Individual Columns Research Articles

Multiscale Pattern Analysis of Orientation-Selective Activity in the Primary Visual Cortex

Although orientation columns are less than a millimeter in width, recent neuroimaging studies indicate that viewed orientations can be decoded from cortical activity patterns sampled at relatively coarse resolutions of several millimeters. One proposal is that these differential signals arise from random spatial irregularities in the columnar map. However, direct support for this hypothesis has yet to be obtained. Here, we used high-field, high-resolution functional magnetic resonance imaging (fMRI) and multivariate pattern analysis to determine the spatial scales at which orientation-selective information can be found in the primary visual cortex (V1) of cats and humans. We applied a multiscale pattern analysis approach in which fine- and coarse-scale signals were first removed by ideal spatial lowpass and highpass filters, and the residual activity patterns then analyzed by linear classifiers. Cat visual cortex, imaged at 0.3125 mm resolution, showed a strong orientation signal at the scale of individual columns. Nonetheless, reliable orientation bias could still be found at spatial scales of several millimeters. In the human visual cortex, imaged at 1 mm resolution, a majority of orientation information was found on scales of millimeters, with small contributions from global spatial biases exceeding approximately 1 cm. Our high-resolution imaging results demonstrate a reliable millimeters-scale orientation signal, likely emerging from irregular spatial arrangements of orientation columns and their supporting vasculature. fMRI pattern analysis methods are thus likely to be sensitive to signals originating from other irregular columnar structures elsewhere in the brain.

Visible light initiated polymerization of styrenic monolithic stationary phases using 470 nm light emitting diode arrays.

Poly(styrene-co-divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)-(S)-camphorquinone/ethyl-4-dimethylaminobenzoate/N-methoxy-4-phenylpyridinium tetrafluoroborate was activated using a 470 nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100 microm id polytetrafluoroethylene-coated fused-silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725 MPa/cm at 1 microL/min (water, 20 degrees C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns.

Temporal changes in vertical distribution, body orientation and mobility of pike (Esox luciusL.) free embryos: Individual observations under controlled conditions

The vertical distribution, body orientation and mobility of pike free embryos were studied at 10 °C in 25-cm individual water columns. Five steps were identified: (1) a resting phase, up to day (D) 4 post-hatching; (2) an ascent phase (D1–D4); (3) a plateau (D5–D8), characterized by a wall-attachment behaviour in the subsurface zone; (4) a break-off phase (D9–D13); and (5) a final localization between mid-water and surface, corresponding to the air filling of the swim bladder and to the transition to active, horizontal swimming (D14–D17). Free embryos could be: side-lying (phase 1, late phase 4 and phase 5); lying upright (phases 4 and 5); vertically suspended with adhesion to the wall (phases 2–3 and early phase 4); and in oblique or horizontal position (phase 5). The opening of mouth and anus occurred during phases 2 and 3 and swim bladder filling started on days 13–14. Free embryo mobility was low and stable during the first 5 days and increased regularly thereafter to reach maximal levels on days 14–16. This research provides evidence for a more complex and more variable temporal pattern of free embryo vertical distribution, posture and mobility than previously thought.

Automatic Column Coupling System To Operate Chromatographic Supports Closer To Their Kinetic Performance Limit and To Enhance Method Development

A new hardware solution is proposed that allows one to automatically change the length of a chromatographic bed. The setup is based on the serial coupling of chromatographic columns using two rotor-stator valves (with N positions, N + 1 ports). Despite the use of a prototype setup requiring rather long connection tubing, only 9% loss in efficiency is observed for compounds with a retention factor above 4 compared to the efficiency expected on the basis of the individual column results. It has been demonstrated for a number of isocratic and gradient separations that the system allows one to realize considerable analysis time savings by adapting the total column length to the specific sample requirements and/or to the stage of method development wherein one is working. During method development, a separation on a short column length can first be used to rapidly gain insight into the composition of the sample, leaving fewer runs to be done on a column of maximal length (offering efficiencies that are inaccessible with individual column systems). The ease with which information can be obtained on columns of different lengths can furthermore be exploited for screening purposes to detect coeluting components in a stage wherein they still appear completely unresolved (i.e., have a resolution well below R(s) = 0.5).

