Hwanbae Park

Design of bi-directional and multi-channel miniaturized telemetry module for wireless endoscopy

A bi-directional and multi-channel wireless telemetry capsule, 11 mm in diameter, is presented that can transmit video images from inside the human body and receive a control signal from an external control unit. The proposed telemetry capsule includes transmitting and receiving antennas, a demodulator, decoder, four LEDs, and CMOS image sensor, along with their driving circuits. The receiver demodulates the received signal radiated from the external control unit. Next, the decoder receives the stream of control signals and interprets five of the binary digits as an address code. Thereafter, the remaining signal is interpreted as four bits of binary data. Consequently, the proposed telemetry module can demodulate external signals so as to control the behavior of the camera and four LEDs during the transmission of video images. The proposed telemetry capsule can simultaneously transmit a video signal and receive a control signal determining the behavior of the capsule itself. As a result, the total power consumption of the telemetry capsule can be reduced by turning off the camera power during dead time and separately controlling the LEDs for proper illumination of the intestine.

Beneficial effects of Undaria pinnatifida ethanol extract on diet-induced-insulin resistance in C57BL/6J mice

This study was performed to evaluate the beneficial effect of Undaria pinnatifida ethanol extract (UEFx) on insulin resistance in diet-induced obese mice. A high-fat diet was supplemented with the UEFx at 0.69% (wt/wt) dose, which contains an equivalent amount of 0.02% fucoxanthin (wt/wt), or with Fx at 0.02% (wt/wt) dose in diet. After 9 weeks, both UEFx supplement significantly lowered the amount of visceral fat, the size of adipocyte, the fasting blood glucose concentration, the plasma insulin and the insulin resistance index similar to pure as shown by Fx supplement, compared to the high-fat (HF) control group. Blood glucose level was negatively correlated with hepatic glucokinase activity (r = -0.533, p < 0.05), whereas positively correlated with hepatic gluconeogenic enzyme activities (r = 0.463, p < 0.05 for glucose-6-phosphatase; r = 0.457, p < 0.05 for phosphoenolpyruvate carboxykinase). Ratio of hepatic glucokinase/glucose-6-phosphatase and glycogen content were significantly elevated by the UEFx and Fx supplements. Supplementation of the UEFx as well as Fx seemed to stimulate the β-oxidation activity and inhibit the phosphatidate phosphohydrolase activity resulting in a decrease in the hepatic lipid droplet accumulation. The results indicate that the UEFx can prevent insulin resistance and hepatic fat accumulation that is partly mediated by modulating the hepatic glucose and lipid homeostasis in the high fat-induced obese mice.

Luminescence and Scintillation Characteristics of

Luminescence and scintillation properties of Rb2LiCeBr6 single crystal are presented. This is a new elpasolite scintillation material and is grown by vertical Bridgman technique. Under X-ray excitation, Ce3+ luminescence is observed between 365 and 415 nm. An energy resolution of 6.3% (FWHM) is obtained for the 662 keV full γ-ray absorption peak. The sample crystal shows good light yield of 33 000 ph/MeV of absorbed γ -ray energy. The sample crystal also shows 5.0% nonproportionality in the 31 to 1333 keV range. The luminescence decay time curve can be characterized by two decay time components with decay time constants of 55 ns (87%) and 284 ns (13%), respectively. Scintillation properties indicate that this compound can be an attractive candidate for medical imaging and radiation detection applications.

{\rm Rb}_{2}{\rm LiCeBr}_{6}

The aim of this study is to develop scintillation crystals for the study of neutrinoless beta+/EC decay process. The 84Sr isotope is one of the potential candidates for the neutrinoless beta+/EC decay process. None of the scintillation crystals containing a strontium element up till now were used for the study of neutrinoless beta+/EC decay process. In general our crystal growth program include studies of starting material preparation, growth procedures and characterization of grown crystals. We grew a SrCl2 single crystal by using the Czochralski method. The cylindrical shape of the SrCl2 crystal was cut into the dimensions of Oslash2 times 1.5 cm3. The scintillation properties were studied by using various gamma ray sources and an alpha source. The scintillation properties such as energy resolution, light output, linearity and decay time were presented. In particular, the alpha/beta light ratio and possibility of a pulse shape discrimination between alpha and gamma quanta using a 210Po alpha source were studied.

Single Crystal

Avalanche photodiode (APD) is a kind of photodiode that internally amplifies the photocurrent by an avalanche effect. The quantum efficiency of the APD is about 80% which is five times higher than that of typical photomultiplier tube (PMT). A 16 mm diameter of beveled-edge large area avalanche photodiode (LAAPD) made by Advanced Photonics was used for the CsI(Tl) scintillator characterization. A CsI(Tl) crystal was attached to LAAPD and energy spectra were measured with various γ-ray sources. Measurements of energy spectra of the CsI(Tl) crystal to optimize the energy resolutions were performed with different shaping time constants by shaping amplifier and with different gains by high voltage variation. The absolute light yield and energy resolution of CsI(Tl) crystals were measured with the LAAPD for 662 keV γ-rays from a 137Cs source. The LAAPD was calibrated with X-ray of 55Fe source for the calibration of the number of e-h pairs per channel. The absolute light yield of newly developed SrCl2 scintillation crystal is determined by this method. This study shows that it is possible to use the LAAPD for the characterization of newly developed scintillation crystal and for the photo-sensor of scintillation detector.

