Conditions For Alignment Research Articles

Flexible nanofilms coated with aligned piezoelectric microfibers preserve the contractility of cardiomyocytes.

The use of engineered cardiac tissue for high-throughput drug screening/toxicology assessment remains largely unexplored. Here we propose a scaffold that mimics aspects of cardiac extracellular matrix while preserving the contractility of cardiomyocytes. The scaffold is based on a poly(caprolactone) (PCL) nanofilm with magnetic properties (MNF, standing for magnetic nanofilm) coated with a layer of piezoelectric (PIEZO) microfibers of poly(vinylidene fluoride-trifluoroethylene) (MNF+PIEZO). The nanofilm creates a flexible support for cell contraction and the aligned PIEZO microfibers deposited on top of the nanofilm creates conditions for cell alignment and electrical stimulation of the seeded cells. Our results indicate that MNF+PIEZO scaffold promotes rat and human cardiac cell attachment and alignment, maintains the ratio of cell populations overtime, promotes cell-cell communication and metabolic maturation, and preserves cardiomyocyte (CM) contractility for at least 12 days. The engineered cardiac construct showed high toxicity against doxorubicin, a cardiotoxic molecule, and responded to compounds that modulate CM contraction such as epinephrine, propranolol and heptanol.

Precoder Designs for the Relay-Aided X Channel Without Source CSI

In this paper, precoder designs are proposed for the wireless X networks aided by a relay and with no or very limited channel state information at the transmitters (CSIT). First, we derive the general feasibility conditions for interference alignment (IA) for a relay-aided symmetric multi-input-multi-output X channel (also called the X relay channel or XRC) without any CSI at the source transmitters. Next, we propose an IA-based joint beamforming approach with very limited feedback to the transmitters (referred to as “IA-LFB” in this paper), which can attain the maximum degrees of freedom (DoF) of the network under arbitrarily low relay power. Finally, we propose an iterative minimum-sum mean-square-error (MMSE) precoder design for the single-input-single-output XRC for throughput improvement in the finite signal-to-noise ratio (SNR) region. The proposed MMSE precoder also shows better bit error rate results than the IA precoder over a wide SNR range. Since the MMSE precoder can achieve only locally optimal solutions, we propose to initialize the iterative MMSE algorithm with the IA-LFB precoder which, unlike random initializations, not only improves the throughput in the finite SNR regions but also preserves the network DoF even under limited relay power.

Fork gratings based on ferroelectric liquid crystals.

In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices.

On Feasibility Conditions for Linear Interference Alignment over Cognitive Interference Channel: A DoF Analysis with Diversity Tradeoff

ABSTRACTIn a multiple-antennas cognitive radio network, the rate of the primary link is maximized by water-filling power allocation along the spatial directions associated with the singular values of primary channel matrix. Due to transmitter power constraint, even when the primary user occupies the entire spectrum, some spatial opportunities remain that can be utilized by secondary users. This scheme is called opportunistic interference alignment (OIA). The feasibility issue of OIA in a general symbol-extended system considering the diversity tradeoff, in particular, is the topic that is considered in this paper. An outer bound on the achievable degrees of freedom and also a necessary condition on the feasibility of a multiuser OIA network are presented analytically. In the remaining parts of the paper, the diversity and rate tradeoff is considered. In order to achieve diversity, it is assumed that the paired nodes utilize a space-time coder before the OIA pre-coder. A closed-form relation is presented that relates the minimum achievable diversity to interference alignment quality and code rate.

Degrees of Freedom of MIMO Cellular Networks: Decomposition and Linear Beamforming Design

