On the physical explanation of the Perkins instability

2006 ◽  
Vol 111 (A12) ◽  
Author(s):  
Qina Zhou ◽  
John D. Mathews
Keyword(s):  
Physical Explanation ◽  
Perkins Instability

The Metabolic Theory of Ecology

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Metabolic Rate ◽  
Resting Metabolic Rate ◽  
Effect Of Temperature ◽  
Thermal Ecology ◽  
Model Data ◽  
Metabolic Theory ◽  
Physical Explanation ◽  
Boltzmann Factor ◽  
Scaling Exponents ◽  
Metabolic Theory Of Ecology

The model of West, Brown & Enquist (WBE) is built on the assumption that the metabolic rate of cells is determined by the architecture of the vascular network that supplies them with oxygen and nutrients. For a fractal-like network, and assuming that evolution has minimised cardiovascular costs, the WBE model predicts that s=metabolism should scale with mass with an exponent, b, of 0.75 at infinite size, and ~ 0.8 at realistic larger sizes. Scaling exponents ~ 0.75 for standard or resting metabolic rate are observed widely, but far from universally, including in some invertebrates with cardiovascular systems very different from that assumed in the WBE model. Data for field metabolic rate in vertebrates typically exhibit b ~ 0.8, which matches the WBE prediction. Addition of a simple Boltzmann factor to capture the effects of body temperature on metabolic rate yields the central equation of the Metabolic Theory of Ecology (MTE). The MTE has become an important strand in ecology, and the WBE model is the most widely accepted physical explanation for the scaling of metabolic rate with body mass. Capturing the effect of temperature through a Boltzmann factor is a useful statistical description but too simple to qualify as a complete physical theory of thermal ecology.

scholarly journals Visual Appearance of Oil on the Sea

2021 ◽  
Vol 9 (1) ◽  
pp. 97
Author(s):  
Merv Fingas
Keyword(s):  
Water Surface ◽  
Oil Spills ◽  
Discharge Rate ◽  
Physical Explanation ◽  
Visual Appearance ◽  
Oil In Water ◽  
Other Information ◽  
Surface Discharges ◽  
Oil Emulsions ◽  
Spilled Oil

The visual appearance of oil spills at sea is often used as an indicator of spilled oil properties, state and slick thickness. These appearances and the oil properties that are associated with them are reviewed in this paper. The appearance of oil spills is an estimator of thickness of thin oil slicks, thinner than a rainbow sheen (<3 µm). Rainbow sheens have a strong physical explanation. Thicker oil slicks (e.g., >3 µm) are not correlated with a given oil appearance. At one time, the appearance of surface discharges from ships was thought to be correlated with discharge rate and vessel speed; however, this approach is now known to be incorrect. Oil on the sea can sometimes form water-in-oil emulsions, dependent on the properties of the oil, and these are often reddish in color. These can be detected visually, providing useful information on the state of the oil. Oil-in-water emulsions can be seen as a coffee-colored cloud below the water surface. Other information gleaned from the oil appearance includes coverage and distribution on the surface.

scholarly journals Illness perceptions of youths with functional disorders and their parents: An interpretative phenomenological analysis study

2019 ◽  
Vol 25 (1) ◽  
pp. 45-61 ◽  
Author(s):  
Ditte Roth Hulgaard ◽  
Charlotte Ulrikka Rask ◽  
Mette Bech Risor ◽  
Gitte Dehlholm
Keyword(s):  
Interpretative Phenomenological Analysis ◽  
Illness Perceptions ◽  
Psychiatric Treatment ◽  
Psychological Symptom ◽  
Qualitative Interview ◽  
Healthcare Services ◽  
Functional Disorders ◽  
Physical Explanation ◽  
Qualitative Interview Study ◽  
Significant Burden

Background:Functional disorders, defined as disorders with no clear medical explanation, are common and impose a significant burden on youths, their families, healthcare services and society as a whole. Currently, the literature describes resistance among patients and their families towards psychological symptom explanations and treatments. More knowledge about the thoughts and understandings of youths with functional disorders and their parents is needed. The aim of this study was to explore the illness perceptions of youths with severe functional disorders and their parents.Methods:A qualitative interview study using interpretative phenomenological analyses. The study included 11 youths aged 11–15 years with functional disorders and their parents, where interviews were performed at the point of referral from a somatic to a psychiatric treatment setting.Results:Analyses identified three main themes. Themes 1(Ascribing identity to the disorder) and 2 (Monocausal explanations) explore key elements of the participants’ illness perceptions, and theme 3 (Mutable illness perceptions) explores how illness perceptions are influenced by experiences from healthcare encounters.Conclusions:The label ‘functional disorder’ was poorly integrated in the illness perceptions of the youths and their parents. Participants used a monocausal and typically physical explanation rather than a multicausal biopsychosocial explanation for their symptoms.

