Torsional Defects Research Articles

Treatment of rotational tibial malunion after minimal invasive plate osteosynthesis (MIPO): Corrective osteotomy with original plate retention (PR-Osteotomy)

Background and purposeResidual axial and rotational deformities in tibial shaft fracture, after minimally invasive osteosynthesis (MIO) treatment, are widely described in literature. Nevertheless, there is still a lack of evidence about the malunion treatment strategies and results. The aim of our study is to present an innovative technique for tibial shaft malunion: a derotational proximal tibial osteotomy without removing the original plate (Plate-Retaining-Osteotomy: PR-Osteotomy). Materials and methodsWe present the results of two consecutive patients’ treatment, affected by tibial shaft fracture malunion, as sequelae of MIO treatment. The two patients, male 60 years old and female 39 years old, underwent previous surgical treatment with an average of 9 months span time before surgical revision. The affected limb showed significant external torsional defect associated with gait impairment, pain and limping. The amount of rotational deformity and the bone healing condition is assessed through a methodical preoperative planning, including weight bearing lower limbs Xray and bilateral computed tomography (CT) scan of the lower limbs. The surgical technique involves a monoplanar tibial osteotomy, in a perpendicular fashion to the tibial axis, at a level that would allow at least 3 proximal screw-holes to become available for subsequent fixation. Proximal to the osteotomy line the screws are removed, while the distal ones, if stable after testing, are left in place. The amount of torsional correction, planned on CT, is reproduced intraoperatively with the assistance of graduated templates. A fibular osteotomy may be performed if required. After temporary stabilization, the correct functional reduction is checked with the aid of fluoroscopy and empirical rod measurement, using the contralateral limb alignment as a reference. Once the desired correction is achieved, absolute stability is applied to the osteotomy site. Postoperative rehabilitation protocol involves partial weight bearing for 6–8 weeks with progression to full weight bearing by 10–12 weeks. ResultsBoth patients showed complete osteotomy healing at the 13th and 16th week respectively, with no complications and full recovery of normal gait and daily life activities. ConclusionsTo our knowledge, this is the first description of such surgical technique. Less invasiveness, fast recovery time and cost reductions are the foremost proposed benefits. Further larger case series with longer follow up are needed to assess the advantages of the proposed treatment strategy.

Synergistic Effects of Carbon Vacancies in Conjunction with Phosphorus Dopant across Bilayer Graphene for the Enhanced Hydrogen Evolution Reaction.

Bilayer graphene (BLG) exhibits distinct physical properties under external influences, such as torsion and structural defects, setting it apart from monolayer graphene. In this study, we explore the synergistic effects of carbon vacancies, in conjunction with phosphorus dopants, across BLG, focusing on their impact on structural, magnetic, electrical, and hydrogen adsorption properties. Our findings reveal that the substitutional doping of a phosphorus atom into a single carbon vacancy in a graphene layer induces substantial structural distortion in BLG. In contrast, doping phosphorus into a double vacancy maintains the flat structure of graphene layers. These distinct layer structures affect the electron distribution and spin arrangement, leading to varied electronic configurations and intriguing magnetic behaviors. Furthermore, the presence of abundant unsaturated electrons around the vacancy promotes the capture and bonding of hydrogen atoms. Hydrogen adsorption on BLG results in substantial orbital hybridization, accompanied by significant charge transfer. The calculated Gibbs free energies for hydrogen adsorption on BLG range from -0.08 to 0.09 eV, indicating exceptional catalytic activity for the hydrogen evolution reaction. These findings carry implications for optimizing the properties of graphene layers, making them highly desirable for applications such as catalysis.

