Gain tilt of erbium-doped fiber amplifiers due to signal-inducedinversion locking

A theoretical analysis describing an interpretation of the fundamental processes, responsible for the second-order distortion of AM signals in erbium-doped fiber amplifiers (EDFAs) is presented. It is shown that the locked-inversion gain tilt rather than the widely used continuous wave gain tilt is responsible for the distortion. The theoretical analysis is confirmed by experiments showing that the two types of gain tilt may differ by factors of up to 60. In particular, it is demonstrated that the locked-inversion gain-tilt may be significant even at the CW gain peak. Experimental results indicate that the relevant gain tilt can be reduced to acceptable levels by proper design of the EDFA     

Microorganisms associated with Maari, a Baobab seed fermented product

A microbiological study was carried out on Baobab fermented seeds (Maari) obtained from 4 different production sites in Burkina Faso (Mansila, Toulfé, Ouagadougou and Gorgadji).A total of 390 representative isolates comprising 251 aerobic mesophilic bacteria (AMB) and 139 lactic acid bacteria (LAB) were isolated and identified to species level using a combination of pheno- and genotypic methods including conventional morphological analysis, carbohydrate fermentation profiling, rep-PCR ((GTG)₅-fingerprinting) and 16S rRNA gene sequencing.The fermentation of Baobab seeds was initiated by the AMB identified as Bacillus subtilis (82% of AMB isolates) and Staphylococcus sciuri (18% of AMB isolates). No lactic acid bacteria were isolated at the beginning of the process. After 24 h fermentation time, Enterococcus faecium appeared in the fermenting seeds and remained until the end of the fermentation, as the predominant LAB.In Maari collected from retail outlets the AMB count ranged from 6.7 log10 CFU/g to 10 log10 CFU/g while the LAB load ranged from 4.4 log10 CFU/g to 9.9 log10 CFU/g. The AMB were identified as belonging to genus Bacillus (12 species), Staphylococcus (3 species) and one species of Aerococcus, Macrococcus, Leifsonia, Kurthia, Proteus, Acinetobacter and Globicatella, respectively. A putatively novel, previously undescribed Corynebacterium sp. was also found. E. faecium was the dominant LAB in all investigated retail samples except one sample dominated by Pediococcus acidilactici.     

Relying on Interdependencies: Snøhetta in the Middle East

Kjetil Trædal Thorsen and Robert Greenwood of Snøhetta describe how opportunities to build multicultural programmed buildings in the Middle East have opened up the possibilities of developing a new iconography for a new building type, embedded in the emotional translation of a rich iconographic and decorative tradition; an ongoing dialogue with the clients and users; and a Middle Eastern preference to define the present by looking to the future. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrospinning of hollow and core/sheath nanofibers using a microfluidic manifold

In this article, we describe a microfluidic approach to fabricate hollow and core/sheath nanofibers by electrospinning. Key benefits in using microfluidic devices for nanofiber synthesis include rapid prototyping, ease of fabrication, and the ability to spin multiple fibers in parallel through arrays of individual microchannels. Hollow poly (vinylpyrrolidone) (PVP) + titania (TiO₂) composite and core/sheath polypyrrole (PPy)/PVP nanofibers of the order of 100 and 250 nm, respectively, were successfully fabricated using elastomeric microfluidic devices. Fiber characterization was subsequently carried out using a combination of scanning electron microscopy and transmission electron microscopy.     

Stomach cancer. A 10-year material with emphasis on early cancer

Between 1982 and 1991, 112 patients were treated for gastric cancer at Harstad Hospital in Northern Norway. Early gastric cancer accounted for 20% of all the adenocarcinomas (110), which is high compared with figures from other western studies. The role of endoscopy for detecting early gastric cancer is discussed. The five year survival rate after radical surgery was found to be significantly higher for patients with early gastric cancer than for patients who underwent curative surgery for either infiltrative or regional cancer. For patients with a tumour that had invaded the regional lymph nodes the five year survival rate was only 10%. This result can be improved by more extended lymph node dissection. The perioperative mortality rate (8%) was usually a result of severe cancer cachexia or underlying cardial disease, and not anastomotic leakage. The results as regards the cure of early gastric cancer are comparable with those described in other studies.     

