Two-dimensional discrete solitons in dipolar Bose-Einstein condensates

We analyze the formation and dynamics of bright unstaggered solitons in the disk-shaped dipolar Bose-Einstein condensate, which features the interplay of contact (collisional) and long-range dipole-dipole (DD) interactions between atoms. The condensate is assumed to be trapped in a strong optical-lattice potential in the disk's plane, hence it may be approximated by a two-dimensional (2D) discrete model, which includes the on-site nonlinearity and cubic long-range (DD) interactions between sites of the lattice. We consider two such models, that differ by the form of the on-site nonlinearity, represented by the usual cubic term, or more accurate nonpolynomial one, derived from the underlying 3D Gross-Pitaevskii equation. Similar results are obtained for both models. The analysis is focused on effects of the DD interaction on fundamental localized modes in the lattice (2D discrete solitons). The repulsive isotropic DD nonlinearity extends the existence and stability regions of the fundamental solitons. New families of on-site, inter-site and hybrid solitons, built on top of a finite background, are found as a result of the interplay of the isotropic repulsive DD interaction and attractive contact nonlinearity. By themselves, these solutions are unstable, but they evolve into robust breathers which exist on an oscillating background. In the presence of the repulsive contact interactions, fundamental localized modes exist if the DD interaction (attractive isotropic or anisotropic) is strong enough. They are stable in narrow regions close to the anticontinuum limit, while unstable solitons evolve into breathers. In the latter case, the presence of the background is immaterial

UV femtosecond laser inscribes a 300 nm period nanostructure in a pure fused silica

We report on the first recording of a periodic structure of ∼150 nm pitch in a permanently moving sample of a pure fused silica using the tightly focused, 82 nJ, 267 nm, 300 fs, 1 kHz laser pulses. © 2007 IOP Publishing Ltd

Relativistic electrons from sparks in the laboratory

Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic detectors (5 $\rm cm^2$ each) were distributed in various configurations close to the spark gap. Earlier studies have shown (for HV negative) that X-rays are produced when a cloud of streamers is developed 30-60 cm from the negative electrode. This indicates that the electrons producing the X-rays are also accelerated at this location, that could be in the strong electric field from counterstreamers of opposite polarity. Comparing our measurements with modeling results, we find that $\sim$300 keV electrons produced about 30-60 cm from the negative electrode are the most likely source of our measurements. A statistical analysis of expected detection of photon bursts by these fiber detectors indicates that only 20%-45% of the detected bursts could be from soft ($\sim$10 keV) photons, which further supports that the majority of detected bursts are produced by relativistic electrons

Effect of stellar wind induced magnetic fields on planetary obstacles of non-magnetized hot Jupiters

We investigate the interaction between the magnetized stellar wind plasma and the partially ionized hydrodynamic hydrogen outflow from the escaping upper atmosphere of non- or weakly magnetized hot Jupiters. We use the well-studied hot Jupiter HD 209458b as an example for similar exoplanets, assuming a negligible intrinsic magnetic moment. For this planet, the stellar wind plasma interaction forms an obstacle in the planet's upper atmosphere, in which the position of the magnetopause is determined by the condition of pressure balance between the stellar wind and the expanded atmosphere, heated by the stellar extreme ultraviolet (EUV) radiation. We show that the neutral atmospheric atoms penetrate into the region dominated by the stellar wind, where they are ionized by photo-ionization and charge exchange, and then mixed with the stellar wind flow. Using a 3D magnetohydrodynamic (MHD) model, we show that an induced magnetic field forms in front of the planetary obstacle, which appears to be much stronger compared to those produced by the solar wind interaction with Venus and Mars. Depending on the stellar wind parameters, because of the induced magnetic field, the planetary obstacle can move up to ~0.5-1 planetary radii closer to the planet. Finally, we discuss how estimations of the intrinsic magnetic moment of hot Jupiters can be inferred by coupling hydrodynamic upper planetary atmosphere and MHD stellar wind interaction models together with UV observations. In particular, we find that HD 209458b should likely have an intrinsic magnetic moment of 10-20% that of Jupiter.Comment: 8 pages, 6 figures, 2 tables, accepted to MNRA

Micro-holographic methods for sub-micrometer grating fabrication in fused silica with UV femtosecond laser

The optical layouts incorporating binary phase diffractive grating and a standard micro-objective were used for femtosecond microfabrication of periodical structures in fused silica. Two beams, generated in Talbot type interferometer, interfered on a surface and in the bulk of the sample. The method suggested allows better control over the transverse size of the grating pitch, and thus control the reflection strength of the waveguide or fibre grating. We present the examples of direct inscription of the sub-micrometer periodical structures using a 267 nm femtosecond laser radiation

Peculiarities of Spatial Structure of the Central Caucasian High-Mountain Natural Plague Focus

Within the limits of Central Caucasian high-mountain natural plague focus discovered are two zones of natural focality. The first natural focality zone in the mountain steppe of the eastern part of the focus has a parasitic complex similar in structural organization and functioning to lowland foci of the souslik type. Another one, situated in the western part of the focus, is compatible with Tuva mountain natural plague focus, where fleas Neopsylla setosaare absent, and epizootic activity is characterized by a single-humped curve with an apex for July-August period. The similarities stated above can be used for optimization of epidemiological surveillance techniques, preventive measures, and methodology of studying mountain natural plague foci of the souslik type

