Tendency For Alignment Research Articles

Understanding The Cell Behavior on Nano-/Micro-Patterned Surfaces

This article reports on studies conducted in the same laboratory on interactions between patterned substrates with different pattern dimensions and chemistries, and various types of cells. In order to compare the influence of various parameters, bone marrow stromal cells, retinal pigment epithelial cells, human corneal stromal cells (keratocytes), Saos-2 (human osteosarcoma cells), human microvascular endothelial cells and vascular smooth muscle cells were tested on surfaces with different physical patterns and chemical properties. It was observed that cell type and surface topography are more influential than surface chemistry in determining the alignment tendency of a cell on a substrate surface. Low walls (several microns high) could not confine cells into the microgrooves of the films but alignment was still possible if the cells had a natural alignment property. This information is very useful in designing tissue engineering scaffolds and in the long-term success of implants.

MODELING THE ALIGNMENT PROFILE OF SATELLITE GALAXIES IN CLUSTERS

Analyzing the halo and galaxy catalogs from the Millennium simulations at redshifts $z=0,\ 0.5,\ 1$, we determine the alignment profiles of cluster galaxies by measuring the average alignments between the major axes of the pseudo inertia tensors from all satellites within cluster's virial radius and from only those satellites within some smaller radius as a function of the top-hat scale difference. The alignment profiles quantify how well the satellite galaxies retain the memory of the external tidal fields after merging into their host clusters and how fast they lose the initial alignment tendency as the cluster's relaxation proceeds. It is found that the alignment profile drops faster at higher redshifts and on smaller mass scales. This result is consistent with the picture that the faster merging of the satellites and earlier onset of the nonlinear effect inside clusters tend to break the preferential alignments of the satellites with the external tidal fields. Modeling the alignment profile of cluster galaxies as a power-law of the density correlation coefficient that is independent of the power spectrum normalization ($\sigma_{8}$) and demonstrating that the density correlation coefficient varies sensitively with the density parameter ($\Omega_{m}$) and neutrino mass fraction ($f_{\nu}$), we suggest that the alignment profile of cluster galaxies might be useful for breaking the $\Omega_{m}$-$\sigma_{8}$ and $f_{\nu}$-$\sigma_{8}$ degeneracies.

Conventional or navigated total knee arthroplasty affects sagittal component alignment

Navigation systems have recently been developed to achieve highly reliable prosthetic alignment in total knee arthroplasty (TKA). However, component alignment in the sagittal plane is less reliable than that in the coronal plane even when navigation systems are used. Previous reports examining men showed differences in targeted sagittal prosthetic alignments of TKA achieved using the conventional technique and various navigation systems. However, there have been few studies examining the use of this technique in women, who are the primary candidates for TKA. Radiographs of the entire lower extremity were obtained from 20 elder women while standing and sagittal prosthetic alignments in TKA were planned using the conventional technique as well as three navigation approaches to establish reference frames, and the observations were compared. Sagittal alignments simulated using the radiographs for the conventional technique and navigation systems differed within a mean of 3.2° ± 1.7° (mean ± SD) to 6.3° ± 2.0°. The use of different reference points on the distal femoral condyles (insertion point of the intramedullary rod, center of the anteroposterior direction of the femoral condyles, and most distal point of the femoral condyles) for each navigation system resulted in differences in the sagittal plane up to 3.0° ± 1.5°. The use of navigation systems resulted in a more hyperextended position between the femoral and tibial components compared to that for the conventional technique. Targeted sagittal prosthetic alignments of TKA achieved using the conventional technique and various navigation systems differed in elderly women. The use of different reference points on the distal femoral condyle for navigation systems resulted in different alignment in the sagittal plane. This study showed that alignment tendencies are similar in men and women. Prognostic studies, IV.

Self‐assembly of amelogenin proteins at the water–oil interface

Self-assembly of amelogenin plays a key role in controlling enamel biomineralization. Recently, we generated self-aligning nanoribbons of amelogenin in water-in-oil emulsions stabilized by the full-length protein (rH174). Here, we tested the hypothesis that the hydrophilic C-terminus is critical for self-assembly of amelogenin into nanoribbons. The self-assembled structures of two amelogenin cleavage products, rH163 and rH146, were compared with structures of rH174 at different pH values and degrees of saturation using atomic force microscopy, electron microscopy, and dynamic light scattering. We observed that the number density of rH174 nanoribbons increased significantly when the initial pH was raised from 4.5 to 5.6. Nanoribbons, as well as unique helical nanostructures, were also readily observed when amelogenin rH146 was used, but showed little tendency for parallel alignment and did not bundle into fibrils like rH174. In contrast, rH163 rarely formed nanoribbons but predominantly assembled into nanospheres under the same conditions. We conclude that the presence of a hydrophilic C-terminus may not be a prerequisite for nanoribbon formation but may be critical for ribbon alignment and subsequent fibril formation. These results highlight the contribution of the hydrophobic domain in the self-assembly of elongated structures of amelogenins. Molecular mechanisms governing these processes based on the formation of reverse micelles are discussed.

