Basic Physical Factors Research Articles

Influence of spray characteristics on potential spray drift of field crop sprayers: A literature review

Spray drift is a practical consequence of agricultural spraying operations. Because of the agronomical and environmental impacts of this phenomenon, drift has been widely studied and extensive information is available. Here we present a literature review on the relationships between global physical descriptors of agricultural sprays, air conditions and resulting drift, generally studied in wind tunnels. Basic physical factors are droplet size, droplet velocity, and the physicochemical characteristics of the sprayed product. When possible, data available in the literature are collated to draw trends. Contradictory information sometimes appears especially regarding droplet velocity and drift control. The main physical factors consist generally of medians such as Volume Median Diameter (VMD or Dv50) that do not always represent the heterogeneity of a spray and especially the spatial distribution of particle size and velocity. Technological parameters such as nozzle height, spray angle, travel speed are then related to initial physical factors and their contribution to driftability of sprays.

Precipitation efficiency and its relationship to physical factors

The precipitation efficiency and its relationship to physical factors are examined by analyzing a two-dimensional cloud-resolving model simulation during TOGA COARE in this study. The basic physical factors include convective available potential energy, water—vapor convergence, vertical wind shear, cloud ratio, sea surface temperature, air temperature, and precipitable water. Precipitation efficiencies do not show a close relationship to air temperature nor to sea surface temperature nor to precipitable water. The precipitation efficiency increases as the water—vapor convergence rate increases and vertical wind shear weakens, whereas it decreases as the convective available potential energy dissipates and anvil clouds develop.

ChemInform Abstract: Internal and External Factors Promoting the Diels—Alder Reaction

AbstractReview: 175 refs.

Analysis of manifestations and influential factors for acute radiation-induced heart damage after three-dimensional radiotherapy

Objective To investigate the manifestations and influential factors for acute radiationinduced heart damage (RIHD) after three-dimensional radiotherapy in patients with thoracic neoplasms.Methods Three-dimensional conformal radiotherapy or intensity-modulated radiotherapy was delivered to 54 patients with thoracic neoplasms.The status of acute RIHD was evaluated by Common Terminology Criteria for Adverse Events,Version 3.0.The associations of manifestations,basic cardiac function,and clinical and physical factors with acute RIHD were analyzed.A paired t-test was used for comparison between groups;a logistic regression analysis was used for multivariate and univariate analysis.Results The overall incidence rate of acute RIHD was 70％ (38 patients),all of grade 1.Of the 38 acute RIHD patients,37 had abnormal electrocardiogram (ECG),7 had elevation of myocardial enzymes,7 had decrease in left ventricular systolic function,6 had cardiac troponin Ⅰ increase,and 3 had pericardial effusion.Of the 37 patients with abnormal ECG,19 had ST-segment changes,and 12 had sinus tachycardia.None of the basic cardiac function,history of smoking,history of chemotherapy,and history of heart disease was associated with acute RIHD (x2 =0-1.98,P =0.160-0.999),according to the univariate analysis.The multivariate analysis revealed that the relative volume of the heart exposed to 60 Gy irradiation (V60) was the independent influential factor for acute RIHD (x2 =5.10,P =0.024).Conclusions Acute RIHD is less severe after three-dimensional radiotherapy than after conventional radiotherapy,and abnormal ECG is the most common.V60 of the heart is the independent influential factor for acute RIHD. Key words: Radiation-induced heart damage ; Damage-related ; Thoracic neoplasms/three dimensional radiotherapy

Internal and external factors promoting the Diels-Alder reaction

The basic chemical and physical factors determining the rate and equilibrium of the Diels-Alder reaction under standard and high hydrostatic pressures were considered. The search for favorable conditions for this process makes it possible to extend the range of potential reactants and to perform reactions that earlier considered to be forbidden.

Comparative analysis of physical mechanisms of detonation initiation in HMX and in a low-sensitive explosive (TATB)

Based on the concept of hot spots, the basic physical factors determining the macrokinetics of chemical reactions in heterogeneous crystalline explosives are estimated. The macrokinetics in plasticized TATB is shown to be basically determined by the velocity of combustion propagation from microscopic reaction spots (hot spots), whereas the macrokinetics in plasticized HMX is determined by the density of hot spots.

