Combined stereoscopic particle image velocimetry and line integral convolution methods

The flow fields for a sphere sedimenting through a Newtonian and two non-Newtonian liquids near a wall in a square tank are investigated using 3-D stereoscopic particle image velocimetry (PIV) and line integral convolution (LIC) methods. The PIV data were taken using an angular stereoscopic configuration with tilt and shift arrangements for the Scheimpflug condition and a pair of liquid correction prisms. Data were recorded from planes perpendicular and parallel to the wall for each fluid case over a range of distances from the wall. The PIV and LIC results highlight significant differences in the wake structure for all three cases. Out of plane flow was also found to persist up to two sphere diameters downstream in the wake for all cases.     

The rotational analysis of the gamma system (A 3Φ - X′ 3Δ) of the spectrum of zirconium oxide

Rotational analyses of the (0,0), (1,1) and (2,2) bands, and a partial analysis of the (3,3) band, of the γ-system (A³Φ - X′³Δ) of the molecules ⁹⁰Zr¹⁶O, ⁹⁴Zr¹⁶O, ⁹⁶Zr¹⁶O have been performed. The measured wave numbers and their assignments are presented up to high quantum numbers. The rotational constants are calculated and an estimate is made of the spin-coupling coefficients. Both states belong closely to Hund's coupling case a.     

Surface activity of lysozyme and dipalmitoyl phosphatidylcholine vesicles at compressed and supercritical fluid interfaces

The surface activities of lysozyme and dipalmitoyl phosphatidylcholine (DPPC) vesicles at aqueous/compressed fluid interfaces are examined via high-pressure interfacial tension measurements using the pendant drop technique. The density and interfacial tension in compressible fluid systems vary significantly with pressure, providing a versatile medium for elucidating interactions between biomolecules and fluid interfaces and a method to elicit pressure-dependent interfacial morphological responses. The effects of lysozyme concentration (0.0008, 0.01, and 1 mg/mL) and pressure (> or = 7 MPa) on the dynamic surface response in the presence of ethane, propane, N2, and CO2 at 298 K were examined. Interfacial lysozyme adsorption reduced the induction phase and quickly led to interfacial tensions consistent with protein conformational changes and monolayer saturation at the compressed fluid interfaces. Protein adsorption, as indicated by surface pressure, correlated with calculated Hamaker constants for the compressed gases, denoting the importance of dispersion interactions. For DPPC at aqueous/compressed or aqueous/supercritical CO2 interfaces (1.8-20.7 MPa, 308 K), 2-3-fold reductions in interfacial tension were observed relative to the pure binary fluid system. The resulting surface pressures infer pressure-dependent morphological changes within the DPPC monolayer.     

Recommended conventions for defining transition moments and intensity factors in diatomic molecular spectra

Two recommendations are made that can eliminate persistent confusion in the study of diatomic spectroscopy by providing uniform and consistent definitions of the electronic transition moments and the rotational line intensity factors. First, it is recommended that the equation for the line strength of a single rotational line be adopted to specify the relationship between the electronic transition moment and the rotational line intensity factor. Second, it is recommended that the electronic transition moment operator for perpendicular transitions be defined by (1/2^1/2)(μ_x ± iμ_y). The adoption of these conventions results in a value of (2S + 1)(2J + 1) for the sum rule of the rotational line intensity factor for Σ^± ↔ Σ^± transitions and a value of 2(2S + 1)(2J + 1) for the sum rule for all other spin-allowed transitions.     

The rotational analysis of the 1Π-X 1Σ+ system at 649.5 nanometers of zirconium oxide

A red-degraded band head, normally badly overlapped by the gamma system, $\text{A}{}^3\text{Φ}\text{- X′}{}^3\text{Δ}$, of zirconium oxide, appears in emission spectra of zirconium arcs and in absorption spectra of S-type stars and of frozen rare gas matrices containing zirconium. The emission band has been examined at high-resolution with the aid of separated zirconium isotopes. Identification of the band as 0-0 of a ${}^1\text{Π}\text{- X}{}^1\text{Σ}{}^{\mathrm{+}}$ system of zirconium oxide is confirmed by rotational analysis where the following constants (cm^?1) are obtained for ⁹⁰Zr¹⁶O:

