1,518 research outputs found
Burst dynamics during drainage displacements in porous media: Simulations and experiments
We investigate the burst dynamics during drainage going from low to high
injection rate at various fluid viscosities. The bursts are identified as
pressure drops in the pressure signal across the system. We find that the
statistical distribution of pressure drops scales according to other systems
exhibiting self-organized criticality. The pressure signal was calculated by a
network model that properly simulates drainage displacements. We compare our
results with corresponding experiments.Comment: 7 pages, 4 figures. Submitted to Europhys. Let
On integrability of Hirota-Kimura type discretizations
We give an overview of the integrability of the Hirota-Kimura discretization
method applied to algebraically completely integrable (a.c.i.) systems with
quadratic vector fields. Along with the description of the basic mechanism of
integrability (Hirota-Kimura bases), we provide the reader with a fairly
complete list of the currently available results for concrete a.c.i. systems.Comment: 47 pages, some minor change
Lindhard and RPA susceptibility computations in extended momentum space in electron doped cuprates
We present an approximation for efficient calculation of the Lindhard
susceptibility in a periodic system through the use of
simple products of real space functions and the fast Fourier transform (FFT).
The method is illustrated by providing results for the
electron doped cuprate NdCeCuO extended over several
Brillouin zones. These results are relevant for interpreting inelastic X-ray
scattering spectra from cuprates.Comment: 6 pages, 6 figures, accepted in Physical Review
Clostridium perfringens α-toxin interaction with red cells and model membranes.
The effects of Clostridium perfringens α-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction.Royal Society University Research Fellowshi
Breath-Hold Blood Oxygen Level-Dependent MRI: A Tool for the Assessment of Cerebrovascular Reserve in Children with Moyamoya Disease
BACKGROUND AND PURPOSE: There is a critical need for a reliable and clinically feasible imaging technique that can enable prognostication and selection for revascularization surgery in children with Moyamoya disease. Blood oxygen level-dependent MR imaging assessment of cerebrovascular reactivity, using voluntary breath-hold hypercapnic challenge, is one such simple technique. However, its repeatability and reliability in children with Moyamoya disease are unknown. The current study sought to address this limitation. MATERIALS AND METHODS: Children with Moyamoya disease underwent dual breath-hold hypercapnic challenge blood oxygen level-dependent MR imaging of cerebrovascular reactivity in the same MR imaging session. Within-day, within-subject repeatability of cerebrovascular reactivity estimates, derived from the blood oxygen level-dependent signal, was computed. Estimates were associated with demographics and intellectual function. Interrater reliability of a qualitative and clinically applicable scoring scheme was assessed. RESULTS: Twenty children (11 males; 12.1 ± 3.3 years) with 30 MR imaging sessions (60 MR imaging scans) were included. Repeatability was "good" on the basis of the intraclass correlation coefficient (0.70 ± 0.19). Agreement of qualitative scores was "substantial" (κ = 0.711), and intrarater reliability of scores was "almost perfect" (κ = 0.83 and 1). Younger participants exhibited lower repeatability (P = .027). Repeatability was not associated with cognitive function (P > .05). However, abnormal cerebrovascular reactivity was associated with slower processing speed (P = .015). CONCLUSIONS: Breath-hold hypercapnic challenge blood oxygen level-dependent MR imaging is a repeatable technique for the assessment of cerebrovascular reactivity in children with Moyamoya disease and is reliably interpretable for use in clinical practice. Standardization of such protocols will allow further research into its application for the assessment of ischemic risk in childhood cerebrovascular disease
A Smart Bluetooth-based Ad Hoc Management System for Appliances in Home Environments
