Orientation Of Projections Research Articles

Changing sliding characteristics of a droplet on a slope by the shape and orientation of microtriangular projections for droplet transportation

This study provides a method for changing the mobility of a minute droplet by the shape and orientation of a microtriangular prism projection on a slope for droplet transportation. This method applies the characteristics of the static contact angle of a droplet to change the dynamic contact angles of the droplet sliding on a slope. The static contact angle was different at the apex and at the bottom of the isosceles triangular projection, large at the apex and small at the bottom. These characteristics were applied to change the hysteresis of the droplet by placing the apex upward or downward on the slope. This led to closer advancing and receding contact angles and vice versa. The acceleration of the droplet was investigated in terms of the apex angle and orientation of the isosceles triangular projections. The shape of the sliding droplet as a function of the triangular projection was also investigated. The proposed method could change the acceleration of the sliding droplet and directionality to the droplet for an easy movement.

On the rules for filling electron shells and the properties of the atomic Hamiltonian

The aim of this work is to determine the dependence of the total energy of the atomic system on the mutual orientation of the orbital angular moments of electrons. It is shown that the minimum value of the energy is attained for those configurations that are an eigenfunction of the orbital angular momentum operator . Thus, at least for individual atoms of the periodic table it is shown that Dirac’s postulate on the necessity of a wave function to be an eigenfunction of is a consequence that follows from the properties of the Hamiltonian, and it is not a complementary condition. Additionally, it is shown that the second Hund’s rule is incorrect with respect to the mutual orientation of the electron orbital angular momentum projections.

Molecular Ordering in Lipid Monolayers: An Atomistic Simulation.

We report on atomistic simulations of DPPC lipid monolayers using the CHARMM36 lipid force field (and also the Slipid force field as a control case), combined with a four-point OPC water model. The entire two-phase region where domains of the "liquid-condensed" (LC) phase coexist with domains of the "liquid-expanded" (LE) phase has been explored. The simulations are long enough that the complete phase-transition stage, with two domains coexisting in the monolayer, is reached in all cases. Also, system sizes used are larger than those in previous works. As expected, domains of the minority phase are elongated, emphasizing the importance of anisotropic van der Waals and/or electrostatic dipolar interactions in the monolayer plane. The molecular structure is quantified in terms of distribution functions for the hydrocarbon chains and the PN dipoles. In contrast to previous work, where average distributions are calculated, distributions are here extracted for each of the coexisting phases by first identifying lipid molecules that belong to either LC or LE regions. In the case of the CHARMM36 force field, the three-dimensional distributions show that the average tilt angle of the chains with respect to the normal outward direction is (39.0 ± 0.1)° in the LC phase and (48.1 ± 0.5)° in the LC phase. In the case of the PN dipoles, the distributions indicate a tilt angle of (110.8 ± 0.5)° in the LC phase and (112.5 ± 0.5)° in the LE phase. These results are quantitatively different from those in previous works, which indicated a smaller normal component of the PN dipole. Also, the distributions of the monolayer-projected chains and PN dipoles have been calculated. Chain distributions peak along a particular direction in the LC domains, while they are uniform in the LE phase. Long-range ordering associated with the projected PN dipoles is absent in both phases. These results strongly suggest that LC domains do not exhibit dipolar ordering in the plane of the monolayer, the effect of these components being averaged out at short distances. Therefore, the only relevant component of the molecular dipoles, with regard to both intra- and long-range interdomain interactions, is normal to the monolayer. Also, the local orientation of chain projections is almost constant in LC domains and points in the direction along which domains are elongated, suggesting that the line tension driving the phase transition might be anisotropic with respect to the interfacial domain boundary.

Physical exercise induces structural alterations in the hippocampal astrocytes: exploring the role of BDNF-TrkB signaling.

While it has been known that physical activity can improve cognitive function and protect against neurodegeneration, the underlying mechanisms for these protective effects are yet to be fully elucidated. There is a large body of evidence indicating that physical exercise improves neurogenesis and maintenance of neurons. Yet, its possible effects on glial cells remain poorly understood. Here, we tested whether physical exercise in mice alters the expression of trophic factor-related genes and the status of astrocytes in the dentate gyrus of the hippocampus. In addition to a significant increase in Bdnf mRNA and protein levels, we found that 4weeks of treadmill and running wheel exercise in mice, led to (1) a significant increase in synaptic load in the dentate gyrus, (2) alterations in astrocytic morphology, and (3) orientation of astrocytic projections towards dentate granule cells. Importantly, these changes were possibly linked to increased TrkB receptor levels in astrocytes. Our study suggests that astrocytes actively respond and could indeed mediate the positive effects of physical exercise on the central nervous system and potentially counter degenerative processes during aging and neurodegenerative disorders.

