Importance of tetrahedral coordination for high-valent transition metal oxides: YCrO4_4 as a model system

We have investigated the electronic structure of the high oxidation state material YCrO$_4$ within the framework of the Zaanen-Sawatzky-Allen phase diagram. While Cr$^{4+}$-based compounds like SrCrO$_3$/CaCrO$_3$ and CrO$_2$ can be classified as small-gap or metallic negative-charge-transfer systems, we find using photoelectron spectroscopy that YCrO$_4$ is a robust insulator despite the fact that its Cr ions have an even higher formal valence state of 5+. We reveal using band structure calculations that the tetrahedral coordination of the Cr$^{5+}$ ions in YCrO$_4$ plays a decisive role, namely to diminish the bonding of the Cr $3d$ states with the top of the O $2p$ valence band. This finding not only explains why the charge-transfer energy remains effectively positive and the material stable, but also opens up a new route to create doped carriers with symmetries different from those of other transition-metal ions.Comment: 6 pages, 6 figure

On the Performance Analysis of WPT-based Dual-Hop AF Relaying Networks in α-μ Fading

In this paper, a two-hop amplify-and-forward relaying system, where an energy-constrained relay node entirely depends on the energy scavenged from the source signal, is investigated. This paper analyzes the performance of the energy-harvesting (EH) protocols, namely, ideal relaying receiver (IRR), power-splitting relaying (PSR) and time-switching relaying (TSR), over independent but not identically distributed (i.n.i.d.) α-μ fading channels in terms of the ergodic capacity and ergodic outage probability (OP). We derive exact unified and closed-form analytical expressions for the performance metrics with the aforementioned protocols over i.n.i.d. α-μ channels. Three fading scenarios, such as Weibull, Nakagami-m and Rayleigh channels, are investigated. Provided simulation and numerical results validate our analysis. It is demonstrated that the optimal EH time-switching and power-splitting factors of the corresponding TSR and PSR protocols are critical in achieving the best system performance. Finally, we analyzed the impact of the fading parameters α and μ on the achievable ergodic OP

More Robust Decode-and-Forward Relaying over Impulsive Noise Power Line Channels

—This paper discusses the issue of energy-efficiency in power line communication (PLC) systems and introduces decode-and-forward (DF) energy-harvesting based relaying. The performance of the proposed system is analyzed in terms of the energy efficiency for which accurate analytical expressions are derived. To highlight the achievable gains, we also evaluate the performance of both the conventional DF relaying and the directlink systems. The presented simulated results clearly demonstrate the correctness of our analysis as well as the advantage of the proposed system over the conventional relaying and direct-link approaches. Additionally, it is shown that the proposed scheme will become more energy efficient as the harvested noise energy becomes larger

For More Energy Efficient Dual-hop DF Relaying Power Line Communication Systems

Energy efficiency in multi-hop cooperative power line communication (PLC) systems has recently received considerable attention in the literature. In order to make such systems more energy-efficient, this paper proposes a relaying technique equipped with energy-harvesting capabilities. More specifically, we consider a dual-hop decode-and-forward (DF) broadband PLC relaying system in which the relay exploits the high noise inherent in PLC channels to further enhance energy efficiency; this system will be referred to as DF with energy-harvesting (DF-EH). This study deploys, particularly, the time-switching relaying protocol for energy-harvesting. An accurate analytical expression for the energy efficiency and a closed-form expression for the average outage probability of the proposed system are derived and then verified with Monte Carlo simulations. For the sake of comparison and to highlight the achievable gains, we also analyze the energy efficiency performances and the average outage probabilities of the conventional DF relaying system, i.e. without energy-harvesting, as well as that of the direct-link approach. Furthermore, various frequency selection and power allocation strategies, namely, optimal frequency selection, random frequency selection and equal power allocation, exploiting the multiple power cables, are studied. Then, the impact of several system parameters such as the energy-harvesting time factor, various idle power consumption profiles, relay location, power allocation as well as different noise scenarios are examined. The results reveal that the proposed DF-EH system is able to provide energy efficiency improvements of more than 30% compared to the conventional DF relaying scheme. It is also shown that the proposed system with optimal frequency selection performs better at low SNR whereas at high SNR the equal power allocation based system will have the best performance