Rating Alignment, Rating Shopping and Reputation of Credit Rating Agencies: Evidence from the Subprime Crisis

This paper compares conflict of interest incentives and reputational concerns of credit rating agencies (CRAs) in the context of the subprime crisis. We argue that, during up-market periods, ratings levels are affected by both a strong tendency for alignment across CRAs and ratings “shopping” by issuers, while, during periods of economic slowdown, these distortions disappear since CRAs are then more concerned about their long-run reputation. We test our hypotheses by analyzing the gap between Moodys and S&Ps ratings on US residential, subprime mortgage-backed securities before and after the 2007 crisis. Overall, our results show a clear reduction in ratings alignment. Moreover, we find strong evidence that harsher downgrades came from S&P, which had higher ratings before the crisis, and that the gap reduction is strongly correlated with the rating gap before the crisis. We interpret this as evidence that CRAs try to “reverse the gap”, to reduce the impact on their (relative) reputation. Finally, we find that harsher downgrades tend to occur for securities not jointly rated and that the relation between downgrades and initial rating is significantly different across the two agencies, this being consistent with the rating shopping hypothesis.

Effect of Mn substituents on the domain and local structures of Na1/2Bi1/2TiO3–BaTiO3 single crystals near a morphotropic phase boundary

The ferroelectric domain and local structures of Na1/2Bi1/2TiO3-x%BaTiO3 (NBT-BT) and 0.14 at. %Mn substituted Na1/2Bi1/2TiO3-x%BaTiO3 (Mn:NBT-BT) single crystals with x=5.5 near a morphotropic phase boundary have been investigated by transmission electron microscopy. Increased ferroelectric ordering and enhanced in-plane octahedral tilting were observed for Mn:NBT-BT compared with NBT-BT. Bragg-filtered lattice images revealed that the size of the in-phase tilt domains of Mn:NBT-BT were on the order of 2 to 8 nm, with a tendency of alignment along {110}.

Low frequency dielectric relaxations of gold nanoparticles/ferroelectric liquid crystal composites

We present the characterisation and dielectric relaxation spectroscopy of a ferroelectric liquid crystal (FLC), namely KCFLC 7S. It was observed that the studied FLC material possesses the tendency of homeotropic alignment on glass substrates coated with indium tin oxide. A low frequency dielectric mode, along with the Goldstone mode, was observed in the SmC* phase of the FLC material. The low frequency mode became more dominant on doping gold nanoparticles into the FLC material. The occurrence of the low frequency mode was attributed to the ionisation–recombination-assisted diffusion of slow ions present in the FLC material. The behaviour of the relaxation frequency of the low frequency mode with applied dc bias and temperature was also demonstrated.

Development of rolling magnetic microrobots

This paper reports magnetic microrobots with rolling capability. A magnetic object subjected to an externally rotating magnetic field would be rotated due to the tendency of alignment between its internal magnetization and the field. Based on this principle, a magnetic microrobot in a spherical body with a diameter of several hundred microns was designed and fabricated. To remotely power and control the microrobot, a rotating magnet was used to generate a rotating magnetic field. Driven by this field, the microrobot can freely roll on three-dimensional surfaces. These surfaces can be in air, water or silicon oil. In a dry environment, a microrobot with a diameter of 440 µm achieved a maximum linear speed of 13.2 mm s−1.

Absence of magnetic ordering in low dimensional mixed magnetic Mn 1− xNi xCl 2·H 2O

