Influence of the steel plate on the friction behavior of automotive wet disk clutches

Friction behavior is the key parameter for the design of automotive wet disk clutches. On the one hand, the Coefficient of Friction (CoF) level should be high to transmit torque efficiently. On the other hand, the clutch requires a positive slope of the CoF over sliding speed for good controllability, high comfort, and a low tendency to shudder. Clutches used in automatic or dual-clutch transmissions mostly use organic friction lining. These friction systems tend to have low CoF at low sliding speeds due to their high requirements regarding shifting comfort. Nevertheless, they show high values of CoF at high sliding speeds.

This study investigates the influence of different steel plate finishes on friction behavior in different application-relevant operation modes such as brake shift, unsteady slip, and micro slip. Each of these operation modes requires an accurate CoF measurement at different sliding speed ranges. Therefore, we use different test rig setups. We characterize the steel plates by their areal surface topography measured with an optical system using focus variation. We discuss differences in the friction behavior of the corresponding tribological systems at different operating conditions.

Results show an influence of the steel plate surface finish on the CoF level. Therefore, the surface finish of the steel plate influences the functional behavior of wet disk clutches and engineers should consider the surface finish in the early design phase. We discuss the correlation between commonly used surface parameters and friction parameters.

     

Human iPSC-Derived Proinflammatory Macrophages cause Insulin Resistance in an Isogenic White Adipose Tissue Microphysiological System

Chronic white adipose tissue (WAT) inflammation has been recognized as a critical early event in the pathogenesis of obesity-related disorders. This process is characterized by the increased residency of proinflammatory M1 macrophages in WAT. However, the lack of an isogenic human macrophage-adipocyte model has limited biological studies and drug discovery efforts, highlighting the need for human stem cell-based approaches. Here, human induced pluripotent stem cell (iPSC) derived macrophages (iMACs) and adipocytes (iADIPOs) are cocultured in a microphysiological system (MPS). iMACs migrate toward and infiltrate into the 3D iADIPOs cluster to form crown-like structures (CLSs)-like morphology around damaged iADIPOs, recreating classic histological features of WAT inflammation seen in obesity. Significantly more CLS-like morphologies formed in aged and palmitic acid-treated iMAC-iADIPO-MPS, showing the ability to mimic inflammatory severity. Importantly, M1 (proinflammatory) but not M2 (tissue repair) iMACs induced insulin resistance and dysregulated lipolysis in iADIPOs. Both RNAseq and cytokines analyses revealed a reciprocal proinflammatory loop in the interactions of M1 iMACs and iADIPOs. This iMAC-iADIPO-MPS thus successfully recreates pathological conditions of chronically inflamed human WAT, opening a door to study the dynamic inflammatory progression and identify clinically relevant therapies.     

Tuning Nanobodies’ Bioactivity: Coupling to Ultrasmall Gold Nanoparticles Allows the Intracellular Interference with Survivin

Nanobodies are highly affine binders, often used to track disease-relevant proteins inside cells. However, they often fail to interfere with pathobiological functions, required for their clinical exploitation. Here, a nanobody targeting the disease-relevant apoptosis inhibitor and mitosis regulator Survivin (SuN) is utilized. Survivin's multifaceted functions are regulated by an interplay of dynamic cellular localization, dimerization, and protein–protein interactions. However, as Survivin harbors no classical “druggable” binding pocket, one must aim at blocking extended protein surface areas. Comprehensive experimental evidence demonstrates that intracellular expression of SuN allows to track Survivin at low nanomolar concentrations but failed to inhibit its biological functions. Small angle X-ray scattering of the Survivin-SuN complex locates the proposed interaction interface between the C-terminus and the globular domain, as such not blocking any pivotal interaction. By clicking multiple SuN to ultrasmall (2 nm) gold nanoparticles (SuN-N), not only intracellular uptake is enabled, but additionally, Survivin crosslinking and interference with mitotic progression in living cells are also enabled. In sum, it is demonstrated that coupling of nanobodies to nanosized scaffolds can be universally applicable to improve their function and therapeutic applicability.     

