Cone Behavior Research Articles

Global and Local Shielding/Deshielding Variation in C60 and C70 Fullerenes Upon Reduction: Evaluation of Aromaticity, 13C-NMR and Anisotropy Patterns.

Fullerenes are statically pleasant species featuring symmetric cages, which can be modified upon reduction. Here, we theoretically account for the variation of 13C-NMR patterns in C60 and C70 upon six-fold reduction and the overall variation of the enabled shielding/deshielding regions induced by π and σ electrons according to different orientations of the external field and the related anisotropy. Our results show a significant modification of the chemical shift given by the main variation of the σ33 (or δ33) shielding component under the principal axis system (PAS) of the chemical shift anisotropy (CSA) at the representative carbon nucleus. For C60 6- a shielding cone property is enabled from any orientation, accounting for a significant spherical aromatic character. In contrast, in C70 6-, a shielding cone is reserved only for an axial-oriented field, with a deshielding cone behavior obtained from the complementary equatorial orientations. The overall anisotropy shows an inner isotropic region for C60 and C60 6-, with a continuous anisotropic outer contour for the latter. In contrast, C70 and C70 6- both show larger anisotropies, given the lesser spherical shape in addition to the modified π-surface. Such information is useful for further rationalizing the implementation of magnetic anisotropic molecular devices into fullerene-based materials.

Rho GTPase Signaling: A Molecular Switchboard for Regulating the Actin Cytoskeleton in Axon Guidance.

Axon pathfinding is a highly dynamic process regulated by the interactions between cell-surface guidance receptors and guidance cues present in the extracellular environment. During development, precise axon pathfinding is crucial for the formation of functional neural circuits. The spatiotemporal expression of axon guidance receptors helps the navigating axon make correct decisions in a complex environment comprising both attractive and repulsive guidance cues. Axon guidance receptors initiate distinct signaling cascades that eventually influence the cytoskeleton at the growing tip of an axon, called the growth cone. The actin cytoskeleton is the primary target of these guidance signals and plays a key role in growth cone motility, exploration, and behavior. Of the many regulatory molecules that modulate the actin cytoskeleton in response to distinct guidance signals, Rho GTPases play central roles. Rho GTPases are molecular switchboards; their ON (GTP-bound) and OFF (GDP-bound) switches are controlled by their interactions with proteins that regulate the exchange of GDP for GTP or with the proteins that promote GTP hydrolysis. Various upstream signals, including axon guidance signals, regulate the activity of these Rho GTPase switch regulators. As cycling molecular switches, Rho GTPases interact with and control the activities of downstream effectors, which directly influence actin reorganization in a context-dependent manner. A deeper exploration of the spatiotemporal dynamics of Rho GTPase signaling and the molecular basis of their involvement in regulating growth cone actin cytoskeleton can unlock promising therapeutic strategies for neurodevelopmental disorders linked to dysregulated Rho GTPase signaling. This review not only provides a comprehensive overview of the field but also highlights recent discoveries that have considerably advanced our understanding of the complex regulatory roles of Rho GTPases in modulating actin cytoskeleton arrangement at the growth cone during axon guidance.

The Shock Cone Instabilities and Quasi-Periodic Oscillations around the Hartle–Thorne Black Hole

To explain the observed X-ray data in a black hole–accreting matter system and understand the physical mechanisms behind QPOs, we have numerically modeled the dynamical and oscillation properties of the shock cone formed around both slowly and rapidly rotating Hartle–Thorne black holes, resulting from the mechanism of Bondi–Hoyle–Lyttleton (BHL). According to the numerical simulations, an increase in the quadrupole parameter leads to a decrease in the shock cone opening angle around the black hole. A larger quadrupole parameter results in more matter falling into the black hole within the cone. The combination of the quadrupole parameter and black hole rotation causes the matter inside the cone to exhibit chaotic motion. These dynamical changes and chaotic behavior of the shock cones excite the fundamental oscillation modes. Moreover, new frequencies have been formed due to the nonlinear coupling of the fundamental modes. Conversely, we have numerically studied the behavior of cones formed around rapidly rotating Hartle–Thorne black holes and found differences and similarities to those obtained from slowly rotating cases. Finally, comparing the outcomes obtained fromHartle–Thorne gravity with the results fromKerr and Einstein–Gauss–Bonnet (EGB) gravities reveals the impact of the quadrupole parameter on the shock cone and QPOs.

