Search

Novel functional polymers utilizing specific host/guest interactions were designed by introducing α-CD host molecules into poly(e-lysine) chains as side groups. An interesting phase separation was observed as a result of the inclusion complexation between the polymeric host and 3-(trimethylsilyl)propionic acid as a model guest in aqueous media. This water-soluble polymeric host would be useful for various applications, particularly drug delivery, due to its biodegradability, low toxicity, and unique functionality represented as a complexation-induced phase separation.

L-Arginine was immobilized into a supramolecular-structured polyrotaxane to examine the generation of nitric oxide, with a view to improving antithrombosis and the blood compatibility of polymeric biomaterials. L-Arginine was immobilized to the hydroxyl groups of alpha-cyclodextrins in the polyrotaxane via an ester linkage, and the nitric oxide generation and L-arginine release behavior were characterized. L-Arginine-immobilized polyrotaxane was insoluble in water, but was found to generate nitric oxide when placed in Tris-HCI buffer supplemented with activators. L-Arginine-immobilized polyrotaxane exhibited sustained nitric oxide generation for a period of 250 h. L-Arginine was completely released by non-enzymatic hydrolysis from 200 h to 700 h, with a lag-time for the first 200 h. Consequently, after the generation of nitric oxide and the release of L-arginine from the L-arginine-immobilized polyrotaxane, the residual component will be a polyrotaxane with superior biocompatibility and mechanical properties. These results suggest that L-arginine-immobilized polyrotaxane can be useful in a wide range of medical applications, including use as a nitric oxide generative system for antithrombosis, coating and blending materials of hydrophobic extracorporeal circuits, and implantable catheters.

Although the technique of coronary stenting has remarkably improved long-term results in recent years, (sub)acute thrombosis and late restenosis still remain problems to be solved. Metallic surfaces were regarded as thrombogenic, due to their positive surface charges, and stenosis resulted from the activation and proliferation of vascular smooth muscle cells (VSMCs). In this study, a unique surface modification method for metallic surfaces was studied using a self-assembled monolayer (SAM) technique. The method included the deposition of thin gold layers, the chemisorption of disulfides containing functional groups, and the subsequent coupling of PEG derivatives or heparin utilizing the functional groups of the disulfides. All the reactions were confirmed by ATR-FTIR and XPS. The surface modified with sulfonated PEG (Au-S-PEG-SO3) or heparinized PEG (Au-S-PEG-Hep) exhibited decreased static contact angles and therefore increased hydrophilicity to a great extent, which resulted from the coupling of PEG and the ionic groups attached. In vitro fibrinogen adsorption and platelet adhesion onto the Au-S-PEG-SO3 or Au-S-PEG-Hep surfaces decreased to a great extent, indicating enhanced blood compatibility. This decreased interaction of the modified surfaces should be attributed to the non-adhesive property of PEG and the synergistic effect of sulfonated PEG. The effect of the surface modification on the adhesion and proliferation of VSMCs was also investigated. The modified Au-S-PEG-SO3 or Au-S-PEG-Hep surfaces also exhibited decreased adhesion of VSMCs, while the deposited gold layer itself was effective. The enhanced blood compatibility and the decreased adhesion of VSMCs on the modified metallic surfaces may help to decrease thrombus formation and suppress restenosis. It would therefore be very useful to apply these modified surfaces to stents for improved functions. A long-term in vivo study using animal models is currently under way.

A flag-type atom shutter based on a rotating lever that is driven by a bender piezoelectric actuator was developed to manipulate atomic beams. The shutter flag was displaced by ∼10 mm to open and close a 5-mm-diameter aperture with a shutter time of 13 ms that produced small mechanical vibrations. The short-term shutter time stability for each cycle was 0.03 ms and the long-term stability over an average of 20 000 cycles was 0.02 ms. The operational cycle number (lifetime) of the shutter reached 2.0 × 106 cycles after an intermittent operation over a period of eight months in an ultra-high vacuum chamber, and another shutter in an atmospheric environment swung for 2.6 × 107 cycles of continuous operation at 5 Hz for a period of 60 days without major problems. The shutter was shown to be compatible with the operation in an ultra-high vacuum at a low 10−7 Pa level after a gentle baking treatment.

Based on the its nonintrusive characteristics, ballistocardiography(BCG) has applied in the estimation of sleep structure without attaching any sensors to the subject's body. Loadcell or polyvinylidenefluoride (PVDF) film sensors are installed on the mattress for the monitoring of BCG. BCG peak was detected and heart rate variability parameters are derived. Parameters representing sleep structure and quality are estimated using these parameters. Sleep efficiency, four stages of sleep structure and sleep onset latency are estimated and results are compared with the results derived from polysomnographic recording.