Scintillation Characteristics of the SrCl

A Large size of Φ70 mm × 71 mm (2.1 kg) CdWO4 crystal with excellent quality was studied for the energy response of the crystal to the γ-rays. The large crystal was coupled with a green-extended Photomultiplier tube (PMT) and tested at room temperature. We measured light yield and energy resolution of the crystal using various radioactive sources. The energy resolutions of the CdWO4 crystal were obtained to be 9.5 % and 5.3% for 662 keV and 2614 keV, respectively. Linearity of the crystal in different γ-ray energy was also measured. In the environmental background spectrum, well defined peaks of 1461 keV by 40K decay and 2614 keV by 208Tl decay were identified. A simulation study with GEANT4 package was performed for the efficiency comparison with commonly used NaI(Tl) crystal scintillators. The study showed that the CdWO4 crystal is the promising candidate for the boarder control and energetic X-and γ-ray detection equipment.

_{2}

We manufactured and characterized a silicon micro-strip detector to be used in a beam tracker. A silicon detector features a DC-coupled silicon strip sensor with VA1_Prime2 analog readout chips. The silicon strip sensors have been fabricated on 5-in. wafers at Electronics and Telecommunications Research Institute (Daejeon, Korea). The silicon strip sensor is single-sided and has 32 channels with a 1 mm pitch, and its active area is 3.2 by 3.2 cm2 with 380 μm thickness. The readout electronics consists of VA hybrid, VA Interface, and FlashADC & Control boards. Analog signals from the silicon strip sensor were being processed by the analog readout chips on the VA hybrid board. Analog signals were then changed into digital signals by a 12 bit 25 MHz FlashADC. The digital signals were read out by the Linux-operating PC through the FlashADC-USB2 interface. The DAQ system and analysis programs were written in the framework of ROOT package. The beam test with the silicon detector had been performed at CERN beam facility. We used a 150 GeV electron beam out of the SPS(Super Proton Synchrotron) H2 beam line. We present beam test setup and measurement result of signal-to-noise ratio of each strip channel.

Single Crystal for the Neutrinoless

In this paper, we present scintillation properties of the new developed single crystals of BaxSr1-xCl2 for different concentration of x. We manufactured Ba0.12Sr0.88Cl2, Ba0.20Sr0.80Cl2, Ba0.22Sr0.78Cl2 crystals, and CsI(Tl) crystal as reference by using the Czochralski method. The crystals were cut into a size of 5 times 10 times 10 mm3. The X-ray diffraction technique was used to verify the structure of crystals. The emission spectra were measured with X-ray excitation at room temperature. Scintillation properties of the crystals such as pulse height spectra, energy resolution, alpha/beta ratio, relative light output, proportionality, and fluorescence decay time were measured with the various radioactive gamma sources at room temperature. The light output of these crystals were compared with that of the CsI(Tl) crystal. The differences in relative light outputs, energy resolutions, and decay times among these crystals were studied in detail.

\beta^{+}

A portable data acquisition (DAQ) system with embedded microcontroller was developed for radiation detection and environment monitoring purpose. The developed DAQ system consists of an ATMEGA128 of high performance, low-power 8-bit AVR microcontroller made by ATMEL and a AD7746 24-bit capacitance to digital converter. A software based Universal Serial Bus (USB) and a RS-232 serial port is used for the communication between the developed system with a main computer. The developed DAQ system has 8-channels analog to digital converter (ADC) with 10-bit resolution. The ADC has singled ended mode, differential mode using inside amplifier and it has maximum signals sampling rate 50-Kbit per second. It has discriminator capability with an analog comparator and signal counter capability with a 16-bit timer/counter. It can also measure precious capacitance, temperature and voltage with the functionality of the AD7746. The developed embedded DAQ system was tested with scintillation crystal irradiated with in radioactive sources. This embedded DAQ system is simple but portable and useful for radiation and environment monitoring.

/EC Decay Search

In Hyperball-J experiments, the lutetium oxyorthosilicate (Lu₂SiO₅:Ce, LSO) scintillators are constantly used to monitor and calibrate the Ge detectors. The LSO crystal has ¹⁷⁶Lu as a natural radioactive source. A new CsI:Na crystal that contains a ¹³³Ba radioactive source was developed in this study. This developed crystal can be used for detector calibration instead of LSO scintillators. The crystal was grown using a 2-zone vertical Bridgman method with a pulling speed of 0.5 mm/h. The CsI:Na, ¹³³Ba crystal was cut to Φφ 10 mm x 5 mm. Under X-ray excitation, the emission band of the crystal was observed between 330 nm and 650 nm. The scintillation properties of the CsI:Na, ¹³³Ba crystal such as light yield, energy resolution and decay time, were also measured using a ¹³⁷Cs γ-ray source. A High Purity Germanium (HPGe) detector was used to estimate the radioactivity in the crystal. The γ-ray peaks were identiήed from ¹³³Ba decay in the CsI:Na, ¹³³Ba crystal with a HPGe detector.