Trans-polyacetylene based organic spin valve for a multifunctional spin-based device: A first principle analysis

Carbon-based materials are the promising candidates for the design of multifunctional spintronic devices, owing to their fascinating inherent attributes such as the ballistic transport nature, long spin coherence time, etc. Here, we report the spin-dependent electron transport properties of a trans-polyacetylene channel sandwiched between two semi-infinite hydrogen-passivated zigzag graphene nanoribbon (ZGNR) electrodes within the framework of spin-polarized density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalisms. The proposed device exhibits an excellent spin-dependent transport behavior within the bias window of [-0.5 V, 0.5 V]. In parallel configuration (PC), the device offers an ideal spin filtration efficiency of almost 100% within the bias range of [-0.4 V, 0.4 V], and in antiparallel configuration (APC), it exhibits negative differential resistance (NDR), dual-spin rectification, and dual-spin filtration effects. Also, a high tunnel magnetoresistance (TMR) of 1.2× 10 5 % is achieved. To validate the aforementioned effects, the transmission spectra along with the area enclosed by the curve, eigenvalues, eigenstates, and quantum conductance have also been analyzed. In addition, the impact of hybridization and torsion defects on the spin-dependent transport phenomenon through trans-polyacetylene has been investigated. Furthermore, the modelled device is observed to exhibit the spin Seebeck effect in PC under the influence of temperature gradient. The proposed device may stand as a good contender for various spintronic and spin caloritronic applications. • First principle based analysis of a trans-polyacetylene based multifunctional spin-based device. • The device displays a perfect spin filtration efficiency and dual rectification effects. • A high tunnel magnetoresistance (TMR) of 1.2× 10 5 % is achieved. • Thermal Spin Seebeck and spin filtering effects are observed in the proposed model. • A potential candidate in the field of spintronic and spin caloritronic applications.

Computer-Aided Surgical Simulation through Digital Dynamic 3D Skeletal Segments for Correcting Torsional Deformities of the Lower Limbs in Children with Cerebral Palsy

Torsional deformities of the lower limb are common in children with cerebral palsy (CP)-determining gait problems. The mechanisms underlying transverse plane gait deviations arise from a combination of dynamic and static factors. The dynamic elements may be due to spasticity, contractures and muscle imbalances, while the static ones may result from excessive femoral anteversion, which decreases the efficiency of the hip abductors by reducing the muscular lever arms. A therapeutic approach has been identified in multi-level functional surgery for the lower limb. Treating the malalignments of the lower limb with femoral or tibial derotation provides optimal results, especially when supported by adequate biomechanical planning. This planning requires an integrated static-dynamic approach of morphological and functional evaluation, based on radiological measurements, physical examination and gait analysis. Instrumented gait analysis has been confirmed as essential in the evaluation and surgical decision making process for children affected by CP with transverse plane deformities. Computational simulations based on musculoskeletal models that integrate patient-specific CT morphological data into gait analysis can be used for the implementation of a surgical simulation system in pre-operative planning to test the possible effects of the different surgical treatment options on the torsional defects of the lower limbs. Recently, a computer-aided simulation process has been implemented in the preoperative planning of complex osteotomies for limb deformities in children. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software. The aim of this study is to integrate the patient-specific CT musculoskeletal model with morphological data and gait analysis data, with the personalized calculation of kinematic and kinetic parameters, which allow us to generate an “avatar” of the patient for a more in-depth evaluation of the gait abnormalities. The computational simulation platform proposed provides a realistic movable musculoskeletal model in a virtual environment, with the possibility of planning and monitoring the effects of virtual three-dimensional surgical corrections.

The effect of local random defects on the response of pantographic sheets

In the last decade, pantographic structures have attracted the attention of many scientists because of their exotic mechanical behaviors. Despite several studies conducted on this field, probabilistic remarks cannot be found in the literature. This paper aims to fill this gap by providing the first stochastic study on pantographic sheets. A new simplified procedure is proposed to investigate the effects of local axial, bending, and torsional defects on their mechanical responses. The suggested approach involves a generalization of an existing theoretical result and the use of Monte Carlo simulations to derive probability density functions, mean values, standard deviations, and coefficients of variation of the random kinematic unknowns. It, surely, can be applied to any mechanical system. The achieved results allow stating that pantographic structures are not particularly affected by local random defects thanks to their redundant and complex microstructures. Moreover, the interdependencies among their substructures, beams, and pivots, make it not easy to find the positions of defects that minimize, once fixed all the other things, the randomness of the mechanical responses. A minimization problem should be solved and a work on this topic is in progress.

