Average Bending Angle Research Articles

Regional differences in electroactive response of the sclera.

The sclera exhibits mechanical response when subjected to an external electric stimulation. The scleral electroactive response is a function of its charge density, mechanical properties, thickness, and strength of the applied electric voltage. The primary objective of the present work was to investigate the regional differences in the electroactive response of porcine sclera. To this end, we cut scleral strips in meridional directions from superior-temporal, superior-nasal, inferior-temporal, and inferior-nasal quadrants. In addition, we excised samples circumferentially from the posterior, equatorial, and anterior regions. The electroactive bending response of these samples was measured under 10 and 15 V in 0.15 M NaCl solution. The meridional samples were tested under two different configurations by clamping them either from their anterior or posterior end. It was observed that the scleral electroactive deformation increased with increasing the the electric voltage. Furthermore, regardless of the region from which meridional strips were excised, their electroactive response was considerably larger when they were clamped from their anterior end. Unlike meridional strips, the electroactive response of circumferential samples was significantly dependent on the location, that is, the average maximum bending angle of posterior samples was significantly larger than that of equatorial and anterior strips. The regionally different electroactive bending response of the sclera was discussed in terms of the variation in its biochemical and biomechanical properties throughout the eyeball.

Design and Performance Analysis of Wavy Nonrotating Pneumatic Soft Actuator

Abstract Soft robots can accomplish hand rehabilitation training to ensure better safety and compliance for hand rehabilitation. In this study, a wavy nonrotating soft actuator structure was proposed for hand rehabilitation, and an axial stiffener was added to the main structure of the actuator according to the function of the bamboo fiber. A physical model of the actuator was fabricated using a multistep casting molding method, and the performance of the designed soft actuator was tested experimentally. The results showed that the bending angle and contact force gradually increased with increasing pressure. The average maximum bending angle and contact force can reach 286 ± 14.3 deg and 1.04 ± 0.051 N, with a pressure of 72 kPa. Meanwhile, the bending torques of the soft actuator at each joint of the finger were tested, to verify that it can meet the needs of soft actuators for hand applications. Furthermore, the load lifting of the soft actuator with axial stiffeners can increase by 6 mm on average compared with a soft actuator without axial stiffeners under negative pressure. In conclusion, the pneumatic soft actuator can produce two different motion functions under the action of one cavity. In addition, a soft actuator with an axial stiffener can improve the load capacity under negative pressure. By assembling the actuators, a three-finger gripper was manufactured. The gripper could grasp and lift objects. Therefore, this work provides a new route for the development of pneumatic soft actuators and soft robots, which has efficient driving.

Dynamic Simulation Analysis of the Working Process of the Picking Mechanism of a Sugarcane Leaf Cutting and Returning Machine

Leaf–device interaction can effectively be modeled with a finite element model when proper finite element model parameters are applied. In order to investigate the contact mechanism of picking up sugarcane leaf during the operation of a sugarcane leaf cutting and returning machine, a geometric solid model of sugarcane leaf picking was established. A finite element numerical model to analyze the large deformation problem of flexible bodies was developed in LS-DYNA to simulate the picking process of the returning machine. A dynamic simulation of the sugarcane leaf-picking process was carried out to obtain the change of stress field and the motion posture of the sugarcane leaf and the elastic teeth. The picking process of the picking mechanism, the change in posture of the sugarcane leaves, the change in stress on the sugarcane leaf, the change in the bending angle of the sugarcane leaf and the change in stress on the elastic teeth were analyzed in detail. The results showed that the picking process can be divided into four stages: picking, lifting, pushing and retrieving. The posture changes of sugarcane leaf are “C”, logarithmic curve, wavy shape and “V”, in turn. During the picking process, the sugarcane blade showed some breakage, the sugarcane vein remained intact, and the elastic teeth did not fail. During the whole picking cycle, the maximum Von Mises stress of the blade, vein and elastic teeth were 22.8 MPa, 17.5 MPa and 900 MPa, respectively. An evaluation criterion of bending angle was creatively put forward to measure the bending deformation of leaves. The trend in the sugarcane leaf bending angle shows that it is largely variable, gradually decreasing, fluctuating and increasing with interval fluctuations. The working process of the picking mechanism was observed through a quick camera experiment. Comparing the experiment with the simulation, the changing trend of the simulation data and experimental data was generally similar. The experimental and simulation values of the average sugarcane leaf bending angle were 27° and 19°, respectively. The relative error of the average bending angle was 29.6%. It was concluded that the developed finite element model is substantial and could be applied to optimize and improve the picking mechanism. In addition, some references were provided for the contact mechanism between the picking mechanism and the sugarcane leaf.

