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101.
A. V. Govorkov A. Ya. Polyakov T. G. Yugova N. B. Smirnov E. A. Petrova M. V. Mezhennyi A. V. Markov I. -H. Lee S. J. Pearton 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):380-385
The relation between the density of etch pits revealed in GaN by etching in a KOH/NaOH eutectic and the density of dislocations determined by transmission electron microscopy (TEM) is studied along with the relation between the density of dislocations and the density of dark spot defects observed in GaN by microcathodoluminescence (MCL) and electron-beam-induced current (EBIC). It is demonstrated that selective etching is a reliable rapid method for the determination of the type and density of dislocations in GaN in the range 106–108 cm?2, while MCL and EBIC can be used for the rapid nondestructive determination of the density of dislocations in the range 106–108 cm?2. It is also found that some deep electron and hole traps are related to dislocations. 相似文献
102.
Mary E. Neubert DAVID G. ABDALLAH Jr Sandra S. Keast Julie M. Kim Soonnam Lee Ryan M. Stayshich Margaret E. Walsh Rolfe G. Petschek Shin-Tson Wu 《Liquid crystals》2003,30(6):711-731
New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1-4; and X = C n H 2n + 1 , F, CF 3 or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF 3 when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices.
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
Four of the diacetylenes with m = 1 ( A, B = H) were also prepared ( X = C 6 H 13 , F, n = 2, 3). When X was C 6 H 13 ( n = 2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X = F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X = C 6 H 13 and n = 2 had a melting temperature below room temperature. 相似文献
103.
104.
Proton relaxation times in human red bone marrow by volume selective magnetic resonance spectroscopy
F. Schick H. Bongers W. -I. Jung B. Eismann M. Skalej H. Einsele O. Lutz C. Claussen 《Applied magnetic resonance》1992,3(6):947-963
In hematological diseases the composition of red bone marrow shows alterations. The relaxation timesT 1 andT 2 of water and lipids in human hemopoietic bone marrow of 14 normal volunteers and 10 patients with acute leukemia and bone marrow carcinosis are determined using a double spin echo spectroscopy sequencein vivo. The volumes of interest (VOI) of (13 mm)3 in the center of vertebral bodies are examined using different measurement parameters. ForT 1 measurements an inversion-recovery method is used.T 2 is evaluated from spectra with differentTE. T 1 (water) is found in a range between 1000 and 1700 ms,T 1 (lipids) in a range between 260 and 320 ms in healthy volunteers.T 2 (water) is determined between 32 and 65 ms. In some cases phase distortions of the water signals occur in the spectra. Water flow within the VOI may be a possible reason.T 2 (lipids) is evaluated between 73 and 91 ms. The patients with acute leukemia exhibit clearly reduced lipid signals in their spectra. Lipid relaxation times could not be determined in these cases.T 2 (water) is prolonged in acute leukemia to 51–98 ms.T 1 (water) was not significantly different from values of healthy volunteers in our measurements. Results are discussed in comparison to relaxometric data from imaging and STEAM spectroscopic methods of other authors. 相似文献
105.
Hyunkook Park Machiko Tsukiji Kazuaki Wagatsuma SangChun Lee 《Analytical sciences》2007,23(9):1133-1136
The emission characteristics of several Cu lines emitted from a Ne-Ar mixed gas glow discharge plasma were investigated. The addition of small amounts of Ar to a Ne plasma increases the sputtering rate of a Cu sample because Ar ions, which work as the impinging ions for cathode sputtering, are predominantly produced through Penning ionization collisions between Ne metastables and Ar atoms. Ar addition also elevates the number density of electrons in the plasma. These changes occurring in the Ne-Ar mixed gas plasma result in enhanced emission intensities of the Cu lines. The Cu II 270.10-nm and the Cu II 224.70-nm lines yield different intensity dependence on the Ar partial pressure added. This phenomenon is because these Cu II lines are excited principally through different charge transfer processes: collisions with Ne ions for the Cu II 270.10-nm line and collisions with Ar ions for the Cu II 224.70-nm line. The shape of sputtered craters in the Ne-Ar glow discharge plasma was measured. The depth resolution was improved when Ar was added to a Ne plasma because the crater bottoms were flatter with larger Ar partial pressures. 相似文献
106.
A systematic study of the upper semicontinuity and the lower semicontinuity of the solution map in parametric affine variational
inequalities is given in this paper. Several examples are constructed to analyze the results.
This work was supported by Korea Research Foundation Grant (KRF 2001-015-DP0049), the APEC Postdoctoral Fellowships Program,
and the KOSEF Brain Pool Program. 相似文献
107.
On the harmonic Bergman space of the half-space, we give characterizations for an arbitrary positive Toeplitz operator to
be a Schatten (or Schatten-Herz) class operator in terms of averaging functions and Berezin transforms. Examples are provided
to show that various results are sharp.
This research was supported by KOSEF(R01-2003-000-10243-0). 相似文献
108.
We demonstrated a unified two-band broadband light source based on erbium-doped fiber. The proposed scheme generates high output power at both bands and saves doped-fiber and pump lasers. 相似文献
109.
Ju Yeon Woo Eun Hee Kim Byung Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5590-5596
Doping of conductive fullerene particles to the formulation of conventional holographic polymer dispersed liquid crystal‐induced dual effects of reducing both droplet coalescence and operating voltage. Fullerene induced an induction period which otherwise does not exist, followed by a gradual increase of diffraction efficiency to a saturation value being increased with increasing fullerene content. The increased diffraction efficiency was caused by the decreased droplet coalescence which was due to the hindered migration of LC by the fullerene particles. On the other hand, doped fullerene particles augmented the conductivity of polymer phase and hence the local electrical field imposed on LC droplet, which overcome the threshold for driving and reduced operating voltage and response times. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5590–5596, 2007 相似文献
110.
Currently, self-organized magnetic array (SOMA) is a non-oriented media, with randomly distributed easy axis directions. We investigate the recording performance of SOMA under two different head types—Ring Head (RH) and single pole head (SPH). Our results show an interesting dependence of the recorded transition pattern on the field strength of RH, where a weak RH field generates longitudinal transition pattern and a strong RH field generates a perpendicular transition pattern in the media. The SPH only generates perpendicular transition patterns and has a higher signal-to-noise ratio (SNR) than that of the RH. 相似文献