Singlet-triplet splitting, correlation and entanglement of two electrons in quantum dot molecules

Starting with an accurate pseudopotential description of the single-particle states, and following by configuration-interaction treatment of correlated electrons in vertically coupled, self-assembled InAs/GaAs quantum dot-molecules, we show how simpler, popularly-practiced approximations, depict the basic physical characteristics including the singlet-triplet splitting, degree of entanglement (DOE) and correlation. The mean-field-like single-configuration approaches such as Hartree-Fock and local spin density, lacking correlation, incorrectly identify the ground state symmetry and give inaccurate values for the singlet-triplet splitting and the DOE. The Hubbard model gives qualitatively correct results for the ground state symmetry and singlet-triplet splitting, but produces significant errors in the DOE because it ignores the fact that the strain is asymmetric even if the dots within a molecule are identical. Finally, the Heisenberg model gives qualitatively correct ground state symmetry and singlet-triplet splitting only for rather large inter-dot separations, but it greatly overestimates the DOE as a consequence of ignoring the electron double occupancy effect.Comment: 13 pages, 9 figures. To appear in Phys. Rev.

Impact of Plant-Based Meat Alternatives on the Gut Microbiota of Consumers: A Real-World Study

Eating less meat is increasingly seen as a healthier, more ethical option. This is leading to growing numbers of flexitarian consumers looking for plant-based meat alternatives (PBMAs) to replace at least some of the animal meat they consume. Popular PBMA products amongst flexitarians, including plant-based mince, burgers, sausages and meatballs, are often perceived as low-quality, ultra-processed foods. However, we argue that the mere industrial processing of ingredients of plant origin does not make a PBMA product ultra-processed by default. To test our hypothesis, we conducted a randomised controlled trial to assess the changes to the gut microbiota of a group of 20 participants who replaced several meat-containing meals per week with meals cooked with PBMA products and compared these changes to those experienced by a size-matched control. Stool samples were subjected to 16S rRNA sequencing. The resulting raw data was analysed in a compositionality-aware manner, using a range of innovative bioinformatic methods. Noteworthy changes included an increase in butyrate metabolising potential—chiefly in the 4-aminobutyrate/succinate and glutarate pathways—and in the joint abundance of butyrate-producing taxa in the intervention group compared to control. We also observed a decrease in the Tenericutes phylum in the intervention group and an increase in the control group. Based on our findings, we concluded that the occasional replacement of animal meat with PBMA products seen in flexitarian dietary patterns can promote positive changes in the gut microbiome of consumers

Electric field control and optical signature of entanglement in quantum dot molecules

The degree of entanglement of an electron with a hole in a vertically coupled self-assembled dot molecule is shown to be tunable by an external electric field. Using atomistic pseudopotential calculations followed by a configuration interaction many-body treatment of correlations, we calculate the electronic states, degree of entanglement and optical absorption. We offer a novel way to spectroscopically detect the magnitude of electric field needed to maximize the entanglement.Comment: 4 pages, 6 figure

Shotgun Metagenomic Sequencing Revealed the Prebiotic Potential of a Fruit Juice Drink with Fermentable Fibres in Healthy Humans

Fibre-based dietary interventions are at the forefront of gut microbiome modulation research, with a wealth of 16S rRNA information to demonstrate the prebiotic effects of isolated fibres. However, there is a distinct lack of data relating to the effect of a combination of soluble and insoluble fibres in a convenient-to-consume fruit juice food matrix on gut microbiota structure, diversity, and function. Here, we aimed to determine the impact of the MOJU Prebiotic Shot, an apple, lemon, ginger, and raspberry fruit juice drink blend containing chicory inulin, baobab, golden kiwi, and green banana powders, on gut microbiota structure and function. Healthy adults (n = 20) were included in a randomised, double-blind, placebo-controlled, cross-over study, receiving 60 mL MOJU Prebiotic Shot or placebo (without the fibre mix) for 3 weeks with a 3-week washout period between interventions. Shotgun metagenomics revealed significant between-group differences in alpha and beta diversity. In addition, the relative abundance of the phyla Actinobacteria and Desulfobacteria was significantly increased as a result of the prebiotic intervention. Nine species were observed to be differentially abundant (uncorrected p-value of <0.05) as a result of the prebiotic treatment. Of these, Bifidobacterium adolescentis and CAG-81 sp900066785 (Lachnospiraceae) were present at increased abundance relative to baseline. Additionally, KEGG analysis showed an increased abundance in pathways associated with arginine biosynthesis and phenylacetate degradation during the prebiotic treatment. Our results show the effects of the daily consumption of 60 mL MOJU Prebiotic Shot for 3 weeks and provide insight into the functional potential of B. adolescentis

