Bound States for the Spin-1/2 Aharonov-Bohm Problem in a Rotating Frame

In this paper, we study the effects of rotation in the spin-1/2 non-relativistic Aharonov-Bohm problem for bound states. We use a technique based on the self-adjoint extension method and determine an expression for the energies of the bound states. The inclusion of the spin element in the Hamiltonian guarantees the existence of bound state solutions. We perform a numerical analysis of the energies and verify that both rotation and the spin degree of freedom affect the energies of the particle. The main effect we observe in this analysis is a cutoff value manifested in the Aharonov-Bohm flux parameter that delimits the values for the positive and negative energies.

Aharonov–Bohm-like scattering in the generalized uncertainty principle-corrected quantum mechanics

We discuss classical electrodynamics and the Aharonov–Bohm effect in the presence of the minimal length. In the former, we derive the classical equation of motion and the corresponding Lagrangian. In the latter, we adopt the generalized uncertainty principle (GUP) and compute the scattering cross-section up to the first-order of the GUP parameter [Formula: see text]. Even though the minimal length exists, the cross-section is invariant under the simultaneous change [Formula: see text], [Formula: see text], where [Formula: see text] and [Formula: see text] are azimuthal angle and magnetic flux parameter. However, unlike the usual Aharonv–Bohm scattering, the cross-section exhibits discontinuous behavior at every integer [Formula: see text]. The symmetries, which the cross-section has in the absence of GUP, are shown to be explicitly broken at the level of [Formula: see text].

One size fits all? Calibrating an ocean biogeochemistry model for different circulations

Global biogeochemical ocean models are often tuned to match the observed distributions and fluxes of inorganic and organic quantities. This tuning is typically carried out “by hand”. However, this rather subjective approach might not yield the best fit to observations, is closely linked to the circulation employed and is thus influenced by its specific features and even its faults. We here investigate the effect of model tuning, via objective optimisation, of one biogeochemical model of intermediate complexity when simulated in five different offline circulations. For each circulation, three of six model parameters have been adjusted to characteristic features of the respective circulation. The values of these three parameters – namely, the oxygen utilisation of remineralisation, the particle flux parameter and potential nitrogen fixation rate – correlate significantly with deep mixing and ideal age of North Atlantic Deep Water (NADW) and the outcrop area of Antarctic Intermediate Waters (AAIW) and Subantarctic Mode Water (SAMW) in the Southern Ocean. The clear relationship between these parameters and circulation characteristics, which can be easily diagnosed from global models, can provide guidance when tuning global biogeochemistry within any new circulation model. The results from 20 global cross-validation experiments show that parameter sets optimised for a specific circulation can be transferred between similar circulations without losing too much of the model's fit to observed quantities. When compared to model intercomparisons of subjectively tuned, global coupled biogeochemistry–circulation models, each with different circulation and/or biogeochemistry, our results show a much lower range of oxygen inventory, oxygen minimum zone (OMZ) volume and global biogeochemical fluxes. Export production depends to a large extent on the circulation applied, while deep particle flux is mostly determined by the particle flux parameter. Oxygen inventory, OMZ volume, primary production and fixed-nitrogen turnover depend more or less equally on both factors, with OMZ volume showing the highest sensitivity, and residual variability. These results show a beneficial effect of optimisation, even when a biogeochemical model is first optimised in a relatively coarse circulation and then transferred to a different finer-resolution circulation model.

One size fits all? – Calibrating an ocean biogeochemistry model for different circulations

Global biogeochemical ocean models are often tuned to match the observed distributions and fluxes of inorganic and organic quantities. This tuning is typically carried out by hand. However, this rather subjective approach might not yield the best fit to observations, is closely linked to the circulation employed, and thus influenced by its specific features and even its faults. We here investigate the effect of model tuning, via objective optimisation, of one biogeochemical model of intermediate complexity when simulated in five different offline circulations. For each circulation, three of six model parameters have adjusted to characteristic features of the respective circulation. The values of these three parameters – namely, the oxygen utilisation of remineralisation, the particle flux parameter and potential nitrogen fixation rate – correlate significantly with deep mixing and ideal age of NADW and the outcrop area of AAIW and SAMW in the Southern Ocean. The clear relationship between these parameters and circulation characteristics, which can be easily diagnosed from global models, can provide guidance when tuning global biogeochemistry within any new circulation model. The results from 20 global cross-validation experiments show that parameter sets optimised for a specific circulation can be transferred between similar circulations without losing too much of the model's fit to observed quantities. When compared to model intercomparisons of subjectively tuned, global coupled biogeochemistry-circulation models, each with different circulation and/or biogeochemistry, our results show a much lower range of oxygen inventory, OMZ volume and global biogeochemical fluxes. Export production depends to a large extent on the circulation applied, while deep particle flux is mostly determined by the particle flux parameter. Oxygen inventory, OMZ volume, primary production and fixed nitrogen turnover depend more or less equally on both factors, with OMZ volume showing the highest sensitivity, and residual variability. These results show a beneficial effect of optimisation, even when a biogeochemical model is first optimised in a relatively coarse circulation, and then transferred to a different, finer resolution circulation model.

