Rigid Groups Research Articles

Pilot study of oblique lumbar interbody fusion using mobile percutaneous pedicle screw and validation by a three-dimensional finite element assessment

The purpose of this study was to try oblique lateral interbody fusion (OLIF) using percutaneous pedicle screws (PPS) with mobility.Twelve patients who underwent single-level OLIF were observed for at least one year. These included 6 patients with conventional PPS (rigid group), and 6 with movable PPS (semi-rigid group). Mobile PPS used cosmicMIA, which is a load sharing system. The anterior and posterior disc height, screw loosening and bone healing period, and implant failure were evaluated at final observation by CT. Moreover, the stress on the vertebral body-cage, on the vertebral body-screw/rod and on the bone around the screw was estimated using a three-dimensional finite element assessment in both groups.There was no significant difference in surgical time, amount of bleeding, JOA score, or low back pain VAS between groups. There were no differences between groups in anterior and posterior disc height, screw loosening, and implant failure at final observation. The bone healing period was significantly shorter in the semi-rigid screw group (18.3 months vs 4.8 months, p = 0.01). The finite element analysis showed that the lower stress on the rod/screw would contribute to fewer implant fractures and that lower stress on the bone around the screw would reduce screw loosening, and that higher compressive force on the cage would promotes bone healing.OLIF combined with a movable screw accelerated bone healing by nearly 75%. We conclude that mobile PPS in combination with OLIF promotes bone healing and can be a better vertebral fusion technique.

Rigid group actions on complex tori are projective (after Ekedahl)

In this paper, we give a detailed proof of a result due to Torsten Ekedahl, describing complex tori admitting a rigid group action and showing explicitly their projectivity and their structure in terms of CM-fields. In the appendix, joint with Claudon, we show, using a method of Green-Voisin, that all group actions on complex tori deform to projective ones.

Bridging and Conformational Control of Porphyrin Units through Non-Traditional Rigid Scaffolds.

Connecting two porphyrin units in a rigid linear fashion, without any undesired electron delocalization or communication between the chromophores, remains a synthetic challenge. Herein, a broad library of functionally diverse multi‐porphyrin arrays that incorporate the non‐traditional rigid linker groups cubane and bicyclo[1.1.1]pentane (BCP) is described. A robust, reliable, and versatile synthetic procedure was employed to access porphyrin‐cubane/BCP‐porphyrin arrays, representing the largest non‐polymeric structures available for cubane/BCP derivatives. These reactions demonstrate considerable substrate scope, from utilization of small phenyl moieties to large porphyrin rings, with varying lengths and different angles. To control conformational flexibility, amide bonds were introduced between the bridgehead carbon of BCP/cubane and the porphyrin rings. Through varying the orientation of the substituents around the amide bond of cubane/BCP, different intermolecular interactions were identified through single crystal X‐ray analysis. These studies revealed non‐covalent interactions that are the first‐of‐their‐kind including a unique iodine‐oxygen interaction between cubane units. These supramolecular architectures indicate the possibility to mimic a protein structure due to the sp3 rigid scaffolds (BCP or cubane) that exhibit the essential conformational space for protein function while simultaneously providing amide bonds for molecular recognition.

Analysis of clinical effect and radiographic outcomes of Isobar TTL system for two-segment lumbar degenerative disease: a retrospective study

BackgroundNonfusion fixation is an effective way to treat lumbar degeneration. In the present study, we analyzed the clinical effects and radiographic outcomes of the Isobar TTL system used to treat two-segment lumbar degenerative disease.MethodForty-one patients diagnosed with two-segment lumbar degenerative disease underwent surgical implantation of the Isobar TTL dynamic stabilization system (n = 20) or a rigid system (n = 21) from January 2013 to June 2017. The mean follow-up time was 23.6 (range 15–37) months. Clinical results were evaluated with the Oswestry Disability Index (ODI), modified Macnab criteria, and the visual analog score (VAS). Radiographic evaluations included the height of the intervertebral space and the range of motion (ROM) of the treated and adjacent segments. The intervertebral disc signal was classified using the modified Pfirrmann grading system and the University of California at Los Angeles (UCLA) system.ResultsThe clinical results, including the ODI and VAS, showed that there was significant improvement in the two groups after implantation and that the difference between the two groups was not significant. In addition, the clinical efficacy indicated by the modified Macnab criteria for the two groups was similar. Radiological outcomes included the height of the intervertebral space, lumbar mobility, and intervertebral disc signal. The height of the intervertebral space of the upper adjacent segment L2/3 in the rigid group was significantly lower than that in the Isobar TTL group at the last follow-up. Furthermore, the number of ROMs of the fixed-segment L3/4 in the Isobar TTL group was significantly less than that before implantation, suggesting that the fixed-segment ROMs in the Isobar TTL group were limited. In addition, the ROM of the upper adjacent segment L2/3 in the last follow-up of the rigid group increased significantly, while that of the Isobar TTL group did not change after implantation. Finally, the incidence of adjacent-segment degeneration (ASD) was significantly greater in the rigid group than in the Isobar TTL group according to the UCLA system.ConclusionThe Isobar TTL system can be clinically effective for treating two-segment lumbar degenerative disease. Compared with rigid fixation, the Isobar TTL system yielded better radiographic outcomes and maintained the mobility of the treated segments with less impact on the proximal adjacent segment.