The development of an Yb optical lattice clock at the Korea Research Institute of Standards and Science (KRISS) is reported with current systematic uncertainty of 2.9×10. A highly stable clock laser at 578 nm was developed with a shortterm linewidth of 3.5 Hz. The laser was locked to the clock transition and the fractional frequency stability was 2.0×10 at 1 s. Collisional frequency shift for Rabi spectroscopy was theoretically and experimentally investigated and the uncertainty was greatly reduced to 2.9×10. We identified conditions to further reduce the collisional shift uncertainty to 10 level. Index Terms — Optical clock, optical lattice, Ytterbium, collisional shift, sub-Hz laser.

Difficulties in the extraction of membrane proteins from cell membrane and their solubilization in native conformations have hindered their structural and biochemical analysis. To overcome these difficulties, an amphipathic polypeptide was synthesized by the conjugation of octyl and glucosyl groups to the carboxyl groups of poly-γ-glutamic acid (PGA). This polymer, called amphipathic PGA (APG), self-assembles as mono-disperse oligomers consisted of 4-5 monomers. APG shows significantly low value of critical micelle concentration and stabilization activity toward membrane proteins. Most of the sodium dodecyl sulfate (SDS)-solubilized membrane proteins from Escherichia coli remain soluble state in the presence of APG even after the removal of SDS. In addition, APG stabilizes purified 7 transmembrane proteins such as bacteriorhodopsin and human endothelin receptor Type A (ETA ) in their active conformations. Furthermore, ETA in complex with APG is readily inserted into liposomes without disrupting the integrity of liposomes. These properties of APG can be applied to overcome the difficulties in the stabilization and reconstitution of membrane proteins.

Rhoptry protein 6 (ROP6) from Toxoplasma gondii is a 480-amino acid protein with no homology to any reported excretory or secretory protein. Especially, unlike the many other rhoptry protein types, ROP6 does not have a kinase domain. The biochemical and biophysical properties of ROP6 are unknown. Here, we investigated its structure using an in silico analysis method and overexpression and purification using an Escherichia coli system. The protein was purified to more than 85% homogeneity using immobilized metal affinity chromatography in denaturing conditions. After purification, ROP6 showed slow migration in SDS–PAGE, including fast proteolysis. This implies that ROP6 has a high percentage of flexible regions or extended loop structures. Secondary structure prediction and prediction of intrinsically disordered regions by using various bioinformatics tools, indicated that approximately 60% of ROP6 is predicted to be intrinsically disordered or random coil regions. These observations indicate that ROP6 is an intrinsically disordered protein.

This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring.

Long-term monitoring of electrocardiogram (ECG) is one of the basic measurement in healthcare and provides decisive information regarding cardiovascular system status. In all ECG applications, the R-wave detection is important. However, it is difficult to detect R-wave automatically because signals obtained in daily life frequently include noise from various sources. Daily life monitoring ECG signal is particularly measured over cloth during walking and sleeping states by using non-invasive sensor, so that it usually presents higher noise level. To improve detection accuracy under noisy condition, we developed algorithm which has some noise tolerance techniques that analyze characteristics of R-wave. The proposed algorithm was evaluated by using the records of the MIT-BIH Polysomnographic database and the data from nonintrusive vital sign monitoring system previously developed in our laboratory. Algorithm reliability was assessed by detection error rate (De), sensitivity (Se) and positive predictivity (P+). The result shows average De of 2.62%, average Se of 98.29% and average P+ of 99.03%. We suggest that our R-wave detection method is useful in the presence of noisy signals.

Supramolecular-structured hydrogels were prepared on basis of the inclusion complexation between poly(ethylene glycol) grafted dextrans and α-cyclodextrins (α-CDs) in aqueous media. The inclusion complexes from the PEG grafted dextrans showed a unique gel−sol phase transition which cannot be obtained from usual polymer inclusion complexes that form crystalline precipitates. The gel−sol transition was based on the supramolecular assembly and dissociation, and the transition was reversible with hysteresis. The transition temperature was controllable by variation in the polymer concentration and the PEG content in the graft copolymers as well as the stoichiometric ratio between the guest and host molecules. The properties of the hydrogel were characterized by DSC, X-ray diffraction, and 13C CP/MAS NMR. The X-ray diffraction data indicated that the gel contains a channel-type crystalline structure, demonstrated by a strong reflection at 2θ = 20° (d = 4.44 A). It was confirmed from the DSC and 13C CP/MAS NMR m...

A novel surface modi"cation method has been developed to improve biocompatibility of polymeric biomaterials. This approach involves ozonation and then followed by graft polymerization with acrylates containing PEG, sulfonated PEG or by coupling of PEG derivatives. All the reactions were con"rmed by ATR FT-IR and ESCA. The degree of ozonation measured by the iodide method was dependent on the ozone permeability of the polymers used. Surface hydrophilicity was investigated by measuring the contact angles. Ozonation itself yielded a slight increase in hydrophilicity and a decrease in platelet adhesion, but PEG immobilization showed a signi"cant e!ect on surface hydrophilicity and platelet adhesion to con"rmwell-known PEG 's passivity which minimize the adhesion of blood components on polymer surfaces. Both graft polymerization and coupling were e!ective for PU. In contrast, only grafting gave enough yields for PMMA and silicone. Platelet adhesion results demonstrated that all PEG modi"ed surfaces adsorbed lower platelet adhesion than untreated or ozonated ones. Polymers coupled with sulfonated PEG exhibited the lowest platelet adhesion when compared with control and PEG coupled ones by virtue of the synergistic e!ect of non-adhesive PEG and negatively charged SO groups. This PEG or sulfonated PEG immobilization technology using ozonation is relatively simple for introducing uniformsurface modi "cation and therefore very useful for practical application of blood contacting medical devices. 2001 Elsevier Science Ltd. All rights reserved.

