Locking of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction with one-dimensional spatial periodic forcing

We use the photosensitive chlorine dioxide-iodine-malonic acid reaction-diffusion system to study wavenumber locking of Turing patterns with spatial periodic forcing. Wavenumber-locked stripe patterns are the typical resonant structures that labyrinthine patterns exhibit in response to one-dimensional forcing by illumination when images of stripes are projected on a working medium. Our experimental results reveal that segmented oblique, hexagonal and rectangular patterns can also be obtained. However, these two-dimensional resonant structures only develop in a relatively narrow range of forcing parameters, where the unforced stripe pattern is in close proximity to the domain of hexagonal patterns. Numerical simulations based on a model that incorporates the forcing by illumination using an additive term reproduce well the experimental observations. These findings confirm that additive one-dimensional forcing can generate a two-dimensional resonant response. However, such a response is considerably less robust than the effect of multiplicative forcing.     

Accurate explicitly correlated wave functions for two electrons in a square

An explicitly correlated linear-r(12) variational method is developed for a system of two electrons confined to a two-dimensional square well with infinite walls. The wave function is written as an expansion in products of non-negative integer powers of the relative and center-of-mass electronic coordinates and powers of r(12) restricted to 0 and 1. This form indirectly includes higher powers of the interelectronic distance and exhibits a much faster convergence than a similar expansion without r(12)-dependent terms. The method is implemented using high-precision floating-point arithmetic. Ground-state total energies are reported with at least 12 accurate significant figures for squares with sides from 1 to 50 bohrs. The method can be used "as is" for excited states and for two-dimensional rectangular wells. We also show that wave functions for two electrons in a square and in a rectangle have a higher symmetry than can be accounted for by the point group of the system.     

Two-dimensional polyacrylamide gel electrophoresis, with immobilized pH gradients in the first dimension, of barley seed proteins: discrimination of cultivars with different malting grades.

The suitability of high-resolution two-dimensional gel electrophoresis for barley cultivar discrimination and for classification with respect to their malting properties was studied. Seed proteins of 14 barley cultivars with different malting qualities were extracted with urea/dithiothreitol/Nonidet P-40 buffer and subjected to two-dimensional gel electrophoresis with immobilized pH gradients in the first dimension (IPG-DALT). The results of IPG-DALT were compared to the protein patterns obtained by a standard technique, sodium dodecyl sulfate polyacrylamide gel electrophoresis of hordeins. Sodium dodecyl sulfate-gel electrophoresis yielded seven different "B" and four different "C" hordein patterns; "A" and "D" hordein patterns were uniform in all cultivars tested. Four cultivars could be distinguished unequivocally, the others were classified into three groups containing between two and five cultivars. In contrast to these findings. IPG-DALT yielded three different "A", eight different "B", four different "C" and two different "D" hordein patterns. When the "A", "B", "C" and "D" hordein patterns were combined, ten cultivars exhibited unique hordein patterns whereas the remaining ones were classified into two groups containing two cultivars each. Moreover, when albumin and globulin proteins were used for evaluation in addition to the hordeins, all cultivars could be discriminated by IPG-DALT. IPG-DALT, performed on small-scale and/or ready-made gels, proved to be an ideal complementary system to one-dimensional electrophoretic methods for routine seed testing purposes because of its speed, reliability, and simplicity. IPG-DALT was also applied to study the relationship between the different polypeptide patterns and the malting quality. Although cultivars with identical one-dimensional protein patterns but different malting quality could be successfully differentiated by IPG-DALT, a direct correlation between specific protein spots or protein patterns to the malting quality was not found within the cultivars tested.     

Chromatography with a two-dimensional column

Summary A chromatographic method using a flat, square column developed along one direction and then eluted along the perpendicular direction, using a second retention mechanism widely different from the first one is described. Such a method would offer a potential peak capacity of several thousands, at least ten times more than either conventional column chromatography or two-dimensional thin-layer chromatography. Equipment capable of satisfying the requirements derived from a theoretical study of the operation of a two-dimensional column is also described. Results are satisfactory.Presented at the 14th International Symposium on Chromatography London, September, 1982 as a plenary lecture.     

