Wedge-shaped Cell Research Articles

On the selection of Saffman–Taylor viscous fingers for divergent flow in a wedge

We study self-similar viscous fingering for the case of divergent flow within a wedge-shaped Hele-Shaw cell. Previous authors have conjectured the existence of a countably infinite number of selected solutions, each distinguished by a different value of the relative finger angle. Interestingly, the associated solution branches have been posited to merge and disappear in pairs as the surface tension decreases. For the first time, we demonstrate how the selection mechanism can be derived based on exponential asymptotics. Asymptotic predictions of the finger-to-wedge angle are additionally given for different sized wedges and surface-tension values. The merging of solution branches is explained; this feature is qualitatively different to the case of classic Saffman–Taylor viscous fingering in a parallel channel configuration. Moreover, because the asymptotic framework does not highly depend on specifics of the wedge geometry, the proposed theory for branch merging in our self-similar problem likely relates much more widely to tip-splitting instabilities in time-dependent flows in circular and other geometries, where the viscous fingers destabilise and divide in two.

Optical Analysis Method for Turbid Media Based on Wedge-Shaped Cells at Different Angles.

The wedge-shaped sample cell, by offering a comprehensive representation of scattering information in turbid media, significantly enhances the informational content conveyed by spectral images compared to flat sample cells. To further refine the accuracy of turbid medium component detection utilizing wedge-shaped sample cells, this work undertakes modeling and analysis of the influence of different wedge angles on detection precision. In this study, employing a 5° gradient in the incident angle of light, we investigate the impact of incident angles ranging from 10 to 45° on the turbid medium component analysis. Validation experiments are performed by utilizing solutions of Indian ink and fat emulsion at varying ratios. Experimental findings demonstrate that under identical experimental conditions, the wedge-shaped sample cell model at an incident angle of 35° yields optimal analysis results. Utilizing partial least-squares regression (PLSR) for the corresponding optical parameters, the highest value of Rp reached 0.980, with an RMSEP of 0.002. When compared to the model with a 30° incident angle, Rp increased by 0.033, and RMSEP decreased by 0.008. In comparison to the flat sample cell model, Rp increased by 0.041, and RMSEP decreased by 0.004. This study, through continuous variation of wedge angles and PLSR modeling and prediction, further enhances the accuracy of turbid medium component detection, laying an experimental foundation for subsequent analysis of turbid medium components based on wedge-shaped sample cells.

Parafuscosporella xishuangbannaensis sp. nov. (Fuscosporellales, Sordariomycetes) from submerged wood in China

In this study, a novel lignicolous freshwater species, Parafuscosporella xishuangbannaensis, which was collected from Manfeilong reservoir in Xishuangbanna, Yunnan Province, China, is described and illustrated. The new species was established based on morphological characteristics and multi-locus phylogenetic analyses of combined LSU, SSU, ITS and rpb2 sequence data. Parafuscosporella xishuangbannaensis is characterized by reduced conidiophores, holoblastic, monoblastic, integrated, terminal, hyaline, cylindrical conidiogenous cells, and acrogenous, obovoid to subglobose, brown to dark brown conidia with a septum near the base and a paler, wedge-shaped basal cell. Parafuscosporella xishuangbannaensis differs from its phylogenetically close sister taxon P. pyriformis in lacking cylindrical or moniliform conidiophores.

Modular All-Metal Ultrawideband Cylindrical Array for Multifunction Operation

Legacy cylindrical phased array systems are constrained to narrowband operation due to antenna element limitations amid a growing need to support advanced multifunctional platform requirements. In this article, a notch-based all-metal ultrawideband (UWB) antenna element suitable for cylindrical arrays is introduced. The proposed element is designed to operate over 2.75–10 GHz while being highly amenable to a cylindrical architecture via modularized assembly of compact scalable column facets. The primary enabling technical innovations are: 1) a new shunt-loaded stepped-impedance (SI) gap design scheme to improve low-frequency performance without increasing profile and 2) the design of a tongue-and-groove azimuthal crosswall that precisely conforms to the wedge-shaped unit cell for simple yet robust cylinder assembly. For a proof-of-concept demonstration, a 120° sector array is built having a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12^{\prime \prime }$ </tex-math></inline-formula> outer diameter and 21 columns—each comprising eight single-polarized elements (168 total feed points). Measurements are presented for active phase-mode impedance and embedded element patterns of a central element, demonstrating good agreement with full-wave simulations.

