210 research outputs found
Statistical research and simulation of MEMS gyros measurements
This article provides results of the statistical analysis and numerical evaluation of noise level components in the MEMS gyroscopes measurements. The Simulink-model of measurement errors for the ADIS16250 angular rate sensors was build, and test data and simulation results were analyzed
Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs
The connection between the radio emission from "lightnings" produced by the
absorption of high-energy photons from the cosmic gamma-ray background in a
neutron star magnetosphere and radio bursts from rotating radio transients
(RRATs) is investigated. The lightning length reaches 1000 km; the lightning
radius is 100 m and is comparable to the polar cap radius. If a closed
magnetosphere is filled with a dense plasma, then lightnings are efficiently
formed only in the region of open magnetic field lines. For the radio emission
from a separate lightning to be observed, the polar cap of the neutron star
must be directed toward the observer and, at the same time, the lightning must
be formed. The maximum burst rate is related to the time of the plasma outflow
from the polar cap region. The typical interval between two consecutive bursts
is ~100 s. The width of a single radio burst can be determined both by the
width of the emission cone formed by the lightning emitting regions at some
height above the neutron star surface and by a finite lightning lifetime. The
width of the phase distribution for radio bursts from RRATs, along with the
integrated pulse width, is determined by the width of the bundle of open
magnetic field lines at the formation height of the radio emission. The results
obtained are consistent with the currently available data and are indicative of
a close connection between RRATs, intermittent pulsars, and extreme nullers.Comment: 24 pages, no figures, references update
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Oxygen diffusion in Sr<sub>0.75</sub>Y<sub>0.25</sub>CoO<sub>2.625</sub>: a molecular dynamics study
Oxygen diffusion in Sr0.75Y0.25CoO2.625 is investigated using molecular dynamics simulations in conjunction with an established set of Born model potentials. We predict an activation energy of diffusion for 1.56 eV in the temperature range of 1000-1400 K. We observe extensive disordering of the oxygen ions over a subset of lattice sites. Furthermore, oxygen ion diffusion both in the a-b plane and along the c axis requires the same set of rate-limiting ion hops. It is predicted that oxygen transport in Sr0.75Y0.25CoO2.625 is therefore isotropic
On the possible observational manifestation of supernova shock impact on the neutron star magnetosphere
Impact of supernova explosion on the neutron star magnetosphere in a massive
binary system is considered. The supernova shock striking the NS magnetosphere
filled with plasma can lead to the formation of a magnetospheric tail with
significant magnetic energy. The magnetic field reconnection in the current
sheet formed can convert the magnetic energy stored in the tail into kinetic
energy of accelerated charged particles. Plasma instabilities excited by beams
of relativistic particles can lead to the formation of a short pulse of
coherent radio emission with parameters similar to those of the observed bright
extragalactic millisecond radio burst (Lorimer et al. 2007).Comment: 8 pages, Astron. Lett. in pres
Does Pulsar B1757--24 Have a Fallback Disk?
Radio pulsars are thought to spin-down primarily due to torque from magnetic
dipole radiation (MDR) emitted by the time-varying stellar magnetic field as
the star rotates. This assumption yields a `characteristic age' for a pulsar
which has generally been assumed to be comparable to the actual age. Recent
observational limits on the proper motion of pulsar B1757-24, however, revealed
that the actual age (>39 kyr) of this pulsar is much greater than its MDR
characteristic age (16 kyr) - calling into question the assumption of pure MDR
spin-down for this and other pulsars. To explore the possible cause of this
discrepancy, we consider a scenario in which the pulsar acquired an accretion
disk from supernova ejecta, and the subsequent spin-down occurred under the
combined action of MDR and accretion torques. A simplified model of the
accretion torque involving a constant mass inflow rate at the pulsar
magnetosphere can explain the age and period derivative of the pulsar for
reasonable values of the pulsar magnetic field and inflow rate. We discuss
testable predictions of this model.Comment: Accepted by ApJ Letters. 15 pages with 1 figur
The Appearance of a Radio-Pulsar Magnetosphere from a Vacuum with a Strong Magnetic Field. Accumulation of Particles
The accumulation of electrons and positrons in the vacuum magnetosphere of a
neutron star with a surface magnetic field of B~10^12 G is considered. It is
shown that particles created in the magnetosphere or falling into the
magnetosphere from outside undergo ultra-relativistic oscillations with a
