Process stabilization with an adaptronic spindle system

For economical reasons it is necessary to reduce the machining time and to increase the process automation. This leads to the need for fast machine tools with high process stability in order to enhance the material removal rate. However, the machine often does not limit the process stability but the tool because of its compliance. This paper presents a new possibility of expanding the stable process range of long and slender end mills with an adaptronic spindle system. The system is able to position the spindle dynamically in the range of microns with three piezo actuators. In order to disturb the regenerative effect, which leads to an instable process, the chip thickness is modulated by a dynamic spindle actuation. This is realized by a superposition of vibrations of the tool in feed direction. In milling tests the degree of stabilization is verified for different superpositions. Hence, the stable process range could be improved for spindle speeds up to 5,000?rpm.     

Development of an advanced micro-positioning system for increasing operation accuracy: consideration of high pressure sealing

This paper presents the development of a micro-positioning system for the increase of operation accuracy of machine tools. A highly dynamic piezo-actuated micropump coupled with a hydraulic cylinder transforms small strokes of the piezoelectric actuator into a continuous piston movement. Fast-switching active valves direct the volume flow. Crucial for the functionality of the pump module is the sealing function of the membrane to isolate the piezoelectric actuator unit against high pressure fluid. Therefore, the requirements for foil membrane selection are investigated by means of a developed test bench. It is demonstrated that a successful test of foil membrane materials provides a closer insight into the entire valve characteristics.     

Substrate oxidation at rest and during exercise: effects of menstrual cycle phase and diet composition

The estrogen hormones have been shown to be highly glycogenic as well as lipolytic in nature. It is unknown whether the metabolic actions of estrogens impact upon energy metabolism during exercise. The composition of prior diet, however, does affect exercise energy metabolism. This study examined the influence of menstrual cycle phase (mid-follicular [FP; low estrogen] vs. mid-luteal [LP; high estrogen]) and diet composition on the rate of substrate oxidation for carbohydrate (CHO) and lipid at rest and during various intensities of physical exercise. Nine subjects completed an experimental session under four different menstrual cycle-diet conditions: 1) FP following a 3-day high CHO diet [75% total caloric intake], 2) FP following a 3-day low CHO diet [35% total caloric intake], 3) LP following a 3-day high CHO diet, and 4) LP following a 3-day low CHO diet. In each of the experimental sessions substrate oxidation was determined at rest and during cycle ergometer exercise at intensities of 30, 50, and 70% VO2max, respectively. Statistically significant (p < 0.05) interaction effects on substrate oxidation due to the menstrual cycle phase and diet conditions were found at rest and during 30%-50% exercise. In general, CHO oxidation was lowest and lipid oxidation highest in the LP under a low CHO diet condition.     

Procoagulant Extracellular Vesicles Alter Trophoblast Differentiation in Mice by a Thrombo-Inflammatory Mechanism

Procoagulant extracellular vesicles (EV) and platelet activation have been associated with gestational vascular complications. EV-induced platelet-mediated placental inflammasome activation has been shown to cause preeclampsia-like symptoms in mice. However, the effect of EV-mediated placental thrombo-inflammation on trophoblast differentiation remains unknown. Here, we identify that the EV-induced thrombo-inflammatory pathway modulates trophoblast morphology and differentiation. EVs and platelets reduce syncytiotrophoblast differentiation while increasing giant trophoblast and spongiotrophoblast including the glycogen-rich cells. These effects are platelet-dependent and mediated by the NLRP3 inflammasome. In humans, inflammasome activation was negatively correlated with trophoblast differentiation marker GCM1 and positively correlated with blood pressure. These data identify a crucial role of EV-induced placental thrombo-inflammation on altering trophoblast differentiation and suggest platelet activation or inflammasome activation as a therapeutic target in order to achieve successful placentation.     

Interpretation and optimization of material flow via system behavior reconstruction

In this article, a method for a scalable autonomous data acquisition for an analysis and optimization of production systems based on interpretation of the material flow within small and medium-sized manufacturing enterprises is presented. The data is acquired locally and combined centrally to interpret the material flow as a basis for the optimization of the material flow as well as individual processes. When it is not completely observable for efficiency reasons or due to technical restrictions, one can also reconstruct relevant but unobservable system behavior based on system knowledge and actual measurements. A validation of the method is carried out in a company maintaining engines. The application of the model shows that with the presented method it is possible to reduce buffers in the production, optimize transportation routes and reduce waiting and therefore cycle times in job shop productions for an increasing productivity.     

Electrical spin injection from an n-type ferromagnetic semiconductor into a III-V device heterostructure

The use of carrier spin in semiconductors is a promising route towards new device functionality and performance. Ferromagnetic semiconductors (FMSs) are promising materials in this effort. An n-type FMS that can be epitaxially grown on a common device substrate is especially attractive. Here, we report electrical injection of spin-polarized electrons from an n-type FMS, CdCr(2)Se(4), into an AlGaAs/GaAs-based light-emitting diode structure. An analysis of the electroluminescence polarization based on quantum selection rules provides a direct measure of the sign and magnitude of the injected electron spin polarization. The sign reflects minority rather than majority spin injection, consistent with our density-functional-theory calculations of the CdCr(2)Se(4) conduction-band edge. This approach confirms the exchange-split band structure and spin-polarized carrier population of an FMS, and demonstrates a litmus test for these FMS hallmarks that discriminates against spurious contributions from magnetic precipitates.     

Graphene as a tunnel barrier: graphene-based magnetic tunnel junctions

Graphene has been widely studied for its high in-plane charge carrier mobility and long spin diffusion lengths. In contrast, the out-of-plane charge and spin transport behavior of this atomically thin material have not been well addressed. We show here that while graphene exhibits metallic conductivity in-plane, it serves effectively as an insulator for transport perpendicular to the plane. We report fabrication of tunnel junctions using single-layer graphene between two ferromagnetic metal layers in a fully scalable photolithographic process. The transport occurs by quantum tunneling perpendicular to the graphene plane and preserves a net spin polarization of the current from the contact so that the structures exhibit tunneling magnetoresistance to 425 K. These results demonstrate that graphene can function as an effective tunnel barrier for both charge and spin-based devices and enable realization of more complex graphene-based devices for highly functional nanoscale circuits, such as tunnel transistors, nonvolatile magnetic memory, and reprogrammable spin logic.