Description of the feeding rhythm of cone snails in French Polynesia

ABSTRACT The Conidae is a family of marine gastropod molluscs that includes carnivorous and venomous species. The venom they produce is remarkably diverse and has recently drawn much interest from a pharmacological perspective. To respond to this growing interest, a better understanding of the ecology and biology of the species is required. Only a few studies have examined the feeding behaviour and the trophic specialization of these species in detail. In this study, we investigated diet through hunger and satiety experiments of eight species of cones that occur in French Polynesia and that present different feeding modes (piscivorous, molluscivorous or vermivorous). Monitoring behaviour of cones during fasting periods demonstrated a correlation between increased hunger and nocturnal cone activity, mainly for piscivorous species, while the molluscivores did not show this correlation. In the study on satiety, we defined an average frequency of feeding for cone species that were fed prey ad libitum. Finally, this study provided indications that will help to define an equilibrium feeding frequency in further studies involving the cultivation of cones.

Theoretical Research on the Movement Law of Water Cone Behavior in Heavy Oil Reservoirs with Bottom Water

Aiming at the unclear reorganization of a water cone shape, its sweep range, and water saturation distribution of horizontal well in heavy oil reservoirs with bottom water, a mathematical method was proposed in this paper to establish a microtube model and physical model with the starting pressure gradient (SPG) to study the water cone behavior. The results showed that the different water-cut stage, mobility, depth from oil-water interface (DOWI), and liquid production strength have an obvious impact on water cone behavior. Moreover, we found an interesting phenomenon on an extreme point in water saturation derivation among water cone, which could be a reason for further adjustment. Finally, we confirmed the calculation results with physical simulation, which is highly consistent. The new method proposed in this paper was significant in the water cone behavior study and has a broad application in heavy oil reservoir development in the future.

Loss of Neuropilin2a/b or Sema3fa alters olfactory sensory axon dynamics and protoglomerular targeting

BackgroundOlfactory Sensory Neuron (OSN) axons project from the zebrafish olfactory epithelium to reproducible intermediate target locations in the olfactory bulb called protoglomeruli at early stages in development. Two classes of OSNs expressing either OMP or TRPC2 exclusively target distinct, complementary protoglomeruli. Using RNAseq, we identified axon guidance receptors nrp2a and nrp2b, and their ligand sema3fa, as potential guidance factors that are differentially expressed between these two classes of OSNs.MethodsTo investigate their role in OSN axon guidance, we assessed the protoglomerular targeting fidelity of OSNs labeled by OMP:RFP and TRPC2:Venus transgenes in nrp2a, nrp2b, or sema3fa mutants. We used double mutant and genetic interaction experiments to interrogate the relationship between the three genes. We used live time-lapse imaging to compare the dynamic behaviors of OSN growth cones during protoglomerular targeting in heterozygous and mutant larvae.ResultsThe fidelity of protoglomerular targeting of TRPC2-class OSNs is degraded in nrp2a, nrp2b, or sema3fa mutants, as axons misproject into OMP-specific protoglomeruli and other ectopic locations in the bulb. These misprojections are further enhanced in nrp2a;nrp2b double mutants suggesting that nrp2s work at least partially in parallel in the same guidance process. Results from genetic interaction experiments are consistent with sema3fa acting in the same biological pathway as both nrp2a and nrp2b. Live time-lapse imaging was used to examine the dynamic behavior of TRPC2-class growth cones in nrp2a mutants compared to heterozygous siblings. Some TRPC2-class growth cones ectopically enter the dorsal-medial region of the bulb in both groups, but in fully mutant embryos, they are less likely to correct the error through retraction. The same result was observed when TRPC2-class growth cone behavior was compared between sema3fa heterozygous and sema3fa mutant larvae.ConclusionsOur results suggest that nrp2a and nrp2b expressed in TRPC2-class OSNs help prevent their mixing with axon projections in OMP-specific protoglomeruli, and further, that sema3fa helps to exclude TRPC2-class axons by repulsion from the dorsal-medial bulb.

