Search

Polycarbonate (PC), an engineering plastic, has excellent mechanical strength and toughness. Moreover, this transparent polymer material can be used in fields where materials require mechanical properties and transparency. Nevertheless, PC is known to have a high melt viscosity. Moreover, blending with polystyrene (PS), an inherently brittle material, has been used to adjust its melt viscosity. As a result, the PS makes PC/PS polymer blends more brittle than PC alone. As described herein, after attempting to achieve compatibility with inorganic particles, the results show that the dispersion of small amounts of inorganic clay and silica particles in PC/PS polymer blends maintained transparency while improving the impact strength to a level comparable to that of polycarbonate. Apparently, the inorganic particles promote the fine dispersion of PS. Moreover, the spherical morphology of the inorganic particles is more effective at compatibilizing the polymer blend because the inorganic particles can apply isotropic interaction forces.

Thermoplastic resins, which are lighter than metals and ceramics, have many features such as excellent processability. They are used in widely various fields for daily necessities and for transportation equipment. Even for the same material, the elastic properties of the thermoplastic resin can vary depending on the molecular weight, molding temperature and conditions. Therefore, the elastic properties required for structural analysis must be evaluated each time. After this study derived a formula for yield initiation stress of injection-molded thermoplastics, the formula was applied for a method of obtaining the longitudinal elastic modulus and Poisson's ratio from results of a three-point bending test. From actual examination using polypropylene (PP) and polystyrene (PS), the calculated longitudinal elastic modulus and Poisson's ratio showed good agreement with literature values. Results clarified that these values depend on the injection molding temperature. Furthermore, the bulk modulus and shear modulus were obtained from the longitudinal modulus and Poisson's ratio. Their injection molding temperature dependences were investigated. The shear modulus showed the same tendency as that of the longitudinal elastic modulus, but results indicated the dependence of bulk modulus as small in PP: bulk modulus of PS increased with increasing injection molding temperature.

Sphingosine 1-phosphate (S1P) regulates lymphocyte trafficking through the type 1 sphingosine 1-phosphate receptor (S1P1) and participates in many pathological conditions, including autoimmune diseases. We developed a novel S1P1-selective antagonist, TASP0277308, which is structurally unrelated to S1P. This antagonist competitively inhibited S1P-induced cellular responses, such as chemotaxis and receptor internalization. Furthermore, differing from previously reported S1P1 antagonists, TASP0277308 demonstrated in vivo activities to induce lymphopenia, a block in T cell egress from the thymus, displacement of marginal zone B cells, and upregulation of CD69 expression on both T and B cells, all of which recapitulate phenotypes of S1P1-deficient lymphocytes. In a mouse collagen-induced arthritis model, TASP0277308 significantly suppressed the development of arthritis, even after the onset of disease. These findings provide the first chemical evidence to our knowledge that S1P1 antagonism is responsible for immunosuppression in the treatment of autoimmune diseases and also resolve the discrepancies between genetic and chemical studies on the functions of S1P1 in lymphocytes.

Effects of LTI addition on the mode I fracture energy of HA/PLLA/PCL were examined and the micro-structural modification due to LTI addition was investigated. Both the mode I energy release rate, Gin, and averaged fracture energy, Ef, are improved dramatically due to LTI addition. The reason is considered to be the improvements of the interfacial structure connecting HA particles with PLLA/PCL matrix and the miscibility between PLLA and PCL. These changes of blend morphology and interfacial structure reduce the stress concentration and lead to the ductile deformation and resulted in the increase of those fracture properties.

Lysine tri-isocyanate (LTI) was added to a biodegradable polymer blend of poly(lactic acid) (PLA) and poly (e-caprolacton) (PCL) under melt-mixing condition in order to improve the miscibility of PLA and PCL. It was found that the mode I fracture energy of the polymer blend effectively increases with increase of LTI content. Microscopic examination also showed that the size of PCL phase decreases due to LTI addition, leading to the reduction of void formation and suppression of local stress concentration, thus the improvement of the fracture energy. The improved miscibility also contributes to the ductility enhancement, which further increases the fracture energy.