Evaluation of each electron beam and exposure results with four column cells in multicolumn e-beam exposure system

In the Mask D2I project at ASET, the authors assembled an electron beam exposure system to prove the concept of the multicolumn cell with character projection capability. They performed beam calibrations in individual column cell to evaluate beams after character deflections. They measured the impacts on beam positions in one column cell caused by deflections in other column cells and concluded that there were no deflection impacts on beam positions from neighboring column cells in the multicolumn cell system. They also evaluated stitching errors of the patterns exposed by different column cells. Present stitching errors of the patterns between the different column cells were estimated to be less than 20nm.

Separation of l-tryptophan present in an aromatic amino acids mixture in a four-column simulated moving bed: experimental and simulation studies

An experimental and theoretical study is presented for the fractionation of L-Tryptophan (Trp) from L-phenylalanine (Phe) and L-tyrosine (Tyr). A Simulated-Moving Bed (SMB) with four-column system was tested, and the results are presented as effluent histories of the raffinate and extract ports. L-phenylalanine and L-tyrosine were recovered as major products in the raffinate, while L-Tryptophan was recovered at the extract. To simulate the L-Tryptophan separation, a general rate model was used to represent the mass transfer phenomena that occur in each individual column of the SMB, for each solute present in the multicomponent system. A hybrid method was used to solve the model. An analytic solution was used for the intra-particle concentration, and was correlated to the liquid bed concentration by Duhamel's theorem. The results from simulation are compared with the experimental data presented in this work.

Accurate and efficient reconstruction of deep phylogenies from structured RNAs

Ribosomal RNA (rRNA) genes are probably the most frequently used data source in phylogenetic reconstruction. Individual columns of rRNA alignments are not independent as a consequence of their highly conserved secondary structures. Unless explicitly taken into account, these correlation can distort the phylogenetic signal and/or lead to gross overestimates of tree stability. Maximum likelihood and Bayesian approaches are of course amenable to using RNA-specific substitution models that treat conserved base pairs appropriately, but require accurate secondary structure models as input. So far, however, no accurate and easy-to-use tool has been available for computing structure-aware alignments and consensus structures that can deal with the large rRNAs. The RNAsalsa approach is designed to fill this gap. Capitalizing on the improved accuracy of pairwise consensus structures and informed by a priori knowledge of group-specific structural constraints, the tool provides both alignments and consensus structures that are of sufficient accuracy for routine phylogenetic analysis based on RNA-specific substitution models. The power of the approach is demonstrated using two rRNA data sets: a mitochondrial rRNA set of 26 Mammalia, and a collection of 28S nuclear rRNAs representative of the five major echinoderm groups.

Atomic-resolution imaging of lithium inAl3Liprecipitates

Using an aberration-corrected transmission electron microscope, we report on imaging individual atomic columns of Li in the intermetallic compound ${\text{Al}}_{3}\text{Li}$. The effect of electron energy on the imaging characteristic of Li is investigated by performing measurements at 80 kV employing a monochromated electron beam with an energy spread $\ensuremath{\Delta}E$ of 0.2 eV and at 300 kV with $\ensuremath{\Delta}E$ of 0.8 eV. These settings enable similar information transfer at both microscope operation conditions and allow a direct comparison between the 80 and the 300 kV measurements. Our experimental data show that the phase of the reconstructed exit-plane wave is highly sensitive to light atoms and that the displacement damage of light elements of low threshold recoil energy can be larger at 80 kV than at 300 kV. This behavior can be understood in terms of the relativistic elastic-scattering cross section between electrons and atoms.

Studies on the Behavior of Single and Group of Geosynthetic Encased Stone Columns

The stone columns (or granular piles) are increasingly being used as ground reinforcement elements for supporting a wide variety of structures including buildings and flexible structures. The stone columns derive their load capacity from the confinement offered by the surrounding soil. In very soft soils this lateral confinement may not be adequate and the formation of the stone column itself may be doubtful. Wrapping the individual stone columns with suitable geosynthetic is one of the ideal forms of improving the performance of stone columns. This type of encasement by geosynthetic makes the stone columns stiffer and stronger. In addition, encasement prevents the lateral squeezing of stones in to the surrounding clay soil and vice versa, preserves drainage function of the stone column and frictional properties of the aggregates. In spite of many advantages, the behavior and the mechanism of the geosynthetic encased stone columns is not thoroughly understood. This paper investigates the qualitative and quantitative improvement of individual load capacity of stone column by encasement through laboratory model tests conducted on stone columns installed in clay bed prepared in controlled condition in a large scale testing tank. The load tests were performed on single as well as group of stone columns with and without encasement. Tests were performed with different geosynthetics for the encasement of stone column. The results from the load tests indicated a clear improvement in the load capacity of the stone column due to encasement. The increase in the axial load capacity depends very much upon the modulus of the encasement and the diameter of the stone column. The increase in the stress concentration on the stone columns due to encasement was also measured in the tests. The results from the tests were used to develop the design guidelines for the design of geosynthetic encasement for the given load and settlement.

