Infinite Sheet Research Articles

Water Absorption Characteristics and Volume Changes of Milled and Brown Rice During Soaking

ABSTRACTThe water absorption characteristics and volume changes of rice with various degrees of milling during soaking were measured at five temperatures (5–40°C). The measured data were fitted to the exact solution for the infinite plane sheet diffusion model, which is an exact solution for the diffusion equation. The measured results agreed well with the model. The effects of temperature and the degree of milling on the water absorption rate constant were investigated. Volume changes of samples were determined by measuring particle density and bulk density. An empirical equation relating the moisture content of the sample during soaking and at temperatures of 10–50°C to specific volume was derived. In addition, bulk density was related to the quadratic function of the moisture content of the sample during soaking.

Two-Dimensional Indium Sulfide Framework Constructed from Pentasupertetrahedral P1 and Supertetrahedral T2 Clusters

A new open-framework indium sulfide ([In12S24H2]10-) constructed from pentasupertetrahedral sulfide clusters ([In8S17H],9- P1) and supertetrahedral sulfide clusters ([In4S10H],7-) T2) has been prepared through hydrothermal synthesis. Unlike previously reported P1 clusters that require divalent metal cations, the P1 cluster reported here consists of only trivalent ions (In3+) and is the only known example of tetrahedral clusters with a core sulfur site bonded to four trivalent ions. Each P1 cluster is joined to three T2 clusters (vice versa) to form an infinite two-dimensional sheet stacked along the crystallographic c-axis. In contrast with known three-dimensional open-framework indium sulfides in which locations of extraframework amines are rarely known due to disorder, structure-directing amine molecules are much less disordered as a result of host-guest N-H...S hydrogen bonding. The UV-vis diffuse reflectance spectrum shows that this material is a wide band gap semiconductor.

Application of van der Waals Density Functional to an Extended System: Adsorption of Benzene and Naphthalene on Graphite

It is shown that it is now possible to include van der Waals (vdW) interactions via a nonempirical implementation of density functional (DF) theory to describe the correlation energy in electronic structure calculations on infinite systems of no particular symmetry. The vdW-DF theory [Phys. Rev. Lett. 92, 246401 (2004)] is applied to the adsorption of benzene and naphthalene on an infinite sheet of graphite, as well as the binding between two graphite sheets. A comparison with recent thermal-desorption data [Phys. Rev. B 69, 155406 (2004)] shows great promise for the vdW-DF method.

Subcell FDTD analysis of shielding effectiveness of a thin-walled enclosure with an aperture

An improved subcell model is presented for including thin material sheets method in the finite-difference time-domain (FDTD) method. This improved subcell can be used to simulate a thin magnetic (mu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S </sub> ne mu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) sheet. Then, the improved subcell model is applied to the analysis of the shielding effectiveness (SE) of the electromagnetic wave propagating through a thin infinite material sheet, which is verified by comparison with the analytical results. Updated equations for components of the field on special spatial grids which are on edges and corners of the enclosure are presented, and the subcell model is used for the analysis of a thin-walled enclosure with an aperture. The FDTD results are in very good agreement with the test results

Electrodynamical characteristics of the polar ionosphere over the auroral and polar cap regions based on incoherent scatter radar measurements

Electrodynamical characteristics of the polar ionosphere over the auroral and polar cap regions are examined based on incoherent scatter radar measurements particularly in terms of electric field and ionospheric conductivity. For this purpose, 43 and 109 days of measurements from the Chatanika and Sondrestrom incoherent scatter radars, respectively, are utilized. The ionospheric current density inferred from the radar measurements of ionospheric conductance and electric field is compared with the corresponding ground magnetic disturbance. Also estimated is the global field-aligned current (FAC) that affects the ground magnetic disturbance, particularly of the D component. Several interesting characteristics about the polar ionosphere are emerging from this study: (1) the sun determines largely the conductance over the Sondrestrom radar, while the nighttime conductance distribution over the Chatanika radar is significantly affected by auroral precipitation. (2) The regions of the maximum N–S component of the electric field over the Chatanika radar are located approximately at the dawn and dusk sectors, while they tend to shift towards dayside over the Sondrestrom radar with the N–S component over Sondrestrom being slightly stronger than Chatanika. However, the E–W component over Chatanika is negligible compared to that of Sondrestrom. (3) The E–W component of the ionospheric current, J E, over Chatanika flows dominantly in the night hemisphere while it flows in the sunlit hemisphere over Sondrestrom. The N–S component of the ionospheric current, J N, over Chatanika flows prominently in the dawn and dusk sectors, while a strong southward current flows over Sondrestrom in the pre-noon sector. (4) The assumption of infinite sheet current approximation is far from realistic, underestimating the current density by a factor of 2 or more. It is particularly serious at higher latitudes. (5) The correlation between Δ H and J E is higher than the one between Δ D and J N indicating that FAC affects significantly Δ D. (6) The total upward and downward FAC are quite comparable and they are approximately 5.9×10 5 and 2.2×10 5 A over Chatanika and Sondrestrom, respectively. With enhancement of magnetic activity, FAC increases drastically over Chatanika by a factor of 4 or 5 while it is insignificant over Sondrestrom.

