Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number M_L=0 and M_L=1 at a laser wavelength of 390 nm and peak intensity of 10(14) W/cm(2). Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for M_L. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with M_L=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.

Universal tight binding model for chemical reactions in solution and at surfaces. II. Water

A revised water model intended for use in condensed phase simulations in the framework of the self consistent polarizable ion tight binding theory is constructed. The model is applied to water monomer, dimer, hexamers, ice, and liquid, where it demonstrates good agreement with theoretical results obtained by more accurate methods, such as DFT and CCSD(T), and with experiment. In particular, the temperature dependence of the self diffusion coefficient in liquid water predicted by the model, closely reproduces experimental curves in the temperature interval between 230 K and 350 K. In addition, and in contrast to standard DFT, the model properly orders the relative densities of liquid water and ice. A notable, but inevitable, shortcoming of the model is underestimation of the static dielectric constant by a factor of two. We demonstrate that the description of inter and intramolecular forces embodied in the tight binding approximation in quantum mechanics leads to a number of valuable insights which can be missing from ab initio quantum chemistry and classical force fields. These include a discussion of the origin of the enhanced molecular electric dipole moment in the condensed phases, and a detailed explanation for the increase of coordination number in liquid water as a function of temperature and compared with ice-leading to insights into the anomalous expansion on freezing. The theory holds out the prospect of an understanding of the currently unexplained density maximum of water near the freezing point. 

Using SILAC proteomics to investigate the effect of the mycotoxin, alternariol, in the human H295R steroidogenesis model

The mycotoxin alternariol (AOH) is an important contaminant of fruits and cereal products. The current study sought to address the effect of a non-toxic AOH concentration on the proteome of the steroidogenic H295R cell model. Quantitative proteomics based on stable isotope labeling by amino acids in cell culture (SILAC) coupled to 1D-SDS-PAGE-LC-MS/MS was applied to subcellular-enriched protein samples. Gene ontology (GO) and ingenuity pathway analysis (IPA) were further carried out for functional annotation and identification of protein interaction networks. Furthermore, the effect of AOH on apoptosis and cell cycle distribution was also determined by the use of flow cytometry analysis. This work identified 22 proteins that were regulated significantly. The regulated proteins are those involved in early stages of steroid biosynthesis (SOAT1, NPC1, and ACBD5) and C21-steroid hormone metabolism (CYP21A2 and HSD3B1). In addition, several proteins known to play a role in cellular assembly, organization, protein synthesis, and cell cycle were regulated. These findings provide a new framework for studying the mechanisms by which AOH modulates steroidogenesis in H295R cell model. 

Tangible applications for regular objects:An end-user model for pervasive computing at home

This paper describes an end-user model for a domestic pervasive computing platform formed by regular home objects. The platform does not rely on pre-planned infrastructure; instead, it exploits objects that are already available in the home and exposes their joint sensing, actuating and computing capabilities to home automation applications. We advocate an incremental process of the platform formation and introduce tangible, object-like artifacts for representing important platform functions. One of those artifacts, the application pill, is a tiny object with a minimal user interface, used to carry the application, as well as to start and stop its execution and provide hints about its operational status. We also emphasize streamlining the user's interaction with the platform. The user engages any UI-capable object of his choice to configure applications, while applications issue notifications and alerts exploiting whichever available objects can be used for that purpose. Finally, the paper briefly describes an actual implementation of the presented end-user model. © (2010) by International Academy, Research, and Industry Association (IARIA).

Dynamics of interacting Dicke model in a coupled-cavity array

We consider the dynamics of an array of mutually interacting cavities, each containing an ensemble of N two-level atoms. By exploring the possibilities offered by ensembles of various dimensions and a range of atom-light and photon-hopping values, we investigate the generation of multisite entanglement, as well as the performance of excitation transfer across the array, resulting from the competition between on-site nonlinearities of the matter-light interaction and intersite photon hopping. In particular, for a three-cavity interacting system it is observed that the initial excitation in the first cavity completely transfers to the ensemble in the third cavity through the hopping of photons between the adjacent cavities. Probabilities of the transfer of excitation of the cavity modes and ensembles exhibit characteristics of fast and slow oscillations governed by coupling and hopping parameters, respectively. In the large-hopping case, by seeding an initial excitation in the cavity at the center of the array, a tripartite W state, as well as a bipartite maximally entangled state, is obtained, depending on the interaction time. Population of the ensemble in a cavity has a positive impact on the rate of excitation transfer between the ensembles and their local cavity modes. In particular, for ensembles of five to seven atoms, tripartite W states can be produced even when the hopping rate is comparable to the cavity-atom coupling rate. A similar behavior of the transfer of excitation is observed for a four-coupled-cavity system with two initial excitations.