This paper investigates the symmetric degrees of freedom (DoF) of multiple-input multiple-output (MIMO) cellular networks with $G$ cells and $K$ users per cell, having $N$ antennas at each base station and $M$ antennas at each user. In particular, we investigate techniques for achievability that are based on either decomposition with asymptotic interference alignment or linear beamforming schemes and show that there are distinct regimes of $(G,K,M,N)$ , where one outperforms the other. We first note that both one-sided and two-sided decomposition with asymptotic interference alignment achieve the same DoF. We then establish specific antenna configurations under which the DoF achieved using decomposition-based schemes is optimal by deriving a set of outer bounds on the symmetric DoF. Using these results, we completely characterize the optimal DoF of any $G$ -cell network with single-antenna users. For linear beamforming schemes, we first focus on small networks and propose a structured approach to linear beamforming based on a notion called packing ratios. Packing ratio describes the interference footprint or shadow cast by a set of transmit beamformers and enables us to identify the underlying structures for aligning interference. Such a structured beamforming design can be shown to achieve the optimal spatially normalized DoF (sDoF) of two-cell two-user/cell network and the two-cell three-user/cell network. For larger networks, we develop an unstructured approach to linear interference alignment, where transmit beamformers are designed to satisfy conditions for interference alignment without explicitly identifying the underlying structures for interference alignment. The main numerical insight of this paper is that such an approach appears to be capable of achieving the optimal sDoF for MIMO cellular networks in regimes where linear beamforming dominates asymptotic decomposition, and a significant portion of sDoF elsewhere. Remarkably, polynomial identity test appears to play a key role in identifying the boundary of the achievable sDoF region in the former case.

Feasibility of Interference Alignment for the MIMO Interference Channel

We study vector space interference alignment for the multiple-input multiple-output interference channel with no time or frequency diversity, and no symbol extensions. We prove both necessary and sufficient conditions for alignment. In particular, we characterize the feasibility of alignment for the symmetric three-user channel where all users transmit along d dimensions, all transmitters have M antennas and all receivers have N antennas, as well as feasibility of alignment for the fully symmetric (M = N) channel with an arbitrary number of users. An implication of our results is that the total degrees of freedom available in a K-user interference channel, using only spatial diversity from the multiple antennas, is at most 2. This is in sharp contrast to the K/2 degrees of freedom shown to be possible by Cadambe and Jafar with arbitrarily large time or frequency diversity. Moving beyond the question of feasibility, we additionally discuss computation of the number of solutions using Schubert calculus in cases where there are a finite number of solutions.

Topological polymer dispersed liquid crystals with bulk nematic defect lines pinned to handlebody surfaces.

Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields.

Effect of inorganic 1D nanoparticles on electrooptic properties of 5CB liquid crystal

Electrooptic properties of mixtures of 4-cyano-4′-pentylbiphenyl (5CB) thermotropic liquid crystal with four different inorganic dopants: (i) MoSI nanowires, (ii) MnO2 nanorods, (iii) Ag nanowires, and (iv) WS2 nanotubes were investigated by a conventional optical measurement technique. The dopant concentrations were in the range from 0.1 to 0.5 wt%. In all mixtures aggregation of the 1D nanoparticle (1D-NP) material was observed, therefore electrooptic response was probed in the regions in-between the aggregates. All four 1D-NP dopants produce a decrease of the threshold voltage for electrooptic switching and also a decrease of the corresponding switching times. The most profound effects are observed for MnO2/5CB system, which exhibits a reduction of the threshold voltage by a factor of 1.7 and a reduction of the total switching time by a factor of 1.5. The effect is associated with an increase of the dielectric anisotropy of the mixture. The specific behaviour of the MnO2 nanorods is attributed to their relatively low aspect ratio that provides most suitable conditions for good alignment in the liquid crystal host.

Growth and Alignment of Thin Film Organic Single Crystals from Dewetting Patterns

Studying and understanding the conditions under which organic semiconductors can be engineered to form aligned single crystals in thin films is of primary importance owing to their unique orientation-dependent optoelectronic properties. Efforts to reach this goal by self-assembly from solution-processed films have been rewarded only with limited success. In this article we present a new method to grow single crystalline thin films via solvent annealing. We identify solvate crystal growth in combination with a specific film dewetting morphology as key to successful fabrication of single crystals. Furthermore, these 2D single crystals can align on chemically patterned substrates to minimize their interfacial energy. We explore in situ the conditions for crystal formation and alignment.

The Feasibility Conditions for Interference Alignment in MIMO Networks

Interference alignment (IA) has attracted great attention in the last few years for its breakthrough performance in interference networks. However, despite the numerous works dedicated to IA, the feasibility conditions of IA remains unclear for most network topologies. The IA feasibility analysis is challenging as the IA constraints are sets of high-degree polynomials, for which no systematic tool to analyze the solvability conditions exists. In this work, by developing a new mathematical framework that maps the solvability of sets of polynomial equations to the linear independence of their first-order terms, we propose a sufficient condition that applies to MIMO interference networks with general configurations. We have further proved that this sufficient condition matches with the necessary conditions under a wide range of configurations. These results further consolidate the theoretical basis of IA.