Flexible cystoscopy can improve anxiety and subjective feelings of bladder cancer patients during follow-up.

IntroductionThe effect of repeated cystoscopy on bladder cancer (BC) patient anxiety and feelings is rarely evaluated.AimTo compare the difference of patients’ anxiety and subjective feelings caused by different cystoscopes.Material and methodsWe prospectively included 192 BC patients who accepted regular cystoscopy follow-up after transurethral resection of bladder tumor (TURBT): 93 in the flexible group and 99 in the rigid group. The method of anesthesia and the order of examinations were consistent between different groups. We analyzed the anxiety level before cystoscopy, the maximum pain during the examination and the change of lower urinary tract symptoms (LUTS) before and after cystoscopy. Meanwhile, we analyzed the rate of gross hematuria and pyuria after cystoscopy. The anxiety and pain levels were evaluated by the Amsterdam Preoperative Anxiety and Information Scale (APAIS) and visual analogue scale (VAS). LUTS was reflected by the Core Lower Urinary Tract Symptom Score (CLSS). We distinguished gender during analysis.ResultsThe median APAIS score of male patients undergoing flexible or rigid cystoscopy was 8 vs. 12 (p < 0.01), and this result for females was 8 vs. 9 (p = 0.048). The median pain scores for men in the two groups was 1 vs. 2 (p < 0.01), respectively, and this outcome in female patients was 0 vs. 1 (p < 0.01). Patients in the rigid group had more CLSS change (0 vs. 1, p < 0.01). There was no difference in pyuria or gross hematuria rate after examination. Analysis in respective groups showed that men have more severe pain than women, 1 vs. 0 (p = 0.001) in the flexible group and 2 vs. 1 (p = 0.009) in the rigid group.ConclusionsA flexible cystoscope can improve anxiety and subjective feelings of BC patients during cystoscopy follow-up.

Does Long-Term Rigid Contact Lens Wear Lead to Acquired Blepharoptosis in Chinese Eyes?

To determine whether long-term rigid contact lens wear leads to acquired blepharoptosis and whether its development is affected by lens removal methods. Ninety rigid contact lens wearers (45 rigid gas permeable [RGP] [15-19 years old] and 45 ortho-k [15-40 years old]) who had worn lenses for at least 2 years and 45 spectacle-wearing controls (15-19 years old) were recruited. Margin reflex distance (MRD) and palpebral fissure height (PFH) were measured both subjectively and objectively, but levator function (LF) could only be measured subjectively. For RGP subjects, measurements were made before and 5 min after lens removal. Measurements were compared among the groups and, for rigid lens wearers, between two different lens removal techniques: using a suction holder or by finger-lid manipulation. No significant differences in MRD, PFH, and LF were found between different lens removal techniques in the rigid lens groups (P>0.05). No significant correlations were found between the parameters of interest and duration of lens wear (P>0.05). For the RGP group, MRD, PFH, and LF were significantly greater after than before lens removal (P<0.05), and after lens removal, MRD was significantly smaller than that of the ortho-k and spectacle groups (P<0.001, P=0.01, respectively) and PFH was significantly smaller than that of the ortho-k group (P=0.001). However, after lens removal, according to the definition (amount) for ptosis, no subject was diagnosed as having ptosis. Long-term rigid contact lens wear did not lead to acquired blepharoptosis in Chinese eyes. Margin reflex distance, PFH, and LF were not affected by different lens removal techniques.

Equational Noethericity of Metabelian r-Groups

The author had earlier defined the concept of an r-group, generalizing the concept of a rigid (solvable) group. This article proves that every metabelian r-group is equationally Noetherian; i.e., each system of equations in finitely many variables with coefficients in the group is equivalent to some finite subsystem.

