Electronic properties of a single-walled carbon nanotube/150mer-porphyrin system measured by point-contact current imaging atomic force microscopy

The electronic properties of a single-walled carbon nanotube/150mer of porphyrin polymer wire system were investigated. Current-voltage (I-V) curves were measured simultaneously along with topographic observations using point-contact current imaging atomic force microscopy. Symmetric I-V curves were obtained at bare single-walled carbon nanotubes but characteristic asymmetrical rectifying behavior was found at the single-walled carbon nanotube/150mer-porphyrin junctions. This finding is of key importance for the development of new nanoscale molecular electronic devices.     

High purity InxGa1−xSb single crystals with cutoff wavelength of 7–8 µm grown by melt epitaxy

For the first time, InGaSb single crystals with a cutoff wavelength of 7–8 μm were successfully grown on GaAs substrates by a new growth technique named melt epitaxy. The band gap of InGaSb layers obviously narrowed compared with those with the same compositions grown by ordinary methods and the longest cutoff wavelength reached 8.3 μm. High electron mobility of 8.05×10⁴ cm²/Vs and low carrier density of 1×10¹⁵ cm⁻³ at 77 K were obtained indicating high purity of InGaSb epilayers.     

An 850-nm InAlGaAs strained quantum-well vertical-cavitysurface-emitting laser grown on GaAs (311)B substrate withhigh-polarization stability

The polarization stability of 850-nm InAlGaAs strained quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) grown on GaAs (311)B substrate was investigated by comparing it with that of GaAs unstrained QW VCSEL grown on GaAs (311)B substrate. Photoluminescence measurement showed that strained QWs grown on GaAs (311)B substrate had larger anisotropy in optical gain than unstrained QWs. The VCSEL with strained QWs showed an orthogonal polarization suppression ratio (OPSR) as high as 21 dB under CW operation. Time-dependent OPSR measurement indicated that the strained QW VCSEL had higher polarization stability than the unstrained QW VCSEL under zero-bias modulation     

In vivo comparison of PET and SPECT radiopharmaceuticals in detecting breast cancer

Various radiopharmaceuticals for breast cancer detection have been used for scintimammography and PET. However, few comparative studies have described the uptake of radiopharmaceuticals as a method of detecting breast cancer. The aim of this study was to assess the radiopharmaceuticals for breast cancer imaging in experimental mice implanted with breast cancer cells. METHODS: Six radiopharmaceuticals were studied: three for PET [18F-fluorodeoxyglucose (FDG), L-18F-alpha-methyltyrosine (FMT) and 11C-methionine (C-Met)] and three for scintimammography [99mTc-tetrofosmin (TF), 99mTc-sestamibi (MIBI) and 201Tl-chloride (Tl)]. Biodistributions of six different tracers in mice implanted with MCF-7 breast cancer cells were studied 1 and 3 hr after injection. RESULTS: Tumor uptake 1 hr after injection was FMT = C-Met > FDG = TF > MIBI = Tl. Thallium-201-chloride showed the highest tumor-to-blood ratio (T/B) among all radiopharmaceuticals because of its fast clearance from circulation. The T/B of the six radionuclides used in this study ranged from 1.26 for C-Met to 12.83 for Tl. Tumor-to-muscle ratio (T/M) revealed FMT = C-Met > FDG > MIBI > TF = Tl. The T/M ranged from 0.20 for TF to 2.29 for FMT. Tumor-to-lung ratio (T/L) varied from 0.45 for TF to 2.41 for FMT. FMT revealed the highest T/L of all six radiopharmaceuticals. CONCLUSION: Among radiopharmaceuticals for PET, FMT seemed to be suitable in detecting MCF-7 tumor; whereas for scintimammography, MIBI, TF and Tl appeared to have almost the same detectability of MCF-7 tumor. The results of this study strongly suggest that FMT may have a potential in breast cancer imaging.     

Comparison of the feedback source between shaft displacement and load variation in controlled bearings

There has been much research into improving the characteristics of an externally pressurized thrust bearing and this has used two methods: a flow control device and sensing mechanisms. This report uses the latter method and deals with an externally pressurized thrust gas bearing which has a variable flow control device controlled by two signals. One source of signal is shaft displacement and the other is load variation. The results predict that a bearing controlled by load variation has a much higher performance than that controlled by shaft displacement. In the experiment a bearing which feeds back load variation showed a high performance for shaft displacement over a wide range of frequencies.     

