Search PubMed⌕ Search

Biomedical subjects

T Yoshinobu

Publications and source records attributed to T Yoshinobu.

15 recordsLinked to original sources
PubMed2005

The light-addressable potentiometric sensor for multi-ion sensing and imaging.

The light-addressable potentiometric sensor (LAPS) is a semiconductor-based chemical sensor with an electrolyte-insulator-semiconductor structure. The LAPS can have many measuring points integrated on the sensing surface, which are individually accessed by a light beam. By modifying the measuring points with different materials, a single sensor plate can be used as a multi-analyte sensor. In this paper, instrumentation and application of LAPS to multi-ion sensing and imaging are described. As a new application of LAPS, potentiometric imaging of a microfluidic channel is proposed.

Biosensing Techniques↗
PubMed2001

Atomic surface characterisation and modification of the layered compounds Bi2Se3, Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3.

In this work, we show atomic STM images of the layered compound Bi2Se3. We study the effect in the surface of the substitution of 5% and 20% of the Bi atoms for Sb in Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3. The images of the three samples show similar trigonal structures corresponding probably to the van der Waals Se atoms. The distance measured between surface atoms in Bi2Se3 is 4.04 A, in Bi1.9Sb0.1Se3 is 4.16 A and in Bi1.6Sb0.4Se3 is 4.26 A. In Bi1.6Sb0.4Se3 some atomic sites appear brighter than others. The effect is accentuated at higher tunnelling currents and is not observed in the other compounds. Nanoscopic range depressions on the sample might be related to the skeletal crystal structure since the images show atomic corrugations that align slightly in one direction. We explain the results as the effects of the interactions between tip and sample, and discuss two interpretations: on the one hand, localised depression of the individual atomic sites, and on the other the possible elevation of the atoms of the surface due to a phase transition of the compounds induced by STM.

Journal Article↗
PubMed2001

Nanotribology of Si oxide layers on Si by atomic force microscopy.

Atomic force microscopy (AFM) has been used for tribological studies of Si surfaces covered by oxide layers of various kinds: chemical oxides prepared by the SC1 (NH4OH/H2O2/H2O) and the SC2 (HCl/H2O2/H2O) treatments and a thermal oxide. In the case of the SC1 chemical oxide, the oxide layer was scratched and the underlying Si substrate was ploughed by the Si3N4 AFM tip. On the other hand, no wear of the sample was noted on the other surfaces: the AFM often produced elevated patterns in the shape of the scanned area, which were no longer visible after HF etching. By annealing the SC1-treated surface in N2 gas at above 200 degrees C for 30 min, the oxide layer could not be scratched any more. By soaking the thermal oxide in KOH, the oxide layer was then scratched. It is concluded that the presence of OH bases is the necessary condition for the nano-scratching of the oxide layers.

Journal Article↗
PubMed2000

Formation of nano-pyramids of layered materials with AFM

We have been able to raise squares of around 2 A in height of the layered materials Bi1.6Sb0.4Se3, Bi1.9Sb0.1Se3 and Bi2Se3 by means of contact atomic force microscopy in air. By raising squares on/beneath previously produced squares, Mayan-like pyramids have been constructed, each step of the pyramid being around 2 A in height. We neither remove matter from the surface nor produce a localized oxidation of the sample; we elevate a portion of it. When the surface is oxidized, the AFM cantilever pulls the oxide off producing holes. The raising of the squares is also possible in a nitrogen atmosphere.

Journal Article↗
PubMed2000

Scanning tunneling microscopy nanofabrication of electronic industry compatible thermal Si oxide

We report here a nanofabrication result on a 2.7 nm thermal oxide layer using the low-energy e-beam/scanning tunneling microscope (STM) technique in conjunction with thermal annealing, in which line windows with average width of 50 nm can be formed. Comparing to the low-energy e-beam processing on thin layers of native Si oxide, this nanofabrication shows a uniform etching of the electronic industry compatible Si oxide, with which nanoscale trenches can be formed. In addition to demonstrating further the nanofabrication capability of this technique on the thermal oxide, the results present critical evidence to our previous discussions on the mechanism of the low-energy e-beam/STM nanofabrication.

