Packing structure of semiflexible rings

Unraveling the packing structure of dense assemblies of semiflexible rings is not only fundamental for the dynamical description of polymer rings, but also key to understand biopackaging, such as observed in circular DNA of viruses or genome folding. Here we use X-ray tomography to study the geometrical and topological features of disordered packings of rubber bands in a cylindrical container. Assemblies of short bands assume a liquidlike disordered structure, with short-range orientational order, and reveal only minor influence of the container. In the case of longer bands, the confinement causes folded configurations and the bands interpenetrate and entangle. Most of the systems are found to display a threading network which percolates the system. Surprisingly, for long bands whose diameter is more than twice the diameter of the container, we found that all bands interpenetrate each other, in a complex fully entangled structure.Fil: Gomez, Leopoldo Raimundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: García, Nicolás. Institut Laue Langevin; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Poschel, Thorsten. Universitat Erlangen-nurnberg. Institute Of Multiscale Simulation.; Alemani

A device for studying fluid-induced cracks under mixed-mode loading conditions using x-ray tomography

We introduce an innovative instrument designed to investigate fluid-induced fractures under mixed loading conditions, including uniaxial tension and shear stress, in gels and similar soft materials. Equipped with sensors for measuring force, torque, and fluid pressure, the device is tailored for compatibility with x-ray tomography scanners, enabling non-invasive 3D analysis of crack geometries. To showcase its capabilities, we conducted a study examining crack-front segmentation in a hydrogel subjected to air pressure and a combination of tension and shear stress.Fil: Santarossa, Angel Agustín. Universitat Erlangen-Nuremberg; AlemaniaFil: Ortellado, Laureano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Sack, Achim. Universitat Erlangen-Nuremberg; AlemaniaFil: Gomez, Leopoldo Raimundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Poschel, Thorsten. Universitat Erlangen-Nuremberg; Alemani

Irrigation Scheduling to Promote Corn Productivity in Central Alabama

Agriculture is the largest consumer of water in the United States. Results from previous studies have shown thatit is possible to substantially reduce irrigation amounts and maintain corn yield. The objectives of this study wereto evaluate the advantages and disadvantages of two irrigation scheduling methods for corn production inAlabama. Two irrigation scheduling methods evaluated were: a) Checkbook, which is one of the conventionalmethods used by farmers that is based on the soil water balance estimated using water lost by evapotranspirationand its replacement through rainfall or irrigation, and b) Sensor-based, which was based on soil matric potentialvalues recorded by soil moisture tension sensors installed in the field. The experimental field was divided intotwo irrigation management zones (zone A and zone B) based on soil properties of each field. During the 2014season in zone A, significant grain yield differences were observed between the two irrigation methods. TheCheckbook plots exhibited greater yield than Sensor-based plots: 10181 kg ha-1 and 9696 kg ha-1, respectively.The greater yield on the Checkbook plots could be associated with higher irrigation rate applied, 148 mm more,compared with the Sensor-based plots. In zone B, there were no significant yield differences between bothirrigation methods; however, Sensor-based plots out yielded Checkbook plots, with 9673 kg ha-1 and 9584 kgha-1, respectively. Even though the irrigation amount applied in Checkbook located in zone B was higher, 102mm more, there were no significant yield differences. Therefore, it suggests that the Sensor-based method waspromissory irrigation scheduling strategy under the conditions of zone B. In 2015, there were no significant grainyield differences between zone A and zone B when the data from the Checkbook plots were analyzed. However,the Sensor-based treatment produced a statistically significant difference of grain yield of 13597 kg ha-1 in zoneA and 11659 kg ha-1 in zone B, also both zones received the same amount of irrigation. Overall results of bothgrowing seasons indicated that the use of the Sensor-based irrigation scheduling treatment resulted in similarvalues of total profit per hectare when compared to Checkbook method. The Sensor-based method seems apromising strategy that could result in water and financial savings, but more research is required.Fil: Da Cunha Leme Filho, Jose F.. Virginia Polytechnic Institute; Estados UnidosFil: Ortiz, Brenda V.. Auburn University.; Estados UnidosFil: Damianidis, Damianos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Oliveros; ArgentinaFil: Balkcom, Kipling S.. Usda-soil Dynamics Research; Estados UnidosFil: Dougherty, Mark. Auburn University.; Estados UnidosFil: Poschel, Thorsten. Auburn University.; Estados Unido

