Nanoscale compressive deformation mechanisms and yield properties of hydrated bone extracellular matrix

Bone features a hierarchical architecture combining antagonistic properties like toughness and strength. In order to better understand the mechanisms leading to this advantageous combination of properties, its postyield and failure behavior was analyzed on the length scale of a single lamella. Micropillars were compressed to large strains in saline solution to measure their anisotropic yield and post-yield behavior under near-physiological conditions. An increase in strength compared to the macroscale by a factor of 1.55 was observed in line with theory for size effects in quasi-brittle materials. Furthermore, a clear influence of hydration with a reduction by 60% compared to in vacuo results was found. This is well in line with literature nanoindentation data and the known change in properties of the organic phase upon hydration. Please click Additional Files below to see the full abstract

In-situ micropillar compression of bone shows remarkable strength and ductility but no damage

Bone is a hierarchical composite material featuring a cell-seeded mineralized collagen matrix. It is designed for mechanical support, metabolizing minerals and storing bone marrow. Its strength depends on the amount of mineral measured by clinical densitometry, but also on the micromechanical properties of the bone hierarchical organization. A good understanding has been reached for elastic properties on several length scales, but up to now there is a lack of data with respect to plasticity at the lower length scales. An experimental setup for micromechanical testing allowing a straightforward interpretation of the data due to the uniaxial stress state is micropillar compression. Micron sized pillars were produced by milling of the material using a focused Ga-ion beam and compressed uniaxially to extract mechanical properties such as yield stress and strength. 40 monotonic and 10 cyclic micropillar com-pression tests observed in situ in a scanning electron microscope complemented by micro-indentations and 26 macroscopic cyclic uni-axial compression tests were performed on dry ovine bone to identify its mechanical properties as well as deformation and failure mechanisms [1]. While the elastic properties measured during micropillar compression, microindentation and macroscopic compression tests were consistent, the plastic deformation and failure mechanisms differed between the two length scales. A majority of the micropillars showed a highly ductile behavior with continuous strain hardening until failure by localization in a shear plane, while the macroscopic samples failed in a quasi-brittle fashion. The microscopic compressive strength was 2.4 times higher than at the macroscale (0.75 GPa vs. 0.31 GPa), the maximum plastic strain 6 times higher. Also, cyclic compression tests showed no reduction in elastic modulus of the micropillars as opposed to the macroscopic samples. These experiments illustrate a transition in bone under compression from ductile behaviour at the microscale to a quasi-brittle response driven by the growth of microcracks along interfaces or in the vicinity of pores associated with modulus reduction at the macroscale. The insights obtained from this study may help to improve our understanding of the fragility of bone due to ageing and disease in the future

Estimated physical activity in Bavaria, Germany, and its implications for obesity risk: Results from the BVS-II Study

BACKGROUND: Adequate physical activity (PA) is considered as a key factor in the fight against the obesity epidemic. Therefore, detailed description of the actual PA and its components in the population is necessary. Additionally, this study aims to investigate the association between PA and obesity risk in a representative population sample in Bavaria, Germany. METHODS: Data from 893 participants (age 13–80 years) of the Bavarian Food Consumption Survey II (BVS II) were used. In each participant, three computer-based 24-hour recalls were conducted by telephone assessing type and duration of PA in the domains occupation, sports, other strenuous leisure time activities (of mostly moderate intensity) as well as TV/PC use in leisure time and duration of sleeping. After assigning metabolic equivalents (METs) to each activity, estimates of energy expenditure (MET*h) and total daily PA level (PAL(est.)) were calculated. In a subgroup of adults (n = 568) with anthropometric measurements logistic regression models were used to quantify the impact of PA on obesity risk. RESULTS: Estimated average PA in women and men was 38.5 ± 5.0 and 40.6 ± 9.3 MET*h/d, respectively, corresponding to PAL(est. )values of 1.66 ± 0.22 and 1.75 ± 0.40. Obese subjects showed lower energy expenditure in the categories sports, occupation, and sleeping, while the time spent with TV/PC during leisure time was highest. This is confirmed in logistic regression analyses revealing a statistically significant association between obesity and TV/PC use during leisure time, while sports activity was inversely related to obesity risk. Overall, less than 1/3 of the study participants reached the recommended PAL of ≥ 1.75. Subjects within the recommended range of PA had an about 60 % (odds ratio = 0.43; 95% CI: 0.21–0.85) reduced risk of obesity as compared to inactive subjects with a PAL(est. )<1.5. CONCLUSION: Based on the results of short-term PA patterns, a major part of the Bavarian adult population does not reach the recommendations (PAL>1.75; moderate PA of > 30 min/d). Despite the limitations of the study design, the existing associations between sports activity, TV/PC use and obesity risk in this population give further support to the recommendation of increasing sports activity and reducing sedentary behaviour in order to prevent rising rates of obesity

SIGLEC-1 in Systemic Sclerosis: A Useful Biomarker for Differential Diagnosis

Systemic Sclerosis (SSc) is a clinically heterogeneous disease that includes an upregulation of type I interferons (IFNs). The aim of this observational study was to investigate the IFN-regulated protein Sialic Acid–Binding Ig-like Lectin 1 (SIGLEC-1) as a biomarker for disease phenotype, therapeutic response, and differential diagnosis in SSc. Levels of SIGLEC-1 expression on monocytes of 203 SSc patients were determined in a cross-sectional and longitudinal analysis using multicolor flow cytometry, then compared to 119 patients with other rheumatic diseases and 13 healthy controls. SSc patients higher SIGLEC-1 expression on monocytes (2097.94 ± 2134.39) than HCs (1167.45 ± 380.93; p = 0.49), but significantly lower levels than SLE (8761.66 ± 8325.74; p < 0.001) and MCTD (6414.50 ± 1846.55; p < 0.001) patients. A positive SIGELC-1 signature was associated with reduced forced expiratory volume (p = 0.007); however, we were unable to find an association with fibrotic or vascular disease manifestations. SIGLEC-1 remained stable over time and was independent of changes in immunosuppressive therapy. However, SIGLEC-1 is suitable for differentiating SSc from other connective tissue diseases. SIGLEC-1 expression on monocytes can be useful in the differential diagnosis of connective tissue disease but not as a biomarker for SSc disease manifestations or activity

Is Aggressive Surgical Palliation of Proximal Bile Duct Cancer With Involvement of Both Main Hepatic Ducts Worthwhile?