Efficient User Clustering Using a Low-Complexity Artificial Neural Network (ANN) for 5G NOMA Systems

Non-orthogonal multiple access (NOMA) has gained considerable interest from the 3GPP community as a potential radio access strategy for the future fifth-generation (5G) wireless networks. Compared to orthogonal multiple access (OMA), NOMA is more efficient from the perspective of throughput performance making it more favorable for 5G systems. Existing NOMA techniques merely offer a rigid user grouping without exploring channel heterogeneity and diversity to cluster users, resulting in a poor throughput performance. An adaptive user clustering (AUC) approach has been proposed to search through all possible combinations to obtain the best clusters with the highest throughput. This scheme exploits the channel diversity of users to maximize throughput, however, the brute-force search (B-FS) method to find the optimal combinations results in a prohibitive complexity. In this paper, a novel artificial neural network (ANN) approach is proposed for user clustering in the downlink of the 5G NOMA system in order to maximize throughput performance at an acceptable complexity. In the proposed strategy, ANN model is first trained with the historical dataset, which contains the transmitting powers and channel gains of the downlink NOMA users, along with the information of the corresponding clusters which maximize the throughput performance of the system. Next, validation is performed to tune the values of hyper-parameters such as learning rate, length of training data, and epoch learned during training to validate cluster formation and to avoid over-fitting of the model. Finally, the ANN model is tested with the learned parameters and tuned hyper-parameters, to predict the formation of clusters and to evaluate the accuracy of the model. Simulation results demonstrate that the proposed scheme is able to obtain a significant reduction in terms of complexity with a performance of 98% for throughput (near-optimal throughput performance) when compared with the optimal approaches.

Self-assembly of amphiphilic alternating copolymers with stimuli-responsive rigid pendant groups

Amphiphilic alternating copolymers (AACs) possess unique self-assembly behaviours owing to their unique regular architecture.

Synthesis and Aggregation Behavior of Jellyfish-Shaped Triazine Hexamer Quaternary Ammonium Chloride Surfactant

A novel jellyfish-shaped triazine hexamer quaternary ammonium chloride surfactant (TH12QC) was synthesized, which consisted of one triazine spacer group and six long flexible hydrophobic chains. The molecular structure and aggregation behavior of TH12QC was investigated by nuclear magnetic resonance (NMR), surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscope (TEM), etc. The results show that the jellyfish-shaped TH12QC has better surface activity and lower surface tension than traditional ionic and Gemini surfactants in aqueous solution. There are two inflection points in the curve of conductivity versus concentration of the TH12QC aqueous solution, which correspond to the critical aggregation concentration (CAC) and the critical micelle concentration (CMC) respectively. The existence of CAC indicates that there is a pre-aggregation process before TH12QC forms micelles. The results of DLS and TEM show that network pre-aggregation, spherical aggregation and dense spherical aggregation were observed in different concentration of TH12QC aqueous solution, and the electrostatic equilibrium of the system subtly depends on the concentration of the solution. In addition, intramolecular and intermolecular hydrogen bonding is also an important factor. This study provides a method for studying the aggregation behavior and morphology of oligomeric surfactants with rigid spacer groups.

The local-global property for bitangents of plane quartics

We study the arithmetic of bitangents of smooth quartics over global fields. With the aid of computer algebra systems and using Elsenhans--Jahnel's results on the inverse Galois problem for bitangents, we show that, over any global field of characteristic different from $2$, there exist smooth quartics which have bitangents over every local field, but do not have bitangents over the global field. We give an algorithm to find such quartics explicitly, and give an example over $\mathbb{Q}$. We also discuss a similar problem concerning symmetric determinantal representations. This paper is a summary of the first author's talk at the JSIAM JANT workshop on algorithmic number theory in March 2019. Details will appear elsewhere.

