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Raman spectroscopy is widely used for characterization of carbon-based mate- rials including light-absorbing carbonaceous (LAC) matter. However, informa- tion on polarization properties of these materials are generally lacking, and often the polarization characteristics of experiments are not presented in the literature thereby giving uncertainty to presented data. In this work, the polari- zation properties of various LACs are studied using Raman spectroscopy. The Raman spectra have been compared while varying the relative polarization, particularly the relative direction of the electric field between the incident light and the detected scattered light. Specifically, the intensity ratio between the D1 and G peaks (ID1/IG) was analyzed in parallel and perpendicular polarization configurations for samples taken from a sooting flame, in the exhaust of a soot generator and carbon blacks. In this work, the parallel and perpendicular polarization configurations mean that the polarization of the detected scattered light is parallel and orthogonal, respectively, to the linearly polarized incident light. It was found that the (ID1/IG) ratio decreased in the more ordered carbo- naceous structures when changing the polarization configuration from parallel to perpendicular. Additionally, based on the depolarization ratios (Dp < 0.75), the prominent Raman peaks of LAC were found to originate from totally sym- metric vibrations. For the G peak, the depolarization ratio was measured to be in the range 0.46–0.56 for all LAC materials. (Less)

For connecting flow-through analytical methods with capillary electrophoresis, a chip working in the air-assisted flow gating interface regime is cast from poly(dimethylsiloxane). In the injection space, the exit from the delivery capillary is placed close to the entrance to the separation capillary. Prior to injecting the sample into the separation capillary, the background electrolyte is forced out of the injection space by a stream of air. In the empty space, a drop of the sample with a volume of

The cation-π interaction is a strong non-covalent interaction that can be used to prepare high-strength, stable supramolecular materials. However, because the molecular plane of a cation-containing group and that of aromatic structure are usually perpendicular when forming a cation-π complex, it is difficult to exploit the cation-π interaction to prepare a 2D self-assembly in which the molecular plane of all the building blocks are parallel. Herein, a double cation-π-driven strategy is proposed to overcome this difficulty and have prepared 2D self-assemblies with long-range ordered molecular hollow hexagons. The double cation-π interaction makes the 2D self-assemblies stable. The 2D self-assemblies are to be an effective carrier that can eliminate metal-nanoparticle aggregation. Such 2D assembly/palladium nanoparticle hybrids are shown to exhibit recyclability and superior catalytic activity for a model reaction.

Azoheteroarene photoswitches have attracted attention due to their unique properties. We present the stationary photochromism and ultrafast photoisomerization mechanism of thiophenylazobenzene (TphAB). It demonstrates impressive fatigue resistance and photoisomerization efficiency, and shows favorably separated (E)‐ and (Z)‐isomer absorption bands, allowing for highly selective photoconversion. The (Z)‐isomer of TphAB adopts an unusual orthogonal geometry where the thiophenyl group is perfectly perpendicular to the phenyl group. This geometry is stabilized by a rare lone‐pair⋅⋅⋅π interaction between the S atom and the phenyl group. The photoisomerization of TphAB occurs on the sub‐ps to ps timescale and is governed by this interaction. Therefore, the adoption and disruption of the orthogonal geometry requires significant movement along the inversion reaction coordinates (CNN and NNC angles). Our results establish TphAB as an excellent photoswitch with versatile properties that expand the application possibilities of AB derivatives., My own way: Thiophenylazobenzene is a sulfur‐based azoheteroarene photoswitch with impressive fatigue resistance, photoisomerization efficiency, and highly selective photoconversion. Its (Z)‐isomer adopts an unusual orthogonal geometry stabilized by an intramolecular lone‐pair⋅⋅⋅π interaction governing the ultrafast photoisomerization, which requires a mechanism involving significant movement along the inversion reaction coordinate.

The upper beak bone of birds is known to be overlain by the rhinotheca, which is composed of the horny sheath of keratinous layers. However, the details of the structure and growth pattern of the rhinotheca are yet to be understood. In this study, the microstructure of the rhinotheca from chicken specimens of different growth stages (ranging from 1 to ~ 80 days old) was analyzed using a combination of thin section and scanning electron microscopy observations, and small-angle X-ray scattering analysis. We found that the rhinotheca comprises three different layers - outer, intermediate, and inner layers - throughout its growth. The outer layer arises from the proximal portion of the beak bone and covers the dorsal surface of the rhinotheca, whereas the intermediate and inner layers originate in the distal portion of the beak bone and underlie the outer layer. This tri-layered structure of the rhinotheca was also observed in wild bird specimens (grey wagtail, king quail, and brown dipper). On the median plane, micro-layers making up the outer and inner layers are bedded nearly parallel to the rostral bone at the base. However, more distally positioned micro-layers of the outer layer are more anteverted distally. The micro-layers of the intermediate layer are bedded nearly perpendicular to those of the outer and inner layers on the median plane. The growth of micro-layers in the intermediate layer adds thickness to the rhinotheca, which causes the difference in profile between the beak bone and the rhinotheca in the distal portion of the beak. Moreover, the entire intermediate layer grows distally as new proximal micro-layers form. The outer layer is dragged distally by the intermediate layer as a result of its distal growth, for the three layers are closely packed to each other at their boundaries. Furthermore, the occurrence of the intermediate and inner layers in the distal portion of the rostral bone may be because the distal end of the beak is frequently used and worn, and the rhinotheca therefore needs to be replaced more frequently at the distal end. The rhinotheca structure described here will be an important and useful factor in the reconstruction of the beaks of birds in extinct taxa.

