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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.

Molecular functions depend on conformations and motions of the corresponding molecular species. An air-water interface is a suitable asymmetric field for the control of molecular conformations and motions under a small applied force. In this work, double-paddled binuclear PtII complexes containing pyrazole rings linked by alkyl spacers were synthesized and their orientations and emission properties dynamically manipulated at the air-water interface. The complexes emerge from water with concurrent variation of interface orientation of the planes of the PtII complexes from perpendicular to parallel during mechanical compression suggesting a unique 'submarine emission'. Phosphorescence of the complexes is quenched at the air-water interface prior to monolayer formation with intensities subsequently rapidly increasing during monolayer compression. These results indicate that asymmetric reactions and motions might be controlled by applying mechanical force at the air-water interface.

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.

Internally 3,3'-biphenyl-, 2,2',5,5'-bithiophene-, and 2,5-thieno[3,2-b]thiophene-bridged [46]decaphyrins were prepared. In addition to the global 46π-conjugated circuits, the internal core-modified [32]heptaphyrin- and [30]hexaphyrin moieties in 2,2',5,5'-bithiophene- and 2,5-thieno[3,2-b]thiophene-bridged [46]decaphyrins also possess doubly twisted topologies (|Lk |=2) and are regarded as (doubly-twisted-annuleno)doubly-twisted-annulene variants. All these decaphyrins display distinct Huckel aromaticity owing to the global 46π-electronic networks but the contributions of the local half circuits were almost negligible due to the perpendicular orientation of the bridges.

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.

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.

Patterned surfaces of responsive polymers find applications in diverse fields. However, it is still a great challenge to fabricate hierarchical patterns with long-range orders. Herein controllable hierarchical surface patterns that can be fabricated by combining nanoembossing techniques with the surface instability of supramolecular hydrogels are presented. Nanoembossed nanostripe arrays of polyethylene glycol (PEG)-based polyurethane-urea supramolecular hydrogels are fabricated and exposed to water, whereby the lateral expansion of nanostripes is confined and leads to the formation of folded in-plane or out-of-plane patterns depending on the aspect ratios. The direction of folds is perpendicular to the nanostripes. Both the amplitude and the wavelength of out-of-plane folds are proportional to the thickness of nanostripes. Therefore, hierarchical structures, in which one periodicity is defined by the nanoembossing processes and the other is determined by surface buckling, can be quickly fabricated in supramolecular hydrogel thin films.

SCM-14 (Sinopec Composite Material No. 14), a new stable germanosilicate zeolite with a 12×8×8-ring channel system, was synthesized using commercially available 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs) in fluoride medium. The framework structure of SCM-14 was determined using rotation electron diffraction (RED), and refined against synchrotron X-ray powder diffraction (SXPD) data for both as-made and calcined materials. The framework structure of SCM-14 is closely related to that of three known zeolites: mordenite (MOR), GUS-1 (GON), and IM-16 (UOS). SCM-14 has the same projection as that of mordenite and GUS-1 when viewed along the 12-ring channels, and possesses two more straight 8-ring channels running perpendicular to the 12-ring channels. The structure of SCM-14 can be constructed by either the same layers as that of GUS-1 or the same columns as that of IM-16. Based on their structural relationship, three topologically reasonable hypothetical zeolites were predicted.

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.

This work presents the modeling of a vertical falling film expanding or shrinking from the inlet manifold. Considering a stationary approach, the film shape, the flow field and the absorption rate of an ambient gas are computed. For the flow field, one dimensional (1-D) second-order weighted integral boundary layer (WIBL) model is shown to accurately reproduce the film deformations. The gas transfer is then solved in a 2-D predeformed domain to investigate the impact of the film deformations on the gas absorption rate. It is found that a significant mass transfer enhancement, as compared to a flat film, is obtained when the film is expanding due to the concomitant increase of the concentration gradient perpendicular to the interface. On the contrary, a slight hindrance of the mass transfer is observed when the film is shrinking, although it remains in this case very close to the flat film analytical solution. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4370–4378, 2017

Dithienosiloles bearing 2,4,6-triisopropylphenyl (Tip) and mesityl (Mes) groups at the 2,6-positions have been synthesized, and their structures and electronic properties have been examined. X-ray crystallography showed that the bulky aryl groups have a nearly perpendicular orientation to dithienosilole. In the UV/Vis spectra, the lowest energy absorption bands of these dithienosiloles are shifted bathochromically compared to that of the hydrogen-substituted analog. Theoretical calculations showed that the electronic effect of the bulky aryl groups can be explained by the σ–π and σ*–π* conjugation between the σ and σ* orbitals of the C−C bonds of the perpendicular benzene rings and the π and π* orbitals of the dithienosilole moiety. Furthermore, these dithienosiloles show intense blue fluorescence with high fluorescence quantum yields, as an effect of the perpendicular bulky aryl groups.

