中国中心发达城市边缘区域的崛起

城乡人口的变迁与城市经济结构的变革使中国大城市开发其边缘区域的需求激增。中国城市边缘区域正以空前的速度成长,然而其发展方式与西方国家的理论和实践却大相径庭。城市边缘区域的兴起,归因于城市产业向高附加值产业以及服务业转移、城市化脚步加快和消费模式的改变。迅猛的变化更凸显了中国城市边缘区域规划所面临的挑战——一切要从零开始建设。此类项目成本的高昂可想而知,有力的试点项目至关重要。这些大型项目在中心城区以外改变着中国传统的城区土地利用方式、人口结构和交通方式。     

Syntheses of hydroxypropyl methylcellulose phthalate hydrogels in Na2CO3 aqueous solutions with electron‐beam irradiation

Novel cellulose ether hydrogels were prepared by the radiation‐induced crosslinking of hydroxypropyl methylcellulose phthalate (HPMCP) in a solution of Na₂CO₃. The effects of several factors, such as the HPMCP concentration, Na₂CO₃ concentration, absorbed dose, and dose rate, on the crosslinking of HPMCP were investigated in detail. An increase in the HPMCP concentration resulted in an increasing content of the gel fraction, and this meant that the crosslinking probability increased as well. Na₂CO₃ was essential for dissolving HPMCP in water, and a 4–5% Na₂CO₃ aqueous solution was optimal for the crosslinking of HPMCP. The dose rate also affected the radiation crosslinking of HPMCP; hydrogels with higher gel fractions and transparency could be formed at lower dose rates. The ratio of degradation to crosslinking of the gel was calculated according to the Charlesby–Rosiak equation, and it showed good agreement with the experimental results. Some important properties, such as the swelling kinetics, ion and ionic strength dependence, and pH dependence, of the HPMCP hydrogels were also investigated. The HPMCP hydrogels possessed excellent swelling rates and swelling ratios in some solvents, such as water and methanol, with a high hydrogen‐bonding parameter. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2123–2130, 2003     

Preparation of crosslinked carboxymethylated chitin derivatives by irradiation and their sorption behavior for copper(II) ions

To obtain highly efficient adsorbents that were insoluble in acidic and basic aqueous solutions, we synthesized new types of crosslinked chitin derivatives (carboxymethylchitin and carboxymethylchitosan) with ionizing radiation, and we investigated the sorption of Cu(II) ions onto these crosslinked chitin derivatives. Sorption kinetic studies indicated the rapid removal of copper(II) ions from the aqueous solutions. Also, isothermal sorption data revealed that Cu(II) was removed by these crosslinked carboxymethylated chitin derivatives with high efficiency. Sorption isothermal data were interpreted well by the Langmuir equation. The uptake of Cu(II) ions was 161 mg/g on crosslinked carboxymethylchitin and 172 mg/g on crosslinked carboxymethylchitosan at pH 5.5. A low pH was favorable for Cu(II) desorption. The Cu(II) ions were desorbed from the crosslinked matrix rapidly and completely after a treatment in a diluted HCl solution, and at the same time, the adsorbents were regenerated to be used again to adsorb heavy metal ions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 556–562, 2004     

Formation of porous α-CD ethanol dihydrate by crystal transformation method

The crystal transformation method using ethanol as a dehydration medium is a new method which can create a porous crystal. In this study α-cyclodextrin (α-CD) hexahydrate was transformed by this method and porous ethanol dihydrate crystal was obtained. The pore volume measured was 0.25 mL/g and the median pore diameter was 0.11 μm. Dissolution rate of this crystal was several times higher than that of (α-CD) hexahydrate or anhydrate obtained by drying.     

Modification of the surgical strategy based on intraoperative echographic findings of atherosclerotic ascending aorta

