Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 9 de 9
Filter
Add more filters










Database
Publication year range
1.
Dalton Trans ; 51(30): 11295-11301, 2022 Aug 02.
Article in English | MEDLINE | ID: mdl-35819169

ABSTRACT

The incorporation of Sc3+ can stabilize calcite-phase LuBO3:Ce3+ to grow large-sized single crystals but leads to the significant degradation of scintillation performance. In the present work, alkali metal ion (A+ = Li+, Na+, K+)-incorporated (Lu, A, Sc)BO3:Ce was rapidly synthesized in batches via a high-throughput sol-gel method. The aliovalent substitution of Lu3+ with A+ is balanced by the generation of oxygen vacancies by forming complexes. Thanks to the increased oxygen vacancies, the luminescence and XEL intensity of (Lu, Li, Sc)BO3:Ce are significantly enhanced by 2.2 times and 1.9 times, respectively. Further, the incorporation of A+ is attributed to the improved transition efficiency of charge carriers. The prepared scintillation screen fabricated with LASBO:Ce and PMMA shows that the spatial resolution can reach 8.6 lp mm-1, indicating its potential application in efficient and low-cost non-destructive X-ray detection. This work is of great significance in improving the luminescence and scintillation performance of (Lu, Sc)BO3:Ce single crystals and thin films and their application in the scintillation field.

2.
Inorg Chem ; 59(19): 14513-14525, 2020 Oct 05.
Article in English | MEDLINE | ID: mdl-32941030

ABSTRACT

The application of LuBO3:Ce3+ (LBO:Ce) crystal as an excellent scintillation material has been limited due to its poor phase stability at high temperature or high pressure, so improving the phase stability is essential for promoting its development. Ga stabilized LuBO3:Ce3+ (LGBO:Ce) is synthesized by solid-state reaction at 1200 °C. Powder X-ray diffraction patterns and Raman spectra at ambient pressure show that all the samples are pure calcite phase. In situ high-pressure synchrotron radiation XRD patterns illustrate that calcite phase LGBO:Ce exhibits more excellent phase stability than that of LBO:Ce under high pressure due to the superior compressibility of the [GaO6] octahedral unit. The optical band gap of LGBO decreases from 5.58 to 4.64 eV after introducing 10% Ga, which leads to the decreased nonradiative transition and about double luminescence intensity as expected. More interestingly, the charge transition from O2- to Ce4+ is observed at about 290 nm in the absorption spectra. The X-ray photoelectron spectroscopy spectra indicate the ratio of Ce4+/Ce3+ increases with increasing concentration of Ga3+, which can be attributed to the variation of energy separation between the 4f ground state of Ce3+ and the Fermi energy level position. In contrast to the enhancement of PL intensity, the integrated X-ray excited luminescence intensity decreases after Ga3+ incorporation attributing to the result of both decreased effective atomic number and ionization energy between 5d1 level and conduction band. The thermal luminescence spectra show that after the incorporation of Ga3+ the oxygen vacancy and intrinsic defects in LBO remain unchanged but that the concentration of oxygen vacancy significantly reduces. The mechanism of Ga3+ incorporation on phase stability and luminescence properties of LBO:Ce has been proposed and discussed systematically.

3.
ACS Appl Mater Interfaces ; 12(18): 20849-20858, 2020 May 06.
Article in English | MEDLINE | ID: mdl-32233356

ABSTRACT

Carbon dots (CDs) as new fluorescent materials with excellent fluorescence properties have shown enormous potential applications, especially in anticounterfeiting and cell imaging. Herein, nitrogen-doped CDs (NCDs) with excellent biocompatibility were prepared by a simple thermal sintering method. An extremely large red shift (∼130 nm) of the emission peak was observed when the excitation wavelength changes from 355 to 550 nm, indicating that NCDs are excellent fluorescent labeling materials for multiple cell imaging. On the other hand, NCDs showed obvious changes of emission intensity and peak position when the temperature increased from 223 to 323 K and the pH values changed from 1 to 13, respectively, which has been demonstrated by the "horse" pattern printed with NCD water-soluble fluorescent inks. The nontoxic NCDs dispersed in a multiple matrix are highly sensitive to excitation wavelength, temperature, and pH, indicating their great potential application in multiple anticounterfeiting and multiple cell imaging.


