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[BACKGROUND] We aimed to develop and externally validate a novel machine learning model that can classify CT image findings as positive or negative for SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR). [METHODS] We used 2, 928 images from a wide variety of case-control type data sources for the development and internal validation of the machine learning model. A total of 633 COVID-19 cases and 2, 295 non-COVID-19 cases were included in the study. We randomly divided cases into training and tuning sets at a ratio of 8:2. For external validation, we used 893 images from 740 consecutive patients at 11 acute care hospitals suspected of having COVID-19 at the time of diagnosis. The dataset included 343 COVID-19 patients. The reference standard was RT-PCR. [RESULTS] In external validation, the sensitivity and specificity of the model were 0.869 and 0.432, at the low-level cutoff, 0.724 and 0.721, at the high-level cutoff. Area under the receiver operating characteristic was 0.76. [CONCLUSIONS] Our machine learning model exhibited a high sensitivity in external validation datasets and may assist physicians to rule out COVID-19 diagnosis in a timely manner at emergency departments. Further studies are warranted to improve model specificity.

OBJECTIVES Indications of limited resection, such as segmentectomy, have recently been reported for patients with solid-predominant lung cancers ≤2 cm. This study aims to identify unfavourable prognostic factors using three-dimensional imaging analysis with artificial intelligence (AI) technology. METHODS A total of 157 patients who had clinical N0 non-small cell lung cancer with a radiological size ≤2 cm, and a consolidation tumour ratio > 0.5, who underwent anatomical lung resection between 2011 and 2017 were enrolled. To evaluate the three-dimensional structure, the ground-glass nodule/Solid Automatic Identification AI software Beta Version (AI software; Fujifilm Corporation, Japan) was used. RESULTS Maximum standardized uptake value (SUVmax) and solid-part volume measured by AI software (AI-SV) showed significant differences between the 139 patients with adenocarcinoma and the 18 patients with non-adenocarcinoma. Among the adenocarcinoma patients, 42 patients (30.2%) were found to be pathological upstaging. Multivariable analysis demonstrated that high SUVmax, high carcinoembryonic antigen level and high AI-SV were significant prognostic factors for recurrence-free survival (RFS; P CONCLUSIONS High AI-SV, high SUVmax and abnormal carcinoembryonic antigen level were unfavourable prognostic factors of patients with solid-predominant lung adenocarcinoma with a radiological size ≤2 cm. Our results suggest that lobectomy should be preferred to segmentectomy for patients with these prognostic factors.

We prepared poly(d,l-lactide) (PLA) microspheres by anionic dispersion polymerization of d,l-lactide. The polymerization was carried out in xylene/heptane (1:2 in v/v) mixture solution at 368 K for 9 h, with poly(dodecyl methacrylate)-co-poly[α-methacryloxyethoxy-poly(l-lactide)] (PDMA-co-P(MA-PLLA)) synthesized in this study, as a dispersion stabilizer. The number-averaged diameter and diameter distribution (coefficient of variation) of obtained PLA microspheres ranged from 180 to 800 nm and 14–40%, respectively, depending on the preparation condition. Furthermore, the time courses of monomer conversion, particle diameter, and particle number were investigated to clarify the formation mechanism of microspheres with PDMA-co-P(MA-PLLA) as a dispersion stabilizer. From this experiment, we found that the aggregation of primary particles occurred in anionic dispersion polymerization, and the particle diameter of obtained PLA microspheres decreased with increasing PDMA-co-P(MA-PLLA) concentration. In conclusion, we clarified that PDMA-co-P(MA-PLLA) effectively contributed to the stability of primary particles.

A new horseradish peroxidase (HRP)-catalyzed redox initiating system was successfully applied in the emulsion polymerization of styrene, producing stable polymer colloids and nanospheres. The particle size was about 30–50 nm with a diameter distribution (CV) 14–20% obtained by SEM. The molecular weight, \({\overline {\rm M}}{\rm n},\) was around 105, and \({\overline {\rm M}}{\rm w}\) was around 106. All the results were well consistent with the control, potassium persulfate (KPS)-initiating polymerization. The obtained experimental results supported a micelle mechanism similar to that of conventional emulsion polymerization of styrene.