Galactic dynamo seeds and black hole singularities driven by Einstein–Cartan QCD walls

Torsion spin polarised wall solution of Einstein–Cartan equations as torsion defects (Garcia de Andrade, Ann Phys 432 (2021)) where spin is distributed orthogonally to the wall has recently been obtained. Moreover, torsional inflating defect [Class and Quantum Gravity, 16 (1999) 2097] in the form of a dilatonic domain wall has also been found. Our goal in this paper is to obtain thin torsion wall solutions as teleparallel and Riemann–Cartan (RC) spacetime walls, with Einstein–Cartan stress–energy tensor, similar to Kalb–Ramond torsion fields. In thin teleparallel wall, we show that torsion is proportional to a time Dirac delta function which possesses a time singularity at the wall like Big Bang and black hole GR ones. This magnetic field has a torsional contribution of BQCD∼1017G in RC walls, which is suitable for dynamo amplification from a seed field of Bseed∼1012G as Big Bang Nucleosynthesis (BBN). From QCD cosmic time scale of tQCD∼10−6s torsion of the order of J0∼10−11cm−1 is obtained. From a 1 MeV torsion and seed field of Bseed∼10−32G, found by Barrow et al [PRD] in the framework of general relativity (GR) which is suitable to seed galactic dynamo field. In this case a domain wall magnetic field of BDW∼10−28G which is stronger, and more suitable as a galactic dynamo seed, is obtained. Magnetic field seed of 10−14G, quite close to orders of magnitude of O(10−15−10−18G) obtained by Atrayed et al. (EPJC (2018) 78: 1027) on a torsionless GR domain wall, generates a wall (DW) magnetic field of order of BDW∼1018G obtained at 1 kpc scales. These similarities between GR results and teleparallel one were expected due to the fact that the teleparallel theory of gravity considered in this paper is the teleparallel equivalent to GR or (TEGR). Chiral dynamos in dilatonic conformally flat metric are also discussed.

Optimization of the Forming Method on Torsion Defect in Cold-Roll Forming of Z Section Steel.

The knurling design is the basis of cold-roll forming, which is related to the subsequent roll design. It is also the basis to determine the roll pass. As a typical cross-section, Z-shaped steel is widely used in automobile, household appliance manufacturing, and building structure installation. However, torsion defects often occur in the cold-roll forming of Z-shaped steel, resulting in unqualified products that are unusable. The web deflection angle is a typical factor to affect the torsion defects in the cold-roll forming of Z-shaped steel. Therefore, it is necessary to discuss the influence of web deflection on the torsion of the Z-shaped steel. The web deflection angle optimized is determined by the result. According to the theoretical calculation, the best antitorsion angle is 32°, and the conjecture is proved by experiments. Also, we obtain the forming method optimized with the least torsion. This study could provide some guidance for the design of the process flow of cold-formed Z-beam.

Thermo-Magneto-Electric Transport through a Torsion Dislocation in a Type I Weyl Semimetal

Herein, we study electronic and thermoelectric transport in a type I Weyl semimetal nanojunction, with a torsional dislocation defect, in the presence of an external magnetic field parallel to the dislocation axis. The defect is modeled in a cylindrical geometry, as a combination of a gauge field accounting for torsional strain and a delta-potential barrier for the lattice mismatch effect. In the Landauer formalism, we find that due to the combination of strain and magnetic field, the electric current exhibits chiral valley-polarization, and the conductance displays the signature of Landau levels. We also compute the thermal transport coefficients, where a high thermopower and a large figure of merit are predicted for the junction.

