Rotational Freedom Research Articles

Gauge Parameterization of the n-Field

We propose gauge parameterization of the three-dimensional $n$-field using orthogonal SO(3)-matrix which, in turn, is defined by a field taking values in the Lie algebra so(3) (rotational-angle field). The rotational-angle field has an additional degree of freedom, which corresponds to the gauge degree of freedom of rotations around the $n$-field. As a result, we obtain a gauge model with local SO(2)=U(1) symmetry that does not contain a U(1) gauge field.

Numerical Simulation of Fluid-Structure Interaction of D-shape Iced Conductor

At present, the numerical simulation on the aerodynamic response and force of the iced conductor are mainly based on the quasi steady criterion, which ignored the interaction between the conductor and the flow field. This paper presents a numerical study of three kinds of fluid-structure interaction models for D-shape conductor. The effects of reduced velocity, degree of freedom and wind attack angle on aerodynamic response of the iced conductor are discussed. The results show that the rotational freedom has certain influence on the across-wind vibration. The mean value of drag coefficient decreases with the increase of wind attack angle, while the lift and moment coefficient increase with the increase of wind attack angle. When the maximum amplitude of vibration displacement occurs, the corresponding reduced velocity is not entirely consistent with that of the maximum aerodynamic force.

IrIII as a strategy for preorganisation in H-bonded motifs

ABSTRACT We report how four sets of thiourea-based heterodimers interact, and how incorporation of a metal centre imparts reduced degrees of rotational freedom. Through single-crystal X-ray diffraction, 1H NMR, and UV-vis analysis, the interactions of these systems are dissected and presented. These motifs are considered to be stable and desirable for supramolecular hydrogen-bonded functional materials. Interpretation of the structural design of thiourea-based ligand and its incorporation into metal complexes can contribute to the understanding of preorganised self-assembly and open new pathways in design of novel soft materials. This work also contributes to the unexplored library of hydrogen-bonded metal complexes based on iridium. As such we examined the photoluminescence of the system of general formula [Ir(C^N)2(N^S)] and the effect of hydrogen bonding on the emission properties when combined with different n-heteroacenes.

Rotational Freedom, Steric Hindrance, and Protein Dynamics Explain BLU554 Selectivity for the Hinge Cysteine of FGFR4.

Aberration in FGFR4 signaling drives carcinogenesis and progression in a subset of hepatocellular carcinoma (HCC) patients, thereby making FGFR4 an attractive molecular target for this disease. Selective FGFR4 inhibition can be achieved through covalently targeting a poorly conserved cysteine residue in the FGFR4 kinase domain. We report mass spectrometry assays and cocrystal structures of FGFR4 in covalent complex with the clinical candidate BLU554 and with a series of four structurally related inhibitors that define the inherent reactivity and selectivity profile of these molecules. We further reveal the structure of FGFR1 with one of our inhibitors and show that off-target covalent binding can occur through an alternative conformation that supports targeting of a cysteine conserved in all members of the FGFR family. Collectively, we propose that rotational freedom, steric hindrance, and protein dynamics explain the exceptional selectivity profile of BLU554 for targeting FGFR4.

Titanium and Zirconia External Connection Abutments Produced Following a Digital Protocol: An In Vitro Study.

To assess the quality of precision at the implant-abutment interface of single-tooth restorations with titanium and zirconia abutments with hexagonal external connections produced using a digital protocol. A total of 20 abutments were produced with commercially pure titanium, and 20 abutments with zirconia, both following a necessary digital protocol. Rotational freedom of all the abutments was assessed. All data were analyzed according to procedures established by software package STATA 14.2. No significant differences relative to rotational freedom emerged between the two groups. This study showed that both types of abutments constantly demonstrated approximately 2 degrees of rotational freedom between implant and abutment where the hexagonal external connection was concerned.

