Approximate Query Answering and Result Refinement on XML Data

Today, many economic decisions are based on the fast analysis of XML data. Yet, the time to process analytical XML queries is typically high. Although current XML techniques focus on the optimization of query processing, none of these support early approximate feedback as possible in relational Online Aggregation systems. In this paper, we introduce a system that provides fast estimates to XML aggregation queries. While processing, these estimates and the assigned confidence bounds are constantly improving. In our evaluation, we show that without significantly increasing the overall execution time our system returns accurate guesses of the final answer long before traditional systems are able to produce output

Dynamic range multiwavelength particle characterization using analytical ultracentrifugation

We demonstrate how a sophisticated data analysis methodology enables us to perform multiwavelength evaluations of dynamic rotor speed gradient experiments obtained by analytical ultracentrifugation equipped with a multiwavelength detector. Our data evaluation tool HDR-MULTIFIT allows for the accurate analysis of sedimentation coefficient distributions which can be converted to particle size distributions. By means of multiwavelength evaluation, species dependent extinction spectra can be determined even for complex mixtures. Moreover, optical and hydrodynamic properties can be correlated for spherical particles of known optical properties applying multiwavelength evaluation and Mie's theory leading to a significant increase in the dynamic range of the experiment. We provide the theoretical background about the operation principle of our methodology and compare the performance of the multiwavelength analysis to the conventional single wavelength analysis as it is applied in turbidity analysis. We validate our technique using NIST traceable reference particles and show that our technique is universally applicable to materials of known and unknown optical properties, thus clearly extending the possibilities of particle analysis

Characteristics of a semi-industrial downer reactor for the rounding of irregular polymer particles

In the past additive manufacturing processes such as laser beam melting (LBM) were almost exclusively applied for the generation of prototypes. In recent years, however, these methods have gradually been transferred to serial production (1). With this grown relevance on industrial applications, the demands on the powder material have increased as well. In consequence, there is a need for fine powders of different polymers showing good powder flowability and high bulk density (2) It has been shown that different polymers can be ground down to the micron size range by a wet grinding process (2). Due to the grinding process the produced particles are in a chiseled state, which leads to a bad flowability. To solve this problem the single particles are melted in a heated downer reactor and spherical particles are obtained by using the effect of the surface tension (3). The rounding process was performed in a reactor with a length of 6 m and a diameter of 0.1 m. The main focus of this work is to describe the flow characteristics of both, gas and particles in the reactor. Other influencing parameters on the outcome of the rounding such as particle load and temperature distribution will also be addressed. One major critical point, the influence of the particle and gas inlet on the flow pattern will be discussed in detail. The mechanism of the rounding process in dependence of particle size, interfacial tension and melt viscosity will be shown within a sintering model (4). Please click Additional Files below to see the full abstract

Concentration-dependent sedimentation and diffusion coefficient in analytical ultracentrifugation experiments

Experimental data of analytical ultracentrifugation (AUC) experiments is defined by sedimentation and diffusion transport of molecules in solution. While the sedimentation properties define the position of the measured sedimentation boundaries, information on the diffusion is included in the broadening. Both effects are then analysed with well-established finite element solutions of Lamm’s equation The results from this multidimensional analysis provide e.g. molecular mass or size distributions or information on core-shell structures [1,2]

Two- versus three-dimensional ultrasound in the second and third trimester of pregnancy: impact on recognition and maternal-fetal bonding. A prospective pilot study

Objective: To assess the impact of three-dimensional (3D) versus two-dimensional (2D) ultrasound (US) on maternal-fetal bonding. Study design: Prospective randomized pilot study among low risk women with singleton fetuses in the second and third trimester. Dependent on the randomization pattern, US was commenced either with 2D US or 3D US and the effects were recorded with standardized questionnaires. Results: Sixty patients were included. Although the quality of 2D US, assessed by the examinator, was superior to 3D US, maternal recognition was higher with 3-D US (P=0.004). With 2D US, nulliparous patients had significantly more difficulties visualizing the fetus, than multiparous (P=0.03). However, the maternal preference of 3D US had no significant impact on maternal-fetal bonding. Conclusion: Ultrasound had no significant effect on maternal-fetal bonding. Three-dimensional images may facilitate recognition of the fetus, but 3D US did not have higher impact on maternal-fetal bonding. This finding may be a reason not to consider 3D ultrasound for routine scannin