Hypervelocity Spherically-Blunted Cone Flows in Mars Entry Ground Testing

Bow-shock standoff distances over sphere and spherically-blunted cone geometries were examined through experiments in two facilities capable of high-stagnation enthalpy hypersonic flows simulating Mars planetary entry conditions. High-speed and high-resolution schlieren images were obtained in the California Institute of Technology T5 reflected shock tunnel and the Hypervelocity Expansion Tube to examine facility independence of the measurements. Accompanying reacting Navier–Stokes simulations were carried out. A recently developed unified model for sphere and sphere–cone behavior was first verified for high-stagnation enthalpy flows through simulations with thermal and chemical nonequilibrium. Shock standoff distance measurements in both facilities were found to be in good agreement with model predictions. The need to account for the divergence of the streamlines in conical nozzles was highlighted and an existing model extended to account for changes in shock curvature between parallel and conical flows. The contributions of vibrational and chemical nonequilibrium to the stagnation-line density profile were quantified using the simulation results comparing three chemical kinetic models.

Cone photoreceptor reflectance variation in the northern tree shrew and thirteen-lined ground squirrel.

In vivo images of human cone photoreceptors have been shown to vary in their reflectance both spatially and temporally. While it is generally accepted that the unique anatomy and physiology of the photoreceptors themselves drives this behavior, the exact mechanisms have not been fully elucidated as most studies on these phenomena have been limited to the human retina. Unlike humans, animal models offer the ability to experimentally manipulate the retina and perform direct in vivo and ex vivo comparisons. The thirteen-lined ground squirrel and northern tree shrew are two emerging animal models being used in vision research. Both models feature cone-dominant retinas, overcoming a key limitation of traditional rodent models. Additionally, each possesses unique but well-documented anatomical differences in cone structure compared to human cones, which can be leveraged to further constrain theoretical models of light propagation within photoreceptors. Here we sought to characterize the spatial and temporal reflectance behavior of cones in these species. Adaptive optics scanning light ophthalmoscopy (AOSLO) was used to non-invasively image the photoreceptors of both species at 5 to 10 min intervals over the span of 18 to 25 min. The reflectance of individual cone photoreceptors was measured over time, and images at individual time points were used to assess the variability of cone reflectance across the cone mosaic. Variability in spatial and temporal photoreceptor reflectance was observed in both species, with similar behavior to that seen in human AOSLO images. Despite the unique cone structure in these animals, these data suggest a common origin of photoreceptor reflectance behavior across species. Such data may help constrain models of the cellular origins of photoreceptor reflectance signals. These animal models provide an experimental platform to further explore the morphological origins of light capture and propagation.

Axon guidance at the spinal cord midline-A live imaging perspective.

During neural circuit formation, axons navigate several choice points to reach their final target. At each one of these intermediate targets, growth cones need to switch responsiveness from attraction to repulsion in order to move on. Molecular mechanisms that allow for the precise timing of surface expression of a new set of receptors that support the switch in responsiveness are difficult to study in vivo. Mostly, mechanisms are inferred from the observation of snapshots of many different growth cones analyzed in different preparations of tissue harvested at distinct time points. However, to really understand the behavior of growth cones at choice points, a single growth cone should be followed arriving at and leaving the intermediate target. Existing ex vivo preparations, like cultures of an “open‐book” preparation of the spinal cord have been successfully used to study floor plate entry and exit, but artifacts prevent the analysis of growth cone behavior at the floor plate exit site. Here, we describe a novel spinal cord preparation that allows for live imaging of individual axons during navigation in their intact environment. When comparing growth cone behavior in our ex vivo system with snapshots from in vivo navigation, we do not see any differences. The possibility to observe the dynamics of single growth cones navigating their intermediate target allows for measuring growth speed, changes in morphology, or aberrant behavior, like stalling and wrong turning. Moreover, observation of the intermediate target—the floor plate—revealed its active participation and interaction with commissural axons during midline crossing.