For a single, intense 7 μm linearly polarized laser pulse, we found that the branching ratio for the fragmentation of ClCHO+ → Cl + HCO+ , H + ClCO+ , HCl+ +CO depended strongly on the orientation of the molecule (J. Phys. Chem. Lett. 2012, 3 2541). The present study explores the possibility of controlling the branching ratio for fragmentation by using two independent pulses with different frequencies, alignment and delay. Born-Oppenheimer molecular dynamics simulations in the laser field were carried out with the B3LYP/6-311G(d,p) level of theory using combinations of 3.5, 7 and 10.5 μm sine squared pulses with field strengths of 0.03 au (peak intensity of 3.15×1013 W/cm2 ) and lengths of 560 fs. A 3.5 μm pulse aligned with the C-H bond and a 10.5 μm pulse perpendicular to the C-H bond produced a larger branching ratio for HCl+ +CO than a comparable single 7 μm pulse. When the 10.5 μm pulse was delayed by one quarter of the pulse envelope, the branching ratio for the high energy product, (HCl+ +CO 73%) was a factor of three larger than the low energy product (Cl + HCO+ , 25%). By contrast, when the 3.5 μm pulse was delayed by one quarter of the pulse envelope, the branching ratio was reversed (HCl+ +CO 38%; Cl + HCO+ , 60%). Continuous wavelet analysis was used to follow the interaction of the laser with the various vibrational modes as a function of time. © 2018 Wiley Periodicals, Inc.

The vicinity of the electron diffusion region (EDR) at the core of magnetic reconnection is frequently characterized by agyrotropic electron velocity distributions such as perpendicular velocity-sp...

Polarization-resolved second harmonic generation (P-SHG) microscopy is a technique capable of characterizing nonlinear optical properties of noncentrosymmetric biomaterials by extracting the nonlinear susceptibility tensor components ratio χð2Þ0 zzz =χ ð2Þ0 zxx , with z-axis parallel and x-axis perpendicular to the C6 symmetry axis of molecular fiber, such as a myofibril or a collagen fiber. In this paper, we present two P-SHG techniques based on incoming and outgoing circular polarization states for a fast extraction of χ ð2Þ0 zzz =χ ð2Þ0 zxx : A dual-shot configuration where the SHG circular anisotropy generated using incident right- and left-handed circularly-polarized light is measured; and a single-shot configuration for which the SHG circular anisotropy is measured using only one incident circular polarization state. These techniques are used to extract the χ ð2Þ0 zzz =χ ð2Þ0 zxx of myosin fibrils in the body wall muscles of Drosophila melanogaster larva. The results are in good agreement with values obtained from the double Stokes-Mueller polarimetry. The dual- and single-shot circular anisotropy measurements can be used for fast imaging that is independent of the in-plane orientation of the sample. They can be used for imaging of contracting muscles, or for high throughput imaging of large sample areas.

Success in obtaining higher-order twistarenes with precise structures is very important for fundamentally understanding the relationship between the structures and physical properties/optoelectronic applications. In this research, by using the advantages from a retro-Diels-Alder process (clean reaction) and the cross-conjugated nature of the pyrene unit, a novel dodeca-twistarene was prepared for the first time. Its structure, confirmed by single-crystal XRD analysis, indicates that it possesses a twisted angle (≈30°), and two neighboring molecules in the crystal lattice are perpendicular to each other because of the twisted character and the strong intermolecular CH-π interactions. However, its basic physicochemical properties suggest its instability in air derives from its elevated HOMO energy level, although NICS calculations confirm that the pyrene units contribution poorly to the π conjugation of the overall molecule. Ministry of Education (MOE) Accepted version Q.Z acknowledges financial support from AcRF Tier 1 (RG 111/17, RG 2/17, RG 114/16, RG 8/16) and Tier 2 (MOE 2017- T2-1-021), Singapore. Dr. Liu acknowledges funding support from M4062018.

Treatment of oblique and spiral fractures remains challenging. The aim of this study was to introduce and investigate the new LagLoc technique for locked plating with generation of interfragmentary compression, combining the advantages of lag screw and locking-head-screw techniques. Oblique fracture was simulated in artificial diaphyseal bones, assigned to three groups for plating with a seven-hole locking compression plate. Group I was plated with three locking screws in holes one, four, and seven. The central screw crossed the fracture line. In group II the central hole was occupied with a lag screw perpendicular to fracture line, whereas holes one and seven were occupied with locking screws. Group III was instrumented applying the LagLoc technique as follows. Hole four was predrilled perpendicularly to the plate, followed by overdrilling of the near cortex and insertion of a locking screw-crossing the fracture line-whose head was covered by a holding sleeve to prevent temporarily the locking in the plate hole and generate interfragmentary compression. Subsequently, the screw head was released and locked in the plate hole. Holes one and seven were occupied with locking screws. Interfragmentary compression in the fracture gap was measured using pressure sensors. All screws in the three groups were tightened with 4 Nm torque. Interfragmentary compression in group I (167 ± 25 N) was significantly lower in comparison to groups II (431 ± 21 N) and III (379 ± 59 N), p ≤ 0.005. The difference in compression between groups II and III remained not significant (p = 0.999). The new LagLoc technique offers an alternative tool to generate interfragmentary compression with the application of locking plates by combining the biomechanical advantages of lag screw and locking screw fixations. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2886-2891, 2018.

