A two-phase model of collective memory decay with a dynamical switching point.

Public memories of significant events shared within societies and groups have been conceptualized and studied as collective memory since the 1920s. Thanks to the recent advancement in digitization of public-domain knowledge and online user behaviors, collective memory has now become a subject of rigorous quantitative investigation using large-scale empirical data. Earlier studies, however, typically considered only one dynamical process applied to data obtained in just one specific event category. Here we propose a two-phase mathematical model of collective memory decay that combines exponential and power-law phases, which represent fast (linear) and slow (nonlinear) decay dynamics, respectively. We applied the proposed model to the Wikipedia page view data for articles on significant events in five categories: earthquakes, deaths of notable persons, aviation accidents, mass murder incidents, and terrorist attacks. Results showed that the proposed two-phase model compared favorably with other existing models of collective memory decay in most of the event categories. The estimated model parameters were found to be similar across all the event categories. The proposed model also allowed for detection of a dynamical switching point when the dominant decay dynamics exhibit a phase shift from exponential to power-law. Such decay phase shifts typically occurred about 10 to 11 days after the peak in all of the five event categories.

A mechanically adaptive hydrogel with a reconfigurable network consisting entirely of inorganic nanosheets and water.

Although various biomimetic soft materials that display structural hierarchies and stimuli responsiveness have been developed from organic materials, the creation of their counterparts consisting entirely of inorganic materials presents an attractive challenge, as the properties of such materials generally differ from those of living organisms. Here, we have developed a hydrogel consisting of inorganic nanosheets (14 wt%) and water (86 wt%) that undergoes thermally induced reversible and abrupt changes in its internal structure and mechanical elasticity (23-fold). At room temperature, the nanosheets in water electrostatically repel one another and self-assemble into a long-periodic lamellar architecture with mutually restricted mobility, forming a physical hydrogel. Upon heating above 55 °C, the electrostatic repulsion is overcome by competing van der Waals attraction, and the nanosheets rearrange into an interconnected 3D network of another hydrogel. By doping the gel with a photothermal-conversion agent, the gel-to-gel transition becomes operable spatiotemporally on photoirradiation.

Laparoscopy-assisted combined resection for synchronous gastric and colorectal cancer: report of three cases.

In gastric cancer patients, the most common form of synchronous cancer is colorectal cancer. To reduce the invasiveness of the resection, a laparoscopy-assisted combined resection was performed in three patients with synchronous gastric and colorectal cancer. Although all gastric lesions were in the early stages, two colorectal lesions were advanced cases. In all cases, the laparoscopic gastric resection and reconstruction was performed first, followed by the colorectal resection. In the case of right-side colon cancer in addition to gastric cancer, it was relatively easy to perform the combined resection with lymph node dissection sharing the same ports used for the gastrectomy, although we needed an additional port. In one case, in which rectal cancer was present in addition to gastric cancer located in the upper portion of the stomach, a totally laparoscopic proximal gastrectomy was combined with a laparoscopy-assisted low anterior resection, leaving only a lower abdominal minilaparotomy wound. All patients quickly returned to normal activity without remarkable complications, with the exception of a wound infection in one patient. With a mean follow-up of 30.7 months, all patients survived without any sign of recurrence. This procedure represents a feasible option for minimally invasive treatment of synchronous gastric and colorectal cancer.

Laparoscopic function-preserving surgery for early gastric cancer in the upper third of the stomach: vagus-sparing proximal gastrectomy with side-to-side esophagogastric-tube anastomosis.