The synthesis and crystal structures of two-dimensional coordination polymers of Ph2P(O)-CH2CH2-P(O)Ph2 and Ph2P(O)-C5H3N-P(O)Ph2 with praseodymium

Reactions of Pr(NO3)3 with Ph2P(O)-CH2CH2-P(O)Ph2 and Ph2P(O)-C5H3N-P(O)Ph2 yielded layered network coordination polymers with bidentate ligands spanning the lanthanide atoms in a bridging fashion. The praseodymium cations with "spacer" ligands form two-dimensional building blocks assembling into either square grid or herringbone network.     

Cardiac muscle protein analysis by high-resolution and microscale two-dimensional gel electrophoresis

An improved method of two-dimensional gel electrophoresis of small muscle samples is described. Isoelectric focusing of cardiac whole muscle homogenate in agarose gels containing urea and detergent has a markedly increased resolution. Equilibration of the first-dimensional gels with detergent before application to the second-dimensional gels is unnecessary in this system. By applying this method to rat cardiac whole muscle, high-molecular weight proteins, such as myosin heavy chains, are focused on the first-dimensional gels and, in addition, minor components are resolved on the second-dimensional gels, without loss during equilibration with detergent. The two-dimensional electrophoretic patterns of rat cardiac whole muscle obtained with this method reveal numerous clearly separated spots. By analyzing the two-dimensional electrophoretic patterns of rat cardiac whole muscle and various rat cardiac fractions, and by staining the calcium-binding proteins with "Stains-all", we identified some cardiac muscle components, such as myosin heavy and light chains, actin, tropomyosin, and troponin C, but additional work is required to identify the remaining spots. The two-dimensional electrophoretic system described here makes possible the effective resolution of whole cardiac muscle homogenate from small samples, and looks promising as an aid to muscle research.     

Spontaneous segregation on a hybrid chiral surface

Segregation of enantiomers in two-dimensional adsorbed layers is a process that is usually controlled by anisotropic directional interactions between adsorbed molecules. In this contribution, we propose a simple theoretical model in which the chiral segregation occurs even though the lateral interactions are neglected. In particular, we consider a solid surface composed of two domains with different patterns of active sites being mirror images of each other. The domains of opposite handedness represent crystal facets of a composite chiral material which are adjoined to form a heterochiral adsorbing surface. To explore equilibrium properties of the system, we use Canonical Ensemble Monte Carlo method for a square lattice. The influence of factors such as energetic properties of the surface and density of the adsorbed layer on the extent of separation is examined. The obtained results indicate that effective two-dimensional separation on the hybrid chiral surface assumed in our model can be achieved only at sufficiently low adsorbate densities. The results also suggest that the segregation on the hybrid surface would be a promising method of enantiodiscrimination for those chiral molecules which do not exhibit strong lateral interactions.     

Dynamic mechanism of photochemical induction of turing superlattices in the chlorine dioxide-iodine-malonic acid reaction-diffusion system

We study the mechanism of development of superlattice Turing structures from photochemically generated hexagonal patterns of spots with wavelengths several times larger than the characteristic wavelength of the Turing patterns that spontaneously develop in the nonilluminated system. Comparison of the experiment with numerical simulations shows that interaction of the photochemical periodic forcing with the Turing instability results in generation of multiple resonant triplets of wave vectors, which are harmonics of the external forcing. Some of these harmonics are situated within the Turing instability band and are therefore able to maintain their amplitude as the system evolves and after illumination ceases, while photochemically generated harmonics outside the Turing band tend to decay.     

Nonequilibrium restructuring in two-dimensional Lennard-Jones system induced by a simple square start configuration

In the present paper, we report a molecular dynamics simulation of two-dimensional Lennard-Jones system with a simple square start configuration. Mean square displacement was computed showing interesting dependence on high pressure conditions in short time scale, corresponding to an abrupt restructurization. This paper is the first to report the qualitative and quantitative details of this phenomenon.     

NMR diffusometry with beds of nanoporous host particles: an assessment of mass transfer in compartmented two-phase systems

Molecular diffusion in a bed of zeolite crystallites is mimicked by dynamic Monte Carlo simulation of a particle hopping on a two-dimensional square lattice. The resulting probability distribution of molecular propagation (the "mean propagator") is used for a rigorous determination of the resulting dependencies of diffusion measurement by pulsed field gradient NMR. In the limiting cases of intracrystalline, restricted, and long-range diffusion, these dependencies are found to coincide with the well-known relations resulting from the application of a simplifying exchange model (the "two-region" approximation). The intensity of transport resistances on the boundary between the intra- and intercrystalline spaces, i.e., on the compartment boundaries, is only accessible in the intermediate case, i.e., for observation times comparable with the mean lifetimes within the different compartments. In this case, significant differences between the results of the rigorous treatment and the "two-region" approximation may occur.     