A novel chemical modification of biological tissues was developed aimed at improving biocompatibility and calcification resistance. This method involved the additional grafting of sulfonated PEO (PEO-SO(3)) or heparin after conventional glutaraldehyde (GA) fixation of bovine pericardium (BP). The amino groups of PEO-SO(3) or heparin were utilized to react to the GA residues to block them. The PEO-SO(3) or heparin grafted tissues demonstrated a slightly higher shrinkage temperature and tensile strength, but greater resistance to collagenase digestion, than GA treated ones. These results suggest that modified tissues have improved durability due to the grafting and filling effect of PEO-SO(3) or heparin in addition to the GA cross-linking. At the direct contact cytotoxicity test in vitro, PEO-SO(3) or heparin grafted tissue was shown to be nontoxic, while relatively significant cytotoxicity was observed for the GA treated tissues, possibly due to the release of GA. From the in vivo calcification study, calcium contents deposited on the modified tissues were much less than those on GA treated tissues. Such a decreased calcification might be explained by the decrease of residual GA groups during the additional treatment, and the space-filling effect and the nonadhesive property and/or the blood compatibility of PEO-SO(3) or heparin grafted covalently. The newly modified tissue patch was observed to show improved pathological assessibility including less inflammation and tissue reactions. This simple modification method may be useful for calcification-resistant and blood-compatible tissue patches for cardiovascular implants.

Novel poly(ethylene glycol) (PEG) and sulfonated PEG (PEG-SO(3)) acrylate copolymers have been prepared and characterized to apply as coating and blending materials for biomedical applications. The modified surfaces using acrylate copolymers demonstrated increased hydrophilicity, possibly due to the hypothesized reorientation of PEG/PEG-SO(3) chains into water phase. All copolymer surfaces demonstrated less platelet adhesion than control. In addition, platelet adhesion on copolymer surfaces decreased as the chain length of PEG and sulfonated PEG in copolymers increases. All copolymer surfaces reduced bacterial adhesion significantly and the adhesion level differs depending on surfaces as well as media. The obtained results attest to the usefulness of these copolymers as a coating or additive material to improve the blood compatibility of blood contacting devices.

We design a high temperature oven for measuring the saturation intensity of the transition line $4f^ 6/6s^{2 7}7F_0 ↔ 4f^6/6s6p $^1$ P(J = 1)$ of the samarium atom. We first constructed a high temperature oven to generate the samarium vapor column and study the thermal characteristics of the oven. The oven is able to operate at a temperature up to about 1400 $^{\circ}C$ and the operation is tested by using several metals with high melting points. We describe two wave mixing experiment with the samarium vapor generated in the high temperature oven and obtain the saturation intensity by analyzing the first diffraction signal.

The formation of spontaneous transverse optical patterns was investigated in a single feedback mirror system using nematic liquid crystals as nonlinear optical media. By varying the size of an input beam and the feedback distance, we obtained various interesting transverse optical patterns as well as the hexagonal pattern which are predicted theoretically assuming plane wave input. We can explain theoretically these characteristics of various pattern by introducing a ratio of the beam half width and spatial wavelength of the patterns. We have observed that as this ratio increased, the number of spot constituting the patterns also increased. Finally the patte군 evolved into the sucessive hexagon in the transverse plane.

We fabricated a new top-gate n-type depletion-mode polycrystalline silicon (poly-Si) thin-film transistor (TFT) employing alternating magnetic-field-enhanced rapid thermal annealing. An n+ amorphous silicon (n+ a-Si) layer was deposited to improve the contact resistance between the active Si and source/drain (S/D) metal. The proposed process was almost compatible with the widely used hydrogenated amorphous silicon (a-Si:H) TFT fabrication process. This new process offers better uniformity when compared to the conventional laser-crystallized poly-Si TFT process, because it involves nonlaser crystallization. The poly-Si TFT exhibited a threshold voltage (VTH) of -7.99 V at a drain bias of 0.1 V, a field-effect mobility of 7.14 cm2/V ldr s, a subthreshold swing (S) of 0.68 V/dec, and an ON/OFF current ratio of 107. The diffused phosphorous ions (P+ ions) in the channel reduced the VTH and increased the S value.

