Showing papers by "University of Delaware published in 1991"
TL;DR: In this article, the authors investigated the emotional, attentional and physiological aspects of stress reducing influences of nature, and found that both the stressor film and the nature settings elicited high levels of involuntary or automatic attention.
3,669 citations
TL;DR: The NTP synchronization system is described, along with performance data which show that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few milliseconds, even in cases of failure or disruption of clocks, time servers, or networks.
Abstract: The network time protocol (NTP), which is designed to distribute time information in a large, diverse system, is described. It uses a symmetric architecture in which a distributed subnet of time servers operating in a self-organizing, hierarchical configuration synchronizes local clocks within the subnet and to national time standards via wire, radio, or calibrated atomic clock. The servers can also redistribute time information within a network via local routing algorithms and time daemons. The NTP synchronization system, which has been in regular operation in the Internet for the last several years, is described, along with performance data which show that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few milliseconds, even in cases of failure or disruption of clocks, time servers, or networks. >
2,114 citations
TL;DR: In this article, the authors present the technical basis for establishing sediment quality criteria using equilibrium partitioning (EqP), which is chosen because it addresses the two principal technical issues that must be resolved: the varying bioavailability of chemicals in sediments and the choice of the appropriate biological effects concentration.
Abstract: The purpose of this review paper is to present the technical basis for establishing sediment quality criteria using equilibrium partitioning (EqP). Equilibrium partitioning is chosen because it addresses the two principal technical issues that must be resolved: the varying bioavailability of chemicals in sediments and the choice of the appropriate biological effects concentration.
The data that are used to examine the question of varying bioavailability across sediments are from toxicity and bioaccumulation experiments utilizing the same chemical and test organism but different sediments. It has been found that if the different sediments in each experiment are compared, there is essentially no relationship between sediment chemical concentrations on a dry weight basis and biological effects. However, if the chemical concentrations in the pore water of the sediment are used (for chemicals that are not highly hydrophobic) or if the sediment chemical concentrations on an organic carbon basis are used, then the biological effects occur at similar concentrations (within a factor of two) for the different sediments. In addition, the effects concentrations are the same as, or they can be predicted from, the effects concentration determined in water- only exposures.
The EqP methodology rationalizes these results by assuming that the partitioning of the chemical between sediment organic carbon and pore water is at equilibrium. In each of these phases, the fugacity or activity of the chemical is the same at equilibrium. As a consequence, it is assumed that the organism receives an equivalent exposure from a water-only exposure or from any equilibrated phase, either from pore water via respiration, from sediment carbon via ingestion; or from a mixture of the routes. Thus, the pathway of exposure is not significant. The biological effect is produced by the chemical activity of the single phase or the equilibrated system.
Sediment quality criteria for nonionic organic chemicals are based on the chemical concentration in sediment organic carbon. For highly hydrophobic chemicals this is necessary because the pore water concentration is, for those chemicals, no longer a good estimate of the chemical activity. The pore water concentration is the sum of the free chemical concentration, which is bioavailable and represents the chemical activity, and the concentration of chemical complexed to dissolved organic carbon, which, as the data presented below illustrate, is not bioavailable. Using the chemical concentration in sediment organic carbon eliminates this ambiguity.
Sediment quality criteria also require that a chemical concentration be chosen that is sufficiently protective of benthic organisms. The final chronic value (FCV) from the U.S. Environmental Protection Agency (EPA) water quality criteria is proposed. An analysis of the data compiled in the water quality criteria documents demonstrates that benthic species, defined as either epibenthic or infaunal species, have a similar sensitivity to water column species. This is the case if the most sensitive species are compared and if all species are compared. The results of benthic colonization experiments also support the use of the FCV.
Equilibrium partitioning cannot remove all the variation in the experimentally observed sediment- effects concentration and the concentration predicted from water-only exposures. A variation of approximately a factor of two to three remains. Hence, it is recognized that a quantification of this uncertainty should accompany the sediment quality criteria.
The derivation of sediment quality criteria requires the octanol/water partition coefficient of the chemical. It should be measured with modern experimental techniques, which appear to remove the large variation in reported values. The derivation of the final chronic value should also be updated to include the most recent toxicological information.
1,369 citations
TL;DR: Proper treatment of the thermal averaging and the annihilation after freeze-out shows that the dip in relic abundance caused by a pole is not nearly as sharp or deep as previously thought.
