Fracture of bone tissue: The 'hows' and the 'whys'

The mechanical performance of bone is of paramount importance for the quality of life we experience. The structural integrity of bone, its hierarchical structure, organisation and its physicochemical constitution, all influence its ability to withstand loads, such as those seen occasionally in everyday life loading scenarios, which are either above the norm, prolonged, or repetitive. The present review explores three interconnected areas of research where significant progress has been made lately: (i) The recorded mechanical behaviour of bone and the way it fails; (ii) the inner architecture, organisational, hierarchical structure of bone tissue; and (iii) the bone properties at the micro/nanostructural and biophysical level. Exercising a line of thought along a structure/function based argument we advance from ‘how’ bone fractures to ‘why’ it fractures, and we seek to obtain a fresh insight in this field

Evidence for an elementary process in bone plasticity with an activation enthalpy of 1 eV

The molecular mechanisms for plastic deformation of bone tissue are not well understood. We analysed temperature and strain-rate dependence of the tensile deformation behaviour in fibrolamellar bone, using a technique originally developed for studying plastic deformation in metals. We show that, beyond the elastic regime, bone is highly strain-rate sensitive, with an activation volume of ca 0.6 nm3. We find an activation energy of 1.1 eV associated with the basic step involved in the plastic deformation of bone at the molecular level. This is much higher than the energy of hydrogen bonds, but it is lower than the energy required for breaking covalent bonds inside the collagen fibrils. Based on the magnitude of these quantities, we speculate that disruption of electrostatic bonds between polyelectrolyte molecules in the extrafibrillar matrix of bone, perhaps mediated by polyvalent ions such as calcium, may be the rate-limiting elementary step in bone plasticity

Impact of RAN Virtualization on Fronthaul Latency Budget: An Experimental Evaluation

In 3GPP the architecture of a New Radio Access Network (New RAN) has been defined where the evolved NodeB (eNB) functions can be split between a Distributed Unit (DU) and Central Unit (CU). Furthermore, in the virtual RAN (VRAN) approach, such functions can be virtualized (e.g., in simple terms, deployed in virtual machines). Based on the split type, different performance in terms of capacity and latency are requested to the network (i.e., fronthaul) connecting DU and CU. This study experimentally evaluates, in the 5G segment of the Advanced Research on NetwOrking (ARNO) testbed (ARNO-5G), the fronthaul latency requirements specified by Standard Developing Organizations (SDO) (3GPP in this specific case). Moreover it evaluates how much virtualization impacts the fronthaul latency budget for the the Option 7-1 functional split. The obtained results show that, in the considered Option 7-1 functional split, the fronthaul latency requirements are about 250 μs but they depend on the radio channel bandwidth and the number of the connected UEs. Finally virtualization further decreases the latency budget.This work has been partially funded by the EU H2020 5GTransformer Project (grant no. 761536

Biochemical Characterization of High Mercury Tolerance in a Pseudomonas Spp. Isolated from Industrial Effluent

A mercury resistant Pseudomonas spp. was isolated from industrial effluent that was able to tolerate 200 µM HgCl2. The Hg2+-resistant Pseudomonas spp. exhibited elevated stress-regulatory mechanisms as indicated by its high and inducible mercury reductase activity, high intrinsic catalase activity and enhanced resistance to Hg2+-induced release of protein-bound iron. An enhanced resistance of the bacterium to Hg2+-induced lipid peroxidation was observed as indicated by 40% lower conjugated diene and 60% lower lipid hydroperoxide content compared to a non-mercury resistant strain Pseudomonas aeruginosa (ATCC 27853). Phospholipid (PL) analysis of both the species reveled intrinsic differences in their PL composition. We observed 80% PE, 15% PG and 5% of an unidentified PL (U) in MRP compared to 65% PE, 20% PG and 17% CL in Pseudomonas aeruginosa (ATCC 27853). Mercury toxicity led to significant reorganization of PL in Pseudomonas aeruginosa (ATCC 27853) compared to MRP. While HgCl2 led to 25% increase in PE, 35% depletion in CL and 27% depletion in PG content of Pseudomonas aeruginosa (ATCC 27853), MRP exhibited only 5% enhancement in PE content that was accompanied by 20% depletion in PG content, indicating that MRP resists mercury induced PL organization. Interaction of the MRP with polystyrene surface showed two fold higher Hg2+-induced exopolysaccharide secretion and elevated biofilm forming ability compared to Pseudomonas aeruginosa (ATCC 27853). Our investigation reveals a novel Pseudomonas spp. with high Hg2+-tolerance mechanisms that can be utilized for efficient bioremediation of mercury

