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Search Results: 1 - 10 of 434 matches for " Yoshikazu Toyoki "
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Union Influence on Wage and Change in Employment Rate in an Overlapping Generations Economy  [PDF]
Toyoki Matsue
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.812172
Abstract: The effect of labor market institutions on the unemployment rate has been widely studied in macroeconomic dynamics. Union influence is one of the most important issues in the labor market institutions. Thus, this study investigates the effects of union influence on wages with regard to employment dynamics using an overlapping generations model with closed economy. We assume a wage setting equation that is discussed in the existing literature and we consider an economy in which unemployment exists. The model shows that high upward pressure on wages leads to low employment rates not only in the steady state but also on the equilibrium path.
A case of invasive hemolymphangioma of the pancreas
Yoshikazu Toyoki, Kenichi Hakamada, Shunji Narumi, Masaki Nara, Daisuke Kudoh, Keinosuke Ishido, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: Hemolymphangioma of the pancreas is a very rare benign tumor. There were only five reports of this disease until March 2008. Herein, we report a case of hemolymphangioma of the pancreas with gastrointestinal bleeding due to duodenal invasion. A 53-year-old man had been admitted a referral hospital because of severe anemia due to gastrointestinal bleeding in December 2005. He was then transferred to our institute with a diagnosis of a tumor of the head of the pancreas with duodenal invasion in January 2006. No abnormalities were revealed except for anemia in laboratory data including CEA and CA19-9. Gastrointestinal endoscopy revealed bleeding at the duodenum. Computed tomography also demonstrated a heterogenous mass at the pancreatic head and suspected invasion to the duodenal wall. Ultrasonography showed a huge mass at the pancreatic head with a mixture of high and low echoic areas. Pylorous-preserving pancreatoduodenectomy was performed. The pancreatic tumor was soft and had invaded to the duodenum. The pathological diagnosis was a hemolymphangioma of the pancreas invaded to the duodenum. His postoperative course was uneventful and he was discharged on the 26th d after surgery. Hemolymphangioma of the pancreas is a very rare benign tumor. In a literature review until March 2008, we found five case reports. Major symptoms are abdominal pain and distension due to the enlarged tumor. However, we experienced a case of hemolymphangioma of the pancreas with gastrointestinal bleeding due to invasion to the duodenum. This disease is a very rare entity, but should be considered when patients have gastrointestinal bleeding.
Anaplastic carcinoma associated with a mucinous cystic neoplasm of the pancreas during pregnancy: Report of a case and a review of the literature
Kenichi Hakamada, Takuya Miura, Akitoshi Kimura, Masaki Nara, Yoshikazu Toyoki, Shunij Narumi, Mutsuo Sasak
World Journal of Gastroenterology , 2008,
Abstract: Oncogenesis of anaplastic carcinoma of the pancreas is a subject of controversy, because it shows sarcomatous nature with extremely poor prognosis. We herein report an unusual case of anaplastic carcinoma occurring with a recurrent mucinous cystic neoplasm in a 38-year-old female. A 10-cm retroperitoneal cystic mass was pointed out in the first pregnancy and a probable diagnosis of mucinous cystic neoplasm was made in October 2000. She refused surgery first and delivered her baby uneventfully. During her second pregnancy in 2002, however, she presented hematemesis and underwent urgent distal pancreatectomy, splenectomy and partial resection of the gastric wall where the tumor perforated. A diagnosis of borderline-type mucinous cystic neoplasm with ovarian-like stroma was made. Nine months later, CT visualized a recurrent cystic tumor near the pancreatic stump, which was subsequently resected. Pathology revealed that the tumor was composed of two different components of borderline-type mucinous cystic neoplasm and anaplastic carcinoma. The latter was intensely positive for vimentin, CD68, p53 and focally for cytokeratin, suggesting both sarcomatous and carcinomatous differentiation. She survived four years after the second surgery without tumor recurrence. Although the origin of anaplastic carcinoma has not been determined yet, it should be remembered that anaplastic carcinoma can occur in association with mucinous cystic neoplasm of more benign histology.
