Stratospheric negative ion composition measurements,ion abundances and related trace gas detection

Negative ion spectra obtained during four flights with a balloon-borne quadrupole mass spectrometer are reported and critically investigated. Ion abundances for NO₃⁻ and HSO₄⁻ core ions are reported and concentrations of HNO₃ and H₂SO₄ at altitudes between 32 and 35 km are deduced. The detection of minor mass peaks in negative ion spectra obtained at an altitude of 32 km is discussed. Major mass peaks observed at lower altitudes (from 20 to 28 km) are mainly NO₃⁻ due to core ions.     

Stratospheric positive ion composition measurements,ion abundances and related trace gas detection

Positive ion spectra obtained from measurements with a balloon-borne mass spectrometer during three balloon flights are critically investigated and compared with other data. Ion abundances for proton hydrates [H⁺(H₂O)_n ions] at different stratospheric temperatures are compared, as well as the abundances of non proton hydrates H⁺X_itl(H₂O)_m, X being most likely CH₃CN.The detection of trace gases from ion composition measurements is discussed and an upper limit for the number densities of minor constituents such as NH₃ and CH₃OH is estimated at 35 km. Although sodium compounds cannot be responsible for the major positive ions, a closer investigation of high resolution daytime spectra suggests a small contribution of sodium in daytime ion chemistry.     

Stratospheric and tropospheric wave measurements near the Andes mountains

Experimental results and interpretation of temperature, pressure and wind velocity measurements, performed with an instrumented balloon, are presented. The balloon, an open-type stratospheric one was launched from Mendoza (Argentina), near the Andes mountains. The data analysis suggests the presence of a large amplitude quasi-inertial gravity wave, with intrinsic period close to 0.5 days, and vertical wavelength of around 1.7 km just below the tropopause. The possible orographic origin of this wave is discussed. A Fourier analysis confirms the existence of this mode, simultaneously in the temperature and in the wind velocity components. A hodograph of the zonal and meridional wind components shows the expected counterclockwise sense of rotation of the horizontal velocity with increasing altitude, corresponding to a long period gravity wave, in the southern hemisphere.It is found that the vertical wind velocity variations measured by the anemometer, are mainly due to buoyancy force variations induced by the wave on the open stratospheric balloon. The vertical profile obtained by the anemometer is anticorrelated with the rate of ascent or descent of the gondola. As a consequence, the wave induced velocity is very difficult to obtain using these balloons, contrary to the case of radiosonde balloon data. The differences in the response of open stratospheric and radiosonde-type balloons to the presence of internal gravity waves may be explained by their different design and material characteristics.     

In situ measurements of middle atmosphere composition

Experimental data based on aircraft, balloon and rocket measurements of trace species in the middle atmosphere are briefly reviewed. Some ground based observations are also included where no other information is available. The scarcity of values relevant to the vertical distributions is emphasized as well as the lack of knowledge of time and geographic variabilities necessary to understand the physical and chemical properties of the middle atmosphere as well as to monitor its stability over long periods of time.     

Critique as delight,theory as praxis,mucking in

In this commentary, I call for a regenerative approach to critique, a ‘good judgment’ through which academics might nurture the capacity to name and undermine racist, patriarchal, colonising, and homophobic practices, while working relationally to create new worlds. Drawing from Eva Sedgwick's critique of ‘paranoid theory’ and taking inspiration from post‐colonial, feminist, and anti‐racist social movements and research collectives, I consider what it might mean to be an academic who ‘mucks in’, who is not afraid of putting her hands in the dung, and who moves reflexively towards, rather than away from, difficult questions and risky engagements.     

Decadence as historical myth and cultural theory

This article traces the early history of the concept of European decadence with special emphasis on its manifestations in French literary production in the period between 1860 and 1900. It argues that decadence was not a historical reality, but a cultural myth, that gave expression to a new, specifically urban experience of modernity first thematized in Baudelaire's poetry and prose work. It further claims that this concept continues to have important contemporary relevance in the form of debates about the “second modernity” and the new “cosmopolitanism.”     

