Concave Morphology Research Articles

Gm-APD Lidar Distance Image Recovery Based on Intensity Image Target Edge Guidance

Abstract Gm-APD LiDAR in the detection of long-distance targets, the laser by the atmospheric effects of attenuation is serious, so that the target echo sparse, easy to cause the target distance like edge missing, details of fuzzy and other problems, the traditional method can’t make targeted treatment of the above problems. Therefore, this paper proposes a Gm-APD LIDAR distance image recovery method based on intensity image target edge guidance. The method introduces one-dimensional intensity information as an aid, combines the inverse distance weighting function to guide the reconstruction of the target edge contour information of the distance image, and then applies morphological image processing to correct the target distance value in a partition, and recovers a distance image with sharp edges and clear details. Experiments are carried out on the distance targets, and the results show that the method improves the target restoration by 19.21% and the peak signal-to-noise ratio by 3.12% compared with the concave morphology restoration algorithm, which verifies the advantages and effectiveness of the method proposed in this paper.

Occurrence of methane in organic pores with surrounding free water: A molecular simulation study

Free water contained in shale reservoirs can influence the enrichment and transportation of shale gas. To accurately assess shale gas adsorption in shale reservoirs and improve recovery, it is crucial to understand the occurrence of gas and water. In this study, the occurrence of methane occupying the organic pores surrounded by free water is investigated using Grand Canonical Monte Carlo/Molecular Dynamics simulations, considering the effects of pressure, temperature and pore size. The center of the model represents methane adsorbed/free within the organic pores, while the regions on either side depict free water. Although water does not significantly penetrate organic pores, pressure, temperature, and pore size have a notable impact on the wettability of water on organic surfaces, resulting in variations in the concave liquid surface morphology. This results in varying degrees of competitive adsorption of water and methane near the carbonyl group. At lower pressures, although the capillary pressure decreases sharply with increasing pore size, the improved water wettability increases the extent of its intrusion along the pore surface, thereby enhancing the competitive adsorption of methane and water. At higher pressures, capillary pressure acts as a resistance, preventing water from invading the organic pores in significant quantities. Due to the weak affinity of organic pores for water, the same phenomenon was observed even after increasing the pore size and temperature to improve water wettability. In addition, high temperatures can lead to more pronounced water intrusion. Finally, it is hypothesized that competitive adsorption of methane and water is more pronounced at shallower burial depths and slightly larger pore sizes. This result is expected to provide insights for the accurate evaluation of gas adsorption in water-bearing shales.

Morphology of true lumen and surgical outcomes of acute type A aortic dissection repair with superior mesenteric artery malperfusion

BackgroundAcute type A aortic dissection (ATAD) can cause visceral malperfusion. Central aortic repair may resolve malperfusion, but some require further intervention. This study aimed to review outcomes after ATAD presenting with visceral malperfusion and to evaluate the predictive value of true lumen (TL) morphologies in preoperative computed tomography scan for persistent superior mesenteric artery (SMA) ischemia after central repair. MethodsOpen surgical repair of ATAD performed between 2008 and 2023 at our institution was reviewed retrospectively. Patients with central repair first approach were included for analysis. Patients with inadequate computed tomography scan data to assess luminal morphology were excluded. TL morphology was reviewed at the diaphragm level and categorized as concave or convex. The malperfusion pattern, static vs dynamic, was assessed at SMA orifices. Data were analyzed using a contingency table and parametric and nonparametric methods. ResultsA total of 543 open ATAD repairs were performed. Of these, 263 patients were eligible under the inclusion criteria and, subsequently, analyzed. The mean age was 57±14, and 83 (31%) patients were female. SMA malperfusion developed in 42 (16%) of the 263 patients, including 26 patients with dynamic obstruction, 6 patients with static obstruction, and 10 patients with dynamic and static obstruction. Regarding dissection flap morphology, 78 patients (30%) exhibited concave morphology, while 185 patients (70%) had convex morphology. TL diameter was significantly larger in convex than concave (concave: 6 mm vs convex: 16 mm; P < .0001). The prevalence of clinically significant SMA malperfusion was higher in concave-shaped TL (concave 41% vs convex 5%; P < .0001). Dynamic SMA obstruction was more frequently observed in the concave group (concave 72% vs convex 30%; P < .001). However, significantly more patients with convex-shaped TL required bowel resection than concave (concave 13% vs convex 70%; P < .001). The operative mortality was higher in the convex group, although statistically insignificant (concave 19% vs convex 50%; P = .0059). ConclusionsCentral repair first strategy could resolve more than 80% of SMA malperfusion in ATAD when the TL is concave-shaped at the level of the diaphragm. Convex-shaped TL morphology was associated with less incidence of SMA malperfusion but was more frequently associated with static obstruction and higher incidence of bowel resection. The morphology evaluation of the TL at the diaphragm level may be simple and beneficial for surgical planning for ATAD presenting with SMA malperfusion.