Parallel sheet structure in cyclopropane γ-peptides stabilized by C–H⋯O hydrogen bonds

A three-residue trans-cyclopropane gamma-peptide adopts an infinite parallel sheet structure in the solid state stabilized by intermolecular C-H...O hydrogen bonds, as demonstrated by single crystal X-ray diffraction.

Stability of domain walls coupled to Abelian gauge fields

Rozowsky, Volkas and Wali recently found interesting numerical solutions to the field equations for a gauged U1xU1 scalar field model. Their solutions describe a reflection-symmetric domain wall with scalar fields and coupled gauge configurations that interpolate between constant magnetic fields on one side of the wall and exponentially decaying ones on the other side. This corresponds physically to an infinite sheet of supercurrent confined to the domain wall with a linearly rising gauge potential on one side and Meissner suppression on the other. While it was shown that these static solutions satisfied the field equations, their stability was left unresolved. In this paper, we analyse the normal modes of perturbations of the static solutions to demonstrate their perturbative stability.

A Twisted Four-Sheeted Model for an Amyloid Fibril

The formation of amyloid fibers and their deposition in the body is a characteristic of a number of devastating human diseases. Here, we propose a structural model, based on X-ray diffraction data, for the basic structure of an amyloid fibril formed by using the variants of the B1 domain of IgG binding protein G of Streptococcus. The model for the fibril incorporates four beta sheets in a bundle with a diameter of 45 A. Its cross-section, or layer, consists of four strands, one strand from each sheet. Layers stack on top of each other to form the fibril, which has an overall helical twist with a periodicity of about 154 A. Each strand interacts in a parallel fashion with the strands in the layers above and below it, in an infinite beta sheet. Some geometric features of this model and the logic behind it may be applicable for constructing other related cross-beta amyloid fibrils.

Giant vortex state in mesoscopic superconductors

Using the self-consistent solution of the nonlinear Ginzburg-Landau equations, the superconducting state of a type II mesoscopic cylinder and of an infinite thin sheet with a circular hole (antidot), in the presence of an homogeneous magnetic field is studied. Close to the third critical field, the magnetic field penetrates the sample in the form of a vortex around the axis of the cylinder or of the antidot. This result has been found previously by other authors. The vortex, called a giant vortex, can carry several flux quanta. The giant vortex is persistent when the state is metastable and evolves to the so called paramagnetic Meissner effect (PME) within the cylinder. The behaviour of this effect as a function of the Ginzburg-Landau (GL) parameter is studied and the results are discussed. Gibbs free energy, order parameter and magnetic induccion as a function of the applied field and of the GL parameter are also studied. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Current layers: Influence of the finite size and non-uniform current distribution

One of the key parameters of the auroral regions is the currents which flow parallel to the magnetic field and transfer the energy and momentum between the ionosphere and the external regions of the magnetosphere. Satellite magnetic field measurements provide information about such currents. The commonly adopted technique to deduce the current characteristics from the magnetic perturbations is based on the approximation of current sheet of three dimensions, two of them, i.e. along the magnetic field and in a perpendicular direction, are infinite. This approach is valid when the magnetic perturbations are observed far from the current edges, which is not always the case. In this paper, we compare the infinite sheet approximation with the solution for the current layer of finite transverse sizes and discuss the influence of the current edges on the deduced parameters. In addition, the current distribution inside the layer is rarely uniform, but comprises filamentary structures with typical sizes that correspond to the characteristic scales of the processes which originate them. Both, the filamentary currents and the current sheet edges, create a component of the magnetic perturbation normal to the current sheet, which is absent in the model of the infinite uniform current layer. The discussion is illustrated with simultaneous observations of a current double-layer made at the altitude of 860 km by the magnetometers on board the Ørsted satellite and at ∼300 km by the coherent SuperDARN radars.

