Papers by sverker hartwig
Journal of Radiation Research, 2014
In studies reported in the 1960s and since, blood plasma from radiation-exposed individuals has b... more In studies reported in the 1960s and since, blood plasma from radiation-exposed individuals has been shown to induce chromosome damage when transferred into lymphocyte cultures of non-irradiated persons. This effect has been described to occur via clastogenic factors, whose nature is still mostly unknown. We have previously examined clastogenic factors from irradiated individuals by looking at plasma-induced DNA damage in reporter cells. Plasma was tested from ca. 30 locally exposed clinical patients receiving fractionated radiation treatment, as well as from three radiological accident victims exposed in 1994, albeit sampled 14 years post-accident. In the current work, proteome changes in the plasma from all subjects were examined with 2D gel electrophoresis-based proteomics techniques, in order to evaluate the level of protein expression with respect to the findings of a clastogenic factor effect. No differences were observed in protein expression due to local radiation exposure ( pre-vs post-exposure). In contrast, plasma from the radiation accident victims showed alterations in the expression of 18 protein spots (in comparison with plasma from the control group). Among these, proteins such as haptoglobin, serotransferrin/transferrin, fibrinogen and ubiquitin-60S ribosomal protein L40 were observed, none of them likely to be clastogenic factors. In conclusion, the proteomics techniques applied were unable to identify changes in the proteome of the locally irradiated patients, whereas such differences were observed for the accident victims. However, association with the clastogenic effect or any specific clastogenic factor remains unresolved and thus further studies with more sensitive techniques are warranted.
Summary: Precise and continuous ethylene detection is needed in various fruit storage application... more Summary: Precise and continuous ethylene detection is needed in various fruit storage applications. One of the main goals of the presented work is the development of gas sensor systems for ethylene monitoring based on miniaturized low cost infrared spectroscopy. The developments concentrate on systems based on small multi pass reflection cells, novel micromachined IR-emitters and thermopile arrays in order to measure at a wavelength of 10.6µm, a rotational vibrational region (fingerprint region) of ethylene. First ethylene measurements were carried out.
tm - Technisches Messen, 2005
Abstract Oberflächenemittierende Halbleiterlaser (VCSEL) werden zur spektroskopischen Sauerstoffm... more Abstract Oberflächenemittierende Halbleiterlaser (VCSEL) werden zur spektroskopischen Sauerstoffmessung im Wellenlängenbereich bei 762 nm eingesetzt. Hierfür wurden besonders polarisationsstabile Laserdioden auf der Basis von AlGaAs entwickelt. Im Vergleich zu kantenemittierenden Lasern lassen sich VCSELs deutlich besser über den Betriebsstrom abstimmen, während sich die Temperaturmodulation in der gleichen Größenordnung bewegt. Bei dem konventionellen Verfahren der Abstimmung über Stromrampen wurde 1 kHz als Messfrequenz gewählt. Weiterhin wurde der Einsatz besonders schneller Peltierelemente für die schnelle Abstimmung durch Temperaturrampen über mehrere Gasabsorptionslinien gezeigt.
Hollow fibers can be used for compact infrared gas sensors. The guided light is absorbed by the g... more Hollow fibers can be used for compact infrared gas sensors. The guided light is absorbed by the gas introduced into the hollow core. High sensitivity and a very small sampling volume can be achieved depending on fiber parameters i.e. attenuation, flexibility, and gas exchange rates. Different types of infrared hollow fibers including photonic bandgap fibers were characterized using quantum cascade lasers and thermal radiation sources. Obtained data are compared with available product specifications. Measurements with a compact fiber based ethanol sensor are compared with a system simulation. First results on the detection of trace amounts of the explosive material TATP using hollow fibers and QCL will be shown.
This work describes the design, simulation, fabrication and characterization of a TiN/Pt microhea... more This work describes the design, simulation, fabrication and characterization of a TiN/Pt microheater prepared on GaAs micromechanical structure as a prospective device for MEMS gas sensor array. We use the electro-thermal simulation to verify the properties of the designed microstructure, which conformed achievement of the operating temperatures in the range of 200 to 320°C with heating power less than 25 mW. The average temperature gradient in the active area does not exceed 0.6 K/μm. We demonstrated the fabrication of GaAs suspended membranes, realized in two steps, by combination of surface and bulk micromachining. We also describe the development and characterization of a microheater on a GaAs membrane. The power consumption at an operating temperature of approximately 550 K is about 30 mW and the achieved thermal resistance value is 8.43 K/mW.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Proceedings of SPIE - The International Society for Optical Engineering, 2005
Precise and continuous ethylene detection is needed in various fruit storage applications. The ai... more Precise and continuous ethylene detection is needed in various fruit storage applications. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 µm wavelength. For this reason optical components and signal processing electronics need to be developed, tested and integrated in a compact measurement system. The present article describes the proposed system set-up, the status of the development of component prototypes and results of gas measurements performed using a first system set-up. Next to a microstructured IR-emitter, a miniaturised multi-reflection cell and a thermopile-array with integrated optical filters and microstructured Fresnel lenses for the measurement of ethylene, two interfering gases and one reference channel are proposed. Recently a miniaturised White cell as absorption path is tested with various commercial and a self-developed thermal emitter. First ethylene measurements have been performed with commercial twofold thermopile detectors and a Lock-in-amplifier. These showed significant absorption at an ethylene concentration of 100ppm. For the detection module different types of thermopiles were tested, first prototypes of Fresnel lenses have been fabricated and characterised and the parameters of the optical filters were specified. Furthermore a compact system electronics for signal processing containing a preamplification stage and Lock-in-technique is in development.
