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The continuously growing demands on standard components of machine elements with respect to power density, efficiency and durability while operating can reach the borders of load bearing capacity and lead to premature failure. Especially in engineering applications with insufficiently predictable operating conditions, bearings can usually meet these requirements. Possible correctives are the use of new materials with modified properties or changes in the design. In the railway industry, particularly high impact loads on bearing cages can occur. Brass cages are primarily used here. Thus, new brass alloys are applied whose properties have been improved in terms of their mechanical and tribological behaviour. Various brass alloys have been selected on the basis of the mechanical properties and cost aspects. Using a modified test rig for precision bearings, these alloys have been studied with respect to the tribological properties, which are correlated with the results of tests with brass rolling bearing cages. This gives the possibility to choose optimised brass materials for bearing cage application under increased requirements. [ABSTRACT FROM AUTHOR]

Intermetallic clathrates are promising materials for thermoelectric applications at elevated temperatures. In the search for cost-competitive representatives, we investigate the thermoelectric properties of quaternary type I clathrates with nominal compositions BaCuSiGe (4.5 ≤ x ≤ 7). The specimens were prepared by melting and annealing with subsequent ball milling and hot pressing. X-ray diffraction and energy-dispersive x-ray spectroscopy were used for an accurate structure determination and for an analysis of the phase purity and microstructure, respectively. The transport properties show a systematic variation with the Cu content in the clathrate phase. The highest dimensionless thermoelectric figure of merit ZT of 0.31 is achieved for BaCuSiGe at about 250°C (520 K). [ABSTRACT FROM AUTHOR]

Ba8Ga16-xGe30+x is the clathrate with the highest thermoelectric figure of merit known to date. However, no p-type material could be obtained by conventional synthesis from the melt. Here we show that the time and cost-effective melt spinning technique can produce Ba8Ga16-xGe30+x in a metastable state, where x can be varied continuously from negative to positive values, resulting in both p- and n-type materials. The quenched phases were characterized by x-ray powder diffraction and transmission electron microscopy. It was surprising that they were perfectly crystalline, with large grain sizes of the order of a micrometer. Temperature dependent measurements of the electrical resistivity, Hall effect, thermopower, and thermal conductivity are presented and discussed in terms of a two-band model. [ABSTRACT FROM AUTHOR]

Abstract: Attempts to introduce rare earth elements other than Eu as guest atoms into intermetallic clathrates have remained elusive to date. Besides fundamental interest, their motivation is to create “strongly correlated” clathrates with correlation-enhanced “giant” thermopower values in addition to the much discussed low thermal conductivities, and thus with enhanced thermoelectric figures-of-merit. In Eu clathrates no sizeable hybridization of the 4f electrons with the conduction electrons is observed. Here we present our attempts to incorporate Yb in Eu8Ga16Ge30. Yb leads to strong correlation effects in many intermetallic compounds. Along with the standard melting and annealing procedure an alternative route, namely quick quenching of the melt by melt spinning, was tested. Samples obtained in both ways were investigated by XRD, SEM/EDX, and TEM/EDX techniques. No sizable substitution of Eu by Yb in the clathrate phase was found. [Copyright &y& Elsevier]

The high specific surface area and high reactivity of nanoscale zero-valent iron (nZVI) particles have led to much research on their application to environmental remediation. The reactivity of nZVI is affected by both the water chemistry and the properties of the particular type of nZVI particle used. We have investigated the reactivity of three types of commercially available Nanofer particles (from Nanoiron, s.r.o., Czech Republic) that are currently either used in, or proposed for use in full scale environmental remediation projects. The performance of one of these, the air-stable and thus easy-to-handle Nanofer Star particle, has not previously been reported. Experiments were carried out first in batch shaking reactors in order to derive maximum reactivity rates and provide a rapid estimate of the Nanofer particle's reactivity. The experiments were performed under near-natural environmental conditions with respect to the pH value of water and solute concentrations, and results were compared with those obtained using synthetic water. Thereafter, the polyelectrolyte-coated Nanofer 25S particles (having the highest potential for transport within porous media) were chosen for the experiments in column reactors, in order to elucidate nanoparticle reactivity under a more field-site realistic setting. Iopromide was rapidly dehalogenated by the investigated nZVI particles, following pseudo-first-order reaction kinetics that was independent of the experimental conditions. The specific surface area normalized reaction rate constant (kSA) value in the batch reactors ranged between 0.12 and 0.53Lm(-2)h(-1); it was highest for the uncoated Nanofer 25 particles, followed by the polyacrylic acid-coated Nanofer 25S and air-stable Nanofer Star particles. In the batch reactors all particles were less reactive in natural water than in synthetic water. The kSA values derived from the column reactor experiments were about 1000 times lower than those from the batch reactors, ranging between 2.6×10(-4) and 5.7×10(-4)Lm(-2)h(-1). Our results revealed that the easy-to-handle and air-stable Nanofer Star particles are the least reactive of all the Nanofer products tested. The reaction kinetics predicted by column experiments were more realistic than those predicted by batch experiments and these should therefore be used when designing a full-scale field application of nanomaterials for environmental remediation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The mobility of nanoscale zero-valent iron (nZVI), which is used for in situ groundwater remediation, is affected by chemical and physical heterogeneities within aquifers. Carbonate minerals in porous aquifers and the presence of divalent cations reduce nZVI mobility. This study assesses the potential for enhancing the mobility of polyacrylic acid coated nZVI (PAA-nZVI) in such aquifers through the co-injection of polyelectrolytes (natural organic matter, humic acid, carboxymethyl cellulose, and lignin sulfonate). When applied at the same concentration, all of the polyelectrolytes produced similar enhancement of PAA-nZVI mobility in carbonate porous media. This increase in mobility was a result of increased repulsion between PAA-nZVI and the carbonate matrix. Lignin sulfonate, an environmentally friendly and inexpensive agent, was identified as the most suitable polyelectrolyte for field applications. The greatest increase in PAA-nZVI mobility was achieved with co-injection of lignin sulfonate at concentrations ≥50 mg L(-1); at these concentrations the maximum PAA-nZVI travel distance in carbonate porous media was twice of that in the absence of lignin sulfonate., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The limited transport of nanoscale zero-valent iron (nZVI) in porous media is a major obstacle to its widespread application for in situ groundwater remediation. Previous studies on nZVI transport have mainly been carried out in quartz porous media. The effect of carbonate minerals, which often predominate in aquifers, has not been evaluated to date. This study assessed the influence of the carbonate minerals in porous media on the transport of polyacrylic acid modified nZVI (PAA-nZVI). Increasing the proportion of carbonate sand in the porous media resulted in less transport of PAA-nZVI. Predicted travel distances were reduced to a few centimeters in pure carbonate sand compared to approximately 1.6 m in quartz sand. Transport modeling showed that the attachment efficiency and deposition rate coefficient increased linearly with increasing proportion of carbonate sand., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

