High-pass filters for spectral background suppression in airborne passive Fourier transform infrared spectrometry

High-pass (HP) digital filtering and second-derivative (SD) filtering are evaluated as methods of removing background contributions from spectra collected by passive Fourier transform infrared spectrometry. In measurements performed with a downward-looking spectrometer mounted on an aircraft platform, the effects of non-constant background radiance from the ground make it challenging to build automated classifiers for detecting an analyte of interest. Applying HP digital filtering to the spectra to remove background contributions is evaluated as a strategy to help improve classifier performance. This methodology is tested by building classifiers for detecting heated ethanol plumes released from a portable emission stack. The classifiers are trained with data collected on the ground with the spectrometer viewing the plumes against a synthetic backdrop designed to simulate a terrestrial radiance source. The resulting classifiers are tested with data collected by the same spectrometer mounted on an aircraft flying over the emission stack. Support vector machines are employed as a classification algorithm with HP filtered spectra used as input patterns. Butterworth filters are used to implement HP digital filtering, while Savitzky-Golay filters are used to implement SD filtering. Significant improvement in classification performance is achieved by use of the HP filters. Because of variation in backgrounds between the training and prediction data, the best classifier obtained with unfiltered spectra is unable to detect ethanol in 37% of the test cases. HP filtering of spectra with an optimized Butterworth filter (order 8, cutoff frequency 0.060) improves the prediction results, resulting in no missed ethanol detections and false positive rates of less than 0.4%.     

First soluble M@C60 derivatives provide enhanced access to metallofullerenes and permit in vivo evaluation of Gd@C60[C(COOH)2]10 as a MRI contrast agent

M@C(60) and related endohedral metallofullerenes comprise a significant portion of the metallofullerene yield in the traditional arc synthesis, but their chemistry and potential applications have been largely overlooked because of their sparse solubility. In this work, procedures are described to solublize Gd@C(60) species for the first time by forming the derivative, Gd@C(60)[C(COOCH(2)CH(3))(2)](10), and its hydrolyzed water-soluble form, Gd@C(60)[C(COOH)(2)](10). Imparting water solubility to Gd@C(60) permits its evaluation as a magnetic resonance imaging (MRI) contrast agent. Relaxometry measurements for Gd@C(60)[C(COOH)(2)](10) reveal it to possess a relaxivity (4.6 mM(-1) s(-1) at 20 MHz and 40 degrees C) comparable to that of commercially available Gd(III) chelate-based MRI agents. An in vivo MRI biodistribution study in a rodent model reveals Gd@C(60)[C(COOH)(2)](10) to possess the first non-reticuloendothelial system (RES) localizing behavior for a water-soluble endohedral metallofullerene species, consistent with its lack of intermolecular aggregation in solution as determined by light-scattering measurements. This first derivatization and use of a M@C(60) species suggests new potential for metallofullerene technologies by reducing reliance on the chromatographic purification procedures normally employed for the far less abundant M@C(82) and related endohedrals. The recognition that water-soluble fullerene derivatives can be designed to avoid high levels of RES uptake is an important step toward fullerene-based pharmaceutical development.     

Determination of the crystal structure and the spectroscopic data of Pd(N,N′ -dicyclopentyldithiooxamide)2

Summary The title compound exhibits a PdS₄ coordination geometry, demonstrated by crystallographic and n.m.r. measurements. The bond distances and valence angles of the complex are discussed using the information provided by i.r. measurements. Despite the strong S,S steric hindrance in the compound, the C-C bond distance is shorter in the complex than in the free ligand. The i.r. spectra also provide evidence for strong intramolecular hydrogen bonds.     

Activity coefficient of hydrochloric acid in the system HCl−KCl−H2O at 25°C and lonic strengths from 0.1 to 3 moles-kg−1

The activity coefficient of hydrochloric acid has been determined in HCl–KCl–H₂O mixtures at 25°C and for seven values of the ionic strength between 0.1 and 3.0 mole-kg^–1, using the cellPt;H ₂(g, 1atm)\HCl(m _A ),KCl _B AgCl;Ag The results are compared with those of previous studies of the same system and are interpreted in terms of ionic interactions specific to the mixture by use of Pitzer's treatment of mixed electrolyte solutions.     