Improve bendability of a Cr-alloyed press-hardening steel through an in-line quenching and non-isothermal partitioning process

A new hot stamping process consisting of an in-line quenching and simultaneous non-isothermal partitioning was applied to improve the bendability of a Cr-alloyed press-hardening steel (Fe-0.23C-1.1Mn-(Cr + Si) < 5.0, wt%). The quenching temperature was controlled by the dwell time during die quench, and the non-isothermal partitioning was achieved through the subsequent air cooling after die opening. The feasibility of carbon partitioning during the air cooling stage was verified by kinetics calculation. Compared with the conventional hot stamping (HS) sample, around 6 vol% nano-sized metastable austenite was obtained in the sample processed by hot stamping with the in-line quenching and non-isothermal partitioning process (HS&QP). As a result, the average bending angle of the HS&QP samples increased by 10 % from 51.2° to 56.2°, and the total absorbed energy increased by 11 % from 28.7 J to 31.9 J compared with conventional HS samples, respectively. Meanwhile, the average ultimate tensile strength (1590 MPa) and total elongation (7.6 %) of the HS&QP samples are still better than that of the commercial-grade AlSi-coated 22MnB5. The proposed in-line quenching and non-isothermal partitioning process can significantly improve the bending properties of the newly developed Cr-alloyed PHS, increase press utilization, while balancing the requirements for strength, ductility and dimensional accuracy. It is a technically promising alternative to the conventional hot stamping process with economic value suitable for the newly developed Cr-alloyed PHS.

Incommensurate lamellar phase from long chain Mannosides: Investigation by X-Ray scattering and replica exchange molecular dynamics (REMD)

We report the synthesis and phase behaviour of two anhydrous mannosides (αManC18 and αManC18:1) with stearyl and monounsaturated oleyl hydrocarbon chains that can be obtained from vegetable sources. These mannosides have been characterised by differential scanning calorimetry, polarised optical microscopy and small- and wide-angle X-ray scattering. The two compounds exhibited multiple d-spacing bilayer structures. αManC18:1 gives a distinct incommensurate lamellar that persists until high temperature. On the other hand, αManC18 forms an incommensurate gel phase only at low temperature but undergoes a transition into the lamellar (Lα) liquid crystal phases on heating. The results were confirmed by replica exchange molecular dynamics (REMD). The average hydrocarbon chain/headgroup tilt angles 〈ϕ〉/〈θ〉, and average chain bending angle 〈ψ〉 were calculated for the simulated bilayer systems at ∼ 25 °C. The multiple averaged headgroup tilt angles 〈θ〉 explain the observed incommensurate bilayer structures with different bilayer thicknesses in these long hydrocarbon chain of mannosides. Moreover, different tilting angles of the headgroup result in different surface areas per lipid. Relating the incommensurate phase properly to molecular parameters is important especially in multi-component membranes, where the interplay of different molecule types is difficult to predict on intuitive grounds.