Advances in model-independent restoration of the liquid crystal surface anchoring potential

We extend further the theoretical and experimental studies of the actual surface anchoring potential restoration by polarization microscope technique in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean-Cano Wedge). To realize the theoretically predicted options of observation of large director deviation angles from the easy axes the experimental studies of director distribution in Grandjean-Cano zones were performed for differing easy axes orientations at the wedge surfaces. A weak surface anchoring at one wedge surface was obtained by a photo-alignment technique. A strong surface anchoring at the second wedge surface was also obtained by a photo-alignment technique with an enlarged irradiation dose. There were observed walls with weak jumps of the director orientation between first neighboring Grandjean-Cano zones. Some experimentally obtained polarization microscope images demonstrate partially unwound director structures in zero Grandjean-Cano zone. To ensure optimal parameters of the further experiments on the actual surface anchoring potential restoration theoretical calculations of the director distribution in individual Grandjean-Cano zones were performed for various model surface anchoring potentials. It was found that especially promising for description of the experimentally found director distribution is the D-potential. As a result of the present studies the angular range of a model-independent actual azimuthal surface anchoring potential restoration was enlarge (up to π/3) and the ways of an actual surface anchoring potential restoration in a whole angular range of its determination are discussed.

Capillarity and active cell movement at mesendoderm translocation in the Xenopus gastrula.

During Xenopus gastrulation, leading edge mesendoderm (LEM) advances animally as a wedge-shaped cell mass over the vegetally moving blastocoel roof (BCR). We show that close contact across the BCR-LEM interface correlates with attenuated net advance of the LEM, which is pulled forward by tip cells while the remaining LEM frequently separates from the BCR. Nevertheless, lamellipodia persist on the detached LEM surface. They attach to adjacent LEM cells and depend on PDGF-A, cell-surface fibronectin and cadherin. We argue that active cell motility on the LEM surface prevents adverse capillary effects in the liquid LEM tissue as it moves by being pulled. It counters tissue surface-tension effects with oriented cell movement and bulges the LEM surface out to keep it close to the curved BCR without attaching to it. Proximity to the BCR is necessary, in turn, for the maintenance and orientation of lamellipodia that permit mass cell movement with minimal substratum contact. Together with a similar process in epithelial invagination, vertical telescoping, the cell movement at the LEM surface defines a novel type of cell rearrangement: vertical shearing.

Structural transformations of growing thin colloidal crystals in confined space via convective assembly

The structural evolution of growing thin colloidal crystals in a confined space via the convective assembly technique has been investigated. The thin colloidal crystals were grown in a wedge-shaped cell, where the height of the cell increased with increased crystal growth. Triangle and square patterns, denoted as [111]- and [100]-oriented grains, respectively, were formed alternately as the height of the cell increased. The structural transformation was associated with an increase in the number of layers when the n-layer [100]-oriented grains changed to n + 1-layer [111]-oriented grains. Between the different grain structures, a stripe pattern was observed, which was a transitional region, where particle configuration gradually changed. The structural transformation occurred through the continuous change of particle configuration rather than through the abrupt formation of a grain boundary. The interval of the strip pattern lengthened as the number of layers increased, which is understood to be the structure with the highest packing density. The findings of the study give a better insight into convective assembly in a confined space, and also contribute to the greater structural control of colloidal crystals, useful for a number of applications.

Dual-camera design for hyperspectral and panchromatic imaging, using a wedge shaped liquid crystal as a spectral multiplexer

In this paper, we present a new hyperspectral compact camera which is designed to have high spatial and spectral resolutions, to be vibrations tolerant, and to achieve state-of-the-art high optical throughput values compared to existing nanosatellite hyperspectral imaging payloads with space heritage. These properties make it perfect for airborne and spaceborne remote sensing tasks. The camera has both hyperspectral and panchromatic imaging capabilities, achieved by employing a wedge-shaped liquid crystal cell together with computational image processing. The hyperspectral images are acquired through passive along-track spatial scanning when no voltage is applied to the cell, and the panchromatic images are quickly acquired in a single snapshot at a high signal-to-noise ratio when the cell is voltage driven.