Bone Marrow Endothelial Progenitor Cell Transplantation After Ischemic Stroke: An Investigation Into Its Possible Mechanism.

We tested the hypothesis that endothelial progenitor cell (EPC)-mediated functional recovery after stroke may be associated with the endothelial nitric oxide synthase (eNOS)/brain-derived neurotrophic factor (BDNF) signaling pathway. Mice were infused with either EPCs or saline after being subjected to middle cerebral artery occlusion. The EPC-treated mice also received intravenous injections of either Nω-nitro-l-arginine methyl ester (L-NAME, the NOS inhibitor) or saline. The activation of eNOS and the expression of BDNF were significantly increased in ischemic brain of the EPC-treated mice, along with increased angiogenesis and neurogenesis. On diffusion tensor imaging (DTI), significant increases in fractional anisotropy and fiber count were observed in white matter, indicating axonal growth stimulated by EPCs. However, the EPC-treated mice that were received an L-NAME injection failed to exhibit the observed increases in angiogenesis, neurogenesis, and axonal growth. In addition, the neurons cocultured with EPCs in vitro exhibited the increased expression of BDNF and decreased apoptosis after oxygen-glucose deprivation compared with the control group. This EPC-induced protective effect was virtually absent in the L-NAME treatment group. The eNOS/BDNF pathway may be involved in the EPC-mediated functional recovery of stroke mice. DTI is feasible for dynamically tracking the orientation of axonal projections after EPC treatment.

Determining the area of convergence in Bloodstain Pattern Analysis: A probabilistic approach

A complete procedure for identifying the area of convergence of blood drops originated from a single static source is presented. Both for bloodstains lying on a horizontal and on a vertical plane a complete study is developed, based on error analysis and on an opportunely defined joint probability density for the orientation of the horizontal projections of the trajectories of the drops. The method generates a probabilistic map for the area of convergence, directly linking the angles of impact, and their uncertainties, to the projection on the ground of the point of origin. One of the objectives consists in providing a statistical definition of area of convergence, extending to this topic the mathematical accuracy of the calculation of the angle of impact in bloodstain pattern analysis (BPA).

Morphology and Postdepositional Dynamics of Eggs of the Predator Podisus distinctus (Stål) (Heteroptera: Pentatomidae: Asopinae).

The predator Podisus distinctus (Stål) (Heteroptera: Pentatomidae: Asopinae) has been reared to control lepidopteran defoliators. In this study, we describe this predator's morphology, postdepositional dynamics and eggs in different developmental stages under scanning electron microscope. Its eggs are subglobular and ovoid, narrower at the base than at the top, with a convex, circular operculum. They measure 1.09±0.03 mm in height and 0.90±0.04 mm in diameter. The aero-micropylar processes number 16.00±2.00 and are arranged radially at the egg anterior pole. Immediately after laying, the egg color is pearl-like, and soon after turns gray. Orientation of the spine-like projections and aero-micropylar processes also change after deposition. Though the eggs of P. distinctus are similar to those of other species of the genus Podisus, certain aspects, including the egg size and shape, chorion micro-sculptures, and number of aero-micropylar processes, are specific, allowing for differentiation from other related species.

Detection of rupture lines for active scanning

Corner and junction detection is an important preprocessing step in image registration, data fusion, object recognition, and many other tasks. This work deals with corner and junction detection of characteristic features of the structure resulting from cross-pattern projection. The ultimate aim is to adapt the positions and orientation of the cross-pattern projections to what has been observed. The use of this projected light pattern in the framework of active vision allows us to identify certain points of interest on 3-D objects, to directly acquire a synthesis, which thus permits simplified detection, measurement, recognition, or tracking. We present detection methods for corners and junctions in the context of Hough transform detection.

