Local projection stabilization for advection–diffusion–reaction problems: One-level vs. two-level approach

Local projection stabilization (LPS) of finite element methods is a new technique for the numerical solution of transport-dominated problems. The main aim of this paper is a critical discussion and comparison of the one- and two-level approaches to LPS for the linear advection–diffusion–reaction problem. Moreover, the paper contains several other novel contributions to the theory of LPS. In particular, we derive an error estimate showing not only the usual error dependence on the mesh width but also on the polynomial degree of the finite element space. Based on this error estimate, we propose a definition of the stabilization parameter depending on the data of the solved problem. Unlike other papers on LPS methods, we observe that the consistency error may deteriorate the convergence order. Finally, we explain the relation between the LPS method and residual-based stabilization techniques for simplicial finite elements.     

FINITE ELEMENTS WITH LOCAL PROJECTION STABILIZATION FOR INCOMPRESSIBLE FLOW PROBLEMS

In this paper we review recent developments in the analysis of finite element methods for incompressible flow problems with local projection stabilization （LPS）. These methods preserve the favourable stability and approximation properties of classical residual-based stabilization （RBS） techniques but avoid the strong coupling of velocity and pressure in the stabilization terms. LPS-methods belong to the class of symmetric stabilization techniques and may be characterized as variational multiscale methods. In this work we summarize the most important a priori estimates of this class of stabilization schemes developed in the past 6 years. We consider the Stokes equations, the Oseen linearization and the NavierStokes equations. Furthermore, we apply it to optimal control problems with linear（ized） flow problems, since the symmetry of the stabilization leads to the nice feature that the operations ＂discretize＂ and ＂optimize＂ commute.     

An experimental value for the B(1u) C-H stretch mode in benzene

We here present experimental infrared spectra on two (C(6)H(6))(C(6)D(6)) benzene dimer isomers in the gas phase. The spectra show that the two benzene molecules in the dimer are symmetrically inequivalent and have distinct IR signatures. One of the two molecules is in a site of low symmetry, which leads to the IR activation of fundamental modes that are IR forbidden by symmetry in the monomer. In the spectra, all four fundamental C-H stretch modes of benzene are observed. Modes in the dimer are shifted up to 3 cm(-1) to the red, compared to the modes that are known for the monomer. For the nu(13) B(1u) C-H stretch fundamental mode of benzene, a first experimental value of 3015(+2) (-5) cm(-1) is determined, in excellent agreement with anharmonic frequency calculations presented here.     

Detection enhancement in nano-channels using micro-machined silicon groove

The present paper reports on an experimental study of the possibility to use a micro-machined detection groove to enhance the detection sensitivity in flat-rectangular nano-channels for ultra-rapid liquid chromatography separations. Transversally running detection grooves with three different axial widths (respectively, 2, 4 and 6mum) and one depth (4.75mum) were tested in glass and silicon channels for the whole range of detectable fluorescein isothiocyanate isomer I, FITC, concentrations. The groove with the most square-like cross-section (i.e., 4mum wide and 4.75mum deep) yielded the best combination of detection gain and minimal additional band broadening. In a 1cm long channel, the effective plate loss caused by the 4mum wide groove would only be of the order of 20%, while the gain in S/N-ratio was of the order of a factor of 5. The detection groove concept yields larger gains in silicon channel substrates than in glass channel substrates, due to the larger stray light losses occurring in the latter.     

Ultra-rapid separation of an angiotensin mixture in nanochannels using shear-driven chromatography

The present paper reports on the separation of a mixture of fluorescein isothiocyanate-labeled angiotensin I and II peptides in a shear-driven nanochannel with a C18-coating and using an eluent consisting of 5% acetonitrile in 0.02 M aqueous phosphate buffer at pH 6.5. The flat-rectangular nanochannel in fused silica consisted of an etched structure in combination with a flat moving wall. The very fast separation kinetics that can be achieved in a nanochannel allowed to separate the angiotensin peptides in less then 0.2 s in a distance of only 1.8 mm. Plate heights as small as 0.4 microm were calculated after substraction of the injection effect.     