Poly( l -lactide) (PLLA) has actively been used as a biomaterial for resorbable bone fixation devices for use in orthopedic and oral surgeries. Recently, in order to improve the fracture properties of brittle PLLA, polymer blends of PLLA and a ductile bioabsorbable polymer, poly(e-caprolactone) (PCL), have been developed. The aim of the present study is to elucidate details of the fracture behavior and toughening mechanisms of PLLA/PCL blends. PLLA/PCL blends with different PCL contents were developed, and the critical energy release rate at crack initiation, Gin, was then measured to assess the effect of PCL content. It was shown that Gin is dramatically improved by blending PCL with PLLA, and the maximum 51% of increase of Gin is acheived with 5 wt% of PCL. Polarizing optical microscopy (POM) and scanning electron microscopy (SEM) of crack growth behavior were also performed to characterize the fracture mechanism. PLLA/PCL showed multiple craze formation in the crack-tip region, and elongated fibrils and voids construct the crazes. SEM of fracture surface also indicated that stretched fibril structures are formed on the surface as a result of elongation of PCL spherulites under high tensile stress condition in the crack-tip region. Thus, these damage formations are considered to be the primary energy dissipation mechanisms that resulted in the improvement of fracture energy.

LTI was attempted to modify the microstructure of poly (l-lactic acid) (PLLA) and to improve its mechanical properties in this study. Bending modulus, strength and fracture toughness of PLLA/LTI were evaluated, and compared to those of the base PLLA to assess the effectiveness of LTI blending. Effect of LTI addition on fracture micromechanism was also investigated by observing and comparing the fracture surfaces of PLLA/LTI and PLLA using a field emission scanning electron microscope (FE-SEM). Experimental results showed that the bending properties such as the bending modulus and the strength are effectively improved due to polymerization of PLLA molecules by LTI blending. The fracture toughness value was also improved due to increase of ductile deformation, i.e., energy dissipation in the crack-tip region.

Lysine triisocyanate (LTI) was used to blends of poly(lactide) (PLA) with poly(e-caprolactone) (PCL) to improve the immiscibility of the two different kinds of biodegradable polymers. Fracture properties such as the J-integral at initiation, Jin, and the total fracture energy, Jf, of PLA/PCL and PLA/PCL/LTI were evaluated, and compared the results to assess the effectiveness of LTI additive on improvement of the fracture properties. Fracture surfaces were also examined using a scanning electron microscope (SEM) to characterize fracture mechanism. The results of the SEM observation exhibited that the size of PCL spherulites became smaller by adding LTI, and therefore void formation was inhibited, resulting in improvement of the fracture properties.

P(LLA-CL) copolymer was additionally blended to PLLA/PCL polymer blend to improve the immiscibility between PLLA and PCL. Mechanical properties such as the bending modulus, strength and the maximum J-integral were then measured and the phase morphology and fracture surface were observed using FE-SEM. Crystallinity values of PLLA and PCL were also evaluated using DSC. It is seen that those mechanical properties successfully increased due to P(LLA-CL) addition. The results of FE-SEM observation and crystallinity measurement suggests that the immiscibility is improved by P(LLA-CL) blending and as a result, spherulites of PCL dispersed in the blend are reduced, resulting in effective increase of ductile deformation. It is thought that this kind of phase structural change causes the improvement of the mechanical properties.

