Accurate micro-computed tomography imaging of pore spaces in collagen-based scaffold

In this work we have used X-ray micro-computed tomography (μCT) as a method to observe the morphology of 3D porous pure collagen and collagen-composite scaffolds useful in tissue engineering. Two aspects of visualizations were taken into consideration: improvement of the scan and investigation of its sensitivity to the scan parameters. Due to the low material density some parts of collagen scaffolds are invisible in a μCT scan. Therefore, here we present different contrast agents, which increase the contrast of the scanned biopolymeric sample for μCT visualization. The increase of contrast of collagenous scaffolds was performed with ceramic hydroxyapatite microparticles (HAp), silver ions (Ag⁺) and silver nanoparticles (Ag-NPs). Since a relatively small change in imaging parameters (e.g. in 3D volume rendering, threshold value and μCT acquisition conditions) leads to a completely different visualized pattern, we have optimized these parameters to obtain the most realistic picture for visual and qualitative evaluation of the biopolymeric scaffold. Moreover, scaffold images were stereoscopically visualized in order to better see the 3D biopolymer composite scaffold morphology. However, the optimized visualization has some discontinuities in zoomed view, which can be problematic for further analysis of interconnected pores by commonly used numerical methods. Therefore, we applied the locally adaptive method to solve discontinuities issue. The combination of contrast agent and imaging techniques presented in this paper help us to better understand the structure and morphology of the biopolymeric scaffold that is crucial in the design of new biomaterials useful in tissue engineering.     

Numerical simulation of the system “fixture–workpiece” for lever machining

In this article, the new configuration of fixture was proposed for ensuring the sufficient tool accessibility, which allows carrying out multiaxis machining of levers in one setup. The research based on numerical simulation was confirmed that the proposed fixture corresponds to all the accuracy parameters. Workpieces from steel, cast iron and aluminium alloy were investigated within the simulation. The values of displacements and stresses occurring during machining are less for proposed fixture in comparison with the existing fixtures that was confirmed by the deflected mode analysis. The modal analysis proved that the proposed fixture has much higher value of eigenfrequency than the other fixtures. To optimize the machining, the dependences for displacements and stresses on the cutting depth were determined. Oscillations of the system “fixture–workpiece” during machining were investigated for various manufacturing steps of levers machining of the fixtures from different fixture systems. The results of harmonic analysis showed that the dynamic stiffness of the proposed fixture was higher than that for the dedicated and modular fixtures. The oscillation amplitudes in the places of machined surfaces in the proposed fixture do not exceed the tolerance requirements for lever manufacturing.     

Fretting fatigue wear behavior of Y‐TZP dental ceramics processed by non‐conventional microwave sintering

The fretting wear behavior of self‐mated Y‐TZP dental materials obtained by nonconventional microwave and conventional sintering has been investigated. Two 3Y‐TZP materials, a widely utilized commercial dental ceramic (LAVA) and a lab‐prepared 3Y‐TZP powder based equivalent have been assessed. Relative density and mechanical properties as well as the grain size variations upon sintering have been evaluated. After exposure to selected gross slip regime fretting wear conditions, the wear tracks have been characterized allowing the measurement of the coefficient of friction, track profiles, and pit features. The results indicate that microwave sintering results in a similar fretting wear behavior as observed for conventional‐sintered 3Y‐TZP, as the measured volumetric wear loss is of a comparable order of magnitude. Regarding the influence of the grain size, the analysis revealed that a large grain size (>300 nm) results in an increased wear volume and that a higher resistance to fretting wear is constrained to a mid‐range particle size (100–250 nm). Since the fracture toughness of all investigated ceramic grades was comparable, the influence of the fracture toughness on fretting could not be assessed. Abrasive grooving, delamination, and microcracking have been identified as major wear mechanisms inside the wear tracks for both conventional‐ and microwave‐sintered 3Y‐TZP. In general, microwave sintering can provide 3Y‐TZP dental materials with a comparable fretting wear resistance as that observed for conventional sintering using lower dwell sintering temperatures and a shorter processing time.     

Transformations of structures: An algebraic approach

This paper introduces a new mathematical approach to transformations of structures, where the concept of structure is extremely general. Many structures and transformations that arise in biology as well as computer science are special cases of our concepts. A structure may be changed by finding an occurrence of a pattern and replacing it by another pattern as specified by a rule. To prove theorems about long sequences of applications of complicated rules, we need precise and tractable mathematical definitions of rules and how to apply them. This paper presents such definitions and three fundamental theorems, together with brief remarks on applications to control flow analysis, record handling, and evaluation of recursively defined functions. Unlike some previous efforts toward a rigorous theory of transformations of structures, this paper uses ideas and results from abstract algebra to minimize the need for elaborate constructions.A condensation of an earlier version of this paper was presented as [9] at the 7th Symposium on Mathematical Foundations of Computer Science, September 1978, Zakopane, Poland. Work by Ehrig was partially supported by IBM Germany and IBM World Trade Corp. Work by Rosen and Maggiolo-Schettini was partially supported by the Laboratorio di Cibernetica del C.N.R.     

Detection and localization of selected acoustic events in acoustic field for smart surveillance applications

A method for automatic determination of position of chosen sound events such as speech signals and impulse sounds in 3-dimensional space is presented. The events are localized in the presence of sound reflections employing acoustic vector sensors. Human voice and impulsive sounds are detected using adaptive detectors based on modified peak-valley difference (PVD) parameter and sound pressure level. Localization based on signals from the multichannel acoustic vector probe is performed upon the detection. The described algorithms can be employed in surveillance systems to monitor behavior of public events participants. The results can be used to detect sound source position in real time or to calculate the spatial distribution of sound energy in the environment. Moreover, the spatial filtration can be performed to separate sounds arriving from a chosen direction.     

