Magnetic glassy state at low spin state of Co3+ in EuBaCo2O5+δ (δ = 0.47) cobaltite

The magnetic glassy state is a fascinating phenomenon, which results from the kinetic arrest of the first order magnetic phase transition. Interesting properties, such as metastable magnetization and nonequilibrium magnetic phases, are naturally developed in the magnetic glassy state. Here, we report magnetic glass property in the low spin state of Co³⁺ in EuBaCo₂O_5+δ (δ  =  0.47) cobaltite at low temperature (T  <  60 K). The measurements of magnetization under the cooling and heating in unequal fields, magnetization relaxation and thermal cycling of magnetization show the kinetic arrest of low magnetization state below 60 K. The kinetically arrested low temperature magnetic phase is further supported through the study of isothermal magnetic entropy, which shows the significant entropy change. The present results will open a new window to search the microscopic relation between the spin state transitions and the kinetic arrest induced magnetic glassy phenomena in complex materials.

The association between season of birth, age at onset, and clozapine use in schizophrenia

OBJECTIVE

This study aimed to determine whether the rate of clozapine use, an indicator of refractoriness in schizophrenia, is associated with the season of birth and age at onset in patients with schizophrenia based on nationwide data.

METHODS

Patients with schizophrenia (n = 114 749) who received prescriptions for antipsychotic medication between 2008 and 2014 were retrospectively identified from the Korean National Health Insurance Service database. The study population was divided into three groups based on their age at the onset of schizophrenia (early, middle, and late onset). We assessed differences in the month of birth between patients and the general population. In addition, the cumulative clozapine use was calculated.

RESULTS

Compared to the late-onset schizophrenia group, the early- and middle-onset groups showed a higher probability of birth during the winter season. In addition, the early-onset group showed the highest cumulative clozapine use rate. In the middle-onset group, the initiation of clozapine use was significantly earlier for patients born in winter compared to those born in summer.

CONCLUSION

Our results indicate that the age at onset is an important factor in predicting the prognosis of schizophrenia patients. The season of birth also affects the prognosis, but with less robustness. Specifically, it appears that early disease onset and winter birth might be associated with poor outcomes in Korean patients with schizophrenia.

Transmission of 51.56-Gb/s OOK signal using 1.55-μm directly modulated laser and duobinary electrical equalizer

We demonstrate the transmission of 51.56-Gb/s on-off keying (OOK) signals generated by using a 1.55-μm directly modulated laser (DML) over 15-km long standard single-mode fiber. In this experiment, a duobinary electrical equalizer based on a finite-impulse-response filter is used at the receiver to increase the dispersion-limited transmission distance. We evaluate the performances of the 51.56-Gb/s OOK signals with respect to the transmission distance by using the frequency response analysis of the proposed system. This result is used to explain why it is effective to utilize the duobinary equalization (instead of binary equalization) for increasing the transmission distance.

Crosstalk analysis in homogeneous multi-core two-mode fiber under bent condition

We analyze the inter-core crosstalk in homogeneous multi-core two-mode fibers (MC-TMFs) under bent condition by using the coupled-mode equations. In particular, we investigate the effects of the intra-core mode coupling on the inter-core crosstalk for two different types of MC-TMFs at various bending radii. The results show that the inter-core homo-mode crosstalk of LP(11) mode is dominant under the gentle fiber bending condition due to its large effective area. However, as the fiber bending becomes tight, the intra-core mode coupling is significantly enhanced and consequently makes all the inter-core crosstalk levels comparable to each other regardless of the mode. A similar tendency is observed at a reduced bending radius when the difference in the propagation constants between modes is large and core pitch is small.

Simple carrier-phase estimator for high-speed RSOA-based coherent WDM PON

It has been recently reported that reflective semiconductor optical amplifiers (RSOAs) can be used as phase modulators for the cost-effective implementation of the high-speed wavelength-division-multiplexed passive optical networks (WDM PONs). For the detection of the phase-shift-keying (PSK) signal generated by using an RSOA, we should be able to estimate its carrier phase accurately at the digital coherent receiver. However, when the baud rate of this PSK signal is set to be much higher than the RSOA's modulation bandwidth, the conventional M-th power algorithm cannot estimate its carrier phase accurately. To solve this problem, we develop a simple carrier-phase estimation technique for the high-speed (>10 Gb/s) PSK signals generated by using bandwidth-limited RSOAs. This technique estimates the carrier phase of the PSK signal by measuring the angular direction of the opening occurred in the trajectory of the phasor diagram. By using the proposed technique, we demonstrate the upstream transmission of the 25.78-Gb/s quadrature phase-shift-keying (QPSK) signal generated by using an RSOA (3-dB bandwidth: 3.2 GHz) in a 60-km reach coherent WDM PON.