Recent years, considerable attention has been paid to biodegradable polymers, mainly owing to increasing interest for preservation of environment and substitution of petrochemical polymers. Poly (lactic acid) (PLA), one of typical biodegradable polymers, is being considered for use in a variety of industrial fields including car, computer and electric appliances. PLA is also utilized as a biomaterial in medical fields such as orthopedics and oral surgery [1, 2], due to bioabsorbability and biocompatibility. Fracture properties and fracture behavior of PLA have been studied, and it was found that crazes are formed in crack-tip region prior to crack initiation, that is similar to the fracture behavior of brittle polymers such as PP and PS [3–7]. Improvement of the fracture properties of such brittle polymers can generally be achieved by blending a ductile secondary phase to the base polymer. Poly (e-caprolacton) (PCL), a ductile biodegradable polymer, has been chosen as a blending partner for PLA [8–14], and the fracture properties of PLA/PCL was found to be greater than those of neat PLA [9]. However, it was also found that the immiscibility of PLA and PCL causes phase separation, and tends to lower the fracture properties especially when PCL content increases. In the present study, lysine triisocyanate (LTI) was used as an additive for PLA/PCL blend to improve such immiscibility. Impact fracture properties of PLA/PCL/LTI blend was evaluated and compared to those of PLA/PCL blend to assess the effectiveness of LTI addition. Effect of LTI addition on fracture micromechanism was also investigated by observing their fracture surfaces using a scanning electron microscope (SEM). PLA/PCL and PLA/PCL/LTI blends were fabricated from PLA pellets (Lacty #9030, Shimadzu Co. Ltd), PCL pellets (CelgreenH7, Daicel Chemistry Industries Co.) and LTI (Kyowa Co. Ltd) by melt-mixing in a conventional melt-mixer at 180 C for 20 min at a rotor speed of 50 rpm. The mixing ratio of PLA and PCL was fixed at 85:15 in weight fraction, and the LTI content was chosen to be 1 wt% in this study. Plates of 2-mm thick were then fabricated from the mixtures using a hot press attached with water-cooling system. These mixtures were melted at 180 C and pressed at 30 MPa, and then quenched to room temperature using the cooling system. Single-edge-notchbend (SENB) specimens were prepared from these PLA/ PCL and PLA/PCL/LTI plates. The J-integral at crack initiation, Jin, and the average fracture energy, Jf, were evaluated at an impact rate of 1.4 m/s using an instrumented drop weight impact testing system with dynamic displacement measuring apparatus [15, 16]. Jin and Jf were calculated using the following formulae

ポリ乳酸 (PLA) とポリ (e-カプロラクトン) (PCL) のブレンドを溶融混合法により作製し, 混合時にリジントリイソシアネート (LTI) を添加することで相構造を制御し破壊特性の改善を試みた. 破壊特性としてき裂進展開始時のエネルギー解放率Jinを計測し, またPLAの結晶化度 (xc, PLA) と重量平均分子量 (Mw) を測定した. LTI添加量の増加とともにJinとMwは増加し, xc, PLAは低下する傾向にあった. LTIをPLA/PCLブレンドに添加すると架橋反応が生じてMwが増大する一方で結晶化は抑制されxc, PLAは減少すると理解された. また, 巨視的な破壊エネルギーを決定する因子として球状PCLのサイズが考えられ, LTIを添加することによってPCLのサイズが減少し, 結果としてJinが向上したと考えられた.

Phase morphology of blends of biodegradable polymers, PLA and PCL, was controlled by introducing an additive, LTI, to improve the mechanical properties of the mixture. Fracture properties such as the J-integral at initiation Jin, and the total fracture energy Jf, of PLA/PCL blends with different LTI contents were evaluated, and were compared to assess the effect of LTI content on these properties. Both Jin and Jf values were dramatically improved by LTI addition. Fracture surfaces were also examined using SEM to characterize the effect of LTI addition on the fracture mechanism. It was confirmed that the size of PCL spherulites became smaller due to the activation of LTI as a surface-active agent. As a result, void formation was inhibited, and plastic deformation to be larger, resulting the improvement of fracture properties.

