Zhou X.,Ewha Womans University |
Zhou X.,Yanbian University |
Lee S.,Ewha Womans University |
Xu Z.,CAS Dalian Institute of Chemical Physics |
Yoon J.,Ewha Womans University
Chemical Reviews | Year: 2015
The development of chemosensors has become an important research topic in supramolecular analytical chemistry, and as a result, it has attracted the continuous interest of academic researchers in chemistry and biology. The strategy of using pH indicators was first employed in the construction of fluorescent sensors for CO2. Another strategy was developed based on the chemical reaction between amine and CO2 in which CO2 is a weak electrophile that can react with an active basic amine to form corresponding carbamate salt and ammonium salt. On the basis of this chemical mechanism, a series of fluorescent sensors has been achieved to date. One approach is directly inserting an amine group into the conjugated fluorophore. Sessler and co-workers constructed two colorimetric- and fluorescence-based CO2 sensors based on N-fused compounds. Chang and colleagues developed the fluorescent sensor by using a commercial resorufin for sulfite detection. In this case, sulfite can selectively react with the carbonyl carbon of the levulinate and yield a tetrahedral intermediate. This corresponding intermediate can next undergo an intermolecular cyclization to release the free resorufin moiety, resulting in an up to 57-fold fluorescence enhancement with a detection limit of 49 μM in aqueous solution. Fluorescent sensors for NO containing o-phenylenediamine (OPD) moieties and fluorophores have been developed by Nagano?s group and shown to be highly effective for visualizing this gas in vitro and in vivo.
Xu C.,Yanbian University
Applied Mechanics and Materials | Year: 2013
This paper presents a new illumination normalization method for robust face recognition under varying lighting conditions. In the proposed method, the illumination component is estimated by applying nonlocal total variation model in the logarithmic domain, and then the reflectance component is obtained based on reflectance model. The proposed method restrains the halo effect effectively while preserves the adequate texture information on the reflectance images. As an illumination invariant facial features, the reflectance images are directly utilized for face recognition. Experimental results on Yale face database B and CMU PIE database show that the performance of proposed method is robust and reliable in illumination invariant face recognition. © (2013) Trans Tech Publications, Switzerland.
Inorganic-organic hybrid membranes with anhydrous proton conduction prepared from tetraethoxysilane, 3-glycidyloxypropyltrimethoxysilane, trimethyl phosphate and diethylethylammonium trifluoromethanesulfonate
Luo W.-H.,Yanbian University |
Zhao L.-H.,Yanbian University
Journal of Membrane Science | Year: 2014
New silicon source (3-glycidyloxypropyltrimethoxysilane (GPTMS)) was used to make non-glass inorganic-organic hybrid membranes with diethylethylammonium trifluoromethanesulfonate ([dema][TfO]) by the sol-gel method. The hybrid membranes were studied with respect to their structural, thermal, proton conductivity and pores properties. The Fourier transform infrared spectroscopy (FT-IR) results showed that there was intermolecular interaction between ionic liquid and Si-O-Si skeleton structure in the inorganic-organic hybrid membranes. The thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis showed that the hybrid membranes displayed good chemical stability and were thermally stable up to more than 200°C in air. The N2 adsorption test showed the hybrid membranes had good pore property and ionic liquid influenced the structure of hybrid membrane. Proton conductivity was measured from 20°C to 220°C and high conductivity of 1.2×10-2S/cm was obtained for a 60wt% [dema][TfO] doped hybrid membrane (ionogel) at 220°C under anhydrous conditions. This method for the preparation of hybrid membranes is promising and may be used for the proton exchange membrane in fuel cells. © 2013 Elsevier B.V.
Zheng N.,Yanbian University |
Jin Y.,Yanbian University
Journal of Magnetism and Magnetic Materials | Year: 2012
Half-metals, which show 100% spin polarization at the Fermi level, have potential applications in spintronics. We investigated the half-metallicity of full-Heusler Ti 2YAl (Y=V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) alloys with an Hg 2CuTi-type structure by means of the all-electron full-potential linearized augmented plane-wave method within the generalized gradient approximation. The Ti 2MnAl alloy is found to be a half-metallic antiferromagnet, and the Ti 2YAl (Y=Fe, Co, and Ni) alloys are half-metallic ferrimagnets, whereas the Ti 2YAl (Y=V, Cr, Cu, and Zn) alloys are conventional ferromagnets. Total magnetic moments (M t) of the Ti 2YAl (Y=Mn, Fe, Co, and Ni) alloys are calculated to be integers and linearly scaled with the total number of valence electrons (Z t) by Mt= Zt-18. Band-gaps are demonstrated to be mainly determined by the bonding t 2 and antibonding t2 states created from the hybridizations of the d states between the Ti(A)-Ti(B) coupling and Y (Y=Mn, Fe, Co, and Ni) atom. © 2012 Elsevier B.V. All rights reserved.
