Investigation on the formation process of metal atomic filament for metal sulfide atomic switches by electrical measurement.

We have studied the formation process of the metal atomic filament for metal sulfide atomic switches by electrical measurement. The switching between ON and OFF states of the atomic switch is controlled by the application of the bias voltage for the atomic switches. The SET (OFF â†’ ON) and RESET (ON â†’ OFF) voltages were investigated for the atomic switch where the Ag2S or Cu2S layer were sandwiched between the Pt and Ag or Cu electrodes. The SET and RESET voltages of the Ag/Cu2S/Pt and Cu/Ag2S/Pt were close to those of the Ag/Ag2S/Pt atomic switch, and different from those of the Cu/Cu2S/Pt atomic switch. These results indicated that the dominant chemical species of the making and breaking part of the metal filament was Ag, and that the source of the metal filament was both the sulfide layer and the metal electrode.

Stretch dependent electronic structure and vibrational energy of the bipyridine single molecule junction.

We have studied the stretch dependence of the electronic structure and vibrational energy for the 4,4'-bipyridine (BPY) single molecule junction, which was fabricated by the mechanically controllable break junction (MCBJ) using the highly stable nano MCBJ electrodes. The electronic structure and vibrational energy of the single molecule junction were studied by the current-voltage (I-V) curve and surface enhanced Raman scattering (SERS), respectively. The simultaneous SERS and I-V curve measurements revealed the lowest unoccupied molecular orbital (LUMO) and vibrational energy of the C-C stretching mode decreased with an increase in the metal-molecule distance. The molecular orbital energy shift and vibrational energy shift can be explained by the change in the degree of the hybridization of molecular and metal orbitals.

Impact of junction formation processes on single molecular conductance.

We have investigated the electric conductance and atomic structure of single molecular junctions of pyrazine (Py), 4,4'-bipyridine (BiPy), fullerene (C60), and 1,4-diaminobutane (DAB). The single molecular junctions were fabricated by breaking Au contacts between an Au tip and the Au electrode surface in the presence of the target molecules (breaking process) or approaching the Au tip to the Au electrode surface covered by the molecules (making process). In the making process, no major conductance state was observed in the conductance histogram for DAB, while single conductance states were observed for the π-conjugated molecules of Py (10 mG0, G0∼ 77.45 µΩ-1), BiPy (3 mG0), and C60 (5 mG0). In contrast to the making process, two major conductance states were observed for Py (1 mG0 and 0.3 mG0), BiPy (0.6 mG0 and 0.2 mG0), and C60 (30 mG0 and 3 mG0) in the breaking process. The observed conductance behavior could be explained by the characters of the anchoring unit of molecules. In the making process, anchoring of molecules cannot be established by the point contact between the Au electrode and the localized lone pair of the N atom of DAB, Py, and BiPY, while molecules anchor on the Au electrode by using the plane-like contact between the Au electrode and the delocalized π electrons in the aromatic ring of Py, BiPY, and C60, which explains the difference in the observed conductance behavior between DAB and the π conjugated molecules of Py, BiPY, and C60 in the making process. In the breaking process, the delocalized π-electrons of Py, BiPY, and C60 can make a contact with the Au electrode surface and the lone pair on the N atom of DAB as well as Py and BiPY can bind to Au atoms, and therefore, single molecular junctions were formed for all systems. The present results indicate that the π-plane is important for making metal-molecule contacts and for the formation of the single molecular junction in the making process.

Chemically induced topological zero mode at graphene armchair edges.

The electronic and magnetic properties of chemically modified graphene armchair edges are studied using a combination of tight-binding calculations, first-principles modelling, and low temperature scanning tunneling microscopy (STM) experiments. The atomically resolved STM images of the hydrogen etched graphitic edges suggest the presence of localized states at the Fermi level for certain armchair edges. We demonstrate theoretically that the topological zero-energy edge mode may emerge at armchair boundaries with asymmetrical chemical termination of the two outermost atoms in the unit cell. We particularly focus our attention on armchair edges terminated by various combinations of the hydrogen (H, H2) and methylene (CH2) groups. The inclusion of the spin component in our calculations reveals the appearance of π-electron-based magnetism at the armchair edges under consideration.

