Basal Edge Research Articles

A cellular tilting mechanism important for dynamic tissue shape changes and cell differentiation in Drosophila

Dynamic changes in three-dimensional cell shape are important for tissue form and function. In the developing Drosophila eye, photoreceptor differentiation requires the progression across the tissue of an epithelial fold known as the morphogenetic furrow. Morphogenetic furrow progression involves apical cell constriction and movement of apical cell edges. Here, we show that cells progressing through the morphogenetic furrow move their basal edges in opposite direction to their apical edges, resulting in a cellular tilting movement. We further demonstrate that cells generate, at their basal side, oriented, force-generating protrusions. Knockdown of the protein kinase Src42A or photoactivation of a dominant-negative form of the small GTPase Rac1 reduces protrusion formation. Impaired protrusion formation stalls basal cell movement and slows down morphogenetic furrow progression and photoreceptor differentiation. This work identifies a cellular tilting mechanism important for the generation of dynamic tissue shape changes and cell differentiation.

Flow Topology of a Slanted Cylinder with Rounded-Edges Under Compressible Conditions

In this study, the slanted afterbody was modified to more closely represent cargo aircraft afterbodies through the addition of a basal edge fillet. Two slant angles ( and ) were explored over two Mach numbers ( and ) and two Reynolds numbers ( and ) using oil flow visualization and pressure-sensitive paint to identify surface flow phenomena, while the spanwise shadowgraph enabled the observation of mean wake phenomena. The rounded-edge afterbody surface measurements displayed a centerline-separated vortex state with flow features and regions of suction qualitatively similar to those of the baseline sharp-edge case, with some notable differences. For example, a separation bubble at the slant leading edge is nearly twice the size of the baseline sharp-edge model. This is accompanied by the presence of a “source point,” indicated by a region of high pressure where the flow reattaches, and a tighter counter-rotating vortex pair in comparison to the baseline. The rounded-edge prevented the previously seen compressible transition to a fully separated wake state within the Mach number range studied while showing an increase in separation bubble size with increasing Mach number. Also noteworthy was the existence of a new vortex state for the model, where the flow remains attached at the model centerline. This is in contrast to the previously observed flow topology of the centerline-separated vortex state in the sharp-edge model, which formed a separation bubble at the model centerline. The transition between the new centerline-attached vortex state and the traditional centerline-separated vortex state was shown to be dependent on both Mach number and Reynolds number, revealing the importance of boundary-layer development on the rounded afterbody flowfield. Overall, these observations indicate that the rounded afterbody produces flowfields with distinct features that vary from the previously described sharp-edge afterbody wake field under certain conditions.

Skin tumor grown within an altarpiece from the 16th century

Fragments of the so-called "Straußfurt Retable", temporarily acquired by Nazi leader Hermann Goering and therefore later suspected as looted art, are exemplary for problems of provenance investigation in poorly documented objects. The central shrine is acarved high relief showing the coronation of the virgin Mary. Damages from the end of WWII are described and illustrated in the literature. Avery astonishing dermatologic finding, however, was never mentioned, or never seen: alarge exophytic "skin"-colored tumor on the cheekbone of Christ, covered by the coherent original color layer with fine crevices in the basal edges. Only on closer examination does it become clear that the protrusion could not have existed in this location from the beginning. Its (relative!) growth is aresult of "working" of wood fibers without cell proliferation, with nearly no longitudinal, but very considerable transverse shrinkage. This tumor represents masses of vertical fibers belonging to abranch that was above the surface of the wood. The starting point of the tumor growth was a"knot" in the Lime wood that would not have been suspected by the carver-500years ago.

