Continuous generating grinding—Tooth root machining and use of CBN-tools

Profile accuracy, no burning and residual compressive stresses at the tooth root fillet are required for the durability of highly stressed gears. This paper reveals the challenges for continuous generating grinding with corundum and CBN. For this purpose, material removal simulations and experimental investigations were carried out to gain knowledge of the tool–workpiece contact conditions. The potential of CBN tools was analysed due to the fact that the mechanical loads at the grinding worm tip result in high profile wear of the corundum tools. In this context, especially the interrelationship between the dressing strategy and the workpiece quality was investigated in detail.     

TPA‐PPEs – New alternating donor copolymers for potential application in photovoltaic devices

A series of phenyleneethynylene copolymers with triphenylamine units as hole‐transporting moieties (TPA‐PPEs) were synthesized by the palladium‐catalyzed cross‐coupling polycondensation of diethynyltriphenylamines and selected dihalogen comonomers, for instance substituted benzene, thiophene, benzothiadiazole, or anthracene. Incorporation of the electron‐rich amino group into the PPE backbone does not interrupt the main chain conjugation. Furthermore, it has a decreasing effect on the oxidation potential, thus makes these polymers interesting as hole‐injection/hole‐transporting materials. The chemical structure of the new alternating copolymers was confirmed by ¹H and ¹³C NMR spectroscopy and elemental analysis and gel‐permeation chromatography (GPC; THF, M_n ≈ 15,000–30,000 g/mol) was conducted. Furthermore, their optical properties were investigated by UV/vis spectroscopy. The TPA‐PPEs exhibit absorption maxima at around 400 nm (π‐π*), except anthracene containing copolymer 3f (λ_max = 514 nm in THF) and benzothiadiazole containing one 3g (λ_max = 503 nm in THF). The TPA copolymers have oxidation potentials about 1.1 V (Ag/AgCl). They are good photoconducting materials ( 3a : I_Photo = 4 × 10^?10 A at 425 nm (400 V), 3g : I_Photo = 1.3 × 10^?11 A at λ_max = 500 nm (20 V)) and show emission after excitation at around 450 nm (560 nm 3f ). Their application in nonoptimized polymer solar cells (bulk heterojunction) led to power conversion efficiencies of around 1–1.8% after illumination with 100 mW/cm² of AM1.5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Coating of polyelectrolyte multilayer thin films on nanofibrous scaffolds to improve cell adhesion

The adhesion of L929 cells to poly(?‐caprolactone) (PCL) nanofibers was successfully improved via coating with polyelectrolyte multilayer thin films (PEMs), which enhanced the potential of this material as a scaffold in tissue engineering applications. With the electrostatic self‐assembly technique, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4‐styrene sulfonate) (PSS) were formed as four‐bilayer PEMs on electrospun PCL nanofiber mats. Because PDADMAC and PSS are strong polyelectrolytes, they provided stable films with good adhesion on the fibers within a wide pH range suitable for the subsequent processes and conditions. PDADMAC and gelatin were also constructed as four‐bilayer PEMs on top of the PDADMAC‐ and PSS‐coated nanofibers with the expectation that the gelatin would improve the cell adhesion. L929 cells from mouse fibroblasts were then seeded on both uncoated and coated scaffolds to study the cytocompatibility and in vitro cell behavior. It was revealed by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay that both the uncoated and coated nanofiber mats were nontoxic as the cell viability was comparable to that of those cultured in the serum‐free medium that was used as a control. The MTT assay also demonstrated that cells proliferated more efficiently on the coated nanofibers than those on the uncoated ones during the 48‐h culture period. As observed by scanning electron microscopy, the cells spread well on the coated nanofibers, especially when gelatin was incorporated. The surface modification of PCL nanofiber mats described in this research is therefore an effective technique for improving cell adhesion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Unraveling the Secrets of Protein–Metabolite Interactions

Saghatelian and colleagues recently introduced a global metabolite‐profiling approach that allows protein–metabolite interactions (PMI) to be identified. This approach represents an excellent strategy and valuable tool for unraveling the many secrets of the metabolome. The key features of the methodology will be summarized here.

     

DiPAMP’s Big Brother “i‐Pr‐SMS‐Phos” Exhibits Exceptional Features Enhancing Rhodium(I)‐Catalyzed Hydrogenation of Olefins

Switching Knowles DiPAMP’s {DiPAMP=1,2‐bis[(o‐anisyl)(phenyl)phosphino]‐ ethane} MeO groups with i‐PrO ones led to the i‐Pr‐SMS‐Phos {i‐Pr‐SMS‐Phos=1,2‐bis[(o‐isoprop‐ oxyphenyl)(phenyl)phosphino]ethane} ligand which displayed a boosted catalyst activity coupled with an enhanced enantioselectivity in the rhodium(I)‐catalyzed hydrogenation of a wide‐range of representative olefinic substrates (dehydro‐α‐amido acids, itaconates, acrylates, enamides, enol acetates, α,α‐diarylethylenes, etc). The rhodium(I)‐(i‐Pr‐SMS‐Phos) catalytic profile was investigated revealing its structural attributes and robustness, and in contrast to the usual trend, ³¹P NMR analysis revealed that its methyl (Z)‐α‐acetamidocinnamate (MAC) adduct consisted of a reversed diastereomeric ratio of 1.4:1 in favour of the most reactive diastereomer.     

