Kinetic and oscillating processes in aqueous solutions.

The first part of the thesis is concerned with oscillating chemical reactions, The Belousov - Zhabotinskii reaction is examined experimentally with respect to the dependence of the frequency of oscillation on temperature for a variety of initial conditions. In another series of experiments, the Belousov - Zhabotinskii reaction is perturbed from its oscillatory phase by the rapid addition of solutions containing either Ce(IV) or Br ions. Both species are intermediates in the reaction scheme. The results are compared with a computer analysis of model schemes for the reaction. In the second part, the kinetics of reaction between the tris(1,10 - phenanthroline) iron (ll) cation and hydroxide ions in water - methyl alcohol and acetone - water mixtures are examined. Here the second order rate constants are determined, The results are analysed in terms of the transfer parameters for the change in chemical potential on going from water to the cosolvent - water mixture. In the case of methyl alcohol - water mixtures the analysis is extended with the aid of an empirical model based upon naphthalene and naphthol, First order rate constants (aquation) are also reported. The final part is concerned with an application of the pair potential model for the interaction between two species in solution. Computation by means of the Hypernetted Chain integral approximation yields values of the osmotic coefficient of a salt in solution. Kinetic data from the literature for the hydrolysis of t-butyl chloride in solutions containing the ion K+ and the tetramethylammonium cation are used to calculate Setchenow coefficients. These values yield information concerning solute - solute interactions in the initial state and the transition state of the hydrolysis

Lion sightings in the eastern Maghreb of Algeria and Tunisia, 1881–1900 (Ksour Mountains, Saharan Atlas, Tell Atlas, Ouled-Nail, Aurès Mountains).

<p>NP = one of several National Parks established across the region in the 1980s–1990s.</p

The last sightings of lions in the Western Maghreb: Morocco to Western Sahara, 1830s–1940s (Rif Mountains, Anti Atlas, Middle Atlas and High Atlas).

<p>NP = one of several National Parks established across the region since the 1940s.</p

Distribution of recent sightings of lions in North Africa (AD 1900–1960).

<p>Grey shading indicates Mediterranean scrubland ecosystems <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060174#pone.0060174-Dobson1" target="_blank">[8]</a>. Circular markers indicate sightings in western Maghreb (8–21 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060174#pone-0060174-t001" target="_blank">Table 1</a>); triangular markers indicate sightings in eastern Maghreb (134–149) from incidents described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060174#pone-0060174-t006" target="_blank">Table 6</a>. The dotted line indicates the air route across the Atlas Mountains (Casablanca-Agadir-Dakar) during which the last wild lion was photographed. Asterisks (*) denote locations of human population centers. Dashed lines indicate national boundaries.</p

Last lion sightings recorded in the eastern Maghreb of Algeria, 1900–1960 (Ksour Mountains, Saharan Atlas, Tell Atlas, Ouled-Nail, Aurès Mountains).

<p>Last lion sightings recorded in the eastern Maghreb of Algeria, 1900–1960 (Ksour Mountains, Saharan Atlas, Tell Atlas, Ouled-Nail, Aurès Mountains).</p

A lion seen in the Atlas Mountains, during a flight on the Casablanca-Dakar air route.

<p>The photograph taken by Marcelin Flandrin in 1925 is the last visual record of a wild ‘Barbary’ lion of North Africa.</p

Lion sightings in the eastern Maghreb of Algeria and Tunisia, 1851–1860 (Ksour Mountains, Saharan Atlas, Tell Atlas, Ouled-Nail, Aurès Mountains).

<p>NP = one of several National Parks established across the region in the 1980s–1990s.</p

Lion sightings in the eastern Maghreb of Algeria and Tunisia, 1861–1880 (Ksour Mountains, Saharan Atlas, Tell Atlas, Ouled-Nail, Aurès Mountains).

<p>NP = one of several National Parks established across the region in the 1980s–1990s.</p

Molecular fingerprinting of wetland organic matter using pyrolysis-GC/MS: an example from the southern Cape coastline of South Africa

Pyrolysis–gas chromatography mass spectrometry (py-GC/MS) allows the characterisation of complex macromolecular organic matter. In lakes and wetlands this can potentially be used to assess the preservation/diagenesis and provenance of sediment organic matter. It can complement palaeoenvironmental investigations utilising ‘bulk’ sediment variables such as total organic carbon (TOC) and TOC/total nitrogen ratios. We applied py-GC/MS analyses to a ~32,000-year sediment record from the southern Cape coastline of South Africa. We used the results to evaluate the sources and extent of degradation of organic matter in this semi-arid environment. Marked down-core changes in the relative abundance of multiple pyrolysis products were observed. Correspondence analysis revealed that the major driver of this down-core variability in OM composition was selective preservation/degradation. Samples comprising highly degraded OM are primarily confined to the lower half of the core, older than ~12,000 years, and are characterised by suites of low-molecular-weight aromatic pyrolysis products. Samples rich in organic matter, e.g. surface sediments, are characterised by products derived from fresh emergent or terrestrial vegetation, which include lignin monomers, plantderived fatty acids and long-chain n-alkanes. Pyrolysates from the late glacial-early Holocene period, approximately mid-way down the core are characterised by distinct suites of long-chain n-alkene/n-alkane doublets, which may reflect the selective preservation of recalcitrant aliphatic macromolecules and/or enhanced inputs of the algal macromolecule algaenan/polymerised algal lipids. Increased TOC, lower δ[superscript 13]C and increased abundance of more labile lignin and fatty acid products at the same depths suggest this period was associated with increased lake primary productivity and enhanced inputs of terrestrial OM. TOC is the only ‘bulk’ parameter correlated with the correspondence analysis axes extracted from the py-GC/MS data. Distinct fluctuations in TOC/total nitrogen ratio are not explained by variation in organo-nitrogen pyrolysis products. Notwithstanding, the study suggests that py-GC/MS has potential to complement palaeolimnological investigations, particularly in regions such as southern Africa, where other paleoenvironmental proxy variables in sediments may be lacking or equivocal

Bootstrapped mean number of reptiles that died within a year of acquisition, over five years preceding the study, including 95% confidence intervals, estimated for additive (aRRT) and direct questions (DQ) via 1000 bootstrap samples.

<p>Note that mean number of reptiles that died refers to the actual number not the mortality rate. Mortality rates incorporate the numbers of reptiles owned and are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141460#pone.0141460.g001" target="_blank">Fig 1</a>.</p><p>^a estimates for ‘all reptiles’ were derived post-data collection by combining ‘all snakes’, ‘all chelonians’ and ‘all lizards’ for individual respondents, therefore an aRRT response is not available for this category.</p><p>Bootstrapped mean number of reptiles that died within a year of acquisition, over five years preceding the study, including 95% confidence intervals, estimated for additive (aRRT) and direct questions (DQ) via 1000 bootstrap samples.</p