Steven's Law Research Articles

Human capability in the perception of extensional and shear viscosity

Shear and extensional deformation are two basic rheological properties which occur during food manipulation, mastication, deglutition executed during oral consumption and also in the processing and packaging of foods. Fluid resistance against shear and extensional deformation differ widely and whilst this has been confirmed theoretically and experimentally, a clear understanding of human perception of these properties will have beneficial returns to the food industry in designing and manufacturing of high quality, nutritious food to suit consumers' need (Laguna, Aktar, Ettelaie, Holmes, & Chen, 2016).

Dynamic range in the C. elegans brain network.

We study external electrical perturbations and their responses in the brain dynamic network of the Caenorhabditis elegans soil worm, given by the connectome of its large somatic nervous system. Our analysis is inspired by a realistic experiment where one stimulates externally specific parts of the brain and studies the persistent neural activity triggered in other cortical regions. In this work, we perturb groups of neurons that form communities, identified by the walktrap community detection method, by trains of stereotypical electrical Poissonian impulses and study the propagation of neural activity to other communities by measuring the corresponding dynamic ranges and Steven law exponents. We show that when one perturbs specific communities, keeping the rest unperturbed, the external stimulations are able to propagate to some of them but not to all. There are also perturbations that do not trigger any response. We found that this depends on the initially perturbed community. Finally, we relate our findings for the former cases with low neural synchronization, self-criticality, and large information flow capacity, and interpret them as the ability of the brain network to respond to external perturbations when it works at criticality and its information flow capacity becomes maximal.

Chemical reduction of odour in fresh sewage sludge in the presence of ferric hydroxide

To assess the potential of ferric hydroxide (FH) to reduce odour emission from dewatered sewage sludge with a moisture of approximately 86%, odour reduction was evaluated using an electronic nose and measurements of odorous compounds (hydrogen sulphide, ammonia and volatile fatty acids (VFAs)). The sulphur species including sulphate, acid-volatile sulphide (AVS), Cr(II)-reducible sulphide (CRS) and elemental sulphur (ES), were analysed by a modified cold diffusion sequential extraction method before and after anaerobic incubation. Within 32 days, 69.3, 83.8 and 88.6% of the odour (or 81.3, 93.7 and 97.5% of hydrogen sulphide) were eliminated, respectively, at the rates of 0.05, 0.10 and 0.25% (wt) of FH. The sulphur species analysis indicated that FeS, FeS2 and a small portion of S0 were formed by FH-sulphide reaction. This study also found that the relationship between odour and H2S concentrations could be well expressed by Steven's law. We believe that FH can be a cost-effective reagent for sludge odour control in sewage treatment processes.

Psychophysical estimation of acid intensity and determination of sweet-acid interaction in a fish paste containing glycerol

In a fish paste made with cooked Brazilian flathead (Percophis brasiliensis), glycerol (17%), sodium chloride (1.5%) and potassium sorbate (0.1%) the following acid percentages: 0.2; 0.4; 0.6; 0.8, 1 and 1.5% w/w were incorporated to determine the relationship between added acetic acid and the sensorially perceived intensity, and the effects of the combination of sweet-acid tastes. Tests for paired comparison, ranking and structured verbal scales for sweet and acid attributes and psychophysical test were carried out. There was a perceptible difference among samples for differences of 0.4 units of acid concentration. Samples indicated as sweeter by 89.47% of the judges were those containing a lesser acid concentration. A reduction in glycerol sweetness when increasing acid levels was observed. Acetic acid reduced the sweetness of glycerol and inversely glycerol reduced the acidity of acetic acid. The data obtained with the magnitude estimation test agree with Steven's law.

P‐42: Understanding Gamma Correction for High Dynamic Range Displays

AbstractGamma correction is required for a display to have linear gray scale. The standard gamma correction should be replaced by the DICOM gray scale function for a correction that extends over a larger dynamic range The DICOM correction is consistent with a Modified Steven's law.

