Measurements of Isoprene-Derived Organosulfates in Ambient Aerosols by Aerosol Time-of-Flight Mass Spectrometry—Part 2: Temporal Variability and Formation Mechanisms

Organosulfate species have recently gained attention for their potentially significant contribution to secondary organic aerosol (SOA); however, their temporal behavior in the ambient atmosphere has not been probed in detail. In this work, organosulfates derived from isoprene were observed in single particle mass spectra in Atlanta, GA during the 2002 Aerosol Nucleation and Characterization Experiment (ANARChE) and the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Real-time measurements revealed that the highest organosulfate concentrations occurred at night under a stable boundary layer, suggesting gas-to-particle partitioning and subsequent aqueous-phase processing of the organic precursors played key roles in their formation. Further analysis of the diurnal profile suggests possible contributions from multiple production mechanisms, including acid-catalysis and radical-initiation. This work highlights the potential for additional SOA formation pathways in biogenically influenced urban regions to enhance the organic aerosol burden

A Method to Tackle First Order Differential Equations with Liouvillian Functions in the Solution - II

We present a semi-decision procedure to tackle first order differential equations, with Liouvillian functions in the solution (LFOODEs). As in the case of the Prelle-Singer procedure, this method is based on the knowledge of the integrating factor structure.Comment: 11 pages, late

Fe on W(001) from continuous films to nanoparticles: Growth and magnetic domain structure

The evolution of the structural and magnetic properties of Fe films during growth on the W(001) surface have been studied with low energy electron diffraction, real-time low energy electron microscopy, and quasi-real-time, spin-polarized low energy electron microscopy in the absence of a magnetic field (virgin state). Depending on the growth temperature, different growth modes are observed: growth of atomically rough and highly strained (10.4% tensile) pseudomorphic films at room temperature, kinetically limited layer-by-layer growth (quasi–Frank-van der Merwe growth mode) of smooth pseudomorphic films up to 4 monolayers at around 500 K and growth of fully relaxed three-dimensional Fe islands on top of a thermodynamically stable 2-monolayer-thick wetting layer (Stranski-Krastanov growth mode) at and above 700 K. Around 500 K, layered growth is terminated by partial (2 monolayers) dewetting of the metastable Fe film and formation of thin, partially relaxed, elongated islands on a thermodynamically stable 2 monolayer film. Ferromagnetic order is first detected during growth at room temperature at 2.35 monolayer Fe film thickness. The magnetization is in-plane with a thickness-dependent direction, rotating from the substrate ⟨110⟩ directions at 3 monolayers toward the ⟨100⟩ directions at 4 monolayers and back again toward the ⟨110⟩ directions at about 8 monolayers. The in-plane spin reorientation that occurs at room temperature is accompanied by significant changes of the magnetic domain structure. In the Frank-van der Merwe growth regime, large magnetic domains are observed in metastable 3 and 4 monolayer films. The isolated three-dimensional Fe islands that form in the Stranski-Krastanov regime have vortex, quasi-single domain (C state), or single magnetic domain structures, depending on their size and shape. The detailed results that are obtained with high thickness, lateral and azimuthal angular resolution with spin-polarized low energy electron microscopy are compared with earlier laterally averaging and laterally resolving magnetic studies, and discrepancies are explained

Measurements of Isoprene-Derived Organosulfates in Ambient Aerosols by Aerosol Time-of-Flight Mass Spectrometry - Part 1: Single Particle Atmospheric Observations in Atlanta

Organosulfate species have recently been identified as a potentially significant class of secondary organic aerosol (SOA) species, yet little is known about their behavior in the atmosphere. In this work, organosulfates were observed in individual ambient aerosols using single particle mass spectrometry in Atlanta, GA during the 2002 Aerosol Nucleation and Characterization Experiment (ANARChE) and the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Organosulfates derived from biogenically produced isoprene were detected as deprotonated molecular ions in negative-ion spectra measured by aerosol time-of-flight mass spectrometry; comparison to high-resolution mass spectrometry data obtained from filter samples corroborated the peak assignments. The size-resolved chemical composition measurements revealed that organosulfate species were mostly detected in submicrometer aerosols and across a range of aerosols from different sources, consistent with secondary reaction products. Detection of organosulfates in a large fraction of negative-ion ambient spectra − ca. 90−95% during ANARChE and ~65% of submicrometer particles in AMIGAS − highlights the ubiquity of organosulfate species in the ambient aerosols of biogenically influenced urban environments