Folding pattern design and deformation behavior of origami based conical structures

In recent times, origami-inspired deployable structures have received significant interest from the research community as a major area of research in the fields of science and technology. This paper deals with the geometry and the deformation behavior of deployable cones based on the four-fold line origami concept. First, a novel geometric design algorithm is presented to develop axially foldable conical structures based on generalized Miura-ori pattern, which is then utilized to investigate the influence of four design parameters on folding geometry. The foldability of thus obtained origami patterns is verified with the help of physical models. The geometric incompatibilities during the deployment are highlighted using a simple experiment, showing the unfolding sequence of a paper model. The deformations due to incompatibilities are analyzed by adopting the concept of pin-jointed truss modeling of the origami structures. A mathematical model of the deployment problem is formulated to capture the deployment deformations of the structure, on the basis of which an algorithm for deformation analyses is developed. One example is considered to characterize the deformation behavior of the conical origami structures as the design parameters of the folding pattern are varied. The analytical findings demonstrate that the fold line strains of the origami cone are very sensitive to the changes in three design parameters, number of origami units (m), fold angle (α0), and angle θ2; except the length ratio (lr0). The variation in design parameters may induce bi-stability in the deployment path of the conical structure. The findings of the analytical investigation are verified numerically, demonstrating that the strain responses obtained from the numerical analyses are completely consistent with the analytical results.

Undrained shear strength assessment using piezocone and shear wave measurements

In this paper, a new approach is proposed to determine the undrained shear strength of intact clays using the undrained rigidity index inferred from piezocones and shear wave velocity measurements based on the theory of spherical cavity expansion. The derived cone factors are further simplified for young, uncemented (non-structured) clays to be solely expressed in terms of the cone behaviour type index. Moreover, an empirical expression is suggested to relate the undrained shear strength of fissured clays to the cone and shear wave measurements. The proposed approach is used to assess the values of undrained shear strengths in several well-reported test sites. The estimated strengths are found to be in a good agreement with the related field and laboratory measurements in intact clays, whereas in fissured clays, the estimated undrained strengths are shown to match less favourably with the laboratory measurements. This may be attributed to the strong dependence of the undrained shear strength of such clays on the site-specific orientations and properties of the prevailing fissures.

Collapse of Conical Shells Having Single Dimple Imperfection Under Axial Compression

Abstract This paper aims to provide experimental results into the buckling behavior of cones having single dimple imperfection subjected to axial compression. Results of eight laboratory scaled conical test models and their accompanying numerical data are presented. Cones were manufactured in pairs with single dimple imperfection amplitude, A, of 0.0, 0.56, 1.12, and 1.68. Experimental results reveal good repeatability of collapse load. The errors between each pair were found to be 3%, 7%, 11%, and 1%. Furthermore, the comparison between test data and the numerically predicted collapse load was seen to be good. The ratio of collapse test load to finite element predicted values are [(0.96, 0.99), (1.04, 1.10), (1.06, 0.94), (1.0, 1.01)]. The buckling of axially compressed conical shells using the single dimple imperfection type appears to be strongly influenced by: (i) the dimple/imperfection amplitude, (ii) the cone geometric parameter, i.e., radius-to-thickness ratio and cone angle, and (iii) the location of the dimple.