Odor Determination at Wastewater Collection Systems: Olfactometry versus H2S Analyses

AbstractH2S is usually the main indicator parameter to assess when nuisance odors arise in wastewater handling systems. However, sampling and measurement of H2S need to be made with utmost care and analytical methods are neither easy nor cheap. Although Jerome meters from Arizona Instruments are used in some parts of the world, the cost and difficulty of measuring H2S in odorous gases is a general problem. It should also be kept in mind that a simple linear relationship between H2S concentrations and odor perception by the public is not available, especially in complex odorous gas mixtures. This leads to the conclusion that measuring the H2S alone is neither easy nor accurate in describing and resolving public complaints due to odors from wastewater collection and treatment systems. In this study, data for odors and H2S measurements from two pumping stations of the wastewater collection system of Çesme, Izmir, Turkey are evaluated. Concentrations of H2S were measured with chemical methods. Results indicated concentrations several orders of magnitude above the odor threshold level, which is generally accepted as 0.1 μg/m3 for pure H2S in air. The statistical relationships between analytical and sensory odor data were established. Correlations indicated power law relationships between odor and H2S concentrations (R2 between 0.88–0.92). Steven's law between the intensity of human perception and concentration of stimulants is obeyed.

Relationships between Odorant Concentration and Aroma Intensity

Aroma intensity of 5 concentrations (0.5, 2.5, 12.5, 62.5, and 312.5 ppm) of dimethyl trisulfide, methional [3-(methylthio) propionaldehyde], linalool (3,7-dimethyl-1, 6-octadien-3-ol), and vanillin (4-hydroxy-3-methoxybenzaldehyde) were evaluated by using sensory panels (n= 15) and gas chromatography olfactometry (GCO, n= 3) coupled with the Osme technique. The exponent (n) from Steven's Power Law was calculated as the slope of the logarithmic scale of perceived intensity versus compound concentration. Both sensory analysis and GCO data demonstrated that all odorants of interest followed Steven's Power Law (R2= 0.92 to 0.99). The relationship between concentration and aroma intensity was more completely explained by Steven's Law than by dilution methods. Results also revealed that GCO-Osme is a time-saving method that provides valuable information about odorants in foods. This method may also be used with other GCO techniques such as combined hedonic aroma response measurement (CHARM) and aroma extraction dilution analysis (AEDA) to more completely explain the contribution of compounds to the flavor of food products.

Quantitative prediction of overall seat discomfort

Static seat characteristics (seat stiffness) and dynamic seat characteristics (vibration magnitude) can both influence judgements of seat comfort. It is proposed that seat comfort can be predicted on the basis of Steven's psychophysical law: ψ = kϕn , where ψ is a sensation magnitude, ϕ is the stimulus magnitude and k is a constant. The law is modified to: ψ = a + bϕns s + cϕnv v, where ϕ s ϕ v represent seat stiffness and vibration magnitude, n s and n v are exponents determined by the rate of increase in discomfort associated with the stiffness and vibration magnitude, and a, b and c are constants. The stiffness of foam loaded to 490 N may indicate static seat comfort, while the vibration dose value (VDV) on the seat surface may indicate vibration discomfort. Two experiments with 20 subjects investigated this approach. The first experiment with five magnitudes of vibration, three foams and a rigid wooden flat seat yielded 0.929 for the exponent, n v, for VDV. In the second experiment subjects judged the overall seat discomfort while exposed six vibration magnitudes with the same four seating conditions. This experiment yielded 1.18 for the exponent, n s, for seat stiffness. The overall prediction of seat discomfort was given by: ψ = -50.3+ 2.68 ϕ s 1.18+ 101 ϕ v 0.929. The prediction equation provided more accurate estimates of subject discomfort than models using either the VDV alone or the stiffness alone, especially when the vibration magnitude was low or the seats were similar. An interaction variable between the VDV and the stiffness slightly improved the prediction. The equivalence of the two stimuli was given by log10 (stiffness) = 0.787 log10 (VDV)+ 1.34, or log10 (VDV) = 1.27 log10 (stiffness)− 1.70.