Polyethylene oxide (PEO) surfaces were prepared by the addition of PEO- and sulfonated PEO-containing amphiphilic block copolymers as surface-modifying additives in a segmented polyurethane (PU). PEO-PPO-PEO triblock copolymers (Pluronics) with different PEO chain lengths (from 2 to 80) were used as additives. The prepared film surfaces were characterized by the measurement of dynamic water contact angles and electron spectroscopy for chemical analysis. It was observed that the PU films containing 10 wt % of PEO additives were surface-saturated with the additives regardless of their PEO chain length, but the PEO chains were more projected from the film surfaces containing the additives with longer PEO chains. The water absorption of the films increased largely with the increasing PEO chain length of the additives. The addition of PEO additives produced film surfaces that were in a gel-like state. The films demonstrated some extraction of the PEO additives. However, the additives with higher molecular weights were entrapped more stably into the PU matrix. The mechanical properties (tensile strength and elongation) of the films were changed by the addition of PEO additives, but the differences were not significant compared to the control PU. The platelet adhesion on the film surfaces decreased with increasing PEO chain length of the additives. The film surface containing additives with long PEO chains (chain length of 80) was particularly effective in preventing platelet adhesion. The effect of negatively charged sulfonate groups on the prevention of platelet adhesion appeared only on the film surfaces containing additives with short PEO chains. For longer PEO chains, the chain mobility effect was more dominant than the negative charge effect on the prevention of platelet adhesion. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 314–323, 1998.

Age-related changes of NADPH-diaphorase (NADPH-d) and vasoactive intestinal polypeptide (VIP) were examined in the rat brain. Aged (24 months) rats showed a significant decrease in the number of VIP-immunoreactive (IR) neurons in the cerebral cortex when compared with control (4 months) rats. However, the number of NADPH-d-positive neurons was not significantly different in the two groups. Quantitative analysis of cell areas revealed a significant shrinkage of VIP-IR neurons in the aged group, whereas no further cell shrinkage was noted for NADPH-d-positive neurons compared with the control group. These morphometric results demonstrate that NADPH-d-containing neurons are more resistant to aging than the VIP-IR neurons in the cerebral cortex of rats.

A stable single-frequency fiber ring laser is proposed that operates in a single mode for more than an hour by incorporating unpumped erbium-doped fiber (EDF) as a saturable absorber filter and optimizing the length of EDF used as gain medium. This laser can be continuously tuned to 25-GHz spacing that precisely matches the ITU-T grids by temperature control of etalon filter. This laser had a signal-to-source spontaneous emission ratio higher than 70 dB, and lasing frequencies of 361 channels was matched to ITU-T grids with excellent flatness. Frequency offset from the ITU-T grid was less than 0.14 GHz. The linewidth and the relative intensity noise value was less than 1.3 kHz and 130 dB/Hz (above 250 kHz), respectively.

The phosphate-specific transport substrate binding protein-1 (PstS1) is a potential antigen used for the serological diagnosis of tuberculosis. For a highly specific diagnostic result, it is important that the recombinant PstS1 be highly pure and correctly folded. In this study, the PstS1 was expressed as fusion protein with glutathione-S-transferase (PstS1-GST) and Escherichia coli trigger factor (PstS1-TF) and their immunodiagnostic potentials were evaluated. The insoluble PstS1-GST was denatured and refolded to the native conformation by a step-gradient dilution, followed by purification with affinity chromatography on immobilized glutathione whereas the soluble PstS1-TF was directly purified by Ni-NTA affinity and size-exclusion chromatographies. The levels of antibody responses to PstS1-TF and PstS1-GST were measured by enzyme-linked immunosorbent assay (ELISA) in the sera of 22 tuberculosis patients with smear-positive and culture-positive tuberculosis as well as 20 healthy individuals; the antigenicities of the samples were evaluated in terms of sensitivity and specificity. To determine the diagnostic accuracy, receiver operation characteristic (ROC) curves were constructed and then the areas under the ROC curves (AUC) were calculated; the AUC values for PstS1-TF and PstS1-GST were 0.971 and 0.877 with 95% confidence intervals (CI) of 0.927-1.000 and 0.768-0.986, respectively. The specificity of PstS1-TF was reduced from 89.5% to 84.2%, but in case of PstS1-GST it dropped drastically from 78.9% to 26.3% when the sensitivity was raised from 86.4% up to 95.5%. These results indicate that PstS1-TF is capable of producing more accurate and consistent serodiagnostic results than PstS1-GST, possibly due to its conformation being closer to the native state.

Uridinediphospho-N-acetylglucosamine enolpyruvyl transferase (MurA, E.C. 2.5.1.7) is an essential bacterial enzyme that catalyzes the first step of the cell wall biosynthetic pathway, which involves the transfer of an enolpyruvyl group from phosphoenolpyruvate to uridinediphospho-Nacetylglucosamine. In this study, novel inhibitors of Haemophilus influenzae MurA (Hi MurA) were identified using high-throughput screening of a chemical library from the Korea Chemical Bank. The identified compounds contain a quinoline moiety and have much lower effective inhibitory concentrations (IC(50)) than fosfomycin, a wellknown inhibitor of MurA. These inhibitors appear to covalently modify the sulfhydryl group of the active site cysteine (C117), since the C117D mutant Hi MurA was not inhibited by these compounds and excess dithiothreitol abolished their inhibitory activities. The increased mass value of Hi MurA after treatment with the identified inhibitor further confirmed that the active-site cysteine residue of Hi MurA is covalently modified by the inhibitor.

