Inexpensive digital imaging?

The capture of digital images through the use of a frame grabber provides tremendous advantages to scanning electron microscopy. Accessory frame grabbers can range in price from very inexpensive to several thousand dollars. This work investigates the application of one inexpensive “consumer product” frame grabber which has recently been introduced to scanning electron microscope (SEM) imaging. The application of this frame grabber to the SEM as a low-cost, entry-level digital imaging tool is explored, and its performance is compared with a more expensive system.     

Modular construction of extended DNA recognition surfaces: mutant DNA-binding domains of the 434 repressor as building blocks

Single-chain derivatives of the 434 repressor containing onewild-type and one mutant DNA-binding domain recognize the generaloperator ACAA–6 base pairs–NNNN, where the ACAAoperator subsite is contacted by the wild-type and the NNNNtetramer by the mutant domain. The DNA-binding specificitiesof several single-chain mutants were studied in detail and theoptimal subsites of the mutant domains were determined. Thecharacterized mutant domains were used as building units toobtain homo- and heterodimeric single-chain derivatives. TheDNA-binding properties of these domain-shuffled derivativeswere tested with a series of designed operators of NNNN–6base pairs–NNNN type. It was found that the binding specificitiesof the mutant domains were generally maintained in the new environmentsand the binding affinities for the optimal DNA ligands werehigh (with K_d values in the range of 10^–11–10^–10M). Considering that only certain sequence motifs in place ofthe six base pair spacer can support optimal contacts betweenthe mutant domains and their subsites, the single-chain 434repressor mutants are highly specific for a limited subset of14 base pair long DNA targets.     

Asymptotic Distribution of Eigenvalues for Damped String Equation: Numerical Approach

In the present paper, we consider a one-parameter family of the nonself-adjoint operators, which are the dynamics generators for systems governed by the wave equations containing dissipative terms. The equations contain viscous damping terms and are equipped with the boundary conditions involving an arbitrary complex parameter. In the current engineering literature, this type of boundary condition is used to model the action of smart materials (self-sensing/self-straining actuators). In the previous research of the first writer, the aforementioned dynamics generators have been studied analytically and precise asymptotic formulas for the eigenvalues have been derived (the asymptotic when the number of the eigenvalues tends to infinity). The goal of the present paper is to demonstrate that the analytic formulas are not only important theoretically, but also extremely efficient practically. Namely, we show that the leading terms in the asymptotic formulas approximate the actual eigenvalues with excellent accuracy. To justify the results, we use two methods, i.e., the Newton method and the Tchebychev method. First, Newton’s method is applied to the characteristic equation using asymptotic formulas as initial guesses to find the eigenvalues. The convergence of Newton’s method is improved by modifying the asymptotic formula. Second, we use Tchebychev discretization to circumvent the nonlinear characteristic equation and to obtain a finite-dimensional generalized eigenvalue problem that approximates the infinite-dimensional one. Finally, to solve the generalized eigenvalue problem, we use the QT algorithm.     

Once is too much: Conditioned changes in accumbens dopamine following a single saccharin-morphine pairing.

The present study tested whether presentation of a taste cue would support conditioned suppression of dopamine in the nucleus accumbens (NAcc) following a single taste-drug pairing. Nondeprived male Sprague-Dawley rats were given 20-min access to a 0.15% saccharin conditioned stimulus (CS). Immediately thereafter, experimental rats were injected with morphine (15 mg/kg ip); standard controls were injected with saline; and explicitly unpaired controls were injected with morphine, but approximately 24 hr later. All rats were then given one 20-min CS-only test. Microdialysis samples from the NAcc were measured over 20-min intervals before, during, and after CS access on the conditioning and test trial. The results showed that a single saccharin-morphine pairing led to a marked reduction in CS intake, and the reduction in intake was accompanied by a conditioned blunting of the accumbens dopamine response to the saccharin reward cue. In turn, a single exposure to the saccharin cue also blunted the unconditioned dopamine response to morphine. Reward comparison effects, then, are cross-modal, bidirectional, and immediate, resulting in both unconditioned and conditioned changes in brain and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-reactivity matrices increase the sensitivity of matrix enhanced secondary ion mass spectrometry