frequency of 10-100 MHz. These oscillations decay due to energy losses to
curvature radiation and bremsstrahlung, with their frequencies reaching 1-10
GHz. Simultaneously, the particles undergo regular motion along the force-free
surface along closed trajectories. This leads to the gradual accumulation of
particles at the force-free surface and the formation of a fully
charge-separated plasma layer with a density of the order of the
Goldreich-Julian density. The presence of a constant source of
electron-positron pairs in the magnetosphere due to the absorption of energetic
cosmic gamma-rays leads to the growth of this layer, bringing about a rapid
filling of the pulsar magnetosphere with electron-positron plasma if the
pair-creation multiplication coefficient is sufficiently high.Comment: 22 pages, 2 figure
Measuring close proximity interactions in summer camps during the COVID-19 pandemic
Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing close proximity interactions, which drive the spread of the disease. A deeper knowledge of human physical interactions has revealed necessary, especially in all settings involving children, whose education and gathering activities should be preserved. Despite their relevance, almost no data are available on close proximity contacts among children in schools or other educational settings during the pandemic. Contact data are usually gathered via Bluetooth, which nonetheless offers a low temporal and spatial resolution. Recently, ultra-wideband (UWB) radios emerged as a more accurate alternative that nonetheless exhibits a significantly higher energy consumption, limiting in-field studies. In this paper, we leverage a novel approach, embodied by the Janus system that combines these radios by exploiting their complementary benefits. The very accurate proximity data gathered in-field by Janus, once augmented with several metadata, unlocks unprecedented levels of information, enabling the development of novel multi-level risk analyses. By means of this technology, we have collected real contact data of children and educators in three summer camps during summer 2020 in the province of Trento, Italy. The wide variety of performed daily activities induced multiple individual behaviors, allowing a rich investigation of social environments from the contagion risk perspective. We consider risk based on duration and proximity of contacts and classify interactions according to different risk levels. We can then evaluate the summer camps’ organization, observe the effect of partition in small groups, or social bubbles, and identify the organized activities that mitigate the riskier behaviors. Overall, we offer an insight into the educator-child and child-child social interactions during the pandemic, thus providing a valuable tool for schools, summer camps, and policy makers to (re)structure educational activities safely
The effect of hypoxia on photocytotoxicity of tics tricaebocyanine dye in vitro
To evaluate the effect of cell oxygenation on photocytotoxicity of a novel tricarbocyanine indolenine dye covalently bound to glucose (TICS). Methods: HeLa cells were incubated with 5 µM TICS, 2 h later irradiated by laser at 740 nm with a light dose of
10 J/cm2, delivered at a power density of 10, 20, 25 or 30 mW/cm2, in air or in argon atmosphere, and then scored for viability. Results: The photocytotoxicity of TICS increased dramatically as the power density was reduced. Under hypoxia TICS-photosensitized cell death was determined but its value was lowered, compared to photoirradiation in the air. Conclusion: Photosensitizing
effect of TICS is only partially dependent on the oxygenation of tumor cells
Absorption of Gamma-Ray Photons in a Vacuum Neutron Star Magnetosphere: I. Electron-Positron Pair Production
The production of electron-positron pairs in a vacuum neutron star
magnetosphere is investigated for both low (compared to the Schwinger one) and
high magnetic fields. The case of a strong longitudinal electric field where
the produced electrons and positrons acquire a stationary Lorentz factor in a
short time is considered. The source of electron-positron pairs has been
calculated with allowance made for the pair production by curvature and
synchrotron photons. Synchrotron photons are shown to make a major contribution
to the total pair production rate in a weak magnetic field. At the same time,
the contribution from bremsstrahlung photons may be neglected. The existence of
a time delay due to the finiteness of the electron and positron acceleration
time leads to a great reduction in the electron-positron plasma generation rate
compared to the case of a zero time delay. The effective local source of
electron-positron pairs has been constructed. It can be used in the
hydrodynamic equations that describe the development of a cascade after the
absorption of a photon from the cosmic gamma-ray background in a neutron star
magnetosphere.Comment: 29 pages, 1 figur
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