Resource
2015 EN
S. F. Shimobayashi · B. M. Mognetti · L. Parolini
+3 more
Multivalent interactions between deformable mesoscopic units are ubiquitousin biology, where membrane macromolecules mediate the interactions betweenneighbouring living cells and between cells and solid substrates. Lately,analogous artificial materials have been synthesised by functionalising theouter surface of compliant Brownian units, for example emulsion droplets andlipid vesicles, with selective linkers, in particular short DNA sequences. Thisdevelopment extended the range of applicability of DNA as a selective glue,originally applied to solid nano and colloidal particles. On very deformablelipid vesicles, the coupling between statistical effects of multivalentinteractions and mechanical deformation of the membranes gives rise to complexemergent behaviours, as we recently contributed to demonstrate [Parolini etal., Nature Communications, 2015, 6, 5948]. Several aspects of the complexphenomenology observed in these systems still lack a quantitative experimentalcharacterisation and fundamental understanding. Here we focus on theDNA-mediated multivalent interactions of a single liposome adhering to a flatsupported bilayer. This simplified geometry enables the estimate of themembrane tension induced by the DNA-mediated adhesive forces acting on theliposome. Our experimental investigation is completed by morphologicalmeasurements and the characterisation of the DNA-melting transition, probed byin-situ F\"{o}rster Resonant Energy Transfer spectroscopy. Experimental resultsare compared with the predictions of an analytical theory that couples thedeformation of the vesicle to a full description of the statistical mechanicsof mobile linkers. With at most one fitting parameter, our theory is capable ofsemi-quantitatively matching experimental data, confirming the quality of theunderlying assumptions.
Resource
2015 EN
Michele Marrocco
Classical physics fails where quantum physics prevails. This commonunderstanding applies to quantum phenomena that are acknowledged to be beyondthe reach of classical physics. Here, we make an attempt at weakening thissolid belief that classical physics is unfit to explain the quantum world. Thetrial run is the quantization of the free radiation field that will beaddressed by following a strategy that is free from operators orquantum-mechanical concepts
Resource
2015 EN
Rasheed Hussain · Donghyun Kim · Michele Nogueira
+3 more
Recently an online electric vehicle (OLEV) concept has been introduced, wherevehicles are propelled through the wirelessly transmitted electrical power fromthe infrastructure installed under the road while moving. The absence ofsecure-and-fair billing is one main hurdle to widely adopt this promisingtechnology. This paper introduces a secure and privacy-aware fair billingframework for OLEV on the move through the charging plates installed under theroad. We first propose two extreme lightweight mutual authenticationmechanisms, a direct authentication and a hash chain-based authenticationbetween vehicles and the charging plates that can be used for differentvehicular speeds on the road. Second we propose a secure and privacy-awarewireless power transfer on move for the vehicles with bidirectionalauditability guarantee by leveraging game-theoretic approach. Each chargingplate transfers a fixed amount of energy to the vehicle and bills the vehiclein a privacy-aware way accordingly. Our protocol guarantees secure,privacy-aware, and fair billing mechanism for the OLEVs while receivingelectric power from the road. Moreover our proposed framework can play a vitalrole in eliminating the security and privacy challenges in the deployment ofpower transfer technology to the OLEVs.
Resource
2015 EN
University of Oxford Michele Cappellari
Cappellari (2008) presented a flexible and efficient method to model thestellar kinematics of anisotropic axisymmetric and spherical stellar systems.The spherical formalism could be used to model the line-of-sight velocitysecond moments allowing for essentially arbitrary radial variation in theanisotropy and general luminous and total density profiles. Here we generalizethe spherical formalism by providing the expressions for all three componentsof the projected second moments, including the two proper motion components. Areference implementation is now included in the public JAM package available athttp://purl.org/cappellari/software
Resource
2015 EN
Lucio Maria Calcagnile · Giacomo Bormetti · Michele Treccani
+2 more
Recent years have seen an unprecedented rise of the role that technologyplays in all aspects of human activities. Unavoidably, technology has heavilyentered the Capital Markets trading space, to the extent that all majorexchanges are now trading exclusively using electronic platforms. The ultrafast speed of information processing, order placement, and cancelling generatesnew dynamics which is still not completely deciphered. Analyzing a largedataset of stocks traded on the US markets, our study evidences that since 2001the level of synchronization of large price movements across assets hassignificantly increased. Even though the total number of over-threshold eventshas diminished in recent years, when an event occurs, the average number ofassets swinging together has increased. Quite unexpectedly, only a minorfraction of these events -- regularly less than 40% along all years -- can beconnected with the release of pre-announced macroeconomic news. We alsodocument that the larger is the level of sistemicity of an event, the larger isthe probability -- and degree of sistemicity -- that a new event will occur inthe near future. This opens the way to the intriguing idea that systemic eventsemerge as an effect of a purely endogenous mechanism. Consistently, we presenta high-dimensional, yet parsimonious, model based on a class of self- andcross-exciting processes, termed Hawkes processes, which reconciles themodeling effort with the empirical evidence.
