Precise positioning of carbon nanotubes by ac dielectrophoresis using floating posts

Single-walled carbon nanotubes (SWNTs) have been precisely aligned and positioned in device architectures using ac dielectrophoresis by patterning floating metal posts or strips within the electrode gaps. These structures perturb the electric field, causing local enhancements in the field intensity, as seen in simulation, that guide the nanotubes along a predictable path in given directions, in zigzag patterns, or as single or a sequence of tubes along a series of posts. This method enables the assembly of SWNTs in complex multi-electrode geometries, when specifying the electrode voltages is not sufficient to direct the desired assembly. The device characteristics of the dielectrophoretically-aligned SWNTs are discussed. PACS 61.46.Fg; 73.63.-b; 87.15.Tt     

State-specific reactions and autoionization dynamics of Ar produced by synchrotron radiation

The long-lived excited states of doubly charged rare gases can markedly affect their reactivity. In this paper we demonstrate the presence of strong state-specific effects in the charge exchange of Ar²⁺ (³P, ¹D and ¹S) with several neutral targets (He, Ne, Kr, Xe, D₂, and CH₄). State sensitive measurements have been performed by producing the different Ar²⁺ electronic states via tunable synchrotron radiation (Elettra-Trieste, Italy and SuperACO-Orsay, France). From the product ion yield data of charge transfer, state-selected total cross-sections have been deduced. Using the state-specific reactivity of Ar²⁺ towards different neutral targets, it has been possible to extract the photon-energy-dependent production branching of the three doubly charged states and to investigate the autoionization dynamics of neutral or singly charged Ar in the vicinity of the double ionization threshold.     

A fast algorithm for solving a linear feasibility problem with application to Intensity-Modulated Radiation Therapy

The goal of Intensity-Modulated Radiation Therapy (IMRT) is to deliver sufficient doses to tumors to kill them, but without causing irreparable damage to critical organs. This requirement can be formulated as a linear feasibility problem. The sequential (i.e., iteratively treating the constraints one after another in a cyclic fashion) algorithm ART3 is known to find a solution to such problems in a finite number of steps, provided that the feasible region is full dimensional. We present a faster algorithm called ART3+. The idea of ART3+ is to avoid unnecessary checks on constraints that are likely to be satisfied. The superior performance of the new algorithm is demonstrated by mathematical experiments inspired by the IMRT application.     

Pyranocyclopropanyl sugar amino acids,a new class of constrained (di)peptide isosteres

The design, synthesis and application of oxabicyclo[4.1.0]heptane amino acids as conformationally restricted sugar amino acid dipeptide isosteres are reported.     

Invariants for Equivalence of Central Simple <Emphasis Type="Italic">G</Emphasis>-algebras

This paper surveys recent results on the problem of describing the equivalence classes of finite-dimensional central simple G-algebras over a field. Improvements to these results are provided in some situations.     

Visual spatial memory is enhanced in female rats (but inhibited in males) by dietary soy phytoestrogens

Background  

In learning and memory tasks, requiring visual spatial memory (VSM), males exhibit superior performance to females (a difference attributed to the hormonal influence of estrogen). This study examined the influence of phytoestrogens (estrogen-like plant compounds) on VSM, utilizing radial arm-maze methods to examine varying aspects of memory. Additionally, brain phytoestrogen, calbindin (CALB), and cyclooxygenase-2 (COX-2) levels were determined.