Volatile and nonvolatile selective switching of a photo-assisted initialized atomic switch.

A photo-assisted atomic switch, which has a photoconductive molecular layer in a gap of about 20 nm between an Ag2S electrode and a Pt electrode, is set to a conventional gap-type atomic switch operation mode by light irradiation with the application of a small bias that precipitates Ag atoms from an Ag2S electrode. After this initialization, the switch operates only with application of a bias. In this study, we also found that after the set-operation a photo-assisted initialized atomic switch shows different switching modes depending on the bias range, i.e., volatile switching when the applied bias is smaller than the threshold bias, and nonvolatile switching when the applied bias is larger than the threshold bias. These characteristics can be useful in reconfiguring a circuit such as in neural computing systems.

Quantized conductance atomic switch.

A large variety of nanometre-scale devices have been investigated in recent years that could overcome the physical and economic limitations of current semiconductor devices. To be of technological interest, the energy consumption and fabrication cost of these 'nanodevices' need to be low. Here we report a new type of nanodevice, a quantized conductance atomic switch (QCAS), which satisfies these requirements. The QCAS works by controlling the formation and annihilation of an atomic bridge at the crossing point between two electrodes. The wires are spaced approximately 1 nm apart, and one of the two is a solid electrolyte wire from which the atomic bridges are formed. We demonstrate that such a QCAS can switch between 'on' and 'off' states at room temperature and in air at a frequency of 1 MHz and at a small operating voltage (600 mV). Basic logic circuits are also easily fabricated by crossing solid electrolyte wires with metal electrodes.

Forming and switching mechanisms of a cation-migration-based oxide resistive memory.

We report detailed current-voltage and current-time measurements to reveal the forming and switching behaviors of Cu/Ta(2)O(5)/Pt nonvolatile resistive memory devices. The devices can be initially SET (from the OFF state to the ON state) when a low positive bias voltage is applied to the Cu electrode. This first SET operation corresponds to the first formation of a metal filament by inhomogeneous nucleation and subsequent growth of Cu on the Pt electrode, based on the migration of Cu ions in the stable Ta(2)O(5) matrix. After the forming, the device exhibits bipolar switching behavior (SET at positive bias and RESET (from the ON state to the OFF state) at negative bias) with increasing the ON resistance from a few hundred Ω to a few kΩ. From the measurements of the temperature stability of the ON states, we concluded that the RESET process consists of the Joule-heating-assisted oxidation of Cu atoms at the thinnest part of the metal filament followed by diffusion and drift of the Cu ions under their own concentration gradient and the applied electric field, disconnecting the metal filament. With ON resistances of the order of a few kΩ, the SET and RESET operations are repeated by the inhomogeneous nucleation and the Joule-heating-assisted dissolution of a small filament on a remaining filament. This switching model is applicable to the operation of cation-migration-based resistive memories using other oxide materials.

Investigation of Ag and Cu Filament Formation Inside the Metal Sulfide Layer of an Atomic Switch Based on Point-Contact Spectroscopy.

The atomic switches have attracted wide attention owing to their applications in nonvolatile electric devices. The atomic switch is operated by the formation and dissipation of a metallic filament inside a metal sulfide film, which is controlled by a solid electrochemical reaction. Although the metallic filament is considered to consist of metal atoms, the chemical species of the metallic filament are difficult to be identified due to challenges in observing the metallic filament inside the solid. In this study, we report the investigation on the metallic filament in the atomic switch with metal sulfide based on point-contact spectroscopy (PCS). By cooling the atomic switch, the switch voltage increased to 1 V, which allowed for the PCS measurement. The PCS revealed that the metallic filament was composed of Ag atoms in the case of the Pt/Ag2S/Ag atomic switch. We applied this technique to the Pt/Cu2S/Ag and Pt/Ag2S/Cu atomic switches to uncover the formation process of the metallic filament. In both atomic switches, the chemical species of the metallic filament were Ag. The metal atoms were supplied from both the metal electrode and the sulfide layer.

Growth suppression of subcutaneously inoculated hepatic tumors after injection of syngeneic liver cells into the subcutaneous tissue of rats.

One week after the sc injection of minced tissues of the livers, kidneys, or spleens of W, Donryu, and MP rats into the left back of syngeneic rats, ascites-type tumor cells derived from rat hepatoma (AH 130) or Walker carcinosarcoma cells derived from rat breast tumor were inoculated sc into the right back. Ascites hepatoma cell growth was slowest in the group given the liver preparation, whereas no significant difference was noted in the growth of Walker carcinosarcoma in all groups. The results were similar in all strains.

Highly diverse TTV population in infants and their mothers.

