Prognostic Value of the Persistence or Change in Pericardial Effusion Status on Serial Echocardiograms in Pulmonary Arterial Hypertension

Background: Pericardial effusion in pulmonary arterial hypertension (PAH) is an indicator of right heart failure and a marker of poor prognosis; its significance on serial transthoracic echocardiograms (TTE) is not clear. Methods: We examined our database for PAH patients followed at our center (10/99-11/07). Baseline and follow-up TTE (1.0±0.5y) and outcomes were studied (N=200). The presence of pericardial effusion was evaluated at baseline and follow-up. The persistence or change in pericardial effusion status was categorized into four categories. Kaplan Meier methods were used to estimate survival functions of the various categories. Cox proportional hazards modeling was used to adjust for other covariates and identify independent predictors. Results: Over a mean follow-up of 4.6 ± 2.6 y, 53% (n=106) patients died. Pericardial effusion was present in 20% (n=40) at baseline and 22% (n=44) during follow up. Patients with pericardial effusion at baseline or follow-up had significantly higher creatinine, pulmonary vascular resistance, lower cardiac output, and were more likely to be treated with prostanoids. During follow-up, there was significantly increased prostanoids (58% vs. 28%) and combination therapy (8% vs. 2%) use compared to baseline. New or persistence of pericardial effusion was associated with worse outcomes (p<0.001) and an independent predictor of survival after adjusting for age, creatinine, sodium, cardiac output, mean right atrial pressure, New York Heart Association (NYHA ) functional class, and presence of connective tissue disease as the etiology of PAH (p-value<0.001). Conclusion: New or persistent pericardial effusion in PAH despite vasoactive therapy predicts worse outcomes; absence or resolution of pericardial effusion with therapy suggests better prognosis. Its public health significance is the ability to identify patients that may benefit from closer follow-up for reassessment and consideration of more aggressive medical therapy or referral for lung transplant to prevent worsening health and/or death

Detection and accurate localization of harmonic chipless tags

We investigate the detection and localization properties of harmonic tags working at microwave frequencies. A two-tone interrogation signal and a dedicated signal processing scheme at the receiver are proposed to eliminate phase ambiguities caused by the short signal wavelength and to provide accurate distance/position estimation even in the presence of clutter and multipath. The theoretical limits on tag detection and localization accuracy are investigated starting from a concise characterization of harmonic backscattered signals. Numerical results show that accuracies in the order of centimeters are feasible within an operational range of a few meters in the RFID UHF band

Statistics of the MLE and Approximate Upper and Lower Bounds - Part 2: Threshold Computation and Optimal Signal Design

Threshold and ambiguity phenomena are studied in Part 1 of this work where approximations for the mean-squared-error (MSE) of the maximum likelihood estimator are proposed using the method of interval estimation (MIE), and where approximate upper and lower bounds are derived. In this part we consider time-of-arrival estimation and we employ the MIE to derive closed-form expressions of the begin-ambiguity, end-ambiguity and asymptotic signal-to-noise ratio (SNR) thresholds with respect to some features of the transmitted signal. Both baseband and passband pulses are considered. We prove that the begin-ambiguity threshold depends only on the shape of the envelope of the ACR, whereas the end-ambiguity and asymptotic thresholds only on the shape of the ACR. We exploit the results on the begin-ambiguity and asymptotic thresholds to optimize, with respect to the available SNR, the pulse that achieves the minimum attainable MSE. The results of this paper are valid for various estimation problems

Communicating with Large Intelligent Surfaces: Fundamental Limits and Models

This paper analyzes the optimal communication involving large intelligent surfaces (LIS) starting from electromagnetic arguments. Since the numerical solution of the corresponding eigenfunctions problem is in general computationally prohibitive, simple but accurate analytical expressions for the link gain and available spatial degrees-of-freedom (DoF) are derived. It is shown that the achievable DoF and gain offered by the wireless link are determined only by geometric factors, and that the classical Friis' formula is no longer valid in this scenario where the transmitter and receiver could operate in the near-field regime. Furthermore, results indicate that, contrarily to classical MIMO systems, when using LIS-based antennas DoF larger than 1 can be exploited even in strong line-of-sight (LOS) channel conditions, which corresponds to a significant increase in spatial capacity density, especially when working at millimeter waves.Comment: Presented in part at thge IEEE International Conference on Communications (ICC), 2020. In publication on IEEE Journal on Selected Areas in Communications, Special issue on Wireless Networks Empowered by Reconfigurable Intelligent Surfaces, 2020 (IEEE JSAC, Nov 2020

Statistics of the MLE and Approximate Upper and Lower Bounds - Part 1: Application to TOA Estimation