Subject(s)
Fluorescent Dyes/chemistry , Fraud/prevention & control , Ink , Quantum Dots/chemistry , Alginates/chemistry , Carbon/chemistry , Carbon/radiation effects , Carbon/toxicity , Fluorescent Dyes/chemical synthesis , Fluorescent Dyes/radiation effects , Fluorescent Dyes/toxicity , HeLa Cells , Humans , Hydrogen-Ion Concentration , Microscopy, Confocal , Microscopy, Fluorescence , Nitrogen/chemistry , Nitrogen/radiation effects , Nitrogen/toxicity , Quantum Dots/radiation effects , Quantum Dots/toxicity , Temperature
5.
Am J Med Sci ; 343(5): 382-7, 2012 May.
Article in English | MEDLINE | ID: mdl-22052411

ABSTRACT

INTRODUCTION: To explore the mechanisms of rosiglitazone (ROS), a selective peroxisome proliferator-activated receptor gamma ligand, in reversing mitomycin C (MMC) resistance in a human drug-resistant gastric cancer cell line. METHODS: The vincristine-resistant human gastric cancer cell line SGC7901/VCR and its parental cell line SGC7901 were treated with ROS, MMC (negative control), cyclosporine A+MMC (positive control) or ROS+MMC. A tetrazolium blue (methyl thiazolyl tetrazolium) assay was used to evaluate the sensitivity to these treatments. Flow cytometry analysis and acridine orange-ethidium bromide (AO-EB) fluorescent staining were used to determine the effects of ROS on MMC-induced apoptosis. Reverse transcription polymerase chain reaction and western blotting were used to measure the expression of multidrug resistant 1 (MDR1), Livin and P-glycoprotein (P-gp). RESULTS: ROS administration dose dependently increased the reversal index in MMC-treated SCG7901/VCR cells. ROS increased apoptosis in SGC7901/VCR cells compared with the blank group and MMC group. ROS+MMC also increased apoptosis in SGC7901/VCR cells compared with other groups (P < 0.05 or P < 0.01). The mRNA expression of MDR1 and Livin and the protein expression of P-gp in SGC7901/VCR cells were significantly higher than those in SGC7901 cells (P < 0.01). However, ROS or ROS+MMC treatment markedly upregulated the mRNA expression of MDR1 and Livin and the protein expression of P-gp in SGC7901/VCR cells (P < 0.01). CONCLUSIONS: ROS reverses MMC resistance in human gastric cancer SGC7901/VCR cells by reducing expression of MDR1, Livin and P-gp and increasing apoptosis.


Subject(s)
Carcinoma/metabolism , Drug Resistance, Neoplasm/drug effects , Hypoglycemic Agents/therapeutic use , Stomach Neoplasms/metabolism , Thiazolidinediones/therapeutic use , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Adaptor Proteins, Signal Transducing/metabolism , Antibiotics, Antineoplastic/therapeutic use , Apoptosis/drug effects , Cell Line, Tumor/drug effects , Drug Evaluation, Preclinical , Humans , Hypoglycemic Agents/pharmacology , Inhibitor of Apoptosis Proteins/metabolism , Mitomycin/therapeutic use , Neoplasm Proteins/metabolism , RNA, Messenger/metabolism , Rosiglitazone , Thiazolidinediones/pharmacology
6.
Sheng Li Xue Bao ; 58(5): 407-14, 2006 Oct 25.
Article in English | MEDLINE | ID: mdl-17041723