Practical 12.5-Gb/s, 12.5-GHz spaced ultra-dense WDM PON

We report a practical 12.5-Gb/s, 12.5-GHz-spaced ultra-dense wavelength-division-multiplexed passive optical network (UD-WDM PON). For the cost-effectiveness, we implement the downstream links by using electro-absorption modulated lasers (EMLs) in the 4-level pulse amplitude modulation (4PAM) format and PIN receivers, and the upstream links by using reflective semiconductor optical amplifiers (RSOAs) modulated in the quadrature phase-shift-keying (QPSK) format and low-cost self-homodyne receivers. To further enhance its cost-effectiveness, we also utilize an optical frequency comb generator, instead of a large number of wavelength-selected lasers, to provide the seed light for these colorless RSOAs. We optimize the operating conditions of the EMLs and RSOAs to maximize the power margins in the presence of the crosstalk arising from closely spaced neighboring channels and the inter-symbol interference (ISI) caused by the narrow passband of the cascaded arrayed-waveguide gratings (AWGs) as well as the limited modulation bandwidths of RSOAs. The experimental results show that we can secure the power margins of >2.5 dB for both upstream and downstream links of the proposed UD-WDM PON.

Optical performance monitoring technique using software-based synchronous amplitude histograms

We propose and demonstrate a simple technique to monitor both the optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD) by using the software-based synchronous amplitude histogram (SAH) analysis. We exploit the software-based synchronization technique to construct SAHs from the asynchronously sampled intensities of the signal. The use of SAHs facilitates the accurate extraction of the monitoring parameters at the center of the symbol. Thus, unlike in the case of using the technique based on the asynchronous amplitude histogram (AAH), this technique is not affected by the transient characteristics of the modulated signals. The performance of the proposed monitoring technique is evaluated experimentally by using 10-Gbaud quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM) signals over wide ranges of OSNR and CD. We also evaluate the robustness of the proposed technique to the signal's transient characteristics.

Achievable capacity improvement by using multi-level modulation format in trench-assisted multi-core fiber system

We evaluate the impacts of using multi-level modulation formats on the transmission capacity of the multi-core fiber (MCF) having trench-assisted index profile and hexagonal layout. For this evaluation, we utilize the spectral efficiency per unit area, defined as the spatial spectral efficiency (SSE). The results show that the SSE improvement achievable by using the higher-level modulation format can be reduced due to its lower tolerance to the inter-core crosstalk. We also evaluate the effects of using large effective area on the transmission capacity of the trench-assisted MCF. The results show that the use of large effective area can decrease this capacity due to the increased inter-core crosstalk and lengthened cable cutoff wavelength, although it can help increase the transmission distance. Thus, it is necessary to optimize the effective area of MCF by considering both the SSE and transmission distance. However, the results indicate that the effect of using different effective areas on the SSE-distance product is not significant, and it is not useful to increase the effective area of the trench-assisted MCF to be larger than ~110 μm(2).

3-D imaging, illustration, and quantitation of enteric glial network in transparent human colon mucosa

BACKGROUND

Enteric glia form a network in the intestinal mucosa and have been suggested to engage in multidirectional interactions with the epithelium, blood vessels, nerves, and immune system. However, due to the dispersed nature of the glial network, standard histology cannot provide a global view of the network architecture. We prepared transparent human colon mucosa for three-dimensional (3-D) confocal microscopy with S100B immunostaining to reveal the location-dependent glial network for qualitative and quantitative analyses.

METHODS

Full-thickness human colons were acquired from colectomies performed for colorectal cancer. We targeted the mucosa away from the tumor site to characterize the glial network morphology. Optical clearing (use of immersion solution to reduce scattering) was applied to generate transparent specimens for deep-tissue microscopy.

KEY RESULTS

Two features of the glial network were seen: (i) A dense glial population resides at the crypt base/mucosal boundary in contact with the lymphatic vessels, and (ii) from the base, the glial network elongates along the crypt axis with peri-cryptic and peri-vascular connections toward the opening. We quantified the mucosal glia as the S100B-positive cells with at least two processes extending from the cell body. Examples of the global and in-depth imaging of adenoma were given to illustrate the morphological correlation between the loss of glial fibers and the aberrant crypts.

CONCLUSIONS & INFERENCES

We have established a useful approach for 3-D imaging, panoramic illustration, and quantitation of the enteric glia in the human colon mucosa to help characterize their roles with mucosal components in health and disease.

Transmission of 40-Gb/s QPSK upstream signal in RSOA-based coherent WDM PON using offset PDM technique

We demonstrate the 40-Gb/s upstream transmission in the 60-km reach wavelength-division-multiplexed passive optical network (WDM PON) implemented by using directly modulated reflective semiconductor optical amplifiers (RSOAs) and self-homodyne receivers. It is difficult to operate the RSOA at 40 Gb/s due to its limited modulation bandwidth. To overcome this problem and generate 40-Gb/s upstream signal, we utilize the quadrature phase-shift-keying (QPSK) format and the offset polarization-division-multiplexing (PDM) technique. For this purpose, we install two RSOAs at each ONU and provide the seed light for these RSOAs by polarization-multiplexing the outputs of two lasers with a small frequency offset (20 GHz). This frequency offset is used to separate the polarization-multiplexed seed light by using a simple delay-line interferometer (DLI), instead of the polarization-beam splitter and polarization controller, at the ONU. The separated seed light is modulated by each RSOA at 20 Gb/s in the QPSK format, and then combined again by the DLI before sent back to the central office (CO). The results show that this WDM PON can support the transmission of 40-Gb/s channels spaced at 50 GHz over 60 km without using any remote optical amplifiers.

