An FTIR spectrometer for remote measurements of atmospheric composition

The JPL IV interferometer, and infrared Michelson interferometer, was built specifically for recording high resolution solar absorption spectra from remote ground-based sites, aircraft and from stratospheric balloons. The instrument is double-passed, with one fixed and one moving corner reflector, allowing up to 200-cm of optical path difference (corresponding to an unapodised spectral resolution of 0.003/cm). The carriage which holds the moving reflector is driven by a flexible nut riding on a lead screw. This arrangement, together with the double-passed optical scheme, makes the instrument resistant to the effects of mechanical distortion and shock. The spectral range of the instrument is covered by two liquid nitrogen-cooled detectors: an InSb photodiode is used for the shorter wavelengths (1.85 to 5.5 microns, 1,800 to 5,500/cm) and a HgCdTe photoconductor for the range (5.5 to 15 microns, 650 to 1,800/cm). For a single spectrum of 0.01/cm resolution, which requires a scan time of 105 seconds, the signal/noise ratio is typically 800:1 over the entire wavelength range

Infrared aircraft measurements of stratospheric composition over Antarctica during September 1987

The JPL Mark IV interferometer recorded high resolution, infared solar spectra from the NASA DC-8 aircraft during flights over Antarctica in September 1987. The atmospheric absorption features in these spectra were analyzed to determine the overburdens of O3, NO, NO2, HNO3, ClONO2, HCl, HF, CH4, N2O, CO, H2O and CFC-12. The spectra were obtained at latitudes which ranged between 64 degrees S and 86 degrees S, allowing the composition in the interior of the polar vortex to be compared with that at the edge. The latitude dependence observed for NO, HO2, HNO3, ClONO2, HCl and HF are summerized. The values at 30 deg S were observed on the ferry flight from New Zealand to Hawaii. The dashed lines connecting the two were interpolated across the region for which there are no measurements. The chemically perturbed region is seen to consist of a collar of high HNO3 and ClONO2 surrounding a core in which the overburdens of these and of HCl and NO2 are very low. Clear increases in the overburdens of HF and HNO3 were observed during the course of September in the vortex core. HCl and NO2 exhibited smaller, less significant increases. The overburdens of the tropospheric source gases, N2O, CH4, CF2Cl2, and H2O were observed to much smaller over Antarctica than at mid-latitudes. This, together with the fact that HF over Antarctica was more that double its mid-latitude value, suggests that downwelling has occurred

Genetic Correlations Greatly Increase Mutational Robustness and Can Both Reduce and Enhance Evolvability.

Mutational neighbourhoods in genotype-phenotype (GP) maps are widely believed to be more likely to share characteristics than expected from random chance. Such genetic correlations should strongly influence evolutionary dynamics. We explore and quantify these intuitions by comparing three GP maps-a model for RNA secondary structure, the HP model for protein tertiary structure, and the Polyomino model for protein quaternary structure-to a simple random null model that maintains the number of genotypes mapping to each phenotype, but assigns genotypes randomly. The mutational neighbourhood of a genotype in these GP maps is much more likely to contain genotypes mapping to the same phenotype than in the random null model. Such neutral correlations can be quantified by the robustness to mutations, which can be many orders of magnitude larger than that of the null model, and crucially, above the critical threshold for the formation of large neutral networks of mutationally connected genotypes which enhance the capacity for the exploration of phenotypic novelty. Thus neutral correlations increase evolvability. We also study non-neutral correlations: Compared to the null model, i) If a particular (non-neutral) phenotype is found once in the 1-mutation neighbourhood of a genotype, then the chance of finding that phenotype multiple times in this neighbourhood is larger than expected; ii) If two genotypes are connected by a single neutral mutation, then their respective non-neutral 1-mutation neighbourhoods are more likely to be similar; iii) If a genotype maps to a folding or self-assembling phenotype, then its non-neutral neighbours are less likely to be a potentially deleterious non-folding or non-assembling phenotype. Non-neutral correlations of type i) and ii) reduce the rate at which new phenotypes can be found by neutral exploration, and so may diminish evolvability, while non-neutral correlations of type iii) may instead facilitate evolutionary exploration and so increase evolvability.This work was funded under EP/P504287/1 by the Engineering and Physical Sciences Research Council (https://www.epsrc.ac.uk). SEA is supported by The Royal Society (https://royalsociety.org/).This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/10.1371/journal.pcbi.100477

A Critical Review of Clinical Arteriogenesis Research

In human hearts, an extensive pre-existing collateral network is present. This was shown unequivocally some 50 years ago in a series of very detailed post-mortem angiographic studies. In these studies, it was also observed that the pre-existent collateral vessels enlarge upon closure of an epicardial coronary artery, resulting in large collateral conduit arteries, in sharp contrast to earlier claims that human coronary arteries are functional end arteries. These insights still form the basis for the concept of arteriogenesis as positive remodeling of pre-existent arteriolar connections. Subsequent experimental studies disclosed the putative role of circulating cells, especially monocytes, which invade the proliferating vessel wall and secrete growth factors, degrading enzymes and survival factors that are required for the development of a mature collateral circulation. Experimental stimulation of arteriogenesis is feasible but to date a relatively low number of clinical studies, with no or limited success, have been performed. The use of intracoronary derived collateral flow index can increase the sensitivity to detect the effects of pharmacological compounds on arteriogenesis, which is important in first proof-of-principle studies. These invasive measurements also allow the detection of patients with an innate defect in their arteriogenic response to coronary obstruction. In a reversed bedside-to-bench approach, the characterization of ribonucleic acid and protein expression patterns in these patients generated new targets for therapeutic arteriogenesis

Surgery groups of the fundamental groups of hyperplane arrangement complements

Using a recent result of Bartels and Lueck (arXiv:0901.0442) we deduce that the Farrell-Jones Fibered Isomorphism conjecture in L-theory is true for any group which contains a finite index strongly poly-free normal subgroup, in particular, for the Artin full braid groups. As a consequence we explicitly compute the surgery groups of the Artin pure braid groups. This is obtained as a corollary to a computation of the surgery groups of a more general class of groups, namely for the fundamental group of the complement of any fiber-type hyperplane arrangement in the complex n-space.Comment: 11 pages, AMSLATEX file, revised following referee's comments and suggestions, to appear in Archiv der Mathemati

Imaging the Electrocyte of Torpedo Marmorata by Scanning Force Microscopy

Scanning force microscopy (SFM) and scanning electron microscopy (SEM) were used to examine the tissue structure of the electric organ of Torpedo marmorata in air and in liquid after applying fracturing and cryosectioning techniques and chemical fixation. The electric organ is organized in columns of stacked electrocytes, arranged in a honeycomb pattern. The columns were cut along a plane normal to the cell stack and thin sections were transferred to polylysine coated glass coverslips. The polarity of the electrocytes was made apparent by immunofluorescence microscopy directed to different domains of the acetylcholine receptor (AChR), thus revealing the innervated face of the cell. SFM and SEM both showed cell surfaces to be overlaid by a network of collagen fibers by their characteristic banding pattern with about 64 nm periodicity and about 2.5 nm corrugation amplitude. In liquid, significantly lower structural resolution was achieved by SFM, probably due to sample elasticity