Investigation of carrier transport in ZnO and ZnO:Al thin films sputtered at different oxygen conditions

Undoped and doped zinc oxide in film form is used in a wide range of applications. Its electrical and optical properties depend on the oxide conditions during preparation, which are influenced by many deposition parameters. The aim of this work was to experimentally investigate the properties of films deposited under clearly defined oxygen-rich and oxygen-poor conditions. The observed property changes were then described based on theoretical assumptions about internal defects formed in ZnO under different oxygen conditions. To achieve the objective, the ZnO and ZnO:Al films were sputtered in a mixture of argon and oxygen to ensure oxygen-rich conditions. Oxygen-poor conditions were provided by co-sputtering from oxide and metal targets in argon. We have found that the growth in oxygen-rich conditions leads to approximately stoichiometric ZnO films and the films prepared under oxygen-poor conditions are strongly oxygen deficient. The resistivity of undoped ZnO films can be controlled from 108 to 10−2 Ωcm while maintaining high transparency in the visible spectrum. The high resistivity is caused by the formation of deep acceptors under oxygen-rich conditions. The high concentration of zinc interstitials is responsible for the low resistivity in oxygen poor conditions. Even in the case of ZnO:Al films, the carrier concentration is strongly reduced at oxygen-rich conditions by the deep acceptors. These defects tend to relax during vacuum annealing at 300 °C due to self-diffusion. The carrier mobility is mainly related to the crystallinity. The formation of a high number of basal edge dislocations has been identified as a reason for the reduction in transmittance.

Atomistic simulation of the dislocation interactions with the Al2Ca Laves phase in Mg–Al–Ca alloy

The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases, including the Al2Ca phase. Laves phases are generally considered to be brittle and have a detrimental effect on the ductility of Mg. Recently, the Al2Ca phase was shown to undergo plastic deformation in a dilute Mg-Al-Ca alloy to increase the ductility and work hardening of the alloy. In the present study, we investigated the extent to which the deformation of Al2Ca is driven by dislocations in the Mg matrix by simulating the interactions between the basal edge dislocations and Al2Ca particles. In particular, the effects of the interparticle spacing, particle orientation, and particle size were considered. Shearing of small particles and dislocation cross-slips near large particles were observed. Both events contribute to strengthening, and accommodate to plasticity. The shear resistance of the dislocation to bypass the particles increased as the particle size increased. The critical resolved shear stress (CRSS) for activating dislocations and stacking faults was easier to reach for small Al2Ca particles owing to the higher local shear stress, which is consistent with the experimental observations. Overall, this work elucidates the driving force for Al2Ca particles in Mg–Al–Ca alloys to undergo plastic deformation.

Alkyne Coupling and Cyclization on Metal Cluster Complexes. Additions and Couplings of Dimethyl acetylenedicarboxylate to Ru6(μ6-C)(CO)14(μ3-η4-C4H4)

Reactions of the hexaruthenium cluster complex Ru6(μ6-C)(CO)14(μ3−η4−C4H4), 2 with dimethyl acetylenedicarboxylate (DMAD) at 25 °C yielded five new compounds: Ru6(μ5-C)(CO)16(μ−η4−C4H4), 3; Ru6(μ6-C)(CO)14[η6-1,2-C6H4(CO2Me)2], 4; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 5; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 6 and Ru6(μ6-C)(CO)14[μ3−η6−1,2−C6H4(CO2Me)2], 7. Compounds 4 and 7 are isomers that contain the six-membered arene, dimethyl phthalate, 1,2−C6H4(CO2Me)2, as a ligand. Compound 3 was formed as a side product in low yield (6%) by the simple addition of CO to 2. The addition of CO to 2 causes the cluster to open to that of a spiked, square pyramid. Direct reaction of CO to 2 provided 3 in a good yield (72%). A DMAD ligand was added to the cluster of 2 as a simple triply-bridging ligand to form open Ru6 clusters in compounds 5 and 6. Addition of DMAD to 3 yielded the DMAD derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)[μ−C2(CO2Me)2], 8 which contains a DMAD ligand bridging a basal edge of an opened spiked-square pyramidal Ru6 cluster. Compound 5 was thermally converted to the new complex Ru6(μ5-C)(CO)14[μ4−η6−CHCHCHCC(CO2Me)C(CO2Me)](μ-H), 9 that contains a bridging CHCHCHCC(CO2Me)C(CO2Me) ligand formed by a coupling of the DMAD ligand to the bridging C4H4 ligand in 5 accompanied by a cleavage of one CH bond and formation of a bridging hydrido ligand. Decarbonylation of 3 with Me3NO yielded the NMe3 derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)(NMe3), 10 in which the NMe3 ligand is coordinated to the spiked metal atom on the square-pyramidal Ru5 cluster. Treatment of 4 and 7 with CO at 25 °C induced elimination of the 1,2−C6H4(CO2Me)2 ligand to yield free dimethyl phthalate, 11 and formation of the known parent carbonyl complex Ru6(μ6-C)(CO)17. All of the new cluster compounds were characterized by single-crystal X-ray diffraction analyses.

