Generation of fast protons by interaction of modest laser intensities with H2O “snow” nano-wire targets

We report on the generation of protons with energies of 5.5 MeV when irradiating an H₂O nano-wire layer grown on a sapphire plate with an intensity of 5×10¹⁷ W/cm². A theoretical model is suggested in which plasma near the tip of the wire is subject to enhanced electrical fields and protons are accelerated to several MeVs.     

Feature selection for the classification of movements from single movement-related potentials

Classification of movement-related potentials recorded from the scalp to their corresponding limb is a crucial task in brain-computer interfaces based on such potentials. Many features can be extracted from raw electroencephalographic signals to be used for classification, but the utilization of irrelevant or superfluous features is detrimental to the performance of classification algorithms. It is, therefore, necessary to select a small number of relevant features for the classification task. This paper demonstrates the use of two feature selection methods to choose a small number (10-20) of relevant features from a bank containing upward of 1000 features. One method is based on information theory and the other on the use of genetic algorithms. We show that the former is poorly suited for the aforementioned classification task and discuss the probable reasons for this. However, using a genetic algorithm on data recorded from five subjects we demonstrate that it is possible to differentiate between the movements of two limbs with a classification accuracy of 87% using as little as 10 features without subject training. With the addition of a simple coding scheme, this method can be applied to multiple limb classification and a 63% classification accuracy rate can be reached when attempting to distinguish between three limbs.     

Transport phenomena in the human nasal cavity: a computational model

Development and growth of V1 begins during embryogenesis and continues postnatally. The growth of V1 has direct implications on the organization of features such as the retinotopic map and the pattern of visual cortical columns. We have examined the postnatal growth and two-dimensional shape of V1 in macaque monkeys, cats, and rats. The perimeter, area, and anterior-posterior length of V1 were measured from unfolded and flattened sections from neonatal and adult animals from each of these species. Although there were substantial differences in the overall amount of postnatal growth, from 18% in macaque monkeys to more than 100% in cats, in all three species the shape of V1 did not change during development. Thus, growth of the mammalian visual cortex is well described as an isotropic expansion, so the layout of the global features, such as the arrangement of ocular dominance columns and the retinotopic map, does not need to change during development. Furthermore, quantification of the shape confirms the observations that there is a similar, egg-like oval shape to the visual cortex of these mammalian species.     

A two-state electronic antigen and an antibody selected to discriminate between these states

Inspired by biology where pathways are triggered and suppressed by specific binding of two molecules, we realize a functional interface between electronics and biology by replacing one of the pair molecules with a two-state "electronic antigen" device comprising a hydroquinone monolayer assembled on gold, and choosing for the pair molecule an antibody that discriminates between the two electrically selected redox states of the monolayer. Application of an oxidative +0.6 V pulse to the antigen switches it to its benzoquinone state where antibodies bind the layer. A subsequent -0.6 V pulse reduces the monolayer back to the unbinding hydroquinone state, releases the specifically bound antibody molecules, and prevents further binding.     

Mapping Diversities and Tracing Trends of Cultural Homogeneity/Heterogeneity in Cyberspace

Many Internet global commercial services were originally initiated in the United States and later exported to other countries, continents, and cultures. By analyzing content and form characteristics of two leading portal sites—MSN and Yahoo!—on 33 and 23 (respectively) of their local country homepages in a comparative and longitudinal study over a period of six months, this study addresses two research questions: What differences, if any, are found among homepages of the same parent site located in different cultures (or targeted at audiences in different cultures)? What trends, if any, do those differences show over time? Although MSN is a U.S. brand, the analysis of its homepages reveals increasing cultural heterogeneity and localization of content and form. In contrast, Yahoo!’s homepages are found to be more similar to each other and to the “parent” American portal. A metric was developed to measure the distance between various websites in terms of form and content, along with a structured procedure to analyze and cluster groups of websites. The results suggest that the diversity of local homepages in MSN and Yahoo! follows the geographic and ethnographic scatter of their countries.     

