Variation In Rigidity Research Articles

Study of skin rigidity variations due to UV radiation using digital holographic interferometry

The skin elasticity is a relevant biomechanical property that can be related to different physiological processes and diseases: hence, it is important to understand and characterize the mechanisms that affect the skin pathologies. In this work, an analysis of the rigidity variations of porcine skin caused by exposure to ultraviolet radiation is presented. For this purpose digital holographic interferometry (dhi) is used as a non-invasive optical technique to study these skin affectations. A new mathematical scheme for the skin rigidity variations was developed and the experimental data was used to study and determine the rigidity coefficients for the samples before and after ultraviolet exposure of the skin. The results after high doses of ultraviolet radiation at 8 mW/cm2 UVA, 8 mW/cm2 UVB and 10 mW/cm2 UVC for periods of 3 min showed that these rigidity coefficients increased above 100% (more than twice) their value after the ultraviolet exposure. The latter suggests a considerable reduction of the porcine skin elasticity when exposed to high doses of ultraviolet radiation, a feature that has been proved to lead to skin melanoma.

Influence of the Solar Wind and Geomagnetic Activity Parameters on Variations in the Cosmic Ray Cutoff Rigidity during Strong Magnetic Storms

The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and the Dst index of geomagnetic activity during one moderate and six strong storms of solar cycles 23 and 24 has been calculated. The ΔR values have been obtained with two methods: (1) the spectrographic global survey method (SGS), in which the determination of the cutoff rigidity RSGS is based on observational data from the neutron monitor network, and (2) a method in which the particle trajectories are calculated numerically in a model magnetic field of the magnetosphere to determine the cutoff rigidity Reff. In general, the results obtained by the two methods are in close agreement. The Dst index of geomagnetic activity has the greatest effect on ΔR, and the correlation increases with storm intensity. The sensitivity of ΔR to interplanetary parameters vary greatly for different storms. The most geoeffective interplanetary parameter is the solar-wind speed V. A significant anticorrelation of ΔR and V can be traced for almost all storms. The correlation of ΔRSGS with the Bz component of the interplanetary magnetic field is observed only for two storms, on November 7–14, 2003, and November 7–8, 2004, for which the absolute Bz value was very high (≈−50 nT). At the same time, there is a rather high correlation of ΔReff with Bz for most storms. The azimuthal component of the interplanetary field By and the solar-wind dynamic pressure P show almost no connection with ΔR.

Development of Damping Cutter Construction with Rigidity Variation on Holder Length

Development of Damping Cutter Construction with Rigidity Variation on Holder Length

Dye-insertion dynamic breathing MOF as dual-emission platform for antibiotics detection and logic molecular operation

Antibiotic pollution as a hot topic of global concern is greatly sought after due to the adverse effect on ecosystems and human health stemming from the excessive use and deficient management. Achieving detection of antibiotics residues in water is extremely crucial but remains challenging. Herein, four metal-organic frameworks 1–4 with different luminescent behaviors were demonstrated by variation of the systematic rigidity and assemble form. To fabricate the solid dual-emission probe, the gust dye 4-(4-diethylaminostyryl)-1-methylpyridinium (DEASM) is successfully encapsulated into a non-porous flexible MOF 4 ascribed to the dynamic breathing effect. The resulting composite displays the dual-emission behavior with the color linearly tuned from green to red and ratiometric luminescent response to pH with controllable sensitivity, supported by dimensionality dependent energy transfer. Furthermore, 4⊃DEASM exhibits sensitive and selective sensing performances towards nitrofurazone and could be integrated into a logic operation. Thus, our study may bring new perspective for the design of dye encapsulated MOF dual-emission ratiometric sensor to monitor antibiotic in water.

Enhancement of Galloylation Efficacy of Stigmasterol and β-Sitosterol Followed by Evaluation of Cholesterol-Reducing Activity.

In this study, incorporation of gallic acid into typical phytosterols (β-sitosterol and stigmasterol) through Steglich esterification was optimized employing the protection and deprotection strategy. A novel mechanism leading to side esterification was discovered. Complication of the phenolic hydroxyl groups and side reactions were successfully reduced under the optimized conditions. The structural identity and purity of galloyl stigmasterol and galloyl β-sitosterol were confirmed by NMR, FT-IR, and HPLC-MS. Evaluation of galloyl β-sitosterol and galloyl stigmasterol revealed their excellent antioxidant and cholesterol-reducing activities. Significant enhancement of cholesterol-reducing activity by galloylation was unveiled especially for β-sitosterol. Galloyl β-sitosterol had slightly better antioxidant activity at ambient temperature and better cholesterol-reducing activity. Molecular modeling suggested that a subtle difference of galloyl β-sitosterol and galloyl stigmasterol in activities could be attributed to variation of molecular rigidity and conformation. The excellent properties of galloyl β-sitosterol and galloyl stigmasterol suggested their great potential application in the food industry.

