Optoelectronic Key Elements for Polymeric Fiber Transmission Systems

In short-range communication 1 mm PMMA SI-POF established itself as a reasonable alternative to the traditional data communication media such as glass fibers, copper cables, and wireless systems. Due to multiple advantages such as a large core diameter, tolerance to fiber facet damages, and low installation costs, the SI-POF is already applied in industrial automation, automotive industry, and in-house/office networks. To experimentally demonstrate the feasibility and potential of a high-speed POF WDM concept, a four-channel data transmission setup was realized. A four-legged multiplexing POF bundle was developed to combine the signals from four visible laser diodes onto SI-POF link. For the separation of wavelength channels, the interference filter-based demultiplexer with two-stage configuration was used. It was shown that POF WDM with lower channel rates and simple transmission technique (NRZ + FFE) could provide aggregate bit rates comparable to those achieved with the single-wavelength systems that used advanced modulation formats (DMT or PAM + DFE) and required significant signal processing. In addition, the 50 m SI-POF link at an aggregate bit rate of 7.8 Gb/s was demonstrated over 50 m SI-POF, respectively, at the BER = 10–3

Selective laser sintering of amorphous metal powder

For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powde

Monte Carlo simulation of subsurface ordering kinetics in an fcc-alloy model

Within the atom-vacancy exchange mechanism in a nearest-neighbor interaction model we investigate the kinetics of surface-induced ordering processes close to the (001) surface of an fcc A_3B-alloy. After a sudden quench into the ordered phase with a final temperature above the ordering spinodal, T_f > T_sp, the early time kinetics is dominated by a segregation front which propagates into the bulk with nearly constant velocity. Below the spinodal, T_f < T_sp, motion of the segregation wave reflects a coarsening process which appears to be slower than predicted by the Lifschitz-Allen-Cahn law. In addition, in the front-penetrated region lateral growth differs distinctly from perpendicular growth, as a result of the special structure of antiphase boundaries near the surface. Our results are compared with recent experiments on the subsurface ordering kinetics at Cu_3Au (001).Comment: 10 pages, 9 figures, submitted to Phys. Rev. B, in prin

High-Speed Optical In-House Networks Using Polymeric Fibers

Data communication over polymer optical fibers (POF) is a good alternative method for local area networks to use an optical medium to transmit data in short-range environments like cars or copper in-house networks on the basis of IEEE 802.3. Many companies offer transceivers for the area of Ethernet networks in the visible wavelength range. In the first part of the chapter, a system comparison of manufacturers with interoperability check is presented. Here, the real transfer rates within a manufacturer and between all manufacturers are measured as a cross-check. In the second part of the chapter, the limitation of bandwidth due to the use of only one wavelength channel is discussed. Wavelength Division Multiplexing (WDM) is a promising candidate to significantly increase bandwidth in POF to more than 40 Gbit/s. Here, the problems in the development and manufacture of a demultiplexer (DEMUX) for WDM over POF as well as the results of the optical separation of four wavelength channels are described. At least, the possible extension of a WDM grid of ITU G.694.2 is discussed, which seems to be a hopeful candidate to introduce a standardized WDM grid for POF in the visible range to reach data rates of 40 Gbit/s up to 50 m POF

Reasons to withhold intra-arterial thrombolysis in clinical practice

Background: In selected stroke centers intra-arterial thrombolysis (IAT) is used for the treatment of acute stroke patients presenting within 6hours of symptom onset. However, data about eligibility of acute stroke patients for IAT in clinical practice are very scarce. Methods: We collected prospectively data on indications advising for or against IAT of 230 consecutive stroke patients in a tertiary stroke center. Results: 76 patients (33.0%) presented within 3hours, 69 (30%) between 3 and 6hours of symptom onset and 85 (37%) later than 6hours. Arteriography was performed in 71 patients (31%) and IAT in 46 (20%). In 11 patients no or only peripheral branch occlusions were seen on arteriography and therefore IAT was not performed. In 9 patients the ICA was occluded and barred IAT and in five anatomical or technical difficulties made IAT impossible. 72 patients presenting within 6hours did not undergo arteriography and thrombolysis, mostly because of mild (n=44) or rapidly improving neurological deficits (n=13). Other reasons to withhold IAT were CT and/or clinical findings suggesting lacunar stroke due to small vessel occlusion (n=7), limiting comorbidty (n=7) and baseline international normalized ratio>1.7 (n=1). Conclusions: A third of the patients underwent diagnostic arteriography and one fifth received IAT. The most important reasons to withhold thrombolysis were presentation beyond the 6hours time window and mild or rapidly improving symptom

