Elastic energy storage across speeds during steady-state hopping of desert kangaroo rats (Dipodomys deserti)

Small bipedal hoppers, including kangaroo rats, are thought to not benefit from substantial elastic energy storage and return during hopping. However, recent species-specific material properties research suggests that, despite relative thickness, the ankle extensor tendons of these small hoppers are considerably more compliant than had been assumed. With faster locomotor speeds demanding higher forces, a lower tendon stiffness suggests greater tendon deformation and thus a greater potential for elastic energy storage and return with increasing speed. Using the elastic modulus values specific to kangaroo rat tendons, we sought to determine how much elastic energy is stored and returned during hopping across a range of speeds. In vivo techniques were used to record tendon force in the ankle extensors during steady-speed hopping. Our data support the hypothesis that the ankle extensor tendons of kangaroo rats store and return elastic energy in relation to hopping speed, storing more at faster speeds. Despite storing comparatively less elastic energy than larger hoppers, this relationship between speed and energy storage offer novel evidence of a functionally similar energy storage mechanism, operating irrespective of body size or tendon thickness, across the distal muscle-tendon units of both small and large bipedal hoppers.

Connections, rituals and identities: healthcare students’ descriptions of objects that represent resilience

Purpose Health-care student resilience is a well-researched topic, although the concept continues to evolve, not least as “resilience-building” has become an expected feature of health-care student professional education. The study aimed to understand the concept of resilience from the point of view of student nurses and midwives. Design/methodology/approach The study used a novel arts-informed method, informed by Miller’s and Turkle’s work on “evocative objects.” A total of 25 student nurses and midwives from a London-based university selected “resilience objects” which were photographed and discussed during interviews with an artist-researcher. Findings Analysis of the interviews revealed that “resilience” was founded on identity, connection, activity and protection. “Resilience objects” were used in everyday rituals and “resilience” was a characteristic that developed over time through the inhabiting of multiple identities. Practical implications Given that resilience is intertwined with notions of identity, health-care faculties should enhance students’ sense of identity, including, but not exclusively, nursing or midwifery professional identity, and invite students to develop simple rituals to cope with the challenges of health-care work. Originality/value To the best of the authors’ knowledge, this is the first study to locate health-care students’ resilience in specific material objects. Novel insights are that health-care students used everyday rituals and everyday objects to connect to their sense of purpose and manage their emotions, as means of being resilient.

Populizm a praworządność: między władzą ludu a „regułami gry”

The growing influence of populists on the exercise of power in many European countries made it necessary to analyze populism also in the context of its relation to law and jurisprudence. Populism as an anti-liberal structure introduces a different view on many demoliberal legal institutions, including the key concept of the rule of law. The first part of the article focuses on the concept of populism and its analysis to the extent that is justified by the chosen topic. Investigating the current scientific discourse allows the thesis that populism has a dualistic character. On the one hand, it can be seen as a set of ideas, based on specific “material” assumptions, but on the other hand, it is a specific modus operandi used to promote any ideology. The second part of the article attempts to analyze the concept of the rule of law and focuses on its goals as well as the role it plays in the structue of liberal democracy. In this context, it should be noted that the meaning of the rule of law cannot be reduced solely to the principle that not only citizens, but also authority can act only within the limits of valid and binding law. For the rule of law — by clearly delineating the boundaries of power — also creates a broader context for the functioning of the system: specific “rules of the game” which define the way and rules of its functioning. In this sense, the rule of law is a key element of liberal democracy, which, although based on the power of the poeple, constitutes procedures and mechanisms that prevent its implementation to an unlimited extent. The third part of the paper summarizes the theses indicated in previous parts. Among the basic ideological tenets of populists is the pursuit of institutional unlimited power of the people. However, such a belief is incompatible with the basic demoliberal assumption that all power and its functioning should be subject to a rigid procedural framework, the violation of which is unacceptable. would seem that the rule of law — which is, after all, the realization of those restrictions within the liberal democracy framework — will be rejected by populists in advance. However, the populists do not deny the necessity of the rule of law existing, but modify it in such a way that complies with their tenets. Populists emerge from the agonistic conviction that the rule of law in the demoliberal discourse — although presented as politicaly neutral — in fact served only the interests of the elites and the establishment. With populist views gaining real influence on power, the time comes for the rule of law to be an instrument in the hands of the people, serving only the realization of their free will in the greatest possible extent.

