Eulerian simulation of complex suspensions and biolocomotion in three dimensions.

We present a numerical method specifically designed for simulating three-dimensional fluid-structure interaction (FSI) problems based on the reference map technique (RMT). The RMT is a fully Eulerian FSI numerical method that allows fluids and large-deformation elastic solids to be represented on a single fixed computational grid. This eliminates the need for meshing complex geometries typical in other FSI approaches and greatly simplifies the coupling between fluid and solids. We develop a three-dimensional implementation of the RMT, parallelized using the distributed memory paradigm, to simulate incompressible FSI with neo-Hookean solids. As part of our method, we develop a field extrapolation scheme that works efficiently in parallel. Through representative examples, we demonstrate the method's suitability in investigating many-body and active systems, as well as its accuracy and convergence. The examples include settling of a mixture of heavy and buoyant soft ellipsoids, lid-driven cavity flow containing a soft sphere, and swimmers actuated via active stress.

Meta-analysis as a system of springs.

Meta-analysis results are usually presented in forest plots, which show the individual study results and the summary effect along with their confidence intervals. In this paper, we propose a system of linear springs as a mechanical analogue of meta-analysis that enables visualization and enhances intuition. The length of a spring corresponds to a study treatment effect and the stiffness of the spring corresponds to its inverse variance. To synthesize study springs we use two main operations: connection in parallel and connection in series. We show the equivalence between meta-analysis and linear springs for fixed effect and random effects pairwise meta-analysis and we also derive indirect treatment effects. We use examples to illustrate the different meta-analytical schemes using the corresponding system of springs. The proposed visualization can serve as an educational tool, especially useful for researchers with no statistical background. The analogy between meta-analysis and springs facilitates intuition for notions such as heterogeneity and the differences between fixed and random effects meta-analysis.

Sensory studies, or when physics was psychophysics: Ernst Mach and physics between physiology and psychology, 1860-71.

This paper highlights the significance of sensory studies and psychophysical investigations of the relations between psychic and physical phenomena for our understanding of the development of the physics discipline, by examining aspects of research on sense perception, physiology, esthetics, and psychology in the work of Gustav Theodor Fechner, Hermann von Helmholtz, Wilhelm Wundt, and Ernst Mach between 1860 and 1871. It complements previous approaches oriented around research on vision, Fechner's psychophysics, or the founding of experimental psychology, by charting Mach's engagement with psychophysical experiments in particular. Examining Mach's study of the senses and esthetics, his changing attitudes toward the mechanical worldview and atomism, and his articulation of comparative understandings of sensual, geometrical, and physical spaces helps set Mach's emerging epistemological views in the context of his teaching and research. Mach complemented an analytic strategy focused on parallel psychic and physical dimensions of sensation, with a synthetic comparative approach - building analogies between the retina, the individual, and social life, and moving between abstract and sensual spaces. An examination of the broadly based critique that Mach articulated in his 1871 lecture on the conservation of work shows how his historical approach helped Mach cast what he now saw as a narrowly limiting emphasis on mechanics as a phase yet to be overcome.

Coulomb friction in twisting of biomimetic scale-covered substrate.

Biomimetic scale-covered substrates provide geometric tailorability via scale orientation, spacing and also interfacial properties of contact in various deformation modes. No work has investigated the effect of friction in twisting deformation of biomimetic scale-covered beams. In this work, we investigate the frictional effects in the biomimetic scale-covered structure by developing an analytical model verified by finite element simulations. In this model, we consider dry (Coulomb) friction between rigid scales surfaces, and the substrate as the linear elastic rectangular beam. The obtained results show that the friction has a dual contribution on the system by advancing the locking mechanism due to change of mechanism from purely kinematic to interfacial behavior, and stiffening the twist response due to sharp increase in the engagement forces. We also discovered, by increasing the coefficient of friction potentially using engineering scale surfaces to a critical coefficient, the system could reach to instantaneous post-engagement locking. The developed model outlines analytical relationships between geometry, deformation, frictional force and strain energy, to design biomimetic scale-covered metamaterials for a wide range of applications.

Determinants of occupational health hazards among roadside automobile mechanics in Sokoto Metropolis, Nigeria.

