance in the treatment of MBC.
Miscibility Transition in a Binary Bose-Einstein Condensate Induced by Linear Interconversion
Authors: Merhasin Ilya M , Malomed Boris A , Driben Rodislav
Published: September 2005

We consider a model of a two-component condensate in one dimension, where the components represent two different spin states of the same atom. We demonstrate that linear interconversion between them, induced by a resonant electromagnetic wave, can make the immiscible binary condensate miscible. This transition is predicted by means of a variational approximation, and is then confirmed by direct numerical solutions of the symmetric and asymmetric models (the asymmetry is accounted for by a chemical-potentil difference between the components). The dependence of the corresponding order parameters on the linear-coupling strengths reveals a typical phase transition of the second kind. However, in dynamic states the species may remain separated, even if they would get mixed in a static configuration.
Observation of the Magnetic Vector Potential à la Aharonov-Bohm Along One Dimension in a Magnetic Field in the Correspondence Limit
Authors: Varma Ram K
Published: September 2005

We report here the observation of the curl-free vector potential a la' Aharonov-Bohm in the classical macro-domain for one-dimensional motion of a charged particle in a magnetic field. The nature of this observation is emphasized here as being a hitherto unfamiliar quantum manifestation of the behaviour of the transition amplitude in the correspondence limit of large Landau quantum numbers.
Motion of Charged Nonspherical Dust Grains in the Plasma Sheath and Influence of their Rotation on Wave Instability
Authors: Tskhakaya D D , Shukla P K
Published: September 2005

The motion of nonspherical (elongated) dust grains in a plasma sheath are analytically investigated. It is found that charged dust grains execute quivering (vibrating) and bouncing motions due to coupling of the dust dipole moment with the plasma sheath electric field and action on the gravity force. Dust rotational motion can be set up by circularly polarized electromagnetic fields. The results are in accord with the laboratory observation of dust cloud motion. The dispersion properties of dusty plasmas are examined. A kinetic equation for the dust grains is derived. The dispersion relations are analyzed to demonstrate that the dust grain rotation introduces new classes of instabilities involving low-frequency waves.
The Collisional Hydrodynamic Equations of Dusty Plasmas
Authors: de Angelis U
Published: September 2005

In the parameter regime where the collisions of electrons and ions with dust particles dominate with respect to the plasma binary collisions, the collisional hydrodynamic equations of dusty plasmas are derived from the kinetic equations which consistently take into account the elastic and inelastic (charging) collisions of plasma particles with dust and the effects of dust charge fluctuations.
Parallel Propagating Electromagnetic Solitons and Oscillitons in Space Plasmas and in Relativistic Electron-Positron Plasmas
Authors: Verheest Frank , Cattaert Tom
Published: September 2005

An overview is given of methods to study weak and strong nonlinear modes in multispecies plasmas, with a discussion of how they correspond (or not) for phenomena at not too strong amplitudes. Reductive perturbation analysis leads for weak nonlinear waves to several well known nonlinear evolution equations. In contrast, strong nonlinear phenomena are dealt with by immediately looking for stationary solutions of the model equations. While this works well for electrostatic modes via the Sagdeev pseudopotential technique, large amplitude, parallel propagating solitary electromagnetic waves occur as oscillitons, for which the correct nonlinear evolution equation is still lacking. Electromagnetic modes in (relativistic) electron-positron plasmas are an exception, in that they give pure solitons, both at large and smaller nonlinear amplitudes. The behaviour of the wave magnetic field is expressed through an energy integral that involves the Mach number of the structure, thus yielding the limits on the allowable Mach numbers and soliton amplitudes.
A Quasi-Particle Approach to Modulational Instabilities in Wave-Plasma Interactions
Authors: Trines R , Bingham R , Silva L O , Mendonça J T , Shukla P K , Mori W B
Published: September 2005

