Optimal scale translations in noisy measurement systems

In engineering, medicine, biology and agriculture, it is often desired to replace an invasive or slow measurement method, by nondestructive, faster or less expensive methods. The inevitable question is whether the two measurement methods are interchangeable. To answer this question, the common practice is to use linear regression based equations, as scale translation rules. It is shown that this approach is not optimal, when both measurement methods are noisy. Accordingly, a new approach for method comparisons is proposed, by high fidelity translation of the readings taken on the scale of one test, to the scale of another test, and vice versa. The proposed scale translation mode is based on minimizing the sum of squares of the differences between the absolute values of the fast Fourier transform (FFT) series, derived from the readings of the compared measurement methods. Whereas regression methods attempt to find the parameters of a line that provides the best fit to the observed data pairs, the FFT equalization method strives to find the parameters of a line that can render the difference between the translated readings as close to zero as possible. The line taken is illustrated by a comparative study on several artificial datasets of linearly related paired X, Y readings, with various levels of measurement noise. Quality criteria were developed for quantitative comparison of linear regression based, scale translation models versus the new method, while using the results from the artificially generated datasets for illustration. The comparisons indicate that scale translation by the FFT equalization method is optimal in terms of these quality indexes.     

Enhanced red cell sodium-hydrogen exchange in microvascular angina

OBJECTIVES: Enhanced calcium content in arterial smooth muscle cells and altered reactivity of coronary vessels to alkalinization have been reported in angina pectoris due to impaired motility of coronary arteries. An altered function of sodium-hydrogen exchange, a ubiquitous membrane transport system that links proton efflux to calcium drifts, may mediate these phenomena. DESIGN AND SUBJECTS: Twenty patients with microvascular angina (stable effort angina, reversible perfusion defects during effort thallium 201 heart scintigraphy, and angiographically normal coronary arteries) were compared to 20 patients with stable effort angina due to coronary atherosclerosis and 20 healthy subjects. The sodium-hydrogen exchange was defined as the initial fraction of the amiloride-sensitive proton efflux from red cells with inhibited anion exchanger (pHi 6.00-6.05) into an Na(+)-containing medium (pHo 8.00-8.05). 12-0-tetradecanoylphorbol-13-acetate (TPA, 600 nmol.l-1) and staurosporine (100 nmol.l-1) were used as phosphorylation modulators in vitro. RESULTS: The mean red blood cell Na+/H+ exchange was increased in patients with microvascular angina (451 +/- 37 vs 142 +/- 17 and 124 +/- 21 umol H+.1 cells-1.min-1, P < 0.01). TPA and staurosporine abolished differences between the groups. CONCLUSIONS: Microvascular angina is associated with enhanced Na+/H+ exchange in erythrocytes, probably due to more extensive phosphorylation of the membrane antiporter sites.     

Models for the compressibility of layered polymeric sponges

The characteristic sigmoid compressive stress-strain relationships of sponges and their layered arrays are described by two kinds of mathematical models having three experimentally determined parameters. Since sponge compression is not accompanied by a significant cross-sectional area expansion, it was assumed that the stress in a multilayered array is the same in each layer. This enables prediction of the array's stress-strain relationship from the parameters of the individual layers and their known thickness. The applicability of the method is demonstrated with experimental data of two kinds of double-layered arrays of polyurethane sponges. It is shown that the arrays' compressive behavior can be satisfactorily predicted irrespective of the mathematical form of the model and whether the strain is expressed as engineering strain or Hencky's.     

Tailoring texture for the elderly: Theoretical aspects and technological options

The perception of what is known as “texture” is a result of a variety of primarily mechanical and acoustical events. These are sensed by receptors of different kinds that are unevenly distributed in the sensing organ(s) (tongue, jaws, fingers) and neighboring tissues. The perceived intensity of textural properties is time dependent and can be influenced by other stimuli, notably chemical and thermal. The exact mode in which mechanical and geometrical properties are translated into perceived texture is not known. There are, however, known trends based on empirical observations, and growing understanding of the operation of individual receptors and the physiology and biomechanics of the sensation process itself. This body of knowledge can provide rational guidelines” for the development of special products for the elderly and other people with special needs. For example, it is possible to increase fragility and maintain crunchiness or to make chewy foods that require a reduced effort in mastication to minimize fatigue. The technology to make such products is already in place and its future use by the food industry will depend only on marketing opportunities.     

