Hybrid fiber amplifiers consisting of cascaded TDFA and EDFA for WDM signals

The detailed gain characteristics of hybrid fiber amplifiers that consist of cascaded thulium-doped fiber amplifiers (TDFAs) and erbium-doped fiber amplifiers (EDFAs) are reported. The experimental results showed that the hybrid amplifiers have gains of over 20 dB with the bandwidth of more than 80 nm in the wavelength range between 1460 and 1560 nm. The low noise figure (NF) below 7 dB was obtained in 1460-1540 nm when placing a TDFA in the first stage followed by an EDFA and in 1480-1560 nm when placing amplifiers in a reversed order. The gain of TDFA and EDFA was optimized for minimizing the gain variation ratio (GVR=(maximumgain-minimumgain)/minimumgain: in the unit of decibels) of the hybrid amplifiers, and it could be minimized to less than 0.4 for the amplifiers that have gain in the wavelength region from 1460 to 1537 nm. The gain-equalization technique was applied, and the hybrid amplifier that had an average gain of 20 dB, a gain excursion of less than 2 dB, an output power of 14.5 dBm, and an NF of less than 7 dB in the 77-nm gain band was achieved.     

Pseudoxanthoma elasticum-like papillary dermal elastolysis: report of four Japanese cases and an immunohistochemical study of elastin and fibrillin-1

Fourier transform infrared and Raman (FT-IR and FT-Raman) microspectroscopy were used to study materials found in human tissue. Individual cases involving cholesterol, calcium stearate, and a polystyrenesulfonate ion exchange resin demonstrate the utility of the spectroscopic data. Characteristic spectral bands for these materials were compared with those of authentic chemical species to confirm their identities. The role of vibrational spectroscopy in pathologic diagnoses is discussed.     

Anesthetic management for a patient with pheochromocytoma using magnesium sulfate and epidural block

A 54-year-old woman with pheochromocytoma was anesthetized using magnesium sulfate infusion. Anesthesia was induced with thiopental and fentanyl, and maintained with 0.5% sevoflurane in nitrous oxide/oxygen and 60 mg.hr-1 of epidurally infused lidocaine. Muscle relaxation was achieved with intermittent administration of vecuronium under neuromuscular monitoring. Magnesium 2 g was infused prior to the tracheal intubation and followed by continuous infusion of 2 g.hr-1. These anesthetic techniques made hemodynamic state stable, and no additional vasoactive agents were needed. However, the infusion rate of magnesium was reduced to a half because of PQ interval prolongation. Magnesium is believed to be useful for anesthetic management for patients with pheochromocytoma, but the proper dose and the way of administration should be further investigated for their safe clinical use.     

Average thresholds in the 8 to 20 kHz range in young adults

RATIONALE AND OBJECTIVES: The Comprehensive Clinical Assessment (CCA) examination at the University of Michigan Medical School is a series of test stations through which the mastery of clinical skills is evaluated. The purpose of this study was to determine whether student performance on the radiology station improved in years when radiology faculty presented case-of-the-week unknowns to the 3rd-year students. MATERIALS AND METHODS: The authors compared four separate classes of medical students in examination years 1993, 1994, 1995, and 1996 by using the total CCA examination score, the radiology station score, and radiology station pass/fail rates. Radiology case-of-the-week presentations were given by the radiology faculty only in academic years 1993-1994 and 1994-1995 (examination years 1994 and 1995). RESULTS: The means and standard deviations of the radiology station scores for the examination years when case-of-the-week presentations were not given, 1993 and 1996, were 78.92 +/- 13.62 and 79.76 +/- 13.62, respectively. In the years case-of-the-week presentations were given, 1994 and 1995, the radiology station scores averaged 90.83 +/- 8.58 and 89.97 +/- 9.66, respectively (P < .001, global alpha = .05). Total CCA percentage correct scores were similar for all years studied. In 1993 and 1996, 7.6% and 5.3% of students, respectively, failed the radiology station. In 1994 and 1995, 0.4% and 0% of students, respectively, failed (P < .0001). CONCLUSION: Case-of-the-week presentations by radiology faculty increased 3rd-year students' basic radiologic knowledge as evidenced by increased scores on the radiology station of the CCA examination.     

