Plane Of Sheet Research Articles

Ciliary proteins link basal body polarization to planar cell polarity regulation

Planar cell polarity (PCP) refers to coordinated polarization of cells within the plane of a cell sheet. A conserved signaling pathway is required for the establishment of PCP in epithelial tissues and for polarized cellular rearrangements known as convergent extension. During PCP signaling, core PCP proteins are sorted asymmetrically along the polarization axis; this sorting is thought to direct coordinated downstream morphogenetic changes across the entire tissue. Here, we show that a gene encoding a ciliary protein (a 'ciliary gene'), Ift88, also known as Polaris, is required for establishing epithelial PCP and for convergent extension of the cochlear duct of Mus musculus. We also show that the proper positioning of ciliary basal bodies and the formation of polarized cellular structures are disrupted in mice with mutant ciliary proteins ('ciliary mutants'), whereas core PCP proteins are partitioned normally along the polarization axis. Thus, our data uncover a distinct requirement for ciliary genes in basal body positioning and morphological polarization during PCP regulation.

Spontaneous symmetry breaking in graphene subjected to an in-plane magnetic field

Application of the magnetic field parallel to the plane of the graphene sheet leads to the formation of electron- and holelike Fermi surfaces. Such situation is shown to be unstable with respect to the formation of an excitonic condensate even for an arbitrary weak magnetic field and interaction strength. At temperatures lower than the mean-field temperature, the order parameter amplitude is formed. The order parameter itself is a U(2) matrix allowing for the combined rotations in the spin and valley spaces. These rotations smoothly interpolate between site and bond centered spin-density waves and spin-flux states. The trigonal warping, short-range interactions, and the three-particle umklapp processes freeze some degrees of freedom at temperatures much smaller than the mean-field transition temperature, and make either Berezinskii-Kosterlitz-Thouless [Sov. Phys. JETP 32, 493 (1971); J. Phys. C 5, L124 (1972); 6, 1181 (1973)] (driven either by vortices or half-vortices) or Ising type transitions possible. Strong logarithmic renormalization for the coupling constants of these terms by the Coulomb interaction is calculated within one-loop renormalization group. It is found that in the presence of the Coulomb interaction, some short-range interaction terms become much greater than one might expect from the naive dimensionality counting.

The evolution of dark matter halo properties in clusters, filaments, sheets and voids

We use a series of high-resolution N-body simulations of the concordance cosmology to investigate the redshift evolution since z = 1 of the properties and alignment with the large-scale structure (LSS) of haloes in clusters, filaments, sheets and voids. We find that (i) once a rescal-ing of the halo mass with M * (z), the typical mass scale collapsing at redshift z, is performed, there is no further significant redshift dependence in the halo properties; (ii) the environment influences the halo shape and formation time at all investigated redshifts for haloes with masses M ≤ M * and (iii) there is a significant alignment of both spin and shape of haloes with filaments and sheets. In detail, at all redshifts up to z = 1: (a) haloes with masses below ∼ M * tend to be more oblate when located in clusters than in the other environments; this trend is reversed at higher masses: above about M * , haloes in clusters are typically more prolate than similar massive haloes in sheets, filaments and voids. (b) The haloes with M ≥ M * in filaments spin more rapidly than similar mass haloes in clusters; haloes in voids have the lowest median spin parameters. (c) Haloes with M ≤ M * tend to be younger in voids and older in clusters. (d) In sheets, halo spin vectors tend to lie preferentially within the sheet plane independent of halo mass; in filaments, instead, haloes with M ≤ M * tend to spin parallel to the filament and higher mass haloes perpendicular to it. For halo masses M ≥ M * , the major axis of haloes in filaments and sheets is strongly aligned with the host filament or the sheet plane, respectively. Such halo-LSS alignments may be of importance in weak lensing analyses of cosmic shear. A question that is opened by our study is why, in the 0 < z < 1 redshift regime that we have investigated, the mass scale for gravitational collapse, M * , sets roughly the threshold below which the LSS environment either begins to affect, or reverses, fundamental properties of dark matter haloes.

Formation of textural inhomogeneity in a Zn-1.1% Al alloy during superplastic deformation

The Zn-1.1% Al alloy with a strong rolling texture has been tested under the conditions of superplasticity. The samples were cut from a sheet 5 mm thick at an angle of 20° with the sheet plane. The material in the initial state was characterized by the absence of a texture gradient over the sample thickness. Deformation led to a substantial weakening of texture maxima inside the sheet and their retention at the surface. Estimate of intragrain slip revealed that the contribution from slip was greater in deeper layers and smaller at the sheet surface. The effect was explained by different conditions of accommodation of grain-boundary sliding at the surface and inside the sheet.