Limiting velocities and transonic dislocations in Mg

To accurately predict the mechanical response of materials, especially at high strain rates, it is important to account for dislocation velocities in these regimes. Under these extreme conditions, it has been hypothesized that dislocations can move faster than the speed of sound. However, the presence of such dislocations remains elusive due to challenges associated with measuring these experimentally. In this work, molecular dynamics simulations were used to investigate the dislocation velocities for the basal edge, basal screw, prismatic edge, and prismatic screw dislocations in Mg in the sub-, trans-, and supersonic regimes. Our results show that only prismatic edge dislocations achieve supersonic velocities. Furthermore, this work demonstrates that the discrepancy between the theoretical limiting velocity and the MD results for Mg is due to its sensitivity to large hydrostatic stress around the dislocation core, which was not the case for fcc metals such as Cu.

Visible-light-responsive Z-scheme heterojunction MoS2 NTs/CuInS2 QDs photoanode for enhanced photoelectrocatalytic degradation of tetracycline

A direct Z-scheme heterojunction coupling hierarchical nanosheet MoS2 nanotubes with CuInS2 quantum dots was successfully prepared to fabricate MoS2 NTs/CuInS2 QDs photoanodes for enhanced photoelectrocatalytic (PEC) activity. The MoS2 NTs with stacked nanosheets and tubular structure have high surface area and abundant basal edges, which can create more active reaction sites. Simultaneously, the continuous and broad photo-absorption range of MoS2 NTs improved the utilization of visible-light and increased the separation efficiency of photo-induced electron-hole pairs. The integration of MoS2 NTs with CuInS2 QDs onto Cu foil yielded direct Z-scheme heterojunction photoanode. The formation of Z-scheme heterojunction inhibited the recombination of photo-induced electron-hole pairs and produced more active electrons and holes to facilitate the generation of highly active species. Under visible light illumination, the prepared MoS2 NTs/CuInS2 QDs photoanode showed superior PEC activity by applying a suitable bias voltage. In PEC process, the generated holes, hydroxyl radicals and superoxide radicals with strong oxidative were employed to achieve highly efficient degradation of tetracycline. The prepared photoanode exhibited high stability, reusability, and broad application potential in PEC degradation of organic pollutants. Moreover, a possible mechanism of the transfer pathway of photo-induced electron-hole pairs on the MoS2 NTs/CuInS2 QDs photoanode was proposed based on a direct Z-scheme heterojunction.