O2 adsorption on Pt surfaces is of great technological importance owing to its relevance to reactions for the purification of car exhaust gas and the oxygen reduction on fuel-cell electrodes. Although the O2/Pt(111) system has been investigated intensively, questions still remain concerning the origin of the low O2 sticking probability and its unusual energy dependence. We herein clarify the alignment dependence of the initial sticking probability (S0) using the single spin-rotational state-selected [(J,M)=(2,2)] O2 beam. The results indicate that, at low translational energy (E0) conditions, direct activated chemisorption occurs only when the O2 axis is nearly parallel to the surface. At high energy conditions (E0>0.5 eV), however, S0 for the parallel O2 decreases with increasing E0 while that of the perpendicular O2 increases, accounting for the nearly energy-independent O2 sticking probability determined previously by a non-state-resolved experiment.

Various DNA-based nanodevices have been developed on the nanometer scale using light as regulation input. However, the programmed controllability is still a major challenge for these artificial nanodevices. Herein, we demonstrate a rotary DNA nanostructure in which the rotations are controlled by light. A bar-shaped DNA rotor, fabricated as a stiff double-crossover molecule, was placed on the top of a rectangular DNA tile. The photoresponsive oligonucleotides modified with azobenzenes were employed as switching motifs to release/trap the rotor at specific angular position on DNA tile by switching photoirradiations between ultraviolet and visible light. As a result, two reconfigurable states (perpendicular and parallel) of rotor were obtained, in which the angular changes were characterized by AFM and fluorescence quenching assays. Moreover, the reversible rotary motions during the photoirradiation were directly visualized on the DNA tile surface in a nanometer-scale precision using a second-scale scanning of the high-speed AFM.

Electronic energy transfer (EET) between chromophores is of fundamental importance for many biological processes and optoelectronic devices. However, common models fall short in fully describing the process, especially in bichromophoric model systems with a donor and acceptor connected by a rigid linker providing perpendicular geometries. Herein, we report a novel strategy for preparing bichromophores containing adamantane or 2-(2-adamantylidene)adamantane as rigid spacers, providing a fixed distance between chromophores, and their parallel or perpendicular arrangement without chromophore rotation. New fluorophores were developed and linked via spiroatoms. Bichromophores with identical (blue-blue) or different (blue-red) chromophores were synthesized, either in orthogonal or parallel geometry. These were characterized by absorption/fluorescence spectroscopy, time-resolved fluorescence anisotropy, and fluorescence antibunching measurements. Based on the Förster point-dipole approximation, EET efficiencies were estimated by using geometrical parameters from (time-dependent) density functional calculations. For bichromophores with parallel geometry, the predicted EET efficiencies were near unity and fit the measurements. In spite of estimated values around 0.4 and 0.5, 100 % efficiency was observed also for bichromophores with orthogonal geometry. The new rigid scaffolds presented here open new possibilities for the synthesis of bichormophores with well-defined parallel or perpendicular geometry.

Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are well supported by the latest experimental observations.

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.

Variable-temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) 1 possesses a singlet ground state, 1(S0), while the 90° twisted triplet 1(T1) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic 1(T1) at temperatures between 300 and 500 K yields the exchange interaction Jex/h c=3351 cm−1 and a singlet–triplet energy splitting of 9.6 kcal mol−1, which is in excellent agreement with calculations (9.3 kcal mol−1 at the UKS BP86/B3LYP/revPBE level of theory). In contrast, the zero-field splitting parameter D is very small (calculated value −0.018 cm−1) and unmeasurable.

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.

Temozolomide was paired with guanine, 6-selenoguanine, and 6-thioguanine, as well as the SH tautomer of the latter. The potential energy surface of each heterodimer was searched for all minima, using Dispersion-Corrected Density Functional Theory and MP2 methods. Among the dozens of minima, three categories were observed. Stacked geometries place the aromatic systems of the two molecules parallel to one another, while the two systems are roughly perpendicular to one another in a second category. Also found are coplanar structures held together by H-bonds. Dispersion proves to be a dominating attractive force for the stacked structures, less so for perpendicular, and smallest for the coplanar dimers. Geometries and energetics are relatively insensitive to S and Se substitution, but tautomerization reverses relative stabilities of different geometries.

