521 research outputs found
Electromechanical Imaging of Biological Systems with Sub-10 nm Resolution
Electromechanical imaging of tooth dentin and enamel has been performed with
sub-10 nm resolution using piezoresponse force microscopy. Characteristic
piezoelectric domain size and local protein fiber ordering in dentin have been
determined. The shape of a single collagen fibril in enamel is visualized in
real space and local hysteresis loops are measured. Because of the ubiquitous
presence of piezoelectricity in biological systems, this approach is expected
to find broad application in high-resolution studies of a wide range of
biomaterials.Comment: 12 pages, 4 figures, submitted for publication in Appl. Phys. Let
Discontinuous Bifurcations under 2-DOF Vibroimpact System Moving
Dynamic behaviour of strongly nonlinear non-smooth discontinuous vibroimpact system isstudied. Under variation of system parameters we find the disconti nuousbi furcati onsthat are the dangerousones. It is phenomenon
unique to non-smooth systems with discontinuous right-hand side. We investigate the 2-DOF vibroimpact system by numerical parameter continuation method in conjunction with shooting and Newton-Raphson methods,
Wife simulate the impact by nonlinear contact interactive force according to Hertz's contact law. We find the discontinuous bifurcations by Floquet multipliers values. At such points set-valued Floquet multipliers cross the
unit circle by jump that istheir moduli becoming more than unit by jump. Wealso learn the bifurcation picture
change when the impact between system bodi es became the soft one due the change of system parameters, This
paper is the continuation of the previous works
Infrared studies of a La_(0.67)Ca_(0.33)MnO_3 single crystal: Optical magnetoconductivity in a half-metallic ferromagnet
The infrared reflectivity of a La_(0.67)Ca_(0.33)MnO_3 single crystal is studied over a broad range of temperatures (78–340 K), magnetic fields (0–16 T), and wave numbers (20–9000cm^(-1)). The optical conductivity gradually changes from a Drude-like behavior to a broad peak feature near 5000cm-1 in the ferromagnetic state below the Curie temperature T_C=307K. Various features of the optical conductivity bear striking resemblance to recent theoretical predictions based on the interplay between the double exchange interaction and the Jahn-Teller electron-phonon coupling. A large optical magnetoconductivity is observed near T_C
Infrared Studies of a La_{0.67}Ca_{0.33}MnO_3 Single Crystal: Optical Magnetoconductivity in a Half-Metallic Ferromagnet
The infrared reflectivity of a single crystal
is studied over a broad range of temperatures (78-340 K), magnetic fields (0-16
T), and wavenumbers (20-9000 cm). The optical conductivity gradually
changes from a Drude-like behavior to a broad peak feature near 5000 cm
in the ferromagnetic state below the Curie temperature . Various
features of the optical conductivity bear striking resemblance to recent
theoretical predictions based on the interplay between the double exchange
interaction and the Jahn-Teller electron-phonon coupling. A large optical
magnetoconductivity is observed near .Comment: 4 pages, 4 figures, Latex, PostScript; The 7th Joint MMM-Intermag
Conference,San Francisco, January 6-9, 1998; The Int. Conf. on Strongly
Correlated Electron Systems, Paris, July 15-18,199
Modelling of continual fracture of spatial bodies under long-term static and cyclic loading
Представлено методику моделювання процесів континуального руйнування кругових та
призматичних тіл складної форми в умовах тривалого статичного і багатоциклового навантаження:
скінчено-елементна база для визначення напружено-деформованого стану просторових тіл на основі
напіваналітичного методу скінчених елементів (НМСЕ), алгоритми визначення феноменологічного
параметра пошкодженості та моделювання еволюційних процесів розповсюдження зон континуального
руйнування. Наведено результати розв’язання практичних задач із визначення розрахункового і
додаткового ресурсу відповідальних просторових об’єктів.Techniques of continual fracture process modelling of complex shape circular and prismatic
bodies under elastic high-cycle deformation and in condition of creep under prolonged static load is presented
in this paper. The semianalytic finite element method (SFEM) to determine the stress-strain state is used. SFEM
involves the application of finite element mesh in the cross section of the body, and using one finite element in
the direction of straight or curved creating, which provides significantly lower computational cost for three-
dimensional problems solving. The Kachanov-Rabotnov’s scalar damage parameter to describe the continual
fracture of the material and the degree dependence of the damage parameter accumulation rate of on the stress
