On the edge: changing geographies of the global city precariat in London and Hong Kong

Global cities are marked by precarity, yet little attention has been paid to the spatial overlap between work precarity among migrants and third sector organizations that sustain them. In this paper, we estimate the location of precarious work migrants in two global cities, London and Hong Kong, for both the 2001 and 2011 censuses, using a variety of spatial demographic and quantitative techniques, and then analyze the spatial overlap between this population and immigrant-serving third sector organizations. The results suggest both similarity, in particular between accommodation and work precarity, and difference, with an increasingly tenuous overlap in London by 2011.     

Reactions of Cl Atoms with Selected VOCs: Kinetics, Products and Mechanisms

The reactions of isoprene, MBO (2-methyl-3-buten-2-ol) and toluene with chlorine atoms have been studied at 298 ± 5 K and 740 ± 5 Torr with the use of FTIR spectroscopy. Major products of the isoprene-Cl reaction and of the MBO-Cl reaction have been identified and quantified, and reaction mechanisms have been tentatively proposed in order to explain the products formed. The reaction between isoprene and Cl atoms yields mainly HCl, formyl chloride, formic acid, methylglyoxal (pyruvic aldehyde), CO and CO2, while the MBO-Cl reaction forms acetone, HCl, formyl chloride, formic acid, CO, CO2. As products from the reaction between toluene and Cl we identified and quantified HCl and benzaldehyde. The rate constants for the reactions of isoprene and toluene with Cl atoms have also been determined using a relative rate method. The measured values are: kisoprene = (5.5 ± 1.0) × 10–10 cm3 molecule–1 s–1 and ktoluene = (5.6 ± 1.3) × 10–11 cm3 molecule–1 s–1. Atmospheric lifetimes have been estimated from these values.     

Occurrence and distribution of “moganite” in agate/chalcedony: a combined micro-Raman, Rietveld, and cathodoluminescence study

Agate/chalcedony samples of different origin were investigated by performing Raman, X-ray diffraction (using Rietveld refinement), and cathodoluminescence measurements. These analyses were performed to measure the content and spatial distribution of the silica polymorph moganite, which is considered to represent periodic Brazil-law twinning of α-quartz at the unit-cell scale in agate/chalcedonies. Homogeneous standard samples including the nearly α-quartz free moganite type material from Gran Canaria were analysed in order to compare results of the X-ray diffractometry and Raman spectroscopy techniques and to provide a calibration curve for the Raman results. However, due to the different length scales analysed by the two techniques, the “moganite content” in microcrystalline SiO₂ samples measured by Raman spectroscopy (short-range order) was found to be considerably higher than the “moganite content” measured by X-ray diffractometry (long-range order). The difference is explained by the presence of moganite nanocrystals, nano-range moganite lamellae, and single Brazil-law twin-planes that are detected by vibrational spectroscopy but that are not large enough (in the sense of coherently scattering lattice domains) to be detected by X-ray diffractometry. High resolution Raman analysis provides a measure of the moganite content and its spatial variation in microcrystalline silica samples with a lateral resolution in the μm-range. Variations in the moganite-to-quartz ratio are revealed by varying intensity ratios of the main symmetric stretching-bending vibrations (A₁ modes) of α-quartz (465 cm⁻¹) and moganite (502 cm⁻¹), respectively. Traces of Raman microprobe analyses perpendicular to the rhythmic zoning of agates revealed that the moganite-to-quartz ratio is often not uniform but shows a cyclic pattern that correlates with the observed cathodoluminescence pattern (colour and intensity). Data obtained from an agate sample from a fluorite deposit near Okorusu, Namibia and from a volcanic agate from Los Indios, Cuba were selected for detailed presentation. Variations of cathodoluminescence and Raman data between single bands in agates suggest alternating formation of fine-grained, highly defective chalcedony intergrown with moganite, and coarse-grained low-defect quartz. Multiple zones indicate dynamic internal growth during a self-organizational crystallization process from silica-rich fluids. Received: 4 December 1997 / Accepted 19 June 1998     

