Mutual selection in time-varying networks

Time-varying networks play an important role in the investigation of the stochastic processes that occur on complex networks. The ability to formulate the development of the network topology on the same time scale as the evolution of the random process is important for a variety of applications, including the spreading of diseases. Past contributions have investigated random processes on time-varying networks with a purely random attachment mechanism. The possibility of extending these findings towards a time-varying network that is driven by mutual attractiveness is explored in this paper. Mutual attractiveness models are characterized by a linking function that describes the probability of the existence of an edge, which depends mutually on the attractiveness of the nodes on both ends of that edge. This class of attachment mechanisms has been considered before in the fitness-based complex networks literature but not on time-varying networks. Also, the impact of mutual selection is investigated alongside opinion formation and epidemic outbreaks. We find closed-form solutions for the quantities of interest using a factorizable linking function. The voter model exhibits an unanticipated behavior as the network never reaches consensus in the case of mutual selection but stays forever in its initial macroscopic configuration, which is a further piece of evidence that time-varying networks differ markedly from their static counterpart with respect to random processes that take place on them. We also find that epidemic outbreaks are accelerated by uncorrelated mutual selection compared to previously considered random attachment.

Network growth model with intrinsic vertex fitness

We study a class of network growth models with attachment rules governed by intrinsic node fitness. Both the individual node degree distribution and the degree correlation properties of the network are obtained as functions of the network growth rules. We also find analytical solutions to the inverse, design, problems of matching the growth rules to the required (e.g., power-law) node degree distribution and more generally to the required degree correlation function. We find that the design problems do not always have solutions. Among the specific conditions on the existence of solutions to the design problems is the requirement that the node degree distribution has to be broader than a certain threshold and the fact that factorizability of the correlation functions requires singular distributions of the node fitnesses. More generally, the restrictions on the input distributions and correlations that ensure solvability of the design problems are expressed in terms of the analytical properties of their generating functions.

Monolithic integration of microfluidic channels and optical waveguides in silica on silicon

Sealing of the flow channel is an important aspect during integration of microfluidic channels and optical waveguides. The uneven topography of many waveguide-fabrication techniques will lead to leakage of the fluid channels. Planarization methods such as chemical mechanical polishing or the etch-back technique are possible, but troublesome. We present a simple but efficient alternative: By means of changing the waveguide layout, bonding pads are formed along the microfluidic channels. With the same height as the waveguide, they effectively prevent leakage and hermetically seal the channels during bonding. Negligible influence on light propagation is found when 10-mum-wide bonding pads are used. Fabricated microsystems with application in absorbance measurements and flow cytometry are presented.

[The psychophysics of sweet taste. 8. Interindividual variability of differential findings]

Contribution to the psychophysics of sweet taste. Part 8. On the inter-individual variability of the difference sensitivity. The variability of sensitivity of volunteers is a considerable imponderability for the comparison of sensoric results. The paper deals with the quantitative determination of the different sensitivity of sweet taste of 132 persons, 38 men and 94 women at the age of 19 to 64 years, using a statistically defined method. The numbers of errors are estimated for each person by means of one test difference of two saccharose concentrations using 10 pairs of comparisons and 4 runs. The average number of error of 10 comparisons corresponds to the individual measure of sensitivity. The medium value of the total distribution is 1.54 and the standard deviation is 1.19 errors. The value is only less above the binomial calculated number. In random test women show in comparison to men a significant higher variance at the statistical identical mean. A variance analysis based on the cutting of the distribution edges in the range of 0.5 to 4.0 errors can detect high significantly the steady learning effect of the volunteers during the runs. The method is applicable to determine classified subjective characteristics. The calculations of necessary group numbers for such experiments on the base of binomial distribution are discussed.

[The psychophysics of sweet taste. 7. New determination of sweet taste parameters of acesulfame, aspartame, cyclamate, saccharin, glucose and sorbitol]

By means of a new method (double staircase) concentration pairs of equal intensity for the sweet compounds acesulfame-K, aspartame, cyclamate-Na, saccharine-Na, dextrose and glucitol were determined with sucrose on 6 or 7 equidistant scaled levels, respectively, with 4 repetitions. The parameters maximal intensity Rm, the concentration coefficient b and the mean Rm/b, respectively, are calculated for each substance from the known parameters for sucrose using the exponential function R = Rm(1-e-bS/Rm), which describes the sweetness intensity R in dependence of the concentration S. For exact determination of the maximal intensity the upper concentration level was fixed at very high degree. Additionally, the relative sweetness of each concentration level of each substance is calculated. In all cases the exponential function is valid without limitation. The statistical parameters are homogenous and are laying within the applied staircase method. Systematical deviations could not be found.

