Decrease In Curvature Research Articles

SPECIFIC CORNEAL PARAMETERS AND VISUAL ACUITY CHANGES AFTER CORNEAL CROSSLINKING TREATMENT FOR PROGRESSIVE KERATOCONUS.

To evaluate the effect of crosslinking (CXL) therapy on the change in the quality of visual acuity and the change in the topographic properties of the cornea - curvature, pachymetry, and change of astigmatism, coma abberation and CLMIaa (Cone Localisation and Magnitude Index). Aretrospective analytical study included 29 eyes of 24 patients who had progressed in the last 12 months and were suitable candidates for CXL surgery. The monitored parameters were the steepest, flatest and mean anterior instantaneous curvature (AICS, AICF, AICM) and the steepest, flatest and mean posterior instantaneous curvature (PICS, PICF, PICM) of the cornea, corneal thickness in the centre of the cornea (PACHC) and in the thinnest point of the cornea (PACHT), corneal astigmatism (ASTIG). coma (COMA), Cone Localization and Magnitude Index (CLMIaa) and uncorrected distance visual acuity (UDVA) with corrected distance visual acuity (CDVA). Data were analysed before surgery and 12 months after surgery. The AIC, COMA, CLMIaa and ASTIG parameters were analysed by paired t test. As the parameters of UDVA, CDVA, PIC and PACH did not meet the conditions of normal distribution, the Wilcoxon test was used to investigate the change in these parameters after CXL. Twelve months after the procedure, we recorded an improvement in UDVA (p=0.371) and CDVA (p=0.825), an increase in PICS, PICF and PICM (p=0.902; p=0.87 and p=0.555), adecrease in PACHCC (p=0.294) and adecrease in CLMIaa (p=0.113) that did not reach statistical significance. The decrease in PACHT (p=0.027), decrease in COMA (p=0.037) and decrease in anterior corneal curvature of AICS, AICF and AICM were statistically significant (p=0.019; p=0.010 and p=0.005). The decrease in the value of astigmatism did not show statistical significance, as p=0.297. CXL corneal therapy has been shown to be an effective method to stabilize the cornea in progressive keratoconus, and to improve the higher order of coma. This contributes to the possible improvement of UDVA and CDVA.

Anionic-Surfactant-Stabilized Hydrophobic Ionic-Liquid-Based Bicontinuous Microemulsion as a Medium for Enzymatic Oxidative Polymerization of Aniline.

The hydrophobic ionic liquid [C8mim][PF6] (1-octyl-3-methylimidazolium hexafluorophosphate)-based bicontinuous microemulsion stabilized by the anionic surfactant [C4mim][AOT] (1-butyl-3-methylimidazolium bis(2-ethylhexyl) sulfosuccinate) was first tried as a medium for horseradish peroxidase (HRP)-triggered oxidative polymerization of aniline. The effects of the mass ratio of [C8mim][PF6]-to-water (α), the mass fraction of [C4mim][AOT] in the total mixture (γ), and temperature (T) on the enzymatic polymerization were investigated using UV–vis–NIR absorption, electron spin resonance, and small-angle X-ray scattering spectroscopy techniques. The bicontinuous microemulsion is demonstrated to play a template role in the biosynthesis of polyaniline (PANI). The conductivity of the resulting PANI depends on the microemulsion microstructure and the microstructure- and T-dependent catalytic properties of the solubilized HRP. With the increase in α, the conductivity of the synthesized PANI decreases due to the increase in the template curvature (decrease of the microdomain size) and the decrease in the activity and stability of HRP. Compared with α, γ has little effect on the microdomain size of the template; so, the γ-dependent change in the conductivity of PANI is mainly caused by the changes of the microstructure-dependent activity and stability of HRP. Over the range of 20–35 °C, T has little effect on the microdomain size, but it greatly changes the activity and stability of HRP. With the increase in T, the activity of HRP increases steadily, but its stability decreases significantly, which should be one of the reasons why the conductivity of PANI decreases with increasing T. In conclusion, lower values of α, γ, and T are favorable for the biosynthesis of conductive PANI. The present study not only deepens the insight into the role of the template in the process of PANI synthesis, but also opens up a green new way for the biosynthesis of the conducting polymer.

