用USB电源对超级电容器充电至7V的电路

初看来,用5V USB端口为超级电容器充电似乎是简单的事,但是要将三只超级电容充电至7V,并将输入电流限制在USB端口的最大极限500mA内,就比较困难了.     

Preparation and characterization of heparin-loaded polymeric microparticles

Microparticles containing heparin were prepared by a water-in-oil-in-water emulsification and evaporation process with pure or blends of biodegradable (poly-epsilon-caprolactone and poly(D,L-lactic-co-glycolic acid)) and of positively-charged non-biodegradable (Eudragit RS and RL) polymers. The influence of polymers and some excipients (gelatin A and B, NaCl) on the particle size, the morphology, the heparin encapsulation rate as well as the in vitro drug release was investigated. The diameter of the microparticles prepared with the various polymers ranged from 80 to 130 microns and was found to increase significantly with the addition of gelatin A into the internal aqueous phase. Microparticles prepared with Eudragit RS and RL exhibited higher drug entrapment efficiency (49 and 80% respectively) but lower drug release within 24 h (17 and 3.5% respectively) than those prepared with PCL and PLAGA. The use of blends of two polymers in the organic phase was found to modify the drug entrapment as well as the heparin release kinetics compared with microparticles prepared with a single polymer. In addition, microparticles prepared with gelatin A showed higher entrapment efficiency, but a significant initial burst effect was observed during the heparin release. The in vitro biological activity of heparin released from the formulations affording a suitable drug release has been tested by measuring the anti-Xa activity by a colorimetric assay with a chromogenic substrate. The results confirmed that heparin remained unaltered after the entrapment process.     

Low molecular weight heparin-loaded polymeric nanoparticles: formulation,characterization, and release characteristics

The aim of the present work was to investigate the preparation of low molecular weight heparin (LMWH) nanoparticles (NP) as potential oral heparin carriers. The NP were formulated using an ultrasound probe by water-in-oil-in-water (w/o/w) emulsification and solvent evaporation with two biodegradable polymers [poly-epsilon-caprolactone, PCL and poly(D,L-lactic-co-glycolic acid) 50/50, PLGA] and two non-biodegradable positively charged polymers (Eudragit RS and RL) used alone or in combination. The mean diameter of LMWH-loaded NP ranged from 240 to 490 nm and was dependent on the reduced viscosity of the polymeric organic solution. The surface potential of LMWH NP prepared with Eudragit polymers used alone or blended with PCL and PLGA was changed dramatically from strong positive values obtained with unloaded NP to negative values. The highest encapsulation efficiencies were observed when Eudragit polymers took part in the composition of the polymeric matrix, compared with PCL and PLGA NP exhibiting low LMWH entrapment. The in vitro LMWH release in phosphate buffer from all formulations ranged from 10 to 25% and was more important (two- to threefold) when esterase was added into the dissolution medium. The in vitro biological activity of released LMWH, determined by the anti-factor Xa activity with a chromogenic substrate, was preserved after the encapsulation process, making these NP good candidates for oral administration.     

简单高效可调电流源

往往需要宽电流范围易调节的简单电流源。本文所示的电路(见图1)用200KHz脉宽调制(PWM)降压开关稳压器IC来产生50mA~1.5A范围的可编程恒定电流。8引脚IC(LT1510CS-8)需少量外部元件,它具有内部开关,电流感测电阻器,热停机和欠压闭锁特性。输入电压范围8~30V。PROG引脚用于设置输出电流。图1用最少元件的可调恒流源(a),任选编程方法(b),(c)和提高输出电流和效率的配置(d)往往需要宽电流范围易调节的简单电流源。本文所示的电路(见图1)用200KHz脉宽调制(PWM)降压开关稳压器IC来产生50mA~1.5A范围的可编程恒定电流。8引脚IC(LT15…     

Exposure-based integrated vs. pure psychodynamic treatment of agoraphobic inpatients.

Compared treatment outcomes for 19 agoraphobic inpatients who received either integrated, exposure-based, behavioral-psychodynamic treatment (IT) or general psychodynamic therapy (PT). All Ss completed an agoraphobic cognitions scale, the Multidimensional Health Locus of Control Scale, the Beck Depression Inventory, and a phobic avoidance rating scale after admission to the hospital and 11 wks later at discharge. Both IT and PT Ss improved significantly on almost all measures. Changes in IT Ss were relatively stable at a 1-yr follow-up, while PT Ss showed significant relapse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

纤巧型双电池太阳能板给紧凑和离网型设备中的电池充电

引言如今,低功率电子技术的发展允许将电池供电的传感器和其他设备安置在远离电网的地方.在理想的情况下,为了真正摆脱电网的束缚,就应免除更换电池的需要,而代之以由局部环境提供的可再生能源(如太阳能)对电池进行再充电.本设计要点说明了怎样构建一款依靠小型双电池太阳能板工作的紧凑型电池充电器.该设计的独特之处在于DC/DC转换器运用功率点控制以从太阳能板吸取最大的功率.