143 research outputs found
The INGRID project: Development of Solutions for Sustainable and Highly Interconnected Grids
One of the current main challenges in green-power storage and smart grids is the lack of effective solutions for accommodating the unbalance between renewable energy sources - offering intermittent electricity supply - and a variable electricity demand. Integrating intermittent renewable energy sources by safe and cost-effective energy storage systems is today achievable. Coupled with electrolizers, high-capacity solid-state storage of green-hydrogen is practicable to sustain integration, monitoring and control of large quantity of GWh from renewable generation. The 23.9 MLN Euros INGRID European large demonstrative project started in July 2012 combines magnesium-based material solid-state hydrogen storage systems with advanced ICT technologies to intelligently interconnect miscellaneous energy networks (i.e. electricity and gas) and safely delivering green-hydrogen to various existing or forthcoming markets. One solution INGRID project addresses is an off-grid utility to store renewable electricity captured from wind sources to refill full-battery electric cars
Low Energy Properties of the (n,n) Carbon Nanotubes
According to band theory, an ideal undoped (n,n) carbon nanotube is metallic.
We show that the electron-electron interaction causes it to become Mott
insulating with a spin gap. More interestingly, upon doping it develops
superconducting fluctuations.Comment: 5pages, 2eps figures, one reference added, final version, accepted to
PR
Unified analysis of terminal-time control in classical and quantum systems
Many phenomena in physics, chemistry, and biology involve seeking an optimal
control to maximize an objective for a classical or quantum system which is
open and interacting with its environment. The complexity of finding an optimal
control for maximizing an objective is strongly affected by the possible
existence of sub-optimal maxima. Within a unified framework under specified
conditions, control objectives for maximizing at a terminal time physical
observables of open classical and quantum systems are shown to be inherently
free of sub-optimal maxima. This attractive feature is of central importance
for enabling the discovery of controls in a seamless fashion in a wide range of
phenomena transcending the quantum and classical regimes.Comment: 10 page
Cardiogenic shock as a complication of acute mitral valve regurgitation following posteromedial papillary muscle infarction in the absence of coronary artery disease
A 48 year old man was transferred to our department with cardiogenic shock, pyrexia, a high white cell count and significant serum troponin T level. Clinical evaluation revealed severe mitral regurgitation secondary to a flail of both mitral valve leaflets. An emergency cardiac catheterisation did not reveal any significant coronary artery disease. Left ventricular angiogram and echocardiography demonstrated a good left ventricular function and massive mitral regurgitation. Blood cultures were negative for aerobics, anaerobics and fungi. The patient underwent emergency mitral valve replacement with a mechanical valve. Intraoperatively, the posteromedial papillary muscle was found to be ruptured. Histology of the papillary muscle revealed myocardial necrosis with no signs of infection. Cultures obtained from a mitral valve specimen were negative. The patient's recovery was uneventful and he was discharged on the 6th postoperative day
The Central Velocity Field in NGC 253 : Possible Indication of a Bar
We have investigated whether motion of gas in a bar-like potential can
account for the peculiar but systematic velocity field observed in the nuclear
region of the starburst galaxy NGC 253. This unusual velocity field with
gradients along both major and minor axes was revealed in a high resolution
(1.8^{\arcsec}\times 1.0^{\arcsec}) H92 recombination line
observation by Anantharamiah and Goss (1996). A simple logarithmic potential is
used to model the bar. Assuming that the bulk of the gas flows along closed and
non-intersecting x1 (bar) and x2 (anti-bar) orbits of the bar potential, we
have computed the expected velocity field and position-velocity diagrams and
compared them with the observations. A comparison of the integrated CO
intensity maps with the spatial distribution of the x1 and x2 orbits in the
model indicates that the nuclear molecular gas in NGC 253 lies mainly on the x2
orbits. We also find that the velocity field observed in the central 100 pc
region in the H92 recombination line is well accounted for by the bar
model if most of the ionized gas resides in the inner x2 orbits. However, the
model is unable to explain the velocity field on a larger scale of
pc observed using the OVRO interferometer with a resolution of
5^{\arcsec}\times 3^{\arcsec}. The direction of the observed CO velocity
field appears twisted compared to the model. We suggest that this perturbation
in the velocity field may be due to an accretion event that could have occurred
years ago.Comment: 26 latex pages, 7 figures, accepted in Astrophysical Journa
Quasiparticle Band Structure and Density Functional Theory: Single-Particle Excitations and Band Gaps in Lattice Models