Wave Interaction with an Oscillating Wave Surge Converter, Part 1: Viscous Effects

Bottom hinged oscillating wave surge converters are known to be an efficient method of extracting power from ocean waves. The present work deals with experimental and numerical studies of wave interactions with an oscillating wave surge converter. It focuses on two aspects: (1) viscous effects on device performance under normal operating conditions; and (2) effects of slamming on device survivability under extreme conditions. Part I deals with the viscous effects while the extreme sea conditions will be presented in Part II. The numerical simulations are performed using the commercial CFD package ANSYS FLUENT. The comparison between numerical results and experimental measurements shows excellent agreement in terms of capturing local features of the flow as well as the dynamics of the device. A series of simulations is conducted with various wave conditions, flap configurations and model scales to investigate the viscous and scaling effects on the device. It is found that the diffraction/radiation effects dominate the device motion and that the viscous effects are negligible for wide flaps.

Simulating reinforced concrete members. Part 1: partial interaction properties

Reinforced concrete members are extremely complex under loading because of localised deformations in the concrete (cracks, sliding planes) and between the reinforcement and concrete (slip). An ideal model for simulating behaviour of reinforced concrete members should incorporate both global behaviour and the localised behaviours that are seen and measured in practice; these localised behaviours directly affect the global behaviour. Most commonly used models do not directly simulate these localised behaviours that can be seen or measured in real members; instead, they overcome these limitations by using empirically or semi-empirically derived strain-based pseudo properties such as the use of effective flexural rigidities for deflection; plastic hinge lengths for strength and ductility; and energy-based approaches for both concrete softening in compression and concrete softening after tensile cracking to allow for tension stiffening. Most reinforced concrete member experimental testing is associated with deriving these pseudo properties for use in design and analysis, and this component of development is thus costly. The aim of the present research is to reduce this cost substantially. In this paper, localised material behaviours and the mechanisms they induce are described. Their incorporation into reinforced concrete member behaviour without the need for empirically derived pseudo properties is described in a companion paper.

Intravitreal AAV2.COMP-Ang1 prevents neurovascular degeneration in a murine model of diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population in the United States. The vision-threatening processes of neuroglial and vascular dysfunction in DR occur in concert, driven by hyperglycemia and propelled by a pathway of inflammation, ischemia, vasodegeneration, and breakdown of the blood retinal barrier. Currently, no therapies exist for normalizing the vasculature in DR. Here we show that a single intravitreal dose of adeno-associated virus serotype 2 encoding a more stable, soluble, and potent form of angiopoietin 1 (AAV2.COMP-Ang1) can ameliorate the structural and functional hallmarks of DR in Ins2Akita mice, with sustained effects observed through six months. In early DR, AAV2.COMP-Ang1 restored leukocyte-endothelial interaction, retinal oxygenation, vascular density, vascular marker expression, vessel permeability, retinal thickness, inner retinal cellularity, and retinal neurophysiological response to levels comparable to non-diabetic controls. In late DR, AAV2.COMP-Ang1 enhanced the therapeutic benefit of intravitreally-delivered endothelial colony-forming cells by promoting their integration into the vasculature and thereby stemming further visual decline. AAV2.COMP-Ang1 single-dose gene therapy can prevent neurovascular pathology, support vascular regeneration, and stabilize vision in DR.

Biosensor analysis of dynamics of interleukin 5 receptor subunit beta(c) interaction with IL5:IL5R(alpha) complexes

To gain insight into IL5 receptor subunit recruitment mechanism, and in particular the experimentally elusive pathway for assembly of signaling subunit beta(c), we constructed a soluble beta(c) ectodomain (s(beta)(c)) and developed an optical biosensor assay to measure its binding kinetics. Functionally active s(beta)(c) was anchored via a C-terminal His tag to immobilized anti-His monoclonal antibodies on the sensor surface. Using this surface, we quantitated for the first time direct binding of s(beta)(c) to IL5R(alpha) complexed to either wild-type or single-chain IL5. Binding was much weaker if at all with either R(alpha) or IL5 alone. Kinetic evaluation revealed a moderate affinity (0.2-1 microM) and relatively fast off rate for the s(beta)(c) interaction with IL5:R(alpha) complexes. The data support a model in which beta(c) recruitment occurs with preformed IL5:R(alpha) complex. Dissociation kinetics analysis suggests that the IL5-alpha-beta(c) complex is relatively short-lived. Overall, this study solidifies a model of sequential recruitment of receptor subunits by IL5, provides a novel biosensor binding assay of beta(c) recruitment dynamics, and sets the stage for more advanced characterization of the roles of structural elements within R(alpha), beta(c), and cytokines of the IL5/IL3/GM-CSF family in receptor recruitment and activation.