Collapse and Fragmentation of Molecular Cloud Cores. VIII. Magnetically Supported Infinite Sheets

The collapse and fragmentation of initially sheetlike, magnetic molecular clouds is calculated in three dimensions with a gravitational, radiative hydrodynamics code. The code includes a crude representation of magnetic field effects and ambipolar diffusion through the magnetic pressure and magnetic tension approximations and a simple parameterization based on previous magnetohydrodynamic calculations, respectively. The computational volume is a spherical portion of an initially isothermal, infinite sheet of self-gravitating gas, symmetric about its midplane, with the portion of the cloud exterior to the spherical volume represented through its effect on the gravitational potential inside the spherical volume. The gas layer is initially in hydrostatic equilibrium, but with a mass equal to or greater than the critical mass (~1 M☉) for the growth of gravitational instability. The magnetic field pressure acts to further stabilize the initial cloud. Over 106 active grid points are employed in the models, sufficient to resolve the Jeans length and so avoid artificial fragmentation. The parameters varied are the ratio of the ambipolar diffusion time to the midplane free fall time (10 or 20), the cloud's reference magnetic field strength (100 or 200 μG, corresponding to initially magnetically supercritical or subcritical clouds, respectively), the ratio of rotational to gravitational energy of the sheet (0.0 or 0.01), and the form of the initial density perturbation applied to the infinite sheet. Three types of outcomes are observed: formation of one or two protostars near the edge of the spherical volume, formation of a protostar near (but not at) the center of the cloud, or formation of a rotating ring near the center of the cloud, which appears likely to fragment into two or more protostars. Flow speeds of ~0.1 km s-1 are generated as the sheet begins to break up into collapsing protostars. The forming protostars are separated by distances approximately equal to the cloud diameter, consistent with the spacing predicted by the linear theory of the gravitational stability of an infinite sheet.

무한 빙판에서의 쇄빙력과 파단 빙편의 크기 예측

Ice rubble pieces broken by the bow impact load and side hull of an icebreaking vessel usually pass along the ship's bottom hull and may hit the propeller/rudder or other stern structures causing serious damage to ship's hull . Therefore it is important to estimate the size of broken ice pieces during the icebreaking process. The dynamic interaction process of icebreaker with infinite ice sheet is simplified as a wedge type beam of finite length supported by elastic foundation. The wedge type ice beam is leaded with vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum dynamic bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a failure length of broken ice sheet given design parameters. The results are compared to Nevel(1961)'s analytical solution for static load and observed pattern of ice sheet failure onboard an icebreaker. Also by comparing computed failure length with the characteristic length, the meaning of ice rubble sizes is discussed.

Characteristics of the Polar Ionosphere Based on the Chatanika and Sondrestrom Incoherent Scatter Radars

The climatological characteristics of the polar ionospheric currents obtained from the simultaneous observations of the ionospheric electric field and conductivity are examined. For this purpose, 43 and 109 days of measurements from the Chatanika and Sondrestrom incoherent scatter radars are utilized respectively. The ionospheric current density is compared with the corresponding ground magnetic disturbance. Several interesting characteristics about the polar ionosphere are apparent from this study: (1) The sun determines largely the conductance over the Sondrestrom radar, while the nighttime conductance distribution over the Chatanika radar is significantly affected by auroral precipitation. (2) The regions of the maximum N-S electric field over the Chatanika radar are located approximately at the dawn and dusk sectors, while they tend to shift towards dayside over the Sondrestrom radar. The N-S component over Son-drestrom is slightly stronger than Chatanika. However, the E-W component over Chatanika is negligible compared to that of Sondrestrom. (3) The E-W ionospheric current flows dominantly in the night hemisphere over Chatanika, while it flows in the sunlit hemisphere over Sondrestrom. The N-S current over Chatanika flows prominently in the dawn and dusk sectors, while a strong southward current flows in the prenoon sector over Sondrestrom. (4) The assumption of infinite sheet current approximation is far from realistic, underestimating the current density by a factor of 2 or more. It is particularly serious for the higher latitude region. (5) The correlation between <TEX>${\Delta}H\;and\;J_E$</TEX> is higher than the one between <TEX>${\Delta}D\;and\;J_N$</TEX>, indicating that field-aligned current affects <TEX>${\Delta}D$</TEX>significantly.