Forming process and evaluation of chip in machining of high-strength steel by an independent-developed microgroove turning tool.

Chip morphology is one of the evaluation indexes of cutting performance of cutting tools, and chip forming process has a direct and important influence on chip morphology. High-strength steel 40CrMnMo is one of typical oil country tubular goods (OCTG) and difficult-to-cut materials, and its chip morphology represents the machining quality of OCTG. The chip forming process of a new independent-developed microgroove turning tool for turning oil country tubular goods 40CrMnMo is researched, combining machining experiments with theoretical analysis. Research results show that with the increase of cutting speed, the initial radius of curvature of the chip fluctuates slightly, but the overall trend is upward. However, the ultimate radius of curvature decreases and the chip's radius ratio also decreases. The relative ideal chip can be obtained if the proper cutting velocity and feed rate are given. Chip morphology results from the comprehensive effect of the two processes: The fracture and separation process of the workpiece during passing through the shear deformation zone and the process of curling and breaking away of the chip after passing through the rake face of the tool. The research results have a certain guiding significance for controlling the cutting process of machining the other material with similar performance.

Curved space equilibration versus flat space thermalization: A short review

We discuss equilibration process in expanding Universes as compared to the thermalization process in Minkowski spacetime. The final goal is to answer the following question: Is the equilibrium reached before the rapid expansion stops and quantum effects have a negligible effect on the background geometry or stress–energy fluxes in a highly curved early Universe have strong effects on the expansion rate and the equilibrium is reached only after the drastic decrease of the spacetime curvature? We argue that consideration of more generic non-invariant states in theories with invariant actions is a necessary ingredient to understand quantum field dynamics in strongly curved backgrounds. We are talking about such states in which correlation functions are not functions of such isometry invariants as geodesic distances, while having correct UV behavior. The reason to consider such states is the presence of IR secular memory effects for generic time-dependent backgrounds, which are totally absent in equilibrium. These effects strongly affect the destiny of observables in highly curved spacetimes.

Thermosetting supramolecular polymerization of compartmentalized DNA fibers with stereo sequence and length control

Thermosetting supramolecular polymerization of compartmentalized DNA fibers with stereo sequence and length control

Changes in the geometry of modern daily disposable soft contact lenses during wear

The geometry of contact lenses can be altered by wear but determining the changes that occur in soft contact lenses (SCLs) is challenging. This study aimed to investigate the shape alterations of daily disposable SCLs after wear using swept-source optical coherence tomography (SS-OCT). Forty-five eyes with myopia of − 3.00 diopters (D) were enrolled. The participants wore three types of SCLs: hydrogel lens (nesofilcon A) and silicone hydrogel lenses (delefilcon A and stenfilcon A). The SCLs were scanned 3–6 min after lens removal. We found a significant decrease in the SCL anterior curvature: 0.24 ± 0.17 mm for nesofilcon A, 0.44 ± 0.21 mm for delefilcon A, and 0.53 ± 0.29 mm for stenfilcon A. The changes in the anterior curvature of SCLs correlated moderately with the mean corneal keratometry; Pearson’s correlation coefficients for nesofilcon A and delefilcon A were 0.57 and 0.52, respectively (P < 0.001). A statistically significant change in the total diameter was observed in SCL made of stenfilcon A (0.39 mm, P < 0.001). To conclude, the central radii of curvature decreased after a wearing period for all three types of daily disposable SCLs to imitate the anterior corneal surface, however, the changes in other geometrical parameters measured with SS-OCT were lens-specific.