Background: The efficacy of rabeprazole sodium 20 mg/d for the treatment of reflux esophagitis has been demonstrated in several studies in Japan. However, studies of rabeprazole sodium 10 mg/d are lacking. Objective: This study was conducted to assess the efficacy and tolerability of rabeprazole 10 mg/d for the treatment of reflux esophagitis. Methods: Patients diagnosed with reflux esophagitis in routine clinical practice were enrolled in this single-center, open-label, practice-based, post-marketing surveillance investigation. Patients were to receive 10 mg of rabeprazole once daily for 8 weeks. The efficacy of rabeprazole was assessed on the basis of symptoms and endoscopic findings in accordance with the modified Los Angeles classification. Tolerability was assessed using subjective symptoms recorded before, during, and after treatment. Results: Of a total of 61 patients enrolled in this study, 47 (77%; 29 men, 18 women; mean age, 63 years) were included in the efficacy and tolerability analyses. Fourteen (23%) patients, including 5 (8.2%) patients who were treated with rabeprazole 20 mg/d, were excluded from the analyses. Endoscopic examinations were performed before and after treatment in 32 of 47 (68.1%) patients; mucosal lesions were healed in 20 of 32 (62.5%) patients after rabeprazole treatment. In patients with mild mucosal lesions prior to treatment, complete remission was achieved in 17 of 24 (70.8%) patients after treatment. Rates of improvement of symptoms were as follows: epigastralgia, 76%; heartburn, 76.7%; dull pain in the esophagus, 86.7%; and belching, 72.2%. Rabeprazole was well tolerated throughout the study; no serious symptomatic adverse events were reported. Although 1 case each of elevated alkaline phosphatase and gamma-glutamyltranspeptidase levels were reported, these changes were mild and improved after continuous treatment with rabeprazole. Conclusion: In this study, rabeprazole 10 mg/d was well tolerated and was shown to have satisfactory efficacy in the healing of esophagitis and the relief of the symptoms of esophagitis.

Synthesis and structure-activity relationship of a novel series of isoquinoline CRTH2 antagonists bearing a methylene linker between the isoquinoline and benzamide moieties were described. Optimization focusing on the substituents of the benzamide portion in the right hand part of the molecule led to the identification of TASP0412098 (9l), which is a potent, selective CRTH2 antagonist (binding affinity: IC50=2.1 nM, functional activity: IC50=12 nM). Compound 9l, which was orally bioavailable in mice and guinea pigs, showed in vivo efficacy after oral administration in a bronchial asthma model of guinea pigs.

胆管内発育型胆管細胞癌の報告は非常にまれであり, その1切除例を経験したので報告する. 症例は65歳女性. 閉塞性黄疸にて来院し, 経皮経肝胆道ドレナージ術を施行した.胆管像では乳頭状の陰影欠損によって肝門部胆管は閉塞し, 腹部CTでは右尾状葉から右葉後区域にかけて径30mmの腫瘍を認めた. 経皮経肝胆道鏡検査では右肝管から総肝管まで伸びる乳頭状腫瘍を認め, 生検にて腺癌の診断を得た. 経皮経肝門脈造影では門脈右枝は左右分岐部直後で閉塞していた. 術前の癌進展度診断により, 右尾状葉から発生した胆管内発育型胆管細胞癌と診断し, 肝右葉切除, 尾状葉全切除, 胆管切除, 下大静脈合併切除を施行した.本疾患の鑑別診断には経皮経肝胆道鏡検査による胆管内腫瘍の診断が有用であった. また, 手術術式決定の上では胆管内腫瘍と主腫瘍の存在, 部位, 進展範囲, 進展様式の診断が重要であった.

