148 research outputs found
Cortical networks are disturbed in people with cirrhosis even in the absence of neuropsychometric impairment
OBJECTIVE: Hepatic encephalopathy is a common complication of cirrhosis; it is characterised by neuropsychometric/neurophysiological abnormalities. Its pathophysiology is complex but glial neuronal communication is likely to be disrupted and to impact on oscillatory networks and cortical connectivity. The aim of this study was to use multichannel electroencephalography (EEG) to investigate functional connectivity, as a surrogate for cortical networks, in patients with cirrhosis. METHODS: Resting EEGs were recorded in 98 healthy controls and in 264 patients with cirrhosis characterised psychometrically using the Psychometric Hepatic Encephalopathy Score (PHES). Functional connectivity was calculated using the phase-lag index with stratification into standard EEG frequency bands. The findings were validated in a further cohort of 39 healthy controls and 106 patients with cirrhosis. RESULTS: Widespread disruption in functional connectivity was observed in the patients compared with the controls; connectivity was increased in the theta (4-8 Hz) band and decreased in the delta (1-3.5 Hz), alpha (8.5-13 Hz) and beta (13.5-26.5 Hz) bands. Changes were apparent even in patients who were psychometrically unimpaired compared with healthy controls viz mean ± SEM theta 0.107 ± 0.001 vs. 0.103 ± 0.002 (p < 0.05) and alpha 0.139 ± 0.003 vs. 0.154 ± 0.003 (p < 0.01); more pronounced changes were observed with increasing neuropsychometric impairment. The findings were replicated in the second cohort. CONCLUSIONS: Cortical networks are disturbed in patients with cirrhosis even in the absence of psychometric impairment. SIGNIFICANCE: These findings will facilitate further exploration of the pathophysiology of this condition and provide a robust means for assessing treatment effects in research settings
BioConcens: Biomass and bioenergy production agriculture – consequences for soil fertility, environment, spread of animal parasites and socio-economy
The research programme called “international research cooperation and organic integrity” was commenced for a period 2006-2010. It is coordinated by DARCOF (The Danish Research Centre for Organic Farming). The whole programme, with acronym DARCOF III, consists of 15 projects (http://www.darcof.dk/research/darcofiii/index.html). One of them is BIOCONCENS - Biomass and bioenergy production in organic farming – consequences for soil fertility, environment, spread of animal parasites and socio-economy (http://www.bioconcens.elr.dk/uk/). The production of bioenergy in organic agriculture (OA) can reduce its dependency of fossil fuels and decrease green house gasses emission; consequently it will increase sustainability of organic farms. Biorefinery concept based on co-production of biogas, bioethanol and protein fodder in organic farming will be developed within the BIOCONCENS project and the background for the project and the different work packages will be presented in this paper
Polyakov loop correlators from D0-brane interactions in bosonic string theory
In this paper we re-derive the effective Nambu-Goto theory result for the
Polyakov loop correlator, starting from the free bosonic string and using a
covariant quantization. The boundary conditions are those of an open string
attached to two D0-branes at spatial distance R, in a target space with compact
euclidean time. The one-loop free energy contains topologically distinct
sectors corresponding to multiple covers of the cylinder in target space
bordered by the Polyakov loops. The sector that winds once reproduces exactly
the Nambu-Goto partition function. In our approach, the world-sheet duality
between the open and closed channel is most evident and allows for an explicit
interpretation of the free energy in terms of tree level exchange of closed
strings between boundary states. Our treatment is fully consistent only in
d=26; extension to generic d may be justified for large R, and is supported by
Montecarlo data. At shorter scales, consistency and Montecarlo data seem to
suggest the necessity of taking into account the Liouville mode of Polyakov's
formulation.Comment: 17 pages, 4 figures, minor corrections, a few references added,
version accepted for publication in JHE
Conformal Invariance and Degrees of Freedom in the QCD String
We demonstrate that the Hagedorn-like growth of the number of observed meson
states can be used to constrain the degrees of freedom of the underlying
effective QCD string. We find that the temperature relevant for such string
theories is not given by the usual Hagedorn value MeV, but is
