Determination of the antioxidant capacity: influence of the sample concentration on the measured values

The aim of the present analysis was to study the influence of the sample concentration on the measured antioxidant capacity, since such investigations are scarce but necessary to ensure the reproducibility of the results. Pure substances (ascorbic acid, gallic acid, Trolox^®, uric acid) and food extracts (strawberry nectar, tomato extract, white tea) were analysed using seven common antioxidant capacity assays (three versions of Trolox equivalent antioxidant capacity, TEAC; ferric reducing antioxidant power, FRAP; photochemiluminescence, PCL; oxygen radical absorbance capacity, ORAC and total phenolics assay). For all applied pure substances and in most of the assays effects of the sample concentration on the measured antioxidant capacity were observed. Since it remains speculative how sample concentration does affect the measured antioxidant capacity exactly, it is strongly recommended to use at least three sample concentrations for analysis to detect and to discuss concentration-dependent effects.     

Two-layer channel routing with vertical unit-length overlap

We show that anyn-net 2-terminal channel routing problem of densityd can be wired on a two-layer grid of widthw =d +O(d ^2/3) when vertical wire segments are allowed to overlap for a distance of length 1. This is a considerable asymptotic improvement over the best known, and optimal, channel width of 2d-1 for models in which no vertical overlap is allowed [RBM, PL]. Our result also improves the 3d/2+O(1) channel width achieved by a recent algorithm [G] for the same vertical overlap model. The algorithm presented in this paper produces at most 4 overlaps of unit length between any two nets, usesO(n) contacts, and can be implemented to run inO(nd ^2/3) time. We also generalize the algorithm to multi-terminal channel routing problems for which our algorithm uses a width ofw = 2d +O(d ^2/3).This work was supported by the Office of Naval Research under Contract N00014-84-K-0502 and by the National Science Foundation under Grant DMC-84-13496.     

Optimierung von Wasserkraft und Ökologie bei Erneuerung oder Revitalisierung bestehender Anlagen – „win-win“-Ansatz

In Austria, using hydropower has a centuries-long tradition. Whereas we first placed mills along our rivers to put water’s power to use, today we have over 5,200 water power stations of various types, from the smallest facilities to pumped-storage hydroelectric plants in the Alps. Today, water power accounts for roughly 60 % of our domestic power production, though the various types of power stations used have diverse ecological effects. This article presents a “win-win” approach to improving both hydropower production and ecological outcomes on the basis of the Kamp River in Lower Austria. The Kamp is not only home to a pumped-storage hydroelectric plant and the major plants Ottenstein, Dobra-Krumberg and Thurnberg-Wegscheid, but also to 14 smaller plants with turbines that are between 25 and 75 years old, many of them with energy conversion efficiency ratios of well under 0.7. Using the case study of a small water power plant, the chances of achieving a win-win situation are presented in detail. In this context, replacing the turbines is a major aspect of improving these plants. Extensive analyses have demonstrated that balanced planning approaches can yield both higher efficiency and better conditions for aquatic ecology, thanks to increased residual flows. Further, energy calculations and numerical habitat simulations have confirmed that a win-win situation is feasible for the small power plant studied, especially if Kaplan turbines are used. For example, they show that, despite the increased residual flow of up to 800 l/s, a considerable performance increase over the status quo is possible (maximum performance increase of 17 % without considering residual flow). If the residual flow was only 400 l/s, which tests indicate would mean an improvement in the habitat conditions for all ages of the dominant fish species (the brown trout) of > 50 %, a performance increase of 8 % would be the result. Thanks to the generally applicable methodology used, the win-win approach presented here can broadly be used in the optimization, efficiency improvement and revitalization of current hydropower plants, producing both more electricity and higher residual flow levels to improve local ecological conditions. In order to make this win-win situation a reality, innovative and integrative financial models for e.g. new turbines related to the fields of green energy production and environmental protection will be essential.     

Expression Profiles of ASIC1/2 and TRPV1/4 in Common Skin Tumors

The acid-sensing ion channels ASIC1 and ASIC2, as well as the transient receptor potential vanilloid channels TRPV1 and TRPV4, are proton-gated cation channels that can be activated by low extracellular pH (pH_e), which is a hallmark of the tumor microenvironment in solid tumors. However, the role of these channels in the development of skin tumors is still unclear. In this study, we investigated the expression profiles of ASIC1, ASIC2, TRPV1 and TRPV4 in malignant melanoma (MM), squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and in nevus cell nevi (NCN). We conducted immunohistochemistry using paraffin-embedded tissue samples from patients and found that most skin tumors express ASIC1/2 and TRPV1/4. Striking results were that BCCs are often negative for ASIC2, while nearly all SCCs express this marker. Epidermal MM sometimes seem to lack ASIC1 in contrast to NCN. Dermal portions of MM show strong expression of TRPV1 more frequently than dermal NCN portions. Some NCN show a decreasing ASIC1/2 expression in deeper dermal tumor tissue, while MM seem to not lose ASIC1/2 in deeper dermal portions. ASIC1, ASIC2, TRPV1 and TRPV4 in skin tumors might be involved in tumor progression, thus being potential diagnostic and therapeutic targets.     

