Large Torsion Angle Research Articles

Nonlinear Model for LTB Prediction of RHS Beams Under Combined Axial and Bending Loads With Distortional Deformation Allowed

ABSTRACTThe aim of the present study is to develop an efficient and accurate analytical model for the lateral torsional buckling (LTB) prediction of RHS beams. To this end, a coherent nonlinear geometric theory is formulated assuming large torsion angles. This theory is based on a new kinematic model that incorporates the distortion deformations in addition to the bending and torsion ones. Ritz's method is employed to discretize the governing equilibrium equations basing on trigonometric shape functions, and then the eigenvalue problem is defined according to the fundamental state. The Buckling loads are obtained by imposing the singularity condition of the tangential stiffness matrix. The numerical investigation is carried out to prove the accuracy of the proposed model in LTB load evaluation, when compared with the nonlinear shell finite element simulation using Abaqus software. The numerical results reveal that the classical linear models associated with moderate torsion angles, such as those provided by Generalized Beam Theory (GBT) and the classical eigenvalue shell finite element method, tend to underestimate the correct value of LTB loads of simply supported RHS beams. In accordance with linear and non‐linear models, the numerical study is focused on the impact of load height, intensity of introduced compressive load and section ratio b/h in the LTB loads prediction.

Deepening insights of AIE plus TICT activated fluorescent sensor mechanism in probe molecule DPA-CI

The DPA-CI molecule is a novel fluorescent sensing probe synthesized with TICT and AIE properties. It can detect phosgene, generating DPA-CI-PS. We investigated their photophysical mechanisms in THF solvent using DFT and TD-DFT methods. Large torsion angles and noticeable charge separation confirmed that the TICT occurs in DPA-CI. Due to the formation of a robust cyclic structure, the TICT is inhibited in DPA-CI-PS. Besides, based on NBO analysis, we demonstrated that DPA-CI-PS exhibits significant AIE characters. This work clearly illuminates the detection mechanism, which offers theoretical insights valuable for developing efficient fluorescent sensing probes.

Seismic response analysis of frame structures with uneven settlement of foundation considering soil-structure interaction

Uneven settlement of foundation (USF) has a significant effect on the seismic response of rigid foundation structures. However, the main reason for USF is that the balance between superstructure and site soil is failure. For investigating seismic response characteristics of the USF structure considering soil-structure interaction (SSI), USF closer to reality is achieved by nonlinear direct integration method and Stage-Construction method. And the model reliability is verified by Sway-Rocking model and Lagrange energy method. Five different models, three seismic intensities, and different values of USF are performed. The natural period, inter-story drift ratios, the plastic hinges rate, and torsional angles are extracted to investigate structural seismic response. The results show that the effect of SSI on the magnitude of increase in structural inter-story drift ratio is not monotonous with the increase of USF in the presence of earthquakes. The USF structure considering SSI may significantly affect its seismic response, and will suffer more structural damage compared to the rigid foundation and the even settlement foundation. The rigid foundation structure with large value of USF leads to severe stretching on the settlement area and increases damage to the structure. Finally, the USF structures have relatively large torsional angles at the top story, and will exhibit significant torsional behavior. Hence, it is necessary and reasonable to consider SSI in the seismic design of USF structures. The research results can provide some references for seismic design.

Exploration of violet-to-blue thermally activated delayed fluorescence emitters based on "CH/N" and "H/CN" substitutions at diphenylsulphone acceptor. A DFT study.