Production of Ti-6Al-4V Sheets for Low Temperature Superplastic Forming

The availability to produce Ti-6Al-4V sheet material with submicron-grained microstructure for superplastic forming (SPF) has been studied. The laboratory scale sheets with an average grain size of 0.3 μm and the commercial size sheets with an average grain size of 0.65 μm were produced by pack rolling manufacturing technique from the forgings with pre-formed submicrocrystalline (SMC) structure. The sheets possessing isotropic mechanical properties in the sheet plane had higher yield strength, ultimate tensile strength. Over the exceptionally low temperature range of 700-750°C the SMC sheets demonstrated enhanced superplastic properties, namely an initial flow stress of 20-25 MPa and elongation more than 600% at the strain rate of 3×10-4/s. The sheet material with SMC structure was characterized by well formability compared to a conventional sheet under low temperature superplastic conditions.

Creating Helical Tool Paths for Single Point Incremental Forming

Single point incremental forming (SPIF) is a relatively new sheet forming process. A sheet is clamped in a rig and formed incrementally using a rotating single point tool in the form of a rod with a spherical end. The process is often performed on a CNC milling machine and the tool movement is programed using CAM software intended for surface milling. Often the function called profile milling or contour milling is applied. Using this milling function the tool only has a continuous feed rate in two directions X and Y, which is the plane of the undeformed sheet. The feed in the vertical Z direction is done in the same angular position in the XY plane along a line down the side of the work piece. This causes a scarring of the side and also results in a peak in the axial force when the tool is moved down. The present paper offers a solution to this problem. A dedicated program uses the coordinates from the profile milling code and converts them into a helical tool path with continuous feed in all three directions. Using the helical tool path the scarring is removed, the part is otherwise unchanged and a major disadvantage of using milling software for SPIF is removed. The solution is demonstrated by SPIF of three different geometries: a pyramid, a cone and a complex part.

Planar cell polarity: one or two pathways?

In multicellular organisms, cells are polarized in the plane of the epithelial sheet, revealed in some cell types by oriented hairs or cilia. Many of the underlying genes have been identified in Drosophila melanogaster and are conserved in vertebrates. Here we dissect the logic of planar cell polarity (PCP). We review studies of genetic mosaics in adult flies - marked cells of different genotypes help us to understand how polarizing information is generated and how it passes from one cell to another. We argue that the prevailing opinion that planar polarity depends on a single genetic pathway is wrong and conclude that there are (at least) two independently acting processes. This conclusion has major consequences for the PCP field.

Stability of shear modulus of glass-reinforced plastics based on adhesive prepreg in a humid medium

Strength properties and moisture absorption of glass-and carbon-reinforced plastics prepared using solvent-free adhesive prepregs are studied in a humid atmosphere. The main advantage of the studied materials is a more than tenfold-higher sealing of honeycombed constructions. The ultimate moisture saturation, diffusion coefficient, shear modulus, and swelling are studied. A cyclic action of moisture and temperature is shown to cause a reduction in the shear modulus along the sheet plane upon moistening and an incomplete recovery of the modulus after drying. It is established that, after the second, third, and fourth cycles, irreversible changes become insignificant, thus indicating the stabilization of the shear modulus along the sheet plane during the subsequent cycles. The dependences of the shear modulus on the preparation process of the glass-reinforced plastics are determined under humid conditions.

Dynamics of equilibrium upset and electromagnetic energy transformation in the geomagnetotail: A theory and simulation using particles. 1. Evolution of configurations in an MHD approximation

The process of equilibrium disruption in the system with a current sheet (CS) under the conditions of small magnetic field component normal to CS, which is induced by an external disturbance, has been theoretically studied within the scope of MHD. In the geomagnetotail, this disturbance can be caused by a tearing instability developing in the more distant tail section, or by a ballooning instability in the tail nearest section, or by a rapid reconfiguration at the magnetopause during the disturbance passage in the solar wind. Locally, in a limited CS section, a longitudinal momentum balance is rapidly (on the Alfven time scale) upset when a fast MHD disturbance, the form of which depends on the presence of CS, passes along the tail. The nonequilibrium temperature, which subsequently evolves through splitting of CS into several current structures, originates on a substantially larger (due to the smallness of the normal field component) time scale. Such a reconfiguration SPONTANEOUSLY develops after the initial equilibrium upset under the action of an external (weak) disturbance. During an analysis within the scope of MHD, this reconfiguration can be described as the well-known process with two pairs of nonlinear waves propagating in both directions from the central sheet plane at constant velocities: these are fast rarefaction waves and the following slow “switching-off” shocks. However, the kinetic theory reveals substantially different relaxation channels. These channels are studied in the second and third work sections, where the kinetic numerical simulation of the problem is presented and the results of this simulation are analyzed.