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.

We synthesized a novel banana-shaped molecule based on a 1,7-naphthalene central core that exhibits a distinct mesomorphism of the nematic-to-nematic phase transition. Both the X-ray profile and direct imaging of atomic force microscopy (AFM) investigations clearly indicates the formation of an anomalous nematic phase possessing a two-dimensional (2D) tetragonal lattice with a large edge (ca. 59 Å) directed perpendicular to the director in the low-temperature nematic phase. One plausible model is proposed by an analogy of skyrmion lattice in which two types of cylinders formed from left- and right-handed twist-bend helices stack into a 2D tetragonal lattice, diminishing the inversion domain wall.

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

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.

Ethylenediammonium sulfate (EDS) crystals were grown from aqueous solution and cleaved into thin (100-500 micron) plates. The 422 point group of EDS was confirmed by X-ray diffraction. The constitutive relations of EDS crystals were determined through generalized ellipsometry with an instrument that uses four photoelastic modulators (4PEM). The optical rotation at 500 nm, for example, was + 22.9°/mm along the optic axis and - 12.1°/mm perpendicular to the optic axis for the P41 21 2 crystals. Enantiomorphous twins frequently form across the (001) plane. Mirrored halves must be separated by cleavage in advance of optical measurements. Chirality 28:460-465, 2016. © 2016 Wiley Periodicals, Inc.

Traditionally, it is believed that three-dimensional transport networks are preferable to those of lower dimensions. We demonstrate that inter-layer electronic couplings may result in a drastic decrease of charge mobilities by utilizing field-effect transistors (FET) based on two phases of titanyl phthalocyanine (TiOPc) crystals. The α-phase crystals with electronic couplings along two dimensions show a maximum mobility up to 26.8 cm(2) V(-1) s(-1) . In sharp contrast, the β-phase crystals with extra significant inter-layer electronic couplings show a maximum mobility of only 0.1 cm(2) V(-1) s(-1) . Theoretical calculations on the bulk crystals and model slabs reveal that the inter-layer electronic couplings for the β-phase devices will diminish remarkably the device charge transport abilities owing to the coupling direction perpendicular to the current direction. This work provides new insights into the impact of the dimensionality and directionality of the packing arrangements on charge transport in organic semiconductors.

The stability of a ring-like sheet of Ag atoms wrapping a carbon nanotube (CNT) is examined though density-functional theory (DFT) simulation. We propose various candidates for stable sheet-like rings of Ag atoms wrapping the CNT. We perform structural relaxation calculations and DFT molecular dynamics (DFT-MD) simulations. We compare a single-ring chain and sheet-like rings wrapping the CNT with a 3D nanocluster beside the CNT. Although the relative energies of the ring structures are higher than that of the 3D aggregate of Ag atoms beside the CNT, the ring structures are observed to have metastable states after the structural relaxations. For multiple stacked rings, we found that the sheet-like ring structure, whose geometrical feature involves a baseline of each triangle of Ag atoms being parallel to the CNT axis, is relatively stable in comparison with the perpendicular case. We clarify that this difference can be examined through structural relaxation calculations with random displacements and DFT-MD simulations.

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.

Silicon nitride (Si3N4) materials with preferentially aligned β-Si3N4 grains were tribologically characterized with respect to their possible application in a high-pressure gasoline pump. Tribological tests were performed under oscillating sliding conditions lubricated with isooctane as a substitute for gasoline using Si3N4 counterbodies. Performance in terms of wear of the aligned materials surpassed that of nonaligned reference Si3N4, as well as that of self-mated silicon carbide, zirconia, alumina, and a steel sliding pair. The plane perpendicular to the extruding direction and parallel to the hot-pressing axis was the most wear resistant.