Non-structural protein 1 (NS1) of the influenza A virus (IAV) inhibits the host's innate immune response by suppressing the induction of interferons (IFNs). Therefore, blocking NS1 activity can be a potential strategy in the development of antiviral agents against IAV infection. In the present study, we selected a single-stranded DNA aptamer specific to the IAV NS1 protein after 15 cycles of systematic evolution of ligands by exponential enrichment (SELEX) procedure and examined the ability of the selected aptamer to inhibit the function of NS1. The selected aptamer binds to NS1 with a Kd of 18.91±3.95nM and RNA binding domain of NS1 is determined to be critical for the aptamer binding. The aptamer has a G-rich sequence in the random sequence region and forms a G-quadruplex structure. The localization of the aptamer bound to NS1 in cells was determined by confocal images, and flow cytometry analysis further demonstrated that the selected aptamer binds specifically to NS1. In addition, luciferase reporter gene assay, quantitative RT-PCR, and enzyme-linked immunosorbent assay (ELISA) experiments demonstrated that the selected aptamer had the ability to induce IFN-β by suppressing the function of NS1. Importantly, we also found that the selected aptamer was able to inhibit the viral replication without affecting cell viability. These results indicate that the selected ssDNA aptamer has strong potential to be further developed as a therapeutic agent against IAV.

Human Nopp140 is a highly phosphorylated nucleolus protein and involved in the biogenesis of the nucleolus. It interacts with a variety of proteins related to the synthesis and assembly of the ribosome including a ubiquitous protein kinase CK2 which mediates cell growth and prevents apoptosis. We showed that hNopp140 is a highly intrinsically disordered protein (IDP) lacking stable secondary structures over its entire sequence of 710 residues. In this work, we employed various biophysical approach, for example, Circular Dichroism (CD), Electron Paramagnetic Resonance (EPR) and Forster resonance energy transfer (FRET), to investigate the intrinsic nature of hNopp140 and its structural changes by various conditions, interaction with CK2alpha.

The relaxation dynamics of nonlinear optical chromophores in photo-polymer composites is studied for a basic understanding of the poling mechanism. The composite films are made up of a photo-polymer containing 0.5 % by weight of 4-dimethylamino-4′-nitrostilbene. They are poled under an external dc electric field at room temperature, followed by UV curing. It is found that for such composite films both the optical retardation and the second harmonic generation (SHG) intensity clearly decay as similar stretched-exponentials in time, and their relaxation behavior is predominantly governed by the period for UV curing. It is suggested that the optical retardation involves mostly the axial order while the SHG intensity is strongly correlated to the degree of polar ordering of the chromophores.

We demonstrate self-aligned and high-performance liquid crystal (LC) systems doped with 1-dimensional (1D) chain-like clusters of CuInS(2) (CIS)-ZnS core-shell quantum dots (QDs). By changing the cell fabrication method of the LC-QD composites, we can selectively control the orientation of the LC molecules between the homogeneous and homeotropic states without conventional LC alignment layers. The homeotropic alignment of LCs was achieved by random dropcasting and the homogeneous alignment was performed using a capillary injection of LC-QDs due to the random or linear diffusion of QD clusters into ITO defects. The electrically compensated bend (ECB)- and vertically aligned (VA) mode LC displays (LCDs) containing our LC-QD composite both showed superior electro-optic (EO) properties. A 37.1% reduction in the threshold voltage (V(th)) and a 36.6% decrease in the response time were observed for ECB mode LCDs, and a 47.0% reduction in the V(th) and a 38.3% decrease in the response time were observed for VA mode LCDs, meaning that the proposed LC-QD composites have a great potential for the production of advanced flexible LCDs.

A laser source at 578 nm with output power of more than 10 mW was obtained using a waveguide periodically-poled-lithium-niobate crystal as a nonlinear medium for second harmonic generation. To achieve this result, we made a high power 1156-nm external-cavity diode laser with maximum output power of more than 250 mW. This system is expected to be an excellent alternative to systems using sum-frequency generation with advantages of simplicity and cost-effectiveness, and will be used as a clock laser of an ytterbium optical lattice clock with robust and reliable operation.

An Yb optical lattice clock is under development at KRISS. Yb atoms were trapped in an optical lattice and further optimization is underway. Linewidth of the probe laser at 578 nm developed by sum frequency generation (SFG) method was reduced to less than 100 Hz. We also developed an optical frequency synthesizer (OFS) with the carrier-envelope-offset frequency locked to 0 Hz using the “direct locking method.”

