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Recently, extracellular vesicles (EVs) have been developed as therapeutic targets for various diseases. Biodistribution is crucial for EVs intended for therapeutic purposes because it can determine the degree of on‐ and off‐target effects. This study aimed to explore techniques to evaluate the biodistribution of unmodified EVs. We devised a novel quantitative polymerase chain reaction (qPCR)‐based assay to detect unmodified EVs by targeting mitochondrial deoxyribonucleic acid (mtDNA), a constituent of EVs. We focused on specific mtDNA regions that exhibited homologous variations distinct from their rodent mtDNA counterparts to establish this analytical approach. Herein, we successfully designed primers and probes targeting human and rodent mtDNA sequences and developed a highly specific and sensitive qPCR method. Furthermore, the quantification range of EVs isolated from various cells differed based on the manufacturer and cell source. IRDye 800CW‐labelled Expi293F EV mimetics were administered to the animals via the tail vein to compare the imaging test and mtDNA‐qPCR results. The results obtained from imaging tests and mtDNA‐qPCR to investigate EV biodistribution patterns revealed differences. The results revealed that our newly developed method effectively determined the biodistribution of unmodified EVs with high sensitivity and reproducibility. [ABSTRACT FROM AUTHOR]

Locomotion of an organism interacting with an environment is the consequence of a symmetry-breaking action in space-time. Here we show a minimal instantiation of this principle using a thin circular sheet, actuated symmetrically by a pneumatic source, using pressure to change shape nonlinearly via a spontaneous buckling instability. This leads to a polarized, bilaterally symmetric cone that can walk on land and swim in water. In either mode of locomotion, the emergence of shape asymmetry in the sheet leads to an asymmetric interaction with the environment that generates movement--via anisotropic friction on land, and via directed inertial forces in water. Scaling laws for the speed of the sheet of the actuator as a function of its size, shape, and the frequency of actuation are consistent with our observations. The presence of easily controllable reversible modes of buckling deformation further allows for a change in the direction of locomotion in open arenas and the ability to squeeze through confined environments--both of which we demonstrate using simple experiments. Our simple approach of harnessing elastic instabilities in soft structures to drive locomotion enables the design of novel shape-changing robots and other bioinspired machines at multiple scales. [ABSTRACT FROM AUTHOR]

Nanostructured surfaces with quasi-random geometries can manipulate light over broadband wavelengths and wide ranges of angles. Optimization and realization of stochastic patterns have typically relied on serial, direct-write fabrication methods combined with real-space design. However, this approach is not suitable for customizable features or scalable nanomanufacturing. Moreover, trial-and-error processing cannot guarantee fabrication feasibility because processing–structure relations are not included in conventional designs. Here, we report wrinkle lithography integrated with concurrent design to produce quasi-random nanostructures in amorphous silicon at wafer scales that achieved over 160% light absorption enhancement from 800 to 1,200 nm. The quasi-periodicity of patterns, materials filling ratio, and feature depths could be independently controlled. We statistically represented the quasi-random patterns by Fourier spectral density functions (SDFs) that could bridge the processing–structure and structure–performance relations. Iterative search of the optimal structure via the SDF representation enabled concurrent design of nanostructures and processing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Center for Time and Frequency at the Korea Research Institute of Standards and Science (KRISS) is responsible for the maintenance, improvement, and dissemination of time and frequency standards in Korea. In this paper, we will introduce current research activities regarding the development of precision atomic clocks, atomic gravimeters, miniature atomic clocks, and Bloch oscillation interferometers. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances across the visible regime—and within a single system—has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances. This dynamic modulation of particle–particle spacing enabled either dipolar or quadrupolar lattice modes to be selectively accessed and individually optimized. Programmable plasmon modes offer a robust way to achieve real-time tunable materials for plasmon-enhanced molecular sensing and plasmonic nanolasers and opens new possibilities for integrating with flexible electronics. [ABSTRACT FROM AUTHOR]

