Physicians as Fundraisers: Medical Philanthropy and the Doctor-Patient Relationship

Lisa Lehmann and colleagues discuss how “grateful patient” programs that solicit donations from wealthy individuals who receive care may be problematic for physicians and propose policies that mitigate these risks. Please see later in the article for the Editors' Summar

Distributed algorithms for spectral and energy-efficiency maximization of K-user interference channels

In this paper, we propose a cooperative distributed framework to optimize a variety of rate and energy-efficiency (EE) utility functions, such as the minimum-weighted rate or the global EE, for the K-user interference channel. We focus on the single-input multiple-output (SIMO) case, where each user, based solely on local channel state information (CSI) and limited exchange information from other users, optimizes its transmit power and receive beamformer, although the framework can also be extended to the multiple-output multiple-input (MIMO) case. The distributed framework combines an alternating optimization approach with majorization-minimization (MM) techniques, thus ensuring convergence to a stationary point of the centralized cost function. Closed-form power update rules are obtained for some utility functions, thus obtaining very fast convergence algorithms. The receivers treat interference as noise (TIN) and apply the beamformers that maximize the signal-to-interference-plus-noise (SINR). The proposed cooperative distributed algorithms are robust against channel variations and network topology changes and, as our simulation results suggest, they perform close to the centralized solution that requires global CSI. As a benchmark, we also study a non-cooperative distributed framework based on the so-called "signal-to-leakage-plus-noise ratio" (SNLR) that further reduces the overhead of the cooperative version.The work of Ignacio Santamaria was supported in part by the Ministerio de Ciencia e Innovación (Gobierno de España) / Agencia Española de Investigación (AEI) / FEDER funds of the European Union (EU) under Grant PID2019-104958RB-C43 (ADELE)

Improper Gaussian signaling for the K-user MIMO interference channels with hardware impairments

This paper investigates the performance of improper Gaussian signaling (IGS) for the K-user multiple-input, multiple-output (MIMO) interference channel (IC) with hardware impairments (HWI). HWI may arise due to imperfections in the devices like I/Q imbalance, phase noise, etc. With I/Q imbalance, the received signal is a widely linear transformation of the transmitted signal and noise. Thus, the effective noise at the receivers becomes improper, which means that its real and imaginary parts are correlated and/or have unequal powers. IGS can improve system performance with improper noise and/or improper interference. In this paper, we study the benefits of IGS for this scenario in terms of two performance metrics: achievable rate and energy efficiency (EE). We consider the rate region, the sum-rate, the EE region and the global EE optimization problems to fully evaluate the IGS performance. To solve these non-convex problems, we employ an optimization framework based on majorization-minimization algorithms, which allow us to obtain a stationary point of any optimization problem in which either the objective function and/or constraints are linear functions of rates. Our numerical results show that IGS can significantly improve the performance of the K-user MIMO IC with HWI and I/Q imbalance, where its benefits increase with the number of users, K, and the imbalance level, and decrease with the number of antennas.The work of Mohammad Soleymani and Peter J. Schreier was supported by the German Research Foundation (DFG) under Grant SCHR 1384/8-1. The work of Ignacio Santamaria was supported in part by Ministerio de Ciencia e Innovacion of Spain, and in part by AEI/FEDER funds of the E.U. under Grants TEC2016-75067-C4-4-R (CARMEN) and PID2019-104958RB-C43 (ADELE)

Transient cooling of a lithium-ion battery module during high-performance driving cycles using distributed pipes - A numerical investigation

Transient effects are often excluded from the design and analysis of battery thermal management systems (BTMS). However, electric vehicles are subjected to significant dynamic loads causing transient battery heating that is not encountered in a steady state. To evaluate the significance of such effects, this paper presents a time-dependent analysis of the battery cooling process, based on an existing cooling system that satisfactorily operates in steady conditions. To resemble realistic conditions, the temporal variations in the battery power withdrawal are inferred from different standard driving cycles. Computational fluid dynamics is then utilized to predict the coolant and battery temperatures inside a battery module for a period of 900 s. It is shown that, for air cooling, the batteries temperature can exceed the safe limit. For example, in a high-performance driving cycle, after 200 s, the battery temperature goes beyond the critical value of 308 K. Nonetheless, the temperatures are always within the safe region when liquid is used to cool the battery module. Also, during a high-performance cycle where the flow rate is 1.230 g/s, the battery temperature decreased below the critical threshold and reached 304 K. In addition, to maintain the temperature of the batteries below the critical threshold during NYCC traffic and US06 driving cycles, a maximum coolant pressure inlet of 1.52 and 0.848 g/s, equivalent to 100 Pa and 50 Pa, respectively, are required. The temporal changes in Nusselt number distribution over the battery module, induced by the acceleration of the vehicle during the driving cycles, are also discussed. It is concluded that the assumption of a steady state might lead to the non-optimal design of BTMSs

Eating disorder-specific rumination moderates the association between attentional bias to high-calorie foods and eating disorder symptoms:Evidence from a reliable free-viewing eye-tracking task