The violet-to-blue thermally activated delayed fluorescence (TADF) emitters were created employing several substituents based on 5,5-dimethyl-5,10-dihydropyrido [2,3-b][1,8] naphthyridine-diphenylsulphone (DMDHPN-DPS) called 1a via "CH/N" and "H/CN" substitutions at the diphenylsulphone acceptor (DPS) moiety. The parent compound 1a was selected from our former work after extensive research employing "CH/N" substitution on Dimethyl-acridine (DMAC) donor moiety. There is a little overlap amid the highest occupied molecular orbitals (HOMOs) and lowest un-occupied molecular orbitals (LUMOs) due to the distribution of HOMOs and LUMOs primarily on the DMDHPN donor and the DPS acceptor moieties, respectively. It resulted in a narrower energy gap (∆E ST) between the lowest singlet (S1) and triplet (T1) excited state. In nearly all derivatives, the steric hindrance results in a larger torsional angle (85°-98°) between the plane of the DMDHPN and the DPS moieties. The predicted ΔE ST values of the compounds with "H/CN" substitution were lower than those of the comparable "CH/N" substituents, demonstrating the superiority of the reversible inter-system crossing (RISC) from the T1 → S1 state. All derivatives have emission wavelengths (λ em) in the range of 357-449nm. The LUMO → HOMO transition energies in the S1 states are lowered by the presence of -CN groups or -N = atoms at the ortho or meta sites of a DPS acceptor unit, causing the λ em values to red-shift. Furthermore, the λ em showed a greater red-shift as there were more-CN groups or -N = atoms. Three of the derivatives named 1b, 1g, and 1h, emit violet (394nm, 399nm, and 398nm, respectively), while two others, 1f and 1i, emit blue shade (449nm each) with reasonable emission intensity peak demonstrating that these derivatives are effective violet-to-blue TADF nominees. The lower ΔE ST value for derivative 1i (0.01eV) with λ em values of 449nm make this molecule the finest choice for blue TADF emitter amongst all the studied derivatives. We believe our research might lead to the development of more proficient blue TADF-OLEDs in the future.

One-pot Synthesis of Helical Azaheptalene and Chiroptical Switching of an Isolable Radical Cation.

A nitrogen-centered heptalene, azaheptalene, was designed as a representative of a new class of redox-responsive molecules with a large steric strain that originates from the adjacent seven-membered rings. The pentabenzo derivative of azaheptalene was efficiently synthesized by a palladium-catalyzed one-pot reaction of commercially available reagents. Bromination led to mono- and dibrominated derivatives, the latter of which is interconvertible with isolable radical cation species exhibiting near-infrared absorption. Since the azaheptalene skeleton shows configurationally stable helicity with a large torsion angle, enantiomers could be successfully separated. Thus, optically pure azaheptalenes with P- or M-helicity showed strong chiroptical properties (|gabs| ≥ 0.01), which could be changed by an electric potential.

Realization of Pyreno[4,5-d]imidazole-based HLCT emissions through tuning the energy level of the charge-transfer state

Organic light-emitting diodes (OLEDs) have lately been used in tablet displays, for instance in mobile phones and televisions, and are considered to be the next generation of displays and solid-state lighting due to their light weight, high flexibility, and energy efficiency. Hybridized local and charge-transfer (HLCT) excited state fluorophores, capable of making full use of excitons by reverse intersystem crossing from high-lying triplet states to singlet states, have drawn increasing attention in OLED applications. The HLCT state can be efficiently achieved by constructing D-π-A type molecules, whose characteristics of their excited state are widely influenced by the difference of torsion angles between donor (D) and acceptor (A). Herein, pyreno[4,5-d]imidazole and triphenylamine were selected as the electron acceptor and electron donor, respectively. Based on this molecular design, two D-π-A type molecules, pTPA-PyI and mTPA-PyI were designed and synthesized with different torsion angles between D and A. In addition, the introduction of fluorine atoms in molecules could provide more and stronger charge transfer (CT) state components into the excited states of the molecule, which could facilitate the formation of HLCT states with improving exciton utilization of the molecule. As a result, pTPA-PyI with linear molecular geometry possessed HLCT properties, which could achieve a large yield of singlet exciton formation. The non-doped pTPA-PyI-based OLED demonstrated steady blue emission with a peak at 460 nm and CIE coordinates of (0.15, 0.20). The highest current efficiency was 7.7 cd A−1, the maximum brightness was 48637 cd m−2, and the external quantum efficiency (EQE) was 6.38%. When the brightness was 1000 cd m−2, the efficiency roll-off was incredibly low as 0.6%, yet the EQE of 6.34% was still achievable. Additionally, it possesses a high exciton-utilization efficiency of up to 97%. However, the locally excited (LE) and CT states of mTPA-PyI could not sufficiently hybridize due to its larger torsion angle between D and A with the smaller dipole moment and the interrupted conjugation structure of the molecule which led to high energy level of CT state. As a result, by altering the torsion angle between D and A, it is feasible to change the constituents and levels of the LE and CT states in order to actualize the HLCT feature.