Multivariate analysis of landscape wildfire dynamics in a Mediterranean ecosystem of Greece

This paper focuses on spatial distribution of long‐term fire patterns versus physical and anthropogenic elements of the environment that determine wildfire dynamics in Greece. Logistic regression and correspondence analysis were applied in a spatial database that had been developed and managed within a Geographic Information System. Cartographic fire data were statistically correlated with basic physical and human geography factors (geomorphology, climate, land use and human activities) to estimate the degree of their influence at landscape scale. Land cover types of natural and agricultural vegetation were the most influential factors for explaining landscape wildfire dynamics in conjunction with topography and grazing.

Discharged generator of singlet oxygen for oxygen-iodine laser. Transport kinetics of O2(a 1δg) and O2(b 1σ g + ) molecules and O(3 P) atoms in Ar:O2 and He:O2 flows excited by a 13.56-MHz discharge

To understand and reveal the basic physical factors providing the possibility of scaling of a discharged singlet oxygen generator (DSOG) in an oxygen-iodine laser, the production, and transport kinetics of metastable O2(a 1δg) and O2(b 1σ g + ) molecules, as well as O(3 P) atoms, were investigated in Ar:O2 and He:O2 gas flows excited by a 13.56-MHz discharge in a wide range of pressures (4–40 Torr) and oxygen percentages. It is shown that the densities and transport kinetics of O2(a 1δg), O2(b 1σ g + ), and O(3 P) appear similar for oxygen mixtures with argon and helium in the same conditions independent of discharge mode. Compared to pure O2, the dilution of oxygen with an inert gas allows higher energy inputs per an oxygen molecule to achieved, especially under conditions of the homogeneous discharge mode (α-mode), which gives a higher efficiency of O2(a 1δg) excitation in Ar:O2 and He:O2 mixtures. But the maximum attainable yield of singlet oxygen in Ar:O2 and He:O2 at fixed partial O2 pressure is found to be comparable with the O2(a 1δg) yield in pure oxygen at the same pressure. The reason for this is the increased three-body deactivation of O2(a 1δg) by atomic oxygen in the mixtures because of the greater total pressure. The estimation of the rate constant of O2(a 1δg) three-body quenching by O(3 P) in Ar:O2 and He:O2 mixtures as (1.5 ± 0.5) × 10−32 cm6/s was carried out from the analysis of transport kinetics of singlet and atomic oxygen in the discharge afterglow at high pressures exceeding ∼10 Torr. A similar analysis for the lower pressures has revealed that losses both of metastable O2(a 1δg) and O2(b 1σ g + ) molecules, and of O(3 P) atoms on the surface of the discharge tube, are determined by the density of each of the components. The obtained loss probabilities of O2(a 1δg), O2(b 1σ g + ), and O(3 P) on the silica surface show that the surface loss probabilities of all the species can increase noticeably under the discharge exposure. Thus, the key parameters determining the maximal O2(a 1δg) yield in the DSOG are a homogeneous volumetric mode of the discharge, energy input per oxygen molecule in this mode, and a low rate of O2(a 1δg) quenching. Just three-body quenching of O2(a 1δg) by O(3 P) limits the singlet oxygen yield with increasing pressure. The fast removal of atomic oxygen both in discharge and in the earlier afterglow could provide DSOG scaling with pressure.

