弱谐波情况下透射光栅衍射效率标定方法

同步辐射光源中的高次谐波会使透射光栅衍射效率标定精度变差。为了校正光源中的高次谐波对透射光栅衍射效率标定的影响,提出了一种光源存在弱谐波情况下的透射光栅衍射效率标定方法,通过使用谐波X射线的衍射效率修正基波衍射效率标定中谐波的影响,从而得到更为准确的透射光栅衍射效率。使用该标定方法在北京同步辐射光源上开展了透射光栅相对衍射效率标定工作。实验结果表明:在100~800eV存在高次谐波能段,修正后透射光栅一级与零级的相对衍射效率与理论模拟结果吻合较好,修正后光栅二级与一级的相对衍射效率更接近理论模拟结果,但与理论模拟结果仍有较大偏差,该偏差主要来源光栅较弱的二级衍射。     

The value of diffusion-weighted MRI to evaluate the response to radiochemotherapy for cervical cancer

Purpose

To investigate the value of apparent diffusion coefficient (ADC) to predict and monitor the therapy response for cervical cancer patients receiving concurrent radiochemotherapy, and to analyze the influence of different b-value combinations on ADC-based evaluation of treatment response.

Material and Methods

Seventy-five cervical cancer patients treated with radiochemotherapy received conventional MRI and DWI prior to therapy, after 2 weeks of therapy, after four weeks of therapy and after therapy completion. Treatment response was classified as complete response (CR, n = 35), partial response (PR, n = 22) and stable disease (SD, n = 18), which was determined according to final tumor size after 6 months of therapy completion. Dynamic changes of apparent diffusion coefficients (ADC) and tumor size in the three tumor groups were observed and compared. All the ADCs were calculated from b = 0, 600 s/mm² and b = 0, 1000 s/mm².

Results

The ADC increased percentage was higher in CR group than those in PR and SD groups after two weeks and four weeks of therapy, with significant differences in absolute ADCs between CR and PR, SD groups after therapy completion; the overall discriminatory capability for differentiation of CR and PR, SD groups was higher for high b-value combination (0, 1000 s/mm²) than for low b-value combination (0, 600 s/mm²).

Conclusion

DWI can be used as a predictive and monitoring biomarker of treatment response to radiochemotherapy in patients with cervical cancer. High b-value combination may be more reliable to evaluate the treatment response for cervical cancer.     

Fabrication of nanopatterned sapphire substrates by annealing of patterned Al thin films by Laser Interference Lithography

Nanopatterned sapphire substrates were fabricated by annealing of patterned Al thin films. Square-patterned Al thin films with the diagonal length of 600 nm, period of 1 um and height of ～200 nm were obtained by the Laser Interference Lithography and Reactive Ion Etching. Patterned Al thin films were subsequently subjected to dual stage annealing due to the melting temperature of Al thin films (660 ^°C). The first comprised a low temperature oxidation anneal. The hillocks formation on Al thin films was minimized with an oxidation annealing at 450 ^°C for 24 h. The little change in the morphology of patterned Al thin films was observed at 450 ^°C for 24 h. This was followed by a high temperature annealing to induce growth of the underlying sapphire single crystal to consume the oxide layer. The SEM results show the patterns were retained on sapphire substrates after high temperature annealing at less than 1200 ^°C. The XRD and Raman results reveal that the orientation of island patterns by dual stage annealing of patterned Al thin films for 24 h at 450 ^°C, and 1 h at 1000 ^°C, was the same as that of the sapphire (0001) substrates.     

Omnidirectional non-radiative wireless power transfer with rotating magnetic field and efficiency improvement by metamaterial

In this paper, omnidirectional wireless power transfer (OWPT) via magnetic resonant coupling is proposed based on rotating magnetic field. In contrast to conventional WPT, the proposed wireless power transmitter consists of two orthogonal loops with 90° feeding phase difference. Both theoretical analyses and numerical simulations show that such transmitter generates rotating magnetic field and can provide wireless power to multiple receivers moving around it. In addition, a cylindrical metamaterial slab with negative permeability is used to improve the efficiency of the OWPT system, for the unique property of enhancing evanescent wave of metamaterials. It is shown that the efficiency of the OWPT can be improved to more than five times of that of the original one by the metamaterial slab.     

Theoretical investigations of the spin Hamiltonian parameters for the tetragonal [Rh(CN)4Cl2] complex in KCl

The spin Hamiltonian parameters (g factors, hyperfine structure constants and superhyperfine parameters) for the tetragonal [Rh(CN)₄Cl₂]⁴⁻ complex in KCl are theoretically investigated from the perturbation formulas of these parameters for a 4d⁷ ion in a tetragonally elongated octahedron. This center can be assigned to the substitutional Rh²⁺ on host K⁺ site reduced from Rh³⁺ by capturing one electron during the electron irradiation, associated with the two axial ligands CN⁻ replaced by two Cl⁻. The crystal-fields of the two axial Cl⁻ are weaker than those of the four planar CN⁻, yielding the tetragonal elongation distortion. This system belongs to the case of low spin (S = 1/2) under strong crystal-fields, different from that of high spin (S = 3/2) under weak and intermediate crystal-fields (e.g., 3d⁷ ions such as Fe⁺ and Co²⁺ in conventional chlorides). The calculated spin Hamiltonian parameters show good agreement with the experimental data. The above [Rh(CN)₄Cl₂]⁴⁻ complex due to the different axial and perpendicular ligands is unlike the tetragonally elongated [RhCl₆]⁴⁻ complex due to the Jahn–Teller effect in the similar NaCl:Rh²⁺ crystals.     