Synthesis and crystal structure of [Ag2(μ4-hmt)(NO2)2]n. A two-dimensional network with square cavities self-assembled by hmt (hmt = Hexamethylenetetramine)

AgNO₂ (1 mol) reacts with hexamethylenetetramine (hmt) (1 mol) in MeCN–H₂O to yield a two-dimensional coordination polymer [Ag₂( ₄-hmt)(NO₂)₂]_n with square cavities. The Ag2 atom is located in a linear structure coordination environment with two nitrogen atoms from two hmt molecules respectively. The Ag1 atom is coordinated in a triangular prism surrounded by two nitrogen atoms from two hmt molecules respectively and four oxygen atoms from two NO^– ₂ ions respectively. The four nitrogen atoms of each hmt unit are all connected to Ag^I to form a two-dimensional network.     

Freeze-fracture electron microscopy study of mesophases in mixtures of polyoxyethylene (14) oleylether and water

Mixtures of polyoxyethyleneoleylether, with an average of 14 oxyethylene units per molecule, and water, were investigated at between 20 and 100C using polarization microscopy. A lamellar (L ), hexagonal (H ₁), viscous isotropic (V ₁) and cubic (I ₁) mesophase were found and an outline of the pseudo binary phase diagram was constructed. The mesophases were investigated with freeze-fracture electron microscopy and micrographs of characteristic textures are presented.L andH ₁ displayed well known features, the repeat distances observed were in good agreement with findings from X-ray diffraction.H ₁ showed fracture planes with and without a ribbed pattern. Using specific decoration with ice crystals, fracture planes with the ribbed pattern were found to be more hydrophilic.V ₁ showed regular patterns, in some places forming a square lattice, in other places resembling a network of short rods with two-dimensional hexagonal symmetry. The repeat spacing observed in the textures was about 11 nm.I ₁ showed foremost fractured layers with a fine texture of spherical units in a two-dimensional hexagonal array. The centre-to-centre distance between these units was about 8–9 nm.     

Explorative data analysis of two-dimensional electrophoresis gels

Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots on the gels for further investigation. The explorative approach in analysis of 2-D gels makes it possible, in a fast and convenient way, to screen many gels in order to determine the protein patterns that form clusters and could be selected for further examination.     

Cu(pyrazine-2-carboxylate)2]2Cd4I8: unprecedented 1-D serpentine inorganic chains and regular 2-D metal-organic square grids in a 3-D framework

A novel three-dimensional coordination polymer containing an unprecedented one-dimensional serpentine motif conjoined with a two-dimensional square grid motif is presented.     

Two novel four-coordinated zinc(II) polymers: Synthesis,structures, and properties

The synthsis, crystal structure, thermal analysis and spectroscopic studies of two novel zinc(II) coordination polymers Zn₄(NA)₄Dpa₂ (I) and Zn(Inic)(Bpdc)_0.5 (II) (NA = niacin, Inic = isonictinic acid, Dpa = 2,2′-biphenyldicarboxlate, Bpdc = 4,4′-biphenyldicarboxylate) are presented here. The crystal structure of I is a two-dimensional network whose tetranuclear unit is a slightly distorted square. Two kinds of ligand connect adjacent zinc(II) ions, respectively, in a coordinate direction. The structure of II is a three-dimensional and it consist of corrugated square layers of isonictinic acid-bridged zinc(II) ions which are pillared by 4,4′-biphenyldicarboxylate. The rod-ligands in II appear as useful tools to control the interlayer metal-metal separation. Each zinc(II) ion in I and II is four-coordinated with three oxygen atoms and one nitrogen atom building distorted tetrahedron environments.     

