1,721,274 research outputs found
Digital PCR as New Approach to SNP Genotyping in Sugar Beet
No full textReal-time PCR (qPCR) allelic discrimination and high-resolution melting (HRM) methods are widely adopted for the detection of single nucleotide polymor- phisms (SNP). Digital PCR (dPCR) is a new method recently proposed for the detection of low-frequency and/ or rare SNP. The molecular marker SNP_BvBTC1 is used in sugar beet to distinguish between annual and biennial flowering plants. The CC genotype at this SNP locus is associated with biennial beets, while the CA and AA genotypes are typically found in annual beets. In this study, we compared the sensitivity of qPCR, HRM and dPCR in detecting the allele A from two pools of bulk beet DNA composed of 90 biennial ? 10 annual plants (B1) and 99 biennial ? 1 annual plant (B2), respectively. All annual plants were found to have the AA genotype. qPCR could not detect allele A in either the B1 or B2 pool and HRM detected allele A only at moderate frequencies (10 %), in the B1 pool. dPCR, on the contrary, was able to detect allele A in both pools. We therefore concluded that dPCR is a suitable method for the quantitation of SNP_BvBTC1 within bulked DNA samples of sugar beet
"A theoretical framework for the interpretation of STM images of adsorbates"
No full textA theoretical formalism for the interpretation of STM images of adsorbates is developed by approaching the calculation of the observed current as a transport problem in quantum statistical mechanics. The STM configuration is treated as a system of three groups of states - the substrate, the adsorbate and the tip - in contact with a thermal reservoir, with which it exchanges energy. A new definition of current is introduced, and shown to be related to that given in the traditional transfer Hamiltonian approach. The transport instrument used for the description is the stochastic Liouville equation, known to have the advantage of allowing the incorporation of thermal effects as well as arbitrary degree of coherence in the quantum transport. Some preliminary calculations of STM images of simple adsorbate models are presented
Mechanism of nonrandom pattern formation of polar-conjugated molecules in a partial wetting regime
No full textAn original nucleation and growth process has been investigated for vacuum-deposited films of a polarconjugated molecule, tris-(8-hydroxyquinoline) aluminum (III) (Alq3), onto the apolar H-terminated Si(100). Homogeneous nucleation of amorphous Alq3 clusters is restricted to the early stage of deposition and is characterized by a large critical nucleus size i = 5, as determined from the dependence of the density of stable nuclei N on deposition rate κ. Alq3 clusters grow in a partial wetting regime to form correlated droplet patterns. For moderate deposition rates around 1 nm/min, patterns exhibit both (i) a typical scale invariance of the droplet size distribution with coverage and substrate temperature and (ii) strong correlations between the size and position of the droplets. Both these characteristics result from the absence of coarsening - e.g., Ostwald ripening, secondary nucleation, and coalescence during growth. Spatial correlations are analyzed by using Voronoi tesselation, which demonstrates the validity of a phenomenological capture zone model for correlated growth. Correlations emerge in the early stage of growth via direct ripening and further develop during growth by diffusive interactions between domains. Direct ripening manifests itself by the introduction of a minimum cutoff distance between droplets, which causes a significant narrowing of the droplet size distribution. During growth, diffusive interactions between droplets cause their centers of mass to move towards empty depleated areas, which results in enhanced spatial correlations. This peculiar nucleation and growth mechanism allows one to obtain droplet patterns where the interdroplet distance and droplet size can be tuned independently via deposition temperature and time
Scaling of mobility in pentacene transistors and stabilization using alkanethiol treated gold electrodes
No full textWe investigate the scaling of field-effect mobility as a function of channel length in case of pentacene-based transistors with coplanar geometry. The apparent variation of mobility is mainly attributed to the effect of disorder at the metal-semiconductor interface and injection limited charge transport in case of smaller channel length. The scaling is modified using drain-source electrodes, treated with self-assembly monolayer of alkanethiol with varying carbon atoms. Copyright © 2007 Materials Research Society
Fabrication of material patterns by grid-assisted deposition
No full textWe developed a simple patterning approach where a grid with micrometer rule is used in order to control the deposition of a solute. Ordered patterns were obtained, over large areas, in a few seconds. The patterning process we propose here is fast and low cost. It can also be applied to diverse soluble molecular and supramolecular species. We also investigated what parameters have to be changed in order to have total control on the final tridimensional architecture of the material
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