Threshold Phenomena in Nonlinear Currents Upon Metallization of Si(001)

1992 ◽  
Author(s):  
S. Arekat ◽  
S. D. Kevan ◽  
G. L. Richmond
Keyword(s):  
Threshold Phenomena

scholarly journals Wetting front dynamics in an isotropic porous medium

2012 ◽  
Vol 694 ◽  
pp. 399-407 ◽  
Author(s):  
Yulii D. Shikhmurzaev ◽  
James E. Sprittles
Keyword(s):  
Porous Medium ◽  
Incompressible Liquid ◽  
Porous Matrix ◽  
Viscous Incompressible Liquid ◽  
Pore Scale ◽  
Wetting Front ◽  
Model Case ◽  
New Approach ◽  
Threshold Phenomena ◽  
Front Dynamics

AbstractA new approach to the modelling of wetting fronts in porous media on the Darcy scale is developed, based on considering the types (modes) of motion the menisci go through on the pore scale. This approach is illustrated using a simple model case of imbibition of a viscous incompressible liquid into an isotropic porous matrix with two modes of motion for the menisci, the wetting mode and the threshold mode. The latter makes it necessary to introduce an essentially new technique of conjugate problems that allows one to link threshold phenomena on the pore scale with the motion on the Darcy scale. The developed approach (a) makes room for incorporating the actual physics of wetting on the pore scale, (b) brings in the physics associated with pore-scale thresholds, which determine when sections of the wetting front will be brought to a halt (pinned), and, importantly, (c) provides a regular framework for constructing models of increasing complexity.

scholarly journals Devising a development test of auditory perception: Problems and prospects

1971 ◽  
Vol 18 (1) ◽  
Author(s):  
Arnold Abramovitz
Keyword(s):  
Hearing Aids ◽  
Emotionally Disturbed ◽  
Auditory Perception ◽  
Speech Sound ◽  
Pattern Discrimination ◽  
Auditory Training ◽  
Environmental Sounds ◽  
Threshold Phenomena ◽  
Sound Discrimination ◽  
Hearing Children

It is certain that many children whose auditory perception is queried by audiologists, speech therapists, educationists and psychologists elude the diagnostic screens presently available in each of these disciplines. The need for a qualitative and quantitative psychological assessment of the child's auditory abilities and disabilities led to the development of a test which was intended to evaluate the following functions:(a) Recognition of environmental sounds, (b) Auditory figure-ground discrimination, (c) Speech-sound discrimination (phonemic and intonational) and (d) Tonal pattern discrimination (pitch, loudness, duration and interval). It was not intended to investigate threshold phenomena as such but rather to supplement and complement pure-tone and speech audiometry. The test was applied to 205 children, aged five to ten years, drawn from a normal school population, and 232 children with difficulties and handicaps varying both in degree and kind. Only the first two sub-tests were found to be clinically and experimentally viable, and data for the curtailed test are presented. The following results are noteworthy: (1) The test measures functions which are positively related to both age and intelligence. (2) Brain-injured, retarded and emotionally disturbed children generally test low on auditory figure-ground discrimination; this vulnerability is most likely due to perseveration. (3) Previously unsuspected peripheral hearing losses may sometimes be detected by the use of the test. On the other hand, some children said to have high degrees of hearing loss test at or above their age-level. (4) Many deaf and hard-of-hearing children test higher without their hearing-aids; this is probably due to amplification being achieved at the cost of distortion. (5) Children of average intelligence with reading and/or spelling difficulties often test low on auditory figure-ground discrimination. (6) Blind children who have received auditory training are equal to sighted children in recognition of environmental sounds, but superior in auditory figure-ground discrimination. This does not, however, necessarily signify superior auditory perception as such on the part of the blind. In general it is concluded that the development of tests of auditory perception could add significantly to the psycho-educational assessment of both "normal" and handicapped children.

scholarly journals Blind love, Romanticism, and Rousseauʼs novel Julie ou La Nouvelle Héloïse

2018 ◽  
Vol 7 ◽  
pp. 305-350
Author(s):  
Alexandra Schamel
Keyword(s):  
Eighteenth Century ◽  
Epistolary Novel ◽  
Threshold Phenomena ◽  
Rhetorical Dimension