Cover Feature: Interplay Between Planar and Spherical Aromaticity: Shielding Cone Behavior in Dual Planar‐Planar, Planar‐Spherical and Spherical‐Spherical Aromatics (ChemPhysChem 13/2020)

Cover Feature: Interplay Between Planar and Spherical Aromaticity: Shielding Cone Behavior in Dual Planar‐Planar, Planar‐Spherical and Spherical‐Spherical Aromatics (ChemPhysChem 13/2020)

Research on Water Cone Behavior in a Heavy Oil Reservoir with Bottom Water Considering the Starting Pressure Gradient.

Aiming at the unclear reorganization of the water cone shape and its flooding scope for a horizontal well in a heavy oil reservoir with bottom water, a new method was proposed in this paper to establish a numerical model with the starting pressure gradient (SPG) by commercial software to study water cone behavior. The results show that there exists SPG in heavy oil reservoirs ranging from 10–4 to 10–3 magnitude with mobility under 30 μm2/mPa·s. With a mobility of 33 μm2/mPa·s, the water cone and flooding scope from the model with SPG is 120 m shorter than that without SPG. Upon increasing the mobility from 11 to 90 μm2/mPa·s, the flooding scope of the model with SPG changes from 125 to 315 m, showing a power exponential form. The new method proposed in this paper was significant for the water cone behavior study and has broad applications in heavy oil reservoir development in the future.

Interplay Between Planar and Spherical Aromaticity: Shielding Cone Behavior in Dual Planar-Planar, Planar-Spherical and Spherical-Spherical Aromatics.

The shielding cone concept is one of the most characteristic aspects of planar aromatic species. Herein, we explored how two neighbor aromatic moieties behave as dual planar-planar, planar-spherical, and spherical-spherical species given by biphenyl, [PhCB11 H11 ]- , and [CB11 H11 ]2 2- , respectively. Our results show two separate aromatic regimes given by Clar's sextet and spherical aromatic states, with independent shielding cones sharing shielding regions of moderate strength, which can be extended for networks involving multiple independent aromatic states.

Fall cone behavior of non-plastic silts and undrained shear strength from DSS tests

Fall cone penetration behaviour of clays had been investigated for years, however, very little is known about the fall cone penetration behaviour of silts, especially low to non-plastic ones. Extensive fall cone tests were done on three different non-plastic silts over a broad penetration range. The results were compared with the behaviour of various soils with low and high plasticity. It was observed that the fall cone penetration water content relationship is typically non-linear for most plastic soils. However, it surprisingly becomes linear at the extreme sides of plasticity. More explicitly, the change of penetration depth with water content of non-plastic silts and bentonites are shown to be expressed with the same linear equation with different coefficients. Next, undrained shear strengths of silts were determined from direct simple shear tests performed under at least three vertical consolidation stresses. The simple power relationship between water content and undrained shear strength, proposed for remoulded clays in the literature, is observed to work very well for reconstituted non-plastic silts as well. Finally, undrained shear strengths of silts were predicted based on their liquid limits obtained from fall cone tests by modifying a relationship in the literature, which was developed mainly on clays.

Nestin Selectively Facilitates the Phosphorylation of the Lissencephaly-Linked Protein Doublecortin (DCX) by cdk5/p35 to Regulate Growth Cone Morphology and Sema3a Sensitivity in Developing Neurons.

Nestin, an intermediate filament protein widely used as a marker of neural progenitors, was recently found to be expressed transiently in developing cortical neurons in culture and in developing mouse cortex. In young cortical cultures, nestin regulates axonal growth cone morphology. In addition, nestin, which is known to bind the neuronal cdk5/p35 kinase, affects responses to axon guidance cues upstream of cdk5, specifically, to Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, and changes in microtubules and actin filaments are well studied. In contrast, the roles of intermediate filament proteins in this process are poorly understood, even in cultured neurons. Here, we investigate the molecular mechanism by which nestin affects growth cone morphology and Sema3a sensitivity. We find that nestin selectively facilitates the phosphorylation of the lissencephaly-linked protein doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected by nestin. We uncover that this substrate selectivity is based on the ability of nestin to interact with DCX, but not with other cdk5 substrates. Nestin thus creates a selective scaffold for DCX with activated cdk5/p35. Last, we use cortical cultures derived from Dcx KO mice to show that the effects of nestin on growth cone morphology and on Sema3a sensitivity are DCX-dependent, thus suggesting a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating the intracellular kinase signaling environment in developing neurons. The sex of animal subjects is unknown.SIGNIFICANCE STATEMENT Nestin, an intermediate filament protein highly expressed in neural progenitors, was recently identified in developing neurons where it regulates growth cone morphology and responsiveness to the guidance cue Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, but the roles of intermediate filaments in this process are poorly understood. We now report that nestin selectively facilitates phosphorylation of the lissencephaly-linked doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected. This substrate selectivity is based on preferential scaffolding of DCX, cdk5, and p35 by nestin. Additionally, we demonstrate a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating intracellular kinase signaling in developing neurons.

