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1.
Ann Afr Med ; 19(2): 80-88, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32499463

RESUMO

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.


Assuntos
Automóveis , Conhecimentos, Atitudes e Prática em Saúde , Exposição Ocupacional/efeitos adversos , Saúde do Trabalhador , Adulto , Estudos Transversais , Humanos , Masculino , Mecânica , Pessoa de Meia-Idade , Nigéria , Inquéritos e Questionários , Local de Trabalho , Adulto Jovem
2.
Nutrients ; 11(9)2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31487935

RESUMO

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.


Assuntos
Pão , Índice Glicêmico , Técnicas In Vitro/métodos , Digestão , Farinha/análise , Hidrólise , Mecânica , Tamanho da Partícula , Amido/química , Triticum/química
3.
PLoS One ; 14(6): e0218666, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31242233

RESUMO

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.


Assuntos
Jogos e Brinquedos , Rotação , Vibração , Simulação por Computador , Engenharia , Humanos , Mecânica , Modelos Teóricos , Movimento (Física) , Madeira
5.
Biosystems ; 178: 16-24, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30695703

RESUMO

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.


Assuntos
Adaptação Fisiológica/genética , Carcinogênese/genética , Neoplasias Colorretais/genética , Teoria Quântica , DNA/genética , DNA/metabolismo , Humanos , Isomerismo , Mecânica , Mutação , Neoplasias/genética , RNA/genética , RNA/metabolismo
6.
Int J Periodontics Restorative Dent ; 39(2): 175­184, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-29244887

RESUMO

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.


Assuntos
Fibra de Carbono , Prótese Dentária Fixada por Implante , Força de Mordida , Cerâmica , Estética Dentária , Humanos , Mastigação , Mecânica
7.
Nat Commun ; 9(1): 4512, 2018 10 30.
Artigo em Inglês | MEDLINE | ID: mdl-30375395

RESUMO

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.


Assuntos
DNA/metabolismo , Compostos Macrocíclicos/metabolismo , Proteínas Motores Moleculares/metabolismo , Cinética , Mecânica , Pinças Ópticas
8.
J Mater Sci Mater Med ; 29(11): 162, 2018 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-30357538

RESUMO

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.


Assuntos
Biofilmes/efeitos dos fármacos , Materiais Dentários , Nanodiamantes/química , Polímeros/química , Animais , Sobrevivência Celular/efeitos dos fármacos , Mecânica , Camundongos , Células RAW 264.7 , Streptococcus mutans/efeitos dos fármacos
9.
Actas Esp Psiquiatr ; 46(4): 133-45, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30079927

RESUMO

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.


Assuntos
Educação Médica , Estudantes de Medicina/psicologia , Pensamento , Humanos , Matemática , Mecânica , Filosofia Médica
10.
J Mater Sci Mater Med ; 29(8): 128, 2018 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-30062387

RESUMO

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.


Assuntos
Materiais Biocompatíveis , Substitutos Ósseos , Fosfatos de Cálcio/química , Álcool de Polivinil/química , Linhagem Celular , Sobrevivência Celular , Humanos , Hidrogéis , Teste de Materiais , Mecânica , Microscopia Eletroquímica de Varredura , Osteoblastos , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Água
11.
Biogerontology ; 19(3-4): 251-269, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29748778

RESUMO

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.


Assuntos
Envelhecimento , Entropia , Mecânica , Sobrevida , Cronologia como Assunto , Humanos , Modelos Estatísticos , Fenômenos Físicos
12.
Arch Environ Occup Health ; 73(1): 42-47, 2018 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-28157439

RESUMO

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.


Assuntos
Mecânica , Doenças Profissionais/epidemiologia , Exposição Ocupacional , Dermatopatias/epidemiologia , Adolescente , Adulto , Idoso , Automóveis , Criança , Estudos Transversais , Egito/epidemiologia , Humanos , Masculino , Pessoa de Meia-Idade , Doenças Profissionais/etiologia , Prevalência , Fatores de Risco , Dermatopatias/etiologia , Adulto Jovem
13.
JCI Insight ; 2(22)2017 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-29202458

RESUMO

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.


Assuntos
Técnicas de Imagem Cardíaca/métodos , Coração/diagnóstico por imagem , Coração/fisiologia , Mecânica , Microscopia de Fluorescência/métodos , Realidade Virtual , Algoritmos , Animais , Biologia do Desenvolvimento , Fibroblastos , Ácido Hialurônico , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Canais de Potássio , Peixe-Zebra
14.
J R Soc Interface ; 14(135)2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29070591

RESUMO

This paper presents a robotic anchoring module, a sensorized mechanism for attachment to the environment that can be integrated into robots to enable or enhance various functions such as robot mobility, remaining on location or its ability to manipulate objects. The body of the anchoring module consists of two portions with a mechanical stiffness transition from hard to soft. The hard portion is capable of containing vacuum pressure used for actuation while the soft portion is highly conformable to create a seal to contact surfaces. The module is integrated with a single sensory unit which exploits a fibre-optic sensing principle to seamlessly measure proximity and tactile information for use in robot motion planning as well as measuring the state of firmness of its anchor. In an experiment, a variable set of physical loads representing the weights of potential robot bodies were attached to the module and its ability to maintain the anchor was quantified under constant and variable vacuum pressure signals. The experiment shows the effectiveness of the module in quantifying the state of firmness of the anchor and discriminating between different amounts of physical loads attached to it. The proposed anchoring module can enable many industrial and medical applications where attachment to environment is of crucial importance for robot control.