The combined application of the contrast-to-noise index and 80 kVp for cardiac CTA scanning before atrial fibrillation ablation reduces radiation dose exposure.

INTRODUCTION: To compare the radiation dose, diagnostic accuracy, and the resultant ablation procedures using 80 and 120-kVp cardiac computed tomography angiography (CCTA) protocols with the same contrast-to-noise ratio in patients scheduled for atrial fibrillation (AF) ablation. METHODS: This retrospective study was performed following institutional review board approval. We divided 140 consecutive patients who had undergone CCTA using a 64-MDCT scanner into two equal groups. Standard deviation (SD) of the CT number was set at 25 Hounsfield units (HU) for the 120-kVp protocol. To facilitate a reduction in radiation dose it was set at 40 HU for the 80 kVp protocol. We compared the two protocols with respect to the radiation dose, the diagnostic accuracy for detecting left atrial appendage (LAA) thrombi, matching for surface registration, and the resultant ablation procedures. RESULTS: At 120 kVp, the dose length product (DLP) was 2.2 times that at 80 kVp (1269.0 vs 559.0 mGy cm, p < 0.01). The diagnostic accuracy for thrombus detection was 100% using both protocols. There was no difference between the two protocols with respect to matching for surface registration. The protocols did not differ with respect to the subsequent time required for the ablation procedures and the ablation fluoroscopy time, and the radiation dose (p = 0.54, 0.33, and 0.32, respectively). CONCLUSION: For the same CNR, the DLP at 80 kVp (559.0 mGy cm) was 56% of that delivered at 120 kVp (1269.0 mGy cm). There was no reduction in diagnostic accuracy. IMPLICATIONS FOR PRACTICE: Maintaining CNR allows for a reduction in the radiation dose without reducing the image quality.

Tolerance to Stretching in Thiol-Terminated Single-Molecule Junctions Characterized by Surface-Enhanced Raman Scattering.

We investigated the change in the metal-molecule interaction in a 1,4-benzenedithiol (BDT) single-molecule junction using a combination of surface-enhanced Raman scattering spectra and current-voltage curves. During the stretching process, the conductance of the junction systematically decreased, accompanied by an increase in the vibrational energy of the CC stretching mode. By analyzing the current-voltage curves and Raman spectra, we found that the interaction between the π orbital of BDT and the electronic states of Au was diminished by the orientation change of BDT during the stretching process. A comparison with a 4,4'-bipyridine single-molecule junction revealed that the reduction of coupling of the Au-S contacts was smaller than that of Au-pyridine contacts. Therefore, the electronic states originating from the contact geometry are responsible for the tolerance to the stretching of thiol-terminated molecular junctions.

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.

The effect of bonding of a CO molecule on the conductance of atomic metal wires.

We have measured the effect of bonding of a CO molecule on the conductance of Au, Cu, Pt and Ni atomic contacts at 4.2 K. When CO gas is admitted to the metal nanocontacts, a conductance feature appears in the conductance histogram near 0.5 of the quantum unit of conductance, for all metals. For Au, the intensity of this fractional conductance feature can be tuned with the bias voltage, and it disappears at high bias voltage (above approximately 200 mV). The bonding of CO to Au appears to be weakest, and associated with the formation of monatomic Au wire.

Effects of NMDA and MK-801 injected into the substantia nigra pars reticulata on jaw movements evoked by dopamine D1-/D2 receptor stimulation in the ventrolateral striatum: studies in freely moving rats.