A 50-year-old asymptomatic woman was detected having an abdominal tumor at a medical checkup. abdominal ultrasonography revealed a 3cm-sized circular and internally heterogenous hypoechoic picture at the retropancreatic region and in the right front of the aorta. Abdominal CT visualized a circular, homogenous, and well-defined low density area adjacent to the retropancreatic region and the liver, excepting a part of the center of the area. Angiography showed a stenosis in the left gastric artery and displacement at the root of SMA. ERCP revealed no abnormalities in the bile and pancreatic ducts. The patient was diagnosed as having a retroperitoneal tumor and was operated on. The tumor adhered to the common hepatic artery and celiac artery, where both the tumor and celiac artery existed in a condition enclosed in the plexus. With exposure of the arterial wall the tumor was freed from the artery and excised. The excised tumor was 25×23×20mm in size, elastic soft, encapsulated and well-defined. The section was yellowish brown with hemorrhage in the center. Histopathologically it was Antoni type A neurinoma. No malignancy was detected. Based on intraoperative findings, the tumor appeared to be arised in the celiac plexus.

Poly (lactic acid) (PLA), made from natural resources such as starch of plants, is one of typical biodegradable thermoplastic polymers and has extensively been used in medical fields such as orthopedics, neurosurgery and oral surgery as bone fixation devices mainly due to biocompatibility and bioabsorbability (Higashi et al., 1986; Ikada et al., 1996; Middleton & Tipton, 2000; Mohanty, 2000). Its importance has led to many studies on its mechanical properties and fracture behavior which found that the mode I fracture behavior of PLA is relatively brittle in nature (Todo et al., 2002; Park et al., 2004, 2005, 2006). Therefore, blending with a ductile biodegradable and bioabsorbable polymer such as poly (e-caprolacton) (PCL) has been adopted to improve the fracture energy of brittle PLA (Broz et al., 2003; Dell’Erba et al., 2001; Chen et al., 2003; Todo et al., 2007; Tsuji & Ikada, 1996, 1998; Tsuji & Ishizuka, 2001; Tsuji et al., 2003); however, it was also found that phase separation originated by immiscibility of PLA and PCL tends to degrade the mechanical properties of PLA/PCL blends (Todo et al., 2007). It has recently been found that such phase separation can dramatically be improved by using an isocyanate group, lysine tri-isocyanate (LTI) (Takayama et al., 2006; Takayama & Todo, 2006; Harada et al., 2007, 2008), and the fracture properties of PLA/PCL/LTI are much higher than those of PLA/PCL. In this chapter, firstly the fracture behavior and micromechanism of pure PLA are summarized (Park et al., 2004, 2005, 2006; Todo et al., 2002). Effects of crystallization behavior and loading-rate on the mode I fracture behavior are discussed. Effect of unidirectional drawing on the fracture energy is also presented as one of the effective ways to improve the brittleness of PLA (Todo, 2007). Secondly, the fracture behavior of PLA/PCL blends is discussed on the basis of the relationship between the microstructure and the fracture property (Todo et al., 2007b). In the third section, improvement of microstructural morphology of PLA/PCL by using LTI is discussed (Takayama et al., 2006; Takayama & Todo, 2006; Todo & Takayama, 2007; Todo et al., 2007a). It has been found that addition of LTI effectively improves the phase morphology of PLA/PCL, resulting in dramatic improvement of fracture energy. Effects of annealing on the mechanical properties of PLA/PCL/LTI blend are discussed in the last section (Takayama et al., 2011). It has been found that a thermal annealing process can effectively improve the mechanical properties of the polymer blend, as a result of strengthened structures due to crystallization of PLA.

Poly(lactic acid) (PLA) has been used as a biomaterial for bone fixation devices in oral and orthopedic surgery because of good biocompatibility and bioabsorbability. Because Poly(e-Caprolactone) (PCL) is a ductile, bioabsorbable and biodegradable polymer, many types of PLA/ PCL polymer blends have been developed to improve its material strength and impact resistance. The stress-strain curves of PLA and PLA/PCL polymer blends were measured using a split Hopkinson pressure bar (Kolsky bar) method and a universal testing machine. The effect of PCL content on Young's modulus and yield stress was examined. The values of constants in Cowper-Symonds equation with respect to yield stress were determined for PLA and PLA/PCL polymer blend specimens. PLA/PCL specimens were observed using a scanning electron microscope. Godkänd; 2009; 20090912 (parj)