Indentation and self-healing mechanisms of a self-assembled monolayer:a combined experimental and modeling study

A combination of in situ vibrational sum-frequency generation (SFG) spectroscopy and molecular-dynamics (MD) simulations has allowed us to study the effects of indentation of self-assembled octadecylphosphonic acid (ODPA) monolayers on α-Al2O3(0001). Stress-induced changes in the vibrational signatures of C–H stretching vibrations in SFG spectra and the results of MD simulations provide clear evidence for an increase in gauche-defect density in the monolayer as a response to indentation. A stress-dependent analysis indicates that the defect density reaches saturation at approximately 155 MPa. After stress is released, the MD simulations show an almost instantaneous healing of pressure-induced defects in good agreement with experimental results. The lateral extent of the contact areas was studied with colocalized SFG spectroscopy and compared to theoretical predictions for pressure gradients from Hertzian contact theory. SFG experiments reveal a gradual increase in gauche-defect density with pressure before saturation close to the contact center. Furthermore, our MD simulations show a spatial anisotropy of pressure-induced effects within ODPA domains: molecules tilted in the direction of the pressure gradient increase in tilt angle while those on the opposite side form gauche-defects

Isoelectric Point of Proteins at Hydrophobic Interfaces

Structural and colloidal stability of proteins at different surfaces and interfaces is of great importance in many fields including medical, pharmaceutical, or material science. Due to their flexibility, proteins tend to respond to their environmental conditions and can undergo structural and conformational changes. For instance, alterations in physiological factors such as temperature, ions concentration, or pH as well as the adsorption to an interface can initiate protein aggregation. Therefore, at different surfaces and interfaces the characterization of the structural and colloidal stability of proteins, which is mainly influenced by their electrostatic and hydrophobic interactions, is of fundamental importance. In this study, we utilized sum frequency generation (SFG) spectroscopy to assess the role of solution pH on the polarity and magnitude of the electric field within the hydration shell of selected model proteins adsorbed to a hydrophobic surface. We used polystyrene (PS) as a model hydrophobic surface and determined the isoelectric point (IEP) of four structurally different model proteins. Comparing the measured IEP of proteins at the PS/solution or air/solution interface with that determined in the bulk solution via zeta potential measurement, we found significant similarities between the IEP of surface adsorbed proteins and those in the bulk aqueous phase. The pH dependence behavior of proteins was correlated to their amino acid composition and degree of hydrophobicity

Carboxylate ion pairing with alkali-metal ions for β-Lactoglobulin and its role on aggregation and interfacial adsorption

We report a combined experimental and computational study of the whey protein β-lactoglobulin (BLG) in different electrolyte solutions. Vibrational sum-frequency generation (SFG) and ellipsometry were used to investigate the molecular structure of BLG modified air–water interfaces as a function of LiCl, NaCl, and KCl concentrations. Molecular dynamics (MD) simulations and thermodynamic integration provided details of the ion pairing of protein surface residues with alkali-metal cations. Our results at pH 6.2 indicate that BLG at the air–water interface forms mono- and bilayers preferably at low and high ionic strength, respectively. Results from SFG spectroscopy and ellipsometry are consistent with intimate ion pairing of alkali-metal cations with aspartate and glutamate carboxylates, which is shown to be more effective for smaller cations (Li⁺ and Na⁺). MD simulations show not only carboxylate–alkali-metal ion pairs but also ion multiplets with the alkali-metal ion in a bridging position between two or more carboxylates. Consequently, alkali-metal cations can bridge carboxylates not only within a monomer but also between monomers, thus providing an important dimerization mechanism between hydrophilic surface patches