Proceedings of SPIE - The International Society for Optical Engineering, 2007
In various fruit storage applications precise and continuous ethylene detection is needed. The ai... more In various fruit storage applications precise and continuous ethylene detection is needed. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 µm wavelength. For this reason optical components and signal processing electronics were developed, tested and integrated in a compact measurement system. The present article describes the optical components, the integration of the optical system, electronics and results of gas measurements. Next to a Silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous measurement at four channels for ethylene, two interfering gases and the reference signal were integrated in the optical system. Optical filters were attached to fourfold thermopile-arrays by flipchip-technology. Silicon-based Fresnel multilenses were processed and attached to the cap of the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with Antireflection layers made of Zinc sulphide. For the signal processing electronics a preamplification stage and a Lock-in-board has been developed. First ethylene measurements with the optical system with miniaturised gas cell, Silicon-based IR-emitter, a commercial thermopile detector and the self-developed system electronics showed a detection limit of smaller than 20ppm.
Summary: Precise and continuous ethylene detection is needed in various fruit storage application... more Summary: Precise and continuous ethylene detection is needed in various fruit storage applications. One of the main goals of the presented work is the development of gas sensor systems for ethylene monitoring based on miniaturized low cost infrared spectroscopy. The developments concentrate on systems based on small multi pass reflection cells, novel micromachined IR-emitters and thermopile arrays in order to measure at a wavelength of 10.6µm, a rotational vibrational region (fingerprint region) of ethylene. First ethylene measurements were carried out.
Sensors and Actuators B: Chemical, 2003
The development of a miniaturized mid-infrared grating spectrometer operating at in the wavelengt... more The development of a miniaturized mid-infrared grating spectrometer operating at in the wavelength range 8–12.5μm is reported. This measurement device can be used for detecting organic contaminants in waste water, leakage fluids, and when redeveloping contaminated soils. The spectrometer system was tested at laboratory conditions. Measurements of chlorinated hydrocarbons revealed a detection limit of 900ppb for tetrachloroethylene.
Microsystem Technologies, 2007
Precise and continuous ethylene detection is needed in various fruit ripening applications. The a... more Precise and continuous ethylene detection is needed in various fruit ripening applications. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 lm wavelength. For this reason optical components and signal processing electronics were developed, tested and integrated in a compact measurement system. The main optical components, their integration of the optical system, as well as a description of the developed electronics and the first results of gas measurements are described in this paper. In fact the application conditions demand not a single channel system but a multichannel one. A silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous measurement with four channels including, ethylene, two interfering gases and the reference signal were integrated in the optical system. The new inner architecture of the detector module, consisted of optical filters which were directly attached by flip-chip technology onto the thermopile-arrays, allowing silicon-based Fresnel multilenses to be attached to the cap of the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with zinc sulphide antireflection layers. For the signal processing electronics a preamplification stage and a DSP-based lock-in-amplifier has been developed. Although some of this work is still on-going, first ethylene measurements with the miniaturised gas cell, silicon-based IR-emitter, a commercial thermopile detector and the selfdeveloped system electronics showed a detection limit better than 20 ppm.
Journal of Micromechanics and Microengineering, 2000
ABSTRACT
Journal of Applied Physics, 2011
We present an optical gas sensor based on the classical nondispersive infrared technique using ul... more We present an optical gas sensor based on the classical nondispersive infrared technique using ultracompact photonic crystal gas cells. The ultracompact device is conceptually based on low group velocities inside a photonic crystal gas cell and low-reflectivity antireflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. We show that, theoretically, for an optimal design enhancement factors of up to 60 are possible in the region of slow light. However, the overall transmission of bulk photonic crystals, and thus the performance of the device, is limited by fluctuations of the pore diameter. Numerical estimates suggest that the positional variations and pore diameter fluctuations have to be well below 0.5% to allow for a reasonable transmi...
