Value Of Cos Research Articles

Topographic information of sand dunes as extracted from shading effects using Landsat images

Topographic variations affect the reflectance properties of the Earth's surface and are often removed in remote sensing studies, especially when significant terrain variations exist. In this study, however, we show that shading effects assessed by Landsat can be treated as a signal that stores important topographic information, especially when the spectral characteristics of a surface are homogenous. The coastal transverse dunes of the Ashdod area, and the desert linear dunes of Nizzana (both located in Israel), were selected to investigate the abovementioned idea. The dune heights in these areas are 10 m on average (relative to their surroundings) and have maximum slopes of 33°. An innovative method for extracting slope, aspect, and height data for sand dunes using Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) images was developed, based on the regularity and periodicity of dunes' landscapes. Using two Landsat images representing different sun zenith and azimuth angles, reflectance values of each image were converted to cos( i) values ( i=incident angle between the surface normal and the solar beam radiation), applying histogram matching methods. The slope and aspect of each pixel were determined as those that give the best prediction of the observed value of cos( i). Height profiles were then extracted, using simple trigonometric relationships. The accuracies of heights and slopes along selected profile lines were to the order of 1 m and 3°, respectively (at a spatial resolution of 15 m). Best results were obtained when the images included one from the summer and the other from the winter, corresponding to maximum difference in solar zenith and azimuth angles. Errors in heights were attributed to surface heterogeneity (e.g., presence of biogenic soil crusts in the rainy season), geometric correction errors, cast shadows, and Bidirectional Reflectance Distribution Function (BRDF) effects. Comparison to Advanced Thermal Emission and Reflection Radiometer (ASTER) 3D information showed that the proposed method is better in representing the topographic variation of the area than the digital elevation model (DEM) produced by ASTER.

Four-neutrino oscillations at SNO

We discuss the potential of the Sudbury Neutrino Observatory (SNO) to constraint the four-neutrino mixing schemes favoured by the results of all neutrino oscillations experiments. Our results show that some information on the value of cos 2(ϑ 23) cos 2(ϑ 24) can be obtained by the first SNO measurement of the CC ratio, while considerable improvement on the knowledge of this mixing will be achievable after the measurement of the NC/CC ratio.

Photophysical properties of long rodlike meso-meso-linked zinc(II) porphyrins investigated by time-resolved laser spectroscopic methods.

The molecular design of directly meso-meso-linked porphyrin arrays as a new model of light-harvesting antenna as well as a molecular photonic wire was envisaged to bring the porphyrin units closer for rapid energy transfer. For this purpose, zinc(II) 5,15-bis(3,5-bis(octyloxy)phenyl)porphyrin (Z1) and its directly meso-meso-linked porphyrin arrays up to Z128 (Zn, n represents the number of porphyrins) were synthesized. The absorption spectra of these porphyrin arrays change in a systematic manner with an increase in the number of porphyrins; the high-energy Soret bands remain at nearly the same wavelength (413-414 nm), while the low-energy exciton split Soret bands are gradually red-shifted, resulting in a progressive increase in the exciton splitting energy. The exciton splitting is nicely correlated with the values of cos[pi/(N + 1)] according to Kasha's exciton coupling theory, providing a value of 4250 cm(-1) for the exciton coupling energy in the S(2) state. The increasing red-shifts for the Q-bands are rather modest. The fluorescence excitation anisotropy spectra of the porphyrin arrays show that the photoexcitation of the high-energy Soret bands exhibits a large angle difference between absorption and emission dipoles in contrast with the photoexcitation of the low-energy exciton split Soret and Q-bands. This result indicates that the high-energy Soret bands are characteristic of the summation of the individual monomeric transitions with its overall dipole moment deviated from the array chain direction, while the low-energy Soret bands result from the exciton splitting between the monomeric transition dipoles in line with the array chain direction. From the fluorescence quantum yields and fluorescence lifetime measurements, the radiative coherent length was estimated to be 6-8 porphyrin units in the porphyrin arrays. Ultrafast fluorescence decay measurements show that the S(2) --> S(1) internal conversion process occurs in less than 1 ps in the porphyrin arrays due to the existence of exciton split band as a ladder-type deactivation channel, while this process is relatively slow in Z1 (approximately 1.6 ps). The rate of this process seems to follow the energy gap law, which is mainly determined by the energy gap between the two Soret bands of the porphyrin arrays.