Diffusive and total oxygen uptake of deep-sea sediments in the eastern South Atlantic Ocean:in situ and laboratory measurements

Total O₂ uptake rates were measured by the benthic flux chamber lander ELINOR, and O₂ microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O₂ fluxes through the diffusive boundary layer and the depth distribution of O₂ consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O₂ consumption rate agreed closely with the diffusive O₂ uptake at all stations. Total O₂ uptake was 1.2–4.2 times the diffusive O₂ uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O₂ uptake and O₂-penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O₂ uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O₂ penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O₂ profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O₂ uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna.     

Eelgrass (Zostera marina L.) as an indicator organism of trace metals in the Limfjord,Denmark

The concentrations of Pb, Cu, Cd and Zn were determined in above- and belowground parts of eelgrass (Zostera marina L.) at forty stations in a shallow, brackish water area (the Limfjord, Denmark). The concentrations of the trace metals were significantly elevated near the cities of Aalborg (Pb, Cu) and Struer (Cd). Trace metal concentrations in above and belowground parts of eelgrass were log-normal distributed and the concentrations of Cd, Cu and Zn in aboveground parts were significantly higher than in belowground parts. Furthermore, a significant correlation between trace metal concentrations in above- and belowground parts was found. The background level of trace metal concentrations in eelgrass in the Limfjord was estimated.The application of eelgrass as a monitoring organism is discussed; it is suggested that the concentration of some trace metals in above- and belowground parts of eelgrass may be used as a measure of the bioavailable fraction of these trace metals in ambient and interstitial water (sediment), respectively.     

High-resolution Echo-sounding and Detection of Embedded Archaeological Objects with Nonlinear Sub-bottom Profilers

Sub-bottom profilers based on nonlinear acoustics offer many advantages especially for detecting and locating embedded objects in shallow waters. They have a narrow beam in spite of small transducers and virtually no side lobes. It is possible to realize mobile low-frequent sub-bottom profilers, which transmit very short sound pulses. Excellent vertical as well as horizontal resolutions at reasonable penetrations are proven benefits of using this technique. In this paper some technical aspects are discussed and a new experimental nonlinear scanning sub-bottom profiler system is described. Results from a field trial in archaeological prospection are shown to illustrate the successful application in practice.     

Lecithotrophic nauplius of the family Dirivultidae (Copepoda; Siphonostomatoida) hatched on board over the Mid-Atlantic Ridge (5°S)

Abstract A copepod nauplius of the family Dirivultidae Humes & Dojiri 1980 is described for the first time. The lecithotrophic nauplius of the widespread symbiotic copepod Stygiopontius pectinatus Humes 1987 was released from females bearing paired egg sacs that included only one yolky embryo each. The ovigerous females of S. pectinatus were washed from the branchial chamber of alvinocaridid shrimps ( Rimicaris exoculata Williams & Rona 1986 ) collected at a deep-sea hydrothermal field on the Mid-Atlantic Ridge at 5° S (Red Lion site, chimney 'Shrimps Farm', depth 3,048 m) by ROV Quest 4000 and maintained in a laboratory on the R/V METEOR (cruise M64/1, 2005). The nauplius of S. pectinatus , appears to be a stage I nauplius because it bears only one pair of caudal setae and the setose bud of maxilla 1 is absent. Like nauplii of other copepods of the order Siphonostomatoida, this nauplius of S. pectinatus possesses a reduced labrum and the body is filled with yolky granules; it also lacks a masticatory process on the antennal coxa. The presence of two inner setae (instead of one seta) on the mandibular endopod is hypothesized to be a primitive character of dirivultids that distinguishes them from the remaining siphonostomatoid genera. The Dirivultidae is a widespread and diverse family of copepods endemic to the deep-sea hydrothermal vents of the Pacific and Atlantic Oceans. Morphological features of the planktonic nauplius of S. pectinatus suggest nutritional independence during their dispersal.