This study evaluated the influence of different finish line designs and abutment materials on the stress distribution of bilayer and monolithic zirconia crowns using three-dimensional finite element analysis (FEA). Three-dimensional models of two types of zirconia premolars - a yttria-stabilized zirconia framework with veneering ceramic and a monolithic zirconia ceramic - were used in the analysis. Cylindrical models with the finish line design of the crown abutments were prepared with three types of margin curvature radius (CR): CR = 0 (CR0; shoulder margin), CR = 0.5 (CR0.5; rounded shoulder margin), and CR = 1.0 (CR1.0; deep chamfer margin). Two abutment materials (dentin and brass) were analyzed. In the FEA model, 1 N was loaded perpendicular to the occlusal surface at the center of the crown, and linear static analysis was performed. For all crowns, stress was localized to the occlusal loading area as well as to the axial walls of the proximal region. The lowest maximum principal stress values were observed when the dentin abutment with CR0.5 was used under a monolithic zirconia crown. These results suggest that the rounded shoulder margin and deep chamfer margin, in combination with a monolithic zirconia crown, potentially have optimal geometry to minimize occlusal stress.

Research on engineered materials that integrate different 2D crystals has largely focused on two prototypical heterostructures: Vertical van der Waals stacks and lateral heterostructures of covalently stitched monolayers. Extending lateral integration to few layer or even multilayer van der Waals crystals could enable architectures that combine the superior light absorption and photonic properties of thicker crystals with close proximity to interfaces and efficient carrier separation within the layers, potentially benefiting applications such as photovoltaics. Here, the realization of multilayer heterstructures of the van der Waals semiconductors SnS and GeS with lateral interfaces spanning up to several hundred individual layers is demonstrated. Structural and chemical imaging identifies {110} interfaces that are perpendicular to the (001) layer plane and are laterally localized and sharp on a 10 nm scale across the entire thickness. Cathodoluminescence spectroscopy provides evidence for a facile transfer of electron‐hole pairs across the lateral interfaces, indicating covalent stitching with high electronic quality and a low density of recombination centers., Multilayer heterostructures with localized and sharp lateral interfaces across hundreds of individual van der Waals layers are realized from the anisotropic layered semiconductors SnS and GeS. Cathodoluminescence spectroscopy shows the transfer of electron–hole pairs across the lateral interfaces, demonstrating excellent connectivity without interfacial recombination. The results are promising for applications benefiting from thick layered crystals combined with in‐plane carrier manipulation.

Semiconducting mesocrystalline bulk polymer specimens that exhibit near-intrinsic properties using channel-die pressing are demonstrated. A predominant edge-on orientation is obtained for poly(3-hexylthiophene-2,5-diyl) (P3HT) throughout 2 mm-thick/wide samples. This persistent mesocrystalline arrangement at macroscopic scales allows reliable evaluation of the electronic charge-transport anisotropy along all three crystallographic axes, with high mobilities found along the π-stacking. Indeed, charge-carrier mobilities of up to 2.3 cm2 V-1 s-1 are measured along the π-stack, which are some of the highest mobilities reported for polymers at low charge-carrier densities (drop-cast films display mobilities of maximum ≈10-3 cm2 V-1 s-1 ). The structural coherence also leads to an unusually well-defined photoluminescence line-shape characteristic of an H-aggregate (measured from the surface perpendicular to the materials flow), rather than the typical HJ-aggregate feature usually found for P3HT. The approach is widely applicable: to electrical conductors and materials used in n-type devices, such as poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200) where the mesocrystalline structure leads to high electron transport along the polymer backbones (≈1.3 cm2 V-1 s-1 ). This versatility and the broad applicability of channel-die pressing signifies its promise as a straightforward, readily scalable method to fabricate bulk semiconducting polymer structures at macroscopic scales with properties typically accessible only by the tedious growth of single crystals.

Layered 2D (PbI2 )1-x (BiI3 )x materials exhibit a nonlinear dependence in structural and charge transport properties unanticipated from the combination of PbI2 and BiI3 . Within (PbI2 )1-x (BiI3 )x crystals, phase integration yields deceptive structural features, while phase boundary separation leads to new conductance switching behavior observed as large peaks in current during current-voltage (I-V) measurements (±100 V). Temperature- and time-dependent electrical measurements demonstrate that the behavior is attributed to ionic transport perpendicular to the layers. High-resolution transmission electron microscopy reveals that the structure of (PbI2 )1-x (BiI3 )x is a "brick wall" consisting of two phases, Pb-rich and Bi-rich. These brick-like features are 10s nm a side and it is posited that iodide ion transport at the interfaces of these regions is responsible for the conductance switching action.

A completely novel 3D dissection approach is taken to re-investigate high-density polyethylene (HDPE) crystallized into periodic architectures in a wide range of Tc . This work first discovers that ring bands present in HDPE are crystallized in a quite wide Tc range (90-120 °C) all within regime-III growth. With further detailed analyses of the top-surface-relief patterns and 3D architectures of HDPE spherulites, this work has fully clarified the periodic morphology packed with alternate ways of single-crystal aggregates in correlation with the optical banding patterns. The proposed assembly mechanism sheds light that the periodic bands are actually composed of a cross-hatch grating structure in that the alternately perpendicular orientations from the ridge to valley bands being related to the interior radial to tangential lamellae. Such grating architectures in the interiors of HDPE can be viewed as a mimicry resembling shish-kebab lamellae self-aligned by Archimedean spiral-spins from the nucleus center.