Development of an early psychosis intervention system in Korea: focus on the continuing care system for first-episode psychosis treatment in Seoul

Providing intensive psychosocial intervention within the 5-year critical period following the first psychotic episode is important for both symptomatic and functional recovery. Recently, community mental health centres in Korea have begun to shift their main roles from care of those with chronic schizophrenia to early detection of and interventions for those with first-episode psychosis. This pioneering approach was initiated by the Seoul Mental Health Center, which established a community network, formed a clinical consortium with hospitals and clinics, and developed guidelines for early psychosis detection and management and for the Social Treatment for Early Psychosis (STEP) programme. The One-STEP programme, provided during hospitalisation, has been especially efficient in obtaining a high acceptance rate for community services. Several key issues are discussed with regard to the successful establishment of the close partnership between community mental health centres and hospitals / clinics.

Long-reach 10-Gb/s RSOA-based WDM PON employing QPSK signal and coherent receiver

We demonstrate a long-reach wavelength-division-multiplexed passive optical network (WDM PON) operating at the symmetric rate of 10.3 Gb/s. For the cost-effectiveness, we realize the upstream transmission by utilizing directly-modulated TO-can packaged reflective semiconductor optical amplifiers (RSOAs) and digital coherent receivers. In addition, to overcome the limited modulation bandwidth of this TO-can packaged RSOA (~2.2 GHz) and operate it at 10.3 Gb/s, we utilize the quadrature phase shift keying (QPSK) format and the electronic phase equalization technique. The result shows that we can extend the maximum reach of the 10.3-Gb/s RSOA-based WDM PON to ~80 km without using any remote amplifiers.

Correlation-based OTDR for in-service monitoring of 64-split TDM PON

We demonstrate that the correlation-based optical time domain reflectometer (OTDR) can be used for the in-service monitoring of the 64-split time-division-multiplexed passive optical network (TDM PON). To achieve this objective, we superimpose a pseudo noise (PN) sequence having a modulation depth of ~40% to the downstream signal and utilize it for the correlation detection. However, the use of such a large PN sequence can seriously deteriorate the performance of the downstream receiver. Thus, we apply 8B/10B encoding to the downstream signal, and then filter out the PN sequence at the downstream receiver by using a high-pass filter. As a result, the power penalty caused by the use of a large PN sequence is reduced to an acceptable level (<3 dB), while the dynamic range of this correlation-based OTDR is increased to ~30 dB. We then evaluate the performance of the proposed OTDR in the fiber link similar to the optical distribution network of the 64-split TDM PON. The results show that this OTDR can detect both the reflective and non-reflective events occurred in the feeder fiber as well as the reflective events in the drop fibers even in the 64-split TDM PON.

Large-scale mitochondrial DNA deletions in weak goslings

1. Evidence has accumulated in mammals to support the idea that mitochondrial DNA (mtDNA) deletions and mutations might contribute to ageing and reproductive failure. White Roman geese were monitored to evaluate the effect of large-scale deletions of mtDNA in an avian species. 2. A total of 340 samples from 114 dead embryos, 111 weak goslings, and 115 normal goslings were used in this experiment. The regions of these two large-scale mtDNA deletions, ΔmtDNA6829 and ΔmtDNA6992, were between the COI and ND5 genes. A 3·6% (4 out of 111) positive sample was detected in the weak goslings. In contrast, no large-scale mitochondrial DNA deletions were detected in either the dead embryos (0 out of 114) or the normal goslings (0 out of 115). 3. Large-scale mtDNA deletions may be a factor causing weak goslings.

Clinical significance of tumor suppressor PTEN in colorectal carcinoma

BACKGROUND

It has been demonstrated that the deletion, mutation, hypermethylation and subcellular location of the tumor suppressor phosphatase and tensin homologue (PTEN) are closely correlated with carcinogenesis, progression and prognosis of malignancy. Both mutation and the microsatellite instability of the PTEN gene influence regulation of the PI3K/Akt signaling pathway. This study investigated whether loss of nuclear PTEN is correlated with chemosensitivity, clinicopathological parameters and survival.

METHODS

Intracellular levels of PTEN of multiple cell lines of colorectal carcinoma (CRC) were evaluated by Western blotting and immunocytochemistry. The chemosensitivity of cell lines with various expression levels of PTEN was evaluated using 5-flurouracil (5-FU), oxaliplatin and irinotecan (CPT), and clinical significance was evaluated by immunohistochemical analysis of 133 CRC specimens.

