Locational disadvantage of the hub

We show how spatial evolution is different between the two representative models of economic geography: [Krugman 99:483–499, 1991] and [Ottaviano et al. 43:409–436, 2002]. We analyze the impacts of falling transport costs on the spatial distribution of economic activities and welfare for a network economy consisting of three regions located on a line. It is normally considered that a hub city, i.e., a central region, always has locational advantage and manufacturing workers gain from trade. This is true in the former model, but not in the latter when markets are opened up to trade. This is because the price competition is so keen in the central region that the manufacturing sector moves to the peripheral regions, which aggravates the social welfare. We then show that when goods are close substitutes and share of manufacturing is of an intermediate level, the manufacturing activities completely disappear from the central region leading to a full agglomeration in one peripheral region.

Genes and Gene Networks Involved in Sodium Fluoride-Elicited Cell Death Accompanying Endoplasmic Reticulum Stress in Oral Epithelial Cells

Here, to understand the molecular mechanisms underlying cell death induced by sodium fluoride (NaF), we analyzed gene expression patterns in rat oral epithelial ROE2 cells exposed to NaF using global-scale microarrays and bioinformatics tools. A relatively high concentration of NaF (2 mM) induced cell death concomitant with decreases in mitochondrial membrane potential, chromatin condensation and caspase-3 activation. Using 980 probe sets, we identified 432 up-regulated and 548 down-regulated genes, that were differentially expressed by >2.5-fold in the cells treated with 2 mM of NaF and categorized them into 4 groups by K-means clustering. Ingenuity^® pathway analysis revealed several gene networks from gene clusters. The gene networks Up-I and Up-II included many up-regulated genes that were mainly associated with the biological function of induction or prevention of cell death, respectively, such as Atf3, Ddit3 and Fos (for Up-I) and Atf4 and Hspa5 (for Up-II). Interestingly, knockdown of Ddit3 and Hspa5 significantly increased and decreased the number of viable cells, respectively. Moreover, several endoplasmic reticulum (ER) stress-related genes including, Ddit3, Atf4 and Hapa5, were observed in these gene networks. These findings will provide further insight into the molecular mechanisms of NaF-induced cell death accompanying ER stress in oral epithelial cells.     

Effects of operating and design parameters on PEFC cold start

During startup from subzero temperatures the water produced in a polymer electrolyte fuel cell (PEFC) forms ice/frost in the cathode catalyst layer (CL), blocking the oxygen transport and causing cell shutdown once all CL pores are plugged with ice. This paper describes an experimental study on the effects of operating and design parameters on PEFC cold-start capability. The amount of total product water in mg cm⁻² during startup is used as an index to quantify the cold-start capability. The newly developed isothermal cold-start protocol is used to explore the basic physics of cold start, and the effects of purge methods prior to cold start, startup temperature and current density, and the membrane thickness are shown. The experimental data also confirm the current density effect predicted earlier by a multiphase model of PEFC cold start.     

MR imaging of idiopathic trigeminal neuralgia: correlation with non-surgical therapy

Urinary drainage by indwelling double J ureteral stent is well documented in the urologic literature. We used these stents in 91 patients. The majority of stents were placed endoscopically (68%). Indications were: -Ureteral obstruction (39 cases) such as tuberculous ureteral strictures, obstruction due to urolithiasis and pelvic malignancies. -Upper urinary tract surgery (29 cases) mainly pyeloplasty, pyelolithotomy, ureterovaginal fistula repair and ureteroneocystostomy. -Adjunct to endourologic treatment (16 cases) such as ureteroscopy and endopyelotomy. -Preparation for extracorporeal lithotripsy (7 cases). The complication rate associated with placement of double J stents was minimal (6.6%). The major complication was migration (3 cases). The average drainage time was 5.8 weeks. In view of these results we conclude that double J stent is safe, effective and has minimal complications.     

A study of robust generation mix under uncertain environments

In recent years, the trend has been toward factors (e.g., demand for load, energy cost) becoming more and more uncertain in power system expansion planning. Thus, it has become necessary to take this uncertainty into account in determining generation plans. In this paper, a robust generation plan is defined explicitly as a plan that ensures fixed performance (economy) despite deviations in these factors. In addition, a new formulation of the robust generation mix problem, whose purpose is to determine the most robust combination of plants in a target year, is proposed. It is generally difficult to solve the formulated problem with parameters. However, by analyzing a proposed formulation from the viewpoint of optimization, we show that the proposed formulation is transformed into the conventional optimization problem without parameters. The simulation results on a typical model show that the generation mix produced by the proposed formulation is more robust than that produced by the conventional formulation. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 26–35, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.2009     

Permeability properties of glycol chitosan membrane modified with thiol groups

Water-soluble glycol chitosan (GC), having the ability to form a membrane, was modified with 3,3′-dithiodipropionic acid (DTPA), a functional group that causes the thiol ? disulfide transition through redox reaction. The membrane derived from this modified GC was water-insoluble. The permeabilities of KCI and socrose through the GC membrane modified with DTPA (M_DTPA), the reduced membrane (M_SH), and the oxidized membrane (M_SS) were investigated. The permeability through the M_SH membrane increased twofold relative to that through the M_DTPA membrane, and the M_SS membrane showed a 60% decrease in the permeability, which had increased in the case of the M_SH membrane. The permeability of sucrose was lower and more changeable than that of KCl. These permeation phenomena were discussed from the viewpoint that the thiol ? disulfide transition is responsible for the water content of each membrane.     

Estimation of creep crack growth rate in IN-100 based on the Q* parameter concept

Since the high-strength Ni-based superalloy, cast IN-100, is considered to be brittle at high temperatures, the stable creep crack growth region is limited. Therefore, technically, it is very difficult to perform creep tests and there are few experimental results on the creep crack growth behaviour of this material. We performed creep crack growth tests using Ni-based superalloy, cast IN-100, and derived the Q* parameter for this material, which characterizes the creep crack growth rate. Using this Q* parameter, we derived a law for the creep rupture life of this material.