Sex determination and sex expression in higher plants

New quantitative criteria of erythrocytes functional state, based on automated registration of acid erythrogramme parameters, have been proposed. Enwidened analysis of adaptive processes in rats erythropoietic system after ionizing radiation exposure (gamma-rays, 60Co, in doses 0.5; 1.0 and 6.0 Gy) has shown, that existing in norm mechanism of stimulating effects of dieresis products on genesis of young red cell forms has been maintained only at exposure 0.5 Gy and stops to function at higher gamma-ray irradiation doses.     

Risk factors for neurologic deterioration after revascularization surgery in patients with moyamoya disease

To investigate the risk factors for postoperative neurological deterioration in patients with moyamoya disease, we retrospectively reviewed the perioperative course of 368 cases of revascularization surgery in 216 patients with this disease. Risk factors anecdotally associated with postoperative ischemic events were analyzed by comparing groups with or without a history of such events on the operative day. Ischemic events were noted in 14 cases (3.8%), 4 of which were defined as strokes and the others as transient ischemic attack (TIA). Postoperative neurological deterioration more often developed in patients who suffered from frequent TIAs, had precipitating factors for TIA, and underwent indirect nonanastomotic revascularization. The authors conclude that the incidence of postoperative ischemic events were related more to the severity of moyamoya disease and the type of surgical procedure than to other factors, including anesthetic management. IMPLICATIONS: Although preventing stroke is the major concern for patients with moyamoya disease, risk factors for perioperative cerebral ischemia have not been clarified. We retrospectively analyzed the perioperative course in 368 cases with this disease and found that the severity of the disease and type of surgical procedure were major determinants of postoperative cerebral ischemia.     

Performance analysis of variable optical delay circuit using highly nonlinear fiber parametric wavelength converters

The performance of a variable optical delay circuit that employs a fiber loop with highly nonlinear fiber parametric wavelength converters is discussed using both experiments and simulations. In our optical delay circuit, the delay time is determined from the number of circulations, which is controlled by the initially selected wavelength of the optical signal. We discuss the factors that limit the number of circulations described in our previous paper, derive the parameters that provide good performance levels, and confirm the performance by simulation. The simulated results indicate that 100 wavelength conversions can be achieved, namely, 100 different delay times can be given to optical packets.     

Molecular cloning and nucleotide sequence of an endo-1,5-alpha-L-arabinase gene from Bacillus subtilis

The nucleotide sequence of the gene encoding an endo-1,5-alpha-L-arabinase (protopectinase C) of Bacillus subtilis was determined by sequencing fragments amplified by the cassette-ligation-mediated PCR (CLM-PCR). The gene covering the start and stop codon was amplified by PCR with two specific primers, which were designed from the sequence data determined by CLM-PCR. An approximately 1.5-kb amplification product was cloned into the vector pUC119, forming a plasmid termed pPPC. An ORF that encodes the arabinase composed of 324 amino acids including a 33-amino-acid signal peptide was assigned. Comparison of the deduced amino acid sequence of the enzyme with that of an Aspergillus niger endoarabinase showed 37% identity in a 207-amino-acid overlap. The optimal nucleotide sequence for catabolite repression of B. subtilis was found upstream of the structural gene. In a culture of Escherichia coli DH5alpha cells harboring pPPC, no arabinase activity was detected, either intracellularly or extracellularly, suggesting that the B. subtilis promotor is not functional in this transformant. In B. subtilis IFO 3134 strain, production of protopectinase C was repressed by readily metabolizable carbohydrates. In contrast, productivity (total enzyme activity/bacterial growth) of the enzyme was increased about fourfold in the presence of 0.75 M potassium phosphate in the culture medium. The phosphate anion seemed to be involved in the stimulation of protopectinase C production in this stain.