Building Bridges in Catalysis Science. Monodispersed Metallic Nanoparticles for Homogeneous Catalysis and Atomic Scale Characterization of Catalysts Under Reaction Conditions

The reactivity of small (<1.5?nm), highly oxidized metallic nanoparticles and the utilization of Sum Frequency Generation spectroscopy (SFG) and Scanning Tunneling Microscopy (STM) for investigations of catalysts under reaction conditions are discussed in this review paper. Batch and flow reactor studies were carried out using highly oxidized 40 atom clusters (Pt, Pd and Rh) to measure reaction rate and product distribution of electrophilic reactions, using toluene as a solvent. These heterogeneous catalysts show reactivity which is similar and sometimes even higher than the homogeneous catalysts. The combination of an in situ SFG and STM measurements facilitate a detection of the surface structure and reaction intermediates under reaction conditions. While the STM detects the surface reconstruction and the mobility of products and reactants molecules, the SFG can correlate the reactivity and more importantly the selectivity, to the active surface intermediates. The recent developments in these two research areas are detailed in this review paper.     

Mixed alkanethiol monolayers on submicrometric gold patterns: a controlled platform for studying cell-ligand interactions

Nanoscale organization of surface ligands often has a critical effect on cell-surface interactions. We have developed an experimental system that allows a high degree of control over the 2-D spatial distribution of ligands. As a proof of concept, we used the developed system to study how T-cell activation is independently affected by antigen density and antigen amount per cell. Arrays of submicrometer gold islands at varying surface coverage were defined on silicon by electron beam lithography (EBL). The gold islands were functionalized with alkanethiol self-assembled monolayers (SAMs) containing a small antigen, 2,4,6-trinotrophenyl (TNP), at various densities. Genetically engineered T-cell hybridomas expressing TNP-specific chimeric T-cell antigen receptor (CAR) were cultured on the SAMs, and their activation was assessed by IL-2 secretion and CD69 expression. It was found that, at constant antigen density, activation increased monotonically with the amount of antigen, while at constant antigen amount activation was maximal at an intermediate antigen density, whose value was independent of the amount of antigen.     

Shape from moments - an estimation theory perspective

This paper discusses the problem of recovering a planar polygon from its measured complex moments. These moments correspond to an indicator function defined over the polygon's support. Previous work on this problem gave necessary and sufficient conditions for such successful recovery process and focused mainly on the case of exact measurements being given. In this paper, we extend these results and treat the same problem in the case where a longer than necessary series of noise corrupted moments is given. Similar to methods found in array processing, system identification, and signal processing, we discuss a set of possible estimation procedures that are based on the Prony and the Pencil methods, relate them one to the other, and compare them through simulations. We then present an improvement over these methods based on the direct use of the maximum-likelihood estimator, exploiting the above methods as initialization. Finally, we show how regularization and, thus, maximum a posteriori probability estimator could be applied to reflect prior knowledge about the recovered polygon.     

On bending invariant signatures for surfaces

Isometric surfaces share the same geometric structure, also known as the "first fundamental form." For example, all possible bendings of a given surface that includes all length preserving deformations without tearing or stretching the surface are considered to be isometric. We present a method to construct a bending invariant signature for such surfaces. This invariant representation is an embedding of the geometric structure of the surface in a small dimensional Euclidean space in which geodesic distances are approximated by Euclidean ones. The bending invariant representation is constructed by first measuring the intergeodesic distances between uniformly distributed points on the surface. Next, a multidimensional scaling technique is applied to extract coordinates in a finite dimensional Euclidean space in which geodesic distances are replaced by Euclidean ones. Applying this transform to various surfaces with similar geodesic structures (first fundamental form) maps them into similar signature surfaces. We thereby translate the problem of matching nonrigid objects in various postures into a simpler problem of matching rigid objects. As an example, we show a simple surface classification method that uses our bending invariant signatures.