RESULTS

Colon cancer cell lines HT-29, LoVo and SW480 differed in expression of PTEN, with high, moderate and low levels, respectively. HT-29 and LoVo PTEN expression was suppressed by a low concentration of 5-FU and oxaliplatin; however, SW480 was insensitive to these chemotherapeutic agents. Nuclear PTEN was overexpressed in most (>80%) normal colon mucosa samples, but the incidence significantly decreased (89.2% → 53.4%) in the CRC group. PTEN in the nucleus was negatively correlated with tumor size and vascular invasion in CRC, and CRC patients with negative PTEN expression in the nucleus exhibited poor survival.

CONCLUSION

Cell lines with a high expression of PTEN are sensitive to chemotherapy with 5-FU and oxaliplatin. Nuclear PTEN expression gradually decreases after malignant transformation, and loss of PTEN expression in the nucleus is associated with tumor progression and poor clinical outcome in CRC.

Phasor monitoring of DxPSK signals using software-based synchronization technique

We develop a novel phasor monitor to obtain the constellation diagram from asynchronously sampled data measured by using the delay-detection technique. This phasor monitor consists of three parts; a phase-adjustment-free delay-interferometer, an optical front-end made of three photodetectors, and analog-to-digital (A/D) convertors, and a digital signal processor. We operate the A/D convertor at the sampling rate much slower than the symbol rate and acquire the data asynchronously. However, despite the use of such a slow and asynchronous sampling rate, we obtain the clear eye and constellation diagrams by utilizing the software-based synchronization technique based on a novel phased-reference detection algorithm. Thus, the proposed phasor monitor can be implemented without using high-speed A/D convertors and buffer memories, which have been the major obstacles for the cost-effective realization of the phasor monitor. For a demonstration, we realize the proposed phasor monitor by using an A/D converter operating at 9.77 MS/s and used it for the constellation monitoring and bit-error-rate (BER) estimation of 10.7-Gsymbol/s differential quadrature phase-shift keying (DQPSK) and differential 8-ary phase-shift keying (D8PSK) signals.

Transmission of 1.25-Gb/s PSK signal generated by using RSOA in 110-km coherent WDM PON

We generate the phase-modulated signal by utilizing the chirp characteristics of the directly-modulated reflective semiconductor optical amplifier (RSOA) for the cost-effective realization of a long-reach wavelength-division-multiplexed passive optical network (WDM PON). We first investigate the relation between the amplitude and phase modulation indices in a directly-modulated RSOA and optimize these modulation indices to maximize the symbol distance on the constellation diagram. The results show that, by operating the RSOA under this optimum condition, we can achieve the excellent receiver sensitivity of -49.8 dBm at 1.25 Gb/s. We implement a long-reach WDM PON by using the phase-modulated RSOAs and self-homodyne receivers, and demonstrate the error-free transmission of 1.25-Gb/s signal over a 110-km long link without using any optical amplifiers.

Optical performance monitoring technique using asynchronous amplitude and phase histograms

We report a new optical performance monitoring technique based on the amplitude and phase histograms of the optical signal. The amplitude and phase histograms are obtained by using an intradyne receiver and the asynchronous delay-tap sampling method. From these histograms, we can evaluate the amplitude and phase Q-factors of the optical signal regardless of its modulation format. In addition, by using these Q-factors, we can estimate the bit-error rate (BER) of the monitoring signal.

Transmission of 108-Gb/s PDM 16ADPSK signal on 25-GHz grid using non-coherent receivers

We demonstrate the transmission of 108-Gb/s polarization-division-multiplexed (PDM) 16-ary amplitude- and differential phase-shift-keying (16ADPSK) signal by using a non-coherent receiver. We generate the 16ADPSK signal by using a differential 8-ary phase-shift-keying (D8PSK) modulator and a phase-distortion-free amplitude-shift-keying (ASK) modulator. On the other hand, the receiver is implemented by using a delay interferometer based on a 3x3 fiber coupler and the data-aided phase-noise estimation (DAPNE) algorithm. By using these transmitter and receiver, we achieve a nearly quantum-limited receiver sensitivity in the back-to-back condition. In addition, we examine the possibility of transmitting 108-Gb/s signals on a 25-GHz grid without using the coherent detection technology. The results show that we can secure a sufficient optical-signal-to-noise (OSNR) margin after the transmission of 80-km long dispersion managed link. The achieved spectral efficiency is 4.0 bit/s/Hz.

Daytime sleepiness and sleep quality among Malaysian medical students

Poor sleep quality and daytime somnolence is reported to be associated with cardiovascular events, road traffic accident, poor academic performance and psychological distress. Some studies documented that it is prevalent in most populations but its frequency among medical students has not been documented in Malaysia. This is a self-administered questionnaire survey of medical students from International Medical University, Malaysia. Daytime sleepiness of medical students was assessed using Epworth Sleepiness Scale (ESS). Student scoring ESS > 11 was regarded as having excessive daytime sleepiness. Psychological distress was measured using 12-item General Health Questionnaire (GHQ-12). A total of 799 medical students participated in this survey (response rate 69.5%). Daytime sleepiness occurred in 35.5%, psychological distress was present in 41.8% and 16.1% reported bad sleep quality. Daytime sleepiness was significantly more common among the clinical students, those with self-reported bad sleep quality and psychological distress; but unrelated to the number of hours sleep at night. We have documented high prevalence of daytime sleepiness, poor sleep quality and psychological distress. Higher frequency among clinical students and the significant relationship with psychological distress suggest possible link to the stressful clinical training.

Effect of PDL-induced coherent crosstalk on polarization-division-multiplexed direct-detection systems

We analyze the effect of polarization-dependent loss (PDL) on the performance of the polarization-division-multiplexed (PDM) signals in direct-detection systems. We present the theoretical analysis of the sensitivity penalty caused by PDL-induced coherent crosstalk and compare the results with experimental data obtained by using a simple variable PDL emulator based on a LiNbO3 Mach-Zehnder modulator. Also presented is the performance degradation caused by the polarization misalignment between the received signals and the polarization beam splitter at the receiver in the presence of PDL.

High-strength nitrogenous wastewater treatment in biofilm and granule anammox processes

Biofilm and granule reactors were employed to remove nitrogen via an anammox reaction applying synthetic nitrogen wastewater, whose concentration was in the range of 20 to 1,400 mg N/L as total nitrogen. A biofilm reactor was packed with non-woven fabric and a granule reactor was filled with anaerobic granular sludge taken from the brewery wastewater treatment plant. Both reactors were seeded with Planctomycetes KSU-1 and operated for 450 days. The biofilm reactor showed high NH(4) (+)-N and NO(2) (-)-N removal efficiencies of over 88% and 94%, respectively, until total nitrogen concentration was reached at 800 mg N/L. However, the biofilm reactor showed severe inhibition at over 1,000 mg N/L of total nitrogen due to nitrogen overloading. The granule reactor revealed better nitrogen removal performance than the biofilm reactor, showing high NH(4) (+)-N and NO(2) (-)-N removal efficiencies of over 90%, even at a total nitrogen concentration of 1,400 mg N/L. However, aggregation of anammox bacteria grown in the sludge bed after long-term operation resulted in the deterioration of nitrogen. The removal ratio of NH(4) (+)-N and NO(2) (-)-N was close to 1:1, suggesting other reactions related to ammonium oxidation could occur simultaneously. Free ammonia inhibition as well as NO(2) (-)-N could be significant when high-strength nitrogenous wastewater was applied.

Interactions between CB(1) receptors and TRPV1 channels mediated by 12-HPETE are cytotoxic to mesencephalic dopaminergic neurons

BACKGROUND AND PURPOSES

We recently proposed the existence of neurotoxic interactions between the cannabinoid type 1 (CB(1)) receptor and transient receptor potential vanilloid 1 (TRPV1) channels in rat mesencephalic cultures. This study seeks evidence for the mediator(s) and mechanisms underlying the neurotoxic interactions between CB(1) receptors and TRPV1 in vitro and in vivo.

EXPERIMENTAL APPROACH

The mediator(s) and mechanism(s) for the interactions between CB(1) receptors and TRPV1 were evaluated by cell viability assays, immunocytochemistry, Fura-2 calcium imaging, mitochondrial morphology assay, ELISA and Western blot assay in vitro in neuron-enriched mesencephalic cultures. Injections into the substantia nigra and subsequent cell counts were also used to confirm these interactions in vivo.

KEY RESULTS

The neurotoxic interactions were mediated by 12(S)-hydroperoxyeicosatetraenoic acid (12(S)-HPETE), an endogenous TRPV1 agonist. CB(1) receptor agonists (HU210 and WIN55,212-2) increased the level of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), a downstream metabolite of 12(S)-HPETE, which stimulates TRPV1-mediated death of mesencephalic neurons, both in vitro and in vivo. The neurotoxicity was mediated by increased intracellular Ca(2+) concentration ([Ca(2+)](i)) through TRPV1, consequently leading to mitochondrial damage and was attenuated by baicalein, a 12-lipoxygenase inhibitor.

CONCLUSION AND IMPLICATIONS

Activation of CB(1) receptors in rat mesencephalic neurons was associated with biosynthesis of 12(S)-HPETE, which in turn stimulated TRPV1 activity, leading to increased [Ca(2+)](i), mitochondrial damage and neuronal death.