The effects of NMDA and MK-801 injected into the substantia nigra pars reticulata on jaw movements evoked by dopamine D1/D2 receptor stimulation in the ventrolateral striatum were examined in freely moving rats, by using a magnet-sensing system combined with intracerebral drug microinjection technique. Bilateral injections of a mixture of SKF 82958 (5 microg) and quinpirole (10 microg), agonist at dopamine D1 and D2 receptors respectively, into the ventrolateral striatum elicited repetitive jaw movements. Bilateral injections of NMDA (0.01 and 0.05 microg/0.2 microl in each side) into the substantia nigra pars reticulata, which alone did not produce jaw movements, reduced the repetitive jaw movements evoked by the dopamine D1/D2 receptor agonist mixture in a dose-dependent manner. Injection of the non-competitive NMDA receptor antagonist, MK-801 (0.1 and 0.5 microg/0.2 microl in each side), into the substantia nigra pars reticulata, which alone did not produce jaw movements, prevented the dopaminergic jaw movements in a dose-dependent manner. Moreover, other behaviors such as grooming, rearing, yawning, vacuous chewing, and locomotor activity that occurred after injections of the dopamine receptor agonist mixture were not significantly altered by the bilateral injections of NMDA or MK-801 into the substantia nigra pars reticulata. Given our previous results showing that both agonist and antagonist of GABA(A) receptors injected into the substantia nigra pars reticulata inhibit the jaw movements elicited by dopamine D1/D2 receptor stimulation in the ventrolateral striatum, the present results suggest that there are complex functional interactions between NMDA and GABA(A) receptors within the substantia nigra pars reticulata that may be responsible for the common profiles in the effects of NMDA and GABA(A) receptor agents.

Rat two-generation reproductive toxicity study of bisphenol A.

This study was conducted to determine the low-dose effects of bisphenol A (BPA) in a rat two-generation reproduction study. Groups of 25 male and 25 female Crj: CD (SD) IGS rats were given BPA at 0.2, 2, 20, or 200 microg/kg/day by gastric intubation throughout the study beginning at the onset of a 10- and 2-week premating period, in F0 males and females, respectively, and continuing through the mating, gestation, and lactation periods, for two generations. There were adult (F0, F1, F2) and postnatal day (PND) 22 (F1, F2) necropsies: the oldest F2 males and females being killed at postnatal weeks 7 and 14, respectively. No compound-related clinical signs or effects on body weight or food consumption were observed in any generation. There were no compound-related changes in surface righting reflex, negative geotaxis reflex, mid-air righting reflex, pinna detachment, incisor eruption, eye opening, testes descent, preputial separation, or vaginal opening in F1 and F2 generations, or behavior in the open field or water filled multiple T-maze in the F1 generation. No test compound-related changes in estrous cyclicity, copulation index, fertility index, number of implantations, gestation length, litter size, pup weight, pup sex ratio, pup viability, or other functional reproductive measures were noted in any generation. A few significant changes in the anogenital distance (AGD) per cube root of body weight ratio were found at 0.2 and 20 microg/kg in F1 males, at 2, 20, and 200 microg/kg in F1 females, and at 20 and 200 microg/kg in F2 females. However, the changes in the AGD were consistently small (within 5% of control values), and no continuous changes in the AGD or AGD/cube root of body weight ratio were detected. There were no compound-related changes in epididymal sperm counts or motility in F0 and F1 males. No compound-related necropsy findings or effects on organ weight including the reproductive organs were found in any generation. Histopathologic examinations revealed no evidence of compound-related changes in any organs including the reproductive organs of both sexes. The data indicate that oral doses of BPA of between 0.2 and 200 microg/kg over 2 generations did not cause significant compound-related changes in reproductive or developmental parameters in rats.

Comparative study of colorimetric method using diazotization reaction and high-performance liquid chromatographic method in determination of para-aminohippuric acid.

