21,478 research outputs found
Close Encounters of the European Kind: Structural Reforms, Economic Integration and Sectoral Heterogeneity
This paper addresses two main questions: (a) Has European integration hindered the implementation of labour, financial and product market structural reforms? (b) Do the effects of these reforms vary more across sectors than across countries? Using more granular reform measures, longer time windows and a larger sample of countries than previous studies, we confirm that the euro triggered product but neither labour nor financial market reforms. Differently from previous studies, we find that: (a) the Single Market has similar effects to the euro, and (b) sectoral heterogeneity appears less important in explaining the economic impacts of reforms than country heterogeneity
PHYTOCHEMICAL SCREENING AND GC–MS ANALYSIS OF BIOACTIVE COMPOUNDS PRESENT IN HYDROETHANOLIC LEAF EXTRACT OF SOLANUM AETHIOPICUM (L)
Solanum aethiopicum is a popular traditional vegetable cultivated widely in tropical Africa. It is a species of garden egg grown mostly for the nutritional and medicinal values of its leaves and fruits. This research was carried out to investigate the phytochemicals and GC-MS analysis of the hydroethanolic leaf extract of Solanum aethiopicum.
Fresh, healthy, and young leaves of the plant were collected from a farm in Omuokiri in Aluu, Port Harcourt, Rivers State, Nigeria. These collected leaves were air-dried and grounded into a powdered form and subjected to selective sequential extraction using water and ethanol to obtain a hydroethanolic extract. The extract was then subjected to qualitative and quantitative phytochemical analyses as well as gas chromatography and mass spectrometry (GC-MS), to determine its bioactive constituents.
The quantitative determination of the different biologically active compounds from the hydroethanolic leaf extract of the plant using gas chromatography-mass spectrometry revealed the presence of fifteen (15) bioactive and chemical entities of known biological activities. These chemical entities found in the leaf of the studied plant were found to vary in their molecular weights and amounts present and were considered to be biologically and pharmacologically important.
The study has established the chemical composition of the leaf of Solanum aethiopicum and therefore provides the basis for accounting for its anti-cancerous, anti-inflammatory, anti-diabetic, weight reduction, antioxidant, anti-inflammatory, cardio-protective, and immuno-modulatory activities
Linear and Nonlinear Modeling of Cerebral Flow Autoregulation Using Principal Dynamic Modes
Cerebral Flow Autoregulation (CFA) is the dynamic process by which cerebral blood flow is maintained within physiologically acceptable bounds during fluctuations of cerebral perfusion pressure. The distinction is made with “static” flow autoregulation under steady-state conditions of perfusion pressure, described by the celebrated “autoregulatory curve” with a homeostatic plateau. This paper studies the dynamic CFA during changes in perfusion pressure, which attains critical clinical importance in patients with stroke, traumatic brain injury and neurodegenerative disease with a cerebrovascular component. Mathematical and computational models have been used to advance our quantitative understanding of dynamic CFA and to elucidate the underlying physiological mechanisms by analyzing the relation between beat-to-beat data of mean arterial blood pressure (viewed as input) and mean cerebral blood flow velocity(viewed as output) of a putative CFA system. Although previous studies have shown that the dynamic CFA process is nonlinear, most modeling studies to date have been linear. It has also been shown that blood CO2 tension affects the CFA process. This paper presents a nonlinear modeling methodology that includes the dynamic effects of CO2 tension (or its surrogate, end-tidal CO2) as a second input and quantifies CFA from short data-records of healthy human subjects by use of the modeling concept of Principal Dynamic Modes (PDMs). The PDMs improve the robustness of the obtained nonlinear models and facilitate their physiological interpretation. The results demonstrate the importance of including the CO2 input in the dynamic CFA study and the utility of nonlinear models under hypercapnic or hypocapnic conditions
The Meissner effect in a strongly underdoped cuprate above its critical temperature
The Meissner effect and the associated perfect "bulk" diamagnetism together
with zero resistance and gap opening are characteristic features of the
superconducting state. In the pseudogap state of cuprates unusual diamagnetic
signals as well as anomalous proximity effects have been detected but a
Meissner effect has never been observed. Here we have probed the local
diamagnetic response in the normal state of an underdoped La1.94Sr0.06CuO4
layer (up to 46 nm thick, critical temperature Tc' < 5 K) which was brought
into close contact with two nearly optimally doped La1.84Sr0.16CuO4 layers (Tc
\approx 32 K). We show that the entire 'barrier' layer of thickness much larger
than the typical c axis coherence lengths of cuprates exhibits a Meissner
effect at temperatures well above Tc' but below Tc. The temperature dependence
of the effective penetration depth and superfluid density in different layers
indicates that superfluidity with long-range phase coherence is induced in the
underdoped layer by the proximity to optimally doped layers; however, this
induced order is very sensitive to thermal excitation.Comment: 7 pages, 7 figures + Erratu
Quantum Diffusion in Separable d-Dimensional Quasiperiodic Tilings
We study the electronic transport in quasiperiodic separable tight-binding
models in one, two, and three dimensions. First, we investigate a
one-dimensional quasiperiodic chain, in which the atoms are coupled by weak and
strong bonds aligned according to the Fibonacci chain. The associated
d-dimensional quasiperiodic tilings are constructed from the product of d such
chains, which yields either the square/cubic Fibonacci tiling or the labyrinth
tiling. We study the scaling behavior of the mean square displacement and the
return probability of wave packets with respect to time. We also discuss
results of renormalization group approaches and lower bounds for the scaling
exponent of the width of the wave packet.Comment: 6 pages, 4 figures, conference proceedings Aperiodic 2012 (Cairns
Modeling and simulations of beam stabilization in edge-emitting broad area semiconductor devices
A 2+1 dimensional PDE traveling wave model describing spatial-lateral
dynamics of edge-emitting broad area semiconductor devices is considered. A
numerical scheme based on a split-step Fourier method is presented and
implemented on a parallel compute cluster. Simulations of the model equations
are used for optimizing of existing devices with respect to the emitted beam
quality, as well as for creating and testing of novel device design concept
Intermittent dislocation flow in viscoplastic deformation
The viscoplastic deformation (creep) of crystalline materials under constant
stress involves the motion of a large number of interacting dislocations.
Analytical methods and sophisticated `dislocation-dynamics' simulations have
proved very effective in the study of dislocation patterning, and have led to
macroscopic constitutive laws of plastic deformation. Yet, a statistical
analysis of the dynamics of an assembly of interacting dislocations has not
hitherto been performed. Here we report acoustic emission measurements on
stressed ice single crystals, the results of which indicate that dislocations
move in a scale-free intermittent fashion. This result is confirmed by
numerical simulations of a model of interacting dislocations that successfully
reproduces the main features of the experiment. We find that dislocations
generate a slowly evolving configuration landscape which coexists with rapid
collective rearrangements. These rearrangements involve a comparatively small
fraction of the dislocations and lead to an intermittent behavior of the net
plastic response. This basic dynamical picture appears to be a generic feature
in the deformation of many other materials. Moreover, it should provide a
framework for discussing fundamental aspects of plasticity, that goes beyond
standard mean-field approaches that see plastic deformation as a smooth laminar
flow
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