When Meta-Surfaces Meet Users: Optimization of Smart Radio Environments in 6G Sub-THz Communications

We consider a smart radio environment where meta-surfaces are employed to improve the performance of wireless networks working at sub-THz frequencies. To this end, we propose a comprehensive mathematical channel model, taking into account both the ability of the meta-surfaces to redirect the impinging signal towards a desired direction, and the signal reflection due to large objects. We show how the design of both the meta-surface and the transmitter precoder influences the network throughput. Furthermore, we compare several algorithms to optimize the effect of the meta-surfaces in a realistic scenario. As a result, a simpler algorithm that associates network users and meta-surfaces provides a performance comparable to more complex numerical optimization methods. Simulation results suggest how many users are supported in the designed system

Upper and lower bounds to the information rate transferred through the Pol-Mux channel

Pol-Mux transmission is a well established technique that enhances spectral efficiency by simultaneously transmitting over horizontal and vertical polarizations of the electrical field. However, cross-coupling of the two polarizations impairs transmission. Under the assumption that the cross-coupling matrix is a Markov process with free-running state, we propose upper and lower bounds to the information rate that can be transferred through the channel. Simulation results show that the two bounds are tight for values of the cross-coupling power of practical interest and modulation formats up to 16-QAM (quadrature amplitude modulation)

Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study

BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223

Does the organizational life cycle affect the management accounting system (MAS) change pattern? a review of case studies

Drawing from previous research on accounting change and on the impacts on MAS of stages in the life-cycle, the paper aims at discussing how the MAS change process changes at birth, at growth, at maturity, at revival and at decline in the life of an organization. Using a framework developed by Zoni et al (2012) the paper documents key phases and features of the management accounting change process to highlight its organizational nature in five longitudinal case studies of design and implementation of MAS changes. The field study shows how accounting systems are difficult to change despite the formally acknowledged need for change. Findings highlight that the success of change depends on how effectively organizations managed key phases in the MAS change, which in turn depends on the stage of the organization life cycle. Conclusions posit that in order to manage MAS change successfully the organization would pay more attention to the design phase at birth and at revival and more attention to the implementation phase at growth, at maturity and at decline. Furthermore, we could conclude that the main aim of MAS change spans from selection to variation of MAS along the stages of the life cycle: variations are more frequent at birth and at revival, selections are more frequent at growth and at decline stages

Association between religiosity or spirituality and internet addiction: A systematic review

Introduction: The literature provides evidence of religiosity being associated with physical and mental health, and also with behavioral addictions. This systematic review examines the data on the link between religiosity or spirituality and the emerging internet addictions. Methods: A systematic literature review was conducted in the PubMed and Scopus databases to identify observational (cross-sectional, cohort, and case-control) studies conducted on adolescents and young adults to investigate the association between religiosity or spirituality and internet addiction. Of the 854 articles identified in the databases, 13 met our inclusion criteria and were included in our systematic review. Results: Eleven of the 13 studies reviewed specifically investigated religiosity and internet addiction: six found an inverse association between religiosity and internet addiction; three found no evidence of any association; and one found a direct association. One study examining both religiosity and spirituality generated mixed results. Only one study investigated spirituality unrelated to religion, and found a direct association with internet addiction. Two of three studies specifically considering internet gaming addiction found it inversely associated with high levels of religiosity, while the third found no association. Conclusion: This review supports a possible role for religiosity as a protective factor, as emerged from the majority of the studies examined. Religiosity also seemed to be associated with lower internet gaming rates among adolescents