[Fe(tvp)(2)(NCS)(2)] (1) (tvp=trans-(4,4-vinylenedipyridine)) consists of two independent perpendicular stacks of mutually interpenetrated two-dimensional grids. This uncommon supramolecular conformation defines square-sectional nanochannels (diagonal approximate to 2.2nm) in which inclusion molecules are located. The guest-loaded framework 1@guest displays complete thermal spin-crossover (SCO) behavior with the characteristic temperature T-1/2 dependent on the guest molecule, whereas the guest-free species 1 is paramagnetic whatever the temperature. For the benzene-guest derivatives, the characteristic SCO temperature T-1/2 decreases as the Hammet sigma(p) parameter increases. In general, the 1@guest series shows large entropy variations associated with the SCO and conformational changes of the interpenetrated grids that leads to a crystallographic-phase transition when the guest is benzonitrile or acetonitrile/H2O., The research reported herein was supported by the Spanish Ministerio de Economia y Competitividad (MINECO) and FEDER funds (CTQ2013-46275-P; MAT2012-34740), the Basque Government (project IT-779-13), and Generalitat Valenciana (PROMETEO/2012/049). T.R.M. thanks the Spanish Ministerio de Economia y Competitividad (MINECO) for a predoctoral grant (FPI.). L.P.-L. thanks the Generalitat Valenciana for a predoctoral fellowship in the frame of the project PROMETEO/2012/049.

Three dimensional self-consistent field theoretic simulations have been performed to determine the equilibrium morphologies formed by linear ABC triblock polymer melts confined between two parallel plates that favor the middle block. Our primary goal is to elucidate the conditions under which the perpendicular lamella is stabilized, since this morphology plays a central role in many nanotechnology applications. Key factors, namely, the chain architecture, surface energy and the mismatch between the film thickness d and the bulk lamella period, L0, determine the final morphologies, e.g., perpendicular and parallel lamella, perforated lamella and wet substrate with parallel cylinders in the core, have been identified. Overall, our findings are fully consistent with the results of limited experimental studies focused on morphology development in thin films of triblock polymer melts. Finally, we have clearly demonstrated that ABC triblocks hold technological advantages over diblocks for nano-lithographic fabrications.

The photodetachment of hydrogen negative ion near different inelastic surfaces is investigated by the semiclassical closed orbit theory for arbitrary laser polarization direction . A two-term formula of photodetachment cross section consisting of a smooth background term and an oscillatory term is derived. The oscillatory term contains an extra angular factor that describes the dependence of oscillations in total cross section on the laser polarization direction. It is observed that the amplitude of oscillations in cross section reaches maximum at when laser polarization is parallel to the z-axis and it approaches zero as the laser polarization direction becomes perpendicular to the z-axis. It is also observed that as the reflection coefficient , which accounts for the inelastic behavior of the surfaces, increases the amplitude of oscillation also increases. © 2015 Wiley Periodicals, Inc.

Purpose To identify optimal pulsed gradient spin‐echo (PGSE) and oscillating gradient spin‐echo (OGSE) sequence settings for maximizing sensitivity to axon diameter in idealized and practical conditions. Methods Simulations on a simple two‐compartment white matter model (with nonpermeable cylinders) are used to investigate a wide space of clinically plausible PGSE and OGSE sequence parameters with trapezoidal diffusion gradient waveforms. Signal sensitivity is measured as a derivative of the signal with respect to axon diameter. Models of parallel and dispersed fibers are investigated separately to represent idealized and practical conditions. Results Simulations show that, for the simple case of gradients perfectly perpendicular to straight parallel fibers, PGSE always gives maximum sensitivity. However, in real‐world scenarios where fibers have unknown and dispersed orientation, low‐frequency OGSE provides higher sensitivity. Maximum sensitivity results show that on current clinical scanners (G max = 60 mT/m, signal to noise ratio (SNR) = 20) axon diameters below 6 µm are indistinguishable from zero. Scanners with stronger gradient systems such as the Massachusetts General Hospital (MGH) Connectom scanner (G max = 300 mT/m) can extend this sensitivity limit down to 2–3 µm, probing a much greater proportion of the underlying axon diameter distribution. Conclusion Low‐frequency OGSE provides additional sensitivity to PGSE in practical situations. OGSE is particularly advantageous for systems with high performance gradients. Magn Reson Med 75:688–700, 2016. © 2015 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