Three-body correlation functions and recombination rates for bosons in three and one dimensions

We investigate local three-body correlations for bosonic particles in three and one dimensions as a function of the interaction strength. The three-body correlation function g(3) is determined by measuring the three-body recombination rate in an ultracold gas of Cs atoms. In three dimensions, we measure the dependence of g(3) on the gas parameter in a BEC, finding good agreement with the theoretical prediction accounting for beyond-mean-field effects. In one dimension, we observe a reduction of g(3) by several orders of magnitude upon increasing interactions from the weakly interacting BEC to the strongly interacting Tonks-Girardeau regime, in good agreement with predictions from the Lieb-Liniger model for all strengths of interaction.Comment: 5 figure

Outcomes of the South African National Antiretroviral Treatment Programme for children: The IeDEA Southern Africa collaboration

Objectives. To assess paediatric antiretroviral treatment (ART)outcomes and their associations from a collaborative cohortrepresenting 20% of the South African national treatment programme.Design and setting. Multi-cohort study of 7 public sectorpaediatric ART programmes in Gauteng, Western Cape andKwaZulu-Natal provinces. Subjects. ART-naive children (.16 years) who commenced treatment with .3 antiretroviral drugs before March 2008.Outcome measures. Time to death or loss to follow-up were assessed using the Kaplan-Meier method. Associations between baseline characteristics and mortality were assessed with Cox proportional hazards models stratified by site. Immune status, virological suppression and growth were described in relation to duration of ART.Results. The median (interquartile range) age of 6 078 childrenwith 9 368 child-years of follow-up was 43 (15 - 83) months, with 29% bein

Breast Milk Macronutrients in Relation to Infants’ Anthropometric Measures

BACKGROUND: Breast milk (BM) is the main nutritional source for newborns before they are capable to eat and consume other foods. BM has carbohydrates, lipids, complex proteins, and other biologically active components which have a direct effect on infant growth. AIM: The aim of the study was to correlate anthropometric data of the infant to macronutrients in BM (fat, protein, and carbohydrates) and to find some modifiable issues affecting macronutrient contents of BM for the benefits of upcoming infants. METHODS: One hundred breastfeeding mothers participated in the study, they were recruited from the outpatient clinic, El Demerdash Hospital, Ain Shams University, from September 2019, to December 2019. BM was expressed by an electric pump, macronutrient content was assessed. Anthropometric data of the babies and mothers were obtained, gestational age, parity, age of the women, and the route of birth were recorded. RESULTS: For the macronutrients content of milk, a positive significant correlation was observed between BM fat, protein, and lactose. Infants’ body mass index (BMI) was negatively related to the fat content of BM, while no relation was found between BMI and protein or lactose content of the milk. BM fat content was negatively correlated with gestational age and maternal age. Positive correlations were found between BMI and protein, lactose and infant age. Protein content was negatively correlated with parity. No impact of infant’s sex on BM composition and as regards maternal diet, high protein consumption leading to increase BM protein content. CONCLUSIONS: The current study confirms that BM macronutrient composition has a wide variability; this variability is associated with each macronutrient, respectively. To improve BM composition, one could aim for improving the nutritional balance in lactating women, especially for protein intake. More well-designed longitudinal studies about factors that influence human milk compositions are warranted

Spontaneous Rupture of Malarial Spleen: Report of Two Cases

Malaria is endemic in many tropical and subtropical regions of the world, including Saudi Arabia. The infection has serious consequences in those residing in non endemic regions on travelling to endemic areas, due to lack of immunity to the parasite. In this report, we describe the clinical course of two patients who travelled to a malaria endemic area. Both contracted the infection and presented with splenic rupture. They received splenectomy in addition to the appropriate antimalarial medications, with successful outcome