Influence of the N,N,N-Trimethyl-1-adamantyl Ammonium Structure-Directing Agent on Al Substitution in SSZ-13 Zeolite

Structure-directing agents (SDAs) influence not only zeolite structures but also the distribution of Al on zeolite lattices. The origins of this Al-directing influence are not well understood. Here, we use first-principles methods to explore the interactions between an N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) OSDA and framework [AlO2]− in the dilute limit within an SSZ-13 lattice. Molecular dynamics and geometric and electronic structures illuminate the rotational freedom of TMAda+ OSDA within an SSZ-13 cage, the primarily electrostatic nature of its interactions with [AlO2]−, the effect of the solvent in screening the electrostatics, and the relative invariance of that interaction within a subset of Al locations within the same SSZ-13 major cavity. These results indicate that the Al distribution patterns observed in relevant SSZ-13 samples are not consequences of the location bias for Al substitution within a single TMAda+–cage complex but likely involve long-range electrostatics among multiple TMAd...

Insights into Kinesin-1 Stepping from Simulations and Tracking of Gold Nanoparticle-Labeled Motors

High-resolution tracking of gold nanoparticle-labeled proteins has emerged as a powerful technique for measuring the structural kinetics of processive enzymes and other biomacromolecules. These techniques use point spread function (PSF) fitting methods borrowed from single-molecule fluorescence imaging to determine molecular positions below the diffraction limit. However, compared to fluorescence, gold nanoparticle tracking experiments are performed at significantly higher frame rates and utilize much larger probes. In the current work, we use Brownian dynamics simulations of nanoparticle-labeled proteins to investigate the regimes in which the fundamental assumptions of PSF fitting hold and where they begin to break down. We find that because gold nanoparticles undergo tethered diffusion around their anchor point, PSF fitting cannot be extended to arbitrarily fast frame rates. Instead, camera exposure times that allow the nanoparticle to fully populate its stationary positional distribution achieve a spatial averaging that increases fitting precision. We furthermore find that changes in the rotational freedom of the tagged protein can lead to artifactual translations in the fitted particle position. Finally, we apply these lessons to dissect a standing controversy in the kinesin field over the structure of a dimer in the ATP waiting state. Combining new experiments with simulations, we determine that the rear kinesin head in the ATP waiting state is unbound but not displaced from its previous microtubule binding site and that apparent differences in separately published reports were simply due to differences in the gold nanoparticle attachment position. Our results highlight the importance of gold conjugation decisions and imaging parameters to high-resolution tracking results and will serve as a useful guide for the design of future gold nanoparticle tracking experiments.

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks.

We report the synthesis of five dicarboxylic acid-substituted dipolar molecular rotors for the use as linker molecules in metal-organic frameworks (MOFs). The rotor molecules exhibit very low rotational barriers and decent to very high permanent, charge free dipole moments, as shown by density functional theory calculations on the isolated molecules. Four rotors are fluorescent in the visible region. The linker designs are based on push–pull-substituted phenylene cores with ethynyl spacers as rotational axes, functionalized with carboxylic acid groups for implementation in MOFs. The substituents at the phenylene core are chosen to be small to leave rotational freedom in solids with confined free volumes. The dipole moments are generated by electron-donating substituents (benzo-1,3-dioxole, benzo-1,4-dioxane, or benzo-2,1,3-thiadiazole annelation) and withdrawing substituents (difluoro, or dicyano substitution) at the opposite positions of the central phenylene core. A combination of 1,4-dioxane annelation and dicyano substitution generates a theoretically predicted, very high dipole moment of 10.1 Debye. Moreover, the molecules are sufficiently small to fit into cavities of 10 Å3. Hence, the dipolar rotors should be ideally suited as linkers in MOFs with potential applications as ferroelectric materials and for optical signal processing.

Partitioning surface ligands on nanocrystals for maximal solubility

A typical colloidal nanoparticle can be viewed as a nanocrystal-ligands complex with an inorganic single-crystalline core, the nanocrystal, bonded with a monolayer of organic ligands. The surface chemistry of nanocrystal-ligands complexes is crucial to their bulk properties. However, deciphering the molecular pictures of the nonperiodic and dynamic organic-inorganic interlayer is a grand technical challenge, and this hampers the quantitative perception of their macroscopic phenomena. Here we show that the atomic arrangement on nanocrystal surface and ligand-ligand interactions can be precisely quantified through comprehensive solid-state nuclear magnetic resonance (SSNMR) methodologies. The analyses reveal that the mixed ligands of n-alkanoates on a CdSe nanocrystal segregate in areal partitions and the unique arrangement unlocks their rotational freedom. The mathematical model based on the NMR-derived ligand partition and dynamics successfully predicts the unusual solubility of nanocrystal-ligands complexes with mixed ligands, which is several orders of magnitude higher than that of nanocrystal-ligands complexes with pure ligands.