Effect of Geometrical Factors on Torsion in Cold Roll Forming of the Lower Side Beam of a Car

Cold roll forming is a continuous metal forming process used to produce a large variety of profiles. A significant product of cold roll forming is asymmetric profiles, whose application is expanding in the construction of cars, houses, bridges, etc. Torsion is one of the common defects in the cold roll forming process of asymmetric section steel and sometimes seriously affects cold roll forming products. With the development of the economy and technology, many asymmetric cold roll-formed parts are being gradually applied to automobiles. Three-dimensional finite element analysis models of 12 stands with 700L sheet material were carried out using the professional COPRA RF and MSC MARC software, taking the lower beam of an automobile as the research object. Five geometric factors of the lower side beam were researched, and the influence rules of different geometric elements on the forming torsion were analyzed. We found that with the increase of web width, flange width, and vertical edge height and the decrease of the corner radius and strip thickness, the torsion defects of cold roll forming were improved to different degrees. The results also showed that the width of the flange has the most significant effect on torsion.

Magnetic monopole as a spacetime defect

We propose that the only possible realization of a magnetic pole is emergent, it being an artifact of a torsion defect in a curved spacetime. This special phase is built upon a class of degenerate metric spacetime solutions of first-order gravity in vacuum. The (apparent) magnetic charge is shown to have a topological origin, given by a lower-dimensional counterpart of the Nieh-Yan invariant. At the invertible metric phase at a distance, this topological charge gets reflected as the (magnetic) Reissner-Nordstr\"om charge to an asymptotic observer, even though the monopole defect itself remains hidden.

Hybridization and torsion defects influenced electron transport in trans-polyacetylene

The polymers are usually insulators by nature, however those with inherent conjugation take an exception, hence called conducting polymers . Trans-polyacetylene is a conducting polymer with a HOMO-LUMO gap comparable to the band gap of silicon semiconductor. Thus, this conducting plastic is been widely studied to gain a better understanding of its properties, so as to revolutionize various technological fields. In this work, we provide a comprehensive report of the transport phenomenon (electrical as well as thermal) through trans-polyacetylene conducting polymer in presence of hybridization and torsion defects. Moreover, in order to gain insights of the polymer behavior in real time device environment, it has been subjected to external tensile stress and studied for the transport properties. Our analysis revealed that this conducting polymer is very sensitive to hybridization and torsion defects, with about 66 times reduction in drive current for hybridization defect, while the torsion defect has caused a further current degradation by 1.45 times. The defects are observed to cause lesser degradation in thermal conductance in comparison to the electrical conductance. Interestingly, the simultaneous induction of hybridization and torsion defects in the polymer has resulted a negative differential resistance (NDR) effect. It has been observed that subjecting this polymer to external tensile stress not only reduces its stability but also greatly influences the drive current. • DFT based analysis of electronic and thermal transport behavior of modeled saturated and unsaturated linear organic molecular chains. • Variations in hybridization and geometrical torsion has been investigated for the pristine linear chain. • Structural deformation in carbon chain drastically decreases the thermal as well as electrical conductivities. • Study observes about 66 times reduction in drive current due to hybridization defect, and 1.45 times further reduction due to torsion defect. • As a result of external stress, the polymer shows degradation in the stability, as well as in drive current.

The Chemistry and Applications of Heteroisoindigo Units as Enabling Links for Semiconducting Materials.