The interaction of broadband turbulence with monochromatic plasma waves has been studied. A kinetic equation for quasi-particles is used to describe the turbulence. Beam instabilities occur in this interaction when the group velocity of the shortwavelength wave packets, or quasi-particles, is nearly equal to the phase velocity of the long-wavelength monochromatic wave. Depending on the bandwidth of the turbulence, either a kinetic resonant instability, e.g. quasi-particle Landau damping, or a hydrodynamic instability, e.g. a modulational instability, will develop. This establishes a direct link between short- and long-wavelength perturbations of the medium. In this paper, the interaction between broadband drift mode turbulence and nearly monochromatic zonal flows has been studied numerically. Simulations have been conducted in which a particle-in-cell representation is used for the quasi-particles, while a fluid model is employed for the plasma. The interactions have been studied in both a tokamak-like configuration and a pseudo-shockwave configuration. Simulation results show the development of a zonal flow through the modulational instability of the drift wave distribution, as well as the existence of solitary zonal flow structures drifting towards steeper relative density gradients. The coupling between short- and long-wavelength modes found here is distinct from the usual picture of direct and inverse energy cascades, and it can be used as a new paradigm for the fluid and plasma turbulence theories.
Nonlinear Drift-Kinetic Evolution of the Electron Distribution Function in Two-Dimensional Magnetic Reconnection
Authors: Pegoraro F , Liseikina T , Echkina E Yu
Published: September 2005

The nonlinear evolution of the electron distribution function in collisionless magnetic field line reconnection is investigated by adopting a drift-kinetic description of the electron response. A two dimensional magnetic configuration with a null line and a strong perpendicular guide magnetic field is considered. Using the conservation of the parallel canonical momentum, the fluid and the drift-kinetic regimes of the collisionless reconnection instability are shown to share common features in terms of the advection and mixing of the Lagrangian invariants.
Experimental Study of Dusty Plasma Kinetics
Authors: Petrov O F , Fortov V E , Vaulina O S , Chernyshev A V , Antipov S N , Gavrikov A V , Shakhova I A
Published: September 2005

The results of investigation of transport processes such as diffusion of dust particles and formation of dust vortices in strongly coupled dusty plasma of gas discharges are considered. Pair correlation functions, velocity spectra, and diffusion coefficients of macroparticles were measured. Results are given of experimental investigation of three-particle correlation for liquid plasma-dust structures. The obtained threeparticle correlation functions for experimental and numerical data are analyzed and compared with the superposition approximation.
A Note on the Ion Surface Waves in a Pair-Ion Plasma
Authors: Hasegawa Akira , Shukla P K
Published: September 2005

The propagation of ion surface waves in a pairion plasma is considered. The dispersion relation for the ion surface waves is derived. The ion surface wave frequency is found to be in good agreement with observations from a recent laboratory experiment.
Effect of the Bounce Orbit's Turning-Point Location on Bounce-Resonance Landau Damping
Authors: Koepke M E
Published: September 2005

The distinction between the bounce-resonant and the velocity-resonant conditions involving electrostatically trapped particles and standing waves in plasma are clarified for the bounce-resonance Landau damping mechanism. Depending on the ratio between the turning-points' separation L for bouncing particles and the end-nodes' separation L' for standing waves in a square electrostatic well, damping can be possible by particles that are bounce resonant but not velocity resonant. The effect of non-coincident locations for the particle turning points and the wave nodes L ≠ L' is investigated. Also presented is the effect of a cut-off in the velocity distribution of the particles, above which no particles exist. It is shown that adjusting the particle turning points with respect to the wave nodes permits damping in the absence of velocity-resonant particles.
Parallel Simulations in Turbulent MHD
Authors: Gómez Daniel O , Mininni Pablo D , Dmitruk Pablo
Published: September 2005

The large-scale dynamics of plasma flows can often be described within a fluidistic approximation known as onefluid magnetohydrodynamics. Complex flows such as those corresponding to turbulent regimes are ubiquitous in laboratory plasmas and in astrophysics, because of their typically very large Reynolds numbers.

Numerical simulations have become a powerful tool for the study of complex plasma flows in recent years. The aim of the present paper is to introduce the reader to some of the standard numerical approximations used for the integration of the magnetohydrodynamic equations. In particular, we focus on pseudospectral methods and on how to develop parallel codes to speed up large Reynolds number simulations. We show the results arising from numerical simulations of astrophysical interest such as the development of turbulent flows in reduced magnetohydrodynamics and the generation of magnetic fields by dynamo mechanisms in three dimensional magnetohydrodynamics.
On Soliton-like Solutions of the Grad-Shafranov Equation
Authors: Shukla P K , Stenflo L , Pokhotelov O A
Published: September 2005

