Principal Alignment Research Articles

Line fitting tolerance estimation for Wolter-I microscope

Characterized by a high resolution, high throughput (large effective area), and large field of view, the Wolter-I microscope is the main grazing incidence imaging device for x-rays and neutrons. It is necessary to estimate the tolerance of surface deformation to achieve the required resolution in typical applications. Traditional tolerance estimation method based on Monte Carlo method required a large random sampling in a given sampling area and has a low efficiency. We derived the transverse ray aberration equations to investigate the image quality degradation caused by principal figure and alignment errors and proposed a line fitting tolerance estimation method. Finally, the figure and alignment error tolerances of a Wolter-I microscope are discussed.

Secessionists vs. Unionists in Catalonia: Mood, Emotional Profiles and Beliefs about Secession Perspectives in Two Confronted Communities

Political tensions created by Catalonian secessionism within Spain are unsettled one year after the failed proclamation of independence at 27th October 2017. A big segment of citizens (38% - 48% of the region population) supports secession, but there is another portion of citizenry, of similar size, that has resisted secessionist aspirations. Secessionism acquired forceful impetus along the last decade, wining consecutive regional elections and two (illegal) consultations about self-determination. A rise of activism, however, showed by unionists both at street demonstrations and at the last Regional election, consolidated a draw within a deeply polarized and divided society. We present an analysis of survey data that distinguish prevalent mood and emotion profiles among unionist vs. secessionist segments. Despite their protracted and unsuccessful venture, secessionists felt much less tired and confused than unionists, and they referred to be much less fearful and more hopeful about political and economic future. We link those distinctive feelings and disparate beliefs about current difficulties with a cognitive distortion noticeable only among secessionists, about the real magnitude of their force. We discuss these findings connecting such cognitive and affective profiles with features of a compounded ethno-cultural frontier based mainly on habitual language (Catalan vs. Spanish) and family-descent origins that have probably worked as the principal alignment vector. This social cleavage might function as a fracture line for extremist aggravations of a serious political conflict within the European Union.

Rheology Effects on Predicted Fiber Orientation and Elastic Properties in Large Scale Polymer Composite Additive Manufacturing

Short fiber-reinforced polymers have recently been introduced to large-scale additive manufacturing to improve the mechanical performances of printed-parts. As the short fiber polymer composite is extruded and deposited on a moving platform, velocity gradients within the melt orientate the suspended fibers, and the final orientation directly affects material properties in the solidified extrudate. This paper numerically evaluates melt rheology effects on predicted fiber orientation and elastic properties of printed-composites in three steps. First, the steady-state isothermal axisymmetric nozzle melt flow is computed, which includes the prediction of die swell just outside the nozzle exit. Simulations are performed with ANSYS-Polyflow, where we consider the effect of various rheology models on the computed outcomes. Here, we include Newtonian, generalized Newtonian, and viscoelastic rheology models to represent the melt flow. Fiber orientation is computed using Advani–Tucker fiber orientation tensors. Finally, elastic properties in the extrudate are evaluated based from predicted fiber orientation distributions. Calculations show that the Phan–Thien–Tanner (PTT) model yields the lowest fiber principal alignment among considered rheology models. Furthermore, the cross section averaged elastic properties indicate a strong transversely isotropic behavior in these composites, where generalized Newtonian models yield higher principal Young’s modulus, while the viscoelastic fluid models result in higher shear moduli.

Anisotropy and inter-condyle heterogeneity of cartilage under large-strain shear

We were the first to examine the mechanical responses of skeletally mature bovine femoral cartilage under large-strain simple shear (up to ±20%) using a multiaxial shear testing device. Since shear loading is critical in both tissue failure and chondrocyte responses, we aimed to probe (1) anisotropy with respect to the split-line direction (principal alignment of the collagen fibers near the articulating surface), (2) heterogeneity between femoral condyles, and (3) the influence of local cartilage thickness. We harvested a total of 48 cuboid cartilage specimens from four bovine knee joints. With each specimen we applied shear strains both parallel and perpendicular to the local split-line direction at a rate of 75μm/min and calculated the peak-to-peak shear stresses, shear strain–energy dissipation densities, and peak effective shear moduli. The Wilcoxon signed rank test revealed that the medial condyle was anisotropic in some mechanical measures at applied shear strains above 5%, while the lateral condyle was mechanically isotropic at all applied shear strains. The Kruskal–Wallis test revealed no significant differences in the median mechanical behavior of the lateral and medial condyles. Spearman׳s rank correlations revealed statistically significant negative monotonic correlations among thickness and most of our mechanical measures for both lateral and medial condyles at most applied strains and directions of applied shear. These results suggest that large-strain analyses account for nonlinear, anisotropic and location-dependent effects not fully realized at small strains. Our findings may inspire new experiments and models that consider anisotropy and heterogeneity of cartilage in ways previously ignored.