High temperature thermoelectric (TE) properties for triple-filled skutterudites (Sr(x)Ba(x)Yb₁₋₂x)(y)Co₄Sb₁₂ were investigated for alloy compositions in two sections of the system: (a) for x = 0.25 with a filling fraction y ranging from 0.1 to 0.25 and (b) for 0 < x < 0.5 and y = 0.11 + 0.259x. The representation of the figure of merit, ZT, as a function of skutterudite composition, defined the compositional range (0.25 < x < 0.4; 0.18 < y < 0.24) with ZT over 1.4 at 800 K. It was shown that an enhanced TE performance for these triple-filled skutterudites is caused by low electrical resistivities and low lattice thermal conductivities, as well as by a fine tuning of the chemical composition. Low temperature measurements for the samples with the highest ZT values showed that even a small change of the filler ratios changes the contribution of scattering effects, the carrier concentration and the mobility.

The heavy fermion compound Ce3Pd20Si6 is one of the rare examples of a cubic system with a readily accessible quantum critical point. Ce atoms at the two different sites 4a and 8c of the crystal structure have recently been shown to have different crystal field ground states (Γ7 and Γ8, respectively) and are assumed to be responsible for the two different low-temperature phase transitions at T(L) and T(U), which have been tentatively attributed to antiferromagnetic and antiferroquadrupolar order, respectively. Here we present electrical resistivity measurements in a wide temperature range (50 mK-300 K) on two new representatives of the La substitution series Ce(3 - x)La(x)Pd20Si6, x=1/3 and 2/3. Put in the context of previously published data our results indicate that La preferentially occupies the 4a site and that Ce ions at the 8c site have a sizably larger Kondo temperature. Low-temperature resistivity measurements in applied magnetic fields suggest that (disorder smeared) quantum critical points exist in the x=1/3 and 2/3 samples at fields below 1 T.

Process mining is an emerging technology in the context of Business Process Management with the goal to derive process models from observed system behavior. The global goals are: to detect previously unknown process structures, to implement consistent process controlling which may involve computation of realistic cycle times and frequency of occurrence of process pathways, or to quantify the conformance to guidelines. We did a detailed hands-on evaluation and analysis of established process-mining approaches and assessed their abilities to cope with the challenges of clinical environments. None of the examined 7 approaches fulfilled all requirements, but 2 could be circle out, which are to some degree suitable for clinical process mining.

This work is part of an ongoing effort to examine and improve clinical workflows in radiology. Classical workflow analysis is time consuming and expensive. Here we present a purely data-driven approach using data mining techniques to detect causes for poor data quality and areas with poor workflow performance. Data has been taken from a operational RIS system. We defined a set of four key indicators for both data quality and workflow performance. Using several mining techniques such as cluster analysis and correlation tests we were able to detect interesting effects regarding data quality and an abnormality in the workflow for some organizational units of the examined radiology departments. We conclude that data-driven data mining approaches may act as a valuable tool to support workflow analysis and can narrow down the problem space for a manual on-site workflow analysis. This can save time and effort and leads to less strain for clinicians and workflow analysts during interviews.

A 64 year old female patient was diagnosed with scleroderma and has been bed-ridden for 25 years. She wears no clothing whatsoever on the grounds of an intolerance to textiles, and has spent the last eight years uninterruptedly in bed in a construction of kitchen paper towels and rubber bed sheets. A somatic disease has been be ruled out and cenesthesic schizophrenia diagnosed. As differential diagnoses, somatization, somatiform disorders and hypochondria were considered. The patient refused any psychiatric treatment.

Thermoproteus tenax possesses two different glyceraldehyde-3-phosphate dehydrogenases, one specific for NADP+ and the other for NAD+. NADP(H) inhibits the NAD+-specific enzyme competetively with respect to NAD+ whereas NAD(H) virtually does not interact with the NADP+-specific enzyme. Both enzymes represent homomeric tetramers with subunit molecular masses of 39 kDa (NADP+-specific enzyme) and 49 kDa (NAD+-specific enzyme), respectively. The NADP+-specific enzyme shows significant homology to the known glyceraldehyde-3-phosphate dehydrogenases from eubacteria and eukaryotes as indicated by partial sequencing. The enzymes are thermostable, the NADP+-specific enzyme with a half-life of 35 min at 100 degrees C, the NAD+-specific enzyme with a half-line of greater than or equal to 20 min at 100 degrees C, depending on the protein concentration. Both enzymes show conformational and functional changes at 60-70 degrees C.