Wnt5a functions in planar cell polarity regulation in mice

Planar cell polarity (PCP) refers to the polarization of cells within the plane of a cell sheet. A distinctive epithelial PCP in vertebrates is the uniform orientation of stereociliary bundles of the sensory hair cells in the mammalian cochlea. In addition to establishing epithelial PCP, planar polarization is also required for convergent extension (CE); a polarized cellular movement that occurs during neural tube closure and cochlear extension. Studies in Drosophila and vertebrates have revealed a conserved PCP pathway, including Frizzled (Fz) receptors. Here we use the cochlea as a model system to explore the involvement of known ligands of Fz, Wnt morphogens, in PCP regulation. We show that Wnt5a forms a reciprocal expression pattern with a Wnt antagonist, the secreted frizzled-related protein 3 (Sfrp3 or Frzb), along the axis of planar polarization in the cochlear epithelium. We further demonstrate that Wnt5a antagonizes Frzb in regulating cochlear extension and stereociliary bundle orientation in vitro, and that Wnt5a −/− animals have a shortened and widened cochlea. Finally, we show that Wnt5a is required for proper subcellular distribution of a PCP protein, Ltap/Vangl2, and that Wnt5a interacts genetically with Ltap/Vangl2 for uniform orientation of stereocilia, cochlear extension, and neural tube closure. Together, these findings demonstrate that Wnt5a functions in PCP regulation in mice.

Ultrasonic system for in-plane paper characterisation

. Some of these previous studies investigated plate wave’s propagation in paper, in an attempt to obtain correlations with mechanical properties using contactless methods due to the impossibility of using traditional contact techniques [1,2,7] . Other researchers have developed on-line systems that can measure certain properties in a moving web [3,8-10] . Ultrasonic analysis is a very interesting technique because it is fast, non-destructive and is very sensitive to the cellulose-fibre-based structure of the paper . In this paper a computer-controlled, fully-automated ultrasonicbased system composed of a measuring head and peripheral hardware was conceived. The system performs ultrasonic velocity measurements in the plane of the paper sheet which can be used to establish the tensile stiffness index (TSI). This parameter has an increased acceptance as a measure of paper strength properties [2] . Once TSI for the different orientations is known, the tensile stiffness orientation angle (TSO), defined by the orientation of the maximum of the TSI plot and the paper machine direction, can be evaluated. Another important factor in the paper industry is the use of mineral fillers that are applied for economic reasons, because fillers impart to paper specific properties. Bulk, air permeability, porosity, light scattering, stiffness, gloss and printability are some of the paper properties that are dependent on mineral fillers and on filler level [10] . Paper strength is reduced by filler incorporation, due to the reduction in bonded area of cellulose fibres. Mineral fillers have very different elastic properties from cellulose fibre, so the overall elastic property of the paper with fillers is different from a paper that has only cellulose fibres. Due to the good linear correlation between the mineral filler content in paper and ultrasonic velocities, the prediction of the elastic properties variation can be achieved. 2. Background The measurement of ultrasonic velocities is a powerful technique for non-destructive analysis of the mechanical properties of materials. Typically, the propagation velocity of a plane wave through a material is equal to the square root of the Young’s modulus divided by the mass density. So, the Young’s modulus can be obtained from velocity measurements. In our case we are interested in the analysis of planar materials. These are defined as plates that have lateral dimensions larger than the wavelength of in-plane bulk waves and whose thickness is small compared to the wavelength of out-ofplane bulk waves [11]

Planar cell polarity signaling in vertebrates

Planar cell polarity (PCP) refers to the polarization of a field of cells within the plane of a cell sheet. This form of polarization is required for diverse cellular processes in vertebrates, including convergent extension (CE), the establishment of PCP in epithelial tissues and ciliogenesis. Perhaps the most distinct example of vertebrate PCP is the uniform orientation of stereociliary bundles at the apices of sensory hair cells in the mammalian auditory sensory organ. The establishment of PCP in the mammalian cochlea occurs concurrently with CE in this ciliated epithelium, therefore linking three cellular processes regulated by the vertebrate PCP pathway in the same tissue and emerging as a model system for dissecting PCP signaling. This review summarizes the morphogenesis of this model system to assist the interpretation of the emerging data and proposes molecular mechanisms underlying PCP signaling in vertebrates.