Core structure and Peierls barrier of basal edge dislocations in Ti[formula omitted]AlC[formula omitted] MAX phase

In the MAX phase, the nucleation and motion of basal dislocations dominate the plastic deformation at room temperature. Therefore, information on the dislocation core properties and energy barrier for dislocation glide is essential to understand their plasticity. Dislocations in MAX phases are mainly 〈a〉-type basal edge dislocations (b=a/3[112̄0]) and can glide in the basal plane (typical slip) or form kink bands depending on the load direction and crystal orientation owing to the strong plastic anisotropy. In this study, we determined the core structure, Peierls barrier, and corresponding stress of a/3(0001)[112̄0] edge dislocations in Ti3AlC2 MAX phase by multiple computational approaches using the semidiscrete variational Peierls–Nabarro method, density functional theory, and classical bond-order-potential-based molecular statics calculations. The a/3[112̄0] basal edge dislocation was dissociated into two Shockley partial dislocations with a 2–2.5b-wide stacking fault in between. These partial dislocations glide between the Ti(4f) and Al atomic layer. For straight dislocation motion, the Peierls barrier was single-humped and the corresponding Peierls stress was estimated to be approximately 182 MPa.

Stalling interkinetic nuclear migration in curved pseudostratified epithelium of developing cochlea.

The bending of epithelial tubes is a fundamental process in organ morphogenesis, driven by various multicellular behaviours. The cochlea in the mammalian inner ear is a representative example of spiral tissue architecture where the continuous bending of the duct is a fundamental component of its morphogenetic process. Although the cochlear duct morphogenesis has been studied by genetic approaches extensively, it is still unclear how the cochlear duct morphology is physically formed. Here, we report that nuclear behaviour changes are associated with the curvature of the pseudostratified epithelium during murine cochlear development. Two-photon live-cell imaging reveals that the nuclei shuttle between the luminal and basal edges of the cell is in phase with cell-cycle progression, known as interkinetic nuclear migration, in the flat region of the pseudostratified epithelium. However, the nuclei become stationary on the luminal side following mitosis in the curved region. Mathematical modelling together with perturbation experiments shows that this nuclear stalling facilitates luminal-basal differential growth within the epithelium, suggesting that the nuclear stalling would contribute to the bending of the pseudostratified epithelium during the cochlear duct development. The findings suggest a possible scenario of differential growth which sculpts the tissue shape, driven by collective nuclear dynamics.

Molecular dynamics simulations on the interactions between basal edge dislocation and point defects in magnesium at low temperature

In this work, we performed molecular dynamics (MD) simulations on the interactions between a basal edge < a > dislocation and point defects including vacancies and self-interstitial atoms in magnesium. Simulation results suggest that both self-interstitial atoms and vacancies have a blocking effect on dislocation motion, but the blocking effect of vacancies is much weaker than that of self-interstitial atoms. During interactions, self-interstitial atoms are absorbed and move with dislocation, and the edge dislocation climbs after absorbing self-interstitial atoms. In contrast, vacancies cannot be absorbed. To explain these observations, the binding energy and migration energy are calculated. The binding energy of both vacancies and self-interstitial atoms increases as they approach the dislocation core, seemingly indicating that they can be absorbed. However, the migration barrier of a vacancy is found to be about two orders in magnitude higher than that of a self-interstitial atom. Therefore, only self-interstitial atoms are absorbed, while vacancies cannot.

Synthesis, Structures, and Transformations of Bridging and Terminally-Coordinated Trimethylammonioalkenyl Ligands in Zwitterionic Pentaruthenium Carbido Carbonyl Complexes.

