Constant of Motion for several one-dimensional systems and outlining the problem associated with getting their Hamiltonians

The constants of motion of the following systems are deduced: a relativistic particle with linear dissipation, a no-relativistic particle with a time explicitly depending force, a no-relativistic particle with a constant force and time depending mass, and a relativistic particle under a conservative force with position depending mass. The problem of getting the Hamiltonian for these systems is determined by getting the velocity as an explicit function of position and generalized linear momentum, and this problem can be solved a first approximation for the first above system.Comment: 15 pages, Te

Genomic Evolution of Two Acinetobacter baumannii Clinical Strains from ST-2 Clones Isolated in 2000 and 2010 (ST-2_clon_2000 and ST-2_clon_2010)

Acinetobacter baumannii is a successful nosocomial pathogen due to its ability to persist in hospital environments by acquiring mobile elements such as transposons, plasmids, and phages. In this study, we compared two genomes of A. baumannii clinical strains isolated in 2000 (ST-2_clon_2000) and 2010 (ST-2_clon_2010) from GenBank project PRJNA308422

Space Evaluation of Optical Modulators for Microwave Photonic On-Board Applications

Since several years, perspectives and assets offered by photonic technologies compared with their traditional RF counterparts (mass and volume reduction, transparency to RF frequency, RF isolation), make them particularly attractive for space applications [1] and, in particular, telecommunication satellites [2]. However, the development of photonic payload concepts have concurrently risen and made the problem of the ability of optoelectronic components to withstand space environment more and more pressing. Indeed, photonic components used in such photonic payloads architectures come from terrestrial networks applications in order to benefit from research and development in this field. This paper presents some results obtained in the frame of an ESA-funded project, carried out by Thales Alenia Space France, as prime contractor, and Alter Technology Group Spain (ATG) and Universidad Politecnica de Madrid (UPM), as subcontractors, one objective of which was to assess commercial high frequency optical intensity modulators for space use through a functional and environmental test campaign. Their potential applications in microwave photonic sub-systems of telecom satellite payloads are identified and related requirements are presented. Optical modulator technologies are reviewed and compared through, but not limited to, a specific figure of merit, taking into account two key features of these components : optical insertion loss and RF half-wave voltage. Some conclusions on these different technologies are given, on the basis of the test results, and their suitability for the targeted applications and environment is highlighted

Structure of Thermoreversible Poly(vinyl alcohol) Cryo-Hydrogels as studied by Proton Low Field NMR Spectroscopy

The network structure of Poly(vinyl alcohol) (PVA) hydrogels obtained by freezing-thawing cycles was investigated by solid state 1H low field NMR spectroscopy. By application of multiple-quantum NMR experiments, we obtain information about the segmental order parameter, which is directly related to the restrictions to chain motion (crosslinks) formed upon gelation. These measurements indicate that the network mesh size, as well as the relative amount of non-elastic defects (i.e. non-crosslinked chains, dangling chains, loops) decreases with the number of freezing-thawing cycles, but it is independent of the polymer concentration. The formation of the PVA network is accompanied by an increasing fraction of polymer with fast magnetization decay (∼20μs). The quantitative study of this rigid phase with a specific refocusing pulse sequence shows that it is composed of a primary crystalline polymer phase (around 5%), which constitutes the main support of the network structure and determines the mesh size, and a secondary population of more imperfect crystallites, which increase the number of elastic chain segments in the polymer gel but does not affect the average network mesh size appreciably. Correspondingly, progressive melting of the secondary crystallites with increasing temperature does not affect the network mesh size but only the amount of network defects, and melting of the main PVA crystallites at around 80 ºC leads to destruction of the network gel and formation of an isotropic PVA solution.Peer reviewe

Effective portals to heavy neutral leptons

The existence of right-handed neutrinos, or heavy neutral leptons (HNLs), is strongly motivated by the observation of neutrino masses and mixing. The mass of these new particles could lie below the electroweak scale, making them accessible to low-energy laboratory experiments. Additional new physics at high energies can mediate new interactions between the Standard Model particles and HNLs, and is most conveniently parametrized by the neutrino Standard Model Effective Field Theory, or νSMEFT for short. In this work, we consider the dimension six νSMEFT operators involving one HNL field in the mass range of O (1) MeV < MN < O (100) GeV. By recasting existing experimental limits on the production and decay of new light particles, we constrain the Wilson coefficients and new physics scale of each operator as a function of the HNL mass.1The authors would like to thank the Instituto de Física Teórica (IFT UAM-CSIC) in Madrid for support via the Centro de Excelencia Severo Ochoa Program under Grant CEX2020-001007-S, during the Extended Workshop “Neutrino Theories”, where this work developed. The research of MH was supported by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development and by the Province of Ontario through the Ministry of Research, Innovation and Science. JLP acknowledges support from Generalitat Valenciana through the plan GenT program (CIDEGENT/2018/019) and from the Spanish Ministerio de Ciencia e Innovacion through the project PID2020-113644GB-I00. EFM and MGL were also supported by the Spanish Research Agency (Agencia Estatal de Investigación) through the grant PID2019-108892RB-I00 funded by MCIN/AEI/ 10.13039/501100011033. EFM, MGL, and JLP also acknowledge support from European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreements No 860881-HIDDeN and No 101086085- ASYMMETRY. JHG warmly thanks the hospitality of Albert de Roeck and the EP Neutrino group during his stay at CERN; where this project has been completed PID2019-108892RB-I0

Spontaneous Symmetry Breakdown in non-relativistic Quantum Mechanics

The advantages and disadvantages of some pedagogical non-relativistic quantum-mechanical models, used to illustrate spontaneous symmetry breakdown, are discussed. A simple quantum-mechanical toy model (a spinor on the line, subject to a magnetostatic interaction) is presented, that exhibits the spontaneous breakdown of an internal symmetry.Comment: 19 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1111.1213. Equations (30) and (31) have been corrected. Other minor correction

Uses of Native Plant Species of a Communal Rangeland within ‘Sierra de Huautla’ Protected Area, México

Sustainability of communal rangelands has become a major concern at national and international levels because land use conflicts and associated social conflicts allows for over-utilization of selected species making a high pressure on them and given away their places to species with no use at all becoming lands degraded and unproductive. The objective of the study was to determine floristic composition and native plant uses by local peasants. The range surface is of 4262 ha, belongs to the communal land ‘El Limon’, in Tepalcingo, Morelos, Mexico, and it is within the Natural Reserve Area “Sierra de Huautla”. Native vegetation is mainly of deciduous shrubs, high temperatures year round and a rainy season of 4 months. Local peasants were surveyed on uses of the collected and previously identified plants. Number of species was 456, distributed in 266 and 76 botanical genders and families, respectively. Of the species identified 66, 22 and 12% had one, two or more than two uses according to local peasants. Among uses: 59% of the species were used as forage, 8% eatable, 7% firewood or ornamental, 6% medical herb, lumber or other use 4 %, construction material 3 % and for resin or handcraft 1%. The range showed a very high plant biodiversity, this feature allows for a high resiliency toward human activities