The solitary toroidal vortex solutions of the Grad-Shafranov equations are revisited.
Supernovae and Dark Energy
Authors: John L Tonry
Published: September 2005

Type Ia supernovae provide a precise luminosity distance at redshift as high as z 2. At present nearly 200 SN Ia paint a consistent picture that Ω
A
- 1.4Ω
M
= 0.35 ± 0.14 (if w = -1). If Ω
T
= 1, SN Ia tell us Ω
M
= 0.28 ± 0.05, independent of any other measurements. Adopting a prior based on the 2dF redshift survey constraint on Ω
M
and assuming a flat universe, then -1.48 < w < -0.72 at 95% confidence. If we further assume that w > -1, we obtain w < -0.73 at 95% confidence.

Understanding systematic errors is of paramount importance, both because they may affect our present results and they will limit the eventual precision achievable. Possible sources of error include photometric error, dust extinction, evolution of SN Ia selection effects, K-corrections, and gravitational lensing, all which could vary with redshift. There are many efforts underway to push to higher redshift and to control possible observational systematic errors the bottom line is that the acceleration reported earlier appears to be confirmed.

The propagation of systematic error in luminosity distance to inferred w or w(z) depends critically on how much is known about Ω
M
. For example, at fixed Ω
M
a systematic uncertainty in d
lum of 0.04 mag corresponds to a 10% uncertainty in w, but this becomes much worse if Ω
M
is not known. We will have some good constraints on Ω
M
, either directly from 2dF or SDSS, or indirectly from WMAP whose constraints in the (Ω
M
, w) plane run more or less perpendicular to the SN Ia (but they can also have systematic errors themselves).

Theoretical models for SN Ia are now able to make multi-wavelength light curves and spectra which are a decent match to observation. The luminosity-decline rate correlation depends primarily on the amount of 56Ni produced in the explosion. There are other, more subtle effects which are also being elucidated, for example, increasing initial metallicity (in the form of neutron-rich 56Fe and 22Fe) diminishes the neutron-poor 56Ni and dims the explosion. Unfortunately we have very little idea at present about what causes a WD to explode. A small fraction of WD explode, and those that do wait a long time between their formation and their explosion. Without initial conditions, there is a lot of room for systematic error at the 0.02 mag level from SN Ia explosions, and whether they depend in a serious way with z and therefore limit our ability to measure w(z) remains to be seen. It may be that we can measure d
lum(z) to 1% (0.02 mag) by controlling only observational systematics, or it may be that we incur significant systematic errors for which we do not have the requisite information to realize their presence or correct for them.
What Have We Learned from Cosmic Microwave Background Fluctuations
Authors: David N Spergel
Published: September 2005

How microwave background
observations probe physical conditions in the early universe is reviewed and the relationship between initial conditions and the statistical properties of CMB Fluctuations is discussed. The sensitivity of the angular power spectrum to the basic properties of the universe: its geometry, the abundance of
atoms and dark matter, and the amplitude of initial fluctuations is discussed and the recent results from the Wilkinson Microwave Anisotropy Probe are reviewed. The predictions of the WMAP best fit model are compared with other astronomical observations.
Quintessential Ideas
Authors: Paul J Steinhardt
Published: September 2005

Dark energy may be a form of quintessence, a time-evolving, spatially-varying energy component with negative pressure. This paper reviews current models and discusses the implications of quintessence for the cosmological constant problem, the cosmic coincidence problem, and the history of the universe.
Holographic Cosmology 3.0*
Authors: T Banks  , W Fischler
Published: September 2005

We present a new version of holographic cosmology, which is compatible with present observations. A primordial p = ρ phase of the universe is followed by a brief matter dominated era and a brief period of inflation, whose termination heats the universe. The flatness and horizon problems are solved by the p = ρ dynamics. The model is characterized by two parameters, which should be calculated in a more fundamental approach to the theory. For a large range in the phenomenologically allowed parameter space, the observed fluctuations in the cosmic microwave background were generated during the p = ρ era, and are exactly scale invariant. The scale invariant spectrum cuts off sharply at both upper and lower ends, and this may have observational consequences. We argue that the amplitude of fluctuations is small but cannot yet calculate it precisely.
Bouncing Universes in String Theory?
Authors: Joseph Polchinski
Published: September 2005

