Rocket effluent: Its ice nucleation activity and related properties

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions

Airborne measurements of cloud-forming nuclei and aerosol particles in stabilized ground clouds produced by solid rocket booster firings

Airborne measurements of cloud volumes, ice nuclei and cloud condensation nuclei, liquid particles, and aerosol particles were obtained from stabilized ground clouds (SGCs) produced by Titan 3 launches at Kennedy Space Center, 20 August and 5 September 1977. The SGCs were bright, white, cumulus clouds early in their life and contained up to 3.5 g/m3 of liquid in micron to millimeter size droplets. The measured cloud volumes were 40 to 60 cu km five hours after launch. The SGCs contained high concentrations of cloud condensation nuclei active at 0.2%, 0.5%, and 1.0% supersaturation for periods of three to five hours. The SGCs also contained high concentrations of submicron particles. Three modes existed in the particle population: a 0.05 to 0.1 micron mode composed of aluminum-containing particles, a 0.2 to 0.8 micron mode, and a 2.0 to 10 micron mode composed of particles that contained primarily aluminum

Quantum dots in axillary lymph node mapping: Biodistribution study in healthy mice

<p>Abstract</p> <p>Background</p> <p>Breast cancer is the first cause of cancer death among women and its incidence doubled in the last two decades. Several approaches for the treatment of these cancers have been developed. The axillary lymph node dissection (ALND) leads to numerous morbidity complications and is now advantageously replaced by the dissection and the biopsy of the sentinel lymph node. Although this approach has strong advantages, it has its own limitations which are manipulation of radioactive products and possible anaphylactic reactions to the dye. As recently proposed, these limitations could in principle be by-passed if semiconductor nanoparticles (quantum dots or QDs) were used as fluorescent contrast agents for the <it>in vivo </it>imaging of SLN. QDs are fluorescent nanoparticles with unique optical properties like strong resistance to photobleaching, size dependent emission wavelength, large molar extinction coefficient, and good quantum yield.</p> <p>Methods</p> <p>CdSe/ZnS core/shell QDs emitting around 655 nm were used in our studies. 20 μL of 1 μM (20 pmol) QDs solution were injected subcutaneously in the anterior paw of healthy nude mice and the axillary lymph node (ALN) was identified visually after injection of a blue dye. <it>In vivo </it>fluorescence spectroscopy was performed on ALN before the mice were sacrificed at 5, 15, 30, 60 min and 24 h after QDs injection. ALN and all other organs were removed, cryosectioned and observed in fluorescence microscopy. The organs were then chemically made soluble to extract QDs. Plasmatic, urinary and fecal fluorescence levels were measured.</p> <p>Results</p> <p>QDs were detected in ALN as soon as 5 min and up to 24 h after the injection. The maximum amount of QDs in the ALN was detected 60 min after the injection and corresponds to 2.42% of the injected dose. Most of the injected QDs remained at the injection site. No QDs were detected in other tissues, plasma, urine and feces.</p> <p>Conclusion</p> <p>Effective and rapid (few minutes) detection of sentinel lymph node using fluorescent imaging of quantum dots was demonstrated. This work was done using very low doses of injected QDs and the detection was done using a minimally invasive method.</p

The geochemical cycling of reactive chlorine through the marine troposphere

Heterogeneous reactions involving sea‐salt aerosol in the marine troposphere are the major global source for volatile inorganic chlorine. We measured reactant and product species hypothesized to be associated with these chemical transformations as a function of phase, particle size, and altitude over the North Atlantic Ocean during the summer of 1988. Concentrations of HCl were typically less than 1.0 ppbv near the sea surface and decreased with altitude and with distance from the U.S. east coast. Concentrations of Cl volatilized from aerosols were generally equivalent to the corresponding concentrations of HCl and ranged from less than detection limits to 125 nmol m−3 STP. Highest absolute and percentage losses of particulate Cl were typically associated with elevated concentrations of anthropogenic combustion products. Concentrations of product nss SO42− and N03− in coarse aerosol fractions indicate that on average only 38% of measured Cl− deficits could be accounted for by the combined effects of acid‐base desorption and reactions involving nonacidic N gases. We hypothesize a mechanism for the Cl loss initiated by reaction of O3 at sea‐salt aerosol surfaces, generating Cl2 followed by rapid photochemical conversion of Cl2 to HCl via Cl atoms (Cl˙) and eventual recapture of HCl by the aerosol. Simulations with a zero‐dimension (0‐D) photochemical model suggest that oxidation by Cl˙ may be an important tropospheric sink for dimethyl sulfide and hydrocarbons. Under low‐NOx conditions, the rapid cycling of reactive Cl would provide a catalytic loss mechanism for O3, which would possibly explain the low O3 concentrations often observed above the world\u27s oceans

Dynamic Imaging of CD8+ T Cells and Dendritic Cells during Infection with Toxoplasma gondii

To better understand the initiation of CD8+ T cell responses during infection, the primary response to the intracellular parasite Toxoplasma gondii was characterized using 2-photon microscopy combined with an experimental system that allowed visualization of dendritic cells (DCs) and parasite specific CD8+ T cells. Infection with T. gondii induced localization of both these populations to the sub-capsular/interfollicular region of the draining lymph node and DCs were required for the expansion of the T cells. Consistent with current models, in the presence of cognate antigen, the average velocity of CD8+ T cells decreased. Unexpectedly, infection also resulted in modulation of the behavior of non-parasite specific T cells. This TCR-independent process correlated with the re-modeling of the lymph node micro-architecture and changes in expression of CCL21 and CCL3. Infection also resulted in sustained interactions between the DCs and CD8+ T cells that were visualized only in the presence of cognate antigen and were limited to an early phase in the response. Infected DCs were rare within the lymph node during this time frame; however, DCs presenting the cognate antigen were detected. Together, these data provide novel insights into the earliest interaction between DCs and CD8+ T cells and suggest that cross presentation by bystander DCs rather than infected DCs is an important route of antigen presentation during toxoplasmosis