Unique magnetic shielding and bonding in Pnicogen nortricyclane Zintl clusters

Abstract Using first principle calculations, in-depth bonding and aromaticity pattern of bare anionic nortricyclane, E73− (E = P, As, Sb, and Bi) Zintl clusters have been explored. A detailed topological analysis reveals that every cluster comprises of nine 2c-2e σ-bond with an occupation number of 1.96–1.99 |e|. We find an impressive covalence in the E73− cluster which decreases down the group from P73− to Bi73−. The nucleus independent chemical shift (NICS) foretell about the aromatic property of the Zintl cluster which is also decreasing along the group. In addition, the response with respect to external magnetic field of the nucleus independent shielding tensor was obtained to explore the possible formation of the shielding cone behavior.

Quantitative Evaluation on the Evolution of Water Cone Behavior in a Heavy Oil Reservoir With Bottom Water

Abstract In order to solve the problem of the unclear understanding of the water cone behavior and its influencing factors of horizontal well in a heavy oil reservoir with bottom water, in this paper, a series of physical models were established to quantitatively describe the inner relationships between them and further illustrated their influence on the water-cut increasing law. The results showed that the water cone and water-cut grew quickly in the heavy oil reservoir with bottom water. The sweep efficiency of the basic 2D sand-pack model reaches 0.68. The decrement of crude oil viscosity increases the sweep efficiency to about 0.08. The increment of production pressure drop increases the sweep efficiency to about 0.05–0.07. Heterogeneity enhancement decreases the sweep efficiency to about 0.06. The addition of adjustment well and barriers increases the sweep efficiency to about 0.20 and 0.08, respectively. The final sweep efficiency of the whole water cone in the 3D sand-pack model reaches 0.42. Finally, we found that the water-cut increment rules are mainly affected by water cone behavior, production schedule, and the location and distribution of barriers. The study in this paper lays a foundation for the rational and effective development of heavy oil reservoirs with bottom water, which has a broad field application prospects in the future.

Light cone dynamics in excitonic states of two-component Bose and Fermi gases

We consider the non-equilibrium dynamics of two-component one dimensional quantum gases in the limit of extreme population imbalance where the minority species has but a single particle. We consider the situation where the gas is prepared in a state with a single spatially localized exciton: the single particle of the minority species is spatially localized while the density of the majority species in the vicinity of the minority particle sees a depression. Remarkably, we are able to consider cases where the gas contains on the order of N = 100 particles, comparable to that studied in experiments on cold atomic gases. We are able to do so by exploiting the integrability of the gas together with the observation that the excitonic state can be constructed through a simple superposition of exact eigenstates of the gas. The number of states in this superposition, rather than being exponentially large in the number of particles, scales linearly with N.We study the evolution of such spatially localized states in both strongly interacting Bose and Fermi gases. The behavior of the light cones when the interaction strength and density of the gas is varied can be understood from exact results for the spin excitation spectrum in these systems. We argue that the light cone in both cases exhibits scaling collapse. However unique to the Bose gas, we show that the presence of gapped finite-momentum roton-like excitations provide the Bose gas dynamics with secondary light cones.