Secondary ion mass spectrometry (SIMS) is a desorption/ionization method in which ions are generated by the impact of a primary ion beam on a sample. Classic matrix assisted laser desorption and ionization (MALDI) matrices can be used to increase secondary ion yields and decrease fragmentation in a SIMS experiment, which is referred to as matrix enhanced SIMS (ME-SIMS). Contrary to MALDI, the choice of matrices for ME-SIMS is not constrained by their photon absorption characteristics. This implies that matrix compounds that exhibit an insufficient photon absorption coefficient have the potential of working well with ME-SIMS. Here, we evaluate a set of novel derivatives of the classical MALDI matrices α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) for usability in ME-SIMS. This evaluation was carried out using peptide mixtures of different complexity and demonstrates significant improvements in signal intensity for several compounds with insufficient UV absorption at the standard MALDI laser wavelengths. Our study confirms that the gas-phase proton affinity of a matrix compound is a key physicochemical characteristic that determines its performance in a ME-SIMS experiment. As a result, these novel matrices improve the performance of matrix enhanced secondary ion mass spectrometry experiments on complex peptide mixtures.     

Wafer-scale MOCVD growth of monolayer MoS2 on sapphire and SiO2

Nano Research - High-quality and large-scale growth of monolayer molybdenum disulfide (MoS2) has caught intensive attention because of its potential in many applications due to unique electronic...     

Formalizing the construction of populations in multi-agent simulations

In individual-centered simulations, the variety and consistency of agents' behaviors reinforce the realism and validity of the simulation. Variety increases the diversity of behaviors that users meet during the simulation. Consistency ensures that these behaviors improve the users' feeling of immersion. In this work, we address the issue of the simultaneous influence of these two elements. We propose a formalization of the construction of populations for agent-based simulations, which provides the basis for a generic and non-intrusive tool allowing an out-of-the-agent design. First, the model uses behavioral patterns to describe standards of behaviors for the agents. They provide a behavioral archetype during agents' creation, and are also a compliance reference, that allows to detect deviant behaviors and address them. Then, a specific process instantiates the agents by using the specification provided by the patterns. Finally, inference enables to automate behavioral patterns configuration from real or simulated data. This formalization allows for the easy introduction of variety in agents' behaviors, while controlling the conformity to specifications. We applied the model to traffic simulation, in order to introduce driving styles specified using behavioral patterns (e.g. cautious or aggressive drivers). The behavioral realism of the traffic was therefore improved, and the experimentations we conducted show how the model contributes to increase the variety and the representativeness of the behaviors.     

Moderate anisotropy in the electrical conductivity of bulk MWCNT/epoxy composites

Bulk aligned multi-walled carbon nanotube films and their epoxy composites were prepared and their DC and AC conductivity studied. Nanotube films of up to 2 mm thickness were grown by catalytic chemical vapor deposition. Composites of nanotubes were made by infiltrating the films with a commercial epoxy. DC electrical resistivities in the axial direction of as-grown and purified films were found to be ∼1.2 Ωmm and ∼3.4 Ωmm, respectively. For the transverse direction the resistivity values were higher only with a factor of ∼2. In the case of composites, anisotropy is more pronounced showing more than an order of magnitude higher resistivity in the transverse direction (∼71.4 Ωmm) as compared to the axial value (∼4.2 Ωmm). AC behavior of the films investigated between 1 MHz and 3 GHz shows the presence of inductive and capacitive components at frequencies above ∼100 MHz. The moderate anisotropy for both DC and AC electrical properties are explained on the basis of the films’ structure combined with percolation theory and equivalent circuit models.