Resource
2015 EN
Roy Timo · Michele Wigger
We consider a cache-aided communications system in which a transmittercommunicates with many receivers over an erasure broadcast channel. The systemserves as a basic model for communicating on-demand content during periods ofhigh network congestion, where some content can be pre-placed in local cachesnear the receivers. We formulate the cache-aided communications problem as ajoint cache-channel coding problem, and characterise some information-theoretictradeoffs between reliable communications rates and cache sizes. We show thatif the receivers experience different channel qualities, then using unequalcache sizes and joint cache-channel coding improves system efficiency.
Resource
2015 EN
Rolando Magnanini · Michele Marini
We characterize all the solutions of the heat equation that have their(spatial) equipotential surfaces which do not vary with the time. Suchsolutions are either isoparametric or split in space-time. The result gives afinal answer to a problem raised by M. S. Klamkin, extended by G. Alessandrini,and that was named the Matzoh Ball Soup Problem by L. Zalcman. Similar resultscan also be drawn for a class of quasi-linear parabolic partial differentialequations with coefficients which are homogeneous functions of the gradientvariable. This class contains the (isotropic or anisotropic) evolutionp-Laplace and normalized p-Laplace equations.
Resource
2015 EN
Pier Stanislao Paolucci · Roberto Ammendola · Andrea Biagioni
+7 more
This short note regards a comparison of instantaneous power, total energyconsumption, execution time and energetic cost per synaptic event of a spikingneural network simulator (DPSNN-STDP) distributed on MPI processes whenexecuted either on an embedded platform (based on a dual socket quad-core ARMplatform) or a server platform (INTEL-based quad-core dual socket platform). Wealso compare the measure with those reported by leading custom and semi-customdesigns: TrueNorth and SpiNNaker. In summary, we observed that: 1- we spent 2.2micro-Joule per simulated event on the "embedded platform", approx. 4.4 timeslower than what was spent by the "server platform"; 2- the instantaneous powerconsumption of the "embedded platform" was 14.4 times better than the "server"one; 3- the server platform is a factor 3.3 faster. The "embedded platform" ismade of NVIDIA Jetson TK1 boards, interconnected by Ethernet, each mounting aTegra K1 chip including a quad-core ARM Cortex-A15 at 2.3GHz. The "serverplatform" is based on dual-socket quad-core Intel Xeon CPUs (E5620 at 2.4GHz).The measures were obtained with the DPSNN-STDP simulator (Distributed Simulatorof Polychronous Spiking Neural Network with synaptic Spike Timing DependentPlasticity) developed by INFN, that already proved its efficient scalabilityand execution speed-up on hundreds of similar "server" cores and MPI processes,applied to neural nets composed of several billions of synapses.
Resource
2015 EN
Giovanni Alessandrini · Michele Di Cristo · Elisa Francini
+1 more
We treat the stability issue for the three dimensional inverse imagingmodality called Quantitative Photoacoustic Tomography. We provide universalchoices of the illuminations which enable to recover, in a H\"older stablefashion, the diffusion and absorption coefficients from the interior pressuredata. With such choices of illuminations we do not need the nondegeneracyconditions commonly used in previous studies, which are difficult to beverified a-priori.
Resource
2015 EN
Michele Arzano · Giulia Gubitosi · Joao Magueijo
+1 more
We examine vacuum fluctuations in theories with modified dispersion relationswhich represent dimensional reduction at high energies. By changing units ofenergy and momentum we can obtain a description rendering the dispersionrelations undeformed and transferring all the non-trivial effects to theintegration measure in momentum space. Using this description we propose ageneral quantization procedure, which should be applicable whether or not thetheory explicitly introduces a preferred frame. Based on this scheme weevaluate the power spectrum of quantum vacuum fluctuations. We find that in{\it all} theories which run to 2 dimensions in the ultraviolet the vacuumfluctuations, in the ultraviolet regime, are scale-invariant. This is true inflat space but also for "inside the horizon" modes in an expanding universe. Wespell out the conditions upon the gravity theory for this scale-invariance tobe preserved as the modes are frozen-in outside the horizon. We also digress onthe meaning of dimensionality (in momentum and position space) and suggest thatthe spectral index could itself provide an operational definition ofdimensionality.