Influences of channel bed morphology on flow structures in continuous curved channels

Introduction: The formation of bars and pools, characterized by concave and convex bed morphology, is a typical feature of curved rivers. The channel bed morphology has a significant influence on the flow structures in curved channels.Methods: Based on data from physical model experiments, this study employs the RNG k-ε model and the VOF (Volume of Fluid) method to perform three-dimensional numerical simulations of flow in continuous curved channels.Results: By comparing the variations in flow structures between channels with a flat bed and channels with bars and pools, the results show that the presence of bars and pools leads to an increase in longitudinal flow velocity on the convex bank side near the entrance of the upstream bend, while in the downstream bend it is opposite. The high-velocity region shifts slower towards the concave bank along the bend. The presence of point bars weakens the circulation near the convex bank in the upstream bend, resulting in a smaller circulation intensity. The decrease in circulation intensity is the largest (−23.91%) at the apex of the bend. In the downstream bend, the remaining circulation from the upstream bend attenuates slower in the pool and has a greater impact distance, increasing the circulation intensity in the downstream bend. The section near the bend entrance shows the largest increase in circulation intensity, with a rate of 128.18%. The unevenness of the bed topography increases the unevenness of the bed shear stress in the downstream bend.Discussion: The findings of this study contribute to a deeper understanding of the complex flow structures and evolution trends in natural curved rivers, providing scientific basis for the management of curved river channels.

Can zoledronic acid reduce the risk of cage subsidence after oblique lumbar interbody fusion combined with bilateral pedicle screw fixation in the elderly population? A retrospective study

BackgroundThe objective of this study was to evaluate the potential of zoledronic acid for reducing the incidence of cage subsidence and enhancing interbody fusion rates following oblique lumbar interbody fusion (OLIF) surgery, particularly as the first reported evidence of the role of zoledronic acid combined with OLIF.MethodsA retrospective analysis was conducted on data from 108 elderly patients treated for degenerative lumbar diseases using OLIF combined with bilateral pedicle screw fixation from January 2018 to December 2021. Patients were divided into the zoledronic acid (ZOL) group (43 patients, 67 surgical segments) and the control group (65 patients, 86 surgical segments). A comparative analysis of the radiographic and clinical outcomes between the groups was performed, employing univariate and multivariate regression analyses to explore the relationships between cage subsidence and the independent variables.ResultsRadiographic outcomes, including anterior height, posterior height, disc height, coronal disc angle, foraminal height, and lumbar lordosis, were not significantly different between the two groups. Similarly, no statistically significant differences were noted in the back visual analog scale (VAS) scores and Oswestry Disability Index (ODI) scores between the groups. However, at the 1-year follow-up, the leg VAS score was lower in the ZOL group than in the control group (P = 0.028). The ZOL group demonstrated a notably lower cage subsidence rate (20.9%) than did the control group (43.0%) (P < 0.001). There was no significant difference in the interbody fusion rate between the ZOL group (93.0%) and the control group (90.8%). Non-use of zoledronic acid emerged as an independent risk factor for cage subsidence (OR = 6.047, P = 0.003), along with lower bone mineral density, lower postoperative anterior height, and concave endplate morphology. The model exhibited robust discriminative performance, with an area under the curve (AUC) of 0.872.ConclusionThe administration of zoledronic acid mitigates the risk of cage subsidence following OLIF combined with bilateral pedicle screw fixation in elderly patients; however, it does not improve the interbody fusion rate.

The Impact of Marangoni and Buoyancy Convections on Flow and Segregation Patterns during the Solidification of Fe-0.82wt%C Steel.