ASM-Based Objectionable Image Detection in Social Network Services

This paper presents a method for detecting harmful images using an active shape model (ASM) in social network services (SNS). For this purpose, our method first learns the shape of a woman's breast lines through principal component analysis and alignment, as well as the distribution of the intensity values of the corresponding control points. This method then finds actual breast lines with a learned shape and the pixel distribution. In this paper, to accurately select the initial positions of the ASM, we attempt to extract its parameter values for the scale, rotation, and translation. To obtain this information, we search for the location of the nipple areas and extract the location of the candidate breast lines by radiating in all directions from each nipple position. We then locate the mean shape of the ASM by finding the scale and rotation values with the extracted breast lines. Subsequently, we repeat the matching process of the ASM until saturation is reached. Finally, we determine objectionable images by calculating the average distance between each control point in a converged shape and a candidate breast line.

Regions of interest extraction from SPECT images for neural degeneration assessment using multimodality image fusion

The aging population highlights the importance of early diagnosis of neurodegenerative diseases in the elderly. Current diagnoses of such diseases rely on visual assessment of the neuron activity of the specific regions in the brain revealed by SPECT imaging with a specific tracer, 99mTc-TRODAT-1. However, due to the difficulties in defining the regions of interest (ROI) in SPECT images, efficient indices are lacking for quantitative analysis. In this study, we performed simultaneous CT and SPECT scans and used the CT images as the medium to register the MR and SPECT images, such that the ROI delineated in the MR image can be mapped onto the SPECT image in the corresponding area. A robust registration scheme is proposed, including coarse registration using principal axes alignment and then fine-tuning the registration using a combination of maximal cross-section area detection and the general Hough transform. The results from three clinical datasets all show improved accuracy of registration as compared with the results obtained using conventional principal axes alignment alone. Based on these registration results, a correct ROI can be defined in the SPECT images and ROI-based quantitative indices can be further derived.

Managing Value in Supply Chain – Case Studies on the Sourcing Hub Concept

In this paper, we postulate that a firm's sourcing knowledge can be a strategic resource for the firm, and explore how firms can capture and build on their sourcing knowledge. We examine the sourcing experiences of four firms in four different countries in the automotive industry, who are in the process of improving their supply-chain partnerships. We study upstream sourcing of these firms: their suppliers and their suppliers' suppliers, and focus on identifying the sourcing knowledge and sourcing cost related parameters with appropriate theoretical explanations. Synthesizing the learnings from these case studies, we propose the concept of the Sourcing Hub, a collaborative center involving the firm, its suppliers and raw material suppliers, as the principal alignment mechanism for managing value in upstream sourcing. Our research shows that deploying a sourcing hub can help firms create value by better management of upstream sourcing related knowledge and costs.

Bone Alignment Using the Iterative Closest Point Algorithm

Computer assisted surgical interventions and research in joint kinematics rely heavily on the accurate registration of three-dimensional bone surface models reconstructed from various imaging technologies. Anomalous results were seen in a kinematic study of carpal bones using a principal axes alignment approach for the registration. The study was repeated using an iterative closest point algorithm, which is more accurate, but also more demanding to apply. The principal axes method showed errors between 0.35 mm and 0.49 mm for the scaphoid, and between 0.40 mm and 1.22 mm for the pisiform. The iterative closest point method produced errors of less than 0.4 mm. These results show that while the principal axes method approached the accuracy of the iterative closest point algorithm in asymmetrical bones, there were more pronounced errors in bones with some symmetry. Principal axes registration for carpal bones should be avoided.

Flake Alignment and Linear Expansion of Various Oriented Strandboard

Flake alignment level (FAL) is a primary variable in oriented strandboard (OSB) manufacture that significantly affects the properties of OSB panels such as linear expansion (LE). Realizing the differences of FAL and LE among various OSB manufacturers will help the users have a better understanding of OSB performances in utilization. FAL and LE of various commercial OSB were investigated in this study. FAL was analyzed through percent alignment (PA) proposed by R. L. Geimer. This measures the average angle deviation from a reference angle of 45 degrees to the principal alignment direction of the board. It was found that different OSB manufacturers and even the same company showed significant variations in PA. In general, the front sides of panels had superior PA compared to the back sides. LE of commercial OSB had no clear relationships with PA. So it is hard to predict LE from flake alignment for commercial OSB.

Complex of Calmodulin with a Ryanodine Receptor Target Reveals a Novel, Flexible Binding Mode

Calmodulin regulates ryanodine receptor-mediated Ca(2+) release through a conserved binding site. The crystal structure of Ca(2+)-calmodulin bound to this conserved site reveals that calmodulin recognizes two hydrophobic anchor residues at a novel "1-17" spacing that brings the calmodulin lobes close together but prevents them from contacting one another. NMR residual dipolar couplings demonstrate that the detailed structure of each lobe is preserved in solution but also show that the lobes experience domain motions within the complex. FRET measurements confirm the close approach of the lobes in binding the 1-17 target and show that calmodulin binds with one lobe to a peptide lacking the second anchor. We suggest that calmodulin regulates the Ca(2+) channel by switching between the contiguous binding mode seen in our crystal structure and a state where one lobe of calmodulin contacts the conserved binding site while the other interacts with a noncontiguous site on the channel.