A new mixed magnet, Mn 1− x Ni x Cl 2·H 2O, is examined by dc magnetization and susceptibility measurements across the entire composition range. The pure components are quasi-one-dimensional Heisenberg antiferromagnets ordering at 2.17 K (Mn) and 5.6 5 K (Ni) due to weaker interchain exchange supplementing the dominant exchange along MCl 2MCl 2M… chemical and structural chains. High temperature magnetic susceptibilities yield Curie and Weiss constants in χ M= C/( T− θ). C( x) is linear but θ( x) displays curvature, which is analyzed to show that unlike-ion exchange is ferromagnetic and similar in size to like-ion. Most notable is the absence of antiferromagnetic susceptibility maxima down to 1.6 K from x=0.10 to 0.95. For x=0.05 a susceptibility maximum appears, with T max almost 20% lower than in the pure Mn component but T c reduced by 2%. The size of the susceptibility is enhanced by admixture, the effect of disrupted antiferromagnetic tendencies. Magnetization isotherms evolve with composition. Larger values of magnetization, under the same measuring conditions, occur for mixtures than for pure components, consistent with frustration, which weakens antiferromagnetic alignment tendencies. The competing ferromagnetic (Ni) and antiferromagnetic (Mn) intrachain interactions, along with disorder and low dimensional characteristics, presumably lead to the absence of magnetic order over a remarkably broad composition range.

Goals and expectations as elements of attitudes toward political parties

The main goal of presented research has been testing of the expectancy-value theory (which originally connects level or strength of motivation of an individual to stand for particular goal, at one side, and product of belief that desired goal is reachable and value or valence of that goal, at the other side), or more exactly, to see is it possible and in which degree, to apply this theory to attitudes toward political parties in Serbia. To accomplish this, 255 subjects has estimated importance of 18 social and 19 personal goals, then they estimated expectancies of main political parties to fulfill those goals, and finally subjects has been questioned about their attitudes (global evaluations) toward the parties. Results confirm assumption that products of expectancies from the parties and acceptances of appropriate goals (both social and personal) are in positive correlation with attitudes toward those parties. However, the assumption that attitudes and products of expectancies and goals would correlate higher than attitudes and only expectancies has not be confirmed. This means that expectancy has more importance than goal in the expectancy-goal product. As a conclusion, there is a tendency of alignment between affective relationship toward parties and expectancies (as cognitive elements) that parties can manage to fulfill different goals. .

PH-responsive aqueous/LC interfaces using SGLCP-b-polyacrylic acid block copolymers

Block copolymers that combine a side-group liquid crystalline polymer (SGLCP) block and a pH-responsive hydrophilic block, poly(acrylic acid) (PAA), are shown to confer pH-dependent anchoring of the director orientation at the aqueous/LC interface. The SGLCP block, poly(4-cyanobiphenyl-4-oxyundecylacrylate), was chosen based on its ability to influence the director field of the 5CB (4-cyano-4′-pentylbiphenyl). At low pH the PAA block collapses and the inherent, planar alignment tendency of 5CB at a water interface prevails. As pH increases, the polyelectrolyte block becomes increasingly charged and expands, producing a change to homeotropic anchoring. The change in anchoring occurs as quickly as the buffer can be changed (within ∼2 s) and is reversible, with a response that is repeatable over as many cycles as were tested (approximately 20 cycles). The polymer-mediated anchoring persists for 6 days, indicating that the SGLCP block secures the self-assembled layer on the 5CB, even under conditions that cause repulsive interactions among the PAA blocks. Thus, SGLCP blocks can translate conformational changes of a responsive hydrophilic block into rapid, reversible changes in the director field.

Tunable quasi-homeotropic liquid crystal pretilt angle based on competing alignment layers

The liquid crystal alignment properties of a spincoated mixture of two commercial homeotropic and planar aligning polyamic acids are investigated. Baking the coated substrates induces cleaving of the long alkyl side chains of the first polyamic acid which weakens the tendency for homeotropic alignment while the imidisation ratio of both polyamic acids changes in favour of planar alignment. By detailed measurement of the retardation induced by the liquid crystal, we show that the combination of these two mechanisms in the proposed mixture yields a spatially uniform liquid crystal pretilt angle that is tunable with the baking temperature in the quasi-homeotropic range 0–10°, which is important for the Vertically Aligned Nematic technology.

Inkjet printing of laminin gradient to investigate endothelial cellular alignment

To investigate the influence of the protein surface-density gradient on endothelial cell alignment, a novel approach for the fabrication of a laminin gradient on gold-coated substrates has been developed in this study. Our approach involves programmed inkjet printing of an alkanethiol (11-mercaptoundecanoic acid, C 10COOH, MUA) gradient onto gold-coated substrates, followed by backfilling with 11-mercapto-1-undecanol (C 11OH, MUD). The –COOH moieties were activated and then covalently linked with laminin. This treatment led to a surface-density gradient of laminin. Contact angle measurement, X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy were employed to characterize the self-assembled monolayers (SAMs) and protein gradient, respectively. Results proved the feasibility of the fabrication of a protein gradient by using the inkjet printing technique. The self-assembled monolayer gradients displayed a high packing density, as indicated by dynamic contact angle measurement. More importantly, the gradient slope was easily tunable over a significant distance from 20 to 30 mm. The laminin gradient was clearly visible by fluorescence microscopy observation. Endothelial cells cultured on the surface-density gradient of laminin demonstrated a strong alignment tendency in parallel to the gradient. The higher the laminin density the more cells were observed. The result indicates that cell attachment is dependent on the surface density of laminin. This work broadens our methodology to investigate chemical stimuli-induced cell directional alignment. It is potentially important for understanding cell alignment/ingrowth behavior for angiogenesis and implant technology including tissue-engineered structures.