Optical Properties of Liquid Crystalline Alkoxy Benzoic Acids with Dispersed Citrate-Capped Gold Nanoparticles

Abstract Citrate-capped gold nanoparticles (Gnps) have multiple applications in all optical devices and influence the properties of birefringence in liquid crystalline (LC) molecules. In the present paper, systematic studies have been carried out on LC compounds p-n-undecyloxy benzoic acid (11oba) and p-n-dodecyloxy benzoic acid (12oba) with dispersed citrate-capped Gnps in different low molar concentrations. The phase transition temperatures of the LC nanocomposites obtained from polarizing thermal microscopy (POM), differential scanning calorimetry (DSC) and modified spectrometry are found to be reduced with the increase in concentration of dispersed citrate-capped Gnps. The information was obtained from textural data utilizing the simple technique gradient measurement of standard deviation (GMSD) using the MATLAB tool, which is analogous to DSC. Further, the existence of citrate-capped Gnps in 11oba and 12oba was determined by spectroscopic techniques like ultraviolet-visible spectrometry and scanning electron microscopy. The birefringence measurements were carried out at different wavelengths (460, 500, 570 and 635 nm) using a wedge-shaped cell with a modified spectrometer. The birefringence (δ n) increases with increase in weight concentration of citrate-capped Gnps in the nematic thermal range. Further, the order parameter S values obtained from the Kuczynski internal field model, the Vuks model, the Haller extrapolation model and the effective geometry parameter methods are in good agreement. It is found that the order parameter S increases with increase in dispersion of concentration of citrate-capped Gnps. This is due to strong Van der Waal’s interaction between the LC molecules and citrate-capped Gnps, which increases the alignment of the LC molecules.

Studies of the liquid crystal surface anchoring potential using Grandjean–Cano wedge

ABSTRACTWe extend further the theoretical and experimental studies of the actual surface anchoring potential restoration by polarisation microscope technique and using micro-images in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean–Cano (GC) Wedge). To realize the theoretically predicted options of observation of large director deviation angles from the easy axes, the experimental studies of director distribution in GC zones were performed for differing easy axes orientations at the wedge surfaces in white light. A weak surface anchoring at one wedge surface was obtained by a photo-alignment technique. A strong surface anchoring at the second wedge surface was obtained by a rubbing. There were observed for the first time jump-less walls (without jumps of the director orientation) between neighbouring GC zones and jumps in colour in the Newton’s rings (lines) at the positions of the walls between GC zones. Qualitative explanations of the both phenomena are presented and an expression for the jump in colour value in the Newton’s rings (lines) at the positions of the walls between GC zones is presented. Some experimentally found by the polarisation microscope and by the microphoto technique images demonstrate jump-less walls between the first GC zones. To ensure optimal parameters of the further experiments on the actual surface anchoring potential restoration, theoretical calculations of the director distribution in individual GC zones were performed for various model surface anchoring potentials. It was found that especially promising for description of the experimentally found director distribution looks the modified D-potential. As a result of the present studies, the ways to enlarge (compared to the previous studies) angular range of the actual surface anchoring potential restoration were proposed.

2D Optical Gratings Based on Hexagonal Voids on Transparent Elastomeric Substrate.

A chromatic vectorial strain sensor constituted by hexagonal voids on transparent elastomeric substrate has been successfully fabricated via soft colloidal lithography. Initially a highly ordered 1.6 microns polystyrene spheres monolayer colloidal crystal has been realized by wedge-shaped cell method and used as a suitable mold to replicate the periodic structure on a polydimethylsiloxane sheet. The replicated 2D array is characterized by high periodicity and regularity over a large area, as evidenced by morphological and optical properties obtained by means of SEM, absorption and reflectance spectroscopy. In particular, the optical features of the nanostructured elastomer have been investigated in respect to uniaxial deformation up to 10% of its initial length, demonstrating a linear, tunable and reversible response, with a sensitivity of 4.5 ± 0.1 nm/%. Finally, it has been demonstrated that the specific geometrical configuration allows determining simultaneously the vectorial strain-stress information in the x and y directions.