Assuntos
Desenho de Equipamento , Mecânica , Octopodiformes/fisiologia , Robótica , Animais , Biomimética , Análise de Falha de Equipamento , Extremidades , Estresse Mecânico
15.
J Mater Sci Mater Med ; 28(10): 145, 2017 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-28823063

RESUMO

For many practitioners, longevity of full glass ceramic crowns in the posterior area, molars and premolars, remains a real challenge. The purpose of this article is to identify and evaluate the parameters that can significantly influence their resistance when preparing a tooth. The analysis proposed in this article relies on interrelated studies conducted at three levels: in vitro (mechanical tests), in silico (finite elements simulations) and in vivo (clinical survival rates). The in vitro and the in silico studies proved that an appropriate variation of the geometric design of the preparations enables to increase up to 80% the mechanical strength of ceramic reconstructions. The in vivo clinical study of CAD/CAM full ceramic crowns was performed in accordance with the principles stated within the in vitro and the in silico studies and provided a 98.97% success rate over a 6 years period. The variations of geometric design parameters for dental preparation allows for reconstructions with a mechanical breaking up to 80% higher than that of a non-appropriate combination. These results are confirmed in clinical practice.


Assuntos
Dente Pré-Molar , Cerâmica , Desenho Assistido por Computador , Dente Molar , Coroa do Dente , Cimentação/métodos , Materiais Dentários , Falha de Restauração Dentária , Humanos , Teste de Materiais , Mecânica
16.
Phys Biol ; 14(3): 03LT01, 2017 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-28535148

RESUMO

The intrinsic stochasticity of gene expression can give rise to large fluctuations and rare events that drive phenotypic variation in a population of genetically identical cells. Characterizing the fluctuations that give rise to such rare events motivates the analysis of large deviations in stochastic models of gene expression. Recent developments in non-equilibrium statistical mechanics have led to a framework for analyzing Markovian processes conditioned on rare events and for representing such processes by conditioning-free driven Markovian processes. We use this framework, in combination with approaches based on queueing theory, to analyze a general class of stochastic models of gene expression. Modeling gene expression as a Batch Markovian Arrival Process (BMAP), we derive exact analytical results quantifying large deviations of time-integrated random variables such as promoter activity fluctuations. We find that the conditioning-free driven process can also be represented by a BMAP that has the same form as the original process, but with renormalized parameters. The results obtained can be used to quantify the likelihood of large deviations, to characterize system fluctuations conditional on rare events and to identify combinations of model parameters that can give rise to dynamical phase transitions in system dynamics.


Assuntos
Regulação da Expressão Gênica , Expressão Gênica , Modelos Genéticos , Regiões Promotoras Genéticas , Cadeias de Markov , Mecânica , Probabilidade
17.
Diabetes Metab Syndr ; 11 Suppl 1: S223-S227, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28011231

RESUMO

AIMS: To determine occupational association with metabolic syndrome among auto technicians and school teachers. METHODS: One hundred and sixty six subjects were selected for this study. Clinical data was obtained while laboratory investigations including plasma glucose and lipid profile were performed. Statistical analysis was done with SPSS 20.0. P<0.05 was taken as statistically significant. RESULTS: School teachers had significantly higher mean total cholesterol and LDL-cholesterol compared to auto technicians. Mean serum triglycerides was significantly higher among auto-technicians compared to school teachers in this study. The prevalence of some conventional cardiovascular risk factors was significantly higher among auto-technicians compared to school teachers: Impaired blood glucose (9.6% vs. 1.2%, p<0.05), hypertriglyceridaemia (18.1% vs. 7.2%, p<0.05) and low HDL-Cholesterol (47.0% vs. 37.3%, p<0.05) respectively. However elevated LDL-cholesterol (56.6% vs. 32.5%, p<0.05) was significantly more common among school teachers compared to auto-technicians. Based on the WHO and the Harmonized criteria, metabolic syndrome was more frequent among auto-technicians compared to school teachers. (8.4% vs. 1.2% and 19.3% vs. 7.2% respectively, p<0.05) CONCLUSION: The prevalence of metabolic syndrome appears to be significantly higher among auto technicians despite their high level of physical activity, exertion and education compared to teachers. This may be related to the increased occupational exposure to organic and inorganic materials from dust particles, oil and oil related matter and particulate matter among auto technicians. Prompt definitive evaluation of this concept and appropriate health education to encourage safety mechanism can reduce this burden of metabolic syndrome among auto technicians in Nigeria.