Reactions of the pentaruthenium cluster complexes Ru5(μ5-C)(CO)15 (5), Ru5(μ5-C)(CO)14[μ-η2-O═C(NMe2)](μ-H) (6), and Ru5(μ5-C)(CO)15Cl(μ-H) (7) with ethyne (C2H2) in the presence of Me3NO yielded the zwitterionic complexes Ru5(μ5-C)(CO)13[μ-η2-CHCH(NMe3)] (8), Ru5(μ5-C)(CO)13[μ-η2-O═C(NMe2)](η1-E-CH═CH(NMe3)(μ-H) (9), and Ru5(μ5-C)(CO)13Cl[η1-E-CH═CH(NMe3)](μ-H) (11). Each product contains a positively charged trimethylammonioethenyl ligand, CH═CH(+NMe3), that is derived from a 2-trimethylammonioethenide, -CH═CH(+NMe3), zwitterion that formally has a positive charge on the nitrogen atom and a negative charge on the terminal enyl carbon atom. The trimethylammonioethenyl ligand, CH═CH(+NMe3) in 8 is a η2-ligand that bridges a Ru-Ru bond on a basal edge of the square-pyramidal Ru5 cluster by a combination of σ + π cooordination of the ethenyl group. Compounds 9 and 11 each contain a η1-terminally coordinated [η1-E-CH═CH(+NMe3)] ligand with an E stereochemistry at the C═C double bond in open Ru5 cluster complexes. Compound 9 was decarbonylated to yield the compound Ru5(μ5-C)(CO)12[μ-η2-O═C(NMe2)][μ-η2-CH═CH(NMe3)](μ-H) (10) containing a η2-bridging CHCH(+NMe3) ligand. Compound 10 was converted back to 9 by the addition of CO. Two zwitterionic products, Ru5(μ5-C)(CO)14[η1-E-CH═CH(NMe3)] (12) and Ru5(μ5-C)(CO)15[η1-E-CH═CH(NMe3)] (13), were obtained by the addition of CO to 8. Compound 12 is an intermediate en route to 13. Compound 12 contains a terminally coordinated η1-E-CH═CH(+NMe3) ligand on one of the basal Ru atoms of a square-pyramidal Ru5 cluster. Compound 13 also contains a terminally coordinated η1-E-CH═CH(+NMe3) ligand on the wing-tip bridging Ru atom of a butterfly Ru4C cluster. Treatment of 6 with methyl propiolate (HC≡CCO2Me) yielded the zwitterionic complex Ru5(μ5-C)(CO)13[μ-η2-O═C(NMe2)][η1-E-(MeO2C)C═C(H)NMe3](μ-H) (14) that is structurally similar to 9 but contains a η1-E-(MeO2C)C═C(H)(+NMe3) ligand. Compound 14 eliminated the NMe3 group to yield the compounds Ru5(μ5-C)(CO)13[μ-η2-O═C(NMe2)][μ-η2-(MeO2C)HC═CH] (15) which contains a bridging methoxycarbonyl-substituted alkenyl ligand and the known compound Ru5(μ5-C)(CO)13[μ-η2-O═C(NMe2)](HNMe2)(μ-H) (16).

Bias for the Basal Edge Dislocation Loop in Zirconium: Numerical Analysis

Recent numerical calculation of the coefficients of diffusion of radiation point defects in hexagonal crystals have shown that the main assumption of the theory of radiation growth of zirconium—namely, the assumption about diffusional anisotropy difference (DAD)—is not fulfilled. Thus, the elastic ideology based on the concept of bias of sinks, i.e., elastic interaction difference (EID), remains relevant. In this connection, bias for the basal edge loop of zirconium in a toroidal reservoir is numerically calculated by the finite difference method under consideration of the elastic anisotropy of a hexagonal crystal. The toroidal geometry of the reservoir allows one to perform calculations for a loop with any size and without any correction for the elastic field in the region, in which it has an effect. The dependences of the bias of the loop on its radius and nature are obtained for various drain densities. The essential role of the shape of the boundary condition on the external surface of the reservoir is shown. Prospects for further research in constructing the theory of radiation growth of zirconium on the basis of elastic ideology are outlined.

Nanocrystalline hematite α-Fe2O3 synthesis with different precursors and their composites with graphene oxide

