Diffraction-optimized aperiodic surface structures for enhanced current density in organic solar cells.

Novel diffractive surface structures are designed, evaluated, and optimized to achieve a significant increase in current density in organic solar cells. The surface relief phase gratings are patterned based on concentric rings, a Fermat's spiral, and an Archimedean spiral, respectively, and thus diffract incident light independent of its azimuthal angle, as they all exhibit circularly symmetric diffraction patterns. The grating pillars are arranged on the rings or spirals according to periodic or deterministic aperiodic Thue-Morse and Rudin-Shapiro sequences, tailoring the desired diffraction patterns. After evaluating the surface patterns against each other and further parameter optimization, a final current density enhancement of 5 % is achieved for one of the most promising patterns, the Thue-Morse sequence on an Archimedean spiral.

Dynamic modulation of Poincaré beams.

Generation of complex Poincaré beams is enabled by amplitude and phase modulation accompanied by simultaneous spatially polarization structuring. A holographic system to tailor complex light fields and optical angular momentum structures forecasts promising applications in quantum communication and optical trapping. Experimental results are presented together with simulations of complex Poincaré beams embedding different types of polarization singularities. Additionally, parameters of the dynamic polarization modulation system are discussed and analyzed to demonstrate the enormous capability of the method.

Electro-optical tunable waveguide Bragg gratings in lithium niobate induced by femtosecond laser writing.

We report the fabrication of femtosecond laser-induced, first-order waveguide Bragg gratings in lithium niobate in the low repetition rate regime. Type-II waveguides are written into an x-cut lithium niobate wafer and structured periodically to achieve narrowband reflections at wavelengths around 1550 nm. Additionally, electrodes are employed to allow for electro-optic tuning of the spectral response. We demonstrate wavelength control of the central reflection peak by applying a static external electric field. A maximum shift of the reflection peak of Δλ = 625 pm is observed.

Enhanced Cerenkov second-harmonic emission in nonlinear photonic structures.

We study experimentally and theoretically the Cerenkov-type second-harmonic generation in a one-dimensional nonlinear photonic crystal. We demonstrate that the power of emitted second-harmonic can be enhanced 270 times by varying the angle of incidence of the fundamental beam such that the reciprocal lattice vector of the crystal can be used to compensate for the phase mismatch in the transverse direction enabling interaction in the nonlinear Bragg diffraction regime.

Mathieu beams as versatile light moulds for 3D micro particle assemblies.

We present tailoring of three dimensional light fields which act as light moulds for elaborate particle micro structures of variable shapes. Stereo microscopy is used for visualization of the 3D particle assemblies. The powerful method is demonstrated for the class of propagation invariant beams, where we introduce the use of Mathieu beams as light moulds with non-rotationally-symmetric structure. They offer multifarious field distributions and facilitate the creation of versatile particle structures. This general technique may find its application in micro fluidics, chemistry, biology, and medicine, to create highly efficient mixing tools, for hierarchical supramolecular organization or in 3D tissue engineering.

[Economic benefits of overlapping induction: investigation using a computer simulation model]. / Okonomischer Nutzen der überlappenden Einleitung: Untersuchung mithilfe eines Computersimulationsmodells.

The aim of this study was to investigate the potential economic benefit of overlapping anaesthesia induction given that all patient diagnosis-related groups (AP DRG) are used as the model for hospital reimbursement. A computer simulation model was used for this purpose. Due to the resource-intensive production process, the operating room (OR) environment is the most expensive part of the supply chain for surgical disciplines. The economical benefit of a parallel production process (additional personnel, adaptation of the process) as compared to a conventional serial layout was assessed. A computer-based simulation method was used with commercially available simulation software. Assumptions for revenues were made by reimbursement based on AP DRG. Based on a system analysis a model for the computer simulation was designed on a step-by-step abstraction process. In the model two operating rooms were used for parallel processing and two operating rooms for a serial production process. Six different types of surgical procedures based on historical case durations were investigated. The contribution margin was calculated based on the increased revenues minus the cost for the additional anaesthesia personnel. Over a period of 5 weeks 41 additional surgical cases were operated under the assumption of duration of surgery of 89+/-4 min (mean+/-SD). The additional contribution margin was CHF 104,588. In the case of longer surgical procedures with 103+/-25 min duration (mean+/-SD), an increase of 36 cases was possible in the same time period and the contribution margin was increased by CHF 384,836. When surgical cases with a mean procedural time of 243+/-55 min were simulated, 15 additional cases were possible. Therefore, the additional contribution margin was CHF 321,278. Although costs increased in this simulation when a serial production process was changed to a parallel system layout due to more personnel, an increase of the contribution margin was possible, especially with procedures of shorter duration (<120 min). For longer surgical times, the additional costs for the workforce result in a reduced contribution margin depending on the models chosen to handle overtime of the technical OR personnel. Important advantages of this approach for simulation are the use of the historical production data and the reflection of the specificities of the local situation. Computer simulation is an ideal tool to support operation room management, particularly regarding the planning of resource allocation and the coordination of workflow.