IEEE Transactions on Consumer Electronics, 2000
Today, we observe the creation of an increasing number of multimedia consumer devices for mobile ... more Today, we observe the creation of an increasing number of multimedia consumer devices for mobile and home use. This includes set-top-boxes, game consoles, Personal Digital Assistants (PDA), e-books, but also mobile phones. Although these devices have many things in common with desktop PCs -above all internet accessit is widely accepted that they will serve a different purpose. Many committees and companies are currently trying to define the open application platform .for tomorrow's consumer terminals ,for home use, among others the so-called Multimedia Home PlaEform (MHP) of the European Digital Video Broadcasting (DVB) project. Meanwhile, on the cellular end of the multimedia business, portable appliances like cellular phones, e-books and PDAs are evolving to multimedia terminals. starting from narrow band Internet services like the Wireless Application Protocol (WAP) and slow[y adopting video technologies. One of the main obstacles to overcome is bandwidth limitationeven for 3G mobile systemsand broadcast technology is considered to be a serious candidate to fill this gap, both for TV and data services. A special challenge is to provide multimedia services in vehicles, where, due to the static environment relative to the driver, some requirements for mobile and static terminals apply at the same time. This paper shall summarize some trends and opportunities of mobile multimedia -especially in the DVB and GSM (Global System for Mobile communications) domain, while outlining the different requirements jor mobile, home, and car use of multimedia services,
Diabetic Medicine, 2013
Aim To validate the German Diabetes Risk Score within the population-based cohort of the Cardiova... more Aim To validate the German Diabetes Risk Score within the population-based cohort of the Cardiovascular Disease -Living and Ageing in Halle (CARLA) study. Methods The sample included 582 women and 719 men, aged 45-83 years, who did not have diabetes at baseline. The individual risk of every participant was calculated using the German Diabetes Risk Score, which was modified for 4 years of follow-up. Predicted probabilities and observed outcomes were compared using Hosmer-Lemeshow goodness-of-fit tests and receiver-operator characteristic analyses. Changes in prediction power were investigated by expanding the German Diabetes Risk Score to include metabolic variables and by subgroup analyses. We found 58 cases of incident diabetes. The median 4-year probability of developing diabetes based on the German Diabetes Risk Score was 6.5%. The observed and predicted probabilities of developing diabetes were similar, although estimation was imprecise owing to the small number of cases, and the Hosmer-Lemeshow test returned a poor correlation (chi-squared = 55.3; P = 5.8*10 -12 ). The area under the receiver-operator characteristic curve (AUC) was 0.70 (95% CI 0.64-0.77), and after excluding participants 66 years old, the AUC increased to 0.77 (95% CI 0.70-0.84). Consideration of glycaemic diagnostic variables, in addition to self-reported diabetes, reduced the AUC to 0.65 (95% CI 0.58-0.71). A new model that included the German Diabetes Risk Score and blood glucose concentration (AUC 0.81; 95% CI 0.76-0.86) or HbA 1c concentration (AUC 0.84; 95% CI 0.80-0.91) was found to peform better. Conclusions Application of the German Diabetes Risk Score in the CARLA cohort did not reproduce the findings in the European Prospective Investigation into Cancer and Nutrition (EPIC) Potsdam study, which may be explained by cohort differences and model overfit in the latter; however, a high score does provide an indication of increased risk of diabetes.
Composition of animal communities can be shaped by both local and regional processes. Among other... more Composition of animal communities can be shaped by both local and regional processes. Among others, dispersal of organisms links local and regional patterns and determines the similarity of communities at increasing spatial distances. Unique and shared spatial and environmental contributions to fish community composition were calculated for watercourse distances between 49 hydrologically connected lakes in the German lowland area. Variation partitioning indicated a dominant unique effect of spatial predictors on fish community composition, whereas the effects of lake morphometry and productivity were weaker. The spatial effect was attributable to an uneven occurrence of small, littoral fish species found even at the small spatial extension covered here (maximum spatial distance ~550 km). Distance decay of community similarity was moderate, but significant, if all 31 fish species were considered, but the slope of the decay function became steeper if only 11 small-sized, primarily littoral species were included. These results suggest that fish in European lowland lakes can be considered a metacommunity with limited dispersal along watercourse connections in particular for small-sized species. The analysis supports that for an appropriate evaluation of spatial effects on fish community similarity, reliable estimates of local richness are required which include in particular also rare, small-sized species occurring primarily in littoral areas. Furthermore, watercourse distance is a more reliable approximation than Euclidean distance to the real spatial dimension of fish dispersal.
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Papers by sverker hartwig