Secondary organic aerosol from limona ketone: insights into terpene ozonolysis via synthesis of key intermediates

Limona ketone was synthesized to explore the secondary organic aerosol (SOA) formation mechanism from limonene ozonolysis and also to test group-additivity concepts describing the volatility distribution of ozonolysis products from similar precursors. Limona ketone SOA production is indistinguishable from alpha-pinene, confirming the expected similarity. However, limona ketone SOA production is significantly less intense than limonene SOA production. The very low vapor pressure of limonene ozonolysis products is consistent with full oxidation of both double bonds in limonene and furthermore with production of products other than ketones after oxidation of the exo double bond in limonene. Mass-balance constraints confirm that ketone products from exo double-bond ozonolysis have a minimal contribution to the ultimate product yield. These results serve as the foundation for an emerging framework to describe the effect on volatility of successive generations of organic compounds in the atmosphere.     

Association thickener by host guest interaction of a β-cyclodextrin polymer and a polymer with hydrophobic side-groups

A host polymer with pending β-cyclodextrin side-groups and a guest polymer with pending hydrophobic 4-tert-butylanilide side groups were synthesized by polymeranalogous reactions starting from poly[(maleic anhydride)-alt-(isobutene)] (M̄_w = 60000). The inclusions of both polymers with complementary monomeric guests and hosts are proven by microcalorimetry. The interaction of the host polymer and the guest polymer in aqueous solution is accompanied by a tremendous increase in viscosity.     

Ion-Dependent Hydration and Transparency of the Corneal Stroma,a Polyelectrolyte Biogel

The cornea is the clear outer window of the eye, composed primarily of dense regular connective tissue called the stroma. The tissue is composed of 70% water and parallel collagen fibrils surrounded by proteoglycans containing high concentrations of acidic and neutral glycosaminoglycans (GAGs) and contains ∼2 – 10% cells by volume. When the surface membranes covering the stroma are damaged by injury or disease, the stroma swells due to the hydrophilic nature of the polysaccharides. At the same time, swelling spreads the collagen fibrils apart and the tissue loses transparency. We investigated the role of different salts in modifying swelling behavior and transparency loss. In saline (148 mM NaCl) solution, hydration increases as a multi exponential function of time: Initially the stroma gains hydration at a fast rate, then slows down. In the presence of divalent cations, swelling behavior significantly decreased, and the effect was weakly anion-dependent. Under imposed stromal swelling pressures, Ca⁺⁺ and Mg⁺⁺ inhibited hydration equally, and their effects were additive, indicating that they work by similar mechanisms. They were also concentration-dependent, with no apparent ceiling to the effect within normal biological ionic strengths. As stated above, Mg⁺⁺ and Ca⁺⁺ both dehydrate stromas and decrease swelling rates compared to saline, and as a stroma hydrates, it loses transparency: visible spectrophotometry of stromas bathed in NaCl lose transparency faster than those bathed in MgSO₄, because MgSO₄ solutions hydrate stromas slower. Stromas bathed in Ca⁺⁺ hydrated slower than those bathed in NaCl, but interestingly, high (49 – 148 mM) concentrations of Ca⁺⁺ caused transparency loss almost instantly. In hyaluronin (a collagen fibril-free polyanionic biogel), when similar concentrations of Ca⁺⁺ were added, transparency also decreased. Our conclusion is that the dehydrating effects of Mg⁺⁺ and low concentrations of Ca⁺⁺ are due to shielding of electrostatic repulsion between anionic GAGs. The higher concentrations of Ca⁺⁺ dehydrate by a combination of covalent binding to (precipitating) GAGs and/or shielding their electrostatic repulsions, and scatter light by precipitating GAGs and disrupting collagen fibril order. These techniques and ionic probes are useful for studying the structure and function of polyionic hydrogels and may be useful for modifying the materials properties of biological and synthetic gels.     

Exploring complex CIDEP of p-benzosemiquinones with time resolved CW-EPR

The time and magnetic field dependent magnetization of polarized signals in the presence of chemically induced magnetization transfer is described by means of a kinetic matrix incorporated into the Bloch equations. The approach is transformed into a computer algorithm accounting for all hyperfine lines present in the system. Solutions are readily obtained by numerical methods. Calculations are applied to the time resolved EPR (TR-EPR) spectroscopic signals of p-benzoquinone after laser flash photolysis. In an aqueous alcoholic solution at pH 2.0, chemical exchange via intermolecular proton transfer is found present between neutral semiquinones. At pH 8.3, the TR-EPR spectrum shows only a uniform signal of the semiquinone. At pH 5.4, a superposition of neutral and anionic radicals is observed together with a protonation-deprotonation equilibrium. A two-step hydrogen atom transfer, consisting of electron transfer followed by protonation, is proposed to account for the formation of both neutral and anionic semiquinone species prior to observation. Experiments in partly deuterated solvent mixtures indicate the existence of three semiquinone forms: BQH^?, BQ^?-, and BQD^? prior to observation. The origin of the proton/deuteron transferred to the anion radical in the precursor state is discussed.     