Fire-Walking: Physical explanation

1914 ◽  
Vol s11-IX (217) ◽  
pp. 152-152
Author(s):  
Tom Jones
Keyword(s):  
Physical Explanation

Size distributions of sea-source aerosol particles: A physical explanation of observed nearshore versus open-sea differences

1987 ◽  
Vol 92 (D12) ◽  
pp. 14850 ◽  
Author(s):  
H. Sievering ◽  
J. Boatman ◽  
L. Gunter ◽  
H. Horvath ◽  
D. Wellman ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Size Distributions ◽  
Physical Explanation ◽  
Open Sea

Johann Kiessling, the Krakatoa event and the development of atmosheric optics after 1883

2000 ◽  
Vol 54 (2) ◽  
pp. 249-258 ◽  
Author(s):  
W. Schröder ◽  
K-. H. Wiederkehr
Keyword(s):  
Nuclear Physics ◽  
Cloud Chamber ◽  
Physical Explanation ◽  
Dust Clouds

Johann Kiessling studied the sensational twilights that followed the eruption of Krakatoa (1883) and looked for their physical explanation. He believed that the cause of the extraordinary optical appearances essentially lay in diffraction through particles in the condensation and dust clouds which, following the eruption of the volcano, reached high strata in the atmosphere and travelled around the globe. Research concerning the generation of fog in the atmosphere was greatly forwarded by Kiessling's ideas and experiments. The studies of C.T.R. Wilson, F.R.S., which led to the construction of his cloud chamber and its use in nuclear physics, were strongly influenced by Kiessling's work.

Anomalous electron absorption effects in metal foils: theory and comparison with experiment

1962 ◽  
Vol 269 (1336) ◽  
pp. 80-103 ◽  
Keyword(s):  
Fourier Coefficients ◽  
Stacking Faults ◽  
Formal Theory ◽  
Dynamical Theory ◽  
Anomalous Absorption ◽  
Physical Explanation ◽  
Absorption Effect ◽  
Metal Foils ◽  
Comparison With Experiment ◽  
Transmission Electron

The two-beam dynamical theory of electron diffraction in absorbing crystals has been applied to explain features of bend and thickness extinction contours and of images of stacking faults observed on transmission electron micrographs of metal foils. Inelastic scattering processes affect the intensities of the elastically scattered waves and give rise to 4 anomalous ’ transmission (Borrmann) effects. The formal theory takes account of these effects phenomenologically by the use of a complex lattice potential but ignores the contribution of the inelastically scattered electrons to the image. In the theory absorption is described by certain parameters ξ' 0 and ξ' g with dimensions of length. These parameters are determined by Fourier coefficients of the imaginary part of the potential in the same manner as the extinction distance ξ g is determined by the Fourier coefficient of the real part. A simple physical explanation of the ‘anomalous’ absorption effect is developed in terms of the two crystal wave fields. This explanation is particularly helpful in understanding details of bend and thickness contours and of images of stacking faults. The theory is at present phenomenological because the detailed mechanism of the absorption process is not understood. Nevertheless, comparison of the theory with observations enables the absorption parameters to be roughly estimated.

Quasi-periodic occurrence of earthquakes in the 1978-1986 Bishop-Mammoth Lakes sequence, eastern California

1987 ◽  
Vol 77 (4) ◽  
pp. 1347-1358
Author(s):  
J. C. Savage ◽  
Robert S. Cockerham
Keyword(s):  
Standard Deviation ◽  
Confidence Interval ◽  
Convincing Evidence ◽  
Data Selection ◽  
Individual Event ◽  
Physical Explanation ◽  
Interevent Interval ◽  
Prior Event ◽  
Important Activity ◽  
Mammoth Lakes

Abstract In December 1984, Ryall and Hill noted that the five principal events in the Bishop-Mammoth Lakes earthquake sequence occurred at intervals of about 1.5 yr with a standard deviation for an individual event of 0.25 yr. Some data selection was involved in identifying the principal events, although the choices seemed reasonable. The recent Chalfant Valley earthquake (ML = 6.4; 21 July 1986) followed the last prior principal event in the Bishop-Mammoth Lakes sequence by 1.65 yr, and no important activity intervened except one aftershock from the prior event. Thus, the Chalfant Valley earthquake could have been forecast from the observed periodicity. However, the precision of the forecast (±0.8 yr for the 95 per cent confidence interval) is not sufficient to furnish convincing evidence that the Bishop-Mammoth Lakes sequence is quasi-periodic. Extrapolation of the trend established by the six previous events suggests that the next event in the Bishop-Mammoth Lakes sequence would be expected in December 1987 ± 0.7 yr (95 per cent confidence interval). The regularity of the Bishop-Mammoth Lakes sequence is comparable to that of the Parkfield, California, sequence (average interevent interval 20.8 yr with a standard deviation for an individual interval of 6.2 yr). Both sequences consist of six events. There is a plausible physical explanation for the periodicity observed at Parkfield; such an explanation for the Bishop-Mammoth Lakes sequence is lacking.

scholarly journals Modeling and Extraction of Parameters Based on Physical Effects in Bipolar Transistors

2011 ◽  
Vol 2011 ◽  
pp. 1-8
Author(s):  
Agnes Nagy ◽  
Alicia Polanco ◽  
Manuel Alvarez
Keyword(s):  
Integrated Circuits ◽  
Extraction Method ◽  
Bipolar Transistors ◽  
Electronic Systems ◽  
Emission Coefficient ◽  
Physical Explanation ◽  
Simulation Procedure ◽  
Physical Effects ◽  
Precise Simulation ◽  
Theoretical Results

The rising complexity of electronic systems, the reduction of components size, and the increment of working frequencies demand every time more accurate and stable integrated circuits, which require more precise simulation programs during the design process. PSPICE, widely used to simulate the general behavior of integrated circuits, does not consider many of the physical effects that can be found in real devices. Compact models, HICUM and MEXTRAM, have been developed over recent decades, in order to eliminate this deficiency. This paper presents some of the physical aspects that have not been studied so far, such as the expression of base-emitter voltage, including the emitter emission coefficient effect (n), physical explanation and simulation procedure, as well as a new extraction method for the diffusion potentialVDE(T), based on the forward biased base-emitter capacitance, showing excellent agreement between experimental and theoretical results.

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