$\text{B}{}_0\text{′(R,P) = 0.40142 D}{}_0\text{′(R,P) = 3.51 × 10}{}^{\mathrm{?7}}$

$\text{B}{}_0\text{′(Q) = 0.40166 D}{}_0\text{′(Q) =3.52 × 10}{}^{\mathrm{?7}}$

$\text{B}{}_0\text{″ = 0.42263 D}{}_0\text{″ =3.19 × 10}{}^{\mathrm{?7}}$

$\text{ν}{}_0\text{= 15383.81s}$

The Λ-type doubling in the ¹Π state and the question of whether $\text{X}{}^1\text{Σ}{}^{\mathrm{+}}$ or $\text{X′}{}^3\text{Δ}$ is the true ground state of ZrO are discussed.     

A convenient one-pot synthesis of ethylene blue

We have developed an efficient one-pot, two-step preparation of ethylene blue by eliminating aqueous work-ups and cumbersome purification techniques. Our procedure generates ethylene blue in good overall yields of 45-56% with approximately 95% purity, which is uncommon for the synthesis of a phenothiazinium salt. Due to its unique properties, ethylene blue has great potential for a broad range of biological applications and, as a result, an efficient procedure for the synthesis of ethylene blue is critical.     

Angular correlation of electrons in the ground state of helium

The spatial angular correlation of electrons in the ground state of the helium atom has been examined using configuration interaction and Hylleraas wave-functions. It was found that, in general, the average angle between the electrons is not a maximum when the two electrons are at the same distance from the nucleus. For configuration interaction wave-functions there is a position of the electrons for which the average value of the angle between the electrons is a maximum. Hylleraas wave-functions do not show this behavior.     

Bacterial sunscreen: layer-by-layer deposition of UV-absorbing polymers on whole-cell biosensors

UV-protective coatings on live bacterial cells were created from the assembly of cationic and UV-absorbing anionic polyelectrolytes using layer-by-layer (LbL) methodology. A cationic polymer (polyallylamine) and three different anionic polymers with varying absorbance in the UV range (poly(vinyl sulfate), poly(4-styrenesulfonic acid), and humic acid) were used to encapsulate Escherichia coli cells with two different green fluorescent protein (GFP) expression systems: constitutive expression of a UV-excitable GFP (GFPuv) and regulated expression of the intensely fluorescent GFP from amphioxus (GFPa1) through a theophylline-inducible riboswitch. Riboswitches activate protein expression after specific ligand-RNA binding events. Hence, they operate as a cellular biosensor that will activate reporter protein synthesis after exposure to a ligand target. E. coli cells coated with UV-absorbing polymers demonstrated enhanced protection of GFP stability, metabolic activity, and viability after prolonged exposure to radiation from a germicidal lamp. The results show the effectiveness of LbL coatings to provide UV protection to living cells for biotechnological applications.     

High-resolution absorption cross sections of formaldehyde in the 30,285-32,890 cm(-1) (304-330 nm) spectral region

Absolute room temperature (294 ± 2 K) absorption cross sections for the ?(1)A(2)-X?(1)A(1) electronic transition of formaldehyde have been measured over the spectral range 30,285-32,890 cm(-1) (304-330 nm) using ultraviolet (UV) laser absorption spectroscopy. Accurate high-resolution absorption cross sections are essential for atmospheric monitoring and understanding the photochemistry of this important atmospheric compound. Absorption cross sections were obtained at an instrumental resolution better than 0.09 cm(-1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (～0.07 cm(-1)) and so we were able to resolve all but the most closely spaced lines. Comparisons with previous data as well as with computer simulations have been made. Pressure broadening was studied for the collision partners He, O(2), N(2), and H(2)O and the resulting broadening parameters have been measured and increase with the strength of intermolecular interaction between formaldehyde and the collision partner. The pressure broadening coefficient for H(2)O is an order of magnitude larger than the coefficients for O(2) and N(2) and will contribute significantly to spectral line broadening in the lower atmosphere. Spectral data are made available as Supporting Information.