A liquid phosphorus-containing imidazole derivative as flame-retardant curing agent for epoxy resin with enhanced thermal latency, mechanical, and flame-retardant performances

The development of phosphorus-containing flame retardants combining good compatibility with matrix, low curing temperature, and mechanically reinforcing effect has remained a major challenge. Herein, we reported the synthesis of a liquid flame-retardant curing agent (DA) via the nucleophilic substitution between diphenylphosphinic chloride and 1-(3-aminopropyl)-imidazole (AI). DA exhibited good blending and latency towards epoxy resin (EP) at room temperature. According to DSC studies, DA could rapidly cure EP at moderate temperature. Compared with EP/AI sample, EP/DA samples displayed comparable or higher glass transition temperature (Tg) and enhanced mechanical properties due to the introduction of rigid diphenylphosphinyl group and improved cross-linking density. Moreover, DA improved the flame-retardant performances of EP thermoset. For instance, the LOI and UL94 rating of EP/DA-16 sample achieved 37.2 % and V-0, respectively. In addition, the peak of heat release rate (PHRR), average of heat release rate (AHRR), fire growth rate (FIGRA), and total heat release (THR) for EP/DA-16 sample reduced by 32 %, 42 %, 28 % and 27 % in comparison to EP/AI sample, respectively. DA was characterized by its good compatibility with EP, moderate curing temperature, fast curing rate, suitable thermal latency, mechanical reinforcing and flame-retardant effects, and thus it had a broad application prospect in various industrial fields.

Hyperbranching-Enhanced-Emission Effect Discovered in Hyperbranched Poly(4-(cyanomethyl)phenyl methacrylate).

To disclose the effect of architecture over fluorescence behaviors of polymers, linear and hyperbranched poly(4-(cyanomethyl)phenyl methacrylate)s (PCPMAs) were synthesized by using atom transfer radical polymerization (ATRP). Compared to linear PCPMAs with weakly AIE (AIE: aggregation-induced-emission) characteristics and small-molecule analogues of 4-(cyanomethyl)phenyl isobutyrate (CPB) with ACQ (ACQ: aggregation-caused-quenching) behaviors, hyperbranched PCPMA showed dramatically stronger fluorescence at both solution and solid states and more significant AIE characteristics, which were further enhanced by increasing the branching degree, indicating a significant hyperbranching-enhanced-emission effect (HEE). The HEE effect was attributed to the strong promotion of hyperbranched architecture over the formation of a nitrile group cluster with through-space conjugation (TSC). The HEE effect provided a promising methodology to construct efficient nontraditional fluorescent polymers without large-conjugated, rigid, and planar emitter groups.

Four novel 3D RE-MOFs based on maleic hydrazide: Syntheses, structural diversity, efficient electromagnetic wave absorption and antibacterial activity properties

Maleic hydrazide (MH), a six-membered heterocycle, contains two rigid lactam groups. Although MH has more than one coordination site, structural information regarding its metal organic frameworks (MOFs), especially rare-earth metal organic frameworks (RE-MOFs), is barely reported. In this work, four novel RE-MOFs [Y2(MH)6]n·DMF (1), [Er2(MH)6]n (2), [Yb2(MH)6]n (3), and [La(MH)3]n (4) were successfully synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analyses, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). The organic linkers bind to the central metal ions through oxygen atoms in MOFs 1–3 (isostructural), and the organic linkers bind to the central ions through both oxygen atoms and nitrogen atoms in MOF 4. The electromagnetic wave absorption (EMWA) studies of MOFs 1–4 demonstrate that these MOFs with special porous structures have impressive EMWA performance. A maximum reflection loss (RL) value of −22.78 dB, with a broad effective absorption bandwidth of 2.24 GHz, can be obtained for MOF 1. Additionally, for MOF 2, a maximum RL value of −20 dB can be obtained. Both MOF 3 and MOF 4 have narrow effective EMWA bandwidths with maximum RL values of −28.14 dB and −13.07 dB. The excellent EMWA property may be attributed to the synergetic and complementary effects of permittivity and permeability. Additionally, MOFs 1–4 were tested for antibacterial activity. The results show that all the tested MOFs exhibit significant antibacterial properties. In particular, MOF 4 has the strongest antibacterial activity against two tested pathogenic bacteria compared to MOFs 1–3.

Spatially ordered chelating resin based on liquid‐crystal phase with highly selective removal of metal ions

In this study, an ordered spatial chelating resin was synthesized, and its selective adsorption of various cations was investigated. By using polyethyleneimine (PEI) as the main chain, methoxy biphenyl group as the rigid group, and methylene units as the flexible chains, a series of side-chain liquid crystal chelating resins were synthesized (labeled as POMen, where n is the spacer length varying between three to six methylene units). The analysis of the thermal properties of POMens showed that they are thermotropic liquid crystals with smectic structure. In its liquid state, out of all POMens, POMe6 demonstrated excellent adsorption capacity relative to Pb2+ with maximum value equal to 387 mg/g. In particular, L-POMe6 demonstrates an excellent selectivity for the removal of Pb2+ in the presence of competitive heavy metal ions. Density functional theory (DFT) calculations were carried out to analyze the binding energies of L-POMe6 structures and their corresponding metal ion complexes. L-POMe6 demonstrated the lowest binding energy with Pb2+ complexes compared other complexes. Furthermore, the adsorption of Pb2+ onto L-POMe6 adsorbents fitted to the Langmuir adsorption and pseudo-second-order kinetic model. The regeneration capacities of L-POMe6 were studied, that the adsorption capability remains high after several cycles of adsorption-desorption process.