Four β-nucleated polypropylene samples with increasing die draw ratio (DDR) were prepared to modify lamellae arrangement. The DSC, SEM, and 2D-XRD results show that all four cast films had similar crystallinity, high contents of β-crystal but lowering stability of β-lamellae with ascending DDR. Meanwhile, the anisotropy of β-lamellae distribution strengthens gently and the stacked lamellae structure perpendicular to the machine direction (MD) predominates dramatically. Tensile testing at 25 °C and 90 °C were conducted along MD and transverse direction (TD), respectively. The markedly expanding difference of deformation indicates the anisotropy highlighted significantly. Additionally, when the samples stretched along MD, a more homogeneous deformation occurs with ascending anisotropy, which is completely opposite to the β-lamellae stability. But samples deformed more heterogeneous when stretched along TD. The characterization of morphological evolutions during stretching shows that the stacked lamellae debonds uniformly and abundant microvoids formed when the sample stretched along MD with higher anisotropy, resulting in evenly dispersion of stress, consequently making a more uniform distribution of defects and a better isotropic deformation. Moreover, the microfibrils and defects distributed uniformly within higher orientation sample after longitudinal stretching stretched along MD, leading to the dramatic improvement of pore size distribution of the membrane after biaxial stretching. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

A highly crystalline graphite powder was prepared from the low temperature (800-1000 °C) graphitization of renewable hard carbon precursors using a magnesium catalyst. The resulting graphite particles are composed of Voronoi-tessellated regions comprising irregular sheets; each Voronoi-tessellated region having a small "seed" particle located near their centroid on the surface. This suggests nucleated outward growth of graphitic carbon, which has not been previously observed. Each seed particle consists of a spheroidal graphite shell on the inside of which hexagonal graphite platelets are perpendicularly affixed. This results in a unique high surface area graphite with a high degree of graphitization that is made with renewable feedstocks at temperatures far below that conventionally used for artificial graphites.

Dendritic BaTiO3 ceramic powders (d-BT) were prepared by hydrothermal method in order to improve the dielectric properties of d-BT/P(VDF-TrFE) composites, in which, KOH was used as the branch-directing agent. The effect of hydrothermal time on the branch length of d-BT particle was mainly studied. The results showed that 1.0-2.5 μm d-BT particles were obtained after hydrothermal treating for 12 hours. The particle was composed of two kinds of branches, one was primary branch with about 800 nm in length and another with150-250 nm. A d-BT/P(VDF-TrFE) composites were formed by solution casting, in which d-BT powders as dielectric fillers and the composites exhibited high-energy storage performance. Its maximum energy density reached to 9.78 J/cm3, twice as compared with pure P(VDF-TrFE). The branches of d-BT particles may act as key roles when the composites existed in electric field. Some branches perpendicular to the external electric field provided the increase in the breakdown strength and others parallel to the external electric field brought the enhancement of the dielectric constant, which simultaneously resulted in high energy density of the composites.

Additive manufacturing receives nowadays opulent attention in both media and ongoing research. In particular, the techniques involving full melting of the raw material, enabling the fabrication of directly deployable components, are of high interest. To date, there are still secondary influences which are yet to be considered, leading to substantial, mainly directional dependent, deviations. The study at hand investigated the surface roughness dependencies in plane, focusing on the interaction of the unidirectional inert gas stream with the irradiation sequence; more precisely the weld splashes emerging from the melt pool, and the resulting in plane pattern. The surface roughness of the upwards orientated faces revealed clear fluctuations, being lowest close to the gas-inlet and also in the back area of the machine. Perpendicular to the fabrication plane aligned surfaces did not reveal any volatility regarding the inert gas stream. Increasing the energy density of the irradiation led to an increase in the surface roughness of all side faces, but to an improved roughness of the upwards facing surfaces coupled with a significant reduction in evident weld splashes.

A new configuration for Transmission Kikuchi Diffraction (TKD) in a scanning electron microscope is presented; called 'on-axis TKD'. Compared to the usual off-axis configuration, the scintillator is placed perpendicular to the incident beam under the electron-transparent sample, not in vertical position. In this way, the setup benefits from intense forward scattered electrons enabling short acquisition times. At equivalent diffraction pattern quality, the electron dose needed on the sample is estimated to be 20 times lower in comparison to the off-axis configuration. The technique is particularly suited to the characterisation of severe plastic deformation induced ultrafine grained microstructures. The evolution of the microstructure of an Al-Mg alloy deformed by high pressure tube twisting was analysed. It is shown that the grain refinement was in the steady state stage for a shear strain of 24 with a mean grain size of 120 nm.

This paper focuses on studying the fatigue crack growth (FCG) characteristics and fracture behaviours of 30 wt% B4C/6061Al composites fabricated by using powder metallurgy and hot extrusion method. Compact tension (CT) specimens having incisions parallel to the extrusion direction (T-D) and perpendicular to the extrusion direction (E-D) were investigated through FCG tests. Results show that, at low/medium stress-intensity factor range levels (ΔK ≤ 9), crack propagation rate in E-D specimens is lower than that in T-D specimens because the elongated B4C particles parallel to the extrusion direction in E-D specimens can deflect the crack. The scanning electron microscope micrographs of the fractured surface illustrate that crack mainly propagates in the matrix alloy at the initial stage of its propagation and propagates more remarkably near the particle-matrix interface with the increase of ΔK value. B4C particles are also found to be easy to fracture during the rapid crack propagation. Based on fracture analyses, considering the impacts of factors like crack deviation, plastic zone size at the crack tip, and crack driving force, a 2-D crack propagation model was developed to study the fatigue crack propagation mechanism in the 30 wt% B4C/6061Al composite.