Abstract: The calculation of relic abundances of elementary particles by following their annihilation and freeze-out in the early Universe has become an important and standard tool in discussing particle dark-matter candidates. We find three situations, all occurring in the literature, in which the standard methods of calculating relic abundances fail. The first situation occurs when another particle lies near in mass to the relic particle and shares a quantum number with it. An example is a light squark with neutralino dark matter. The additional particle must be included in the reaction network, since its annihilation can control the relic abundance. The second situation occurs when the relic particle lies near a mass threshold. Previously, annihilation into particles heavier than the relic particle was considered kinematically forbidden, but we show that if the mass difference is \ensuremath{\sim}5-15%, these "forbidden" channels can dominate the cross section and determine the relic abundance. The third situation occurs when the annihilation takes place near a pole in the cross section. Proper treatment of the thermal averaging and the annihilation after freeze-out shows that the dip in relic abundance caused by a pole is not nearly as sharp or deep as previously thought.
1,346 citations
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01 Jan 1991TL;DR: In this paper, the basic dimensions of personality are discussed, and the consistency of personality traits and their relationship with behavioral genetics and personality traits are discussed. But they do not discuss the relationship between these dimensions and specific personality traits.
Abstract: 1. Basic dimensions of personality 2. Consistency of personality 3. Behaviour genetics and personality traits 4. Neuropsychology 5. Psychopharmacology 6. Psychophysiology 7. Learning 8. Anxiety disorders 9. Antisocial personality and other disinhibitory disorders 10. Measures and models, problems and progress References Figure captions.
865 citations
TL;DR: A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD), which appears to be more competitive with traditional solution methods.
Abstract: A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.
630 citations
TL;DR: In this article, the cylindrical pore model is used for the transformation of argon adsorption data on a zeolite into a micropore size distribution.
Abstract: The sensitivity of the calculated micropore size of zeolite Y in a fluidized cracking catalyst based on empirical models for argon adsorption has been tested by examining the effect of curvature and by systematically verifying the magnitude of physical constants in the model equations. With a consistent set of physical parameters the slit model provided a pore size value of 0.45 nm, while the new cylindrical models provided values of 0.69 and 0.74 nm. The latter values are found to correspond well with the known aperture size of zeolite Y, 0.74 nm. By separately varying the magnitudes of five of the physical constants in the model over a range of ±30%, it was concluded that the diameter of the oxide ion at the surface had a large effect on the calculated pore size, while the other parameters had only moderate to small effects. Preliminary application of the cylindrical pore model to isotherms of argon on other zeolites and molecular sieves leads to promising results, especially for medium to large pore zeolites. These results suggest that the cylindrical pore model is a useful means for the transformation of argon adsorption data on a zeolite into a micropore size distribution.
468 citations
TL;DR: This chapter addresses the applications of DNA markers to plant breeding, allowing researchers to begin to tap the potential of this technology to the benefit of both basic biology and agricultural productivity.
Abstract: Publisher Summary Genetic markers are held for a detailed investigation of complex questions in quantitative biology. The advent of DNA markers, greatly expanding the number of genetic markers available, is allowing researchers to begin to tap the potential of this technology, to the benefit of both basic biology and agricultural productivity. Genetic markers make a major contribution to the biological sciences, especially agriculture, for the foreseeable future. DNA markers can significantly accelerate many breeding endeavors. They may provide new approaches to some objectives, which have proven difficult to achieve with classical techniques, such as introgression of valuable traits from exotic germplasm into domestic cultivars. This chapter addresses the applications of DNA markers to plant breeding. Genetic markers represent genetic variation, permitting one to estimate relatedness between different genotypes and to predict which matings might produce new and superior gene combinations.
468 citations
TL;DR: In this article, the authors examined the lability of dissolved organic carbon (DOC) in the upper ocean and found that DOC turnover rates can range from 0.025 to 0.363 per day and were consistent with bacterial biomass production and uptake of dissolved nitrogen.
Abstract: OCEANIC dissolved organic carbon (DOC) is one of the Earth's largest carbon reservoirs, but until recently its role in the carbon cycle has been neglected. New methodology1, however, has led to larger estimates of DOC concentrations and also to renewed interest in the biochemical lability of DOC2. Previous work found that the mean age of DOC in the surface ocean was > 1,000 years3. To examine the lability of DOC in greater detail, we have conducted experiments to estimate DOC turnover rates in the upper ocean. We directly observed rapid DOC turnover by bacterioplank-ton during the spring phytoplankton bloom in the North Atlantic ocean. Potential turnover rates, measured in 0.8-um filtered samples, ranged from 0.025 to 0.363 per day, and were consistent with bacterial biomass production and uptake of dissolved nitrogen (NH+4, NO-3 and urea). Our results indirectly suggest that cycling of dissolved organic nitrogen (DON) differs from that of DOC. The high estimates of DOC concentrations and turnover rates repeated here, if found to be general, would seem to demand changes in models4 of carbon cycling and of the ocean's role in buffering increases in atmospheric CO2.