Infants born to serum HCV-positive 12 mothers were enrolled in the study. Nucleotide sequences amplified by primers deduced from a noncoding region were compared between mothers and their infants. The rates for detection of serum TTV in 12 mothers and their infants were 10/12 (83%) and 9/12 (75%), respectively. Serum TTV DNA was not detected in any infant at 1 month of age, but was detected for the first time between 1.5 and 8 months after birth. Positivity persisted thereafter throughout the follow-up period. In seven randomly selected mother-infant pairs, intrahost TTV heterogeneity was lower in infants than in mothers. Furthermore, one of seven mother-infant pairs showed a high degree of similarity (98.7-100%) in all clones, while in four infants, all nucleotide sequences differed by >10% from those of their mothers. However, the degree of homology in the two mother-infant pairs was 89-98.7% in family 2 and 88.1-99.4% in family 5. In the present study, with only one exception, it was shown that TTV from infants is not identical to TTV from mothers. The mechanism is discussed briefly in this paper.

Influence of flavonoids on cell cycle phase as analyzed by flow-cytometry.

Flavonoids were previously reported to have cytostatic activity in vitro and in vivo. In the present study each phase of the cell cycle was observed by flow-cytometry after HCT-15 cells had been cultured with flavonoids for 2 days. In the control group, two peaks were observed on the histogram, the first peak representing double strands of DNA, and the second, tetra strands. Chalcone, which is known to be a precursor of all flavonoids, seemed to block the passage from S to G2 and M phase. Flavonone, which is freely transformed into chalcone in vivo, showed a similar histogram as chalcone. Among the anthocyanins most effective in suppressing the tumor cell growth, cyanin and pelargonidin made a mild rise between the 1st and 2nd peak suggesting block between G1 and S phase. Delphinidin gave a high percent of cells in G1 phase, suggesting prolongation of G1 phase. When quercetin or kaempherol, both of which are flavonols were added to the culture, the second peak rose significantly, indicating a block between G2 and M phases. Thus, the site of these cytostatic agents seems to differ depending on the kind of flavonoid.

Antitumor effect of anthocyanin fractions extracted from red soybeans and red beans in vitro and in vivo.

Many bioflavonoids extracted from petals of higher plants and from fruit rinds, as well as purified flavonoids, have been reported to have antitumor effects in vitro and in vivo. Bioflavonoids extracted from red soybeans are mostly cyanin conjugated with glucose and rhamnose, whereas bioflavonoids of red beans are cyanin conjugated with rhamnose as revealed by thin-layer chromatogram. Flavonoids extracted from red soybeans were effective in inhibiting the growth of HCT-15 cells in vitro. On the other hand, flavonoids from red beans were not effective, although their hydrolyzed sugar-free forms were growth inhibitory. Sugar-bonded bioflavonoids extracted from both red soybeans and red beans were effective in prolonging the survival of Balb/C mice bearing syngeneic tumor-Meth/A cells, when they were dissolved in drinking water and given at a dose of approximately 500 micrograms/mouse/day.

Flavonoid-mediated tumor growth suppression demonstrated by in vivo study.

Many of flavonoids as well as bioflavonoids extracted from higher plants, which were earlier revealed to have tumor cell growth suppression activity in vitro, were examined for their effect on tumors in vivo. Balb/c mice were inoculated i.p. with syngeneic tumor cells, meth/a, and then provided with flavonoids dissolved in their drinking water during the course of their survival time. Many flavonoids were effective in prolonging the survival period. Furthermore, flavonoids that did not show suppressive activities in the in vitro experiments were effective in the in vivo assay. The data suggested that sugar bonded to the A ring, which suppresses tumor growth inhibition in vitro, plays an important role. Many aglycones that were effective in the in vitro assay on the tumor growth suppression were not effective in the in vivo assay. The reason for this seems to be that most aglycones are unstable and thus break down in vivo. No acute nor chronic toxicity of flavonoids was observed in the mice.

[Postoperative immunochemotherapy for gastric carcinoma with peritoneal dissemination--the effects with the combination of CDDP, 5-FU and lentinan].

Three cases of postoperative gastric cancer with peritoneal dissemination were treated by combined administration of CDDP, 5-FU and Lentinan. CDDP was given intravenously at 20 mg/body on days one to five. At the same time, 5-FU was infused continuously 250-500 mg/body per day for more than two weeks, and Lentinan was given at a dose of 2 mg per week. Two courses were repeated every 3 weeks. This combination treatment was very effective because the median survival rate for the three patients was 13 months with no sign of recurrence, and the quality of life has been good.