An easier method for performing a pancreaticojejunostomy for the soft pancreas using a fast-absorbable suture
Kenichi Hakamada, Shunji Narumi, Yoshikazu Toyoki, Masaki Nara, Kenosuke Ishido, Takuya Miura, Norihito Kubo, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: AIM: To clarify the usefulness of a new method for performing a pancreaticojejunostomy by using a fast-absorbable suture material irradiated polyglactin 910, and a temporary stent tube for a narrow pancreatic duct with a soft pancreatic texture.METHODS: Among 63 consecutive patients with soft pancreas undergoing a pancreaticoduodenectomy from 2003 to 2006, 35 patients were treated with a new reconstructive method. Briefly, after the pancreatic transaction, a stent tube was inserted into the lumen of the pancreatic duct and ligated with it by a fast-absorbable suture. Another tip of the stent tube was introduced into the intestinal lumen at the jejunal limb, where a purse-string suture was made by another fast-absorbable suture to roughly fix the tube. The pancreaticojejunostomy was completed by ligating two fast-absorbable sutures to approximate the ductal end and the jejunal mucosa, and by adding a rough anastomosis between the pancreatic parenchyma and the seromuscular layer of the jejunum. The initial surgical results with this method were retrospectively compared with those of the 28 patients treated with conventional duct-to-mucosa anastomosis.RESULTS: The incidences of postoperative morbidity including pancreatic fistula were comparable between the two groups (new; 3%-17% vs conventional; 7%-14% according to the definitions). There was no mortality and re-admission. Late complications were also rarely seen.CONCLUSION: A pancreaticojejunostomy using an irradiated polyglactin 910 suture material and a temporary stent is easy to perform and is feasible even in cases with a narrow pancreatic duct and a normal soft pancreas.
Hemosuccus pancreaticus: Problems and pitfalls in diagnosis and treatment
Yoshikazu Toyoki, Kenichi Hakamada, Shunji Narumi, Masaki Nara, Keinosuke Ishido, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: Hemosuccus pancreaticus is a rare cause of intermittent upper gastrointestinal bleeding. We report two cases of hemosuccus pancreaticus with multiple episodes of upper gastrointestinal bleeding. The causes of hemorrhage were rupture of pseudoaneurysm of the splenic artery and bleeding from the wall of pancreatic pseudocyst. Interventional radiology is the first modality for early diagnosis and possible treatment of hemosuccus pancreaticus. When angiography shows no abnormal findings or interventional radiological therapy can not be successful, surgery should be considered without delay. Our patients herein underwent surgery without recurrence or sequelae. Intraoperative ultrasonography and pancreatoscopy were helpful modalities for confirming the source of hemorrhage and determining the cutting line of the pancreas. When we encounter intermittent upper gastrointestinal bleeding with an obscure source, hemosuccus pancreaticus should be included in differential diagnoses especially in patients with chronic pancreatitis, which would lead to a prompt and proper treatment.
Intraoperative ultrasound as an educational guide for laparoscopic biliary surgery
Kenichi Hakamada, Shunji Narumi, Yoshikazu Toyoki, Masaki Nara, Motonari Oohashi, Takuya Miura, Hiroyuki Jin, Syuichi Yoshihara, Michihiro Sugai, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: AIM: To analyze the efficacy of routine intraoperative ultrasound (IOUS) as a guide for understanding biliary tract anatomy, to avoid bile duct injury (BDI) after laparoscopic cholecystectomy (LC), as well as any burden during the learning period.METHODS: A retrospective analysis was performed using 644 consecutive patients who underwent LC from 1991 to 2006. An educational program with the use of IOUS as an operative guide has been used in 276 cases since 1998.RESULTS: IOUS was highly feasible even in patients with high-grade cholecystitis. No BDI was observed after the introduction of the educational program, despite 72% of operations being performed by inexperienced surgeons. Incidences of other morbidity, mortality, and late complications were comparable before and after the introduction of routine IOUS. However, the operation time was significantly extended after the educational program began (P < 0.001), and the grade of laparoscopic cholecystitis (P = 0.002), use of IOUS (P = 0.01), and the experience of the surgeons (P = 0.05) were significant factors for extending the length of operation.CONCLUSION: IOUS during LC was found to be a highly feasible modality, which provided accurate, real-time information about the biliary structures. The educational program using IOUS is expected to minimize the incidence of BDI following LC, especially when performed by less-skilled surgeons.
