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排序方式: 共有313条查询结果,搜索用时 15 毫秒
31.
Intermodulation distortion in a multiple-quantum-well semiconductor optical amplifier 总被引:1,自引:0,他引:1
Y.C. Chung J.M. Wiesenfeld G. Raybon U. Koren Y. Twu 《Photonics Technology Letters, IEEE》1991,3(2):130-132
The measurement of intermodulation distortion (IMD) induced by carrier-density modulation in a multiple-quantum-well (MQW) semiconductor amplifier is reported. The results show that MQW amplifiers have 15 dB less IMD than conventional buried-heterostructure semiconductor amplifiers. The IMD is dependent on the output power of the amplifiers, which confirms that the carrier-density modulation is the dominant nonlinear mechanism in MQW amplifiers. In addition, the results show that, unlike conventional buried-heterostructure amplifiers, MQW amplifiers have at least two time constants (200-250 ps and <10 ps) for the gain recovery process.<> 相似文献
32.
The study of the incidence and etiological pattern of infectious complications included 376 patients operated for acquired valvular disease. 40,280 bacteriological tests of the materials from the patients obtained during the operations and during the postoperative period as well as 30,113 sanitary bacteriological tests of the specimens from the cardiological operation unit were conducted. The possible use of the results of bacteriological monitoring for prediction of septic complications and optimization of antibiotic prophylaxis and therapy as well as for development and operation of a system of sanitary and hygienic measures for infection prevention was shown and statistically confirmed. 相似文献
33.
Raybon G. Koren U. Miller B.I. Chien M. Dreyer K. Chandrasekhar S. Behringer R.E. Tennant D.M. Feder K. 《Photonics Technology Letters, IEEE》1998,10(2):215-217
Reconfigurable optoelectronic wavelength conversion to 11 100-GHz spaced wavelengths is achieved using a wavelength selectable laser array with an integrated electroabsorption (EA) modulator at a bit rate of 2.5 Gb/s. Wide dynamic range at the input from -24.2 to -6.5 dBm is achieved and uniform back-to-back transmission performance is measured for all wavelengths 相似文献
34.
J Trupl A Kunová E Oravcová P Pichna E Kukucková S Grausova E Grey S Spanik A Demitrovicová K Kralóvicová J Lacka I Krupova J Svec P Koren V Krcméry 《Canadian Metallurgical Quarterly》1997,36(6):643-649
A phase III, open label randomized study was conducted in 50 patients comparing halothane and sevoflurane for paediatric day case surgery. A graded inhalational induction resulted in only slightly more rapid induction with sevoflurane (3.34 +/- 0.92 versus 3.85 +/- 1.02 minutes; P > 0.05). In children receiving sevoflurane, systolic blood pressure decreased to a lesser extent during induction (143 +/- 19.2 versus 26.9 +/- 10.9 percent decrease from resting values; P < 0.01) and heart rate was maintained. Respiratory events (coughing, breath-holding, bronchospasm, laryngospasm) were more common during induction with halothane, and excitement more common in children receiving sevoflurane. Emergence times were significantly more rapid in children who had received sevoflurane (21.4 +/- 10.9 versus 33.1 +/- 13.7 minutes; P < 0.01). Objective pain/discomfort scores were higher in patients receiving sevoflurane at 10, 20, 30 and 40 minutes after arrival in the recovery room, and the incidence of excitement during emergence was higher in this group. It is concluded that sevoflurane is well tolerated for inhalational induction and has an improved cardiovascular profile compared to halothane. Emergence was significantly more rapid following sevoflurane. 相似文献
35.
LJ Seidman JM Goldstein JM Goodman D Koren WM Turner SV Faraone MT Tsuang 《Canadian Metallurgical Quarterly》1997,42(2):104-115
We investigated the hypothesis that different prefrontal brain systems (i.e., dorsal vs. ventral) and sex contribute differentially to cognitive deficit in schizophrenia. Performance was assessed among clinically stable, chronic schizophrenic outpatients and matched normal control subjects on olfactory identification [on the University of Pennsylvania Smell Identification Test (UPSIT)] and on executive functions [using the Wisconsin Card Sorting Test (WCST)]. Patients were impaired on both tests compared to controls, and male schizophrenics were impaired on the WCST compared to female schizophrenics. The pattern of results suggests that gender differences on the UPSIT are mildly accentuated in schizophrenia. The data support our previous study indicating that UPSIT performance is largely independent of the executive or attentional deficits typically associated with schizophrenia, with the exception of verbal ability. Further research with larger samples is required to test the hypothesis that there is a severely impaired subgroup of male patients with diffuse prefrontal dysfunctions. 相似文献
36.
Koren U. Miller B.I. Tucker R.S. Eisenstein G. Bar-Joseph I. Miller D.A.B. Chemla D.S. 《Electronics letters》1987,23(12):621-622
We describe the structure and performance characteristics of an InGaAs/InP multiple-quantum-well (MQW) electro-absorption buried-mesa optical modulator. The device is fabricated with two metal-organic chemical-vapour-deposition (MOCVD) growth steps, wherein small-area circular (40?m diameter) PIN diodes are buried with Fe-doped semiinsulating (SI) InP regrowth. The modulator has a relatively low insertion loss (4.5 dB) with 25% modulation depth and very high modulation bandwith (5.3 GHz) operating at 1.62?m wavelength. 相似文献
37.
A Pastrakuljic R Schwartz C Simone LO Derewlany B Knie G Koren 《Canadian Metallurgical Quarterly》1998,63(26):2333-2342
Our objective was to study the characteristics of transfer and biotransformation of nicotine in the human term placenta. Nicotine transfer was studied by dually perfusing an isolated cotyledon of the human placenta in vitro. Nicotine metabolism to cotinine was investigated in intact tissue during perfusion and in placental microsomal fractions. Following the addition of nicotine (40 ng/ml) to the maternal side of the placenta, distribution into placental tissue (0.43 +/- 0.13 ng/ml/min) was three times higher than transfer to the fetal side of the placenta (0.15 +/- 0.01 ng/ml/min). The steady-state maternal-to-fetal transfer of nicotine was approximately 90% that of antipyrine (a marker of flow-dependent transfer). There was no evidence of nicotine metabolism to cotinine by intact placental tissue or in microsomal fractions. The observation that nicotine readily crosses the human placenta with no evidence of metabolism suggests that nicotine has the potential to cause adverse affects on the developing fetus. 相似文献
38.
Abraham D. Nagar R. Ruberto M.N. Eisenstein G. Koren U. Zyskind J.L. DiGiovanni D.J. 《Photonics Technology Letters, IEEE》1993,5(4):377-379
The authors demonstrate optical frequency tuning by direct electrical means as well as FM and AM mode-locking in an erbium-doped fiber laser with an intracavity distributed Bragg reflector active filter/modulator. They obtained a 6 nm discrete tuning range and pulses of 38 and 78 ps duration in AM and FM mode-locking, respectively 相似文献
39.
Woodward S.L. Mizrahi V. Koch T.L. Koren U. Lemaire P.J. 《Photonics Technology Letters, IEEE》1993,5(6):628-630
A control loop that stabilizes the wavelength of a tunable distributed-Bragg-reflector (DBR) laser is discussed. An in-fiber Bragg grating is used as the wavelength reference. Over a 25-hour period, this control loop held the laser wavelength constant to within 0.022 nm. This variation is traced to the temperature dependence of the in-fiber Bragg grating and can be reduced by controlling the grating's temperature 相似文献
40.