Seismic Behaviour of PC-encased HCSC Composite Shear Walls under Vertical Tension and Horizontal Cyclic Loading

ABSTRACT The integrity of precast concrete (PC) shear walls depends strongly on the structural measures and construction quality of the reinforcement connections, which impedes complete equivalence with cast-in-place connections, the construction height, and the applicability to high-seismicity regions. The seismic behaviour of hybrid precast concrete-encased concrete-filled twin steel tube (PCCS)-reinforced composite shear walls was investigated under combined vertical tension and horizontal cyclic loading. Embedded cast-in-place high-strength concrete-filled thin-walled twin steel tube cores (HCSCs) were used to position a PC shear wall panel and stiffen vertical connections for improved load-bearing. Quasi-static cyclic tests were conducted on six PCCS composite shear wall specimens with a shear-span ratio of 1.84 to investigate how the HCSC cross-section ratio, out-of-plane eccentricity, and initial axial tension affected the seismic performance. The specimens failed by combined shear-bending, and the HCSCs served as reliable connections and reinforcements. The specimens exhibited relatively high load-bearing capacities, complete hysteretic curves, good deformation and energy dissipation, and large residual stiffnesses at failure. Shear deformation contributed approximately 21% to the total lateral displacement. The average ultimate drift ratio of 1/42 and average ductility factor of 5.0 of the specimens demonstrated excellent assembly integrity. A parametric analysis of the bearing capacity of the cross-section revealed that as the HCSC cross-section ratio increased, both the shear capacity and lateral stiffness increased, where the latter produced a rapid decrease in the deformation curvature. The shear capacity decreased with increasing initial axial tension and out-of-plane eccentricity. The deformation curvature was increased using an appropriate axial tension level and deteriorated by the out-of-plane eccentricity.

Role of the left coronary artery geometry configuration in atherosusceptibility: CFD simulations considering sPTT model for blood

The achievement of clinically viable methodologies to simulate the hemodynamics in patient-specific coronary arteries is still a major challenge. Therefore, the novelty of this work is attained by the introduction of the viscoelastic property of blood in the numerical simulations, to study the role of the left coronary artery (LCA) geometry configuration in the atherosusceptibility. Apparently healthy patients were used and four different methodologies were tested. The methodology giving the most accurate results at the same time of having the lowest computational time is the one considering the viscoelastic property of blood and computational fluid dynamics. A Pearson correlation analysis was used to highlight relationships between geometric configuration and hemodynamic descriptors based on the simulated wall shear stress (WSS). The left main stem (LMS) has the greatest atherosusceptibility followed by the left anterior descending artery (LAD) since the relative residence time (RRT) average values are 3.81 and 3.70 Pa−1, respectively. The geometric parameters with relevant contribution to directional flow change are the cross-sectional areas, especially the one of LMS segment (ALMS), and the curvature of LMS segment. For LMS and LAD segments, when ALMS increases, blood flow disturbance (r = 0.81 in LMS and r = 0.74 in LAD) and atherosusceptibility (r = 0.84 in LMS and r = 0.85 in LAD) increases. When the LMS curvature decreases, the WSS magnitude (r = 0.80 in LMS and r = 0.83 in LAD) decreases, and disturbance (r=-0.80 in LMS and r=-0.91 in LAD) and atherosusceptibility (r=-0.74 in LMS and r=-0.74 in LAD) increases.

Study the effect of anti-vibration edge length on process stability of milling thin-walled Ti-6Al-4V alloy