I discuss the understanding of cosmological bounces in string theory. I argue that at present, there is no controlled approximation to string theory that gives a bouncing solution (aside from those already allowed in the effective low energy field theory, driven by potential energy). I expect that such bounces do not occur, but it is an important open question.
Remarks on Tachyon Driven Cosmology
Authors: Ashoke Sen
Published: September 2005

We begin by reviewing the results on the decay of unstable D-branes in type II string theory, and the open–closed string duality proposal that arises from these studies. We then apply this proposal to the study of tachyon driven cosmology, namely cosmological solutions describing the decay of unstable space filling D-branes. This naturally gives rise to a time reversal invariant bounce solution with positive spatial curvature. In the absence of a bulk cosmological constant the universe always begins with a big bang and ends in a big crunch. In the presence of a bulk cosmological constant one may get non-singular cosmological solutions for some special range of initial conditions on the tachyon.
Filtering Gravity: Modification at Large Distances
Authors: G Dvali
Published: September 2005

In this lecture I address the issue of possible large distance modification of gravity and its observational consequences. Although, for the illustrative purposes we focus on a particular simple generally-covariant example, our conclusions are rather general and apply to large class of theories in which, already at the Newtonian level, gravity changes the regime at a certain very large crossover distance r
c. In such theories the cosmological evolution gets dramatically modified at the crossover scale, usually exhibiting a `self-accelerated' expansion, which can be differentiated from more conventional `dark energy' scenarios by precision cosmology. However, unlike the latter scenarios, theories of modified-gravity are extremely constrained (and potentially testable) by the precision gravitational measurements at much shorter scales. The reason is that modification implies the new propagating light degrees of freedom (additional polarizations of graviton) which penetrate at short distances in a rather profound way, and lead to the deviations from Einstein's gravity at the source-dependent scales, that for the light sources are way below r
c. At the level of the straightforward perturbative expansion in Newtonian coupling, new polarizations exhibit a `strong coupling' behavior, which invalidates the linearized approximation at short distances and is essential for the observational viability of the theory. We clarify some physical aspects of this phenomenon and the role of the resummed solutions.
In-Phantom Imaging of Absorbed Dose: Intercomparison of Gel-Dosimeter, Gafchromic and Radiographic Film Reliability
Authors: G Gambarini  , M Carrara  , M Cortesi  , U Danesi  , S Gay  , M Lualdi  , R Marchesini  , L Pirola  , S Tomatis
Published: September 2005

The results obtained utilising radiochromic films (Gafchromic MD-55 and HD-810, ISP Technologies Inc.), radiographic films (Kodak EDR2) and laboratory-made Fricke-xylenol-orange-infused gel dosimeters in form of layers have been intercompared. Dose calibration curves have been attained for all kinds of dosimeters and in-phantom measurements have been performed. From the detected in-phantom dose images, depth-dose profiles have been extracted and compared with reference values obtained with an ionisation chamber. The performance of the different dosimeters, their precision and reliability, are presented.
Investigation of the Uranium Solubility and Absorption
Authors: I Anicin  , R Banjanac  , A Dragic  , D Jokovic  , V Udovicic
Published: September 2005

Particles of uranium oxides were produced by combustion of depleted uranium (isotopic contents: 99.8% 238U, 0.2% 235U). Solubility of uranium oxides as well as solubility of metallic uranium in water of various pH values was investigated by x-ray spectroscopy. Also, eventual absorption of dissolved uranium oxides by plants from uranium contaminated ground was investigated. A thin uranium-oxide layer was spread on the soil planted with various vegetables. After a two-month vegetation period the uranium originated radioactivity in the vegetable samples were measured by x-ray spectroscopy and compared with the measurements of samples treated likewise, but in soil without addition of uranium. Due to low radioactivity of the vegetable samples, the spectra were analyzed using Bayesian inference, too.
Ultra-Precise Measurement of Distance by Fabry-Perot Resonator
Authors: O Číp  , F Petrů  , J Lazar  , Z Buchta
Published: September 2005