Lower Limb Alignment in Children

A full-length standing anteroposterior radiograph of the entire lower extremity has become the standard imaging modality for assessing lower limb alignment. Although reference values of frontal plane deformity parameters based on adult subjects have been established, such values may not be applicable to the pediatric population. The purpose of our study was to establish the reference values of frontal plane alignment and joint orientation angles in children based on a standing full-length radiograph. A database at a single institution was searched for patients who were aged between 1 and 18 years at the time of undergoing a standing full-length radiograph of the lower extremities. Radiographic analysis of lower extremities without any abnormalities was performed by a single observer. Mechanical axis deviation, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibiofemoral angle, joint line convergence angle, and mechanical axis station were calculated at yearly intervals. The data were summarized using descriptive statistics, and simple regression analysis was performed to determine the relationship between the patients' age and the magnitude of LDFA and MPTA. A total of 354 unaffected lower extremities in 253 children were analyzed. Between the ages of 1 and 2 years, the tendency for varus alignment of the lower limb was related to the varus orientation of the distal femur with a mean LDFA of 95 degrees (95% confidence interval [CI], 93-97 degrees). By the age of 3 years, the limb alignment changed to valgus related to a combination of decreasing varus orientation of the distal femur and a mild increase in valgus orientation of the proximal tibia with the mean MPTA changing from 89 degrees (95% CI, 88-90 degrees) to 91 degrees (95% CI, 90-92 degrees). After the age of 7 years, all joint orientation angles were noted to be within the range of reference values that are available for the adult population. Despite changes in limb alignment with growth, the mean mechanical axis of the lower extremity remained within the central half of the knee joint in children older than 1 year of age. The change in alignment of the lower limb from 1 to 4 years of life from varus to valgus is primarily related to a progressive decrease in varus orientation of the distal femur. In children younger than 7 years old, age-specific reference values for joint orientation angles of the lower extremity should be used instead of values derived from adult subjects.

Non-linear advection–diffusion equations approximate swarming but not schooling populations

Advection–diffusion equations (ADEs) are concise and tractable mathematical descriptions of population distributions used widely to address spatial problems in applied and theoretical ecology. We assessed the potential of non-linear ADEs to approximate over very large time and space scales the spatial distributions resulting from social behaviors such as swarming and schooling, in which populations are subdivided into many groups of variable size, velocity and directional persistence. We developed a simple numerical scheme to estimate coefficients in non-linear ADEs from individual-based model (IBM) simulations. Alignment responses between neighbors within groups quantitatively and qualitatively affected how populations moved. Asocial and swarming populations, and schooling populations with weak alignment tendencies, were well approximated by non-linear ADEs. For these behaviors, numerical estimates such as ours could enhance realism and efficiency in ecosystem models of social organisms. Schooling populations with strong alignment were poorly approximated, because (in contradiction to assumptions underlying the ADE approach) effective diffusion and advection were not uniquely defined functions of local density. PDE forms other than ADEs are apparently required to approximate strongly aligning populations.

Radial Alignment in Simulated Clusters

Observational evidence for the radial alignment of satellites with their dark matter host has been accumulating steadily over the past few years. The effect is seen over a wide range of scales, from massive clusters of galaxies down to galaxy-sized systems, yet the underlying physical mechanism has still not been established. To this end, we have carried out a detailed analysis of the shapes and orientations of dark matter substructures in high-resolution N-body cosmological simulations. We find a strong tendency for radial alignment of the substructure with its host halo: the distribution of halo major axes is very anisotropic, with the majority pointing toward the center of mass of the host. The alignment peaks once the subhalo has passed the virial radius of the host for the first time, but is not subsequently diluted, even after the halos have gone through as many as four pericentric passages. This evidence points to the existence of a very rapid dynamical mechanism acting on these systems, and we argue that tidal torquing throughout their orbits is the most likely candidate.