Ballistocardiographs (BCGs), which record the mechanical activity of the heart, have been a subject of interest for several years because of their advantages in providing unobtrusive physiological measurements. BCGs could also be useful for monitoring the biological signals of infants without the need for physical confinement. In this study, we describe a physiological signal monitoring bed based on load cells and assess an algorithm to extract the heart rate and breathing rate from the measured load-cell signals. Four infants participated in a total of 13 experiments. As a reference signal, electrocardiogram and respiration signals were simultaneously measured using a commercial device. The proposed automatic algorithm then selected the optimal sensor from which to estimate the heartbeat and respiration information. The results from the load-cell sensor signals were compared with those of the reference signals, and the heartbeat and respiration information were found to have average performance errors of 2.55% and 2.66%, respectively. The experimental results verify the positive feasibility of BCG-based measurements in infants. [ABSTRACT FROM AUTHOR]

Intercellular bridges are a conserved feature of spermatogenesis in mammalian germ cells and derive from arresting cell abscission at the final stage of cytokinesis. However, it remains to be fully understood how germ cell abscission is arrested in the presence of general cytokinesis components. The TEX14 (testis-expressed gene 14) protein is recruited to the midbody and plays a key role in the inactivation of germ cell abscission. To gain insights into the structural organization of TEX14 at the midbody, we have determined the crystal structures of the EABR [endosomal sorting complex required for transport (ESCRT) and ALIX-binding region] of CEP55 bound to the TEX14 peptide (or its chimeric peptides) and performed functional characterization of the CEP55-TEX14 interaction by multiexperiment analyses. We show that TEX14 interacts with CEP55-EABR via its AxGPPx3Y (Ala793, Gly795, Pro796, Pro797, and Tyr801) and PP (Pro803 and Pro804) sequences, which together form the AxGPPx3YxPP motif. TEX14 competitively binds to CEP55-EABR to prevent the recruitment of ALIX, which is a component of the ESCRT machinery with the AxGPPx3Y motif. We also demonstrate that a high affinity and a low dissociation rate of TEX14 to CEP55, and an increase in the local concentration of TEX14, cooperatively prevent ALIX from recruiting ESCRT complexes to the midbody. The action mechanism of TEX14 suggests a scheme of how to inactivate the abscission of abnormal cells, including cancer cells. [ABSTRACT FROM AUTHOR]

In this study, we developed and tested a capacitively coupled electrocardiogram (ECG) measurement system using conductive textiles on a bed, for long-term healthcare monitoring. The system, which was designed to measure ECG in a bed with no constraints of sleep position and posture, included a foam layer to increase the contact region with the curvature of the body and a cover to ensure durability and easy installation. Nine healthy subjects participated in the experiment during polysomnography (PSG), and the heart rate (HR) coverage and heart rate variability (HRV) parameters were analyzed to evaluate the system. The experimental results showed that the mean of R-peak coverage was 98.0% (95.5%-99.7%), and the normalized errors of HRV time and spectral measures between the Ag/AgCl system and our system ranged from 0.15% to 4.20%. The root mean square errors for inter-beat (RR) intervals and HR were 1.36 ms and 0.09 bpm, respectively. We also showed the potential of our developed system for rapid eye movement (REM) sleep and wake detection as well as for recording of abnormal states. [ABSTRACT FROM AUTHOR]