In this study, colorimetric method and high-performance liquid chromatographic (HPLC) method were improved and established, respectively, in order to minimize analytical errors in determination of para-aminohippuric acid (PAH) in rat urine and plasma. In terms of the colorimetric method, an operative step following addition of Tsuda reagent was modified as follows: after the addition of Tsuda reagent, reaction mixture was kept at 40 degrees C for 70 min before spectrophotometry. Linearities were observed both in the higher range of 0 and 2.5 to 12.5 micrograms and in the lower range of 0 and 100 to 1,000 ng per test tube, and its practical detection limit was 100 ng per test tube. In terms of HPLC method, using a reversed-phase column (Nucleosil 5 C18), PAH was separated by a mobile phase of acetonitrile/50 mM KH2PO4 (pH 2.8) = 9/95. Linearities were observed in the higher range of 0 and 10 ng to 2 micrograms and in the lower range of 0 and 1 to 10 ng per injection, and its practical detection limit was 1 ng per injection. These results denote that the above two methods are applicable to routine PAH determination. In addition, our HPLC method is considered to be applicable to microassay of PAH, because its sensitivity is more sensitive and minimization of volume system is more easily achieved as compared with the colorimetric method.

[Chronic toxicity study of AC-1370 sodium, an antibiotics, intravenously administered in rats].

A study on chronic toxicity of AC-1370 sodium (AC) in addition to recovery from its toxicity, was carried out using the rat. AC was administered to the rat through the tail vein in doses of 30, 100, 300 and 1000 mg/kg body weight/day, with the periods for administration and recovery being 26 and 13 weeks, respectively. The results obtained from the present study were as follows. In each group, neither death case nor fatal damage was observed throughout the whole process. In the group of 1000 mg/kg, the below findings were observed in one or both sexes: suppression in increase of body weight, increases in drunk amount of water, urinary volume and urinary excretions of electrolytes, degeneration in renal tubules and several correlated changes, tendency of anemia, changes in serum biochemical tests, and changes in each organ weight. In the group of 300 mg/kg, the above findings were observed slightly in comparison to the group of 1000 mg/kg. In the groups of 100 and 30 mg/kg, any changes suggesting the damages were not observed. In the recovery test, the group of 1000 mg/kg was found to be incompletely restored from the damages, with the partially residual damages being shown. In contrast, the group of 300 mg/kg showed to be almost restored from the damages. These results denotes that the maximal non-toxic dose of AC in this study is 100 mg/kg/day in long-term administration.

[Three-month oral subacute toxicity study of mofezolac (N-22) in rats].

A three-month oral subacute toxicity study of mofezolac (N-22), a non-steroidal anti-inflammatory agent, was performed using dose levels of 6, 20, 60 and 200 mg/kg in rats, and recovery was also assessed one month after withdrawal. 1. Toxic signs caused by N-22 administration, observed only in the 200 mg/kg group, were as follows: soiling around the mouth and/or nose, piloerection, anemia, diarrhea, emaciation and decreased spontaneous locomotor activity. Nine males and thirteen females in the 200 mg/kg group excreted bloody diarrhea and died of general exhaustion between weeks four and thirteen of study. 2. In the 200 mg/kg group, decrease in food consumption and suppression of body weight gain were noted in males from about week four and in females from about week six after initiation of administration, and increase in water consumption was noted in males from about week seven. 3. Urinary examination revealed a decline in urinary pH in males of the 20 mg/kg and above groups and elevation of urobilinogen levels in males of the 60 and 200 mg/kg groups. 4. Hematological examination showed decreases in erythrocyte count (RBC), hematocrit value (Ht) and hemoglobin concentration (Hb) and increase in reticulocyte rate in both sexes of the 200 mg/kg group and an increase in neutrophil rate in males of the 200 mg/kg group. 5. Biochemical examination demonstrated a decrease in chloride (Cl-) in males receiving the 20 mg/kg or above doses and a decrease in calcium (Ca++) in males of the 60 and 200 mg/kg groups. Moreover, there were decreases in cholinesterase (ChE) activity, total protein (TP) and albumin (Alb) values, as well as increases in blood urea nitrogen (BUN), uric acid (UA) and potassium (K+) in both sexes of the 200 mg/kg group, along with elevations in GOT and lactate dehydrogenase (LDH) activities in females of the 200 mg/kg group. 6. The absolute and/or relative organ weights for liver, kidneys, spleen and adrenals were increased in the 200 mg/kg group. 7. On pathological examination, perforating ulceration in the jejunum and ileum, turbid ascites, adhesion and inflammatory changes in capsules of the abdominal organs, splenomegaly, mesenteric lymph node hyperplasia and inflammatory changes in the thoracic cavity were observed in dead animals of the 200 mg/kg group. Similar pathological changes were observed in a few survival cases of the 200 mg/kg group. 8. After a one month recovery period, the above-mentioned changes had mostly recovered, indicating that they were reversible.(ABSTRACT TRUNCATED AT 250 WORDS)

[Three-month subacute oral toxicity study of mofezolac (N-22) in dogs].

