Characterization of a highly stable zwitterionic hydrophilic interaction chromatography stationary phase based on hybrid organic–inorganic particles

We have characterized a sulfobetaine stationary phase based on 1.7 μm ethylene-bridged hybrid organic–inorganic particles, which is intended for use in hydrophilic interaction chromatography. The efficiency of a column packed with this material was determined as a function of flow rate, demonstrating a minimum reduced plate height of 2.4. The batch-to-batch reproducibility was assessed using the separation of a mixture of acids, bases, and neutrals. We compared the retention and selectivity of the hybrid sulfobetaine stationary phase to that of several benchmark materials. The hybrid sulfobetaine material gave strong retention for polar neutrals and high selectivity for methyl groups, hydroxy groups, and configurational isomers. Large differences in cation and anion retention were observed among the columns. We characterized the acid and base stability of the hybrid sulfobetaine stationary phase, using accelerated tests at pH 1.3 and 11.0, both at 70°C. The results support a recommended pH range of 2–10. We also investigated the performance of columns packed with this material for metal-sensitive analytes, comparing conventional stainless steel column hardware to hardware that incorporates hybrid surface technology to mitigate interactions with metal surfaces. Compared to the conventional columns, the hybrid surface technology columns showed a greatly improved peak shape.     

An Organoruthenium Anticancer Agent Shows Unexpected Target Selectivity For Plectin

Organometallic metal(arene) anticancer agents require ligand exchange for their anticancer activity and this is generally believed to confer low selectivity for potential cellular targets. However, using an integrated proteomics-based target-response profiling approach as a potent hypothesis-generating procedure, we found an unexpected target selectivity of a ruthenium(arene) pyridinecarbothioamide (plecstatin) for plectin, a scaffold protein and cytolinker, which was validated in a plectin knock-out model in vitro. Plectin targeting shows potential as a strategy to inhibit tumor invasiveness as shown in cultured tumor spheroids while oral administration of plecstatin-1 to mice reduces tumor growth more efficiently in the invasive B16 melanoma than in the CT26 colon tumor model.     

Evidence of Structure Sensitivity in the Fischer–Tropsch Reaction on Model Cobalt Nanoparticles by Time-Resolved Chemical Transient Kinetics

The Fischer–Tropsch process, or the catalytic hydrogenation of carbon monoxide (CO), produces long chain hydrocarbons and offers an alternative to the use of crude oil for chemical feedstocks. The observed size dependence of cobalt (Co) catalysts for the Fischer–Tropsch reaction was studied with colloidally prepared Co nanoparticles and a chemical transient kinetics reactor capable of measurements under non-steady-state conditions. Co nanoparticles of 4.3 nm and 9.5 nm diameters were synthesized and tested under atmospheric pressure conditions and H₂/CO=2. Large differences in carbon coverage (Θ_C) were observed for the two catalysts: the 4.3 nm Co catalyst has a Θ_C less than one while the 9.5 nm Co catalyst supports a Θ_C greater than two. The monomer units present on the surface during reaction are identified as single carbon species for both sizes of Co nanoparticles, and the major CO dissociation site is identified as the B₅-B geometry. The difference in activity of Co nanoparticles was found to be a result of the structure sensitivity caused by the loss of these specific types of sites at smaller nanoparticle sizes.     

Isolation of berberine tannate using a chromatography activity-guided fractionation from root bark of Berberis hispanica Boiss. & Reut.

Root bark of Berberis hispanica Boiss. & Reut. constitutes an important source of alkaloids and is traditionally used in Algeria and Morocco in many herbal formulations particularly for the treatment of stomach infections and colon cancer. Activity-guided fractionation of Berberis extract is developed by step-gradient elution on column chromatography followed by preparative HPLC to isolate the most antistaphylococcal compound. Solvent extraction-activity screening indicates that ethanol should be used as the extracting solvent as it has exhibited the highest activity against Staphylococcus aureus(Rosenbach ATCC6538) followed by water extract, whereas no activity is recorded for acetone and hexane extracts. Screening of collected fractions from chromatographic separations indicates that the fraction presenting the highest antistaphylococcal activity is identified as berberine tannate by UV spectrum, melting point measurement and confirmed by liquid chromatography coupled to mass spectrometry (LC/MS). The minimal inhibition concentration value of berberine tannate against S. aureus is evaluated at 5?µg?mL^?1.     

Fourth-order compact schemes for a parabolic-ordinary system of European option pricing liquidity shocks model

This paper provides a numerical investigation for European options under parabolic-ordinary system modeling markets to liquidity shocks. Our main results concern construction and analysis of fourth order in space compact finite difference schemes (CFDS). Numerical experiments using Richardson extrapolation in time are discussed.     

Some aspects of the optical techniques for strain determination

In a general view, a comparison is made of different optical methods where either photoelastic models, opaque bodies with transparent coatings or noncontacted objects are examinèd with coherent light. Further, it is tried to show that some common features are contained by the three groups. These aspects concern the separation, by controlled determination, of displacement, rotation and strain (or of certain of their components), the multiplication of the optical effects in the detection and the elimination of secondary influences. In particular, the noncontacting method of wavefront reconstruction with double-exposure holograms is discussed and the role of the localization condition for the fringes in space is analyzed. On the other hand, it is illustrated that, besides the generally known birefringence and diffraction. use could be made of nonorthodox effects like rotation of the plane of polarization, second-harmonic generation in nonlinear optics, etc. This may, for instance, contribute to the optical instrumentation when transparent models and bodies with photoelastic coatings are investigated under the above aspects.     

Gauge invariance and charge conservation in non-Abelian gauge theories

It is shown that for gauge-tensor field theories which have their field equations derivable from a variational principle, the assumptions of gauge invariance and charge conservation are equivalent.     

On the Discretization of Distributed-Parameter Systems with Quadratic and Cubic Nonlinearities

Approximate methods for analyzing the vibrations of an Euler--Bernoulli beam resting on a nonlinear elastic foundation are discussed. The cases of primary resonance ( _n ) and subharmonic resonance of order one-half ( 2 _n ), where is the excitation frequency and _n is the natural frequency of the nth mode of the beam, are investigated. Approximate solutions based on discretization via the Galerkin method are contrasted with direct application of the method of multiple scales to the governing partial-differential equation and boundary conditions. The amplitude and phase modulation equations show that single-mode discretization leads to erroneous qualitative as well as quantitative predictions. Regions of softening (hardening) behavior of the system, the spatial dependence of the response drift, and frequency-response curves are numerically evaluated and compared using both approaches.     

Dependence of the zero shear-rate viscosity and the viscosity function of linear high-density polyethylenes on the mass-average molar mass and polydispersity

Linear high-density polyethylenes with molar masses M _w between 240 and 1,000,000 g/mol, obtained by metallocene catalysts, were characterized in shear using oscillatory and creep tests. The polydispersities of the molar mass distributions (MMDs) lay between 1 and 16. The resulting zero shear-rate viscosities η₀ covered a range from 2.5×10⁻³ to around 10⁸ Pas. Above a critical molar mass of M _c≈2,900 g/mol, the experimental results can be described by the relation η₀ ∼ M _w^3.6, independently of the MMD. The oscillatory data were fitted with a Carreau–Yasuda equation. The resulting parameters were correlated to molecular structure. The parameter a, being a quantity for the width of the transition between the Newtonian and the non-Newtonian regime, showed a dependence on the molar mass M _w but not on M _w/M _n. The parameter λ of the Carreau-Yasuda equation was found to be the reciprocal crossover frequency for all samples with a log-Gaussian MMD. λ depends on the molar mass M _w and also on M _w/M _n.