A 4D statistical model of wrist bone motion patterns

Direct imaging of ligament damage in the wrist remains a challenge. Still, such damage can be assessed indirectly through the analysis of changes in wrist pose and motion pattern. For this purpose we built a statistical reference model that describes healthy motion patterns. We show that such a model can also be used to detect and quantify pathologies. A model that only describes the global translations and rotations of the carpal bones is insufficiently accurate due to size and shape variations of the bones. We present a local statistical motion model that minimizes the influence of size and shape differences by analyzing the coordinate differences of pairs of points on adjacent bone surfaces. These differences are determined in a set of 14 healthy example wrists imaged in a range of poses by means of 4D-RX imaging. The distribution of the differences as a function of the pose form the local statistical motion model (LSMM). Translations of 2 mm and rotations of 20° with respect to the healthy example wrists are detected as outliers in the point pair distributions. An evaluation involving wrists with a damaged ligament between scaphoid and lunate shows that not only joint space widenings can be detected, but also shifts of congruent bone surfaces. The LSMM is also used to perform a virtual reconstruction of the most likely healthy wrist after a simulated perturbation of bones. The reconstruction precision is shown to be about 1 mm. Therefore, the presented 4D statistical model of wrist bone movement may become a valuable clinical tool for diagnosis and surgical planning.     

New achievements in visco-elastoplastic constitutive model and temperature sensitivity of glasphalt

This paper focuses on the experimental investigation on temperature sensitivity and visco-elastoplastic behaviour of glasphalt. Classic Burgers creep model could only describe the viscoelastic behaviour of materials before the third creep-phase, so a viscoplastic string is added in series with classic Burgers model in order to predict the visco-elastoplastic behaviour of glasphalt. In this research, the effects of loading stress and temperature on creep behaviour of glasphalt under dynamic loading are investigated. In addition, some methods were used to solve model parameters and then predictions from proposed model were compared with experimental results. It was shown that creep testing curves coincided well with theoretic curves, validating that modified Burgers model can completely characterise creep behaviour of glasphalt. Besides, temperature sensitivity of glasphalt was evaluated by using indirect tensile stiffness modulus test, and stiffness modulus behaviour model of glasphalt was presented based on the experimental results and numerical analysis.     

A novel porous nanocomposite of aminated silica MCM‐41 and nylon‐6: Isotherm,kinetic, and thermodynamic studies on adsorption of Cu(II) and Cd(II)

Porous amine‐modified MCM‐41/Nylon‐6 nanocomposite (NH₂‐MCM‐41/NY6 NC) was synthesized by a facile solution casting protocol, which was used as an effective adsorbent for the removal of Cu(II) and Cd(II) from aqueous media. The physicochemical properties of NH₂‐MCM‐41/NY6 NC were studied by scanning and transmission electron microscopies, thermogravimetric analysis, etc. The influence of pH, adsorbent dose, contact time and initial concentration on adsorption performance were investigated in detail. Kinetic and isotherm parameters were evaluated and the data fitted well to the pseudo‐second order and Freundlich isotherm model, respectively. The maximum adsorption capacities of Cu(II) and Cd(II) were about 35.84 and 27.5 mg·g^?1, respectively. The K_d of NH₂‐MCM‐41/NY6 NC for Cu(II) (> ) and Cd(II) (> ) ions uptake in aqueous solution, showed very good values. Thermodynamic parameters suggest that the adsorption is a spontaneous process with an endothermic nature. According to the results obtained, we conclude that this novel porous NH₂‐MCM‐41/NY6 NC could be used for the removal of heavy metal ions from an aqueous solution. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45383.     

Polypyrrole/multiwall carbon nanotube nanocomposites electropolymerized on copper substrate

Polypyrrole/multiwall carbon nanotube (PPy/MWCNT) nanocomposites were successfully synthesized by electropolymerization of MWCNT-dispersed pyrrole solution on the surface of copper electrodes. The obtained nanocomposites were characterized with scanning electron microscopy (SEM), linear sweep voltammetry (LSV) and thermal gravimetric analysis (TGA). Polypyrrole structures which embraced the MWCNTs led to the formation of nanocomposite striated parallel walls. MWCNTs acted as appropriate substrates for electrodeposition of polypyrrole particulate structures and high yield synthesis of PPy was observed on them. Smooth PPy/MWCNT nanocomposite films were obtained on Cu electrodes by decreasing the potential scan rate. Thermogravimetric analysis showed that MWCNTs increased the thermal stability of polypyrrole.     

CFRP Effect on the Buckling Behavior of Dented Cylindrical Shells

Considering that the use of thin-walled shells is expanding every day, it is important to examine the problem of instability in this form of structure. Many steel structures such as high-water tanks, water and oil reservoirs, marine structures, and pressure vessels, including shell elements, are under stress tension. In addition, shell elements are subject to instability owing to the loads applied. Ten thin-walled cylindrical shell specimens in two groups with different dent depths of t_c and 2t_c, and the different dent number subject to uniform external pressure were tested in the present research (t_c is the thickness of cylindrical shell). The samples were modified to include either one or two dent line with amplitudes of h/3 in height (h the height of cylinder shell). Moreover, CFRP Strips on the dent depth was used in one of the groups. The results of testing under different theories and codes are compared.

