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The article includes statistics from measurement of California ground squirrel olfactory bulbs' contamination from manganese (Mn) and cadmium (Cd). Lab rats are used as a control group. The authors stress the importance of toxin transfer factors in the assessment of chemical exposure.

In this work, the physical properties of binary mixtures of bicyclohexyl and 1,2,3,4-tetrahydronaphthalene (tetralin) or trans-decahydronaphthalene (trans-decalin) were measured. Densities and viscosities were measured at temperatures from 293.15 to 373.15 K, and speeds of sound were measured at temperatures from 293.15 to 343.15 K. At 303.15 K, pure component values of density (960.9, 878.93, 862.29 kg•m-3), viscosity (1.85, 3.18, 1.79 mPa•s), and speed of sound (1450.2, 1422.7, 1357.5 m•s-1) are consistent with literature values for tetralin, bicyclohexyl, and trans-decalin, respectively. Density mole fraction data were fit to second- or third-order polynomials. Viscosity mole fraction data were fit using the three-body McAllister model. The bulk modulus ranged from 1206 to 2149 MPa over 293.15 to 343.15 K. For tetralin mixtures, increasing tetralin increased density, speed of sound, bulk modulus, and surface tension and decreased viscosity and flash point. For trans-decalin mixtures, increasing trans-decalin decreased all properties measured. Increasing temperature decreased all properties values. At room temperature, surface tensions ranged from 30.5 to 35.6 mN•m-1. Flash points ranged from 328.7 to 361.2 K. These data are useful for comparing the properties of mixtures of components of coal and wood-based liquid fuels with those of petroleum-based fuels. [ABSTRACT FROM AUTHOR]

Inthis work, the physical properties of binary mixtures of n-heptane and 2,2,4-trimethylpentane were measured. Densityand speed of sound were measured at temperatures ranging from (293.15to 338.15) K, and viscosity was measured at temperatures ranging from(293.15 to 333.15) K. At 298.15 K, pure component values for heptaneof 679.61 kg·m–3, 0.389 mPa·s, and 1130.1m·s–1for density, viscosity, and speed ofsound, respectively, agree with literature values. Similarly for 2,2,4-trimethylpentane,the values of 687.70 kg·m–3, 0.501 mPa·s,and 1081.7 m·s–1for density, viscosity, andspeed of sound, respectively, agree with literature values. Densitymole fraction and temperature data were fit to a second-order polynomial.Bulk moduli ranged from (551.7 to 907.1) MPa over (293.15 to 338.15)K. Viscosity mole fraction data were fit using the three-body McAllistermodel, while the viscosity deviations were fit to a Redlich–Kistertype equation. For the mixtures, an increase in mole fraction of 2,2,4-trimethylpentaneresulted in an increase in density and viscosity and in a decreasein speed of sound, bulk modulus, and surface tension. Increases intemperature decreased density, viscosity, speed of sound, and bulkmodulus. At room temperature, the surface tension values ranged from(18.7 to 20.3) mN·m–1. These data can be usedby researchers who are modeling the combustion process of mixturesof primary reference fuels and are modeling the physical propertiesof fuels. [ABSTRACT FROM AUTHOR]

Inthis work, the physical properties of binary mixtures of n-hexadecane with toluene or ethylbenzene were measured.Density and viscosity were measured at temperatures ranging from (293.15to 373.15) K, and the speed of sound was measured at temperaturesranging from (293.15 to 333.15) K. Density mole fraction and temperaturedata were fit to a fourth-order polynomial. Viscosity mole fractiondata were fit using the three-body McAllister model, while the viscositydeviations were fit to a Redlich–Kister type equation. Forboth two-component mixtures, the speed of sound at 293.15 K decreasedas the mole fraction of the aromatic compound increased until a minimumwas reached after which the speed of sound increased slightly to thevalue of the pure aromatic compound. The bulk modulus was calculatedfrom density and speed of sound data. For both 2-component mixtures,the bulk modulus at 293.15 K decreased slightly as the mole fractionof the aromatic compound increased until a minimum was reached afterwhich the bulk modulus increased to its highest value, which is thevalue for the aromatic compound. Flash points for the mixtures rangedfrom (278.5 to 408) K, and surface tension values ranged from (27.3to 29.2) mN·m–1. [ABSTRACT FROM AUTHOR]

The extinction cross-sections ofindividual, optically confinedaerosol particles with radii of a micrometer or less can, in principle,be measured using cavity ring-down spectroscopy (CRDS). However, whenthe particle radius is comparable in magnitude to the wavelength oflight stored in a high-finesse cavity, the phenomenological cross-sectionretrieved from a CRDS experiment depends on the location of the particlein the intracavity standing wave and differs from the Mie scatteringcross-section for plane-wave irradiation. Using an evaporating 1,2,6-hexanetriolparticle of initial radius ∼1.75 μm confined within the4.5 μm diameter core of a Bessel beam, we demonstrate that thescatter in the retrieved extinction efficiency of a single particleis determined by its lateral motion, which spans a few wavelengthsof the intracavity standing wave used for CRDS measurements. Fitsof experimental measurements to Mie calculations, modified to accountfor the intracavity standing wave, allow precise retrieval of therefractive index of 1,2,6-hexanetriol particles (with relative humidity,RH < 10%) of 1.47824 ± 0.00072. [ABSTRACT FROM AUTHOR]

