Updating constraint preconditioners for KKT systems in quadratic programming via low-rank corrections

This work focuses on the iterative solution of sequences of KKT linear systems arising in interior point methods applied to large convex quadratic programming problems. This task is the computational core of the interior point procedure and an efficient preconditioning strategy is crucial for the efficiency of the overall method. Constraint preconditioners are very effective in this context; nevertheless, their computation may be very expensive for large-scale problems, and resorting to approximations of them may be convenient. Here we propose a procedure for building inexact constraint preconditioners by updating a "seed" constraint preconditioner computed for a KKT matrix at a previous interior point iteration. These updates are obtained through low-rank corrections of the Schur complement of the (1,1) block of the seed preconditioner. The updated preconditioners are analyzed both theoretically and computationally. The results obtained show that our updating procedure, coupled with an adaptive strategy for determining whether to reinitialize or update the preconditioner, can enhance the performance of interior point methods on large problems.Comment: 22 page

Papular-purpuric gloves and socks syndrome due to parvovirus B19: a report of two simultaneous cases in cohabitant families.

The so-called papular-purpuric gloves and socks syndrome (PPGSS) is a condition characterized by acute onset of intense erythema, edema and petechiae with a typical localization on the hands and feet, besides mucosal lesions of the oral cavity. The syndrome has a favorable and self-limited course, requiring only a symptomatic therapy. In the 50% of the cases described in literature (ninety cases in 22 years), is documented an acute infection caused by parvovirus B19 and in only two cases the onset of PPGSS is reported among different members of the same family. The aim of the work is to describe two cases of PPGSS arisen during a short time period in two family members affected by an acute parvovirus B19 infection found by serum sampling. The peculiarity of the study was the infrequence of the syndrome and the rareness of the description of PPGSS in rheumatology. This syndrome is usually described in dermatology, but it is also interesting for the rheumatologist because it comes in differential diagnosis with various autoimmune diseases

Distributed coherent radars enabled by fiber networks

In the last few years, we have been proposing the use of photonics to bring new functionalities in radar systems, exploiting its precision and tunability to give radars improved performance and reconfigurability. This paper will present the most recent evolution of the original idea of photonics-based radars, which considers the exploitation of the increasingly available fiber connections to implement a network of widely distributed radars. The centralized photonic approach allows driving several separated radars simultaneously, enabling the novel class of distributed coherent radar systems. Through the implementation of specific multi-input multi-output (MIMO) processing, the photonics-enabled radar network is capable to push the radar detection resolution far beyond the limits usually set by the signal bandwidth alone

Widely distributed photonics-based dual-band MIMO radar for harbour surveillance

A new architecture for a widely distributed dual-band coherent multiple-input multiple-output (MIMO) radar system is illustrated, and its implementation and testing are reported. The system consists in a central unit where radar signals are coherently generated and detected, which serves multiple remote sensors connected over transparent WDM optical network. Every remote node operates coherently both in the S- and X-band, and is displaced over distances of several kilometers, allowing to monitor a scene under different angles of view. All the remote sensors share the same oscillator and digital signal processing unit, both located in the central office, allowing to perform centralized raw data fusion on the acquired signals. By virtue of the system coherence, the system takes advantage of the coherent MIMO processing strategy to offer a superior spatial resolution, which is even magnified by the dual-band approach

Photonics enabling coherent MIMO radar networks

The potential of coherent MIMO radar networks enabled by photonics is introduced. The first coherent dual-band 2 × 4 MIMO radar experiment is presented. Range/cross-range maps demonstrate the higher cross-range resolution due to the coherence and the enhanced performance introduced by dual-band operation

Suspended accounts align with the Internet Research Agency misinformation campaign to influence the 2016 US election