In nonlinear deterministic parameter estimation, the maximum likelihood estimator (MLE) is unable to attain the Cramer-Rao lower bound at low and medium signal-to-noise ratios (SNR) due the threshold and ambiguity phenomena. In order to evaluate the achieved mean-squared-error (MSE) at those SNR levels, we propose new MSE approximations (MSEA) and an approximate upper bound by using the method of interval estimation (MIE). The mean and the distribution of the MLE are approximated as well. The MIE consists in splitting the a priori domain of the unknown parameter into intervals and computing the statistics of the estimator in each interval. Also, we derive an approximate lower bound (ALB) based on the Taylor series expansion of noise and an ALB family by employing the binary detection principle. The accurateness of the proposed MSEAs and the tightness of the derived approximate bounds are validated by considering the example of time-of-arrival estimation

The Political-Economy of RECONSTRUCT to Urban Post-Conflict Reconstruction: The Case of Jobar

This thesis aims to understand the failures in traditional approaches to urban post-conflict reconstruction, assess them from a political economy perspective, and compare them with the bottom-up and participatory RECONSTRUCT approach developed by the Università Iuav di Venezia. The dissertation learns from the mistakes of top-down reconstruction approaches in Beirut, Mosul, and Kabul to argue that a RECONSTRUCT framework that takes into consideration political economy dynamics can help achieve social cohesion and economic empowerment in post-conflict settings. These case studies aim to explain where top-down reconstruction failed in achieving sustainability and inclusiveness, and how this kept those cities vulnerable to relapse to conflict. The Syrian government is preparing for a highly centralised, exclusive, top-down, and unaffordable urban planning approach in the Jobar town in northeast Damascus and elsewhere in government-controlled provinces. This approach does not represent local communities that remained or were forced into displacement. As such, RECONSTRUCT is proposed as an approach to revive the fully-destroyed town and help achieve much-needed social cohesion and peace, while being affordable and driven by the local community. However, RECONSTRUCT lacks a political economy framework. Therefore, the thesis aims to build on RECONSTRUCT while taking into consideration the political economy of Jobar. The aim of the political economy framework is to understand the diverse challenges facing the proposed classical reconstruction approach set forth by the central government without any community consultation or consideration of demographic changes due to displacement and the economic fabric damage that took place during the past decade. The thesis concludes that RECONSTRUCT is affordable because it is owned and driven by the people. It is also a reflection of local communities’ histories and cultures. The research aims to contribute to literature on reconstruction by explaining the shortfalls of traditional approaches, proposing RECONSTRUCT as an alternative approach for a more inclusive and sustainable approach to urban revival, and introducing a political economy framework to that approach. It also aims to make RECONSTRUCT more relevant and viable as a policy option for reconstruction, and not just a technical process

Direct position estimation from wavefront curvature with single antenna array

In this paper we investigate the possibility to perform direct positioning by retrieving information from the wavefront curvature. Despite such an approach has been considered in the past at microwave and acoustic frequencies using extremely large antennas, it is of interest to investigate its potential exploitation at mm-wave with practical size antennas in the context of next 5G systems. Thus, here we first consider a dedicated model to gather the source position information from the wavefront curvature for different array architectures, i.e., traditional and lens-based arrays, and successively we derive the maximum likelihood estimator to investigate the attainable performance. Results, obtained for different number of antennas, i.e., for different array apertures, confirm the possibility to achieve interesting positioning performance using a single antenna array with limited dimensions

Communication Modes with Large Intelligent Surfaces in the near Field

This paper proposes a practical method for the definition of communication modes when antennas operate in the near-field region, by realizing ad-hoc beams exploiting the focusing capability of large antennas. The beamspace modeling proposed to define the communication modes is then exploited to derive expressions for their number (i.e., the degrees of freedom) in a generic setup, beyond the traditional paraxial scenario, together with closed-form definitions for the basis set at the transmitting and receiving antennas for several cases of interest, such as for the communication between a large antenna and a small antenna. Numerical results show that quasi-optimal communication can be obtained starting from focusing functions. This translates into the possibility of a significant enhancement of the channel capacity even in line-of-sight channel condition, without the need of implementing optimal but complex phase/amplitude profiles on transmitting/receiving antennas as well as resorting to intensive numerical solutions. Traditional results valid under paraxial approximation are revised in light of the proposed modeling, showing that similar conclusions can be obtained from different perspectives

Time Domain Measurements of Signals Backscattered by Wideband RFID Tags

Passive wideband RFID is increasing interest for its capability of providing high-accuracy tag localization in addition to identification and tag-reader communication. The measurement of backscattering capabilities of wideband antennas is usually conducted in the frequency domain by using network analyzers, which does not allow for the extraction of the antenna mode component of the backscattered signal when the antenna load is time variant. To overcome this issue, in this paper we present a novel setup for time domain measurements of signals backscattered by wideband RFID tags. Experimental evaluations are presented for comparing different wideband antennas and show the effects of the setup characteristics and of the processing schemes on the achievable measurement results