Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks

This paper investigates the performance of open-loop multi-antenna point-to-point links in ad hoc networks with slotted ALOHA medium access control (MAC). We consider spatial multiplexing transmission with linear maximum ratio combining and zero forcing receivers, as well as orthogonal space time block coded transmission. New closed-form expressions are derived for the outage probability, throughput and transmission capacity. Our results demonstrate that both the best performing scheme and the optimum number of transmit antennas depend on different network parameters, such as the node intensity and the signal-to-interference-and-noise ratio operating value. We then compare the performance to a network consisting of single-antenna devices and an idealized fully centrally coordinated MAC. These results show that multi-antenna schemes with a simple decentralized slotted ALOHA MAC can outperform even idealized single-antenna networks in various practical scenarios.Comment: 51 pages, 19 figures, submitted to IEEE Transactions on Information Theor

Asymptotic SER and Outage Probability of MIMO MRC in Correlated Fading

This letter derives the asymptotic symbol error rate (SER) and outage probability of multiple-input multiple-output (MIMO) maximum ratio combining (MRC) systems. We consider Rayleigh fading channels with both transmit and receive spatial correlation. Our results are based on new asymptotic expressions which we derive for the p.d.f. and c.d.f. of the maximum eigenvalue of positive-definite quadratic forms in complex Gaussian matrices. We prove that spatial correlation does not affect the diversity order, but that it reduces the array gain and hence increases the SER in the high SNR regime.Comment: 10 pages, 2 figures, to appear in IEEE Signal Processing Letter

Performance Analysis of MIMO-MRC in Double-Correlated Rayleigh Environments

We consider multiple-input multiple-output (MIMO) transmit beamforming systems with maximum ratio combining (MRC) receivers. The operating environment is Rayleigh-fading with both transmit and receive spatial correlation. We present exact expressions for the probability density function (p.d.f.) of the output signal-to-noise ratio (SNR), as well as the system outage probability. The results are based on explicit closed-form expressions which we derive for the p.d.f. and c.d.f. of the maximum eigenvalue of double-correlated complex Wishart matrices. For systems with two antennas at either the transmitter or the receiver, we also derive exact closed-form expressions for the symbol error rate (SER). The new expressions are used to prove that MIMO-MRC achieves the maximum available spatial diversity order, and to demonstrate the effect of spatial correlation. The analysis is validated through comparison with Monte-Carlo simulations.Comment: 25 pages. Submitted to the IEEE Transactions on Communication

Pharmacy Apps: a new frontier on the digital landscape?

Background: Over the course of recent years smartphone and tablet technology has evolved rapidly. Similarly, the sphere of healthcare is constantly developing and striving to embrace the newest forms of technology in order to optimise function. Many opportunities for mobile applications (i.e. ‘apps’) pertinent to the healthcare sector are now emerging.Objective: This study will consider whether registered pharmacists within the United Kingdom (UK) believe it appropriate to use mobile apps during the provision of healthcare within the community setting.Methods: Further to Liverpool John Moores University (LJMU) ethical approval, the 30 item questionnaire was distributed to UK registered pharmacists (n=600) practising within inner city Manchester, Liverpool and Newcastle. The questions were formatted as multiple choice, Likert scales or the open answer type. On questionnaire completion and return, data were analysed using simple frequencies, cross tabulations and non-parametric techniques in the Statistical Package for the Social Sciences (SPSS) (v18).Results: The majority of respondents (78.4% of 211 participants) confirmed that they were confident when using mobile apps on their technology platform. In general, mobile apps were perceived to be useful in facilitating patient consultations (55%) and supporting healthcare education (80%). The main barrier for mobile app use within the workplace was company policy, deemed significant in the case of regional / national chain pharmacies (p<0.001). Pharmacists alluded to the fact that whilst mobile apps demonstrate potential in modern day practise, they will have a greater impact in the future (p<0.001).Conclusion: The data indicate that although pharmacists are supportive of mobile apps in healthcare, a number of factors (i.e. risk, company policy and lack of regulation) may preclude their use in modern day pharmacy practise. Clearly, limitations of the technology must be addressed in order to maximise uptake within healthcare systems. Pharmacists suggest that as the younger generation ages, mobile apps will become a more accepted method by which to manage healthcare in the wider population

Elasticity-Dependent Self-assembly of Micro-Templated Chromonic Liquid Crystal Films

We explore micropatterned director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on square lattice cylindrical-micropost substrates. The structures are manipulated by modulating the LCLC mesophases and their elastic properties via concentration through drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films, dried from nematics, form two distinct director and defect configurations: a diagonally aligned director pattern with local squares of defects, and an off-diagonal configuration with zig-zag defects. The formation of these states appears to be tied to the relative splay and bend free energy costs of the initial nematic films. The observed nematic and columnar configurations are understood numerically using a Landau-de Gennes free energy model. Among other attributes, the work provide first examples of quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC films in general, and it demonstrates alignment and configuration switching of typically difficult-to-align LCLC films via bulk elastic properties.Comment: 9 pages; 9 figures; accepted for publication in Soft Matte

Effects of Chronic Cannabis Use on Adolescents

This literature will examine the relationship of chronic cannabis use during adolescence to psychological and morphological abnormalities into adulthood. As states continue to decriminalize or legalize cannabis consumption for recreational purposes, concerns about the potential negative effects of cannabis consumption on neurological development during adolescence may be ignored. This review examined 44 journal articles and government reports published between 1997 and 2021. The conclusions drawn from the literature review indicate that over a 19-year time span, cannabis potency has increased from ~4% to ~12%. Secondly, the chronic exposure to exogenous cannabinoids during this time can result in a variety of negative outcomes due to the dysregulation of the endocannabinoid system, one of the systems responsible for fostering brain development. Finally, the literature suggests that specific domains of worry are those of memory, attention, cognition, and emotional regulation as regions responsible for these functions are highly susceptible to alterations because of their elevated levels of CB1 receptors. Inconsistencies in terminology and parameters used to define chronic use are also addressed across all literature referenced in this review. Keywords: cannabis, marijuana, chronic use, THC, cannabinoids adolescent, development, brain, maturation, potency, dysregulatio

On the Mutual Information Distribution of OFDM-Based Spatial Multiplexing: Exact Variance and Outage Approximation

This paper considers the distribution of the mutual information of frequency-selective spatially-uncorrelated Rayleigh fading MIMO channels. Results are presented for OFDM-based spatial multiplexing. New exact closed-form expressions are derived for the variance of the mutual information. In contrast to previous results, our new expressions apply for systems with both arbitrary numbers of antennas and arbitrary-length channels. Simplified expressions are also presented for high and low SNR regimes. The analytical variance results are used to provide accurate analytical approximations for the distribution of the mutual information and the outage capacity.Comment: 18 pages, 10 figures, accepted for publication in IEEE Transactions on Information Theor