We present our recent results from constant temperature-pressure (NPT) molecular dynamics (MD) simulations of a bead-spring copolymer model, in which the polymer is confined between two crystalline substrates. Our goal was to study the combined effect of the polymer crosslinking density and the degree of confinement on the glass-transition temperature and the equilibrium structure of the films. In the direction perpendicular to the substrates, the polymer chains are ordered in layers of increasing density towards the substrates, for all crosslinking densities and the degrees of confinement. In the direction parallel to the substrates, the polymer films display an amorphous structure, just like in the bulk. The glass-transition temperature increases with confinement and crosslinking density, with the former having a large effect compared to the later. POLYM. COMPOS., 36:1012–1019, 2015. © 2015 Society of Plastics Engineers

This study discusses the design aspects for the construction of a microfluidic device for comprehensive spatial two-dimensional liquid chromatography. In spatial two-dimensional liquid chromatography each peak is characterized by its coordinates in the plane. After completing the first-dimension separation all fractions are analyzed in parallel second-dimension separations. Hence, spatial two-dimensional liquid chromatography potentially provides much higher peak-production rates than a coupled column multi-dimensional liquid chromatography approach in which the second-dimension analyses are performed sequentially. A chip for spatial two-dimensional liquid chromatography has been manufactured from cyclic olefin copolymer and features a first-dimension separation channel and 21 parallel second-dimension separation channels oriented perpendicularly to the former. Compartmentalization of first- and second-dimension developments by physical barriers allowed for a preferential flow path with a minimal dispersion into the second-dimension separation channels. To generate a homogenous flow across all the parallel second-dimension channels, a radially interconnected flow distributor containing two zones of diamond-shaped pillars was integrated on-chip. A methacrylate ester based monolithic stationary phase with optimized macroporous structure was created in situ in the confines of the microfluidic chip. In addition, the use of a photomask was explored to localize monolith formation in the parallel second-dimension channels. Finally, to connect the spatial chip to the liquid chromatography instrument, connector ports were integrated allowing the use of Viper fittings. As an alternative, a chip holder with adjustable clasp locks was designed that allows the clamping force to be adjusted.

Anatomic differences on the toe pad epithelial cells of torrent and tree frogs (elongated versus regular geometry) are believed to account for superior ability of torrent frogs to attach to surfaces in the presence of running water. Here, the friction properties of artificial hexagonal arrays of polydimethylsiloxane (PDMS) pillars (elongated and regular) in the presence of water are compared. Elongated pillar patterns show significantly higher friction in a direction perpendicular to the long axis. A low bending stiffness of the pillars and a high edge density of the pattern in the sliding direction are the key design criteria for the enhanced friction. The elongated patterns also favor orientation-dependent friction. These findings have important implications for the development of new reversible adhesives for wet conditions.

Soft devices can be bent, stretched, and compressed reversibly, but conventional wires are rigid. This work describes stretchable composites that are easily fabricated with simple tools and commodity materials, and that can provide a strategy for electrical wiring that meets certain needs of soft devices. These composites are made by combining metal wool and elastomeric polymers. Embedding fi ne (average fi ber width ≈25 µm) steel wool (or other metal wools) in a silicone polymer creates an electrically conductive path through the nonconductive elastomer. This composite is fl stretchable, compressible, inexpensive, and simple to incorporate into the bodies of soft devices. It is also electrically anisotropic, and shows maximum conductivity along the majority axis of the fi bers, but maximum extension perpendicular to this axis. The utility of this composite for creating an electrically conductive path through an elastomer was demonstrated in several devices, including: a soft, solderless breadboard, a soft touch sensor, and a soft strain gauge.

Achieving sub-10 nm high-aspect-ratio patterns from diblock copolymer self-assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high-χ copolymer typically have very different surface energies, favoring in-plane microdomain orientations. A fully perpendicular orientation of a high-χ block copolymer, poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through-thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of micro­domains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film.

Shave-off depth profiling uses a Ga focused ion beam micro-machining process to provide highly precise depth profiles with nanometer-scale resolution. This method is a very unique process for acquiring a depth profile using the shave-off scan mode, in which the primary ion beam perpendicular to the direction of depth irradiates the sample. In our previous study, we confirmed by molecular dynamics simulation that the shave-off scan mode has a low mixing effect compared with the conventional scan mode, which uses the normal incident angle. However, the current understanding of measurement using the shave-off scan mode is insufficient. In this study, in order to estimate the sample damage in the shave-off scan mode, we investigated the degree of mixing effects after the primary ion bombardment under shave-off conditions using atom probe tomography. To evaluate the mixing effects, the intermixing of silicon isotope multilayers induced by ion beam irradiation was investigated. The depth of the damage from the sample surface caused by Ga focused ion beams was analyzed for both the shave-off scan mode and the conventional scan mode using the normal incident angle. Results showed that the shave-off scan mode has a significantly smaller mixing effect thanthe conventionalscanmode. Inaddition, results showed that the attenuations of the damage and the Ga concentration exhibited almost the same tendency. Copyright © 2014 John Wiley & Sons, Ltd.