[Clinical effects of postoperative immunochemotherapy with a combination of 5-FU, CDDP and lentinan for stage IVb gastric carcinoma and long-term pharmacokinetic studies on CDDP and 5-FU].

Eleven patients with postoperative-stage IVb gastric cancer were treated by combined administration of CDDP, 5-FU and Lentinan. CDDP was given intravenously at 20 mg/body on days one to five. At the same time, 5-FU was continuously administered 250 or 500 mg/body/day via the central venous catheter for more than two weeks, while Lentinan was given at the dose of 2 mg per week. Two courses were repeated every 3 weeks. The mean response duration and survival period for the eleven patients were 13 and 21 months, respectively, and one- and two year survival rates were 82% and 27%. This combination therapy was thus considered to be very effective. Next, the pharmacokinetics of long-term CDDP and 5-FU was studied. Our method could maintain the optimum serum concentration of total CDDP. Furthermore, the continuous infusion of 5-FU at a daily dose of 250 mg/day could sufficiently maintain the effective plasma concentration, although its peak fluctuated over time. Thus, in the plasma level of 5-FU in patients in poor condition requires periodic measurement.

[Using CEA for diagnostic, therapeutic and prognostic evaluation in colorectal cancers].

Serum CEA measured by radioimmunoassay was studied in 63 colorectal cancer patients. The present study was designed to assess the usefulness of serum CEA assay on the diagnosis of colorectal cancer at various stages and in the care of prognosis. CEA was examined before and after surgery at appropriate intervals. Serum CEA test was positive (over 2.5 ng/ml) in 10.5% of the 19 patients with Dukes stage A, in 61.9% of 21 patients with Dukes stage B, and in 78.3% of 23 patients with Dukes stage C. Curative resection was able to perform in all of colorectal cancer patients with values of less than 2.5 ng/ml, in 75% of them with values of 2.5-10 ng/ml and in 45% of them with values of greater than 10 ng/ml. High serum CEA levels decreased to normal levels within 1-3 months after curative resection. High CEA levels were observed before the secondary operation in 4 out of 5 patients who underwent reoperation because of the evidence of recurrence. CEA decreased to normal levels in 3 of them and increased to 500 ng/ml in 1 case. In the last case CEA sustained high levels until the death due to metastasis to the lung and lymph nodes.

[Clinical and experimental study of the host defense mechanism from the aspect of tumor immunology].

The host defense mechanism was fundamentally and clinically investigated from the aspect of tumor immunology. The behavior of macrophages in the immune systems of experimental animals demonstrated different patterns of response in the bone marrow, peritoneal cavity and spleen, respectively. It was doubtless that the spleen occasionally exerted an immunosuppressive action. Ectopic immunization of syngeneic rats with normal liver cells resulted in specific inhibition of the growth of the tumor cells (AH-I30) derived from liver. This seemed to strongly suggest a local immune response. In clinical cases, the host defense mechanism was found to collapse due to surgical intervention, malnutrition and immunosuppressive substances. The relation between complements and host defense mechanism has been controversial. Our studies indicated the serum complement level to be the most reliable parameter for understanding the host defense mechanism. Since the combination of immunostimulants and anticancer drugs is likely to induce anticancer drugs to exert an adverse effect depending on the time of such combination, timing of combined administration of drugs should be chosen with great care.

[A case of retroperitoneal mucinous cystadenoma of borderline malignancy].

Surgical experience of a rare case of malignant retroperitoneal cyst is reported. A 41-year-old female was admitted on Feb. 26, 1986, complaining of left lower abdominal tumor and mild abdominal pain. She underwent complete removal of an abdominal tumor located at the left flank lateral to the sigmoid colon on March 5. The tumor was well encapsulated, cystic and oval, 12 X 10 X 9 cm in size. Histologic feature of the tumor is classified as mucinous cystadenoma of low grade malignancy by WHO classification.

[Ogilvie's syndrome--a case report and review].

Ogilvie's syndrome is caused from functional obstruction of the colon without mechanical stenosis and also termed as pseudo-obstruction of the colon. This disease is seen in patient who has other causative distress. The pathogenesis of this rare entity is unknown but it is suspected that there may be an underlying autonomic disturbance which causes non-mechanical obstruction of the colon. Most of the case reports on Ogilvie's syndrome have appeared in European and North American journals but are extremely rare in Japan. Some cases which have been categorized "spastic ileus" may be included in this syndrome. We recently experienced a patient with cerebral infarction who developed non-mechanical obstruction of the colon. This patient was treated successfully with an exploratory laparotomy and sigmoidostomy. It is considered that early diagnosis is an essential part of the initial management of this syndrome. Conservative treatment is indicated for most of the patients but a definitive surgical therapy is occasionally necessary.