Many-Body Approaches to Quantum Dots

In this thesis, we studied numerically systems consisting of several interacting electrons in two-dimensions, confi ned to small regions between layers of semiconductors. These arti cially fabricated electron systems are dubbed quantum dots in the literature. Quantum dots provide a new challenge to theoretical calculations of their properties using many-body methods. The size of these arti cial atoms is several orders of magnitude larger than that of atoms, leading to a much greater sensitivity to magnetic fields. The full many-body problem of quantum dots is truly complex and simulating a quantum dot constrained by a magnetic field may be even more complicated. Of particular interest is the reliability of the Hartree-Fock (HF) method for studies of quantum dots in two-dimensions as a function of the external magnetic field. In order to achieve this goal, we developed a Hartree-Fock code for electrons trapped in a single harmonic oscillator potential in two-dimensions. We also developed a code implementing many-body perturbation theory (MBPT) up to third order either directly applied to the harmonic oscillator basis or as a correction to the Hartree-Fock energy. A discussion of the results compared with large-scale diagonalisation methods indicated a quadractic error growth of HF and MBPT as the interaction strength increases. We tested also the reliability of a single Slater determinant approximation for the ground state of closed shell systems as a function of varying interaction strength. We found that the Hartree-Fock method, compared with large-scale diagonalization methods, has a limited range of applicability as function of the interaction strength and increasing number of eletrons in the dot, indicating a break of the computational technique before entering the limit of validity of the closed-shell model. Our study also showed that the HF approximation might become less accurate compared to MBPT as the number of electrons in the dot increases

Improved health, welfare and viability in young pigs: general information and legislation

This factsheet provides an overview of EU organic regulations that aim to ensure piglet health in organic pigs. Additionally, it presents the results of the Core Organic Cofund project POWER on the impact of improvement of health and reduction of mortality in piglets on animal welfare and the environment

Improved health, welfare and viability in young pigs: oral iron supply in neonatal piglets to avoid anaemia

This factsheet evaluates strategies of iron supplementation to avoid anaemia and reduce piglet mortality and health problems. Additionally, it presents the results of the Core Organic Cofund project POWER on iron supplementation’s relevance for animal welfare and its environmental impact

Rap1 controls cell adhesion and cell motility through the regulation of myosin II

We have investigated the role of Rap1 in controlling chemotaxis and cell adhesion in Dictyostelium discoideum. Rap1 is activated rapidly in response to chemoattractant stimulation, and activated Rap1 is preferentially found at the leading edge of chemotaxing cells. Cells expressing constitutively active Rap1 are highly adhesive and exhibit strong chemotaxis defects, which are partially caused by an inability to spatially and temporally regulate myosin assembly and disassembly. We demonstrate that the kinase Phg2, a putative Rap1 effector, colocalizes with Rap1–guanosine triphosphate at the leading edge and is required in an in vitro assay for myosin II phosphorylation, which disassembles myosin II and facilitates filamentous actin–mediated leading edge protrusion. We suggest that Rap1/Phg2 plays a role in controlling leading edge myosin II disassembly while passively allowing myosin II assembly along the lateral sides and posterior of the cell

Surgical Management of Ovarian Endometrioma: Impact on Ovarian Reserve Parameters and Reproductive Outcomes

Ovarian endometriomas have a negative impact on a patient’s reproductive potential and are likely to cause a reduction in ovarian reserve. The most commonly employed ovarian reserve parameters are anti-Müllerian hormone (AMH) and antral follicular count (AFC). Surgical management options of endometrioma include cystectomy, ablative methods, ethanol sclerotherapy and combined techniques. The optimal surgical approach remains a matter of debate. Our review aimed to summarize the literature on the impact of surgical management of endometrioma on AMH, AFC and fertility outcomes. Cystectomy may reduce recurrence rates and increase chances of spontaneous conception. However, a postoperative reduction in AMH is to be anticipated, despite there being evidence of recovery during follow-up. The reduction in ovarian reserve is likely multi-factorial. Cystectomy does not appear to significantly reduce, and may even increase, AFC. Ablative methods achieve an ovarian-tissue-sparing effect, and improved ovarian reserve, compared to cystectomy, has been demonstrated. A single study reported on AMH and AFC post sclerotherapy, and both were significantly reduced. AMH levels may be useful in predicting the chances of conception postoperatively. None of the aforementioned approaches has a clearly demonstrated superiority in terms of overall chances of conception. Surgical management of endometrioma may, overall, improve the probability of pregnancy. Evidence on its value before medically assisted reproduction (MAR) is conflicting; however, a combination of surgery followed by MAR may achieve the optimal fertility outcome. In view of the complexity of available evidence, individualization of care, combined with optimal surgical technique, is highly recommended

