One-dimensional ultracold atomic gases: Impact of the effective range on integrability

Three identical bosons or fermions are considered in the limit of zero-range interactions and finite effective range. By using a two channel model, we show that these systems are not integrable and that the wave function verifies specific continuity conditions at the contact of three particles. This last feature permits us to solve a contradiction brought by the contact model which can lead to an opposite result concerning the integrability issue. For fermions, the vicinity of integrability is characterized by large deviations with respect to the predictions of the Bethe ansatz

Second-order virial expansion for an atomic gas in a harmonic waveguide

International audienceThe virial expansion for cold two-component Fermi and Bose atomic gases is considered in the presence of a waveguide and in the vicinity of a Feshbach resonance. The interaction between atoms and the coupling with the Feshbach molecules is modeled using a quantitative separable two-channel model. The scattering phase-shift in an atomic waveguide is defined. This permits us to extend the Beth-Uhlenbeck formula for the second-order virial coefficient to this inhomogeneous case

Quelques problèmes à petit nombre d'atomes froids dans des guides d'onde.

This manuscript is motivated by the possibility of exploring many quantum regimes using cold atoms: interactions can be tuned very precisely by using Feshbach resonances and low-dimensional regimes can be approached with external potentials. Here, we study some properties of cold atoms trapped into uni- or bidimensional waveguides in the vicinity of a Feshbach resonance. The transition from a tridimensionnal to a low-dimensional system can then be studied by varying the intensity of the confinement. Interactions are described with a two-channel model that includes the coherent coupling between atoms and Feshbach molecules. We highlight a unidimensional regime, that can be described with a contact model and in which the effective range parameter is essential. Thus we investigate the three-body problem in this regime for bosons and also in the equivalent regime for totally polarized fermions, in particular their integrability properties. Finally, we study the virial expansion of a gas of cold atoms. Using a diagrammatic approach, we derive a generalization of the Beth and Uhlenbeck formula, that takes into account both the Feshbach molecules and the existence of a waveguide.Ce manuscrit est motivé par la possibilité d’explorer de nombreux régimes quantiques grâce aux atomes froids : l’utilisation de résonances de diffusion rend possible un contrôle très fin des effets des interactions et l’ajout de pièges extérieurs permet de s’approcher de régimes de dimension réduite. Nous étudions ici quelques propriétés d’atomes froids piégés dans des guides d’onde uni- ou bidimensionnels au voisinage de résonances de Feshbach. En jouant sur l’intensité du confinement, on peut étudier la transition entre un système tridimensionnel et un système en dimension réduite. Nous modélisons les interactions par un modèle à deux voies qui inclut le couplage cohérent entre atomes et molécules de Feshbach. Nous mettons en évidence l’existence d’un régime unidimensionnel, que l’on peut décrire par un modèle de contact, et dans lequel la portée effective est un paramètre essentiel. Nous examinons alors le problème à trois corps dans ce régime pour des bosons ainsi que dans le régime équivalent pour des fermions totalement polarisés, en particulier leurs propriétés d’intégrabilité. Enfin, nous étudions le développement du viriel d’un gaz d’atomes froids. Nous démontrons, grâce à une approche diagrammatique, une généralisation de la formule de Beth et Uhlenbeck qui prend en compte à la fois les molécules de Feshbach et l’existence d’un guide d’onde

Single-track sequencing for genotyping of multiple SNPs in the N-acetyltransferase 1 (NAT1) gene

BACKGROUND: Fast, cheap and reliable methods are needed to identify large populations, which may be at risk in relation to environmental exposure. Polymorphisms in NAT1 (N-acetyl transferase) may be suitable markers to identify individuals at risk. RESULTS: A strategy allowing to address simultaneously 24 various genetic variants in the NAT1 gene using the single sequencing reaction method on the same PCR product is described. A modified automated DNA sequencing using only one of the sequence terminators was used to genotype PCR products in single-track sequencing reactions of NAT1 and was shown to be universal for both DNA sequencing using labeled primers and labeled nucleotides. By this method we detected known SNPs at site T640G, which confers the NAT1*11 allele with frequency of 0.036, further T1088A and C1095A with frequency of 0.172 and 0.188, respectively and a deletion of TAATAATAA in the poly A signal area with a frequency 0.031. All observed frequencies were in Hardy Weinberg equilibrium and comparable to those in Caucasian population. The single-track signatures of the variant genotypes were verified on samples previously genotyped by RLFP. CONCLUSIONS: The method could be of great help to scientists in the field of molecular epidemiology of screening of large populations for known informative biomarkers of susceptibility, such as NAT1

Understanding the positive effects of the COVID-19 pandemic on women’s fertility in Norway

This study examines the effect of the COVID-19 pandemic on fertility in Norway at the individual level. Studies using data at the macro level have found a positive short-term effect of the pandemic on fertility level in Norway, but women’s fertility response to the pandemic may differ depending on their life situation. We use the first lockdown on March 12, 2020 as a marker of the pandemic and apply a regression discontinuity design to compare births of women that were conceived before the pandemic started with those conceived during the first eight months of the pandemic. The positive effect on women’s fertility in Norway was mainly driven by women in life phases that have generally high fertility rates (women aged 28–35 years and women who already have children). These groups are likely to be in an economic and socially secure and stable situation in which the restrictions due to the pandemic had limited influence. Besides two exceptions, we do not find differences in the effect of the pandemic on childbearing by women’s work situation. This is most likely related to the strong welfare state and the generous additional pandemic-related measures taken by the Norwegian government

Recombination and selectional forces in cyanopeptolin NRPS operons from highly similar, but geographically remote Planktothrix strains

