169 research outputs found
USING DNA AND ISOZYME MARKERS TO STUDY GENETIC RELATIONSHIP AMONG HIGH REGENERATIVE INTERSPECIFIC HYBRIDS OF HELIANTHUS EGGERTII SMALL. X HELIANTHUS ANNUUS L
ABSTRACT RAPD, AP-PCR, IFLP, SSR and isozymes marker
Economic efficiency of breeding dairy sheep in the mountain and hilly regions of Bulgaria
Sheep breeding is an important means of livelihood for the population living in the mountain and hilly regions of the country. The object of the present study is to analyze the economic efficiency of breeding dairy sheep in the mountain and hilly regions of Bulgaria. Object of the study are 2 models of farms with 100 ewes from the dairy type and the relevant categories lambs and rams. We compare and analyze two levels of milk productivity - 70 l per lactation in the first farm and 100 l per lactation in the second farm. The whole grain and roughage necessary for feeding ewes are calculated while hay is self-provided. The average fertility per ewe is 115%, the average wool yield is 2.2 kg and the repair of the flock is 20%. Incomes and costs are estimated at current prices for the 2013 - 2014. It was found that in the terms of the present study we may draw the conclusion that in case the farmer is not getting subsidy from the State Fund 'Agriculture' will be efficiently to raise only ewes that have milk productivity 100 l per lactation; in support of the farm subsidies by the State Fund 'Agriculture' and the two levels of milk production is appropriate breeding of dairy sheep in the mountainous and hilly regions of the country; in order to improve the economic efficiency farmers should pay attention to increasing the fertility of ewes and protection of the new-born lambs as well as increasing of milk productivity of ewes
Pure phase-locking of beta/gamma oscillation contributes to the N30 frontal component of somatosensory evoked potentials
BACKGROUND: Evoked potentials have been proposed to result from phase-locking of electroencephalographic (EEG) activities within specific frequency bands. However, the respective contribution of phasic activity and phase resetting of ongoing EEG oscillation remains largely debated. We here applied the EEGlab procedure in order to quantify the contribution of electroencephalographic oscillation in the generation of the frontal N30 component of the somatosensory evoked potentials (SEP) triggered by median nerve electrical stimulation at the wrist. Power spectrum and intertrial coherence analysis were performed on EEG recordings in relation to median nerve stimulation. RESULTS: The frontal N30 component was accompanied by a significant phase-locking of beta/gamma oscillation (25-35 Hz) and to a lesser extent of 80 Hz oscillation. After the selection in each subject of the trials for which the power spectrum amplitude remained unchanged, we found pure phase-locking of beta/gamma oscillation (25-35 Hz) peaking about 30 ms after the stimulation. Transition across trials from uniform to normal phase distribution revealed temporal phase reorganization of ongoing 30 Hz EEG oscillations in relation to stimulation. In a proportion of trials, this phase-locking was accompanied by a spectral power increase peaking in the 30 Hz frequency band. This corresponds to the complex situation of 'phase-locking with enhancement' in which the distinction between the contribution of phasic neural event versus EEG phase resetting is hazardous. CONCLUSION: The identification of a pure phase-locking in a large proportion of the SEP trials reinforces the contribution of the oscillatory model for the physiological correlates of the frontal N30. This may imply that ongoing EEG rhythms, such as beta/gamma oscillation, are involved in somatosensory information processing.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe
Electron scale structures and magnetic reconnection signatures in the turbulent magnetosheath
Collisionless space plasma turbulence can generate reconnecting thin current
sheets as suggested by recent results of numerical magnetohydrodynamic
simulations. The MMS mission provides the first serious opportunity to check if
small ion-electron-scale reconnection, generated by turbulence, resembles the
reconnection events frequently observed in the magnetotail or at the
magnetopause. Here we investigate field and particle observations obtained by
the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel
bow shock geometry. We observe multiple small-scale current sheets during the
event and present a detailed look of one of the detected structures. The
emergence of thin current sheets can lead to electron scale structures where
ions are demagnetized. Within the selected structure we see signatures of ion
demagnetization, electron jets, electron heating and agyrotropy suggesting that
MMS spacecraft observe reconnection at these scales
On the deviation from Maxwellian of the ion velocity distribution functions in the turbulent magnetosheath
The degree of deviation from the thermodynamic equilibrium in the ion
velocity distribution functions (VDFs), measured by the Magnetospheric
Multiscale (MMS) mission in the Earth's turbulent magnetosheath, is
quantitatively investigated. Taking advantage of MMS ion data, having a
resolution never reached before in space missions, and of the comparison with
Vlasov-Maxwell simulations, this analysis aims at relating any deviation from
Maxwellian equilibrium to typical plasma parameters. Correlations of the
non-Maxwellian features with plasma quantities such as electric fields, ion
temperature, current density and ion vorticity are very similar in both
magnetosheath data and numerical experiments, and suggest that distortions in
the ion VDFs occur close to (but not exactly at) peaks in current density and
ion temperature. Similar results have also been found during a magnetopause
crossing by MMS. This work could help clarifying the origin of distortion of
the ion VDFs in space plasmas
Energy input from the exterior cusp into the ionosphere: Correlated ground-based and satellite observations
The energy transport from the exterior cusp into the ionosphere is investigated using coordinated ground-based (EISCAT and MIRACLE) and satellite ( Cluster) observations. EISCAT and MIRACLE data are used to estimate the plasma heating in the F-region and the Joule heating in the E-region. Cluster measurements are used to derive the electromagnetic and particle energy fluxes at the high altitudes. These fluxes are then compared with the energy deposition into the ionospheric cusp during a 30 minutes long time interval in which Cluster and EISCAT are nearly conjugated. It is shown that the particles seen at about 9 Re in the exterior cusp carry an earthward energy flux that corresponds to the observed heating of the F-region. The estimated earthward Poynting flux is more than enough to account for the Joule heating in the E-region
Age-related delay in information accrual for faces: Evidence from a parametric, single-trial EEG approach
Background: In this study, we quantified age-related changes in the time-course of face processing
by means of an innovative single-trial ERP approach. Unlike analyses used in previous studies, our
approach does not rely on peak measurements and can provide a more sensitive measure of
processing delays. Young and old adults (mean ages 22 and 70 years) performed a non-speeded
discrimination task between two faces. The phase spectrum of these faces was manipulated
parametrically to create pictures that ranged between pure noise (0% phase information) and the
undistorted signal (100% phase information), with five intermediate steps.