Dependency of the twist-bend nematic phase formation on the molecular shape of liquid crystal dimers: A view through the lens of DFT

In view of the importance of molecular structural features, particularly the molecular curvature, that form the basis for the appearance and stabilization of the twist-bend nematic (Ntb) phase, the present work reports a computational study on a set of cyanobiphenyl dimers. In these dimers, the chemical nature of the linkage between the spacer and mesogenic units has been systematically varied by incorporating either methylene, ether, or thioether groups. Through computational modeling, we calculated the bend angle between the two mesogenic arms from all-trans conformations as well as Boltzmann-weighted average bend angle from conformational ensembles for each dimer. It was observed that the incidence of the Ntb phase is not only sensitive to the degree of molecular bend angle but also the conformational distribution. The present analysis recognized that the Ntb phase is only seen in liquid crystal dimers that have a sufficiently bent molecular structure. In addition, we have found a strong dependency of transitional properties upon these molecular factors. The changes in the phase transition temperatures appear to be a direct consequence of discrete changes in the molecular bend angle, as this is the major difference when comparing these dimers.

Experimental and numerical analysis of electroactive characteristics of scleral tissue

The sclera provides mechanical support to retina and protects internal contents of the eye against external injuries. The scleral extracellular matrix is mainly composed of collagen fibers and proteoglycans (PGs). At physiological pH, collagen molecules are neutral but PGs contain negatively charged glycosaminoglycan chains. Thus, the sclera can be considered as a polyelectrolyte hydrogel and is expected to exhibit mechanical response when subjected to electrical stimulations. In this study, we mounted scleral strips, dissected from the posterior part of porcine eyes, at the center of a custom-designed container between two electrodes. The container was filled with NaCl solution and the bending deformation of scleral strips as a function of the applied electric voltage was measured experimentally. It was found that scleral strips reached to an average bending angle of 3°, 10° and 23° when subjected to 5V, 10V, and 15V, respectively. We also created a chemo-electro-mechanical finite element model for simulating the experimental measurements by solving coupled Poisson-Nernst-Plank and equilibrium mechanical field equations. The scleral fixed charge density and modulus of elasticity were found by fitting the experimental data. The ion concentration distribution inside the domain was found numerically and was used to explain the underlying mechanisms for the scleral electroactive response. The numerical simulations were also used to investigate the effects of various parameters such as the electric voltage and fixed charge density on the scleral deformation under an electric field. Statement of significanceThis manuscript investigates the electroactive response of scleral tissue. It demonstrates that the sclera deforms mechanically when subjected to electrical stimulations. A chemo-electro-mechanical model is also presented in order to numerically capture the electromechanical response of the sclera. This numerical model is used to explain the experimental observations by finding the ion distribution inside the tissue under an electric field. This work is significant because it shows that the sclera is an electroactive polyanionic hydrogel and it provides new information about the underlying mechanisms governing its mechanical and electrical properties.

Study on the Influence of Anchorage Angle on the Anchorage Effect of Soft-Hard Interbedded Toppling Deformed Rock Mass

The toppling deformation of a rock mass is an important form of rock slope failure that often occurs during the excavation process of anti-dip rock slopes. The toppling deformation is very important for controlling slope deformation, determining reasonable anchorage support modes and ensuring the effectiveness of support measures during construction and operation. In this paper, an indoor test was designed and an indoor test model was developed according to engineering practice and the analogy method to study the influence of the anchorage angle and find the most suitable anchoring method for a soft-hard interbedded toppling deformed rock mass. The effect of different anchorage angles on the anchorage effect of toppled deformation slopes was studied by indoor tests. The number of cracks, the number of broken fractures, the average depth of broken fractures, the number of toppling-bending slabs, and the average bending angle of the model were determined through the tests. According to the comprehensive results of the test analysis and analytic hierarchy process, an anchorage angle of 45° is optimal. The results obtained by the test analysis and the analytic hierarchy process were consistent. The test and analysis results have a guiding significance for engineering applications and help to select the best anchorage angle and anchorage mode for actual soft-hard interbedded toppling deformation slopes.