Microneedle array features were fabricated by micro-injection molding using biocompatible polymers such as polycarbonate (PC), polypropylene (PP) and polylacticacid (PLA). PC and PP based microneedle array features with high aspect ratio for needle height was fabricated by several injection molding techniques. Injection compression molding and injection molding with super critical carbon dioxide fluid with or without vacuum process inside the cavity of mold were performed. Effects of process parameters on processability and surface replication of the molded parts were evaluated. The height replication ratio for micro-needle was improved by using injection compression molding. Moreover, the effect of vacuum process inside cavity of mold under filling process was small. However the height replication ratio for micro-needle showed the highest values using the injection molding with super critical carbon dioxide fluid with vacuum inside the cavity of mold process. In addition, hydroxyapatite (HAp) particle dispersed PLA composites based microneedle array features were also fabricated by twin screw extrusion and micro-injection molding. The viscosity of PLA was reduced by HAp dispersion because of acceleration of hydrolysis degradation during both processing. The micro-needle array of HAp/PLA composites for application to biomedical parts was obtained and the needle height was improved by the optimum composition of HAp to polymer.

We studied 349 patients with chronic infection due to hepatitis C virus (HCV), including 83 with coagulopathy, 122 with community-acquired infection, 20 with chronic posttransfusion hepatitis C, and 124 for whom the transmission mode was unknown. The prevalence of mixed-subtype HCV infection was investigated in each group of patients. The serum HCV RNA concentration and the response to interferon (IFN) therapy were evaluated. HCV infection with mixed subtypes was more frequent in patients who had been at high risk for exposure to HCV, such as those with coagulopathy or community-acquired infection. HCV RNA concentrations were lower in patients infected with mixed subtypes, except for those with subtypes 1a and 1b. Ten of 11 patients with mixed subtypes (not including those with 1a and 1b) achieved complete clearance of HCV RNA with IFN therapy.

肝疾患診断におけるcomputed tomography(以下CTと略す)の意義と限界を明らかにする目的で,瀰漫性肝疾患90例と腫瘤性肝疾患37例を対象として第3世後半のCT装置(GECT/T 8800)を用いて各疾患のCT像を比較検討した.肝硬変症ではRIスキャンで認められる右葉萎縮や左葉肥大などの所見は明らかで無く,脾臓前後径の増大,肝表面の凹凸,腹水の存在が特異的な所見であった.脂肪肝は全例で肝臓のCT値が低値を示し,肝臓と脾臓のCT値の比が0.9以下という基準は脂肪肝のスクリーニングとして有用と言えた.急性肝炎では肝内胆管拡張を認めない点が肝外閉塞性黄疸との鑑別に役立つと考えられた.SOLの存在診断能はRIスキャンより優れており,嚢胞に関しては質的診断も可能であった.現段階ではCTにより高度の脂肪,鉄沈着や広汎な壊死以外の肝組織学的変化を知ることは不可能であり,また固形腫瘤の質的診断も困難な場合が多い.

組織学的に確定診断された肝瀰漫性脂肪化56例,慢性肝炎41例,肝硬変39例のCT像を対比して,CTによる脂肪化の診断能と診断基準を検討した.軽度脂肪化は診断困難であったが,高度脂肪化(脂肪肝)に関しては肝CT値/脾CT値比が0.85未満という診断基準の設定が可能であった.上腹部CT 6,800件中,197件(2.9%),実数169例(瀰漫性141例,限局性28例)がこれに該当した.成因としては瀰漫性,限局牲いずれも肥満,糖尿病,多飲酒の順に多かった.血液生化学検査正常例が肝生検にもとづく従来の報告よりも高率にみられた.反復施行37例の検討では,肝CT値の推移は各成因の改善度をよく反映し,CTは治療効果判定にも有用であった.瀰漫性,限局性脂肪肝は相互に移行がみられたので,限局性脂肪肝は脂肪肝の進展や改善途中で生ずる一過性の病態と考えられる.