The military-technical revolution of the ХХI st century (Philosophical and analytical review)

The article discusses the history of the military-technical revolution, revealing its main characteristics. It was interesting to explain to others theconnection between the revolution and the technical and technological structure ofsociety, on the one hand, and the changes in modern warfare, its timing, the scale of the deployment of hostilities, on the other hand. The study is based on the methodology of systems analysis, as well as the use of logical generalization, synthesis, and abstraction. The authors rely on a wide range of illustrative material, which allowed to show the changes of the sixth military-technological revolution. The nature of the use of unmanned aerial vehicles in modern warfare is considered factual material. Based on specific material, it is argued that the nature of modern warfare is hybrid in nature, but this hybridization itself is heterogeneous. Possible options for waging war and using certain equipment are shown. Based on analytical research, the authors focused on the transformation’s characteristic of modern wars. It is concluded that there is a transition period between the sixth and seventh technical-military revolutions that demand future interdisciplinary research.

Analysis of the Dispersion of Viscoelastic Clusters in the Industrial Rotor-Stator Equipment

Materials with complex rheology and viscoelasticity may require special equipment for processing, such as for dispergation. Rheological and mechanical data of the material can help with finding the required equipment or designing equipment. For highly viscous and complex material, a rotor-stator mixer can be a good choice for dispergation. Due to the laminar or creeping mechanism of flow inside the equipment, the dispergation mechanism is assumed to be a combination of the shear stress and slicing of the material by the rotor and stator blades. For the validation of the theory, the mechanical properties of the viscose identified in a previous work were used for comparison with the data from the CFD simulation of the rotor-stator mixer. The comparison showed that the rotor-stator device can overcome the complex shear modulus and ultimate strength of the material and homogenize the solution through a combination of the shear stress and slicing. The theory was also confirmed on the process line proposed for homogenization of the specific material. The stability of viscosity during the process of homogenization was measured and used as the main parameter for quality assessment.

Fast X-Ray Diffraction (XRD) Tomography for Enhanced Identification of Materials

X-ray computed tomography (CT) can provide 3D images of density, and possibly the atomic number, for large objects like passenger luggage. This information, while generally very useful, is often insufficient to identify threats like explosives and narcotics, which can have a similar average composition as benign everyday materials such as plastics, glass, light metals, etc. A much more specific material signature can be measured with X-ray diffraction (XRD). Unfortunately, XRD signal is very faint compared to the transmitted one, and also challenging to reconstruct for objects larger than a small laboratory sample. In this article we analyze a novel low-cost scanner design which captures CT and XRD signals simultaneously, and uses the least possible collimation to maximize the flux. To simulate a realistic instrument, we derive a formula for the resolution of any diffraction pathway, taking into account the polychromatic spectrum, and the finite size of the source, detector, and each voxel. We then show how to reconstruct XRD patterns from a large phantom with multiple diffracting objects. Our approach includes a reasonable amount of photon counting noise (Poisson statistics), as well as measurement bias, in particular incoherent Compton scattering. The resolution of our reconstruction is sufficient to provide significantly more information than standard CT, thus increasing the accuracy of threat detection. Our theoretical model is implemented in GPU (Graphics Processing Unit) accelerated software which can be used to assess and further optimize scanner designs for specific applications in security, healthcare, and manufacturing quality control.

