Effect of humidity on nitric acid uptake to mineral dust aerosol particles

International audienceThis study presents the first laboratory observation of HNO3 uptake by airborne mineral dust particles. The model aerosols were generated by dry dispersion of Arizona Test Dust (ATD), SiO2, and by nebulizing a saturated solution of calcium carbonate. The uptake of 13N-labeled gaseous nitric acid was observed in a flow reactor on the 0.2?2 s reaction time scale at room temperature and atmospheric pressure. The amount of nitric acid appearing in the aerosol phase at the end of the flow tube was found to be a linear function of the aerosol surface area. SiO2 particles did not show any significant uptake, while the CaCO3 aerosol was found to be more reactive than ATD. Due to the smaller uncertainty associated with the reactive surface area in the case of suspended particles as compared to bulk powder samples, we believe that we provide an improved estimate of the rate of uptake of HNO3 to mineral dust. The fact that the rate of uptake was smaller at a concentration of 1012 than at 1011 was indicative of a complex uptake mechanism. The uptake coefficient averaged over the first 2 s of reaction time at a concentration of 1012 molecules cm-3 was found to increase with increasing relative humidity, from 0.022±0.007 at 12% RH to 0.113±0.017 at 73% RH , which was attributed to an increasing degree of solvation of the more basic minerals. The extended processing of the dust by higher concentrations of HNO3 at 85% RH led to a water soluble coating on the particles and enhanced their hygroscopicity

Neurofilament light protein levels in cerebrospinal fluid predict long-term disability of Guillain-Barre syndrome: A pilot study

Objectives: Although the recovery from Guillain‐Barré syndrome (GBS) is good in most patients, some develop permanent severe disability or even die. Early predictors would increase the likelihood to identify patients at risk for poor outcome at the acute stage, allowing them intensified therapeutic intervention. Materials and Method: Eighteen patients with a history of GBS 9‐17 years ago were reassessed with scoring of neurological disability and quality of life assessment (QoL). Their previous diagnostic work‐up included clinical examination with scoring of disability, neurophysiological investigation, a battery of serology tests for infections, and cerebrospinal fluid (CSF) examination. Aliquots of CSF were frozen, stored for 20‐28 years, and analyzed by ELISA for determination of neurofilament light protein (NFL) and glial fibrillary acidic protein (GFAP). Results: Patients with poor outcome (n = 3) had significantly higher NFL and GFAP levels at GBS nadir than those with good outcome (n = 15, P < .01 and P < .05, respectively). High NFL correlated with more prominent disability and worse QoL at long‐term follow‐up (r = .694, P < .001, and SF 36 dimension physical component summary (PCS) (r =−.65, P < .05), respectively, whereas GFAP did not correlate with clinical outcome or QoL. Conclusion: High NFL in CSF at the acute stage of GBS seems to predict long‐term outcome and might, together with neurophysiological and clinical measures, be useful in treatment decisions and clinical care of GBS

Tracking system analytic calibration activities for the Mariner Mars 1969 mission

Calibration activity of Deep Space Network in support of Mars encounter phase of Mariner Mars 1969 missio

Evidence of two viscous relaxation processes in the collective dynamics of liquid lithium

New inelastic X-ray scattering experiments have been performed on liquid lithium in a wide wavevector range. With respect to the previous measurements, the instrumental resolution, improved up to 1.5 meV, allows to accurately investigate the dynamical processes determining the observed shape of the the dynamic structure factor, $S(Q,\omega)$. A detailed analysis of the lineshapes shows the co-existence of relaxation processes with both a slow and a fast characteristic timescales, and therefore that pictures of the relaxation mechanisms based on a simple viscoelastic model must be abandoned.Comment: 5 pages, 4 .PS figure

A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles

International audienceAtmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/citric acid and in the ammonium sulfate/glutaric acid cases. However, we observe significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces

Estrogen inhibits GH signaling by suppressing GH-induced JAK2 phosphorylation, an effect mediated by SOCS-2

