Electrokinetic characterization of poly(dimethylsiloxane) microchannels

This paper characterizes the basic electrokinetic phenomena occurring within native poly(dimethylsiloxane) (PDMS) microchannels. Using simple buffers and current measurements, current density and electroosmosis data were determined in trapezoidal, reversibly sealed PDMS/PDMS and hybrid PDMS/glass channels with a cross-sectional area of 1035.5 microm(2) and about 6 cm length. This data was then compared to that obtained in an air-thermostated 50 microm inner diameter (1963.5 microm(2) cross-sectional area) fused-silica (FS) capillary of 70 cm length. Having a pH 7.8 buffer with an ionic strength (I) of 90 mM, Ohms's law was observed in the microchannels with electric field strengths of up to about 420 V/cm, which is about twice as high as for the FS capillary. The electroosmotic mobility (micro(EO)) in PDMS and FS is shown to exhibit the same general dependences on I and pH. For all configurations tested, the experimentally determined micro(EO) values were found to correlate well with the relationship micro(EO) = a + b log(I), where a and b are coefficients that are determined via nonlinear regression analysis. Electroosmotic fluid pumping in native PDMS also follows a pH dependence that can be estimated with a model based upon the ionization of silanol. Compared to FS, however, the magnitude of the electroosmotic flow in native PDMS is 50-70% smaller over the entire pH range and is difficult to maintain at acidic pH values. Thus, the origin of the negative charge at the inner wall of PDMS, glass, and FS appears to be similar but the density is lower for PDMS than for glass and FS.     

Sorption of Pu(VI) onto TiO2

The sorption of Pu(VI) onto TiO(2) was studied as a function of pH (2-10) and Pu concentration (10(-8)-10(-4) M) under an N(2) atmosphere, in 0.016 and 0.1 M NaClO(4). A batch-wise method was used, in which pH was measured in separate experimental containers after removal of a sample to determine the amount of Pu that had been sorbed. As Pu is radioactive, it was used as a tracer and measured by liquid scintillation counting. No ionic strength dependence was discerned, which was taken as an indication of inner sphere complex formation. In the interval of pH 2-7 the system could be described by the formation of two positively charged surface complexes using a 1-pK Stern model. Sorption of the plutonyl ion (PuO(2)(2+)) and the first hydrolysis species (PuO(2)(OH)(+)) was estimated using FITEQL to logK(1)=6.9 and logK(2)=1.4, respectively.     

On the spectrum of the Cesàro operator on spaces of analytic functions

This paper concerns the Cesàro operator acting on various spaces of analytic functions on the unit disc. The remarkable fact that this operator is subnormal when acting on the Hardy space H² has lead to extensive studies of its spectral picture on other spaces of this type. We present some of the methods that have been used to obtain information about the spectrum of the Cesàro operator acting on Hardy and Bergman spaces and give a unified approach to these problems which also yields new results in this direction. In particular, we prove that the Cesàro operator is subdecomposable on H¹ and on the standard weighted Bergman spaces , α0.     

On the spectral expansion of hyperbolic Eisenstein series

In this article, we determine the spectral expansion, meromorphic continuation, and location of poles with identifiable singularities for the scalar-valued hyperbolic Eisenstein series. Similar to the form-valued hyperbolic Eisenstein series studied in Kudla and Millson (Invent Math 54:193–211, 1979), the scalar-valued hyperbolic Eisenstein series is defined for each primitive, hyperbolic conjugacy class within the uniformizing group associated to any finite volume hyperbolic Riemann surface. Going beyond the results in Kudla and Millson (Invent Math 54:193–211, 1979) and Risager (Int Math Res Not 41:2125–2146, 2004), we establish a precise spectral expansion for the hyperbolic Eisenstein series for any finite volume hyperbolic Riemann surface by first proving that the hyperbolic Eisenstein series is in L ². Our other results, such as meromorphic continuation and determination of singularities, are derived from the spectral expansion.     

Azido-Derivate des Pentamethylcyclopentadienyl-Vanadium(IV)-Fragments. Molekülstrukturen der Zweikernkomplexe [Cp*VCl(N3)(μ-N3)]2 und [Cp*V(N3)2(μ-N3)]2

Azido Derivatives of the Pentamethylcyclopentadienyl Vanadium(IV)-Fragment. Molecular Structures of the Binuclear Complexes [Cp*VCl(N₃)(μ-N₃)]₂ and [Cp*V(N₃)₂(μ-N₃)]₂ The stepwise reaction of Cp*VCl₃ with excess trimethylsilyl azide (Me₃Si–N₃) in solution leads to the paramagnetic, azido-bridged complexes [Cp*VCl₂(μ-N₃)]₂ ( 3 ), [Cp*VCl(N₃)(μ-N₃)]₂ ( 4 ) and [Cp*V(N₃)₂(μ-N₃)]₂ ( 5 ) which were characterized by their IR and mass spectra. The azide-rich binuclear complex 5 is also formed if a pentane solution of Cp*V(CO)₄ is stirred in the presence of excess Me₃Si–N₃ in an open vessel. According to the X-ray structure analyses both 4 and 5 are centrosymmetric molecules with a planar V(N)₂V four-membered ring. In the absence of free trimethylsilyl azide, solutions of 3 – 5 lose dinitrogen slowly; in the presence of traces of air, 5 is thereby converted to the diamagnetic, oxo-bridged complex [Cp*V(O)(N₃)]₂(μ-O) ( 6 ).     

Stable strontium isotopic ratios from archaeological organic remains from the Thorsberg peat bog

Stable strontium isotope ratios in archaeological finds have frequently been used to determine their place of origin, in order to reconstruct migration and trade. Peat bogs offer favourable burial conditions for the preservation of organic remains such as woollen textiles and leather by a natural tanning process. However, these finds are impregnated by peat substances including contaminant strontium which is likely to mask the original (87)Sr/(86)Sr isotopic ratio of the specimens. In this paper, we present a pilot study analysing stable strontium isotopic ratios from Iron Age textile and leather finds from the Thorsberg peat bog, focusing on a sample processing method which permits the quantitative removal of contaminating strontium from the specimens.     

Preparation de membranes hydrophiles obtenues par le greffage de la n-vinylpyrrolidone dans le poly(chlorure de vinyle)

PVC films were radiation-grafted in NVP-methanol solutions. Unusual kinetics relations were observed: an increase in monomer concentration or in temperature decreased the reaction rate. These effects are attributed to a higher mobility of the growing chains leading to faster chain termination and resulting in a drop of the overall rate and shortening of grafted chains. The graft copolymers swell homogeneously in water and in methanol. The swelling rate and limiting swelling ratio increase linearly with the grafting ratio. The swelling ratio was found to depend on chain length, being higher for short chains. An irreversible increase of the swelling ratio was found by raising the temperature. These unusual swelling properties of the grafted films are attributed to strong interactions between pyrrolidone groups and the Cl atoms of the PVC.     

Dependence of the Water/Gas Partition Coefficient of Volatile Organic Compounds on the Ionic Strength of Sodium Chloride Solution

Headspace method has been applied to the water/gas partition coefficient investigations for 10 volatile organic compounds at temperature of 20°C. The values of the partition coefficients have been determined at different NaCl concentrations, ranging from 0.5% to 3.6%. A regular decrease in the values of the partition coefficient with the increasing salt concentration in solution has been observed. Additionally, the NaCl salting-out coefficient has been determined for all the examinated compounds. Using the dependence of the logarithm of the partition coefficient on the salinity of the solution has enabled to present the results as a straight – line function.