Effect of rebamipide, a novel antiulcer agent, on Helicobacter pylori adhesion to gastric epithelial cells

We examined regional cerebral blood flow (rCBF) during a long-term recognition memory task for words in schizophrenic patients and in healthy subjects using positron emission tomography (PET). The task was designed so that performance scores were similar in the patient and control subjects. This memory retrieval task did not increase rCBF in the patients' prefrontal cortex, precuneus and cerebellum as much as it did in the control group. These results point to a dysfunctional corticocerebellar circuit leading to poorly coordinated mental activity ('cognitive dysmetria'), which could explain the broad range of schizophrenic symptoms. In addition, other brain areas were more activated by the task in the patient group than in the control group and may form a compensatory network performing the memory retrieval task by assisting or replacing the dysfunctional cortico-cerebellar circuit.     

Photoluminescence study of GaAs films on Si(100) grown by atomic hydrogen-assisted molecular beam epitaxy

Preliminary experimental results and analysis of photoluminescence (PL) measurements performed on GaAs heteroepitaxial films, which have been grown on Si(100) substrates by atomic hydrogen-assisted low-temperature molecular beam epitaxy technique have been presented and discussed. The results have also been compared with those obtained for GaAs homoepitaxial films. Furthermore, minority carrier lifetimes in n-GaAs on Si have been characterized by the PL decay method and an average lifetime of as high as 8.0 ns has been successfully obtained, which is the highest value ever reported to date.     

A multirate acoustic echo canceler structure

A new subband echo canceler (SBEC) structure is proposed to reduce the transmission delay introduced by conventional SBEC structures, without distorting the near-end signal. The proposed structure is based on computing two output errors, one for using during single-talk and the other one for using during double-talk periods. With the SBEC structure we propose a double-talk detector with a subband configuration which allows a fast and accurate detection of double-talk periods, enabling the SBEC algorithm to track changes in the echo path impulse response when the near-end signal is absent. Computer simulations using actual speech signals, and subjective evaluation tests are given to show the convergence performance, tracking and double-talk detection ability, of the proposed scheme     

Phonological and semantic activation in reading kanji characters.

In a large proportion of the complex kanji characters resulting from the combination of two radicals, the left radical gives information about the meaning of the whole character, and the right one gives cues to pronunciation. In this study, this feature was exploited to investigate the relative contribution of semantic and phonological information in the process of recognizing a word written in kanji. In 2 experiments, a technique was used in which part of the target character (i.e.. the left radical, carrying the semantic information; the right, phonetic radical, or a fragment) was presented shortly (60 or 180 ms stimulus onset asynchrony [SOA]) before the exposure of the whole character, which had to be named as fast as possible. Earlier exposure of the phonetic radical produced facilitation of the naming response, which was stronger at the 180-ms SOA than at the 60-ms SOA, whereas preexposure of the semantic radical had a weak facilitatory effect at the 60-ms SOA and some inhibition at the 180-ms SOA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of control technology for HTTR hydrogen production system with mock-up test facility: System controllability test for loss of chemical reaction

The Japan Atomic Energy Agency has been planning the demonstration test of hydrogen production with the High Temperature Engineering Test Reactor (HTTR). In a HTTR hydrogen production system (HTTR-H2), it is required to control a primary helium temperature within an allowable value at a reactor inlet to prevent a reactor scram. A cooling system for a secondary helium with a steam generator (SG) and a radiator is installed at the downstream of a chemical rector in a secondary helium loop in order to mitigate the thermal disturbance caused by the hydrogen production system. Prior to HTTR-H2, the simulation test with a mock-up test facility has been carried out to establish the controllability on the helium temperature using the cooling system against the loss of chemical reaction. It was confirmed that the fluctuations of the helium temperature at chemical reactor outlet, more than 200 K, at the loss of chemical reaction could be successfully mitigated within the target of ±10 K at SG outlet. A dynamic simulation code of the cooling system for HTTR-H2 was verified with the obtained test data.