On the way of reconstruction of the liquid crystal surface anchoring potential

We extend further the theoretical and experimental studies of the actual surface anchoring potential reconstruction by polarization microscope technique in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean-Cano Wedge) and present the material for the sake of the reader convenience with a short coherent survey of our previous results. To realize the theoretically predicted options of observation of large director deviation angles from the easy axes φ at a wedge surfaces (up to π/2) the experimental studies of director distribution in Grandjean-Cano zones were performed. A weak surface anchoring at one wedge surface was obtained by photo-alignment technique. A strong surface anchoring at the second wedge surface was obtained by rubbing. The measurements were performed using polarizing microscope. The experimentally found director distributions in Grandjean-Cano zones were compared with theoretical ones calculated for various model surface anchoring potentials. As a result of the present studies the ways to enlarge (compared to the previous studies) angular range of the actual surface anchoring potential restoration were proposed and it was found that the experimentally found surface potential is nicely fitted by a new model surface anchoring potential, the so called model D-potential WD(φ)~φ2.

Mechanics of plio-quaternary faulting around the Karliova triple junction: implications for the deformation of Eastern part of the Anatolian Scholle

ABSTRACTThe intersection of the Eurasian and Arabian plates and the smaller Anatolian Scholle created the Karlıova Triple Junction (KTJ) in eastern Turkey. In this study, we present analogue model experiments for this region and compare the results with our field observations and data from remote sensing imagery. Our comparison suggests that the sense of slip along curvilinear faults at the west of the KTJ changes along strike moving away from the principal displacement zones, from strike-slip to oblique normal and then to pure normal slip. Although, the active Prandtl cell model has been proposed to explain the overall regional fault pattern at eastern part of the Anatolian Scholle, the map view orientation of the secondary faults within the Karlıova wedge and performed analogue modelling results suggest that the passive wedge-shaped Prandtl cell model with a normal dip-slip component along slip lines is more appropriate in order to explain not only deformation pattern around the KTJ but also internal deformation of eastern part of the Anatolia. Moreover, these faults accumulate the significant amount of deformation that causes to the irregular earthquake behavior and the relatively lower geologic slip-rates along the main fault branch of boundary faults around the KTJ.Abbreviations: Strike-slip; Karlıova Triple Junction (KTJ); continental deformation; North Anatolian Fault Zone (NAFZ); East Anatolian Fault Zone (EAFZ);Varto Fault Zone (VFZ)

Subwavelength coupling strengthened optical amplification in nematic liquid crystal cells

We observed strikingly different first reflection dynamics of two counter-propagating laser beams passing through a wedge-shaped C60-doped liquid crystal cell sandwiched between two ZnSe-coated ITO glass plates without applied electric field, suggesting a strong subwavelength energy coupling between light beams. Exponential gain coefficient as high as 10 574 cm−1 was obtained from the 1.1 μm-thick portion of the cell under applied voltage U0 = 3.0 V, consisting with the subwavelength coupling picture. Surface plasmon polariton (SPP) supporting layer is identified by considering dipolar properties of liquid crystal molecules that are well aligned. The specific features in energy coupling dynamics and 2D diffraction patterns perceived suggest that SPP mediated coupling is responsible for all the findings.

Response of Soft Continuous Structures and Topological Defects to a Temperature Gradient.

Thermophoresis, which is mass transport induced by a temperature gradient, has recently attracted considerable attention as a new way to transport materials. So far the study has been focused on the transport of discrete structures such as colloidal particles, proteins, and polymers in solutions. However, the response of soft continuous structures such as membranes and gels to a temperature gradient has been largely unexplored. Here we study the behavior of a lamellar phase made of stacked surfactant bilayer membranes under a temperature gradient. We find the migration of membranes towards a low-temperature region, causing the increase in the degree of membrane undulation fluctuations towards that direction. This is contrary to our intuition that the fluctuations are weaker at a lower temperature. We show that this can be explained by temperature-gradient-induced migration of membranes under the topological constraint coming from the connectivity of each membrane. We also reveal that the pattern of an edge dislocation array formed in a wedge-shaped cell can be controlled by a temperature gradient. These findings suggest that application of a temperature gradient provides a novel way to control the organization of soft continuous structures such as membranes, gels, and foams, in a manner essentially different from the other types of fields, and to manipulate topological defects.