In order to reduce the initial burst from polylactide (PLA) microspheres enclosing an antitumor agent, we prepared the microspheres with a smooth surface by varying solvent evaporation conditions such as operating temperature and pressure. PLA microspheres enclosing irinotecan hydrochloride (CPT) were prepared using the O/O emulsion system for solvent evaporation. The mean diameter and enclosing efficiency were almost constant because they were independent of solvent evaporation conditions. Scanning electron microscopic (SEM) observation verified the smooth surface of the PLA microspheres produced by varying the preparation conditions. In vitro release experiments show that the initial burst of microspheres with a smooth surface was less than that of those with a rough surface.

Polyvinyl alcohol (PVA)–DNA nanoparticles have been developed by ultra high pressure (UHP) technology. Mixture solutions of DNA and PVA having various molecular weights (Mw) and degree of saponifications (DS) were treated under 10,000 atmospheres (981 MPa) condition at 40 °C for 10 min. Agarose gel electrophoresis and scanning electron microscope observation revealed that the PVA–DNA nanoparticles with average diameter of about 200 nm were formed. Using PVA of higher Mw and degree of saponifications, the amount of nanoparticles formed increased. The driving force of nanoparticle formation was the hydrogen bonding between DNA and PVA. In order to apply the PVA–DNA nanoparticles for gene delivery, the cytotoxicity and the cellular uptake of them were investigated using Raw264 cell lines. The cell viability was not influenced whether the presence of the PVA–DNA nanoparticles. Further, the nanoparticles internalized into cells were observed by fluorescent microscope. These results indicates that the PVA–DNA nanoparticles prepared by UHP technology showed be useful as drug carrier, especially for gene delivery.

The pore structure, the hardness and the mechanical properties of three-dimensional titanium models formed by the selective laser melting method with a neodymium-doped yttrium aluminium garnet (Nd:YAG) pulsed laser are investigated. The optical and scanning electron micrographs show that pore structure depends on the peak power, the scan speed and the hatching pitch. The Vickers hardness of the laser formed specimens is around 240 HV (0.2 kgf), higher than that of the wrought material (125-160 HV). Depth profiling by X-ray photoelectron spectroscopy (XPS) indicates that oxygen pick-up occurs during laser forming of the titanium model processed in a closed chamber filled with argon. The fatigue strength of the titanium models formed by changing the hatching pitch and the laser power were measured. It is possible to improve the fatigue strength of the as-formed models by decreasing the hatching pitch or by hot isostatic pressing (HIP). The specimens after HIP have a fatigue strength comparable to the wrought material.

This research was conducted to clarify the membrane formation mechanism of cross-linked polyurea microcapsules by phase separation method, especially the role of polymeric surfactant, such as poly(ethylene-alt-maleic anhydride) (poly(E-MA)) at the interface of O/W emulsion. It was found that poly(E-MA) was necessary for the formation of cross-linked polyurea membrane. The addition of sodium dodecyl sulphate (SDS) prohibited the membrane formation reaction at the interface, even in the case of poly(E-MA) concentration enough for polymeric microcapsule formation. From the results in this study, poly(E-MA) was found to be adsorbed on the O/W emulsion and provide the reaction site for the membrane formation of polymeric microcapsules.

A very thin image capturing system called TOMBO (thin observation module by bound optics) is developed with compound-eye imaging and digital post-processing. As an application of TOMBO, a multispectral imaging system is proposed. With a specific arrangement of the optical system, spatial points can be observed by multiple photodetectors simultaneously. A filter array inserted in front of the image sensor enables observation of the spectrum of the target. The captured image is reconstructed by a modified pixel rearranging method extended to treat multi-channel spectral data, in which pixels in the captured image are geometrically rearranged onto a multi-channel virtual image plane. Experimental results of the image reconstruction show the effectiveness of the proposed system.