A Vision-Based Coordinated Motion Scheme for Dual-Arm Robots

With the rise of service robots, research on cooperation between two-arm robots has become increasingly important. In this paper, two NAO two-armed robots are used as the experimental platform and are combined with projective geometry, vision, robotics and other knowledge to carry out theoretical derivation and experiments on the coordinated movements of dual-arm robots. From the aspect of visual information processing, we analyse and solve the detailed target recognition process. Then, on this basis, we propose a set of complete coordinated motion control schemes. For object recognition, in this paper, we propose a highly adaptable linear stick recognition method. To solve the control flow of coordinated movement, we calculate the inverse kinematics of the unreachable pose of a single NAO manipulator by ignoring the degree of freedom of rotation around an end axis, and propose a trajectory planning method for the vertical constraint relationship between the tool and the workpiece plane in the coordinated manipulator movement. A comparison of the results of a simulation and a real experiment reveals that the trajectories of a workpiece clamped at the ends of the two robots’ mechanical arms are roughly the same; consequently, the coordinated control scheme proposed in this paper is feasible. Moreover, the scheme proposed in this paper is sufficiently accurate to meet service robot applications in daily life. Because the joint active clearance of the NAO robot arm is large and its sensor sensitivity is high, clearance change can be used in the future to replace the force sensor for hybrid control.

Diseño de Sistema de Posicionamiento de Sondas en Túnel de Viento

El presente trabajo trata sobre el diseño de un sistema de posicionamiento de sondas direccionales, denominado traverser, para realizar mapeos de estela detrás y alrededor de las maquetas. Para este fin los requerimientos del sistema son poder posicionar una sonda según los 3 ejes de referencia de la sección de ensayos del túnel de viento (XYZ) con una precisión inferior a 1mm. El posicionamiento de la sonda se diseño para que sea completamente automático y controlado desde la PC central, mediante software de desarrollo especifico. Se incluyó un grado de libertad adicional en rotación sobre el plano xy, de manera tal que pudiera posicionarse la sonda en un ángulo al plano de la maqueta.

Gaze stabilization in mantis shrimp in response to angled stimuli

Gaze stabilization is a fundamental aspect of vision and almost all animals shift their eyes to compensate for any self-movement relative to the external environment. When it comes to mantis shrimp, however, the situation becomes complicated due to the complexity of their visual system and their range of eye movements. The stalked eyes of mantis shrimp can independently move left and right, and up and down, whilst simultaneously rotating about the axis of the eye stalks. Despite the large range of rotational freedom, mantis shrimp nevertheless show a stereotypical gaze stabilization response to horizontal motion of a wide-field, high-contrast stimulus. This response is often accompanied by pitch (up-down) and torsion (about the eye stalk) rotations which, surprisingly, have no effect on the performance of yaw (side-to-side) gaze stabilization. This unusual feature of mantis shrimp vision suggests that their neural circuitry for detecting motion is radially symmetric and immune to the confounding effects of torsional self-motion. In this work, we reinforce this finding, demonstrating that the yaw gaze stabilization response of the mantis shrimp is robust to the ambiguous motion cues arising from the motion of striped visual gratings in which the angle of a grating is offset from its direction of travel.

Lateral Torsional Buckling of Steel Beams Elastically Restrained at the Support Nodes

The study shows the results of theoretical investigations into lateral torsional buckling of bisymmetric I-beams elastically restrained against warping and against rotation in the plane of lateral torsional buckling (i.e., against lateral rotation) at the support nodes. The analysis accounted for the whole variation range of node stiffnesses, from complete warping freedom to full restraint, and from complete lateral rotation freedom to full restraint. It was assumed the beams are simply supported against bending about the major axis of the section. To determine the critical moment, the energy method was used. Both the twist angle function and the lateral deflection function of the beam were described using power polynomials with simple physical interpretation. Computer programmes were developed to make numerical and symbolic “computations”. General approximation formulas for the critical moment for lateral torsional buckling were derived. The formulas covered the basic and most frequently found loading diagrams. Detailed computations were performed for different values of the index of fixity against warping and against rotation in the plane of lateral torsional buckling. The critical moments determined using the programmes devised and approximation formulas were compared with the values obtained with LTBeam software (FEM). A very good congruence of results was found.

