10-Gb/s optical transmission up to 253 km via standard single-modefiber using the method of dispersion-supported transmission

Using the new method of dispersion-supported transmission, 10 Gb/s signals at 1.53 μm wavelength are transmitted on standard single-mode fiber with zero dispersion at 1.3 μm via the record length of 253 km without in-line regeneration. Detailed experiments with a directly modulated laser demonstrate the system performance for different fiber lengths ranging from 0 up to 253 km     

Development of an optimal protocol for the ultrastructural examination of skin by transmission electron microscopy

The intercellular lipid bilayers of the stratum corneum provide the permeability barrier of the skin. To perform an electron microscopical examination of the ultrastructure of these bilayers, ruthenium tetroxide fixation is required. In this study an optimal fixation protocol was developed and selected upon comparing seven different fixation procedures, using glutaraldehyde (GA) and the postfixatives ruthenium red, osmium tetroxide (OsO₄) and ruthenium tetroxide (RuO₄) in combination with potassium ferrocyanide (K₄Fe(CN)₆) and potassium ferricyanide (K₃Fe(CN)₆). Instead of fixing skin with either OsO₄ or RuO₄, these two fixatives were combined in one protocol. In addition, the use of RuRed was introduced and the influence of both K₄Fe(CN)₆ and K₃Fe(CN)₆ in combination with RuO₄ were examined. Furthermore, we compared two dehydration solvents, methanol and acetone.
The most satisfying results were obtained when the skin was prefixed in GA and postfixed in OsO₄ and RuO₄ with K₃Fe(CN)₆, i.e. with Fe in its highest oxidation state (Fe³⁺). No differences were observed between dehydration in methanol and acetone.     

Comparison of results after transanal endoscopic microsurgery and radical resection for T1 carcinoma of the rectum

BACKGROUND: We compared the results of transanal endoscopic microsurgery and radical surgery in patients with T1 carcinomas of the rectum. METHODS: We performed a retrospective study (1985-96) to compare the results obtained in 103 patients with T1 rectal carcinomas (low-risk T1, n = 80; high-risk T1; n = 23) undergoing transanal endoscopic microsurgery and radical surgical therapy. RESULTS: The complication rate in patients undergoing local excision was 3.4% (two of 58); it was 18% (eight of 45) in the group treated with radical surgery. Two of 45 patients (3.8%) died after radical resection; there were no deaths after local excision. With regard to the actuarial 5-year survival rate, no difference was observed in the group with low-risk T1 carcinoma between patients treated with local excision (79%) and those who had radical resection (81%) (p = 0.72). In patients with high-risk T1 carcinoma, lymph node metastases were identified in four of 11 patients undergoing radical resection (36%). Four of 12 patients with high-risk T1 carcinoma treated by local excision developed recurrences, whereas none of the patients undergoing primary radical surgery had a recurrence. CONCLUSIONS: Transanal endoscopic microsurgery for the treatment of low-risk T1 carcinomas is associated with a significantly lower complication rate than radical surgical therapy. There is no difference in 5-year survival between local and radical surgical therapy in patients with low-risk T1 carcinoma.     

Cryotherapy of liver metastases. Initial results

PATIENTS AND METHOD: Between 1 Jan 1996 and 1 Apr 1998 29 patients underwent cryosurgical therapy for liver metastasis at the Department of Surgery at the University of Mainz. RESULTS: No complications occurred following cryosurgery alone (n = 12). Within the group of patients with a combined procedure (n = 11) 1 patient had temporary liver failure and 1 patient died of sepsis. Following freezing of the cutting zone (n = 6) 1 patient showed a bile fistula and 1 ascites. In 15 cases of 28 dismissed patients with remaining destroyed tumor tissue the follow-up showed no tumor recurrence (median follow-up 11 months). On the other hand 9 patients had a tumor recurrence within the liver, 3 patients at extrahepatic regions and 7 patients developed a tumor recurrence within the freezing zone.     

A self-organizing publish/subscribe middleware for dynamic peer-to-peer networks

Peer-to-peer needs new middleware technologies and counterparts to the widely established CORBA, EJB, COM+, and messaging systems products. Specially designed middleware would release the advantages of peer-to-peer networks to a broad spectrum of applications. Network-specific advantages like scalability, fault tolerance, and resource availability could easily be utilized without any concerns about their underlying infrastructure and resources. We address this need with our P2P Messaging System, which focuses on high-performance group communication based on a publish/subscribe model. The P2P Messaging System considers the heterogeneous and dynamic character of peer-to-peer networks by an augmented topology and its supporting features. The P2P Messaging System was evaluated by experimental benchmark tests, and the results provide evidence of its efficiency and scalability.     

Numerische Erfahrungen bei der Lösung des dreidimensionalen Transportproblems

To find an initial basic feasible solution is a special problem on solving the three dimensional transportation problem. It is not possible to do this work in a similar simple way as it can be done in the usual transportation problem. In [3] Haley proposes to solve a new problem that is essentionally the old one with the addition of a set of artificial variables. However, numerical investigations have shown that this procedure enlarges the amount of computing very much. This paper now gives another procedure for finding an initial basic solution for the three dimensional transportation problem. A great number of examples is discussed which demonstrate the efficiency of this procedure.     

