To investigate the outcome of intravitreal bevacizumab (IVB) compared with laser photocoagulation in type I retinopathy of prematurity (ROP).
Case records of 54 consecutive very low birth weight ...(VLBW) infants with type I ROP (posterior ROP, n=33; peripheral zone II, n=21) who were treated either with IVB (n=37) or laser photocoagulation (n=17) between 2011 and 2015 were retrospectively evaluated.
Patients with posterior ROP displayed significantly faster regression of active ROP within 12 days (range 9-15 days) if treated with IVB compared with laser photocoagulation, where active ROP regressed within 57 days (range 28-63 days) (p>0.001). No difference was observed in peripheral zone II.Five of seven patients (12%) who developed a recurrence in both eyes after IVB required additional laser photocoagulation within a mean of 12.7 weeks (11.3-15.6 weeks) after the previous treatment. After laser photocoagulation one patient with posterior ROP developed macular dragging and another patient developed a temporary exudative retinal detachment in both eyes. 12 months after treatment the spherical equivalent was not statistically significant different between IVB and laser photocoagulation in posterior ROP patients. However, IVB lead to a significant lower spherical equivalent in infants with posterior ROP (+0.37 dioptres, range -0.5 to +1.88 dioptres) compared with peripheral zone II (+3.0 dioptres range +2.0 to +4.0 dioptres, p<0.001).
IVB leads to faster regression of active ROP in infants with posterior ROP compared with laser photocoagulation. Spherical equivalent after 12 months was comparable in those treated with IVB and laser photocoagulation, but it was significantly lower in posterior ROP than in peripheral zone II.
Wireless power transmission systems can be optimized by matching the resonance frequency of a receiver. However, in certain applications, such as, e.g., a multireceiver system, it is desired to match ...the individual resonance frequencies of the receiver to a fixed (e.g., common) operation frequency. In this publication, a method is proposed to match the resonant frequency dynamically without changing the physical value of the components. Instead, it is changed "virtually" by a method, which is named "frozen resonance state" by the author. The basic idea is to maintain the state of a resonant circuit (to "freeze" the state) for a fraction of the resonant period, e.g., by freewheeling the current of the resonant inductor or maintaining the voltage of the resonant capacitor. This additional time extends virtually the resonant period leading to an effective lower resonant frequency. By adjusting the additional time, the effective resonant frequency can be matched to the operation frequency individually for each receiver. This publication explains the basic idea more in detail and gives an overview of the different possible circuit topologies. Furthermore, the method is applied to an exemplary receiver of a capacitive wireless power transmission system, where measurements are presented.
The integration of passive components into the printed circuit board (PCB) as embedded passives integrated circuits (emPIC) results in a higher power density of power converters. To achieve a highly ...automated, low cost, integral manufacturing, the devices are constructed layer wise. Materials and processes necessary for the manufacturing of such circuits are described in this publication. Especially for magnetic components like inductors and transformers the design of such thin components is challenge. Because of the high aspect ratio, traditionally used models lead to a high calculation effort or use nonappropriate approximations. This contribution presents an analytic approach for the design. The model considers the magnetic flux distribution in the core and in the winding area and therefore allows a precise calculation of the inductivity as well as the losses in the device and their distribution. It is very well suited for a parametric analysis and thus for the synthesis of thin planar magnetic components. Material technologies for the construction of the capacitive layers and the magnetic cores are investigated. A ferrite polymer compound is adapted to be compatible with the PCB laminating process. Accordingly a 60-W offline converter was designed and fabricated using the new technology. Its transformer is entirely integrated in the PCB as well as 11 capacitors. Standard PCB lamination processes are used for the layerwise integration of the components. The circuit needs an area of the size of a credit card with a PCB thickness of 4 mm. Up to 82% efficiency could be demonstrated.
InGaN light-emitting diodes of stripe geometries have been demonstrated. The elongated geometry facilitates light spreading in the longitudinal direction. The chips are further shaped by ...laser-micromachining to have partially-inclined sidewalls. The light extraction efficiencies of such 3D chip geometries are enhanced by ~12% (~8% according to ray-trace simulations), leading to a reduction of junction temperatures. The effective emission area is also increased four times compared to a cubic chip. The stripe LEDs are thus more efficient emitters with reduced luminous exitance, making them more suitable for a wide range of lighting applications.
Based on a survey on over 1400 commercial LED drivers and a literature review, a range of LED driver topologies are classified according to their applications, power ratings, performance and their ...energy storage and regulatory requirements. Both passive and active LED drivers are included in the review and their advantages and disadvantages are discussed. This paper also presents an overall view on the technical and cost aspects of the LED technology, which is useful to both researchers and engineers in the lighting industry. Some general guidelines for selecting driver topologies are included to aid design engineers to make appropriate choices.
In inductive wireless power transmission systems often soft-magnetic shielding is used to avoid lossy eddy currents being induced in electrically conducting components like batteries or ground layers ...of electronic circuits. Datasheet information on such shielding materials are often limited to magnetic permeability and sometimes exemplary loss information. For designing inductive wireless power systems e.g. at variable frequency or different flux excitation, detailed loss information are of interest. Therefore, it is proposed to measure the impact of these materials on the power transmission in a standardized setup, which is closely related to the real application. Here, a configuration as described in the Qi standard for wireless charging of mobile devices published by the Wireless Power Consortium is used as reference. A Figure of Merit (FoM) is presented to qualify materials concerning both a) shielding against conducting components on the backside of the receiving coil and b) establishing a high mutual inductance of the transformer coils, resulting in higher system efficiencies. Furthermore, this paper derives that material saturation is not given in properly designed 5W applications using single material sheets of 20μm thickness.