New bound on γ from B±→ πK decays

A bound on the angle γ of the unitarity triangle is derived using experimental information on the CP-averaged branching ratios for the rare decays B ±→ π ± K 0 and B ±→ π 0 K ±. The theoretical description is cleaner than the Fleischer–Mannel analysis of the decays B ±→ π ± K 0 and B 0→ π ∓ K ± in that the two decay rates differ only in a single isospin amplitude, which has a simple structure in the SU(3) limit. As a consequence, electroweak penguin contributions and strong rescattering effects can be taken into account in a model-independent way. The resulting bound excludes values of cos γ around ≈0.6 and is thus largely complementary to indirect constraints derived from a global analysis of the unitarity triangle.

Field Dependence of Magnetoresistance in Granular Ag–Co Thin Films

The proportionality of the giant magnetoresistance (MR) to <cos θ>2, where θ is the angle between the local magnetization and the applied field, was tested in granular Ag–Co (20 at.%) thin films. The assumption that <cos θ>2=(M/Ms)2 does not give a linear relation. To deduce the granule size distribution, magnetization data for the superparamagnetic state were fitted using a set of Langevin functions on a granule size histogram. Assuming that the scattering rate is proportional to the surface area of each granule in such a system and that the granules are spherical, we weight the average of cos θ in the size distribution by the surface area. If granules containing more than 900 Co atoms are ignored when determining the average value of cos θ, the MR varies linearly with this quantity, which is denoted as <cos θ> sur.av.2. We suggest that the surface roughness enhances the contribution of smaller granules to the MR.

Misfit dislocations in strained InxGa1−xAs heterostructure on patterned GaAs (001) substrate

〈110〉 60° and 〈100〉 edge misfit dislocations in In0.06Ga0.94As heterostructures grown on patterned GaAs (001) substrates with relatively low misfit f(f=0.0043) have been investigated. The reduction of 〈110〉 misfit dislocation density on mesas is observed by cathodoluminescence, while the 〈100〉 misfit dislocation density on mesas observed by synchrotron radiation double crystal topography remains unchanged. The critical thickness is calculated by modifying the Matthews mechanical equilibrium theory introduced by Chidambarrao et al. The calculated results can be applied to both the nonpatterned area and the sidewalls of the mesa. The critical thickness of one side of the mesa is larger than that of nonpatterned areas. The critical thickness of both sides of mesas is dependent on the angle between the sidewall and (001) GaAs. This is likely due to different values of cos φ/sin ψ, which determines the values of the friction force FF with different sidewall angles. It is suggested that the 〈100〉 misfit dislocations are generated by climb and they can cross mesas by climbing along 〈100〉 directions.

Orbits of short period comets captured from the Oort cloud

Oort cloud comets occasionally obtain orbits which take them through the planetary region. The perturbations by the planets are likely to change the orbit of the comet. We model this process by using a Monte Carlo method and cross sections for orbital changes, i.e. changes in energy, inclination and perihelion distance, in a single planet-comet encounter. The influence of all major planets is considered. We study the distributions of orbital parameters of observable comets, i.e. those which have perihelion distance smaller than a given value. We find that enough comets are captured from the Oort cloud in order to explain the present populations of short period comets. The median value of cos i for the Jupiter family is 0.985 while it is 0.27 for the Halley types. The results may explain the orbital features of short period comets, assuming that the active lifetime of a comet is not much greater than 400 orbital revolutions.

Carbonyl sulfide emissions from biomass burning in the tropics

Carbonyl sulfide emissions from biomass burning have been studied during field experiments conducted both in an African savanna area (Ivory Coast) and rice fields, central highland pine forest and savanna areas in Viet-Nam. During these experiments CO2, CO and C2H2 or CH4 have also been also monitored. COS values range from 0.6 ppbv outside the fires to 73 ppbv in the plumes. Significant correlations have been observed between concentrations of COS and CO (R2=0.92,n=25) and COS and C2H2 (R2=0.79,n=26) indicating a COS production during the smoldering combustion. COS/CO2 emission factors (ΔCOS/ΔCO2) during field experiments ranged from 1.2 to 61×10−6 (11.4×10−6 mean value). COS emission by biomass burning was estimated to be up to 0.05 Tg S/yr in tropics and up to 0.07 Tg S/yr on a global basis, contributing thus about 10% to the global COS flux. Based on the S/C ratio measured in the dry plant biomass and the ΔCOS/ΔCO2 emission factor, COS can account for only about 7% of the sulfur emitted in the atmosphere by biomass burning.

