Interchannel nonlinear transmission penalties in polarization-multiplexed 2 x 10 Gbit/s differential phase-shift keying transmission.

We discuss the performance of a multichannel 2 x 10 Gbit/s polarization-multiplexed differential phase-shift keying transmission system. Through simulations and transmission experiments we find that, despite the constant power envelope of non-return-to-zero phase-shift keying modulation formats, polarization multiplexing strongly reduces the nonlinear tolerance and transmission performance at a 2 x 10 Gbit/s line rate with multichannel transmission. This results in a 10 dB power penalty when comparing single- and nine-channel transmission. Additionally, multichannel impairments in differential phase-shift keying and on-off keying are compared for 2 x 10 Gbit/s polarization-multiplexed transmission.

[Results and critical analysis of the treatment of obesity with the intragastric balloon]. / Ergebnisse und kritische Analyse der Adipositasbehandlung mit dem intragastralen Ballon.

UNLABELLED: In 54 patients with excessive obesity a silicone balloon was implanted endoscopically into the stomach. The overweight amounted to 76% (median) by Broca's formula. The therapeutical plan included balloon-implantation, dietary treatment, psychotherapeutical guidance, kineto-therapy and balloon-extraction. According to their therapeutical compliance there were three different groups of patients: G1 - maintenance of therapy; G2 - discontinuation of therapy; G3 - no additional therapy at all after balloon implantation. Up to the sixth week a weight reduction of 9.5-20.5 kg could be demonstrated in all groups. Only in the first group a further weight reduction by a mean of 20 kg after 20 weeks was noted. Patients in group 2 and 3 - in some the balloon was still implanted - had a renewed weight increase sometimes surmounting the original weight. COMPLICATIONS: 3 gastric respectively duodenal ulcers, one subileus. The long-term success can only be obtained by a multi-component therapy plan.

Pulmonary clearance of 99mTc-DTPA during halothane anaesthesia.

We studied the integrity of the alveolo-capillary barrier during different forms of anaesthesia by measuring the pulmonary clearance of inhaled 99mTc-DTPA. We studied four groups of rabbits. Groups I and II were anaesthetized with nembuthal only and the fractional concentration of inspired oxygen (F1O2) was 0.30 and 1.00, respectively. Groups III and IV were anaesthetized with 1% halothane and F1O2 was 0.30 and 0.99, respectively. 99mTc-DTPA was administered as a fine aerosol and the clearance of the tracer from the lungs was subsequently measured with a gamma camera. The mean half-life of the tracer in the lungs in Groups I-IV was 60, 58, 59 and 26 min, respectively. The rapid pulmonary clearance of 99mTc-DTPA in Group IV indicates that halothane in combination with high oxygen concentration increases the permeability of the alveolo-capillary barrier. This may be due to effects on the pulmonary surfactant system and/or the alveolar epithelium.

Volume-controlled ventilation with superimposed high frequency ventilation during expiration in healthy and surfactant-depleted pig lungs.

In the healthy and surfactant-depleted lungs of five pigs the influence of different forms of high frequency ventilation superimposed on conventional mechanical ventilation during the expiratory phase of the ventilatory cycle (SHFVE) on gas exchange and cardiocirculatory parameters was investigated. Subsequently the effects of end-expiratory flushing (EF), i.e. cleaning the large airways and connecting tubes from the ventilator free from end-expiratory CO2, with a volume greater than the dead space of the large airways and connecting tubes was investigated. SHFVE and EF resulted in a significant improvement in CO2 elimination in both healthy and surfactant-depleted lungs. Furthermore, in stiff lungs, at a certain level of oxygenation and CO2 elimination, SHFVE produced the lowest peak and mean airway pressure without any additional depression of cardiocirculatory parameters.

[Experiences with 2,200 laparoscopic cholecystectomies as the treatment concept in gallstone disease]. / Erfahrungen nach 2200 laparoskopischen Cholezystektomien als Behandlungskonzept des Gallensteinleidens.