Full Alignment of Colloidal Objects by Programed Forcing

By analysis and simulation, we demonstrate two methods for achieving complete orientational alignment of a set of identical asymmetric colloidal objects dispersed randomly in a fluid. Sedimentation or electrophoresis in a constant field can lead to partial alignment, in which the objects rotate about a common body axis, but the phases of rotation for these objects are random. We show that this phase disorder can be removed by two forms of programed forcing. First, simply alternating the forcing between two directions reduces the statistical entropy of the orientation arbitrarily. Second, the addition of a small rotating component to the applied field in analogy to magnetic resonance can lead to phase locking of the objects' orientation. We identify conditions for alignment of a broad class of generic objects and discuss practical limitations.

Semiconductor nanorod layers aligned through mechanical rubbing

AbstractLarge‐scale lateral alignment of nanorods (NRs) is of interest for manifestation of their anistropic properties including polarized emission and directional electrical transport. This study investigates the utility of mechanical rubbing for macroscopic scale alignment of colloidal semiconductor NRs. CdSe/CdS seeded‐rods, exhibiting linearly polarized emission, are aligned by mechanical rubbing of a spin‐coated glass substrate. The dragging force exerted by the rubbing fibers results in deflection and reorientation of the NRs along the rubbing direction. The rubbed samples were characterized by various methods including absorption, polarized emission, optical fluorescence microscopy, atomic force microscopy, and ultra‐high resolution scanning electron microscopy. The emission polarization contrast ratio (CR), defined as the ratio between emission intensities parallel and perpendicular to the rubbing direction, was used to characterize the rods alignment. The effects of substrate treatments on the CR were studied, showing that partially hydrophobic surface provides optimal conditions for alignment. Excess organic ligands added to the deposited NR solution strongly affect the extent of alignment. This was studied for a series of NR samples of different dimensions and an optimal additive ratio of ∼3 ligand molecules per 1 nm2 NR surface area was found to yield the highest CR. Average CR values of 3.5 were detected over the entire 6 cm2 substrate area, with local values exceeding 4.5. While samples of rubbed spherical quantum dots and spin‐coated films of NRs show no emission polarization, the emission intensity from rubbed NR samples is polarized obeying Malus' law (wherein, the intensity is proportional to cos2(θ)). Mechanical rubbing, well known for its use in LC devices, may be considered as a method for large‐scale alignment of NRs on substrates.

Feasibility Condition for Interference Alignment With Diversity

This paper studies the diversity benefit of different interference alignment solutions. While most research about interference alignment was aiming at deriving or realizing the maximum achievable multiplexing gain, the symbol error rate performance, which can be characterized by the diversity gain is of equal importance. Different interference alignment solutions are classified into two categories called diversity interference alignment and zero-forcing interference alignment. Although these two types of solutions are not distinguishable in terms of the multiplexing gain, this paper will show their difference lies in the fact that they have different diversity gains. In this paper, a K-user (M × N) interference channel is used, with each user sending 1 degree of freedom of information by using interference alignment precoding and receiving filters but without space-time codes. The feasibility conditions for diversity interference alignment to be achieved are analyzed and the diversity orders different solutions can provide are compared. The results imply that diversity interference alignment solutions offer both multiplexing and diversity gains simultaneously. It also tells us two important rules about the interference alignment precoding filters design: an optimal design has to take both desired and interference channel matrices into consideration and the separation of interference alignment precoding filters design and space-time codes design may not be optimal in general.

Least Squares Approach to Joint Beam Design for Interference Alignment in Multiuser Multi-Input Multi-Output Interference Channels

In this correspondence, the problem of interference alignment for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> -user time-invariant multi-input multi-output interference channels is considered. The necessary and sufficient conditions for interference alignment are converted to a system of linear equations that have dummy variables. Based on this linear system, a new algorithm for beam design for interference alignment is proposed by minimizing the overall <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">interference misalignment</i> . The proposed algorithm consists of solving a least squares problem iteratively. The convergence of the proposed algorithm is established, and its complexity is analyzed. The performance of the proposed algorithm is also evaluated numerically. It is shown that the proposed algorithm has faster convergence and lower complexity than the previous method with a comparable sum rate performance in the most practical case of two receive antennas.