ABSTRACT

It was previously found that the efficacy of synaptic transmission between retinal cone systems and luminosity-type horizontal cells (LHCs) was activity-dependent. Repetitive activation of red-cone pathway increased the LHCos hyperpolarizing response to red light, and the response enhancement was reversible. In this study, intracellular recording and pharmacological method were applied to investigate the mechanism(s) underlying red-flickering-induced response enhancement. Lowering intracellular Ca(2+) in the LHC by intracellular injection of Ca(2+) chelator EGTA prevented the development of red-flickering-induced response enhancement, which implicates the importance of postsynaptic calcium signal. The response enhancement could also be eliminated by a potent antagonist of Ca(2+)-permeable AMPA receptor (CP-AMPAR), which suggests the possibility that Ca(2+) influx via glutamate-gated calcium channels is related to the changes of [Ca(2+)](i). Furthermore, the administration of ryanodine or caffeine also attenuated the phenomenon, which gives evidence that the local calcium signal caused by intracellular calcium-induced calcium release (CICR) may be involved. Taken together, our data implicate that postsynaptic CICR and CP-AMPAR are related to the activity-dependent response enhancement.


Subject(s)
Calcium/metabolism , Neuronal Plasticity/physiology , Retina/cytology , Retinal Cone Photoreceptor Cells/physiology , Signal Transduction/physiology , Synapses/physiology , Animals , Caffeine/pharmacology , Carps , Receptors, AMPA/physiology , Ryanodine/pharmacology , Ryanodine Receptor Calcium Release Channel/physiology
7.
Colloids Surf B Biointerfaces ; 39(4): 195-8, 2004 Dec 25.
Article in English | MEDLINE | ID: mdl-15555903

ABSTRACT

Using FT-Raman spectroscopy, column wicking technique and the equations of Washburn as well as van Oss et al., the surface properties of xylan, the main component in hemicelluloses, has been characterized and estimated. Raman spectrum showed that xylan has been structured by acetyl group and methyl-bonded glucurono group. Obtained results show that the surface free energy of xylan is higher in comparison with literature reported values for cellulose because the former has a larger Lifshitz-van der Waals component than the latter. However, xylan has been found to have very smaller polarity and orientation data than that of cellulose.


Subject(s)
Polysaccharides/chemistry , Spectrum Analysis, Raman/methods , Xylans/chemistry , Glucuronides/chemistry , Surface Properties , Thermodynamics
8.
Biol Cybern ; 90(5): 360-7, 2004 May.
Article in English | MEDLINE | ID: mdl-15221396

ABSTRACT

In retinal cone-HC synapse, it has been found that repetitive stimulation could induce postsynaptic short-term responsiveness enhancement. However, the detailed mechanism underlying this short-term plasticity in the retinal graded neurons remains unclear. In this study, based on an ion-channel model described using Hodgkin--Huxley equations, the possible mechanism of repetitive-stimulation-induced short-term plasticity in the synapse between retinal cones and horizontal cells was investigated. The computational simulation results, together with evidence from experimental observations, suggest that the short-term modification of signal transmission between the retinal graded neurons is likely to be attributed to the regulatory effects that calcium-dependent process exerts on the single-channel properties of the postsynaptic AMPA receptors.


Subject(s)
Computational Biology/methods , Neuronal Plasticity/physiology , Photic Stimulation/methods , Retinal Cone Photoreceptor Cells/physiology , Synapses/physiology , Animals , Electric Stimulation/methods , Goldfish
9.
J Colloid Interface Sci ; 267(2): 333-6, 2003 Nov 15.
Article in English | MEDLINE | ID: mdl-14583209

ABSTRACT

In this paper, the surface properties, e.g., the total surface free energy and the related Lifshitz-van der Waals and Lewis acid-base components, of polyacrylonitrile (PAN) precipitation polymerized in supercritical CO(2) have been characterized. Moreover, the influence of molecular weight varying has been also investigated. Results show that the surface properties of PAN resulting from supercritical CO(2) are different from those obtained by the conventional method. Of these data, one important finding is that the supercritical CO(2) PAN seems to decrease the surface free energy with the increased molecular weight. Based on previous recorded NMR spectra of this PAN and especially compared to commercial PAN, such phenomena are discussed and ascribed to an increase of the H-bonds and a reduction of the isotacticity in the supercritical CO(2) condition for PAN.

SELECTION OF CITATIONS
SEARCH DETAIL
...