Due to the high computational costs of the Eulerian multiphase model, which solves the conservation equations for each considered phase, a two-phase mixture model is proposed to reduce these costs in the current study. Only one single equation for each the momentum and enthalpy equations has to be solved for the mixture phase. The Navier-Stokes and energy equations were solved using the 3D finite volume method. The model was used to simulate the liquid-solid phase transformation of a Fe-0.82wt%C steel alloy under the effect of both thermocapillary and buoyancy convections. The alloy was cooled in a rectangular ingot (100 × 100 × 10 mm3) from the bottom cold surface to the top hot free surface by applying a heat transfer coefficient of h = 600 W/m2/K, which allows for heat exchange with the outer medium. The purpose of this work is to study the effect of the surface tension on the flow and segregation patterns. The results before solidification show that Marangoni flow was formed at the free surface of the molten alloy, extending into the liquid depth and creating polygonized hexagonal patterns. The size and the number of these hexagons were found to be dependent on the Marangoni number, where the number of convective cells increases with the increase in the Marangoni number. During solidification, the solid front grew in a concave morphology, as the centers of the cells were hotter; a macro-segregation pattern with hexagonal cells was formed, which was analogous to the hexagonal flow cells generated by the Marangoni effect. After full solidification, the segregation was found to be in perfect hexagonal shapes with a strong compositional variation at the free surface. This study illuminates the crucial role of surface-tension-driven Marangoni flow in producing hexagonal patterns before and during the solidification process and provides valuable insights into the complex interplay between the Marangoni flow, buoyancy convection, and solidification phenomena.

Ir-Doped CuPd Single-Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C-C Bond.

The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir-doped CuPd single-crystalline mesoporous nanotetrahedrons (Ir-CuPd SMTs) as high-performance electrocatalyst for promoting oxidation cleavage of C-C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co-nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore-forming surfactant and extra Br- as the facet-selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well-defined (111) facets, single-crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir-CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high-energy-barrier C-C bond of EG for desired C1 products. More interestingly, Ir-CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Ir‐Doped CuPd Single‐Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C−C Bond

AbstractThe development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir‐doped CuPd single‐crystalline mesoporous nanotetrahedrons (Ir‐CuPd SMTs) as high‐performance electrocatalyst for promoting oxidation cleavage of C−C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co‐nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore‐forming surfactant and extra Br− as the facet‐selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well‐defined (111) facets, single‐crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir‐CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high‐energy‐barrier C−C bond of EG for desired C1 products. More interestingly, Ir‐CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Formation of Corrugated Damage on Bearing Race under Different AC Shaft Voltages.

Corrugated damage to bearings is a common fault in electrical facilities such as new energy vehicles, wind power, and high-speed railways. The aim of this article is to reveal the microscopic characteristics and formation mechanism of such damages. The corrugation with alternating "light" and "dark" shape was produced on GCr15 bearing races in the experimental conditions. Compared to the light area, the dark area (in the images generated by optical microscope) has more severe electrical erosion, lower hardness, more concave morphology, and lower oxidation. As the voltage increases, the width of the corrugation, the height difference between corrugation, and surface roughness all increase. It is believed that the formation of corrugated damage requires a sufficiently high voltage to induce the periodic destruction and reconstruction of the lubrication film. When the bearing is in a metal-lubrication film-metal contact state, the high voltage causes the lubrication film to break down and induce electrical erosion. Then, the contact area is in metal-metal contact, and the surface is mainly damaged by mechanical rolling. After the reconstruction of lubrication film, the next round of electrical erosion begins. The results are helpful for a deeper understanding of the mechanism of bearing erosion in electrical application.

Effect of a traveling magnetic field on cadmium zinc telluride growth by the traveling heater method

The growth of high-quality cadmium zinc telluride (CZT) crystals using the traveling heater method (THM) is strongly influenced by the morphology of growth interface. Here, we investigate the effect of a traveling magnetic field (TMF) on the growth of CZT single crystals by the THM using the multi-physics numerical simulation method. When no magnetic field is applied, the concave morphology of the growth interface caused by the gravity-driven natural convection is confirmed using a multi-component mass transfer model based on the Maxwell-Stefan equations. In contrast, the application of an upward TMF accelerates the flow near the crucible wall and hence the lateral flow along the growth interface, finally leading to a relatively flat growth interface. Conversely, the increase of a downward TMF intensity significantly weakens natural convection in the central melt region; particularly, when the magnetic induction strength is increased to 300 mT at a frequency of 50 Hz, the desired convex-shaped growth interface can be achieved with the appearance of strong vortices at the dissolution interface. Therefore, we conclude that both the upward and downward TMF can improve the growth interface and thereby facilitates the growth of high-quality single crystals.