Journal Article↗
PubMed2000

Lift-off patterning of thin Au films on Si surfaces with atomic force microscopy

We studied a new lift-off process of thin Au film on silicon surfaces in nanometer-scale, combining anodic oxidation patterning with AFM, deposition of Au thin film on the patterned substrate and chemical etching processes of the Si oxide underneath the Au film. For Au films of thickness of 2-5 nm, the Au films on the Si oxide patterns were left unbroken and bent down to stick to Si surface after the removal of the oxide by the chemical etching. For an Au film of 1 nm in thickness, it was possible to lift-off the Au film on oxide patterns of the lines and dots in nanometer-scale using Si oxide as a sacrificial mask.

Journal Article↗
PubMed1999

Ligation errors in DNA computing.

DNA computing is a novel method of computing proposed by Adleman (1994), in which the data is encoded in the sequences of oligonucleotides. Massively parallel reactions between oligonucleotides are expected to make it possible to solve huge problems. In this study, reliability of the ligation process employed in the DNA computing is tested by estimating the error rate at which wrong oligonucleotides are ligated. Ligation of wrong oligonucleotides would result in a wrong answer in the DNA computing. The dependence of the error rate on the number of mismatches between oligonucleotides and on the combination of bases is investigated.

Animals↗
PubMed1999

Kinetic roughening in electrodissolution of copper.

We studied kinetic roughening of copper surfaces electrochemically dissolved at constant current densities by atomic force microscopy. The surface was found to roughen with time and the surface width increased with the length scale with the roughness exponent alpha of 0.73+/-0.05 in the stationary state. This value is different from that in electrochemical deposition, 0.87, under the stable growth condition [A. Iwamoto et al., Phys. Rev. Lett. 72, 4025 (1994)]. The observed roughening in the dissolution process is discussed in terms of nonlocal effects.

Journal Article↗
PubMed1992

[Treatment of pericardial cyst under thoracoscopy].

Thoracoscopic therapy was carried out on two cases of pericardial cyst. The first patient was a 24-year-old male. An abnormal shadow on a chest X-ray was pointed out at a regular checkup. Thoracoscopy was carried out under the local anesthesia and a thin-walled cyst was discovered. The cyst was punctured and serous fluid was aspirated. Then, several biopsy specimens were obtained from the cyst wall, a pathological diagnosis of the cyst was made as a pericardial cyst. One year after the thoracoscopy, no abnormal shadow is observed on chest X-ray. The second patient was a 26-year-old male. It was also discovered that he had an abnormal shadow on a chest X-ray at a regular medical checkup. Since a solid mass couldn't be completely denied, thoracoscopy was carried out in preparing for thoracotomy under the general anesthesia. The cyst observed between SVC and the azygos vein, and serous fluid was aspirated form the cyst. Following this, the cyst wall was biopsied and opened. Since no cases of malignant pericardial cysts have been reported, an operation is not usually required for these patients. We suggest that thoracoscopy is very useful tool for the final diagnosis and therapy of pericardial cyst because this method is easily carried out under local anesthesia.

Adult↗
PubMed1990

[Basic study on the chemosensitivity test by miniaturized improved nucleic acid precursor incorporation assay (MINI assay)].

UNLABELLED: Miniaturized improved nucleic acid precursor incorporation assay (MINI assay) has been developed by Kern D. H. and Tanigawa N. et al since 1985. We investigated in vitro effects of mitomycin C (MMC), cisplatin (CDDP) and bleomycin (BLM) against A 549 lung cancer cells and HeLa cells by MINI assay. RESULTS: 3H-thymidine (3H-TdR) uptake in the positive control was 734.2 cpm +/- 10 cpm. The cut-off level for in vitro sensitivity was defined as more than 80% inhibition of 3H-TdR uptake in the drug treated cells compared to the positive controls. A 549 cells were sensitive to MMC (81.6%), CDDP (78.6%), but not to BLM (-57%). HeLa cells were sensitive to MMC (91%), CDDP (79.4%), but not to BLM (43%). MINI assay could be done with fewer cells than other methods and the results were obtained within 5 days. This method was considered to be useful for the chemosensitivity test with human tumors.

Antineoplastic Agents↗