3-Triethylsilyloxypentadienyllithium,a Versatile 1,3-Diene- or Vinyl Ketone-Building Block

Deprotonation of the 3-trialkylsilyloxy-1,4-diene 3a and subsequent electrophilic substitution of the non-isolated 3-trialkylsilyoxypentadienyllithium 4 gives the α- and γ-products 8 and/or 6 in good yields. Whereas alkylation of 4 proceeds with variable regioselectivity (Table 1) aldehydes and ketones attack preferentially the γ-position of 4 (Table 2). The desired γ-products 6 may be directly subjected to inter- and intramolecular [4 + 2]-additions as demonstrated by the reactions 5a (? 6d ) → 7 and 6h → 19 (Schemes 4 and 12). Alternatively, smooth fluoride-promoted silylether-cleavage 6 → 11 (Scheme 8) provides a convenient approach to substituted vinyl ketones such as to the natural products 11f (Table 3). The stereoselective conversion 6k → 23 (Scheme 13) implies an endo-selective intramolecular Diels-Alder addition ( 26 → 23 ) and exemplifies the use of 4 as an equivalent of the hypothetical anion IV . Furthermore, some electrophilic substitutions of the hexadienyllithium 15 have been studied (Scheme 10).     

Semiclassical calculation of the vibrational echo

The infrared echo measurement probes the time scales of the molecular motions that couple to a vibrational transition. Computation of the echo observable within rigorous quantum mechanics is problematic for systems with many degrees of freedom, motivating the development of semiclassical approximations to the nonlinear optical response. We present a semiclassical approximation to the echo observable, based on the Herman-Kluk propagator. This calculation requires averaging over a quantity generated by two pairs of classical trajectories and associated stability matrices, connected by a pair of phase-space jumps. Quantum, classical, and semiclassical echo calculations are compared for a thermal ensemble of noninteracting anharmonic oscillators. The semiclassical approach uses input from classical mechanics to reproduce the significant features of a complete, quantum mechanical calculation of the nonlinear response.     

High-field asymmetric waveform ion mobility spectrometry: a new tool for mass spectrometry

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is a new technology for ion separation at atmospheric pressure. This review introduces the reader to FAIMS, covering topics ranging from the fundamentals and extraction of physical parameters from the raw data, to applications of FAIMS extending from homeland security to environmental analysis to proteomics. The investigation of FAIMS as an ion pre-processing tool for mass spectrometry is in its infancy, but reports in the literature illustrate that FAIMS separates isobaric ions including diastereoisomers, separates isotopes, reduces background ions by isolating ions of interest, and simplifies spectra of complex mixtures by dividing the mixture into a series of simpler subsets of ions. Applications ranging from quantitative analysis of inorganic and organometallic compounds, to studies of the conformers of intact proteins, have been reported. This review is a launching point for further exploration of FAIMS.     

A numerical examination of certain null geodesies of a high angular momentum kerr field

An observer situated anywhere but in the equatorial plane of a high angular momentum Kerr field cannot see the ring singularity. In the visual field of such an observer, what demarcates his own universe from that through the ring?The projections onto a certain submanifold of the null geodesics which pass through a point on the symmetry axis of a specific Kerr field are examined numerically. All the distinct projections are obtained by varying one parameter, essentially the quadratic Killing tensor constant. Various interesting features of the geodesics emerge.Through the ring is a region in which there exist closed time-like curves and which can be used to construct closed time-like curves through any non-singular point of the manifold. Only geodesies of negative angular momentum can enter this region.     

A method for the analysis of equilibrium multipart prices in oligopolistic markets

Motivated by the fact that both long distance and local telephone business are evolving into markets consisting of a few firms having different cost structures and offering multipart pricing schedules, and by the fact that there are almost no analyses of markets of this type in the economics literature, a methodology is developed for the analysis of multipart prices in these markets. The approach makes use of variational inequality theory to model static Nash equilibria in multipart prices, and a marketing type product space model for differentiated products imbedded in a discrete choice model framework to model the demand. The approach is designed to be applicable to real world problems; it is flexible and constraints encountered in the real world can be imposed. Two specific models are developed for two-part tariffs, one without resale of services allowed and one allowing for resale. Some qualitative results concerning existence and uniqueness are presented, but the strength of the methodology is quantitative analysis. An algorithm for finding equilibria is presented. An example market representing business WATS is presented to demonstrate the method. The variety of scenarios that can be investigated using the methodology demonstrate its potential to be a very useful tool for the analysis of oligopolistic markets in which multipart prices are prevalent.