Scanning Electron Microscopy Observation of the Voltage Contrast Image of the Ferroelectric Domain Structure in the LiNbO3 Crystal

This paper reports a scanning electron microscopy study of the formation of the voltage contrast image of the ferroelectric domain structure in the LiNbO3 crystal. We investigated the formation of the pyroelectric voltage contrast image of the regular domain structure. For our experiment, we used ZY cut of a LiNbO3 crystal which had a regular domain structure with a domain width of -55 μm. The regular domain structure in the LiNbO3 crystal was formed by the method of thermo-electrical treatment after growth. The pyroelectric voltage contrast image of the regular domain structure in the scanning electron microscope was formed by applying the pyroelectric effect along polar axis Z. The difference in the voltage contrast in the neighboring domains connect with opposite directions of polar axis Z in the neighboring domains. It is shown that the voltage contrast of the ferroelectric domain structures is defined by the physical properties and orientation of the ferroelectric crystals

Fermionic field theory for directed percolation in (1+1) dimensions

We formulate directed percolation in (1+1) dimensions in the language of a reaction-diffusion process with exclusion taking place in one space dimension. We map the master equation that describes the dynamics of the system onto a quantum spin chain problem. From there we build an interacting fermionic field theory of a new type. We study the resulting theory using renormalization group techniques. This yields numerical estimates for the critical exponents and provides a new alternative analytic systematic procedure to study low-dimensional directed percolation.Comment: 20 pages, 2 figure

Scanning Electron Microscopy Observation of the Interaction Between the Surface Acoustic Waves and Regular Domain Structures in the LiNbO3 Crystals

This paper reports a scanning electron microscope study of the interaction between the surface acoustic waves and regular domain structures in LiNbO3 crystals. The regular domain structures in LiNbO3 crystals were formed by the method of the thermo-electric treatment after growth. We investigated two modes of interaction: the surface-acoustic-waves propagate along and across the regular domain structures. It is shown that the regular domain structures in the first case can be used as an acoustical wave-guide, because the power-flow vector of the surface acoustic waves has the direction along the domain structure. Also we observed that the surface acoustic wave inverts the voltage contrast of the image in the scanning electron microscope by π during the process of the propagation across the domain walls

Differential selection pressures exerted by host resistance quantitative trait loci on a pathogen population: a case study in an apple × Venturia inaequalis pathosystem

Understanding how pathogens evolve according to pressures exerted by their plant hosts is essential for the derivation of strategies aimed at the durable management of resistant cultivars. The spectrum of action of the resistance factors in the partially resistant cultivars is thought to be an important determinant of resistance durability. However, it has not yet been demonstrated whether the pressures exerted by quantitative resistance are different according to their spectrum of action.To investigate selection pressures exerted by apple genotypes harbouring various resistance quantitative trait loci (QTLs) on a mixed inoculum of the scab disease agent, Venturia inaequalis, we monitored V. inaequalis isolate proportions on diseased apple leaves of an F1 progeny using quantitative pyrosequencing technology and QTL mapping. Broad-spectrum resistances did not exert any differential selection pressures on the mixed inoculum, whereas narrow-spectrum resistances decreased the frequencies of some isolates in the mixture relative to the susceptible host genotypes. Our results suggest that the management of resistant cultivars should be different according to the spectrum of action of their resistance factors. The pyramiding of broad-spectrum factors or the use of a mixture of apple genotypes that carry narrow-spectrum resistance factors are two possible strategies for the minimization of resistance erosion

Impact of improving glove using on the hand hygiene compliance

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Photoluminescence of single colour defects in 50 nm diamond nanocrystals

We used optical confocal microscopy to study optical properties of diamond 50 nm nanocrystals first irradiated with an electron beam, then dispersed as a colloidal solution and finally deposited on a silica slide. At room temperature, under CW laser excitation at a wavelength of 514.5 nm we observed perfectly photostable single Nitrogen-Vacancy (NV) colour defects embedded in the nanocrystals. From the zero-phonon line around 575 nm in the spectrum of emitted light, we infer a neutral NV0 type of defect. Such nanoparticle with intrinsic fluorescence are highly promising for applications in biology where long-term emitting fluorescent bio-compatible nanoprobes are still missing.Comment: proceedings of ICDS 23 conference (23rd International Conference on Defects in Semiconductors, July 24 - July 29, 2005, Awaji Island, Hyogo, Japan); to appear in "Physica B

Experimental observation of nonlinear Thomson scattering

A century ago, J. J. Thomson showed that the scattering of low-intensity light by electrons was a linear process (i.e., the scattered light frequency was identical to that of the incident light) and that light's magnetic field played no role. Today, with the recent invention of ultra-high-peak-power lasers it is now possible to create a sufficient photon density to study Thomson scattering in the relativistic regime. With increasing light intensity, electrons quiver during the scattering process with increasing velocity, approaching the speed of light when the laser intensity approaches 10^18 W/cm^2. In this limit, the effect of light's magnetic field on electron motion should become comparable to that of its electric field, and the electron mass should increase because of the relativistic correction. Consequently, electrons in such high fields are predicted to quiver nonlinearly, moving in figure-eight patterns, rather than in straight lines, and thus to radiate photons at harmonics of the frequency of the incident laser light, with each harmonic having its own unique angular distribution. In this letter, we report the first ever direct experimental confirmation of these predictions, a topic that has previously been referred to as nonlinear Thomson scattering. Extension of these results to coherent relativistic harmonic generation may eventually lead to novel table-top x-ray sources.Comment: including 4 figure

Measurement and interpretation of hand hygiene compliance rates: importance of monitoring entire care episodes

SummaryOur objective was to assess the importance of monitoring hand hygiene compliance (HHC) during series of successive contacts with patients or surroundings for measurement and interpretation of the compliance rates. A direct observational study of HHC was performed in four intensive care units (ICUs) and four healthcare settings with non-intensive care wards (NICWs). Hand hygiene (HH) opportunities were differentiated into two categories: extra-series opportunities (ESOs) (before or after a single contact, and before the first contact or after the last contact of a series of successive contacts) or as intra-series opportunities (ISOs) (from the opportunity following the first contact to the opportunity preceding the last in the same series). In all, 903 opportunities of HH were performed in ICUs and 760 in NICWs. The proportion of ISOs was 46.0% in ICUs and 22.9% in NICWs. The overall HHC was significantly higher in NICWs than in ICUs (61.2% vs 47.5%, P < 0.00001). The HHC was significantly higher for ESOs than for ISOs (67.7% vs 28.5%, P < 0.00001). The HHC for ISOs was significantly higher in ICUs (32.2% vs 19.0%, P < 0.005). If the distribution of categories of HH opportunities observed in NICWs had been the same as in ICUs, the overall HHC would have been similar in NICWs (46.4%) and in ICUs (47.5%). Monitoring HHC during entire care episodes in series of successive contacts is necessary to avoid a strong overestimation of the overall compliance rates. Concurrently, comparison of compliance data should take into account the proportion of ISOs included in the evaluation study