Six SNPs and a TTG indel in sheep desmoglein 4 gene are in complete linkage disequilibrium

Desmoglein 4 (DSG4) plays an important role in the regulation of growth and differentiation of hair follicles in mammals. In this study, a 755 bp long segment of DSG4 was screened in 544 sheep sampled from nine Chinese indigenous breeds and two Western breeds using PCR-SSCP assay with three different pairs of primers. Two of the three fragments showed polymorphisms with genotypes defined as AA, AB, BB and BC, and DD, DE, and EE, respectively. Interestingly, polymorphisms in these two fragments were in strong linkage disequilibrium. Only three haplotypes were found, of which haplotype AD determined by alleles A and D was the major one in all breeds, while haplotype BE was only found in Chinese breeds that possess divergent frequencies ranging from 0.02 to 0.43; haplotype CD was very rare and present in only one Chinese sheep. Sequences of the three haplotypes showed seven single nucleotide polymorphisms (SNPs) and a TTG insertion/deletion (indel), leading to five amino acid substitutions and a glycine indel. Our study provides valuable genetic markers in evaluating the impact of the DSG4 gene on wool traits in sheep.Key words: Sheep, DSG4 gene, single-strand conformational polymorphism (SSCP), variation, linkage disequilibrium

The Directed Dominating Set Problem: Generalized Leaf Removal and Belief Propagation

A minimum dominating set for a digraph (directed graph) is a smallest set of vertices such that each vertex either belongs to this set or has at least one parent vertex in this set. We solve this hard combinatorial optimization problem approximately by a local algorithm of generalized leaf removal and by a message-passing algorithm of belief propagation. These algorithms can construct near-optimal dominating sets or even exact minimum dominating sets for random digraphs and also for real-world digraph instances. We further develop a core percolation theory and a replica-symmetric spin glass theory for this problem. Our algorithmic and theoretical results may facilitate applications of dominating sets to various network problems involving directed interactions.Comment: 11 pages, 3 figures in EPS forma

Bio-Inspired Aggregation Control of Carbon Nanotubes for Ultra-Strong Composites

High performance nanocomposites require well dispersion and high alignment of the nanometer-sized components, at a high mass or volume fraction as well. However, the road towards such composite structure is severely hindered due to the easy aggregation of these nanometer-sized components. Here we demonstrate a big step to approach the ideal composite structure for carbon nanotube (CNT) where all the CNTs were highly packed, aligned, and unaggregated, with the impregnated polymers acting as interfacial adhesions and mortars to build up the composite structure. The strategy was based on a bio-inspired aggregation control to limit the CNT aggregation to be sub 20--50 nm, a dimension determined by the CNT growth. After being stretched with full structural relaxation in a multi-step way, the CNT/polymer (bismaleimide) composite yielded super-high tensile strengths up to 6.27--6.94 GPa, more than 100% higher than those of carbon fiber/epoxy composites, and toughnesses up to 117--192 MPa. We anticipate that the present study can be generalized for developing multifunctional and smart nanocomposites where all the surfaces of nanometer-sized components can take part in shear transfer of mechanical, thermal, and electrical signals

Positron-annihilation study of compensation defects in InP

Positron-annihilation lifetime and positron-annihilation Doppler-broadening (PADB) spectroscopies have been employed to investigate the formation of vacancy-type compensation defects in n-type undoped liquid encapsulated Czochrolski grown InP, which undergoes conduction-type conversions under high temperature annealing. N-type InP becomes p-type semiconducting by short time annealing at 700°C, and then turns into n-type again after further annealing but with a much higher resistivity. Long time annealing at 950°C makes the material semi-insulating. Positron lifetime measurements show that the positron average lifetime τ av increases from 245 ps to a higher value of 247 ps for the first n-type to p-type conversion and decreases to 240 ps for the ensuing p-type to n-type conversion. The value of τ av increases slightly to 242 ps upon further annealing and attains a value of 250 ps under 90 h annealing at 950°C. These results together with those of PADB measurements are explained by the model proposed in our previous study. The correlation between the characteristics of positron annihilation and the conversions of conduction type indicates that the formation of vacancy-type defects and the progressive variation of their concentrations during annealing are related to the electrical properties of the bulk InP material. © 2002 American Institute of Physics.published_or_final_versio