[Simulation-based analysis of novel therapy principles. Effects on the efficiency of operating room processes]. / Simulationsbasierte Analyse neuer Therapieprinzipien. Auswirkungen auf die Leistungsfähigkeit der OP-Prozesse.

BACKGROUND: The introduction of innovative drugs in anesthesiological treatment has the potential to improve perioperative efficiency. This article examines the impact of the new muscle relaxant encapsulator Bridion on emergence from anesthesia and on the efficiency of the perioperative organization. METHODS: To analyze the effects of medical innovations, computer simulation was used as an experimental frame. The simulation was based on a realistic model of an operating room setting and used historical data to study the effect of innovation on the operational performance and the economic outcomes. RESULTS: The use of medical innovations in anesthesiological emergence yields new potentials for a hospital under certain conditions. Due to shorter block times and anesthesia-controlled times, additional benefits for the operating room could be realized. This results in an increase of up to 2.4% additional cases during similar working hours and planning periods. CONCLUSION: The introduction of innovative medicines may reveal more efficient and economical conditions in operating rooms. The overall result depends, for example, on the rate of application of the patient's portfolio or the organization and access rules of the surgical suite. Based on the anesthesia-controlled time no general a priori statement about the economic potentials can be confirmed. Future empirical studies should investigate the impact on quality and economic benefits for the entire patient pathway.

[Controlling and reporting in operating room management: analysis of the state of development]. / Controlling und Berichtswesen im OP-Management: Analyse des Entwicklungsstands.

The operating room (OR) is one of the most expensive facilities in most hospitals. The demands on a professional and process-oriented controlling and reporting in the OR are increased due to the increasingly more limited financial margins at the end of the diagnosis related groups (DRG) convergence phase. This study gives an overview of the current situation for cost calculation, controlling and reporting in OR management in German hospitals in 2007. The data from 69 hospitals were evaluated and this represents the largest currently available data pool on this topic.

[The optimization of a medicinal process and the organization of work in an operating-room].

In most hospitals, the operating-room is a most expensive therapeutic subdivision. A clear and understandable concept of organization of the management of a medical process in an operating room should be introduced into all clinics in order to satisfy increasing needs for professional and technological management. Within the framework of a promising management program to optimize a medical process and to organize work in the operating-room, the surgeons are provided with surgical equipment intended for an operating-room in accordance with their assessed needs and with their participation in budgeting, which made it possible to evaluate the efficiency of a medical process and the work of each user of an operating-room.

Two dimensional counterpropagating spatial solitons in photorefractive crystals.

We demonstrate experimentally the existence of two transverse-dimensional counterpropagating (CP) incoherent spatial solitons in a 5 x 5 x 23 mm SBN:60Ce photorefractive crystal and investigate their dynamical behavior. We carry out numerical simulations that confirm our experimental findings. Substantially different behavior from the copropagating incoherent solitons is found. A symmetry breaking transition from stable overlapping CP solitons to unstable transversely displaced CP solitons is observed. We perform linear stability analysis that predicts the threshold for the split-up transition, in qualitative agreement with numerical simulations and experimental results.

Two-dimensional solitons with hidden and explicit vorticity in bimodal cubic-quintic media.

We demonstrate that two-dimensional two-component bright solitons of an annular shape, carrying vorticities (m,+/-m) in the components, may be stable in media with the cubic-quintic nonlinearity, including the hidden-vorticity (HV) solitons of the type (m,-m) , whose net vorticity is zero. Stability regions for the vortices of both (m,+/-m) types are identified for m=1 , 2, and 3, by dint of the calculation of stability eigenvalues, and in direct simulations. In addition to the well-known symmetry-breaking (external) instability, which splits the ring soliton into a set of fragments flying away in tangential directions, we report two new scenarios of the development of weak instabilities specific to the HV solitons. One features charge flipping, with the two components exchanging angular momentum and periodically reversing the sign of their spins. The composite soliton does not directly split in this case; therefore, we identify such instability as an intrinsic one. Eventually, the soliton splits, as weak radiation loss drives it across the border of the ordinary strong (external) instability. Another scenario proceeds through separation of the vortex cores in the two components, each individual core moving toward the outer edge of the annular soliton. After expulsion of the cores, there remains a zero-vorticity breather with persistent internal vibrations.

Counterpropagating beams in biased photorefractive crystals: anisotropic theory.

