Ground state energies of quantum dots in high magnetic fields: A new approach

We present a new method for calculating ground state properties of quantum dots in high magnetic fields. It takes into account the equilibrium positions of electrons in a Wigner cluster to minimize the interaction energy in the high field limit. Assuming perfect spin alignment the many-body trial function is a single Slater determinant of overlapping oscillator functions from the lowest Landau level centered at and near the classical equilibrium positions. We obtain an analytic expression for the ground state energy and present numerical results for up to N=40.Comment: 4 pages, including 2 figures, contribution to the Proceedings of EP2DS-14, submitted to Physica

Transport properties of quantum dots in the Wigner molecule regime

The transport properties of quantum dots with up to N=7 electrons ranging from the weak to the strong interacting regime are investigated via the projected Hartree-Fock technique. As interactions increase radial order develops in the dot, with the formation of ring and centered-ring structures. Subsequently, angular correlations appear, signalling the formation of a Wigner molecule state. We show striking signatures of the emergence of Wigner molecules, detected in transport. In the linear regime, conductance is exponentially suppressed as the interaction strength grows. A further suppression is observed when centered-ring structures develop, or peculiar spin textures appear. In the nonlinear regime, the formation of molecular states may even lead to a conductance enhancement.Comment: 26 pages, 14 figures, Accepted for publication on New Journal of Physic

Anti-LRP/LR specific antibody IgG1-iS18 impedes adhesion and invasion of liver cancer cells.

Two key events, namely adhesion and invasion, are pivotal to the occurrence of metastasis. Importantly, the 37 kDa/67 kDa laminin receptor (LRP/LR) has been implicated in enhancing these two events thus facilitating cancer progression. In the current study, the role of LRP/LR in the adhesion and invasion of liver cancer (HUH-7) and leukaemia (K562) cells was investigated. Flow cytometry revealed that the HUH-7 cells displayed significantly higher cell surface LRP/LR levels compared to the poorly-invasive breast cancer (MCF-7) control cells, whilst the K562 cells displayed significantly lower cell surface LRP/LR levels in comparison to the MCF-7 control cells. However, Western blotting and densitometric analysis revealed that all three tumorigenic cell lines did not differ significantly with regards to total LRP/LR levels. Furthermore, treatment of liver cancer cells with anti-LRP/LR specific antibody IgG1-iS18 (0.2 mg/ml) significantly reduced the adhesive potential of cells to laminin-1 and the invasive potential of cells through the ECM-like Matrigel, whilst leukaemia cells showed no significant differences in both instances. Additionally, Pearson's correlation coefficients suggested direct proportionality between cell surface LRP/LR levels and the adhesive and invasive potential of liver cancer and leukaemia cells. These findings suggest the potential use of anti-LRP/LR specific antibody IgG1-iS18 as an alternative therapeutic tool for metastatic liver cancer through impediment of the LRP/LR- laminin-1 interaction.National Research Foundation.NCS201

Cats with diabetes mellitus have diastolic dysfunction in the absence of structural heart disease

Diabetes mellitus (DM) can result in cardiovascular dysfunction and heart failure characterized by diastolic dysfunction with or without the presence of systolic dysfunction in people and laboratory animals. The objective of this prospective study was to determine if cats with newly diagnosed DM had myocardial dysfunction and, if present, whether it would progress if appropriate antidiabetic therapy was commenced. Thirty-two diabetic cats were enrolled and received baseline echocardiographic examination; of these, 15 cats were re-examined after 6 months. Ten healthy age- and weight-matched cats served as controls. Diabetic cats at diagnosis showed decreased diastolic, but not systolic function, when compared to healthy controls, with lower mitral inflow E wave (E) and E/E' than controls. After 6 months, E and E/IVRT' decreased further in diabetic cats compared to the baseline evaluation. After excluding cats whose DM was in remission at 6 months, insulin-dependent diabetic cats had lower E, E/A and E' than controls. When classifying diastolic function according to E/A and E'/A', there was shift towards impaired relaxation patterns at 6 months. All insulin-dependent diabetic cats at 6 months had abnormal diastolic function. These results indicate that DM has similar effects on diastolic function in feline and human diabetics. The dysfunction seemed to progress rather than to normalize after 6 months, despite antidiabetic therapy. In cats with pre-existing heart disease, the development of DM could represent an important additional health risk

