Development and testing of porous ionizer materials, part I Summary report, Feb. 1965 - May 1966

Development and testing of porous tungsten ionizer materials for cesium contact engine

Dissipative Tunneling in 2 DEG: Effect of Magnetic Field, Impurity and Temperature

We have studied the transport process in the two dimensional electron gas (2DEG) in presence of a magnetic field and a dissipative environment at temperature T. By means of imaginary time series functional integral method we calculate the decay rates at finite temperature and in the presence of dissipation. We have studied decay rates for wide range of temperatures -- from the thermally activated region to very low temperature region where the system decays by quantum tunneling. We have shown that dissipation and impurity helps the tunneling. We have also shown that tunneling is strongly affected by the magnetic field. We have demonstrated analytical results for all the cases mentioned above.Comment: 8 pages, 2 figure

Key inflammatory pathway activations in the MCI stage of Alzheimer's disease

OBJECTIVE: To determine the key inflammatory pathways that are activated in the peripheral and CNS compartments at the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). METHODS: A cross-sectional study of patients with clinical and biomarker characteristics consistent with MCI-AD in a discovery cohort, with replication in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort. Inflammatory analytes were measured in the CSF and plasma with the same validated multiplex analyte platform in both cohorts and correlated with AD biomarkers (CSF Aβ42, total tau (t-tau), phosphorylated tau (p-tau) to identify key inflammatory pathway activations. The pathways were additionally validated by evaluating genes related to all analytes in coexpression networks of brain tissue transcriptome from an autopsy confirmed AD cohort to interrogate if the same pathway activations were conserved in the brain tissue gene modules. RESULTS: Analytes of the tumor necrosis factor (TNF) signaling pathway (KEGG ID:4668) in the CSF and plasma best correlated with CSF t-tau and p-tau levels, and analytes of the complement and coagulation pathway (KEGG ID:4610) best correlated with CSF Aβ42 levels. The top inflammatory signaling pathways of significance were conserved in the peripheral and the CNS compartments. They were also confirmed to be enriched in AD brain transcriptome gene clusters. INTERPRETATION: A cell-protective rather than a proinflammatory analyte profile predominates in the CSF in relation to neurodegeneration markers among MCI-AD patients. Analytes from the TNF signaling and the complement and coagulation pathways are relevant in evaluating disease severity at the MCI stage of AD

Measuring the quantum efficiency of single radiating dipoles using a scanning mirror

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.Comment: 4 pages, 4 figure

Determination of the blood oxygenation in the brain by time-resolved reflectance spectroscopy: contribution of vascular absorption and tissue background absorption

The possibility of measuring the blood oxygenation in the brain with near infrared light has been studied. The goal of this study was to quantify the influence of different brain layers on brain blood oxygenation measurements. Experimental results obtained from time resolved reflectance measurements on layered tissue phantoms were compared to Monte Carlo simulations of layered models, diffusion theory, and in vivo measurements on the human head. Both the experimental results and simulations show that the absorption coefficient (mu) a, which is closely related to the blood oxygenation, of deeper layers can be accessed in the time domain. Thus fitting analytical expressions found from diffusion theory only to the late part of the time resolved reflectance allows us to determine (mu) a and subsequently the blood oxygenation of the deepest medium (e.g. brain tissue)

Long-term tropospheric formaldehyde concentrations deduced from ground-based fourier transform solar infrared measurements

International audienceLong-term total column measurements of formaldehyde (HCHO) covering a 12 year period from 1992 to 2004 are reported from spectra recorded with a high-resolution Fourier Transform Spectrometer (FTS) using the sun as a light source at a Southern Hemisphere site (Lauder, New Zealand). The ambient HCHO concentrations at this rural location are often at background levels (15 molecules cm?2, the maximum occurring in the summer. A simple box model of CH4 oxidation reproduces the seasonal cycle, but significantly underestimates the maximum HCHO ground concentrations deduced from the column observations, particularly in summer. This implies the existence of a significant source of HCHO that cannot be explained by oxidation of CH4 alone. The ground-based FTS column data compares well with collocated HCHO column measurements from the Global Ozone Monitoring Experiment (GOME) satellite instrument (r2=0.65, mean bias=10%, n=48)

Intercomparison Methods for Satellite Measurements of Atmospheric Composition: Application to Tropospheric Ozone from TES and OMI

We analyze the theoretical basis of three different methods to validate and intercompare satellite measurements of atmospheric composition, and apply them to tropospheric ozone retrievals from the Tropospheric Emission Spectrometer (TES) and the Ozone Monitoring Instrument (OMI). The first method (in situ method) uses in situ vertical profiles for absolute instrument validation; it is limited by the sparseness of in situ data. The second method (CTM method) uses a chemical transport model (CTM) as an intercomparison platform; it provides a globally complete intercomparison with relatively small noise from model error. The third method (averaging kernel smoothing method) involves smoothing the retrieved profile from one instrument with the averaging kernel matrix of the other; it also provides a global intercomparison but dampens the actual difference between instruments and adds noise from the a priori. We apply the three methods to a full year (2006) of TES and OMI data. Comparison with in situ data from ozonesondes shows mean positive biases of 5.3 parts per billion volume (ppbv) (10%) for TES and 2.8 ppbv (5%) for OMI at 500 hPa. We show that the CTM method (using the GEOS-Chem CTM) closely approximates results from the in situ method while providing global coverage. It reveals that differences between TES and OMI are generally less than 10 ppbv (18%), except at northern mid-latitudes in summer and over tropical continents. The CTM method further allows for CTM evaluation using both satellite observations. We thus find that GEOS-Chem underestimates tropospheric ozone in the tropics due to possible underestimates of biomass burning, soil, and lightning emissions. It overestimates ozone in the northern subtropics and southern mid-latitudes, likely because of excessive stratospheric influx of ozone.Earth and Planetary SciencesEngineering and Applied Science