Approximations to wave scattering by an ice sheet of variable thickness over undulating bed topography

An investigation is carried out into the effect on wave propagation of an ice sheet of varying thickness floating on water of varying depth, in three dimensions. By deriving a variational principle equivalent to the governing equations of linear theory and invoking the mild-slope approximation in respect of the ice thickness and water depth variations, a simplified form of the problem is obtained from which the vertical coordinate is absent. Two situations are considered: the scattering of flexural–gravity waves by variations in the thickness of an infinite ice sheet and by depth variations; and the scattering of free-surface gravity waves by an ice sheet of finite extent and varying thickness, again incorporating arbitrary topography. Numerical methods are devised for the two-dimensional versions of these problems and a selection of results is presented. The variational approach that is developed can be used to implement more sophisticated approximations and is capable of producing the solution of full linear problems by taking a large enough basis in the Rayleigh–Ritz method. It is also applicable to other situations that involve wave scattering by a floating elastic sheet.

Magnetic field annihilators: invisible magnetization at the magnetic equator

SUMMARY Some distributions of magnetization give rise to magnetic fields that vanish everywhere above the surface, rendering these distributions of magnetization completely invisible. They are the annihilators of the magnetic inverse problem. Known examples are the infinite sheet with constant magnetization and the spherical shell of constant susceptibility magnetized by an arbitrary internal field. Here, we show that remarkably more interesting annihilators exist for the Earth’s dipole-dominated inducing field. Indeed, any susceptibility profile along the magnetic equator can be extended north/south into an annihilator. Consequently, the induced magnetization along the magnetic equator is entirely undetermined by the visible magnetic field. In contrast to the Backus effect, this ambiguity persists even if the full magnetic vector field is known.

The analytical energy gradient scheme in the Gaussian based Hartree–Fock and density functional theory for two-dimensional systems using the fast multipole method

The analytical total energy gradient scheme for the Hartree–Fock and density functional crystalline orbital theory is formulated for infinitely extended periodic systems of general dimensions and implemented for those of two dimensions. Two major differences between the analytical gradient scheme for extended systems and that for molecular systems are described in detail. The first is the treatment of the long-range Coulomb interactions, which arise due to the infinite nature of the system size. The long-range effect is efficiently included by the multipole expansion technique and its extension, the fast multipole method. The use of the fast multipole method enables us to include the long-range effect up to the order of micrometer to millimeter region around the reference unit cell by virtue of the logarithmic cost scaling of the algorithm achieved by regrouping distant multipoles together and reducing the number of pairwise interactions. The second is the formulation of analytical gradient expressions with respect to unit cell parameters. In HF theory they can be calculated by accumulating forces acting on atoms multiplied by some appropriate factors, while there is an extra term which requires a special numerical treatment in grid-based density functional theory. Specifically, it is shown that the quadrature weight derivatives do not vanish even in the limit of infinitely fine grid when calculating the gradients with respect to unit cell parameters, and are essential in evaluating those gradients. Combining the analytical gradient scheme and an efficient inclusion of the long-range interaction makes it feasible to perform a full geometry optimization of extended systems at ab initio levels. As an illustration, the long-range interaction energies are computed for a two-dimensional sheet of hydrogen-fluoride. The CPU time reduction on going from the explicit evaluation of the two-electron integrals to multipole expansion, and from the multipole expansion to fast multipole method is significant. Geometry optimizations are performed on an infinite two-dimensional hexagonal boron-nitride sheet and the dependence of the gradients on various parameters are investigated.