Length measurements in the region of nanometers by help of laser interferometers are influenced by the nonlinearity of their scale, which is usually ten or more nanometers. We developed and experimentally verified a new method, which has the resolution and linearity of the scale in the order of hundredth part of a nanometer. This method uses an optical Fabry-Perot resonator as a measuring element and by its help it is possible to measure small lengths and to test the nonlinearity of any interferometer with an uncertainty smaller than 0.1 nm The method takes advantage of a direct conversion of the relative changes of the optical path in measuring the arm of the Michelson interferometer to relative changes of the resonant optical frequency of the Fabry-Perot resonator. Frequency changes of the resonator resonance frequency have been monitored by a beat-frequency comparison between tunable He-Ne or semiconductor ECL (Extended Cavity Laser) laser and He-Ne-I2 optical frequency standard at 633 nm.
Direct Measurement of Index of Refraction of Air by Means of High-Resolution Laser Interferometry
Authors: O Číp  , F Petrů  , V Matoušek  , J Lazar
Published: September 2005

Laser interferometers are precise distance measurement devices with resolution in nanometer or sub-nanometer region. If interferometric measurements are carried out under atmospheric conditions (usual situation in industry), they measure the optical path length of an unknown distance instead of its true geometrical value. It is caused by an index of refraction of air that introduces a multiplicative constant to measured results. If we would like to obtain correct values of the unknown distance the knowledge of the index of refraction is necessary. In this work, we present design and the first experimental results of two methods of the direct measurement of the index of refraction, where a Fabry-Perot (FP) interferometer is used as a detection system. The first method employs an evacuable cell inserted into the mirrors of the FP interferometer and the other method consists of a differential setup of two FP interferometers, one of which is permanently evacuated.
Analysis of Bragg Diffraction Filters Applied to Image Processing
Authors: A Márquez  , C Neipp  , S Gallego  , M Ortuño  , A Beléndez  , I Pascual
Published: September 2005

In this work we study the properties offered by holographically recorded volume gratings when applied to image processing in imaging systems. Angular selectivity due to Bragg diffraction modifies the transfer function of the imaging system and spatial filtering operations are performed with no need of a Fourier plane. We use Kogelnik's coupled wave theory to calculate these transfer functions. We demonstrate both edge enhancement and image smoothing in amplitude objects and in phase-only objects. To obtain satisfactory processed images we analyze the influence of the different parameters of the volume grating. Both experimental and simulated results are shown with an excellent agreement. In certain applications image processing by Bragg diffraction offers an interesting alternative with respect to Fourier plane based strategies.
Numerical and Experimental Analysis of Large Deflections of Cantilever Beams Under a Combined Load
Authors: T Beléndez  , M Pérez-Polo  , C Neipp  , A Beléndez
Published: September 2005

We analyzed the large deflections of a uniform cantilever beam under the action of a combined load consisting of an external vertical concentrated load at the free end and a uniformly distributed load. The problem involves geometrical non-linearity and a differential equation governing the behavior of the beam is presented. The numerical solution was obtained using an algorithm based on the Runge-Kutta-Felhberg method. This algorithm was used to numerically evaluate the system, and the slopes and deflections were determined for various loads. Finally, we compared the numerical results with the experimental ones obtained in the laboratory and calculated Young's modulus for the beam material.
Holographic Characteristics of an Acrylamide/Bisacrylamide Photopolymer in 40–1000 µm Thick Layers
Authors: M Ortuño  , S Gallego  , C García  , I Pascual  , C Neipp  , A Beléndez
Published: September 2005

In this study we analyze the holographic behaviour of an acrylamide/bisacrylamide photopolymer in layers that range in thickness from 40 to 1000 µm. The photopolymer is composed of acrylamide as polymerizable monomer, N,N' methylene-bis-acrylamide as crosslinker, triethanolamine as radical generator, yellowish eosin as sensitizer and polyvinyl alcohol as binder. The composition and method of depositing the solution varies depending on the desired thickness of the final layer. For each thickness we analyze the holographic behaviour of the material during recording of unslanted diffraction gratings using a continuous argon laser (514 nm) at an intensity of 5 mW/cm2. The response of the material is monitored in real time with an He-Ne laser. The results obtained for the different parameters evaluated vary considerably depends on the layer thickness. Therefore, the different potential applications of the material (fabrication of holographic optical elements, use as recording material in holographic interferometry, or manufacture of holographic memories) depends on its thickness.
Effective Index Method for Modelling Sub-Wavelength Two-Dimensional Periodic Structures
Authors: G Lifante
Published: September 2005