Design consideration and fabrication of 1.2-kV 4H-SiC trenched-and-implanted vertical junction field-effect transistors

We present the design consideration and fabrication of 4H-SiC trenched-and-implanted vertical junction field-effect transistors （TI-VJFETs）. Different design factors, including channel width, channel doping, and mesa height, are con- sidered and evaluated by numerical simulations. Based on the simulation result, normally-on and normally-off devices are fabricated. The fabricated device has a 12 μm thick drift layer with 8 × 10^15 cm^-3 N-type doping and 2.6 μm channel length. The normally-on device shows a 1.2 kV blocking capability with a minimum on-state resistance of 2.33 mΩ.cm2, while the normally-off device shows an on-state resistance of 3.85 mΩ.cm2. Both the on-state and the blocking performances of the device are close to the state-of-the-art values in this voltage range.     

Nondestructive discrimination of Greenberger-Horne-Zeilinger-basis states via two-qubit parity detection

We propose new methods to construct universal Greenberger-Horne-Zeilinger (GHZ)-state analyzers without destroying the qubits by using two-qubit parity gates. The idea can be applied to any physical systems where the two-qubit parity gate can be realized. We also investigate the feasibility of nondestructively distinguishing the GHZ-basis states for photonic qubits with such an idea. The nondestructive GHZ-state analyzers can act as generators of GHZ entangled states and are expected to find useful applications for resource-saving quantum information processing.     

The suitability of barium monofluoride for laser cooling from ab initio study

ABSTRACT

The feasibility of laser cooling the ¹³⁸Ba¹⁹F molecule is performed using ab initio quantum chemistry. Three low-lying doublet electronic states X ²Σ⁺, A' ²Δ and A ²Π are determined by the multireference configuration-interaction (MRCI) method, where the spin–orbit coupling (SOC) effect is also taken into account in the electronic structure calculations. The computed spectroscopic constants and permanent dipole moments agree well with the available experimental data. The Franck–Condon factors of the A ²П → X ²Σ⁺ transition show highly diagonal dominance (f₀₀ = 0.981, f₁₁ = 0.940, f₂₂ = 0.896) and the A ²П state has a radiative lifetime of τ = 37.8 ns, allowing for rapid laser cooling. Our calculation indicates that the laser-cooling scheme require only three lasers at 822 nm, 855 nm and 856 nm proceeded on the A ²П (ν′) ← X ²Σ⁺ (ν′′) transitions. The appeared intervening state A' ²Δ between the X ²Σ⁺ and A ²П states is the main challenge for laser cooling this molecule. In fact, the calculated vibrational branching loss ratio to the intermediate A' ²Δ state is almost negligible at a level of η < 4.5 × 10^?9. Thus, BaF is a promising laser-cooling candidate with a relatively simple laser-cooling scheme.     

Solder joint inspection based on neural network combined with genetic algorithm

To improve the performance of automatic optical inspection (AOI), a neural network combined with genetic algorithm for the diagnosis of solder joint defects on printed circuit boards (PCBs) assembled in surface mounting technology (SMT) is presented. Six types of solder joint have been classified in respect to the reality in the manufacture. The images of solder joint under test are acquired and 14 features are extracted as input features for the classification. The neural network is easily become over-fitting because these input features are not independent of each other, so the genetic algorithm is introduced to select and remove redundant input features. The experimental results have proved that the neural network combined with genetic algorithm reduced the number of input feature and had a satisfying recognition rate.     

Investigations on the EPR parameters and tetragonal distortions for Cu2+ in alkali lead tetraborate glasses

The electron paramagnetic resonance parameters (g factors and hyperfine structure constants) and local structures are theoretically investigated for Cu²⁺ in alkali lead tetraborate 90R₂B₄O₇·9PbO·CuO (R = Li, Na and K) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d⁹ complex. The [CuO₆]^10? complexes are found to experience the relative tetragonal elongation ratios 18%, 23% and 30% for R = Li, Na and K, respectively, due to the Jahn–Teller effect, much larger than those for similar ARbB₄O₇ (A = Li, Na and K) glasses. This point is attributed to the lattice expansion (longer A–O bond lengths) with doped PbO, yielding lower force constants and more intense Jahn–Teller elongations in the 90R₂B₄O₇·9PbO·CuO glasses. The increasing tendency (Li > Na > K) of the relative elongation ratio λ, covalency and the ratio Δg_///Δg_⊥ for g-shifts are systematically analysed in a uniform way.