[en] We report the fabrication and characterization of two-dimensional silicon-based photonic crystal (PhC) structures realized by a combination of electron-beam lithography and dry-etching techniques. PhCs of various lattices with very high aspect ratios up to 20 have been achieved, and PhC chips were prepared by standard semiconductor technologies, including thinning and cleaving. The chips consisting of high-aspect-ratio air rods or dielectric rods permit a direct transmission measurement, and they were observed to demonstrate pronounced photonic bandgap effects. Several photonic bandgap behaviors were identified by comparing transmission with reflection and experimental results with numerical results, and by considering detecting beam property. Copyright 2001 Optical Society of America

[en] The phenomenon of the broadband transmission enhancement of acoustic waves is important for its prospective applications in various devices. To achieve broadband transmission enhancement of acoustic waves, we investigate the acoustic transmission in a metallic grating device with linearly tapered slits through eigen-mode matching theory (EMMT) and finite element (FE) simulation. The tapering provides a gradual filling fraction variation from the entrance to the exit of the slits, destroying the Fabry–Perot resonance and thus leading to broadband and wide-angle enhanced transmission in the audible regime. In addition, acoustic waves are strongly localized and enhanced at the slit exits, in contrast with straight slits.

[en] Using a first-principles method, we have investigated site preference and diffusion properties of carbon (C) in copper (Cu). A single C atom energetically prefers to occupy the octahedral interstitial site (OIS) instead of the tetrahedral interstitial site. Double C atoms tend to be paired up at the nearest neighboring OIS’s along the 〈1 0 0〉 direction mediated by a bridging Cu atom with a distance of 3.85 Å and a binding energy of 0.15 eV. This suggests that an indirectly attractive interaction between C atoms exists, which might lead to a local higher concentration of C in Cu. We demonstrate that the OIS → OIS path is the optimal diffusion path of C in Cu with diffusion barrier of 0.93 eV. By the estimation of pre-exponential factor according to a classical thermodynamics model, the diffusion coefficient as a function of temperature has been determined, which is 3.68 × 10"−"1"5 m"2/s at a typical temperature of 600 K. The results provide a good reference to understand the behavior of C in Cu

[en] The feasibility of building the BTCF(Beijing τ-charm Factory) on the BEPC site is being studied, but many technical difficulties remain. For the injector, full energy injection and very high beam current are still challenging problems for the BEPC linac. A lot of R and D work remains: on the X-band pulse compressor, on the high current multibunch electron gun and on the subharmonic buncher etc. (author)

[en] The annual Live Interventional Neuroradiology and Neurosurgery Course (LINNC) is one of the most important congresses in the neurosurgery and neuroradiology field. LINNC 2009 was held on May 25th this year and lasted for 3 days. In this article, the authors introduced the main points of the congress. The congress mainly discussed some hot topics at present time, including both the clinical and fundamental studies of cerebral arteriovenous malformation, ischemic cerebral disease and intracranial aneurysm, etc. Both neurological and neuroradiological case demonstrations related to the topics, and the main course of the congress were alternately performed. Recent advances in imaging technique and clinical application, such as Dyna-CT and Xper-CT, were also presented on the congress. (authors)

[en] In our previous paper, we pointed out that the experimental results on the axial spontaneous magnetic field given by Najmudin et al. can be explained by our kinetic model. We also found that the azimuthal magnetic field B_θ given by our kinetic model is much weaker than the axial spontaneous magnetic field, which is not consistent with particle-in-cell simulation results. In the present paper, we reinvestigate the generation mechanism of the spontaneous magnetic fields from relativistic Vlasov-Maxwell equations. It is found that the azimuthal spontaneous magnetic field B_θ can be same order as the axial spontaneous magnetic field if the laser beam self-focus effect is considered. It is also obtained that the magnitude of the spontaneous magnetic field is proportional to the plasma density for the case of low plasma density, but is independent of the plasma density for the case of high plasma density. (author)

[en] We propose a vacancy trapping mechanism for carbon—vacancy (C—V) complex formation in copper (Cu) according to the first-principles calculations of the energetics and kinetics of C—V interaction. Vacancy reduces charge density in its vicinity to induce C nucleation. A monovacancy is capable of trapping as many as four C atoms to form C_nV (n = 1, 2, 3, 4) complexes. A single C atom prefers to interact with neighboring Cu at a vacancy with a trapping energy of −0.21 eV With multiple C atoms added, they are preferred to bind with each other to form covalent-like bonds despite of the metallic Cu environment. For the C_nV complexes, C₂V is the major one due to its lowest average trapping energy (1.31 eV). Kinetically the formation of the C_nV complexes can be ascribed to the vacancy mechanism due to the lower activation energy barrier and the larger diffusion coefficient of vacancy than those of the interstitial C

[en] Objective: To evaluate the endovascular treatment of cerebral arteriovenous malformation (AVM) associated with aneurysms and to investigate the further strategy and approaches. Methods: Fifty-one cases of cerebral AVM associated with aneurysms were treated from Jan. 1996 to Dec. 2003. The therapeutic strategy was planed according to the site of aneurysms on angiography and clinical manifestation. The authors often treated the aneurysms initially through endovascular approach under general anesthesia. Results: All together 6 aneurysms located at Willis circle with 4 of them ruptured and treated before embolization of AVM and the 2 remained untreated and followed-up. Among 16 aneurysms in feeding arteries, 11 were occluded with microcoils, 4 with NBCA and one with Onyx. Twenty-eight intranidal aneurysms were treated with NBCA glue and the other one with Onyx. Follow-up angiogram in 22 cases showed stable results. Conclusions: Aneurysms associated with brain AVM should be the primary targets for endovascular treatment. (authors)

[en] The influences of specific heat capacity C _P, temperature step ΔT, electric field step ΔE, and initial electric field E ₁ on predicted electrocaloric (EC) temperature ΔT of monodomain BaTiO₃ are examined by combining the Maxwell equation and phenomenological theory. Since the procedure is similar to indirect measurement of the EC effect, the results can serve as a reference for experiments. The results suggest that (i) it is reasonable to use zero-field C _P, (ii) optimized ΔT should be 2 K, (iii) it is better to keep ΔE < E _C, and (iv) E ₁ < E _C. Here, E _C is the coercive field of material. (paper)

[en] Objective: The radiographic outcomes of endovascular stenting combined with coiling for treating intracranial wide-necked aneurysms were summarized for investigating the efficacy of this procedure. Methods: sixty two patients with intracranial wide-necked aneurysms were treated with combined stenting and coiling procedure and all were undergoing clinical and angiographic follow-up after the initial treatment. Results: The stents were deployed in all aneurysms and total occlusion was obtained in 47 cases and subtotal occlusion in 15 cases. Follow-up angiograms during 1-6 months showed complete obliteration in 57 cases, neck remnant with further thrombosis in 4 cases, recanalization in one case which needed another occlusion. 12-37 months follow-up angiogram in 43 cases suggested total occlusion in 40 cases with two neck remnant and one recanalization. Conclusions: Endovascular stent placement changes flow characteristics and facilitate thrombosis inside the aneurysm pouch resulting in radiographically healing by promoting endothelization at aneurysmal neck. (authors)