Controlled directional spreading of a droplet on a smart high-adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm(-1) by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V- or inverse-V-shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.

Summary This paper introduces a double-image multiple-beam Fizeau fringes system. The introduced system can dynamically determine the variations of the refractive indices for both parallel and perpendicular polarization simultaneously. This is achieved by the simultaneous capturing of two multiple-beam interference patterns during the mechanical processing of isotactic polypropylene fibre. This parallel determination of the refractive indices of both polarization directions allowed us to determine the full-field distribution of the stress vector, S. To accomplish this, a mathematical model was deduced to calculate the components of the stress vector, S, i.e. parallel stress component, S1, and perpendicular stress component, S2. Double-image Fizeau fringes system and the deduced mathematical model were used to investigate the variation of the refractive index and stress components of the fibre during the stretching process and propagation of necked regions.

A biologically inspired, multilayer laminate structural design is deployed into nanocomposite films of graphene oxide-poly(methyl methacrylate) (GO-PMMA). The resulting multilayer GO-PMMA films show greatly enhanced mechanical properties compared to pure-graphene-oxide films, with up to 100% increases in stiffness and strength when optimized. Notably, a new morphology is observed at fracture surfaces: whereas pure-graphene-oxide films show clean fracture surfaces consistent with crack initiation and propagation perpendicular to the applied tensile load, the GO-PMMA multilayer laminates show terracing consistent with crack stopping and deflection mechanisms. As a consequence, these macroscopic GO-PMMA films become defect-tolerant and can maintain their tensile strengths as their sample volumes increase. Linear elastic fracture analysis supports these observations by showing that the stiffness modulation introduced by including PMMA layers within a graphene oxide film can act to shield or deflect cracks, thereby delaying failure and allowing the material to access more of its inherent strength. Together, these data clearly demonstrate that desirable defect-tolerant traits of structural biomaterials can indeed be incorporated into graphene- oxide-based nanocomposites.

Four new layered pentaborates Rb4Ba2.5B20O34Br, Rb2Ba4B20O34Br2, Rb4Ba2.5B20O34Cl, and KBaB5O9 have been successfully synthesized via a high-temperature solution method; the former three are the first series of compounds reported in the Rb-Ba-B-O-X (X = halogen) system. Interestingly, the structures of the above compounds are composed of the same [B5O11]7– fundamental building block (FBB), which could be further linked to form 2∞[B10O17]4– double layers for the former three compounds and 2∞[B5O9]3– single layers for the last one. The structure comparisons among all the available anhydrous pentaborates reveal that the structures of the anionic framework are affected by the relationship between the orientation of [B5O11]7– FBB axes and the layer plane (parallel or perpendicular), which will produce the different number of terminal O atoms in the initial pentaborate blocks. The viewpoints give us a feasible way to investigate the layered structures and expand the structural diversity of borates. Furthermore,...

From Fe3Si/FeSi2 artificial lattices, wherein Fe3Si layers are partially epitaxially grown from the first layer on Si(111) up to the top layer across the FeSi2 layers with the same orientation relationship as that in the first layer, current-perpendicular-to-plane (CPP) structures that partially contain current-in-to-plane (CIP) structural portions were fabricated by a mask method. It was confirmed that the antiparallel alignment of magnetization at a zero magnetic field due to antiferromagnetic interlayer coupling is changed to parallel alignment with the applied magnetic field by polarized neutron reflectometry. The MR ratio was comparable to that of CIP structural films. It might be because a current should predominantly flow in the CIP portion since the CIP structural portion is dimensionally so large as compared with that of the CPP portion. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A nickel-nickel-bonded complex, [{Ni(μ-L(.-))}2] (1; L=[(2,6-iPr2C6H3)NC(Me)]2), was synthesized from reduction of the LNiBr2 precursor by sodium metal. Further controllable reduction of 1 with 1.0, 2.0 and 3.0 equiv of Na, respectively, afforded the singly, doubly, and triply reduced compounds [Na(DME)3]·[{Ni(μ-L(.-))}2] (2; DME=1,2-dimethoxyethane), [Na(Et2O)]Na[(L(.-))Ni-NiL(2-)] (3), and [Na(Et2O)]2Na[L(2-)Ni-NiL(2-)] (4). Here L represents the neutral ligand, L(.-) denotes its radical monoanion, and L(2-) is the dianion. All of the four compounds feature a short Ni-Ni bond from 2.2957(6) to 2.4649(8) Å. Interestingly, they display two different structures: the perpendicular (1 and 2) and the coaxial (3 and 4) structure, in which the metal-metal bond axis is perpendicular to or collinear with the axes of the α-diimine ligands, respectively. The electronic structures, Ni-Ni bonding nature, and energetic comparisons of the two structure types were investigated by DFT computations.