The article examines to what extent Rousseau’s epistolary novel Julie ou la Nouvelle Héloïse modifies the visual paradigm of eighteenth-century anthropology, as seen in Rousseau’s ideology of substantial nature, by introducing dynamics which produce obscurité, an unattainable dimension of inwardness. The argument leads to the proposal that the subject’s strategies of hiding, masking and transforming its epistemological darkness in the penetrating regime of virtue create central aspects of the romantic mind. The term obscurité is illustrated as a dynamic of semantic “desubstantialisation” originated from the love-wound which permanently requires the supplément (Coelen, Derrida). The need for subordination under Wolmar’s “omniscient eye” effects a process of sublimation, in which the obscure semantics of love are transferred into legitimate areas of ontological diffusion, such as dreams, memories, wistfulness and even sacrifying death, the very precursors of romanticism. Respective examples, set in the context of romantic painting, illustrate how Rousseau constructs these threshold phenomena as semantic (and specter-like) substitutes for the love affect which is also more and more transmitted into the rhetorical dimension of the letters.

Threshold Phenomena and Influence: Perspectives from Mathematics, Computer Science, and Economics

2005 ◽  
Author(s):  
Gil Kalai ◽  
Shmuel Safra
Keyword(s):  
Computer Science ◽  
Political Science ◽  
Monotone Function ◽  
Majority Voting ◽  
Simple Majority ◽  
Condorcet’S Jury Theorem ◽  
Threshold Phenomenon ◽  
Threshold Phenomena ◽  
Aggregation Of Information ◽  
Jury Theorem

Threshold phenomena refer to settings in which the probability for an event to occur changes rapidly as some underlying parameter varies. Threshold phenomena play an important role in probability theory and statistics, physics, and computer science, and are related to issues studied in economics and political science. Quite a few questions that come up naturally in those fields translate to proving that some event indeed exhibits a threshold phenomenon, and then finding the location of the transition and how rapid the change is. The notions of sharp thresholds and phase transitions originated in physics, and many of the mathematical ideas for their study came from mathematical physics. In this chapter, however, we will mainly discuss connections to other fields. A simple yet illuminating example that demonstrates the sharp threshold phenomenon is Condorcet's jury theorem, which can be described as follows. Say one is running an election process, where the results are determined by simple majority, between two candidates, Alice and Bob. If every voter votes for Alice with probability p > 1/2 and for Bob with probability 1 — p, and if the probabilities for each voter to vote either way are independent of the other votes, then as the number of voters tends to infinity the probability of Alice getting elected tends to 1. The probability of Alice getting elected is a monotone function of p, and when there are many voters it rapidly changes from being very close to 0 when p < 1/2 to being very close to 1 when p > 1/2. The reason usually given for the interest of Condorcet's jury theorem to economics and political science [535] is that it can be interpreted as saying that even if agents receive very poor (yet independent) signals, indicating which of two choices is correct, majority voting nevertheless results in the correct decision being taken with high probability, as long as there are enough agents, and the agents vote according to their signal. This is referred to in economics as asymptotically complete aggregation of information.

Influences and Threshold Phenomena

2013 ◽  
pp. 262-287
Author(s):  
Stéphane Boucheron ◽  
Gábor Lugosi ◽  
Pascal Massart
Keyword(s):  
Threshold Phenomena

Patterns in the Submerged Macrophyte Biomass of Lakes and the Importance of the Scale of Analysis in the Interpretation

1990 ◽  
Vol 47 (2) ◽  
pp. 357-363 ◽  
Author(s):  
Carlos M. Duarte ◽  
Jacob Kalff
Keyword(s):  
Plant Biomass ◽  
Phosphorus Concentration ◽  
Total Phosphorus Concentration ◽  
Site Specific ◽  
Light Levels ◽  
Threshold Phenomena ◽  
Site Characteristics ◽  
Specific Biomass ◽  
Regulation Mechanisms ◽  
Lake Characteristics