Organic adhesive assisted underwater submerged-arc welding

Abstract Underwater welding technology has become indispensable to the construction, maintenance, and repair of many offshore structures in oceanographic engineering industry. However, the existing disadvantages of current underwater welding technologies make them be unpopular and limited. An innovative organic adhesive assisted underwater submerge-arc welding was proposed to avoid the water disturbances to the maximum extent in wet condition. The mixture composed of bisphenol-A epoxy resin (EP) and welding flux in a weight ratio of 4:6 was placed on the metal surface before welding. Welding arc totally submerged in the mixture and maintained stable burning between the wire and base metal. The coverage effectively isolated the serious direct disturbances from surrounding water and greatly reduced the cooling rate of the welded joints to 19.57 °C/s. High-performance and defect-free welded joints were achieved with fine microstructures. The average tensile strength and maximum bending angle of the welded joints obtained by underwater submerged arc welding reached 463 MPA and 180°, respectively. Especially, low temperature impact toughness still keep 63 J/cm2 in 0 °C, which means far better mechanical properties compared with underwater wet welding. For the wet condition, this provides a possibility to acquire high-quality underwater welded joints comparable to that in air.

Strongly Bent Double-Stranded DNA: Reconciling Theory and Experiment.

The strong bending of polymers is poorly understood. We propose a general quantitative framework of polymer bending that includes both the weak and strong bending regimes on the same footing, based on a single general physical principle. As the bending deformation increases beyond a certain (polymer-specific) point, the change in the convexity properties of the effective bending energy of the polymer makes the harmonic deformation energetically unfavorable: in this strong bending regime the energy of the polymer varies linearly with the average bending angle as the system follows the convex hull of the deformation energy function. For double-stranded DNA, the effective bending deformation energy becomes non-convex for bends greater than ~ 2° per base-pair, equivalent to the curvature of a closed circular loop of ~ 160 base pairs. A simple equation is derived for the polymer loop energy that covers both the weak and strong bending regimes. The theory shows quantitative agreement with recent DNA cyclization experiments on short DNA fragments, while maintaining the expected agreement with experiment in the weak bending regime. Counter-intuitively, cyclization probability (j-factor) of very short DNA loops is predicted to increase with decreasing loop length; the j-factor reaches its minimum for loops of ≃ 45 base pairs. Atomistic simulations reveal that the attractive component of the short-range Lennard-Jones interaction between the backbone atoms can explain the underlying non-convexity of the DNA effective bending energy, leading to the linear bending regime. Applicability of the theory to protein-DNA complexes, including the nucleosome, is discussed.

Molecular Flexibility and Bend in Semi-Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State.

The NTB phase phases possess a local helical structure with a pitch length of a few nanometers and is typically exhibited by materials consisting of two rigid mesogenic units linked by a flexible oligomethylene spacer of odd parity, giving a bent shape. We report the synthesis and characterisation of two novel dimeric liquid crystals, and perform a computational study on 10 cyanobiphenyl dimers with varying linking groups, generating a large library of conformers for each compound; this allows us to present molecular bend angles as probability weighted averages of many conformers, rather than use a single conformer. We validate conformer libraries by comparison of interproton distances with those obtained from solution‐based 1D 1H NOESY NMR, finding good agreement between experiment and computational work. Conversely, we find that using any single conformer fails to reproduce experimental interproton distances. We find the use of a single conformer significantly overestimates the molecular bend angle while also ignoring flexibility; in addition, we show that the average bend angle and flexibility are both linked to the relative stability of the NTB phase.

A multi-segmented shape memory alloy-based actuator system for endoscopic applications

This paper describes the design, fabrication and testing of a shape memory alloy based actuator system to provide three degrees of freedom bending with high flexibility and repeated use capability without any performance loss for minimally invasive surgery. The flexibility, long-term endurance and thermal characteristics of this system were studied. The system consisted of 3 segments, front, middle and back. Thermal simulations showed an increase in temperature of 1–2 °C at the segment nearest to the activated segment and a temperature increase of 1 °C at the segment furthest from the activated segment. Transformation strain simulations showed that the 8 mm width design has the lowest strain (2%). The average maximum bending angle was above 30° across most actuator segments but a reformation angle of only 50% of the maximum angle. The endurance test showed that all actuators can operate for 7000 actuation cycles with a standard deviation of 0.6154, 0.8293 and 0.0364 mm for sections A, B and C, respectively. The system was capable of high angle of bending across all segments and capable of continuous long-term use with little performance deviation. The system will allow surgeons to have more flexibility during surgery and thus enable reaching difficult regions in minimally invasive surgery.

