76 research outputs found
NRLMSIS 2.1: An Empirical Model of Nitric Oxide Incorporated Into MSIS
We have developed an empirical model of nitric oxide (NO) number density at altitudes from âŒ73 km to the exobase, as a function of altitude, latitude, day of year, solar zenith angle, solar activity, and geomagnetic activity. The model is part of the NRLMSISÂź 2.1 empirical model of atmospheric temperature and species densities; this upgrade to NRLMSIS 2.0 consists solely of the addition of NO. MSIS 2.1 assimilates observations from six space-based instruments: UARS/HALOE, SNOE, Envisat/MIPAS, ACE/FTS, Odin/SMR, and AIM/SOFIE. We additionally evaluated the new model against independent extant NO data sets. In this paper, we describe the formulation and fitting of the model, examine biases between the data sets and model and among the data sets, compare with another empirical NO model (NOEM), and discuss scientific aspects of our analysis
Corrigendum to âComparison of nitric oxide measurements in the mesosphere and lower thermosphere from ACE-FTS, MIPAS, SCIAMACHY, and SMRâ published in Atmos. Meas. Tech., 8, 4171â4195, 2015
HEPPA-II modelâmeasurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008-2009
We compare simulations from three high-top (with upper lid above 120âŻkm) and five medium-top (with upper lid around 80âŻkm) atmospheric models with observations of odd nitrogen (NOxâŻâ=ââŻNOâŻ+âŻNO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, and SMR on Odin) during the Northern Hemisphere (NH) polar winter 2008/2009. The models included in the comparison are the 3-D chemistry transport model 3dCTM, the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the modelling tools for SOlar Climate Ozone Links studies (SOCOL and CAO-SOCOL), and the Whole Atmosphere Community Climate Model (WACCM4). The comparison focuses on the energetic particle precipitation (EPP) indirect effect, that is, the polar winter descent of NOx largely produced by EPP in the mesosphere and lower thermosphere. A particular emphasis is given to the impact of the sudden stratospheric warming (SSW) in January 2009 and the subsequent elevated stratopause (ES) event associated with enhanced descent of mesospheric air. The chemistry climate model simulations have been nudged toward reanalysis data in the troposphere and stratosphere while being unconstrained above. An odd nitrogen upper boundary condition obtained from MIPAS observations has further been applied to medium-top models. Most models provide a good representation of the mesospheric tracer descent in general, and the EPP indirect effect in particular, during the unperturbed (pre-SSW) period of the NH winter 2008/2009. The observed NOx descent into the lower mesosphere and stratosphere is generally reproduced within 20âŻ%. Larger discrepancies of a few model simulations could be traced back either to the impact of the models\u27 gravity wave drag scheme on the polar wintertime meridional circulation or to a combination of prescribed NOx mixing ratio at the uppermost model layer and low vertical resolution. In MarchâApril, after the ES event, however, modelled mesospheric and stratospheric NOx distributions deviate significantly from the observations. The too-fast and early downward propagation of the NOx tongue, encountered in most simulations, coincides with a temperature high bias in the lower mesosphere (0.2â0.05âŻhPa), likely caused by an overestimation of descent velocities. In contrast, upper-mesospheric temperatures (at 0.05â0.001âŻhPa) are generally underestimated by the high-top models after the onset of the ES event, being indicative for too-slow descent and hence too-low NOx fluxes. As a consequence, the magnitude of the simulated NOx tongue is generally underestimated by these models. Descending NOx amounts simulated with medium-top models are on average closer to the observations but show a large spread of up to several hundred percent. This is primarily attributed to the different vertical model domains in which the NOx upper boundary condition is applied. In general, the intercomparison demonstrates the ability of state-of-the-art atmospheric models to reproduce the EPP indirect effect in dynamically and geomagnetically quiescent NH winter conditions. The encountered differences between observed and simulated NOx, CO, and temperature distributions during the perturbed phase of the 2009 NH winter, however, emphasize the need for model improvements in the dynamical representation of elevated stratopause events in order to allow for a better description of the EPP indirect effect under these particular conditions
Gamma-ray spectroscopy measurements and simulations for uranium mining
AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration evaluation by means of gamma measurements. This paper reports gamma-ray spectra, recorded with a high-purity coaxial germanium detector, on standard cement blocks with increasing uranium content, and the corresponding MCNP simulations. The detailed MCNP model of the detector and experimental setup has been validated by calculation vs. experiment comparisons. An optimization of the detector MCNP model is presented in this paper, as well as a comparison of different nuclear data libraries to explain missing or exceeding peaks in the simulation. Energy shifts observed between the fluorescence X-rays produced by MCNP and atomic data are also investigated. The qualified numerical model will be used in further studies to develop new gamma spectroscopy approaches aiming at reducing acquisition times, especially for ore samples with low uranium content
Modulation of spinal excitability following neuromuscular electrical stimulation superimposed to voluntary contraction
Purpose. Neuromuscular electrical stimulation (NMES) superimposed on voluntary muscle contraction has been recently
shown as an innovative training modality within sport and rehabilitation, but its effects on the neuromuscular system are
still unclear. The aim of this study was to investigate acute responses in spinal excitability, as measured by the Hoffmann
(H) reflex, and in maximal voluntary contraction (MVIC) following NMES superimposed to voluntary isometric
contractions (NMES+ISO) compared to passive NMES only and to voluntary isometric contractions only (ISO). Method.