ConspectusBecause of their low-temperature processing properties and inherent mechanical flexibility, semiconducting materials are promising candidates for enabling flexible displays, renewable energy, biological sensors, and healthcare. Progress has been made in materials performance by developing judicious materials design strategies. For example, improvements in electron transport have required new electron-deficient aromatics. Among them, isoindigo (IID) is an important functional group utilized in conjugated aromatics, where the structure combines two sets of five-membered electron-withdrawing lactam rings, exhibiting enhanced solubility, excellent chemical and thermal stabilities, broad absorption, and intriguing electron affinity.In the past decade, researchers have mainly focused on IID-based materials. However, the effect of heteroatom modification of the IID core has rarely been systemically investigated. In conventional conjugated polymers, single bonds connect the monomers, leading to energetic disorder and torsion defects, while ladder-type polymers are often intractable because of their fused nature. In this regard, the molecular design of new π scaffolds based on IID is central to the development of high-performance semiconductor polymers. Especially, a complete refresh of molecular design strategies and novel conjugated polymers with unique structures are needed to circumvent the disadvantages of the conventional ladder-type polymers.In this Account, we systematically summarize our recent progress in the design, synthesis, and structure-property relationships of IID- and particularly hetero-IID-based functional materials. More specifically, starting with molecular engineering of hetero-IIDs with variable electronic effects, conjugation lengths, and numbers of heterorings, we discuss the effect of the heteroring on the absorption spectra and energy levels. Additionally, we investigate a series of electron-withdrawing substitution of IIDs and hetero-IIDs and their molecular self-assembly behavior and the device performance. Furthermore, we discuss a series of IID-bis(EDOT) copolymers with hydrophilic ethylene glycol side chains for accumulation-mode organic thin-film electrochemical transistors, in which the relationships among the molecular structure, operational stability, film morphology, and device performance were revealed. Compared with IID polymers, the HOMO levels and optical band gaps of the thiophene and thienothiophene IID copolymers markedly decrease, and these polymers exhibit ambipolar charge transport. When we further expanded the IID core to a thieno[3,2-b][1]benzothiophene isoindigo (TBTI) core, such as in TBTIT, bulk-heterojunction solar cells employing this polymer class as the electron donor achieved good efficiency for additive- and annealing-free device conditions. When we introduced electron-deficient pyridine on the IID core, both the LUMO and HOMO energy levels of the copolymers markedly decreased, which significantly improved the electron mobility. In addition, we compare the correlation between the polymer structures of IID and hetero-IID copolymers with thiophene and benzothiophene as comonomers and their absorption spectra and energy levels. In particular, we evaluate the planarity and the dihedral angle between the repeat units, with systematic analysis by theoretical calculations to support our design concepts. We discuss polymer designs arising from simple aldol condensation, where the rigid backbone conformation has been locked by the double bonds. Our polymers display broad absorption from the visible to the NIR-II region, and more importantly, the high electron affinities of these polymers provide a platform to realize ambient-stable electron transport in solution-processed organic thin-film transistors. These exciting results are expected to open doors to new horizons of semiconducting materials in terms of other charming applications and the design and synthesis of superior materials.

First-principles description of intra-chain exciton migration in an oligo(para-phenylene vinylene) chain. II. ML-MCTDH simulations of exciton dynamics at a torsional defect

The first-principles parameterized Frenkel-Holstein Hamiltonian developed in Paper I [R. Binder et al., J. Chem. Phys. 152, 204119 (2020)] is employed to carry out full quantum-dynamical simulations of an elementary exciton migration event in an oligo-(para-phenylene vinylene) chain with 20 repeat units (OPV-20). We consider a dynamic scenario where an initial torsional defect, creating a conjugation break, relaxes on a time scale of about 500 fs toward a planarized structure and triggers the spatial displacement of the photogenerated exciton. Accurate quantum dynamical simulations are performed using the multi-layer multi-configuration time-dependent Hartree method as applied to an OPV-20 system comprising 20 electronic states of Frenkel type and 60 vibrational modes. These include site-local quinoid-distortion modes, site-correlated bond-length alternation (BLA) modes, and an active ring torsional mode at the central junction. The simulations fully account for correlations between the ring torsional mode and the anharmonically coupled BLA coordinate located at the same junction. In accordance with our earlier studies of a related oligothiophene (OT) system [R. Binder, D. Lauvergnat, and I. Burghardt, Phys. Rev. Lett. 120, 227401 (2018)], these simulation results highlight that exciton migration is a coherent process driven by the fluctuations of "soft" modes, exemplified by the ring torsions. Conversely, these results also show that trapping due to high-frequency modes, leading to energetic stabilization of the exciton-polaron species, is weaker in OPV than in the OT system. This underscores not only the generic features of exciton dynamics in conjugated polymer systems, but also the role of molecular specificities.