Li X.,University of Maryland Baltimore County |
Li X.,Yanbian University |
Xu C.,University of Maryland Baltimore County |
Yang P.,University of Maryland Baltimore County
Diabetes | Year: 2013
Embryos exposed to high glucose exhibit aberrant maturational and cytoarchitectural cellular changes, implicating cellular organelle stress in diabetic embryopathy. c-Jun-N-terminal kinase 1/2 (JNK1/2) activation is a causal event in maternal diabetes-induced neural tube defects (NTD). However, the relationship between JNK1/2 activation and endoplasmic reticulum (ER) stress in diabetic embryopathy has never been explored. We found that maternal diabetes significantly increased ER stress markers and induced swollen/enlarged ER lumens in embryonic neuroepithelial cells during neurulation. Deletion of either jnk1 or jnk2 gene diminished hyperglycemia-increased ER stress markers and ER chaperone gene expression. In embryos cultured under high-glucose conditions (20 mmol/L), the use of 4- phenylbutyric acid (4-PBA), an ER chemical chaperone, diminished ER stress markers and abolished the activation of JNK1/2 and its downstream transcription factors, caspase 3 and caspase 8, and Sox1 neural progenitor apoptosis. Consequently, both 1 and 2 mmol/L 4-PBA significantly ameliorated high glucose- induced NTD. We conclude that hyperglycemia induces ER stress, which is responsible for the proapoptotic JNK1/2 pathway activation, apoptosis, and NTD induction. Suppressing JNK1/2 activation by either jnk1 or jnk2 gene deletion prevents ER stress. Thus, our study reveals a reciprocal causation of ER stress and JNK1/2 in mediating the teratogenicity of maternal diabetes. © 2013 by the American Diabetes Association.
Zhou X.,Yanbian University |
Jin X.,Yanbian University |
Sun G.,Yanbian University |
Wu X.,Yanbian University
Chemistry - A European Journal | Year: 2013
A new strategy for fast fluorescent detection of cysteine (Cys), based on a response-assisted electrostatic attraction, is demonstrated. By utilizing this strategy, we designed and synthesized three fluorescent probes for the specific detection of Cys under actual physiological conditions. The probe m-CP, a coumarin fluorophore conjugated with a substituted methyl pyridinium group through an unsaturated ketone unit, showed highly selective and sensitive detection for cysteine (Cys) over homocysteine (Hcy) and glutathione (GSH). The kinetic analysis indicated that the sensing process was highly accelerated (a response time less than 1 min) by the response-assisted electrostatic attraction. More importantly, control experiments with isomeric probes first demonstrated that the spatial charge configuration of the probe played an important role in Cys-preferred selectivity and kinetic rate acceleration. Furthermore, the practical utility of the probe m-CP in the fluorescent labeling of Cys residues within proteins was demonstrated. Finally, these probes were employed in living cell imaging with HeLa cells, in which it displayed satisfactory cell permeability and enabled us to distinguish active thiols in the cytoplasm, nucleus, and mitochondria. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Gu G.-R.,Yanbian University |
Ito T.,Osaka University
Applied Surface Science | Year: 2011
Nano-sheet carbon films (NSCFs) coated with very thin (≈5-nm-thick) metal layers were fabricated on Si wafer chips by means of quartz-tube-type microwave-plasma chemical-vapour-deposition method with hydrogen-methane gas mixture and an electron beam evaporation method. Field emission (FE) current densities obtained at a macroscopic average electric field, E, of ≈10 V/μm changed from 13 mA/cm2 for NSCF with no coated metal to 1.7, 0.7 and 30 mA/cm2 for Ti-, Al- and Au-coated NSCFs, respectively, while the threshold E varied from 4.4 V/μm for the former one to 5.3, 5.4 and 2.0 V/μm for the corresponding latter ones, respectively. As the FE currents of Au-coated NSCFs tended to be saturated in a higher E region, compared to those of NSCFs with no coated metal, no simple Fowler-Nordheim (F-N) model is applicable. A modified F-N model considering statistic effects of the FE tip structures and a space-charge-limited-current effect is successfully applied to an explanation for the FE data observed in the low and high E regions. © 2010 Elsevier B.V. All rights reserved.