In the present work, the dislocation structure evolution around and underneath the spherical indentations in (001) oriented single crystalline strontium titanate (STO) was revealed by using an etch-pit technique and molecular dynamics (MD) simulations. The 3D defect structure at various length scales and subsurface depths was resolved with the help of a sequential polishing, etching, and imaging technique. This analysis, combined with load–displacement data, shows that the incipient plasticity (manifested as sudden indenter displacement bursts) is strongly influenced by preexisting dislocations. In the early stage of plastic deformation, the dislocation pile-ups are all aligned in 〈100〉 directions, lying on {110}45 planes, inclined at 45° to the (001) surface. At higher mean contact pressure and larger indentation depth, however, dislocation pile-ups along 〈110〉 directions appear, lying on {110}90 planes, perpendicular to the (100) surface. MD simulations confirm the glide plane nature and provide further insights into the dislocation formation mechanisms by tracing the evolution of the complete dislocation line network as function of indentation depth.

Large tilt angle (LTA) implantation has been employed in Si manufacturing processes in many applications, such as lightly doped drain and halo implant. The depth profile of boron ions usually consists of only single peak at incident angle of 0° with respect to the perpendicular of the silicon surface. However, an abnormal dual-peak profile was observed at LTA (>40°) with incident energy of 160 keV. By using a Monte Carlo method to simulate the ion implant process, it was found that the projected range of boron ions agrees completely with the formation of the first peak position that is shallower in depth, while the cause for the second peak that corresponds with a depth much deeper in the Si substrate was unknown. During the simulation, it was also found that when the tilt angle was increased, the sputtering yields and Si displacements increased significantly, and this phenomenon indicates that during LTA implantation, Si damage may not be negligible anymore. The Si damage effect that was as due to either low Si density or transient Si displacement in the simulation could have led to partial incident boron ions penetrating much deeper into the Si substrate and thus, caused the emergence of the second peak. Copyright © 2016 John Wiley & Sons, Ltd.

We report Electron Spin Resonance (ESR) measurements on stage-I potassium intercalated graphite (KC$_8$). Angular dependent measurements show that the spin-lattice relaxation time is longer when the magnetic field is perpendicular to the graphene layer as compared to when the magnetic field is in the plane. This anisotropy is analyzed in the framework of the Elliott-Yafet theory of spin-relaxation in metals. The analysis considers an anisotropic spin-orbit Hamiltonian and the first order perturbative treatment of Elliott is reproduced for this model Hamiltonian. The result provides an experimental input for the first-principles theories of spin-orbit interaction in layered carbon and thus to a better understanding of spin-relaxation phenomena in graphene and in other layered materials as well.

The embedding of photonic crystals within stimuli‐responsive hydrogels has attracted tremendous interest because it provides new applications such as optical switches, displays, and sensors. However, the production of electrically tunable photonic hydrogels with a wide range of color tunability, fast electrical response, and high stability for repeated use is still challenging. Here, electrically tunable photonic hydrogels are fabricated using ultrahigh‐water‐content polyelectrolyte layered hydrogels composed of thousands of bilayer domain structures. The layered hydrogel exhibits versatile color tunability by applying an electric field parallel or perpendicular to the direction of the gel layers. The hydrogel exhibits homogeneous color tuning when a perpendicular electric field is applied, while it shows a large rainbow‐like electric‐optic response in the visible to near‐infrared region when a parallel electric field is applied. Additionally, by a simple method using patterned electrodes, a reflective display showing the designed characters is demonstrated and maintained for hours underwater without an external source of energy. Moreover, the electrically induced optical patterns can be erased, and the responsive photonic hydrogel shows excellent stability for repeated use. We anticipate that this study will provide the foundation for the development of responsive photonic hydrogels with new and large electro‐optical effects for future chromatic applications.

International audience; Many active materials used in shape-morphing respond to an external stimulus by stretching or contracting along a director field. The programming of such actuators remains complex because of the single degree of freedom (the orientation) in local actuation. Here, texturing this field in zigzag patterns is shown to provide an extended family of biaxial active stretches out of an otherwise single uniaxial active deformation, opening a larger parameter space. By further modulating the zigzag patterns at the larger scale of the structure, its deployed shape can be controlled. This notion of texturing over hierarchical length scales follows geometrical principles, and is robust against changes in size and materials. The robustness of the approach is demonstrated by considering three different responsive materials: inextensible flat fabrics, channel-bearing elastomer (respectively, contracting and expanding perpendicularly to the director field when actuated pneumatically), and 3D-printed thermoplastic (composed of extruded filaments that contract when heated). It is shown that large-scale shape-morphing structures can be generated and that their geometry can be controlled with high accuracy.

During the manufacturing of composite complex shape parts, defects such as tow buckles characterised by out of plane elevation may appear. The parameters controlling the appearance and growth of the defect are not completely understood and need to be investigated. A device capable of reproducing tow buckles has been used to study the tow buckling phenomenon. Several techniques able to measure out of plane elevations are discussed to detect the appearance and evaluate continuously the growth of the tow buckle in relation to its size and shape. The fringe projection technique was chosen as it gives the best compromise between the size of the defect to measure and its resolution. If the in-plane bending angle is the main criterion at the origin of the tow buckle appearance and growth, it is not the only one. This work shows that the fabric architecture such as the space between the tows perpendicular to the one showing the buckle is also crucial to control the buckle’s appearance and growth. It also shows that the differential bi-axial loading of the fabric as well as the stiffness of the tows in the three main directions greatly in fluences the appearance of the defect.

The molecular anisotropy that is developed in microscale, centrifugally spun atactic-polystyrene fibers prepared from the solution state is examined and comparisons are made to electrospun fibers. Utilizing small angle neutron scattering, a ratio of the radius of gyration parallel to-/perpendicular to- the fiber axis is measured and a model of chain anisotropy development in the centrifugal spinning process is described.

