A Gas Filtration System for Concentrations of 10 −5 Particles/cm3

Experiments were made to determine the lowest absolute levels of particle concentrations achievable by filtration. Two commercially available PVDF membrane filters were evaluated, namely, a 25-cm pleated filter cartridge (Milli-pore Durapore-TP ^{1 1}Liquid Air is a member of the L'Air Liquide Group. View all notes) and a smaller point-of-use filter with integrated housing (Millipore Wafergard In-Line ^{2 2}Durapore-TP and Wafergard In-Line are trade marks of Millipore Corp. View all notes). These filters have established penetration probabilities of less than 3 × 10^?9. Tests were performed at steady flow rates up to 1.4 Nm³/min and 0.1 Nm³/min, respectively. Data were taken with a condensation nuclei counter and two laser particle spectrometers. Measurements covering the size range from about 0.01 to 3 μm show that average concentrations of less than three particles/m³ (ca. 0.1 particle/ft³) can be attained continuously. Twenty-four hour periods without detection of a single particle are not uncommon. At these levels, the limiting factor is the cleanliness of all surfaces on the downstream side of the filter, and not filter efficiency in the traditional sense.     

Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2-Methyl-3-Buten-2-ol (MBO) in the Atmosphere

2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C(5)H(12)O(6)S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM(2.5)) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM(2.5) collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA.     

Phospholipase D (PLD) catalyzed synthesis of phosphatidyl-glucose in biphasic reaction system

Presence of saccharides in glycophospholipids may increase its potential to form supramolecular structures, which are not only stable for an extended period of time as compared to other PLs like phosphatidylcholine, but may also confer an antioxidative property. Most syntheses routes for glycophospholipid involved the usage of toxic chemicals or solvents, complicated steps and low yield. The present work attempted to develop an enzymatic method for the production of glycophospholipids. Phosphatidyl-glucose (PL-Glu) was synthesized as a model glycophospholipid. The effects of organic solvents, water content, substrate ratio, pH and temperature on glycophospholipid yield (mol%) were examined in this study. Under optimum reaction conditions, more than 95 mol% of PL-Glu was obtained in 1.5 h. The conversion rate is significantly higher than previously reported findings. The established model reaction system in the present work was used to synthesize other types of glycophospholipid.     

Acidization—V: The prediction of the movement of acid and permeability fronts in sandstone

A new model has been developed which describes the acidization of sandstone cores. The results show that the reaction of hydrofloric acid with the dissolvable minerals occurs in a narrow zone which moves as a reaction front through the sandstone core. The width of the reaction front is related to the Damkohler Number and the velocity of the reaction front is related to the acid capacity number. The model has virtually no adjustable parameters and agrees extremely well with the experimental results.     

Pulsed V-band m.b.e. Si IMPATT diodes

Single drift Impatt diodes of m.b.e. material are described which deliver pulse output power over 5 W at V-band. Maximum chirp frequency is less than 10 MHz, making the devices favourable for coherent radar applications.     

4-Gb/s transmission experiment over 117 km of optical fiber using a Ti:LiNbO3external modulator

We report a single-channel optical fiber data link with the largest bit-ratexrepeater spacing product achieved to date- ∼ 0.5 Tb . km/s. The multi-gigabit per second system is the first to incorporate a Ti:LiNbO3external modulator as the data encoder.     

New Sodium Borate Glasses

The glass-forming regions for the sodium borate system were determined using a roller-quencher. The new regions are R=0 to 0.8 and R=1.2 to 4.9for samples prepared from sodium carbonate (where R=mol% Na₂O/mol% B₂O₃). Above R=2.0 retention of'C02 occurs. Quantitative measures of CO₂ retention as a function of R are reported. The results using sodium carbonate extend by a considerable amount the limits reported by Imaoka and are comparable to the recent data of Ota and Soga.     

Electrical properties and luminescence of CuInSe2

We have studied the electrical properties and luminescence spectra of melt-grown CuInSe₂ single crystals and the doping of the crystals with intrinsic defects and extrinsic impurities. The preparation and the properties of p-n junctions are also discussed. We find that the low temperature photoluminescence spectra of crystals as-grown or annealed between 400 and 700 C are characteristic of the conductivity type. At 77 K, p-type crystals emit in a band peaked at 1.00 eV (type A spectrum) whereas the emission of n-type crystals peaks at 0.93 eV (type B spectrum). Type A and type B spectra can be interchanged by alternate anneals in minimum or maximum Se pressure. Type B emission dominates the electroluminescence spectrum of p-n junctions. These features are explained by the appearing and disappearing of a donor level as a consequence of annealing in vacuum or in Se atmosphere. We find that Zn and Cd act as donors. Crystals doped with these impurities have electron concentrations above 10¹⁸ cm⁻³. Zn-dopped samples exhibit a very broad recombination band below the bandgap in photoluminescence both at 77 and 300 K.     

Gut-derived intraepithelial lymphocytes induce long term immunity against Toxoplasma gondii

Intraepithelial lymphocytes (IEL) of the intestine represent an important barrier in the prevention of infection against orally acquired pathogens. Adoptive transfer of Ag-primed IEL into a naive host can protect against challenge. Using a murine model, we demonstrate in two genetically distinct mouse strains (C57BL/6 and CBA/J) that protective IEL can be isolated at specific times after oral infection with cysts containing bradyzoites. Adoptive transfer of IEL obtained from the intestine of infected mice at these specific times can provide long term protection, as determined by mortality and cyst number against challenge. The protective IEL appear to be CD8+, TCR-alpha/beta and are at least partially dependent upon the presence of TCR-gamma/delta T cells in the host. Endogenous production of the pivotal cytokine, IFN-gamma, is essential for host immunity. These findings demonstrate that gut-derived IEL represent a potentially important mechanism to provide long term immunity to the host.