225 research outputs found
NE2001p: A Native Python Implementation of the NE2001 Galactic Electron Density Model
The Galactic electron density model NE2001 describes the multicomponent
ionized structure of the Milky Way interstellar medium. NE2001 forward models
the dispersion and scattering of compact radio sources, including pulsars, fast
radio bursts, AGNs, and masers, and the model is routinely used to predict the
distances of radio sources lacking independent distance measures. Here we
present the open-source package NE2001p, a fully Python implementation of
NE2001. The model parameters are identical to NE2001 but the computational
architecture is optimized for Python, yielding small (<1%) numerical
differences between NE2001p and the Fortran code. NE2001p can be used on the
command-line and through Python scripts available on PyPI. Future package
releases will include modular extensions aimed at providing short-term
improvements to model accuracy, including a modified thick disk scale height
and additional clumps and voids. This implementation of NE2001 is a springboard
to a next-generation Galactic electron density model now in development.Comment: 3 pages, 1 figure, code available at https://pypi.org/project/mwprop
Heat dissipation after nonanatomical lung resection using a laser is mainly due to emission to the environment: an experimental ex vivo study
Laser-directed resection of lung metastases is performed more frequently in recent years. The energy-loaded laser rays heat up the lung tissue, considerably. It is still unclear which mechanism is more important for tissue heat dissipation: the lung perfusion or the tissue emission. Therefore, we created a special experimental model to investigate the spontaneous heat dissipation after nonanatomical lung resection using a diode-pumped laser with a high output power. Experiments were conducted on paracardiac pig lung lobes (n = 12) freshly dissected at the slaughterhouse. Nonanatomical resection of lung parenchyma was performed without lobe perfusion in group 1 (n = 6), while group 2 (n = 6) was perfused at a physiological pressure of 25 cm H(2)O at 37 °C with saline via the pulmonary artery. For this, we used a diode-pumped neodymium-doped yttrium aluminum garnet (Nd:YAG) LIMAX® 120 laser (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) with a wavelength of 1,318 nm and a power output of 100 W. Immediately after completing laser resection, the lungs were monitored with an infrared camera (Type IC 120LV; Trotec, Heinsberg, Germany) while allowed to cool down. The resection surface temperature was taken at 10-s intervals and documented in a freeze-frame until a temperature of 37 °C had been reached. The temperature drop per time unit was analyzed in both groups. Immediately after laser resection, the temperature at the lung surface was 84.33 ± 8.08 °C in group 1 and 76.75 ± 5.33 °C in group 2 (p = 0.29). Group 1 attained the final temperature of 37 °C after 182.95 ± 53.76 s, and group 2 after 121.70 ± 16.02 s (p = 0.01). The temperature drop occurred exponentially in both groups. We calculated both groups’ decays using nonlinear regression, which revealed nearly identical courses. The mean time of tissue temperature of >42 °C, as a surrogate marker for tissue damage, was 97.14 ± 26.90 s in group 1 and 65.00 ± 13.78 s in group 2 (p = 0.02). Heat emission to the environment surpasses heat reduction via perfusion in nonanatomically laser-resected lung lobes. In developing a cooling strategy, a topical cooling method would be promising
High School Enrollment and Costs
During the last half century, there have been many surveys of city school systems. These surveys have been general; they have compared an entire school system with another of similar size. This thesis is also a compartive study of a school system but it compares the costs and enrollment in the four high schools of a single city. The aim of this thesis is then, (1) to compare the enrollment and costs of a single subject in the four high schools and (2) to compare the enrollment and costs of the various subjects in one school
Constraining Galaxy Haloes from the Dispersion and Scattering of Fast Radio Bursts and Pulsars
Fast radio bursts (FRBs) can be scattered by ionized gas in their local
environments, host galaxies, intervening galaxies along their lines-of-sight,
the intergalactic medium, and the Milky Way. The relative contributions of
these different media depend on their geometric configuration and the internal
properties of the gas. When these relative contributions are well understood,
FRB scattering is a powerful probe of density fluctuations along the
line-of-sight. The precise scattering measurements for FRB 121102 and FRB
180916 allow us to place an upper limit on the amount of scattering contributed
by the Milky Way halo to these FRBs. The scattering time , where is the dispersion measure,
quantifies electron density variations with for a
smooth medium, and the dimensionless constant quantifies the
difference between the mean scattering delay and the scattering time
typically measured. A likelihood analysis of the observed scattering and halo
DM constraints finds that is at least an order of magnitude smaller
in the halo than in the Galactic disk. The maximum pulse broadening from the
halo is s at 1 GHz. We compare our analysis of the Milky
Way halo with other galaxy haloes by placing limits on the scattering
contributions from haloes intersecting the lines-of-sight to FRB 181112 and FRB
191108. Our results are consistent with haloes making negligible or very small
contributions to the scattering times of these FRBs.Comment: 14 pages, 6 figures, accepted to Ap
Correlation transfer by layer 5 cortical neurons under recreated synaptic inputs in vitro
Correlated electrical activity in neurons is a prominent characteristic of cortical microcircuits. Despite a growing amount of evidence concerning both spike-count and subthreshold membrane potential pairwise correlations, little is known about how different types of cortical neurons convert correlated inputs into correlated outputs. We studied pyramidal neurons and two classes of GABAergic interneurons of layer 5 in neocortical brain slices obtained from rats of both sexes, and we stimulated them with biophysically realistic correlated inputs, generated using dynamic clamp. We found that the physiological differences between cell types manifested unique features in their capacity to transfer correlated inputs. We used linear response theory and computational modeling to gain clear insights into how cellular properties determine both the gain and timescale of correlation transfer, thus tying single-cell features with network interactions. Our results provide further ground for the functionally distinct roles played by various types of neuronal cells in the cortical microcircuit
Radio Scattering Horizons for Galactic and Extragalactic Transients
Radio wave scattering can cause severe reductions in detection sensitivity
for surveys of Galactic and extragalactic fast (ms duration) transients.