     

Wood–high‐density polyethylene composites: Water absorption and mechanical properties

In this research, the effect of water absorption on the mechanical properties of wood/high‐density polyethylene (HDPE) composites were investigated. HDPE (44005ARPC) was used as the polymer matrix, and spruce sawdust was used as the filler at a maximum loading of 50 wt % of the total weight of each compound. All compounds contained 5 wt % magnesium stearate as a lubricant and 0.5 wt % Irgafos 168 as a heat stabilizer. Four factors in two levels were chosen [talc (filler) at levels of 5 and 15 wt %, zinc borate (fungicide) at levels of 0 and 1 wt %, maleic anhydride polyethylene (coupling agent) at levels of 4 and 6 wt %, and method of mixing (one‐step vs. two‐step mixing)], and eight compounds were prepared with an L8 Taguchi orthogonal array which has 8 combinations of levels. The effects of each factor at two levels on the diffusion constant and the tensile and bending strengths (under wet and dry conditions) were investigated by the analysis of variance of means with 90% confidence. The optimum level for each factor is reported. The results show that there was a linear correlation between the diffusion constant and tensile and bending strengths when the samples were immersed in distilled water. A higher diffusion constant resulted in much lower tensile and bending strengths with immersion in distilled water until saturation was reached. Scanning electron microscopy images confirmed good mixing when two‐steps mixing was used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and linear-elastic moduli of random network solids

The effective linear-elastic moduli of disordered network solids are analyzed by voxel-based finite element calculations. We analyze network solids given by Poisson-Voronoi processes and by the structure of collagen fiber networks imaged by confocal microscopy. The solid volume fraction ? is varied by adjusting the fiber radius, while keeping the structural mesh or pore size of the underlying network fixed. For intermediate ?, the bulk and shear modulus are approximated by empirical power-laws K(phi)proptophin and G(phi)proptophim with n≈1.4 and m≈1.7. The exponents for the collagen and the Poisson-Voronoi network solids are similar, and are close to the values n=1.22 and m=2.11 found in a previous voxel-based finite element study of Poisson-Voronoi systems with different boundary conditions. However, the exponents of these empirical power-laws are at odds with the analytic values of n=1 and m=2, valid for low-density cellular structures in the limit of thin beams. We propose a functional form for K(?) that models the cross-over from a power-law at low densities to a porous solid at high densities; a fit of the data to this functional form yields the asymptotic exponent n≈1.00, as expected. Further, both the intensity of the Poisson-Voronoi process and the collagen concentration in the samples, both of which alter the typical pore or mesh size, affect the effective moduli only by the resulting change of the solid volume fraction. These findings suggest that a network solid with the structure of the collagen networks can be modeled in quantitative agreement by a Poisson-Voronoi process.     

Functional modeling of astrocytes in epilepsy: a feedback system perspective

Astrocytes, a subtype of glial cells, in the brain provide structural and metabolic supports to the nervous system. They are also active partners in synaptic transmission and neuronal activities. In the present study, a biologically plausible thalamocortical neural population model (TCM) originally proposed by Suffczynski et al. (Neuroscience 126(2):467–484, 2004) is extended by integrating the functional role of astrocytes in the regulation of synaptic transmission. Therefore, the original TCM is modified to consider neuron-astrocyte interactions. Using the modified model, it is demonstrated that the healthy astrocytes are capable to compensate the variation of cortical excitatory input by increasing their firing frequency. In this way, they can preserve the attractor corresponding to the normal activity. Furthermore, the performance of the pathological astrocytes is also investigated. It is hypothesized that one of the plausible causes of seizures is the malfunction of astrocytes in the regulatory feedback loop. That is, pathologic astrocytes are not any more able to regulate and/or compensate the excessive increase of the cortical input. Therefore, pathologic astrocytes lead to the emergence of paroxysmal attractor. Results demonstrate that disruption of the homeostatic or signaling function of astrocytes can initiate the synchronous firing of neurons, suggesting that astrocytes might be one of the potential targets for the treatment of epilepsy.     

Exploring pedagogical opportunities between architecture and planning: the case of University of Nevada,Las Vegas

This study critically explores collaboration opportunities between architects and planners. Architects typically emphasize site design, whereas planners stress prospects for community engagement. The collaboration opportunity prompts these professions to learn from each other synergistically. This case study outlines the efforts of two groups of architecture and planning students who, despite divergent pedagogical emphases, hone their integrative skills. Devising a set of evaluative criteria (permeability, stability and connectivity), enabled the planning students to rank and predict the university–community partnership impacts of eight projects proposed by the architecture students. The three expected partnership models (fortress, developer, and catalytic) enlightened the architecture students to also think about the social impact of their designs. There is a long history of debate about pedagogical and practice divides between planning and architecture. The paper contributes to those debates by examining how disciplinary divides might be overcome through collaborative teaching.