We formulate an anisotropic nonlocal theory of the space charge field induced by the coherent counterpropagating beams in biased photorefractive crystals. We establish that the competition between the drift and diffusion terms has to be taken into account when the crystal c axis is tilted with respect to the propagation direction of the beams. We demonstrate that this configuration combines the features of both spatial soliton formation without energy exchange and two-wave mixing with energy exchange leading to pattern formation.

Dynamics of counterpropagating multipole vector solitons.

Dynamical behavior of counterpropagating (CP) mutually incoherent vector solitons in a 5 x 5 x 23 mm SBN:60Ce photorefractive crystal is investigated. Experimental study is carried out, displaying rich dynamics of three-dimensional CP solitons and higher-order multipole structures, and a theory formulated that is capable of capturing such dynamics. We find that our numerical simulations agree well with the experimental findings for various CP beam structures. Linear stability analysis is also performed, predicting a threshold for the modulational instability of CP beams, and an appropriate control parameter is identified. We attempt at utilizing these results to CP solitons, but find only qualitative agreement with the numerical simulations and experimental findings. However, when broader hyper-Gaussian CP beams are used in simulations, an improved agreement with the theory is obtained.

Transverse modulational instabilities of counterpropagating solitons in photorefractive crystals.

We study numerically the counterpropagating vector solitons in SBN:60 photorefractive crystals. A simple theory is provided for explaining the symmetry-breaking transverse instability of these solitons. Phase diagram is produced that depicts the transition from stable counterpropagating solitons to bidirectional waveguides to unstable optical structures. Numerical simulations are performed that predict novel dynamical beam structures, such as the standing-wave and rotating multipole vector solitonic clusters. For larger coupling strengths and/or thicker crystals the beams form unstable self-trapped optical structures that have no counterparts in the copropagating geometry.

Solitonic lattices in photorefractive crystals.

Two-dimensional spatial solitonic lattices are generated and investigated experimentally and numerically in a Sr(x)Ba(1-x)Nb(2)O(6):Ce crystal. An enhanced stability of these lattices is achieved by exploiting the anisotropy of coherent soliton interaction, in particular the relative phase between soliton rows. The manipulation of individual soliton channels is achieved by the use of supplementary control beams.

Self-trapped bidirectional waveguides in a saturable photorefractive medium.

A time-dependent model for the generation of joint waveguides by counterpropagating light beams in photorefractive crystals is introduced. Depending on initial conditions and parameter values, the beams form stable structures or display periodic and irregular dynamics. Steady-state solutions nonuniform in the direction of propagation are found, representing a general class of self-trapped waveguides that include counterpropagating spatial vector solitons as a particular case.

Dynamic counterpropagating vector solitons in saturable self-focusing media.

We display rich spatial and temporal dynamics of light fields counterpropagating in a saturable self-focusing medium numerically, and analyze instabilities that counterpropagating solitons experience. An expression for the maximum length that the medium must not exceed for the solitons to be stable is derived and connected to the coupling strength of beam interaction. The instability can lead to periodic or irregular temporal dynamics of the light beams. By considering mutually incoherent counterpropagating beams, we show that differences to the copropagating case are due to the different boundary conditions.

[Equipment of physician-staffed ambulance systems in the state of Baden-Wuerttemberg]. / Ausstattung von Notarztbesetzten Rettungsmitteln in Baden-Württemberg.

BACKGROUND: Laws regulating emergency medical systems in the federal state of Baden-Wuerttemberg call for equipment of physician-staffed ambulances that is based on current knowledge in emergency medicine. The grade of implementation is determined using single issue complexes. METHODS: A total of 127 emergency physician bases were located and each received a questionnaire regarding the equipment of the physician-staffed ambulances and helicopters and planned supplementation of the equipment, deadline was 30 June 2001. RESULTS: Of the 127 stations 116 (91.3%) participated. A 12-lead ECG is available in 52.6%, out-of-hospital fibrinolysis is possible in 15 bases (12.9%). Alternatives to endotracheal intubation are carried in 53.3% (cricothyroidotomy: 83.3%) and 31 bases provide capnometry or other devices for verifying correct tube placement. A mobile phone is available in 88 bases (75.9%). CONCLUSIONS: When comparing equipment of physician-staffed ambulances statewide, striking differences can be found.

Generation of higher-order optical (2+1)-dimensional spatial vector solitons in a nonlinear anisotropic medium.

We investigate the generation of higher-order optical vector solitons in two transverse dimensions in anisotropic nonlinear media consisting of an incoherent superposition of a Gaussian beam and a higher-order laser mode with a complex internal modal structure. We demonstrate both numerically and experimentally various examples of these stable self-trapped light structures and show that vortex modes carrying topological charge always decay into multiple-humped structures that remain self trapped during propagation. Furthermore, we demonstrate the mutual stabilization of a triple- and a double-humped transverse light structure leading to the formation of a two-dimensional vector soliton without a stabilizing fundamental Gaussian mode.