Background: Roadside automobile mechanics are in the course of their work exposed to several hazards that put them at risk of severe debilitating health challenges. This group of workers, however, is reported not to know much about such hazards and to have little or no training on workplace safety. Aim: The study aimed to identify the determinants of occupational health hazards among roadside automobile mechanics in Sokoto Metropolis. Methodology: This was a descriptive, cross-sectional study, and using a two-stage sampling technique, a total of 205 roadside mechanics were recruited for the study. A semi-structured interviewer-administered questionnaire was used, and the data were imputed into and analyzed using IBM SPSS. Results: The mean age of the respondents was 31.10 ± 10.19 years, and over one-third of them (38.1%) were general vehicle repairers. Majority of the respondents had good knowledge of and attitude toward workplace hazards. However, a good proportion (91.0%) of the mechanics felt that their occupation was a risky one and 80.1% ate and 86.1% drank while working. Type of training and job description were the predictors of knowledge of workplace hazards. Job description was the only predictor of attitude. Burns, bruises, headache/dizziness, and cuts were the most reported work-related illnesses and injuries. Conclusion: Although most of the auto-mechanics were aware and had good knowledge of workplace hazards, they did not adhere to safety practices in the workplace, mostly due to nonavailability of protective apparels. There is, therefore, need for continuous health education under the platform of the auto-mechanics association so that they can voluntarily adopt safety practices in their workplace.

RésuméContexte: Au cours de leur travail, les mécaniciens d'automobiles au bord de la route sont exposés à plusieurs risques qui les exposent à de graves problèmes de santé débilitants. Cependant, ce groupe de travailleurs ne connaît pas grand-chose à ces dangers et n'a pas ou peu de formation sur la sécurité au travail. Objectif: L'étude visait à identifier les déterminants des risques professionnels en matière de santé chez les mécaniciens automobiles de Sokoto Metropolis. Matériel et Méthodes: Il s'agissait d'une étude transversale descriptive et, en utilisant une technique d'échantillonnage en deux étapes, un total de 205 mécaniciens de bord de route ont été recrutés pour l'étude. Un questionnaire administré par un intervieweur semi-structuré a été utilisé et les données ont été imputées et analysées à l'aide d'IBM SPSS. Résultats: L 'âge moyen des répondants était de 31.10 ± 10.19 et plus d' un tiers d 'entre eux (38.1%) étaient des réparateurs de véhicules généraux. La majorité des répondants avaient de bonnes connaissances et une bonne attitude à l'égard des dangers au travail. Cependant, une bonne partie des mécaniciens estimaient que leur profession était risquée 183 (91,0%) et majoritaire, en mangeait 161 (80,1%) et en buvait 173 (86,1%) pendant qu'ils travaillaient. Le type de formation et la description de poste étaient des prédicteurs de la connaissance des dangers au travail. La description de travail était le seul prédicteur de l'attitude. Les brûlures, les ecchymoses, les maux de tête/vertiges et les coupures étaient les maladies et les blessures liées au travail les plus souvent rapportées. Conclusion: Bien que la plupart des mécaniciens et des mécaniciennes d'automobiles aient été au courant et aient une bonne connaissance des risques au travail, ils n'ont pas respecté les pratiques de sécurité sur le lieu de travail. Il existe donc un besoin d'éducation continue en matière de santé dans le cadre de la plate-forme de l'association de mécanique automobile afin qu'ils puissent adopter volontairement des pratiques de sécurité sur leur lieu de travail.

Expressure: Detect Expressions Related to Emotional and Cognitive Activities Using Forehead Textile Pressure Mechanomyography.

We investigate how pressure-sensitive smart textiles, in the form of a headband, can detect changes in facial expressions that are indicative of emotions and cognitive activities. Specifically, we present the Expressure system that performs surface pressure mechanomyography on the forehead using an array of textile pressure sensors that is not dependent on specific placement or attachment to the skin. Our approach is evaluated in systematic psychological experiments. First, through a mimicking expression experiment with 20 participants, we demonstrate the system's ability to detect well-defined facial expressions. We achieved accuracies of 0.824 to classify among three eyebrow movements (0.333 chance-level) and 0.381 among seven full-face expressions (0.143 chance-level). A second experiment was conducted with 20 participants to induce cognitive loads with N-back tasks. Statistical analysis has shown significant correlations between the Expressure features on a fine time granularity and the cognitive activity. The results have also shown significant correlations between the Expressure features and the N-back score. From the 10 most facially expressive participants, our approach can predict whether the N-back score is above or below the average with 0.767 accuracy.

Effect of Bread Structure and In Vitro Oral Processing Methods in Bolus Disintegration and Glycemic Index.