On the Exploratory Road to Unraveling Factor Loading Non-invariance: A New Multigroup Rotation Approach

Multigroup exploratory factor analysis (EFA) has gained popularity to address measurement invariance for two reasons. Firstly, repeatedly respecifying confirmatory factor analysis (CFA) models strongly capitalizes on chance and using EFA as a precursor works better. Secondly, the fixed zero loadings of CFA are often too restrictive. In multigroup EFA, factor loading invariance is rejected if the fit decreases significantly when fixing the loadings to be equal across groups. To locate the precise factor loading non-invariances by means of hypothesis testing, the factors’ rotational freedom needs to be resolved per group. In the literature, a solution exists for identifying optimal rotations for one group or invariant loadings across groups. Building on this, we present multigroup factor rotation (MGFR) for identifying loading non-invariances. Specifically, MGFR rotates group-specific loadings both to simple structure and between-group agreement, while disentangling loading differences from differences in the structural model (i.e., factor (co)variances).

Design and Synthesis of Bridging Chiral p–t‐Butylcalix[4]arene Tetrahydroisoquinolines and Their Application in Henry Reaction as Chiral Organocatalysts

AbstractA pair of bridging chiral p‐t‐butylcalix[4]arenes (2a and 2b) (were) synthesized from 1 through homologous anionic ortho‐Fries rearrangement, and optically resolved with (1S)‐(+)‐10‐camphorsulfonyl chloride as chiral auxiliary. Bridging chiral p‐t‐butylcalix[4]arene tetrahydroisoquinolines (9a and 9b) as chiral organocatalysts for Henry reaction were designed and synthesized through the structural modification of 2a and 2b, respectively. Compared to the catalytic enantioselectivity of the unmodified tertiary amine (4b: ∼0% ee and 63% yield), those of the tetrahydroisoquinoline derivatives (9b: up to 13.4% ee and 96% yield) were distinctly enhanced. Although the increase magnitude of the catalytic ee is not remarkable, these catalytic results prove that the conformation inversion of calix[4]arene skeleton and the rotational freedom reduction of catalytic amine group indeed bring beneficial effects on the catalytic stereoselectivity.

Early Clinical and Radiological Outcomes of the Metaphyseally Fixed Totally Stabilized Knee Prosthesis in Primary Total Knee Arthroplasty.

The use of valgus-varus constrained (VVC) implant designs in primary total knee arthroplasty (TKA) is considered in situations of severe deformities, bone loss, and inadequate soft tissue balance. It is not known whether the use of such prosthesis designs may predispose to reduced function owing to its constraining design. The components are usually implanted with diaphyseal stem extensions to dissipate the increased forces. The totally stabilized (TS) implant is a contemporary VVC design with metaphyseal fixation only. It has a conforming articulation with increased rotational freedom compared with conventional VVC designs. The aim of this study was to assess whether the use of the contemporary TS implant with its metaphyseally fixed components would be associated with inferior outcomes compared with conventional standard primary posterior stabilized (PS) implants. We reviewed 38 consecutive complex primary TKAs performed using the metaphyseally fixed TS implant and 76 matched patients receiving primary PS TKA, at a minimum follow-up of 24 months. The mean follow-up was 61.1 months (24-102). Only patients with osteoarthritis were included. Clinical outcome was assessed using range of motion (ROM) and Oxford knee score (OKS). Radiographic assessment was performed using the femorotibial angle (FTA) at 6 weeks followed by assessment of bone-implant interface lucencies at final follow-up. There were no major early postoperative complications. The mean postoperative ROM in the TS and PS groups were 114.1 and 112.0, respectively. There was no difference in the mean ROM and OKS between the two groups. The mean FTA for patients in both groups was within 3° of the expected. There was no evidence of progressive lucencies or implant migration at final follow-up. The metaphyseally fixed TS knee design achieves comparable short-term functional outcomes when compared with conventional PS designs in primary knee arthroplasty. Long-term follow-up studies are required to assess survivorship.

