Contemporary designs of engineering structures strive to minimize the use of material in order to reduce cost and weight. However, the approach taken by focusing on materials selection and on the ...design of the exterior shape of structures has reached its limits. By contrast, nature implements bottom-up designs based on a multiple-level hierarchy, spanning from nanoscale to macroscale, which evolved over millions of years in an environmentally sustainable manner given limited resources. Natural structures often appear as laminates in wood, bone, plants, exoskeletons, etc., and employ elaborate micro-structural mechanisms to generate simultaneous strength and toughness. One such mechanism, observed in the scorpion cuticle and in the sponge spicule, is the grading (gradual change) of properties like layers thickness, stiffness, strength and toughness. We show that grading is a biological design tradeoff, which optimizes the use of material to enhance survival traits such as endurance against impending detrimental cracks. We found that such design, when applied in a more vulnerable direction of the laminate, has the potential to restrain propagation of hazardous cracks by deflecting or bifurcating them. This is achieved by shifting material from non-critical regions to more critical regions, making the design sustainable in the sense of efficient use of building resources. We investigate how such a mechanism functions in nature and how it can be implemented in synthetic structures, by means of a generic analytical model for crack deflection in a general laminate. Such a mechanical model may help optimize the design of bioinspired structures for specific applications and, eventually, reduce material waste.
Developed more than a decade ago, the Chronic Care Model (CCM) is a widely adopted approach to improving ambulatory care that has guided clinical quality initiatives in the United States and around ...the world. We examine the evidence of the CCM's effectiveness by reviewing articles published since 2000 that used one of five key CCM papers as a reference. Accumulated evidence appears to support the CCM as an integrated framework to guide practice redesign. Although work remains to be done in areas such as cost-effectiveness, these studies suggest that redesigning care using the CCM leads to improved patient care and better health outcomes.
Local lipid variations in tissues are readily revealed with mass spectrometry imaging (MSI) methods, and the resulting lipid distributions serve as bioanalytical signatures to reveal cell- or ...tissue-specific lipids. Comprehensive MSI lipid mapping requires measurements in both ion polarities. Additionally, structural lipid characterization is necessary to link the lipid structure to lipid function. Whereas some structural elements of lipids are readily derived from high-resolution mass spectrometry (MS) and tandem-MS (MSn), the localization of C═C double bonds (DBs) requires specialized fragmentation and/or functionalization methods. In this work, we identify a multifunctional matrix-assisted laser desorption/ionization (MALDI) matrix for spatially resolved lipidomics investigations that reacts with lipids in Paternò–Büchi (PB) reactions during laser irradiation facilitating DB-position assignment and allows dual-polarity high-resolution MALDI-MSI and MALDI MS2I studies. By screening 12 compounds for improved ionization efficiency in positive-/negative-ion mode and the functionalization yield compared to the previously introduced reactive MALDI matrix benzophenone, 2-benzoylpyridine (BzPy) is identified as the best candidate. The new matrix enables DB localization of authentic standards belonging to 12 lipid classes and helps to assign 133/58 lipid features in positive-/negative-ion mode from mouse cerebellum tissue. The analytical capabilities of BzPy as a multifunctional MALDI-MSI matrix are demonstrated by imaging endogenous and PB-functionalized lipids in mouse kidney sections with 7 μm lateral resolution in both ion modes. Tracking diagnostic lipid DB-position fragment ions in mouse pancreatic tissue with down to 10 μm pixel size allows us to identify the islets of Langerhans associated with lipid isomer upregulation and depletion.
•New and simple design criterion for spherical shells under external pressure.•Detailed studies regarding elastic-imperfect and plastic-imperfect buckling.•Collection of about 600 experimental ...results.•Imperfection sensitivity of orthogrid stiffened sphere assessed.
In this paper a physically based and deterministic design procedure for spherical shells under external pressure is introduced. Within the new design concept the membrane energy of a sphere is incrementally reduced by means of perturbation cutouts, until a bending energy dominate state is identified. The threshold between membrane energy state and bending energy state represents a robust plateau for the buckling pressure.
A comprehensive numerical investigation was performed in order to study the influence of radius-to-thickness ratio (R/t) as well as the dome height-to-base radius ratio (H/r). The results verify that both geometric properties ratios significantly influence the lower-bound buckling pressure, especially if plastic buckling occurs.
Improved shell buckling design factors are given in the form of an simple analytic equation. The corresponding threshold KDFs were validated with a large number of buckling experiments and deliver much higher KDFs than currently used empirical guidelines.
Based on the new design criterion lower-bound estimation for the buckling pressure of a tori-spherical bulkhead and the inner dome of the cryogenic upper stage ESC-A from the European space launch-vehicle Ariane 5 are determined.
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The stability failure of the axially loaded cylindrical shell is considered as the last unresolved classical stability problem, although it has been investigated for over 100years. Therefore ...designers rely on the application of empirical knockdown factors from the 1960s like the NASA SP-8007 for cylindrical shells and the NASA SP-8019 for truncated conical shells which are very conservative for modern shell structures.