Proteomic analyses of the excretory/secretory proteins from the RH strain of Toxoplasma gondii have been performed to understand their functions in the host-parasite interaction. A total of 34 proteins were identified from LC/MS/MS analysis and their abundance was estimated by spectral counting methods. Among them, 8 species of micronemal proteins (MICs), 2 species of rhoptry proteins (ROPs), and 6 species of dense granular proteins (GRAs) were confirmed. Besides these, 18 species of protein were newly identified, and their cellular functions were estimated from sequence analysis. The three most abundant of the 34 identified extractor/secretory proteins GRA1, GRA7 and GRA2 were confirmed to be highly expressed in T. gondii using the spectral count method. This phenomenon is another demonstration of the importance of GRA proteins for the penetration and survival of T. gondii. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Protein kinase CK2 is a ubiquitous kinase that can phosphorylate hundreds of cellular proteins and plays important roles in cell growth and development. Deregulation of CK2 is related to a variety of human cancers, and CK2 is regarded as a suppressor of apoptosis; therefore, it is a target of anticancer therapy. Nucleolar phosphoprotein 140 (Nopp140), which is an intrinsically disordered protein, interacts with CK2 and inhibits the latter’s catalytic activity in vitro. Interestingly, the catalytic activity of CK2 is recovered in the presence of D-myo-inositol 1,2,3,4,5,6-hexakisphosphate (IP6). IP6 is widely distributed in animal cells, but the molecular mechanisms that govern its cellular functions in animal cells have not been completely elucidated. In this study, the crystal structure of CK2 in complex with IP6 showed that the lysine-rich cluster of CK2 plays an important role in binding to IP6. The biochemical experiments revealed that a Nopp140 fragment (residues 568–596) and IP6 competitively bind to the catalytic subunit of CK2 (CK2α), and phospho-Ser574 of Nopp140 significantly enhances its interaction with CK2α. Substitutions of K74E, K76E, and K77E in CK2α significantly reduced the interactions of CK2α with both IP6 and the Nopp140-derived peptide. Our study gives an insight into the regulation of CK2. In particular, our work suggests that CK2 activity is inhibited by Nopp140 and reactivated by IP6 by competitive binding at the substrate recognition site of CK2. [ABSTRACT FROM AUTHOR]

The aligned liquid crystals (LCs) display on SiNx thin films using ion-beam (IB) irradiation was studied with controllability of pretilt angle depending on incident energies of the IB. The LCs alignment property for the SiNx thin films were observed to verify the practical application potential. A good LCs alignment of vertical alignment LCs cells on SiNx thin film surfaces irradiated with incident IB energy of 1800 eV was achieved. The atomic force microscopy (AFM) images of LCs on SiNx thin film surfaces irradiated with IB energy was used for the surface analysis. [ABSTRACT FROM AUTHOR]

We studied liquid crystal (LCs) alignment effects on homogeneous polyimide (PI) surfaces induced by polarised UV (PUV) exposure and rubbing in different directions. We found that the LC orientation is not affected by PUV exposure times of less than 90 min after rubbing, and that PUV exposure times over 90 min after rubbing resulted in LC orientations that were more closely aligned with the direction of PUV exposure than the direction of rubbing. Short-term PUV exposure affects the variation of the pretilt angle of the PI and LC. In addition, as PUV exposure time increases, it can convert the LC alignment direction from the rubbing direction to the PUV direction. [ABSTRACT FROM AUTHOR]

The aligned liquid crystals (LCs) display on SiNx thin films using ion-beam (IB) irradiation was studied with controllability of pretilt angle depending on incident energies of the IB. The LCs alignment property for the SiNx thin films were observed to verify the practical application potential. A good LCs alignment of vertical alignment LCs cells on SiNx thin film surfaces irradiated with incident IB energy of 1800eV was achieved. The atomic force microscopy (AFM) images of LCs on SiNx thin film surfaces irradiated with IB energy was used for the surface analysis. [ABSTRACT FROM AUTHOR]

Abstract  We have synthesized new human body motions from existing motion data, by dividing the body of an animated character into several parts, such as upper and lower body, and partitioning the motion of the character into corresponding partial motions. By combining different partial motions, we can generate new motion sequences. We select the most natural-looking combinations by analyzing the similarity of partial motions, using techniques such as motion segmentation, dimensionality reduction, and clustering. These new combinations can dramatically increase the size of a motion database, allowing more score in selecting motions to meet constraints, such as collision avoidance. We verify the naturalness and physical plausibility of the new motions using an SVM learning model and by analysis of static and dynamic balance. [ABSTRACT FROM AUTHOR]

In order to establish the national frequency standards for the Korea Research Institute of Standards and Science in the 1.5-μm region, we have developed an acetylene-stabilized laser diode locked to the P(16) transition of 13C2H2. We then measured its absolute frequency using an optical-frequency comb based on a mode-locked Ti:sapphire laser whose repetition frequency and carrier-envelope offset frequency were phase locked to an H-maser. The measured absolute frequency of the laser diode locked to the P(16) transition of 13C2H2 was 194 369 569 386.0 kHz, with an uncertainty of 0.3 kHz, based on the measurements of a single system. Including the contribution of the residual offset, the uncertainty was 1.9 kHz. [ABSTRACT FROM AUTHOR]