Pseudopolymorph and Charge-Transfer Co-Crystal of Disubstituted Adamantane containing Dimethoxyphenol Moieties

A disubstituted adamantane containing dimethoxyphenol moieties was synthesized by an acid-condensation reaction. The disubstituted adamantane is a new building block, designed particularly for the rational construction of supramolecular structures that are capable of encapsulating and aligning guest molecules, leading to the formation of extended polymeric networks. Single crystal X-ray analysis revealed that the binary molecule based on adamantane has three types of crystal forms, 1a, 1b, and 1c, containing no additional molecule, water and benzene, and 1,3,5-trinitrobenzene, respectively. In crystal 1a, each hydroxyl group of dimethoxyphenol moieties participates in two intermolecular hydrogen bonds as both donor and acceptor, producing infinite one-dimensional (1D) zigzag chains. Individual chains assemble into a two-dimensional (2D) layered structure via C−H···O interactions between protons of adamantane and oxygen atoms of methoxy groups. Crystal 1b, which is pseudopolymorph of crystal 1a, has a cyclic network consisting of two molecules of disubstituted adamantane and two molecules of water, generated by hydrogen bonds, a benzene molecule accommodated in the cavity. This stacks into a tubular structure via water molecules, which again align into a 2D layered structure through water molecules. Crystal 1c shows a discrete cyclic network accomplished through hydrogen bonds between two molecules of disubstituted adamantane and two molecules of 1,3,5-trinitrobenzene. The finite cyclic network stacks to form 1D columnar aggregates due to van der Waals interactions among the adamantyl groups, resulting in the formation of a channel structure. Individual columns are intermolecularly interdigitated via donor−acceptor interactions between the dimethoxyphenol moieties and 1,3,5-trinitrobenzene, resulting in the formation of a 2D layered structure. The three types of crystals are produced by multiple hydrogen bonding, C−H···O, and donor−acceptor interactions.

Buckling analysis of structural steel frames with inelastic effects according to codes

Steel building frames are often analyzed for stability in an elastic way, while most of their columns behave inelastically at the buckling stage. Most column design provisions allow for inelastic behavior, but overall inelastic stability analysis is rarely performed. In this study the analysis philosophy is centered on the overall frame stability and its true safety factor. As many columns show inelastic behavior at the buckling stage, the proposed procedure takes due consideration of this fact. Once the overall buckling factor for the frame is obtained, individual column effective length factors, and their true slenderness ratios are computed, and used in the design relationships. This procedure circumvents the use of design nomographs and numerous formulas proposed in the past to alleviate their shortcomings. The procedure proposed based on the overall safety factor concept is an iterative one. It starts with a stability analysis and gradually modifies the structural properties to take account of inelasticity and eventually converges to the final buckling factor and mode shape. Any type of lateral restraint can be exactly modeled and taken into consideration without the need for approximate simplifying assumptions. The design philosophy proposed herein is that all columns must have their design parameters as related to buckling capacity must be derived from a single buckling analysis valid for the whole structure, and not considered separately and isolated from the rest of the structure as is currently practiced. Examples are worked out to illustrate the procedure and the results are compared to those of others.