Backflow from a model fracture network: an asymptotic investigation

We develop a model for predicting the flow resulting from the relaxation of pre-strained, fluid-filled, elastic network structures. This model may be useful for understanding relaxation processes in various systems, e.g. deformable microfluidic systems or by-products from hydraulic fracturing operations. The analysis is aimed at elucidating features that may provide insight on the rate of fluid drainage from fracturing operations. The model structure is a bifurcating network made of fractures with uniform length and elastic modulus, which allows for general self-similar branching and variation in fracture length and rigidity between fractures along the flow path. A late-time $t^{-1/3}$ power law is attained and the physical behaviour can be classified into four distinct regimes that describe the late-time dynamics based on the location of the bulk of the fluid volume (which shifts away from the outlet as branching is increased) and pressure drop (which shifts away from the outlet as rigidity is increased upstream) along the network. We develop asymptotic solutions for each of the regimes, predicting the late-time flux and evolution of the pressure distribution. The effects of the various parameters on the outlet flux and the network’s drainage efficiency are investigated and show that added branching and a decrease in rigidity upstream tend to increase drainage time.

Cerebral arteriovenous malformation venous stenosis is associated with hemodynamic changes at the draining vein-venous sinus junction

Cerebral arteriovenous malformations (AVMs) are an uncommon vascular anomaly that carry the risk of rupture and hemorrhage. Several factors have been implicated in the propensity of an AVM to bleed. One such factor is stenosis of AVM draining veins, as impairment of the AVM venous drainage system is associated with increased risk of intracranial hemorrhage. Currently, our understanding of the pathogenesis of AVM venous outflow stenosis is limited, as there is insufficient data on the blood flow patterns and local hemodynamic parameters of these draining veins.The angioarchitecture of AVMs features a nidus lacking a high resistance capillary network. Accordingly, our previous studies on AVM arterial feeders have demonstrated an abnormally high flow volume rate along with low pulsatility and resistance indices on quantitative magnetic resonance angiography. As such, AVM vessels endure high, non-physiologic levels of flow that may partially contribute to ectasia or stenosis depending on whether wall shear stress (WSS) is high or low, respectively.We hypothesize that AVM venous outflow stenosis occurs most commonly near the junction of the draining vein and the dural venous sinus. Increased flow volume rate through the AVM circuit coupled with the variation in compliance and rigidity between the walls of the draining vein and the dural venous sinus likely create turbulence of blood flow. The resulting flow separation, low WSS, and departure from axially aligned, unidirectional flow may create atherogenic conditions that can be implicated in venous intimal hyperplasia and outflow stenosis. We have previously found there to be a significant association between intimal hyperplasia risk factors and venous outflow stenosis. Additionally, we have found a significant association between age and likelihood as well as degree of stenosis, suggesting a progressive disease process.Similar conditions have been demonstrated in the pathophysiology of stenosis of the carotid artery and dialysis arteriovenous fistulas. In both of these conditions, the use of computational fluid dynamics (CFD) has been employed to characterize the local hemodynamic features that contribute to the pathogenesis of intimal hyperplasia and stenosis. We recommend the utilization of CFD to characterize the anatomic and hemodynamic features of AVM venous outflow stenosis. An improved understanding of the possible causative features of venous outflow stenosis may impact how clinicians choose to manage the treatment of patients with AVMs.