Cognitive theories of eating disorders implicate Attentional Bias (AB) towards food-related information in the development and maintenance of eating disorders. Empirical evidence for this proposal, however, has been inconsistent, and the measures used to examine AB to food-related stimuli typically showed poor reliability. The aim of the current study was twofold. Firstly, we aimed to examine the psychometric properties of a newly devised eye-tracking task for the assessment of AB in the context of eating disorders. Secondly, we examined the role of Eating Disorder-specific (ED-specific) rumination as a potential moderator of the association between attentional bias to food images and eating disorder symptoms. One hundred and three female students were recruited and completed an eye-tracking task comprising 21 matrices that each contained 8 low-calorie and 8 high-calorie food images. Each matrix was presented for 6 s. First fixation location, first fixation latency, and total dwell time were assessed for low and high-calorie food images and the dwell-time based AB measure showed good reliability based on Cronbach's alpha, McDonald's Omega, and split-half method. In addition, the results revealed that the ED-specific rumination plays the hypothesized moderating role. Specifically, while participants with high levels of ED-specific rumination exhibited a positive association between AB to high-calorie foods and eating disorder symptoms, this association was not present among participants with lower levels of ED-specific rumination. The employed free-viewing task seems a reliable measure of AB to food-related stimuli, and the moderation analysis emphasizes the critical role of ED-specific rumination for eating disorder symptoms. Implications, limitations, and directions for future research are discussed

Free-viewing multi-stimulus eye tracking task to index attention bias for alcohol versus soda cues:Satisfactory reliability and criterion validity

Cognitive -motivational models point to attention bias (AB) as an important factor in the persistence of problematic drinking behavior. Unfortunately, the measures that have been used to examine AB in addiction typically showed poor psychometric properties. To bring research on AB a critical step further it would be crucial to develop tasks with acceptable reliability and construct validity. Recently, Lazarov and colleagues (2016) developed a multi-stimulus free-viewing task (participants were free to look at any part of the screen and there was no secondary task involved) that showed excellent psychometric properties in the context of social anxiety as well as depression. We, therefore, adapted this task and examined its psychometric quality within the context of alcohol use. Participants with varying levels of alcohol use (N = 100) were presented with 54 matrices each containing 8 alcoholic and 8 non-alcoholic drinks. Each matrix was presented for 6 s. First fixation (100 ms) location and latency and total dwell time were assessed for alcohol and soda pictures. Assessment of AB, craving, and alcohol use (problems) was repeated after 3–8 days. Specifically, the dwell-time based AB-measure showed excellent internal reliability and considerable stability. Supporting the validity of the current AB-measures, it was found that participants with higher scores on craving and alcohol problems (i) dwelt longer on alcohol stimuli, and (ii) more often showed a first fixation on alcohol, whereas (iii) stronger craving was associated with shorter latency of first alcohol fixations. The AB-measure showed promising psychometric properties. Thus, this free-viewing eye-tracking task seems a welcome new tool for being used in future research on AB in addiction

Rate region of the K-user MIMO interference channel with imperfect transmitters

This paper studies the rate region of a multiple-input, multiple-output (MIMO) system with imperfect transmitters when interference is treated as noise at the receiver side. We consider a K-user MIMO interference channel (IC) in which the transmitters suffer from an additive hardware distortion (HWD) modeled as spatially uncorrelated Gaussian noise with covariance matrix proportional to the transmit covariance matrix. We employ the difference of convex programming (DCP) technique to solve the rate-region optimization problem and obtain its stationary points. Our proposed HWD-aware algorithm outperforms the HWD-unaware design that disregards HWD. Our results show that the performance of the K-user MIMO IC is highly affected by HWD, especially in high signal-to-noise-ratio scenarios.The work of M. soleymani and P. J. Schreier was supported by the German Research Foundation (DFG) under grants SCHR 1384/7-1 and SCHR 1384/8-1. The work of I. Santamaria was supported by the Ministerio de Economia y Competitividad (MINECO) and AEI/FEDER funds of the UE, Spain, under projects CARMEN (TEC2016-75067-C4-4-R) and PID2019-104958RB-C43 (ADELE)

Improper signaling for OFDM underlay cognitive radio systems

Improper signaling, where real and imaginary parts of the transmit signal are correlated and/or have unequal power, has received a lot of attention lately because it has been shown to increase achievable rates in many interference-limited communication systems. In this paper, we study whether improper signaling can also benefit an orthogonal frequency-division multiplexing (OFDM) underlay cognitive radio (UCR) system. We assume that the primary user (PU) transmits proper signals, while the secondary user (SU) is allowed to employ improper signaling. We consider two different rate constraints for the rate of the PU: i) the total rate of the PU, and ii) the rate of the PU in each subband. We propose an algorithm to implement improper signaling for each constraint. In both cases, we show that the benefits of improper signaling are relatively small and decrease rapidly with increasing number of subbands. This rather negative result shows that the use of improper signaling in interference scenarios needs to be justified on a case-by-case basis.The work of M. Soleymani, C. Lameiro and P. J. Schreier was supported by the German Research Foundation (DFG) under grants LA 4107/1-1 and SCHR 1384/8-1. The work of I. SantamarÍa has been partially supported by MINECO of Spain and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN)