A photochromic phenoxyquinone based cyanide ion sensor

We have developed a new chemosensor system for cyanide ion that is based on a photochromic material. We observed that addition of cyanide anion to a UV irradiated solution of a phenoxynaphthacenequinone derivative brought about a significant change in the absorption spectra that enabled detection of cyanide ion in a selective and sensitive manner. A carbanion intermediate was shown to be responsible for the long wavelength absorption band (630-940 nm) that is generated by cyanide addition.     

Glass formation and third-order optical nonlinear properties within TeO2–Bi2O3–BaO pseudo-ternary system

Tellurite glasses from TeO₂–Bi₂O₃–BaO pseudo-ternary system were prepared using a conventional melt-quenching method and its glass-forming region was determined. A series of glasses were selected and their third-order optical nonlinearities (TONL) were measured by employing the Z-scan method at a wavelength of 800 nm with femtosecond laser pulses. The results showed that glass former Te⁴⁺ ions exhibited positive influences on the TONL and glass modifiers Ba²⁺ ions behaved similarly; low concentrated Bi³⁺ ions as glass modifiers weakened the nonlinearities, but an excess amount of Bi³⁺ behaved oppositely. FTIR measurements demonstrated that chemical bonds especially Te–O_eq vibrated at a high energy level remarkably promoted the TONL susceptibility χ⁽³⁾, and the glass sample with the highest Bi₂O₃ content exhibited the largest χ⁽³⁾ value which was due to the presence of BiO₃ polyhedra.     

Mitochondrial pyruvate dehydrogenase phosphatase 1 regulates the early differentiation of cardiomyocytes from mouse embryonic stem cells

Mitochondria are crucial for maintaining the properties of embryonic stem cells (ESCs) and for regulating their subsequent differentiation into diverse cell lineages, including cardiomyocytes. However, mitochondrial regulators that manage the rate of differentiation or cell fate have been rarely identified. This study aimed to determine the potential mitochondrial factor that controls the differentiation of ESCs into cardiac myocytes. We induced cardiomyocyte differentiation from mouse ESCs (mESCs) and performed microarray assays to assess messenger RNA (mRNA) expression changes at differentiation day 8 (D8) compared with undifferentiated mESCs (D0). Among the differentially expressed genes, Pdp1 expression was significantly decreased (27-fold) on D8 compared to D0, which was accompanied by suppressed mitochondrial indices, including ATP levels, membrane potential, ROS and mitochondrial Ca²⁺. Notably, Pdp1 overexpression significantly enhanced the mitochondrial indices and pyruvate dehydrogenase activity and reduced the expression of cardiac differentiation marker mRNA and the cardiac differentiation rate compared to a mock control. In confirmation of this, a knockdown of the Pdp1 gene promoted the expression of cardiac differentiation marker mRNA and the cardiac differentiation rate. In conclusion, our results suggest that mitochondrial PDP1 is a potential regulator that controls cardiac differentiation at an early differentiation stage in ESCs.     

Catalytic Vapor Cracking for Improvement of Bio-Oil Quality

Bio-oil has attracted considerable interest as a promising renewable energy resource because it can be utilized as a feedstock in integrated bio-refineries for the production of highly valuable chemicals and next-generation hydrocarbon fuels. However, it is necessary to improve the bio-oil quality before it can be fed to bio-refineries. Currently, catalytic vapor cracking seems a more attractive process than catalytic upgrading technologies, such as hydrotreating and esterification, in order to improve the bio-oil quality. This review presents a summary of recent research and the state of art technology for the catalytic vapor cracking of bio-oil, focusing on the catalysts applied, upgrading methods and reaction mechanisms.     

Mixed-mode stress intensity factors and critical angles of cracks in bolted joints by weight function method

Summary   Mechanical joints, such as bolted or riveted joints, are widely used in structural components. Reliable determination of stress intensity factors for cracks in bolted joints is required to evaluate their safety and fatigue life. The weight function method is an efficient technique to calculate stress intensity factors for various loading conditions by the stress analysis of an uncracked model. In this paper, the mixed-mode stress intensity factors for cracks in bolted joints are analyzed by the weight function method, and coefficients included in the weight function are determined by finite element analysis for reference loadings. The critical angle at which mode I stress intensity factor becomes maximum is determined, and the effects of the amount of clearance and crack length on the critical angle are investigated. Received 28 February 2001; accepted for publication 22 June 2001 RID=" ID=" The authors are grateful for the support provided by a grant from the Korea Science & Engineering Foundation (KOSEF) and Safety and Structural Integrity Research Center at the Sungkyunkwan University.     

In-duct identification of fluid-borne source with high spatial resolution

Source identification of acoustic characteristics of in-duct fluid machinery is required for coping with the fluid-borne noise. By knowing the acoustic pressure and particle velocity field at the source plane in detail, the sound generation mechanism of a fluid machine can be understood. The identified spatial distribution of the strength of major radiators would be useful for the low noise design. Conventional methods for measuring the source in a wide duct have not been very helpful in investigating the source properties in detail because their spatial resolution is improper for the design purpose. In this work, an inverse method to estimate the source parameters with a high spatial resolution is studied. The theoretical formulation including the evanescent modes and near-field measurement data is given for a wide duct. After validating the proposed method to a duct excited by an acoustic driver, an experiment on a duct system driven by an air blower is conducted in the presence of flow. A convergence test for the evanescent modes is performed to find the necessary number of modes to regenerate the measured pressure field precisely. By using the converged modal amplitudes, very-close near-field pressure to the source is regenerated and compared with the measured pressure, and the maximum error was −16.3 dB. The source parameters are restored from the converged modal amplitudes. Then, the distribution of source parameters on the driver and the blower is clearly revealed with a high spatial resolution for kR<1.84 in which range only plane waves can propagate to far field in a duct. Measurement using a flush mounted sensor array is discussed, and the removal of pure radial modes in the modeling is suggested.     

Use of Raman and Raman optical activity for the structural characterization of a therapeutic monoclonal antibody formulation subjected to heat stress

Structural complexity of biological drug products presents an analytical challenge in terms of early detection of aggregation and/or degradation. In the present study, Raman and Raman optical activity (ROA) were evaluated for their sensitivity to detect heat‐induced molecular instability in an Immunoglobulin G4 subclass therapeutic monoclonal antibody present in its formulation matrix. The therapeutic antibody was subjected to heat stress at 50 °C and was analyzed at various time points up to 1 month. The current results suggest that Raman and ROA are sensitive to early‐stage detection of heat‐induced instability of the antibody, in which significant changes could be observed at 1 week of stress. ROA could provide early detection of the subtle differences at the tertiary structure level in a heat‐stressed monoclonal antibody and Raman/ROA spectra could provide early detection in secondary structural changes as well. Copyright © 2015 John Wiley & Sons, Ltd.     

A fluorescence turn-on probe for the detection of thiol-containing amino acids in aqueous solution and bioimaging in cells

A turn-on fluorescent probe, based on a water-soluble terphenyl derivative, for the detection of cysteine and homocysteine is reported. The aldehyde groups in the probe play crucial roles in providing reaction with thiol groups in the amino acids, leading to a formation of thiazolidine (from cysteine) or thiazinane ring (from homocysteine). As a result, the new formation of such rings alters the electronic property of the conjugated system in the probe and results in emission enhancement. The probe in aqueous solution exhibits a remarkable increase in its quantum yield upon exposure to cysteine (up to 20-fold) and to homocysteine (up to 700-fold), while slight quenching is observed in the presence of glutathione. Moreover, an investigation on time-resolved fluorescence spectra of the probe in the presence of cysteine and homocysteine reveals potential discriminatory detection of cysteine and homocysteine. Bioimaging of the thiols in live HeLa cells was successfully applied.