Context Increased bone fragility and reduced energy absorption to fracture associated with type 2 diabetes (T2D) cannot be explained by bone mineral density alone. This study, for the first time reports on alterations in bone tissue's material properties obtained from individuals with diabetes and known fragility fracture status. Objective To investigate the role of T2D in altering biomechanical, microstructural and compositional properties of bone in individuals with fragility fracture. Design Femoral head bone tissue specimens were collected from patients who underwent replacement surgery for fragility hip fracture. Trabecular bone quality parameters were compared in samples of two groups: non-diabetic (n=40) and diabetic (n=30), with a mean duration of disease 7.5±2.8 years. Results No significant difference was observed in aBMD between the groups. Bone volume fraction (BV/TV) was lower in the diabetic group due to fewer and thinner trabeculae. The apparent-level toughness and post-yield energy were lower in those with diabetes. Tissue-level (nanoindentation) modulus and hardness were lower in this group. Compositional differences in diabetic group included lower mineral:matrix, wider mineral crystals, and bone collagen modifications - higher total fAGEs, higher non-enzymatic-cross-link-ratio (NE-xLR), and altered secondary structure (Amide bands). There was a strong inverse correlation between NE-xLR and post-yield-strain, fAGEs and post-yield energy, and, fAGEs and toughness. Conclusion Current study is novel in examining bone tissue in T2D following first hip fragility fracture. Our findings provide evidence of hyperglycemia’s detrimental effects on trabecular bone quality at multiple scales leading to lower energy absorption and toughness-indicative of increased propensity to bone fragility.

We have proposed a method for the dynamic simulation of a collection of self-propelled particles in a viscous Newtonian fluid. We restrict attention to particles whose size and velocity are small enough that the fluid motion is in the creeping flow regime. We have proposed a simple model for a self-propelled particle, and extended the Stokesian Dynamics method to conduct dynamic simulations of a collection of such particles. In our description, each particle is treated as a sphere with an orientation vector p, whose locomotion is driven by the action of a force dipole S p of constant magnitude S 0 at a point slightly displaced from its centre. To simplify the calculation, we place the dipole at the centre of the particle, and introduce a virtual propulsion force F p to effect propulsion. The magnitude F 0 of this force is proportional to S 0 . The directions of S p and F p are determined by p. In isolation, a self-propelled particle moves at a constant velocity u 0 p, with the speed u 0 determined by S 0 . When it coexists with many such particles, its hydrodynamic interaction with the other particles alters its velocity and, more importantly, its orientation. As a result, the motion of the particle is chaotic. Our simulations are not restricted to low particle concentration, as we implement the full hydrodynamic interactions between the particles, but we restrict the motion of particles to two dimensions to reduce computation. We have studied the statistical properties of a suspension of self-propelled particles for a range of the particle concentration, quantified by the area fraction φ a . We find several interesting features in the microstructure and statistics. We find that particles tend to swim in clusters wherein they are in close proximity. Consequently, incorporating the finite size of the particles and the near-field hydrodynamic interactions is of the essence. There is a continuous process of breakage and formation of the clusters. We find that the distribution of particle velocity at low and high φ a are qualitatively different; it is close to the normal distribution at high φ a , in agreement with the experimental measurements of Wu & Libchaber (2000). The motion of the particles is diffusive at long time, and the self-diffusivity decreases with increasing φ a . The pair correlation function shows a large anisotropic buildup near contact, which decays rapidly with separation. There is also an anisotropic orientation correlation near contact, which decays more slowly with separation.

The cylindrical Couettedevice is commonly employed to study the rheology of fluids, but seldom used for dense granular materials.Plasticity theories used for granular flows predict a stress field that is independent of the shear rate, but otherwise similar to that in fluids. In this paper we report detailed measurements of the stress as a function of depth, and show that the stress profile differs fundamentally from that of fluids, from the predictions of plasticity theories, and from intuitive expectation. In the static state, a part of the weight of the material is transferred to the walls by a downward vertical shear stress, bringing about the well-known Janssen saturation of the stress in vertical columns. When the material is sheared, the vertical shear stress changes sign, and the magnitudes of all components of the stress rise rapidly with depth. These qualitative features are preserved over a range of the Couette gap and shear rate, for smooth and rough walls and two model granular materials. To explain the anomalous rheological response, we consider some hypotheses that seem plausible a priori, but show that none survive after careful analysis of the experimental observations. We argue that the anomalous stress is due to an anisotropic fabric caused by the combined actions of gravity, shear,and frictional walls, for which we present indirect evidence from our experiments. A general theoretical framework for anisotropicplasticity is then presented. The detailed mechanics of how an anisotropic fabric is brought about by the above-mentioned factors is not clear,and promises to be a challenging problem for future investigations.

We present measurements of the stress as a function of vertical position in a column of granular material sheared in a cylindrical Couette device. All three components of the stress tensor on the outer cylinder were measured as a function of distance from the free surface at shear rates low enough that the material was in the dense, slow flow regime. We find that the stress profile differs fundamentally from that of fluids, from the predictions of plasticity theories, and from intuitive expectation. We argue that the anomalous stress profile is due to an anisotropic fabric caused by the combined action of gravity and shear.

Long-term Type 2 Diabetes (T2D) affects the normal functioning of heart, kidneys, nerves, arteries, bones, and joints. The T2D gradually alters the intrinsic material properties, and structural integrity of the tissues and prolonged hyperglycemia causes chronic damages to these tissues quality. Clinically no such technique is available which can assess the altered tissues quality associated with T2D. In the present study, the microstructural characterization (surface morphology, surface roughness and density and calcium content), material characterization (modulus, hardness), and macromolecular characterization (disulfide bond content, protein content and its secondary structure) are investigated among healthy, diabetic controlled (DC) and uncontrolled diabetic (UC) group of fingernail plate. It is found that T2D has an adverse effect on the human fingernail plate quality. The parameters of nail plate quality are changing in a pattern among all the three groups. The properties mentioned above are degrading in DC group, but the degradation is even worst in the case of severity of T2D (UC group) as compared to the healthy group (Healthy