Vacuolar iron stores gated by NRAMP3 and NRAMP4 are the primary source of iron in germinating seeds

During seed germination, iron (Fe) stored in vacuoles is exported by the redundant NRAMP3 and NRAMP4 transporter proteins. A double nramp3 nramp4 mutant is unable to mobilize Fe stores and does not develop in the absence of external Fe. We used RNA sequencing to compare gene expression in nramp3 nramp4 and wild type during germination and early seedling development. Even though sufficient Fe was supplied, the Fe-responsive transcription factors bHLH38, 39, 100, and 101 and their downstream targets FRO2 and IRT1 mediating Fe uptake were strongly upregulated in the nramp3 nramp4 mutant. Activation of the Fe deficiency response was confirmed by increased ferric chelate reductase activity in the mutant. At early stages, genes important for chloroplast redox control (FSD1 and SAPX), Fe homeostasis (FER1 and SUFB), and chlorophyll metabolism (HEMA1 and NYC1) were downregulated, indicating limited Fe availability in plastids. In contrast, expression of FRO3, encoding a ferric reductase involved in Fe import into the mitochondria, was maintained, and Fe-dependent enzymes in the mitochondria were unaffected in nramp3 nramp4. Together, these data show that a failure to mobilize Fe stores during germination triggered Fe deficiency responses and strongly affected plastids, but not mitochondria

The fecal microbiota of piglets during weaning transition and its association with piglet growth across various farm environments

This study describes the fecal microbiota from piglets reared in different living environments during the weaning transition, and presents the characteristics of microbiota associated with good growth of piglets after weaning. Fecal samples were collected pre- (d26) and post-weaning (d35) from 288 male piglets in 16 conventional indoor commercial farms located in the West of France. The changes one week after weaning on the most abundant microbial families was roughly the same in all farms: alpha diversity increased, the relative abundance of Bacteroidaceae (-61%), Christensenellaceae (-35%), Enterobacteriaceae (-42%), and Clostridiaceae (-32%) decreased, while the relative abundance of Prevotellaceae (+143%) and Lachnospiraceae (+21%) increased. Among all the collected samples, four enterotypes that were ubiquitous in all farms were identified. They could be discriminated by their respective relative abundances of Prevotella, Faecalibacterium, Roseburia, and Lachnospira, and likely corresponded to a gradual maturational shift from pre- to post-weaning microbiota. The rearing environment influenced the frequency of enterotypes, as well as the relative abundance of 6 families at d26 (including Christensenellaceae and Lactobacillaceae), and of 21 families at d35. In all farms, piglets showing the highest relative growth rate during the first three weeks after weaning, which were characterized as more robust, had a higher relative abundance of Bacteroidetes, a lower relative abundance of Proteobacteria, and showed a greater increase in Prevotella, Coprococcus, and Lachnospira in the post-weaning period. This study revealed the presence of ubiquitous enterotypes among the farms of this study, reflecting maturational stages of microbiota from a young suckling to an older cereal-eating profile. Despite significant variation in the microbial profile between farms, piglets whose growth after weaning was less disrupted were, those who had reached the more mature phenotype characterized by Prevotella the fastest

Exposure to environmental stressors result in increased viral load and further reduction of production parameters in pigs experimentally infected with PCV2b

Porcine circovirus type 2 (PCV2) has been identified as the essential, but not sole, underlying infectious component for PCV-associated diseases (PCVAD). Several co-factors have been suggested to convert an infection with PCV2 into the clinical signs of PCVAD, including co-infection with a secondary pathogen and the genetic background of the pig. In the present study, we investigated the role of environmental stressors in the form of changes in environmental temperature and increased stocking-density on viral load in serum and tissue, average daily weight gain (ADG) and food conversion rate (FCR) of pigs experimentally infected with a defined PCV2b strain over an eight week period. These stressors were identified recently as risk factors leading to the occurrence of severe PCVAD on a farm level. In the current study, PCV2-free pigs were housed in separate, environmentally controlled rooms, and the experiment was performed in a 2 × 2 factorial design. In general, PCV2b infection reduced ADG and increased FCR, and these were further impacted on by the environmental stressors. Furthermore, all stressors led to an increased viral load in serum and tissue as assessed by qPCR, although levels did not reach statistical significance. Our data suggest that there is no need for an additional pathogen to develop PCVAD in conventional status pigs, and growth retardation and clinical signs can be induced in PCV2 infected pigs that are exposed to environmental stressors alone