Liquid-Crystalline Behavior of Adducts between Pyridazine and Silver Alkylsulfonates

The silver-ion-based supramolecular adducts bearing long alkyl chains were prepared by reaction of pyridazine and silver alkylsulfonates. The-liquid crystalline behavior of the adducts was studied by differential scanning calorimetry, polarizing microscopy, temperature-dependent IR, and temperature-dependent X-ray diffraction. Each of the adducts exhibits two rectangular columnar mesophases having P2/a symmetry and has a strong tendency of parallel alignment of the alkyl chains orientating toward the surface of the glass substrate.

Spin‐Kick Correlation in Neutron Stars: Alignment Conditions and Implications

Recent observations of pulsar wind nebulae and radio polarization profiles revealed a tendency for alignment between the spin and velocity directions in neutron stars. We study the condition for spin-kick alignment using a toy model, in which the kick consists of many off-centered, randomly oriented thrusts. Both analytical considerations and numerical simulations indicate that spin-kick alignment cannot be easily achieved if the proto-neutron star does not possess some initial angular momentum, contrary to some previous claims. To obtain the observed spin-kick misalignment angle distribution, the initial spin period of the neutron star must be smaller than the kick timescale. Typically, an initial period of 100 ms or less is required.

Immobilized nerve growth factor and microtopography have distinct effects on polarization versus axon elongation in hippocampal cells in culture

Cell interfacing with biomaterial surfaces dictates important aspects of cell behavior. In particular, axon extension in neurons is effectively influenced by surface properties, both for the initial formation of an axon as well as for the maintenance of axon growth. Here, we investigated how neurons behaved on poly(dimethyl siloxane) (PDMS) surfaces decorated with biochemical and physical cues presented individually or in combination. In particular, nerve growth factor (NGF) was covalently tethered to PDMS to create a bioactive surface, and microtopography was introduced to the material in the form of microchannels. Embryonic hippocampal neurons were used to investigate the impact of these surface cues on polarization (i.e., axon initiation or axogenesis) and overall axon length. We found that topography had a more pronounced effect on polarization (68% increase over controls) compared to immobilized NGF (0.1 ng/mm(2)) (27% increase). However, the effect of NGF was negligible when both types of stimuli were simultaneously presented on the biomaterial surface. In addition to axon formation, chemical and physical cues are also involved in axon growth following the initiation process. Interestingly, for the same studies described above, the effects of microchannels and NGF were opposite from the effects on polarization; the most evident effect was for the immobilized growth factor (10% increase in axon length with respect to controls) whereas there was no effect in general for the microtopography. More importantly, when the two surface stimuli were presented in combination, a synergistic increase in axon length was detected (25% increase with respect to controls), which could be a result of faster polarization triggered by topography plus enhanced growth from NGF. Additionally, axon orientation was also analyzed and we found the well-known tendency of perpendicular or parallel axonal alignment to be dependent on the width and depth of the channels. This investigation thoroughly compared and distinguished the individual and combined impact of material surface properties (chemical and physical) on axogenesis from the effects on axon length. Overall, topography dominated polarization mechanisms, whereas NGF, and particularly a synergy of immobilized NGF plus topography, dominated axon length. These results could be potentially applied for the design of biomaterials in applications were axon growth is critical.

Skyrmions in a Hole Gas with Large Spin Gap and Strong Disorder

Skyrmion [1] is a topological spin excitation of a polarized ground state, energetically favored over a single spin flip due to the tendency for parallel alignment of neighboring spins (i.e., to minimize gradient of the spin projection density). Under certain conditions, it also occurs [2] as an elementary charge excitation in quantum Hall systems, that is in a two-dimensional (2D) system of charge carriers (electrons or holes) in a strong magnetic field B, yielding filling of at most a small number of the Landau levels (LLs). The LL occupation is conveniently defined by a filling factor ν = 2π%λ, where % is the sheet concentration and λ = √ hc/eB is the magnetic length. At the exact filling of the lowest spin-polarized LL, corresponding to ν = 1, the ground state is spin polarized even in the absence of the single-particle Zeeman spin splitting EZ = gμBB (g being the Lande factor). This situation can be described as half-filling of the lowest (n = 0) spin-degenerate LL. The reason is the dominant tendency to maximize exchange. The spin-polarized ν = 1 state is an example of quantum Hall ferromagnet. Remarkably, the spin polarization at EZ = 0 is sensitive to the LL filling. In ideal 2D (zero width) it occurs at any integral ν [3] and also at the Laughlin series of fractions ν = (2p + 1)−1 with integral p [4], but not at nearly any other fraction. It also strongly depends on