[en] Graphical abstract: - Highlights: • Behavior of the SiH_x species on the W surface under cat-CVD conditions. • The adsorption and dissociation mechanisms of SiH_x(x = 1–4) species on W(1 1 1) surface. • H-migration to its neighboring W atoms is more favorable compared to H_2 elimination. - Abstract: The adsorption and dissociation mechanisms of SiH_x(x = 1–4) species on W(1 1 1) surface have been investigated by using the periodic density functional theory with the projector-augmented wave approach. The adsorption of all the species on four surface sites: top (T), bridge (B), shallow (S), and deep (D) sites have been analyzed. For SiH_4 on a top site, T-SiH_4_(_a_), it is more stable with an adsorption energy of 2.6 kcal/mol. For SiH_3, the 3-fold shallow site is most favorable with adsorption energy of 46.0 kcal/mol. For SiH_2, its adsorption on a bridge site is most stable with 73.0 kcal/mol binding energy, whereas for SiH and Si the most stable adsorption configurations are on 3-fold deep sites with very high adsorption energies, 111.8 and 134.7 kcal/mol, respectively. The potential energy surfaces for the dissociative adsorption of all SiH_x species on the W(1 1 1) surface have been constructed using the CINEB method. The barriers for H-atom migration from SiH_x_(_a_) to its neighboring W atoms, preferentially on B-sites, were predicted to be 0.4, 1.0, 4.5 and, 8.0 kcal/mol, respectively, for x = 4, 3, 2, and 1, respectively. The adsorption energy of the H atom on a bridge site on the clean W(1 1 1) surface was predicted to be 65.9 kcal/mol, which was found to be slightly affected by the co-adsorption of SiH_x_−_1 within ± 1 kcal/mol.

[en] HOT1 is a cis-acting recombination-stimulatory sequence isolated from the rDNA repeat unit of yeast. The ability of HOT1 to stimulate mitotic exchange appears to depend on its ability to promote high levels of RNA polymerase I transcription. A qualitative colony color sectoring assay was developed to screen for trans-acting mutations that alter the activity of HOT1. Both hypo-recombination and hyper-recombination mutants were isolated. Genetic analysis of seven HOT1 recombination mutants (hrm) that decrease HOT1 activity shows that they behave as recessive nuclear mutations and belong to five linkage groups. Three of these mutations, hrm1, hrm2, and hrm3, also decrease rDNA exchange but do not alter recombination in the absence of HOT1. Another mutation, hrm4, decreases HOT1-stimulated recombination but does not affect rDNA recombination or exchange in the absence of HOT1. Two new alleles of RAD52 were also isolated using this screen. With regard to HOT1 activity, rad52 is epistatic to all four hrm mutations indicating that the products of the HRM genes and of RAD52 mediate steps in the same recombination pathway. Finding mutations that decrease both the activity of HOT1 and exchange in the rDNA supports the hypothesis that HOT1 plays a role in rDNA recombination

[en] A computational analysis of steady laminar natural convection of cold water within a horizontal annulus with constant heat flux on the inner wall and a fixed temperature on the outer surface has been undertaken to explore the occurrence of density inversion of water and its effects on the flow and temperature fields. Results are generated for three values of radius ratio over various ranges of the modified Rayleigh number and density inversion parameter. For the flow circumstances considered, the occurrence of density inversion is found to be mainly dependent on the density inversion parameter. With a negative inversion parameter, the increase of either the modified Rayleigh number or the radius ratio results in a more pronounced effect of density inversion on the flow and temperature fields in the annulus. (author)

[en] The effect of intersubsystem coupling on the adiabaticity of composite systems and that of its subsystems is investigated. Similar to the adiabatic evolution defined for pure states, nontransitional evolution for mixed states is introduced; conditions for the nontransitional evolution are derived and discussed. An example that describes two coupled qubits is presented to detail the general presentation. The effects due to nonadiabatic evolution on the geometric phase are also presented and discussed

[en] Metal–insulator transition in the Gd-doped (R_1−yGd_y)_1.85Ce_0.15CuO_4−δ systems occurred around y∼0.1 for R=Eu and y∼0.65 for R= Nd with a simultaneous structural transition from the tetragonal T′-phase (space group I4/mmm) to an orthorhombic O′-phase (Acam, a_o⩽b_o∼√2a_t). The structural distortion is due to the lattice mismatch between smaller (R,Gd,Ce)₂O₂ layer and CuO₂ plane which results in an oxygen distortion in the otherwise perfect CuO₂ square plane. The phase diagram indicates that the superconductivity can only occur in the metallic T′-phase cuprates where the metallic state is controlled by a delicate balance between oxygen reduction and structural stability. The Cu²⁺ weak-ferromagnetic/canted-antiferromagnetic (WF/CAF) order observed in the insulating region is the direct result of non-180° α(Cu–O–Cu) canting angle of the O′-phase.