Asymptotic behaviour of the ratio of density gradient to electron density for atomic systems

The asymptotic behaviour of the negative ratio of the density gradient to the electron density, q(r), for neutral and singly charged atoms has been investigated. The results show that, for large r, q(r) can approach its limit √8?, where ? is the first ionization potential, from either above or below depending on the specific system considered.     

Oscillatory structure of confined fluids

The confinement of fluids in pores and wedges is associated with exponentially damped oscillatory packing structure, as observed with the surface forces apparatus. This paper reviews the statistical mechanics of confined fluids and then illustrates the results with density functional data for hard-sphere solvent. The free energy of the pore fluid and its functional derivatives with respect to thermodynamic fields all oscillate, as a function of pore width, with a wavelength close to the solvent diameter. In contrast, the density at the centre of pores oscillates with twice this wavelength, as a function of pore width. The development of a unified physics of confined fluids is considered. Approximations based on one-dimensional physics do extraordinarily well in planar symmetry at three-dimensions.     

Review of Chemometrics Applied to Spectroscopy: 1985-95, Part 3 — Multi-way Analysis

INTRODUCTION

In this third part of a review on chemometrics in spectroscopy we will describe a recent methodology that has attracted increasing interest in spectroscopy. namely multi-way analysis. The application of multi-way analysis in spectroscopy is still relatively new. hence many methodological improvements are being investigated currently. Part of thls review will also be used to describe the algorithmic improvements gained the last decade.     

Eigenvalues of the difference and product of projections

There is an isomorphism between the matrices over the Boolean algebra of subsets of a k-element set and the k-tuples of Boolean binary (i.e. zero-one) matrices. This isomorphism allows many problems concerning nonbinary Boolean matrices to the referred to the binary ease. However, there are some features of the general (i.e. nonbinary) case that have not been mentioned, although they differ somewhat from the binary case. We exhibit characterizations of the linear operators that preserve several invariants of matrices over finite Boolean algebras to illustrate the differences and similarities of the general vs. the binary cases. We employ a canonical form that is useful in applying the isomorphism.     

Comparison of graphite,aluminum, and TransHab shielding material characteristics in a high-energy neutron field

Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study.     

Organometallic Polymers. XXVII. Radical-Initiated Polymerization and Copolymerization of π-(2, 4-Hexadien-1-yl Acrylate) tricarbonyliron

The novel monomer, π-(2, 4-hexadiene- l-yl acrylate) tricarbonyliron (HATI), has been prepared by two routes. It was homopolymerized and copolymerized with acrylonitrile, vinyl acetate, styrene, and methyl acrylate in benzene solutions. In all cases azobisisobutyronitrile was the initiator. The relative reactivity ratios, where HATI is defined as M₁, were determined: r₁ = 0.34, r₂ = 0.74, M₂ = acrylonitrile; r₁ = 2.0, r₂ = 0.05, M₂ = 0.74, M₂ = acrylonitrile; r₁ = 2.0, r₂ = 0.05, M₂ = vinyl acetate; r₁ = 0.26, r₂ = 1.81, M₂ = styrene; and r₁ = 0.30, r₂ = 0.74, M₂ = methyl acrylate. The homo-and copolymers had high values of T_g. When polymerizations are carried out at high concentrations, a very high molecular weight tail is observed in HATI hompolymerizations and in HATI-methyl acrylate copolymerizations. The polymers were characterized by IR, gel permeation chromatography, viscosity, and differential scanning calorimetry studies. Finally, thermal decompositions carried out in air resulted in decomposition of the Fe(CO)₃ group, producing Fe₂O₃ as a fine powder. Thermal decomposition under nitrogen (in solution and on solids ground into KBr pellets) resulted in slow destruction of the Fe(CO)₃ groups but the resulting polymer mass was insoluble, and the question of what form the iron exists in (Fe metal, oxides, carbides, etc.) has not been answered.