Development and validation of reverberation-chamber type whole-body exposure system for mobile-phone frequency

We developed whole-body exposure systems for in-vivo study at cellular (848.5 MHz) and Personal Communication System (PCS, 1,762.5 MHz) frequency, utilizing reverberation chamber. The field uniformities in the test area of the designed chambers were verified by simulation and measurement. In the whole-body exposure environment, Specific Absorption Rate (SAR) distributions inside of mice were calculated using Finite Difference Time Domain (FDTD) simulation. Key results are presented in this article.

Design of a LiNbO(3) ribbon waveguide for efficient difference-frequency generation of terahertz wave in the collinear configuration

We propose and investigate a ribbon waveguide for difference-frequency generation of terahertz (THz) wave from infrared light sources. The proposed ribbon waveguide is composed of a nonlinear optic crystal and has a thickness less than the wavelength of the THz wave to support the surface-wave mode in the THz region. By utilizing the waveguide dispersion of the surface-wave mode, the phase matching condition between infrared pump, idler and THz waves can be realized in the collinear configuration. Owing to the weak mode confinement of the THz wave, the absorption coefficient can also be reduced. We design the ribbon waveguide which uses LiNbO(3) crystal and discuss the phase-matching condition for DFG of THz wave. Highly efficient THz-wave generation is confirmed by numerical simulations.

Analysis of frequency offset in the frequency stabilization of semiconductor laser based on frequency dithering technique

We investigate the frequency offset in the frequency stabilization of a semiconductor laser based on a frequency-dithering technique. An analytical model is presented to describe the effects of the amplitude modulation and the phase delay between the amplitude and frequency modulation on the frequency stabilization. We also experimentally and analytically show that the frequency offset could be reduced by using an appropriate phase-sensitive detection.

Reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based broadband source

We report on the reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based ASE source for injection locking to FPLD. The results show that, to suppress the polarization-induced Q penalty sufficiently less than 0.5 dB, the MQW-SLD output should be depolarized within the locking range of the wavelength-locked FPLD.

Simultaneous monitoring technique for ASE and MPI noises in distributed Raman Amplified Systems

We develop a new technique for simultaneously monitoring the amplified spontaneous emission (ASE) and multi-path interference (MPI) noises in distributed Raman amplified (DRA) systems. This technique utilizes the facts that the degree-of polarization (DOP) of the MPI noise is 1/9, while the ASE noise is unpolarized. The results show that the proposed technique can accurately monitor both of these noises regardless of the bit rates, modulation formats, and optical signal-to-noise ratio (OSNR) levels of the signals.

Optical reflectometry based on correlation detection and its application to the in-service monitoring of WDM passive optical network

We propose and demonstrate a novel technique for measuring the distribution of the reflectivity along an optical fiber transmission line. Unlike the conventional optical time-domain reflectometer (OTDR), the proposed technique utilizes the data-modulated transmitter itself instead of the optical short-pulse source, and monitors the distribution of the back-reflected light by calculating the cross-correlation of the transmitted and back-reflected signals. In this paper, we describe the operating principle of the proposed technique and discuss its potential limitation on the dynamic range. We also show that this limitation can be mitigated by using the discrete-component elimination algorithm. In addition, we experimentally demonstrate that the proposed technique can be used for the in-service monitoring of the transmission fibers in a wavelength-division multiplexed passive optical network (WDM PON).

UV light induced photodegradation of malachite green on TiO2 nanoparticles

The photodegradation of malachite green (MG), a cationic triphenylmethane dye, is examined both under different pH values and amounts of TiO(2). After 15W UV-365nm irradiation for 4h, ca. 99.9% of MG was degraded with addition of 0.5gL(-1) TiO(2) to solutions containing 50mgL(-1) of the MG dye. The HPLC-PDA-ESI-MS technique was used to obtain a better understanding on the mechanistic details of this TiO(2)-assisted photodegradation of the MG dye with UV irradiation. Five intermediates of the process were separated, identified, and characterized for the first time. The results indicated that the N-de-methylation degradation of MG dye took place in a stepwise manner to yield mono-, di-, tri-, and tetra-N-de-methylated MG species generated during the processes. Under acidic conditions, the results indicated that the photodegradation mechanism is favorable to cleavage of the whole conjugated chromophore structure of the MG dye. Under basic conditions, the results showed that the photodegradation mechanism is favorable to a formation of a series of N-de-methylated intermediates of the MG dye.

Electron bunching in transport through quantum dots in a high magnetic field

Shot noise measurements provide information on particle charge and its correlations. We report on shot noise measurements in a generic quantum dot under a quantized magnetic field. The measured noise at the peaks of a sequence of conductance resonances was some 9 times higher than expected, suggesting bunching of electrons as they traverse through the dot. This enhancement might be mediated by an additional level, weakly coupled to the leads or an excited state. Note that in the absence of a magnetic filed no bunching had been observed.