Cancer dormancy: a model of early dissemination and late cancer recurrence

Cancer dormancy is a stage in tumor progression in which residual disease remains occult and asymptomatic for a prolonged period of time. Dormant tumor cells can be present as one of the earliest stages in tumor development, as well as a stage in micrometastases, and/or minimal residual disease left after an apparently successful treatment of the primary tumor. The general mechanisms that regulate the transition of disseminated tumor cells that have lain dormant into a proliferative state remain largely unknown. However, regulation of the growth from dormant tumor cells may be explained in part through the interaction of the tumor cell with its microenvironment, limitations in the blood supply, or an active immune system. An understanding of the regulatory machinery of these processes is essential for identifying early cancer biomarkers and could provide a rationale for the development of novel agents to target dormant tumor cells. This review focuses on the different signaling models responsible for early cancer dissemination and tumor recurrence that are involved in dormancy pathways.

Investigation of tanpura string vibrations using a two-dimensional time-domain model incorporating coupling and bridge friction

Tanpura string vibrations have been investigated previously using numerical models based on energy conserving schemes derived from a Hamiltonian description in one-dimensional form. Such time-domain models have the property that, for the lossless case, the numerical Hamiltonian (representing total energy of the system) can be proven to be constant from one time step
to the next, irrespective of any of the system parameters; in practice the Hamiltonian can be shown to be conserved within machine precision. Models of this kind can reproduce a jvari effect, which results from the bridge-string interaction. However the one-dimensional formulation has recently been shown to fail to replicate the jvaris strong dependence on the thread placement. As a first step towards simulations which accurately emulate this sensitivity to the thread placement, a twodimensional model is proposed, incorporating coupling of controllable level between the two string polarisations at the string termination opposite from the barrier. In addition, a friction force acting when the string slides across the bridge in horizontal direction is introduced, thus effecting a further damping mechanism. In this preliminary study, the string is terminated at the position of the thread. As in the one-dimensional model, an implicit scheme has to be used to solve the system, employing Newton's method to calculate the updated positions and momentums of each string segment. The two-dimensional model is proven to be energy conserving when the loss parameters are set to zero, irrespective of the coupling constant. Both frequency-dependent and independent losses are then added to the string, so that the model can be compared to analogous instruments. The influence of coupling and the bridge friction are investigated.

Monitoring of a novel FlexiArchTM bridge system to investigate soil-structure interaction

Masonry arch bridges are one of the oldest forms of bridge construction and have been around for thousands of years. Brick and stone arch bridges have proven to be highly durable as most of them have remained serviceable after hundreds of years. In contrast, many bridges built of modern materials have required extensive repair and strengthening after being in service for a relatively short part of their design life. This paper describes the structural monitoring of a novel flexible concrete arch known as: FlexiArchTM. This is a bridge system that can be transported as a flat-pack system to form an arch in-situ by the use of a flexible polymeric membrane. The system has been developed under a Knowledge Transfer Partnership between Queen’s University Belfast (QUB) and Macrete Ltd. Tievenameena Bridge in Northern Ireland was a replacement bridge for the Northern Ireland Roads Service and was monitored under different axle loadings using a range of sensors including discrete fiber optic Bragg gratings to measure the change in strain in the arch ring under live loading. This paper discusses the results of a laboratory model study carried out at QUB. A scaled arch system was loaded with a simulated moving axle. Various techniques were used to monitor the arch under the moving axle load with particular emphasis on the interaction of the arch ring and engineered backfill.

Validation of a 3D damage model for predicting the response of composite structures under crushing loads

A 3D intralaminar continuum damage mechanics based material model, combining damage mode interaction and material nonlinearity, was developed to predict the damage response of composite structures undergoing crush loading. This model captures the structural response without the need for calibration of experimentally determined material parameters. When used in the design of energy absorbing composite structures, it can reduce the dependence on physical testing. This paper validates this model against experimental data obtained from the literature and in-house testing. Results show that the model can predict the force response of the crushed composite structures with good accuracy. The simulated energy absorption in each test case was within 12% of the experimental value. Post-crush deformation and the damage morphologies, such as ply splitting, splaying and breakage, were also accurately reproduced. This study establishes the capability of this damage model for predicting the responses of composite structures under crushing loads.