Edge Effect Investigation of DP980 Steel Sheet in Multiple Laser Scanning Process

Due to free spring back, laser forming is an effective non-contact forming technique for hard forming materials. A desired shape is obtained by residual plastic strain which is induced by thermal stresses depending on multiple laser scanning. In this study, the combination of experimental and numerical analysis is employed to investigate the temperature distribution and bending angle of the dual phase (DP980) high strength steel sheet. The edge effect of six cases of laser scanning process involving 1, 2, 3, 4, 5 and 10-time laser scanning are investigated by analyzing their bending angle relative variations and transverse plastic strains. It is found that the edge effect at the middle part of laser scanning line reduces with the increasing number of laser scanning cycles. It is attributed to the fact that the relative variation of the residual plastic strain reduces with the increase of laser scanning cycles. To efficiently reduce the edge effect of DP980 steel sheet, a locally repeated scanning strategy is proposed. The numerical simulation results indicate that the edge effect reduces significantly in the 10-time laser scanning process and the average bending angle simultaneously increases around 20% under the new laser scanning strategy.

Application of curved needling technique in the treatment of trigeminal neuralgia by radiofrequency ablation through foramen rotundum with inward opening

Objective To observe the application effect of radiofrequency puncture needle with individualized and on-demand plastic curved needle technique in the treatment of second-branch trigeminal neuralgia by radiofrequency ablation through foramen rotundum with inward opening. Methods From November 2012 to May 2018, a total of 263 cases of second-branch trigeminal neuralgia were admitted to Department of Anesthesiology, the First Hospital of Jiaxing and underwent foramen rotundum puncture for radiofrequency ablation. All those cases were enrolled into this retrospective analysis. The paranasal sinus model of CT was used to scan the pterygoid fossa with a thickness of 3 mm, and the CT images, including the midpoint of the foramen rotundum tube, the internal and external hole, were selected and the puncture path was designed. The length of the line (puncture depth) and the angle between the straight line and the sagittal plane (the angle of puncture) were measured by using the ruler tool of CT software from the external hole of the foramen rotundum along the lateral wall of the maxillary sinus to the surface of the skin (puncturing point). If the external hole of foramen rotundum demonstrated an inward opening, the angle between the line and the direction of the foramen rotundum tube(the angle of the needle needed to bend) should be measured. The radiofrequency needle was inserted 5 mm into the self-made needle-bender, the corresponding bending angle was pulled out slightly to the side of the needle at the tip of the needle, and the individual radiofrequency needle for the patient was made. Then, puncturing under the guidance of CT followed by designed trajectory. The arc of the needle was turned to the top of the front when the needle reached the external hole of the foramen rotundum. Whereafter, the arc of the needle was turned to the bottom when the needle crossed the external hole. Subsequently, the needle was pushed into the foramen rotundum. Then, electrophysiological test was conducted for radiofrequency treatment. Results Of 263 patients undergoing radiofrequency ablation of the second branch of trigeminal nerve, 71 (27.0%) had an inward opening of the external hole of foramen rotundum, which needed the patient's individually designed radiofrequency puncture needle. The average bending angle was 21.3 °±3.6 °(14°-31 °). When using the individual puncture needle, the needle tip could always reach the puncture target. Using 0.1-0.5 mA current could induce obvious muscle tremor or numbness in the region innervated by the second branch of trigeminal nerve in electrophysiological test. Following radiofrequency ablation, the second-branch trigeminal neuralgia disappeared completely. Ipsilateral palate muscosal numbness and the skin numbness involving the side of the nose, upper lip and zygomatic facial region were reported. None of the patients developed numbness involving the first or third branch of trigeminal nerve. A total of 242 patients were followed up for an average of 3.2±0.6 years. The total recurrence rates at 6 months, 1 year, 2 years, 3 years and 4 years were 2.5% (6/242), 7.9% (19/242), 16.1% (39/242), 24.4% (59/242) and 33.9% (82/242), respectively. Conclusions CT-guided individually made curved needle technology allows the radiofrequency needle tip to bypass the sphenoid bone which obstructs the outer opening of foramen rotundum and enter the middle of foramen rotundum tube with inward opening, so as to improve the radiofrequency effect and reduce the recurrence rate. Key words: Trigeminal neuralgia; Radiofrequency coagulation; Foramen rotundum; Treatment effect