Dinuclear Aluminum Halide Complexes Based on Bis(β-diketiminate) Ligands: Synthesis, Structures, and Electrochemical Characterization.

Twenty-three dinuclear aluminum halide complexes based on bis(β-diketiminate) ligands with various flexible and rigid bridging groups have been synthesized and fully characterized by NMR and IR spectroscopy, cyclic voltammetry, and elemental analysis. In addition, nine complexes were structurally characterized by means of single-crystal X-ray diffraction. Attempts to reduce the dinuclear species using C8K remained unsuccessful, but the reduction potentials investigated by cyclic voltammetry indicate the principle feasibility.

Machine learning-aided analysis for complex local structure of liquid crystal polymers

Elucidation of mesoscopic structures of molecular systems is of considerable scientific and technological interest for the development and optimization of advanced materials. Molecular dynamics simulations are a promising means of revealing macroscopic physical properties of materials from a microscopic viewpoint, but analysis of the resulting complex mesoscopic structures from microscopic information is a non-trivial and challenging task. In this study, a Machine Learning-aided Local Structure Analyzer (ML-LSA) is developed to classify the complex local mesoscopic structures of molecules that have not only simple atomistic group units but also rigid anisotropic functional groups such as mesogens. The proposed ML-LSA is applied to classifying the local structures of liquid crystal polymer (LCP) systems, which are of considerable scientific and technological interest because of their potential for sensors and soft actuators. A machine learning (ML) model is constructed from small, and thus computationally less costly, monodomain LCP trajectories. The ML model can distinguish nematic- and smectic-like monodomain structures with high accuracy. The ML-LSA is applied to large, complex quenched LCP structures, and the complex local structures are successfully classified as either nematic- or smectic-like. Furthermore, the results of the ML-LSA suggest the best order parameter for distinguishing the two mesogenic structures. Our ML model enables automatic and systematic analysis of the mesogenic structures without prior knowledge, and thus can overcome the difficulty of manually determining the specific order parameter required for the classification of complex structures.

Le Problème Inverse de Galois sur les corps des fractions tordus à indéterminée centrale

In this article, we show that the Inverse Galois Problem over a skew field H of finite dimension over its center k is equivalent to a variant of the Inverse Galois Problem over k involving a polynomial constraint. As an application, we show that if k contains an ample field, then the Inverse Galois Problem has a positive answer over the skew field H(t) of rational fractions with central indeterminate.

Inverse Galois problem for del Pezzo surfaces over finite fields

We completely solve the inverse Galois problem for del Pezzo surfaces of degree $2$ and $3$ over all finite fields.

The Fabrication of Rigid Crosslinker-Decorated Gold Nanoparticle Array Film for Catalyzing CO2 Cycloaddition

Abstract In order to precisely design the active sites in two-dimensional (2D) gold-based catalysts, we have developed a convenient and versatile plasma-assisted droplet evaporation-rigid crosslinking method for the fabrication of gold nanoparticle (Au NP) array film. Four kinds of Au NP arrays have been decorated respectively with rigid sulfurated crosslinkers i.e. thieno[3,2-b]thiophene, 2,2′-bithiophene, 1,4-benzenedithiol and 4,4′-thiodibenzenethiol, and the density of crosslinkers can be adjusted under plasma treatment. Particularly, the utilization of 4,4′-thiodibenzenethiol gave uniform particle sizes to form a periodical 2D structure, which provides multiple exposed active sites of gold nanoparticles rather than enwinding by the alkyl chains. Meanwhile, the weaker electron-donating effect and steric hindrance of rigid groups in the crosslinkers could also enhance the catalytic activity. In addition, the Au NP array film can be transferred from the glass substrate and further composited with polymers and metal organic framework (MOF) into self-standing composite membrane. Therefore, this rigid crosslinked array film can serve as an environmentally friendly catalyst for CO2 cycloaddition under atmospheric CO2 pressure, which offers a novel application of Au NPs array film, and opens up a new way for the design and fabrication of 2D hybrid materials.