Surface characterization of poly(N-isopropylacrylamide) grafted tissue culture polystyrene by electron beam irradiation, using atomic force microscopy, and X-ray photoelectron spectroscopy

To understand features of polymers grafted by electron beam (EB) irradiation method, we investigated topology of poly(N-isopropylacrylamide) (PIPAAm) grafted tissue culture polystyrene (TCPS) (PIPAAm-TCPS) prepared by EB irradiation, using atomic force microscopy (AFM) in air and under aqueous conditions. Furthermore, surfaces properties of PIPAAm-TCPS surfaces before and after cell culture were also examined for evaluation of functionality of the surface as biomaterials, using XPS analysis. Three types of PIPAAm-TCPSs with different graft densities (1.0+/-0.1, 1.6+/-0.1, and 2.0+/-0.1 microg/cm2 of the grafted) were obtained (abbreviated as 11PIPAAm-, 16PIPAAm-, and 20PIPAAm-TCPS) by using different initial monomer concentration (20, 55, and 65 wt%). Contact angles (costheta value) of the surfaces increased with an increase in density of the grafted polymer. AFM observation in air clearly revealed that original TCPS surface possesses scratched and grooved topology (ca. 10 nm height of the scratch), while PIPAAm-TCPSs surfaces exhibited nanoordered PIPAAm particle-like domains. The size of the particles also increased proportionally initial IPAAm monomer concentration. The 11PIPAAm-and 16PIPAAm-TCPS surfaces having ca. 10-30 nm and ca. 40-50 nm size of the particles also displayed scratched and grooved topology featured in basal TCPS. However, the larger sizes of the particles (ca. 40-100 nm) formed on 20PIPAAm-TCPS surfaces adequately conceals the topological feature of the basal TCPS surfaces. The AFM images indicate that the graft polymer is as ultra thin as the scratch and grooves featured on basal TCPS are discernible, and the grafted PIPAAm layer become thicker with an increase of the monomer concentration. For 16PIPAAm-TCPS surfaces, the nanoordered particles were also observable in aqueous conditions at 20 degrees C and 37 degrees C. Comparison between the images obtained at 20 degrees C and 37 degrees C suggest that the domains are not likely to exhibit significant swelling and shrinking by temperature change, although the topology of PIPAAm grafted onto clover glass surface (50 microm thickness of the gel layer) were dramatically changed by temperature change in early reports. This difference should be due to ultra thin thickness of the grafted PIPAAm, which is subject to more restricted molecular motion by basal hydrophobic TCPS interfaces, as we reported previously. XPS C1s and N1s spectra of 16PIPAAm-TCPS surface after removal of cells suggest that proteins and/or peptides components possibly remained on the surfaces. Based on results from XPS analysis, we further discuss surface properties of 16PIPAAm-TCPS as biomaterials, comparing those of PIPAAm grafted polystyrene prepared by a radio frequency plasma method used in recent reports.     

Improved microcirculatory effect of D-allose on hepatic ischemia reperfusion following partial hepatectomy in cirrhotic rat liver

D-allose, one of the rare sugars produced from D-psicose, has been shown to be effective against reperfusion injury after ischemia and partial hepatectomy in cirrhotic rat liver by improving remnant liver blood flow and survival rates, and decreasing liver enzyme levels and liver tissue injury levels. These findings demand further study of the clinical implications of this sugar in view to the advancing fields of liver surgery and transplantation.     

On the role of catalyst components in the living metathesis polymerization of substituted acetylenes by MoOCl4-based systems

Summary The role of components in MoOCl₄-based living polymerization catalysts was studied. The MALDI TOF MS spectra of the poly(o-[(trifluoromethyl)phenyl]acetylene)s prepared with n-Bu₄Sn and Et₃Al as cocatalysts suggested a difference of 28(C₂H₄) in polymer molecular weight. This indicates that the formed polymer possesses an alkyl group of cocatalyst in the initiating chain end, which implies the transalkylation between MoOCl₄ and a cocatalyst and the subsequent formation of a Mo carbene. Sterically uncrowded aliphatic alcohols were useful as the third catalyst components. Addition of EtOH to the catalyst system led to the increase of activation enthalpy and the change of activation entropy from a negative to positive value in the propagation reaction, which suggests that EtOH coordinates to the propagating end competitively with the monomer. Received: 10 December 1999/Revised version: 3 February 2000/Accepted: 7 February 2000     

Reservoir characteristics and development plan of the Oguni geothermal field, Kyushu, Japan

Geothermal power development at the Oguni field, central Kyushu, is planned to begin in the year 2001 with a double flash system generating 20 MW_e. The Oguni reservoir has been delineated by systematic geothermal surveys, well tests and reservoir engineering studies. The fractured reservoir is horizontally layered and divided into northern and southern portions. Both of them have NaCl dominant fluids ranging from 200 to 240°C. The northern reservoir covers a large area including the Takenoyu Fault Zone and has a relatively high permeability (kh≈80–230 darcy-m). By contrast, the southern reservoir covers a relatively small area and has limited transmissivity. The southern reservoir has a higher pressure (1 MPa) than the northern reservoir, indicating little connectivity between them. Based on numerical calculations, as well as the surface topography and environmental aspects, the production and reinjection zones have been separated, and a large part of the necessary fluid will be produced from the northern reservoir along the Takenoyu Fault and a small part will be taken from the southern reservoir. The separated water will be reinjected into the northernmost part of the northern reservoir, in order to prevent a cold sweep problem for production.     

Calcium supplements increase bone mineral density in women with low serum calcium levels during long-term estrogen therapy

In order to clarify whether the long-term effect of estrogen on bone mineral density (BMD) is reinforced by low dose calcium supplements, 600-800 mg of calcium lactate was administered to postmenopausal or oophorectomized women who had been undergoing unopposed estrogen therapy for at least 2 years and whose serum calcium level was suppressed to below the normal range. To patients whose serum calcium levels had been within the normal range, the same dose of estrogen alone was continued. Changes in lumbar spine BMD before and after calcium supplementation was measured by dual-energy X-ray absorptiometry. Lumbar spine BMD decreased by -0.37% for 2 years in women treated with estrogen alone, while that of women treated with estrogen and calcium increased by 2.78% (P = 0.003). These results indicate that low dose calcium supplements potentiate the effect of estrogen in women with decreased serum calcium during long-term hormone replacement therapy.