3,987 research outputs found
Symmetries of certain double integrals related to Hall effect devices
Producción CientÃficaOne encounters iterated elliptic integrals in the study of Hall effect devices, as a result of conformal mappings of Schwarz–Christoffel type. Some of these double elliptic integrals possess amazing symmetries with regard to the physical parameters of the underlying Hall effect devices. We give a unified mathematical treatment of such symmetric double integrals, in the context of Hall effect devices with three and four contacts.Junta de Castilla y León (VA057U16) and MINECO (Project MTM2014-57129-C2-1-P)
Botanical Knowledge and its Differentiation by Age, Gender and Ethnicity in Southwestern Niger
Indigenous knowledge is unevenly distributed. Individual knowledge level may be affected by many factors such as gender, age, ethnicity, profession, religious and cultural beliefs, abundance and usefulness of the species. This study documents indigenous knowledge of herbaceous and woody plant species of farmers and herders in southwestern Niger. Specifically, we examine the effects of age, gender, and ethnicity on knowledge of local vegetation. Results from the study showed that on average a higher proportion of woody species was identified by the respondents compared to herbaceous species. Both gender and ethnicity had a significant effect on the identification of herbaceous species but no effect on identification of woody species. Respondents in lower age group (10 to 30 years) identified lower number of species compared to other age classes. There seems to be a curvilinear relationship between age of respondents and number of plant species identified. Results from this study reaffirm the uneven distribution of indigenous knowledge within a given area due to social factors. The main challenge is how to incorporate these social differences in knowledge of native plant species into sustainable management and conservation of community natural resources
Dynamics and efficiency of a self-propelled, diffusiophoretic swimmer
Active diffusiophoresis - swimming through interaction with a self-generated,
neutral, solute gradient - is a paradigm for autonomous motion at the
micrometer scale. We study this propulsion mechanism within a linear response
theory. Firstly, we consider several aspects relating to the dynamics of the
swimming particle. We extend established analytical formulae to describe small
swimmers, which interact with their environment on a finite lengthscale. Solute
convection is also taken into account. Modeling of the chemical reaction
reveals a coupling between the angular distribution of reactivity on the
swimmer and the concentration field. This effect, which we term "reaction
induced concentration distortion", strongly influences the particle speed.
Building on these insights, we employ irreversible, linear thermodynamics to
formulate an energy balance. This approach highlights the importance of solute
convection for a consistent treatment of the energetics. The efficiency of
swimming is calculated numerically and approximated analytically. Finally, we
define an efficiency of transport for swimmers which are moving in random
directions. It is shown that this efficiency scales as the inverse of the
macroscopic distance over which transport is to occur.Comment: 16 pages, 11 figure
Effects of the Nitric Oxide Synthease Inhibitor NG-nitro-L-arginine on the Erectile Response to Cavernous Nerve Stimulation in the Rabbit
Hardware simulator for optical correlation spectroscopy with Gaussian statistics and arbitrary correlation functions
We present a new hardware simulator (HS) for characterization, testing and benchmarking of digital correlators used in various optical correlation spectroscopy experiments where the photon statistics is Gaussian and the corresponding time correlation function can have any arbitrary shape. Starting from the HS developed in [Rev. Sci. Instrum. 74, 4273 (2003)], and using the same I/O board (PCI-6534 National Instrument) mounted on a modern PC (Intel Core i7-CPU, 3.07GHz, 12GB RAM), we have realized an instrument capable of delivering continuous streams of TTL pulses over two channels, with a time resolution of Δt = 50ns, up to a maximum count rate of 〈I〉 ∼ 5MHz. Pulse streams, typically detected in dynamic light scattering and diffuse correlation spectroscopy experiments were generated and measured with a commercial hardware correlator obtaining measured correlation functions that match accurately the expected ones.Peer ReviewedPostprint (published version
Diffusing proteins on a fluctuating membrane: Analytical theory and simulations
Using analytical calculations and computer simulations we consider both the
lateral diffusion of a membrane protein and the fluctuation spectrum of the
membrane in which the protein is embedded. The membrane protein interacts with
the membrane shape through its spontaneous curvature and bending rigidity. The
lateral motion of the protein may be viewed as diffusion in an effective
potential, hence, the effective mobility is always reduced compared to the case
of free diffusion. Using a rigorous path-integral approach we derive an
analytical expression for the effective diffusion coefficient for small ratios
of temperature and bending rigidity, which is the biologically relevant limit.
Simulations show very good quantitative agreement with our analytical result.
The analysis of the correlation functions contributing to the diffusion
coefficient shows that the correlations between the stochastic force of the
protein and the response in the membrane shape are responsible for the
reduction.
Our quantitative analysis of the membrane height correlation spectrum shows
an influence of the protein-membrane interaction causing a distinctly altered
wave-vector dependence compared to a free membrane. Furthermore, the time
correlations exhibit the two relevant timescales of the system: that of
membrane fluctuations and that of lateral protein diffusion with the latter
typically much longer than the former. We argue that the analysis of the
long-time decay of membrane height correlations can thus provide a new means to
determine the effective diffusion coefficient of proteins in the membrane.Comment: 12 pages, 8 figure
HOW ORGANIZATIONAL STRUCTURE AIDS BUSINESS PERFORMANCE.
This paper examined how organizational structure aids business performance. Existing studies have shown that it is nearly impossible for an organization to exist without a defined organizational structure. Studies also revealed that the main purpose of organizational structure is the division of work among members of the organization, and the co-ordination of their activities so they are directed towards the goals and objectives of the organization. The sources of data used for this research are from secondary sources. The secondary sources are from journals and conference articles, the internet, newspapers, magazines and textbooks. This research found that organizational structure has a significant impact on the performance of business organizations. Hence, the researchers recommend that business organizations should endeavor to develop a properly defined structure for the organization so as to achieve set objectives
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