Constructing Interconnected Hollow Mesopore Sn-Si Mixed Oxide Microspheres by Aerosol-Assisted Alkali Treatment with Enhanced Catalytic Performance in Baeyer-Villiger Oxidation

In this work, Sn-Si mixed oxide microspheres with concave hollow morphologies were first synthesized by a simple aerosol method using the very common commercial surfactant cetyl trimethyl ammonium bromide (CTAB) as a template, and then highly interconnected mesoporous and hollow Sn-Si mixed oxide microspheres were synthesized via an alkali (NaOH) treatment in the presence of CTAB. The results show that CTAB plays a crucial role not only in forming hollow morphologies during the aerosol process, but also protecting the amorphous framework and thus preventing the excessive loss of Sn species during the NaOH treatment. More importantly, it widens mesoporous distribution and forms interconnected mesoporous channels. The catalytic performance of Baeyer–Villiger oxidation on the interconnected mesoporous and hollow Sn-Si mixed oxide microspheres with 2-adamantanone and hydrogen peroxide was 9.4 times higher than that of the sample synthesized without the addition of CTAB; 2.3 times that of the untreated parent, which was due to the excellent diffusion properties derived from the hollow and interconnected mesopore structure. This method is mild, simple, low-cost, and can be continuously produced, which has the prospect of industrial application. Furthermore, the fundamentals of this study provide new insights for the rational design and preparation of highly interlinked mesoporous and hollow metal-oxides with unique catalytic performances.

Optimal stability analysis of homogenous soil slopes with an irregular geometric morphology

The common morphologies of slope surfaces in nature include linear, stepped, convex, concave, and their combination types. Many researchers have investigated the stability of slopes with simple linear, stepped convex, or concave geometric morphologies, disregarding the effect of combination of convex and concave morphology. In this paper, slope surfaces with convex-concave characteristics are considered. A model of a slope surface composed of n segments is constructed to realize the arbitrary generation of irregular geometric morphologies. Based on the upper bound limit analysis and the log-spiral failure mechanism, a formula for the factor of safety of slopes with irregular geometric morphology is obtained. Optimal stability analysis of convex, concave and convex-concave combination slopes with different characteristics is carried out. This paper mainly focuses on the effect of the location and extent of convex-concave sections on slope stability and sliding surfaces. In addition, a comparative analysis is carried out from both theoretical and numerical perspectives. The local stability of convex and convex-concave combination slopes is discussed. The results show that the effect of convex-concave characteristics on slope stability is related to the equivalent straight-slope angle. Moreover, some abnormal phenomena have been identified. For example, under certain conditions, the stability of a convex slope is better than that of a straight slope, and a concave morphology is not conducive to slope stability. In addition, when the equivalent straight-slope angle is small, convex-concave combinations can yield the worst or best slope stability. Therefore, the location and extent of convex-concave sections should be comprehensively considered to achieve an optimal design scheme in slope reinforcement design and construction.

Aerosol-Assisted Synthesis of Sn-Si Composite Oxide Microspheres with the Hollow Mesoporous Structure for Baeyer-Villiger Oxidation

Tetravalent Sn species, such as zeolite or oxide, possess Lewis acidic properties, and thus exhibit prominent catalytic performance in several reactions when they are incorporated into the silica framework. Unfortunately, the synthesis of Sn-based zeolite (Sn–Beta) usually suffers from several drawbacks, including a long crystallization time, limited framework Sn content and complex synthesis steps. Sn-based composite oxides are favored in the industry, due to their simple synthesis steps and easy control of their pore structure, morphology and Sn content. In this work, an aerosol-assisted method is used to prepare Sn–Si composite oxide microspheres, using CTAB as template. The method is based on the formation of aerosol from a solution of Sn, Si precursors and a template (CTAB). The introduction of CTAB causes the surface tension of the atomized droplets to decrease. During the fast drying of the droplets, the Sn–Si composite oxide microspheres with a concave hollow morphology were first formed. After calcination, calibrated mesopores of 2.3 nm were also formed, with a specific surface area of 1260 m2/g and a mesopores ratio of 0.84. Sn species are incorporated in the silica network, mainly in the form of single sites. The resulting material proved to exhibit high catalytic performances in the Baeyer–Villiger oxidation of 2-adamantanone by using H2O2 as green oxidant, which was mainly attributed to the enhancement of the access to the catalytic tin sites through both the continuous hollow and mesopore channels, which have a 52% conversion of 2-adamantanone after 3 h of reaction. This method is simple, convenient, cheap and can be continuously produced, meaning it has broad potential for industrial application.