Accelerated Growth Plate Mineralization and Foreshortened Proximal Limb Bones in Fetuin-A Knockout Mice

PMCID: PMC3473050This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

The Secret Life of Collagen: Temporal Changes in Nanoscale Fibrillar Pre-Strain and Molecular Organization during Physiological Loading of Cartilage

Articular cartilage is a natural biomaterial whose structure at the micro- and nanoscale is critical for healthy joint function and where degeneration is associated with widespread disorders such as osteoarthritis. At the nanoscale, cartilage mechanical functionality is dependent on the collagen fibrils and hydrated proteoglycans that form the extracellular matrix. The dynamic response of these ultrastructural building blocks at the nanoscale, however, remains unclear. Here we measure time-resolved changes in collagen fibril strain, using small-angle X-ray diffraction during compression of bovine and human cartilage explants. We demonstrate the existence of a collagen fibril tensile pre-strain, estimated from the D-period at approximately 1–2%, due to osmotic swelling pressure from the proteoglycan. We reveal a rapid reduction and recovery of this pre-strain which occurs during stress relaxation, approximately 60 s after the onset of peak load. Furthermore, we show that this reduction in pre-strain is linked to disordering in the intrafibrillar molecular packing, alongside changes in the axial overlapping of tropocollagen molecules within the fibril. Tissue degradation in the form of selective proteoglycan removal disrupts both the collagen fibril pre-strain and the transient response during stress relaxation. This study bridges a fundamental gap in the knowledge describing time-dependent changes in collagen pre-strain and molecular organization that occur during physiological loading of articular cartilage. The ultrastructural details of this transient response are likely to transform our understanding of the role of collagen fibril nanomechanics in the biomechanics of cartilage and other hydrated soft tissues

Optimal Selection of Short-and Long-Term Mitigation Strategies for Buildings within Communities under Flooding Hazard

Every year, floods cause substantial economic losses worldwide with devastating impacts on buildings and physical infrastructures throughout communities. Techniques are available to mitigate flood damage and subsequent losses, but the ability to weigh such strategies with respect to their benefits from a community resilience perspective is limited in the literature. Investing in flood mitigation is critical for communities to protect the physical and socioeconomic systems that depend on them. While there are multiple mitigation options to implement at the building level, this paper focuses on determining the optimal flood mitigation strategy for buildings to minimize flood losses within a community. In this research, a mixed integer linear programming model is proposed for studying the effects and trade-offs associated with pre-event short-term and long-term mitigation strategies to minimize the expected economic losses associated with floods. The capabilities of the proposed model are illustrated for Lumberton, North Carolina (NC), a small, socially diverse inland community on the Lumber River. The mathematically optimal building-level flood mitigation plan is provided based on the available budget, which can significantly minimize the total expected direct economic loss of the community. The results reveal important correlations among investment quantity, building-level short- and long-term mitigation measures, flood depths of various locations, and buildings’ structure. Additionally, this study shows the trade-offs between short- and long-term mitigation measures based on available budget by providing decision support to building owners regarding mitigation measures for their buildings.This research was partially funded by the National Institute of Standards and Technology (NIST) Center of Excellence for Risk-Based Community Resilience Planning through a cooperative agreement with Colorado State University [70NANB20H008 and 70NANB15H044]. This research was also partially funded by the National Science Foundation (NSF) through award 2052930. Article processing charge was partially provided by the University of Oklahoma Libraries’ Open Access Fund.Ye