Variations of geomagnetic cutoff rigidity in the southern hemisphere close to 70°W (South-Atlantic Anomaly and Antarctic zones) in the period 1975–2010

We report the existence of rapid variations in (effective) geomagnetic cutoff rigidity (Rc) between the equatorial and Antarctic zones adjacent to the Andes Mountains, revealed by the variation rate of geomagnetic cutoff rigidity (VRc) in the period 1975–2010. Our analysis is based on empirical records and theoretical models of the variations in cosmic rays and on the structure of geomagnetic fields. These have given us a different view of variations in Rc in time and space along the 70°W meridian, where secular variations in the geomagnetic field are strongly influenced by the proximity of the South Atlantic Magnetic Anomaly (SAMA), one of the most important characteristics of the terrestrial magnetic field that affects our planet, close from the equator to the 50°S parallel and from South America to South Africa. The VRc presents rapid changes in mid-latitudes where SAMA exerts its influence despite the existence of smooth changes in the geomagnetic field. This shows that these changes occur mainly in the spatial configuration, rather than in the temporal evolution of Rc. The analysis was performed using measurements from the Chilean Network of Cosmic Rays and Geomagnetism Observatories, equipped with BF-3 and latest generation He-3 neutron monitors, Fluxgate magnetometers, geomagnetic reference field (IGRF) and Tsyganenko 2001 model (just for completeness).

Biomimetic Surface with Tunable Frictional Anisotropy Enabled by Photothermogenesis‐Induced Supporting Layer Rigidity Variation

AbstractAnisotropic friction of widespread biological surfaces with micro‐ and nanostructures oriented to supporting layer is proved to be crucial for the purpose of locomotion or transporting items in nature, which is therefore attracting extensive attention. Herein, variation of supporting layer rigidity induced dynamic control of anisotropic friction of biomimetic surface with structures oriented to supporting substrate is demonstrated. The biomimetic surface with oriented hook‐like spines microstructures embedded in polymeric substrate is fabricated by three‐dimensional (3D) printing followed by transfer reproduction. Incorporation of Fe3O4 nanoparticles with excellent near‐infrared (NIR)/infrared (IR) photothermogenesis in the substrate results in its variable rigidity with light on/off, which achieves the tunable anisotropic friction performance of the biomimetic surface. A proof‐of‐concept device with the function of Velcro type strip is demonstrated to unsnap the fastener by remote NIR/IR light, revealing its promising for designing intelligent control devices. It is believed that this novel anisotropic friction controllable system with photothermogenesis‐induced supporting layer rigidity variation will provide wide and potential applications in various fields including sensors, robots, and other bionic devices.

Irregular Transition Layer Beneath the Earth's Inner Core Boundary From Observations of Antipodal PKIKP and PKIIKP Waves

AbstractStandard Earth models assume a simple uniform inner core boundary (ICB) separating the liquid iron outer core from the solid iron inner core. Metallurgical and geodynamic experiments, however, predict lateral variations along this boundary originating from thermochemical and geodynamic instabilities during solidification. We search for evidence of this lateral heterogeneity by exploiting the sensitivity of antipodal PKIIKP waveforms to the shear wave velocity structure of the uppermost inner core beneath their reflection points on the underside of the ICB. Measuring PKIIKP/PKIKP energy ratios from 33 rare antipodal seismograms in the 178o to 180o distance range, we find this ratio varying between 0.1 and 1.1. Synthetic seismograms demonstrate that a laterally homogeneous liquid‐solid ICB cannot account for this variability. Observations instead support a spatially variable ICB transition consisting of either (1) gradients in seismic velocities and density in which they smoothly increase from those at the outer core to those in the bulk of the inner core over a maximum depth of 10 km or (2) a layered transition with localized double discontinuities in velocities and densities separated by 4–10 km. A layered transition can generate a coda following PKIKP if shear velocity is small (<2 km/s) in the transition. Our results imply that the ICB is not uniform and might appear patchy with lateral rigidity variations. Nonuniform small‐scale structural features that we infer to be present at the ICB are consistent with nonlinear solidification mechanisms driven by small‐scale outer core convection in the lowermost outer core.

The effect of polyethylene glycols on the interaction and stability of AOT/water/isooctane microemulsions

The influence of water-soluble polyethylene glycols PEG200 on the properties of sodium bis(2-ethylhexyl)-sulfosuccinate (AOT) water-in-isooctane microemulsions has been investigated by conductivity measurement and isothermal titration microcalorimetry (ITC). The percolation temperatures (Tp), the thermodynamic properties of droplet aggregation and the interaction enthalpy (−ΔHφ) between droplets for AOT/water/PEG200/isooctane with different PEG concentrations and a fixed molar ratio of water to surfactant ω = 22.2 were determined. Based on a two-stage thermodynamic approach of the percolation, we obtained the fusion enthalpy (ΔHf0) of the close contact droplets by a combination of the droplet aggregation enthalpy (ΔHag0) and −ΔHφ. It was found that both (−ΔHφ) and (ΔHf0) varied with the concentration of PEG200 (cPEG) and had the extreme value at cPEG = 25 g L−1. This phenomenon was interpreted by the variation of interface rigidity due to the varied distributions of added PEG200 between the water pool and the surfactant interface.

