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We analyze the bit error probability reduction for direct detection ON-OFF keying optical receivers using return-to-zero (RZ) coding instead of the nonreturn-to-zero (NRZ) format. For the same average optical power, RZ is shown to outperform NRZ, even when employing the same receiver bandwidth. Results are given for receivers whose noise variance is i) dominated by a signal-independent term (e.g., simple pin diode receivers), ii) dominated by a signal-dependent term (e.g., optically preamplified receivers), and iii) made up of two equally important contributions [e,g,, avalanche photodiode (APD) receivers]. Based on semianalytic simulations including intersymbol interference, we show that the achievable RZ sensitivity gain is typically less for dominating signal-independent noise than for dominating signal-dependent noise, where it amounts to about 3 dB. We also quantitatively discuss the influence of the optical pulse shape on the achievable RZ coding gain, and show that finite extinction ratios can significantly reduce that gain, especially when the RZ signals are produced by direct-modulation methods [ABSTRACT FROM PUBLISHER]

In this letter, we investigate both experimentally and by means of simulations, the dependence of receiver sensitivity on the optical filter bandwidth as well as on the bandwidth of the detection electronics for the optical noise limited direct detection case. The experiment is in good agreement with simulations employing advanced Gaussian noise statistics. Bandwidth optimization is performed both for nonreturn-to-zero and return-to-zero coded signals, yielding a measured sensitivity only 1.4 dB off the quantum limit at a data rate of 10 Gb/s [ABSTRACT FROM PUBLISHER]

Photodynamic therapy (PDT) produces localized necrosis with light after prior administration of a photosensitizing drug. As PDT lesions in the gastrointestinal tract heal well, the technique is suitable for repeated endoscopic use. In this study we used PDT to treat benign and malignant gastrointestinal tumors in esophagus, duodenum and rectum in 22 patients, who refused or were not suitable for surgery. Patients were sensitized with 0.15 mg/kg of body weight with mesotetrahydroxyphenylchlorin i.v. m-THPc (2 patients), with 2.0 mg/kg Photofrin i.v. (4 patients) or 60 mg/kg 5-aminolevulinic acid orally ALA (which is converted in vivo to active derivate protoporphyrin IX-PRIX) in fractionated doses (16 patients). Laser treatment was performed 2 days after Photofrin, 2 and 4 days after mTHPc and 4 hours after ALA, using a metal vapour laser (628 nm, 50-150 J/cm2 for ALA and Photofrin, 650 nm and 10-15 J/cm2 for mTHPc). Using ALA, the necrosis was only superficial (up to 1.8 mm depth). Four patients treated with Photofrin showed deeper necrosis, in one case of 8 mm colon cancer complete response, in three cases 1-1.5 cm adenomatous polyps involving the ampulla Vateri 50% longer term reduction in size-seen endoscopically. Two patients with rectal villous adenomas treated with mTHPc showed 60-80% reduction in size (observed endoscopically) within few days after PDT, with better effects for treatment carried out 4 rather than 2 days after the sensitization. In all patients the healing was without any complications. Photofrin and mTHPc work better, but cause cutaneous photosensitivity lasting 12 and 5 weeks, respectively. Better results with ALA are possible when using higher drug doses or modified light dosimetry. PDT is a promising treatment for small localized tumors in patients unsuitable for surgery, but further work is required to optimize the treatment conditions.

The authors report their experience of 34 benign and 17 malignant tumours of the adrenal cortex. Both occurred more frequently in women (79.4% of cortical adenomas and 70.6% of adrenocortical carcinomas). Moreover, females were significantly younger (average age: adenomas: females 44.9 years and males 54.4 years, adrenocortical carcinomas: females 34.1 years and males 58.3 years). Some tumours presented in the form of increased hormone production, while others were hormonally inactive and did not cause clinical signs until later. Pain was the first symptom in the cases of malignant adrenocortical tumours. Adenomas occurred as frequently twice in the left adrenal gland (24 versus 12), whereas carcinomas were more than twice are frequent on the right (10 versus 7). Ultrasonography and CT were appropriate and fully sufficient methods for the diagnosis of adrenal tumours. Arteriography was valuable in the differential diagnosis of large upper abdominal masses when the organ of origin could not be identified by CT and for determination of anatomic conditions and subsequent surgical tactics. For small tumours of the adrenal cortex, the classic lumbar approach through the bed of the resected eleventh rib is adequate. For larger tumours, extended lumbotomy, laparotomy or thoracotomy is necessary.