Fifteen young adults were required to maintain an ankle plantar-flexor torque of 20% MVC for 20 repetitions during each
experimental condition (NMES+ISO, NMES and ISO). Surface electromyography was used to record peak-to-peak Hreflex and motor waves following percutaneous stimulation of the posterior tibial nerve in the dominant limb. An
isokinetic dynamometer was used to assess maximal voluntary contraction output of the ankle plantar flexor muscles.
Results. H-reflex amplitude was increased by 4.5% after the NMES+ISO condition (p < 0.05), while passive NMES and
ISO conditions showed a decrease by 7.8% (p < 0.05) and no change in reflex responses, respectively. There was no
change in amplitude of maximal motor wave and in MVIC torque during each experimental condition. Conclusion. The
reported facilitation of spinal excitability following NMES+ISO could be due to a combination of greater motor neuronal
and corticospinal excitability, thus suggesting that NMES superimposed onto isometric voluntary contractions may
provide a more effective neuromuscular stimulus and, hence, training modality compared to NMES alone
High Resolution Genome-Wide Analysis of Chromosomal Alterations in Burkitt's Lymphoma
Additional chromosomal abnormalities are currently detected in Burkitt's lymphoma. They play major roles in the progression of BL and in prognosis. The genes involved remain elusive. A whole-genome oligonucleotide array CGH analysis correlated with karyotype and FISH was performed in a set of 27 Burkitt's lymphoma-derived cell lines and primary tumors. More than half of the 145 CNAs<2 Mb were mapped to Mendelian CNVs, including GSTT1, glutathione s-transferase and BIRC6, an anti-apoptotic protein, possibly predisposing to some cancers. Somatic cell line-specific CNVs localized to the IG locus were consistently observed with the 244 K aCGH platform. Among 136 CNAs >2 Mb, gains were found in 1q (12/27), 13q (7/27), 7q (6/27), 8q(4/27), 2p (3/27), 11q (2/27) and 15q (2/27). Losses were found in 3p (5/27), 4p (4/27), 4q (4/27), 9p (4/27), 13q (4/27), 6p (3/27), 17p (3/27), 6q (2/27),11pterp13 (2/27) and 14q12q21.3 (2/27). Twenty one minimal critical regions (MCR), (range 0.04â71.36 Mb), were delineated in tumors and cell lines. Three MCRs were localized to 1q. The proximal one was mapped to 1q21.1q25.2 with a 6.3 Mb amplicon (1q21.1q21.3) harboring BCA2 and PIAS3. In the other 2 MCRs, 1q32.1 and 1q44, MDM4 and AKT3 appeared as possible drivers of these gains respectively. The 13q31.3q32.1 <89.58â96.81> MCR contained an amplicon and ABCC4 might be the driver of this amplicon. The 40 Kb 2p16.1 <60.96â61> MCR was the smallest gained MCR and specifically encompassed the REL oncogene which is already implicated in B cell lymphomas. The most frequently deleted MCR was 3p14.1 <60.43â60.53> that removed the fifth exon of FHIT. Further investigations which combined gene expression and functional studies are essential to understand the lymphomagenesis mechanism and for the development of more effective, targeted therapeutic strategies
A comprehensive hybridization model allows whole HERV transcriptome profiling using high density microarray
A Collective Variable for the Rapid Exploration of Protein Druggability
An efficient molecular simulation
methodology has been developed
for the evaluation of the druggability (ligandability) of a protein.
Previously proposed techniques were designed to assess the druggability
of crystallographic structures and cannot be tightly coupled to molecular
dynamics (MD) simulations. By contrast, the present approach, JEDI
(<u>J</u>ust <u>E</u>xploring <u>D</u>ruggability at protein <u>I</u>nterfaces),
features a druggability potential made of a combination of empirical
descriptors that can be collected âon-the-flyâ during
MD simulations. Extensive validation studies indicate that JEDI analyses
discriminate druggable and nondruggable protein binding site conformations
with accuracy similar to alternative methodologies, and at a fraction
of the computational cost. Since the JEDI function is continuous and
differentiable, the druggability potential can be used as collective
variable to rapidly detect cryptic druggable binding sites in proteins
with a variety of MD free energy methods. Protocols for applications
to flexible docking problems are outlined
Effet de la diversité des essences sur la hauteur dominante
L'Ă©tude du fonctionnement des peuplements mĂ©langĂ©s n'est pas prĂšs de s'Ă©puiser. En ce qui concerne l'effet du mĂ©lange sur la productivitĂ©, les travaux ont surtout portĂ© sur la croissance radiale ou en surface terriĂšre. Mais la productivitĂ© dĂ©pend aussi de l'influence du mĂ©lange sur la croissance en hauteur, plus difficile Ă apprĂ©hender : les deux effets sont-ils de mĂȘme ampleur ? Vont-ils dans le mĂȘme sens ? Quels sont les mĂ©canismes ? MĂ©thode d'Ă©tude et premiĂšres rĂ©ponses
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