Colorless polyimides derived from rigid trifluoromethyl-substituted triphenylenediamines

Colorless polyimides (CPIs) have wide applications in flexible photoelectric devices, thanks to their high transparency and heat-resistance. Herein, three rigid aromatic triphenylenediamine monomers containing varied number and position of trifluoromethyl (-CF3) substituents, i.e., c-3FTP, c-6FTP, and s-6FTP, were designed. The corresponding CPI films were fabricated by polycondensation with the commercial 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) or 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA). Due to the steric hindrance of –CF3 groups, three diamines all exhibit large torsion angles within 46.1°–87.1° between benzene rings determined via single crystal analysis. The structure-property analysis reveals that –CF3 substitution located on the central phenyl ring facilitates the high glass transition temperature (Tg), while more –CF3 substitutions are beneficial for high optical transparency. Among all the CPIs, the 6FDA/c-6FTP film exhibits the most remarkable balance in thermal, optical, and dielectric properties, including high thermal resistance (Tg = 385 °C, Td5% = 537 °C), excellent optical transparency (λcutoff = 350 nm, T450 = 84.5%, and b* = 1.44), low dielectric nature (Dk = 2.84, Df = 0.0053) at 10 GHz, and high surface hydrophobicity (θ = 100°, WH2O = 0.25%). This systematic study would complement the basic structure-property relationship of aromatic CPIs and inspire rational development of high-performance aromatic CPI materials toward applications in flexible display or 5G technology.

An ultramicroporous pillar-layer metal-organic framework for high sieving separation of ethylene from ethane

Developing new techniques and materials for ethylene (C2H4) and ethane (C2H6) separation is an industrially significant but challenging task. Here we report two isoreticular pillar-layer metal-organic frameworks, Co(aip)(bpy)0.5 and Co(aip)(pyz)0.5, for the separation of C2H4/C2H6. The pore apertures of the pillar-layer metal-organic frameworks are rationally controlled by changing the length of the pillar ligands. Significantly, Co(aip)(pyz)0.5 with a shorter pillar ligand shows reduced pore size and molecular sieving separation of C2H4 from C2H6. Co(aip)(pyz)0.5 has a moderate C2H4 capacity of 1.78 mmol/g but ultrahigh C2H4/C2H6 selectivity exceeding 2000 at ambient conditions. The molecular simulation revealed that large torsion angle between the organic linker plane and Co–O bond leads to the high energy barrier for C2H6 to enter into the pore, which results in the molecular sieving separation of C2H4/C2H6. Dynamic breakthrough experiments confirmed the high selectivity of Co(aip)(pyz)0.5 for C2H4. And high-purity C2H4 (>97%) with a C2H4 productivity of 19.1 l/kg can be obtained through the desorption process. Meanwhile, the excellent reusability and moisture stability endow it great potential for applications in adsorptive separation.

Benzoxazole-Based Hybridized Local and Charge-Transfer Deep-Blue Emitters for Solution-Processable Organic Light-Emitting Diodes and the In fluences of Hexahydrophthalimido.

Hybridized local and charge-transfer (HLCT) emitters have attracted extensive attention, but the insolubility and severe self-aggregation tendency restrict their applications in solution-processable organic light-emitting diodes (OLEDs), particularly deep-blue OLEDs. Herein, two novel benzoxazole-based solution-processable HLCT emitters (BPCP and BPCPCHY) are designed and synthesized, in which benzoxazole acts as an acceptor, carbazole acts as a donor, and hexahydrophthalimido (HP, with a large intramolecular torsion angle and spatial distortion characteristics) acts as a bulky modified end-group with weak electron-withdrawing effects. Both BPCP and BPCPCHY exhibit HLCT characteristics and emit near ultraviolet in toluene at 404 and 399 nm. Compared to the BPCP, the BPCPCHY solid shows much better thermal stability (Tg, 187 vs 110 °C), higher oscillator strengths of the S1-to-S0 transition (0.5346 vs 0.4809), and faster kr (1.1 × 108 vs 7.5 × 107 s-1) and thus a much higher ΦPL in the neat film. The introduction of HP groups greatly suppresses the intra-/intermolecular charge-transfer effect and self-aggregation trends, and the BPCPCHY neat films placed in air for 3 months can still maintain an excellent amorphous morphology. The solution-processable deep-blue OLEDs utilizing BPCP and BPCPCHY achieved a CIEy of 0.06 with maximum external quantum efficiency (EQEmax) values of 7.19 and 8.53%, respectively, which are among the best results of the solution-processable deep-blue OLEDs based on the "hot exciton" mechanism. All of the above results indicate that benzoxazole is an excellent acceptor for constructing deep-blue HLCT materials, and the strategy of introducing HP as a modified end-group into an HLCT emitter provides a new perspective to develop solution-processable efficient deep-blue OLEDs with high morphological stability.