Quantitative atomic resolution mapping using high-angle annular dark field scanning transmission electron microscopy

A model-based method is proposed to relatively quantify the chemical composition of atomic columns using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) images. The method is based on a quantification of the total intensity of the scattered electrons for the individual atomic columns using statistical parameter estimation theory. In order to apply this theory, a model is required describing the image contrast of the HAADF STEM images. Therefore, a simple, effective incoherent model has been assumed which takes the probe intensity profile into account. The scattered intensities can then be estimated by fitting this model to an experimental HAADF STEM image. These estimates are used as a performance measure to distinguish between different atomic column types and to identify the nature of unknown columns with good accuracy and precision using statistical hypothesis testing. The reliability of the method is supported by means of simulated HAADF STEM images as well as a combination of experimental images and electron energy-loss spectra. It is experimentally shown that statistically meaningful information on the composition of individual columns can be obtained even if the difference in averaged atomic number Z is only 3. Using this method, quantitative mapping at atomic resolution using HAADF STEM images only has become possible without the need of simultaneously recorded electron energy loss spectra.

Effect of electrode location on surface electromyography changes due to eccentric elbow flexor exercise

Experiments were carried out to determine whether the location of electrodes has an effect on eccentric exercise-induced changes in surface electromyography (sEMG) variables in the biceps brachii muscle. sEMG signals were recorded with a grid of 64 electrodes before and up to 4 days post-exercise. Root mean square (RMS) and mean power frequency (MNF) were calculated for: (1) each channel; (2) as an average of all channels; and (3) as an average of individual channel rows and columns. Mean muscle-fiber conduction velocity (CV) was estimated similarly but was based on double-differential channels. Maximal isometric voluntary torque decreased 21.3 +/- 5.6% post-exercise. The average sEMG variables decreased after the exercise and recovered 2 days (RMS and CV) or 4 days (MNF) post-exercise. Site-dependent changes were observed in sEMG variables. We conclude that site-dependent changes in sEMG variables after eccentric exercise can be detected and are influenced in part by anatomical factors.

Determination of axonal transport velocities via image cross- and autocorrelation

On their way to the synapse and back, neuronal proteins are carried in cargo vesicles along axons and dendrites. Here, we demonstrate that the key parameters of axonal transport, i.e., particle velocities and pausing times can be read out from CCD-camera images automatically. In the present study, this is achieved via cross- and autocorrelation of kymograph columns. The applicability of the method was measured on simulated kymographs and data from axonal transport timeseries of mRFP-labeled synaptophysin. In comparing outcomes of velocity determinations via a performance parameter that is analogous to the signal-to-noise ratio (SNR) definition, we find that outcomes are dependent on sampling, particle numbers and signal to noise of the kymograph. Autocorrelation of individual columns allows exact determination of pausing time populations. In contrast to manual tracking, correlation does not require experience, a priori assumptions or disentangling of individual particle trajectories and can operate at low SNR.

Eigenvalue and eigenvector derivatives of second-order systems using structure-preserving equivalences

A “structure-preserving equivalence” in the sense intended here is a mapping between the stiffness, damping and mass matrices describing some initial second-order system and the corresponding three matrices of another second-order system having identical spectrum. Most second-order systems can be “diagonalised” through a mapping of this sort. The mapping provides a new approach to the evaluation and the understanding of eigenvalue and eigenvector derivatives. In place of pairs of eigenvalues, we think of real scalar stiffness, damping and mass quantities representing decoupled single-degree-of-freedom systems. In place of pairs of eigenvectors, we think of individual columns of the matrices involved in the mapping. This approach resolves the completely artificial phenomenon that the eigenvalue and eigenvector derivatives become “undefined” at instants when modification of, say, a damping parameter causes a pair of complex eigenvalues to turn into a pair of real eigenvalues or vice-versa. It also has the advantage of being applicable to cases where any one or more of the system matrices are singular.

Eigenvalue Problem from the Stability Analysis of Slopes

Of the existing methods for the three-dimensional (3D) limit equilibrium analysis of slopes, none can simultaneously satisfy all six equilibrium equations. Except for Fellenius’ method that satisfies only one condition of moment equilibrium, all these methods could encounter numerical problems in their applications. Based on the global analysis procedure that considers the whole sliding body instead of individual columns as the loaded body, it is shown that the 3D limit equilibrium analysis of slopes simply reduces to the solution of a generalized eigenvalue problem in which the largest real eigenvalue is just the factor of safety (FOS). The proposed solution is rigorous and can accommodate any shape of slip surfaces. Under undrained conditions, the problem has a unique solution and the FOS has an explicit expression. In addition, through transforming the volume integrals over the sliding body into the boundary integrals, the proposed method does not need to partition the sliding body into columns.