436 citations
TL;DR: In this paper, the reaction of Fe(II and Fe(III) solutions with polysulfide solutions prepared from freshly synthesized Na2Sx (x = 2, 4, 5) were studied at 25 and 100°C over the pH range 5.5 to 8.
380 citations
TL;DR: This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulator--in the nervous system and describes the monitoring of immunoreGulators by the central nervous system as part of the regulatory factors that induce neurological manifestations frequently accompanying acute and chronic pathological processes.
TL;DR: The properties and most successful methods for producing CuInSe2 films for solarcell applications are reviewed and the production, analysis, and performance of photovoltaic devices based on CuSe2 are discussed in this paper.
Abstract: The properties and most successful methods for producing CuInSe2 films for solar‐cell applications are reviewed and the production, analysis, and performance of photovoltaic devices based on CuInSe2 are discussed. The most successful methods for depositing thin CuInSe2 films for high‐efficiency solar cells are three‐source elemental evaporation and selenization of Cu/In layers in H2Se atmospheres. Devices based on CuInSe2 have achieved the highest conversion efficiencies for any nonepitaxial thin‐film solar cell, 14.1% for a small cell and 10.4% (aperture efficiency) for a 3916‐cm2 (4 sq. ft) device. Furthermore, high‐efficiency devices have been produced by several groups and have shown no evidence of degradation of performance with time. The internal quantum efficiency is remarkably close to 100%, although various losses prevent making use of all of the generated carriers. The high performance results, in part, from the very‐high‐absorption coefficient of CuInSe2, which is of the order of 105 cm−1 for photons with energies slightly above 1 eV. Models of the operation of CuInSe2/CdS heterojunctions have begun to explain the processes limiting the device performance. The success of the models is based, in part, on the large amount of data which has accumulated on CuInSe2 in spite of the relatively short time it has been extensively studied.
TL;DR: In this article, a new study involving 525 subjects in four samples: men and women in Fall and Spring terms was conducted, and the results from traditional factor analyses of the separate groups showed that the loadings of corresponding factors were highly related, and that sets of common factors defined over all four groups had virtually the same explanatory power as separate components computed for each group separately.
TL;DR: The Curie temperature of ferrimagnetic nanoscale particles by means of direct measurement of the magnetization is determined using the finite-size-scaling formula.
Abstract: We have determined the Curie temperature ${\mathit{T}}_{\mathit{c}}$ of ferrimagnetic ${\mathrm{MnFe}}_{2}$${\mathrm{O}}_{4}$ nanoscale particles by means of direct measurement of the magnetization. A considerable enhancement in ${\mathit{T}}_{\mathit{c}}$ compared to the bulk was observed for particles in the size range 7.5 to 24.4 nm. At d=7.5 nm, ${\mathit{T}}_{\mathit{c}}$ is 97 K higher than for the bulk material. The shift in Curie temperature is well described by the finite-size-scaling formula [${\mathit{T}}_{\mathit{c}}$(d)-${\mathit{T}}_{\mathit{c}}$(\ensuremath{\infty})]/${\mathit{T}}_{\mathit{c}}$(\ensuremath{\infty})=(d/${\mathit{d}}_{0}$${)}^{\mathrm{\ensuremath{-}}1/\ensuremath{
u}}$ with \ensuremath{
u}=0.71\ifmmode\pm\else\textpm\fi{}0.07 and ${\mathit{d}}_{0}$=2.0 nm.
01 Jan 1991
TL;DR: In this paper, the solution speciation and solid-phase suspended particulate fractionation of Mn and Fe were investigated in the Black Sea in an effort to understand the biogeochemical cycling of NM and Fe across redox boundaries and to study the scavenging/precipitation reactions affecting their distributions.
Abstract: The solution speciation and solid-phase suspended particulate fractionation of Mn and Fe were investigated in the Black Sea in an effort to understand the biogeochemical cycling of Mn and Fe across redox boundaries and to study the scavenging/precipitation reactions affecting their distributions.