The Influence of Screw Positioning on Cage Subsidence in Patients with Oblique Lumbar Interbody Fusion Combined with Anterolateral Fixation.

Cage subsidence (CS) has been reported to be one of the most common complications following oblique lumbar interbody fusion (OLIF). To reduce the incidence of CS and improve intervertebral fusion rates, anterolateral fixation (AF) has been gradually proposed. However, the incidence of CS in patients with oblique lumbar interbody fusion combined with anterolateral fixation (OLIF-AF) is still controversial. Additionally, there is a lack of consensus regarding the optimal placement of screws for OLIF-AF, and the impact of screw placement on the incidence of CS has yet to be thoroughly investigated and validated. The objective of this investigation was to examine the correlation between screw placements and CS and to establish an optimized approach for implantation in OLIF-AF. A retrospective cohort study was undertaken. From October 2017 to December 2020, a total of 103 patients who received L4/5 OLIF-AF for lumbar spinal stenosis or spondylolisthesis or degenerative instability in our department were followed up for more than 12 months. Demographic and radiographic data of these patients were collected. Additionally, screw placement related parameters, including trajectory and position, were measured by anterior-posterior X-ray and axial CT. Analysis was done by chi-square, independent t-test, univariable and multivariable binary logistic regression to explore the correlation between screw placements and CS. Finally, the receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive ability of screw placement-related parameters. A total of 103 patients were included, and CS was found in 28 (27.18%) patients. Univariable analysis was firstly performed for each parameter. Next, variables with p-value of <0.05, including bone mineral density (BMD), concave morphology, and screw placement-related parameters were included in the multivariate logistic regression analysis. Significant predictor factors for subsidence were coronal plane angle (CPA) (OR 0.580 ± 0.208, 95% CI 1.187-2.684), implantation point (IP) (L4) (OR 5.732 ± 2.737, 95% CI 1.445-12.166), and IP (L5) (OR 7.160 ± 3.480, 95% CI 1.405-28.683). Furthermore, ROC curves showed that the predictive accuracy of CS was 88.1% for CPA, 77.6% for IP (L4) and 80.9% for IP (L5). We demonstrate that the trajectory of vertebral screws, including angle and position, was closely related to CS. Inserting screws parallel to each other and as close to the endplate as possible while keeping the cage inside the range of the superior and inferior screws are an optimal implantation strategy for OLIF-AF.

The Rise of Structurally Anisotropic Plasmonic Janus Gold Nanostars.

Nanostructures intrinsically possessing two different structural or functional features, often called Janus nanoparticles, are emerging as a potential material for sensing, catalysis, and biomedical applications. Herein, we report the synthesis of plasmonic gold Janus nanostars (NSs) possessing a smooth concave pentagonal morphology with sharp tips and edges on one side and, contrastingly, a crumbled morphology on the other. The methodology reported herein for their synthesis - a single-step growth reaction - is different from any other Janus nanoparticle preparation involving either template-assisted growth or a masking technique. Interestingly, the coexistence of lower- and higher-index facets was found in these Janus NSs. The general paradigm for synthesizing gold Janus NSs was investigated by understanding the kinetic control mechanism with the combinatorial effect of all the reagents responsible for the structure. The optical properties of the Janus NSs were realized by corelating their extinction spectra with the simulated data. The size-dependent surface-enhanced Raman scattering (SERS) activity of these Janus NSs was studied with 1,4-BDT as the model analyte. Finite-difference time-domain simulations for differently sized particles revealed the distribution of electromagnetic hot-spots over the particles resulting in enhancement of the SERS signal in a size-dependent manner.