Electron surfing acceleration in a current sheet by perpendicular electrostatic waves

We consider electron acceleration in a 3D current sheet by electrostatic waves generated during magnetic reconnection process. The electrons trapped in the potential of electrostatic waves are shown to be accelerated by ev p c × B z force in the outflow direction of current sheet plane up to the energy required for their de-trap from wave potential. The maximum velocity of electron acceleration is shown to be about the electric drift velocity. In the presence of a longitudinal magnetic field the electron de-trapping velocity increases.

Failure envelope of first‐year Arctic sea ice: The role of friction in compressive fracture

New experiments have been performed on the brittle compressive failure of columnar‐grained, first‐year sea ice with the S2 growth texture, harvested from the floating cover on the Arctic Ocean. The ice was proportionally loaded biaxially across the columns at –10°C at 1.5 × 10−2 s−1; i.e., within the regime of brittle behavior. The results, when combined with earlier measurements of tensile strength by Richter‐Menge and Jones (1993), allow the complete brittle failure envelope to be constructed. The envelope is symmetric about the loading path R = σ2/σ1 = 1, owing to the isotropic character of the material within the horizontal plane of the ice sheet, but is asymmetric with respect to the compressive‐compressive and tensile‐tensile quadrants, owing to the relative weakness of the material under tension. The compressive strength reaches a maximum along the loading path R ∼ 0.5. Terminal failure occurs through either splitting (unconfined loading), Coulombic shear faulting under lower confinement (R &lt; 0.2) or spalling under higher confinement (0.2 &lt; R ≤ 1). An integral component of compressive failure under low confinement is the internal friction coefficient: its value under the conditions of the experiments (μi = 0.92 ± 0.09) is deduced from the failure envelope. The internal friction coefficient is shown through postterminal failure measurements to be closely similar to the coefficient of friction at the onset of sliding along the Coulombic faults. Granite exhibits similar behavior. Modeling reveals that the terminal failure stress under low confinement can be reasonably well described in terms of the comb‐crack mechanism (Schulson et al., 1999; Renshaw and Schulson, 2001) of brittle compressive failure. Comparison with observations and measurements in the field indicate that the failure processes that operate on the smaller scale are similar to at least some of those that operate on the larger scale, implying that the physics of failure may be scale‐independent.

Geometric morphometrics defines shape differences in the cortical area map of C57BL/6J and DBA/2J inbred mice

BackgroundWe previously described planar areal differences in adult mouse visual, somatosensory, and neocortex that collectively discriminated C57BL/6J and DBA/2J inbred strain identity. Here we use a novel application of established methods of two-dimensional geometric morphometrics to examine shape differences in the cortical area maps of these inbred strains.ResultsWe used Procrustes superimposition to align a reliable set of landmarks in the plane of the cortical sheet from tangential sections stained for the cytochrome oxidase enzyme. Procrustes superimposition translates landmark configurations to a common origin, scales them to a common size, and rotates them to minimize an estimate of error. Remaining variation represents shape differences. We compared the variation in shape between C57BL/6J and DBA/2J relative to that within each strain using a permutation test of Goodall's F statistic. Significant differences in shape in the posterior medial barrel subfield (PMBSF), as well as differences in shape across primary sensory areas, characterize the cortical area maps of these common inbred, isogenic strains.ConclusionC57BL/6J and DBA/2J have markedly different cortical area maps, in both size and shape. These differences suggest polymorphism in genetic factors underlying cortical specification, even between common isogenic strains. Comparing cortical phenotypes between normally varying inbred mice or between genetically modified mice can identify genetic contributions to cortical specification. Geometric morphometric analysis of shape represents an additional quantitative tool for the study of cortical development, regardless of whether it is studied from phenotype to gene or gene to phenotype.

Velocity, density and transport measurements in rotating, stratified flows

A technique is presented for measuring velocity, density and scalar transport in a buoyant rotating gravity current. Existing methods for combined PIV and PLIF are modified for use in a stratified flow on a rotating table and strategies for beam alignment, index of refraction matching, surface tension matching and photobleaching correction are presented. In addition, the PIV–PLIF technique is modified to resolve the velocity and density fields in a cross-section of the current perpendicular to the mean flow direction, allowing the transport in this direction to be computed. This is done by rotating the plane of the laser sheet 15° to the horizontal. This sheet angle is high enough that the entire cross-section of the current is contained in the viewing area, but low enough that horizontal PIV particle displacements are resolved. The technique is used successfully to measure the transport of buoyant fluid in a non-rotating channel to within 5% of the prescribed flow. Results from a rotating gravity current experiment are then presented and compared with previous experiments.