The promise of wearable and implantable devices has made stretchable organic semiconductors highly desirable. Though there are increasing attempts to design intrinsically stretchable conjugated polymers, their performance in terms of charge carrier mobility and maximum fracture strain is still lacking behind extrinsic approaches (i.e., buckling, Kirigami interconnects). Here, polymer crosslinking with flexible oligomers is applied as a strategy to reduce the tensile modulus and improve fracture strain, as well as fatigue resistance for a high mobility diketopyrrolopyrrole polymer. These polymers are crosslinked with siloxane oligomers to give stretchable films stable up to a strain e = 150% and 500 strain-and-release cycles of 100% strain without the formation of nanocracks. Organic field-effect transistors are prepared to assess the electrical properties of the crosslinked film under cyclic strain loading. An initial average mobility (μavg) of 0.66 cm2 V−1 s−1 is measured at 0% strain. A steady μavg above 0.40 cm2 V−1 s−1 is obtained in the direction perpendicular to the strain direction after 500 strain-and-release cycles of 20% strain. The μavg in the direction parallel to strain, however, is compromised due to the formation of wrinkles.

Silver nanowires (AgNW) in solution with isopropyl alcohol are deposited on photolithographed gratings of varying depth. The deposition results in a modified coffee ring where the flow is redirected along the grating direction. We investigate the anisotropic character of the flow by performing electrical measurements at different concentrations of the nanowires, and for each of the grating depths used. We measure the electrical current along the directions perpendicular and parallel to the gratings. The current anisotropy tends to disappear at higher concentrations. The flow arranges the NW's into a 2D anisotropic arrangement by analyzing how the electrical percolation behaves. By observing the properties this 2D anisotropic arrangement as a function of concentration and grating depth, we can predict where a quasi-1D interconnect can be obtained.

Intriguing field emission microscopy (FEM) images reflecting subnanometer-sized structures of emitting sites and/or electronic orbitals have been observed from graphene edges. Graphene emitters with free edges (i.e. open edges) show a striped pattern (dubbed as a ‘lip pattern’) consisting of an array of streaked spots (or oval-shaped spots); the direction of striation is perpendicular to the graphene sheet, and each stripe is divided into two wings by a central dark band running parallel to the graphene sheet. The dark band may be due to the distractive interference of electrons emitted from π orbitals with a phase difference of π on either side of the graphene. From the magnification calibration using FEM images of an aluminum cluster with atomic resolution, the spacing of the streaked spots is found to be close to the distance between adjacent carbon atoms aligned along the zigzag and armchair edges. These observations suggest that the lip pattern reflects the symmetry of π states strongly delocalized at edge atoms. Copyright © 2016 John Wiley & Sons, Ltd.

The effect of molecular weight on the molecular aggregation structure of polymers bearing a pendant perylenediimide (PDI) side chain, designated PAc12PDI, was investigated using synchrotron radiation X-ray diffraction measurements. It was found that depending on molecular weight, either the main chain axis or the side chain axis behaves as the longitudinal axis in fiber samples and was aligned parallel to the fiber axis. A similar phenomenon is present in thin film samples, but was complicated by the additional influence of the interfacial free energy of the side chain group. Even in the case of the polymer with lower molecular weight, the face plane of PDI was found to show both parallel and perpendicular orientations to the substrate (i.e., flat-on and edge-on orientations). On the other hand, if the length of the main chain is sufficiently long with respect to the length of the side chain, the face plane of PDI was oriented perpendicular to the substrate, leading to an edge-on orientation in the thin film. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2275–2283

The interfacial reaction products and stress distribution in a selective laser melted Al12Si/SiC composite are studied using confocal Raman microscopy. Results reveal that needle-like Al4C3 and equiaxed Si are located at the interface between the Al matrix and SiC particles. This reaction is triggered by the high temperature within the SiC due to its high laser absorptivity. Raman frequency shifts to lower wavenumber are observed in both the SiC and Si, suggesting the existence of tensile stress within the interface. The tensile stress in SiC is higher in the build direction than in the direction perpendicular to the build direction. No such difference is observed in the Si. The reason is ascribed to the Gaussian distribution of the laser energy density and stress relief through the interfacial reaction.

Suppressing the oppositely orientated hexagonal boron nitride (h-BN) domains during the growth is of great challenge due to its bipolar structure. It is found that h-BN domains grown on onefold symmetric Cu(102) or (103) share a unique orientation, with one zigzag edge of the h-BN triangles perpendicular to the symmetry axis of the substrate surface.

A perpendicular E-plane transition between rectangular waveguide (WG) and suspended stripline (SSL) in the Ku-band is presented. The topology of coupling network is studied and design guidelines are provided. A 10-dB return loss bandwidth (BW) of 12% was obtained using a patch resonator on a double-sided single-layer dielectric substrate combined with a cavity behind the resonator of a very shallow depth as low as 1 mm for a compact design. An insertion loss of 0.18 dB at 13.8 GHz was achieved in the measurement of a back-to-back SSL–WG–SSL transition. Comparison of the measured performances with the state-of-the-art WG transitions to SSL shows a 1.5 times improvement in frequency bandwidth and a three times reduction in electrical dimensions. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1831–1834, 2016