The relative contributions of lake characteristics (i.e. alkalinity, chlorophyll A concentration, total phosphorus concentration, conductivity, and morphometry) and site characteristics (i.e. depth, littoral slope, exposure to waves, and underwater light levels) to the variability in submerged biomass were examined in 25 Canadian and American lakes. Lake-average submerged biomass is a function of water alkalinity and the lake-average littoral slope whereas site-specific biomass is a function of both site and lake characteristics. Plant biomass decreased with increasing slope and wave exposure and increased with increasing alkalinity and light levels. However, these relationships are complex because submerged biomass is also influenced by threshold phenomena (e.g. critical littoral slopes and transparency-dependent critical depths) that set limits to macrophyte colonization and because the relative contributions of the most relevant environmental factors studied (i.e. littoral slope, exposure, water transparency, and alkalinity) are depth dependent. By demonstrating the importance of lake-average and site-specific scales of variation and the existence of noncontinuous (e.g. threshold) regulation mechanisms the findings provide a new conceptual framework for the study of the relationship between submerged macrophytes, and their associated biota as well as their environment.

scholarly journals STATE-DEPENDENT DELAYS ASSOCIATED TO THRESHOLD PHENOMENA IN STRUCTURED POPULATION DYNAMICS

2007 ◽  
Vol 17 (06) ◽  
pp. 877-900 ◽  
Author(s):  
MY LHASSAN HBID ◽  
EVA SÁNCHEZ ◽  
RAFAEL BRAVO DE LA PARRA
Keyword(s):  
Population Dynamics ◽  
Unified Approach ◽  
Structured Population ◽  
Threshold Phenomena ◽  
State Dependent ◽  
Characteristic Lines ◽  
Structured Population Dynamics ◽  
Insect Populations ◽  
The Common ◽  
Age Structured

The aim of this paper is to put in evidence the onset of state-dependent delays in threshold models for structured population dynamics. A unified approach to these models is provided, based on solving the corresponding balance law (hyperbolic P.D.E.) along the characteristic lines and showing the common underlying ideas. Size and age-structured models in different fields are presented: insect populations, cell proliferation and epidemics.

Plateau Potentials in Developing Antennal-Lobe Neurons of the Moth, Manduca sexta

2005 ◽  
Vol 93 (4) ◽  
pp. 1949-1958 ◽  
Author(s):  
A. R. Mercer ◽  
P. Kloppenburg ◽  
J. G. Hildebrand
Keyword(s):  
Electrical Activity ◽  
Manduca Sexta ◽  
Antennal Lobe ◽  
Membrane Properties ◽  
Plateau Potentials ◽  
Extracellular Medium ◽  
Threshold Phenomena ◽  
Plateau State ◽  
Developing Neurons

Using whole cell recordings from antennal-lobe (AL) neurons in vitro and in situ, in semi-intact brain preparations, we examined membrane properties that contribute to electrical activity exhibited by developing neurons in primary olfactory centers of the brain of the sphinx moth, Manduca sexta. This activity is characterized by prolonged periods of membrane depolarization that resemble plateau potentials. The presence of plateau potential–generating mechanisms was confirmed using a series of tests established earlier. Brief depolarizing current pulses could be used to trigger a plateau state. Once triggered, plateau potentials could be terminated by brief pulses of hyperpolarizing current. Both triggering and terminating of firing states were threshold phenomena, and both conditions resulted in all-or-none responses. Rebound excitation from prolonged hyperpolarizing pulses could also be used to generate plateau potentials in some cells. These neurons were found to express a hyperpolarization-activated inward current. Neither the generation nor the maintenance of plateau potentials was affected by removal of Na+ ions from the extracellular medium or by blockade of Na+ currents with TTX. However, blocking of Ca2+ currents with Cd2+ (5 × 10−4 M) inhibited the generation of plateau potentials, indicating that, in Manduca AL neurons, plateau potentials depend on Ca2+. Examining Ca2+ currents in isolation revealed that activation of these currents occurs in the absence of experimentally applied depolarizing stimuli. Our results suggest that this activity underlies the generation of plateau potentials and characteristic bursts of electrical activity in developing AL neurons of M. sexta.

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