In this article, we report the experimental synthesis of reactive polymer microspheres of poly(p-hydroxycinnamic acid). Enzyme-catalyzed polymerization of poly(p-hydroxycinnamic acid) using horseradish peroxidase as a catalyst and hydrogen peroxide as an oxidant took place in a mixture solution of methanol and phosphate buffer solution; it was found that the fraction of methanol in the mixture solution strongly affected the yield of powdery polymer materials. The chemical structure of the polymers was characterized by 1H-NMR and FT-IR spectroscopies, and the molecular weight was measured by gel permeation chromatography. The 1H-NMR chart of the obtained polymer was almost the same as that of the monomer; FT-IR spectra indicated the existence of carboxyl groups. The weight-average molecular weight of the soluble part in tetrahydrofuran was found to be 1,451. Dispersion polymerization of p-hydroxycinnamic acid was carried out in a mixture solution of methanol and phosphate buffer solution by adding a dispersion stabilizer. Of the several such polymers tested, poly(vinyl alcohol) was found to be the most effective in producing reactive poly(p-hydroxycinnamic acid) microspheres.

A compact imaging system called TOMBO (Thin Observation Module by Bound Optics) is proposed in which a microlens array is used for thin hardware configuration. This paper describes a fingerprint-capturing module as an application of the TOMBO. Experimental results by the TOMBO prototype system are shown to clarify the applicability of the TOMBO to the fingerprint capturing. Different types of biometrics, i.e., fingerprint and face images, are captured by the same hardware, which shows the extendability of the system for multimodal identification.

This paper describes an experiment directed toward the preparation of monodispersed porous polymer microspheres with a diameter of ca. 50 μm, which is applicable to the chromatographic separation of biomolecules such as proteins and peptides by size exclusion. Fairly monodispersed polymer microspheres were successfully prepared by suspension copolymerization of polyethylene glycol monomethacrylate and ethylene glycol dimethacrylate as monomer and cross-linker, respectively. Monodispersed O/W emulsion was prepared by the SPG membrane emulsification technique, and was used in the subsequent droplet-swelling process in which monodispersed seed droplets were swollen by adsorbing the secondary emulsion droplets. The effects of the organic diluent in suspension polymerization and comonomer on the porous structure of the polymer microspheres were investigated by scanning electron microscopy and mercury-intrusion porosimetry, and the separation performances of polystyrene, polyethylene glycol, and various biomolecules by size-exclusion chromatography. As a result, it was evident that benzene, 1-butanol, and butyl acetate worked as nonsolvents for the polymer prepared in this study, and that polymer microspheres prepared with these solvents had larger pores. Size-exclusion chromatography revealed that the exclusive limiting molecular weight was 1.9×105 when polystyrene was used as a standard polymer, and 3.5×104 when polyethylene glycol was used as a standard polymer. Furthermore, we confirmed that the monodispersed polymer microspheres with defined pores clearly separated the six representative kinds of biomolecules with molecular weights ranging from 75 to 6.4×105.

Color-imaging methods with an integrated compound imaging system called TOMBO (Thin observation module by bound optics) are presented. The TOMBO is a compact optoelectronic imaging system for image capturing based on compound-eye imaging and post digital processing. First, a general description of the TOMBO system is given, and then two configurations for color imaging are described. Experimental comparison of these configurations is made by use of an experimental TOMBO system. The characteristics and the performance on the proposed methods are briefly discussed.

Divinylbenzene homopolymer microcapsules having porous membranes encapsulating tri‐n‐octylamine as a core material were prepared by in‐situ polymerization accompanied by the evaporation of toluene. The extraction equilibria of hydrochloric acid and precious metals in an acidic solution using the prepared microcapsules were measured at 303 K. The addition of toluene into the dispersed phase resulted in the microcapsule membrane having a porous structure due to the toluene evaporation during in‐situ polymerization, which was verified based on the results obtained both from SEM observation of the microcapsules' morphology and in the extraction equilibrium of hydrochloric acid. Using microcapsules prepared with toluene, hydrochloric acid was sufficiently extracted form an aqueous solution. In contrast, microcapsules prepared without toluene scarcely extracted hydrochloric acid. The microcapsules successfully extracted palladium(II) from the acidic media, and this was explained by the reaction between one pall...