The facile wet chemical co-precipitation method was used for synthesis of hematite (α-Fe2O3) nanoparticles and nanocomposites with graphene oxide (GO) using ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) as different precursor materials. EDTA and DTPA acted as chelating agents to avoid multi nucleation and aggregation of nanoparticles in growth process. For nanocomposite, GO was considered as flexible material with theoretical specific surface area ~1000 m2/g and better surface functionalization due to presence of oxygen containing functional groups i.e. carboxylic, hydroxyl and epoxides groups at basal edge. The structural analysis of prepared nanoparticles and nanocomposites was conducted by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). XRD confirmed various cell parameters and crystalline structure of prepared particles. The crystallite size was found 5 nm–10 nm. After preparation of nanocomposites of hematite α-Fe2O3 (EDTA or DTPA) nanoparticles with GO, they were characterized by Scanning electron microscopy (SEM) and UV–Visible spectroscopy. Current-Voltage (I-V) measurements were also carried out to observe the decrease in resistivity values after mixing with GO. UV–Visible spectroscopy revealed the better photocatalytic degradation of methylene blue (MB) in visible light. Degradation of methylene blue was observed up to 67% with α- Fe2O3 (DTPA) @ GO and 86.06% for α- Fe2O3 (EDTA) @ GO greater than simple α- Fe2O3 (DTPA) 21.2% and α- Fe2O3 (EDTA) 36.8% nanoparticles. As a result, synergistic effect of α- Fe2O3 (EDTA) @ GO showed better photocatalytic action due to GO layer, it acted as electron acceptor and kept high adsorption properties. Electrostatic bonding in α- Fe2O3 (EDTA) @ GO with MB having different functional groups showed the stability of photocatalyst, not to be leached into water. For prolonged time, the charge carrier recombination was suppressed for improved degradation rate of MB in visible light in presence of α- Fe2O3 (EDTA) @ GO.

Plasticity induced superclimb in solid He4 : Direct and inverse effects

During the last decade experimental evidence is building that the mass supertransport through solid Helium-4 as well as the anomalously large matter accumulation in the bulk -- the giant isochoric compressibility (aka the syringe effect) -- are both supported by a network of dislocations with superfluid core. However, a structure of this network as well as its relation to the basal (non-superfluid) dislocations which are responsible for plasticity remain unclear. Here it is shown that superclimbing and basal edge dislocations can form bound pairs. This implies that plastic deformation should produce the syringe effect and vice versa. The experimental test is proposed. While the strength of the effect depends on the average orientation of the paired dislocations, there is a feature unique for the superfluid dislocation scenario -- the supercurrents flow in the direction perpendicular to the plastic deformation.

Atomistic simulations of basal dislocations in Mg interacting with Mg17Al12 precipitates

The mechanical properties of Mg-Al alloys are greatly influenced by the complex intermetallic phase Mg17Al12, which is the most dominant precipitate found in this alloy system. The interaction of basal edge and 30∘ dislocations with Mg17Al12 precipitates is studied by molecular dynamics and statics simulations, varying the inter-precipitate spacing (L), and size (D), shape and orientation of the precipitates. The critical resolved shear stress τc to pass an array of precipitates follows the usual ln((1/D+1/L)−1) proportionality. In all cases but the smallest precipitate, the dislocations pass the obstacles by depositing dislocation segments in the disordered interphase boundary rather than shearing the precipitate or leaving Orowan loops in the matrix around the precipitate. An absorbed dislocation increases the stress necessary for a second dislocation to pass the precipitate also by absorbing dislocation segments into the boundary. Replacing the precipitate with a void of identical size and shape decreases the critical passing stress and work hardening contribution while an artificially impenetrable Mg17Al12 precipitate increases both. These insights will help improve mesoscale models of hardening by incoherent particles.

Injerto de hueso humano no autólogo aplicado a la elevación del seno maxilar superior.

The objective of this study was to evaluate the effectiveness of the use of non-autogenous human bone using the maxillary sinus floor elevation technique to create favorable conditions for the placement of dental implants. Longitudinal clinical study of partially edentulous patients of both genders (included in this study n = 11), older than 18 years. The data were recorded in three time periods: a) at the time of operation: b) control at 7 days, c) control at 180 days, these last two postoperative. The human bone grafts used were lyophilized and irradiated, with a particle size of 0.2 and 1 mm, manufactured by the Hemoderivatives of the National University of Cordoba. The increase in bone tissue was measured by digital orthopantomography, as the distance obtained between the lower basal edge and the resulting alveolar ridge. The population was composed of 8 women and 3 men. The increase in bone reached, at 7 and 180 days, was observed radiographically. There was a significant increase in the mean values of bone mm. Variations were 4-8 mm at the time of operation at mean values of ? 14 mm at 7 and 180 days after surgery.The results indicate that lyophilized human bone can be considered an alternative to bone grafts of animal origin or those of patients.