The end-to-side anastomosis is frequently used in microvascular free flap transfer, but detailed rheological analyses are not available. The purpose of this study was to introduce a new modified end-to-side (Opened End-to-Side, OES-) technique and compare the resulting flow pattern to a conventional technique. The new technique was based on a bi-triangulated preparation of the branching-vessel end, resulting in a "fish-mouthed" opening. We performed two different types of end-to-side anastomoses in forty pig coronary arteries and produced one elastic, true-to-scale silicone rubber model of each anastomosis. Then we installed the transparent models in a circulatory experimental setup that simulated the physiological human blood flow. Flow velocity was measured with the one-component Laser-Doppler-Anemometer system, recording flow axial and perpendicular to the model at four defined cross-sections for seven heart cycles in each model. Maximal and minimal axial velocities ranged in the conventional model between 0.269 and -0.122 m/s and in the experimental model between 0.313 and -0.153 m/s. A less disturbed flow velocity distribution was seen in the experimental model distal to the anastomosis. The OES-technique showed superior flow profiles distal to the anastomosis with minor tendencies of flow separation and represents a new alternative for end-to-side anastomosis.

We have extended a previous model for calculating the effects of dislocations on the characteristics of a Si solar cell to include the effects of front and back surface recombination. This improved dislocation model uses Green's function approach to solve the three-dimensional continuity equation of the minority carriers with suitable boundary conditions corresponding to surface recombination at the n and p sides. The dislocations are considered to be localized lines, extending perpendicular to the front and back surfaces of the cell and having a recombination velocity. We discuss effect of several parameters such as bulk dislocation density, minority carrier diffusion length in p and n regions on the J-V characteristics, and spectral response of the cell. It is shown that these results agree well with previously published, experimental data. Copyright © 2013 John Wiley & Sons, Ltd.

SiC fiber-bonded ceramics, SA-Tyrannohex®, (SA-THX) with perpendicular and parallel fiber orientations were brazed using Ag-, Ni- and Pd-base brazes, and four Si–X (X: Ti, Cr, Y, Ta) eutectics. Outcomes were variable, ranging from bonded joints through partially bonded to un-bonded joints. Prominent Ti- and Si-rich interfaces developed with Cusil-ABA, Ticusil, and Copper-ABA and Ni- and Si-rich layers with MBF-20. Stress rupture tests at 650 and 750°C on Cusil-ABA-bonded joints revealed a temperature-dependent behavior for the perpendicular joints but not for the parallel joints with failure occurring at brazed interface. Higher-use temperatures can be targeted with eutectic Si–Ti and Si–Cr alloys.

A range of triphenylene and phthalocyanine-based discotic liquid crystals (DLCs) can be aligned within micrometer-scale channels formed from SU8 patterned on silicon or glass surfaces. The channels can be filled with the DLC in its isotropic phase using capillary action. Alignment occurs spontaneously as the sample is slowly cooled into the Colh phase. Whilst all of these DLCs align with the columns perpendicular to the surface when they are ‘sandwiched’ between glass slides, in these channels, the DLC aligns with the column director parallel to the surface. It is also constrained to lie across the channels. The same alignment occurs when these DLCs are confined between SU8-topped interdigitated gold electrodes where it gives the optimum orientation for electrode-to-electrode conduction. The quality of the alignment depends on the particular liquid crystal used and on the width of the channel. For the Colr phase of octaoctylphthalocyanine there is additional epitaxial control over the orientation of the lattice such that the a/c face of the lattice is parallel to the surface. This is an important prerequisite for creating a bistable display device that switches by virtue of changing the direction of the tilt of the discs.