5-Aminolaevulinic acid (ALA) is a promising agent for photodynamic therapy (PDT) sensitization as it can be given orally and only causes skin photosensitivity for 1-2 days. In fluorescence and photodynamic studies 26 patients with benign and malignant gastrointestinal tumors were given 30-60 mg ALA orally (single or divided doses) and biopsies were taken of tumor and normal tissue at 1-24 hours for fluorescence microscopy. With 30 mg/kg, highest protoporphyrin IX (PPIX) levels were seen in esophagus, duodenum and less in colon, but without tumor selectivity. Better tumor selectivity was seen in colon after 60 mg/kg (5:1). Six patients had transient rises in transaminases and five mild nausea. Sixteen patients were later treated (after further ALA) with red light (628 nm, bare or diffuser fibre, 50-100 J at 50 mW at each site). All but two showed subsequent necrosis, but only 0.5-1.5 mm of depth. PDT with ALA is simple, safe and promising for tumors in the gastrointestinal tract. Modification of treatment parameters may make it suitable for larger lesions.

A case of mixed hepatoblastoma in a 66-year-old man is discussed. Assessment of malignant mesenchymal and malignant epithelial elements yields the diagnosis. In the reported case, the epithelial area consisted of fetal hepatocytes. Distinct ductal differentiation, chondroid and even asteoid metaplasia were recorded. The morphological and immunohistochemical findings observed in the given patient are compared with data published in the world literature.

The dynamics of cardiac output changes were studied in 23 15-year-old boys subjected to graduated loading up to maximum on an bicycle ergometer and relationships between cardiac output and other indexes of cardiorespiratory functions were determined. The correlation between cardiac output (Q in 1/min) and oxygen consumption (VO2 in 1/min) was Q = 6.84 + 5.64. VO2. CO2-rebreathing was found to be a suitable non-invasive method for determining cardiac output in loading tests in adolescents. Maximum cardiac output correlated with maximum oxygen consumption, maximum pulmonary ventilation, body weight, lean body mass and physical working capacity W 170 and did not correlate with systolic volume, the arteriovenous oxygen difference, the pulse rate and ballistocardiographic force. The absence of any statistically significant differences between the various functional indexes of the physical fitness of trained and untrained boys indicates that training was not very effective.

The authors performed a total of 288 successful endoscopic gastroduodenal polypectomy procedures in 129 patients. Drawing on literary data and the results of follow-up of their own patients, they regard endoscopic gastroduodenal polypectomy as a successful and relatively low-risk method for secondary prevention of gastric cancer. Recurrence of adenomas, with malignant degeneration in 6-75%, was noted, only in the first year after primary polypectomy, in 8% of patients. Four percent of patients after adenoma polypectomy developed gastric carcinoma. Removal of gastroduodenal adenomas by endoscopy represents a final therapeutic procedure significantly reducing the possibility of these originally benign variants transforming into malignant ones. Even polyps smaller than 10 mm in diameter may be adenomas possessing a rather high malignant potential. The authors regard endoscopic polypectomy of hyperplastic polyps as a justified procedure since the literary data compiled and their own experience suggest polyp susceptibility to development of dysplasia. While this tendency gets manifest only rarely, it would be medically wrong to dismiss it as negligible. In case of removal of an early polypoid gastric carcinoma, endoscopic polypectomy is a therapeutic procedure only in clearly defined and histologically well classified cases. In other cases involving prominence of the gastroduodenal mucosa, it is an invaluable diagnostic method whose benefit is that it removes an entire polyp for histologic examination.