Spinor BECs in a double-well: population transfer and Josephson oscillations

The dynamics of an F=1 spinor condensate in a two-well potential is studied within the framework of the Gross-Pitaevskii equation. We derive two-mode equations relating the population imbalances, the phase differences among the condensates at each side of the barrier and the time evolution of the different Zeeman populations for the case of small population imbalances. The case of zero total magnetization is scrutinized in this limit demonstrating the ability of a two mode analysis to describe to a large extent the dynamics observed in the Gross-Pitaevskii equations. It is also demonstrated that the time evolution of the different total populations fully decouples from the Josephson tunneling phenomena. All the relevant time scales are clearly identified with microscopic properties of the atom-atom interactions

Satellites in the prokaryote world

Background Satellites or tandem repeats are very abundant in many eukaryotic genomes. Occasionally they have been reported to be present in some prokaryotes, but to our knowledge there is no general comparative study on their occurrence. For this reason we present here an overview of the distribution and properties of satellites in a set of representative species. Our results provide novel insights into the evolutionary relationship between eukaryotes, Archaea and Bacteria. Results We have searched all possible satellites present in the NCBI reference group of genomes in Archaea (142 species) and in Bacteria (119 species), detecting 2735 satellites in Archaea and 1067 in Bacteria. We have found that the distribution of satellites is very variable in different organisms. The archaeal Methanosarcina class stands out for the large amount of satellites in their genomes. Satellites from a few species have similar characteristics to those in eukaryotes, but most species have very few satellites: only 21 species in Archaea and 18 in Bacteria have more than 4 satellites/Mb. The distribution of satellites in these species is reminiscent of what is found in eukaryotes, but we find two significant differences: most satellites have a short length and many of them correspond to segments of genes coding for amino acid repeats. Transposition of non-coding satellites throughout the genome occurs rarely: only in the bacteria Leptospira interrogans and the archaea Methanocella conradii we have detected satellite families of transposed satellites with long repeats. Conclusions Our results demonstrate that the presence of satellites in the genome is not an exclusive feature of eukaryotes. We have described a few prokaryotes which do contain satellites. We present a discussion on their eventual evolutionary significance.Peer ReviewedPostprint (published version

Dynamic generation of spin-squeezed states in bosonic Josephson junctions

We analyze the formation of squeezed states in a condensate of ultracold bosonic atoms confined by a double-well potential. The emphasis is set on the dynamical formation of such states from initially coherent many-body quantum states. Two cases are described: the squeezing formation in the evolution of the system around the stable point, and in the short time evolution in the vicinity of an unstable point. The latter is shown to produce highly squeezed states on very short times. On the basis of a semiclassical approximation to the Bose-Hubbard Hamiltonian, we are able to predict the amount of squeezing, its scaling with $N$ and the speed of coherent spin formation with simple analytical formulas which successfully describe the numerical Bose-Hubbard results. This new method of producing highly squeezed spin states in systems of ultracold atoms is compared to other standard methods in the literature.Comment: 12 pages, revised discussion + added reference

Unique features of satellite DNA transcription in different tissues of Caenorhabditis elegans

A large part of the genome is known to be transcribed as non-coding DNA including some tandem repeats (satellites) such as telomeric/centromeric satellites in different species. However, there has been no detailed study on the eventual transcription of the interspersed satellites found in many species. In the present paper, we studied the transcription of the abundant DNA satellites in the nematode Caenorhabditis elegans using available RNA-Seq results. We found that many of them have been transcribed, but usually in an irregular manner; different regions of a satellite have been transcribed with variable efficiency. Satellites with a similar repeat sequence also have a different transcription pattern depending on their position in the genome. We also describe the peculiar features of satellites associated with Helitron transposons in C. elegans. Our demonstration that some satellite RNAs are transcribed adds a new family of non-coding RNAs, a new element in the world of RNA interference, with new paths for the control of mRNA translation. This is a field that requires further investigation and will provide a deeper understanding of gene expression and control.This work was supported by grant PID2021-122830OB-C43, funded by MCIN/AEI/10.13039/501100011033 and by “ERDF: A way of making Europe”.Peer ReviewedPostprint (published version

Dna satellites are transcribed as part of the non-coding genome in eukaryotes and bacteria

It has been shown in recent years that many repeated sequences in the genome are expressed as RNA transcripts, although the role of such RNAs is poorly understood. Some isolated and tandem repeats (satellites) have been found to be transcribed, such as mammalian Alu sequences and telomeric/centromeric satellites in different species. However, there is no detailed study on the eventual transcription of the interspersed satellites found in many species. Therefore, we decided to study for the first time the transcription of the abundant DNA satellites in the bacterium Bacillus coagulans and in the nematode Caenorhabditis elegans. We have updated the data for C. elegans satellites using the latest version of the genome. We analyzed the transcription of satellites in both species in available RNA-seq results and found that they are widely transcribed. Our demonstration that satellite RNAs are transcribed adds a new family of non-coding RNAs. This is a field that requires further investigation and will provide a deeper understanding of gene expression and control.This work was supported by Ministerio de Ciencia e Innovación, Spain [Project RTI2018-094403-B-C33 funded by MCIN/ AEI 10.13039/501100011033/ FEDER].Peer ReviewedPostprint (published version

Spin-driven spatial symmetry breaking of spinor condensates in a double-well

The properties of an F=1 spinor Bose-Einstein condensate trapped in a double-well potential are discussed using both a mean-field two-mode approach and a simplified two-site Bose-Hubbard Hamiltonian. We focus in the region of phase space in which spin effects lead to a symmetry breaking of the system, favoring the spatial localization of the condensate in one well. To model this transition we derive, using perturbation theory, an effective Hamiltonian that describes N/2 spin singlets confined in a double-well potential.Comment: 12 pages, 5 figure

Self-trapping of a binary Bose-Einstein condensate induced by interspecies interaction

The problem of self-trapping of a Bose-Einstein condensate (BEC) and a binary BEC in an optical lattice (OL) and double well (DW) is studied using the mean-field Gross-Pitaevskii equation. For both DW and OL, permanent self-trapping occurs in a window of the repulsive nonlinearity $g$ of the GP equation: $g_{c1}<g<g_{c2}$. In case of OL, the critical nonlinearities $g_{c1}$ and $g_{c2}$ correspond to a window of chemical potentials $\mu_{c1}<\mu<\mu_{c2}$ defining the band gap(s) of the periodic OL. The permanent self-trapped BEC in an OL usually represents a breathing oscillation of a stable stationary gap soliton. The permanent self-trapped BEC in a DW, on the other hand, is a dynamically stabilized state without any stationary counterpart. For a binary BEC with intraspecies nonlinearities outside this window of nonlinearity, a permanent self trapping can be induced by tuning the interspecies interaction such that the effective nonlinearities of the components fall in the above window

Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).Abstract: This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared). The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially) and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung) as a result of degradation products being released.Odontologí