Interatomic potentials for the vibrational properties of III-V semiconductor nanostructures

We derive interatomic potentials for zinc blende InAs, InP, GaAs and GaP semiconductors with possible applications in the realm of nanostructures. The potentials include bond stretching interaction between the nearest and next-nearest neighbors, a three body term and a long-range Coulomb interaction. The optimized potential parameters are obtained by (i) fitting to bulk phonon dispersions and elastic properties and (ii) constraining the parameter space to deliver well behaved potentials for the structural relaxation and vibrational properties of nanostructure clusters. The targets are thereby calculated by density functional theory for clusters of up to 633 atoms. We illustrate the new capability by the calculation Kleinman and Gr\"uneisen parameters and of the vibrational properties of nanostructures with 3 to 5.5 nm diameter.Comment: 22 pages, 5 figures; Phys. Rev. B 201

Linkage study of the low-density lipoprotein-receptor gene and cholesterol levels in an Afrikaner family : quantitative genetics and identification of a minor founder effect

CITATION: Brink, P. A. et al. 1990. Linkage study of the low-density lipoprotein-receptor gene and cholesterol levels in an Afrikaner family : quantitative genetics and identification of a minor founder effect. South African Medical Journal, 77:292-296.The original publication is available at http://www.samj.org.zaOverlap of clinical and biochemical characteristics between hypercholesterolaemia in members of the general population and familial hypercholesterolaemic (FH) individuals may lead to misdiagnosis. Quantitative analyisis of family data may circumvent this problem. A way of looking for an association between plasma cholesterol levels and restriction fragment length polymorphism markers (RFLP) on the low-density lipoprotein (LDL) receptor gene by using reference cholesterol distributions was explored. Linkage, with a logarithm of the odds (LOD) score of 6,8 at θ 0, was detected between cholesterol levels and the LDL receptor in an extended Afrikaner family. Two RFLP-haplotypes, one previously found in a majority of Afrikaner FH homozygotes, and a second, Stu I -, BstE II +, Pvu II +, Nco I +, were associated with high cholesterol levels in this pedigree.Publisher’s versio

Influence of the charge carrier tunneling processes on the recombination dynamics in single lateral quantum dot molecules

We report on the charge carrier dynamics in single lateral quantum dot molecules and the effect of an applied electric field on the molecular states. Controllable electron tunneling manifests itself in a deviation from the typical excitonic decay behavior which is strongly influenced by the tuning electric field and inter-molecular Coulomb energies. A rate equation model is developed to gain more insight into the charge transfer and tunneling mechanisms. Non-resonant (phonon-mediated) electron tunneling which changes the molecular exciton character from direct to indirect, and vice versa, is found to be the dominant tunable decay mechanism of excitons besides radiative recombination.Comment: 4 pages, 4 figure

Light filtered concentrated photovoltaic thermal system

Abstract: PV cells generate electricity, but the electrical output is only one component of the total energy produced by a photovoltaic array. A typical PV module has an ideal conversion efficiency of around ±15%, with the remaining energy generated as heat. This heat can raise the temperature by as much as 50°C above ambient temperature, resulting in two concerns: possible structural damage; and PV cell efficiency decreases as temperature increases. Crystalline cells are affected by temperature and their performance drops as cell temperature rises. In the case of combined photovoltaic thermal cells it has been shown that for each 1°C increase in temperature, the power output drops by approximately 0.5% which results in limiting the harvested energy This article aims to introduce the concept of a concentrated Photovoltaic thermal system using an optical filtering technique. To this end concentrated sunlight is filtered into its major components and then utilised in a more appropriate way. The visible light is directed onto a standard PV surface while infrared is filtered before striking the PV surface and directed to a water column for heating purposes