In Vitro Inhibition of Angiogenesis by Antibodies Directed against the 37kDa/67kDa Laminin Receptor

The 37kDa/67kDa laminin receptor (LRP/LR) is a central receptor mediating interactions between tumour cells and the basement membrane and is thereby a key player in adhesion and invasion, essential processes in metastatic cancer. To affect continued tumour growth, tumours induce angiogenesis for the constant delivery of nutrients and oxygen. This study aims to determine the blocking effect of the anti-LRP/LR specific antibody, W3 on the angiogenic potential of HUVE (human umbilical vein endothelial) cells. Flow cytometric analysis revealed that 97% of HUVE cells display cell surface LRP/LR. An angiogenesis assay was conducted employing HUVE cells seeded on the basement membrane reconstituent Matrigel™ supplemented with the pro-angiogenic factor vascular endothelial growth factor (VEGF). Post 18h incubation at 37°C tubular structures, namely tube lengths were assessed. Treatment of established tubular structures with 100 μg/ml anti-LRP/LR specific antibody completely blocked angiogenesis. Our findings suggest a central role of the 37kDa/67kDa LRP/LR in tube formation and recommends anti-LRP/LR specific antibodies as potential therapeutic tools for treatment of tumour angiogenesis.This work was supported by the National Research Foundation, the Republic of South Africa and the Medical Research Council, the Republic of South Africa.NCS201

Two ground-state modifications of quantum-dot beryllium

Exact electronic properties of a system of four Coulomb-interacting two-dimensional electrons in a parabolic confinement are reported. We show that degenerate ground states of this system are characterized by qualitatively different internal electron-electron correlations, and that the formation of Wigner molecule in the strong-interaction regime is going on in essentially different ways in these ground states.Comment: 5 pages, incl 5 Figures and 2 Table

Genome-wide transcriptomic responses of the seagrasses Zostera marina and Nanozostera noltii under a simulated heatwave confirm functional types

Genome-wide transcription analysis between related species occurring in overlapping ranges can provide insights into the molecular basis underlying different ecological niches. The co-occurring seagrass species, Zostera marina and Nanozostera noltii, are found in marine coastal environments throughout the northern hemisphere. Z. marina is often dominant in subtidal environments and subjected to fewer temperature extremes compared to the predominately intertidal and more stress-tolerant N. noltii. We exposed plants of both species to a realistic heat wave scenario in a common-stress-garden experiment. Using RNA-seq (~ 7 million reads/library), four Z. marina and four N. noltii libraries were compared representing northern (Denmark) and southern (Italy) locations within the co-occurring range of the species' European distribution. A total of 8977 expressed genes were identified, of which 78 were directly related to heat stress. As predicted, both species were negatively affected by the heat wave, but showed markedly different molecular responses. In Z. marina the heat response was similar across locations in response to the heatwave at 26 °C, with a complex response in functions related to protein folding, synthesis of ribosomal chloroplast proteins, proteins involved in cell wall modification and heat shock proteins (HSPs). In N. noltii the heat response markedly differed between locations, while HSP genes were not induced in either population. Our results suggest that as coastal seawater temperatures increase, Z. marina will disappear along its southern most ranges, whereas N. noltii will continue to move north. As a consequence, sub- and intertidal habitat partitioning may weaken in more northern regions because the higher thermal tolerance of N. noltii provides a competitive advantage in both habitats. Although previous studies have focused on HSPs, the present study clearly demonstrates that a broader examination of stress related genes is necessary