The redox cycling of Mn (in a distinct “suboxic” zone from 15 to 50 m thick) and the redox cycling of Fe (coincident with total sulfide concentrations exceeding 0.4 μM) occur along isopycnal surfaces which deepen sharply towards the Turkish coast. Dissolved Mn behaves primarily as the free hydrated Mn2+ species and approaches saturation with respect to MnS2 (haurite) in the deep anoxic waters. In the oxic zone, colloidal and organically-complexed Fe species account for 10–30% of the total dissolved Fe, while colloidal Fe-sulfides account for 30–60% of the total in the mid-depth dissolved Fe(II) maximum. The deep waters are close to saturation with respect to FeS (mackinawite) or Fe3S4 (greigite).
A weak-acid soluble Mn phase dominates in the broad particulate Mn maximum in the suboxic zone and appears to be associated with Mn-oxidizing bacteria. More resistant Mn and Fe phases, presumed to be sulfide precipitates, were found in the deep anoxic waters. Particulate Al showed a broad maximum below the sulfide interface, presumably due to offshore transport of resuspended sediment.
A vertical mixing model for dissolved Mn in the central basin of the Black Sea yields removal rates consistent with measured bacterial Mn oxidation rates. The redox cycling of Fe occurs somewhat deeper in the water column. The vertical supply of oxygen cannot account for the Mn oxidation rate. However, horizontal advection and/or seasonal vertical mixing could provide enough oxidizing equivalents.
TL;DR: The response of the marine diatom Trincornutum to Fe deficiency was evaluated in the context of fundamental physiological models of growth and photosynthesis as mentioned in this paper, and it was found that Fe deficiency increased the in vivo absorption cross section normalized to Chl a (a*), but decreased the maximum quantum yield of photosynthesis (4,).
Abstract: The response of the marine diatom Phaeodactylum ,tricornutum to Fe deficiency was evaluated in the context of fundamental physiological models of growth and photosynthesis. Fe deficiency induced chlorosis, which decreased Chl a : C ratios and Chl a-specific light-saturated photosynthesis (P,“). In contrast to Pme, (Ye was slightly increased under Fe deficiency, and photosynthesis in Fedeficient cells became light-saturated at lower irradiances than in Fe-replete cells grown at the same irradiance. Fe deficiency increased the in vivo absorption cross section normalized to Chl a (a*), but decreased the maximum quantum yield of photosynthesis (4,). Thus, the product a* &,,, which equals the Chl a-specific initial slope of the photosynthlesis-irradiance curve (@), was less sensitive to Fe limitation than was a* or 4, alone. Using a pump-and-probe fluorometer, we found that Fe deficiency reduced the maximum fluorescence yield (A@,,), which is consistent with the reduction in &, but increased the absorption cross section of photosystem 2 (gps2). Immunoassays of proteins separated electrophoretically indicated that the reduction in maximum fluorescence yields was accompanied by a reduction in the relative abundance of D 1, the photosystem 2 reaction center protein. Light-harvesting chlorophyll proteins (LHCP) and the large and small subunits of ribulose bisphosphate carboxylase were not affected by Fe deficiency. Changes in the abundance of Dl relative to LHCP suggest an increase in the fraction of nonfunctional reaction centers under Felimited conditions. Fe-deficient cells, growing at ~20% of their maximum growth rate, had reduced cellular C, N, and P contents, but maintained C : N : P ratios at the Redfield proportions. These results imply that C : N : P ratios do not provide an unequivocal index of relative growth rate.
TL;DR: In this paper, an investigation into the two-dimensional cure simulation of thick thermosetting composites is presented, where temperature and degree of cure distributions within arbitrary cross-sectional geometries are predicted as a function of the autoclave temperature history.
Abstract: An investigation into the two-dimensional cure simulation of thick thermosetting composites is presented. Temperature and degree of cure distributions within arbitrary cross-sectional geometries are predicted as a function of the autoclave temperature history. The heat conduction equation for two-dimensional, transient anisotropic heat transfer is coupled to the cure kinetics of the thermosetting composite material. A heat generation term, expressed as a function of cure rate and the total heat of reaction, is introduced to account for the heat liberated during the curing process. A generalized boundary condition formulation is employed, enabling arbitrary temperature boundary conditions to be enforced straightforwardly. An incremental, transient finite difference solution scheme is implemented to solve the pertinent governing equations and boundary conditions. The boundary-fitted coordinate system (BFCS) transformation technique is combined with the Alternating Direction Explicit (ADE) finite difference ...
TL;DR: The linear theory for water waves impinging obliquely on a vertically sided porous structure is examined in this article, where the reflection and transmission coefficients are significantly altered and they are calculated using a plane-wave assumption.
