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ZUSAMMENFASSUNGPeer-to-Peer-(P2P-)Systeme bieten sich auf natürliche Weise zur Realisierung von autonomen Kommunikationsinfrastrukturen für geschlossene Benutzergruppen mit sehr wenigen Teilnehmern an. In dieser Arbeit wird ein zweistufiger Ansatz vorgestellt, der es ermöglicht, solche P2P-Systeme ohne Verwendung von zentralen Komponenten wie Servern oder Verzeichnisdiensten zu realisieren. Als Hilfsmittel nutzt der Ansatz das weit verbreitete P2P-Dateitauschsystem BitTorrent und realisiert den Beitritt zu diesem System mittels einer Suche nach bereits aktiven BitTorrent-Knoten. Nach dem erfolgreichen Beitritt wird BitTorrent zur Lokalisierung anderer Mitglieder der geschlossenen Benutzergruppe verwendet, zwischen denen dann ein P2P-Netz aufgebaut wird. Die Umsetzbarkeit des vorgeschlagenen Ansatzes wird anhand umfangreicher Messungen in realistischen Umgebungen veranschaulicht. Dabei zeigen sich deutlich in der Praxis zu erwartende Einschränkungen, z.B. durch das so genannte Connection Trackingin typischer DSL-Hardware wie NAT-Routern mit integrierter Firewall. Diese Einschränkungen verlangen eine entsprechende Anpassung der verwendeten Mechanismen.

Eight sexually inexperienced, 2-yr-old Morgan stallions were used in a consecutive two-phase design with two groups of four stallions each. Each phase lasted 16 wk, with semen collections every 14 d. Libido scores were assigned to stallions during each semen collection. Scores ranged from zero to four, with zero indicating minimum and four representing maximum libido. In Phase 1, four stallions received daily forced exercise for 16 wk, and the remaining four stallions were confined to box stalls. In Phase 2, the previously exercised stallions were confined to box stalls, and the non-exercised stallions of Phase 1 received daily forced exercise. No week × treatment effect (P>.05) was found in Phase 1. Exercised stallions, however, tended to have lower libido values than non-exercised stallions from wk 10 through wk 16. A week × treatment effect (P<.01) was found in Phase 2. Libido scores were lower (P<.05) over time among exercised stallions, whereas scores of non-exercised stallions tended to remain stable or rise slightly over time. Mean libido scores for exercised and non-exercised stallions were different (P<.05) at the end of Phase 1 (2.06 ± .37 and 3.5 ± .37, respectively). By wk 26, mean libido scores were similar (exercised: 2.62 ± .34; non-exercised: 2.52 ± .34). However, by wk 32, libido values for exercised stallions were lower (P<.05) than non-exercised stallions (1.87 ± .34 and 2.81 ± .34, respectively). In general, mean libido scores of the non-exercised group were higher than exercised stallions after 12 wk of forced daily exercise.

It has been suggested that high frequency oscillatory ventilation (HFV) might improve gas exchange and reduce the risk of pressure-related side-effects compared to conventional mechanical ventilation (CMV). Whereas most studies have used arbitrarily set frequencies for HFV, we evaluated the effects of HFV near resonant frequency (fr). Anaesthetised and tracheotomised adult rabbits (n=10; 3.8–5.1 kg body weight) were ventilated by alternating periods of CMV and HFV near fr. Negative ventilator resistance was used for complete resistive unloading of the respiratory system before each HFV period. This enabled a continuous swinging at resonance thus allowing measurement of fr and selection of exactly that frequency for the HFV run. Intra-animal CMV-HFV comparisons (n=4) were performed on each animal: with healthy lungs at a mean airway pressure (MAP) of 0.5 kPa and after saline lung lavage at MAPs of <1.5 kPa; 1.5–1.8 kPa; >1.8 kPa. Surfactant removal caused total respiratory system compliance (Ctot) to decrease from 44±5 to 22±3 ml/kPa. Corresponding fr was 244±48 and 360±30 min−1, respectively. HFV produced effective pulmonary gas exchange but did not improve arterial oxygenation in comparison with CMV at matched MAPs both before and after surfactant depletion. Volume amplitudes of oscillation necessary to achieve normocapnia were slightly above the natural plus equipment (2 ml) dead space. Maximum intra-alveolar pressure (Pmax) was calculated for the HFV runs from MAP, Ctot, and the volume amplitude of oscillation. Pmax during CMV was nearly twice that during HFV at equivalent PaCo2 and equivalent MAPs throught the experiments.

Abstract: Clinical data from 14 randomized double-blind studies were reviewed to compare the renatl tolerance of non-ionic monomeric contrast agents (iopamidol 300, iopromide 300, iohexol 300) with the non-ionic dimer iotrolan 280. A prospective study of iotrolan 280 versus iohexol 300 in renally impaired patients was also evaluated. Differences between the contrast agents were investigated using sub-group analysis of patients with an increased risk of contrast-induced nephropathy. Both the prospective study and meta-analysis of previous studies indicate that iotrolan 280 has less influence on renal function than the non-ionic monomeric comparator agents.

The aims of this study were to determine the incidence of typical chest radiography findings – (1) uniform improvement, (2) asymmetrical improvement, (3) no improvement or (4) interstitial emphysema – after therapeutic use of surfactant and to analyse clinical course and outcome. Chest radiographs of 138 infants of very low birth weight treated with surfactant were analysed. Twenty-eight infants with a diagnosis other than typical respiratory distress syndrome (RDS), i. e., sepsis, congenital pneumonia and congenital malformation, were excluded. In 110 patients with clinical and radiological evidence of typical RDS (median gestational age 28 weeks, median birth weight 1070 g) adequate chest radiographs from before and within 72 h after surfactant treatment were available. The time of surfactant application ranged between 1 and 12 h after birth. The most common finding after surfactant treatment was uniform or asymmetrical improvement of pulmonary aeration (80 of 110 patients). Patients with uniform clearing had the best long-term outcome. Asymmetrical clearance was often localised on the right side or in central regions of the lung, and usually disappeared after retreatment with surfactant without clinical significance. In 11 patients no change in aeration was found and retreatment was absolutely ineffective. Development of pulmonary inter- stitial emphysema after surfactant treatment was a grave prognostic sign: 73 % of these infants died within the first 2 weeks of life compared with 10 % of those with uniform or asymmetrical improvement of ventilation.

Summary: There is a discrepancy between the results of inhibition tests carried out with human erythrocytes and the values found if chick red cells are used.It is shown, that if an avidity factor is introduced, the disparity in results can be explained. It is possible to eliminate the avidity factor by means of fractionated adding of the virus suspension.The way to avoid possible faults in the future is discussed.