Oral estrogen administration attenuates the metabolic action of growth hormone (GH) in humans. To investigate the mechanism involved, we studied the effects of estrogen on GH signaling through Janus kinase (JAK)2 and the signal transducers and activators of transcription (STATs) in HEK293 cells stably expressing the GH receptor (293GHR), HuH7 (hepatoma) and T-47D (breast cancer) cells. 293GHR cells were transiently transfected with an estrogen receptor-α expression plasmid and luciferase reporters with binding elements for STAT3 and STAT5 or the β-casein promoter. GH stimulated the reporter activities by four- to sixfold. Cotreatment with 17β-estradiol (E2) resulted in a dose-dependent reduction in the response of all three reporters to GH to a maximum of 49-66% of control at 100 nM (P < 0.05). No reduction was seen when E2 was added 1-2 h after GH treatment. Similar inhibitory effects were observed in HuH7 and T-47D cells. E2 suppressed GH-induced JAK2 phosphorylation, an effect attenuated by actinomycin D, suggesting a requirement for gene expression. Next, we investigated the role of the suppressors of cytokine signaling (SOCS) in E2 inhibition. E2 increased the mRNA abundance of SOCS-2 but not SOCS-1 and SOCS-3 in HEK293 cells. The inhibitory effect of E2 was absent in cells lacking SOCS-2 but not in those lacking SOCS-1 and SOCS-3. In conclusion, estrogen inhibits GH signaling, an action mediated by SOCS-2. This paper provides evidence for regulatory interaction between a sex steroid and the GH/JAK/STAT pathway, in which SOCS-2 plays a central mechanistic role

The NR4A subgroup: immediate early response genes with pleiotropic physiological roles

The nuclear hormone receptor (NR) superfamily includes the orphan NR4A subgroup, comprised of Nur77 (NR4A1), Nurr1 (NR4A2) and NOR-1 (NR4A3). These NRs are classified as early response genes, are induced by a diverse range of signals, including fatty acids, stress, growth factors, cytokines, peptide hormones, phorbol esters, neurotransmitters, and physical stimuli (for example magnetic fields, shear stress). The ability to sense and rapidly respond to changes in the cellular environment thus appears to be a hallmark of this subfamily. The members of the NR4A subgroup are well conserved in the DNA binding domain (~91-95%) and the C-terminal ligand-binding domain (~60%), but are divergent in the N-terminal AB region. These receptors bind as monomers, homodimers and heterodimers with RXRs (to mediate retinoid signaling) to different permutations of the canonical NR binding motif. The NR4A subgroup activates gene expression in a constitutive ligand-independent manner. NR4A-mediated trans-activation (LBD) involves unusually active N-terminal AF-1 domains that mediate coactivator recruitment. Moreover, the NR4A receptors encode atypical LBDs and AF-2 domains. For example, the LBDs contain no cavity due to bulky hydrophobic residue side chains, and lack the classical coactivator-binding cleft constituted by helices 3, 4 and 12. However, a hydrophobic patch exists between helices 11 and 12, that encodes a novel cofactor interface that modulates transcriptional activity. In line with the pleiotropic physiological stimuli that induce the NR4A subgroup, these orphan NRs have been implicated in cell cycle regulation (and apoptosis), neurological disease, steroidogenesis, inflammation, carcinogenesis and atherogenesis

Generation, characterization, and medical utilization of laser-produced emission continua

Intense continua of electromagnetic radiation of very brief duration are formed in the interaction of focused ultra-short terawatt laser pulses with matter. Two different kinds of experiments, which have been performed utilizing the Lund 10 Hz titanium-doped sapphire terawatt laser system are being described, where visible radiation and X-rays, respectively, have been generated. Focusing into water leads to the generation of a light continuum through self-phase modulation. The propagation of the light through tissue was studied addressing questions related to optical mammography and specific chromophore absorption. When terawatt laser pulses are focused onto a solid target with high nuclear charge Z, intense X-ray radiation of few ps duration and with energies exceeding hundreds of keV is emitted. Biomedical applications of this radiation are described, including differential absorption and gated-viewing imaging