Positive and negative ion composition measurements in the D- and E-regions during the 26 February 1979 solar eclipse

Two rockets bearing quadrupole mass spectrometers capable of measuring both positive and negative ion composition were launched from Red Lake, Canada, during the solar eclipse. Both instruments had liquid helium cryopumps and shock-attaching conical samplers. The payloads also contained two Gerdien condensers to measure total positive and negative ion concentrations and ion mobilities. Attitude control systems aligned the payloads with the velocity vector throughout ascent and descent. The first rocket was launched so that the D-region was in darkness 35 ± 8 s on the upleg and about 150 ± 15 s on the downleg for the study of ionospheric decay processes. The second rocket was fired after totality into 75% solar illumination for the study of ionospheric recovery. The positive ion composition above 105 km exhibited a strongly increasing NO⁺/O₂⁺ ratio with time after second contact due to O₂⁺ charge transfer with NO and a sharply diminished ionization rate. However, in both nights, the ionization below 105 km was created mainly by energetic particle deposition as exemplified by the increased ion concentrations and the composition signatures of a particle event: asignificant enhancement of O₂⁺ below 105 km and large amounts of H₅O₂⁺ ions in the D-region which result from the O₂⁺ clustering scheme. H₅O₂ was the major ion in the upper D-region while H₇O⁺₃, H₉O₄⁺ and H₅O₂⁺ were dominant ions at lower altitudes. Numerous minor species were also detected. The negative ion distributions in both flights exhibited a distinct shelf at 83 ± 2 km, decreasing by more than an order of magnitude by 90 km and with minima near 75 km. In the 75–90 km range, a significant percentage of the negative ions had masses exceeding 160 a.m.u. Comparisons are made with prior negative ion measurements during similar daytime auroral zone absorption (AZA) events. Two striking characteristics of the precipitating particles were apparent from these and past observations in daytime AZA events: there is a near absence of low energy electrons capable of ionizing above about 105 km and there is'a significant spatial and/or temporal variability in the electron flux. This paper is devoted principally to a presentation of the ion composition measurements and associated uncertainties.     

Klinkenberg gas slippage measurements as a means for shale pore structure characterization

Established techniques that have been successfully used to characterize pore systems in conventional reservoir rocks lack the resolution and scalability required to adequately characterize the nano‐ to micrometer scale pore systems found in shale and cannot be applied on stressed samples. We have therefore investigated the utility of Klinkenberg gas slippage measurements for shale pore structure characterization. In contrast to other approaches, slippage measurements characterize the effective porosity of core samples and can be applied at stress conditions experienced in the reservoir during production. Slippage measurements on horizontally and vertically oriented samples from the Eagle Ford Shale Formation, Texas, USA, at a range of stress states revealed two orders of magnitude in slippage variation over five orders of magnitude permeability range. Slippage measurements are negatively correlated with permeability and follow similar trends to those found in other studies on higher permeability rocks. The samples had varying degrees of slippage anisotropy, which allowed interpretation of the relative contribution of tortuosity and pore size to permeability anisotropy. Slippage and therefore average effective pore size was found to vary up to one order of magnitude at a given permeability, warranting investigation of the significance this might have on flow properties and ultimately hydrocarbon production from shale.     

Stable isotopic composition of chitin from arthropods recovered in archaeological contexts as palaeoenvironmental indicators

The effects of biodegradation and heating on the stable carbon, nitrogen, hydrogen and oxygen isotope ratios of chitin in arthropods were studied. Chitinous exoskeletons from seven aquatic arthropod species were subjected to anaerobic marine biodegradation in mud, to terrestrial biodegradation in soils, and to thermal degradation under anaerobic and aerobic conditions. The isotope ratios of chromatographically separated D-glucosamine hydrochloride and derivatives from treated and untreated specimens were then compared. Carbon, nitrogen, oxygen and hydrogen stable isotope ratios were all found to be conserved during partial degradation of chitin. Micromorphological comparative studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that no fungal chitin or other contaminants were present in the chitins that were chemically isolated from biodegraded substrates. Our results indicate that it will be possible to use stable isotope ratios of archaeological chitin samples for environmental and climatic reconstructions. An illustration of the utility of this approach comes from the observation that the stable isotope ratios of chitin from crustacean exoskeletons recovered from archaeological sites with ages up to 1400 years bp are in good agreement with measurements on modern crustaceans from similar environments.     

Madrid's Retiro Park as publicly-private space and the spatial problems of spatial theory

The scholarly focus on the production of space necessitates a thorough reassessment of the static categories employed in the analysis of spatial processes. Emphasizing space as a process, this essay calls attention to the recent implication of Madrid's Retiro Park in larger processes of capital accumulation. At the same time, it highlights the insufficiency of the tempting yet problematic distinction between public and private space that obtains in easy solutions to the struggles over city-space. As many critics have pointed out, there is design flaw in the idea of public space—it can never explain how a given space, such as a park, comes to be free of the ‘private’ (personal and structural) interests operating throughout its societal context. The story of the Retiro ultimately foregrounds the pivotal role of city-space in the drive for capitalist intercity-competition and suggests that the latter process is insufficiently confronted by idealized notions of the role truly ‘public’ spaces might play in radical democracy and citizenship.     