Orientation determination by wavelets matching for 3D reconstruction of very noisy electron microscopic virus images

BackgroundIn order to perform a 3D reconstruction of electron microscopic images of viruses, it is necessary to determine the orientation (Euler angels) of the 2D projections of the virus. The projections containing high resolution information are usually very noisy. This paper proposes a new method, based on weighted-projection matching in wavelet space for virus orientation determination. In order to speed the retrieval of the best match between projections from a model and real virus particle, a hierarchical correlation matching method is also proposed.ResultsA data set of 600 HSV-1 capsid particle images in different orientations was used to test the proposed method. An initial model of about 40 Å resolutions was used to generate projections of an HSV-1 capsid. Results show that a significant improvement, in terms of accuracy and speed, is obtained for the initial orientation estimates of noisy herpes virus images. For the bacteriophage (P22), the proposed method gave the correct reconstruction compared to the model, while the classical method failed to resolve the correct orientations of the smooth spherical P22 viruses.ConclusionThis paper introduces a new method for orientation determination of low contrast images and highly noisy virus particles. This method is based on weighted projection matching in wavelet space, which increases the accuracy of the orientations. A hierarchical implementation of this method increases the speed of orientation determination. The estimated number of particles needed for a higher resolution reconstruction increased exponentially. For a 6 Å resolution reconstruction of the HSV virus, 50,000 particles are necessary. The results show that the proposed method reduces the amount of data needed in a reconstruction by at least 50 %. This may result in savings 2 to 3 man-years invested in acquiring images from the microscope and data processing. Furthermore, the proposed method is able to determine orientations for some difficult particles like P22 with accuracy and consistency. Recently a low PH sindbis capsid was determined with the proposed method, where other methods based on the common line fail.

The alpha-factor receptor C-terminus is important for mating projection formation and orientation in Saccharomyces cerevisiae.

Successful mating of MATa Saccharomyces cerevisiae cells is dependent on Ste2p, the alpha-factor receptor. Besides receiving the pheromone signal and transducing it through the G-protein coupled MAP kinase pathway, Ste2p is active in the establishment and orientation of the mating projection. We investigated the role of the carboxyl terminus of the receptor in mating projection formation and orientation using a spatial gradient assay. Cells carrying the ste2-T326 mutation, truncating 105 of the 135 amino acids in the receptor tail including a motif necessary for its ligand-mediated internalization, display slow onset of projection formation, abnormal shmoo morphology, and reduced ability to orient the mating projection toward a pheromone source. This reduction was due to the increased loss of mating projection orientation in a pheromone gradient. Cells with a mutated endocytosis motif were defective in reorientation in a pheromone gradient. ste2-Delta296 cells, which carry a complete truncation of the Ste2p tail, exhibit a severe defect in projection formation, and those projections that do form are unable to orient in a pheromone gradient. These results suggest a complex role for the Ste2p carboxy-terminal tail in the formation, orientation, and directional adjustment of the mating projection, and that endocytosis of the receptor is important for this process. In addition, mutations in RSR1/BUD1 and SPA2, genes necessary for budding polarity, exhibited little or no defect in formation or orientation of mating projections. We conclude that mating projection orientation depends upon the carboxyl terminus of the pheromone receptor and not the directional machinery used in budding.

Decay and fission of oriented nuclei

The angular distributions of fragments originating from the binary decay of oriented spherical and deformed nuclei are investigated with allowance for correct transformation properties of wave functions under time inversion. It is shown that, as in the case of protonic decay, the adiabatic approximation for collective rotational degrees of freedom of the systems under investigation is inapplicable in describing the angular distributions of fragments of the deep-subbarrier alpha and cluster decays of nuclei. It is demonstrated that this approximation is justified in describing spontaneous and induced low-energy nuclear fission. The dependence of partial fission widths on the orientation of intrinsic axes, spins, and projections of spins and relative orbital angular momenta of fission fragments is analyzed by using the formalism of the unified theory of nuclear reactions and the theory of open Fermi systems. It is shown that the adiabatic approximation leads to the coherent interference between the wave functions for the relative motion of fragments, whereby the universal angular distributions of fission fragments of oriented nuclei is formed. Deviations from the A. Bohr formula are investigated for these distributions.

Cellular basis for paracrine regulation of ovarian follicle development.

Paracrine factors secreted by oocytes and somatic cells regulate many important aspects of early ovarian follicle development in mammals. From activation of dormant primordial follicles to selection of secondary follicles, locally acting factors have been identified that appear to exert important effects on the growth and differentiation of oocytes and granulosa cells. This article summarizes evidence to support a model for bi-directional paracrine communication that is based on developmental regulation of the delivery and reception of paracrine factors at the oocyte-granulosa cell interface. Transzonal projections that originate from granulosa cells and terminate at the oocyte plasma membrane provide a polarized means to orient the secretory organelles of somatic cells. Characterization of transzonal projections in follicles from normal and genetically modified mice reveals dynamic changes in the density and stability of transzonal projections. On the basis of new data analysing the orientation and cytoskeletal content of transzonal projections in mammalian oocytes, a model is proposed for regulation of paracrine growth factor secretion by follicle-stimulating hormone. These findings have immediate implications for ovarian hyperstimulation protocols and follicle culture models as related to the production of mammalian embryos by assisted reproductive technologies.

