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Measurement Conditions (measurement + condition)
Selected AbstractsNoncontact Operational Modal Analysis of Structural Members by Laser Doppler VibrometerCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2009Dionysius M. Siringoringo The system employs natural excitation technique (NExT) to generate the cross-correlation functions from laser signals, and the eigensystem realization algorithm (ERA) to identify modal parameters of structural members. To facilitate simultaneous modal identification, time-synchronization technique and construction of cross-correlation functions from ambient response of laser signals are proposed. Performance of the proposed system is verified experimentally by evaluating the consistency and accuracy of identification results in different measurement conditions. The work presented here is an extension of the previous study, where a modal-based damage detection method using LDV was formulated. In the present study, application of LDV for structural parameters identification of a combined dynamical system is proposed. A model that represents the connection properties in terms of additional stiffness and damping is developed, and its importance for structural damage detection is discussed. The study shows that the presence of simulated damage in a steel connection can be detected by tracking the modal phase difference and by quantifying the additional stiffness and damping. [source] Non-invasive bioengineering methods in an intervention study in 1020 male metal workers: results and implications for occupational dermatologyCONTACT DERMATITIS, Issue 5 2010Birgitta Kütting Background: Measurements of transepidermal water loss (TEWL) as an indicator of skin barrier function and colorimetry for quantifying erythema have been recommended for monitoring persons at risk of occupational hand dermatitis. Objective: This study examines the practicability and usefulness of biophysical measurements at the workplace. Patients/Material/Methods: A sample of 1020 male metal workers was enrolled; 800 participants were followed up for 1 year. TEWL results and colorimetry (a* value), respectively, were used as effectiveness outcomes, comparing the findings in the four study arms (skin care, skin protection, both combined, and control group). Results: At 1 year follow-up, the TEWL was slightly but significantly lower in the group of participants randomized for application of barrier cream alone, indicating a protective effect. However, addressing both the individual absolute change of a* value and the differences of TEWL (delta-TEWL) of the dominant hand over the study period, no significant difference was found between the four groups. Conclusions: Dermatological examinations at the workplace cannot be replaced by bioengineering techniques. The supplementary benefit is apparently low, possibly because of difficulties in achieving standardized measurement conditions and other technical reasons. [source] An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet-Light Sensors with Enhanced Photocurrent and StabilityADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Xiaosheng Fang Abstract Although there has been significant progress in the fabrication and performance optimization of one-dimensional nanostructure-based photodetectors, it is still a challenge to develop an effective and low-cost device with high performance characteristics, such as a high photocurrent/dark-current ratio, photocurrent stability, and fast time response. Herein an efficient and low-cost method to achieve high-performance ,visible-blind' microscale ZnS nanobelt-based ultraviolet (UV)-light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt-based sensors and an ultrafast time response. The photocurrent stability and time response to UV-light do not change significantly when a channel distance is altered from 2 to 100,µm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150,°C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible-blind UV-light sensors working in the UV-A band. [source] KINETICS OF SOYBEAN LIPOXYGENASES ARE RELATED TO pH, SUBSTRATE AVAILABILITY AND EXTRACTION PROCEDURESJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2008VERONICA S. CHEDEA ABSTRACT The kinetic patterns of pure soy lipoxygenase LOX-1 and crude or defatted soybean extracts containing LOX isoenzymes (LOX-1, LOX-2 and LOX-3) were studied by UV spectrometry at 234 and 280 nm, depending on their extraction and measurement conditions. Different pHs (from 6.0 to 9.0), corresponding to specific activation of LOX isoenzymes and the ratios of enzyme protein per substrate were used in order to evaluate the enzyme rates, as indicators of its affinity for substrate in different environments. The crude soy extract contained mainly LOX-1 activity (measured at 234 nm, at pH 9.0) and LOX-3, in an approximate ratio of 3:1. The LOX-2 activity was very low. The defatted extracts buffered at pH 6.8 and 7.1 showed a low LOX-1 and LOX 2 activity, but mostly LOX-3 activity (measured at 280 nm, at pH 7.1), with a mirror-type relation between the enzyme/substrate ratio and their enzymatic specific activity. The results suggest that defatting inhibits specifically the LOX-1 activity and indicate the possibility to modulate LOX activity by modifications of enzyme/substrate ratios and modifications of pH in the enzyme environment. PRACTICAL APPLICATIONS Because of the