Modification of wettability of a stainless‐steel plate by cathodic plasma polymerization of trimethylsilane–oxygen mixtures

AbstractWettability (by water) of a stainless‐steel plate was modified by depositing an ultrathin layer of a plasma polymer of trimethylsilane (TMS) and an oxygen mixture. Plasma polymerization was carried out by cathodic glow discharge polymerization, in which a substrate stainless‐steel plate was used as the cathode of the de glow discharge. The plasma polymer of TMS (oxygen mol fraction = 0) is very hydrophobic, but the addition of oxygen in the monomer mixture increased the hydrophilicity of the plasma polymer. The value of cos θ (θ: advancing contact angle of water) linearly increased with the mol fraction of oxygen in the monomer mixture. Oxygen in the monomer mixture acts as (1) an ablating agent of a carbon‐based plasma polymer and (2) a comonomer for a silicon‐based plasma polymer. The atomic composition of a plasma polymer, which can be expressed as SiCxOy, changes (x decreases and y increases) as the mol fraction of oxygen increases. © 1995 John Wiley &amp; Sons, Inc.

Variation in Leaf Movements among Common Bean Cultivars

Common beans (Phaseolus vulgaris L.) orient their leaves in response to directionality of the sun's direct beam. This study was initiated to test for genetic variability in leaflet orientation, especially variability related to geographic origin. We also determined genetic variability in diurnal, seasonal, and environmental influences on leaflet orientation. The studies included 75 Mesoamerican and Andean common bean lines and two tepary bean (Phaseolus acutifolius Gray) lines at two sites. Cos i (cosine of the angle of incidence to direct sunlight) varied in the order tepary bean &gt; Andean common bean &gt; Mesoamerican common bean. Within sites, variability in seasonal and year‐to‐year patterns of leaf movement was significant, but there were large differences in rankings of lines across sites. Imposed drought decreased cos i, but values of cos i in drought and irrigated treatments remained correlated. Movements of the two lateral leaflets were highly correlated with each other for most of the day, but within many common bean lines were not related to the movements of the terminal leaflet. Thus, at the canopy level the overall impact of the pronounced movements of the terminal leaflet were diminished by movements of the lateral leaflets. The results show substantial genetic variability in both short‐term and long‐term leaflet movements in beans, some of which is related to geographic origin.

An infra-red spectroscopic study of structural reorganization of a uniaxially drawn VDF/TrFE copolymer in an electric field

A spectroscopic study has been conducted for the analysis of electric field induced microstructural changes in a uniaxially drawn 75 25 vinylidene fluoride/trifluoroethylene copolymer. Based on the relative intensities of the infra-red active bands measured, changes in the average orientation of the CH 2 dipoles after poling could be determined. Upon applying an electric field of 1.0 MV cm −1 to the sample, the mean-squared value of cos α for the CH 2 dipoles in the crystalline domain with respect to the film plane was found to change irreversibly from 0.46 to 0.34. Additionally, an increase in the degree of crystallinity of approximately 8% was observed after poling. Factor analysis was utilized in our spectroscopic analysis. Infra-red spectra for both the crystalline and amorphous regions have been constructed. These spectra are identical to those previously measured for isotropic samples. The conformational distribution for samples after poling contains a larger fraction of trans segments than unpoled samples.

A class of free rotation groups

The following theorem is proved: If cos φ ϵ Q then the subgroup of SO 3( R ) generated by two rotations about the angle ø, with rotation axes perpendicular to each other is free iff cos ø ≠ 0, ± 1 2 , ± 1. This is used to exhibit free subgroups of SO 3( Q ), also to find all rational values of cos ø when ø is a rational multiple of π. A similar result about the values of tan ø, due to P. Walker, is also presented.

