Maximal Pairs of Computably Enumerable Sets in the Computably Lipschitz Degrees

A set A is computably Lipschitz or cl-reducible, for short, to a set B if A is Turing reducible to B by an oracle Turing machine with use function ? such that ? is bounded by the identity function up to an additive constant, i.e., ?(n)??n+O(1). In this paper we study maximal pairs of computably enumerable (c.e.) cl-degrees or maximal pairs, for short, i.e., pairs of c.e. cl-degrees such that there is no c.e. cl-degree that is above both cl-degrees in this pair. Our main results are as follows. (1) A c.e. Turing degree contains a c.e. cl-degree that is half of a maximal pair if and only if this Turing degree contains a maximal pair if and only if this Turing degree is array noncomputable. (2) The cl-degrees of all weak truth-table complete sets are halves of maximal pairs while there is a Turing complete set A such that the cl-degree of A is not half of any maximal pair. In fact, any high c.e. Turing degree contains a c.e. cl-degree that is not half of a maximal pair. (3) Above any c.e. cl-degree there is a maximal pair. (4) There is a maximal pair which at the same time is a minimal pair. (5) There is a pair of c.e. cl-degrees that is not maximal and does not possess a least upper bound. Moreover, we make some observations on the structure of the c.e. cl-degrees in general. For instance, we give a very simple proof of the fact that there are no maximal c.e. cl-degrees.     

CPU demand for web serving: Measurement analysis and dynamic estimation

Managing the resources in a large Web serving system requires knowledge of the resource needs for service requests of various types. In order to investigate the properties of Web traffic and its demand, we collected measurements of throughput and CPU utilization and performed some data analyses. First, we present our findings in relation to the time-varying nature of the traffic, the skewness of traffic intensity among the various types of requests, the correlation among traffic streams, and other system-related phenomena. Then, given such nature of web traffic, we devise and implement an on-line method for the dynamic estimation of CPU demand.

Assessing resource needs is commonly performed using techniques such as off-line profiling, application instrumentation, and kernel-based instrumentation. Little attention has been given to the dynamic estimation of dynamic resource needs, relying only on external and high-level measurements such as overall resource utilization and request rates. We consider the problem of dynamically estimating dynamic CPU demands of multiple kinds of requests using CPU utilization and throughput measurements. We formulate the problem as a multivariate linear regression problem and obtain its basic solution. However, as our measurement data analysis indicates, one is faced with issues such as insignificant flows, collinear flows, space and temporal variations, and background noise. In order to deal with such issues, we present several mechanisms such as data aging, flow rejection, flow combining, noise reduction, and smoothing. We implemented these techniques in a Work Profiler component that we delivered as part of a broader system management product. We present experimental results from using this component in scenarios inspired by real-world usage of that product.     

Magnebike: A magnetic wheeled robot with high mobility for inspecting complex‐shaped structures

This paper describes the Magnebike robot, a compact robot with two magnetic wheels in a motorbike arrangement, which is intended for inspecting the inner casing of ferromagnetic pipes with complex‐shaped structures. The locomotion concept is based on an adapted magnetic wheel unit integrating two lateral lever arms. These arms allow for slight lifting off the wheel in order to locally decrease the magnetic attraction force when passing concave edges, as well as laterally stabilizing the wheel unit. The robot has the main advantage of being compact (180 × 130 × 220 mm) and mechanically simple: it features only five active degrees of freedom (two driven wheels each equipped with an active lifter stabilizer and one steering unit). The paper presents in detail design and implementation issues that are specific to magnetic wheeled robots. Low‐level control functionalities are addressed because they are necessary to control the active system. The paper also focuses on characterizing and analyzing the implemented robot. The high mobility is shown through experimental results: the robot not only can climb vertical walls and follow circumferential paths inside pipe structures but it is also able to pass complex combinations of 90‐deg convex and concave ferromagnetic obstacles with almost any inclination regarding gravity. It requires only limited space to maneuver because turning on the spot around the rear wheel is possible. This high mobility enables the robot to access any location in the specified environment. Finally the paper analyzes the maximum payload for different types of environment complexities because this is a key feature for climbing robots and provides a security factor about the risk of falling and slipping. © 2009 Wiley Periodicals, Inc.     

The hierarchical Tobit model: A case study in Bayesian computing

In this paper we discuss the potentials of a new Bayesian inference tool, called the Gibbs sampler, for the analysis of the censored regression or Tobit model. Tobit models have a wide range of applications in empirical sciences, like econometrics and biometrics. The estimation results of the simple Tobit model will be compared to a hierarchical Tobit model, and the Gibbs sampling approach to the related classical algorithm of expectation-maximisation (EM). The underlying botanical example of this paper is concerned with the censoring mechanism in plant reproduction and proposes the Bayesian Tobit model for the growth relationship between the reproductive part and the rest of the plant.     