We developed an optical pumping magnetometer system for magnetocardiography (MCG). The basic system requirements for measuring MCG are as follows: a 5-μT weak bias field in a magnetically shielded room, a 20-mm cell for spatial resolution, and a 30-Hz bandwidth for heart signals. In order to reduce the environmental magnetic noise, a double-cell gradiometer configuration has been adopted. The measured noise level was ∼10 pT/√Hz. By switching current flows through a symmetrical three-axis rectangular Helmholtz coil set, the system is designed to measure three vector components of the magnetic field gradient. We show that this configuration reduces the error in current dipole localization with respect to the usual normal component detection by computer simulation of confidence-region estimation. Based on the simulation, we suggest that the system is applicable for diagnosing myocardial infarction on the anterior wall of a human heart in coronary artery disease. [ABSTRACT FROM AUTHOR]

In tissue engineering and wound-healing applications, dermal substitutes are used to provide fibroblasts with the mechanical support for their growth and then to facilitate the skin formation. In this study, three-dimensional porous poly(lactic-co-glycolic acid) (PLGA) 65/35 scaffolds were prepared and then the composites of the scaffolds and human fetal dermal fibroblasts were fabricated as a tissue-engineered dermal substitute. The function and tissue compatibility of the artificial dermal substitute were evaluated at the levels of gene expression (by RT-PCR) and protein expression (total collagen quantities), as well as by histological and immunohistochemical analysis. The PCR products indicated that the mRNA of type-I collagen, mainly secreted by the fibroblasts onto the PLGA scaffolds, was clearly expressed after 4 weeks. The amount of total collagen synthesized from the cells was shown to increase gradually during the initial culture period and slightly decreased afterwards. After 8 weeks of culture, the fibroblasts were well attached and migrated entirely throughout the pores of the PLGA scaffold with normal function. Furthermore, the positively stained type-I collagen was intensively detected throughout the pores. These results suggest that the function and tissue compatibility may be important criteria in evaluating an artificial tissue-engineered skin. [ABSTRACT FROM AUTHOR]

The HIV-1 envelope glycoprotein transmembrane subunit, gp41, mediates the fusion of viral and target cell membranes. The 2 helical regions in the ectodomain of gp41, the N-helix and the C-helix, form a helical bundle complex that has been suggested as a fusion-active conformation. Previously, an enzyme-linked immunosorbent assay (ELISA) method had been established to measure the interaction of 2 helical regions of gp41. In this study, the ELISA method was modified to apply high-throughput screening (HTS) of an organic compound library. A few compounds had been identified to prevent the interaction between 2 helical regions of gp41, and they were further shown to inhibit the gp41-mediated viral infection. In addition, they specifically quenched the fluorescence of tryptophan in the N-helix region, indicating that these compounds bound to the N-helix rather than the C-helix of gp41. These results suggested that this assay method targeting gp41 could be used for HTS of HIV fusion inhibitors. (Journal of Biomolecular Screening 2005:13-19) [ABSTRACT FROM AUTHOR]

Highly porous poly(ethylene glycol) (PEG) hydrogel scaffolds crosslinked with hydrolyzable polyrotaxane for cartilage tissue engineering were prepared by a solvent casting/salt leaching technique. The resultant scaffolds have well interconnected microporous structures ranging from 87 to 90%. Pore sizes ranging from 115.5–220.9 μm appeared to be dependent on the size of the sieved sodium chloride particulates. Moreover, a dense surface skin layer was not found on either side of the scaffold surfaces. Using microscopic Alcian blue staining of the chondrocyte-seeded scaffolds, well adhered cells and newly produced glycosaminoglycans (GAG) were confirmed. Following the initial chondrocyte seeding onto the hydrogel scaffolds, the cell number was significantly increased, reaching 149, 877, and 1228 cells/mg of tissue at 8, 15, and 21 days in culture, respectively. The micrograph shows well adhered and spread chondrocytes in the interior pores and a cartilaginous extracellular matrix with a GAG fraction produced from the chondrocytes. Results suggest that the PEG hydrogel scaffolds crosslinked with the hydrolyzable polyrotaxane are a promising candidate for chondrocyte culture. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1087–1092, 2003 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We recently achieved the homogeneous alignment of liquid crystal (LC) on amorphous Ta2O5 layers. This study demonstrates that LC layers could be aligned either homogeneously or vertically by increasing the growth temperature of rf magnetron sputtering device and the irradiation time of the DuoPIGatron type Ar ion beam device causing uniform and dense plasma. We attained two LC orientations by observing Ta 4f and O 1s peak shifts with x-ray photoelectron spectroscopy. Moreover, the decreased thickness of layers with high-k dielectric constants helped to decrease driving LC voltages and in turn to achieve low power consumption. [ABSTRACT FROM AUTHOR]