We compare the quasiparticle band structure for a model insulator obtained
from the fluctuation exchange approximation (FEA) with the eigenvalues of the
corresponding density functional theory (DFT) and local density approximation
(LDA). The discontinuity in the exchange-correlation potential for this model
is small and the FEA and DFT band structures are in good agreement. In contrast
to conventional wisdom, the LDA for this model overestimates the size of the
band gap. We argue that this is a consequence of an FEA self-energy that is
strongly frequency dependent, but essentially local.Comment: 8 pages, and 5 figure
Configurational Entropy and Diffusivity of Supercooled Water
We calculate the configurational entropy S_conf for the SPC/E model of water
for state points covering a large region of the (T,rho) plane. We find that (i)
the (T,rho) dependence of S_conf correlates with the diffusion constant and
(ii) that the line of maxima in S_conf tracks the line of density maxima. Our
simulation data indicate that the dynamics are strongly influenced by S_conf
even above the mode-coupling temperature T_MCT(rho).Comment: Significant update of reference
On the Application of the Non Linear Sigma Model to Spin Chains and Spin Ladders
We review the non linear sigma model approach (NLSM) to spin chains and spin
ladders, presenting new results. The generalization of the Haldane's map to
ladders in the Hamiltonian approach, give rise to different values of the
parameter depending on the spin S, the number of legs and
the choice of blocks needed to built up the NLSM fields. For rectangular blocks
we obtain or depending on wether , is even or
odd, while for diagonal blocks we obtain . Both
results agree modulo , and yield the same prediction, namely that even (
resp. odd) ladders are gapped (resp. gapless). For even legged ladders we show
that the spin gap collapses exponentially with and we propose a
finite size correction to the gap formula recently derived by Chakravarty using
the 2+1 NSLM, which gives a good fit of numerical results. We show the
existence of a Haldane phase in the two legged ladder using diagonal blocks and
finally we consider the phase diagram of dimerized ladders.Comment: 25 pages, Latex, 7 figures in postscript files, Proc. of the 1996 El
Escorial Summer School on "Strongly Correlated Magnetic and Superconducting
Systems". Some more references are adde
Surface impedance anisotropy of YBaCuO single crystals: electrodynamic basis of the measurements
An electrodynamic technique is developed for determining the components of
surface impedance and complex conductivity tensors of HTSC single crystals on
the basis of measured quantities of a quality factor and a resonator frequency
shift. A simple formula is obtained for a geometrical factor of a crystal in
the form of a plate with dimensions in a microwave magnetic field
. To obtain the c-axis complex conductivity from
measurements at we propose a procedure which
takes account of sample size effects. With the aid of the technique involved
temperature dependences of all impedance and conductivity tensors components of
YBaCuO single crystal, grown in BaZrO crucible, are
determined at a frequency of GHz in its normal and superconducting
states. All of them proved to be linear at , and their extrapolation
to zero temperature gives the values of residual surface resistance
and m and
magnetic field penetration depth nm and
m.Comment: 9 pages, 7 figures. Submitted to Phys.Rev.B 05Jun2002; accepted for
publication 21Febr200
What happens for informal caregivers during transition to increased levels of care for the person with dementia? A systematic review protocol
Abstract Background Dementia is a globally prevalent disease that requires ongoing and increasing levels of care, often provided in the first instance by informal caregivers. Supporting transitions in informal caregiving in dementia is a pertinent issue for caregivers, care providers and governments. There is no existing systematic review that seeks to identify and map the body of literature regarding the review question: ‘What happens for informal caregivers during transition to increased levels of care for the person with dementia?’ Methods/design ASSIA, CINAHL+, MEDLINE, PsycINFO, SCIE, Social Service Abstracts and Web of Science will be systematically searched. Specialist dementia research libraries will be contacted. Reviews identified as relevant during the search process, their reference lists, and reference lists of accepted papers will be hand-searched. Qualitative, quantitative and mixed methods studies that seek to represent the experiences of, or examine the impact upon, informal caregivers during transition to increased formal care for the person with dementia will be eligible for inclusion. Synthesis will be segregated into qualitative and quantitative papers. Findings will be summarised, and the review will be prepared for publication. Discussion The review will seek to identify potentially vulnerable groups in need of support and as such, inform the practice of those offering support. It will also inform future research by highlighting areas in which current literature is insubstantial. Systematic review registration PROSPERO CRD4201706724
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