Cluster Formation in Precrystalline Solutions

Small Angle Neutron Scattering (SANS) gives evidence of colloidal structures or clusters in solutions of vanillin in aqueous alcohol. Interpretation of the data gives the same result as the Photon Correlation Spectroscopy technique: stable or metastable fractal clusters. The size of these clusters increases as a function of the parameters that control supersaturation, but is stable with respect to time. These structures, called metastable clusters, are closely related to the observed liquid‐liquid phase separation at high solute concentration. Another type of clusters is found to co‐exist with the metastable clusters at a lower solute concentration. The same type of structures is found in a two‐component system of vanillin in 2‐methyl‐2‐butanol. They slowly grow as a function of time, and are called labile clusters. These colloidal structures are assumed to be precrystalline clusters giving rise to nuclei in crystallization.     

Bioavailability of PAHs: effects of soot carbon and PAH source

The bioavailability of 38 individual polycyclic aromatic hydrocarbon (PAH) compounds was determined through calculation of biota-sediment-accumulation factors (BSAF). BSAF values were calculated from individual PAH concentrations in freshwater mussel, marine clam, and sediment obtained from field and laboratory bioaccumulation studies. Sediment that was amended with different types of soot carbon (SC) was used in some of the bioaccumulation experiments. BSAF values for petrogenic PAH were greater than those for pyrogenic PAH (e.g., 1.57 +/- 0.53 vs 0.25 +/- 0.23, respectively), indicating that petrogenic PAH are more bioavailable than pyrogenic PAH (p < 0.05). This trend was consistent among marine and freshwater sites. Increased SC content of sediment resulted in a linear decrease in the bioavailability of pyrogenic PAHs (r2 = 0.85). The effect of increasing SC content on petrogenic PAH was negligible. SC was considered as an additional sorptive phase when calculating BSAF values, and using PAH-SC partition coefficients from the literature, we obtained unreasonably large BSAF values for all petrogenic PAH and some pyrogenic PAH. This led us to conclude that a quantitative model to assess bioavailability through a combination of organic carbon and soot carbon sorption is not applicable among field sites with a wide range of soot carbon fractions and PAH sources, at least given our current knowledge of PAH-SC partitioning. Our data offer evidence that many factors including analysis of a full suite of PAH analytes, PAH hydrophobicity, sediment organic carbon content, sediment soot carbon content, and PAH source are importantto adequately assess PAH bioavailability in the environment.     

Modelling residential location choice in an area with spatial barriers

A model is presented for residential location choice in rural areas with spatial barriers. We address the problem through comparative static analysis focusing on how residential location choices are affected by a new road link across the spatial barrier. We proceed through a probability theoretical approach: choose a family of utility functions representing every possible location, and equip this family with a probability measure. Then choose a representative within an equivalence class of utility functions, and represent the probability distribution by a parametrized family of distributions. Our analysis demonstrates that investments in new road links do not necessarily represent an adequate instrument for achieving ambitions in regional policy. We identify reasonable situations where a new road link could just as easily generate net migration from the area in which the investments are directed. In general, our analysis demonstrates how agglomeration and centralisation tendencies can be considerably affected by transportation infrastructure innovations. Received: June 1999/Accepted: June 2001 This paper benefited from comments by Bj?rn Sandvik and Lars-G?ran Mattsson.     

SPATIAL CONSEQUENCES OF CHANGES IN THE TRANSPORTATION NETWORK: THEORETICAL ANALYSIS AND NUMERICAL EXPERIMENTS WITHIN A MULTIZONAL THREE SECTOR MODEL

ABSTRACT: In this article a model is presented that is directed toward analysis of spatial consequences of changes in the transportation network. The model is based on a variant of Lowry's economic base model, with three sectors and two nested levels of spatial dis-aggregation. Changes in the locational structure are explained through the interdependency between households and local sector firms. As a numerical experiment, the model is applied to estimate locational impacts of some large-scale investments in transportation infrastructure along the Western coast of Norway.