Y. S. Park

Obscura telescope with a MEMS micromirror array for space observation of transient luminous phenomena or fast-moving objects

We introduce a novel telescope consisting of a pinhole-like camera with rotatable MEMS micromirrors substituting for pinholes. The design is ideal for observations of transient luminous phenomena or fast-moving objects, such as upper atmospheric lightning and bright gamma ray bursts. The advantage of the MEMS obscura telescope over conventional cameras is that it is capable both of searching for events over a wide field of view, and fast zooming to allow detailed investigation of the structure of events. It is also able to track the triggering object to investigate its space-time development, and to center the interesting portion of the image on the photodetector array. We present the proposed system and the test results for the MEMS obscura telescope which has a field of view of 11.3 degrees, sixteen times zoom-in and tracking within 1 ms.

Abstraction of CH3 group from the CH3I molecule adsorbed on Cu(100) by gas-phase hydrogen atoms

The reaction of CH 3 I molecules adsorbed on Cu( 100) with a beam of hydrogen atoms has been studied using a mass spectrometer. CH 4 was produced as the only gas-phase product by abstraction of the CH 3 group by a hydrogen atom even at a surface temperature of 100 K, i.e. CH 3 I (ad) + H (g) →CH 4(g) + I (ad) . This is in contrast to the gas-phase reaction, in which HI is believed to be the principal product. As a minor process, concurrent desorption of CH 3 I was also observed. The time variation of the CH 4 signal showed a step-like jump followed by an exponential decay upon opening the beam, from which a reaction cross section σ r = 1.2 x 10 -16 cm2 was estimated at submonolayer coverages of CH 3 I. Why the reaction of adsorbed CH 3 I with the gas-phase H atom is different from that of CH 3 I (g) is discussed in terms of the energetics modified by the surface.

Giant nonlinear response of terahertz nanoresonators on VO2 thin film

We report on an order of magnitude enhanced nonlinear response of vanadium dioxide thin film patterned with nanoresonators--nano slot antennas fabricated on the gold film. Transmission of terahertz radiation, little affected by an optical pumping for the case of bulk thin film, can now be completely switched-off: DeltaT/T approximately -0.9999 by the same optical pumping power. This unprecedentedly large optical pump-terahertz probe nonlinearity originates from the insulator-to-metal phase transition drastically reducing the antenna cross sections of the nanoresonators. Our scheme enables nanoscale-thin film technology to be used for all-optical switching of long wavelength light.

Program of transient UV event research at Tatiana-2 satellite

[1]xa0In a new Tatiana-2 mission the measurement of transient luminous events (TLE) in the Earth atmosphere in nadir direction are planned. Near UV temporal images of TLE in millisecond scale will be measured together with temporal profiles in 8 channels of wide spectrum of TLE emission. Simultaneously temporal variation of electron flux at the satellite orbit will be measured. Aims of these measurements are to continue research of bright UV flashes, started in the Tatiana-1 mission (Universitetsky–Tatiana satellite), their global distribution, their rate over oceans and continents, and their possible correlation with lunar phase. Special attention will be paid to search for correlation between UV flashes from the atmosphere and variations of electron flux in the atmosphere-magnetosphere system.

UV Radiation from the Night-Time Atmosphere seen from the “Universitetsky-Tatiana” Satellite

Detectors on the “Universitetsky‐Tatiana” satellite measured a smoothly varying intensity of UV radiation from the night‐time atmosphere in the nadir direction and the intensity of the energetic electron flux at the orbit. At high latitudes the UV intensity in the auroral oval is interpreted as being due to electrons penetrating into the atmosphere. At middle latitudes the UV intensity is an order of magnitude less and more data are needed to reveal the origin of this radiation. Millisecond flashes of UV radiation were observed. The flashes’ energy, temporal profile and global distribution are similar to these parameters for Transient Luminous Events (TLEs). These studies will be continued aboard the next satellite “Tatiana‐2”.