Mofezolac (N-22) is a new developed analgesic and anti-inflammatory agent. A subacute oral toxicity test of N-22 was carried out at dose-levels of 0, 2, 6 and 20 mg/kg/day using male and female beagle dogs. Treatment for 3 months was followed by 1 month recovery period except in the case of both sexes receiving 20 mg/kg/day. The results obtained from the present study were as follows. 1. Observation of general conditions revealed vomiting, sporadic bloody feces, anemia, recumbency and hyposthenia in both sexes receiving 20 mg/kg/day. Anemia or erosion of tongue was observed in each female receiving 6 mg/kg/day. 2. Respectively 3 dogs of both sexes receiving 20 mg/kg/day died during dosing period. In these animals, perforating ulcers were observed in the pars pylorica ventriculi or duodenum, and loss of blood, peritonitis and aggravation of general exhaustion were considered as causes of death. 3. Body weight tended to decrease in both sexes receiving 20 mg/kg/day, and food and water consumption levels decreased in males receiving 2 mg/kg/day or above and females receiving 2 mg/kg/day. 4. Urinalysis demonstrated an increasing tendency for specific gravity of urine and a decreasing tendency for urine volume in males receiving 2 mg/kg/day or above. 5. Hematological examination showed decreases in red blood cell count and Hb concentration in males receiving 2 mg/kg/day or above, and in Ht values in males receiving 6 mg/kg/day or above. 6. Serum biochemical examination revealed decreases in total protein and albumin in both sexes receiving 20 mg/kg/day. 7. There were no remarkable changes in hepatic and renal function, ophthalmological findings or electrocardiogram. 8. In the organ weights, significant decrease in thymus weights was observed in the dead animals receiving 20 mg/kg/day. 9. Pathologically, the dead animals receiving 20 mg/kg/day were found to exhibit peritonitis with perforating ulcers in the pars pylorica ventriculi or duodenum. In the surviving animals of this group, scar ulcers in the pars pylorica ventriculi and small intestine were evident on necropsy, and histopathology revealed neutrophils infiltration and thrombosis in blood vessels in the thickened submucosal stomach tissues. Moreover, localized hepatocyte necrosis and intrasinusoidal cellular infiltration in liver, as well as interstitial cellular infiltration, degeneration and dilatation of the renal tubules in the kidney were observed. In females receiving 6 mg/kg/day, the changes in kidney were similar to those in surviving animals receiving 20 mg/kg/day, and male of the group showed atrophy of thymus.(ABSTRACT TRUNCATED AT 400 WORDS)

[Chronic toxicity study of ranitidine hydrochloride orally administered in rats].

Chronic toxicity of ranitidine hydrochloride, a new histamine H2-receptor antagonist, was studied using Sprague Dawley rats. Ranitidine was administered orally at dose levels of 30, 100, 300 and 1000 mg/kg/day for 26 or 53 weeks. In the 1000 mg/kg/day group, ten of 31 females died showing acute toxic signs. In the survived animals of this dose group, changes were observed, such as salivation, depression of body weight gain, increase in water consumption, increase in urinary Na and K excretion, increase in serum albumin content, increase in weights of the liver, kidneys and heart. Main histopathological findings were as follows: centrolobular or midzonal fat deposition in liver, increase in s-ER in hepatocytes, increase in foamy cells in lung and some slight degenerative changes occasionally seen in renal tubules. In the 300 mg/kg/day group, the changes similar to those in the 1000 mg/kg/day group were observed, however, the degree of these changes was more moderate. All of the above-mentioned findings were demonstrated to be reversible in recovery period for 8 weeks. In the 100 and 30 mg/kg/day groups, no remarkable changes were observed in both sexes. It was concluded that the maximum nontoxic dose of ranitidine hydrochloride was 100 mg/kg/day in male and female rats.

