Anti-solvent assisted treatment for improved morphology and efficiency of lead acetate derived perovskite solar cells

An efficient solution-processable route employing Pb(Ac)₂ as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported.     

Die Gaspermeabilität von Polybutylenterephthalat in der Umgebung der Einfriertemperatur

The permeability of poly(butylene terephthalate) was examined for He, Ne, Ar and CO₂ at the temperature range of 293–338 K and an upstream pressure to 1,2 bar. The energies of activation of permeation and diffusion in case of Ne, Ar and CO₂ are higher above glass transition temperature than below, while they are nearly constant in case of He. The dependence of temperature of solubility coefficients does not change at the glass transition temperature.     

An evaluation of the performance of porous polymer monolith assisted electrospray

A novel electrospray interface, which has distinct advantages over conventional pulled silica emitters, has been developed. This novel interface can be easily fabricated by forming a porous polymer monolith (PPM) at the end of a fused-silica capillary that facilitates a stable electrospray over a wide range of flow rates with only a modest increase in back-pressure. A comparison was made between the PPM-assisted electrospray and a commercial nanosprayer in terms of sensitivity, stability and robustness. A PPM-filled electrospray tip produced a day-to-day signal variation of 23% relative standard deviation (RSD) over a 3-day period when spraying a 1.0 microM test peptide solution. Furthermore, three different capillaries fabricated by the same process produced a signal variation of 17% RSD, indicating that the fabrication process shows good reproducibility. The multiple flow paths of the PPM function to split the flow and reduce clogging. Even following the accumulation of debris after prolonged use, a stable spray could still be generated with the PPM-filled capillary while the commercial nanosprayer ceased to function properly. In terms of sensitivity, PPM-assisted electrospray showed an enhancement in sensitivity at infusion flow rates between 100 to 1000 nL/min while commercial nanosprayers performed slightly better at flow rates below 100 nL/min. A sample purification step can be combined with the PPM-assisted sprayer, using the PPM as a stationary phase to desalt and preconcentrate samples prior to mass spectrometric detection.     

A novel reactivity of SeO(2) with 1,3-dienes: formation of syn 1,2- and 1,4-diols via a facile C-Se bond oxidation

[reaction: see text] A novel reaction between 1,3-dienes and selenium dioxide to give syn 1,2- and 1,4-diol cyclic selenites was studied in detail. This study indicates that an initial concerted [4 + 2] cycloaddition followed by a stereospecific carbon-selenium bond oxidation is involved in this unprecedented syn dihydroxy addition reaction mediated by selenium dioxide.     

Solid-phase extraction of fluoxetine and norfluoxetine from serum with gas chromatography-electron-capture detection

A rapid, selective, and sensitive method is described for the purification and analysis of fluoxetine and norfluoxetine using a solid-phase extraction column and gas chromatography-electron-capture detection. Linear quantitative response curves for fluoxetine and norfluoxetine are generated over a concentration range of 20-200 ng/ml. Overall extraction efficiency of the extraction procedure is found to be greater than 90% and greater than 75% with correlation coefficients of 0.997 and 0.993 for fluoxetine and norfluoxetine, respectively.     

Zeta-potentials of self-assembled surface micelles of ionic surfactants adsorbed at hydrophobic graphite surfaces

The zeta-potentials of the self-assembled surface ionic surfactants (sodium dodecyl sulfate—SDS and hexadecyltrimethyl ammonium bromide—CTAB) on graphite surfaces were determined both from streaming potential and electrophoretic mobility measurements. The adsorption of the surfactants at graphite–liquid interfaces has been studied using atomic force microscopy (AFM) soft-contact imaging which shows the formation of linear, parallel hemicylinders with headgroups oriented towards the solution. The magnitude of the zeta-potential increased with an increase in surfactant concentration, reaching a constant value at a concentration corresponding to the point of surface micelle formation as confirmed from AFM imaging. The streaming potential and electrophoretic mobility measurements showed that the zeta-potentials of SDS and CTAB surface micelles adsorbed at the graphite surface were about −75 and +70 mV, respectively, well in agreement with the values reported for bulk phase micelles in the literature.     

ON A CLASS OF METHOD FOR SOLVING PROBLEMS WITH RANDOM BOUNDARY NOTCHES AND/OR CRACKS(Ⅱ) COMPUTATIONS FOR BOUNDARY NOTCHES

This work is a continuation of the discussion of [1], On a class of method for solving problems with random boundary notches and/or cracks, (I) by C. Ouyang (Appl. Math. & Mech., vol. 1, No. 2, 1980). Here computations for boundary notches are made by using the theory and formulas presented in [1]. In the computation modification is also made for the boundary conditions in parametric plane in [1]. Numerical results for examples show that within ranges of parameter considered in the paper, for example L, the present method in quite workable in practical computations.     

Gas Hydrate Formation in Reversed Micelles

We describe a technique to modify protein solubility and optimize enzyme activity in reversed micellar solutions. The technique is based on the ability of hydrates of natural gas to form in the micro-aqueous phase. Clathrate hydrates are crystalline inclusions of water and gas, and their formation in bulk water has traditionally been studied with relevance to natural gas recovery. We have found that hydrates can form in the environment of the microaqueous pools of reversed micelles, and that their extent of formation can be well controlled through the thermodynamic variables of temperature and pressure. Additionally, formation of hydrates affects the size and aggregation number of the micelles, and thus influences the solubility and conformation of encapsulated proteins. We demonstrate how the concept can be used in two applications: (i) protein extraction into reversed micelles and subsequent recovery, and (ii) optimization of enzyme activity in reversed micelles.     

Potentiometric titration of sorbed hydrogen on palladium carrier catalysts

A method of determination of adsorbed and absorbed hydrogen on palladium catalysts with carbon carriers is suggested and verified. The method allows H_ad and H_ab to be determined with an accuracy of about 10% using catalysts containing at least 5% Pd.

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- . . . 10% , , - , 5% Pd.

     

Modification of the electrokinetic properties of reversible electrophoresis gels for the separation and preparation of DNA

The effect of adding linear polymers to a novel reversible electrophoretic was measured. Reversible gels are formed using the polyanionic carbohydrate polymer, gellan gum. Gellan gum forms strong stable gels in the presence of divalent cations or diamines. The gels are reversible (return to solution) by changing the ionic environment or pH. Gellan gum is an anionic polymer, and the electrophoresis gels have considerable electroosmotic flow (EOF) toward the negative electrode. We measured the EOF in gellan gum electrophoresis gels as a function of gel concentration, buffer composition, and linear polymer additive. The linear polymers used in this study were polyethylene oxide and hydroxyethyl cellulose. Both polymers reduced EOF in the gels, in a manner dependent on molecular weight. Polymers with high molecular weight were more effective at reducing EOF. The addition of polymers increased the resolution of low molecular weight DNA. Native gellan gum resolved DNA from approx 50,000 to 1000 bp. Addition of the polymers resolved DNA down to approx 50 bp, in some instances. The influence of the polymers on circular plasmid DNA was also investigated. Addition of high molecular weight polyethylene oxide reduced the electrophoretic mobility of the nicked circular form compared to the supercoiled form.