An interior point method for nonlinear constrained derivative-free optimization

In this paper we consider constrained optimization problems where both the objective and constraint functions are of the black-box type. Furthermore, we assume that the nonlinear inequality constraints are non-relaxable, i.e. their values and that of the objective function cannot be computed outside of the feasible region. This situation happens frequently in practice especially in the black-box setting where function values are typically computed by means of complex simulation programs which may fail to execute if the considered point is outside of the feasible region. For such problems, we propose a new derivative-free optimization method which is based on the use of a merit function that handles inequality constraints by means of a log-barrier approach and equality constraints by means of a quadratic penalty approach. We prove convergence of the proposed method to KKT stationary points of the problem under quite mild assumptions. Furthermore, we also carry out a preliminary numerical experience on standard test problems and comparison with a state-of-the-art solver which shows efficiency of the proposed method.Comment: We dropped the convexity assumption to take into account that convexity is no longer required, we changed the theoretical analysis, exposition of the main algorithm has changed. We first present a simpler method and then the main algorithm. Numerical results have been a lot extended by adding some compariso

Below the Radar: Private Groups, Locked Platforms, and Ephemeral Content—Introduction to the Special Issue

none3noopenBoccia Artieri, Giovanni; Brilli, Stefano; Zurovac, ElisabettaBoccia Artieri, Giovanni; Brilli, Stefano; Zurovac, Elisabett

Gradienti di liveness. Lo shaping socio-tecnico delle arti performative tra online e offline. Introduzione

The present article introduces the third issue of the journal entitled Gradients of liveness: socio-technical shaping of performing arts between online and offline. After situating the issue of liveness within the process of mediatization of society, and the challenges fuelled by the pandemic, we discuss the statute of the field of liveness studies. We then defend the necessity of an approach that understands liveness in terms of the “gradients” with which this phenomenon manifests itself. In the second part, the articles of the issue are presented, showing the multiple branches of the “liveness problem” through heterogeneous performative, technological and theoretical fields, thus highlighting the relevance of this theoretical tool in understanding how the sense of presence and connection is constructed in the context of mediatization. Il presente articolo introduce il terzo numero della rivista dal titolo Gradienti di liveness. Lo shaping socio-tecnico delle arti performative tra online e offline. Dopo aver inquadrato il tema della liveness all’interno del processo di mediatizzazione del sociale e delle sfide alimentate dalla pandemia, viene discusso lo statuto del campo di studi sulla liveness. Si difende quindi e la necessità di uno sguardo che intende la liveness nei termini di “gradienti” con cui tale fenomeno si manifesta. Nella seconda parte vengono presentati i contenuti del numero, i quali mostrano le molteplici diramazioni della questione liveness attraverso ambiti spettacolari, tecnologici e teorici eterogenei, evidenziando la rilevanza di questo strumento d’indagine nel comprendere la costruzione del senso della presenza e della connessione nel contesto della mediatizzazione.&nbsp

Cholesterol-loaded nanoparticles ameliorate synaptic and cognitive function in Huntington's disease mice

Brain cholesterol biosynthesis and cholesterol levels are reduced in mouse models of Huntington's disease (HD), suggesting that locally synthesized, newly formed cholesterol is less available to neurons. This may be detrimental for neuronal function, especially given that locally synthesized cholesterol is implicated in synapse integrity and remodeling. Here, we used biodegradable and biocompatible polymeric nanoparticles (NPs) modified with glycopeptides (g7) and loaded with cholesterol (g7-NPs-Chol), which per se is not blood-brain barrier (BBB) permeable, to obtain high-rate cholesterol delivery into the brain after intraperitoneal injection in HD mice. We report that g7-NPs, in contrast to unmodified NPs, efficiently crossed the BBB and localized in glial and neuronal cells in different brain regions. We also found that repeated systemic delivery of g7-NPs-Chol rescued synaptic and cognitive dysfunction and partially improved global activity in HD mice. These results demonstrate that cholesterol supplementation to the HD brain reverses functional alterations associated with HD and highlight the potential of this new drug-administration route to the diseased brain

Exploring the symbiotic pangenome of the nitrogen-fixing bacterium Sinorhizobium meliloti

<p>Abstract</p> <p>Background</p> <p><it>Sinorhizobium meliloti </it>is a model system for the studies of symbiotic nitrogen fixation. An extensive polymorphism at the genetic and phenotypic level is present in natural populations of this species, especially in relation with symbiotic promotion of plant growth. AK83 and BL225C are two nodule-isolated strains with diverse symbiotic phenotypes; BL225C is more efficient in promoting growth of the <it>Medicago sativa </it>plants than strain AK83. In order to investigate the genetic determinants of the phenotypic diversification of <it>S. meliloti </it>strains AK83 and BL225C, we sequenced the complete genomes for these two strains.</p> <p>Results</p> <p>With sizes of 7.14 Mbp and 6.97 Mbp, respectively, the genomes of AK83 and BL225C are larger than the laboratory strain Rm1021. The core genome of Rm1021, AK83, BL225C strains included 5124 orthologous groups, while the accessory genome was composed by 2700 orthologous groups. While Rm1021 and BL225C have only three replicons (Chromosome, pSymA and pSymB), AK83 has also two plasmids, 260 and 70 Kbp long. We found 65 interesting orthologous groups of genes that were present only in the accessory genome, consequently responsible for phenotypic diversity and putatively involved in plant-bacterium interaction. Notably, the symbiosis inefficient AK83 lacked several genes required for microaerophilic growth inside nodules, while several genes for accessory functions related to competition, plant invasion and bacteroid tropism were identified only in AK83 and BL225C strains. Presence and extent of polymorphism in regulons of transcription factors involved in symbiotic interaction were also analyzed. Our results indicate that regulons are flexible, with a large number of accessory genes, suggesting that regulons polymorphism could also be a key determinant in the variability of symbiotic performances among the analyzed strains.</p> <p>Conclusions</p> <p>In conclusions, the extended comparative genomics approach revealed a variable subset of genes and regulons that may contribute to the symbiotic diversity.</p