Factors affecting the activity of anammox bacteria during start up in the continuous culture reactor

Factors affecting cultivation of extremely slow-growing bacteria (anaerobic ammonium oxidiser, doubling time 11 days) were investigated by using upflow anaerobic sludge blanket (UASB) reactors which can maintain high solid retention time. The effects of concentrations of DO, free ammonia (FA), and nitrite on activation of anammox activity were tested during the start-up period. The reactor was inoculated with granular sludge collected from a full-scale UASB reactor used for treating brewery wastewater, and sludge from a piggery wastewater treatment plant and rotating biological contactor treating sewage. Results of continuous operation showed that concentrations of DO, free ammonia (FA) and nitrite in the reactors played a key role in stimulating the anammox activity during start-up period. It is crucial to keep DO below 0.2 ppm, FA below 2 mg/L and nitrite nitrogen below 35 mg/L to cultivate anammox cells in the continuous bioreactor. When the levels of DO, FA and nitrite in the influent were controlled at less than the inhibition levels, the anammox activity increased gradually in the anaerobic condition. Addition of hydrogen sulphide into the reactor enhanced anammox activity in the continuous culture. Through the SEM, TEM and FISH analysis, anammox bacteria were detected in the granular sludge after 3 months of continuous operation.

Improvement of aquaculture wastewater using chitosan of different degrees of deacetylation

Removal of organic compounds and inorganic nutrients from aquaculture wastewaters prior to discharge can not only minimize deterioration of receiving water quality, but it could also be further reused to culture prawn, fish and shellfish. Chitosan can be used as a coagulant, adsorbent, or bactericide; therefore it has been used to improve aquaculture wastewater quality as it could remove suspended solids (SS), organic compounds, NH3, PO43-, and pathogens. The best performance of chitosan in removing turbidity, SS, chemical oxygen demand (COD), NH3, and PO43- was 90%, 61%, 69.7%, 89.2%, and 95.6%, respectively. In addition, the chitosan could selectively remove the pathogen Edwardsiella ictaluri while leaving beneficial nitrifying bacteria in the aquaculture wastewater unaffected. The treatment efficiency of chitosan was highly dependent on its deacetylation degree and the pH of the wastewater. A high deacetylation degree and low pH value improved the performance of chitosan. In summary, the multi-functional chitosan deserves a wider role in treating aquaculture wastewater.

Effect of polarization-dependent loss on optical signal-to-noise ratio monitoring technique based on polarization-nulling method

We analyzed the probability of errors in the measured optical signal-to-noise ratio (OSNR) by using the polarization-nulling method, when the amplified spontaneous emission noise (ASE) is partially polarized due to the polarization-dependent loss (PDL) in the transmission link.

Feasibility study on the removal of nitrous compounds with a hollow-fiber membrane biofilm reactor

The objective of this study was to develop an integrated nitrogen treatment system using autotrophic organisms. A treatment system consists of an aerobic hollow-fiber membrane biofilm reactor (HfMBR) and anaerobic HfMBR. In the aerobic HfMBR, a mixture gas of air and O2 was supplied through the fibers for nitrification. Denitrification occurred in the anaerobic HfMBR using H2 as the electron donor. The treatment system was continuously operated for 190 days. NH4-N removal efficiencies ranging from 95% to 97% were achieved at NH4-N concentrations of influent ranging from 50 to 100 mg N/L. When glucose was added to the influent, the simultaneous nitrification and denitrification occurred in the aerobic HfMBR, and nitrogen removal rates were changed according to the COD/NH4-N ratio of influent. In the anaerobic HfMBR, autotrophic denitrification using H2 occurred and the removal rates achieved in this study were 23-58 mg N/m2 d. In this study, the achieved removal efficiency was lower than other study findings; however, the result suggested that this hybrid HfMBR system can be used effectively for nitrogen removal in oligotrophic water.

Scattering of bunched fractionally charged quasiparticles

We report the unexpected bunching of Laughlin's quasiparticles, induced by an extremely weak backscattering potential at exceptionally low electron temperatures (T<10 mK), deduced from shot noise measurements. Backscattered charges q=nue, specifically, q=e/3, q=2e/5, and q<3e/7, in the respective filling factors, were measured. For the same settings but at a slightly higher electron temperature, the measured backscattered charges were q=e/3, q=e/5, and q=e/7, as expected. Moreover, the backscattered current exhibited distinct temperature dependence that was correlated to the backscattered charge and the filling factor. This observation suggests the existence of "low" and "high" temperature backscattering states, each with its characteristic charge and energy.

Multiple scattering of fractionally charged quasiparticles

We employ shot noise measurements to characterize the effective charge of quasiparticles, at filling factor nu=1/3 of the fractional quantum Hall regime, as they scatter from an array of identical weak backscatterers. Upon scattering, quasiparticles are known to bunch, e.g., only three e/3 charges, or "electrons" are found to traverse a rather opaque potential barrier. We find here that the effective charge scattered by an array of scatterers is determined by the scattering strength of an individual scatterer and not by the combined scattering strength of the array, which can be very small. Moreover, we also rule out intraedge equilibration of e/3 quasiparticles over a length scale of hundreds of microns.