The only curative treatment for proximal bile duct cancer with involvement of both main hepatic ducts is liver transplantation. Most patients do not fulfill the requirements for liver transplantation. Our treatment strategy in appropriate cases is palliative tumor resection and reconstruction of the biliary passage by sutureless bilioenteric anastomosis. We have treated 12 patients, 5 in combination with intraluminal and percutaneous radiotherapy. Our results indicate that this strategy leads to effective palliation in some cases provided that only microscopic residual tumor is left in-situ. Our survival times compare favourably with survival after liver transplantation

Exploring the mechanical character of molybdenum grain boundaries via nanoindentation and three-point-bending

The interactions of interfaces with dislocations have been extensively studied in the past. Still, there is a lack of high throughput methods, which can potentially be used for systematic studies to cover a wide range of grain boundary types. Nanoindentation offers the opportunity to combine a high spatial resolution with high effectiveness, thus enabling to obtain comprehensive mechanical data in the vicinity of grain boundaries. The present study on coarse-grained molybdenum will show results of mechanical property mapping near grain boundaries. Here, for the first time also the indenter tip rotation angle with respect to the loading axis as well as the grain orientation are considered. Results will show that neglecting these parameters can bias interpretations of the interface/dislocation interactions, as the localized deformation paths around the indentation are thereby significantly changed. Systematic experiments on commercially pure, recrystallized molybdenum have been performed to investigate the dependence of the hardness increase near grain boundaries with respect to the boundary misorientation angle. As a complementary method, three-point-bending is applied on mm-sized specimens until individual grain boundaries delaminate, which in turn will be identified and cross-checked with findings of the nanoindentation tests. Doping molybdenum with elements like carbon and/or boron is known to suppress intercrystalline failure. For this reason, the presented grain boundary characterization methods will be applied to extract mechanical changes caused by these doping elements

Respiratory tract deposition of inhaled roadside ultrafine refractory particles in a polluted megacity of South-East Asia

Recent studies demonstrate that Black Carbon (BC) pollution in economically developing megacities remain higher than the values, which the World Health Organization considers to be safe. Despite the scientific evidence of the degrees of BC exposure, there is still a lack of understanding on how the severe levels of BC pollution affect human health in these regions. We consider information on the respiratory tract deposition dose (DD) of BC to be essential in understanding the link between personal exposure to air pollutants and corresponding health effects. In this work, we combine data on fine and ultrafine refractory particle number concentrations (BC proxy), and activity patterns to derive the respiratory tract deposited amounts of BC particles for the population of the highly polluted metropolitan area of Manila, Philippines. We calculated the total DD of refractory particles based on three metrics: refractory particle number, surface area, and mass concentrations. The calculated DD of total refractory particle number in Metro Manila was found to be 1.6 to 17 times higher than average values reported from Europe and the U.S. In the case of Manila, ultrafine particles smaller than 100 nm accounted for more than 90% of the total deposited refractory particle dose in terms of particle number. This work is a first attempt to quantitatively evaluate the DD of refractory particles and raise awareness in assessing pollution-related health effects in developing megacities. We demonstrate that the majority of the population may be highly affected by BC pollution, which is known to have negative health outcomes if no actions are taken to mitigate its emission. For the governments of such metropolitan areas, we suggest to revise currently existing environmental legislation, raise public awareness, and to establish supplementary monitoring of black carbon in parallel to already existing PM 10 and PM 2.5 measures. © 201

Evidence-based guideline of the German Nutrition Society: fat intake and prevention of selected nutrition-related diseases

As nutrition-related chronic diseases have become more and more frequent, the importance of dietary prevention has also increased. Dietary fat plays a major role in human nutrition, and modification of fat and/or fatty acid intake could have a preventive potential. The aim of the guideline of the German Nutrition Society (DGE) was to systematically evaluate the evidence for the prevention of the widespread diseases obesity, type 2 diabetes mellitus, dyslipoproteinaemia, hypertension, metabolic syndrome, coronary heart disease (CHD), stroke, and cancer through the intake of fat or fatty acids. The main results can be summarized as follows: it was concluded with convincing evidence that a reduced intake of total and saturated fat as well as a larger intake of polyunsaturated fatty acids (PUFA) at the expense of saturated fatty acids (SFA) reduces the concentration of total and low-density lipoprotein cholesterol in plasma. Furthermore, there is convincing evidence that a high intake of trans fatty acids increases risk of dyslipoproteinaemia and that a high intake of long-chain polyunsaturated n-3 fatty acids reduces the triglyceride concentration in plasma. A high fat intake increases the risk of obesity with probable evidence when total energy intake is not controlled for (ad libitum diet). When energy intake is controlled for, there is probable evidence for no association between fat intake and risk of obesity. A larger intake of PUFA at the expense of SFA reduces risk of CHD with probable evidence. Furthermore, there is probable evidence that a high intake of long-chain polyunsaturated n-3 fatty acids reduces risk of hypertension and CHD. With probable evidence, a high trans fatty acid intake increases risk of CHD. The practical consequences for current dietary recommendations are described at the end of this article