A novel route to estimate the photocatalytic activity of titanium dioxide via voltage measurements.

Titanium dioxide is known as a photocatalyst, that may be activated by UV-A light and thus be able to lead to chemical reactions, to mineralize organic compounds, to inactivate biomolecules and to kill microorganisms, respectively. To estimate the capability of the photocatalytic activity a novel experimental setup using photovoltage measurements was studied. A distinct correlation between the photocatalytic activity of the titanium dioxide samples and the measurable photovoltages could be demonstrated. The experimental setups included the construction of different electrochemical cells based on TiO2 and using different liquid and gel electrolytes. The investigations were carried out on titanium dioxide layers as well as on TiO2 particle materials. The electrochemical measurement of the resulting voltage was optimised and the results were compared with conventionally used methods for the determination of the photocatalytic activity like the decolourization of methylene blue solutions. Additionally, the increase of carbon dioxide concentration in the gas phase was taken as a measure for total mineralization. Results indicate strong correlations between the different methods.

Technical and clinical performance of the thermo-test device "Q-Sense" to assess small fibre function: A head-to-head comparison with the "Thermal Sensory Analyzer" TSA in diabetic patients and healthy volunteers.

BACKGROUND: Thermo-test devices are rarely used outside specialized pain centres because of high acquisition costs. Recently, a new, portable device ("Q-Sense") was introduced, which is less expensive but has reduced cooling capacity (20°C). We assessed the reliability/validity of the "Q-Sense" by comparing it with the Thermal Sensory Analyzer (TSA). METHODS: Using a phantom-skin model, the physical characteristics of both devices were compared. The clinical performance was assessed in a multicentre study by performing Quantitative Sensory Testing (QST) in 121 healthy volunteers and 83 diabetic patients (Eudra-Med-No. CIV-12-05-006501). RESULTS: Both device types showed ~40% slower temperature ramps for heating/cooling than nominal data. Cold/warm detection thresholds (CDT, WDT) and heat pain thresholds (HPT) of healthy subjects did not differ between device types. Cold pain thresholds (CPT) were biased for Q-Sense by a floor effect (p < .001). According to intraclass correlation coefficients (ICC), agreement between TSA and Q-Sense was good/excellent for CDT (ICC = 0.894) and WDT (ICC = 0.898), moderate for HPT (ICC = 0.525) and poor for CPT (ICC = 0.305). In diabetic patients, the sensitivity of Q-Sense to detect cold hypoesthesia was reduced in males >60 years. Moderate correlations between thermal detection thresholds and morphological data from skin biopsies (n = 51) were similar for both devices. CONCLUSIONS: Physical characteristics of both thermo-test devices are similarly limited by the poor temperature conduction of the skin. The Q-Sense is useful for thermal detection thresholds but of limited use for pain thresholds. For full clinical use, the lower cut-off temperature should be set to ≤18°C. SIGNIFICANCE: High purchase costs prevent a widespread use of thermo-test devices for diagnosing small fibre neuropathy. The air-cooled "Q-Sense" could be a lower cost alternative, but its technical/clinical performance needs to be assessed because of its restricted cut-off for cooling (20°C). This study provides critical information on the physical characteristics and the clinical validity/reliability of the Q-Sense compared to the "Thermal Sensory Analyzer" (TSA). We recommend lowering the cut-off value of the Q-Sense to ≤18°C for its full clinical use.

Strategies for reliable automatic onset time picking of acoustic emissions and of ultrasound signals in concrete.

Determining the onset of transient signals like seismograms, acoustic emissions or ultrasound signals is very time consuming if the onset is picked manually. Therefore, different approaches exist, especially in seismology. The concepts of the most popular approaches are summarized. An own approach adapted to ultrasound signals and acoustic emissions, based on the Akaike Information Criterion (AIC), is presented. The AIC-picker is compared to an automatic onset detection algorithm based on the Hinkley criterion and also adapted to acoustic emissions. Manual picks performed by an analyst are used as reference values. Both automatic onset detection algorithms are applied to ultrasound signals which are used to monitor the setting and hardening of concrete. They are also applied to acoustic emissions recorded during a pull-out test. The AIC-picker produces sufficient reliable results for ultrasound signals where the deviation from the manual picks varies between 2% and 4%. Concerning acoustic emissions, only 10% of the events result in a mislocation vector greater than 5mm. It can be shown that our AIC-picker is a reliable tool for automatic onset detection for ultrasound signals and acoustic emissions of varying signal to noise ratio.

New approaches for automatic threedimensional source localization of acoustic emissions--Applications to concrete specimens.

The task of locating a source in space by measuring travel time differences of elastic or electromagnetic waves from the source to several sensors is evident in varying fields. The new concepts of automatic acoustic emission localization presented in this article are based on developments from geodesy and seismology. A detailed description of source location determination in space is given with the focus on acoustic emission data from concrete specimens. Direct and iterative solvers are compared. A concept based on direct solvers from geodesy extended by a statistical approach is described which allows a stable source location determination even for partly erroneous onset times. The developed approach is validated with acoustic emission data from a large specimen leading to travel paths up to 1m and therefore to noisy data with errors in the determined onsets. The adaption of the algorithms from geodesy to the localization procedure of sources of elastic waves offers new possibilities concerning stability, automation and performance of localization results. Fracture processes can be assessed more accurately.

Inactivation of LPS and RNase A on photocatalytically active surfaces.

TiO(2) coated surfaces are able to generate highly reactive oxidizing species under mild UV-A light exposure in the presence of water and oxygen. We have demonstrated that these radicals are sufficient to eliminate different pathogenic bacteria, by breaking their cell walls. The photocatalytic activity of surfaces coated with titanium dioxide offers therefore an alternative possibility of disinfection. However, restriction of bacterial growth does not protect surfaces from bacterial derived contaminations, such as endotoxins. Lipopolysaccharides (LPS) and Ribonuclease A (RNAse A) represent the two most abundant contaminations, causing severe problems in biomedical and immunological research as well as in the pharmaceutical industry. Due to their high stability, complete removal of these contaminants is technically challenging. Using irradiated TiO(2) coated glass plates, RNAse A and LPS containing contaminations could be completely inactivated. By establishing highly sensitive immuno-based assays, destruction of the contaminants was quantified and shown to be independent of the initial concentrations, following a zero-order reaction. Exposure for 96 h resulted in a reduction of 11 ng of LPS and 7 units of RNase A cm(-2) surface. These amounts are comparable to contamination levels found under standard working conditions. Titanium dioxide coatings provide therefore a powerful tool for auto-disinfection and self-cleaning of surfaces.