Mathematical Modeling of Solid-State Diffusion during Mechanical Alloying

It is known experimentally that solid-state interdiffusion is substantially enhanced during plastic deformation. This is especially noticeable in Mechanical Alloying (MA) which is used for producing a wide range of metastable materials (supersaturated solid solutions, amorphous phases, nanostructures) with unique properties. However, a physical mechanism of enhanced diffusion during MA is not clearly understood yet, and a comprehensive model of this complex phenomenon has not been developed so far. Moreover, the role of the diffusion process in MA is hotly debated in literature. In this work a new, self-consistent mathematical model of solid-state interdiffusion in a binary substitutional system A-B during periodic plastic deformation is developed. The model includes basic physical factors that affect diffusion, such as generation of non-equilibrium point defects by gliding screw dislocations during deformation and their relaxation in periods between impacts. The cross-link terms are considered, and interaction of point defects with edge dislocations and incoherent phase boundary A/B is taken into account. Computer simulation is performed using realistic data (e.g., quasi-equilibrium self-diffusion coefficients known in literature) and the process parameters typical of MA in a vibratory mill. A repeated “deformation-rest” cycle is considered. The results of modeling reveal the physical mechanism of the enhancement of solid-state diffusion by periodic plastic deformation during MA and demonstrate that within the frame of this approach supersaturated solid solutions can form within a reasonably short processing time.

Statistical characteristics of the observed Ly α forest and the shape of initial power spectrum

Properties of approximately 4500 observed Ly α absorbers are investigated using the model of formation and evolution of dark matter (DM) structure elements based on the modified Zel’dovich theory. This model is generally consistent with simulations of absorber formation, describes the large-scale structure (LSS) observed in the galaxy distribution at small redshifts reasonably well and emphasizes the generic similarity of the LSS and absorbers. The simple physical model of absorbers asserts that they are composed of DM and gaseous matter. It allows us to estimate the column density and overdensity of DM and gaseous components and the entropy of the gas trapped within the DM potential wells. The parameters of the DM component are found to be consistent with theoretical expectations for the Gaussian initial perturbations with the warm dark matter-like power spectrum. The basic physical factors responsible for the evolution of the absorbers are discussed. The analysis of redshift distribution of absorbers confirms the self-consistency of the adopted physical model, Gaussianity of the initial perturbations and allows one to estimate the shape of the initial power spectrum at small scales that, in turn, restricts the mass of the dominant fraction of DM particles to M DM 1.5‐5 keV. Our results indicate possible redshift variations of intensity of the ultraviolet background by approximately a factor of 2‐3 at redshifts z ∼ 2‐3. One of the most promising methods for studying the processes responsible for the formation and evolution of the structure of the Universe is the analysis of properties of absorbers observed in the spectra of the furthest quasars. The great potential of such investigations has been discussed by Oort (1981, 1984) just after Sargent et al. (1980) established the intergalactic nature of the Ly α forest. The available Keck and VLT high-resolution observations of the forest provide a reasonable data base and allow one to apply statistical methods for such investigations. The essential progress achieved recently through numerous highresolution simulations of absorber formation and evolution confirms that this process is closely connected with the initial power spectrum of perturbations. These results allow us to consider the properties of absorbers in the context of the non-linear theory of gravitational instability (Zel’dovich 1970; Shandarin & Zel’dovich 1989) and to apply the statistical description of structure formation and evolu

ORIGIN OF HYSTERESIS AND PLATEAU-LIKE BEHAVIOR OF THE I-V CHARACTERISTICS OF RESONANT TUNNELING DIODES

In terms of numerical calculation of the coupled Wigner function–Poisson equations, the explanation to the origin of hysteresis and plateau-like behavior of the I-V characteristics of double barrier resonant tunneling devices is put forth. Several basic physical factors play key roles in the process of electron tunneling. Among these the most important factors are the interference of the injected and the reflected electron waves which leads to the formation of an emitter quantum well, the coupling between the energy level in the main quantum well and that in the emitter quantum well, and the coupling between the energy level in the main quantum well and the conduction b and edge or the three-dimensional states in the emitter. The interplay of these factors determines the form of the I-V curve of the resonant tunneling structure. The coupling between the energy levels in the emitter quantum-well and the main quantum-well leads to the plateau behavior of the I-V curves. The strength of the coupling determines the average slope of the plateau-like region in the I-V curve. The bias domain that the coupling exists determines the length of the plateau-like structure in the I-V curve. The domain can be controlled by adjusting the width of the barriers. The hysteresis is shown to be a manifestation of the above-mentioned energy level coupling, the coupling between the energy level in the main quantum well and the conduction b and edge or the three-dimensional states in the emitter, and the quantitative accumulation and distribution of electrons in the emitter region. This work provides new insight for underst and ing the nonlinear I-V behavior and establishes a foundation for the future analysis of bistability and oscillation behavior in resonant tunneling structures.