considerably higher. This resolves an apparent conflict with the results from a
static quark-potential analysis, and suggests that conformal invariance and
modular invariance are indeed reflected in the hadronic spectrum. We also find
that the scalar string is in excellent agreement with data.Comment: 13 pages (Standard LaTeX); --> replaced version emphasizes new
results, and agrees with version to appear in Physical Review Letters (Jan
1994
The role of structural evolution on the quantum conductance behavior of gold nanowires during stretching
Gold nanowires generated by mechanical stretching have been shown to adopt
only three kinds of configurations where their atomic arrangements adjust such
that either the [100], [111] or [110] zone axes lie parallel to the elongation
direction. We have analyzed the relationship between structural rearrangements
and electronic transport behavior during the elongation of Au nanowires for
each of the three possibilities. We have used two independent experiments to
tackle this problem, high resolution transmission high resolution electron
microscopy to observe the atomic structure and a mechanically controlled break
junction to measure the transport properties. We have estimated the conductance
of nanowires using a theoretical method based on the extended H\"uckel theory
that takes into account the atom species and their positions. Aided by these
calculations, we have consistently connected both sets of experimental results
and modeled the evolution process of gold nanowires whose conductance lies
within the first and third conductance quanta. We have also presented evidence
that carbon acts as a contaminant, lowering the conductance of one-atom-thick
wires.Comment: 10 page
Biomass and bioenergy production in organic agriculture. Consequences for soil fertility, environment, spread of animal parasites and socio-economy. BioConcnes, a 4-year interdisciplinary project.
Energy production and energy use in organic agriculture (OA) need to be addressed in order to reduce the reliance on non-renewable fossil fuels and minimize greenhouse gas (GHG) emissions. Thus, there is an obligation to find consensus between the apparent opposing aims of renewable (bio) energy production and soil fertility in OA. This project aims at designing and evaluate a combined concept for biomass and bio-energy production in OA, while considering soil fertility
Effective potential and stability of the rigid membrane
The calculation of the effective potential for fixed-end and toroidal rigid
-branes is performed in the one-loop as well as in the approximations.
The analysis of the involved zeta-functions (of inhomogeneous Epstein type)
which appear in the process of regularization is done in full detail.
Assymptotic formulas (allowing only for exponentially decreasing errors of
order ) are found which carry all the dependences on the basic
parameters of the theory explicitly. The behaviour of the effective potential
(specified to the membrane case ) is investigated, and the extrema of this
effective potential are obtained.Comment: 15 PAGE
Partition Functions for the Rigid String and Membrane at Any Temperature
Exact expressions for the partition functions of the rigid string and
membrane at any temperature are obtained in terms of hypergeometric functions.
By using zeta function regularization methods, the results are analytically
continued and written as asymptotic sums of Riemann-Hurwitz zeta functions,
which provide very good numerical approximations with just a few first terms.
This allows to obtain systematic corrections to the results of Polchinski et
al., corresponding to the limits and of
the rigid string, and to analyze the intermediate range of temperatures. In
particular, a way to obtain the Hagedorn temperature for the rigid membrane is
thus found.Comment: 20 pages, LaTeX file, UB-ECM-PF 93/
Structure of aluminum atomic chains
First-principles density functional calculations reveal that aluminum can
form planar chains in zigzag and ladder structures. The most stable one has
equilateral triangular geometry with four nearest neighbors; the other stable
zigzag structure has wide bond angle and allows for two nearest neighbors. An
intermediary structure has the ladder geometry and is formed by two strands.
All these planar geometries are, however, more favored energetically than the
linear chain. We found that by going from bulk to a chain the character of
bonding changes and acquires directionality. The conductance of zigzag and
linear chains is 4e^2/h under ideal ballistic conditions.Comment: modified detailed version, one new structure added, 4 figures,
modified figure1, 1 tabl
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