Abstract The ongoing debate surrounding the impact of the Internet Research Agency’s (IRA) social media campaign during the 2016 U.S. presidential election has largely overshadowed the involvement of other actors. Our analysis brings to light a substantial group of suspended Twitter users, outnumbering the IRA user group by a factor of 60, who align with the ideologies of the IRA campaign. Our study demonstrates that this group of suspended Twitter accounts significantly influenced individuals categorized as undecided or weak supporters, potentially with the aim of swaying their opinions, as indicated by Granger causality

The Role of the IRA in Twitter during the 2016 US Presidential Election: Unveiling Amplification and Influence of Suspended Accounts

The impact of the social media campaign conducted by the Internet Research Agency (IRA) during the 2016 U.S. presidential election continues to be a topic of ongoing debate. While it is widely acknowledged that the objective of this campaign was to support Donald Trump, the true extent of its influence on Twitter users remains uncertain. Previous research has primarily focused on analyzing the interactions between IRA users and the broader Twitter community to assess the campaign's impact. In this study, we propose an alternative perspective that suggests the existing approach may underestimate the true extent of the IRA campaign. Our analysis uncovers the presence of a notable group of suspended Twitter users, whose size surpasses the IRA user group size by a factor of 60. These suspended users exhibit close interactions with IRA accounts, suggesting potential collaboration or coordination. Notably, our findings reveal the significant role played by these previously unnoticed accounts in amplifying the impact of the IRA campaign, surpassing even the reach of the IRA accounts themselves by a factor of 10. In contrast to previous findings, our study reveals that the combined efforts of the Internet Research Agency (IRA) and the identified group of suspended Twitter accounts had a significant influence on individuals categorized as undecided or weak supporters, probably with the intention of swaying their opinions.Comment: 13 Tables, 12 Figure

In-Field Demonstration of a Photonic Coherent MIMO Distributed Radar Network

This paper reports an in-field experiment of a photonics-based coherent MIMO radar network. The use of photonics guarantees the coherence of the transmitted and received RF signals, and allows remoting the antennas exploiting deployed optical fibers, thus a MIMO approach can be applied on a network of widely distributed coherent radars. In the in-field experiment, a photonics-based radar core connects two transmitters and two receivers, with 100-MHz bandwidth signals in X-band, observing a collaborative target. The results demonstrate an improvement in radar precision, and envisage real applications wherever fiber is available for deploying the radar network

Coherent dual-band 2x4 MIMO radar experiment exploiting photonics

In this paper the first coherent dual-band 2x4 MIMO radar experiment is presented. Range/cross-range maps demonstrate the higher cross-range resolution due to the coherence and the enhanced performance introduced by dual-band operatio

Efficacy of atropine 0.01% for the treatment of childhood myopia in European patients

Purpose: To evaluate the efficacy and safety of atropine 0.01% in slowing myopia progression in European paediatric patients. Methods: Retrospective, medical records review study. Medical charts of paediatric patients with a myopia progression > 0.5 D/year treated with atropine 0.01% for at least 1 year were included. Patients receive a complete ophthalmic examination before and 12 months after initiation of atropine treatment. A group of myopic untreated children serves as a control group. The rate of myopia progression at baseline and 12 months after treatment with atropine was evaluated. The rate of myopia progression in treated and untreated patients was also compared. Adverse events were recorded. Results: Medical records of 52 treated and 50 control subjects were analysed. In the atropine group, the mean rate of myopia progression after 12 months of treatment ( 120.54 \ub1 0.61 D) was significantly slower compared with the baseline progression ( 121.20 \ub1 0.64 D; p < 0.0001) and to the progression in the control group ( 121.09 \ub1 0.64; p < 0.0001). The responders patients were 41/52 (79%), whereas 11/52 patients (21%) showed a progression > 0.50 D despite treatment. The only adverse event was temporary photophobia in five patients (9.6%), severe adverse events were not reported, and none of the patients discontinued the treatment. Conclusion: Low-dose atropine significantly slowed the rate of myopia progression in European paediatric patients with a favourable safety profile