Microstructure of near-infrared pulsed laser sintered titanium samples

The microstructure and material properties of near-infrared pulsed laser sintered titanium have been investigated. Several analyses of the selectively laser sintered titanium powder, using characterisation techniques such as compressive strength, microhardness, energy-dispersive X-ray microanalysis, X-ray diffractometry and scanning electron microscopy analysis, allowed the metallurgical description of the sintering process. Only partial melting in a narrow surface layer took place, whereas most of the material stayed clearly below the melting temperatur

The Protomedicato Tribunal and minorities in Castile at the end of the 17th century: the case of surgeon Roldán Solimán

[EN] This note aims to provide a small set of documents which report the vicissitudes of a North-African Muslim surgeon who tried to settle professionally during the late seventeenth century in the Kingdom of Castile. The four letters exchanged between the Royal Palace and the Castilian tribunal of the Protomedicato reveal that the Spanish king Charles II (1661-1700) resoluted supported the surgeon's aspirations, and the Protomedicato's concerted resistence to the royal will. These eloquent documents shed light on the history of the Castilian Protomedicato during the final years of the reign of the last Habsburg king in Spain by providing evidence about the role of this institution in the process of segregation/exclusion of ethnic minorities from the practice of health professions.[ES] El objeto de esta nota es presentar y editar una colección documental muy breve cuyo contenido nos informa sobre las vicisitudes de un cirujano musulmán norteafricano que a finales del siglo XVII busca su asentamiento profesional en la Corona de Castilla. Las cuatro cartas entre el Palacio Real y el Tribunal del Protomedicato, que se conservan en relación a este asunto, revelan tanto el decidido apoyo del Rey Carlos 11 (1665-1700) a las pretensiones del cirujano, como la fuerte resistencia ofrecida por el Protomedicato a la voluntad real. Esta expresiva documentación arroja luz en torno a la historia del Protomedicato en la Corona de Castilla durante los años finales del reinado del último Habsburgo en España, ilustrándonos sobre el papel entonces jugado por esta institución en el proceso de segregación/exclusión de las minorías étnicas, de la práctica de las ocupaciones sanitarias.Peer reviewe

Optical Inhouse Networks

Optical fiber networks are currently the standard for delivering high bandwidth to customers. Various access technologies to business networks with a very high bandwidth up to access networks for buildings and individual consumers have emerged. In the area of business networks, bandwidths of 10 Gb/s have become established, while in the area of customer bandwidths of 100 Mb/s to 1 Gb/s are used. This chapter will focus on the optical network connections inside buildings. The use of optical glass fibers or/and polymeric optical fibers in different network topologies in connection to high-speed actual WIFI- technologies will be discussed

Real-Time Capable Sensor Data Analysis-Framework for Intelligent Assistance Systems

In the industrialized countries, the very old part of the population has been growing rapidly for many years. In the next few years in particular, the age cohort over 65 will increase significantly. This goes hand in hand with illnesses and other physical and cognitive limitations. In order to enable these people to remain in their own homes for as long as possible despite physical and cognitive restrictions, technologies are being used to create ambient assisted living applications. However, most of these systems are neither medically verified nor are latencies short enough, for example, to avoid falls. In order to overcome these problems, a promising approach is to use the new 5G network technology. Combined with a suitable sensor data analysis frame work, the fast care project showed that a real-time situation picture of the patient in the form of an Avatar could be generated. The sensor structure records the heart rate, the breathing rate, analyzes the gait and measures the temperature, the VOC content of the room air, and its humidity. An emergency button has also been integrated. In a laboratory demonstrator, it was shown that the infrastructure realizes a real-time visualization of the sensor data over a heterogeneous network

Kinetics in one-dimensional lattice gas and Ising models from time-dependent density functional theory

Time-dependent density functional theory, proposed recently in the context of atomic diffusion and non-equilibrium processes in solids, is tested against Monte Carlo simulation. In order to assess the basic approximation of that theory, the representation of non-equilibrium states by a local equilibrium distribution function, we focus on one-dimensional lattice models, where all equilibrium properties can be worked exactly from the known free energy as a functional of the density. This functional determines the thermodynamic driving forces away from equilibrium. In our studies of the interfacial kinetics of atomic hopping and spin relaxation, we find excellent agreement with simulations, suggesting that the method is useful also for treating more complex problems.Comment: 8 pages, 5 figures, submitted to Phys. Rev.