FePt Icosahedra with Magnetic Cores and Catalytic Shells

Surprisingly oxidation resistant icosahedral FePt nanoparticles showing hard-magnetic properties have been fabricated by an inert-gas condensation method with in-flight annealing. High-resolution transmission electron microscopy (HRTEM) images with sub-Angstrom resolution of the nanoparticle have been obtained with focal series reconstruction, revealing noncrystalline nature of the nanoparticle. Digital dark-field method combined with structure reconstruction as well as HRTEM simulations reveal that these nanoparticles have icosahedral structure with shell periodicity. Localized lattice relaxations have been studied by extracting the position of individual atomic columns with a precision of about ±0.002 nm. The lattice spacings of (111) planes from the surface region to the center of the icosahedra are found to decrease exponentially with shell numbers. Computational studies and energy-filtered transmission electron microscopy analyses suggest that a Pt-enriched surface layer is energetically favored and that site-specific vacancies are formed at the edges of facettes, which was experimentally observed. The presence of the Pt-enriched shell around an Fe/Pt core explains the environmental stability of the magnetic icosahedra and strongly reduces the exchange coupling between neighboring particles, thereby possibly providing the highest packing density for future magnetic storage media based on FePt nanoparticles.

Shear Load Tests on Stone Columns With and Without Geosynthetic Encasement

Abstract The use of stone columns (otherwise called granular piles) has proved to be an economical and technically viable ground improvement technique for construction on soft clay soils. Though the stone columns are designed to carry vertical compressive loads, soil movements occurring in the field conditions may cause shear deformations in the stone columns. The stone columns, particularly installed in very soft soils, may not be able to resist these shear movements because of the low confinement offered by the surrounding soil. The shear load capacity of such stone columns can be significantly improved by encasing the individual stone columns with suitable geosynthetic. The encasement confines the aggregate and makes the stone column act like a semirigid pile; thus leading to increased shear stiffness of the column. This paper discusses some laboratory model tests performed to investigate the shear load capacity of stone columns with and without geosynthetic encasement. The laboratory tests were performed by inducing lateral soil movements in a stone column treated soft soil. The results have shown qualitative improvement in the shear stiffness of the stone column due to geosynthetic encasement.

Solving Nonograms by combining relaxations

Nonograms, also known as Japanese puzzles, are a specific type of logic drawing puzzles. The challenge is to fill a grid with black and white pixels in such a way that a given description for each row and column, indicating the lengths of consecutive segments of black pixels, is adhered to. Although the Nonograms in puzzle books can usually be solved by hand, the general problem of solving Nonograms is NP-hard. In this paper, we propose a reasoning framework that can be used to determine the value of certain pixels in the puzzle, given a partial filling. Constraints obtained from relaxations of the Nonogram problem are combined into a 2-Satisfiability (2-SAT) problem, which is used to deduce pixel values in the Nonogram solution. By iterating this procedure, starting from an empty grid, it is often possible to solve the puzzle completely. All the computations involved in the solution process can be performed in polynomial time. Our experimental results demonstrate that the approach is capable of solving a variety of Nonograms that cannot be solved by simple logic reasoning within individual rows and columns, without resorting to branching operations. In addition, we present statistical results on the solvability of Nonograms, obtained by applying our method to a large number of Nonograms.

Sintering and microstructure evolution in columnar thermal barrier coatings

Sintering of thermal barrier coatings changes their key properties, such as thermal conductivity and thermal shock resistance, thus adversely impacting their reliability. We present a novel modeling approach to study the evolution of coating structure during sintering. We model the sintering of individual columns using a thermodynamic principle, and incorporate the center-to-center approach rates for the columns calculated using this principle in a larger scale discrete dynamics model for the evolution of a large number of columns. Surface energies, grain boundary energies and strain energies associated with the deformation of the columns are all included in this framework, while sintering is assumed to occur by the concerted action of surface and grain boundary diffusion. Two sets of initial conditions corresponding to different extents of pre-sintering among neighboring columns are considered. When the extent of pre-sintering is small, we observe that small clusters containing 5–20 columns are formed. In contrast, where a larger amount of pre-sintering exists, we observe, especially at large column densities, that clusters containing 50–100 columns separated by large inter-cluster pores/channels that appear to organize themselves into a network are formed. These observations are in good agreement with recently published experimental observations. We also explain how these results can explain the development of a “mud-crack”-like pattern.