Modeling the Lyα\alpha transit absorption of the hot Jupiter HD 189733b

Hydrogen-dominated atmospheres of hot exoplanets expand and escape due to the intense heating by the X-ray and extreme ultraviolet (XUV) irradiation of their host stars. Excess absorption of neutral hydrogen has been observed in the Ly$\alpha$ line during transits of several close-in exoplanets, indicating such extended atmospheres. For the hot Jupiter HD 189733b, this absorption shows temporal variability. Variations in stellar XUV emission and/or stellar wind conditions have been invoked to explain this effect. We apply a 1D hydrodynamic upper atmosphere model and a 3D MHD stellar wind flow model to study the effect of variations of the stellar XUV and wind conditions on the neutral hydrogen distribution, including the production of energetic neutral atoms (ENAs), and the related Ly$\alpha$ transit signature. We obtain comparable, albeit slightly higher Ly$\alpha$ absorption as observed in 2011 with a stellar XUV flux of $1.8\times10^4$ erg cm$^{-2}$ s$^{-1}$, rather typical activity conditions for this star. Flares similar to the one observed 8 h before the transit are unlikely to have caused a significant modulation of the transit signature. The resulting Ly$\alpha$ absorption is dominated by atmospheric broadening, whereas the contribution of ENAs is negligible, as they are formed inside the bow shock from decelerated wind ions that are heated to high temperatures. Thus, within our modeling framework and assumptions, we find an insignificant dependence on the stellar wind parameters. Since the transit absorption can be modeled with typical stellar XUV and wind conditions, it is possible that the non-detection of the absorption in 2010 was affected by less typical stellar activity conditions, such as a very different magnitude and/or shape of the star's spectral XUV emission, or temporal/spatial variations in Ly$\alpha$ affecting the determination of the transit absorption.Comment: 22 pages, 19 figures, 4 tables; A&A, publishe

Observation of Terrestrial Gamma-Ray Flashes at Mid Latitude

We present a sample of Terrestrial Gamma-ray Flashes (TGFs) observed at mid latitudes by the Atmosphere Space Interaction Monitor (ASIM). The events were detected between June 2018 and August 2020 in the latitude bands between 35° and 51° in both hemispheres, which we hereafter refer to as “mid latitudes.” The sample includes the first observations above urn:x-wiley:2169897X:media:jgrd57293:jgrd57293-math-0001 and consists of 14 events clustered in four geographical regions: north-west Atlantic and eastern USA; Mediterranean Sea; the ocean around South Africa; and north-eastern China and Siberia. We examine the characteristics of each event, both standalone and in the context of the global ASIM TGF data set, and we find that our sample is consistent with the global population concerning the number of counts, but shows significantly shorter durations. We analyze the meteorological context and the general evolution of the parent storms and we show that the storms are not extreme in terms of total duration and extension. Whenever possible, we also include the radio sferics and the peak current of the parent stroke. Finally, we present an estimation of the TGF occurrence rate at mid latitudes, based on ASIM's exposure, the local flash rate and tropopause altitude, and we show that it is outside but very close to two standard deviation from the rate of production at tropical latitudes, corrected by the higher atmospheric absorption of higher latitudes. This means that atmospheric absorption plays a major role in the detection of TGFs at mid latitudes, but we cannot rule out other factors.publishedVersio

Pathomorphological and pathochemical characteristic of the osteomyelitis focus in patients with diabetic osteoarthropathy (Charcot foot)

BACKGROUND: Osteomyelitis in diabetic osteoarthropathy occurs in 65 % of cases, and it is the main cause of non-traumatic amputations. The choice of optimal treatment technologies should be based on understanding the pathogenetic characteristics of this disease.AIM: To study the pathomorphological and pathochemical picture of osteomyelitic focus in patients with diabetic neuroosteoarthropathy.MATERIALS AND METHODS: Object — 20 patients (55.3±9.33 years) with Type 2 diabetes mellitus, diabetic neuroosteoarthropathy, chronic osteomyelitis of the foot bones. The treatment consisted in surgical debridement of the purulent focus with the material collection for pathomorphological and biochemical studies, and in reposition and alignment of bone fragments with the leg and foot fixation using the Ilizarov fixator in order to form bone ankylosis of the compromised joint.RESULTS: Subacute and acute course of chronic osteomyelitis was registered in 80 % of cases. As for the pathohistological changes in bone tissue, the following ones were the most significant: necrosis and the presence of an inflammatory infiltrate of varying severity depending on the phase of the inflammatory process. The articular cartilage structure was broken in all the cases. Activation of osteoclasts was observed in the osteomyelitis focus, especially in the subchondral zone. There was no subchondral bone plate in most cases, or only its fragments remained. Pathohistological examination of the soft tissues associated with the osteomyelitis focus indicated the presence of mirocirculatory and denervation disorders due to necrosis and hyalinosis of a significant part of microvessels against the background of compensatory hypervascularisation and chronic inflammation, narrowing and obliteration of the lumens of feeding arteries, almost complete absence of nerve elements in the tissues or their destructive changes. An increase in the activity of lytic enzymes was revealed in the interstitial environment of the tissues surrounding the osteomyelitis focus (138-fold increase in the activity of acid phosphatase, interstitial osteolytic index was 7.2-fold higher than blood serum index).CONCLUSION: The pathomorphological signs of chronic osteomyelitis subacute and acute processing were observed in most patients. Breaking the articular cartilage structure was accompanied by invasion of vessels, inflammatory infiltrate, and by activation of osteoclasts in the subchondral zone. Destructive changes of vessels and nerves in the soft tissues associated with the osteomyelitis focus can be etiopathogenetic factors of this disease development. The technologies for stopping this process should be based on obligatory debridement of the focus with sequestrnecrectomy, with regular monitoring of the operated segment condition