Perturbation approaches for the design of axially loaded cylindrical and conical shells are presented in this paper. These approaches deliver knockdown factors for a physical based estimation of the lower-bound buckling load and are suitable for research and industrial applications as they are independent from imperfection measurements and easy to implement. The corresponding numerical models are validated by means of high-fidelity buckling experiments and it shows that experimental buckling loads can be calculated very precisely in contrast to the previous methodology. Additionally, new robust knockdown factors are proposed for preliminary shell design which are based on curve fitting of numerical knockdown factors of the perturbation approaches.
Thus, it is possible to utilize the load bearing capability of launch-vehicle primary structures up to 40% more effectively, resulting in considerable weight saving potentials for composite shell structures.
The ‘optical fold’ of
Evermanella balbo
covers the ventro-lateral cornea and is presumed to capture illumination that would otherwise remain undetected by the tubular eye of this mesopelagic teleost. ...It contains alternating bands of cellular and acellular material, running approximately perpendicular to the lateral surface of the eye. Only parts of this lamellar body lie within the eyelid-like structure. The cellular lamellae are 2–2.5 μm thick centrally and composed of fibroblast-like cells. The extracellular bands (4.5–5 μm thick) contain regular arrays of collagen fibrils, with layers of thin fibrils sandwiching a region of thicker fibrils. The thin fibrils are organised in alternating sheets where fibrils, although all parallel, change their orientation by 90° between each sheet. All thick fibrils are oriented parallel to the lateral surface of the ‘optical fold’. In the main retina, small bundles of rod inner/outer segments are separated by the processes of the retinal pigment epithelium (rpe) laterally. Centrally, the length of tightly packed rods increases, but rpe processes no longer divide them into bundles. Medially, rod length increases further, but packing is less dense. The accessory retina is significantly thinner, and less well-developed than the main retina. Ventrally, the rods show no regular arrangement and are not grouped. Dorsally, however, rods are arranged into bundles, separated by melanosome-filled rpe processes. The thickness of the retina increases as it approaches the crystalline lens. It is on this dorsal accessory retina that light traversing the ‘optical fold’ most likely falls, facilitating the detection of moving objects in the ventro-lateral field of view.
A lack of cost information has been cited as a barrier to implementation and a limitation of implementation research. This paper explains how implementation researchers might optimize their ...measurement and inclusion of costs, building on traditional economic evaluations comparing costs and effectiveness of health interventions. The objective of all economic evaluation is to inform decision-making for resource allocation and to measure costs that reflect opportunity costs-the value of resource inputs in their next best alternative use, which generally vary by decision-maker perspective(s) and time horizon(s). Analyses that examine different perspectives or time horizons must consider cost estimation accuracy, because over longer time horizons, all costs are variable; however, with shorter time horizons and narrower perspectives, one must differentiate the fixed and variable costs, with fixed costs generally excluded from the evaluation. This paper defines relevant costs, identifies sources of cost data, and discusses cost relevance to potential decision-makers contemplating or implementing evidence-based interventions. Costs may come from the healthcare sector, informal healthcare sector, patient, participant or caregiver, and other sectors such as housing, criminal justice, social services, and education. Finally, we define and consider the relevance of costs by phase of implementation and time horizon, including pre-implementation and planning, implementation, intervention, downstream, and adaptation, and through replication, sustainment, de-implementation, or spread.
Renewable energy technology is being adopted into energy plans worldwide to reduce the mounting CO2 emissions of traditional energy sources. Currently in Thailand, there are approximately 15 million ...solar panels (2600 MW) which will need to be disposed of in the coming years. The average lifespan of a crystalline silicon panel is between 20 and 30 years, and responsible treatment of these end-of-life panels is necessary to minimize environmental burdens. Thailand’s current plan is to landfill these panels. This study hopes to shed light on the environmental and economic paybacks that could materialize from recycling solar panels. It has been hypothesized that recycling solar panels could result in less environmental burdens than landfilling, but at an added monetary cost. Using LCA methodology and the EcoInvent database, this paper compares the environmental impacts of landfilling end-of-life crystalline silicon panels with those of two different recycling methods. By recycling silicon-based solar panels, valuable metals within the panels can be recovered instead of lost to the landfill. Recycling PV panels is less environmentally burdensome than landfilling when credits are applied to the recycling methods for the avoided production of materials that are recovered from the panels. Using the discounted cash flow method, this paper also compares the three waste management plans financially, as costs will inevitably influence how PV waste is managed in Thailand in the years to come. Neither of the recycling facilities were found to be economically profitable, however the cost to recycle could be as little as $0.03 per kg.
We study the effect of the molecular nature of the interface between an epoxy matrix and multi-walled carbon nanotubes (CNTs) on the mechanical properties of the resultant nano-composites, with ...emphasis on toughness. A number of samples based on variously functionalized CNTs, namely, pristine, carboxylated, and aminated CNTs are examined, with different qualities of dispersion. Nano-composite toughness is found to increase with enhanced interfacial adhesion, an effect that is opposite to what is usually observed in traditional fiber-based composites. The classical pull-out energy model is shown to effectively explain this result. It is thus possible to tune the toughness of a nano-composite by adjusting the molecular nature of its interface and the CNT characteristics, namely its strength and its length relative to its critical length.
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