Particle‐to‐bubble adhesion in gas/liquid/solid slurries

AbstractIn gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, for example, during flotation of finely divided minerals and in slurry reactors where particle‐to‐bubble adhesion may result in an enhanced gas absorption rate (Wimmers, 1987; Lindner, 1988). The adhesion of small particles to gas bubbles in water is studied with a modified bubble pick‐up method. The extent of the particle‐to‐bubble adhesion is revealed in the angle αmax, by which the gas‐bubble surface is covered by adhering particles under static conditions. It is shown that αmax depends on the modified Eötvös number, the ratio of the particle and bubble radii, and the effective contact angle θE. It is also found that θE is affected by the curvature of the three‐phase contact ring and by the type of the gas.A “particle‐to‐bubble adhesion” model, indicated by PBA model, based on a balance of forces under static conditions, is developed to calculate the value of θE from the measured values of αmax. The measured values of cos(θE) appeared to be a linear function of the curvature 1/r of the three‐phase contact ring which is in accordance with the extended Young‐Dupré equation.

Dispersion of soil gas around micron gold deposits

Kesler, S.E., Gerdenich, M,J., Steininger, R.C. and Smith, C., 1990. Dispersion of soil gas around micron gold deposits. In: S.E. Kesler (Editor), Soil and Rock Gas Geochemistry. J. Geochem. Explot., 38:117-132. Experimental weathering of sediment-hosted micron gold (SHMG) ore from the Alligator Ridge deposit indicates that ore and adjacent Pilot Shale wallrock release gas with larger concentrations of COS, CS2 and CH4, and lower CH4/(CH4 + C2H4 ) and CH4 / (CH4 + C2H 6 ) ratios than does barren Pilot Shale. The COS and CS2 are derived from decomposition of disseminated pyrite, which is probably more abundant in mineralized zones, and variations in the CH-gas ratios are thought to reflect increased thermal maturity of organic material in the mineralized zones. Surveys designed to determine whether these gases are present in detectable haloes around SHMG mineralization were carried out over the Yankee prospect, a relatively similar deposit several km south of Alligator Ridge. The surveys included analysis of interstitial soil gas, gases desorbed from soils, and gases desorbed from two sets of Carbotrap collectors, one left on the bedrock interface (at depths of about 30-70 cm below the surface) and another placed in holes drilled about 3 m into bedrock. All of the gases observed in the experiments were detected, as well as organo-sulfur and higher alkane and alkene gases. The surveys indicated systematic variations in gas dispersal related to faults and/or mineralization, with the most consistent patterns being elevated COS values and depressed CH4/(CH4 + C2H4) ratios over mineralization. Similar highs in COS, as well as other gases including SO2 and ethyl mercaptan, were associated with faults, and it was not possible to distinguish these two sources of anomalous gas patterns in all cases. In general, best results were obtained with gases desorbed from bulk soil, and no significant advantage was observed with the use of collectors placed in deep holes. Although all of the survey methods yielded anomalous patterns, none of these patterns are sufficiently strong to merit the use of gas geochemistry as a primary guide in exploration for SHMG deposits.

Release of drugs from oil-water microemulsions

The release of five drugs with different lipophilicities from oil-water (o/w) microemulsions (isopropyl myristate as oil, 1-butanol as cosurfactant, aerosol-OT as surfactant and buffer, pH 7.0, as the aqueous phase) was studied by determining mass transfer constants of the drugs through a hydrophilic membrane separating the o/w microemulsions from the receiving aqueous phase. The initial mass transfer constants measured were linearly related to the partition coefficients (P cos) of the drugs in the oil-cosurfactant-water mixtures. The P cos values were used to approximate the drug concentration in the aqueous phase of the emulsion. The initial mass transfer constants of different drugs calculated on the basis of these concentrations were very similar to the mass transfer constants of the drugs obtained by permeation studies through the same membrane using an aqueous phase.