Des-gamma-carboxy prothrombin as an important prognostic indicator in patients with small hepatocellular carcinoma
Kenichi Hakamada, Norihisa Kimura, Takuya Miura, Hajime Morohashi, Keinosuke Ishido, Masaki Nara, Yoshikazu Toyoki, Shunji Narumi, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: AIM: To clarify the effect of a high des-gamma-carboxy prothrombin (DCP) level on the invasiveness and prognosis of small hepatocellular carcinoma.METHODS: Among 142 consecutive patients with known DCP levels, who underwent hepatectomy because of hepatocellular carcinoma, 85 patients met the criteria for small hepatocellular carcinoma, i.e. one ≤ 5 cm sized single tumor or no more than three ≤ 3 cm sized tumors.RESULTS: The overall survival rate of the 142 patients was 92.1% for 1 year, 69.6% for 3 years, and 56.9% for 5 years. Multivariate analysis showed that microscopic vascular invasion (P = 0.03) and serum DCP ≥ 400 mAU/mL (P = 0.02) were independent prognostic factors. In the group of patients who met the criteria for small hepatocellular carcinoma, DCP ≥ 400 mAU/mL was found to be an independent prognostic factor for recurrence-free (P = 0.02) and overall survival (P = 0.0005). In patients who did not meet the criteria, the presence of vascular invasion was an independent factor for recurrence-free (P = 0.02) and overall survivals (P = 0.01). In 75% of patients with small hepatocellular carcinoma and high DCP levels, recurrence occurred extrahepatically.CONCLUSION: For small hepatocellular carcinoma, a high preoperative DCP level appears indicative for tumor recurrence. Because many patients with a high preoperative DCP level develop extrahepatic recurrence, it is necessary to screen the whole body.
Generalized Hamiltonian Formalism of (2+1)-Dimensional Non-Linear $σ$-Model in Polynomial Formulation
Toyoki Matsuyama
Physics , 1998, DOI: 10.1007/s100529901050
Abstract: We investigate the canonical structure of the (2+1)-dimensional non-linear $\sigma$ model in a $polynomial$ formulation. A current density defined in the non-linear $\sigma$ model is a vector field which satisfies a $formal$ flatness (or pure gauge) condition. It is the polynomial formulation in which the vector field is regarded as a dynamical variable on which the flatness condition is imposed as a constraint condition by introducing a Lagrange multiplier field. The model so formulated has gauge symmetry under a transformation of the Lagrange multiplier field. We construct the generalized Hamiltonian formalism of the model explicitly by using the Dirac method for constrained systems. We derive three types of the pre-gauge-fixing Hamiltonian systems: In the first system, the current algebra is realized as the fundamental Dirac Brackets. The second one manifests the similar canonical structure as the Chern-Simons or BF theories. In the last one, there appears an interesting interaction as the dynamical variables are coupled to their conjugate momenta via the covariant derivative.
Resection of a locally advanced hilar tumor and the hepatic artery after stepwise hepatic arterial embolization: A case report
Takuya Miura, Kenichi Hakamada, Takashi Ohata, Shunji Narumi, Yoshikazu Toyoki, Masaki Nara, Keinosuke Ishido, Motonari Ohashi, Harue Akasaka, Hiroyuki Jin, Norihito Kubo, Shuichi Ono, Hiroshi Kijima, Mutsuo Sasaki
World Journal of Gastroenterology , 2008,
Abstract: We herein report a case of a hilar tumor with extensive invasion to the proper hepatic artery, which was successfully treated with a radical resection in a 57-year-old female patient after a stepwise hepatic arterial embolization. She underwent right colectomy and partial hepatectomy for advanced colon cancer two years ago and radiofrequency ablation therapy for a liver metastasis one year ago, respectively. A recurrent tumor was noted around the proper hepatic artery with invasion to the left hepatic duct and right hepatic artery 7 mo previously. We planned a radical resection for the patient 5 mo after the absence of tumor progression was confirmed while he was undergoing chemotherapy. To avoid surgery-related liver failure, we tried to promote the formation of collateral hepatic arteries after stepwise arterial embolization of the posterior and anterior hepatic arteries two weeks apart. Finally, the proper hepatic artery was occluded after formation of collateral flow from the inferior phrenic and superior mesenteric arteries was confirmed. One month later, a left hepatectomy with hepatic arterial resection was successfully performed without any major complications.
A Mathematical Model with Modified Logistic Approach for Singly-Peaked Population Processes
Ryoitiro Huzimura,Toyoki Matsuyama
Physics , 1999,
Abstract: When a small number of individuals of organism of single species is confined in a closed space with limited amount of indispensable resources, their breading may start initially under suitable conditions, and after peaking, the population should go extinct as the resources are exhausted. Starting with the logistic equation and assuming that the carrying capacity of the environment is a function of the amount of resources, a mathematical model describing such pattern of population change is obtained. An application of this model to typical population records, that of deer herds by Scheffer (1951) and O'Roke and Hamerstrome (1948), yields estimations of the initial amount of indispensable food and its availability or nutritional efficiency which were previously unspecified.
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