Abstract: The linear theory for water waves impinging obliquely on a vertically sided porous structure is examined. For normal wave incidence, the reflection and transmission from a porous breakwater has been studied many times using eigenfunction expansions in the water region in front of the structure, within the porous medium, and behind the structure in the down-wave water region. For oblique wave incidence, the reflection and transmission coefficients are significantly altered and they are calculated here. Using a plane-wave assumption, which involves neglecting the evanescent eigenmodes that exist near the structure boundaries (to satisfy matching conditions), the problem can be reduced from a matrix problem to one which is analytic. The plane-wave approximation provides an adequate solution for the case where the damping within the structure is not too great. An important parameter in this problem is Γ 2 = ω 2 h ( s - i f )/ g , where ω is the wave angular frequency, h the constant water depth, g the acceleration due to gravity, and s and f are parameters describing the porous medium. As the friction in the porous medium, f , becomes non-zero, the eigenfunctions differ from those in the fluid regions, largely owing to the change in the modal wavenumbers, which depend on Γ 2 . For an infinite number of values of ΓF 2 , there are no eigenfunction expansions in the porous medium, owing to the coalescence of two of the wavenumbers. These cases are shown to result in a non-separable mathematical problem and the appropriate wave modes are determined. As the two wavenumbers approach the critical value of Γ 2 , it is shown that the wave modes can swap their identity.
TL;DR: In this paper, a new scenario for generating the baryon asymmetry in the universe within the framework of the inflationary cosmology was proposed, where decay of the weakly coupled inflaton field via the heavy Majorana neutrinos produces an asymmetry.
TL;DR: Application of high hydrostatic pressure to chitosan‐treated cultures of E. coli V517 or S. aureus MF‐31 resulted in additional inactivation but an amplified or synergistic effect was not found.
Abstract: Two commercially available water‐soluble chitosan salts, chitosan lactate and chitosan hydroglutamate, were examined for antagonistic effect against Escherichia coli V517, Staphylococcus aureus MF‐31 and Saccharomyces cerevisiae 15. Significant inactivation of each population was evident within 2 min of incubation with Chitosan. S. cerevisiae was the most sensitive of the microorganisms examined. Concentration effects varied but chitosan hydroglutamate was usually the more effective of the chitosans for inactivation of these microorganisms. Application of high hydrostatic pressure (2,380 atmospheres) to chitosan‐treated cultures of E. coli V517 or S. aureus MF‐31 resulted in additional inactivation but an amplified or synergistic effect was not found.
TL;DR: In this article, the authors obtained quantitative data on combined convective and diffusive transport of bovine serum albumin (BSA) through the highly constricted pores of asymetric ultrafiltration membranes with a range of nominal molecular weight cutoffs.
Abstract: The objective of this study was to obtain quantitative data on combined convective and diffusive transport of bovine serumalbumin (BSA) through the highly constricted pores of asymetric ultrafiltration membranes with a range of nominal molecular weight cutoffs.
TL;DR: The authors used a developmental pathway model to consider the role of attachment processes in adolescents' reports of depressive symptoms and found that depressed adolescents engaged in interactions characterized by high levels of maternal dominance and dysfunctional anger.
Abstract: This article uses a developmental pathway model to consider the role of attachment processes in adolescents' reports of depressive symptoms. Teen attachments were assessed with both interview and observational methods. Assessments of teens' strategies in the Adult Attachment Interview (AAI) indicated that insecure and preoccupied strategies were associated with increased reports of depressive symptoms. Observations of mother-teen problem-solving revealed that depressed teens engaged in interactions characterized by high levels of maternal dominance and dysfunctional anger. Maternal reports of teens' negative life events contributed additional variance to a regression model for depressive symptoms. Gender differences further specified pathways to depressive symptoms. Females reported more depressive symptoms, while depressed males engaged in problem-solving interactions characterized by high levels of dysfunctional anger. Competency-based treatments of depressive symptoms designed to improve parent-teen communication and meta-monitoring skills are discussed.
01 Jan 1991
TL;DR: Pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurizing in phosphate-buffered saline.
Abstract: Listeria monocytogenes Scott A and CA, were subjected at 23°C to hydrostatic pressures ranging from 2,380 to 3,400 atm and Vibrio parahaemolyticus T-3765-1 from 680 to 1,700 atm. For L. monocytogenes Scott A, pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurization in phosphate-buffered saline (100 mM, pH 7.0). A population of about 106 CFU/mL L. monocytogenes was killed by exposure to 3,400 atm within 80 min at 23°C in UHT milk. A population of about 106 CFU/mL V. parahaemolyticus was killed by exposure to 1,700 atm within 10 min at 23°C in clam juice.