Graft bending angle affects allograft tendon maturity early after anterior cruciate ligament reconstruction.

The aim of this study was to clarify the association of the anterior cruciate ligament (ACL) graft bending angle and graft maturity of autograft and allograft tendons using high-resolution MRI. Patients with unilateral ACL reconstruction were invited to participate in this study, and they were examined using a 3.0-T MRI scan at 3, 6 and 12months after the operation. Anatomic single-bundle ACL reconstruction was performed on 48 patients using the trans-portal technique, including 28 with autograft hamstring tendons and 20 with allograft tendons. To evaluate graft healing, the signal/noise quotient (SNQ) was measured in four regions of interest (ROIs) of the femoral tunnel, proximal, midsubstance and distal ACL grafts. The graft bending angle was defined as the angle between the femoral bone tunnel and the line connecting the femoral and tibial tunnel apertures. Graft SNQ and graft bending angle were assessed at 3, 6 and 12months postoperatively, and the association between SNQ and the average graft bending angle was analyzed. Generally, the mean graft bending angle of this cohort increased gradually with time. The SNQ value of each graft region increased from 3 to 6months and then decreased from 6 to 12months. In the whole cohort, the graft bending angle had a significant positive association with graft SNQ in the femoral tunnel or proximal site. In the allograft subgroup, the graft bending angle had a significant positive association with the graft SNQ in the femoral tunnel or proximal site at 6months after surgery, while there was no association between the graft bending angle and SNQ at 12months. In the autograft subgroup, the graft bending angle had a significant positive association with graft SNQ in the femoral tunnel or proximal site at 12months after surgery. Generally, the graft bending angle was correlated with a high signal intensity of the proximal graft in the early postoperative period for allograft tendons and in the late postoperative period for allograft tendons. This suggests that the biomechanical effect from the graft bending angle on graft healing may be different for allografts and autografts after ACL reconstruction. III.

Experimental and Numerical Investigation on Micro-Bending of AISI 304 Sheet Metal Using a Low Power Nanosecond Laser

The aim of this experimental study is to identify and characterize the response related to the effects of process parameters in terms of bending angle for micro-bending of AISI 304 sheet using a low power Nd:YVO4 laser source. Numerical simulation is also carried out through a coupled thermo-mechanical formulation with finite element method using COMSOL MULTIPHYSICS. The developed numerical simulation indicates that bending is caused by temperature gradient mechanism in the present investigation involving laser micro-bending. The results of experiment indicate that bending angle increases with laser power, number of irradiations, and decreases with increase in scanning speed. Moreover, average bending angle increases with number of laser passes and edge effect, defined in terms of relative variation of bending angle (RBAV), decreases monotonically with the number of laser scans. The substrate is damaged over a width of about 80 μm due to the high temperatures experienced during laser forming at a low scanning speed.

Development of an economic wireless human motion analysis device for quantitative assessment of human body joint