Unravelling the strain relaxation processes in silicon nanowire arrays by X-ray diffraction

Investigations performed on silicon nanowires of different lengths by scanning electron microscopy revealed coalescence processes in longer nanowires. Using X-ray diffraction (XRD), it was found that the shape of the pole figure in reciprocal space is ellipsoidal. This is the signature of lattice defects generated by the relaxation of the strain concentrated in the coalescence regions. This observation is strengthened by the deviation of the XRD peaks from Gaussianity and the appearance of the acoustic phonon mode in the Raman spectrum. It implies that bending, torsion and structural defects coexist in the longer nanowires. To separate these effects, a grazing-incidence XRD technique was conceived which allows the nanowire to be scanned along its entire length. Both ω and φ rocking curves were recorded, and their shapes were used to extract the bending and torsion profiles, respectively, along the nanowire length. Dips were found in both profiles of longer nanowires, while they are absent from shorter ones, and these dips correspond to the regions where both bending and torsion relax. The energy dissipated in the nanowires, which tracks the bending and torsion profiles, has been used to estimate the emergent dislocation density in nanowire arrays.

Conformational Heterogeneity in Large Macrocyclic Thiophenes.

For conjugated macrocycles, conformational disorder plays a key role in determining whether the unique form of excitons that are fully delocalized over the cyclic framework (cyclic excitons) is formed by photoexcitation. We have investigated the ring size dependence of conformations and photophysical properties of macrocyclic thiophenes of varying ring sizes (C-5NTNV) by using single-molecule fluorescence spectroscopy. We measured modulation depth, M, values and fluorescence intensities. As the ring size increases, the correlation plots of the two parameters show bimodal distributions, revealing that larger macrocycles exhibit extremely congested linear structures. The size dependence of structural changes in macrocyclic thiophenes have been clearly confirmed by molecular dynamics simulation. The number of torsional defects from simulated structures, in conjunction with survival times from fluorescence intensity trajectories and photon coincidence measurements, demonstrated the existence of multiple acyclic chromophores in the larger macrocycles from the ground state due to complete deformation of circular structures.

Manufacturing quality assurance for a rotate vector reducer with vibration technology

To improve the product quality of rotate vector (RV) reducer at a low cost, a kind of vibration technology is introduced to investigate the quality assurance of RV. It includes a torsional vibration test to assess the vibration performance of the reducer and vibration analysis to recognize the manufacturing defects in the reducer’s mechanical components. The mechanical components with manufacturing defects are diagnosed through the signal processing on torsional vibration and defect characteristics recognition, and they are removed from the RV reducer by a reassembling process. As a result, the dynamic behavior of the reducer is evidently improved, the torsional vibration of the reducer is kept within a low level, and the feedback control is realized for product quality during the production process. Therefore, the presented vibration technology is highly recommended to the manufacture quality assurance of RV reducers applied in an industrial robot.

The symmetrical quasi-classical approach to electronically nonadiabatic dynamics applied to ultrafast exciton migration processes in semiconducting polymers.

In the last several years, a symmetrical quasi-classical (SQC) windowing model applied to the classical Meyer-Miller (MM) vibronic Hamiltonian has been shown to be a simple, efficient, general, and quite-accurate method for treating electronically nonadiabatic processes at the totally classical level. Here, the SQC/MM methodology is applied to ultrafast exciton dynamics in a Frenkel/site-exciton model of oligothiophene (OT) as a model of organic semiconductor polymers. In order to keep the electronic representation as compact and efficient as possible, the adiabatic version of the MM Hamiltonian was employed, with dynamical calculations carried out in the recently developed "kinematic momentum" representation, from which site/monomer-specific (diabatic) excitation probabilities were extracted using a new procedure developed in this work. The SQC/MM simulation results are seen to describe coherent exciton transport driven by planarization of a central torsion defect in the OT oligomer as well as to capture exciton self-trapping effects in good agreement with benchmark quantum calculations using the multi-layer multiconfiguration time-dependent Hartree approach. The SQC/MM calculations are also seen to significantly outperform the standard Ehrenfest approach, which shows serious discrepancies. These results are encouraging, not only because they illustrate a significant further application of the SQC/MM approach and its utility, but because they strongly suggest that classical mechanical simulations (with the potential for linear scaling efficiency) can be used to capture, quantitatively, important dynamical features of electronic excitation energy transfer in semiconducting polymers.

