Pattern formation of chevrons in the conduction regime in homeotropically aligned liquid crystals

We report on chevrons (herringbonelike patterns) observed in homeotropically aligned liquid crystals with high electric conductivity. We focus our attention on two types of chevrons observed in the conduction regime. The threshold voltage and the characteristic double periodicity of chevrons (i.e., the short wavelength lambda(1) of the striated rolls and the long wavelength lambda(2) Of the chevron bands) have been measured as functions of the applied electric frequency f. With the aid of a crossed polarizer set, we have, in addition, determined the director field which shows a periodic in-plane rotation for our chevrons (with a wavelength lambda(2)) We arrived at the types of chevrons after qualitatively different bifurcation sequences with increasing voltage. The frequency dependence of lambda(2) also shows a qualitatively different behavior with respect to the two types of chevrons. The experimental results are discussed in terms of recent theoretical investigations.

Eigenvalues of the time-delay matrix in overlapping resonances

We discuss the properties of the lifetime or the time-delay matrix Q(E) for multichannel scattering, which is related to the scattering matrix S(E) by Q = i?S(dS†/dE). For two overlapping resonances occurring at energies E with widths G(? = 1, 2), with an energy-independent background, only two eigenvalues of Q(E) are proved to be different from zero and to show typical avoided-crossing behaviour. These eigenvalues are expressible in terms of the four resonance parameters (E , G) and a parameter representing the strength of the interaction of the resonances. An example of the strong and weak interaction in an overlapping double resonance is presented for the positronium negative ion. When more than two resonances overlap (? = 1, ..., N), no simple representation of each eigenvalue has been found. However, the formula for the trace of the Q-matrix leads to the expression d(E) = -?arctan[(G/2)/(E - E)] + d(E) for the eigenphase sum d(E) and the background eigenphase sum d(E), in agreement with the known form of the state density. The formulae presented in this paper are useful in a parameter fitting of overlapping resonances. © 2006 IOP Publishing Ltd.

Evaluation of Random Delay Insertion against DPA on FPGAs

Side-channel attacks (SCA) threaten electronic cryptographic devices and can be carried out by monitoring the physical characteristics of security circuits. Differential Power Analysis (DPA) is one the most widely studied side-channel attacks. Numerous countermeasure techniques, such as Random Delay Insertion (RDI), have been proposed to reduce the risk of DPA attacks against cryptographic devices. The RDI technique was first proposed for microprocessors but it was shown to be unsuccessful when implemented on smartcards as it was vulnerable to a variant of the DPA attack known as the Sliding-Window DPA attack.Previous research by the authors investigated the use of the RDI countermeasure for Field Programmable Gate Array (FPGA) based cryptographic devices. A split-RDI technique wasproposed to improve the security of the RDI countermeasure. A set of critical parameters wasalso proposed that could be utilized in the design stage to optimize a security algorithm designwith RDI in terms of area, speed and power. The authors also showed that RDI is an efficientcountermeasure technique on FPGA in comparison to other countermeasures.In this article, a new RDI logic design is proposed that can be used to cost-efficiently implementRDI on FPGA devices. Sliding-Window DPA and realignment attacks, which were shown to beeffective against RDI implemented on smartcard devices, are performed on the improved RDIFPGA implementation. We demonstrate that these attacks are unsuccessful and we also proposea realignment technique that can be used to demonstrate the weakness of RDI implementations.

Time delay between photoemission from the 2p and 2s subshells of neon

The R-matrix incorporating time (RMT) method is a method developed recently for solving the time-dependent Schrödinger equation for multielectron atomic systems exposed to intense short-pulse laser light. We have employed the RMT method to investigate the time delay in the photoemission of an electron liberated from a 2p orbital in a neon atom with respect to one released from a 2s orbital following absorption of an attosecond xuv pulse. Time delays due to xuv pulses in the range 76-105 eV are presented. For an xuv pulse at the experimentally relevant energy of 105.2 eV, we calculate the time delay to be 10.2±1.3 attoseconds (as), somewhat larger than estimated by other theoretical calculations, but still a factor of 2 smaller than experiment. We repeated the calculation for a photon energy of 89.8 eV with a larger basis set capable of modeling correlated-electron dynamics within the neon atom and the residual Ne ion. A time delay of 14.5±1.5 as was observed, compared to a 16.7±1.5 as result using a single-configuration representation of the residual Ne⁺ ion. 

Transient Heat Conduction of Variable Stiffness Composite Laminate

Recent research on Variable Stiffness (VS) laminates, which are constructed by steering the fiber orientation as a spatial function of location, have shown to improve laminate performance under mechanical loads. Two distinct cases of stiffness variation can be achieved either by variation of the fiber orientation in the direction of the global x-axis, or perpendicular to it. In the present paper, thermal analysis of a VS laminate is performed to study the effect of steering fibers on transient heat conduction under uniform heat flux using finite element method. The goal of the present paper is a parametric study of the effect of variable stiffness properties on transient response including time to reach steady state and temperature profile. Also, stress resultants and maximum stress location are investigated under different boundary conditions. A FEM algorithm is applied to exactly incorporate the boundary conditions for stress resultant analysis.