A compact image capturing system called TOMBO (thin observation module by bound optics) is proposed. This system is an opto-electronic hybrid system, that utilizes a compound-eye imaging optics to achieve a very thin system configuration. Digital processing of the captured multiple images is used to retrieve the object image. Experimental results using the TOMBO prototype system are presented. As an application, a compact fingerprint capturing system using the TOMBO is described.

In order to evaluate the titanium model to be used for medical purposes in rapid prototyping with the selective laser melting process, the influence of forming conditions on the mechanical properties is investigated. The density and mechanical properties such as tensile and fatigue strengths of the model are measured. In the selective laser melting process, a pulsed yttrium aluminium garnet (YAG) laser with average power of 50 W and maximum peak power of 3 kW is used. The specimens for measuring density and mechanical properties are made from commercial pure titanium powders (grade 1) in a controlled atmosphere with argon gas. It is found that the relative density of the model is higher than 92 per cent and some powder particles remain within the solidified model. The scan speed affects the tensile strength strongly and the tensile strength is around 120 per cent of the standard value of the solid pure titanium when the scan speed is appropriate. However, the fatigue strength is low, about 10 per cent of the solid one, which is still to be improved by post-processing.

We investigated the effect of the polymer-drug interaction on the surface morphology of polymer microspheres and in vitro release properties. Polylactide microspheres enclosing the antitumor agent Irinotecan hydrochloride (CPT) were prepared by the solvent evaporation method of the O/O emulsion system in order to control the concentration of drugs in living organisms. The mean diameter of the polylactide microspheres was kept at approximately 50 μm while varying the content of CPT. The enclosing efficiencies in all runs were around 80%, independent of the CPT content. The surface morphology of polylactide microspheres was significantly affected by the content of the enclosing CPT. Furthermore, the degree of unevenness of the surface was increased with an increase in the CPT content in polylactide microspheres. DSC studies have suggested that the glass transition temperature of polylactide microspheres enclosing CPT shifted to lower temperatures with an increasing CPT content. It was assumed from DSC measurements that the morphological change of polylactide microspheres was induced by a polymer-drug interaction. In vitro release experiments suggested that the release rate in the early period increased with an increasing CPT content. From this study, it was pointed out that the drug, miscible with the matrix polymer, induced a change in surface morphology, providing a significant effect on release properties.

New bioactive composites consisting of partially crystallized glass beads as inorganic fillers and poly(methyl methacrylate) (PMMA) as an organic matrix were developed. Two kinds of partially crystallized glass beads, designated Cry820 and Cry850, were newly prepared by the heating of MgO–CaO–SiO2–P2O5 glass at 820 and 850°C, respectively. The glass beads were mixed with PMMA to form two new composites designated Cry820C and Cry850C, respectively. The goal of this study was to produce a highly osteoconductive and mechanically strong composite cement with these new fillers. A previously reported composite cement designated AWC, which was composed of apatite- and wollastonite-containing glass ceramic (AW-GC) as a powder filler and the same PMMA polymer used in the new composites, was used as a reference material. The quantity of filler added to each composite was 70 wt %. The bending strength of Cry820C was significantly higher than that of Cry850C. Composites were packed into intramedullary canals of rat tibiae to evaluate their osteoconductivity, as determined by an affinity index. The affinity index, which equaled the length of bone in direct contact with the composite surface expressed as a percentage of the total length of the composite surface, was calculated for each composite. The rats were euthanized at 4, 8, and 25 weeks after implantation. At each time interval studied, Cry820C showed a significantly higher affinity index than AWC up to 25 weeks after implantation. Cry850C showed a significantly higher affinity index than AWC up to 8 weeks and a higher affinity index than AWC at 25 weeks, although the difference was not significant. The values for each composite increased significantly with time up to 25 weeks. Our study revealed that the higher osteoconductivity of the new composites was due to the larger quantity of the glassy phase of the crystallized glass beads at the composite surface and the lower solubility of the PMMA powder to methyl methacrylate monomer. In addition, the spherical shape of the crystallized glass beads gave the new composites strong enough mechanical properties to be useful under weight-bearing conditions. The new composites show promise as alternatives, with improved properties, to conventional PMMA bone cement. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 556–563, 2002