<p>Abstract</p> <p>Background</p> <p>Cyanopeptolins are nonribosomally produced heptapetides showing a highly variable composition. The cyanopeptolin synthetase operon has previously been investigated in three strains from the genera <it>Microcystis</it>, <it>Planktothrix </it>and <it>Anabaena</it>. Cyanopeptolins are displaying protease inhibitor activity, but the biological function(s) is (are) unknown. Cyanopeptolin gene cluster variability and biological functions of the peptide variants are likely to be interconnected.</p> <p>Results</p> <p>We have investigated two cyanopeptolin gene clusters from highly similar, but geographically remote strains of the same genus. Sequencing of a nonribosomal peptide synthetase (NRPS) cyanopeptolin gene cluster from the Japanese strain <it>Planktothrix </it>NIES 205 (205-<it>oci</it>), showed the 30 kb gene cluster to be highly similar to the <it>oci </it>gene cluster previously described in <it>Planktothrix </it>NIVA CYA 116, isolated in Norway. Both operons contained seven NRPS modules, a sulfotransferase (S) and a glyceric acid loading (GA)-domain. Sequence analyses showed a high degree of conservation, except for the presence of an epimerase domain in NIES 205 and the regions around the epimerase, showing high substitution rates and Ka/Ks values above 1. The two strains produce almost identical cyanopeptolins, cyanopeptolin-1138 and oscillapeptin E respectively, but with slight differences regarding the production of minor cyanopeptolin variants. These variants may be the result of relaxed adenylation (A)-domain specificity in the nonribosomal enzyme complex. Other genetic markers (16S rRNA, <it>ntc</it>A and the phycocyanin <it>cpc</it>BA spacer) were identical, supporting that these geographically separated <it>Planktothrix </it>strains are closely related.</p> <p>Conclusion</p> <p>A horizontal gene transfer event resulting in exchange of a whole module-encoding region was observed. Nucleotide statistics indicate that both purifying selection and positive selection forces are operating on the gene cluster. The positive selection forces are acting within and around the epimerase insertion while purifying selection conserves the remaining (major) part of the gene cluster. The presence of an epimerase in the gene cluster is in line with the D-configuration of Htyr, determined experimentally in oscillapeptin E in a previous study.</p

Reduction of N-glycan profile variation by using capacitance probes for optimized process control

The glycan profile of therapeutic monoclonal antibodies frequently plays an important role in their biological function and pharmacokinetics. Therefore, improved control of the glycosylation profile of biopharmaceutical monoclonal antibodies has become an increased priority during late stage and commercial manufacturing of New Biological Entities as well as biosimilars. Two ways to obtain better control are through process parameter optimization and/or through addition of media supplements to the production reactor. Cell culture supplementation with mycophenolic acid is one method to efficiently manipulate N-glycan profiles of monoclonal antibodies, notably the level of fucosylation. We have observed at least for some CHO-based cell culture processes, that the timing of mycophenolic acid addition to the cell culture process relative to the cell growth profile is important to fine-tune the effect on the glycoprofile. This poster presents a case study where batch-to-batch variation of the N-glycan content of fucose for a monoclonal antibody at harvest could be correlated to the mycophenolic acid dose timing relative to the viable cell volume profile measured online by use of capacitance probes in 15 kL large-scale manufacturing bioreactors. Scale-down runs performed at 3 L scale with different timing of mycophenolic acid addition supported these observations. These data demonstrates how online capacitance probe measurements potentially could be used to optimize the process parameter mycophenolic acid dose timing, and thereby, further improve control of product N-glycan profile for this process

A genome-wide analysis of nonribosomal peptide synthetase gene clusters and their peptides in a Planktothrix rubescens strain

<p>Abstract</p> <p>Background</p> <p>Cyanobacteria often produce several different oligopeptides, with unknown biological functions, by nonribosomal peptide synthetases (NRPS). Although some cyanobacterial NRPS gene cluster types are well described, the entire NRPS genomic content within a single cyanobacterial strain has never been investigated. Here we have combined a genome-wide analysis using massive parallel pyrosequencing ("454") and mass spectrometry screening of oligopeptides produced in the strain <it>Planktothrix rubescens </it>NIVA CYA 98 in order to identify all putative gene clusters for oligopeptides.</p> <p>Results</p> <p>Thirteen types of oligopeptides were uncovered by mass spectrometry (MS) analyses. Microcystin, cyanopeptolin and aeruginosin synthetases, highly similar to already characterized NRPS, were present in the genome. Two novel NRPS gene clusters were associated with production of anabaenopeptins and microginins, respectively. Sequence-depth of the genome and real-time PCR data revealed three copies of the microginin gene cluster. Since NRPS gene cluster candidates for microviridin and oscillatorin synthesis could not be found, putative (gene encoded) precursor peptide sequences to microviridin and oscillatorin were found in the genes <it>mdn</it>A and <it>osc</it>A, respectively. The genes flanking the microviridin and oscillatorin precursor genes encode putative modifying enzymes of the precursor oligopeptides. We therefore propose ribosomal pathways involving modifications and cyclisation for microviridin and oscillatorin. The microviridin, anabaenopeptin and cyanopeptolin gene clusters are situated in close proximity to each other, constituting an oligopeptide island.</p> <p>Conclusion</p> <p>Altogether seven nonribosomal peptide synthetase (NRPS) gene clusters and two gene clusters putatively encoding ribosomal oligopeptide biosynthetic pathways were revealed. Our results demonstrate that whole genome shotgun sequencing combined with MS-directed determination of oligopeptides successfully can identify NRPS gene clusters and the corresponding oligopeptides. The analyses suggest independent evolution of all NRPS gene clusters as functional units. Our data indicate that the <it>Planktothrix </it>genome displays evolution of dual pathways (NRPS and ribosomal) for production of oligopeptides in order to maximize the diversity of oligopeptides with similar but functional discrete bioactivities.</p