ALBERT

Description: Access of solar and galactic cosmic rays to the Earth's magnetosphere is quantified in terms of geomagnetic cutoff rigidity. Numerically computed grids of cutoff rigidities are used to model cosmic ray flux in Earth's atmosphere and in low Earthorbit. In recent years, the development of more accurate dynamic geomagnetic field models and an increase in computer power have made a real-time data-driven geomagnetic cutoff computation extending over the inner magnetosphere possible. For computational efficiency, numerically computed cutoffs may be scaled to different altitudes and directions of arrival using the known analytic variation of cutoff in a pure dipole magnetic field. This paper is a presentation of numerical techniques developed to compute effective cutoff rigidities for space weather applications. Numerical tests to determine the error associated with scaling vertical cutoff rigidities with altitude in a realistic geomagnetic field model are included. The tests were performed to guide the development of spatial grids for modeling cosmic ray access to the inner magnetosphere and to gain a better understanding of the accuracy of numerically modeled cutoffs.

Description: Analytical Chemistry DOI: 10.1021/acs.analchem.6b01037

Description: [1]  The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) is a real-time, global, physics-based model used to assess radiation exposure to commercial aircrews and passengers. The model is a free-running physics-based model in the sense that there are no adjustment factors applied to nudge the model into agreement with measurements. The model predicts dosimetric quantities in the atmosphere from both galactic cosmic rays (GCR) and solar energetic particles (SEP), including the response of the geomagnetic field to interplanetary dynamical processes and its subsequent influence on atmospheric dose. The focus of this paper is on atmospheric GCR exposure during geomagnetically quiet conditions, with three main objectives. First, provide detailed descriptions of the NAIRAS GCR transport and dosimetry methodologies. Second, present a climatology of effective dose and ambient dose equivalent rates at typical commercial airline altitudes representative of solar cycle maximum and solar cycle minimum conditions, and spanning the full range of geomagnetic cutoff rigidities. Third, conduct an initial validation of the NAIRAS model by comparing predictions of ambient dose equivalent rates with tabulated reference measurement data and recent aircraft radiation measurements taken in 2008 during the minimum between solar cycle 23 and solar cycle 24. By applying the criterion of the International Commission on Radiation Units and Measurements (ICRU) on acceptable levels of aircraft radiation dose uncertainty for ambient dose equivalent greater than or equal to an annual dose of 1 mSv, the NAIRAS model is within 25% of the measured data, which falls within the ICRU acceptable uncertainty limit of 30%. The NAIRAS model predictions of ambient dose equivalent rate are generally within 50% of the measured data for any single-point comparison. The largest differences occur at low latitudes and high cutoffs were the radiation dose level is low. Nevertheless, analysis suggests that these single-point differences will be within 30% when a new deterministic pion-initiated electromagnetic cascade code is integrated into NAIRAS, an effort which is currently underway.

Description: Infrared radiation from nitric oxide (NO) at 5.3 µm is a primary mechanism by which the thermosphere cools to space. The SABER instrument on the NASA TIMED satellite has been measuring thermospheric cooling by NO for over 13 years. In this letter we show that the SABER time series of globally integrated infrared power (Watts) radiated by NO can be replicated accurately by a multiple linear regression fit using the F10.7, A p , and D st indices. This allows reconstruction of the NO power time series back nearly 70 years with extant databases of these indices. The relative roles of solar ultraviolet and geomagnetic processes in determining the NO cooling are derived and shown to vary significantly over the solar cycle. The NO power is a fundamental integral constraint on the thermospheric climate and the time series presented here can be used to test upper atmosphere models over seven different solar cycles.

Description: Abstract Second generation reprogramming of somatic cells directly into the cell type of interest avoids induction of pluripotency and subsequent cumbersome differentiation procedures. Several recent studies have reported direct conversion of human somatic cells into stably proliferating induced neural stem cells (iNSCs). Importantly, iNSCs are easier, faster and more cost‐efficient to generate than induced pluripotent stem cells (iPSCs), and also have a higher level of clinical safety. Stably self‐renewing iNSCs can be derived from different cellular sources, such as skin fibroblasts and peripheral blood mononuclear cells, and readily differentiate into neuronal and glial lineages that are indistinguishable from their iPSC‐derived counterparts or from NSCs isolated from primary tissues. This review focuses on the derivation and characterization of iNSCs and their biomedical applications. We first outline different approaches to generate iNSCs and then discuss the underlying molecular mechanisms. Finally, we summarize the pre‐clinical validation of iNSCs to highlight that these cells are promising targets for disease modeling, autologous cell therapy and precision medicine.