specific kinetic behaviors of the three different LOXs found in crude soy extracts involved in off-flavor generation, one can modulate the inhibition of these isoenzymes during soybean processing. Our experiments showed that pH variation could be a simple solution to inhibit the LOX isoenzymes, and therefore, the off-flavor generation. From the analytical point of view, the techniques described in this article are designed to be as simple as possible, and easy to use at large-scale level in food industry (food chain control). The idea is to minimize the number of separate chemical manipulations and, thereby, minimize errors. These studies can offer the background of further inhibition experiments in vitro using natural extracts. The LOX inhibition by natural antioxidants is related as well to pH and other factors influencing the enzyme's activity; this idea can be also valorized practically in the future. [source] Simulation of the three-dimensional distribution of the red:far-red ratio within crop canopiesNEW PHYTOLOGIST, Issue 1 2007Michaël Chelle Summary ,,It is widely recognized that the red:far-red ratio (,) acts as a signal that triggers plant morphogenesis. New insights into photomorphogenesis have been gained through experiments in controlled environments. Extrapolation of such results to field conditions requires characterization of the , signal perceived by plant organs within canopies. This paper presents a modeling approach to characterize this signal. ,,A wheat (Triticum aestivum) architectural model was coupled with a three-dimensional light model estimating the irradiances of virtual sensors. Architectural parameters and , values were measured on two contrasting spring wheat canopies under outdoor conditions. Light simulations were compared with measurements, and an analysis of sensitivity to measurement conditions was carried out. ,,The model results agreed well with measurements and previously published data. The sensitivity analysis showed that , strongly depends on canopy development as well as on sky conditions, sensor orientation, and sensor field of view. ,,This paper shows that modeling enables investigation of , distribution in a canopy over space and time. It also shows that the characterization of light quality strongly depends on measurement conditions, and that any discrepancies in results are likely attributable to different experimental set-ups. The usefulness of this modeling approach for crop photomorphogenesis studies is discussed. [source] Measuring contrast sensitivity with inappropriate optical correction*OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2000Russell L. Woods Summary Spatial frequency-selective minima (notches) in the contrast sensitivity function (CSF) because of defocus can mimic those that occur with ocular disease. We examined the influence of measurement conditions on CSF shape in simulated clinical testing. CSF notches occurred with almost all levels of defocus for all subjects. Multiple notches were found under some conditions. Notches were found with defocus as small as 0.50 D. Effects of induced astigmatism depended on the orientation of the target. Notches were apparent in defocus conditions after stimulus size and room illuminance were modified and when subjects had insufficient accommodation to compensate for hypermetropic defocus. The equivalent of notches was not noted with the Pelli-Robson chart. As defocus-induced CSF notches may be mistaken for functional loss, careful refractive correction should be conducted prior to clinical or experimental CSF measurement, even at low spatial frequencies. [source] Electrical study of InAs/GaAs quantum dots with two different environmentsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008M. Kaniewska Abstract Unusually complex spectra have been obtained for InAs/GaAs quantum dot (QD) structures when studied as a function of applied bias by deep level transient spectroscopy (DLTS). In spite of their complexity, basic processes for electron escape from the QDs have been recognized. We show that due to the variety of transitions involving direct tunneling and more complex thermal transitions, due to QD size fluctuations, and environmental dependent QD carrier population, measurement conditions have to be carefully suited for characterizing transport properties of the QDs. Additionally, on the basis of results of a comparative study under chosen measurement conditions, we conclude that the states of the InAs QDs shift towards the middle of the energy gap if the QDs are capped with a Ga-rich InGaAs insertion. It explains a red-shift of the emission wavelength that was found by photoluminescence measurements (PL). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrospray ionization mass spectrometric studies of nucleophilic carbenes derived from pyrazolium and indazolium carboxylatesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2005Andreas Schmidt Pyrazolium-3-carboxylate and indazolium-3-carboxylate, which belong to the class of pseudo-cross-conjugated mesomeric betaines and which represent the electronically relevant partial structures of the betaine alkaloid Nigellicin, were examined by electrospray ionization mass spectrometry. These compounds decarboxylate to pyrazol-3-ylidene and indazol-3-ylidene. The formation of adducts of these new nucleophilic carbenes under the measurement conditions was examined. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||