Selecting adjustment operating conditions in open-circuit district heating systems

A procedure for selecting the optimal hydraulic operating conditions for adjustment and alignment of district heating systems is proposed. Results from a study on substantiating efficient operating conditions for adjusting district heating systems are given together with recommendations on how to set up these conditions.

Fabrication of multilayered oxide thermoelectric modules by electrophoretic deposition under high magnetic fields

The authors report the fabrication of grain-aligned [Ca2CoO3−δ]0.62CoO2 (Ca349) thick films and a multilayered thermoelectric unicouple of Ca349 and Ca0.9La0.1MnO3−δ (Mn113) using electrophoretic deposition (EPD) and magnetic alignment methods. Strongly c-axis-oriented Ca349 thick films were obtained by EPD performed under magnetic fields. In addition, the c axis of grains was found to always align parallel to the direction of field, independently of the EPD cell configuration. The required conditions for magnetic grain alignment of fine Ca349 powders were quantitatively discussed based on magnetization anisotropy. An α-Al2O3∕Mn113∕α-Al2O3∕Ca349∕α-Al2O3 multilayered thick film was successfully developed.

Conditions for multiple land use in large-scale urban projects

The implementation of concepts of multiple land use seems to be relevant in the context of large-scale urban projects, which are now predominately monofunctional. However, current governance settings at these projects seem to be unreceptive to this new planning concept. Our in-depth case study of the South Axis project in Amsterdam embraces an actor-centred institutional perspective and seeks to understand how more receptive conditions for norm alignment between key actors can be attained. We reconstruct the introduction of quite radical concepts of multiple land use in this project, which started as an office-development proposal. The implementation was severely hampered by the fact that ambitions were formed in a rather introvert local government – business setting. Only in the last stage, with the adoption of a more extrovert mode of governance that included a variety of national government departments, were more receptive conditions for multiple land use created.

Model for the easy-axis alignment of chemically synthesized L1 FePt nanoparticles

Analytical and computational models of the easy-axis orientation process in magnetic nanoparticle systems are investigated and compared with experimental data. The computational model gives good agreement with experiment on the assumption of a reduced anisotropy constant, which is ascribed to the existence of aggregation. It is found that the degree of orientation depends on the parameter KV∕kT, with K the anisotropy constant and V the nanoparticle volume, which governs the coupling of the easy axis to the magnetic moment. A simple and useful analytical expression is derived, from which the primary conditions for good alignment are determined.

Detailed Characterization of Conditions for Alignment of Single-Stranded and Double-Stranded DNA Fragments on Surfaces

DNA is expected to play a critical role in biomolecular nanotechnology because nucleic acids offer a range of desirable properties for nanometer scale manipulations. We report here a thorough characterization and optimization of conditions for alignment of well extended single- and double-stranded DNA molecules on mica surfaces. The optimum poly-L-lysine concentration range for surface treatment in DNA alignment experiments is 0.5–2 ppm. DNA is best aligned, and the greatest surface density of DNA molecules is observed in the center of the path traversed by the DNA solution droplet during deposition. The alignment procedure induces only a small amount of fragmentation of deposited DNA molecules. Knowledge of the optimum conditions for nucleic acid alignment on surfaces should facilitate the use of DNA based nanotechnology.

Cultivating Consciousness

The case is made for the need for a new educational praxis that can cultivate the levels of consciousness necessary to succeed in the new emerging global contexts. The work of Carl R. Rogers is discussed as a transformational pedagogy. In particular, his work in large person-center community group processes during the past 15 years of his career is described where rapid growth in individual consciousness levels and group consciousness occurs. Elaborated are various configurations of individual and group conscious and how they are related to each other. Also considered is an extraordinary consciousness state observed within groups where high levels of individual consciousness and high levels of group consciousness are aligned. Some facilitative attitudes that may create the enabling conditions for consciousness alignment are described.