Hydrodynamic Fluctuations and Averaging Problems in Dense Granular Flows

: We analize the properties of dense granular systems by assuming a hydrodynamical description, based on conservation laws for the particle number density and linear momentum. We combine analytical methods and experimental and numerical results obtained by ensemble-averaging of data on creep during compaction and molecular dynamics simulations of convective flow. 1 INTRODUCTION In spite of the early and in many aspects successful hydrodynamical approach applied by Haff (P. K. Haff 1983 1986) to granular systems, there still remain many unsolved questions, since the behavior of a granular mass is fundamentally different from that of typical fluids. For instance, in addition to the ordinary source of hydrodynamic fluctuations --which in this case can't be removed by taking the thermodynamic limit, the fact that solid grains in a dense arrangement can't be regarded as points in any length scale leads to a second source of fluctuations; it operates at distances much larger than the typical..

Zig-zag networks of self-excited periodic oscillations in a tunnel diode and a fiber-ring laser

We report numerical evidence showing that periodic oscillations can produce unexpected andwide-ranging zigzag parameter networks embedded in chaos in the control space of nonlinear systems. Such networks interconnect shrimplikewindows of stable oscillations and are illustrated here for a tunnel diode, for an erbium-doped fiber-ring laser, and for the H´enon map, a proxy of certain CO2 lasers. Networks in maps can be studied without the need for solving differential equations. Tuning parameters along zig-zag networks allows one to continuously modify wave patterns without changing their chaotic or periodic nature. In addition, we report convenient parameter ranges where such networks can be detected experimentally

Zig-zag networks of self-excited periodic oscillations in a tunnel diode and a fiber-ring laser

We report numerical evidence showing that periodic oscillations can produce unexpected andwide-ranging zigzag parameter networks embedded in chaos in the control space of nonlinear systems. Such networks interconnect shrimplikewindows of stable oscillations and are illustrated here for a tunnel diode, for an erbium-doped fiber-ring laser, and for the H´enon map, a proxy of certain CO2 lasers. Networks in maps can be studied without the need for solving differential equations. Tuning parameters along zig-zag networks allows one to continuously modify wave patterns without changing their chaotic or periodic nature. In addition, we report convenient parameter ranges where such networks can be detected experimentally

The MyoRobot : a novel automated biomechatronics system to assess voltage/Ca2+ biosensors and active/passive biomechanics in muscle and biomaterials

We engineered an automated biomechatronics system, MyoRobot, for robust objective and versatile assessment of muscle or polymer materials (bio-)mechanics. It covers multiple levels of muscle biosensor assessment, e.g. membrane voltage or contractile apparatus Ca2+ ion responses (force resolution 1 µN, 0–10 mN for the given sensor; [Ca2+] range ~ 100 nM–25 µM). It replaces previously tedious manual protocols to obtain exhaustive information on active/passive biomechanical properties across various morphological tissue levels. Deciphering mechanisms of muscle weakness requires sophisticated force protocols, dissecting contributions from altered Ca2+ homeostasis, electro-chemical, chemico-mechanical biosensors or visco-elastic components. From whole organ to single fibre levels, experimental demands and hardware requirements increase, limiting biomechanics research potential, as reflected by only few commercial biomechatronics systems that can address resolution, experimental versatility and mostly, automation of force recordings. Our MyoRobot combines optical force transducer technology with high precision 3D actuation (e.g. voice coil, 1 µm encoder resolution; stepper motors, 4 µm feed motion), and customized control software, enabling modular experimentation packages and automated data pre-analysis. In small bundles and single muscle fibres, we demonstrate automated recordings of (i) caffeine-induced-, (ii) electrical field stimulation (EFS)-induced force, (iii) pCa-force, (iv) slack-tests and (v) passive length-tension curves. The system easily reproduces results from manual systems (two times larger stiffness in slow over fast muscle) and provides novel insights into unloaded shortening velocities (declining with increasing slack lengths). The MyoRobot enables automated complex biomechanics assessment in muscle research. Applications also extend to material sciences, exemplarily shown here for spider silk and collagen biopolymers