In recent years, the study of human body dynamics has been attracting a significant amount of attention. Currently there are many camera or active sensor based motion analysis systems available on the market. They have been extensively adopted and used by the film and animation or entertainment industries such as film and video game producers. More recently their potential in studying human dynamics/motion for medical purposes has been realised to the extent that they are now used to study full body human biomechanics in the form of gait analysis systems. Most orthopaedic surgeries are usually about joint repair or implants. According health line, revision surgery is usually due to infection, continued pain, joint stiffness, wear, instability, loosening. Apart from infection, the rest can be linked to the operation itself. Currently, surgical planning and placing implants is performed in a subjective manner, relying on the surgeon’s experience and instinct, current systems to help the surgeon to place implant are also bulky, expensive, slow and not user friendly. The aim of this project is to develop an economic and portable motion assessment system which involves a wireless inertial measurement unit (IMU) dedicated to study and assess body joints. Through the data collected from the IMU, the system is capable real time measurement of relative position and orientation of the human joint. Several tests were conducted to validate the data extracted from gyroscope and accelerometer of the IMU. The joint motion results analysed using the device was compared with the results analysed using commercial video motion analysis software and it shows good correlation. It is found that the gyroscope of the IMU under DMP sensor fusion algorithm and calibration capability is able to give the angular velocity with less than 5% error. This has led to a more accurate orientation data which gives 7% error in average bending angle.

Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

ABSTRACTThe twist-bend phase (NTB) is most commonly observed in materials with a gross-bent shape: dimers; bent-cores; bent-oligomers. We had suggested previously that the bend-angle of such systems effectively dictates the relative thermal stability of the NTB phase. However, our earlier paper relied on the use of a single energy-minimum conformer and so failed to capture any information about flexibility and conformational distribution. In the present work, we revisit our hypothesis and examine a second set of dimers with varying linking groups and spacer composition. We have improved on our earlier work by studying the conformational landscape of each material, allowing average bend-angles to be determined as well as the conformer distribution. We observe that the stability of the NTB phase exhibits a strong dependence not only on the Boltzmann-weighted average bend-angle (rather than just a static conformer), but also on the distribution of conformers. To a lesser extent, the flexibility of the spacer appears important. Ultimately, this work satisfies both theoretical treatments and our initial experimental study and demonstrates the importance of molecular bend to the NTB phase.

Statistically average atmospheric bending angle model based on COSMIC experimental data

The retrieval of profiles of meteorological variables from radio occultation observations requires knowledge of bending angle profiles up to heights of no less than 60–70 km. Because of the residual error of the ionospheric correction, retrieved profiles become too noisy by a height of about 40 km. In order to invert the bending angle profiles, the statistical optimization is used. This makes it possible to construct an optimal linear combination of the a priori estimate of the average bending angle profile and a posteriori noisy estimate based on observations. The estimate of the average bending angle profile for the given coordinates and the time of year is usually based on the climatological atmospheric model. MSIS and CIRA models that have been used for this purpose are now obsolete and do not describe the global changes in the atmospheric state. The model of average bending angles BA–IAP (Bending Angle–Institute of Atmospheric Physics) is built based on the processing of the array of COSMIC radio occultation observations during 2006–2013. The proposed model is statistically validated based on the COSMIC database. It is shown that our model describes the average bending angle profiles more accurately than the MSIS model.

Flexible bent rod model with a saturating induced dipole moment to study the electric linear dichroism of DNA fragments

In the present work we make a theoretical study of the steady state electric linear dichroism of DNA fragments in aqueous solution. The here developed theoretical approach considers a flexible bent rod model with a saturating induced dipole moment. The electric polarizability tensor of bent DNA fragments is calculated considering a phenomenological model which theoretical and experimental backgroung is presented here. The model has into account the electric polarizability longitudinal and transversal to the macroion. Molecular flexibility is described using an elastic potential. We consider DNA fragments originally bent with bending fluctuations around an average bending angle. The induced dipole moment is supposed constant once the electric field strength grows up at critical value. To calculate the reduced electric linear dichroism we determine the optical factor considering the basis of the bent DNA perpendicular to the molecular axis. The orientational distribution function has into account the anisotropic electric properties and the molecule flexibility. We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field. From these fits, values of DNA physical properties are estimated. We compare and discuss the results here obtained with the theoretical and experimental data presented by other authors. The original contributions of this work are: the inclusion of the transversal electric polarizability saturating with the electric field, the description of the electric properties with an electric polarizability tensor dependant on the bending angle and the use of an arc model originally bent.