Correlation Induced Inhomogeneity in Circular Quantum Dots

Properties of the "electron gas" - in which conduction electrons interact by means of Coulomb forces but ionic potentials are neglected - change dramatically depending on the balance between kinetic energy and Coulomb repulsion. The limits are well understood. For very weak interactions (high density), the system behaves as a Fermi liquid, with delocalized electrons. In contrast, in the strongly interacting limit (low density), the electrons localize and order into a Wigner crystal phase. The physics at intermediate densities, however, remains a subject of fundamental research. Here, we study the intermediate-density electron gas confined to a circular disc, where the degree of confinement can be tuned to control the density. Using accurate quantum Monte Carlo techniques, we show that the electron-electron correlation induced by an increase of the interaction first smoothly causes rings, and then angular modulation, without any signature of a sharp transition in this density range. This suggests that inhomogeneities in a confined system, which exist even without interactions, are significantly enhanced by correlations.Comment: final version, modified introduction and clarifications, 4 page

Genotyping an Emiliania huxleyi (prymnesiophyceae) bloom event in the North Sea reveals evidence of asexual reproduction

Due to the unprecedented rate at which our climate is changing, the ultimate consequence for many species is likely to be either extinction or migration to an alternate habitat. Certain species might, however, evolve at a rate that could make them resilient to the effects of a rapidly changing environment. This scenario is most likely to apply to species that have large population sizes and rapid generation times, such that the genetic variation required for adaptive evolution can be readily supplied. Emiliania huxleyi (Lohm.) Hay and Mohler (Prymnesiophyceae) is likely to be such a species, as it is the most conspicuous extant calcareous phytoplankton species in our oceans with growth rates of 1 day−1. Here we report on a validated set of microsatellites, in conjunction with the coccolithophore morphology motif genetic marker, to genotype 93 clonal isolates collected from across the world. Of these, 52 came from a single bloom event in the North Sea collected on the D366 United Kingdom Ocean Acidification cruise in June–July 2011. There were 26 multilocus genotypes (MLGs) encountered only once in the North Sea bloom and 8 MLGs encountered twice or up to six times. Each of these repeated MLGs exhibited Psex values of less than 0.05, indicating each repeated MLG was the product of asexual reproduction and not separate meiotic events. In addition, we show that the two most polymorphic microsatellite loci, EHMS37 and P01E05, are reporting on regions likely undergoing rapid genetic drift during asexual reproduction. Despite the small sample size, there were many more repeated genotypes than previously reported for other bloom-forming phytoplankton species, including a previously genotyped E. huxleyi bloom event. This study challenges the current assumption that sexual reproduction predominates during bloom events. Whilst genetic diversity is high amongst extant populations of E. huxleyi, the root cause for this diversity and ultimate fate of these populations still requires further examination. Nonetheless, we show that certain CMM genotypes are found everywhere, while others appear to have a regional bias

Identifying core features of adaptive metabolic mechanisms for chronic heat stress attenuation contributing to systems robustness

The contribution of metabolism to heat stress may play a significant role in defining robustness and recovery of systems; either by providing the energy and metabolites required for cellular homeostasis, or through the generation of protective osmolytes. However, the mechanisms by which heat stress attenuation could be adapted through metabolic processes as a stabilizing strategy against thermal stress are still largely unclear. We address this issue through metabolomic and transcriptomic profiles for populations along a thermal cline where two seagrass species, Zostera marina and Zostera noltii, were found in close proximity. Significant changes captured by these profile comparisons could be detected, with a larger response magnitude observed in northern populations to heat stress. Sucrose, fructose, and myo-inositol were identified to be the most responsive of the 29 analyzed organic metabolites. Many key enzymes in the Calvin cycle, glycolysis and pentose phosphate pathways also showed significant differential expression. The reported comparison suggests that adaptive mechanisms are involved through metabolic pathways to dampen the impacts of heat stress, and interactions between the metabolome and proteome should be further investigated in systems biology to understand robust design features against abiotic stress