Complementary expression of transmembrane ephrins and their receptors in the mouse spinal cord: a possible role in constraining the orientation of longitudinally projecting axons.

In the developing spinal cord, axons project in both the transverse plane, perpendicular to the floor plate, and in the longitudinal plane, parallel to the floor plate. For many axons, the floor plate is a source of long- and short-range guidance cues that govern growth along both dimensions. We show here that B-class transmembrane ephrins and their receptors are reciprocally expressed on floor plate cells and longitudinally projecting axons in the mouse spinal cord. During the period of commissural axon pathfinding, B-class ephrin protein is expressed at the lateral floor plate boundaries, at the interface between the floor plate and the ventral funiculus. In contrast, B-class Eph receptors are expressed on decussated commissural axon segments projecting within the ventral funiculus, and on ipsilaterally projecting axons constituting the lateral funiculus. Soluble forms of all three B-class ephrins bind to, and induce the collapse of, commissural growth cones in vitro. The collapse-inducing activity associated with B-class ephrins is likely to be mediated by EphB1. Taken together, these data support a possible role for repulsive B-class Eph receptor/ligand interactions in constraining the orientation of longitudinal axon projections at the ventral midline.

Estimating the viewing parameters of random, noisy projections of asymmetric objects for tomographic reconstruction

The ability to determine the viewing parameters of objects from their projections has enabled well established tomographic techniques to be employed in the 3D reconstruction of objects from images obtained via modalities where the orientation of the objects cannot be controlled. A method is described for the determination of the viewing parameters of randomly acquired projections of asymmetric objects. It extends upon the common lines algorithm by determining the relative orientation of projections from the location of lines of intersection among the Fourier transforms of the projections in 3D Fourier space. A new technique for finding the lines of intersection in the presence of translational displacement, and for subsequently finding the translational displacement, is presented. The complete algorithm is described and its efficacy is demonstrated using real data. A new technique for dealing with noise is also discussed.

Radon transforms, alignment, and 3d-reconstruction from random projections

Since their inception three-dimensional reconstruction techniques have been based on the theory of Radon transforms. Only much later have Radon transforms been recognized as powerful tools for image processing and pattern recognition. Techniques like the “common lines ” technique for finding the orientation of projections of highly symmetrical particles, which had been developed using Fourier transforms, can easily be translated into a technique that uses Radon transforms. In contrast to Fourier transforms Radon transforms have the advantage of being real valued which simplifies many interpolation steps. The central section theorem known for Fourier transforms also applies to Radon transforms. The two- or three-dimensional Fourier transform on a polar grid can be obtained from the two- or three-dimensional Radon transform by a one-dimensional (radial) Fourier transforms and vice versa. Fourier transforms obtained by a one-dimensional transformation of the Radon transform will be referred to a Fourier/Radon transforms.

Detection of plasma proteins in CNS neurons: conspicuous influence of tissue-processing parameters and the utilization of serum for blocking nonspecific reactions.

Despite the presence of a blood-brain barrier (BBB), plasma proteins have been detected intraneuronally in regions with axonal projections confined to the CNS. This finding raises the question of whether plasma proteins are taken up from the brain interstitium or whether the results are due to experimental artifact. We examined the effect of various protocols for tissue processing on the intraneuronal distribution of plasma proteins using immunohistochemistry. The detection level of plasma proteins decreased after prolonged fixation, irrespective of the fixative and embedding method employed. In cryostat sections, attempts to block nonspecific staining by serum protein caused considerable nonspecific staining in itself. When nonspecific staining was blocked with a serum-free buffer, specifically labeled neuronal perikarya were found in cryostat sections of brains fixed by perfusion with paraformaldehyde without postfixation. Albumin and IgG occurred predominantly in neurons having projections beyond the BBB but also sparsely in neurons having projections confined to the CNS. Transferrin was evenly distributed within neuronal somata, irrespective of the orientation of projections. The immunoreaction product of the three plasma proteins exhibited a specific intraneuronal localization in the differently projecting neurons. In circumventricular organs, plasma proteins were observed extracellularly and in projecting fibers. In conclusion, plasma proteins are present in neurons with projections confined to the CNS and are probably taken up from the brain interstitium.

Cell polarity and the mechanism of asymmetric cell division.