Hintergrund:
Für die Cataract-Operation im Kindesalter gibt es unterschiedliche Zugänge zur Entfernung der Linse. Wir führten eine retrospektive Analyse des postoperativen Verlaufs der in unserer ...Klinik über einen MICS Zugang operierten Kinder durch und legten dabei vor allem den Schwerpunkt auf notwendige Revisionsoperationen, intraokularen Tensioanstieg und postopertive Komplikationen in einem Zeitraum von 3–6 Monaten.
Material + Methoden:
In einem Zeitraum von Dezember 2011 bis August 2012 führten wir an 40 Augen von 30 Kindern im Alter von 8 Wochen bis 16 Jahren eine Katarakt Operation (ab dem 2. LJ mit Implantation einer IOL) mit hinterer Kapselausschneidung und vorderer Vitrektomie über einen MICS Zugang durch. Alle Operationen wurden von demselben Operateur durchgeführt. Wir analysierten retrospektiv die Komplikationsraten (Tensioanstieg, Nachstarentwicklung, Notwendigkeit einer Revisionsoperation) über 3–6 Monate und diskutieren Vor- und Nachteile des Operationszuganges im Vergleich zur Lentektomie über einen Pars-plana-Zugang.
Ergebnisse:
Bei keinem der 40 Augen kam es zu intraoperativen Komplikationen. An einem Auge musste 4 Monate postoperativ aufgrund einer hinteren Kapselphimose eine hintere Kapselausschneidung erfolgen. Keines der Augen wies im Zeitraum von 3–6 Monaten einen Anstieg des Intraokurladruckes >21mmHg auf.
Diskussion:
Die Kataraktoperation im Kindesalter kann mit und ohne Implantation einer Intraokularlinse komplikationslos über einen MICS Zugang erfolgen. Aufgrund der gerade bei jungen Patienten besonders hohen Nachstarrate ist eine große hintere Kapseleröffnung notwendig. Wir haben im Verlauf von bis zu 6 Monaten nur eine erneute Operation zur Nachstarbehandlung durchführen müssen. Aufgrund der Instabilität der dünnen Sklera ist eine Korneoskleralnaht zur Abdichtung des Tunnels notwendig, die in einer weiteren Narkose gezogen werden muss. Die zweite Narkose nutzen wir zur Anpassung einer Kontaktlinse bei Kindern ohne primäre IOL Implantation und zur erneuten vollständigen Narkoseuntersuchung. Wir ziehen den vorderen Zugang einem pars plana Zugang aufgrund der besseren Übersicht und in unserer Serie geringer Komplikationsrate vor.
Inductive power transmission is proposed more and more also for consumer applications. In this work, limitations with respect to efficiency of the whole magnetic system are investigated. The power ...efficiency of a given structure is dependent on resonant matching and on the load impedance. First, the matching conditions for optimal power efficiency are derived. Then the achievable efficiency for inductive transmission structures with varying distance and size ratios are investigated. Recent publications on inductive power transmission are evaluated and discussed based on these results. As a conclusion, inductive power transmission in a larger space (e.g. a whole room) is very inefficient. On the other hand, inductive power transmission at a surface can be efficient as conventional power supplies. Based on this insight, an inductive power transmission pad has been designed and built, with the purpose to charge mobile devices like mobile phones. It can charge an arbitrary number of devices and allows free positioning of the devices on the pad. It consists of an array of planar transmitter coils and has a size of 20 cm times 26 cm. It can detect the position of a receiver and activates only the coils underneath a receiver.
Driver Electronics for LEDs Sauerlander, G.; Hente, D.; Radermacher, H. ...
Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting,
2006-Oct., Volume:
5
Conference Proceeding
Large-volume applications of high-brightness LEDs are well established for signaling and signage. They are expected to replace conventional lamps in automotive applications in the near future and ...incandescent, halogen and fluorescent lamps at least in some general illumination applications within a few years. Innovative driver circuits optimized with respect to functionality, efficiency, cost, size and reliability are an enabler for the successful introduction of new LED based lighting products. This paper consists of two parts. In the first part, the influence of the LED current waveform, which depends on the driver topology and control, on the luminous flux and hence, the luminous efficiency is investigated experimentally for different LEDs, i.e. a red, a green and a blue 1 W LED. In the second part, an LED driver with PCB integrated capacitive layers and a transformer made of ferrite polymer compound having an extreme high power density is presented. This driver uses highly integrated passive components. This new concept is named emPIC (embedded passives integrated circuit). All passive components will be integrated in the printed circuit board (PCB) using structured layers of different materials. Experimental results taken from the driver demonstrate that the LED current ripple stays within the margins defined in the first part of this paper
Drivers for OLEDs Jacobs, J.; Hente, D.; Waffenschmidt, E.
2007 IEEE Industry Applications Annual Meeting,
2007-Sept.
Conference Proceeding
Organic light emitting diodes (OLEDs) are expected to become important light sources in the future. In contrast to point source inorganic LEDs, OLEDs are large area device. This in combination with ...different materials results in differences in performance and electrical behaviour, which on their turn result in different drivers. This work gives an overview of OLED characteristics. Based on these characteristics a simplified equivalent circuit is obtained and driver requirements are derived. It is found that AM dimming is preferred. Additionally, some OLED characteristics are compared with those of inorganic LEDs.
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