Fast X-Ray Diffraction (XRD) Tomography for Enhanced Identification of Materials

X-ray computed tomography (CT) can provide 3D images of density, and possibly the atomic number, for large objects like passenger luggage. This information, while generally very useful, is often insufficient to identify threats like explosives and narcotics, which can have a similar average composition as benign everyday materials such as plastics, glass, light metals, etc. A much more specific material signature can be measured with X-ray diffraction (XRD). Unfortunately, XRD signal is very faint compared to the transmitted one, and also challenging to reconstruct for objects larger than a small laboratory sample. In this article we analyze a novel low-cost scanner design which captures CT and XRD signals simultaneously, and uses the least possible collimation to maximize the flux. To simulate a realistic instrument, we derive a formula for the resolution of any diffraction pathway, taking into account the polychromatic spectrum, and the finite size of the source, detector, and each voxel. We then show how to reconstruct XRD patterns from a large phantom with multiple diffracting objects. Our approach includes a reasonable amount of photon counting noise (Poisson statistics), as well as measurement bias, in particular incoherent Compton scattering. The resolution of our reconstruction is sufficient to provide significantly more information than standard CT, thus increasing the accuracy of threat detection. Our theoretical model is implemented in GPU (Graphics Processing Unit) accelerated software which can be used to assess and further optimize scanner designs for specific applications in security, healthcare, and manufacturing quality control.

Evaluation of geocell-reinforced backfill for airfield pavement repair

After an airfield has been attacked, temporary airfield pavement repairs should be accomplished quickly to restore flight operations. Often, the repairs are made with inadequate materials and insufficient manpower due to limited available resources. Legacy airfield damage repair (ADR) methods for repairing bomb damage consist of using bomb damage debris to fill the crater, followed by placement of crushed stone or rapid-setting flowable fill backfill with a foreign object debris (FOD) cover. While these backfill methods have provided successful results, they are heavily dependent on specific material and equipment resources that are not always readily available. Under emergency conditions, it is desirable to reduce the logistical burden while providing a suitable repair, especially in areas with weak subgrades. Geocells are cellular confinement systems of interconnected cells that can be used to reinforce geotechnical materials. The primary benefit of geocells is that lower quality backfill materials can be used instead of crushed stone to provide a temporary repair. This report summarizes a series of laboratory and field experiments performed to evaluate different geocell materials and geometries in combinations with a variety of soils to verify their effectiveness at supporting heavy aircraft loads. Results provide specific recommendations for using geocell technology for backfill reinforcement for emergency airfield repairs.

High surface area MnO2 catalysts prepared by a metastable aqueous-aqueous interface method and their catalytic oxidation activity

In this work, the metastable aqueous-aqueous interfacial approach was used to prepare MnO2 with enhanced surface area, which helps to save energy, decrease cost and protect the environment. The material characteristic success was proven through using powder X-ray diffraction for the crystalline properties and N2 adsorption-desorption isotherm for high surface area. The relationship between the calcination temperature and the crystallinity as well the specific material surface area was also interested. The catalytic decomposition of hydrogen peroxide was investigated by the closed system measuring produced oxygen. After the H2O2 decomposition comparison between synthesized samples and commercial MnO2 in terms of both the efficiency and the speed, the M-200 sample was considered as a typical sample with outstanding performance to examine the reaction conditions (H2O2 solution concentration, catalyst amount and reaction temperature). The optimal reaction condition results are 0.9% H2O2 solution concentration, 0.2g/L catalyst, and room temperature. Besides, the leaching test and the catalytic regeneration were also conducted.

Biaxial testing of textile material - methodology and instrument assembly procedure

Membrane structures are becoming popular because of the potential usage in structures with higher aesthetic claims. For the roofing of these structures, different textile materials are used. These special materials offer an alternative to conventional roofing materials and allow, besides its lightweightness, also a possibility to roof a difficult floor plan and big span. When designing such a construction, there are some challenges related to the properties of the specific material. In order to exploit the full potential of textile membrane materials, it is necessary to choose an appropriate material model for numerical modelling, which takes into account its nonlinear behaviour. The two most important material characteristics needed for characterizing the behaviour are Young’s modulus of elasticity and Poisson’s ratio. Since the material is orthotropic in most cases, it is necessary to test the material in two directions; therefore, these characteristics need to be obtained from the biaxial test. This contribution is focused on the research of the methodology of biaxial tests and test instrument assembly procedure, which will be used for the following testing of textile materials.