Boundary theory as a means to understanding social space in archaeological sites

Social space in archaeological sites is constructed and produced by differentiation in behavior (habitus) and is characterized by domains or activity areas separated by boundaries. Activity areas vary in their flexibility and permeability to intrusion of other activities. This is reflected in the nature of the boundaries between activity areas. A study of boundaries, archaeologically often represented by transitional space, can provide insight into human behavior, the use and construction of space, and the contemporaneity of activities represented in a site occupation. It is suggested that kill site activities such as primary butchering may have relatively inflexible and impermeable boundaries, that activities such as tool resharpening may be more flexible, and that secondary processing may be more permeable to the intrusion of other activities. A study of a selection of activity areas at Head-Smashed-In Buffalo Jump confirms that these concepts do enhance our understanding of site activity areas and that an examination of boundaries can allow an assessment of activity area contemporaneity.     

Evolution as context-driven actualisation of potential: toward an interdisciplinary theory of change of state

Abstract

It is increasingly evident that there is more to biological evolution than natural selection; moreover, the concept of evolution is not limited to biology. We propose an integrative framework for characterising how entities evolve, in which evolution is viewed as a process of context-driven actualisation of potential (CAP). Processes of change differ according to the degree of non-determinism, and the degree to which they are sensitive to, internalise and depend upon a particular context. The approach enables us to embed phenomena across disciplines into a broad conceptual framework. We give examples of insights into physics, biology, culture and cognition that derive from this unifying framework.     

Shortcomings in our understanding of the lower ionosphere as revealed by an analysis of radiowave absorption measurements

Empirical relationships derived from an extensive series of equatorial ground-based radiowave absorption measurements are analysed in terms of our current understanding of the basic processes that control the formation and behaviour of the lower ionosphere. Multi-frequency absorption and virtual height measurements are combined with the results of a rocket borne experiment to construct an equatorial noontime reference electron density profile corresponding to the conditions of a non-flaring sun at solar cycle maximum. The enhancement in this electron density profile, and hence in the absorption of radio waves, as the solar 1–8 Å flux increases by moderate amounts is then calculated from our knowledge of the ion production and loss processes. In order to bring the calculated increase of absorption into agreement with the empirically established relationship (Gnanalingam, 1974), we find it necessary to reduce by a factor of about 5 the Meira (1971) nitric oxide densities below 90 km.Attention is drawn to the wide disparity between the effective recombination coefficient and the average dissociative recombination coefficient for the known ion composition in both the molecular and cluster ion regions of the lower ionosphere. The factor of 5 reduction in the nitric oxide profile required to explain the solar control of absorption, however, largely eliminates this disparity in the cluster ion region.Our analysis of the diurnal variation of radiowave absorption and virtual height also reveals a gross discrepancy between the calculated and measured variations. In order to resolve this discrepancy, a mechanism is needed which would cause the electron density in the 95–105 km region to decrease with increasing solar zenith angle faster than is predicted by the present theory of ion production and loss processes in this region.Also presented in this work is an ad hoc model of the diurnal variation of the electron density profile which is consistent with the measured diurnal variation of radiowave absorption and virtual height.     

The photochemical time constants of minor constituents and their families in the middle atmosphere

A comprehensive formula is worked out for the photochemical time constant of minor constituents in the middle atmosphere. The formula is particularly useful for evaluating the time constants for families of some chemical species that are strongly coupled by rapid exchange reactions. Height profiles of photochemical time constants are calculated for individual species and their families based on the chemical reaction rate constants recommended in the recent WMO and JPL reports. Potential exchange reactions among various family members are discussed, and the effects of the choice of family membership on the time constant are evaluated.     

Indirect phase height measurements of the lower ionosphere compared with rocket measurements of D-region electron density

A comparison between rocket-measured electron density profiles of the lower ionosphere and the results of ground-based indirect phase height measurements in the LF range, carried out near the Soviet rocket sounding station Volgograd over several years, confirms—to a first-order approximation—the height of the level of electron density which according to magnetoionic ray theory is necessary for reflection of the waves. In a second-order approximation, however, an additional phase path change has to be taken into account, which is caused by the ionization below the reflection level. This makes the observed phase height always slightly smaller than the real geometric height, on average by −1 km, but in extreme cases by up to −4 km, depending on the actual height gradient of electron density below the reflection level. Due to systematic diurnal and seasonal variations of this gradient, the amplitude of the diurnal variation of the observed phase height is found to be slightly larger than that of the real geometric height, whereas the reverse is true for the seasonal variation at constant solar zenith angle.