Results: Behavioural 75% correct thresholds were on average lower, and maximum accuracy was
higher, in younger than older observers. ERPs from each subject were entered into a single-trial
general linear regression model to identify variations in neural activity statistically associated with
changes in image structure. The earliest age-related ERP differences occurred in the time window
of the N170. Older observers had a significantly stronger N170 in response to noise, but this age
difference decreased with increasing phase information. Overall, manipulating image phase
information had a greater effect on ERPs from younger observers, which was quantified using a
hierarchical modelling approach. Importantly, visual activity was modulated by the same stimulus
parameters in younger and older subjects. The fit of the model, indexed by R2, was computed at
multiple post-stimulus time points. The time-course of the R2 function showed a significantly slower
processing in older observers starting around 120 ms after stimulus onset. This age-related delay
increased over time to reach a maximum around 190 ms, at which latency younger observers had
around 50 ms time lead over older observers.
Conclusion: Using a component-free ERP analysis that provides a precise timing of the visual
system sensitivity to image structure, the current study demonstrates that older observers
accumulate face information more slowly than younger subjects. Additionally, the N170 appears to
be less face-sensitive in older observers
Mathematical Modeling of Human Glioma Growth Based on Brain Topological Structures: Study of Two Clinical Cases
Gliomas are the most common primary brain tumors and yet almost incurable due mainly to their great invasion capability. This represents a challenge to present clinical oncology. Here, we introduce a mathematical model aiming to improve tumor spreading capability definition. The model consists in a time dependent reaction-diffusion equation in a three-dimensional spatial domain that distinguishes between different brain topological structures. The model uses a series of digitized images from brain slices covering the whole human brain. The Talairach atlas included in the model describes brain structures at different levels. Also, the inclusion of the Brodmann areas allows prediction of the brain functions affected during tumor evolution and the estimation of correlated symptoms. The model is solved numerically using patient-specific parametrization and finite differences. Simulations consider an initial state with cellular proliferation alone (benign tumor), and an advanced state when infiltration starts (malign tumor). Survival time is estimated on the basis of tumor size and location. The model is used to predict tumor evolution in two clinical cases. In the first case, predictions show that real infiltrative areas are underestimated by current diagnostic imaging. In the second case, tumor spreading predictions were shown to be more accurate than those derived from previous models in the literature. Our results suggest that the inclusion of differential migration in glioma growth models constitutes another step towards a better prediction of tumor infiltration at the moment of surgical or radiosurgical target definition. Also, the addition of physiological/psychological considerations to classical anatomical models will provide a better and integral understanding of the patient disease at the moment of deciding therapeutic options, taking into account not only survival but also life quality
Pre-Stimulus Activity Predicts the Winner of Top-Down vs. Bottom-Up Attentional Selection
Our ability to process visual information is fundamentally limited. This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant. The aim of the present study was to identify, from EEG recordings, pre-stimulus and pre-saccadic neural activity that could predict whether top-down or bottom-up processes would win the competition for attention on a trial-by-trial basis. We employed a visual search paradigm in which a lateralized low contrast target appeared alone, or with a low (i.e., non-salient) or high contrast (i.e., salient) distractor. Trials with a salient distractor were of primary interest due to the strong competition between top-down knowledge and bottom-up attentional capture. Our results demonstrated that 1) in the 1-sec pre-stimulus interval, frontal alpha (8–12 Hz) activity was higher on trials where the salient distractor captured attention and the first saccade (bottom-up win); and 2) there was a transient pre-saccadic increase in posterior-parietal alpha (7–8 Hz) activity on trials where the first saccade went to the target (top-down win). We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture
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