Transient Heat Conduction of Variable Stiffness Composite Laminate

Recent research on Variable Stiffness (VS) laminates, which are constructed by steering the fiber orientation as a spatial function of location, have shown to improve laminate performance under mechanical loads. Two distinct cases of stiffness variation can be achieved either by variation of the fiber orientation in the direction of the global x-axis, or perpendicular to it. In the present paper, thermal analysis of VS laminate is performed to study the effect of steering fibers on transient heat conduction under uniform heat flux using finite element method. The goal of the present paper is a parametric study of the
effect of variable stiffness properties on transient response including time to reach steady state and temperature profile. Also, stress resultants and maximum stress location are investigated under different boundary conditions. A FEM algorithm is applied to exactly incorporate the boundary conditions.

Burkholderia cenocepacia-induced delay of acidification and phagolysosomal fusion in cystic fibrosis transmembrane conductance regulator (CFTR)-defective macrophages

The Burkholderia cepacia complex (Bcc) is a group of opportunistic bacteria chronically infecting the airways of patients with cystic fibrosis (CF). Several laboratories have shown that Bcc members, in particular B. cenocepacia, survive within a membrane-bound vacuole inside phagocytic and epithelial cells. We have previously demonstrated that intracellular B. cenocepacia causes a delay in phagosomal maturation, as revealed by impaired acidification and slow accumulation of the late phagolysosomal marker LAMP-1. In this study, we demonstrate that uninfected cystic fibrosis transmembrane conductance regulator (CFTR)-defective macrophages or normal macrophages treated with a CFTR-specific drug inhibitor display normal acidification. However, after ingestion of B. cenocepacia, acidification and phagolysosomal fusion of the bacteria-containing vacuoles occur in a lower percentage of CFTR-negative macrophages than CFTR-positive cells, suggesting that loss of CFTR function contributes to enhance bacterial intracellular survival. The CFTR-associated phagosomal maturation defect was absent in macrophages exposed to heat-inactivated B. cenocepacia and macrophages infected with a non-CF pathogen such as Salmonella enterica, an intracellular pathogen that once internalized rapidly traffics to acidic compartments that acquire lysosomal markers. These results suggest that not only a defective CFTR but also viable B. cenocepacia are required for the altered trafficking phenotype. We conclude that CFTR may play a role in the mechanism of clearance of the intracellular infection, as we have shown before that B. cenocepacia cells localized to the lysosome lose cell envelope integrity. Therefore, the prolonged maturation arrest of the vacuoles containing B. cenocepacia within cftr(-/-) macrophages could be a contributing factor in the persistence of the bacteria within CF patients.

Burkholderia cenocepacia requires RpoE for growth under stress conditions and delay of phagolysosomal fusion in macrophages

Burkholderia cenocepacia is an opportunistic pathogen causing serious infections in patients with cystic fibrosis. The widespread distribution of this bacterium in the environment suggests that it must adapt to stress to be able to survive. We identified in B. cenocepacia K56-2 a gene predicted to encode RpoE, the extra-cytoplasmic stress response regulator. The rpoE gene is the first gene of a predicted operon encoding proteins homologous to RseA, RseB, MucD and a protein of unknown function. The genomic organization and the co-transcription of these genes were confirmed by PCR and RT-PCR. The mucD and rpoE genes were mutated, giving rise to B. cenocepacia RSF24 and RSF25, respectively. While mutant RSF24 did not demonstrate any growth defects under the conditions tested, RSF25 was compromised for growth under temperature (44 degrees C) and osmotic stress (426 mM NaCl). Expression of RpoE in trans could complement the osmotic growth defect but exacerbated temperature sensitivity in both RSF25 and wild-type K56-2. Inactivation of rpoE altered the bacterial cell surface, as indicated by increased binding of the fluorescent dye calcofluor white and by an altered outer-membrane protein profile. These cell surface changes were restored by complementation with a plasmid encoding rpoE. Macrophage infections in which bacterial colocalization with fluorescent dextran was examined demonstrated that the rpoE mutant could not delay the fusion of B. cenocepacia-containing vacuoles with lysosomes, in contrast to the parental strain K56-2. These data show that B. cenocepacia rpoE is required for bacterial growth under certain stress conditions and for the ability of intracellular bacteria to delay phagolysosomal fusion in macrophages.