Characteristic Properties of an End Burning Grain with Smoke Reduced Ferrocene Containing Composite Propellant

Design, formulation and properties of an end burning grain are described which works for underwater propulsion operating at the level of 1200 N thrust for 20 s burning time. To avoid cavitational noise the formation of hot particles must be prevented. For this reason a smoke reduced composite propellant based on AP/HTPB with 86% energetic solids including 14% HMX and with 1% ferrocene derivative was adapted to grain size and motor configuration. For inhibition a pyrolytically stabilized polyurethane insulation was applied. The thermal insulation was made from a stiff high temperature resistant phenolic resin. The propellant exhibited a smooth burning behaviour with good processibility and mechanical properties. The desired performance was delivered at 120 bar operating pressure connected to 165 mm grain diameter and 93% thrust efficiency. Looking closer to the system it was found that part of the ferrocene derivative and plasticizer migrated from the propellant block to the inhibition layer. In the course of migration a small change of burning but a larger change of mechanical properties occurred in the boundary of the propellant. Despite these disadvantages burning times of 5 s and 10 s had been successfully realized with a case bonded configuration. For larger grain sizes, however, cracks occurred around the surface of the cylindrical propellant block. Calculation of the mechanical stresses which built up upon thermal shrinkage after curing and cooling showed values higher than the mechanical strength of the propellant could fit. These problems finally were overcome by a free standing grain. It led to a successful function of the motor for burning times of 20 s and more.     

Einfache Darstellung von 4-Oxo-tetrahydropyrimidinen

Convenient Synthesis of 4-Oxo-tetrahydropyrimidines Enamino-nitriles as 6 or 11 yield 4-oxo-pyrimidines ( 2 ; 2a ; 10 ; 12a – c ) on treatment with cyclohexanone in basic media. Analogous compounds are obtained using acetone, butyraldehyde, benzaldehyde or substituted benzaldehydes.     

Die Reaktion von E-ß-Nitro-styrolen mit Pyrazolidon-(3)-azomethiniminen – eine nicht-cisoide 1,3-dipolare Cycloaddition

The Reaction of E-ß-Nitro-styrenes with 3-Pyrazolidone-azomethinimines – a Non-cisoid 1,3-Dipolar Cycloaddition Normal flipping at both ring-N-atoms postulated, the thermal addition of E-β-nitro- 5a or E-(4-chloro-β-nitro)-styrene 5b to 3-pyrazolidone-azomethinimine-1,3-dipoles 4a or 4b formally can yield 8 isomeric pairs of enantiomers, 4 of which are “permitted”(cisoid) and 4 of which are “forbidden” according to the concerted [_π4_s + _π2_s]-mechanism. If the addition of 5 to 4 is regiospecific, 2 “permitted”(cisoid) ( 1 and 6 ) and 2 “forbidden”( 3 and 10 ) isomers are conceivable. From pure 5a and 4a we regiospecifically got 1ref,3trans-diphenyl-2cis-nitro- 6a (75%) and 1ref,3trans-diphenyl-2trans-nitro-5-oxo-perhydropyrazolo[1,2-a]pyrazol 10a (25%), from 5b and 4b the corresponding bis(4-chloro-phenyl)-isomers 6b and 10b . The sodium salts 8a, b , gained from 6a, b and 10a, b , are identical. With H⊕ (D⊕) in water (D₂O) 8a, b give 6a, b (2-deutero- 6a, b = 7 a, b ). The ¹H-n.m.r. spectra of 6a, b, 7a, b, 8a, b, 10a, b , and of the 2-amino-isomers 11a/12a , corresponding to 6a/10a , are discussed. For the first time products of a non-cisoid 1,3-dipolar cycloaddition ( 10a, b ) were isolated. In the discussion (E ⇌ Z)-isomerization of 5a , and conceivable mechanisms of isomerizations 6a → 10a are excluded. Theoretical consequences are suggested.     

Characterization of the Structure in Highly Filled Composite Materials by Means of MRI

Modern solid propellants are highly filled composite materials. The essential ingredients of a composite propellant are a crosslinked binder, a polymer like polyurethane and an oxidizer. Furthermore, most propellant formulations contain a stabilizer, ballistic modifiers, high energy fuel additives, a wetting agent, plasticizers and other additives to adjust physical properties. The aging behavior of composite propellants is correlated with a change in mechanical properties. Background of the aging behavior of a composite propellant are micromechanical phenomena. Therefore, the understanding of micromechanical phenomena like matrix filler detachment, crosslinking and chain cleavage is the key to the understanding of aging behavior of composite propellants. In this paper it is shown how micromechanical phenomena can be observed by MRI (Magnetic Resonance Imaging).     

Synthesis of Sulfated Lex-Trisaccharides

The regioselective sulfation of a Le^x-trisaccharide having free hydroxyl groups in 2-, 3- and 4- position of the galactose elucidated their different reactivities and gave mono- and disulfated Le^x derivatives.