Reactions along the astrophysical s-process path and prospects for neutron radiotherapy with the Liquid-Lithium Target (LiLiT) at the Soreq Applied Research Accelerator Facility (SARAF)

The European Physical Journal A - An empirical formula is proposed for the two-proton decay half-lives. This study is an extension of the empirical formula reported recently by us for calculating...     

Lamb wave detection of limpet mines on ship hulls

This paper describes the use of ultrasonic guided waves for identifying the mass loading due to underwater limpet mines on ship hulls. The Dynamic Wavelet Fingerprint Technique (DFWT) is used to render the guided wave mode information in two-dimensional binary images because the waveform features of interest are too subtle to identify in time domain. The use of wavelets allows both time and scale features from the original signals to be retained, and image processing can be used to automatically extract features that correspond to the arrival times of the guided wave modes. For further understanding of how the guided wave modes propagate through the real structures, a parallel processing, 3D elastic wave simulation is developed using the finite integration technique (EFIT). This full field, technique models situations that are too complex for analytical solutions, such as built up 3D structures. The simulations have produced informative visualizations of the guided wave modes in the structures as well as mimicking directly the output from sensors placed in the simulation space for direct comparison to experiments. Results from both drydock and in-water experiments with dummy mines are also shown.     

Electron attachment to POCl3: measurement and theoretical analysis of rate constants and branching ratios as a function of gas pressure and temperature, electron temperature, and electron energy

Two experimental techniques, electron swarm and electron beam, have been applied to the problem of electron attachment to POCl3, with results indicating that there is a competition between dissociation of the resonant POCl3-* state and collisional stabilization of the parent anion. In the electron beam experiment at zero electron energy, the fragment ion POCl2- is the dominant ion product of attachment (96%), under single-collision conditions. Small amounts (approximately 2% each) of POCl3- and Cl- were observed. POCl3- and POCl2- ion products were observed only at zero electron energy, but higher-energy resonances were recorded for POCl-, Cl-, and Cl2- ion products. In the electron swarm experiment, which was carried out in 0.4-7 Torr of He buffer gas, the parent anion branching ratio increased significantly with pressure and decreased with temperature. The electron attachment rate constant at 297 K was measured to be (2.5+/-0.6)x10(-7) cm3 s(-1), with ion products POCl2- (71%) and POCl3- (29%) in 1 Torr of He gas. The rate constant decreased as the electron temperature was increased above 1500 K. Theory is developed for (a) the unimolecular dissociation of the nascent POCl3-* and (b) a stepladder collisional stabilization mechanism using the average energy transferred per collision as a parameter. These ideas were then used to model the experimental data. The modeling showed that D0 o(Cl-POCl2-) and EA(POCl3) must be the same within +/-0.03 eV.     

Nanoprobes for intracellular and single cell surface‐enhanced Raman spectroscopy (SERS)

Surface‐enhanced Raman spectroscopy (SERS) is a promising and powerful label free technique for high resolution analysis of single cells. For intracellular analysis, there is a need for SERS‐active nanoprobes that are minimally invasive to cells, do not affect cell viability, and provide reproducible signals. This work reviews the state‐of‐the‐art tools currently available for intracellular SERS. Various types of SERS probes are considered, including colloidal gold and silver nanoparticles, metallized optical fibers, and tip‐enhanced Raman probes. We also discuss recently developed SERS‐active nanopipettes implemented on the basis of pulled glass microcapillaries. Finally, the critical aspects of selecting an optimal SERS nanoprobe for single‐cell analysis depending on a particular application are summarized. Copyright © 2012 John Wiley & Sons, Ltd.     

A definable failure of the singular cardinal hypothesis

We show first that it is consistent that κ is a measurable cardinal where the GCH fails, while there is a lightface definable wellorder of H(κ ⁺). Then with further forcing we show that it is consistent that GCH fails at ? _ω , ? _ω strong limit, while there is a lightface definable wellorder of H(? _ω+1) (“definable failure” of the singular cardinal hypothesis at ? _ω ). The large cardinal hypothesis used is the existence of a κ ⁺⁺-strong cardinal, where κ is κ ⁺⁺-strong if there is an embedding j: V → M with critical point κ such that H(κ ⁺⁺) ? M. By work of M. Gitik and W. J. Mitchell [12], [20], our large cardinal assumption is almost optimal. The techniques of proof include the “tuning-fork” method of [10] and [3], a generalisation to large cardinals of the stationary-coding of [4] and a new “definable-collapse” coding based on mutual stationarity. The fine structure of the canonical inner model L[E] for a κ ⁺⁺-strong cardinal is used throughout.     

Imprisoned lightning: charge transport in trehalose-derived sugar glasses

Trehalose is a naturally occurring disaccharide noted for its ability to preserve the biological function of proteins and cell membranes during periods of stress—such as water deprivation or extreme temperature—by stabilizing the conformations of the macromolecules within a glassy matrix. This phenomenon makes use of the propensity for trehalose to interact strongly with protein functional groups and solvent water molecules via hydrogen bonding. Previously, it has been shown that trehalose sugar glasses also support long-range charge transport in oxidation-reduction reactions occurring between spatially separated donors and acceptors. Here, through the use of bulk Arrhenius DC-conductivity measurements, we infer that this anomalously high carrier mobility is due to proton hopping along a hydrogen bonding network formed by sorbed “water wires,” a process known as the Grotthuss mechanism. Additionally, we find that the apparent activation energy of the conductivity depends non-monotonically on the bias voltage. The possibility is raised for novel photovoltaic devices based on the entrapment of photosynthetic proteins within these glasses.     

Optimal Control of a Chemical Vapor Deposition Reactor

We study a simple model of chemical vapor deposition on a silicon wafer. The control is the flux of chemical species, and the objective is to grow the semiconductor film so that its surface attains a prescribed profile as nearly as possible. The surface is spatially fast oscillating due to the small feature scale, and therefore the problem is formulated in terms of its homogenized approximation. We prove that the optimal control is bang-bang, and we use this information to develop a numerical scheme for computing the optimal control.