Morphological characteristics and dynamic changes of typical climbing dunes on the Qinghai-Tibet Plateau

Climbing dunes are a form of topographic barrier dunes that feature in the aeolian landforms on the Qinghai-Tibetan Plateau. Topography fundamentally influences the spatial distribution and morphological characteristics of climbing dunes by modifying the near-surface airflow and creating space for sediment deposition. Previous studies have considered several aspects of the influence of topography on aeolian landforms. However, morphological differences between climbing dunes in different geomorphic contexts and dynamic changes in the area have received little attention. Therefore, topographic measurements, near-surface flow field measurements, dune morphology analysis, and remote sensing image analysis were combined to explore relationships between dune morphology and topography. Topographic obstacles can accelerate the near-surface airflow, particularly with a 25–35° slope gradient, which is beneficial for sand transport and deposition. Suitable accommodation space (concave slope morphology) and abundant sediment comprise the primary factors that control the scale and morphological diversity of climbing dunes, which are also influenced by a variable wind direction. In general, the morphology of the climbing dunes becomes progressively more complicated from the bottom to the middle of the windward slope, and the sand ridge lines of the dunes are perpendicular to the prevailing wind direction. Based on the influence of climate and human activities, the total area of climbing dunes in this region has decreased over the past 30 years. Despite general evidence of enhanced human-induced desertification in semi-arid and sub-humid regions, warming has not led to the rapid expansion of climbing dunes in these arid locations. This research offers new insights into the relationship between the terrain and dune morphology, enriching the theoretical basis for the plateau aeolian geomorphology. Furthermore, it allows us to consider the dynamic changes in climbing dunes area in the context of global warming.

Vertebral bone quality score to predict cage subsidence following oblique lumbar interbody fusion

BackgroundCurrent evidence suggests that the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score is a good parameter for evaluating bone quality. We aimed to assess whether the VBQ score can predict the occurrence of postoperative cage subsidence after oblique lumbar interbody fusion (OLIF) surgery.MethodsPatients (n = 102) who had undergone single-level OLIF with a minimal follow-up for 1 year were reviewed in this study. Demographic and radiographic data of these patients were collected. Cage subsidence was defined as ≥ 2 mm of cage migration into the inferior endplate, superior endplate, or both. Further, the MRI-based VBQ score was measured on T1-weighted images. Moreover, univariable and multivariable binary logistic regression analyses were performed. Meanwhile, Pearson analysis was used to evaluate the correlation among the VBQ score, average lumbar dual-energy X-ray absorptiometry (DEXA) T-score, and degree of cage subsidence. Furthermore, ad-hoc analysis was used along with receiver operating characteristic curve analysis to assess the predictive ability of the VBQ score and average lumbar DEXA T-score.ResultsOf 102 participants, cage subsidence was observed in 39 (38.24%) patients. According to the univariable analysis, patients with subsidence had older age, higher antiosteoporotic drug use, larger disk height change, a more concave morphology of inferior and superior endplates, higher VBQ score, and lower average lumbar DEXA T-score compared to patients without subsidence. In the multivariable logistic regression analysis, a higher VBQ score was significantly associated with an increased risk of subsidence (OR = 23.158 ± 0.849, 95% CI 4.381–122.399, p < 0.001), and it was the only significant and independent predictor of subsidence after OLIF. Moreover, the VBQ score was moderately correlated with the average lumbar DEXA T-score (r = − 0.576, p < 0.001) and the amount of cage subsidence (r = 0.649, p < 0.001). Furthermore, this score significantly predicted cage subsidence with an accuracy of 83.9%.ConclusionsThe VBQ score can independently predict postoperative cage subsidence in patients undergoing OLIF surgery.

Electromechanical behaviour of violet phosphorene nanoflakes.

Violet phosphorene (vP), a two-dimensional structure with various unique properties, has attracted much attention recently. The electromechanical behaviour, a mechanical-electrical-thermal coupling failure behaviour, of supported and suspended vP nanoflakes has been investigated by the c-AFM nanoindentation method under different loads and bias voltages in this work. A bump due to the oxidation caused by electric current-induced local heating was observed for the supported vP on substrates under mild load and bias voltage. A concave morphology was observed when a load of 1500 nN and a bias voltage of 10 V were applied. No bump was observed for the suspended vP due to the larger contact area between the probe and the sample, resulting in a lower temperature. Fatigue damage was observed for the vP nanoflakes under constant load and a cycled bias voltage from 10 V to -10 V. The electromechanical behaviour of vP was also analyzed through its specific heat capacity and conductivity by density functional theory.