Analysis of Exposure to Solar and Galactic Cosmic Radiations of Flights Representative of the European International Air Traffic.

This study analyzed the impact of galactic and solar cosmic rays on ambient dose equivalent during airline travel. A high statistic of flights are considered, which is representative of European international air traffic. Flight paths are based on the Eurocontrol Demand Data Repository and consider realistic flight plans with and without regulations or updated with radar data from the Central Flow Management Unit. Ambient dose equivalent during flights was investigated during quiet solar periods and extreme solar flare events. Thus, the statistical analyses presented here take into account route characteristics (departure, arrival, continent, etc.) and space weather conditions. The findings of this work show the important influence of flight path, particularly the latitude, which drives the cutoff rigidity variations. Moreover, dose values vary drastically during ground level enhancement events, with the route path (latitude, longitude and altitude) and the phasing of the solar event. This study highlights the importance of monitoring these solar events and developing a physical approach to obtain reliable assessment of ambient dose equivalents.

Instantaneous cutting-amount planning for machining deformation homogenization based on position-dependent rigidity of thin-walled surface parts

Thin-walled parts with curved surfaces are widely used in industrial applications, and the surface quality is a basic requirement to ensure the functional performance. Due to the thin-walled and curved geometric features, the rigidity for this kind of parts is not only low but also position-dependent. In this way, the deformation of such parts is easy to vary and complex along the toolpath in the machining process, which results in a poor dimensional quality for the thin-walled parts with curved surfaces. However, it is a novel idea that when the machining deformation is homogeneous, the deformation compensation is easily carried out and the improved machining quality can be obtained for the thin-walled curved surface parts. For the machining deformation is affected by the cutting force and the cutting force is affected by the instantaneous cutting-amount in essence, an instantaneous cutting-amount planning approach based on the position-dependent rigidity of thin-walled curved surface parts is proposed in this study, so as to homogenize the machining deformation thus improving the machining quality. Inspired by the generalized Hooke law, the instantaneous cutting-amount is planned here to be harmonious with the rigidity variation along the toolpath, so that the ratio between the cutting force and the rigidity, i.e. the deformation at certain cutting-position, can be kept as a constant value. For this sake, the instantaneous cutting-amount of thin-walled curved surface parts during the five-axis machining process is first modeled, and then, the position-depended rigidity of the parts is calculated. Finally, the instantaneous cutting-amount is scheduled according to the position-dependent rigidity. Experimental results verify the effectiveness of the presented method in homogenizing of the machining deformation. Achievements of this study are significant for enriching the high-quality machining technique of thin-walled parts with curved surfaces.

Minimizing assembly variation in selective assembly for auto-body parts based on IGAOT

PurposeDimensional quality of sheet metal assemblies is an important factor for the final product. However, the part tolerance is not easily controlled because of the spring back deformation during the stamping process. Selective assembly is a means to decrease assembly tolerance of the assembly from low-precision components. Therefore, the purpose of this paper is to propose a fully efficient method of selective assembly optimization based on an improved genetic algorithm for optimization toolbox (IGAOT) in MATLAB.Design/methodology/approachThe method of influence coefficient is first applied to calculate the assembly variation of sheet metal components since the traditional rigid assembly variation model cannot be used due to welding deformation. Afterwards, the IGAOT is proposed to generate optimal selective groups, which consists of advantages of genetic algorithm for optimization toolbox (GAOT) and simulated annealing.FindingsThe cases of two simple planes and the tail lamp bracket assembly are used to illustrate the flowchart of optimizing combinations of selective groups. These cases prove that the proposed IGAOT has better precision than that of GAOT with the same parameters for selective assembly.Originality/valueThe research objective of this paper is to evaluate the changes from rigid bodies to sheet metal parts which are very complex for selective assembly. The method of IGAOT was proposed to the selected groups which has better precision than that of current optimization algorithms.

Variations in the Geomagnetic Cutoff Rigidity during the Magnetic Storm in March 2015

Variations in the planetary system of the geomagnetic cutoff rigidity during the moderate geomagnetic storm in March 2015 are calculated on the basis of data from cosmic-ray measurements at the world network of stations. The distance to the subsolar point and the radius of the ring current are calculated on the basis of the axisymmetric restricted Earth’smagnetosphere model that takes into account currents at the magnetopause and the ring current. The contribution of the ring current to variations in the geomagnetic cutoff rigidity and to the disturbance storm time (Dst) index is also determined within this model.

Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin

Abstract. We present a different view of secular variation of the Earth's magnetic field, through the variations in the threshold rigidity known as the variation rate of geomagnetic cutoff rigidity (VRc). As the geomagnetic cutoff rigidity (Rc) lets us differentiate between charged particle trajectories arriving at the Earth and the Earth's magnetic field, we used the VRc to look for internal variations in the latter, close to the 70° south meridian. Due to the fact that the empirical data of total magnetic field BF and vertical magnetic field Bz obtained at Putre (OP) and Los Cerrillos (OLC) stations are consistent with the displacement of the South Atlantic magnetic anomaly (SAMA), we detected that the VRc does not fully correlate to SAMA in central Chile. Besides, the lower section of VRc seems to correlate perfectly with important geological features, like the flat slab in the active Chilean convergent margin. Based on this, we next focused our attention on the empirical variations of the vertical component of the magnetic field Bz, recorded in OP prior to the Maule earthquake in 2010, which occurred in the middle of the Chilean flat slab. We found a jump in Bz values and main frequencies from 3.510 to 5.860 µHz, in the second derivative of Bz, which corresponds to similar magnetic behavior found by other research groups, but at lower frequency ranges. Then, we extended this analysis to other relevant subduction seismic events, like Sumatra in 2004 and Tohoku in 2011, using data from the Guam station. Similar records and the main frequencies before each event were found. Thus, these results seem to show that magnetic anomalies recorded on different timescales, as VRc (decades) and Bz (days), may correlate with some geological events, as the lithosphere–atmosphere–ionosphere coupling (LAIC).

Impact of inhomogeneity on SH-type wave propagation in an initially stressed composite structure

The present analysis has been made on the influence of distinct form of inhomogeneity in a composite structure comprised of double superficial layers lying over a half-space, on the phase velocity of SH-type wave propagating through it. Propagation of SH-type wave in the said structure has been examined in four distinct cases of inhomogeneity viz. when inhomogeneity in double superficial layer is due to exponential variation in density only (Case I); when inhomogeneity in double superficial layers is due to exponential variation in rigidity only (Case II); when inhomogeneity in double superficial layer is due to exponential variation in rigidity, density and initial stress (Case III) and when inhomogeneity in double superficial layer is due to linear variation in rigidity, density and initial stress (Case IV). Closed-form expression of dispersion relation has been accomplished for all four aforementioned cases through extensive application of Debye asymptotic analysis. Deduced dispersion relations for all the cases are found in well-agreement to the classical Love-wave equation. Numerical computation has been carried out to graphically demonstrate the effect of inhomogeneity parameters, initial stress parameters as well as width ratio associated with double superficial layers in the composite structure for each of the four aforesaid cases on dispersion curve. Meticulous examination of distinct cases of inhomogeneity and initial stress in context of considered problem has been carried out with detailed analysis in a comparative approach.

Evaluation of the Free-Vibration Frequency and the Variation of the Bending Rigidity of Graphene Nanoplates: The Role of the Shape Geometry and Boundary Conditions

Evaluation of the Free-Vibration Frequency and the Variation of the Bending Rigidity of Graphene Nanoplates: The Role of the Shape Geometry and Boundary Conditions

Parameters of current systems in the magnetosphere as derived from observations of cosmic rays during the June 2015 magnetic storm

Basing on measurements of cosmic rays at the worldwide network of stations, we calculate variations in the planetary system of geomagnetic cutoff rigidity for the 2015 June moderate geomagnetic storm. Using the axisymmetric model of the limited magnetosphere taking into account magnetopause currents and the ring current, we determine the distance to the subsolar point and the ring current radius, as well as the contribution of the ring current to variations in the geomagnetic cutoff rigidity and to the Dst index.

Параметры токовых систем в магнитосфере по данным наблюдений космических лучей в период магнитной бури в июне 2015 г.

Basing on measurements of cosmic rays at the worldwide network of stations, we calculate variations in the planetary system of geomagnetic cutoff rigidity for the 2015 June moderate geomagnetic storm. Using the axisymmetric model of the limited magnetosphere taking into account magnetopause currents and the ring current, we determine the distance to the subsolar point and the ring current radius, as well as the contribution of the ring current to variations in the geomagnetic cutoff rigidity and to the Dst index.