Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere...Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere(designated as Na Y/kaolin composites) separately, using a high precision intelligent gravimetric analyzer(IGA). The adsorption isotherms showed normal Langmuir type-Ⅰ behaviors. The increased adsorption heat with an increasing p-xylene coverage supported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for Na Y zeolite and Na Y/kaolin composites respectively. Compared with Na Y zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on Na Y/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed desorption(TPD) of p-xylene on two samples from room temperature to 450 ℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for Na Y zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized Na Y zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.Key words:展开更多
制备了一系列NH4NaY分子筛,采用小角度27 Al MAS NMR考察了焙烧温度、焙烧时间、Na+含量以及空气湿度对焙烧脱铝程度的影响。结果表明:在空气中焙烧NH4NaY分子筛时,焙烧温度会影响脱铝后形成的非骨架铝的总量及非骨架铝物种的组成,焙烧...制备了一系列NH4NaY分子筛,采用小角度27 Al MAS NMR考察了焙烧温度、焙烧时间、Na+含量以及空气湿度对焙烧脱铝程度的影响。结果表明:在空气中焙烧NH4NaY分子筛时,焙烧温度会影响脱铝后形成的非骨架铝的总量及非骨架铝物种的组成,焙烧温度较高时,Na+含量对形成的非骨架铝的量和非骨架铝物种的组成都有影响,焙烧温度较低时,Na+含量仅会影响非骨架铝的量;焙烧时间对脱铝程度的影响与焙烧温度及Na+含量有关,焙烧温度低时,焙烧时间对脱铝程度没有影响,焙烧温度高时,则焙烧时间对脱铝程度的影响随Na+含量的升高而降低;空气湿度对脱铝程度也有一定的影响,空气湿度越大,从骨架上脱出的铝越多。展开更多
Astrocytes can release increased levels of brain-derived neurotrophic factor during cerebral ischemia, but it is unclear whether brain-derived neurotrophic factor affects y-aminobutyric acid type A receptor function i...Astrocytes can release increased levels of brain-derived neurotrophic factor during cerebral ischemia, but it is unclear whether brain-derived neurotrophic factor affects y-aminobutyric acid type A receptor function in normal neurons. Results from this study demonstrated that y-aminobutyric acid at 100 pmol/L concentration raised the intracellular calcium level in neurons treated with medium from cultured hypoxic astrocytes, and the rise in calcium level could be inhibited by y-aminobutyric acid type A receptor antagonist bicuculline or brain-derived neurotrophic factor receptor antagonist k252a, y-aminobutyric acid type A-gated current induced by 100 IJmol/L y-aminobutyric acid was in an inward direction in physiological conditions, but shifted to the outward direction in neurons when treated with the medium from cultured hypoxic astrocytes, and this effect could be inhibited by k252a. The reverse potential was shifted leftward to -93 mV, which could be inhibited by k252a and Na＋-K＋-CI cotransporter inhibitor bumetanide. Brain-derived neurotrophic factor was released from hypoxic astrocytes at a high level. It shifted the reverse potential of y-aminobutyric acid type A-gated currents leftward in normal neurons by enhancing the function of Na＋-K＋-CI- cotransporter, and caused y-aminobutyric acid to exert an excitatory effect by activating y-aminobutyric acid type A receptor.展开更多
Studies have shown that glycolysis increases during seizures, and that the glycolytic metabolite lactic acid can be used as an energy source. However, how lactic acid provides energy for seizures and how it can partic...Studies have shown that glycolysis increases during seizures, and that the glycolytic metabolite lactic acid can be used as an energy source. However, how lactic acid provides energy for seizures and how it can participate in the termination of seizures remains unclear. We reviewed possible mechanisms of glycolysis involved in seizure onset. Results showed that lactic acid was involved in seizure onset and provided energy at early stages. As seizures progress, lactic acid reduces the pH of tissue and induces metabolic acidosis, which terminates the seizure. The specific mechanism of lactic acid-induced acidosis involves several aspects, which include lactic acid-induced inhibition of the glycolytic enzyme 6-diphosphate kinase-1, inhibition of the N-methyl-D-aspartate receptor, activation of the acid-sensitive 1A ion channel, strengthening of the receptive mechanism of the inhibitory neurotransmitter Y-aminobutyric acid, and changes in the intra- and extracellular environment.展开更多
Adsorption behaviors of Na-Y Clinoptilolite(Na-Y-C)to K+from the bittern containing high Ca2+were investigated.It was found that Na-Y-C also showed satisfactory adsorption selectivity to K+in the bittern containing hi...Adsorption behaviors of Na-Y Clinoptilolite(Na-Y-C)to K+from the bittern containing high Ca2+were investigated.It was found that Na-Y-C also showed satisfactory adsorption selectivity to K+in the bittern containing high Ca2+.The influences of pH,temperature and initial concentration on the adsorption of K+were remarkable.At pH 6.0 and 20℃,adsorption rate of Na-Y-C to K+was 85.96%.The adsorption rate of K+was decreased with the increase of temperature.And the adsorption capacity of K+was increased with the increase of initial concentration of K+.Adsorption column could easily be regenerated by 0.1mol/L HCl and saturated sodium chloride solution after adsorption of K+.And that be reused in production process.Thus Na-Y-C can be used as a adsorbent for recovery K+from the bitter containing high Ca2+.展开更多