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

Mitochondria‐Targeting Phototheranostics by Aggregation‐Induced NIR‐II Emission Luminogens: Modulating Intramolecular Motion by Electron Acceptor Engineering for Multi‐Modal Synergistic Therapy

AbstractPhototheranostic agents have thrived as promising tools for cancer theranostics because of the integration of sensitive in situ fluorescence imaging and effective multi‐model synergistic therapy. However, how to manipulate the intangible photon energy transfer to balance the competitive radiative and nonradiative processes is still challenging. Although numerous phototheranostic molecules are reported, their complicated molecular design and tedious synthesis often stumble further their development. Herein, three simple molecules with electron donating−accepting structures are developed. The electron acceptor engineering on molecules by introducing acridinium unit gives rise to TPEDCAc with aggregation‐induced second near‐infrared emission (AIE NIR‐II), high reactive oxygen species generation capability, and excellent photothermal conversion efficiency (44.8%) due to the drastic intramolecular motion of large acridinium rotor and balanced AIE effect. Experimental analysis and calculation on the controlled molecules suggested that large torsional angle and the strong electron‐withdrawing ability of the acridinium unit are keys for NIR‐II emission and balanced photodynamic/photothermal conversion. Impressively, the positively charged TPEDCAc shows mitochondria‐targeting capability and high performance in in vivo multi‐modal cancer theranostics under NIR laser irradiation. Hence, this work not only provides a single NIR‐II AIE‐based multi‐modal cancer theranostic system but inspires new insights into future development of new theranostic platforms.

Curvature of the Retroviral Capsid Assembly Is Modulated by a Molecular Switch.

During the maturation step, the retroviral capsid proteins (CAs) assemble into polymorphic capsids. Their acute curvature is largely determined by 12 pentamers inserted into the hexameric lattice. However, how the CA switches its conformation to control assembly curvature remains unclear. We report the high-resolution structural model of the Rous sarcoma virus (RSV) CA T = 1 capsid, established by molecular dynamics simulations combining solid-state NMR and prior cryoelectron tomography restraints. Comparing this with our previous model of the RSV CA tubular assembly, we identify the key residues for dictating the incorporation of acute curvatures. These residues undergo large torsion angle changes, resulting in a 34° rotation of the C-terminal domain relative to its N-terminal domain around the flexible interdomain linker, without substantial changes of either the conformation of individual domains or the assembly contact interfaces. This knowledge provides new insights to help decipher the mechanism of the retroviral capsid assembly.

Biradicaloid Behavior of a Twisted Double Bond.

A compound with a highly twisted C═C bond in the intermediate bond dissociation region was isolated, and its biradicaloid nature was experimentally demonstrated. A bianthrone derivative substituted with long-chain alkoxy groups was synthesized, and its twisted conformer was assembled into crystals through hydrophobic intermolecular interactions of the introduced alkoxy chains. X-ray crystallography revealed that the C═C bond connecting the two anthrone rings has a long bond length (1.429 Å) and a large torsional angle (57.33°). In addition, ESR studies revealed that the twisted bianthrone has biradicaloid character with a small singlet-triplet energy gap of 23.8 kJ mol-1. The thermally excited triplet species were observed in the ESR spectrum as distinct fine structures along with a ΔMS = ±2 forbidden transition.