Sensory optimization of a powdered chocolate milk formula

Four experiments were carried out to optimize the formulation of a powdered chocolate milk. The first of these compared facial vs. verbal-numeric self-administered scales when measuring sensory acceptability of different attributes among 11-year-old children. Both scales were equivalent. In a second experiment, magnitude estimation was performed to analyze sensory viscosity as a function of gum concentration, and chocolate flavor as a function of cocoa concentration. Steven's Law exponents were: 0.37 for viscosity and 0.78 for chocolate flavor. Third, by using a minimum bias method, the optimum level of sugar concentration resulted in 5.0% for adults and 6.0% for children. In the fourth experiment gum and cocoa concentration were optimized using response surface methodology. Based on Steven's Law exponents, levels were varied geometrically. Contour plots for appearance, texture, flavor and overall preference are presented for children and adults. No unique formula would satisfy both age groups for all attributes.

Lipid microresistor as mimicking olfactory sensor: the rule of the response of lipids to C 1–C 4 alcohols

Phosphatidylcholine (PC) and six other PC-similar lipids are coated on interdigital electrodes, IEs, as sensitive membranes. Eight alcohols (C 1–C 4) are tested in a flow system at room temperature. It is found that all responses are log(response)-log(concentration) linear relations. These results agree with Steven's law in psychophysics. Moreover, the thresholds of the sensors are coincident with human olfactory thresholds. The authors have analysed the data of the lipid hypothesis suggested by Kurihara et al. We have found that this hypothesis is also in agreement with Steven's law. Lipid microresistors are real mimicking olfactory sensors. A definition of an olfactory sensor is suggested.

Sensory and Objective Measurement of Sandiness in Dulce de Leche, a Typical Argentine Dairy Product

Lactose crystallization in Dulce de Leche can produce a sandiness defect. The objective measurement and sensory evaluation of this defect were the thrusts of this study. The technique for the microscopic measurement of the number and size of crystals is described in detail. Sensory panel members found that lactose crystals added to Dulce de Leche produced a sandiness defect equivalent to added sand crystals. The latter are far easier to define by size so they were used for magnitude estimation, where the exponent of Steven's law was approximately 1. Based on this, seven-point a sensory scale for sandiness was developed using Dulce de Leche mixed with sand of crystal sizes varying between 0 and 1500 µm. A double entry table is presented whereby the sensory sandiness threshold can be read as a function of size and number of crystals. With crystal size below 6 µm sandiness is not detected, even if all lactose in Dulce de Leche is crystallized. Above this size, the detection threshold depends on number of crystals.

Anxiety Disorder and Perception of Inspiratory Resistive Loads

Sensations of breathlessness in the absence of respiratory disease are common in anxiety disorders. Perceptions of breathlessness in eight patients with anxiety disorder were compared with eight normal control subjects, matched for age and sex, by the application of Steven's law to the magnitude of resistive load test. All subjects estimated the magnitudes of resistive loads to inspiration while peak inspiratory mouth pressures were monitored. Anxious patients' perceptions of the added loads were significantly less sensitive than normal, even though the effort, determined by peak inspiratory mouth pressure, in overcoming each load was normal. Correlations between estimates of resistive loads and peak inspiratory mouth pressure were significantly less for the anxious patients than for normal subjects. Thus, perception of breathlessness in anxiety disorders may be affected by factors not normally associated with breathlessness and may help account for the greater than normal variability in resistive load perception in respiratory disease.

Inspiratory and expiratory resistive loading as a model of dyspnea in asthma.