The strong dependence of separation behavior on ultrathin-layer chromatography (UTLC) stationary phase microstructure motivates continued UTLC plate design optimization efforts. We fabricated 4.6-5.3 pm thick normal phase silica UTLC stationary phases with several types of in-plane macropore anisotropies using the glancing angle deposition (GLAD) approach to engineering nanostructured thin films. The separation behaviors of two new media, isotropic vertical posts and anisotropic bIadelike ifims, were compared to that of anisotropic chevron media. Channel-like structures within the anisotropic media introduced preferential mobile phase flow directions that could be exploited to give separation tracks diagonal to the development direction. Extraction of chromatograms from these angled tracks required the development of a new analytical approach that involved a commercial flathed film scanner and custom numerical image analysis software. GlAD stationary phase performance was quantified using the Dimethyl Yellow dye separated from a lipophilic dye mixture over migration distances less than -10 mm. The limits of detection were 10 ± 4 ngfor the vertical posts and 11 ± 3 ngfor the bladelike media. We obtained theoretical plate heights that varied with film microstructure between 12 and 28 pm. Unoptimized separation performance was comparable to that of other planar chromatography media. Macropore anisotropies engineered by GLAD may expand the capabilities of future ITFLC stationary phases. [ABSTRACT FROM AUTHOR]

Aerosol droplets are unique microcompartments containing microscopic amounts of material and exhibiting surprising chemical reactivity. Although a diverse set of tools exists to characterize the chemical composition of individual submicron particles in air, comparatively fewer approaches can chemically analyze individual, airborne picolitre droplets. We describe a novel approach for mass spectrometric analysis of individual aqueous picolitre droplets (∼2-180 pL volume) containing down to ∼1 pg analyte mass per droplet. Individual droplets are generated using a microdroplet dispenser, imparted a small amount of net charge, and guided to the inlet of a high-resolution mass spectrometer using a linear quadrupole-electrodynamic balance. Analyte molecules within the aqueous droplet are ionized using droplet assisted ionization, where droplet breakup within the mass spectrometer inlet leads to generation of molecular ions. This single droplet mass spectrometry approach is demonstrated for small molecules and proteins. The approach generates clean mass spectra, permits timing of droplet delivery for chemical analysis, and, by avoiding a separate ionization stage, avoids potential artifacts arising from current electrospray-based approaches for picolitre droplet analysis. It is anticipated this approach will permit exploration of the factors governing accelerated chemical reactions in aerosol droplets and will be suitable for sensitive analysis of particularly precious samples in different application domains.

Optical trapping is a well-established technique to manipulate and levitate micro- and nanoscale particles and droplets. However, optical traps for single aerosol studies are most often limited to trapping spherical nonabsorbing droplets, and a universal optical trap for the stable confinement of particles regardless of their absorption strength and morphology is not established. Instead, new opportunities arise from levitating droplets using electrodynamic traps. Here, using a combined electrodynamic linear quadrupole trap and a cavity ring-down spectrometer, we demonstrate that it is possible to trap single droplets and simultaneously measure their extinction cross sections and elastic scattering phase functions over extended periods of time. To test the novel setup, we evaluated the evaporation of 1,2,6-hexanetriol under low-humidity conditions, and the evolution of aqueous (NH 4 ) 2 SO 4 and NaCl droplets experiencing changing environmental conditions. Our studies extended beyond spherical droplets and we measured particle extinction cross sections after the efflorescence (crystallization) of the inorganic salt particles. Comparison of measured cross sections for crystallized particles with light scattering model predictions (using Mie theory or the T-matrix/extended boundary-condition method (EBCM) implementations for random orientation, with either the spheroid or superellipsoid parameterizations) enables information on particle shape to be inferred. Specifically, we find that cross sections for dry (NH 4 ) 2 SO 4 particles are accounted for by Mie theory and, thus, particle shape is represented well by a sphere. Conversely, the cross sections for dry NaCl particles are only reconciled with light scattering models pertaining to nonspherical shapes. These results will have implications for accurate remote sensing retrievals of dry salt optical properties and for parameterizations implemented in radiative forcing calculations with changing humidity. Moreover, our new platform for precise and accurate measurement of optical properties of micron-scale and sub-micron particles has potential applications in a range of areas of atmospheric science, such as precise light scattering measurements for ice crystals and mineral dust. It represents a promising step toward accurate characterizations of optical properties for nonspherical and light-absorbing aerosols.

We present a first exploratory study to assess the use of aerosol optical tweezers as an instrument for sampling and detecting accumulation- and coarse-mode aerosol. A subpicoliter aqueous aerosol droplet is captured in the optical trap and used as a sampling volume, accreting mass from a free-flowing aerosol generated by a medical nebulizer or atomizer. Real-time measurements of the initial stability in size, refractive index, and composition of the sampling droplet inferred from Raman spectroscopy confirm that these quantities can be measured with high accuracy and low noise. Typical standard deviations in size and refractive index of the sampling droplet over a period of 200 s are <±2 nm and <±0.0005, respectively, equivalent to <±0.04% in both measured quantities. A standard deviation of <±1% over a 200 s period is achieved in the spontaneous Raman intensity measurement. When sampling coarse-mode aerosol, mass changes of <10 pg can be detected by the sampling droplet as discrete coalescence events. With accumulation-mode aerosol, we show that fluxes as low as 0.068 pg s -1 can be detected over a 50 s period, equivalent to ∼3 pg of sampled material.

A Bessel beam optical trap is combined with continuous wave cavity ringdown spectroscopy to measure the extinction cross section of individual aerosol particles. Particles, ∼1 μm in size, can be captured indefinitely and processes that transform size or refractive index studied. The measured light extinction induced by the particle is shown to depend on the position of the particle in the cavity, allowing accurate measurements of the mode structure of a high finesse optical cavity without significant perturbation. The variation in extinction efficiency of a sodium chloride droplet with relative humidity is shown to agree well with predictions from Mie scattering theory.