Assuntos
Automóveis , Mecânica , Síndrome Metabólica/epidemiologia , Exposição Ocupacional/efeitos adversos , Professores Escolares , Adulto , Estudos Transversais , Feminino , Seguimentos , Humanos , Masculino , Síndrome Metabólica/etiologia , Pessoa de Meia-Idade , Nigéria/epidemiologia , Ocupações , Prevalência , Prognóstico
18.
Mil Med ; 181(10): 1314-1323, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27753570

RESUMO

Spine injuries are more prevalent among Iraq and Afghanistan veterans than among veterans of previous conflicts. The purpose of this investigation was to characterize the context, mode, and clinical outcomes of spine injuries sustained by U.S. military personnel in theater. Injury and clinical data from patients who sustained a spine injury in Iraq or Afghanistan between 2003 and 2008 were extracted from the Joint Theater Trauma Registry. Fischer's exact test was used to compare demographic variables between battle and nonbattle spine injuries. Two-sided t tests and univariate analyses were performed to analyze the association between injury context, mechanism, and severity with clinical outcome. A total of 307 patients sustained spine injuries in theater during the study period, and 296 had adequate data for analysis. Most injuries occurred in battle (69.6%), and these injuries were more likely to have an Injury Severity Score considered severe (44.7% vs. 20.0%; p < 0.001) or critical (13.6% vs. 5.6%; p = 0.0458). Blast was the most common mechanism of injury (42.2%) and was more likely to be blunt (81.6%) than penetrating (18.4%; p < 0.0001). Battle-associated spine injuries were most commonly caused by blasts, were more severe, and more likely to involve multiple spinal levels.


Assuntos
Mecânica , Militares/estatística & dados numéricos , Traumatismos da Coluna Vertebral/classificação , Adulto , Estudos de Coortes , Feminino , Humanos , Escala de Gravidade do Ferimento , Masculino , Medicina Militar/estatística & dados numéricos , Medicina Militar/tendências , Prevalência , Sistema de Registros , Estudos Retrospectivos , Traumatismos da Coluna Vertebral/etiologia , Ferimentos e Lesões/epidemiologia
19.
Nature ; 535(7613): 529-32, 2016 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-27466125

RESUMO

The structural complexity of metamaterials is limitless, but, in practice, most designs comprise periodic architectures that lead to materials with spatially homogeneous features. More advanced applications in soft robotics, prosthetics and wearable technology involve spatially textured mechanical functionality, which requires aperiodic architectures. However, a naive implementation of such structural complexity invariably leads to geometrical frustration (whereby local constraints cannot be satisfied everywhere), which prevents coherent operation and impedes functionality. Here we introduce a combinatorial strategy for the design of aperiodic, yet frustration-free, mechanical metamaterials that exhibit spatially textured functionalities. We implement this strategy using cubic building blocks-voxels-that deform anisotropically, a local stacking rule that allows cooperative shape changes by guaranteeing that deformed building blocks fit together as in a three-dimensional jigsaw puzzle, and three-dimensional printing. These aperiodic metamaterials exhibit long-range holographic order, whereby the two-dimensional pixelated surface texture dictates the three-dimensional interior voxel arrangement. They also act as programmable shape-shifters, morphing into spatially complex, but predictable and designable, shapes when uniaxially compressed. Finally, their mechanical response to compression by a textured surface reveals their ability to perform sensing and pattern analysis. Combinatorial design thus opens up a new avenue towards mechanical metamaterials with unusual order and machine-like functionalities.


Assuntos
Mecânica , Propriedades de Superfície , Holografia , Impressão Tridimensional , Próteses e Implantes , Robótica/instrumentação
20.
Stud Hist Philos Sci ; 58: 108-14, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27474191

RESUMO

Kant believed that the ultimate processes that regulate the behavior of material bodies can be characterized exclusively in terms of mechanics. In 1790, turning his attention to the life sciences, he raised a potential problem for his mechanically-based account, namely that many of the operations described in the life sciences seemed to operate teleologically. He argued that the life sciences do indeed require us to think in teleological terms, but that this is a fact about us, not about the processes themselves. Nevertheless, even were we to concede his account of the life sciences, this would not secure the credentials of mechanics as a general theory of matter. Hardly any material properties studied in the second half of the eighteenth century were, or could have been, conceived in mechanical terms. Kant's concern with teleology is tangential to the problems facing a general matter theory grounded in mechanics, for the most pressing issues have nothing to do with teleology. They derive rather from a lack of any connection between mechanical forces and material properties. This is evident in chemistry, which Kant dismisses as being unscientific on the grounds that it cannot be formulated in mechanical terms.


Assuntos
Disciplinas das Ciências Biológicas/história , Química/história , Mecânica , Filosofia/história , História do Século XVIII
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