20 ambulatory asthmatics were questioned regarding their perception of the dyspnea of acute asthmatic attacks; in particular, its relationship to the phase of respiration. 19 (95%) stated that inspiration was more difficult than expiration although 5 (25%) reported that they had been taught that the reverse was 'correct'. In order to explore further these observations, we applied psychophysical methods to determine the phase relationship of the conscious perception of resistive loads in healthy volunteers. 14 subjects of similar age and sex distribution to the asthmatics estimated numerically the magnitude of resistive loads applied in random sequence to either the inspiratory or expiratory arm of a low-resistance breathing circuit. The relationship between perceived magnitude (psi) and physical magnitude (phi) was described by Steven's law: psi = k phi n, where k and n are constants. The mean exponent (n) for inspiratory resistances was 0.69 +/- 0.28 (+/- SD) and for expiratory resistances was 0.51 +/- 0.27 (p less than 0.01 by two-tailed, paired t test). There was a positive correlation (r = 0.82) between inspiratory and expiratory exponents within individuals. In 12 of 14 subjects, the perceived magnitude of inspiratory loads was greater than the perceived magnitude of expiratory loads for all resistances greater than 10 cm H2O/l/s. At a load of 25 cm H2O/l/s, the inspiratory sensation of load exceeded the expiratory sensation in all subjects. Our findings that normal subjects scaled greater breathlessness with inspiratory versus expiratory flow resistive loads were consistent with the clinical observation that inspiratory, rather than expiratory difficulty contributed more to the dyspnea of asthma.

The qunatification of respiratory sensations by normal subjects

The technique of open magnitude scaling was used in normal subjects to define the exponent (n) of Stevens' psychophysical power law for four respiratory variables: tidal volume ( Vt), inspiratory flow (V̇), ventilation ( V̇e), and frequency (f). Steven's psychophysical law states that the perceived magnitude (ψ) of a stimulus is related to the physical magnitude (φ) by a constant (k) and an exponent (n): ψ = k φ n. The mean value of n was for Vt 1.14 ± 0.08 ( SEM), for V ̇ 1.13 ± 0.15 for V ̇ e 1.28 ± 0.11 and for f 1.04 ± 0.15 . There results show that these respiratory variables are judged with an expanded sensory scale. The similarity of exponents for Vt and V̇ leaves open the possibility that both are sensed by the same neurophysiological mechanisms. Further experiments on Vt showed that both passive ventilation and chest vibration impaired the ability of subjects to accurately judge tidal volumes. Our results indicate that the sensation of volume is mediated by afferent information generated by receptors affected by respiratory muscle contraction.

Effect of aging on respiratory sensations produced by elastic loads.

We compared the effects of graded elastic loads on respiratory sensations in 19 healthy subjects greater than 60 yr of age to 21 healthy subjects less than 30 yr old. The magnitude of the respiratory sensation was quantitated by two well-established psychophysical techniques. In the magnitude-estimation method, subjects indicated the intensity of the sensation experienced with numbers; in the cross-modality method, the level of sensation was signaled with a dynamometer activated by thumb pressure. In addition, the effects of nonrespiratory stimuli were compared in the two groups. With both methods, the logarithm of the response to elastic loads was linearly related to the logarithms of the stimulus. The slope of the line relating the log of the response to the log of the stimulus (beta) was significantly greater in the younger group than in the older group using the magnitude-estimation method but not with the cross-modality matching test. There were no differences in the ability of the two groups to assign numbers to line length. However, the older group had a lower beta for magnitude estimation of thumb force than the younger group. The results suggest 1) that respiratory sensation follows Steven's law and grows exponentially with the stimulus; 2) that the growth of sensations produced by elastic loading is less in older than in younger individuals; and 3) differences in the perception of the mode used for matching in the cross-modality test may obscure significant differences in the sensations elicited by respiratory stimuli.

Amplitude des potentielsévoqués moyens auditifs du vertex et intensitédes stimuli

Summary Relations between amplitude of averaged evoked potentials recorded on the human vertex and intensity of acoustic stimuli are established through a statistical approach. The hypothesis of a linear relation of a similar relation to Steven's law established for loudness must be discarded. A somewhat different logarithmic relation appears more suitable. Thus acoustically evoked potentials of the human vertex do not strictly follow the same law as the specific cortical responses of animals nor as the stimulus intensity. But in practice differences are restricted to weak stimuli only. For most intensities, amplitude of averaged potentials of the vertex may be considered to be linearly related to loudness as long as data are collected through an experimental plan including repetitions and subjects, and cancelling other factors.