The laparoscopic cholecystectomy is fully integrated into the therapy concept of gallstone disease. The laparoscopic procedure was successfully performed in 97.5% of 2200 patients. In 2.5% of the patients the operation had to be converted to open surgery. Complications occurred in 3.6%, containing infections of the umbilicus (2.2%), postoperative bleedings (0.4%) and lesions of the d.hepatocholedochus (0.4%). Mortality rate was 0.1%. During the last 2 years the indication for the laparoscopic approach has been rapidly expanded while the indication for primary open surgery was reduced to 2% of the patients. Laparoscopic cholecystectomy proved to be a rapid and safe procedure for treating gallbladder stones.

Safety and efficacy of xenon in routine use as an inhalational anaesthetic.

40 patients (24 male, 16 female, aged 21-59 years) of American Society of Anesthesiologists class I or II who were undergoing routine surgery took part in a randomised, double-blind comparison of the anaesthetic efficacy and potency of xenon and nitrous oxide and their effects on the circulatory and respiratory systems. During anaesthesia, for each rise in blood pressure of more than 20% of the preanaesthetic (baseline) value, the patient received 0.1 mg fentanyl. The total amount of fentanyl required per patient was used as an index of the anaesthetic potency of the study gases. Patients in the xenon group required on average only 0.05 mg fentanyl, whereas those in the nitrous oxide group required 0.24 mg fentanyl; the duration of anaesthesia was similar in the two groups. Changes in blood pressure were significantly greater throughout the study in the nitrous oxide than in the xenon group. Thorax-lung compliance fell during the study period in the nitrous oxide group but not in the xenon group. Thus, xenon is a potent and effective anaesthetic which can be safely used under routine conditions.

Effects of high frequency jet ventilation on the pulmonary clearance of 99mTc-DTPA in respiratory failure in rabbits.

The effects of high frequency jet ventilation (HFJV) at 2 and 15 Hz on the pulmonary clearance of technetium 99m diethylene triamine pentaacetate (99mTc-DTPA) were compared with conventional volume-controlled (VC) ventilation with positive end-expiratory pressure (PEEP), in a model of respiratory failure induced by two lung lavages in adult rabbits. In group 1 the lungs were ventilated with HFJV at 2 Hz, and in group 2 ventilation was with HFJV at 15 Hz; group 3 underwent conventional VC ventilation. Group 4 also had conventional ventilation, but without previous lung lavage and functioned as a control group. In all groups, mean airway pressure was maintained at a value to ensure PaO2 greater than 25 kPa. The measured half-life time (T1/2) of the 99mTc-DTPA (mean (SD] was: group 1, 28 (7.8) min; group 2, 73.5 (7.9) min; group 3, 56.5 (12.4) min and group 4, 92.6 (13.2) min. Assuming that conventional VC with PEEP ventilation causes no additional harm to surfactant depleted lungs, it is concluded that HFJV at 2 Hz leads to further damage of the lungs, whereas HFJV at 15 Hz improves reparative processes, by keeping the lungs constantly inflated.

Design, synthesis, and conformational analysis of a novel series of HIV protease inhibitors.

A combination of structure-based design and both solution, and solid-phase synthesis were utilized to derive a potent (nM) series of HIV-1 protease inhibitors bearing a structurally novel backbone. Detailed structural analysis of several inhibitors prepared in this series has suggested that rigidification of the P1/P2 region of this class of molecules may result in compounds with improved potency.

Design and synthesis of novel conformationally restricted HIV protease inhibitors.

A set of HIV protease inhibitors represented by compound 2 has previously been described. Structural and conformational analysis of this compound suggested that conformational restriction of the P1/P2 portion of the molecule could lead to a novel set of potent protease inhibitors. Thus, probe compounds 3-7 were designed, synthesized, and found to be potent inhibitors of HIV protease.