During development, one mechanism for generating different cell types is asymmetric cell division, by which a cell divides and contributes different factors to each of its daughter cells. Asymmetric cell division occurs throughout the eukaryotic kingdom, from yeast to humans. Many asymmetric cell divisions occur in a defined orientation. This implies a cellular mechanism for sensing direction, which must ultimately lead to differences in gene expression between two daughter cells. In this review, we describe two classes of molecules: regulatory factors that are differentially expressed upon asymmetric cell division, and components of a signal transduction pathway that may define cell polarity. The lin-11 and mec-3 genes of C. elegans, the Isl-1 gene of mammals and the HO gene of yeast, encode regulatory factors that determine cell type of one daughter after asymmetric cell division. The CDC24 and CDC42 genes of yeast affect both bud positioning and orientation of mating projections, and thus may define a general cellular polarity. We speculate that molecules such as Cdc24 and Cdc42 may regulate expression of genes such as lin-11, mec-3, Isl-1 and HO upon asymmetric cell division.

Structure of complement poly-C9 determined in projection by cryo-electron microscopy and single particle analysis

The ring-like complement ‘lesions’ found on membranes of complement lysed cells comprise a complex of components C5b through C9 that coalesce to form hollow cylinders which penetrate the membrane bilayer and create lytic pores. Walls of these C5b-9 membrane attack complex cylinders may consist primarily of the C9 component, since samples of purified, isolated C9 can polymerize into cylindrical structures which appear identical with the fully assembled C5b-9 complex. The structure of these poly-C9 molecules has been investigated using the techniques of cryo-electron microscopy and single particle analysis. Sets of single poly-C9 particles viewed as rings were selected from cryo-EM images, then particles were aligned and treated by correspondence analysis to identify the principle interparticle similarities and variations. The highest ranking variation found was the presence or absence of a dense inner ring of protein density. Other important variations were interpreted as different types of particle tilt. These results were used in selecting a subgroup of untilted particles for averaging and symmetry analysis. The rotational power spectrum of the initial average suggested 13-fold symmetry. The 13-fold symmetry was used to select and group particles for further analysis. Individual particles were 13-fold rotational averaged and those with enhanced peripheral features were placed into either a right-handed subgroup or into a left-handed subgroup based on orientation of the peripheral features. Particles within each group were aligned and averaged, and a poly-C9 structure was produced which shows important structural details and from which the C9 monomer structure can be deduced. The poly-C9 structure contains a dense inner ring of diameter between 113–181 Å and which is modulated into 13 discrete peaks with peak-to-peak separation of approx. 35 Å. The dense inner ring is surrounded by a less dense, concentric outer rim extending to 254 Å diameter. The outer rim contains projections that are contiguous with the inner peaks but are skewed relative to the ring radius to produce the appearance of a pin-wheel. These projections correspond with the peripheral features picked up in the rotationally averaged individual particles; the left- or right-handed orientation of projections may result from the up/down orientation of individual particles in ice. The C9 monomer structure within the cylinder is suggested by the density distribution. The monomer would be a rod with diameter of 35 Å, oriented parallel to the cylinder axis and would be roughly perpendicular to a membrane. A portion of the C9 monomer would form the projecting outer rim. In side views of the complex the outer rim density would be the torus structure seen distal to the membrane-inserting region. These results indicating an extended C9 structure are consistent with C9 unfolding in the transition from monomer to poly-C9 complex.

A method of general moments for orienting 2D projections of unknown 3D objects

We develop a technique using general moments to find the orientation of 2D planar orthographic projections of 3D objects, even if the 3D object has a completely unknown structure. The technique should open new classes of biological materials for ultrastructural analysis, through molecular scale transmission electron microscopy reconstruction applications where the original 3D object's structure is unknown. In machine vision applications where the full 3D structure is known, the technique provides a fast and computationally efficient way to orient projections. The technique can also be used to orient 1D line projections of 2D unknown objects.

Real-space filtering of electron images from optical autocorrelation patterns

The capability for filtering electron images, in real space, is demonstrated to be inherent to a two plate, incoherent optical procedure (originally described by Meyer-Eppler and Darius) for recording autocorrelation functions from transparencies. If an image contains features that occur with more than random frequency, these features may give rise to a resolvable peak in the optically recorded autocorrelation function. The optical requirements for obtaining an image of the transparency that is filtered to observe only features giving rise to some set of such peaks, or to exclude them, are described. The principle is to form an image of the transparency, with a properly placed plano-convex lens, from the incoherent light transmitted through apertures positioned over the peaks in the autocorrelation plane. The application of the method in defining the position and orientation of specific projections of protein molecules, as observed in negative stain by bright-field, or unstained by dark-field electron microscopy, is also described.