Owing to limited rigidity and wall thickness, the machining of thin-walled components leads to chatter, poor surface quality, and low productivity. It is well-acknowledged that end-mill geometry and cutting conditions have a significant influence on the process stability of thin-walled parts. In order to reduce the milling chatter, an anti-vibration milling tool with an anti-vibration edge (60, 90, 120μm) on the flank face is proposed based on the analysis of the process damping effect. The dynamic modeling, numerical computation, and confirmatory experimental analysis are carried out to investigate the effect of anti-vibration edge length on the milling stability of thin-walled titanium-alloy components. The computation results have shown a stable and gradual increase in stable depth-of-cut with the increase of anti-vibration edge length at constant spindle speed. The ultimate stable axial depth increases with the increase of the anti-vibration edge. Besides, the increase of spindle speed reduced the interference between the flank surface of the milling tool and the workpiece due to the decrease of curvature of the vibration mark on the workpiece surface. At higher cutting speed, the relationship between the stability axial depth and anti-vibration edge length reduced. The comparison of computational and experimental results indicate that the anti-vibration edge improved the process damping effect at low cutting speeds, and 120μm anti-vibration edge is optimum to manufacture the flank face of the tools.

Dynamic response of horizontally curved composite steel I-girder bridges

The dynamics behavior of horizontally curved composite steel I-girder bridges is investigated by using three-dimensional finite element models. The analyzed bridge is modeled by using ANSYS 15.0 program with SOILD185 and SHELL181 elements to represent concrete and steel members, respectively. AASHTO HL-93 truck is simulated as 3D mass-spring-damper model consisting of five lumped-masses which connected by rigid beams and supported by spring-damper elements which are used to represent the suspension of vehicle body and tires. Gap and actuator elements are used to represent the separation between the tires and road surface and surface roughness condition, respectively. Four different roughness profiles are generated based on power spectral density (PSD) for very good, good, average, and poor roads. The dynamic analysis is carried out under different cases of vehicular loading positions for bridges with radius of curvature ranged from (35 to 200 m). Seven vehicle speeds are chosen to investigate the effect of this factor on the bridge dynamic response, also the effect of bump height at approach span is studied. The results are presented in terms of Impact Factors (IM). The results show that the IM-radius of curvature relationship is significantly influenced by the position of vehicle on transverse sections of the bridge. For the out-lane loading, the IM values for all girders tend to increase as the radius of curvature decreases. A 45 km/hr vehicle speed provides higher IM value for the good roughness bridge to be at 120 km/hr under poor road surface. The bump heights has a significant effect on IMs at lower speed limit, where the IM value increases with the increasing of bump height.

Study of Unsteady Flow Through and Around an Array of Isolated Square Cylinders

Abstract Flow past a porous square cylinder, which is constituted by an array of small square cylinders, was studied by simplified and highly stable lattice Boltzmann method (LBM) at Re = 4000. The effects of solid volume fractions (SVF) on the flow structure and important aerodynamic parameters were investigated and the internal fluid was described by phase-averaged method and its interaction with the near region. Several energy-contained Strouhal numbers come up in cylinder arrays, and mass flux through arrays is calculated to estimate the effects of blocking. The average total force on the array is found to decrease monotonically with decreasing SVF, and it has a dramatic drop as SVF decreasing from 0.062 to 0.036. The mass flux of array for SVF = 0.062 is smaller than that of 0.073 due to the stagger arrangement of isolated cylinders. The underlying Reynolds stresses reveal the increase in mean wake length as SVF decreases, and it behaves like the solid one for SVF = 0.132. Comparing with the other SVFs, the shear layer region at SVF = 0.132 indicates a significant decrease of curvature and a linear increase of growth rate, but a nonlinear growth rate for the other SVFs can be observed. The local maximum turbulent kinetic energy (TKE) and vorticity in shear layer region reveal the variation during the initial stages following separation. Moreover, detailed investigations of instantaneous wake dynamics provide an assistance to understand the flow physics of cylinder arrays for different SVF.

Corneal Cross-linking for Progressive Keratoconus: Up to 13 Years of Follow-up.