Anisotropic plastic deformation of single crystals of the MAX phase compound Ti3SiC2 investigated by micropillar compression

The anisotropic deformation behavior of single crystals of Ti3SiC2 has been investigated at room temperature as a function of loading axis orientation and specimen size by micropillar compression tests. Basal slip is found to be only the operative slip system at room temperature. The a/3[12¯10] basal dislocation responsible for basal slip dissociates into two partial dislocations of the Shockley-type and glides between Ti1 and Si atomic layers, as confirmed both experimentally and theoretically. The CRSS value for basal slip increases with the decrease in the specimen size, following an inverse power-law relationship with a very large power-law exponent of about 1.0, which is almost the upper limit of those reported for FCC metals. When the loading axis is parallel to the basal plane, kink band formation occurs only after the occurrence of basal-plane delamination and the subsequent activation of a-dislocations gliding on the basal plane. Kink bands consists of a/3[12¯10] basal edge dislocations of the same sign, each of which had glided between Ti1 and Si atomic layers. These results indicates that the kink formation can simply be interpreted by the classical dislocation-based kink-formation model.

Structural and electronic properties of a-edge dislocations along ⟨1-100⟩ in GaN

Computational analysis via molecular dynamics and density functional theory simulations elucidated the structural and electronic properties of a-type basal edge dislocations lying in the ⟨1–100⟩ direction in wurtzite GaN. As a particular and predominant type of misfit dislocations, experimentally identified in coherently grown semipolar heterostructures, understanding of their properties at the atomistic level is crucial for exploring the growth conditions of the material and improving its performance in its various applications. A total of six core configurations are revealed for the first time and investigated systematically. The energetic hierarchy of these core configurations and their electronic structures are determined. The two shuffle core configurations 3-1 and 4-2 are found to be energetically favorable with respect to the glide 2-2 core in both polarities. It is demonstrated that all the core configurations of the a-type basal dislocations introduce multiple gap states which leads to a narrowing of the bandgap in comparison to that of the pristine material, with the N-polar configurations having a more pronounced and detrimental impact. The presence of Ga-related dangling bonds in the vicinity of the core is widely observed, leading to a shift of the Fermi level to the related s orbitals.

A revision of the Cymindis ehlersi complex (Coleoptera: Carabidae: Lebiinae) with description of a new species and ecological notes

In this article we review the Cymindis ehlersi complex, which is regarded to include two subspecies, C. ehlersi ehlersi Putzeys, 1872 and C. ehlersi lelievrei Jeanne, 1985 from the Cantabrian Mountains (Spain). It was found that show such remarkable differences that the latter should be raised to the specific status Cymindis lelievrei Jeanne, 1985 stat. nov. We also describe a new orophilous species of Cymindis Latreille, 1806 from the Sistema Ibérico, Cymindis distercicus sp. nov., that is closely related to C. ehlersi and C. lelievrei stat. nov. on external morphology and genital anatomy. Furthermore, the systematic position of all these taxa within Cymindis is reviewed. The degree of development of the basal edge of the elytra include C.ehlersi in the subgenus Tarulus Bedel, 1906, is very variable, and we propose to retain these taxa in Cymindis s.str. Finally, the Boreoalpine species Cymindis vaporariorum (Linnaeus, 1758) is firstly cited from the Cantabrian Mountains (north of Palencia), far from the area of the species already known in the Iberian Peninsula (Pyrenees). Some bioecological data about all these species are also given.