[The psychophysics of sweet taste. 6. Context effects by use of multiple stimuli sequences]

For the determination of differentiation probabilities in a multiple experimental design the range of stimuli is a significant source of disturbance. In order to determine their efficiency, sequences with 5 equidistant gradated concentrations of sucrose were used, which were compared with a basic concentration. The probability for each gradation was carried out with help of 2-AFC-technique (60 pairs each). 5 gradations at 3 basic concentrations with fixed, average balance were examined in a factorized experimental design. The frequency of the correct judgments is linearily dependent on the sequence of stimuli. In the experimental space the slope of this relationships decreases with increasing gradation hyperbolically (range-effects). The level of the basic stimuli is in this view without any greater importance. When determining the difference thresholds these context effects are to be considered.

[The psychophysics of sweet taste. 5. The use of a sequential staircase method for the determination of equally intense concentration pairs]

The suitability of a sequential staircase-method for the determination of equal stimuli of the gustatory sense is experimentally investigated. The aim is the decrease of experimental expenditure when ruling sources of bias. In order to realize them sucrose solutions are used both for the constant stimulus and also for the sequence of stimuli. Possible factors are the gradation of the sequence of stimuli and its displacement towards the constant stimulus. These are factorized in a two-staged trial arrangement and are interpreted in a form of an analysis of variance. The gradation of sequence (grain) is the key factor. It defines both the occasional bias and also the efficiency of systematical sources of bias. Thus the subject-depending judgement errors, which occur in larger gradation, are avoidable with their adjustment on the half of the difference threshold. The errors, which are due to the direction, are counterbalanced through an up and down trial execution with a following meaning average. A remaining influence of the displacement of sequence is normally neglective. The standard deviation for the single determination lies--independently of the concentration level--dimensionally slightly above the half of the setting grain. The method of constant stimuli requires at least the twofold experimental expenditure for a similar result.

Relationship between a long-term treatment of 2-mercaptoethanol and protein metabolism in the ageing rat

Female RLEF1/Lati rats were chronically treated with 2-mercaptoethanol in a dose of 13 micrograms.100 g bw-1.day-1 dissolved in drinking water. During a 48-h experiment 15N-labelled glycine was given orally in a dose of 5 mg 15N.kg bw-1 and urine samples were collected and analysed by an emission spectrometric isotope method. Protein synthesis and nitrogen excretion rate constants were calculated according to the three-pool model, and 3-methylhistidine excretion rates were also determined. 2-Mercaptoethanol appears to influence protein metabolism; however, the slower rates of protein synthesis proved to be apparent in almost all groups of treated rats. Protein synthesis and nitrogen excretion rate constants have exceptionally high values in 2-year-old rats, possibly explained by the occurrence of hypercompensation mechanisms in old age. These were reflected by the excretion rates of 3-methylhistidine which were reduced as a result of sulphhydryl group interactions in age-dependent cellular metabolic changes.

Prediction of total body lipid from total body water in rats. Part 1. Relations between directly measured major body components

Aimed to the construction of a prediction equation for estimations of lipid content from animal water content body composition was determined by whole body analysis of male rats (1) given access, ad libitum, to a commercial standard diet (n = 144; ranging from 60 to 600 g in weight, and from the 4th to the 34th week of age), and (2) showing striking variations with regard to nutritional state, dietary history, enlarged fat deposition, genetic origin, intestinal microbial status, and advanced age (n = 75). It was shown that a unique coefficient of water content in lipid-free body mass does not exist. The results of statistical analysis for the grouped values of percentage body dry matter (x) and percentage body lipid (y) indicate that the latter can be estimated accurately from body water content directly determined by the use of the quadratic regression equation y = -0.2864 x +0.01615 x2 with a standard deviation of the procedure Sy = +/- 1.40. This prediction equation is valid for a wide developmental span even under highly different experimental states. Differences between the calculated body lipid contents vs. analytically determined values are smaller than by using a linear regression equation or coefficient(s) of hydration of lipid-free body mass.