[Study on toxicity of halopredone acetate. (II). Subacute toxicity study in rats].

Halopredone acetate (THS-201), a synthetic corticosteroid, is expected to be used clinically for intra-articular injection because of its long-lasting activity in the synovial bursa. Subacute toxicity study was carried out on THS-201 by using Jcl: Wistar rats. THS-201 was subcutaneously administered to the rat in doses of 0.1, 0.5, 2.5 and 12.5 mg/kg/day, with the periods for administration and recovery being 3 and 2 months, respectively. Methylprednisolone acetate (MPA) was used for the positive control in dose of 0.5 mg/kg/day. In the group of THS-201 12.5 mg/kg, the below findings were observed: thinning of lumbar hair, swelling of injection site, suppression in body weight gain and decrease of food consumption. The lesions to lymphatic system were indicated by the examinations of peripheral blood, autopsy and histopathology. Slight changes in erythrocytic and biochemical values were seen, and foreign body granuloma was observed in injected subcutis. These findings, exception for lesion of injection site, were almost recovered after the 2 month-recovery period. In the group of THS-201 2.5 mg/kg, some of the changes were noted slightly. In the groups of THS-201 0.5 and 0.1 mg/kg, any toxic changes attributable to THS-201 were not observed. On the other hand, in the group of MPA 0.5 mg/kg, similar findings noted in THS-201 12.5 mg/kg group were observed, but these changes were recovered almost completely at the end of the 2 month-recovery period. It was concluded that the non-toxic dose and the defined toxic dose of THS-201 in this study were 0.5 and 2.5 mg/kg/day, respectively.

[Studies on screening for hard-of-hearing children by questionnaire. 2. Comparison of response rates to individual questions in 1-year-6-month-old children with normal hearing and hearing loss using a health screening questionnaire].

We report the results of studies on responses to questions on hearing impairment, comparing 165 school children whose hearing was diagnosed as normal at the time of admission to primary school and 37 children with hearing loss attending facilities for children with this disability. These children had been covered by similar surveys as part of the health screening for 1-year-6-month-old infants conducted by municipal authorities. Significant differences between the two groups were noted in the response rates to all questions on hearing. Similar differences were noted in the responses to questions on family history of hearing impairment. There were no significant differences in the incidences of asphyxia and jaundice at birth. The most striking differences were noted in the response rates to questions 6, 7, 8, 10, 11, 16, and 18. Most useful and universally valid in this survey were questions 8, 10 and 18 in addition to the question on whether or not parents suspected infantile hearing loss.

Note: wearable near-infrared spectroscopy imager for haired region.

A wearable optical topography system was developed that is based on near-infrared spectroscopy (NIRS) for observing brain activity noninvasively including in regions covered by hair. An avalanche photo diode, high voltage dc-dc converter, and preamplifier were placed in an electrically shielded case to be safely mounted on the head. Rubber teeth and a glass rod were prepared to clear away hair and reach the scalp. These devices realized for the first time a wearable NIRS imager for any region of the cortex. The activity in the motor cortex during finger tapping was successfully observed.

Highly conductive molecular junctions based on direct binding of benzene to platinum electrodes.

Highly conductive molecular junctions were formed by direct binding of benzene molecules between two Pt electrodes. Measurements of conductance, isotopic shift in inelastic spectroscopy, and shot noise compared with calculations provide indications for a stable molecular junction where the benzene molecule is preserved intact and bonded to the Pt leads via carbon atoms. The junction has a conductance comparable to that for metallic atomic junctions (around 0.1-1G0), where the conductance and the number of transmission channels are controlled by the molecule's orientation at different interelectrode distances.