Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.     

Analysis of lipid classes by solid-phase extraction and high-performance size-exclusion chromatography

An improved method to analyze lipid classes of edible oils and fats by solid-phase extraction (SPE) and high-performance size-exclusion chromatography (HPSEC) is presented. A mixture of lipid standards was fractionated by the solid-phase extraction procedure (NH₂ phase) into polar and nonpolar fractions; these were then submitted to analysis by HPSEC. The size-exclusion chromatographic columns were three styrene/divinylbenzene columns with pore sizes of 100 Å and 50 Å. Light-scattering was used for the detection system, and the parameters of the detector were optimized to minimize the difference between the responses of the compounds studied. With this procedure it was possible to separate the following lipid classes: triacylglycerols, diacylglycerols, monoacylglycerols and free fatty acids, sterols, sterol esters, tocopherols and carotenoids. Quantitative analysis was studied for a light-scattering detector with several lipid standards of different molecular weights and unsaturation levels.     

Nucleation and growth of nickel by electrodeposition under galvanostatic conditions

The first stages of nickel electrodeposition on amorphous carbon and polycrystalline silver substrates have been studied under galvanostatic conditions. An island growth mode is observed on the two types of substrate. For equivalent conditions the cluster density is higher on silver substrates than on carbon substrates. Dissolution of some nickel clusters is observed a short time after the onset of electrolysis on carbon substrates. This is confirmed by the evolution of the current efficiency and the evolution of the metal surface cluster density as a function of the quantity of electricity.     

Effects of brefeldin-A on Golgi morphology in human cultured fibroblasts observed in three-dimensional stereo scanning electron microscopy

Brefeldin A (BFA) has been reported to cause disassembly of the Golgi. We have used three-dimensional (3-D) high-resolution scanning electron microscopy (HRSEM) to investigate these effects in human skin fibroblast cells. The spontaneous reassembly during prolonged exposure to BFA and some effects of forskolin were observed. A BFA concentration of 5μg/ml caused Golgi complexes to become vesicular, resulting in a progressive decrease in the size of the Golgi. Morphologic changes were visible within 2 min of BFA incubation, and by 30 min no identifiable Golgi could be found. Spontaneous reassembly of the Golgi apparatus upon the removal of the BFA or with continued long-term exposure with BFA could not be confirmed. Preliminary experiments with forskolin were not effective in reversing or inhibiting the effects of BFA in human fibroblast cells grown in culture. This inability for spontaneous reassembly and nonreversal by forskolin may reflect a differential effect of BFA in various cell types. HRSEM has proven to be useful for observing 3-D morphologic effects of BFA in Golgi.     

Aldosterone and dexamethasone stimulate calcineurin activity through a transcription-independent mechanism involving steroid receptor-associated heat shock proteins

1. PD 81,723 has been shown to enhance binding of adenosine to A1 receptors by stabilizing G protein-receptor coupling ('allosteric enhancement'). Evidence has been provided that in the perfused hearts and isolated atria PD 81,723 causes a sensitization to adenosine via this mechanism. 2. We have studied the effect of PD 81,723 in guinea-pig isolated atrial myocytes by use of whole-cell measurement of the muscarinic K+ current (I[K(ACh)]) activated by different Gi-coupled receptors (A1, M2, sphingolipid). PD 81,273 caused inhibition of I[K(ACh)] (IC50 approximately 5 microM) activated by either of the three receptors. Receptor-independent I[K(ACh)] in cells loaded with GTP-gamma-S and background I[K(ACh)], which contributes to the resting conductance of atrial myocytes, were equally sensitive to PD 81,723. At no combination of concentrations of adenosine and PD 81,723 could an enhancing effect be detected. 3. The compound was active from the outside only. Loading of the cells with PD 81,723 (50 microM) via the patch pipette did not affect either I[K(ACh)] or its sensitivity to adenosine. We suggest that PD 81,723 acts as an inhibitor of inward rectifying K+ channels; this is supported by the finding that ventricular I(K1), which shares a large degree of homology with the proteins (GIRK1/GIRK4) forming I[K(ACh)] but is not G protein-gated, was also blocked by this compound. 4. It is concluded that the functional effects of PD 81,723 described in the literature are not mediated by the A1 adenosine receptor-Gi-I[K(ACh)] pathway.     