Bunching of fractionally charged quasiparticles tunnelling through high-potential barriers

Shot noise measurements have been used to measure the charge of quasiparticles in the fractional quantum Hall (FQH) regime. To induce shot noise in an otherwise noiseless current of quasiparticles, a barrier is placed in its path to cause weak backscattering. The measured shot noise is proportional to the charge of the quasiparticles; for example, at filling factor v=1/3, noise corresponding to q=e/3 appears. For increasingly opaque barriers, the measured charge increases monotonically, approaching q=e asymptotically. It was therefore believed that only electrons, or alternatively, three bunched quasiparticles, can tunnel through high-potential barriers encountered by a noiseless current of quasiparticles. Here we investigate the interaction of e/3 quasiparticles with a strong barrier in FQH samples and find that bunching of quasiparticles in the strong backscattering limit depends on the average dilution of the quasiparticle current. For a very dilute current, bunching ceases altogether and the transferred charge approaches q=e/3. This surprising result demonstrates that quasiparticles can tunnel individually through high-potential barriers originally thought to be opaque for them.

Dominance of Fermi-surface holes in p-type tunneling

In-plane uniaxial stress is used to tune continuously the mixing between the heavy-hole (HH) and light-hole (LH) states in a p-type double-barrier structure. The LH1 and HH2 resonant tunneling peaks shift at almost the same rate with stress, in contrast to the corresponding exciton peaks observed by photoreflectance, which exhibit a strong Fano-related anticrossing. Comparison between the observed shifts and a four-band k x p calculation of the state energies in the well provides the first experimental proof that the flow of holes through off-zone center states dominates the resonant tunneling current in p-type structures.

Hepatoprotective effects of Platycodon grandiflorum on acetaminophen-induced liver damage in mice

The protective effects of an aqueous extract from the roots of Platycodon grandiflorum A. DC (Campanulaceae), Changkil (CK), on acetaminophen (APAP)-induced hepatotoxicities and the possible protective mechanisms involved were investigated in mice. Pretreatment with CK prior to the administration of APAP significantly prevented the increase in serum alanine aminotransferase and aspartate aminotransferase activity and hepatic lipid peroxidation in a dose-dependent manner. APAP-induced hepatotoxicity was also essentially prevented as evidenced by liver histopathology. Hepatic glutathione levels and glutathione-S-transferase activities were not affected by treatment with CK alone, but pretreatment with CK protected the APAP-induced depletion of hepatic glutathione levels. The effects of CK on cytochrome P450 (P450) 1A2 and 2E1, the major isozymes involved in APAP bioactivation, were investigated. In microsomal incubations, CK effectively inhibited P450 lA2-dependent methoxyresorufin O-deethylase activities and the P450 2E1-dependent p-nitrophenol and aniline hydroxylase. The results suggest that the protective effects of CK against the APAP-induced hepatotoxicity may, at least in part, be due to its ability to block P450-mediated APAP bioactivation.

Expression of soluble form carp (Cyprinus carpio) ovarian cystatin in Escherichia coli and its purification

A DNA encoding thioredoxin-mature carp ovarian cystatin (trx-cystatin) fusion protein was ligated into a pET-23a(+) expression vector and then transformed into Escherichia coli AD494(DE3) expression host. After induction by isopropyl beta-D-thiogalactopyranoside, a high level of the soluble form of recombinant trx-cystatin was expressed in the cytoplasm of E. coli. The recombinant trx-cystatin could be purified by Ni(2+)-NTA agarose affinity chromatography. The molecular mass (M) of the recombinant trx-cystatin was approximately 28 kDa composed of recombinant thioredoxin (16 kDa) and recombinant mature carp ovarian cystatin (12 kDa). Both recombinant trx-fused and mature carp ovarian cystatins were stable at pH 6-11. No obvious decrease in activity was observed even after 5 min of incubation at 60 degrees C. They exhibited papain-like protease inhibition activity comparable to that of the mature carp ovarian cystatin, which could inhibit papain and mackerel cathepsins L and L-like, but not cathepsin B.

Purification and characterization of a dimethoate-degrading enzyme of Aspergillus niger ZHY256, isolated from sewage

A dimethoate-degrading enzyme from Aspergillus niger ZHY256 was purified to homogeneity with a specific activity of 227.6 U/mg of protein. The molecular mass of the purified enzyme was estimated to be 66 kDa by gel filtration and 67 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was found to be 5.4, and the enzyme activity was optimal at 50 degrees C and pH 7.0. The activity was inhibited by most of the metal ions and reagents, while it was induced by Cu(2+). The Michaelis constant (K(m)) and V(max) for dimethoate were 1.25 mM and 292 micromol min(-1) mg of protein(-1), respectively.

Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria

Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95%, and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures. The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3. As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited. In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH3. Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency. Conversely, H2S of adequate concentrations would favor the removal of incoming NH3. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50-150 h(-1). Hence, the results would be used as the guideline for the design and operation of biofilters.