Vehicle Contribution to Ambient Carbonaceous Aerosols by Scaled Thermograms

Carbon thermograms, which classify carbon aerosol according to its volatility, were obtained for fine-particle samples from an isolated highway vehicle source and a vehicle-dominated ambient site. The thermograms from the sites were compared after scaling by the carbon monoxide concentration. The high- and low-volatility carbon fractions in the ambient sample agreed to within 10% of the corresponding fractions in the highway vehicle sample. Excess carbon in the range of intermediate volatility comprised 15 to 19% of the ambient carbon mass and is attributed to aerosols from secondary processes and nonvehicular primary sources. When lead was used as a tracer to scale the thermograms, the high- and low-volatility ambient carbon fractions were underestimated by a factor of 2. The low volatility fraction (“black carbon”) present in the atmospheric sample was evolved at lower temperatures than the equivalent fraction in the isolated highway vehicle sample. This creates an ambiguity in defining the low-volatility fraction, which is a problem if black carbon is used as a tracer. The scaling technique described in this work avoids the problem because it does not require an estimation of the low-volatility carbon fraction.     

Comparison of Particle Size Distributions at Urban and Agricultural Sites in California's San Joaquin Valley

As part of the California Regional PM _2.5 and PM ₁₀ Air Quality Study (CRPAQS) particle size distributions were measured simultaneously at two sites; the city of Fresno and the agricultural site of Angiola. Reported here are data obtained by scanning mobility analysis over the size range from 10 nm to 400 nm for the intensive study period from December 1, 2000 through February 6, 2001. These high time resolution data show variability in the character of the distributions, as well as the in the total number concentrations. The most pronounced feature of the data set is a consistent, nighttime maxima in particle number concentrations with a modal diameter near 80 nm during the evening hours at the urban Fresno site. Although these maxima are correlated with CO, NO, and black carbon, the particle size is larger than the 30–40 nm modal diameters observed for traffic aerosols during the commute hours, and is attributed to a non-vehicle source. At the agricultural site, the morning maxima particle number concentration coincides with the maxima in NO concentration, but often precedes the morning maxima in black carbon. Values for the geometric mean particle diameter varied from day to day, but are correlated between the two sites, with somewhat larger particle sizes at Angiola during periods of stagnation.     

Spectroscopic and Theoretical Study on Electronically Modified Chromophores in LOV Domains: 8‐Bromo‐ and 8‐Trifluoromethyl‐Substituted Flavins

Two chemically synthesized flavin derivatives, 8‐trifluoromethyl‐ and 8‐bromoriboflavin (8‐CF₃RF and 8‐BrRF), were photochemically characterized in H₂O and studied spectroscopically after incorporation into the LOV domain of the blue light photoreceptor YtvA from Bacillus subtilis. The spectroscopic studies were paralleled by high‐level quantum chemical calculations. In solution, 8‐BrRF showed a remarkably high triplet quantum yield (0.97, parent compound riboflavin, RF: 0.6) and a small fluorescence quantum yield (0.07, RF: 0.27). For 8‐CF₃RF, the triplet yield was 0.12, and the fluorescence quantum yield was 0.7. The high triplet yield of 8‐BrRF is due to the bromine heavy atom effect causing a stronger spin–orbit coupling. Theoretical calculations reveal that the decreased triplet yield of 8‐CF₃RF is due to a smaller charge transfer and a less favorable energetic position of T₂, required for intersystem crossing from S₁ to T₁, as an effect of the electron‐withdrawing CF₃ group. The reconstitution of the LOV domain with the new flavins resulted in the typical LOV photochemistry, consisting of triplet state formation and covalent binding of the chromophore, followed by a thermal recovery of the parent state, albeit with different kinetics and photophysical properties.     

Parameter estimation from observations of first-passage times of the Ornstein–Uhlenbeck process and the Feller process

Renewal point processes show up in many different fields of science and engineering. In some cases the renewal points become the only observable parts of an anticipated hidden random variation of some physical quantity. The hypothesis might be that a hidden random process originating from zero or some other low value only becomes visible at the time of first crossing of some given value level, and that the process is restarted from scratch immediately after the level crossing. It might then be of interest to reveal the defining properties of this hidden process from a sample of observed first-passage times. In this paper the hidden process is first anticipated as a non-stationary Ornstein–Uhlenbeck (OU) process with unknown parameters that have to be estimated only by use of the information contained in a sample of first-passage times. The estimation method is a direct application of the Fortet integral equation of the OU process. A non-stationary Feller process is considered subsequently. As the OU process, the Feller process has a known transition probability distribution that allows the formulation of the integral equation. The described integral equation estimation method also provides a subjective graphical test of the applicability of the OU process or the Feller process when applied to a reasonably large sample of observed first-passage data.

These non-stationary processes have several applications in biomedical research, for example as idealized models of the neuron membrane potential. When the potential reaches a certain threshold the neuron fires, whereupon the potential drops to a fixed initial value, from where it continuously builds up again until the next firing. Also in civil engineering there are hidden random phenomena such as internal cracking or corrosion that after some random time break through to the material surface and become observable. However, the OU process has as a model of physical phenomena the defect of not being bounded to the negative side. This defect is not present for the Feller process, which therefore may provide a useful modeling alternative to the OU process.