Dual‐Band Double‐Cylindrical‐Ring 3D Frequency Selective Surface

This study presents a dual‐band 3D frequency selective surface that provides a large degree of freedom in frequency and bandwidth adjustability. The proposed structure is evaluated in terms of its structural parameters, and prototypes are fabricated. The radius of the copper rings and the height of the cylinders are considered, and are shown through full‐wave electromagnetic simulations to have a significant effect on the frequency characteristics of the frequency selective surface. The measurement results of the fabricated samples are compared with the simulation results, and a satisfactory agreement is obtained.     

Method matters: Systematic effects of testing procedure on visual working memory sensitivity.

Visual working memory (WM) is traditionally considered a robust form of visual representation that survives changes in object motion, observer's position, and other visual transients. This article presents data that are inconsistent with the traditional view. We show that memory sensitivity is dramatically influenced by small variations in the testing procedure, supporting the idea that representations in visual WM are susceptible to interference from testing. In the study, participants were shown an array of colors to remember. After a short retention interval, memory for one of the items was tested with either a same–different task or a 2-alternative-forced-choice (2AFC) task. Memory sensitivity was much lower in the 2AFC task than in the same–different task. This difference was found regardless of encoding similarity or of whether visual WM required a fine or coarse memory resolution. The 2AFC disadvantage was reduced when participants were informed shortly before testing which item would be probed. The 2AFC disadvantage diminished in perceptual tasks and was not found in tasks probing visual long-term memory. These results support memory models that acknowledge the labile nature of visual WM and have implications for the format of visual WM and its assessment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Basing cryptographic protocols on tamper-evident seals

In this article, we attempt to formally study two very intuitive physical models: sealed envelopes and locked boxes, often used as illustrations for common cryptographic operations. We relax the security properties usually required from locked boxes [such as in bit-commitment (BC) protocols] and require only that a broken lock or torn envelope be identifiable to the original sender. Unlike the completely impregnable locked box, this functionality may be achievable in real life, where containers having this property are called “tamper-evident seals”. Another physical object with this property is the “scratch-off card”, often used in lottery tickets. We consider three variations of tamper-evident seals, and show that under some conditions they can be used to implement oblivious transfer, BC and coin flipping (CF). We also show a separation between the three models. One of our results is a strongly fair CF protocol with bias bounded by O(1/r) (where r is the number of rounds); this was a stepping stone towards achieving such a protocol in the standard model (in subsequent work).     

Low Cycle and Ratchetting Fatigue Behavior of High UTS/YS Ratio Reinforcing Steel Bars

Cyclic deformation behavior of high UTS/YS rebars has been studied employing both symmetric strain-controlled and asymmetric stress-controlled cycles in an attempt to understand the influence of UTS/YS ratio on fatigue life. While strain-controlled cyclic deformation did not exhibit a pronounced influence of UTS/YS ratio, a substantial life enhancement is noted for the asymmetric stress-controlled cycle. Reasons for life enhancement were found to be due to the ratchetting strain development and the associated hardening behavior. An equivalent stress-based model has been used to predict both the symmetric and asymmetric fatigue lives of rebars.     

Modulated On-axis Circular Zone Plates for a Generation of Three-dimensional Focal Curves

Abstract

This paper presents a new kind of computer-generated zone plate, which we call a modulated circular zone plate. These plates reconstruct a special class of focal curves. The curves are three-dimensional and lie on the lateral surface of a cylinder. As a particular case, we propose zone plates which are able to focus light on to a line segment along the optical axis. The experimental results illustrate the focusing properties of the zone plates.     

Helical and tubular lipid microstructures that are electroless-coated with CoNiReP for wireless magnetic manipulation

Hybrid magnetic phospholipidic-based tubular and helical microagents are wirelessly manipulated by means of a 5-DOF electromagnetic system. Two different strategies are used to manipulate these nanostructures in simulated biologic capillaries. Tubules are pulled by applying magnetic field gradients and oriented by magnetic fields. Helices exhibit a cork-screw motion similar to the swimming strategy used by motile bacteria such as E. coli.     

“Designer” scaffolds for tissue engineering and regeneration

Tissue engineering entails the in vitro or in vivo generation of replacement tissues from cells with the aid of supporting scaffolds and stimulating biomolecules, in order to provide biological substitutes for restoration and maintenance of human tissue functions. In this review, we summarize the main classes of degradable polymeric scaffolds, natural and synthetic ones, and the evolution made in this field from adaptation of materials in clinical use to the fabrication of “designer” scaffolds.     

Dinitrobenzene detection by use of one-color laser photolysis and laser-induced fluorescence of vibrationally excited NO

Trace concentrations of 1, 4-dinitrobenzene (DNB) are detected by a combination of laser photolysis and laser-induced fluorescence. A one-color laser is applied to induce DNB photodissociation and for subsequent detection of NO photofragments by excitation and emission through A(v' =0) <-- X(v" = 0 - 2) and A(v' =0) --> X(v" = 0,1) transitions, respectively. The resulting NO rovibrational excitation spectra serve as markers for the presence of DNB. The NO is produced in vibrational ground and excited states with peak height ratios of (v" = 0):(v" = 1):(v" = 2) = 1:0.5:0.13. The limits of detection of DNB mixed with 100 or 500 Torr of air with v" = 2 excitation at 248 nm are 13 and 11 parts in 10(9) by weight, respectively, for a 30-s integration time. The application of this scheme for DNB detection has the advantage that no ambient ground state NO interferes and that the fluorescence is collected at shorter wavelengths than the exciting radiation, precluding background fluorescence.