We present a current status of a Rb/Cs double fountain clock developing at KRISS. Fountain clock has cooling laser beam with (111)-geometry so as to enlarge cooling beam diameter. Currently few 107 Cs atoms are trapped and cooled in MOT. And we observed Ramsey fringes. The linewith of central Ramsey fringe was measured to be 1 Hz with the S/N of 600.

We present a current status of an atomic gravimeter, which is based on Mach-Zehnder-type atom interferometer using stimulated Raman transition, developing at KRISS. Cooling beams with (111) geometric configuration was used for magnetic optical trap (MOT). Rubidium87 (Rb87) atoms are trapped and cooled in MOT. Temperature of the trapped atoms was measured to be about 1.7µK by time of flight measurement after a deep cooling.

Human endothelin receptor type A (ET(A)) is a G-protein coupled receptor that mediates vasoconstriction of blood vessels. To determine the structural characteristics and signaling mechanism of ET(A), we have expressed recombinant ET(A) as a fusion protein with p9 envelope protein from phi6 bacteriophage. The His-tag-labeled p9-ET(A) fusion protein was highly expressed in the membrane fraction of Escherichia coli and purified to homogeneity by single affinity chromatography after solubilization with detergents. Purified p9-ET(A) appeared as an oligomer and presented mainly as an α-helical structure. The protein also showed specific binding to endothelin-1 (ET-1) and the alpha subunit of G(q) protein with apparent K(D) values of 17 and 20 nM, respectively. An antagonist of ET(A), bosentan, prevented the interaction between p9-ET(A) and ET-1 in a concentration-dependent manner. These results indicate that recombinant p9-ET(A) has a competent conformation for interactions with ET-1 and the alpha subunit of G(q) protein.

Heart sounds are generated by the fluctuations of blood velocity and the vibrations of cardiac structure. The auscultation of heart sounds is one of the basic tools for patient diagnosis and provides a lot of information associated with cardiovascular systems. For converting mechanical sound waves into electronic signals, PVDF (polyvinylidene fluoride) film sensor was used as heart sounds measurement device. After suited filtering process, the first (S1) and the second (S2) heart sounds components were plainly distinguished and their peak timings were closely corresponded to reference heart sounds signals measured by microphone. Lastly, there was high correlation between S1 intervals (from PVDF signals) and RR intervals (from ECG signals). So it is expected that S1 intervals can replace RR intervals. In future application, these methods have possibilities for non-intrusive heart rate estimation.

Two series of rigid and semi-rigid polyesters and polyamids with flexible side chains were prepared by solution and melt as well as interfacial polycondensation of 2,5-dialkoxyterephthaloyl chloride with various diols and diamines. Thermal behaviors of the polymers were studied by DSC, TGA and polarizing microscopy. The results indicated that only rigid polymer systems form nematic mesophase. However, none of the semi-rigid polymers formed nematic melts. The structures of both polyesters and polyamides were also examined by the wide angle X-ray scattering. Analysis of sharp reflection, appeared at the lower angle of X-ray diffractograms of rigid polymers, suggested that rigid polymers crystallized to form a layered structure in the solid state.

The linewidth of a distributed-feedback (DFB) diode laser at 1156 nm, of which free-running linewidth was 3 MHz, was reduced to 15 kHz using an all-fiber interferometer with 5-m-long path imbalance. Optical power loss and bandwidth limitation were negligible with this short optical fiber patch cord. This result was achieved without acoustic and vibration isolations, and the frequency lock could be maintained over weeks. In addition to its simplicity, compactness, robustness, and cost-effectiveness, this technique can be applied at any wavelength owing to the availability of DFB diode lasers and fiber-optic components.

S-adenosylmethionine synthetase (SAM-s) catalyzes the synthesis of S-adenosylmethionine (SAM), which is essential for methylation, transcription, proliferation, and production of secondary metabolites. Here SAM-s from Pichia ciferrii were selectively cloned using RNA CapFishing and rapid amplification of cDNA ends (RACE). The putative full-length cDNA of SAM-s encoded a 383 amino acid protein (42.6 kDa), which has highly conserved metal binding sites, a phosphate-binding site, and functionally important motifs. The corresponding enzyme was over-expressed in a heterologous host of Pichia pastoris, and then purified to a homogenous form. Enzyme kinetics, immunoblotting, circular dichroism (CD), high performance liquid chromatography (HPLC), and molecular modeling were conducted to characterize the SAM-s from P. ciferrii. Structural and functional studies of SAM-s will provide important insights for industrial applications.

The long-term carrier-envelope phase (CEP) coherence of a femtosecond laser with same pulse-to-pulse CEP value, obtained using the direct locking method, is demonstrated by employing a quasi-common-path interferometer (QPI). For the evaluation of the CEP stability, the phase noise properties of a femtosecond laser with the CEP stabilized using a QPI are compared with those obtained using a Mach-Zehnder f-2f interferometer, for which the phase power spectral density and the Allan deviation were calculated from the beat signals of the interferometers. With the improved CEP stability, the long-term CEP coherent signal with an accumulated phase noise well below 1 radian can be maintained for more than 56 hours, i.e., the CEP coherence is preserved without a phase cycle slip for more than 1.6 × 10(13) pulses at a repetition rate of 80 MHz. The relative stability is also estimated to be approximately 1.4 × 10(-22) at a central wavelength of 790 nm.