Plastic strain localisation in a sheet specimen was monitored by electronic speckle pattern interferometry during uniaxial tensile tests. The experiments were carried on in the diffuse and localised necking stages until fracture. A kinematic model, which is independent of material characteristics, was used to describe the whole strain rate field with two crossing localisation bands inclined with respect to the tensile direction. Then, the physical features of localisation, such as the width of the two bands, their inclination angles and their maximum strain rates are identified by least-square from the displacements fields and their evolutions are followed from the onset of diffuse necking up to the failure. In particular, the effect of the average strain rate is considered and bandwidth evolution is analysed in detail. It was found that: The band structure appears early, as soon as diffuse necking starts; The separation, in terms of strain rate or bandwidth, of the two bands corresponds to the transition between diffuse and localised necking. The localised necking stage can be divided into two sub-stages: in the first one, the two bands continue to evolve but at different rates, and in the second one, one of the bands stabilises. The transition between the two sub-stages is influenced by the crossbeam velocity; The inclination of the band leading to fracture remains quite stable, while the other rotates towards a situation perpendicular to the tensile direction; The band width decreases exponentially versus the maximum local strain. The two bands follow the same evolution path, but one of them progressively lags behind the other until it stops deforming. Although the average strain rate was only varied by a factor two, it was found that, when the strain rate increases, the two bands stay together longer and thus that the onset of localised necking is delayed.

X-ray diffraction and TEM investigations of MOVPE grown AlN on sapphire with small off-cuts to a- and m-plane reveal the influence of the off-cut direction and angle on the reduction of threading dislocation density by annihilation during growth. Higher off-cut angles as well as off-cut to a-plane seem to facilitate the annihilation, with the main reduction taking place within the first 300 nm layer thickness. On planar substrate the thickness is limited by cracking to below 2 μm which also limits the ability to further reduce the defect density. By epitaxial lateral overgrowth on stripe patterned substrates the crack-free thickness is increased and further reduction of the defect density is possible. This process is effective up to 3–5 μm layer thickness. Using templates with off-cuts ≥0.2° to m-plane, step bunching perpendicular to the stripe direction occurs and bends the vertically directed threading dislocations into inclined grain boundaries starting from the point of coalescence. These partially block/incline threading dislocations over the ridge areas and thus further reduce the dislocation density. The dislocations are concentrated in stripes over the ridges and the coalescence areas. For smaller off-cut to m or especially for off-cut to a-plane, the dislocation distribution is more homogeneous but nevertheless stripe-like with alternating densities of low 108 cm−2 in the laterally overgrown areas and low 109 cm−2 in the areas over the ridges and the coalescence lines.

This report employed molecular statics simulation and density-functional-theory calculation to study the Poisson's ratios of face-centered-cubic materials. We provide numerical and theoretical evidences to show that cubic materials can exhibit auxetic behavior in a principal direction under proper loading conditions. When a stress perpendicular to the loading direction is applied, cubic materials can exhibit a negative Poisson's ratio at finite strain. The negative Poisson's ratio behavior, including its direction and value, is highly dependent on the direction and magnitude of the transversely applied stresses. As a result, we show that it is possible to tune the direction and magnitude of the negative Poisson's ratio behavior of cubic materials by controlling the transverse loadings.

In this paper a novel lateral block size characterization method based on X-ray diffractometry (XRD) is presented. The developed method based on scans of plans perpendicular to the surface visible from the edge of the sample and subconsequent numerical analysis based on Scherrer equation. In presented investigations as a reference sample bulk GaN substrate fabricated by AMMONO Ltd. was used. The GaN layers deposited on sapphire substrate were investigated as a case of study. Moreover, a method of analyzing the magnitude of the tilt and twist mosaicity based on the scans of rocking curves and reciprocal lattice maps (RLM) from the edge of sample is presented. As an example for this methodology highly mosaicited SiC crystal was used. Presented approach allows to directly determine the value of the angular deviation of mosaicity in a direction perpendicular and parallel to the sample surface.

Self-assembly of short peptides into nanostructures has become an important strategy for the bottom-up fabrication of nanomaterials. Significant interest to such peptide-based building blocks is due to the opportunity to control the structure and properties of well-structured nanotubes, nanofibrils, and hydrogels. X-ray crystallography and solution NMR, two major tools of structural biology, have significant limitations when applied to peptide nanotubes because of their non-crystalline structure and large weight. Polarized Raman spectroscopy was utilized for structural characterization of well-aligned D-Diphenylalanine nanotubes. The orientation of selected chemical groups relative to the main axis of the nanotube was determined. Specifically, the C-N bond of CNH3+groups is oriented parallel to the nanotube axis, the peptides' carbonyl groups are tilted at approximately 54° from the axis and the COO- groups run perpendicular to the axis. The determined orientation of chemical groups allowed the understanding of the orientation of D-diphenylalanine molecule that is consistent with its equilibrium conformation. The obtained data indicate that there is only one orientation of D-diphenylalanine molecules with respect to the nanotube main axis.