The Large Strain Flow Stress Behaviour of Aluminium Alloys as Measured by Channel-Die Compression (20-500°C)

Two recent methods for obtaining flow stress-strain relations up to large strains of order 1.5 by channel-die compression are presented: i) for sheet metal formability tests, composite samples have been made of glued sheet layers and deformed at room temperature in a channel-die with the compression axis directed along one of the sheet metal edge directions, i.e. RD or TD. The sheet plane is parallel to the lateral compression die face. It is shown that, using a suitable lubricant, the sample deformation is homogeneous up to strains of 1.5. Tests carried out on 5xxx and 6xxx alloys to evaluate the stress-strain relations show that a generalized Voce law gives a good quantitative fit for the data. ii) for high temperature plate processing, quantitative flow stress data can be obtained up to 500°C with a rapid quench using a hot channel-die set-up. Some new results are presented here for high strain hot PSC tests on Al-Mn and Al-Mg alloys together with microstructure analyses.

Magnetic structures of [Co 3(pyz)(HPO 4) 2F 2], a fluorinated cobalt phosphate with a pillared layer structutre

The magnetic structure of [Co 3(pyz)(HPO 4) 2F 2] compound was characterized by neutron diffraction. The crystal structure of the compound consists of two-dimensional neutral sheets of [Co 3(HPO 4) 2F 2], which are pillared through pyrazine ligand. Magnetic unit cell size perpendicular to the sheet plane is twice the interplane distance, indicating an antiferromagnetic arrangement.

Analysis of Crystallographic Orientation on Textured Ca-doped (ZnO)mIn2O3 Ceramics by Electron Back Scattering Diffraction Pattern

Crystallographic orientation and phase identification on textured Ca-doped (ZnO)mIn2O3 (m=3 and 4, denoted as ZmIO) ceramics were investigated for better understanding and further improvement of the high-efficiency n-type thermoelectric oxide materials. Textured ceramics were prepared by the reactive-templated grain growth (RTGG) method, in which plate-like reactive seeds were exploited. A combination of electron backscatter diffraction pattern (EBSP) and energy dispersive X-ray spectrometry (EDS) techniques was utilized for analyzing the textured specimen parallel and perpendicular to the original sheet plane in detail. We revealed that in the specimen plate-like grains were aligned parallel to the sheet plane with the thickness direction parallel to the c-axis of each grain. Parallel aligned trigonal Z3IO domains with a 60° misorientation angle were observed in a single grain. Coexisting trigonal Z3IO and hexagonal Z4IO phases were also observed in a single grain. These axis-sharing crystallites must be formed by the in situ topotactic conversion from a common hexagonal template crystal.

A flexible approach for modelling flow in multi-component blade formers

A method has been developed for flexible modelling of multi-component twin-wire blade formers. Features such as suction devices, loadable blades, curved blades, and partial contact between the blades and the forming fabrics are easily incorporated. New results include a series of calculations demonstrating the non-trivial interaction between the pressure pulses when the blades are positioned successively closer together, the effects of suction on the pressure pulse generated by a blade applied to the opposing wire, and how blades of modest curvature do not necessarily stay in contact with the fabric along their full width and the implications of this on the pressure gradients in the machine direction. The behaviour of the fibre mats as they experience the first of the blade pulses (after having been formed over a roll) is then considered in detail. Typically, the thickness of the mats decreases during the pulse, which reduces the rate of deposition of new fibres onto the webs. The amount of fibres in the sheets therefore changes marginally. Nevertheless, the resistance to drainage presented by the fibre network is seen to increase significantly due to the low permeability in highly compressed layers of the mat. As a result of the pressure gradients in the machine direction, the shear stresses in the plane of the fibre sheets can attain several hundred Pascal next to the forming fabrics. Further, a model for sheared consolidation of flocculated suspensions is presented that extends the concept of a concentration dependent yield stress, previously employed in studies of uniaxial consolidation, to comprise flocculated phase shear strength. Rate-dependent viscous stresses are also incorporated. The theory is applied to the problem of combined compression and shearing of a strongly flocculated suspension contained between two plates, one being fixed and acting as a perfectly permeable filter, the other movable and acting as a piston by which the load is applied. Qualitatively, the evolution of the volume fraction of solids exhibits the same behaviour as during uniaxial consolidation without shear. Applying shear is however predicted to increase the rate of the drainage process, due to a reduced load bearing capacity of the flocculated phase, and correspondingly higher pore pressures.