Two-dimensional colloid crystals templated by polyelectrolyte multilayer patterns

In this paper, we demonstrate that two-dimensional (2D) periodic patterns of polyelectrolyte multilayers (PEMs) can be used as surface templates for assembling highly ordered 2D colloidal microarrays. We report detailed structural features of the 2D colloid crystals produced by depositing silica microspheres onto periodic micrometer-scale PEM patterns arrayed in a square or hexagonal lattice with a pattern pitch (approximately) twice the pattern diameter. Analysis of the images of these 2D colloid monolayers reveals that the distributions of the distances by which the adsorbed particles deviate from the corresponding PEM pattern centers are typically bell-shaped, with the majority of the deposited particles located within a relatively short distance from the respective pattern centers. We show that this behavior reflects the effect of the electrostatic focusing force that (occurs because of the finite size of the PEM pattern and) becomes effective when the depositing particle approaches the pattern site to a small distance. Also, in these 2D colloid crystals, the orientations of the off-center displacements of the deposited particles are strongly correlated spatially over the entire sample size. We present experimental evidence that this unusually long-ranged orientational correlation is due to the close spacing of the patterns, which causes an overlap of the excluded volumes between the neighboring deposited particles.     

Study of the usability of sinusoidal function heat flux based on enthalpy-porosity technique for PCM-related applications

Journal of Thermal Analysis and Calorimetry - The present study summarizes a two-dimensional (2D) numerical simulation of a phase change material (PCM) melting/solidification processes in a square...     

Scattering from truncated spherulites

A general two-dimensional theory is derived to explain the light scattering from truncated spherulites. The severity of the truncation is expressed by a statistical parameter σ²/ā² which is the ratio of the variance σ² of the size of the spherulite to the square of its average size ā. The H_v light-scattering patterns are calculated for different values of the truncation parameter. It is observed that the truncation decreases the position of maximum scattering intensity of the pattern. It also increases the scattering intensity at small and large angles, but reduces it at intermediate angles. For a spherulitic polyethylene sample, the truncation parameter is found to equal 0.100 ± 0.030 as measured microscopically. The theory can also be used to calculate light-scattering patterns from row-nucleated spherulites. If it is assumed that the interference effect averages out to zero when a large number of spherulites is involved, a single “sliced” spherulite model can be used. Then, the scattering intensity per unit area decreases as the “slice” becomes very thin.     

Square, hexagonal, and row phases of PTCDA and PTCDI on Ag-Si(111)square root(3) x square root(3)R30 degrees

We have investigated the ordered phases of the perylene derivatives perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) and the imide analogue PTCDI on the Ag-Si(111)square root(3) x square root(3)R30 degrees surface using scanning tunneling microscopy. We find that PTCDA forms square, hexagonal, and herringbone phases, which coexist on the surface. The existence of a square phase on a hexagonal surface is of particular interest and is a result of a near commensurability between the molecular dimensions and the surface lattice. Contrast variations across the square islands arise from PTCDA molecules binding to different sites on the surface. PTCDI on Ag-Si(111)square root(3) x square root(3)R30 degrees forms extended rows, as well as two-dimensional islands, both of which are stabilized by hydrogen bonding mediated by the presence of imide groups. We present models for the molecular arrangements in all these phases and highlight the role of hydrogen bonding in controlling this order.     

Detection of polypeptides and amylase isoenzyme modifications related to malting quality during malting process of barley by two-dimensional electrophoresis and isoelectric focusing with immobilized pH gradients.

Two cultivars ("Alexis" and "Lenka") of contrasting final attenuation values were malted, and the protein and amylase isoenzyme composition, as well as the change in protein and amylase isoenzyme composition during malting, was investigated by two-dimensional polyacrylamide gel electrophoresis of total proteins, and isoelectric focusing of amylase isoenzymes, respectively. Isoelectric focusing demonstrated that significant differences exist between the amylase isoenzyme patterns of the two cultivars, suggesting a correlation between the presence of certain amylase isoenzyme bands and final attenuation. This finding was confirmed by analysis of 36 barley cultivars with a wide range of quality. It was shown that all cultivars which are of low or, at best, moderate final attenuation values exhibit the amylase band "B" (isoelectric point approximately 6.8), whereas those cultivars which are predominantly of high malting grade do not possess this "B" isoenzyme band, but exhibit the pronounced "A" isoenzyme band (isoelectric point approximately 6.5) instead, suggesting that these isoenzymes (which we suppose to be beta-amylases) can be utilized to predict the final attenuation values of unknown barley samples or new lines. However, "final attenuation" is a complex function. Preliminary results of two-dimensional gel electrophoresis indicate that other factors, such as total amount of amylases, or a 19 kDa A hordein-like polypeptide, which was degraded faster in the low malting grade cultivar "Lenka", may also have a role in determining quality.