The number of home devices integrating new technologies is continuously increasing. These advances allow us to improve our daily routines. In addition, the improvement in network infrastructure and the development of smart phones and mobile devices allow us access from any place to any of our systems over the Internet. Bearing in mind this idea, we have developed a low-cost ad hoc protocol based on Bluetooth technology that allows us to control all our home appliances and monitor the power consumption of our homes. Our proposal is based on an Android application installed on a mobile device which acts as server. The application allows users to program the various appliances. It is also able to check the status of the appliance, as well as controlling the power consumption of the house and its cost. The system is equipped with a smart algorithm able to manage all appliances and decide which ones should work as a function of various criteria such as time of day or power consumption. Finally, the system is able to detect faults in water and electricity supply for acting accordingly. All data received and sent by the server are stored in a database which the system can check and compare to make their own decisions.Sendra, S.; Laborda, A.; Díaz Santos, JR.; Lloret, J. (2015). A Smart Bluetooth-based Ad Hoc Management System for Appliances in Home Environments. Springer Verlag (Germany): LNCS. 8487:128-141. doi:10.1007/978-3-319-07425-2_10S1281418487Garcia, M., Sendra, S., Lloret, J., Canovas, A.: Saving energy and improving communications using cooperative group-based Wireless Sensor Networks. Telecommunication Systems 52(4), 2489–2502 (2013)Liu, Y., Zhou, G.: Technologies and Applications of Internet of Things. In: Proceedings of 2012 Fifth International Conference on Intelligent Computation Technology and Automation (ICICTA), Zhangjiajie, China, January 12-14, pp. 197–200 (2012)Aiello, M.: The Role of Web Services at Home. In: Proceedings of the Advanced International Conference on Telecommunications and International Conference on Internet and Web Applications and Services (AICT-ICIW 2006), Guadeloupe, France, February 23-25 (2006)Mowafi, M.Y., Awad, F.H., Al-Batati, M.A.: Opportunistic Network Coding for Real-Time Transmission over Wireless Networks. Network Protocols and Algorithms 5(1), 1–19 (2013)Gangadhar, G., Nayak, S., Puttamadappa, C.: Intelligent Refrigerator with monitoring capability through internet. International Journal of Computer Applications. Special Issue on “Wireless Information Networks & Business Information System 2(7), 65–68 (2011)Soucek, S., Russ, G., Tamarit, C.: The Smart Kitchen Project—An Application of Fieldbus Technology to Domotics. In: Proceedings of 2nd International Workshop on Networked Appliances (IWNA 2000), New Brunswick, NJ, USA, November 30-December 1 (2000)Zhang, W., Tan, G.-Z., Ding, N.: Traffic Information Detection Based on Scattered Sensor Data: Model and Algorithms. Adhoc & Sensor Wireless Networks 18(3-4), 225–240 (2013)Ranjit, J.S., Shin, S.: A Modified IEEE 802.15. 4 Superframe Structure for Guaranteed Emergency Handling in Wireless Body Area Network. Network Protocols & Algorithms 5(2), 1–15 (2013)Braeken, A., Singelee, D.: Efficient and Location-Private Communication Protocols for WBSNs. Adhoc & Sensor Wireless Networks 19(3-4), 305–326 (2013)Augusto, J.C., McCullagh, P., McClelland, V., Walkden, J.A.: Enhanced healthcare provision through assisted decision-making in a smart home environment. In: Proceedings of the Second Workshop on Artificial Intelligence Techniques for Ambient Intelligence (AITAmI 2007), Hyderabad, India, January 6-7 (2007)Zhang, L., Zhao, Z., Li, D., Liu, Q., Cui, L.: Wildlife Monitoring Using Heterogeneous Wireless Communication Network. Adhoc & Sensor Wireless Networks 18(3-4), 159–179 (2013)Viani, F., Robol, F., Polo, A., Rocca, P., Oliveri, G., Massa, A.: Wireless Architectures for Heterogeneous Sensing in Smart Home Applications: Concepts and Real Implementation. Proceedings of the IEEE 101(11), 2381–2396 (2013)Lloret, J., Macías, E., Suárez, A., Lacuesta, R.: Ubiquitous Monitoring of Electrical Household Appliances. Sensors 12(11), 15159–15191 (2012)Kamilaris, A., Trifa, V., Pitsillides, A.: The smart home meets the Web of Things. International Journal of Ad Hoc and Ubiquitous Computing 7(3), 145–154 (2011)Kamilaris, A., Trifa, V., Pitsillides, A.: An Application Framework for Web-Based Smart Homes. In: Proceedings of the 18th International Conference on Telecommunications, ICT 2011, Ayia Napa, Cyprus, May 8-11, pp. 134–139 (2011)IEEE Std 802.15.1-2002 – IEEE Standard for Information technology – Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPANs)KNX international Site, http://www.knx.org/knx-en/index.php (last access: February 1, 2014)LonWorks Technology. In: ECHELON web site, http://www.echelon.com/technology/lonworks/ (last access: February 1, 2014)X10 protocol. In: X10 web site, http://x10-lang.org/ (last access: February 1, 2014)Rohini Basak, R., Sardar, B.: Security in Network Mobility (NEMO): Issues, Solutions, Classification, Evaluation, and Future Research Directions. Network Protocols and Algorithms 5(2), 87–111 (2013
Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator
We report the evolution of the surface electronic structure and surface
material properties of a topological crystalline insulator (TCI) Pb1-xSnxSe as
a function of various material parameters including composition x, temperature
T and crystal structure. Our spectroscopic data demonstrate the electronic
groundstate condition for the saddle point singularity, the tunability of
surface chemical potential, and the surface states' response to circularly
polarized light. Our results show that each material parameter can tune the
system between trivial and topological phase in a distinct way unlike as seen
in Bi2Se3 and related compounds, leading to a rich and unique topological phase
diagram. Our systematic studies of the TCI Pb1-xSnxSe are valuable materials
guide to realize new topological phenomena.Comment: 10 pages, 7 figures. Expanded version of arXiv:1403.156
In-Plane Orbital Texture Switch at the Dirac Point in the Topological Insulator Bi2Se3
Topological insulators are novel macroscopic quantum-mechanical phase of
matter, which hold promise for realizing some of the most exotic particles in
physics as well as application towards spintronics and quantum computation. In
all the known topological insulators, strong spin-orbit coupling is critical
for the generation of the protected massless surface states. Consequently, a
complete description of the Dirac state should include both the spin and
orbital (spatial) parts of the wavefunction. For the family of materials with a
single Dirac cone, theories and experiments agree qualitatively, showing the
topological state has a chiral spin texture that changes handedness across the
Dirac point (DP), but they differ quantitatively on how the spin is polarized.
Limited existing theoretical ideas predict chiral local orbital angular
momentum on the two sides of the DP. However, there have been neither direct
measurements nor calculations identifying the global symmetry of the spatial
wavefunction. Here we present the first results from angle-resolved
photoemission experiment and first-principles calculation that both show,
counter to current predictions, the in-plane orbital wavefunctions for the
surface states of Bi2Se3 are asymmetric relative to the DP, switching from
being tangential to the k-space constant energy surfaces above DP, to being
radial to them below the DP. Because the orbital texture switch occurs exactly
at the DP this effect should be intrinsic to the topological physics,
constituting an essential yet missing aspect in the description of the
topological Dirac state. Our results also indicate that the spin texture may be
more complex than previously reported, helping to reconcile earlier conflicting
spin resolved measurements
Theory of Extrinsic and Intrinsic Tunnelling in Cuprate Superconductors
A theory capable of explaining intrinsic and extrinsic tunnelling conductance
in underdoped cuprates has been devised that accounts for the existence of two
energy scales, their temperature and doping dependencies. The asymmetry and
inhomogeneity seen in extrinsic (normal metal - superconductor (NS)) tunnelling
and the normal-state gapped intrinsic (SS) conductance is explained, as well as
the superconducting gap and normal state pseudogap and the temperature
dependence of the full gap.Comment: 14 pages, 10 figures, misprints correcte
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