The growing interest in controlling the glycemic index of starchy-rich food has encouraged research about the role of the physical structure of food. The aim of this research was to understand the impact of the structure and the in vitro oral processing methods on bolus behavior and starch hydrolysis of wheat bread. Two different bread structures (loaf bread and bread roll) were obtained using different shaping methods. Starch hydrolysis during in vitro oro-gastro-intestinal digestion using the INFOGEST protocol was analyzed and oral processing was simulated by applying two different disintegration processes (basic homogenizer, crystal balls). The bread structure, and thus the shaping method during breadmaking, significantly affected the bolus particle size during all digestion stages. The different in vitro oral processing methods affected the bolus particle sizes after the oral phase in both breads, but they affected the particle size distribution after the gastric and intestinal phase only in the case of loaf bread. Aggregates were observed in the gastric phase, which were significantly reduced in the intestinal phase. When simulated oral processing with crystal balls led to bigger particle size distribution, bread rolls presented the highest in vitro starch hydrolysis. The type of in vitro oral processing allowed discrimination of the performance of the structures of the two breads during starch hydrolysis. Overall, crumb structure significantly affected texture properties, but also had a significant impact on particle size during digestion and starch digestibility.

The Notched Stick, an ancient vibrot example.

An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "vibrot", a device designed and built to yield conversion of mechanical vibrations into a rotational motion. The toy, that can be briefly described as a propeller fixed on a stick by means of a nail and free to rotate around it, is investigated from both an experimental and a numerical point of view, under various conditions and settings, to investigate the basic working principles of the device. The conversion efficiency from vibration to rotational motion turns out to be very small, or even not detectable at all, whenever the propeller is tightly connected to the stick nail and perfectly axisymmetrical with respect to the nail axis; the small effects possibly observed can be ascribed to friction forces. In contrast, the device succeeds in converting vibrations into rotations when the propeller center of mass is not aligned with the nail axis, a condition occurring when either the nail-propeller coupling is not tight or the propeller is not completely axisymmetrical relative to the nail axis. The propeller rotation may be induced by a process of parametric resonance for purely vertical oscillations of the nail, by ordinary resonance if the nail only oscillates horizontally or, finally, by a combination of both processes when nail oscillations take place in an intermediate direction. Parametric resonance explains the onset of rotations also when the weight of the propeller is negligible. In contrast with what is commonly claimed in the literature, the possible elliptical motion of the nail, due to a composition of two harmonic motions of the same frequency imposed along orthogonal directions, seems unnecessary to determine the propeller rotation.

Quantum biology and human carcinogenesis.

Quantum-mediated effects have been observed in biological systems. We have previously discussed basis-dependent quantum selection as a mechanism for directed adaptive mutation, a process in which selective pressure specifically induces mutation in those genes involved in the adaptive response. Tumor progression in cancer easily lends itself to the adaptive evolutionary perspective, as the Darwinian combination of heritable variations together with selection of the better proliferating variants are believed to play a major role in multistep carcinogenesis. Adaptive mutation may play a role in carcinogenesis; accordingly, we propose that the principles of quantum biology are involved in directed adaptive mutation processes that promote tumor formation. In this paper, we discuss the intersection between quantum mechanics, biology, adaptive evolution, and cancer, and present general models by which adaptive mutation may influence neoplastic initiation and progression. As a potential theoretical and experimental model, we use colorectal cancer. Our model of "quantum cancer" suggests experiments to evaluate directed adaptive mutation in tumorigenesis, and may have important implications for cancer therapeutics.

Putting the 'me' in mechanical: lessons from the mechanical men of health 1928-1948.

During the interwar years, health exhibitions and pavilions were commonplace in Europe and the USA. Within these exhibitions were a small number of life-sized or oversized mechanical men used to represent physiological processes. Although they received significant press attention at the time, little academic analysis exists to date. These mechanical men, I argue, all provide important insights regarding the way design could be used to heighten the appeal of physiology and crucially, in the formation of a new term-the Accessible Body.First, this study re-introduces three mechanical men of health to an academic audience, identifying provenance and unearthing key details of their performance and visual appearance. I argue that there is much to be gained by their analysis in comparison to the more notorious body representations that they orbited. Through detailed analysis of their forms, the three mechanical men are shown to challenge the dominant notions of the Ideal Body and Fordist Body embodied in the Dresden Transparent Man (1930) and 'Der Mensch als Industriepalast' (1926), respectively. The study examines and classifies these mechanical men as a new type of body- the Accessible Body. This term refers to representations that embody a sense of consciousness, the re-appropriation of popular culture and engagement with humour and visual appeal.The study concludes with discussion about the Accessible Body in contemporary health education. What tropes and approaches may remain significant today? By leaning on contemporary thinking about linguistic rather than visual metaphors in health, this study concludes with provocations for the alignment of other appropriate metaphors within a mechanical man and Accessible Body framework. Ultimately, I call for a reshifting of man/machine visual metaphors as a means of re-engaging the audience today.