Physical Mechanisms in Hyperspectral BRDF Data of Grass and Watercress

A hyperspectral bidirectional reflectance data set of grass lawn and watercress canopies acquired under controlled laboratory conditions at the JRC European Goniometric Facility, at Ispra, Italy was analyzed with respect to basic physical reflectance mechanisms and factors influencing reflectance anisotropy. By normalizing reflectance data with the nadir reflectance as a reference, a strong influence of reflectance intensity on observed reflectance anisotropy is demonstrated for both vegetation canopies. This is explained by multiple scattering effects inside vegetation canopies as a function of canopy spectral absorbance characteristics. Two quantities based on canopy reflectances are utilized for characterizing the spectrally variable dynamics of BRDF effects: the anisotropy factor (ANIF), which is simply a normalization with nadir reflectance, and the anisotropy index (ANIX) defined as the ratio between the maximum and minimum reflectance values in the principal plane (or defined azimuth plane) per spectral band. Using these two quantities the study revealed that the basic physical reflectance mechanisms described by Kimes (1983) for broad spectral bands are extendable to hyperspectral bidirectional reflectance data. In addition, the influences of canopy geometry and multiple scattering on BRDF are clearly demonstrated for the erectophile grass lawn and the planophile watercress canopy. Since multiple scattering effects and canopy geometry are dominant factors regulating BRDF effects, vegetation canopy architecture parameters such as the leaf area index might be derived from hyperspectral BRDF data.

Dielectrophoresis: Using Inhomogeneous AC Electrical Fields to Separate and Manipulate Cells

Dielectrophoresis is the motion of particles caused by electrical polarization effects in inhomogeneous (nonuniform) electric fields. Unlike electrophoresis, the particles do not require a net electrical charge for motion to occur and AC rather than DC fields are employed to exploit the dielectric properties of the particles. Factors controlling the effective dielectric properties of cells and microorganisms include electrical double layers associated with surface charges, the conductivity and permittivity of their membranes and any cell walls, and their morphologies and structural architectures. In recent years, several laboratories have developed separation and manipulation techniques for cells and microorganisms based on dielectrophoresis, using both static and traveling AC fields. In this article, the basic physical factors influencing the dielectrophoretic behavior of particles are outlined, and ways in which these can be employed to achieve selective separation of cells and microorganisms are described.

Thermocapillary instability in deep weld keyholes

A theory is derived for the onset of a thermocapillary instability at the wall of the vapor-gas cavity formed during deep-penetration welding of metals by intense laser radiation. The basic physical factors causing the instability are identified. The quantitative conditions for its occurrence are derived. The curve of neutral (monotonic) stability is derived analytically. This curve relates the critical Marangoni number (or the intensity of the laser radiation) to the parameters of the wave perturbations and properties of the medium. When the thermocapillary effect and capillary perturbations of the free surface are taken into account simultaneously, the threshold for stability of the melt with respect to monotonic perturbations is lowered, particularly at small wave numbers. Estimates of the critical intensities of the laser radiation found here lie in the range (3–6) · 109 W/m2. This range corresponds roughly to the conditions prevailing during the laser processing of metals under deep penetration conditions.

Role of physical factors in solid – liquid interface formation during oriented eutectic growth

AbstractThe basic physical factors affecting the eutectic interface shape observed in the microscopic scale have been discussed regarding the theory of completely coupled growth. The analysis considers phenomena like: heterogeneous nucleation and growth, interface undercooling of the both eutectic phases, phase protrusion and eventually horizontal temperature gradient. The contribution of the transition layer to the interface shape formation is emphasised.