Boundary Layer Flow and Cattaneo-Christov Heat Flux of a Nonlinear Stretching Sheet with a Suspended CNT

Background: In this article the Boundary layer flow and Cattaneo-Christov Heat flux of nonlinear stretching sheet in a suspended carbon nanotube is analyzed. Methods: The governing classical PDE’s are changing into ODE’s using the similarity transformation method. This boundary value problem is solved by using numerical method known as Runge-Kutta fourth order method with effective shooting technique. Presently in this analysis , the flow, velocity and heat transfer characteristics for different heat transferphysical parameters such as nanofluid (ϕ), suction parameter (N>0), heat flux parameter (β) and Prandtl number (Pr) are studied for two cases i.e., single Wall Carbon Nanotube (SWCNT) and Multiwall Carbon Nanotube (MWCNT) respectively. Results: Our results are in good agreement within a limiting condition comparing with previously published results. This study signifies that practical applications in science and engineering fields for example in functional ceramics, nano metals for energy and environmental applications. Conclusion: A theoretical study of boundary layer flow and Catteneo-Christove heat flux is carried out. In this study some of the important findings are collected as follows: 1. The result of nanoparticle volume fraction f and suction parameter N shows that, as increasing f it increases the flow, velocity and temperature while as increasing N which increases the flow and temperature but decreases the velocity at boundary layer. 2. A comparison result is plotted which is an excellent agreement with previously published results. 3. As increasing the Prandtl number and relaxation time of heat flux parameter in the thermal boundary layer which decreases the temperature of thermal boundary layer. 4. Effect of relaxation time of heat flux is same for both local skin friction and local nusselt number i.e. increasing.

Magnetic properties of the protostellar core IRAS 15398-3359

Context. Magnetic fields can significantly affect the star formation process. The theory of the magnetically driven collapse in a uniform field predicts that the contraction initially happens along the field lines. When the gravitational pull grows strong enough, the magnetic field lines pinch inwards, giving rise to a characteristic hourglass shape. Aims. We investigate the magnetic field structure of a young Class 0 object, IRAS 15398-3359, embedded in the Lupus I cloud. Previous observations at large scales have suggested that this source evolved in an highly magnetised environment. This object thus appears to be an ideal candidate to study the magnetically driven core collapse in the low-mass regime. Methods. We performed polarisation observations of IRAS 15398-3359 at 214 μm using the SOFIA telescope, thus tracing the linearly polarised thermal emission of cold dust. Results. Our data unveil a significant bend of the magnetic field lines from the gravitational pull. The magnetic field appears ordered and aligned with the large-scale B-field of the cloud and with the outflow direction. We estimate a magnetic field strength of B = 78 μG, which is expected to be accurate within a factor of two. The measured mass-to-flux parameter is λ = 0.95, indicating that the core is in a transcritical regime.

Optimal neighbourhood to nurture giants: a fundamental link between star-forming galaxies and direct collapse black holes

ABSTRACT Massive 104–5 M⊙ black hole seeds resulting from the direct collapse of pristine gas require a metal-free atomic cooling halo with extremely low H2 fraction, allowing the gas to cool isothermally in the presence of atomic hydrogen. In order to achieve this chemo-thermodynamical state, the gas needs to be irradiated by both Lyman–Werner (LW) photons in the energy range of 11.2–13.6 eV capable of photodissociating H2 and 0.76 eV photons capable of photodetaching H−. Employing cosmological simulations capable of creating the first galaxies in high resolution, we explore if there exists a subset of galaxies that favour direct collapse black hole (DCBH) formation in their vicinity. We find a fundamental relation between the maximum distance at which a galaxy can cause DCBH formation and its star formation rate (SFR), which automatically folds in the chemo-thermodynamical effects of both H2 photodissociation and H− photodetachment. This is in contrast to the approximately three order of magnitude scatter seen in the LW flux parameter computed at the maximum distance, which is synonymous with a scatter in ‘Jcrit’. Thus, computing the rates and/or the LW flux from a galaxy is no longer necessary to identify neighbouring sites of DCBH formation, as our relation allows one to distinguish regions where DCBH formation could be triggered in the vicinity of a galaxy of a given SFR.

Changes of microcirculation in rats detected by laser Doppler flowmetry at physical load accompanied by the development of thrombotic readiness

Introduction. A considerable physical load can lead to the damage of various organs and systems including the system of the microcirculatory bloodstream. Materials and methods. The experimental groups of animals were exposed to 4-hour and 8-hour physical load. The state of the microcirculatory bloodstream was examined by means of laser Doppler flowmetry. Results. 4-hour physical load did not cause any reduction of the microcirculation parameter in rats. 8-hour physical load led to a decrease of the microcirculation parameter and further reduction of flux parameter. Conclusions. Such changes of microcirculation parameters can be one of the symptoms of development of the state of thrombotic readiness and high risk of thrombosis in rats after 8-hour physical load.