We propose a novel segmentation method based on multi-label graph cuts utilizing higher-order potentials to impose shape priors. Each higher-order potential is defined with respect to a candidate shape, and takes a low value if and only if most of the voxels inside the shape are foreground and most of those outside are background. We apply this technique to coronary lumen and plaque segmentation in CT angiography, exploiting the prior knowledge that the vessel walls tend to be tubular, whereas calcified plaques are more likely globular. We use the Hessian analysis to detect the candidate shapes and introduce corresponding higher-order terms into the energy. Since each higher-order term has any effect only when its highly specific condition is met, we can add many of them at possible locations and sizes without severe side effects. We show the effectiveness of the method by testing it on the standardized evaluation framework presented at MICCAI segmentation challenge 2012. The method achieved values comparable to the best in each of the sensitivity and positive predictive value, placing it at the top in average rank.

A new bioactive bone cement (designated GBC), which is a polymethyl methacrylate (PMMA)-based composite consisting of bioactive glass beads as an inorganic filler and high molecular-weight PMMA as an organic matrix, has been developed. The purpose of the present study was to evaluate the effect of the filler content on the mechanical properties and osteoconductivity of GBC, to decide the most suitable filler proportion, and to evaluate the degree of cement degradation with time. The bioactive beads, consisting of MgO-CaO-SiO2-P2O5-CaF2 glass, were added to the cement in various proportions (40–70 wt %). The bending strength of GBC did not differ among the proportions (approximately 136 MPa), but the elastic modulus of bending of GBC increased as the glass bead filler content increased (approximately 4.1–7.2 GPa). The all types of GBC were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface. Rats were sacrificed at 4, 8, 25, and 39 weeks after implantation, and the affinity index was calculated for each type of GBC at each time point. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC containing only 40 wt % of glass beads. The affinity indices of GBC tended to increase as the proportion of glass bead filler increased and as the implantation period increased. In GBC containing 60 or 70 wt % of glass beads, significant rapid increases in the affinity indices were found from 4 to 8 weeks, and the high values (approximately 70%) were maintained up to 39 weeks. A sign of glass bead degradation was observed at the bone–cement interface in the rat tibiae at 39 weeks. We conclude that, when mechanical properties and osteoconductivity are both taken into consideration, GBC containing 60 or 70 wt % of glass beads is the most suitable formulation, but that further studies are needed to investigate and overcome the degradation. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 225–232, 2002

A bioactive bone cement (designated GBC), consisting of bioactive glass beads as an inorganic filler and poly(methyl methacrylate) (PMMA) as an organic matrix, has been developed. The purpose of the present study was to examine the effect of the size of the glass beads added as a filler to GBC on its mechanical properties and osteoconductivity. Serial changes in GBC with time were also examined. Four different sizes of beads (mean diameters 4, 5, 9, and 13 μm) consisting of MgO−CaO−SiO2−P2O5−CaF2 glass were added to four GBC mixes in a proportion of 70 wt %. The bending strength of GBC increased as the mean size of the glass beads decreased. The four GBC mixes were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after surgery. The affinity index, which equaled the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface, was calculated for each cement at each interval. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks. At each time interval, there was a trend for the affinity index of GBC to increase as the mean glass bead size decreased. The affinity indices for all types of GBC increased significantly with time up to 8 weeks. The handling properties of GBC were comparable to those of conventional PMMA bone cement. We concluded that, considering both mechanical properties and osteoconductivity, GBC made with smaller sized glass beads as filler was the most suitable cement. GBC shows promise as an alternative bone cement with improved properties compared to conventional PMMA bone cement. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 452–458, 2001