Accuracy of progress ratios determined from experience curves: the case of crystalline silicon photovoltaic module technology development

Learning curves are extensively used in policy and scenario studies. Progress ratios (PRs) are derived from historical data and are used for forecasting cost development of many technologies, including photovoltaics (PV). Forecasts are highly sensitive to uncertainties in the PR. A PR usually is determined together with the coefficient of determination R², which should approach unity for a good fit of the available data. Although the R² is instructive, we recommend using the error in the PR determined from the fit because it is a direct measure of the range in PR values that is recommended to be used in sensitivity analyses within scenario studies. We present a simple equation to calculate the error in PR from the fit parameters. In the case of crystalline PV module technology development we find a PR = 0·794 ± 0·003 by fitting price data of the period 1976–2006. A moving average approach with a 10‐year time window shows that PR varies from 0·818 ± 0·017 up to a starting year of 1987, and is reduced considerably to a minimum value of 0·704 ± 0·014 for the starting year 1991. For the most recent starting year 1997, the average PR is considerably higher at 0·884 ± 0·022, highlighting the recent silicon feedstock supply problem. When available, error in individual data points can be used to perform weighted fits in order to decrease fitting errors. To illustrate this approach, an analysis of Dutch PV system price development over the period 1992–2002 shows that PR is 0·876 ± 0·010, where the error is decreased with respect to unweighted fitting. The PR = 0·794 has been used to analyze the cost targets stated in the Strategic Research Agenda as formulated by the European PV Technology Platform for the years 2013, 2020 and 2030. Assuming that such a PR is maintained, it is concluded that these targets may be attained at sustained annual growth rates of 21–42%, which seems feasible. Copyright © 2007 John Wiley & Sons, Ltd.     

Striving to further harmonization of sustainability criteria for bioenergy in Europe: Recommendations from a stakeholder questionnaire

This questionnaire analyzed the ongoing development of sustainability criteria for solid and liquid bioenergy in the European Union and further actions needed to come to a harmonization of certification systems, based on EU stakeholder views. The questionnaire, online from February to August 2009, received 473 responses collected from 25 EU member countries and 9 non-European countries; 285 could be used for further processing. A large majority of all stakeholders (81%) indicated that a harmonized certification system for biomass and bioenergy is needed, albeit some limitations. Amongst them, there is agreement that (i) a criterion on ‘minimization of GHG emissions’ should be included in a certification system for biomass and bioenergy, (ii) criteria on optimization of energy and on water conservation are considered of high relevance, (iii) the large variety of geographical areas, crops, residues, production processes and end-uses limits development towards a harmonized certification system for sustainable biomass and bioenergy in Europe, (iv) making better use of existing certification systems and standards improves further development of a harmonized European biomass and bioenergy sustainability certification system and (v) it is important to link a European certification system to international declarations and to expand such a system to other world regions.     

Treatment of tumors of the pancreatic head with suspected but unproved malignancy: is a nihilistic approach justified?

A critical analysis of morbidity and mortality for pancreatico-duodenectomy was performed on 221 patients. During the 1960s and 1970s, the morbidity and mortality for pancreaticoduodenectomy were so high that many thought the operative procedure ought to be abandoned. During the 1980s, however, many centers reported mortality rates around 5% and a morbidity of 25% to 35%. Others still reported a mortality of more than 10% and a morbidity of up to 65%. The reasons for these discrepancies are of major interest. In a prospective case-control study 760 patients with malignant and benign diseases of the pancreas were treated in our hospital between September 1, 1985 and April 30, 1997. In 221 cases (128 men, 93 women; mean age 61 years, range 23-83 years) a partial (n = 209) or total (n = 12) pancreaticoduodenectomy, in 12 cases combined with portal vein resection, was performed. Surgical complications were seen in 25%, but less than half of them were severe. General complications were seen in 18.5%. The 30- and 90-day mortality rates were 3.1%, and 5.7%, respectively. In a regression analysis the intraoperative blood loss, preoperative serum bilirubin, diameter of the pancreatic duct, and occurrence of surgical and nonsurgical complications had an independent influence on mortality. In addition to the experience of the surgeon in selecting the patients and his or her personal technical skills when performing a pancreaticoduodenectomy, better anticipation and management of postoperative complications is essential for improving the results of this operation.     

Explaining the experience curve: Cost reductions of Brazilian ethanol from sugarcane

Production costs of bio-ethanol from sugarcane in Brazil have declined continuously over the last three decades. The aims of this study are to determine underlying reasons behind these cost reductions, and to assess whether the experience curve concept can be used to describe the development of feedstock costs and industrial production costs. The analysis was performed using average national costs data, a number of prices (as a proxy for production costs) and data on annual Brazilian production volumes. Results show that the progress ratio (PR) for feedstock costs is 0.68 and 0.81 for industrial costs (excluding feedstock costs). The experience curve of total production costs results in a PR of 0.80. Cost breakdowns of sugarcane production show that all sub-processes contributed to the total, but that increasing yields have been the main driving force. Industrial costs mainly decreased because of increasing scales of the ethanol plants. Total production costs at present are approximately 340 US$/m_ethanol³ (16 US$/GJ). Based on the experience curves for feedstock and industrial costs, total ethanol production costs in 2020 are estimated between US$ 200 and 260/m³ (9.4–12.2 US$/GJ). We conclude that using disaggregated experience curves for feedstock and industrial processing costs provide more insights into the factors that lowered costs in the past, and allow more accurate estimations for future cost developments.