Cloning and characterization of the human and Caenorhabditis elegans homologs of the Saccharomyces cerevisiae MSH5 gene

Genetic variation among malaria parasites has important consequences with regard to drug resistance, pathogenicity, immunity, transmission, and speciation. In this regard, malaria parasites have been shown to display a high degree of inter- and intra-species genetic divergence. The nuclear genomes of Plasmodium falciparum, Plasmodium yoelii, and Plasmodium gallinaceum are vastly divergent yet share a similar codon usage and total A/T content of approximately 82%. This is in contrast to other primate-specific species including P. vivax which have an A/T content of approximately 67%. To assess the effects of this evolutionary divergence on the conservation of gene content, organization, and codon usage in the mitochondrial DNA (mtDNA) of malaria parasites, we have cloned and sequenced the mitochondrial genome of Plasmodium vivax, and compared it with the mtDNAs of P. falciparum, P. yoelii, and P. gallinaceum. The P. vivax mitochondrial genome was found to be 5990 base pairs in length, and displayed a gene organization identical to that of P. falciparum, P. yoelii, and P. gallinaceum. Furthermore, there was a remarkable 90% conservation of sequence identity between the mitochondrial genomes of all four species. As an example of intra-species conservation, comparison of mtDNAs from two independently cloned P. falciparum isolates, Malay Camp and C10, revealed only a single nucleotide substitution. A/T content of the P. vivax mitochondrial genome was found to be identical to other species of Plasmodium, hence, we have postulated that the mitochondrial genomes of malaria parasites were refractory to the evolutionary shifts in nucleotide content seen among the nuclear genomes of malaria parasites. Among different Plasmodium species, the second position of mitochondrial codons were found to be the least prone to substitutions and displayed a significant bias in pyrimidines. These aspects of mitochondrial codon usage were distinct from the nuclear genome and may reflect functional aspects of decoding by the mitochondrial translational system.     

The transverse acoustic impedance of dilute solutions of3He in superfluid4He

The transverse acoustic impedanceZ=R–iX of dilute solutions of³He in superfluid⁴He has been measured at a frequency (/2) of 20.5 MHz at temperaturesT from 30 mK to the transition at T. The³He concentrations studied werec=0.014, 0.031, 0.053, 0.060, and 0.092 below 1 K, thoughc decreased slightly near the point. The impedance was found from the temperature dependence of the quality factor and the resonant frequency of anAT-cut quartz crystal resonator immersed in the liquid. Below 1 K,Z is due to the Fermi gas of³He quasiparticles, and in the collisionless limit, 1 ( is a relaxation time),R remains constant whileX goes to zero. Measurements ofR(c, T) andX(c, T) were analyzed to determine the momentum accommodation coefficient (c, T) and (c, T). The relaxation times were in good agreement with previous work, while (c, T) was independent ofc, but increased from 0.29±0.03 below 0.1 K to 1.0±0.1 above 0.8 K. Various mechanisms are suggested to explain this. Between 1.0 and 1.5 K the³He quasiparticles and the thermally excited rotons are in the hydrodynamic region, 1. Values of the total viscosity (c, T) were obtained and analyzed to give the³He gas viscosity and the³He-³He and roton-³He scattering rates, both of which were energy-dependent. The superfluid healing length a was also measured. Near the point we founda=(0.1±0.03)^–2/3 nm, where =1–T/T, proportional to the phase coherence length . Our data are consistent with the hypothesis that _s/T is a universal constant for superfluid dilute solutions, where _s is the superfluid density. Between 1.0 and 1.8 K we found thata(c, T) was comparable to measurements in³He-⁴He films.     

High-Temperature Creep Behavior of Mixed Conducting La0.5Sr0.5Fe1−xCoxO3-δ (0.5≤x≤1) Materials

Steady-state compressive creep rate of La_0.5Sr_0.5Fe_0.5Co_0.5O_3−δ (LSFC) and La_0.5Sr_0.5CoO_3−δ (LSC) is reported in the temperature region 900°–1050°C and stress range 5–28 MPa. The stress exponents for the two materials were 1.71±0.18 and 1.24±0.15, respectively. The activation energy for creep was considerably higher for LSC (619±56 kJ/mol) than for LSFC (392±28 kJ/mol). The grain size exponent for LSC was 1.28±0.14. Considerably higher creep rates were observed for both materials in N₂ compared with air. Relaxation by creep of chemical-induced stresses in oxygen-permeable membranes is addressed, especially at low partial pressure of oxygen.     

具有检测电池容量功能的充电器设计

为解决市场主流充电器缺少电池容量检测功能以及电池充满电量后不能自动断电等问题,设计了一种以MSP430单片机为控制核心、DS1302为外围时钟电路芯片、具有检测电池容量功能的充电器,并给出了单元模块设计电路和配套的软件流程图。实验表明,该充电器可对锂电池、镍镉电池进行充电和放电,并提供两种电池容量检测方式,在采用传统电池容量检测方式测量时误差不超过5%;快速检测方式因节省时间,误差稍大。