Description: The RaD-X stratospheric balloon flight organized by the National Aeronautics and Space Administration (NASA) was launched from Fort Sumner on 25 September 2015 and carried several instruments to measure the radiation field in the upper atmosphere at the average vertical cut-off rigidity R c of 4.1 GV. The German Aerospace Center (DLR) in cooperation with Lufthansa German Airlines supported this campaign with an independent measuring flight at the altitudes of civil aviation on a round trip from Germany to Japan. The goal was to measure dose rates under similar space weather conditions over an area on the northern hemisphere opposite to the RaD-X flight. Dose rates were measured in the target areas, i.e. around vertical cut-off rigidity R c of 4.1 GV, at two flight altitudes for about one hour at each position with acceptable counting statistics. The analysis of the space weather situation during the flights shows that measuring data were acquired under stable and moderate space weather conditions with a virtually undisturbed magnetosphere. The measured rates of absorbed dose in silicon and ambient dose equivalent complement the data recorded during the balloon flight. The combined measurements provide a set of experimental data suitable for validating and improving numerical models for the calculation of radiation exposure at aviation altitudes.

Description: The ionization and excitation of atoms and molecules in the upper atmospheres of the Earth and planets are computed by a number of physical models. From these calculations, quantities measurable by dedicated satellite experiments such as airglow and electron fluxes can be derived. It is then possible to compare model and observation to derive more fundamental physical properties of the upper atmospheres, for example, the density as a function of altitude. To ensure the accuracy of these retrieval techniques, it is important to have an estimation of the uncertainty of these models and to have ways to account for these uncertainties. The complexity of kinetic models for computing the secondary production of excited state species (including ions) makes it a difficult evaluation, and studies usually neglect or underestimate it. We present here a Monte-Carlo approach to the computation of model uncertainties. As an example, we studied several aspects of the model uncertainties in the upper atmosphere of Mars, including the computed secondary electron flux and the production of the main ion species. Our simulations show the importance of improving solar flux models, especially on the energy binning and on the photon impact cross sections, which are the main sources of uncertainties on the dayside. The risk of modifying cross sections on the basis of aeronomical observations is highlighted for the case of Mars, while accurate uncertainties are shown to be crucial for the interpretation of data from the particle detectors onboard Mars Global Surveyor. Finally, it shows the importance of AtMoCiad, a public database dedicated to the evaluation of aeronomy cross section uncertainties. A detailed study of the resulting emissions cross sections uncertainties is the focus of a forthcoming paper (Gronoff et al., 2012) in which the outputs discussed in the present paper are used to compute airglow uncertainty, and the overall result is compared with the data from the SPICAM UV spectrometer onboard Mars Express.

Description: Author(s): C. Tserkezis, R. Esteban, D. O. Sigle, J. Mertens, L. O. Herrmann, J. J. Baumberg, and J. Aizpurua The precise structural details of metallic nanogaps within optical antennae are found to dramatically modify the plasmonic response, producing a complex pattern of electromagnetic modes that can be directly observed in scattering experiments. We analyze this situation theoretically in the nanopartic… [Phys. Rev. A 92, 053811] Published Wed Nov 04, 2015

Description: One of the objectives of spectrometers onboard space missions is to retrieve atmospheric parameters (notably density, composition and temperature). To fulfill this objective, comparisons between observations and model results are necessary. Knowledge of these model uncertainties is therefore necessary, although usually not considered, to estimate the accuracy in planetary upper atmosphere remote sensing of these parameters. In Part I of this study, “Computing uncertainties in ionosphere-airglow models: I. Electron flux and species production uncertainties for Mars” (Gronoff et al., 2012), we presented the uncertainties in the production of excited states and ionized species from photon and electron impacts, computed with a Monte-Carlo approach, and we applied this technique to the Martian upper atmosphere. In the present paper, we present the results of propagation of these production errors to the main UV emissions and the study of other sources of uncertainties. As an example, we studied several aspects of the model uncertainties in the thermosphere of Mars, and especially the O(1S) green line (557.7 nm, with its equivalent, the trans-auroral line at 297.2 nm), the Cameron bands CO(a3Π), and CO2+(B2Σu+) doublet emissions. We first show that the excited species at the origin of these emissions are mainly produced by electron and photon impact. We demonstrate that it is possible to reduce the computation time by decoupling the different sources of uncertainties; moreover, we show that emission uncertainties can be large (〉30%) because of the strong sensitivity to the production uncertainties. Our study demonstrates that uncertainty calculations are a crucial step prior to performing remote sensing in the atmosphere of Mars and the other planets and can be used as a guide to subsequent adjustments of cross sections based on aeronomical observations. Finally, we compare the simulations with observations from the SPICAM spectrometer on the Mars Express spacecraft. The production of excited species at the origin of the green line, the CO Cameron bands and the CO2+(B) doublet is found to be on the dayside, consistent with photon and electron impact on CO2 as the main source of excitation of the three emissions, in contrast to the findings of Huestis et al. (2010) for the O(1S) case. Moreover, we re-examine the cross section for the production of the Cameron bands by electron impact on CO2.