Estimating the Frequency of Future High Microbial Counts in Records with an Actual or Potential Trend or Periodicity

Microbial counts records from 2 food plants, showing irregular fluctuating patterns and an apparent trend or periodicity were converted into a series of ratios, Y_n= N_n/N_n‐1 where N_n is the n^tk count and N_n‐1 its predecessor. The distribution of these ratios was described by the logLaplace and lognormal distribution functions, calculated by the method of moments and maximum likelihood estimation. These distributions were used to estimate the probability that a count will exceed its predecessor by given ratios. The estimates obtained with both distribution functions were in reasonable agreement with the actual values observed in fresh data, indicating that the probability of future events can be estimated from records with or without a trend or periodicity.     

Simulation of E. Coli Inactivation by Carbon Dioxide Under Pressure

ABSTRACT: ; Published isobaric semilogarithmic survival curves of E. coli were fitted with logS(t) = - b(P)t^n(P) where b(P) and n(P) are pressure dependent coefficients. Pressure profiles, P(t), were generated with a double logistic model and the corresponding inactivation rate is only a function of the momentary CO₂ pressure and survival ratio, then dlogS(t)/dt = - b(t)-n(t)-{-logS(t)/b(t)^{[n(t) −1]/n(t)}. This differential equation was solved numerically to produce nonisobaric survival curves, which demonstrated the effects of the pressure level, treatment duration, and the come up time. They also enabled theoretical comparison of processes consisting of single and multiple compression-decompression cycles of equivalent duration     

Nonlinear multiresolution: a shape-from-shading example

A method for image resolution reduction that simulates the reduction of shape resolution and is to be used with shape-from-shading algorithms is presented. Resolution reduction is used for accelerating shape-from-shading algorithms using multiresolution pyramids. The goal of this correspondence is to show that resolution reduction based only on image intensities can be inferior to resolution reduction using knowledge of the surface reflectance. This is true for all cases of parameter estimation from intensity images, when the intensity is not a linear function of the parameters. Since optical reduction of images, as when moving a camera away from the object, is a simple gray-level averaging a question is cast on the general scheme of shape-from-shading. It is concluded that for accurate shape-from-shading one needs to know the distance from the object, and the shape should also be known in advance     

Iterative decoding of space-time differentially coded unitary matrix modulation

Noncoherent communication over the Rayleigh flat fading channel with multiple transmit and receive antennas is investigated. Codes achieving bit error rate (BER) lower than 10/sup -4/ at bit energy over the noise spectral density ratio (E/sub b//N/sub 0/) of 0.8 to 2.8 dB from the capacity limit were found with coding rates of 0.5 to 2.25 bits per channel use. The codes are serial concatenation of a turbo code and a unitary matrix differential modulation code. The receiver is based on a high-performance joint iterative decoding of the turbo code and the modulation code. Information-theoretic arguments are harnessed to form guidelines for code design and to evaluate performance of the iterative decoder.     

Mercury depletion events in the troposphere in mid-latitudes at the Dead Sea, Israel

The occurrence of mercury depletion events (MDE) in the Polar Regions during the spring periods has raised global concern due to the biomagnifications of the deposited mercury into the aquatic food chain. However, it now appears that MDE is not limited to the Polar Regions and can also occur at mid-latitudes. Diurnal cycles of mercury, ozone, and BrO behavior based on short-time resolution measurements are presented for the Dead Sea, Israel, for Summer 2006. The results show that mercury depletion events occur almost daily, accompanied always by the presence of BrO and concurrent ozone destruction. The intensity of the MDE corresponded to increasing BrO levels. Mercury depletions of more than 40% were observed when BrO levels rose above 60-70 ppt. Based on the present measurements and supported bytheoretical considerations, it appears that BrOx (BrO + Br) is the primary species responsible for the mercury depletion at the Dead Sea. The present study also suggests, especially at low ozone levels, that the Br atom may play a major role in conversion of the gaseous elemental mercury to the reactive species, HgBr2. The implications of the present study are that even at low BrO levels (<10 ppt), mercury depletion may well occur at other mid-latitude sites and thus needs to be taken into consideration in the global mercury cycle.