To prevent the atheroembolic complications such as brain infarction due to the manipulation of atherosclerotic ascending aorta during cardiac surgery, the ascending aorta of 55 patients including 6 emergencies (mean age: 67.7 +/- 6.9 years, valvular disease: n = 12, ischemic heart disease only or combined with valvular disease: n = 43) were evaluated with intraoperative echography as a routine, to enable a proper placement of the cannulae, clamp etc. Irregular elevated lesions into the aortic lumen from the intima were identified in 7 patients (13%, mean age: 71.0 +/- 6.9 years) of ischemic heart disease, which included 2 emergent cases. Arch cannulation was employed in 3 patients with wide-spread lesions on the posterior wall and femoral cannulation was done in 1 patient with wide-spread lesions on the anterior wall. Two of these patients received CABG with in situ arterial conduits under ventricular fibrillation, and the other 2 patients received CABG with aortic cross clamping at the lesion-free site during proximal anastomosis of vein grafts (single clamp technique). Two patients with localized lesion were done CABG with partial aortic clamping and one of them had cerebral infarction during the operation. We recognized that manipulation of the ascending aorta has to be done with a meticulous care and well away from the diseased site. In another patient with localized lesion, the arch cannulation and the single clamp technique were used 2 cm away from that lesion. The brain infarcted patient completely recovered without any sequelae and the others also had no atheroembolic complications. Although calcified lesions on CT were correlated with atheromatous lesions on echogram (p = 0.004), these atheromatous plaques were not detected by enhanced CT, except in only one patient. For screening of the atherosclerosis of ascending aorta, the CT examination was not so effective and the intraoperative echography was the most sensitive and could be easily accomplished. In conclusion, in order to prevent the atheroembolism that might occur due to the improper manipulation of the diseased ascending aorta during usual procedures, surgical strategies have to be modified according to the position, extent and quality of the atherosclerotic lesions, diagnosed by intraoperative echoscanning of the aorta.     

Thermal and photo-induced surface damage in paratellurite

Long-term operation of TeO2 acousto-optical device is limited by the formation of surface damage caused by the He–Cd laser irradiation. Similar surface damage occurs during the heat treatment of the TeO2 crystal at 350°C. In this study, TeO2 specimens after various surface treatments have been observed by electron microscopy and X-ray photoelectron spectroscopy. The variation of the transmittance for mechanically polished specimens has been measured in situ during heat treatments. It was found that the thermal surface damage at 350°C was formed in the surface layer damaged by mechanical polishing. The mechanically damaged layer was amorphous and deficient in oxygen in the as-polished state. The electron microscopic observation revealed that the surface damage layer induced by heat treatments or by the ultraviolet light irradiation contained tellurium particles (20–40 nm) in diameter dispersed in the TeO2 matrix. On annealing the TeO2 specimen at 500°C in air, however, the particles disappeared because of the melting, evaporation and oxidation of tellurium which restores the transmittance of the crystal. Based on the results, combined with the observation of surface damage induced by the visible light irradiation, a possible mechanism of the surface damage formation has been briefly discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

A 2.5-ns clock access, 250-MHz, 256-Mb SDRAM with synchronousmirror delay

A 256-Mb SDRAM (245.7 mm²) has been developed using (1) a high cell occupation ratio (60.2%) array design for chip size reduction and a high yield, (2) a prefetched pipeline scheme (PPS) using a first-in first-out (FIFO) buffer with parallel serial converter for 250-MHz clock frequency operation, and (3) a synchronous mirror delay (SMD) circuit for 2.5-ns clock access and low standby current     

Fretting fatigue behavior and life prediction of automotive steel bolted joint

Fatigue tests of bolted joints of SAPH400 automotive steel plate were carried out. Effect of groove on fretting fatigue strength was investigated by introducing various geometries of grooves at contact edge. The fretting fatigue strength was improved by introducing groove: the fatigue strength increased with increasing groove depth. As the next step, the applicability of the tangential stress range–compressive stress range diagram to the bolted joints was investigated using the tangential stress range–compressive stress range diagram obtained from conventional laboratory-type SAPH400 steel specimens. The result showed that the fretting fatigue strength of actual component, i.e. the bolted joint could be successfully predicted based on the tangential stress range–compressive stress range diagram.     

Simultaneous determination of N-methylcarbamates and their metabolites in citrus fruits by HPLC avoiding use of halogenic solvents

Twenty-one N-methylcarbamates (NMCs) and 12 of their metabolites or isomers in citrus fruits were simultaneously determined avoiding use of dichloromethane. NMCs in lemon, orange, and grapefruit were extracted with acetone, then the acetone was evaporated off and sodium chloride was added before extraction with ethyl acetate. The extract was evaporated and the residue was cleaned up on a combined mini-column set of Supelclean ENVI-Carb and Mega Bond Elut SAX cartridges. NMCs were determined by HPLC with post-column reaction and fluorescence detection. All of the NMCs in the orange sample were determined without interfering peaks. However 8 NMCs in lemon extract and 10 NMCs in grapefruit extract were not detected because interfering peaks appeared at similar retention times to those of the NMCs. These NMCs were determined using LC/MS (SIM) and were well recovered. Eighty-three data sets obtained by HPLC and LC/MS showed good similarity, with r2 = 0.9178. Recoveries were 60.1 to 97.8% for major NMCs at a fortification level of 0.1 ppm. The limit of detection by HPLC was 0.005 ppm NMCs in samples and a similar level applied to LC/MS.