Analysis of dithiocarbamate fungicides. Second-derivative UV-spectroscopic determination of CS2, COS, and thiram (TMTD)

The application of second-derivative UV-spectroscopy offers a highly sensitive and selective method for the determination of CS₂ and COS, as acid hydrolysis products of dithiocarbamate und thiuram disulphide fungicides, using a methanolic amine absorption reagent (ethylenediamine, piperidine). With standard concentrations of 0.08–1.1 g CS₂/ml and 0.3 to 2.0 g COS/ml, respectively, calibration curves with good correlation coefficients (r>0.999) were obtained. In comparison to the official method of the Deutsche Forschungsgemeinschaft (DFG method S15) the proposed alternative is at least 100 times more sensitive to CS₂. Using the second derivative method it is possible not only to clearly differentiate between CS₂ and COS but also to quantify both gases without resorting to tedious background corrections as compared to the direct photometric methods. Additionally, second derivative spectroscopy allows the direct determination of thiram in the concentration range 1–10 g/ml after its extraction with chloroform. For example, thiram in water (10 g/l) and in thiram/talc standards (10 mg/g) were determined with good precision (±2.0%).

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Analytik der Dithiocarbamat-Fungicide. Bestimmung von CS₂, COS sowie Thiram (TMTD) mittels Derivativ-UV-Spektroskopie

Zusammenfassung Die Anwendung der Derivativ-UV-Spektroskopie (2. Ableitung) erlaubt eine sehr empfindliche Bestimmung von CS₂ und COS als Hydrolyseprodukte der Dithiocarbamat- und Thiuramdisulfid-Fungicide nach Absorption in einem methanolischem Amin-Reagens (Ethylendiamin, Piperidin). Mit Standard-Konzentrationen von 0,08–1,1 g CS₂/ml bzw. 0,3–2,0 g COS/ml zeigten die Eichgeraden gute Korrelationskoeffizienten (r<0,999). Im Vergleich zur DFG-Methode S15 zeichnet sich die vorgeschlagene Alternative durch eine um zwei Zehnerpotenzen höhere Empfindlichkeit bei der CS₂-Bestimmung aus. In der 2. Ableitung wird nicht nur die Unterscheidung von COS und CS₂ eindeutig, sondern auch deren Quantifizierung ohne rechnerische Untergrundkorrekturen ermöglicht. Mit Hilfe der Derivativspektroskopie konnte außerdem Thiram (TMTD) in Konzentrationen von 1–10 g/ml direkt erfaßt werden. So ließen sich nach Extraktion mit Chloroform 10 g/L Thiram in Wasser mit einer Präzision von ±2,0% direkt bestimmen oder Thiram/Talkum-Standards (10 mg/g) überprüfen.

     

Fungicides and photochemistry: Photodegradation of the azole fungicide penconazole

In order to examine the photostability of the fungicide penconazole (1-(2,4-dichloro--propylphenethyl)-1H-1,2,4-triazole,1) in the field, model experiments with organic solvents were performed. Photodegradation (>280 nm) of penconazole was found to be more efficient in isopropanol and cyclohexane solution than in the presence of cyclohexene. Photolysis in isopropanol and cyclohexane resulted in considerable formation of 1-(4-chloro--propylphenethyl)-1H-1,2,4-triazole (2) and 5H,6H-(1,2,4-triazolo)-[5,1-a]-9-chloro-6-propyl-isoquinoline (3). Furthermore, photodehalogenation of3 yielded traces of 5H,6H-(1,2,4-triazolo)-[5,1-a]-6-propyl-isoquinoline (4) and, in the presence of isopropanol 5H,6H-(1,2,4-triazolo)-[5,1-a]-9-(2-hydroxy-2-methylethyl)-6-propyl-isoquioline (5). Additionally, a lot of polar products were found in high yields which could not be isolated and characterized individually. In the presence of cyclohexene, on the other hand, photodecomposition and photodehalogenation to photoproduct2 were found to be the main degradation pathways and photoproduct3 was only detected as a trace component.