TIAN L.,Yanbian University
Journal of Rare Earths | Year: 2010
The photoluminescence (PL) properties of Ca4YO(BO3)3 doped with Bi3+, Dy3+, and Pr3+ ions were investigated. These compounds were prepared using a typical solid-state reaction. The excitation and emission spectra were measured using a spectrofluorometer. For Ca4YO(BO3)3:Bi3+, the excitation spectrum showed the bands at about 228, 309, and 370 nm which correspond to the 1S0→1P1 transition and the 1S0→3P1 transition of Bi3+ ions. The emission band at 390 nm corresponded to the 3P1→1S0 transition of Bi3+ ions. For Ca4YO(BO3)3: Bi3+,Dy3+, energy transfer occurred from Bi3+ to Dy3+ somewhat. In Ca4YO(BO3)3:Bi3+,Dy3+,Pr3+, the excitation band at 367 nm was enhanced obviously due to the energy migration from Bi3+ to Pr3+, which converted efficiently the emission of semiconductor InGaN based light-emitting diode (LED). Therefore, the emission of Dy3+ ions was enhanced due to the energy migration from the process of Bi3+→Pr3+→Dy3+. It resulted in the good color rendering. © 2010 The Chinese Society of Rare Earths.
Wang H.-F.,Yanbian University |
Zhu A.-D.,Yanbian University |
Zhang S.,Yanbian University
Optics Letters | Year: 2014
We propose a one-step scheme to implement a multiqubit controlled phase gate with one qubit simultaneously controlling multiple qubits with three-level atoms at distant nodes in coupled cavity arrays. Selective qubit-qubit couplings are achieved by adiabatically eliminating the atomic excited states and photonic states, and the required phase shifts between the control qubit and any target qubit can be realized through suitable choices of the parameters of the external fields. Moreover, the effective model is robust against decoherence because neither the atoms nor the field modes are excited during the gate operation, leading to a useful step toward scalable quantum computing networks. © 2014 Optical Society of America.
News Article | February 21, 2017
BEIJING (Reuters) - With the suspension of all North Korean coal imports, China has wielded a big stick against its reclusive neighbor, but there is no sign it will cut off all critical links and Beijing is still promoting talks to solve the dispute over Pyongyang's program to develop nuclear weapons. China has been getting increasingly fed up with what it sees as North Korean leader Kim Jong Un's recalcitrance and unwillingness to show any sign of wanting to seek a peaceful resolution to the nuclear weapons issue, according to Chinese experts on North Korea. It has also come under increasing pressure from the United States to get tough with Pyongyang. The Global Times, a widely-read Chinese state-run tabloid, said on Monday that the coal decision showed China's determination to work with the international community to stop North Korea's nuclear schemes but did not mean China's policy toward its neighbor had or would fundamentally change. "Despite participating in UN sanctions, Chinese society's friendship to the North remains unchanged. Chinese sanctions only target at its nuclear weapon program, and we are firmly opposed to Seoul's political fantasy against Pyongyang," it said in an editorial. The fantasy reference related to speculation in the South Korean media that China may have halted the coal shipments to punish North Korea for the killing of leader Kim Jong Un's half brother Kim Jong Nam last week in Malaysia. South Korean officials say they believe that Kim Jong Nam was assassinated by North Korean agents. The economic impact of suspending coal imports would be severe and may force Pyongyang to the negotiating table, some of the Chinese experts said. China imported about $1.89 billion of coal from North Korea last year, a significant proportion of the $2.5 billion in total Chinese imports from North Korea that year. "This is a very severe measure that has broken with previous convention, it shows just how much China has been antagonized by [Pyongyang's] recent missile tests," said Jin Qiangyi, director of the Centre for North and South Korea Studies at Yanbian University, who specializes in China's relationship with North Korea. "The situation is such that doing nothing will only see risks exacerbate; doing this still comes with some risk but it may force North Korea to negotiate." Still, Beijing will want to tread carefully to avoid upsetting Kim too much, according to a source with ties to China's military. One concern is that Kim could even point his missiles in China's direction, the source said. "Kim is like a dog who needs to be both loved and beaten to keep him in line," said the source, who has also visited North Korea. "But beat him too hard and he'll bite back. That's the quandary." Among the Chinese government's other fears is the possibility of a sudden regime collapse in North Korea leading to chaos and the potential for hundreds of thousands of North Korean refugees to head across the Chinese border, diplomatic sources have said. In that scenario, Beijing would also be concerned that U.S. and South Korean armed forces would move into North Korea and soon be on the Chinese border. If China really wanted to throttle Pyongyang, it could simply stop all trade with the country, including oil and food, ban flights to and from North Korea, and end all financial transactions with the country. At the same time as unveiling the coal measures, China has been promoting diplomatic efforts. Chinese Foreign Minister Wang Yi, speaking at a high profile security summit in Munich over the weekend, said China has not given up hope for a new round of diplomacy with North Korea, even as he pledged support for UN sanctions. Wang also took aim at the repeated calls from Washington for Beijing to step up the pressure on Pyongyang - and said the United States had its responsibilities too. "The United States and North Korea are the parties most directly involved, and they must as soon as possible be politically decisive," Wang said, adding China would continue to play a mediating role. Last month, before being sworn into office, U.S. President Donald Trump criticized China for benefiting from economic ties with the U.S. but not doing enough to curb North Korea's erratic behavior.