[en] To enlarge the interaction structure to a feasible dimension and to decrease the required magnetic field to an available strength, the gyrotron devices at THz frequencies must be designed with a high-order-mode interaction, which is weaker in a beam–wave interaction and more susceptible to mode competition. Using the same interaction structure (a circular waveguide) as in the gyrotron traveling-wave amplifier (gyro-TWT), but replacing the axial magnetic field of the gyro-TWT with a tapered helical magnetic field, we found that the gyrating electrons are able to perform strong interaction with the TE11 mode in the THz region. Through an example case, we explored the behavior of the particles and wave fields as in a beam–wave interaction under a modified scheme of the gyro-TWT with a numerical simulation code. The equations required for the simulation are presented. The simulation result of the example case indicates that, through the TE11 beam–wave interaction under the presented scheme, more than one quarter of the beam energy can be converted to the wave at 612.7 GHz and to heat, dissipated on the waveguide wall, of radius 2.5 cm

[en] Polyvinylpyrrolidone-based nano composite fibers containing (Ni₀.6Zn₀.4)Fe₂O₄ have been successfully fabricated by an electro spinning technique. Magnetic measurements were made, individually, on polyvinylpyrrolidone, the ferrite nanoparticles, and several fibrous nano composites. The polymer exhibits a diamagnetic susceptibility comparable to the estimated value from Pascals constants. The nano composites maintain intrinsic properties of pure (Ni₀.6Zn₀.4)Fe₂O₄, with a weighted magnitude according to its concentration in a given fiber. Meanwhile, superparamagnetism prevails with a relatively low blocking temperature, assuring no aggregation of the fine particles. Such electro spun materials are flexible and have large surface area per unit mass, thus suitable for certain applications in environmental and biomedical engineering.

[en] Ni_1_-_xFe_xO nano fibers with different Fe doping concentration have been synthesized by electro spinning method. An analysis of the phase composition and microstructure shows that Fe doping has no influence on the crystal structure and morphology of NiO nano fibers, which reveals that the doped Fe ions have been incorporated into the NiO host lattice. Pure NiO without Fe doping is antiferromagnetic, yet all the Fe-doped NiO nano fiber samples show obvious room-temperature ferromagnetic properties. The saturation magnetization of the nano fibers can be enhanced with increasing Fe doping concentration, which can be ascribed to the double exchange mechanism through the doped Fe ions and free charge carriers. In addition, it was found that the diameter of nano fibers has significant impact on the ferromagnetic properties, which was discussed in detail.

[en] Aiming at the observation of cosmic-ray chemical composition at the 'knee' energy region, a new type air-shower core detector (YAC, Yangbajing Air shower Core array) consisting of a lead plate of 3.5 cm thick and a scintillation counter with an area of 0.5 m${}^2$ has been developed and set up at Yangbajing, 4300 m a.s.l. in Tibet, China since 2014. The main purpose of YAC detector is to separate primary cosmic-ray mass by detecting high energy electromagnetic particles at the air-shower (AS) core generated by the secondary particles after passing through the lead plate. In order to precisely measure the number of shower particles, the calibration procedure of the YAC detector is described in this paper. We found that the linear relationship between YAC scintillation detector output and incident particles is good below 5$\times <!--\; ??\; -->$${10}^6$ MIPs while the non-linearity is less than 3%. Such a wide dynamic range shows that YAC experiment may make it possible to obtain the primary mass composition and energy spectrum covering and above the 'knee' energy region.

[en] Zinc oxides deposited on Tin dioxide nano wires have been successfully synthesized by atomic layer deposition (ALD). The diameter of SnO₂-ZnO core-shell nano wires is 100 nm by ALD 200 cycles. The result of electricity measurements shows that the resistance of SnO₂-ZnO core-shell nano wires (ALD: 200 cycles) is 925Ω, which is much lower than pure SnO₂ nano wires (3.6 x 106Ω). The result of UV light test shows that the recovery time of SnO₂-ZnO core-shell nano wires (ALD: 200 cycles) is 328 seconds, which is lower than pure SnO₂ nano wires (938 seconds). These results demonstrated that the SnO₂-ZnO core-shell nano wires have potential application as UV photodetectors with high photon-sensing properties.