An approximate method is here proposed for modelling two-dimensional sub-wavelength periodic structures. The method is based on the effective index method, where the two-dimensional problem structure is split on two one-dimensional problems, which can be solved by conventional tools. It provides in a natural way the biaxial character of a two-dimensional periodic structure with different period along different directions. The method has been tested by comparing the effective refractive index provided by more exact algorithms with the one provided by the effective index method, showing quite good agreement. Also, the EIM has been used to simulate the reflectance and transmittance behaviour of pyramidal profiles, showing also good agreement with the results supplied by exact calculations using RCWA technique. The main advantages of the method are that it is easy to implement, and the short computational time required to model a given structure.
Advancing the Optical Feed Back Concept: Grating Enhanced External Cavity Diode Laser
Authors: A Wicht  , P Huke  , R-H Rinkleff  , K Danzmann
Published: September 2005

We present theoretical and experimental investigations on a new optical feedback concept for single mode diode lasers. It is based on the optical feedback from a resonant external cavity coupled to the diode laser through the 1st order diffraction of a grating. With a single mode diode laser operating at 852 nm we demonstrate a short term line width of less than 60 kHz, an overall tuneability in excess of 36.4 nm and a continuous tuning range in excess of 45 GHz, both at constant diode temperature.
Emission and Absorption Cross-Section Calculation of Rare Earth Doped Materials for Applications to Integrated Optic Devices
Authors: P L Pernas  , E Cantelar
Published: September 2005

With the increasing sophistication required in integrated-optical devices it has become necessary to develop accurate methods that allow for an optimization of component design. In this paper we present an overview of the theory and the experimental conditions needed to obtain optical cross sections applicable to rare-earth doped materials. The values generated by the method provide the accuracy needed in the modelling of rare earth-doped integrated devices. As a test case, we have applied the method to the 4I13/2 → 4I15/2 transition of Er3+-doped LiNbO3 crystals and Zn diffused Er:LiNbO3 channel waveguides developed in our laboratory. Adverse effects of concentration determination and ion-clustering are investigated.
Reconstruction of In-Line Holograms Using Phase Retrieval Algorithms
Authors: Yan Zhang  , Giancarlo Pedrini  , Wolfgang Osten  , Hans J Tiziani
Published: September 2005

In-line holography is a simple technique for high-resolution imaging, however, due to the fact that the reference and illuminating lights are overlapped during the hologram is recorded, the real image and its twin image are in the same position, which will bring difficulties to distinguish the real one. The Yang-Gu (YG) and Gerchberg-Saxton (GS) algorithms are used to reconstruct pure real object from a single in-line hologram. The differences between the YG and GS algorithms are shown. The modified GS algorithm is also used for phase-contrast imaging and optical metrology. This method can present quantitative phase-contrast image based on only one in-line hologram. The image reconstructed from experimentally obtained data shows the good agreement with the sample.
Decoherence of the Exciton and Decay of the Excitonic Polaron in Quantum Dots
Authors: A Janutka  , L Jacak  , J Krasnyj  , P Machnikowski  , A Radosz
Published: September 2005

Bulk-phonon mechanisms of decoherence of an exciton confined in a quantum dot (QD) are considered in order to establish time limitations for the coherent control of the exciton with relevance to its application in quantum information processing. These are the formation and decay of the excitonic polaron. The estimations of characteristic dephasing times for the InAs/GaAs QD are discussed.
A Method to Separate Stochastic and Deterministic Information from Electrocardiograms
Authors: R M Gutiérrez  , L A Sandoval
Published: September 2005

In this work we present a new idea to develop a method to separate stochastic and deterministic information contained in an electrocardiogram, ECG, which may provide new sources of information with diagnostic purposes. We assume that the ECG has information corresponding to many different processes related with the cardiac activity as well as contamination from different sources related with the measurement procedure and the nature of the observed system itself. The method starts with the application of an improved archetypal analysis to separate the mentioned stochastic and deterministic information. From the stochastic point of view we analyze Renyi entropies, and with respect to the deterministic perspective we calculate the autocorrelation function and the corresponding correlation time. We show that healthy and pathologic information may be stochastic and/or deterministic, can be identified by different measures and located in different parts of the ECG.
Inducing Periodicity in Lattices of Chaotic Maps with Advection
Authors: Pedro G Lind  , Jason A C Gallas
Published: September 2005