To assess the long-term efficacy and safety of epithelium-off corneal cross-linking according to the Dresden protocol (S-CXL) in progressive keratoconus. Patients treated with S-CXL from April 2006 to January 2010 at Humanitas Clinical and Research Center, Rozzano, Italy, who completed at least 10 years of follow-up were included. Corrected distance visual acuity (CDVA), refraction, and corneal topography and tomography with Pentacam (OCULUS Optikgeräte GmbH) were evaluated at baseline and 10+ years after the procedure. The definition of progression after S-CXL was two of the following three criteria: increase of "A" value, increase of "B" value, or decrease of minimum thickness evaluated with the ABCD progression display above 95% CI for the post-CXL population. Twenty-seven eyes of 22 patients were included. At a mean of 11 years of follow-up (maximum 13 years), S-CXL was able to maintain CDVA and induce significant regularization of the corneal surface as demonstrated by a significant decrease of the central keratoconus index (P = .035) and a decrease of anterior curvature ("A" value) starting from 2.54 ± 2.46, which reduced to 1.14 ± 1.60 (P = .005) at 10+ years of follow-up. Two of 27 eyes included showed significant progression after S-CXL (7.4%). S-CXL was confirmed to be a safe and effective treatment for progressive keratoconus with a failure rate of 7.4% at up to 13 years of follow-up. The authors suggest the use of a combined progression system that evaluates anterior and posterior curvature and with thickness map together with the knowledge of the noise level of the testing system. [J Refract Surg. 2020;36(12):838-843.].

Motion of a capsule in a curved tube

Abstract

Influence of the notch curvature on the impact fracture of the three-point bending beam

Studies show that sharp and blunt notches can be classified in the same research system. In the present study, the virtual-real caustics experimental method is applied to investigate the influence of the notch curvature on the impact fracture behavior of the three-point bending beam with a notch. Moreover, the loading characteristics of the drop hammer impact and the dynamic process of specimen fracture are analyzed in detail. Obtained results demonstrate that the drop hammer impact under the experimental conditions is a process of multiple loadings. It is found that as the notch curvature decreases, the moment of the crack initiation gradually postpones and the whole crack propagation time increases at first and then decreases. The initiation behavior of the notch under the impact loading of the drop hammer is an energy-controlled process rather than a loading force-controlled process. Furthermore, it is found that as the notch curvature decreases, both the peak value of the dynamic stress intensity factor and the corresponding peak value of the propagation velocity of the crack tip increase significantly after the initiation. Obtained results from the extended finite element method (XFEM) show that as the crack initiating gradually decreases, the stress σy at the notch end decreases with the decrease of the notch curvature. Meanwhile, the peak position of the stress gradually shifts to both sides of the notch end as the curvature decreases.

Comparison of Vehicle Dynamics Performance When Operating on High-speed Dedicated and Existing Railways

In order to study the parameters difference between the high-speed dedicated and the existing railway tracks, the geometric parameters and irregularity of the two kind of tracks are compared and analyzed. The nonlinear dynamic model of Electric Multiple Units (EMU) is built, and the difference of dynamics performance of vehicle running on different railway tracks is simulated and analyzed. The results show that the track spectrum overall performance of the high-speed lines is better than that of the existing lines. At the same speed, the lateral and vertical Sperling index of vehicle running on the high-speed dedicated railway tracks is better than that of the existing railway tracks. At low speed (160km/h), when the vehicle is running on the high-speed dedicated railway tracks, the maximum and rootmean square values of the frame lateral acceleration are 59.7% and 24.6% of the existing railway tracks operating conditions respectively, and the corresponding maximum and root mean square values of vertical acceleration are 49.1% and 89.8% respectively. At high speeds (350km/h), the maximum and root mean square values of lateral and vertical acceleration of the frame are 54.2%, 32.3% and 27.6%, 55.3%. With the decrease of the track curvature, the lateral wheelset force gradually increases.

Molecular Patchy Clusters with Controllable Symmetry Breaking for Structural Engineering.