The influence of artificial saliva on the cleaning force of interdental rubber picks: an in-vitro comparison

BackgroundThe familiar aids for interdental cleaning such as dental floss or interdental brushes (IDB) are often associated with difficult handling or an increased potential for trauma. Interdental picks (IRP), which have no metal core and silicone flaps instead of nylon brushes, offer the alternative. However, in-vitro studies found a lower cleaning effectiveness combined with higher forces for cleaning compared with conventional IDBs. The aim of this in-vitro study was to measure the experimental cleaning forces (ECF) using IRP with versus without an artificial saliva (AS; GUM Hydral, Sunstar Suisse SA, Etoy, Switzerland).MethodsThe test set-up was developed to investigate the cleaning of 3D-printed interdental area (IDR) mimicking human teeth (Form 2, Formlabs Sommerville, MA, USA) under standardized conditions. Three different morphologies (isosceles triangle, convex, concave) and three different sizes (1.0 mm,1.1 mm,1.3 mm) were used. Two different IRPs (GUM Soft-picks Advanced: SPA versus GUM Soft-picks Advanced Plus: SPA+, Sunstar Suisse SA, Etoy, Switzerland) in three sizes (small, regular, large), were used with versus without AS. ECF during ten cleaning cycles were recorded by a load cell [N].ResultsUsing AS leaded to significant lower values for ECF than without (1.04 ± 0.66 N versus 1.97 ± 1.01 N, p < 0.001). In general, a lower ECF was recorded for convex IDR compared to isosceles triangle and concave morphologies (p < 0.001) as well as for gap sizes of 1.3 mm compared to the smaller sizes (p < 0.001). For SPA+ we found significantly higher force values than for SPA (1.67 ± 0.93 N versus 1.31 ± 0.97 N, p < 0.001) independent of the use of AS.ConclusionWithin the study´s in-vitro limitations, we found AS reduced ECF of IRPs by half and allowed using larger diameters interdentally, which could be associated with (1) a higher cleaning effectiveness and (2) a higher acceptance e.g. of patients with dry mouth. This has to be confirmed by further clinical investigations.

Concave gold nano-arrows (AuCNAs) for efficient catalytic reduction of 4-nitrophenol

Anisotropic gold nanostructures have attracted great attention in different fields including catalysis. Thermodynamically driven selective surface growth offers a reliable and reproducible method for anisotropic gold nanoparticle synthesis with specific morphologies. Herein, monocrystalline concave gold nano-arrows (AuCNAs) are prepared by the over-growth method using Au nanorods (AuNRs) as seeds. The as-prepared AuCNAs consist of a biconical head and four concave structures. Interestingly, silver ions (Ag+) concentration significantly affects the product morphology by tuning the peak positions of surface plasmon resonance (SPR), aspect ratio, arrow, and concave morphology of AuCNAs. The position of longitudinal SPR peaks is observed at 810, 805 and 782 nm at [Ag+]/[Au3+] molar ratios of 1:2, 1:1, and 2:1, respectively. Diameters and lengths of AuCNAs varied from 25 nm to 36 nm; 104 nm, 78 nm, and 120 nm, respectively. Additionally, the AuCNAs are applied for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of excess NaBH4. Compared to gold nanorods (AuNRs), the prepared AuCNAs catalyst shows excellent catalytic activity, demonstrating that concave structures and sharp corners significantly enhance the catalytic activity. The value of pseudo-first-order reaction kinetic constants (kapp) increased from 0.0051 to 0.0195 s−1 with increasing catalyst valume from 7.5 to 37.5 μL. The highest normalized reaction rate constant (Knor) and turnover frequency (TOF) reach 5.84 × 104 min−1 mmol−1 and 443.47 h−1, respectively, at [Ag+]/[Au3+] ratio of 1:1 in AuCNAs catalyst. This study expands catalytic applications of anisotropic gold nanostructures and widens their potential application areas, such as surface plasmon exciton photonics, biomedical photonics, and photocatalysis.