We investigate a lattice of coupled logistic maps where, in addition to the usual diffusive coupling, an advection term parameterized by an asymmetry in the coupling is introduced. The advection term induces periodic behavior on a significant number of non-periodic solutions of the purely diffusive case. Our results are based on the characteristic exponents for such systems, namely the mean Lyapunov exponent and the co-moving Lyapunov exponent. In addition, we study how to deal with more complex phenomena in which the advective velocity may vary from site to site. In particular, we observe wave-like pulses to appear and disappear intermittently whenever the advection is spatially inhomogeneous.
Computational Simulation of Laser Dynamics as a Cooperative Phenomenon
Authors: J L Guisado  , F Jiménez-Morales  , J M Guerra
Published: September 2005

The different kinds of behavior exhibited by the system in a laser dynamics simulation using a cellular automata model are analyzed. Three distinct types of behavior have been found: laser constant operation, laser spiking and a complex behavior showing irregular oscillations. In the last case, the power spectrum follows a power law of the type 1/f
−β with exponent close to β = 2. In the laser spiking regime, the dependence of the decay rate of the oscillations is found to be in good agreement with the predictions of the theoretical laser rate equations and the experimental phenomenology. In our model the system components evolve under local rules which reproduce the physics of the laser system at the microscopic level, and the laser properties appear as cooperative emergent phenomena associated to these rules.
Parallel Genetic Algorithm for Alpha Spectra Fitting
Authors: Carlos J García-Orellana  , Pilar Rubio-Montero  , Horacio González-Velasco
Published: September 2005

We present a performance study of alpha-particle spectra fitting using parallel Genetic Algorithm (GA). The method uses a two-step approach. In the first step we run parallel GA to find an initial solution for the second step, in which we use Levenberg-Marquardt (LM) method for a precise final fit. GA is a high resources-demanding method, so we use a Beowulf cluster for parallel simulation. The relationship between simulation time (and parallel efficiency) and processors number is studied using several alpha spectra, with the aim of obtaining a method to estimate the optimal processors number that must be used in a simulation.
Effects of Lattice Structure in the Dynamics of Coupled Elements
Authors: André S Ribeiro  , Pedro G Lind
Published: September 2005

We investigate the influence of lattice geometry in network dynamics, using a cellular automaton with nearest-neighbor interactions and two admissible local states. We show that there are significant geometric effects in the distribution of local states and in the distribution of clusters, even when the connection topology is kept constant. Moreover, we show that some geometric structures are more cohesive than others, tending to keep a given initial configuration. To characterize the dynamics, we determine the distributions of local states and introduce a cluster coefficient. The lattice geometry is defined from the number of nearest neighbors and their disposition in ‘space', and here we consider four different geometries: a chain, a hexagonal lattice, a square lattice and a cubic lattice.
Frequency of Micronucleated Erythrocytes in Rat Bone Marrow Exposed to 2.45 GHz Radiation
Authors: I Trosic  , I Busljeta
Published: September 2005

Wistar rats were exposed to 2.45 GHz continuous, radiofrequency microwave (RF/MW) field 2 hours daily, 7 days weekly, at power density 5–10 mW/cm2. Four subgroups were created in order to be irradiated 4, 16, 30 and 60 hours. Sham-exposed controls were included in the study. Animals were euthanized on the final irradiation day of each treated subgroup. Bone marrow smears were examined to determine the extent of genotoxicity after the particular treatment time. Mann-Whitney test was used for statistical evaluation of data. In comparison to the sham-exposed subgroups, the findings of polychromatic erythrocytes revealed significant differences for the 8th and 15th experimental day. Bone marrow erythrocyte maturation and/or proliferation initiated by subthermogenic RF/MW irradiation showed temporary disturbance. Thereafter, the frequency of micronucleated bone marrow red cells was significantly increased after 15 irradiation treatments. Comparison of micronucleus frequency data obtained after 2, 8 and 30 irradiation treatments did not reveal statistically significant differences between sham and treated subgroups. Under the applied experimental conditions, RF/MW irradiation initiates transitory cytogenetic effect manifested with micronucleus formation in erythropoietic cells.