Background and Objective Fractional Photothermolysis (FP) is a method of skin treatment that generates a thermal damage pattern consisting of multiple columns of thermal damage, also known as microscopic treatment zones (MTZs). They are very small in diameter and are generated by application of highly focused laser beams. In order to obtain the smallest spot size, the treatment should be performed in the focal plane. Any deviation from the focal plane (DFP) results in an increase of spot size. FP devices typically utilize distance holders in order to facilitate exposures at this specific location. In spite of the use of distance holders, DFP can occur. In particular, variations of contact pressure to the skin surface and anatomical treatment areas of high surface curvature may be prone to DFP during FP treatments. The impact of such distance variation on lesion geometry, such as depth and diameter of the thermal injury, has not previously been evaluated. The objective of this study was to investigate the relation between DFP and the resulting lesion geometry for a selected ablative fractional device. Material and Methods A handpiece of an ablative fractional laser (DeepFX, UltraPulse Encore, Lumenis, Yokneam, Israel) was mounted to a rigid stand. Full thickness human skin obtained from abdominoplasty was mounted to a separate stand perpendicular to the handpiece. The tissue stand allowed the distance between the handpiece and the tissue to be adjusted to produce a variation up to ±3 mm from the focal plane. A 1 × 1 cm2 scanning area of 169 MTZs, 50 mJ energy per MTZ, 120 μm nominal spot size, was applied at −3, −2, −1, 0, +1, +2, and +3 mm deviated from the focal plane. Minus (−) and plus (+) signs indicate decreasing and increasing distance between the handpiece and the tissue, respectively. Depth and diameter of the laser induced tissue lesions were assessed and quantified. Results DFPs produced a significant alteration of the lesion geometry. DFPs of −3, −2, −1, 0, +1, +2, +3 mm resulted in average lesion depths of 1,020 (−40%), 1,180 (−31%), 1,400 (−18%), 1,700 (0%), 1,620 (−5%), 780 (−55%), 680 (−60%) µm, and average lesion diameters of 314 (+26%), 311 (+25%), 273 (+10%), 248 (0%), 256 (+3%), 316 (+27%), 359 (+44%) µm, respectively. The underlined values represent the focal plane. The percentage changes relative to values at focal plane are in parentheses. Conclusions A relatively minor DFP has a marked impact on the thermal injury profile, including lesion depth and diameter, of the laser-exposed tissue. Such marked changes of the thermal injury profile might affect the wound healing, safety, and efficacy of ablative fractional resurfacing procedures. Clinicians should carefully maintain the focal plane during ablative fractional treatment for reproducible results. The presented data are device specific and the clinical impact of such alteration of thermal injury profile warrants further investigation. Lasers Surg. Med. © 2016 Wiley Periodicals, Inc.

The boundaries of 1:2 ordered domains in Ba[(Co, Zn, Mg)1/3Nb2/3]O3 perovskite ceramics are comprehensively studied by high-resolution transmission electron microscopy (HRTEM) on the base of atomic position simulation. The atomic configurations for four types of twin boundaries are determined. A-type and B-type boundary, which lie along (001)c and (110)c planes, respectively, are conservative. C-type boundary parallels to (111)c plane, while Г-type boundary is perpendicular to (111)c plane. At C-type and Г-type boundary, atomic intersection leads to a buffer layer, among which the B-site cations are generally disordered. The width of Г-type boundary is larger than that of C-type boundary, so is the perturbation to the system. The energy of four types of twin boundaries is proved to be “A-type & B-type < C-type < Г-type” according to the magnitude of the destabilization to the system. Single antiphase boundary (APB) is considered to be nonconservative. However, when combined with conservative twin boundary, an extra ordered structure with a periodicity of 1.24 nm along [001]c direction and a periodicity of 0.87 nm along [110]c direction forms. The boundary regions are indeed stabilized by the new superlattice.

Normal strains near a growing fatigue crack have been studied in situ using the Digital Image Correlation (DIC) technique in a compact tension specimen of stainless steel 316L under tension-tension cyclic loading. An error analysis of the measured displacements and strains has been carried out, and the results show that the precisions of displacements and strains in the direction perpendicular to the crack plane and ahead of the crack are better than those parallel to the crack plane and in the wake of the crack. The errors in the measured displacements are in the range of 0.06 to 0.1 m and between 0.2% and 0.4% for the measured strains, the latter are well below the critical strain at the onset of crack growth about 8%. Strain ratchetting was found ahead of the growing fatigue crack tip, albeit very close to the crack tip.

User-programmed meso- to microscale 2D shapes using magnetic nanoparticles as building blocks with magnetic-field-directed self-assembly are created. The assembly templates are magnetically recorded using perpendicular magnetic recording (PMR) media. The results demonstrate that PMR can template user-designed features in two dimensions down to 30 nm in size, i.e., the nanoparticle diameter. It has been also shown that the nanoparticles assemble onto transitions between oppositely magnetized regions in the medium. At these transitions, the magnetic field gradients are extremely large (25 MT m−1 2 nm above the medium) and change rapidly with height (≈1015 T/m/m within 20 nm of the surface). It is found that 30 nm diameter particles assemble into 1–2 layers with feature widths ranging from 30 to 350 nm. It is hypothesized that large lateral growth can occur because the magnetic forces parallel to the disk extend up to 150 nm on either side of a recorded transition, falling off more slowly with distance than the vertical magnetic forces. Once lateral growth saturates, a second layer of nanoparticles begins to assemble on top of the first layer, suggesting strong potential for controlling layer-by-layer assembly through appropriate design of the medium and its resulting field gradient profiles.

Texture evolution is studied by EBSD in Mg–9Gd–4Y–0.4Zr (GW94), Mg–5Gd–4Y–0.4Zr (GW54), and Mg–5Gd–0.4Zr (GW50) alloys after processing with two extrusion-ratios of 19:1 and 8:1. While the alloys show common extrusion textures at the low extrusion-ratio of 8:1, an unusual extrusion texture is observed in the GW94 alloy at the high extrusion-ratio of 19:1 with the (0001) basal planes aligned perpendicular to the extrusion axis. This unusual texture decreases at lower extrusion-ratios and/or lower alloy contents. It is proposed that rare-earth (RE) elements modify the texture by retarding recrystallization in solute drag effects on grain boundaries and pinning effects of RE-rich precipitates.