A resonance Raman spectroscopic and CASSCF investigation of the Franck-Condon region structural dynamics and conical intersections of thiophene

Resonance Raman spectra were acquired for thiophene in cyclohexane solution with 239.5 and 266 nm excitation wavelengths that were in resonance with ∼240 nm first intense absorption band. The spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mostly along the reaction coordinates of six totally symmetry modes and three nontotally symmetry modes. The appearance of the nontotally symmetry modes, the CS antisymmetry stretch +C-C=C bend mode v 21 (B 2) at 754 cm-1 and the H 7 C 3 C 4 H 8 twist 9 (A 2) at 906 cm -1, suggests the existence of two different types of vibronic-couplings or curve-crossings among the excited states in the Franck-Condon region. The electronic transition energies, the excited state structures, and the conical intersection points 1B 1/ 1A 1 and 1B 2 / 1A 1 between 2 1A 1 and 1 1B 2 or 1 1B 1 potential energy surfaces of thiophene were determined by using complete active space self-consistent field theory computations. These computational results were correlated with the Franck-Condon region structural dynamics of thiophene. The ring opening photodissociation reaction pathway through cleavage of one of the C-S bonds and via the conical intersection point 1B/ 1A 1 was revealed to be the predominant ultrafast reaction channel for thiophene in the lowest singlet excited state potential energy hypersurface, while the internal conversion pathway via the conical intersection point 1B 2 / 1A 1 was found to be the minor decay channel in the lowest singlet excited state potential energy hypersurface. © 2010 American Institute of Physics.published_or_final_versio

Positron-lifetime study of compensation defects in undoped semi-insulating InP

Positron-lifetime and infrared-absorption spectroscopies have been used to investigate the compensation defects that render undoped n-type liquid encapsulated Czochralski-grown InP semi-insulating under high-temperature annealing. The positron measurements, carried out over the temperature range of 25-300 K, reveal in the as-grown material a positron lifetime of 282±5 ps which we associate with either the isolated indium vacancy V 3- In or related hydrogen complexes. The shallow donor complex V InH 4, responsible for much of the n-type conductivity and the strong infrared absorption signal at 4320 nm, is ruled out as a significant trapping site on the grounds that its neutral state is present at too low a concentration. After annealing at 950°C, in conjunction with the disappearance of the V InH 4 infrared-absorption signal, trapping into V In-related centers is observed to increase slightly, and an additional positron trapping defect having a lifetime of 330 ps appears at a concentration of ∼10 16 cm -3, indicating divacancy trapping. These results support the recent suggestion that the V InH 4 complex present in as-grown InP dissociates during annealing, forming V InH (3-n)- n (0≤n≤3) complexes and that the recombination of V In with a phosphorus atom results in the formation of EL2-like deep donor P In antisite defect, which compensates the material. It is suggested that the divacancy formed on annealing is V InV P, and that this defect is probably a by-product of the P In antisite formation.published_or_final_versio

Low-temperature microstructural studies on superconducting CaFe2As2.

Undoped CaFe2As2 (Ca122) can be stabilized in two slightly different non-superconducting tetragonal phases, PI and PII, through thermal treatments. Upon proper annealing, superconductivity with a Tc up to 25 K emerges in the samples with an admixture of PI and PII phases. Systematic low-temperature X-ray diffraction studies were conducted on undoped Ca122 samples annealed at 350 °C over different time periods. In addition to the diffraction peaks associated with the single-phase aggregation of PI and PII, a broad intermediate peak that shifts with annealing time was observed in the superconducting samples only. Our simulation of phase distribution suggests that the extra peak is associated with the admixture of PI and PII on the nanometer scale. High-resolution transmission electron microscopy confirms the existence of these nano-scale phase admixtures in the superconducting samples. These experimental results and simulation analyses lend further support for our conclusion that interfacial inducement is the most reasonable explanation for the emergence of superconductivity in undoped Ca122 single crystals