414 research outputs found
The effect of voluntary modulation of the sensory-motor rhythm during different mental tasks on H reflex
Objectives:
The aim of this study was to explore the possibility of the short-term modulation of the soleus H reflex through self-induced modulation of the sensory-motor rhythm (SMR) as measured by electroencephalography (EEG) at Cz.
Methods:
Sixteen healthy participants took part in one session of neuromodulation. Motor imagery and mental math were strategies for decreasing SMR, while neurofeedback was used to increase SMR. H reflex of the soleus muscle was elicited by stimulating tibial nerve when SMR reached a pre-defined threshold and was averaged over 5 trials.
Results:
Neurofeedback and mental math both resulted in the statistically significant increase of H reflex (p = 1.04Ā·10ā 6 and p = 5.47Ā·10ā 5 respectively) while motor imagery produced the inconsistent direction of H reflex modulation (p = 0.57). The average relative increase of H reflex amplitude was for neurofeedback 19.0 Ā± 5.4%, mental math 11.1 Ā± 3.6% and motor imagery 2.6 Ā± 1.0%. A significant negative correlation existed between SMR amplitude and H reflex for all tasks at Cz and C4.
Conclusions:
It is possible to achieve a short-term modulation of H reflex through short-term modulation of SMR. Various mental tasks dominantly facilitate H reflex irrespective of direction of SMR modulation.
Significance:
Improving understanding of the influence of sensory-motor cortex on the monosynaptic reflex through the self-induced modulation of cortical activity
Low-energy electron beam focusing in self-organized porous alumina vacuum windows
Micromachined, micron-thick porous alumina membranes with closed pore endings show high electron transparency above an energy of 5 keV. This is due to the channeling of electrons along the negatively charged insulating pores after surmounting the thin entrance layer. We also find a sharp hightransparency energy window at energies as low as 2 keV which may be the result of a local maximum of channeling, as predicted by simulations, and positive charge up of the entrance layer causing electron electrostatic focusing. Applications for these membranes range from atmospheric electron spectroscopy to self-assembled, nanoscale, large-area electron collimators
Notes on the development of the urban heritage management concept in contemporary policies
This paper seeks to present an overview of the development of the urban heritage management (UHM) concept by analysing documents from key international organisations in this field. The period 1964-2011 is deemed to have been marked by a paradigm shift in the discipline of conservation. Over the course of the last decade, the discussion has been focused on the development of the historic urban landscape (HUL), a concept that incorporates principles of conservation into the integral urban planning framework. However, it seems that the gap between conservation and development is yet to be bridged in practice. The first part of the paper briefly outlines the most important theoretical thought in the fields of conservation and urban planning that contributed to the development of the urban heritage (UH) concept in the 20th century. The second section reviews the UHM policies presented in documents, with an emphasis placed on the roles of particular stakeholders in the process. This paper contributes to overviewing the key aspects of contemporary UHM policies and highlighting perspectives for its future development
Avoidable and unavoidable exergy destruction and exergoeconomic evaluation of the thermal processes in a real industrial plant
Exergy analysis is a universal method for evaluating the rational use of energy. It can be applied to any kind of energy conversion system or chemical process. An exergy analysis identifies the location, the magnitude and the causes of thermodynamic inefficiencies and enhances understanding of the energy conversion processes in complex systems. Conventional exergy analyses pinpoint components and processes with high irreversibility. To overcome the limitations of the conventional analyses and to increase our knowledge about a plant, advanced exergy-based analyses are developed. These analyses provide additional information about component interactions and reveal the real potential for improvement of each component constituting a system, as well as of the overall system. In this paper, a real industrial plant is analyzed using both conventional and advanced exergy analyses, and exergoeconomic evaluation. Some of the exergy destruction in the plant components is unavoidable and constrained by technological, physical and economic limitations. Calculations related to the total avoidable exergy destruction caused by each component of the plant supplement the outcome of the conventional exergy analysis. Based on the all-reaching analysis, by improving the boiler operation (elimination of approximately 1 MW of avoidable exergy destruction in the steam boiler) the greatest improvement in the efficiency of the overall system can be achieved
Gamma-radiation-induced damage of proteins in the thick fraction of egg white
The 60Co gamma-ray irradiation of ovomucin based protein network of the thick fraction of egg white in the absence of oxygen causes both protein cross linking and protein fragmentation. Protein fragmentation in the absence of oxygen is interpreted as a consequence of decreased diffusion of protein radicals within the protein network. Both protein cross linking and fragmentation, are dose dependent processes, with fragmentation prevailing below 10-15 kGy, and cross linking prevailing at the radiation doses >15 kGy. The radiolytic behaviour of the thick fraction of egg white, suggests that gamma irradiation of similar mucine containing structures might also result in accumulation of structurally altered and conceivably non-functional proteins in vivo.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200
Inverse design and implementation of a wavelength demultiplexing grating coupler
Nanophotonics has emerged as a powerful tool for manipulating light on chips.
Almost all of today's devices, however, have been designed using slow and
ineffective brute-force search methods, leading in many cases to limited device
performance. In this article, we provide a complete demonstration of our
recently proposed inverse design technique, wherein the user specifies design
constraints in the form of target fields rather than a dielectric constant
profile, and in particular we use this method to demonstrate a new
demultiplexing grating. The novel grating, which has not been developed using
conventional techniques, accepts a vertical-incident Gaussian beam from a
free-space and separates O-band and C-band
light into separate waveguides. This inverse design concept
is simple and extendable to a broad class of highly compact devices including
frequency splitters, mode converters, and spatial mode multiplexers.Comment: 17 pages, 4 figures, 1 table. A supplementary section describing the
inverse-design algorithm in detail has been added, in addition to minor
corrections and updated reference
Ultra Fast Nonlinear Optical Tuning of Photonic Crystal Cavities
We demonstrate fast (up to 20 GHz), low power (5 ) modulation of
photonic crystal (PC) cavities in GaAs containing InAs quantum dots. Rapid
modulation through blue-shifting of the cavity resonance is achieved via free
carrier injection by an above-band picosecond laser pulse. Slow tuning by
several linewidths due to laser-induced heating is also demonstrated
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