Vertebral bone attenuation on low-dose chest CT: quantitative volumetric analysis for bone fragility assessment

SummaryThis study evaluated the use of low-dose chest computed tomography (LDCT) for detecting bone fragility. LDCT-measured vertebral bone attenuation by volumetric methods showed good correlation with bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA, and good diagnostic performance for identifying osteoporosis and compression fractures. The results of this study suggest the feasibility of obtaining comprehensive information on bone health in subjects undergoing LDCT.IntroductionOsteoporosis is a prevalent but underdiagnosed disease that increases fracture risk. This study evaluated the utility of vertebral attenuation derived from low-dose chest computed tomography (LDCT) compared to dual-energy x-ray absorptiometry (DXA) for detecting bone fragility.MethodsA total of 232 subjects (78 men and 154 women) aged above 50xa0years who underwent both LDCT and DXA within 30xa0days were evaluated. LDCT-measured bone attenuation in Hounsfield units (HU) of four vertebrae (T4, T7, T10, and L1) was evaluated using volumetric methods for correlation with DXA-measured bone mineral density (BMD) and for the diagnosis of compression fractures, osteoporosis, and low BMD (osteoporosis or osteopenia) in men and women, with DXA measurements as the reference standard.ResultsThe average attenuation of the four vertebrae showed strong correlation with DXA-measured BMD of the lumbar spine (ru2009=u20090.726, pu2009<u20090.05). In receiver-operating characteristic (ROC) analyses, the area under the curve (AUC) across LDCT-measured thresholds of the average attenuation to distinguish compression fractures was 0.827, and a threshold of 129.5xa0HU yielded 90.9xa0% sensitivity and 64.4xa0% specificity. Similarly, average attenuation showed high AUCs and good diagnostic performance for detecting osteoporosis and low BMD in both men and women. Among 44 subjects with compression fractures, the average bone attenuation showed strong negative correlation with both the worst fracture grade (ru2009=u2009−0.525, pu2009<u20090.05) and cumulative fracture grade score (ru2009=u2009−0.633, pu2009<u20090.05).ConclusionLDCT-measured bone attenuation by volumetric methods showed good correlation with BMD measured by DXA and good diagnostic performance for identifying bone fragility.

Accuracy Enhancement in the In-Plane Dynamic Measurement of MEMS Actuators using a Laser Doppler Vibrometer with a 45°-Angled Optical Fiber

On-axis LDV (Laser Doppler Vibrometer), where the direction of incident beam is the same as that of the movement, intrinsically offers an accurate dynamic measurement, but it is not presently applicable to the MEMS actuator with in-plane motion due to no accessibility of the sidewall. The only available measurement method is off-axis LDV, which still shows a serious measurement error depending on the device pattern of the target surface. The on-axis FLDV (Fiber-optic LDV) with a 45°-angled optical fiber is proposed to accurately measure the in-plane motion of MEMS actuator. The performance of the proposed FLDV is evaluated in terms of signal stability and the measurable range.

A Novel Telescope with Micromirror for Observation of Transient Luminous Events from Space

A novel type of telescope, a pinhole-like camera with a micromirror array, is introduced for space observation of Transient Luminous Events (TLEs) like gigantic lightning occurring at upper atmosphere currently under question or investigation. The presented telescope has a unique feature of wide field of view (FOV) of surveillance, fast zoom-in and tracking. A high-fill factor, two-axis rotational micromirror array is proposed for the key component of the telescope. To obtain a large static deflection of a mirror, the self-aligned vertical comb-drive actuator is used. Multi-layered structures of a micromirror are fabricated using bulk micromachining techniques, such as deep reactive ion etching and wafer bonding on the full wafer-scale.

Nutritional Intervention for a Patient with Acute Lymphoblastic Leukemia on Allogeneic Peripheral Blood Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) causes many complications such as anorexia, nausea, vomiting, diarrhea, and mucositis. Most patients undergoing HSCT have risk for malnutrition in the process of transplantation so artificial nutrition support is required. The purpose of this case report is to share our experience of applying nutrition intervention during the transplantation period. According to HSCT process, the change of the patients gastrointestinal symptoms, oral intake and nutritional status was recorded. By encouraging oral intake and providing parenteral nutrition, the patient had only 0.3%, losing weight during the transplantation period. In conclusion, it emphasized that the nutritional status changes during the HSCT period should be closely monitored and nutritional management through appropriate nutritional support and interventions in hospital and after discharge.