A Cl- Hinge for Cyclen Macrocycles: Ionic Interactions and Tweezer-Like Complexes.

The supramolecular networks derived from the complexation of polyazamacrocycles with halide anions constitute fundamental building blocks of a broad range of modern materials. This study provides insights into the conformational framework that supports the binding of protonated cyclen macrocyles (1,4,7,10-Tetraazacyclododecane) by chloride anions through NHδ+···Cl− interactions. The isolated complex comprised of two cyclen hosts linked by one Cl− anion is characterized by means of infrared action spectroscopy and ion mobility mass spectrometry, in combination with quantum chemical computations. The Cl− anion is found to act as a hinge that bridges the protonated moieties of the two macrocycles leading to a molecular tweezer configuration. Different types of conformations emerge, depending on whether the trimer adopts an open arrangement, with significant freedom for internal rotation of the cyclen moieties, or it locks in a folded conformation with intermolecular H-bonds between the two cyclen backbones. The ion mobility collision cross section supports that folded configurations of the complex are dominant under isolated conditions in the gas phase. The IRMPD spectroscopy experiments suggest that two qualitatively different families of folded conformations coexist at room temperature, featuring either peripheral or inner positions of the anion with respect to the macrocycle cavities, These findings should have implications in the growth of extended networks in the nanoscale and in sensing applications.

Substituent Effects on the Patterns of Intermolecular Interactions of 3-Alkyl and 3-Cycloalkyl Derivatives of Phenytoin: A Crystallographic and Quantum-Chemical Study

A series of five derivatives of the anticonvulsant drug phenytoin was synthesized, and their crystal structures were determined. The relationship between the molecular and crystal structure of the investigated compounds was rationalized in the context of contribution of intermolecular interactions and supramolecular structural motifs. The conformational preferences were analyzed by comparing the rotational freedom of the phenyl groups in the investigated compounds with 5,5-diphenylhydantoins from the Cambridge Structural Database. With the exception of compound 3 bearing the cyclopropyl group, the crystal packing of the investigated compounds contains centrosymmetric dimers linked by paired N–H···O hydrogen bonds, which further self-organize through pairs of C–H···O interactions and a parallel interaction of two phenyl rings at a large offset into chains running along the c-axis. The principal feature of the crystal structure of compound 3 is formation of the chains by N–H···O hydrogen bonds and C–H···O and C–H···π interactions. The coordination of phenytoin enables more rotational freedom for the phenyl groups. An emphasis was placed on docking of the investigated compounds into the voltage-gated ion channel in the open and closed state. The obtained results indicate that hydrogen bonding and hydrophobic interactions are dominant in stabilizing energetically favored orientations of the investigated compounds bound to the protein.

Electrospinning of Ultrafine Poly(1-trimethylsilyl-1-propyne) [PTMSP] Fibers: Highly Porous Fibrous Membranes for Volatile Organic Compound Removal

Poly(1-trimethylsilyl-1-propyne) [PTMSP] possesses a rigid backbone chain with bulky trimethylsilyl side groups which limit the rotational freedom and provide packing-inefficiency that leads extrem...

Hybrid Growth Modes of PbSe Nanocrystals with Oriented Attachment and Grain Boundary Migration.

The growth of nanocrystals has widely been researched recently through an in situ high‐resolution transmission electron microscopy technique, which reveals the process of morphological and structural evolutions. For nanocrystals, the underlying growth modes are mostly determined by growth environment and crystal morphology. Here, the direct growth process of the PbSe nanocrystals via controlling the temperature is clearly observed. The results show that the PbSe nanocrystals start growth following oriented attachment growth mode, and then change to growth with grain boundary migration at moderate temperature as the heat activated nanocrystals gather together with decreased degree of freedom for crystal rotation. During the grain boundary migration, the smaller nanocrystals are inclined to be assimilated by larger ones through interfacial atom reconfigurations, which are observed to take place through strain mediated atom migration. The growth mode changes in different growth states with a hybrid growth mode of oriented attachment and grain boundary migration during the whole growth process.