Monitoring neuronal oscillations and signal transmission betweencortical regions using time-frequency analysis ofelectroencephalographic activity

Oscillatory states in the electroencephalogram (EEG) reflect the rhythmic synchronous activity in large networks of neurons. Time-frequency (TF) methods, which quantify the spectral content of the EEG as a function of time, are well suited as tools for the study of spontaneous and induced changes in oscillatory states. The use of these methods provides insights into the temporal dynamics of EEG activity in both humans and experimental animals, and aids the study of the neuronal mechanisms that generate rhythmic EEG activity. Further the use of TF coherence analysts, which quantifies the consistency of phase relationships in multichannel EEG recordings, may contribute to the understanding of signal transmission between neuronal populations in different parts of the brain. We have used TF techniques to analyze the flow of activity patterns between two strongly connected brain structures: the entorhinal cortex and the hippocampus. Both of these structures are believed to be involved in information storage. By applying various frequencies of stimulation, we have found a peak in the spectral power in both sites at around 18 Hz, but the coherence between the EEG signals recorded from these sites was found to increase monotonically up to about 35 Hz. We have also found that long-term potentiation, a strong increase in the efficacy of excitatory synapses between these sites, either had no effect or decreased coherence     

Construction and measurement of the pre-series twin aperture resistive quadrupole magnet for the LHC beam cleaning insertions

CERN's Large Hadron Collider (LHC) requires 48 twin aperture resistive quadrupoles in the beam cleaning insertions. Canada is contributing these magnets to CERN in the framework of the TRIUMF-LHC collaboration contracts. A pre-series magnet was produced by Canadian industry and delivered in March 2001. This magnet incorporates important design changes that resulted from experience with a prototype magnet. The construction of this pre-series magnet and the measurements made at ALSTOM and at CERN are reported. A comparison is made between high precision pole distance measurements and the magnetic measurements performed with a rotating coil mole. Conclusions for series production and possibilities for multipole corrections are outlined.     

Chitosan‐based hydrogels: recent design concepts to tailor properties and functions

Chitosan (CS) has received much attention as a functional biopolymer for designing various hydrogels for biomedical applications. This review provides an overview of the different types of CS‐based hydrogels, the approaches that can be used to fabricate hydrogel matrices with specific features and their applications in controlled drug delivery and tissue engineering. Emphasis is laid on the recent design concepts of hybrid hydrogels based on mixtures of CS and natural or synthetic polymers, interpenetrating polymer networks as well as composite hydrogels prepared by embedding nanoparticles into CS matrices. © 2017 Society of Chemical Industry     

Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.     

Microfabricated Lamb wave device based on PZT sol-gel thin film formechanical transport of solid particles and liquids

The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer     

Long-term potentiation in the neocortex of the adult, freely moving rat

Neocortical preparations have proven highly resistant to the induction of long-term potentiation (LTP), and we have only recently determined the conditions sufficient for the induction of neocortical LTP in the adult, freely moving rat. The stimulation trains must be spaced and repeated over a period of days in order to reach asymptotic levels of potentiation. Here we show that, within these constraints, the neocortex is actually highly responsive. LTP could be induced with as few as one brief high frequency train per day or with extremely low-intensity stimulation trains. We also provide evidence for a critical role for N-methyl-D-aspartate (NMDA) receptor activation in LTP induction in this preparation, and demonstrate that this LTP is input-specific. Control pathways showed no potentiation effects. LTP was found in a monosynaptic and two polysynaptic components (average latencies to peak: 8.1, 15.2 and 20.0 ms) and in the superimposed population spikes. Although LTP could be induced with one train per day or with low-intensity trains, larger and longer-lasting potentiation effects could be induced by increasing the number of trains delivered per session, the number of sessions over which trains were delivered, or the pulse intensity of the trains. The LTP decayed slowly and was still evident 5 weeks later. Administration of the competitive NMDA antagonist 3-[(+/-)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid blocked the induction of LTP in a dose-dependent fashion and appeared to unmask a depression of both the population spikes and a polysynaptic component. These results indicate that the neocortex is highly sensitive to LTP induction procedures, as long as the stimulation trains are spaced and applied over a period of days. They are also consistent with the view that the neocortex must operate with a slow learning rate to reduce interference effects in memory.     

A sensitivity analysis of a cost optimality study on the energy retrofit of a single-family reference building in Portugal

Improvement of the energy efficiency of residential buildings must ensure compliance with cost optimality criteria, assuming a specific lifespan of the building. At the same time, the energy retrofit of buildings ought to preserve their intrinsic architectural and heritage value. Portuguese residential buildings constructed before 1960 did not follow any energy efficiency rules. They represent 29% of the housing stock in the country and there is a high potential for increasing their energy efficiency. However, it costs more to implement envelope energy efficiency measures through retrofitting works than to provide for them in new buildings. An evaluation based on cost optimality criteria should therefore be performed. This work evaluates the energy performance of a Portuguese reference building typical of the pre-1960 building stock for different thicknesses of thermal insulation retrofit solutions (roof, facade, and ground floor) and systems. The study describes a sensitivity analysis that took a range of climate data, intervention costs, energy prices, discount rates, and energy needs into account. An energy needs factor dealt with the occupants’ habits and the effective reduction of energy consumption compared with the estimated energy needs.     

On the process relationship between person and situation judgments in attribution.

Ss were timed in 3 experiments as they answered 2 consecutive questions about stimulus sentences. The measure of interest was the extent to which answering the 1st question speeded-up answering the 2nd. The order of questions about person and situation influences on behavior was manipulated. Results indicated that the person judgment facilitated the situation judgment significantly more than the situation judgment facilitated the person judgment. The pattern of facilitation was reversed when Ss answered questions about themselves. Results are consistent with a model of concurrent resource allocation to person and situation information in conditions where the primary judgment task involves salient information. However, they are not consistent with a unidimensional or automatic view of person and situation judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple window time-frequency distribution and coherence of EEGusing Slepian sequences and Hermite functions

Multiple window (MW) time-frequency analysis (TFA) is a newly developed technique to estimate a time-varying spectrum for random nonstationary signals with low bias and variance. In this paper, we describe the application of MW-TFA techniques to electroencephalogram (EEG) and compare the results with those of the conventional spectrogram. We find that the MW-TFA provide us with not only low bias and variance time-frequency (TF) distribution for EEG but also TF coherence estimation between a single realization of EEG recorded from two sites. We also compare the performance of the MW-TFA using two sets of windows, Slepian sequences, and Hermite functions. If care is taken in matching the two windows, we find no noticeable difference in the resulting TF representations.