Conformational Dynamics Guides Coherent Exciton Migration in Conjugated Polymer Materials: First-Principles Quantum Dynamical Study.

We report on high-dimensional quantum dynamical simulations of photoinduced exciton migration in a single-chain oligothiophene segment, in view of elucidating the controversial nature of the elementary exciton transport steps in semiconducting polymers. A novel first-principles parametrized Frenkel J aggregate Hamiltonian is employed that goes significantly beyond the standard Frenkel-Holstein Hamiltonian. Departing from a nonequilibrium state created by photoexcitation, these simulations provide evidence of an ultrafast two-timescale process at low temperatures, involving exciton-polaron formation within tens of femtoseconds (fs), followed by torsional relaxation on an ∼400 fs timescale. The second step is the driving force for exciton migration, as initial conjugation breaks are removed by dynamical planarization. The quantum coherent nature of the elementary exciton migration step is consistent with experimental observations highlighting the correlated and vibrationally coherent nature of the dynamics on ultrafast timescales.

Exciton Relaxation in Highly Rigid Conjugated Polymers: Correlating Radiative Dynamics with Structural Heterogeneity and Wavefunction Delocalization

Conjugated polymers are promising materials for solar cells and other electronic applications due to facile charge and electronic energy migration along the conjugated backbone. Torsional defects due to rotation around single bonds on the backbone are known to decrease the effective conjugation length of these materials, limiting their ability to shuttle charge and electronic energy. We investigated the radiative emission dynamics of a recently synthesized rigid conjugated ladder polymer (LP1) and nonrigid control (CP1) with a similar carbazole backbone moiety. LP1 was prepared using a recently reported synthesis under thermodynamic control, leading to a low backbone defect density. We find that the singlet emission lifetime of LP1 is longer than that of any previously reported ladder conjugated polymer, which we attribute to its low defect density. Further, the emission contains a large-amplitude long component with a lifetime that lasts as long as 5 ns. Our results imply that careful control of defects ...

Retinal Nerve Fiber Layer Damage in Young Myopic Eyes With Optic Disc Torsion and Glaucomatous Hemifield Defect.

To investigate retinal nerve fiber layer (RNFL) status at the opposite hemiretinas of optic disc torsion (ODT) in young myopic subjects with glaucomatous visual field (VF) defects and correlation between its thickness and VF defects using spectral-domain optical coherence tomography (SD-OCT). We assessed the frequency and characteristics of glaucomatous RNFL defects at the opposite hemiretinas of ODT location (ODT-unaffected hemiretinas) in 59 young myopic subjects presenting with glaucomatous VF defects confined to 1 hemifield, and compared the peripapillary RNFL thickness (pRNFLT) in ODT-unaffected hemiretinas of study eyes with that of 60 myopic controls without ODT using Cirrus HD SD-OCT. Linear regression analyses were performed between the pRNFLT measurements at ODT-unaffected hemiretinas and Humphrey field analyzer VF indices. Approximately 42% of study eyes with ODT showed glaucomatous RNFL defects at ODT-unaffected hemiretinas. The mean width of RNFL defects was significantly greater in ODT-affected hemiretinas than in ODT-unaffected hemiretinas (P<0.001). The mean pRNFLT in ODT-unaffected hemiretinas of study group (99.9±12.1 μm) was significantly lower than that in the matched hemiretinas of control group (109.8±14.9 μm; P<0.001). Significant correlations were observed between pRNFLT parameters and Humphrey field analyzer indices for each hemiretina with or without ODT in the study group. Young myopic eyes with ODT and hemifield VF loss often show glaucomatous RNFL defects at both hemiretinas and significantly lower pRNFLT in the ODT-unaffected hemiretinas compared with matched hemiretinas of control eyes. Greater VF loss is associated with more advanced pRNFT loss in ODT-unaffected hemiretinas.