Carbon-Fiber Framework for Full-Arch Implant-Supported Fixed Dental Prostheses Supporting Resin-Based Composite and Lithium Disilicate Ceramic Crowns: Case Report and Description of Features.

This case report presents a new approach for shock-absorbing carbon-fiber composite frameworks for full-arch implant-supported fixed dental prostheses supporting resin-based and lithium disilicate ceramic crowns. It describes the characteristics of the materials used, the procedures for implementing the framework, and the requirements to achieve the best mechanical and clinical properties. The result is a full-arch prosthesis with masticatory load shock-absorption capacities, chemical bonding between materials, good esthetics, and wear similar to natural enamel. A 24-month follow-up full-arch bimaxillary implant-supported rehabilitation, performed with computer-guided surgery, is described.

Novel resin-based dental material with anti-biofilm activity and improved mechanical property by incorporating hydrophilic cationic copolymer functionalized nanodiamond.

There is an increasing clinical need to design dental restorative materials that combine excellent mechanical property and anti-biofilm activity. In the current study, photocurable polycation functionalized nanodiamond (QND) was synthesized and proposed as novel filler for dental resins. By reason of increased repulsive force between nanoparticles and enhanced compatibility with resin matrix, QND dispersed uniformly in reinforced resins, which would help to transfer stress and deformation from the matrix to fillers more efficiently, resulting in a significant improvement in mechanical properties. Notably, the Vickers's hardness, flexural strength and flexural modulus of resins containing 1.0 wt% QND were 44.5, 36.1 and 41.3% higher than that of control, respectively. The antibacterial activity against Streptococcus mutans (S. mutans) showed that QND-incorporated resins produced anti-adhesive property due to their hydrophilic surfaces and could suppress bacterial growth as a result of the contact-killing effect of embedded nanocomposites. As the synergistic effect of anti-adhesive and bactericidal performance, resins loading 1.0~1.5 wt% QNDs displayed excellent anti-biofilm activity. Meanwhile, the results of macrophage cytotoxicity showed that the proliferation of RAW 264.7 cells remained 84.3%, even at a concentration of 1.0 wt% QNDs after 7-day incubation. Therefore, the QND-containing dental resin with the combination of high mechanical property, bacteria-repellent capability and antibacterial performance holds great potential as a restorative material based on this scheme.

Dynamics of individual molecular shuttles under mechanical force.

Molecular shuttles are the basis of some of the most advanced synthetic molecular machines. In these devices a macrocycle threaded onto a linear component shuttles between different portions of the thread in response to external stimuli. Here, we use optical tweezers to measure the mechanics and dynamics of individual molecular shuttles in aqueous conditions. Using DNA as a handle and as a single molecule reporter, we measure thousands of individual shuttling events and determine the force-dependent kinetic rates of the macrocycle motion and the main parameters governing the energy landscape of the system. Our findings could open avenues for the real-time characterization of synthetic devices at the single molecule level, and provide crucial information for designing molecular machinery able to operate under physiological conditions.

Teaching Medical Students How To Think: Narrative, Mechanistic and Mathematical Thinking.

Computers are becoming better than physicians in some activities. To survive, 21st century physicians need to become better thinkers. The most unique human cognitive skill is the ability to understand other human minds by creating stories about oneself and others (narrative thinking). Narrative thinking is at the core of the art of medicine, and dominated medicine until the 19th century when two types of scientific thinking (mechanistic and mathematical thinking) started to become influential. Mechanistic thinking uses mechanisms (abstract concepts which cannot be demonstrated in experiments but are needed for making hypotheses and interpreting observations from the experiments). In the 19th and 20th centuries, physicians grouped symptoms and signs into syndromes with the hope of separating each syndrome into various diseases based on etiopathological and/or physiopathological mechanisms. The 21st century brought mechanisms based on molecular genetics. Mathematical medical thinking expanded in the 20th century with the tools developed by statisticians. Now data mining and/or machine learning is threatening statisticians. The traditional teaching of medical students based on the example of a clinician mentor who does not engage in reflective thought may no longer be enough. The three types of medical thinking, narrative, mechanistic and mathematical, need to be incorporated by the 21st century physician, whose thought process should also consider the biopsychosocial model of disease and its center, which is the patient. Computers will never substitute for a self-reflective medical expert who is aware of the strengths and limitations of human beings and of an environment characterized by information overload.