Anisotropic patchy particles with molecular precision are exquisite building blocks for constructing diverse meso-structures of high complexity. In this research, a library of molecular patchy clusters consisting of a collection of functional polyhedral oligomeric silsesquioxane cages with exact regio-configuration and composition were prepared through a robust and modular approach. By meticulously tuning the composition, molecular symmetry, and other parameters, these patchy clusters could assemble into diverse nanostructures, including unconventional complex spherical phases (i.e., Frank-Kasper σ phase and dodecagonal quasicrystalline phase). As the size of the hydrophilic patch expands, a transition sequence from disorder to hexagonally packed cylinders and then to double gyroids was recorded, corresponding to a progressive decrease of interfacial curvature. On the other hand, regioisomers with the same composition but different regio-configuration adopt similar molecular packing but varied phase stability, as a result of the local self-sorting process to alleviate excess unfavorable interfacial contact. These precisely defined molecular patchy clusters provide a model system for a general understanding of the hierarchical structure formation and evolution based on anisotropic spherical building blocks at the nanoscale.

Baroreflex Modulation During Acute High-Altitude Exposure in Rats.

Baroreflex (BR) control is critically dependent of sympathetic and parasympathetic modulation. It has been documented that during acute hypobaric hypoxia there is a BR control impairment, however, the effect of a natural hypoxic environment on BR function is limited and controversial. Therefore, the aim of this study was to determine the effect of acute High-Altitude exposure on sympathetic/parasympathetic modulation of BR control in normal rats. Male Sprague Dawley rats were randomly allocated into Sea-Level (n = 7) and High-Altitude (n = 5) (3,270 m above sea level) groups. The BR control was studied using phenylephrine (Phe) and sodium nitroprusside (SNP) through sigmoidal analysis. The autonomic control of the heart was estimated using heart rate variability (HRV) analysis in frequency domain. Additionally, to determine the maximum sympathetic and parasympathetic activation of BR, spectral non-stationary method analysis, during Phe (0.05 μg/mL) and SNP administration (0.10 μg/mL) were used. Compared to Sea-Level condition, the High-Altitude group displayed parasympathetic withdrawal (high frequency, 0.6–2.4 Hz) and sympathoexcitation (low frequency, 0.04–0.6 Hz). Regarding to BR modulation, rats showed a significant decrease (p < 0.05) of curvature and parasympathetic bradycardic responses to Phe, without significant differences in sympathetic tachycardic responses to SNP after High-Altitude exposure. In addition, the non-stationary analysis of HRV showed a reduction of parasympathetic activation (Phe) in the High-Altitude group. Our results suggest that acute exposure to High-Altitude produces an autonomic and BR control impairment, characterized by parasympathetic withdrawal after 24 h of high-altitude exposure.

Safety and Efficacy of Collagenase Clostridium histolyticum in the Treatment of Acute Phase Peyronie's Disease: A Multi-institutional Analysis

To study, in a multi-institutional setting, the efficacy/safety outcomes in acute phase Peyronie's disease (PD) of multiple high-volume centers employing CCH to treat PD, which is defined as the abnormal formation of fibrous plaque(s) in the tunica albuginea of the penis. It is a chronic condition that afflicts 3%-13% of the US male population. There is no current multi-institutional research on the efficacy and safety of collagenase Clostridium histolyticum (CCH) in the treatment of acute phase PD. Retrospective data were collected for consecutive patients with PD who underwent treatment with CCH between April 2014 and March 2018 at 5 institutions. 918 patients were included. Patients with duration of PD no longer than 6 months at presentation qualified as being in the acute phase of PD. Main outcomes of interest include the change in curvature after receiving CCH therapy, and frequency of serious treatment-related adverse events. Successful improvement in curvature is defined as an at least 20% decrease in penile curvature from baseline after CCH therapy. A total of 918 patients were included in the analysis, of which 134 (14.6%) qualified as acute phase PD (group 1) and the remaining 784 (85.4%) qualified as stable phase (group 2). Mean duration of PD was 4.44 ± 1.68 months for group 1, and 40.8 ± 61.2 months for group 2. There was no significant difference in final change in curvature between acute and stable phase of PD (13.5° vs 15.6°, P = .09). There was no statistically significant difference in frequency of treatment-related adverse events between the acute phase (16 patients, 11.9%) and the stable phase (77 patients, 9.8%; P=.44). In our multivariate analysis, only number of CCH cycles received was predictive of improvement of curvature. This large multi-institutional analysis confirms that CCH therapy is as safe and efficacious in acute phase PD as it is in stable phase PD.