WATER ABSORPTION CHARACTERISTICS OF WHEAT AND BARLEY DURING SOAKING

Water absorption characteristics of wheat and barley during soaking were measured at five temperatures rangingfrom 10.C to 50.C. From the water absorption characteristic curves, it was determined that water absorption of wheat andbarley was in the second falling rate period. Using the measured data, a nonlinear least squares method was applied to anapproximate solution of the diffusion equation MR = B1 exp(Kt). Values of parameter B1 for the diffusion model wereestimated to be about 0.6 for wheat and about 0.8 for barley. Therefore, the measured data were fitted to the exact solutionfor the sphere diffusion model for wheat and for the infinite plane sheet diffusion model for barley by a nonlinear least squaresmethod. The measured results agreed well with the calculated results. The values determined for the diffusion coefficients were1.1 . 1012 to 1.0 . 1011 (m2/s) for wheat and 3.5 . 1012 to 3.9 . 1011 (m2/s) for barley. An Arrheniustype equation wasused to relate the diffusion coefficient of wheat and barley to temperature (T), and the energy of activation (E) for wheat andbarley was estimated. The values determined were 44.0 kJ/mol for wheat and 45.9 kJ/mol for barley.

Fabrication of infinite two-dimensional sheets of tetragonal metal(II) lattices: X-ray crystal structures and magnetic properties of [M(CA)(pyz)]n (M2+=Mn2+ and Co2+; H2CA=chloranilic acid; pyz=pyrazine)

New cobalt(II) and manganese(II) co-ordination polymers containing tetragonal lattices [M(CA)(pyz)]n (M2+=Mn2+ (1) and Co2+ (2); H2CA=chloranilic acid; pyz=pyrazine) have been synthesized and characterized. Both compounds 1 and 2 are isomorphous. Each metal atom for 1 and 2 displays a six-coordinate geometry with the two bis-chelating CA2− anions and pyz molecules, providing an infinite square grid sheet. The temperature dependence of magnetic susceptibilities revealed the presence of antiferromagnetic interaction with J=−0.32 cm−1, zJ′=−0.34 cm−1, g=2.00 for 1 and J=−1.09 cm−1, J′=−0.55 cm−1, g=2.27 for 2, respectively.

SUPERDARN과 GREENLAND 자력계를 이용한 전리층 전기전도도의 추정

전리층은 우주환경의 변화에 매우 중요한 역할을 하고 있다. 특히 전기전도도 분포에 관한 정보는 자기권-전리층 상호작용을 이해하는데 필수적이다. 이러한 요구에 부응해서 전기전도도를 구하려는 다양한 시도가 있었다. 본 연구에서는 SuperDARN(Super Dual Auroral Radar Network) 레이더망 중 Goose Bay 및 Stokkseyri 레이더에서 관측한 전기장과 Greenland의 서부해안에 설치된 지자기 관측소에서 동시에 얻은 지상 지자기 기록을 이용하여 전기전도도를 추정하였다. 또한 전리층을 흐르는 전류를 무한판상으로 가정하고 Biot-Savart 및 Ohm의 법칙을 적용하여 Hall 및 Pedersen 전기전도도를 추정하였다. 예상한대로 Hall 전기전도도는 오로라 제트전류대의 중심을 따라 상당히 강화됨을 알 수 있었다. 그러나 Pedersen 전기전도도는 광범위한 지역에 서 음의 값이 나타났다. 이러한 문제를 보완하기 위해서 지자기 변화 성분인 <TEX>${\Delta}D$</TEX>에 연자기력선 전류의 효과를 고려하였다. 그 결과 이전에 음으로 나타난 지역이 상당히 감소되었다. 따라서 지상 지자기 변화 자료와 레이더에서 관측된 전기장을 이용해서 전기전도도를 구하는 경우 연자기력선 전류의 효과를 고려해야 한다. The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.

Synthesis and structure of a 3-rings antimony germanate: Sb2Ge3O9

Abstract An antimony germanate (Sb 2 Ge 3 O 9 ) was synthesized under mild solvothermal condition. Organic amine did not incorporate into the structure, although they are used and necessary in synthesis. The structure of this compound can be described as antimony germanate layers constructed from vertex-sharing GeO 4 tetrahedra and SbO 3 trigonal pyramid. The linkage of 3-rings and 9-rings forms an infinite sheet in crystallographic ab plane. The layer stacking together with only van der Waals force between layers. This work open possibilities for synthesizing other antimony germanate with novel structure topologies, since polyhedra such as [SbX 3 ], [SbX 4 ], [SbX 5 ] and [SbX 6 ] (X=O or F) can be formed.