While Galactic sources like pulsars are subject to scattering in the Milky Way
interstellar medium (ISM), extragalactic fast radio bursts (FRBs) can also
experience scattering in their host galaxies and other galaxies intervening
their lines-of-sight. We assess Galactic and extragalactic scattering horizons
for fast radio transients using a combination of NE2001 to model the dispersion
measure (DM) and scattering time () contributed by the Milky Way, and
independently constructed electron density models for other galaxies' ISMs and
halos that account for different galaxy morphologies, masses, densities, and
strengths of turbulence. For FRB source redshifts , an
all-sky, isotropic FRB population has values of ranging between $\sim 1\
\mu\sim 2z_{\rm s}\sim5\tau\sim 0.01 - 10020\%\tau > 5\gtrsim 40\%z_{\rm s} \sim 0.5 - 5\tau \gtrsim 1\nu\leq 800$ MHz. The percentage of FRBs selected against from scattering may
be substantially larger because our scattering predictions are conservative
compared to localized FRBs, and if circumgalactic turbulence causes density
fluctuations larger than those observed from nearby halos.Comment: 24 pages, 14 figures, submitted to Ap
Investigation of the Dzyaloshinskii-Moriya interaction and room temperature skyrmions in W/CoFeB/MgO thin films and microwires
Recent studies have shown that material structures, which lack structural
inversion symmetry and have high spin-orbit coupling can exhibit chiral
magnetic textures and skyrmions which could be a key component for next
generation storage devices. The Dzyaloshinskii-Moriya Interaction (DMI) that
stabilizes skyrmions is an anti-symmetric exchange interaction favoring
non-collinear orientation of neighboring spins. It has been shown that material
systems with high DMI can lead to very efficient domain wall and skyrmion
motion by spin-orbit torques. To engineer such devices, it is important to
quantify the DMI for a given material system. Here we extract the DMI at the
Heavy Metal (HM) /Ferromagnet (FM) interface using two complementary
measurement schemes namely asymmetric domain wall motion and the magnetic
stripe annihilation. By using the two different measurement schemes, we find
for W(5 nm)/Co20Fe60B20(0.6 nm)/MgO(2 nm) the DMI to be 0.68 +/- 0.05 mJ/m2 and
0.73 +/- 0.5 mJ/m2, respectively. Furthermore, we show that this DMI stabilizes
skyrmions at room temperature and that there is a strong dependence of the DMI
on the relative composition of the CoFeB alloy. Finally we optimize the layers
and the interfaces using different growth conditions and demonstrate that a
higher deposition rate leads to a more uniform film with reduced pinning and
skyrmions that can be manipulated by Spin-Orbit Torques
Tunneling magneto thermo power in magnetic tunnel junction nanopillars
We study the tunneling magneto thermo power (TMTP) in CoFeB/MgO/CoFeB
magnetic tunnel junction nanopillars. Thermal gradients across the junctions
are generated by a micropatterned electric heater line. Thermo power voltages
up to a few tens of \muV between the top and bottom contact of the nanopillars
are measured which scale linearly with the applied heating power and hence with
the applied temperature gradient. The thermo power signal varies by up to 10
\muV upon reversal of the relative magnetic configuration of the two CoFeB
layers from parallel to antiparallel. This signal change corresponds to a large
spin-dependent Seebeck coefficient of the order of 100 \muV/K and a large TMTP
change of the tunnel junction of up to 90%.Comment: Revised version containing additional data and analyis. 13 pages, 3
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