Laser frequency standards

This paper gives a brief review of the present status of the problem of developing optical frequency standards. The basic principles of laser-frequency stabilization based on narrow nonlinear optical resonances are presented. The basic physical factors determining the shape and the shift of narrow resonances are discussed. The design of the modern laser frequency standard, based on the use of supernarrow resonances with a relative width of 10−11 and smaller as the reference, is studied. The currently used techniques for stabilizing the frequency of lasers for different ranges and the methods used for measuring the characteristics of the frequency stability are described. Specific achievements in the development of lasers with a narrow radiation line and high long-term frequency stability and reproducibility are presented. Special attention is devoted to the He–Ne laser. For this laser a radiation line width of less than 0.1 Hz and a long-term stability of 10−14–10−15 have been obtained, and the effect of different factors on the shifts of the stabilized frequency are studied in detail. Results achieved in the development of the first optical clocks in the world are presented. The progress achieved in the absolute measurement of submillimeter, IR, and visible range laser frequencies is examined. Some applications of laser frequency standards and the prospects for their further development are described briefly.

Factors affecting industrial relations in the electronics industry of Hong Kong ‐ an empirical research analysis

AbstractThis paper attempts to study the factors affecting industrial relations in the electronics industry in Hong Kong. Comparative surveys were carried out, in selected companies and a major union, with management and workers. Results showed that basic financial, physical and physiological factors are still important for affecting workers' attitude towards industrial relations. However, socio‐psychological satisfactions are increasing as a result of demands by younger and better educated workers, the major workforce of the industry. The ‘pendulum’ attitude of workers towards the management and the unions leads to a delicate situation in the industrial relations of the industry.

Depth profiling by secondary ion mass spectrometry

AbstractThe principles and applications of depth profiling by secondary ion mass spectrometry (SIMS) are reviewed. Discussed are the basic physical processes and instrumental factors which influence the shape of depth profiles and which have to be understood or controlled for successful experimental measurements. Microroughness caused by sputtering, atomic mixing by primary beam knock‐on, and sample consumption limit the depth resolution which can be achieved while the chemical effect of ion yield enhancement by reactive species, matrix effects, and preferential sputtering can strongly affect the secondary ion signal. Instrumental effects to be controlled include beam uniformity, sample charging, and beam, and residual gas contamination. High depth resolution and sensitivity are the reasons for a wide variety of applications for SIMS depth profiling. Reviewed are measurements of the range distribution of ions implanted into semiconductors and their redistribution by subsequent annealing, studies of thin films and of oxide layers, diffusion measurements in metals, semiconductors, and minerals, measurements of elemental surface enhancements in airborne particles, and lunar glass spherules, and the search for solar wind implanted ions in lunar crystals.

Environmental Factors Affecting Soldier Beetle Distribution and Coloration in Columbia

Adults of the soldier beetle species, Chauliognathus proteus, appear on host plant Compositae at successively later dates following emergence with increase in altitude. Appearance is correlated with flowering of the host. Ground color is darker in cool, moist highlands than in the hot, dry lowlands, an example of Gloger's Rule as applied to invertebrates. Selective advantages are discussed as well as basic physical factors affecting the environment in which the species lives. THE LAMPYROID BEETLE family Chauliognathidae has been considered variously as a subfamily (Gorham 1881, Champion 1914, Boving and Craighead 1931, and Arnett 1962) or as a tribe (LeConte 1861, Leng 1920, Delkeskamp 1939, and Blackwelder 1945) of the family Cantharidae. Miskimen (1961a) elevated the group to full family status because of clear-cut morphological and behavioral differences. The new family was divided into two tribes, Chauliognathini and Ichthyurini, based on structure and be-

The Cellular Morphology of Tissue Repair

This chapter focuses on the cellular responses to injury of many different mammalian tissues and organs. The mechanisms of, and relationships between, such important aspects of repair as cell movement, mitosis, and differentiationare being pursued by biologists in many different disciplines, and the observed histological and cytological events during repair processes should act as guides for when and where to look for the basic chemical and physical factors involved. A strong plea must be made for eliminating once and for all the concept of a “lag phase” in the early stages of healing, with its implication that very little of interest is happening in the tissues for the first few days after wounding. In fact this very early period is the stage when activities vital to the whole future conduct of the repair are becoming mobilized, and without this train of events, which must be set in motion within seconds of injury, there can be no optimum sequence of processes leading to the most effective response possible.