Near-field interactions and non-universality in speckle patterns produced by a point source in a disordered medium

A point source in a disordered scattering medium generates a speckle pattern with non-universal features, giving rise to the so-called C_0 correlation. We analyze theoretically the relationship between the C_0 correlation and the statistical fluctuations of the local density of states, based on simple arguments of energy conservation. This derivation leads to a clear physical interpretation of the C_0 correlation. Using exact numerical simulations, we show that C_0 is essentially a correlation resulting from near-field interactions. These interactions are responsible for the non-universality of C_0, that confers to this correlation a huge potential for sensing and imaging at the subwavelength scale in complex media

Dynamic force spectroscopy on multiple bonds: experiments and model

We probe the dynamic strength of multiple biotin-streptavidin adhesion bonds under linear loading using the biomembrane force probe setup for dynamic force spectroscopy. Measured rupture force histograms are compared to results from a master equation model for the stochastic dynamics of bond rupture under load. This allows us to extract the distribution of the number of initially closed bonds. We also extract the molecular parameters of the adhesion bonds, in good agreement with earlier results from single bond experiments. Our analysis shows that the peaks in the measured histograms are not simple multiples of the single bond values, but follow from a superposition procedure which generates different peak positions.Comment: to appear in Europhysics Letter

Spatial coherence in complex photonic and plasmonic systems

The concept of cross density of states characterizes the intrinsic spatial coherence of complex photonic or plasmonic systems, independently on the illumination conditions. Using this tool and the associated intrinsic coherence length, we demonstrate unambiguously the spatial squeezing of eigenmodes on disordered fractal metallic films, thus clarifying a basic issue in plasmonics

Signatures of Le´vy flights with annealed disorder

We present theoretical and experimental results of Le´vy flights of light originating from a random walk of photons in a hot atomic vapor. In contrast to systems with quenched disorder, this system does not present any correlations between the position and the step length of the random walk. In an analytical model based on micro- scopic first principles including Doppler broadening we find anomalous Le´vy-type superdiffusion corresponding to a single-step size distribution P (x) ∝ x−(1+α), with α ≈ 1. We show that this step size distribution leads to a violation of Ohm’s law [Tdiff ∝ L−α/2 ⵬= L−1], as expected for a Le´vy walk of independent steps. Furthermore, the spatial profile of the transmitted light develops power-law tails [Tdiff(r) ∝ r−3−α]. In an experiment using a slab geometry with hot Rb vapor, we measured the total diffuse transmission Tdiff and the spatial profile of the transmitted light Tdiff(r). We obtained the microscopic Le´vy parameter α under macroscopic multiple scattering conditions paving the way to investigation of Le´vy flights in different atomic physics and astrophysics systems.We thank Dominique Delande for fruitful discussions and we acknowledge funding for N.M. and Q.B. by the french Direction Generale de l'Armement. R.P acknowledges the support of LABEX WIFI (Laboratory of Excellence ANR-10-LABX-24) within the French Program "Investments for the Future" under reference ANR-10-IDEX-0001-02 PSL*. E.J.N. and R.K. acknowledge the FCT/CNRS exchange program (441.00 CNRS)

The interrelatedness of cognitive abilities in very preterm and full‐term born children at 5.5 years of age : a psychometric network analysis approach

Background Very preterm (VP) birth is associated with a considerable risk for cognitive impairment, putting children at a disadvantage in academic and everyday life. Despite lower cognitive ability on the group level, there are large individual differences among VP born children. Contemporary theories define intelligence as a network of reciprocally connected cognitive abilities. Therefore, intelligence was studied as a network of interrelated abilities to provide insight into interindividual differences. We described and compared the network of cognitive abilities, including strength of interrelations between and the relative importance of abilities, of VP and full-term (FT) born children and VP children with below-average and average-high intelligence at 5.5 years. Methods A total of 2,253 VP children from the EPIPAGE-2 cohort and 578 FT controls who participated in the 5.5-year-follow-up were eligible for inclusion. The WPPSI-IV was used to measure verbal comprehension, visuospatial abilities, fluid reasoning, working memory, and processing speed. Psychometric network analysis was applied to analyse the data. Results Cognitive abilities were densely and positively interconnected in all networks, but the strength of connections differed between networks. The cognitive network of VP children was more strongly interconnected than that of FT children. Furthermore, VP children with below average IQ had a more strongly connected network than VP children with average-high IQ. Contrary to our expectations, working memory had the least central role in all networks. Conclusions In line with the ability differentiation hypothesis, children with higher levels of cognitive ability had a less interconnected and more specialised cognitive structure. Composite intelligence scores may therefore mask domain-specific deficits, particularly in children at risk for cognitive impairments (e.g., VP born children), even when general intelligence is unimpaired. In children with strongly and densely connected networks, domain-specific deficits may have a larger overall impact, resulting in lower intelligence levels

Wet Granular Materials

Most studies on granular physics have focused on dry granular media, with no liquids between the grains. However, in geology and many real world applications (e.g., food processing, pharmaceuticals, ceramics, civil engineering, constructions, and many industrial applications), liquid is present between the grains. This produces inter-grain cohesion and drastically modifies the mechanical properties of the granular media (e.g., the surface angle can be larger than 90 degrees). Here we present a review of the mechanical properties of wet granular media, with particular emphasis on the effect of cohesion. We also list several open problems that might motivate future studies in this exciting but mostly unexplored field.Comment: review article, accepted for publication in Advances in Physics; tex-style change

Chronic Delivery of Antibody Fragments Using Immunoisolated Cell Implants as a Passive Vaccination Tool

BACKGROUND: Monoclonal antibodies and antibody fragments are powerful biotherapeutics for various debilitating diseases. However, high production costs, functional limitations such as inadequate pharmacokinetics and tissue accessibility are the current principal disadvantages for broadening their use in clinic. METHODOLOGY AND PRINCIPAL FINDINGS: We report a novel method for the long-term delivery of antibody fragments. We designed an allogenous immunoisolated implant consisting of polymer encapsulated myoblasts engineered to chronically release scFv antibodies targeted against the N-terminus of the Aβ peptide. Following a 6-month intracerebral therapy we observed a significant reduction of the production and aggregation of the Aβ peptide in the APP23 transgenic mouse model of Alzheimer's disease. In addition, functional assessment showed prevention of behavioral deficits related to anxiety and memory traits. CONCLUSIONS AND SIGNIFICANCE: The chronic local release of antibodies using immunoisolated polymer cell implants represents an alternative passive vaccination strategy in Alzheimer's disease. This novel technique could potentially benefit other diseases presently treated by local and systemic antibody administration

Cell Nucleus-Targeting Zwitterionic Carbon Dots

An innovative nucleus-targeting zwitterionic carbon dot (CD) vehicle has been developed for anticancer drug delivery and optical monitoring. The zwitterionic functional groups of the CDs introduced by a simple one-step synthesis using beta-alanine as a passivating and zwitterionic ligand allow cytoplasmic uptake and subsequent nuclear translocation of the CDs. Moreover, multicolor fluorescence improves the accuracy of the CDs as an optical code. The CD-based drug delivery system constructed by non-covalent grafting of doxorubicin, exhibits superior antitumor efficacy owing to enhanced nuclear delivery in vitro and tumor accumulation in vivo, resulting in highly effective tumor growth inhibition. Since the zwitterionic CDs are highly biocompatible and effectively translocated into the nucleus, it provides a compelling solution to a multifunctional nanoparticle for substantially enhanced nuclear uptake of drugs and optical monitoring of translocation.open