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Fungicide und Photochemie: Photoabbau des Azol-Fungicides Penconazol

Zusammenfassung Zur Voruntersuchung der Photostabilität des Fungicides Penconazol (1-(2,4-Dichlor--propylphenethyl)-1H-1, 2,4-triazol,1) wurden Modellexperimente in organischen Lösungsmitteln durchgeführt. Der Photoabbau (>280 nm) nimmt von Cyclohexen zu Cyclohexan und Isopropanol hin deutlich zu. Bei Bestrahlung in Isopropanol oder Cyclohexan entstehen als Hauptprodukte (1-(4-Chlor--propylphenethyl)-1H-1, 2,4-triazol (2) und 5H,6H-(1,2,4-Triazolo)-[5,1,-a]-9-chlor-6-propyl-isochinolin (3). Photodehalogenierung von 3 führt in geringem Umfang zu 5H,6H-(1,2,4-Triazo-lo)-[5, 1-a]-6-propyl-isochinolin(4) und in Gegenwart von Isopropanol zu 5H,6H-(1,2,4-Triazolo)-[5,1-a]-9-(2-hydroxy-2-methylethyl)-6-propyl-isochinolin (5) als Photoadditionsprodukt. Daneben entsteht in hohem Ausmaß eine komplexe Fraktion polarer Komponenten, die einer Einzelisolierung und -charakterisierung nicht mehr zugänglich waren. In Cyclohexen hingegen erfolgte neben Photodehalogenierung zu2 hauptsächlich Photolyse zu polaren Komponenten, während Photoprodukt3 nur in Spuren entstand.

     

Covalent Adaptable Microstructures via Combining Two-Photon Laser Printing and Alkoxyamine Chemistry: Toward Living 3D Microstructures

Manufacturing programmable materials, whose mechanical properties can be adapted on demand, is highly desired for their application in areas ranging from robotics, to biomedicine, or microfluidics. Herein, the inclusion of dynamic and living bonds, such as alkoxyamines, in a printable formulation suitable for two-photon 3D laser printing is exploited. On one hand, taking advantage of the dynamic covalent character of alkoxyamines, the nitroxide exchange reaction is investigated. As a consequence, a reduction of the Young´s Modulus by 50%, is measured by nanoindentation. On the other hand, due to its “living” characteristic, the chain extension becomes possible via nitroxide mediated polymerization. In particular, living nitroxide mediated polymerization of styrene results not only in a dramatic increase of the volume (≈8 times) of the 3D printed microstructure but also an increase of the Young's Modulus by two orders of magnitude (from 14 MPa to 2.7 GPa), while maintaining the shape including fine structural details. Thus, the approach introduces a new dimension by enabling to create microstructures with dynamically tunable size and mechanical properties.     

Glyphosate Adsorption from Water Using Hierarchically Porous Metal–Organic Frameworks

The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g⁻¹, which ranks these MOFs among the best-reported adsorbents.     

Efficient numerical methods for the large‐scale,parallel solution of elastoplastic contact problems

Quasi‐static elastoplastic contact problems are ubiquitous in many industrial processes and other contexts, and their numerical simulation is consequently of great interest in accurately describing and optimizing production processes. The key component in these simulations is the solution of a single load step of a time iteration. From a mathematical perspective, the problems to be solved in each time step are characterized by the difficulties of variational inequalities for both the plastic behavior and the contact problem. Computationally, they also often lead to very large problems. In this paper, we present and evaluate a complete set of methods that are (1) designed to work well together and (2) allow for the efficient solution of such problems. In particular, we use adaptive finite element meshes with linear and quadratic elements, a Newton linearization of the plasticity, active set methods for the contact problem, and multigrid‐preconditioned linear solvers. Through a sequence of numerical experiments, we show the performance of these methods. This includes highly accurate solutions of a three‐dimensional benchmark problem and scaling our methods in parallel to 1024 cores and more than a billion unknowns. Copyright © 2015 John Wiley & Sons, Ltd.     

X‐ray diffraction (XRD)‐studies on the temperature dependent interface reactions on hafnium,zirconium, and nickel coated monocrystalline diamonds used in grinding segments for stone and concrete machining

Diamond impregnated metal matrix composites are the state of the art solution for the machining of mineral materials. The type of interface reactions between the metal matrix and diamond surface has an essential influence on the tool performance and durability. To improve the diamond retention, the diamonds can be coated by physical vapour deposition with metallic materials, which enforce interface reactions. Hence, this paper focuses on the investigation of the interfacial area on metal‐coated monocrystalline diamonds. Hafnium and zirconium, both known as carbide forming elements, are used as coating materials. The third coating, which is used to determine its catalytic influences when applied as a physical vapour deposition (PVD)‐layer, is nickel. Additionally, the coated diamond samples were heat‐treated to investigate the starting point of the formation of new phases. X‐ray diffraction‐analyses revealed the assumed carbide formation on hafnium and zirconium coated samples. The formation temperature was identified between 800 °C and 1000 °C for hafnium and zirconium coatings.