Giant Conductance Enhancement of Intramolecular Circuits through Interchannel Gating

Summary For neutral intramolecular circuits with two constitutionally identical branches, a maximum 4-fold increase in total conductance can be obtained according to constructive quantum interference (CQI). For charged intramolecular circuits, however, the strong electrostatic interactions entangle the quantum states of these two parallel pathways, thus introducing complicated transport behavior that warrants experimental investigation of the intramolecular circuit rules. Here, we report that a tetracationic cyclophane with parallel channels exhibits a 50-fold conductance enhancement compared with that of a single-channel control, an observation that supplements intramolecular circuit law in systems with strong Coulombic interactions. Flicker noise measurements and theoretical calculations show that strong electrostatic interactions between charged parallel channels—serving as the chemical gate to promote the effective conductance of each channel—and CQI boosts the total conductance of the two-channel circuit. The molecular design presented herein constitutes a proof-of-principle approach to charged intramolecular circuits that are desirable for quantum circuits and devices.

Violet/deep-blue fluorescent organic light-emitting diode based on high-efficiency novel carbazole derivative with large torsion angle

A novel and highly efficient violet/deep-blue fluorescent carbazole and naphthalene-based compound (1) is designed and synthesized. The compound shows intensive violet/deep-blue fluorescence, high photoluminescence efficiency (0.72 in CH2Cl2, 0.65 in film) and narrow full width at half maximum (48 nm). The large torsion angles between carbazole and naphthalene guarantee the weak intermolecular interactions and suppress the π-π interactions in solid state, resulting in the highly efficient violet/deep-blue fluorescence. The maximum emission peak, luminance and external quantum efficiency for violet/deep-blue electroluminescence are 410 nm, 1326 cd/m2 and ∼2%, respectively.

Influence of Backbone Chlorination on the Electronic Properties of Diketopyrrolopyrrole (DPP)-Based Dimers.

Chlorination of π-conjugated backbones is garnering great interest because of fine-tuning electronic properties of conjugated materials for organic devices. Herein we report a synthesis of thiophene-based diketopyrrolopyrrole (DPP) dimers and their chlorinated counterparts by introducing a chlorine atom in the outer thiophene ring to investigate the influence of the chlorination on charge transport. The backbone chlorination lowers both the HOMO and the LUMO of the dimers and leads to a blue-shift of maximum absorption in compared to unsubstituted counterparts. X-ray analysis reveals that the chlorine atom prompts the outer thiophene ring out of the planarity of the backbone with a relatively large torsional angle. The chlorinated dimers exhibit slipped one-dimensional packing decorated with multiple intermolecular interactions, because of a combination of a negative inductive effect and a positive mesomeric effect of the halogen atom, which might facilitate charge transport within the oligomeric backbones. The mobility in the single-crystal OFET devices of the chlorinated dimers is up to 1.5 cm2 V-1 s-1 , which is two times higher than that of the non-chlorinated DPP dimers. Our results indicate that the chlorine atom plays a key role in directing non-covalent interactions to lock the slipped stacks, enabling electronic coupling between adjacent molecules for efficient charge transport. In addition, our results also demonstrate that these DPP dimers with straight n-octyl chains exhibit higher mobilities than the dimers with branched 2-ethylhexyl chains.

Comparison of Structural and Optical Properties for N‐Embedded Polycyclic and Non‐Embedded Cationic Phosphorescent Iridium(III) Complexes

We designed and synthesized N‐embedded polycyclic based cationic iridium(III) complex Ir‐NO and non‐embedded complexes Ir‐N and Ir‐O. Single crystal structures indicate that the N‐embedded polycyclic unit in Ir‐NO exhibits a certain planarity and induces two interesting π–π‐stackings between 2,2′‐bipyridine moieties of one molecule and two polycyclic units of the other molecule, and their shortest intermolecular distances are both 3.24 Å, which results in a stronger structural distortion of the 2,2′‐bipyridine ligand with a larger torsion angle (12.70°) in comparison with those of Ir‐N (5.51°) and Ir‐O (8.11°). Unpredictably, both Ir‐N and Ir‐O show deep red emission in solution, whereas Ir‐NO exhibits no emission. However, all complexes show significant luminescence in their respective polystyrene (PS) films, and Ir‐NO displays a longer emission lifetime than those of Ir‐N and Ir‐O. DFT calculations reveal that unusual ligand‐to‐metal charge transfer (3LMCT) excited state character can be found in Ir‐NO and Ir‐N, which is in contrast to the metal‐to‐ligand charge transfer (3MLCT) excited state observed in Ir‐O.