Permutation symmetry for the tomographic probability distribution of a system of identical particles

The symmetry properties under permutation of tomograms representing the states of a system of identical particles are studied. Starting from the action of the permutation group on the density matrix we define its action on the tomographic probability distribution. Explicit calculations are performed in the case of the two-dimensional harmonic oscillator.Comment: 13 pages, latex, no figure

Spacetime Emergence and General Covariance Transmutation

Spacetime emergence refers to the notion that classical spacetime "emerges" as an approximate macroscopic entity from a non-spatio-temporal structure present in a more complete theory of interacting fundamental constituents. In this article, we propose a novel mechanism involving the "soldering" of internal and external spaces for the emergence of spacetime and the twin transmutation of general covariance. In the context of string theory, this mechanism points to a critical four dimensional spacetime background.Comment: 11 pages, v2: version to appear in MPL

Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments

We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The NanoImprint lithography is used to align perpendicularly lamellar phases, over distances much larger than the natural lamellar periodicity. The modeling relies on self-consistent field calculations done in two- and three-dimensions. We get a good agreement with the NanoImprint lithography setups. We find that, at thermodynamical equilibrium, the ordered BCP lamellae are much better aligned than when the films are deposited on uniform planar surfaces

Mesoscopic colonization of a spectral band

We consider the unitary matrix model in the limit where the size of the matrices become infinite and in the critical situation when a new spectral band is about to emerge. In previous works the number of expected eigenvalues in a neighborhood of the band was fixed and finite, a situation that was termed "birth of a cut" or "first colonization". We now consider the transitional regime where this microscopic population in the new band grows without bounds but at a slower rate than the size of the matrix. The local population in the new band organizes in a "mesoscopic" regime, in between the macroscopic behavior of the full system and the previously studied microscopic one. The mesoscopic colony may form a finite number of new bands, with a maximum number dictated by the degree of criticality of the original potential. We describe the delicate scaling limit that realizes/controls the mesoscopic colony. The method we use is the steepest descent analysis of the Riemann-Hilbert problem that is satisfied by the associated orthogonal polynomials.Comment: 17 pages, 2 figures, minor corrections and addition

Tropological space : the imaginary space of figuration

The paper is devoted to the concept of tropological space, introduced by Michel Foucault in 1966 and alluded to in Hayden White’s tropics of discourse (1973, 1978, 2000), but never described in any detail in literary semantics or linguistic stylistics. The author presents her theory of a triple functional subdivision of stylistic figures and, consequently, of tropes (micro-, macro- and mega (meta)-level of description) and relates it to a gradually expanding tropological space of particular figures, their chains and groupings within a text. The author postulates that tropological space, the imaginary space created through figuration, is a sub-space of the Wittgensteinian logical space as well as a sub-space of textual / discursive space. Although the discussion refers mostly to literary texts, tropology – a branch of stylistics / poetics / rhetoric makes generalizations valid for the study of all kinds of texts / discourses. Figuration is assumed here to be an inherent feature of conceptual and linguistic expression. Finally, the author raises a methodological query as to the ontological status of tropological space, opting for the approach which treats it as a peculiar kind of semantic space rather than a mere metaphoric term. The discussion is based mostly on the Anglo-American studies on figuration (K. Burke, H. White, P. de Man, J. Hillis Miller, G. Hartman) that are rooted in the neo-classical rhetoric and writings of G. Vico. This line of thinking draws its philosophical inspiration from the European hermeneutics of P. Ricoeur, the Foucaultian theory of discourses and the Derridean deconstructionist ideas on the operation of language. The author brings additionally into consideration the conception of artistic space propagated by the Russian semiotic tradition and V. N. Toporov (1983/2003) in particular

Convex optimization problem prototyping for image reconstruction in computed tomography with the Chambolle-Pock algorithm

The primal-dual optimization algorithm developed in Chambolle and Pock (CP), 2011 is applied to various convex optimization problems of interest in computed tomography (CT) image reconstruction. This algorithm allows for rapid prototyping of optimization problems for the purpose of designing iterative image reconstruction algorithms for CT. The primal-dual algorithm is briefly summarized in the article, and its potential for prototyping is demonstrated by explicitly deriving CP algorithm instances for many optimization problems relevant to CT. An example application modeling breast CT with low-intensity X-ray illumination is presented.Comment: Resubmitted to Physics in Medicine and Biology. Text has been modified according to referee comments, and typos in the equations have been correcte