Transfer-matrix dynamic model of partly gain-coupled 1.55 μm DFBlasers with a strained-layer MQW active grating

A dynamic model for partly gain-coupled 1.55 μm MQW DFB lasers consisting of etched strained-layer multiquantum wells is presented. For the modulation and noise characteristics of DFB lasers, analytical expressions which take into account both the longitudinal distribution of laser parameters and carrier transport effects are derived for the first time using the transfer-matrix method. As a numerical example, the relaxation oscillation frequency is compared to experimental results, and reasonable agreements are obtained between the theory and experiment     

Neutron Diffraction Study on the Structure of Na-Si-O-N Oxynitride Glasses

The local structure of a Na₂O─SiO₂ oxide glass and a Na₂O─iO₂─Si₃N₄ oxynitride glass has been investigated by the pulsed neutron diffraction method. In the oxide glass, the first peak of radial distribution function (RDF) curves appeared at 0.1627 nm corresponding to Si─O boxh length. In the oxynitride glass, the first peak of the RDF curve was shifted to longer distances at 0.1650 nm due to the coexistence of Si─O and Si─N boxhs. The first peak in the RDF curve of the oxynitride glass was deconvoluted into two peaks whose positions are located at 0.1626 and 0.1709 nm. The one at 0.1626 nm is ascribed to Si─O boxhs and the other at 0.1709 nm to Si─N boxhs. The number of silicon atoms around a nitrogen was found to be 2.42, suggesting that not all of the nitrogen atoms are boxhed to three silicon atoms, but 58% twofold (─N─) and 42% threefold (>N─) nitrogens coexist in the present Na-Si-O-N oxynitride glass. The formation of twofold nitrogens may arise from the reaction between ≡Si─O⁻ and ≡Si₃N groups. This model is compatible with the experimental observation that the density and Vickers hardness of oxynitride glasses increase with the nitrogen content.     

An e.s.r. study of the motion of peroxy radicals in isotactic and atactic polypropylenes

E.s.r. spectra of peroxy radicals trapped in isotactic and atactic polypropylenes have been observed at various temperatures. The spectrum observed at 77 K was shown to be composed of one component by comparing it with that at 4 K. The spectra observed at higher temperatures comprised of two spectra arising from the rigid peroxy radicals and the mobile peroxy radicals. All of the observed spectra have been reconstructed by means of computer simulation and the changes in anisotropic g-values with temperature were estimated. The motion of the mobile fraction was shown to be rotation or rotatory vibration of the radicals around the chain axis both in the isotactic polypropylene and in the atactic polypropylene as well as in polyethylene and poly(tetrafluoroethylene) although the structures of the polymers are different, that is helical (polypropylene) or planar zigzag (polyethylene, poly(tetrafluoroethylene)).     

Nano-scale fluctuations in electron beam resist pattern evaluated by atomic force microscopy

The resist pattern fluctuations on the nano-scale are successfully observed using a dynamic force mode AFM. A scaling analysis based on the fractals applies to the AFM images for quantitative evaluation of the fluctuations. The standard deviation of width fluctuations in a ZEP resist pattern is 2.8 nm. The scaling analysis confirms that the surface morphology of the pattern sidewall is almost the same as that of the resist film lightly exposed by an electron beam. The main cause of the fluctuation is structures with a diameter of 20–30 nm which are composed of large groups of molecules.     

Vitamin E and coenzyme Q concentrations in the thyroid tissues of patients with various thyroid disorders

Chylous fistula complicates 1.1% of all radical neck dissections, and 2.4% of left-sided dissections. The standard treatment of established chylous leak in the reported cases is a pressure dressing applied to the lower neck. Here we present a case of chylous fistula, where conservative methods failed to cope with this complication. The additional application of a fibrin adhesive set was a successful modality of treatment.     

High-speed performance of partly gain-coupled 1.55-μmstrained-layer multiple-quantum-well DFB lasers

A partly-gain-coupled 1.55-μm distributed feedback (DFB) laser with a strained-layer multiple-quantum-well (MQW) active region with high relaxation oscillation frequency and maximum intrinsic bandwidth of 28 GHz is reported. An effective differential gain of 1.80×10^-15 cm² was achieved, which may be attributed to the strain effect in the MQW active region as well as the combination of the longitudinal gain/index coupling mechanism and fast lateral carrier injection from the cladding layers into the wells     

Flow cytometric single-cell analysis of cytokine production by CD4+ T cells in synovial tissue and peripheral blood from patients with rheumatoid arthritis

BACKGROUND AND PURPOSE: To detect areas of cerebral perfusion from bypass arteries after vascular reconstruction, we administered selective intraarterial microsphere tracer into the external carotid arteries and determined (via single-photon emission computed tomography [IA-SPECT]) whether the distribution of radiotracer matched the arteriographic distribution of contrast material as shown on external carotid angiograms. METHODS: We compared the extent of regional distribution of tracer after external carotid artery injection of 20 to 40 MBq of 99mTc-HMPAO or 99mTc-ECD with that of contrast medium on the external carotid angiograms in 582 cortical regions in 12 patients with atherosclerotic occlusive disease and in 18 patients with moyamoya disease. RESULTS: Marked accumulation of tracer was found only in the expected, specific, newly developed areas of cerebral perfusion from bypass arteries. The regional distribution of tracer corresponded to that of contrast medium in 523 regions (90%) and did not correspond in 59 regions (10%). Significant overestimation of the distribution of contrast material relative to that of tracer was observed in the patients with moyamoya disease. CONCLUSION: SPECT showed slightly different distribution of tracer from that predicted by conventional angiography. IA-SPECT should enhance the analysis of newly developed areas of cerebral perfusion from the bypass arteries.     

Transient Characteristics of Thermal Conduction in Dispersed Composites

The effective thermal conductivity of dispersed composites with a hot-melt-adhesive matrix, measured using the steady-state method, is compared with the apparent thermal conductivity calculated from the average heat capacity and from the thermal diffusivity measured by the laser-flash method. The transient effect has been observed obviously at higher volume percentages for various dispersed particle sizes and ratios of the thermal conductivity values of dispersed and continuous phases. All of the experimental results are compared with those calculated by existing models and by the finite element method (FEM). An attempt has been made to show how the criterion for the homogeneity of dispersed composites under transient conditions is affected by the percentages of dispersed phase, dispersed particle size, and ratio of the thermal conductivity values of dispersed and continuous phases.