Crystalline poly(ethylene-co-vinyl alcohol) (EVOH) membranes were prepared by a thermally induced phase separation (TIPS) process. The diluents used were 1,3-propanediol and 1,3-butanediol. The dynamic crystallization temperature was determined by DSC measurement. No structure was detected by an optical microscope in the temperature region higher than the crystallization temperature. This means that porous membrane structures were formed by solid–liquid phase separation (polymer crystallization) rather than by liquid–liquid phase separation. The EVOH/butanediol system showed a higher dynamic crystallization temperature and equilibrium melting temperature than those of the EVOH/propanediol system. SEM observation showed that the sizes of the crystalline particles in the membranes depended on the polymer concentration, cooling rate, and kinds of diluents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2449–2455, 2001

The effect of diluents on isotactic polypropylene (iPP) membrane formation via thermally induced phase separation was investigated. The diluents were methyl salicylate (MS), diphenyl ether (DPE), and diphenylmethane (DPM). The cloud-point curve was shifted to a lower temperature in the order iPP–MS, iPP–DPE, and iPP–DPM, whereas the crystallization temperature was not influenced so much by diluent type. Droplet-growth processes were investigated under two conditions: quenching the polymer solution at the desired temperature and cooling at a constant rate. Although droplet sizes were in the order iPP–MS, iPP–DPE, and iPP–DPM in both cases, the difference was more pronounced with the constant cooling rate condition. Scanning electron microscopy indicated that interconnected structures were obtained when the polymer solution was quenched in ice water. The effect of the diluents on these structures was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 169–177, 2001

Porous poly(ethylene-co-vinyl alcohol) (EVOH) membranes were prepared by polymer crystallization by the thermally induced phase separation (TIPS) process. The permeability of these membranes was examined with respect to solutes of various sizes. Higher solute rejection and lower water permeance were obtained by increasing the polymer concentration in the membrane preparation process and by increasing the cooling rate in the TIPS process. These results were discussed based on the crystalline particle sizes formed in the membranes. The membrane performances were influenced by the kinds of diluents used in the TIPS process. The membranes prepared in the EVOH/propanediol system showed a higher rejection coefficient than did those in the EVOH/butanediol system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2456–2463, 2001

Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO2. The carrier of CO2 was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion-exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO2 over N2 and higher CO2 permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion-exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO2 partial pressure in the feed gas was 0.061 atm. Effects of ion-exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001

A new bioactive bone cement, designated GBC, has been developed. It consists of polymethyl methacrylate (PMMA) as an organic matrix and bioactive glass beads as an inorganic filler. The bioactive beads, consisting of MgO--CaO--SiO(2)--P(2)O(5)--CaF(2) glass, have been newly designed, and a novel PMMA powder was selected. The purpose of the present study was to evaluate the effects on mechanical properties and osteoconductivity of adding a phosphoric ester (PE) monomer to the cement as an adhesion-promoting agent. Four kinds of cements were prepared: GBC, GBC with PE (designated GBC/PE), a cement consisting of the same PMMA used in GBC with apatite- and wollastonite-containing glass-ceramic (AW-GC) powder (designated AWC), and AWC with PE (designated AWC/PE). Each filler was added to the cement at 70 wt %. Adding PE to either GBC or AWC resulted in increases in the bending strength and decreases in the Young's modulus compared with the unmodified cements. Cements were packed into the intramedullar canals of rat tibiae to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after operation. The affinity index (length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface) was calculated for each cement. Adding PE to either GBC or AWC resulted in significant increases in the affinity index compared with the unmodified cements. The affinity index for GBC was significantly higher than that of AWC, and that for GBC/PE was also significantly higher than that of AWC/PE. The affinity indices for each cement increased significantly with time up to 8 weeks. Our study revealed that the higher osteoconductivity of GBC/PE was due to the large alkyl group in the PE monomer, to the hydrophilicity of the phosphoric acid in the PE monomer, and to the higher bioactivity of the bioactive glass beads at the cement surface. GBC/PE shows promise as an alternative bone cement with improved properties compared with conventional PMMA bone cement.