High-performance liquid crystals (LCs) driven at a 0.9 V threshold were demonstrated on very thin HfO2 films with vertical (homeotropic) alignment by ion bombardment. Atomic layer deposition was used to obtain LC orientation on ultrathin high-quality films of double-layer HfO2/Al2O3. X-ray photoelectron spectroscopy indicated that full oxidization of HfO2 film surfaces was induced by ion bombardment, shifting the Hf 4f spectra to lower binding energies. The increased intensities of the Hf 4f peaks after ion bombardment confirmed that nonstoichiometric HfOx was converted to the fully oxidized HfO2 surfaces. [ABSTRACT FROM AUTHOR]

Using ion-beam (IB) irradiation, liquid crystals (LCs) were vertically aligned (VA) on a γ-Al2O3 alignment film. Atomic-layer deposition was used to orient the LCs on high-quality γ-Al2O3 alignment films. The LC molecule orientation indicates the vertical direction of the atomic-layer-deposited γ-Al2O3 alignment films. X-ray photoelectron spectroscopy showed that IB irradiation changed the chemical structure, shifting the Al–O binding energy and altering the Al–O bonding intensity. The low-voltage transmittance characteristics of the VA LC displays on the γ-Al2O3 alignment films were also measured, showing reduced voltage and power requirements. [ABSTRACT FROM AUTHOR]

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 · 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

We measured the absolute frequency of the 1S0–3P0 transition of 171Yb atom confined in a one-dimensional optical lattice relative to the SI second. The determined frequency was 518 295 836 590 863.38(57) Hz. The uncertainty was reduced by a factor of 14 compared with our previously reported value in 2013 due to the significant improvements in decreasing the systematic uncertainties. This result is expected to contribute to the determination of a new recommended value for the secondary representations of the second. [ABSTRACT FROM AUTHOR]

We analyze both the s- and p-wave collision induced frequency shifts and propose an over-π pulse scheme to cancel the shifts in optical lattice clocks interrogated by a Rabi pulse. The collisional frequency shifts are analytically solved as a function of the pulse area and the inhomogeneity of the Rabi frequencies. Experimentally measured collisional frequency shifts in an Yb optical lattice clock are in good agreement with the analytical calculations. Based on our analysis, the over-π pulse combined with a small inhomogeneity below 0.1 allows a fractional uncertainty on a level of 10−18 in both Sr and Yb optical lattice clocks by canceling the collisional frequency shift. [ABSTRACT FROM AUTHOR]

We propose a fiber ring laser that operates in a single longitudinal mode by incorporating unpumped erbium-doped fiber as a saturable absorber filter. This laser can be discretely tuned to a 25-GHz-spacing grid that precisely matches ITU-T (International Telecommunication Union, Telecommunication Standardization Sector) grids, which are reference frequencies for optical communication systems. This laser has a signal-to-source spontaneous emission ratio higher than 60 dB, and the lasing frequencies of 361 channels are matched to ITU-T grids with excellent power flatness. With one channel of this fiber laser, we place the reference frequency near the absolute frequency reference (AFR, 193.1 THz). The relative frequency stability of the laser and the frequency offset from the AFR were less than 1.6×10−8 (integrated time, 5 min) and 30 MHz, respectively. [ABSTRACT FROM AUTHOR]