Decoder-driven mode decision in a block-based distributed video codec

Distributed Video Coding (DVC) is a video coding paradigm in which the computational complexity is shifted from the encoder to the decoder. DVC is based on information theoretic results suggesting that, under ideal conditions, the same rate-distortion performance can be achieved as for traditional video codecs. In practice however, there is still a significant performance gap between the two coding architectures. One of the main reasons for this gap is the lack of multiple coding modes in current DVC solutions. In this paper, we propose a block-based distributed video codec that supports three coding modes: Wyner–Ziv, skip, and intra. The mode decision process is entirely decoder-driven. Skip blocks are selected based on the estimated accuracy of the side information. The choice between intra and Wyner–Ziv coding modes is made on a rate-distortion basis, by selecting the coding mode with the lowest rate while assuring equal distortion for both modes. Experimental results illustrate that the proposed block-based architecture has some advantages over classical bitplane-based approaches. Introducing skip and intra coded blocks yields average bitrate gains of up to 33.7% over our basic configuration supporting Wyner–Ziv mode only, and up to 29.7% over the reference bitplane-based DISCOVER codec.     

The effect of wheat grain composition, cuticular lipids and kernel surface microstructure on feeding, egg-laying, and the development of the granary weevil, Sitophilus granarius (L.)

Adult feeding intensity, oviposition, and larval development of Sitophilus granarius (Coleoptera: Curculionidae) were observed on grain from three Polish wheat varieties (Begra, Korweta, and LGR 896/64a) washed with petroleum ether to remove cuticular lipids. Extraction of lipids did not cause any statistically significant changes in the physicochemical, biochemical and technological (milling, rheological and baking) properties of the wheat grain studied. Wheat grain washed with petroleum ether did not show any visible changes in the surface and morphology of the outer layer of the wheat grain. However, differences were noted in the microstructure of the kernel surface. Grain with a thicker seed coat (LGR 896/64a) was infested at a lower rate than the other varieties. Of the 18 hydrocarbons extracted from the grain surface, three compounds - n-heptacosane (C₂₇), n-nonacosane (C₂₉) and n-hentriacontane (C₃₁) - were found in significant amounts. In general, beetles produced 64-95% less dust and laid 7-16% fewer eggs in kernels from which cuticular lipids had been removed. This implies that these compounds have a major role in food selection and the search for an oviposition site prior to grain infestation.     

Changes in microfibril angle in cyclically deformed dry coir fibers studied by in-situ synchrotron X-ray diffraction

Dry coir fibers are characterized by wide-angle X-ray scattering coupled with tensile tests. The fibers exhibit elastic and plastic behavior with the yield point at a strain of about 2%. In-situ experiments document that the cyclic loading and unloading beyond the yield point does not reduce the stiffness of the fibres, since they recover their initial stiffness by every increase of the strain. The diffraction data show that the microfibril angle (MFA) of cellulose fibrils in the coir fibre cells is inversely proportional to the magnitude of the applied strain. In average, the relatively high MFA of about 45° in the unstrained state decreases linearly upon straining until the fibers break at about 35% strain. When the strain is released during the tensile experiment the MFA tends to recover its original magnitude. No significant differences in the dependence of MFA on strain are detected in elastic and plastic regions, respectively. The results demonstrate that the tissue with helical architecture does not have to be saturated with water in order to exhibit the effect of the recovery of the mechanical function when cyclically loaded. This indicates differences in the architecture of the coir cell wall in comparison with that of compression wood with high MFA whereby similar phenomena were observed in the wet state.     

The Role of MAPK3/1 and AKT in the Acquisition of High Meiotic and Developmental Competence of Porcine Oocytes Cultured In Vitro in FLI Medium

The developmental potential of porcine oocytes cultured in vitro was remarkably enhanced in a medium containing FGF2, LIF and IGF1 (FLI) when compared to a medium supplemented with gonadotropins and EGF (control). We analyzed the molecular background of the enhanced oocyte quality by comparing the time course of MAPK3/1 and AKT activation, and the expression of genes controlled by these kinases in cumulus-oocyte complexes (COCs) cultured in FLI and the control medium. The pattern of MAPK3/1 activation in COCs was very similar in both media, except for a robust increase in MAPK3/1 phosphorylation during the first hour of culture in the FLI medium. The COCs cultured in the FLI medium exhibited significantly higher activity of AKT than in the control medium from the beginning up to 16 h of culture; afterwards a deregulation of AKT activity occurred in the FLI medium, which was not observed in the control medium. The expression of cumulus cell genes controlled by both kinases was also modulated in the FLI medium, and in particular the genes related to cumulus-expansion, signaling, apoptosis, antioxidants, cell-to-cell communication, proliferation, and translation were significantly overexpressed. Collectively, these data indicate that both MAPK3/1 and AKT are implicated in the enhanced quality of oocytes cultured in FLI medium.     

Analysis of effect of overloaded vehicles on fatigue life of flexible pavements based on weigh in motion (WIM) data

Overloaded vehicles have a significant impact on pavement fatigue life and distress. As the studies show, the phenomena intensify when the control of traffic is poor. The paper presents the results of the research including analysis of weigh in motion data from eight stations and analysis of asphalt pavement fatigue caused by mixed traffic. Distributions of vehicles axles load including the multiple axles effects are presented. Mixed axle loads were transformed into equivalent number of standard 100 kN axle loads. The regression model of load equivalency factor depending on the axle load distribution and the percentage of overloaded vehicles is presented. The analysis of the effect of overloaded vehicles on decrease of fatigue life of a pavement structure is presented. The analysis has shown that the increase of percentage of overloaded vehicles from 0% to 20% can reduce the fatigue life of asphalt pavement upto 50%.