基金financial support from the National Natural Science Foundation of China(20976077,21076100)the National 973 Foundation of China(2007CB216403)
文摘Para-xylene was chosen as the probe molecule to study adsorption thermodynamics and diffusion kinetics on NaY zeolite and composite structured NaY zeolite synthesized by in-situ crystallization from kaolin microsphere(designated as Na Y/kaolin composites) separately, using a high precision intelligent gravimetric analyzer(IGA). The adsorption isotherms showed normal Langmuir type-Ⅰ behaviors. The increased adsorption heat with an increasing p-xylene coverage supported a mechanism of phase transition, diffusion and re-arrangement of p-xylene molecules during the adsorption process. The rearrangement seemed to be most pronounced at an adsorption loading of 2.13 and 2.29 mmol/g for Na Y zeolite and Na Y/kaolin composites respectively. Compared with Na Y zeolite, a 2—3 times higher in the diffusion coefficient of p-xylene was observed on Na Y/kaolin composites when the pressure was more than 50 Pa. Temperature-programmed desorption(TPD) of p-xylene on two samples from room temperature to 450 ℃ at a special loading has also been investigated by IGA. Results showed only single desorption peak appeared for Na Y zeolite, indicating that adsorption can only occur in the super-cage structure. Comparably, there were two different peaks for in-situ synthesized Na Y zeolite, corresponding to the two thermo desorption processes in both super-cage structure and the channels provided by kaolin, respectively.Key words:
文摘制备了一系列NH4NaY分子筛,采用小角度27 Al MAS NMR考察了焙烧温度、焙烧时间、Na+含量以及空气湿度对焙烧脱铝程度的影响。结果表明:在空气中焙烧NH4NaY分子筛时,焙烧温度会影响脱铝后形成的非骨架铝的总量及非骨架铝物种的组成,焙烧温度较高时,Na+含量对形成的非骨架铝的量和非骨架铝物种的组成都有影响,焙烧温度较低时,Na+含量仅会影响非骨架铝的量;焙烧时间对脱铝程度的影响与焙烧温度及Na+含量有关,焙烧温度低时,焙烧时间对脱铝程度没有影响,焙烧温度高时,则焙烧时间对脱铝程度的影响随Na+含量的升高而降低;空气湿度对脱铝程度也有一定的影响,空气湿度越大,从骨架上脱出的铝越多。
基金the National Natural Science Foundation of China, No. 30471657
文摘Astrocytes can release increased levels of brain-derived neurotrophic factor during cerebral ischemia, but it is unclear whether brain-derived neurotrophic factor affects y-aminobutyric acid type A receptor function in normal neurons. Results from this study demonstrated that y-aminobutyric acid at 100 pmol/L concentration raised the intracellular calcium level in neurons treated with medium from cultured hypoxic astrocytes, and the rise in calcium level could be inhibited by y-aminobutyric acid type A receptor antagonist bicuculline or brain-derived neurotrophic factor receptor antagonist k252a, y-aminobutyric acid type A-gated current induced by 100 IJmol/L y-aminobutyric acid was in an inward direction in physiological conditions, but shifted to the outward direction in neurons when treated with the medium from cultured hypoxic astrocytes, and this effect could be inhibited by k252a. The reverse potential was shifted leftward to -93 mV, which could be inhibited by k252a and Na＋-K＋-CI cotransporter inhibitor bumetanide. Brain-derived neurotrophic factor was released from hypoxic astrocytes at a high level. It shifted the reverse potential of y-aminobutyric acid type A-gated currents leftward in normal neurons by enhancing the function of Na＋-K＋-CI- cotransporter, and caused y-aminobutyric acid to exert an excitatory effect by activating y-aminobutyric acid type A receptor.
基金supported by the National Natural Science Foundation of China,No.30971534125 Project of the Third Xiangya Hospital,China
文摘Studies have shown that glycolysis increases during seizures, and that the glycolytic metabolite lactic acid can be used as an energy source. However, how lactic acid provides energy for seizures and how it can participate in the termination of seizures remains unclear. We reviewed possible mechanisms of glycolysis involved in seizure onset. Results showed that lactic acid was involved in seizure onset and provided energy at early stages. As seizures progress, lactic acid reduces the pH of tissue and induces metabolic acidosis, which terminates the seizure. The specific mechanism of lactic acid-induced acidosis involves several aspects, which include lactic acid-induced inhibition of the glycolytic enzyme 6-diphosphate kinase-1, inhibition of the N-methyl-D-aspartate receptor, activation of the acid-sensitive 1A ion channel, strengthening of the receptive mechanism of the inhibitory neurotransmitter Y-aminobutyric acid, and changes in the intra- and extracellular environment.
文摘Adsorption behaviors of Na-Y Clinoptilolite(Na-Y-C)to K+from the bittern containing high Ca2+were investigated.It was found that Na-Y-C also showed satisfactory adsorption selectivity to K+in the bittern containing high Ca2+.The influences of pH,temperature and initial concentration on the adsorption of K+were remarkable.At pH 6.0 and 20℃,adsorption rate of Na-Y-C to K+was 85.96%.The adsorption rate of K+was decreased with the increase of temperature.And the adsorption capacity of K+was increased with the increase of initial concentration of K+.Adsorption column could easily be regenerated by 0.1mol/L HCl and saturated sodium chloride solution after adsorption of K+.And that be reused in production process.Thus Na-Y-C can be used as a adsorbent for recovery K+from the bitter containing high Ca2+.
