Synthesis and properties of amphiphilic star polysulfides

We here present the synthesis and characterisation of linear and star-shaped amphiphilic block copolymers based on hydrophobic polysulfides (poly(propylene sulfide), PPS) and hydrophilic polyethers (poly(ethylene glycol), PEG). We also discuss the proof of the principle of their responsiveness to oxidising conditions. In a water environment, these polymers aggregate in the form of sub-micron carriers that, due to the sensitivity to oxidation reactions typical of PPS, can be used for responsive drug delivery. In this first study we have focused on the study of large aggregates, which do not apparently show dramatic differences in behaviour when polymer chains with different degrees of branching are studied.     

Functionalized bismuth ferrite harmonic nanoparticles for cancer cells labeling and imaging

Journal of Nanoparticle Research - Nanoparticles form the fundamental building blocks for many exciting applications in various scientific disciplines. However, the problem of the large-scale...     

On the homotopy class of maps with finite p-energy into non-positively curved manifolds

We prove that a map f : M → N with finite p-energy, p > 2, from a complete manifold (M, á , ñ ){\left(M,\left\langle ,\right\rangle \right)} into a non-positively curved, compact manifold N is homotopic to a constant, provided the negative part of the Ricci curvature of the domain manifold is small in a suitable spectral sense. The result relies on a Liouville-type theorem for finite q-energy, p-harmonic maps under spectral assumptions.     

The Downside of Heterogeneity: How Established Relations Counteract Systemic Adaptivity in Tasks Assignments

We study the lock-in effect in a network of task assignments. Agents have a heterogeneous fitness for solving tasks and can redistribute unfinished tasks to other agents. They learn over time to whom to reassign tasks and preferably choose agents with higher fitness. A lock-in occurs if reassignments can no longer adapt. Agents overwhelmed with tasks then fail, leading to failure cascades. We find that the probability for lock-ins and systemic failures increase with the heterogeneity in fitness values. To study this dependence, we use the Shannon entropy of the network of task assignments. A detailed discussion links our findings to the problem of resilience and observations in social systems.     

Gauge Dependence in the Theory of Non-Linear Spacetime Perturbations

Diffeomorphism freedom induces a gauge dependence in the theory of spacetime perturbations. We derive a compact formula for gauge transformations of perturbations of arbitrary order. To this end, we develop the theory of Taylor expansions for one-parameter families (not necessarily groups) of diffeomorphisms. First, we introduce the notion of knight diffeomorphism, that generalises the usual concept of flow, and prove a Taylor's formula for the action of a knight on a general tensor field. Then, we show that any one-parameter family of diffeomorphisms can be approximated by a family of suitable knights. Since in perturbation theory the gauge freedom is given by a one-parameter family of diffeomorphisms, the expansion of knights is used to derive our transformation formula. The problem of gauge dependence is a purely kinematical one, therefore our treatment is valid not only in general relativity, but in any spacetime theory. Received: 21 November 1996 / Accepted: 20 August 1997     

Measure-theoretical properties of the unstable foliation of two-dimensional differentiable area-preserving systems

This article analyzes in detail the statistical and measure-theoretical properties of the nonuniform stationary measure, referred to as the w-invariant measure, associated with the spatial length distribution of the integral manifolds of the unstable invariant foliation in two-dimensional differentiable area-preserving systems. The analysis is developed starting from a sequence of analytical approximations for the associated density. These approximations are related to the properties of the Jacobian matrix of the nth iteration of a Poincaré map. The w-invariant measure plays a fundamental role in the study of transport phenomena in laminar-chaotic fluid-mixing systems, for which it furnishes the asymptotic invariant distribution of intermaterial contact length between two fluids. The w-invariant measure turns out to be singular and exhibits multifractal features. Its associated density displays local self-similarity in an epsilon neighborhood of hyperbolic periodic points. The cancellation exponent of the signed measure associated with the w measure by attaching at each point the direction of the field of the asymptotic unstable eigenvectors is also analyzed. The only case for which the w-invariant measure is absolutely continuous is given by the conjugation of hyperbolic toral automorphisms with a linear automorphism. The connections with the statistical properties, and in particular with the stretching dynamics, are addressed in detail.     

Curving Newtonian Space

We show that the advance of the perihelion of Mercury (and other planets), as well as the deflection of light by the Sun, can be accurately calculated in Newtonian gravity, if one takes into account the fact of the curvature of space.     

Validation of a sensitive HPLC/fluorescence method for assessment of ciprofloxacin levels in plasma and prostate microdialysate samples from rats

Chronic bacterial prostatitis treatment consists of broad‐spectrum antibiotic therapy for long periods of time. Drug penetration into the prostate makes the treatment a challenged. Ciprofloxacin is one of the most prescribed drugs for this treatment. A liquid chromatography with fluorescence detection method was developed and validated for determining ciprofloxacin concentrations in two different matrices: plasma and prostate microdialysate. Ciprofloxacin was separated on a C₁₈ column eluted with a mobile phase constituted of a mixture of 0.4% aqueous triethylamine:methanol:acetonitrile (75:15:10, v/v/v) and 0.4% aqueous triethylamine:acetonitrile (88:12, v/v) for microdialysate and plasma samples, respectively. Linearity was obtained over a concentration range of 5–1000 ng/mL (microdialysate) and 10–2000 ng/mL (plasma), with coefficients of determination ≥0.9956. Precision was determined from the analysis of six quality control samples and showed RSD values <11.1 and 7.4% for intra and inter‐assay precision, respectively. The accuracy ranged from 85.6 to 114.3%. The method was applied to a preliminary pharmacokinetic study to investigate ciprofloxacin concentrations in prostate, sampled by microdialysis, and plasma after a 7 mg/kg intravenous dose to Wistar rats. The method showed high sensitivity using only protein precipitation as plasma sample clean‐up and was successfully applied to investigate ciprofloxacin prostate penetration. Copyright © 2015 John Wiley & Sons, Ltd.