OBJECTIVE: Proximal gastrectomy with an anti-reflux procedure has been a treatment option for gastric cancer in the upper third of the stomach. For early gastric cancer, laparoscopic function-preserving gastrectomy with limited lymphadenectomy can be performed. Objective of this study was to develop a new surgical technique for gastric cancer in the upper third of the stomach. METHODS: We present here our totally laparoscopic proximal gastrectomy with vagus-sparing lymphadenectomy and gastric-tube reconstruction. Six patients (five males and one female; mean age 74 years) with gastric cancer in the upper third of the stomach underwent the procedure. Detailed operative procedure and preliminary results were presented. RESULTS: We have successfully performed the procedure with no conversion to open surgery. The mean operative time and blood loss were 413 minutes and 85 mL. No intraoperative and postoperative complications occurred except for reflux esophagitis in one patient. At the mean follow up of 25 months, all patients were alive without any sign of recurrence. CONCLUSION: Although long-term follow up and a larger number of patients are required to evaluate functional outcomes and oncological adequacy, our new technique provides a minimally invasive surgical option for early gastric cancer in the cardiac area.

Laparoscopy-assisted resection of an appendiceal mucinous cystadenoma.

We present a 48-year-old man with a complaint of dull right-lower abdominal pain who was diagnosed with mucocele of the appendix. He underwent laparoscopy-assisted resection of the tumor. In the procedure, the entire right colon was freed from the retroperitoneal structures without rupturing the tumor; and ileocecal resection and anastomosis were performed extracorporeally. The pathological diagnosis of the tumor was mucinous cystadenoma of the appendix, measuring 9.0 cm × 8.0 cm × 4.0 cm. The postoperative course was uneventful, and he had no recurrent disease at a 2-year follow up. When resecting an appendiceal mucinous tumor laparoscopically, it is essential (1) to keep the tumor intact during manipulation, and to use a wound-protecting device when delivering the lesion; (2) to consider the extent of tumor resection with a negative surgical margin as well as prophylactic lymph node dissection in cases of suspected adenocarcinoma, even though the oncological adequacy of the laparoscopic procedure for carcinoma remains to be elucidated; and (3) to check whether any mucinous fluid has accumulated in the abdominal cavity, which represents an indication for open surgery.

[A case of advanced gastric cancer with a tumor embolus in the portal vein successfully treated with TS-1 and CDDP].

A 71-year-old man was admitted to our hospital in February 2002 with a diagnosis of advanced gastric cancer with a tumor embolus in the portal vein. TS-1 (120 mg/day) was administered orally daily for 21 days, and CDDP (90 mg/day) was infused intravenously on day 8. After 1 course of this regimen, medication was discontinued in accordance with the patient's request. The patient was readmitted with a history of tarry stools in July 2003. Despite no cancer treatment for almost 1.5 years, the primary lesion and the metastatic lymph nodes had decreased significantly in size and the tumor embolus in the portal vein had disappeared completely on the CT scan. He was therefore treated with TS-1 alone (120 mg/day) under a 4-weeks-on and 2-weeks-off regimen. After 1 course of TS-1 administered alone, the primary lesion showed a further significant decrease in size as viewed by GI endoscopy, and biopsies did not reveal any evidence of malignancy.

Matrix metalloproteinase inhibitor, marimastat, decreases peritoneal spread of gastric carcinoma in nude mice.

Marimastat, a matrix metalloproteinese inhibitor, was examined for the ability to prevent peritoneal dissemination of a human gastric cancer xenograft, TMK-1. Even with novel approaches such as molecular targeting of cancer chemotherapy, peritoneal dissemination of gastric cancer has little sensitivity to anticancer drugs, and it is impossible to inhibit its growth completely. Intraperitoneal injection of TMK-1 into nude mice at 5 x 10( 5) cells / body resulted in carcinomatous peritonitis that mimicked clinical cases. Continuous administration of marimastat (18 mg / kg / day) from 24 h after the tumor inoculation successfully inhibited the growth of peritoneal dissemination nodules. Combined administration of marimastat (18 mg / kg / day) and mitomycin C (MMC, 2 mg / kg) showed synergistic inhibition of growth of peritoneal dissemination, being superior to MMC alone (2 mg / kg). Although marimastat alone could not increase survival time with statistical significance, combined administration of marimastat and MMC had a survival benefit with statistical significance. The combination of marimastat and MMC increased the preventive effect on peritoneal dissemination. Marimastat seems to be a candidate for the prevention of peritoneal spread of gastric carcinoma.