Proteomics in cancer research: methods and application of array-based protein profiling technologies

With the human genome sequence now determined, the field of molecular medicine is moving beyond genomics to proteomics, the large-scale analysis of proteins.It is now possible to examine the expression of more than 1000 proteins using mass spectrometry technology coupled with various separation methods.Microarray technology is a new and efficient approach, for extracting relevant biomedical data and has a wide range of applications. It provides a versatile tool to study protein-protein, protein-nucleic acid, protein-lipid, enzyme-substrate and protein-drug interactions.This review paper will explore the key themes in proteomics and their application in clinical cancer research.     

Performance limits of monolithic and packed capillary columns in high-performance liquid chromatography and capillary electrochromatography

A method is proposed for the comprehensive characterization and comparison of columns in the high-performance liquid chromatographic (HPLC) and capillary electrochromatographic (CEC) modes. Using this approach, column parameters such as the number of plates, the eddy-diffusion and mass-transfer contributions to peak broadening, the permeability, and the analysis time are incorporated in a single graph and a comparison in terms of efficiency and speed is obtained. The chromatographic performance of silica-based and polymer-based monolithic capillary columns is discussed and a comparison is made with the performance of packed columns. Also, the potential of ultra-high-pressure liquid chromatography is discussed in this context. In the HPLC mode, the best results were obtained with silica monoliths; in the CEC mode, the low-density methacrylate-ester-based monoliths showed the best performance.     

Significance of Auditory and Kinesthetic Feedback to Singers'' Pitch Control

An accurate control of fundamental frequency (F0) is required from singers. This control relies on auditory and kinesthetic feedback. However, a loud accompaniment may mask the auditory feedback, leaving the singers to rely on kinesthetic feedback. The object of the present study was to estimate the significance of auditory and kinesthetic feedback to pitch control in 28 students beginning a professional solo singing education. The singers sang an ascending and descending triad pattern covering their entire pitch range with and without masking noise in legato and staccato and in a slow and a fast tempo. F0 was measured by means of a computer program. The interval sizes between adjacent tones were determined and their departures from equally tempered tuning were calculated. The deviations from this tuning were used as a measure of the accuracy of intonation. Statistical analysis showed a significant effect of masking that amounted to a mean impairment of pitch accuracy by 14 cent across all subjects. Furthermore, significant effects were found of tempo as well as of the staccato/legato conditions. The results indicate that auditory feedback contributes significantly to singers' control of pitch.     

Accurate determination of extra-column band broadening using peak summation

The present contribution addresses the problem of the accurate determination of the extra-column band-broadening dispersion by applying the method of moments (MOM) on pulse response experiments. The MOM provides the only mathematically rigorous way to determine the variance of a pulse response, but suffers from the fact that the obtained variance values usually depend very strongly and unpredictably on the selected integration boundaries. In the present study, it is investigated whether the MOM cannot be made more accurate by repeating the pulse response experiment a number of times, then add all measured peaks (after retention time alignment) and subsequently perform the integration on this summed peak. Testing this approach for a number of different integration boundary detection methods consistently more accurate results are obtained than when the different repeat response pulses are integrated individually and the variances are averaged afterwards. It was also found that adding five repeats already leads to a significant improvement of the variance estimate, whereas the addition of 10-20 repeats is needed before the variance estimate converges to a steady value.     

Hydrodynamic chromatography separations in micro- and nanopillar arrays produced using deep-UV lithography (J. Sep. Science 35'15)

DOI: 10.1002/jssc.201200076 Micro-pillar array columns with an inter-pillar spacing down to 500 nm have been designed and fabricated enabling hydrodynamic chromatography separations of fluorescently labeled polystyrene nano-particles. Injecting sub-nanoliter sized sample volumes and detecting the fluorescent signal on-chip, fluorescein, 20 and 40 nm diameter particles could be separated in less than 1.5 minutes.