Open systems with error bounds: spin boson model with spectral density variations

In the study of open quantum systems, one of the most common ways to describe environmental effects on the reduced dynamics is through the spectral density. However, in many models this object cannot be computed from first principles and needs to be inferred on phenomenological grounds or fitted to experimental data. Consequently, some uncertainty regarding its form and parameters is unavoidable; this in turn calls into question the accuracy of any theoretical predictions based on a given spectral density. Here, we focus on the spin-boson model as a prototypical open quantum system, and find two error bounds on predicted expectation values in terms of the spectral density variation considered, and state a sufficient condition for the strongest one to apply. We further demonstrate an application of our result, by bounding the error brought about by the approximations involved in the Hierarchical Equations of Motion resolution method for spin-boson dynamics.Comment: 5+5 pages, minor edits since last unpublished versio

Optimized auxiliary oscillators for the simulation of general open quantum systems

A method for the systematic construction of few-body damped harmonic oscillator networks accurately reproducing the effect of general bosonic environments in open quantum systems is presented. Under the sole assumptions of a Gaussian environment and regardless of the system coupled to it, an algorithm to determine the parameters of an equivalent set of interacting damped oscillators obeying a Markovian quantum master equation is introduced. By choosing a suitable coupling to the system and minimizing an appropriate distance between the two-time correlation function of this effective bath and that of the target environment, the error induced in the reduced dynamics of the system is brought under rigorous control. The interactions among the effective modes provide remarkable flexibility in replicating non-Markovian effects on the system even with a small number of oscillators, and the resulting Lindblad equation may therefore be integrated at a very reasonable computational cost using standard methods for Markovian problems, even in strongly non-perturbative coupling regimes and at arbitrary temperatures including zero. We apply the method to an exactly solvable problem in order to demonstrate its accuracy, and present a study based on current research in the context of coherent transport in biological aggregates as a more realistic example of its use; performance and versatility are highlighted, and theoretical and numerical advantages over existing methods, as well as possible future improvements, are discussed.Comment: 23 + 9 pages, 11 + 2 figures. No changes from previous version except publication info and updated author affiliation

Patient- and parent-reported outcome measures of developmental adaptive abilities in visually impaired children: The Visual Impairment Developmental Autonomy (VIDA) scale

In the pediatric context, parents’ and patients’ engagement in the care process is strongly recommended and could be pursued using patient-reported outcome measures (PROMs), which therefore become useful for planning and monitoring treatments. Nevertheless, few data are available from families of children with neurodevelopmental disorders such as visual impairment (VI). The Visual Impairment Developmental Autonomy (VIDA) project aims to develop and validate a patient- and parent-reported tool to measure the most relevant aspects concerning everyday adaptive abilities in children and adolescents with visual impairment: the VIDA scale. The present paper illustrates the Delphi process of item generation engaging parents and patients and presents a protocol for the validation of this new co-designed tool in an Italian visually impaired pediatric population. Twenty-three families and five adolescents provided a list of 192 items and assessed their relevance. Items were categorized in 5 areas of adaptive abilities (i.e., table manners, clothing, personal hygiene, orientation and mobility, and socio-affectivity) and into three age ranges based on the patient's age. The final 102-item Vida Scale will be administered to a minimum of 300 visually impaired children together with measures of quality of life and child adjustment to investigate its psychometric properties

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Energy efficiency for radio communication systems in mission-critical applications

The continuous rise in the levels of greenhouse gases due to energy consumption and the influence of the Information and Communication Technologies (ICTs) massive use is constantly increasing. In the sector of communication networks for mission critical, security and public safety applications the environmental issue becomes crucial even if traditionally underestimated to the advantage of data throughput, coverage and voice transmission properties. Actually, one of the fundamental requirements of public safety infrastructures is the total and continuous coverage throughout the day in the served area. This constant and high energy demand makes mission critical networks particularly interesting for a comparative study on the consumption of the systems and related different technologies. This work aims to investigate the current energy consumption of principal standards for the Professional Mobile Radio sector, in particular TETRA (Terrestrial Trunked Radio) and DMR (Digital Mobile Radio) technologies, providing new and ad-hoc performance indicators with respect to energy efficiency

Hybrid Renewable Power System for Radio Networks in Mission Critical Applications

The most frequent problem detected by the companies in the telecommunications sector is the loss of power supply in site, usually located in remote zones. This is more delicate when the radio network has the specific objective to guarantee 'mission critical' communications. The object of this study is to propose and evaluate a way to decrease the number of maintenance operations necessary to restore the correct functioning, aiming at previously defined critic and strategic sites in a wide and complex radio network. This to obtain an increased availability, longer continuity and technical and economic benefits. Finally, the developed methods and the algorithms are applied to a real 'mission critical' case study