The manufacture of a very high precision x-ray collimator array for rapid tomographic energy dispersive diffraction imaging (TEDDI)

A very high resolution x-ray collimator array has been constructed for use with tomographic energy dispersive diffraction imaging (TEDDI). The collimator consists of a 16 × 16 array of 50 µm diameter holes in a series of 0.1 mm tungsten plates aligned to a tolerance of ±2 µm. The minimum angular divergence of the transmitted x-ray beams through each transmission pathway in the collimator array has been designed to be 0.02°, which is equivalent to an energy dispersed resolution of 250 eV with an aspect ratio of 6000:1. The collimator array has been matched to the development of an energy sensitive x-ray detector array (Seller et al 1998 Proc. SPIE 3445 584–92) for TEDDI studies of materials. The very high tolerance of the aperture size and placement was achieved by utilizing high intensity femtosecond pulse duration laser machining from a diode pumped solid state laser (DPSS). Using a novel arrangement the laser acted as the principal alignment and cutting tool. The collimator transmission function has been tested using a uniform synchrotron radiation flood field. The transmission and spatial uniformity were found to be consistent with the design parameters for TEDDI applications and also as a diffracted beam collimator for monochromatic powder diffraction studies.

Protein fold recognition through application of residual dipolar coupling data.

Residual dipolar coupling (RDC) represents one of the most exciting emerging NMR techniques for studying protein structures. However, solving a protein structure using RDC data alone is a highly challenging problem as it often requires that the starting structure model be close to the actual structure of a protein, for the structure calculation procedure to be effective. We report in this paper a computer program, RDC-PROSPECT, for identification of a structural homolog or analog of a target protein in PDB, which best matches the 15N-1H RDC data of the protein recorded in a single ordering medium. The identified structural homolog/analog can then be used as a starting model for RDC-based structure calculation. Since RDC-PROSPECT uses only RDC data and predicted secondary structure information, its performance is virtually independent of sequence similarity between a target protein and its structural homolog/analog, making it applicable to protein targets out of the scope of current protein threading techniques. We have tested RDC-PROSPECT on all 15N-1H RDC data (representing 33 proteins) available in the BMRB database and the literature. The program correctly identified the structural folds for approximately 80% of the target proteins, significantly better than previously reported results, and achieved an average alignment accuracy of 97.9% residues within 4-residue shift. Through a careful algorithmic design, RDC-PROSPECT is at least one order of magnitude faster than previously reported algorithms for principal alignment frame search, making our algorithm fast enough for large-scale applications.

Exact solutions for chemical bond orientations from residual dipolar couplings.

New methods for determining chemical structures from residual dipolar couplings are presented. The fundamental dipolar coupling equation is converted to an elliptical equation in the principal alignment frame. This elliptical equation is then combined with other angular or dipolar coupling constraints to form simple polynomial equations that define discrete solutions for the unit vector(s). The methods are illustrated with residual dipolar coupling data on ubiquitin taken in a single anisotropic medium. The protein backbone is divided into its rigid groups (namely, its peptide planes and Calpha frames), which may be solved for independently. A simple procedure for recombining these independent solutions results in backbone dihedral angles phi and psi that resemble those of the known native structure. Subsequent refinement of these phi-psi angles by the ROSETTA program produces a structure of ubiquitin that agrees with the known native structure to 1.1 A Calpha rmsd.

Principal Curvature Alignment Technique for Machining Complex Surfaces

Machining complex three dimensional surfaces is a challenging task. This paper presents two methods of machining these surfaces on a 4 and 5 axis machine, using a toroidal shaped cutter. The methods propose to align the principal axis of curvature of the machining surface with that of the machined surface in order to increase the volume of material removed. The increase in material removal at a point reduces the scallop height. Thus, fewer passes are required to achieve the same surface finish.

Parametric representation of Stiles-Crawford functions: normal variation of peak location and directionality.

Evidence suggests that the psychophysically determined Stiles-Crawford effect of the first kind (SCE) reflects waveguide properties of human photoreceptors. The peak of the SCE data set is assumed to reflect the principal alignment tendencies, and the spread (e.g., rho value, the curvature or width at half-height) is assumed to reflect the directionality (i.e., interreceptor differences in alignment) of the population of photoreceptors being tested. As such, disruption of the normal SCE can be used and/or has been used (1) to document early natural history of retinal pathology involving the photoreceptors, (2) to provide a firm rationale for therapeutic intervention, and (3) to provide a method for monitoring therapies designed to alter the natural course of retinal-disease processes. We report large-sample norms for foveal SCE peak location and spread (horizontal peak location, nasal 0.51 +/- 0.72, horizontal rho value 0.047 +/- 0.013, vertical peak location, superior 0.20 +/- 0.64, vertical rho value 0.053 +/- 0.012), compare these norms with values determined in other laboratories, and discuss the various mathematical forms used for the empirical description of SCE data sets.

Necessary and sufficient stability criterion for systems with structured uncertainties: the major principal direction alignment principle

A necessary and sufficient stability criterion is proved for multivariable systems in the presence of element-by-element bounded perturbations. The result constitutes a solution to the problem of computing the μ function for this class of perturbations, and the paper also provides an explicit approximation to the exact criterion.