Intracellular survival of Burkholderia cenocepacia in macrophages is associated with a delay in the maturation of bacteria-containing vacuoles

Strains of the Burkholderia cepacia complex (Bcc) are opportunistic bacteria that can cause life-threatening infections in patients with cystic fibrosis and chronic granulomatous disease. Previous work has shown that Bcc isolates can persist in membrane-bound vacuoles within amoeba and macrophages without bacterial replication, but the detailed mechanism of bacterial persistence is unknown. In this study, we have investigated the survival of the Burkholderia cenocepacia strain J2315 within RAW264.7 murine macrophages. Strain J2315 is a prototypic isolate of the widespread and transmissible ET12 clone. Unlike heat-inactivated bacteria, which reach lysosomes shortly after internalization, vacuoles containing live B. cenocepacia J2315 accumulate the late endosome/lysosome marker LAMP-1 and start fusing with lysosomal compartments only after 6 h post internalization. Using fluorescent fluid-phase probes, we also demonstrated that B. cenocepacia-containing vacuoles continued to interact with newly formed endosomes, and maintained a luminal pH of 6.4 +/- 0.12. In contrast, vacuoles containing heat-inactivated bacteria had an average pH of 4.8 +/- 0.03 and rapidly merged with lysosomes. Additional experiments using concanamycin A, a specific inhibitor of the vacuolar H+-ATPase, revealed that vacuoles containing live bacteria did not exclude the H+-ATPase. This mode of bacterial survival did not require type III secretion, as no differences were found between wild type and a type III secretion mutant strain. Collectively, our results suggest that intracellular B. cenocepacia cause a delay in the maturation of the phagosome, which may contribute to facilitate bacterial escape from the microbicidal activities of the host cell.

Optimization of Composite Structures to Delay Mode Jump Instabilities

Numerous studies have shown that postbuckling stiffened panels may undergo abrupt changes in buckled mode
shape when loaded in uniaxial compression. This phenomenon is often referred to as a mode jump or secondary
instability. The resulting sudden release of stored energy may initiate damage in vulnerable regions within a
structure, for example, at the skin-stiffener interface of a stiffened composite panel. Current design practice is to
remove a mode jump by increasing the skin thickness of the postbuckling region. A layup optimization methodology,
based on a genetic algorithm, is presented, which delays the onset of secondary instabilities in a composite structure
while maintaining a constant weight and subject to a number of design constraints. A finite element model was
developed of a stiffened panel’s skin bay, which exhibited secondary instabilities. An automated numerical routine
extracted information directly from the finite element displacement results to detect the onset of initial buckling and
secondary instabilities. This routine was linked to the genetic algorithm to find a revised layup for the skin bay, within
appropriate design constraints, to delay the onset of secondary instabilities. The layup optimization methodology,
resulted in a panel that had a higher buckling load, prebuckling stiffness, and secondary instability load than the
baseline design.

Lay-up optimization of composite plates to delay mode-jump instabilities

Experimental and numerical studies have shown that the occurrence of abrupt secondary instabilities, or mode-jumps, in a postbuckling stiffened composite panel may initiate structural failure. This study presents an optimisation methodology, using a genetic algorithm and finite element analysis for the lay-up optimisation of postbuckling composite plates to delay the onset of mode-jump instabilities. A simple and novel approach for detecting modejumps is proposed, based on the RMS value of out-of-plane pseudo-velocities at a number of locations distributed over the postbuckling structure

Availability of stage at diagnosis, cancer treatment delay and compliance with cancer guidelines as cancer registry indicators for cancer care in Europe:Results of EUROCHIP-3 survey

EUROCHIP (European Cancer Health Indicators Project) focuses on understanding inequalities in the cancer burden, care and survival by the indicators "stage at diagnosis," "cancer treatment delay" and "compliance with cancer guidelines" as the most important indicators. Our study aims at providing insight in whether cancer registries collect well-defined variables to determine these indicators in a comparative way. Eighty-six general European population-based cancer registries (PBCR) from 32 countries responded to the questionnaire, which was developed by EUROCHIP in collaboration with ENCR (European Network of Cancer Registries) and EUROCOURSE. Only 15% of all the PBCR in EU had all three indicators available. The indicator "stage at diagnosis" was gathered for at least one cancer site by 81% (using TNM in 39%). Variables for the indicator "cancer treatment delay" were collected by 37%. Availability of type of treatment (30%), surgery date (36%), starting date of radiotherapy (26%) and starting date of chemotherapy (23%) resulted in 15% of the PBCRs to be able to gather the indicator "compliance to guidelines". Lack of data source access and qualified staff were the major reasons for not collecting all the variables. In conclusion, based on self-reporting, a few of the participating PBCRs had data available which could be used for clinical audits, evaluation of cancer care projects, survival and for monitoring national cancer control strategies. Extra efforts should be made to improve this very efficient tool to compare cancer burden and the effects of the national cancer plans over Europe and to learn from each other. © 2012 UICC.