Combinatorial design of calcium meta phosphate poly(vinyl alcohol) bone-like biocomposites.

The incidence of degenerative diseases and the ageing population have added to the growing demand for bone grafts. Although autologous bone continues to be the gold standard, limited yield and potential morbidity of the donor site pose considerable challenges. Currently, clinically used synthetic grafts based on calcium phosphates are mechanically brittle and not compliant hence composite scaffolds are expected to be provide viable solutions. In this study we report composites of calcium meta phosphate-poly (vinyl alcohol) with tunable mechanical properties, low swelling and excellent biocompatibility. The elastomeric nature of the composites resist brittle fracture and the scaffolds can be easily shaped to the bone defect by the surgeon. Testing on bone plug shaped specimens of the scaffolds, exhibited superior mechanical properties compared to currently commercially available bone plugs with additional advantages being the ability to increase porosity without compromising properties in compression and degree of swelling, which make these composites promising synthetic alternatives for bone grafts and bone tissue engineering.

Mechanics of population aging and survival.

In this paper we extend the previous work of Witten and her team on defining a classical physics-driven model of survival in aging populations (Eakin, Bull Math Biol 56(6):1121-1141, 1994; Eakin and Witten, Mech Aging Dev 78(2):85-101, 1995; Witten and Eakin, Exp Gerontol 32(2):259-285, 1997) by revisiting the concept of a force of aging and introducing the concepts of a momentum of aging, a kinetic energy and a potential energy of an aging population. We further extend the analysis beyond the deterministic Newtonian mechanics of a macroscopic population as a whole by considering the probabilistic nature of survival of individual population cohort members, thus producing new statistical physics-based concepts of entropy and of a gerontological "temperature". These new concepts are then illustrated with application to the classic parametric Gompertz survival model, which is a commonly used empirical descriptor for survival dynamics of mammalian species, human populations in particular. As a function of chronological age the Gompertz Model force, momentum, and power are seen to have an asymmetric unimodal peak profile, while the potential energy has a descending sigmoidal profile similar to that of the survival fraction. The "temperature" is an exponential function of age and the entropy for a future age at a current census age can be represented as a topological surface with an asymmetric unimodal hump.

Dermatoses among automobile mechanics in Mansoura, Egypt.

This cross-sectional study was carried out in Mansoura, Egypt to assess the prevalence of occupational dermatoses and their possible risk factors on a convenience sample of car mechanics. Sociodemographic and occupational data were collected, and clinical examination was done. Prevalence of skin diseases was 45.4% and that of exclusively occupational skin diseases was 9.2%. Irritant contact dermatitis, eczema, and tar/oil acne were the most common types (4.6%, 3.1%, 3.1%, respectively). The logistic regression analysis revealed that the risk of occupational dermatoses increased significantly with lack of use of personal protective equipment, longer duration of work, and presence of workplace chemicals (adjusted odds ratio [95% CI] were 7.2 [2.7, 19.0], 4.3 [1.7, 10.9], and 3.7 [1.3, 10.5], respectively). Health education and safety measures are essential for prevention and control of hazardous workplace practices and exposure.

Integrating light-sheet imaging with virtual reality to recapitulate developmental cardiac mechanics.

Currently, there is a limited ability to interactively study developmental cardiac mechanics and physiology. We therefore combined light-sheet fluorescence microscopy (LSFM) with virtual reality (VR) to provide a hybrid platform for 3D architecture and time-dependent cardiac contractile function characterization. By taking advantage of the rapid acquisition, high axial resolution, low phototoxicity, and high fidelity in 3D and 4D (3D spatial + 1D time or spectra), this VR-LSFM hybrid methodology enables interactive visualization and quantification otherwise not available by conventional methods, such as routine optical microscopes. We hereby demonstrate multiscale applicability of VR-LSFM to (a) interrogate skin fibroblasts interacting with a hyaluronic acid-based hydrogel, (b) navigate through the endocardial trabecular network during zebrafish development, and (c) localize gene therapy-mediated potassium channel expression in adult murine hearts. We further combined our batch intensity normalized segmentation algorithm with deformable image registration to interface a VR environment with imaging computation for the analysis of cardiac contraction. Thus, the VR-LSFM hybrid platform demonstrates an efficient and robust framework for creating a user-directed microenvironment in which we uncovered developmental cardiac mechanics and physiology with high spatiotemporal resolution.