state parameters are used. Stepping algorithms for the stress-strain state and damage parameter determining for
considered deformation process have been developed. The algorithm of simulation of evolutionary processes of
macroscopic defects (continual fracture zone) growth after local loss of material bearing capacity because of
damage parameter’s critical value has been obtained. A solution of practical problems of determining of the
calculated lifetime (to local loss of material bearing capacity) and the additional lifetime (time of continual
fracture zone growth) for high pressure connecting pipe and the gas turbine blade has been presented. It is
shown, that for the connecting pipe which represents thick-wall rotation body, lifetime is not limited to local loss
of material bearing capacity and can be significantly extended by additional lifetime. At the same time for the
blade under creep condition lifetime is completely determined by the local loss of material bearing capacity,
because the value of additional lifetime is related to the continual fracture zone growth of only about 5% of the
calculated lifetime
Optical vortex generation from molecular chromophore arrays
The generation of light endowed with orbital angular momentum, frequently termed optical vortex light, is commonly achieved by passing a conventional beam through suitably constructed optical elements. This Letter shows that the necessary phase structure for vortex propagation can be directly produced through the creation of twisted light from the vacuum. The mechanism is based on optical emission from a family of chromophore nanoarrays that satisfy specific geometric and symmetry constraints. Each such array can support pairs of electronically delocalized doubly degenerate excitons whose azimuthal phase progression is responsible for the helical wave front of the emitted radiation. The exciton symmetry dictates the maximum magnitude of topological charge; detailed analysis secures the conditions necessary to deliver optical vortices of arbitrary order
Theoretical and methodological approaches to management of resource flow processes of development projects on macro-, mezzo-, microlevels
Paper is devoted to the actual problem of managing resource flows of development projects as complex, unique, and open systems, across the different project lifecycle stages that differ in content and are distributed in space and time. The idea was to create a single throughout system for managing resource flow processes of the long-term projects. The research goal included development of theoretical and methodological approaches that can be used in order to manage the combination of development project resource flows using "order from chaos"paradigm. That includes by-stage organization of resource flow processes on of macro-, meso- and microscale, going from sources and sinks of the chaotic project environment resolve to ordered stages of project life cycles. It is proposed to implement resource flow management in form of the stage and resource-based "project-logistic"relay of a triune movement, ordering and transformation of the resource flow processes. This relay is created within a project-logistic field of project management that change by project phases. Synergetic effects of self-organization and self-control appear in the project logistic field due to horizontal interactions, sharing experience, competences, and values among the stakeholders in course of transforming entropic resource-flow processes into the negentropy processes related to project phase goals (attractors). Results can be used to forecast and develop multilevel resource-flow and process systems arranged by resource sources and sinks, and chaotically ordered for projects in different application areas. Further research perspectives include development of self-control and self-organization forms for development projects stakeholders that would comply with international best practices, and fit corresponding project stages. © Published under licence by IOP Publishing Ltd
INFLUENCE OF HELIOGEOPHYSICAL FACTORS ON HUMAN HEALTH
The purpose of this work is the development of the connection between a level of geomagnetic activity and a quantity of emergency calls for cardiovascular diseases. To perform the study we analyzed data on the quantity of emergency calls in Irkutsk during 8years period (2001-2004, 2007-2010). In total we analyzed 1460 days, 8942 cases of acute myocardial infarction and 1953 cases of intra-cerebral hemorrhage. There is a significant positive correlation between the number of ambulance calls for acute vascular pathology (myocardial infarction, intracerebral hemorrhage) and the Kp index over all years of study
- …