Microstructural Optimization of Fe‐Rich Intermetallic in Al–12 wt% Si–2 wt% Fe alloys by Adding Travelling Magnetic Fields

Iron can cause negative effects on the recycling and mechanical performance of Al–Si alloys, because it is difficult to remove, and easy to form Fe‐rich intermetallic with large size. In this regard, travelling magnetic fields are performed to optimize Fe‐rich intermetallic in Al–12 wt% Si–2 wt% Fe alloys; and experiments and simulations are conducted to study the related evolutions induced by different Fe content from 0.1 to 2 wt% and by travelling magnetic fields. Current findings conclude that the increase of Fe content changes the precipitation sequence, causing Fe‐rich intermetallic to preferentially form and convert from α‐Al8Fe2Si to β‐Al9Fe2Si2; accompanied by the increase of aspect ratio and max‐length from 1.81 and 15.0 μm ( wt% Fe) to 50.2 and 578.2 μm (2 wt% Fe) respectively, as well as the decrease of curvature from 0.079 μm−1 (0.1 wt% Fe) to 0.001 μm−1 (2 wt% Fe). Moreover, precipitates containing Cu shift from adhering to the (Al, Si) phases to Fe‐rich intermetallic. In additionally, primary Si particles and Al–Si eutectic phases decrease. Noteworthily, travelling magnetic fields can reduce nucleate radius and generate intense long‐range directional melt flows, further to distribute temperature and solute uniformly and break up Fe‐rich intermetallic, so as to optimize them. Consequently, max‐length and aspect ratio decrease by 43.7% and 44.6%, whereas curvature increases by 2.7 times.

Analog Models of Fold-and-Thrust Wedges in Progressive Arcs: A Comparison With the Gibraltar Arc External Wedge

The timing and kinematics of the different type of structures and the associated vertical axis-rotations that permit an arcuate external wedge to acquire progressively its curved shape throughout its deformation history --known as progressive arcs-- are key questions in natural cases of arcuate fold-and-thrust belts, that we want to address through analogue modelling. We present laboratory models of fold-and-thrust belts formed with a backstop that deforms in map view to simulate progressive arcs in a thin-skinned tectonic regime. Our set-up makes use of a deformable backstop rigid enough to push-from-behind the initial parallelepiped but deformable in map view. This innovative design permits us to increase the amplitude of the arc indenting in the model as its radius of curvature decreases, that is, it simulates a progressive arc. Taking the Gibraltar arc external wedge situated in the western Mediterranean to scale our models in terms of rheology, velocities and sizes, four types of experiments were made. We varied the type of substratum (sand or silicone), the silicone thickness and the width and length of the initial analogue pack in order to test the influence of each of these parameters on the resulting fold-and-thrust belts. All experiments led to the formation of arcuate wedges where strain was partitioned into: a) arc-perpendicular shortening, accommodated by thrusts which main structural trend is broadly subparallel to the indenter shape and with divergent transport directions, and b) arc-parallel stretching, accommodated by normal and conjugate strike-slip faults. The normal and strike-slip faults contributed to the fold-and-thrust belt segmentation and the formation of independent blocks that rotated clockwise and counterclockwise depending on their position within the progressive arc. Our experiments allow simulating and understanding the finite deformation mode of the external wedge of the Gibraltar arc. Accordingly, they shed light on how an arcuate fold-and-thrust belt can develop progressively in terms of structural trend and transport directions, types and distribution of the structures accommodating strain partition and timing of vertical-axis rotations.