TL;DR: The results indicate that physical therapists' VOGA assessments are only slightly to moderately reliable and that improved interrater reliability of the assessments of physical therapists utilizing this technique is needed and suggests that there is a need for greater standardization of gait-analysis training.
Abstract: The purpose of this study was to determine the interrater reliability of videotaped observational gait-analysis (VOGA) assessments. Fifty-four licensed physical therapists with varying amounts of clinical experience served as raters. Three patients with rheumatoid arthritis who demonstrated an abnormal gait pattern served as subjects for the videotape. The raters analyzed each patient's most severely involved knee during the four subphases of stance for the kinematic variables of knee flexion and genu valgum. Raters were asked to determine whether these variables were inadequate, normal, or excessive. The temporospatial variables analyzed throughout the entire gait cycle were cadence, step length, stride length, stance time, and step width. Generalized kappa coefficients ranged from .11 to .52. Intraclass correlation coefficients (2,1) and (3,1) were slightly higher. Our results indicate that physical therapists' VOGA assessments are only slightly to moderately reliable and that improved interrater reliability of the assessments of physical therapists utilizing this technique is needed. Our data suggest that there is a need for greater standardization of gait-analysis training.
TL;DR: In this paper, the scattering of supersymmetric dark matter particles from nuclei at nonzero momentum transfer was studied and a spin-dependent cross-section of the spin-independent cross-sections was derived.
TL;DR: In this paper, the authors examine how D. Kahneman and A. Tversky's (1979, 1984) assertions from prospect theory, that mental accounts are organized topically, might relate to sunk cost effects in decision-making.
TL;DR: In this article, the problem of wave propagation through a periodic medium is considered and an effective medium model of the propagation phenomena is obtained using the Bloch expansion, which is shown to be dispersive.
Abstract: The problem of wave propagation through a periodic medium is considered. It is assumed that the ratio between the cell size and the shortest wavelength of the initial disturbance is small. Within this regime, an effective medium model of the propagation phenomena is obtained using the Bloch expansion. The effective medium obtained is shown to be dispersive. It is known that a dominant feature of the transient wave train in a periodic medium is that of dispersion. It is shown that our model recovers homogenization formally when the cell size approaches zero. Explicit formula for the constants appearing in the effective medium equation is derived for the case of one dimension. The accuracy of the resulting approximation is assessed in numerical simulations.
TL;DR: It appears that day-to-day mortality fluctuations are much more sensitive to weather than to pollution concentrations, as the oppressive category associated with the greatest mortality possessed levels of six major pollutants that were not noteworthy.
Abstract: The objective of this study is to introduce a new procedure to determine the impact of climate on human mortality with the use of a synoptic climatological approach. The holistic nature of synoptic categories allows for the simultaneous evaluation of numerous weather elements as they realistically appear within air masses. In addition, this approach allows for a better distinction between pollution-induced mortality and weather-induced mortality. A synoptic categorization was performed for St. Louis, Missouri, and each category was evaluated in terms of its mean daily mortality. Of 10 summer categories found in St. Louis, one possessed the highest mean mortality by far, and 8 of the top 10 mortality days in St. Louis occurred when this category was present. Further analysis determined that long, consecutive day periods of this hot, oppressive category are associated with a continuing rise in mortality. It was determined that the procedure described here has the potential to be used in a weather/mortality watch-warning system. Finally, it appears that day-to-day mortality fluctuations are much more sensitive to weather than to pollution concentrations, as the oppressive category associated with the greatest mortality possessed levels of six major pollutants that were not noteworthy.
TL;DR: Presentation d'une formulation basee sur des arguments statistiques pour evaluer la fraction volumique critique des cylindres necessaire a la formation d'un reseau de percolation tridimensionnel.
Abstract: A formulation based on statistical arguments is presented for estimating the critical volume fraction of cylinders necessary for the formation of a three-dimensional percolation network. Parameters included in the analysis are the geometry of the cylinder and the state of orientation of the cylinders. The principal cylinder geometric parameter is shown to be the cylinder aspect ratio. The cylinder orientation distribution is described in terms of two orientation parameters; one describes the orientation state with respect to an ``axial'' orientation and the other with respect to a ``planar'' orientation. The analysis shows that the critical volume fraction for the formation of the percolation network will vary from less than 1% to more than 20%.