Polypropylene particles were prepared by a thermally induced phase separation. The particle formation occurred by the nucleation and growth mechanism in the metastable region. The particle growth was followed by the dynamic light scattering measurement. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particle diameter d increased with time t in accordance with the relation of d3∝t in all cases. Detailed consideration on the slope values indicated that the particles grew by the coalescence mechanism. The particle size distribution, which was obtained by SEM observation, became broader when the polymer concentration was higher.

Anisotropic (gradation in pore size) and asymmetric (dense surface skin) polypropylene membranes were produced by the thermally induced phase separation (TIPS) process and solute rejection by these membranes was investigated. Anisotropic membranes were obtained by inducing a polymer concentration gradient in the polymer-diluent solution prior to phase separation. The concentration gradient was established by controlled evaporation of diluent from one side of the solution. The anisotropic membranes showed much higher rejection coefficients for latex particles with diameter of 100 nm than an isotropic polypropylene membrane prepared by the TIPS method without evaporation. Asymmetric structures were achieved by imposing a cooling rate gradient across the membrane. The membrane had a skin layer of about 1 μm thickness at the surface that was rapidly cooled. The solute rejection coefficient reached more than 0.95 for lysozyme of molecular weight of 14 600. This result shows that ultrafiltration polypropylene membranes can be produced by the TIPS process if asymmetry is induced during the membrane formation process.

Phase separation mechanisms during the membrane formation by dry-cast process were investigated by light scattering in the cellulose acetate/dimethylformamide (DMF)/2-methyl-2,4-pentanediol system. Phase separation occurred by spinodal decomposition (SD) when paths of the composition changes due to the evaporation of DMF were close to the critical point in the phase diagram. Characteristic properties of the early stage of SD such as an apparent diffusion coefficient and an interface periodic distance were obtained from the Cahn theory. Phase separation occurred by nucleation and growth (NG) when paths of the composition changes were far from the critical point. SEM observation confirmed that the membrane formed by the SD mechanism had interconnected structure, whereas that by the NG mechanism had the closed cell porous structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 776–782, 2000

Thermally induced phase separation was studied by the light scattering in polypropylene/methyl salicylate system. Data could be well fitted with the linear Cahn theory for spinodal decomposition (SD) in the early stage of phase separation. Characteristic properties of the early stage of SD, such as an apparent diffusion coefficient and an interphase periodic distance, were obtained. The periodic distance ranged from 3 μm to 4 μm. The growth of the phase-separated structure obeyed power-law scaling in the later stage, and the structure factor could be scaled into a universal time-independent form. Domain sizes obtained from the light-scattering measurements were consistent with the optical microscope measurements. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1028–1036, 2000

Total hip arthoplasties (THAs) were performed in beagle dogs using a bioactive bone cement (BABC) consisting of a silane-treated apatite- and wollastonite-containing glass–ceramic (AW glass–ceramic) powder and a silica glass powder as the filling particles and a bisphenol-A-glycidyl dimethacrylate-based resin (Bis-GMA-based resin) as the organic matrix. The outcomes were compared with the results of polymethylmethacrylate (PMMA) bone cement. The mechanical properties of the BABC were stronger than those of PMMA bone cement. The bonding strength of the BABC to bone in the dogs' femora increased with time and reached 3.7 MPa at 24 months after implantation whereas that of PMMA bone cement was 2.0 MPa (p < 0.05). Histological examination showed direct bonding between the BABC and the femoral bone for up to 24 months after implantation. However, with PMMA bone cement an intervening soft-tissue layer consistently was observed at the bone–cement interface. Direct bonding at the interface between the BABC and the bone through a calcium phosphorous layer 30 μm-thick was revealed by scanning electron microscopy. Femoral bone resorption was observed at 24 months after implantation in the BABC group, but it was not observed in the PMMA bone cement group. Direct bonding between BABC and the bone may have accelerated femoral bone resorption. Cement fractures of the BABC were observed on the acetabular side 24 months after implantation. Weak bonding between the BABC and an acetabular component made of ultrahigh molecular weight polyethylene (UHMWPE), relatively high elastic characteristics of BABC, and weakness of the calcium phosphorous layer formed on the surface of this cement seemed to lead to failure at 24 months on the acetabular side. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 49, 273–288, 2000.