Rotational Malalignment of the Knee Extensor Mechanism: Defining Rotation of the Quadriceps and Its Role in the Spectrum of Patellofemoral Joint Instability.

Background:Osseous rotational malalignment of the lower limb is widely accepted as a factor contributing to patellofemoral instability, particularly in pediatric patients. Patellar instability occurs when the lateral force vector generated by the quadriceps exceeds the restraints provided by osseous and soft-tissue anatomy. The anatomy and activation of the quadriceps are responsible for the force applied across the patellofemoral joint, which has previously been measured using the quadriceps (Q)-angle. To our knowledge, the contribution of the quadriceps anatomy in generating a force vector in the axial plane has not previously been assessed. The primary aim of this study was to introduce the quadriceps torsion angle, a measure of quadriceps rotational alignment in the juvenile population. The secondary aims of this study were to determine the inter-assessor and intra-assessor reliability of the quadriceps torsion angle in the juvenile population and to investigate whether a large quadriceps torsion angle is a classifier of patellar dislocator group membership in a mixed cohort of patellar dislocators and typically developing controls.Methods:Participants between the ages of 8 and 19 years were recruited as either controls or recurrent patellar dislocators. A total of 58 knees in both groups were assessed from magnetic resonance imaging scans of the entire lower limbs. Axial cuts midway between the superior aspect of the femoral head and the articular surface of the medial femoral condyle were used to calculate the proximal reference for the quadriceps torsion angle. The quadriceps torsion angle was defined as the angle between the line connecting the anterior aspect of the sartorius and the junction of the anterior and posterior compartments at the lateral intermuscular septum and the posterior condylar axis line. Inter-assessor reliability was calculated using the intraclass correlation coefficient. The relationship between the quadriceps torsion angle and the femoral torsion was assessed in the entire cohort. These values were compared between the control group and the dislocator group to determine if the raw values or an interplay between the 2 factors played a role in the pathoanatomy of recurrent patellofemoral dislocation.Results:The quadriceps torsion angle was a reproducible assessment in both inter-assessor and intra-assessor reliability analyses. A moderate positive correlation (r = 0.624; p < 0.01) was found between the femoral torsion and the quadriceps torsion angle. Although the quadriceps torsion angle was a fair classifier of patellar dislocation group membership, femoral torsion was not.Conclusions:This study has quantified the rotational alignment of the extensor mechanism using the quadriceps torsion angle. The measurement is shown to be reliable and reproducible and a fair classifier of patellofemoral instability.Clinical Relevance:This article introduces an objective measure of soft-tissue rotational malalignment in the pathogenesis of recurrent patellar dislocation.

Parametric Investigation of Dual‐Mass Flywheel Based on Driveline Start‐Up Torsional Vibration Control

This paper is aimed to investigate the influence of dual‐mass flywheel (DMF) kinetic parameters on driveline torsional vibration in engine start‐up process, which prescribes the design requirements under start‐up condition for DMF matching. On the basis of driveline excitation analysis during engine start‐up, the analytical model of DMF driveline torsional vibration system is built and simulated. The vehicle start‐up test is conducted and compared with the simulation results. On account of the partial nonstationary characteristic of driveline during start‐up, the start‐up process is separated into 3 phases for discussing the influence of DMF rotary inertia ratio, hysteresis torque, and nonlinear torsional stiffness on attenuation effect. The test and simulation results show that the DMF undergoes severe oscillation when driveline passes through resonance zone, and the research model is verified to be valid. The DMF design requirements under start‐up condition are obtained: the appropriate rotary inertia ratio (the 1st flywheel rotary inertia‐to‐the 2nd flywheel rotary inertia ratio) is 0.7∼1.1; the interval of DMF small torsion angle should be designed as being with small damping, while large damping is demanded in the interval of large torsion angle; DMF should be equipped with low torsional stiffness when working in start‐up process.