Inhibitors of inducible NO synthase expression: total synthesis of (S)-curvularin and its ring homologues

(S)-Curvularin and its 13-, 14-, and 16-membered lactone homologues were synthesized through a uniform strategy in which a Kochi oxidative decarboxylation and ring-closing metathesis reactions constitute the key processes. In the evaluation of the anti-inflammatory effects of the synthesized compounds in assays using cells stably transfected with a human iNOS promoter-luciferase reporter gene construct, the 14- and 16-membered homologues showed a slightly higher inhibitory effect towards iNOS promoter activity than curvularin itself. However, the larger ring homologues also exhibited higher cytotoxicity, manifest in downregulated eNOS promoter activity. In contrast, the di-O-acetyl and 4-chloro derivatives of (S)-curvularin showed higher inhibitory efficiency towards induction of the iNOS promoter and less negative effect on eNOS promoter activity than curvularin.     

Bootstrap Unit‐Root Tests: Comparison and Extensions

Abstract. In this article, we study and compare the properties of several bootstrap unit‐root tests recently proposed in the literature. The tests are Dickey–Fuller (DF) or Augmented DF, based either on residuals from an autoregression and the use of the block bootstrap or on first‐differenced data and the use of the stationary bootstrap or sieve bootstrap. We extend the analysis by interchanging the data transformations (differences vs. residuals), the types of bootstrap and the presence or absence of a correction for autocorrelation in the tests. We show that two sieve bootstrap tests based on residuals remain asymptotically valid. In contrast to the literature which focuses on a comparison of the bootstrap tests with an asymptotic test, we compare the bootstrap tests among themselves using response surfaces for their size and power in a simulation study. This study leads to the following conclusions: (i) augmented DF tests are always preferred to standard DF tests; (ii) the sieve bootstrap performs better than the block bootstrap; (iii) difference‐based tests appear to have slightly better size properties, but residual‐based tests appear more powerful.     

Synthesis,Characterization and Application of New Rhodium Complexes for Indirect Electrochemical Cofactor Regeneration

Electroenzymatic synthesis often suffers from electrochemical reaction steps which proceed slower than the coupled enzyme reaction. For indirect electrochemical cofactor regeneration, we here report two new mediators with superior properties compared to the established rhodium complex (2,2′‐bipyridyl)(pentamethylcyclopentadienyl)rhodium [Cp*Rh(2,2′‐bipyridine)]. After constructing a robotic system for fast and reliable cyclic voltammetry measurements, we screened twelve rhodium complexes with substituted 2,2′‐bipyridine ligands for their reduction potentials and catalytic activity towards the reduction of NADP. Promising complexes were investigated in more detail by cyclic voltammetry and under batch electrolysis conditions. The new complexes Cp*Rh(5,5′‐methyl‐2,2′‐bipyridine) and Cp*Rh(4,4′‐methoxy‐2,2′‐bipyridine) reduced NADP to NADPH three times faster than the established mediator, resulting in volumetric productivities of up to 136 mmol L⁻¹ d⁻¹ and turnover frequencies of up to 113 h⁻¹. This increased reaction rate of these new mediators makes indirect electrochemical approach significantly more competitive to other methods of cofactor regeneration. Abbreviations: ADH=alcohol dehydrogenase; Ag|AgCl=silver|silver chloride reference electrode; bpy=2,2′‐bipyridine; ci=current increase; Cp*=pentamethylcyclopentadienyl; CV=cyclic voltammetry; Ep=peak potential; equiv=equivalent; NADP/NADPH=nicotinamide adenine dinucleotide phosphate oxidised/reduced form.     

An easy entry to novel early–late oligonuclear transition metal complexes containing π-conjugated systems

Heterotrinuclear Ti–Cu–Ru (5) and heterotetranuclear Ti–Cu–Pt–Fe (7) containing complexes are accessible by using {[Ti](CC^tBu)₂}CuMe (1) ([Ti]=(η⁵-C₅H₄SiMe₃)₂Ti) as key molecule; in 5 and 7, the corresponding early and late transition metal atoms are linked by π-conjugated organic moieties.     

Droplet Entrainment Analysis in a Flash Evaporator with an Image-Based Measurement Technique

Local droplet sizes and volumes of entrained liquid are captured with an image-based measurement technique for comparison with a conventional, integral method for entrainment analysis. Experiments in a forced circulation flash evaporation were performed for different operating conditions and with two different chemical systems. Droplet size and frequency rise with an increase in thermal energy input. The local readings confirm the trends found by the integral measurement method. The modification of the image-based probe enables the detection of small (≈ 10 µm) and at the same time fast droplets under challenging operating conditions, such as vacuum and superheated feed similar to industrial process conditions.