We introduce the characteristics of the titanium dioxide (TiO(2)) inorganic film deposited by rf magnetron sputtering for liquid crystal display applications. The TiO(2) films demonstrated vertical alignment (VA) of the liquid crystals (LCs) obtained by using ion-beam (IB) bombardment. As observed by using x-ray photoelectron spectroscopy, the chemical structure of the TiO(2) was changed by IB bombardment, altering the Ti-O bonding of the Ti 2p spectra to lower intensity levels. Breaking Ti-O bonding by IB bombardment created pretilt angles between the TiO(2) film and LC molecules. The better voltage-transmittance characteristics of the VA LCDs based on TiO(2) film were measured and compared with the same characteristics of polyimide film.

The weighted mean is widely used in combining data sets of experimental measurements with a weight proportional to the value of the data number divided by the sample variance in a conventional method. However, this standard procedure is not appropriate for obtaining the weighted mean frequency of a phase-stabilized signal with white phase noise, since the data are autocorrelated. The autocorrelation is obtained in the case of white phase noise and a new weighting method is proposed. Using this, the uncertainty associated with the weighted mean frequency of a phase-stabilized signal with white phase noise is given. The effect of counter dead-time is also discussed. The result is significantly different from the conventional method, so that the weight is proportional to the square of data number divided by the sample variance, and as a result the uncertainty of the estimated mean is proportional to the sample standard deviation divided by the data number. In an optical frequency comb comparison, frequency combs are phase-locked to a common frequency reference and the frequency difference between optical frequency combs shows white phase noise properties. Thus, it is expected that this new weighting method can be utilized in frequency comparisons of optical frequency combs, settling existing controversy, and providing a way of achieving lower uncertainty.

Bacterial UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) catalyzes the transfer of enolpyruvate from phosphoenolphyruvate (PEP) to uridine diphospho-N-acetylglucosamine (UNAG), which is the first step of bacterial cell wall synthesis. We identified thimerosal, thiram, and ebselen as effective inhibitors of Heamophilus influenzae MurA by screening a chemical library that consisted of a wide range of bioactive compounds. When MurA was preincubated with these inhibitors, their 50% inhibitory concentrations (IC50s) were found to range from 0.1 to 0.7 microM. In particular, thimerosal suppressed the growth of several different Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium at a concentration range of 1-2 microg/ml. These inhibitors covalently modified the cysteine residue near the active site of MurA. This modification changed the open conformation of MurA to a more closed configuration, which may have prevented the necessary conformational change from occurring during the enzyme reaction.

Electro-optic performance of a liquid-crystal (LC) system is enhanced by TiO(2) nanoparticle dispersed in nematic liquid crystal (NLC). The 2.5 V threshold voltage of LC for device operation is lowered to 0.5 V through TiO(2) nanoparticle mixing up to 2 wt.%. To characterize the shape and size distribution of the nanoparticles, high-resolution transmission electron microscopy is employed. Transmittance spectra for the TiO(2) dispersed LC structure and nondispersed LC structure showed that transparency of the TiO(2) dispersed LC is similar to that of pure liquid LC.

Seven transmembrane (7TM) synthetic peptides mimicking the α-helical TM domains of the human serotonin receptor subtype-6 (5-HT 6 ) were autonomously reconstituted in detergent micelle and liposome environments. The degree of assembly of the 7TM peptides was characterized by monitoring the fluorescence resonance energy transfer (FRET) between donor and acceptor probes labeled at the amino termini of the second and fourth TM-peptides, respectively. The FRET efficiency of these peptides significantly increased when the 7TM peptides were reconstituted in liposome compare to detergent micelles. Furthermore, the 7TM peptides reconstituted in liposomes selectively bound to free serotonin and serotonin-conjugated magnetic beads, yielding a dissociation constant of 0.84 μM. These results show that the seven individual TM domains of 5-HT 6 can spontaneously assemble into liposomes in a conformation that mimics a native structure, and further demonstrate that specific interactions between TM helices play a critical role in the folding and stabilizing of GPCRs. The autonomous assembly of 7TM-peptides can be applied to the screening of agonists for GPCRs that are difficult to manipulate.