Measurements on the liquid rise in glass capillaries at microemulsion/oil/brine interfaces

The height of liquid rise in Pyrex glass capillaries at microemulsion/oil and microemulsion/brine interfaces was measured for the toluene-brine-sodium dodecyl sulfate-butanol system, as a function of brine salinity. Results show that, in the two phase regions, σ og > σ μg at lower salinities and σ μg > σ wg at higher salinities, where σ og, σ μg , σ wg are the interfacial tensions between glass and the oil, microemulsion, and brine phases, respectively, these differences increasing with distance from the three-phase region. In the three-phase region, σ μg > σ wg > σ og for freshly etched glass, and σ wg > σ μg > σ og for untreated glass surfaces, the differences being small. Values of cos θ c ( θ c = contact angle) were estimated using the interfacial tension data of A. Pouchelon (thesis, Universite Pierre et Marie Curie, Paris, 1983; and with J. Meunier, D. Langevin, D. Chatenay, and A. M. Cazabat, Chem. Phys. Lett. 76, 277, 1980 ).

Ehrenfest theorem for angular displacement

Because of domain considerations for the z component of the angular momentum operator, the time rate of change of the expectation value of the angular displacement φ is not equal to the expectation value of the angular velocity operator. The angular velocity operator is the angular momentum operator divided by the moment of inertia. Ehrenfest’s theorem is obtained for the time rate of change of the expectation value of cos φ and sin φ.

Multistation observations of SITECs over a full solar cycle

Total electron content records from four southern hemisphere stations show 43 SITECs (sudden increases of the total electron content) in the period 1966–1977. Relating these to solar flare data shows that the probability that a given flare will produce a SITEC increases with the peak 10.7‐cm solar flux; with the value of cos χ, where χ is the solar zenith angle; and with decreasing central distance of the flare. The sizes of SITECs also increase significantly with the solar flux. SITECs are generally larger at lower latitudes in summer but show little latitudinal variation in winter. This pattern occurs at both solar maximum and solar minimum and is explained by seasonal changes in cos χ and in ionospheric loss rates. SITEC size versus latitude, however, is more variable during magnetically disturbed periods. Relative loss rates at different stations are obtained from the observed rise rates of corresponding SITECs. Results show that rapid ionospheric recombination (due to molecular ions) is more important at higher latitudes in summer and at lower latitudes in winter. This reflects primarily seasonal and latitudinal changes in the ratio N2/O, at heights above approximately 150 km. Similar variations are revealed in an analysis of five SITECs recorded at two northern hemisphere stations. SITEC rise rate measurements therefore provide a useful tool for studying differences in atmospheric composition at different sites.

Strengthening of the triplet relationship. II. A new probabilistic approach inP1

The probabilistic approach recently described in P{\bar 1} [Giacovazzo, Acta Cryst. (1976), A32, 967-976] is generalized to non-centrosymmetric space groups. The method enables us to derive the expected value of cos (ϕH + ϕH2 - ϕH1 + H2) and its variance, given |EH1|, |EH2|, |EH1 + H2| and one or more triples ( |EK|, |EH1 + K|, |EH1 + H2 + K|).

High-resolution nuclear magnetic resonance spectra of tetrahedral molecules and ions in anisotropic environments

Dipole-dipole and nuclear quadrupole splittings are reported for the tetrahedral ions NH 4 +, ND 4 + and BF 4 − in lyotropic liquid crystal phases. The splittings are due to distortion of the tetrahedra through interaction with their anisotropic environment. Two simple models of the distortion are discussed. In one, the C 3 v model, an XY bond of the tetrahedron XY 1 is parallel to the axis of the nematic medium and its angle with the other three bonds is increased by δ from the undistorted value of cos −1(− 1 3 ) ; allowance is made for interchanging all four XY bonds. In the D 2 d model, two pairs of XY bonds reduce their interbond angle by φ as in the E bending vibration of a tetrahedral molecule, and the S 4 axis of symmetry is parallel to the axis of the nematic medium; again, allowance is made for interchanging the four bonds. The observed dipole-dipole splittings of both XY and YY nuclear pairs, and the quadrupole splittings of X and Y nuclei, can be explained if the distortion is represented as a combination of the two models. The distortion angles δ and φ are of the order of 10 −2 degree. Distortions of at least this magnitude must be expected to occur in molecules of lower symmetry, indicating the need for caution in interpreting the NMR spectra of partially oriented molecules when the alignment is small.