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

Report of 4 Cases and Review of the Literature

We reviewed the clinical, microbiologic, and outcome characteristics of 72 patients with human immunodeficiency virus (HIV)-associated histoplasmosis (4 newly described) reported in Europe over 20 years (1984-2004). Seven cases (9.7%) were acquired in Europe (autochthonous), whereas the majority involved a history of travel or arrival from endemic areas. The diagnosis of progressive disseminated histoplasmosis (PDH) was made during life in 63 patients (87.5%) and was the acquired immunodeficiency syndrome (AIDS)-presenting illness in 44 (61.1%). Disease was widespread in 66 patients (91.7%) and localized in 6 (8.3%), with the skin being the most frequent site of localized infection. Overall skin involvement was reported in 47.2% of the patients regardless of whether histoplasmosis was acquired in Africa or South America. Reticulonodular or diffuse interstial infiltrates occurred in 52.8%. The diagnosis was made during life by histopathology plus culture in 44 patients (69.8%), histopathology alone in 18 (28.5%), and culture alone in 1 (1.5%). During the induction phase amphotericin B and itraconazole (74.6%) were the single most frequently used drugs. Both drugs were also used either in combination (10.2%) or in sequential therapy (11.8%). Cumulative mortality rate during the induction phase of treatment was 15.2%. Overall, 37 patients died (57.8%); death occurred early in the course in 18 (28.1%). Seven of 40 patients (17.5%) who responded to therapy subsequently relapsed. Autopsy data in 13 patients confirmed the widespread disseminated nature of histoplasmosis (85%) among AIDS patients with a median of 4.5 organs involved. The results of the present report highlight the need to consider the diagnosis of PDH among patients with AIDS in Europe presenting with a febrile illness who have traveled to or who originated from an endemic area

Statistical Assessment of New Methods to Optimize the Power Flux Distribution in TV-sat Broadcasting at 20 GHz

In this paper we present the results of a statistical performance assessment of a new advanced TV-sat system operating in the ka band. The on-board transmission system is based on the idea of reconfigurable antenna, i.e. the antenna directivity can be modified so as to irradiate more power to the regions affected by bad weather. The core is a power flux distribution optimizer based on the “derivative slicing” method, whose mathematical basis is described in the companion paper [1] presented at this Conference. Here, the above technique is assessed by verifying the system performance through a statistical analysis over six-months. The simulations make use of a meteorological database provided by the European Centre for Medium-range Weather Forecasts (ECMWF). The constraints unavoidably posed by the usage of a physically realizable Beam-Forming Network (BFN) are taken into account as well. The results presented allow a preliminary assessment of the predicted advantage (in terms of availability) of an adaptive system over non-adaptive systems currently implemented, which are based on long-term climatological data. The BFN used to distribute the signal power across the service area (Europe) is constituted by a set of 8x8 multiport amplifiers, each driven by a Butler-Like Matrix (BLM), covering the area with 64 beams. The BFN excitation coefficients are refreshed every 3-6 hours, in accordance with the update rate of the input meteorological data. Our analysis shows that the number of users lost due to atmospheric effects is reduced by a factor of about 5 with respect to the case of a non-reconfigurable system fed by the same transmitted power. Morevoer, the theoretical reduction factor achievable by the "derivative slicing” method removing the system constraints (i.e. the BLM elements) would increase to 10

A novel in vivo vascular imaging approach for hierarchical quantification of vasculature using contrast enhanced micro-computed tomography

The vasculature of body tissues is continuously subject to remodeling processes originating at the micro-vascular level. The formation of new blood vessels (angiogenesis) is essential for a number of physiological and pathophysiological processes such as tissue regeneration, tumor development and the integration of artificial tissues. There are currently no time-lapsed in vivo imaging techniques providing information on the vascular network at the capillary level in a non-destructive, three-dimensional and high-resolution fashion. This paper presents a novel imaging framework based on contrast enhanced micro-computed tomography (micro-CT) for hierarchical in vivo quantification of blood vessels in mice, ranging from largest to smallest structures. The framework combines for the first time a standard morphometric approach with densitometric analysis. Validation tests showed that the method is precise and robust. Furthermore, the framework is sensitive in detecting different perfusion levels after the implementation of a murine ischemia-reperfusion model. Correlation with both histological data and micro-CT analysis of vascular corrosion casts confirmed accuracy of the method. The newly developed time-lapsed imaging approach shows high potential for in vivo monitoring of a number of different physiological and pathological conditions in angiogenesis and vascular development

Blood perfusion map of the mouse lower hind limbs 2 days after ligation of right femoral artery, obtained with laser Doppler imaging.

<p>The color bar represents blood flow (or perfusion) levels, from blue (low) to red (high). Note the much lower perfusion levels of the right (ligated) paw compared to the left (control) paw.</p

Robustness results for morphometric analysis of the lower hind limb when 50% and 100% of the standard contrast volume were injected.

<p>All assessed parameters (A) VV/TV, B) VS/TV, C) V.Th, D) V.Sp, E) V.N) exhibited significant differences between half and full dose measurements. ***p<0.001, **p<0.01. N = 7/group.</p

Reproducibility of morphometric analysis for large vessels.

<p>PE = Precision Error; ICC = Intraclass Correlation Coefficient. Assessed parameters are: VV/TV (Vessel Volume per Tissue Volume), VS/TV (Vessel Surface per Tissue Volume), V.Th (Vessel Thickness), V.Sp (Vessel Spacing), V.N (Vessel Number). N = 7.</p

Cross-sections used in the calculation of vascular density.

<p>Representative cross-sections of the reference region (neck, A–C) and the region of interest (right lower hind limb, D–F). A) Neck region pre-contrast injection. B) Neck region post-contrast injection. C) In red, mask of the region used to quantify the average X-ray absorption in blood (µ_blood). D) Lower hind limb region pre-contrast injection. E) Lower hind limb post-contrast injection. F) In green, mask of the region used to quantify the average X-ray absorption in muscle (µ_muscle). Grey (bone) and black (skin and surroundings of bone) areas were excluded from the evaluation. Numbers represent anatomical structures of interest: 1) Vertebra; 2) Trachea; 3) <i>V. jugularis</i>; 4) Tibia; 5) Fibula; 6) <i>V. poplitea</i>.</p