The frequency of a laser diode is stabilized onto the line centers of double-resonance optical pumping spectra, and the absolute frequencies of the hyperfine-structure components of the $5{P}_{3/2}\text{\ensuremath{-}}4{D}_{3/2}$ excited-state transition for two isotopes of $^{87}\text{R}\text{b}$ and $^{85}\text{R}\text{b}$ atoms are measured using a fiber femtosecond frequency comb system. The $4{D}_{3/2}$ state hyperfine-structure constants of the two Rb isotopes are determined by utilizing the measured absolute optical frequency and the ratio of the hyperfine-structure constants for the two Rb isotopes from the accurately determined values of other states of rubidium. The magnetic-dipole constants $A$ are determined to be 24.75(12) MHz for $^{87}\text{R}\text{b}$ and 7.329(35) MHz for $^{85}\text{R}\text{b}$. The uncertainties of both results are reduced by one order compared to previous results. The electric-quadrupole constants $B$ are determined to be 2.19(11) and 4.52(23) MHz for $^{87}\text{R}\text{b}$ and $^{85}\text{R}\text{b}$, respectively

Small cracks or chips of a product appear very frequently in the course of continuous production of an automatic press process system. These phenomena become the cause of not only defective product but also damage of a press mold. In order to solve this problem AE system was introduced. AE system was expected to be very effective to real time detection of the defective product and to prevention of the damage of the press molds. In this study, for pick and analysis of AE signals generated from the press process, AE sensors/pre-amplifier/analysis and processing board were used as frequently found in the other similar cases. For analysis and processing the AE signals picked in real time from the good or bad products, specialized software called cdm8 was used. As a result of this work it was conformed that intensity and shape of the various AE signals differ depending on the weight and thickness of metal sheet and process type.

This study was performed to investigate a short time change (one week after fire) on soil properties due to the fire inPinus densiflora Sieb. et Zucc stands of the Kosung area in Kangwon Province in Korea. Twenty seven sampling plots [16 burned (8 low intensity fire, 8 high intensity fire) and 11 unburned plots] were chosen. Mineral soil samples from three depths (0–5, 5–15, and 15–25 cm) under the forest floor were collected. Forest fire in the area affected soil chemical properties. Soil pH, total nitrogen, available phosphorus, potassium, calcium, and magnesium in the surface soil (0–5 cm) of the burned area compared with the unburned area increased, but there was no marked change in the subsurface soil (5–25 cm). Organic matter, total nitrogen, available phosphorus, and exchangeable cations in the surface soil were generally lower in the high than in the low intensity fire areas. This indicates that these nutrients on the high intensity fire may be volatilized. The results suggest that change in soil chemical properties in the area was restricted mainly to the surface soil and was different between the high and the low intensity fire types.

Nopp140, a highly phosphorylated nucleolar protein, negatively regulates CK2, a kinase essential for cell proliferation. We quantitatively analyzed the interaction between two subunits of CK2 and Nopp140 and characterized the mechanism by which InsP(6) inhibits the interaction. Nopp140 specifically binds to the catalytic subunit of CK2 (CK2alpha) with a dissociation constant of (K(d)) of 4nM, which interferes with the catalytic activity of CK2. The C-terminal region of Nopp140 is determined as CK2alpha-binding region by a yeast two-hybrid method as well as a direct measurement of the interaction between CK2alpha and deletion mutants of Nopp140. InsP(6) specifically binds to CK2alpha and disrupts the interaction between CK2alpha and Nopp140 with an IC(50) value of 25 microM, thereby attenuating the Nopp140-mediated repression of CK2 activity.

We performed an absolute frequency measurement of an acetylene stabilized laser utilizing a femtosecond injection locking technique that can select one component among the fiber laser comb modes. The injection locking scheme has all the fiber configurations. Femtosecond comb lines of 250 MHz spacing based on the fiber femtosecond laser were used for injection locking of a distributed feedback (DFB) laser operating at 1542 nm as a frequency reference. The comb injected DFB laser serves as a selection filter of optical comb modes and an amplifier for amplification of the selected mode. The DFB laser injection locked to the desired comb mode was used to evaluate the frequency stability and absolute frequency measurement of an acetylene stabilized laser. The frequency stability of the acetylene stabilized laser was measured to be 1.1 x 10(-12) for a 1 s averaging time, improving to 6.9 x 10(-14) after 512 s. The absolute frequency of the laser stabilized on the P(16) transition of (13)C(2)H(2) was measured to be 194 369 569 385.7 kHz.

This paper describes the current status of an ytterbium lattice clock under development at KRISS. After the success of 399 nm magneto-optical-trap (MOT) at a temperature 1 mK, we constructed the 2nd stage cooling laser system at a wavelength of 556 nm to cool atoms further down to several muK. We are also developing an ultra-narrow linewidth laser at a wavelength of 578 nm to probe the clock transition by doubling the frequency output of a commercial 1156 nm ECDL. Efforts to reduce the linewidth are under way.

We have developed a simple laser system for generation of coherent 556 nm light by using frequency doubling of a diode laser. 1112 nm light from an external cavity diode laser is amplified via Yb-doped fiber amplifier and 200 mW of the amplified light is injected to wave-guided MgO-doped PPLN, which produces a 30 mW green light. The frequency diode laser is stabilized to a resonance peak of a high-finesse cavity with finesse ~10000.