Director distribution in Grandjean-Cano wedge and restoration of surface anchoring potential

ABSTRACTWe extend further the performed early both theoretically and experimentally studies of the director distribution of a chiral nematic liquid crystal placed in a wedge-shaped cell with weak surface anchoring aimed to restore the actual surface anchoring potential. As a result of the present and previous experimental studies [1–3] it was found that the experimentally found surface potential (obtained from the measured potential derivative) is very nice fitted by a new model surface anchoring potential, the so called model D-potential (Ws(ϕ) = (W/2)ϕ2), in a wide angular range −π/4< ϕ<π/4.

Confinement Induced Plastic Crystal-to-Crystal Transitions in Rodlike Particles with Long-Ranged Repulsion.

Colloidal particles in geometrical confinement display a complex variety of packing structures different from their three-dimensional (3D) bulk counterpart. Here, we confined charged rodlike colloids with long-ranged repulsions to a thin wedge-shaped cell and show, by quantitative 3D confocal microscopy, that not only their positional but also their orientational order depends sensitively upon the slit width. Synchronized with transitions in lattice symmetry and number of layers confinement induces plastic crystal-to-crystal transitions. A model analysis suggests that this complex sequence of more or less rotationally ordered states originates from the subtle competition between the electrostatic repulsion of a rod with the wall and with its neighbors.

Fabrication of 3D inverse opal structured photonic crystal by using wedge-shaped cell method

A simple and low cost fabrication method for three dimensional inverse opal structured photonic crystal by using wedge-shaped cell (WSC) was suggested and demonstrated. The key idea of our method in the infiltration process was that the opal template was attached on the upper plate of the WSC, by which we could prevent the surface sedimentation of suspension. The micro shape and the transmission spectrum of the fabricated inverse opal structured photonic crystal were measured and discussed.

29 Direct observation of living laryngeal carcinoma cells during invasion of healthy cell formation

In the presentation a time lapse movie is shown, allowing direct observation of living laryngeal carcinoma cells during invasion of healthy cell formation. After cloning of laryngeal carcinoma cells from tumor fragments obtained during surgery, the behavior of pure tumor cells was investigated under the inverted microscope. In tissue culture flasks, separately grown tumor cell layers and fibroblast layers were cocultured to visualize the invasion of malignant cells into healthy tissue. Using a time-lapse camera, the cells were recorded. The tumor cells often penetrated the healthy cell formation in a wedge-shaped cell formation. Near the tumor front, an elevated cell motility was found accompanied by continuous changes in the cell shape. Intercellular gaps were broader in the front line than in the more posterior parts of the tumor cell formation. The profound motility of the carcinoma cell enabled selected cells to leave the tumor cell formation completely and to migrate as single cells through healthy tissue. Eventually, some of the single tumor cells migrating through the fibroblast layer moved back to the tumor cell formation. Thus they left healthy appearing tissue behind, which was earlier infiltrated by a malignant cell.

Epithelial morphogenesis: the mouse eye as a model system.

Morphogenesis is the developmental process by which tissues and organs acquire the shape that is critical to their function. Here, we review recent advances in our understanding of the mechanisms that drive morphogenesis in the developing eye. These investigations have shown that regulation of the actin cytoskeleton is central to shaping the presumptive lens and retinal epithelia that are the major components of the eye. Regulation of the actin cytoskeleton is mediated by Rho family GTPases, by signaling pathways and indirectly, by transcription factors that govern the expression of critical genes. Changes in the actin cytoskeleton can shape cells through the generation of filopodia (that, in the eye, connect adjacent epithelia) or through apical constriction, a process that produces a wedge-shaped cell. We have also learned that one tissue can influence the shape of an adjacent one, probably by direct force transmission, in a process we term inductive morphogenesis. Though these mechanisms of morphogenesis have been identified using the eye as a model system, they are likely to apply broadly where epithelia influence the shape of organs during development.