Sub-wavelength surface IR imaging of soft-condensed matter

Outlined here is a technique for sub-wavelength infrared surface imaging performed using a phase matched optical parametric oscillator laser and an atomic force microscope as the detection mechanism. The technique uses a novel surface excitation illumination approach to perform simultaneously chemical mapping and AFM topography imaging with an image resolution of 200 nm. This method was demonstrated by imaging polystyrene micro-structures

ON THE CONVERGENCE OF MAPPINGS WITH k-FINITE DISTORTION.

We prove that a locally uniform limit of a sequence of homeomorphisms with finite k-distortion is also a mapping with finite k-distortion. We obtain also an estimation for the distortion coefficient of the limit mapping

Development of a methodology for molecular genetic monitoring for the cholera causative agent

Background. The ongoing cholera pandemic determines the relevance of the development and improvement of methods for analysis of data on genome-wide sequencing of the cholera pathogen. This is of particular importance in the light of the challenges of import substitution of foreign products, including software. The aim of the study was to develop a methodology for molecular genetic monitoring for the cholera causative agent using online geographic information system (GIS) and analysis with its help of strains isolated in Russia earlier. Materials and methods. Data from genome-wide sequencing of 2598 toxigenic (ctxAB+tcpA+) strains of V. cholerae O1 El Tor, both obtained by the authors on the MiSeq (Illumina) platform, and retrieved from the NCBI database were used in the study. The SNP analysis software was developed in the Java and Python programming languages. Cytoscape program was used to visualize the dendrogram. The development of online GIS was carried out using the programming languages HTML, JavaScript and PHP. The freely distributed Leaflet library written in JavaScript was used as the core. Maps obtained from the OpenStreetMap community were used as cartographic data. Results and discussion. A universal set of SNPs and software have been developed to analyze the data of genome-wide sequencing of cholera vibrio strains. It was shown that the majority of strains were distributed among several large clusters. The most closely related strains for cholera vibrions isolated in Russia since 2001 have been identified. An online GIS "Molecular genetic monitoring for V. cholerae" has been created, which allows the recognition of closely related strains directly on an electronic map

Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets

The multiplicity of inclusive photons has been measured on an event-by-event basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (rho_max) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.13+-0.03 for the exponent. The mean transverse momentum, , of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing rho_max. Results are compared with model predictions.Comment: 16 pages including 4 figure

Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV

Transverse energy, charged particle pseudorapidity distributions and photon transverse momentum spectra have been studied as a function of the number of participants (N_{part}) and the number of binary nucleon-nucleon collisions (N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A scaling of the transverse energy pseudorapidity density at midrapidity as N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the charged particle pseudorapidity density at midrapidity we find a scaling as N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C (revised results for scaling exponents

Optical parametric generation of a midinfrared continuum in orientation-patterned GaAs

We have generated an ultrabroad mid-infrared continuum by using single-pass optical parametric generation (OPG) in orientation-patterned GaAs (OP-GaAs). The spectrum spans more than an octave, from 4.5 to 10.7 m, measured 20 dB down from the peak. The 17.5 mm long, 0.5 mm thick, all-epitaxially-grown OPGaAs sample with a 166.6-m quasi-phase-matching period was pumped with 3.1-3.3 m wavelength, 1 ps pulses up to 2 J in energy. The OPG threshold was observed at 55 nJ pump energy with the pump polarized along the [111] crystal direction. The slope efficiency near threshold was 51%, and the external conversion efficiency was as high as 15%. © 2006 Optical Society of America OCIS codes: 190.2620 Gallium arsenide is a promising material for parametric frequency conversion because of its large nonlinear susceptibility (d 14 = 94 pm/ V for frequency doubling of f =4 m), 1 broad infrared transparency range ͑ = 0.9-17 m͒, and high thermal conductivity. Also of interest are its highly symmetric nonlinear susceptibility tensor and linear optical isotropy, which facilitate nonlinear optical interactions that use a rich variety of polarization configurations. However, the optical isotropy of GaAs prevents birefringent phase matching; efficient interactions can instead be obtained by quasi-phase-matching. Orientation-patterned GaAs (OP-GaAs) is a type of quasi-phase-matched (QPM) GaAs in which periodic inversions of the crystallographic orientation are grown into the material. The advantage of OP-GaAs compared with other QPM GaAs methods [such as diffusion-bonded GaAs (Ref. 2) and Fresnel QPM GaAs (Ref. 3)] is that OP-GaAs has lithographically defined periods, which permit excellent periodicity control and access to small QPM periods. To fabricate OP-GaAs, a process based on photolithography and molecular beam epitaxy is used to grow a thin-film template with periodic crystal inversions. 4,5 A thick film (0.5-1 mm) is then grown upon this template by hydride vapor phase epitaxy to produce bulk OP-GaAs. 6,7 With OP-GaAs, efficient second-harmonic generation, 1 difference-frequency generation, Anomalously wide tuning bandwidths for parametric processes are associated with wavelength 0 , where the group-velocity dispersion, d 2 k /d 2 , of a material goes to zero. 11 If one pumps a nonlinear crystal at 0 / 2, broadband gain around the degenerate signal-idler wavelength can be obtained. Use of OPG is a convenient way to investigate the broadband gain that occurs for GaAs when pumping at ϳ 0 / 2 = 3.31 m. Slightly detuning the pump from 0 / 2 and choosing an appropriate QPM period to compensate for the phase-mismatch results in even broader gain bandwidths (at the expense of some gain variation), as plotted i