Labour time in South African gold mines : 1886-2006.

The core question of this thesis is why working time in South African gold mining has been so stable and addresses the significance of this fact. The working or labour time of miners and mineworkers is shown to have been remarkably stable for a century since 1911. By construing the length of the migrant labour contract as a measure of labour time, which systematically lengthens over the same period until it aligns with the annual rhythm of industrial working time, the evidence is provided for the argument that labour time constitutes the hitherto unrecognised foundation for the exploitation of mine labour in the South African gold mines. The phenomena - and importance for value-creation - of both relatively long, stable industrial working hours and the ever-longer migrant labour contracts over a century, are explained in terms of the value labour power creates in the mining labour process, as well as how the sheer expenditure of extended periods of labour time create the necessary skills mining requires. The fortunes of the platinum mining sector largely follow suit. Whereas the revisionist literature focused on the acquisition of a mine labour supply, this thesis argues that the retention of mine labour, by way of extending, intensifying and sustaining labour time in mining production, completes our understanding of its exploitation. It does so by employing a value-theoretic analysis which reveals the genesis of value creation in productive social class-based relationships. It shows how a series of qualitative, socially constructive effects, intra-working class occupational differentiation for example, emanate from the very expenditure of labour time underground when measured as a quantitative amount of labour time. It is argued that the substantive study of labour time has been surprisingly ignored in Marxist theory within which it plays a central role in the labour theory of value. A range of research methodologies have been employed to make this case. An ethnographic participant observation research method was aimed at articulating an agent-sensitive approach. The candidate lived in the hostel compounds and worked underground with mining personnel and has been both subject to the working time regimes on the mines as well as having actively participated, via various forms of research, in dealing with restructuring and changing working time schedules. The thesis goes on to show in close empirical detail, informed by actual experience and adopting a triangulated research methodology, how working time arrangements within which labour time is expended, remains immured in complexity. Why capital and labour, for instance, adopt competing stances regarding the restructuring of working time arrangements is explained. I conclude that workers’ production demands need to be taken seriously when working time is restructured in mining

The roles of visual parallax and edge attraction in the foraging behaviour of the butterfly Papilio xuthus.

Several examples of insects using visual motion to measure distance have been documented, from locusts peering to gauge the proximity of prey, to honeybees performing visual odometry en route between the hive and a flower patch. However, whether the use of parallax information is confined to specialised behaviours like these or represents a more general purpose sensory capability, is an open question. We investigate this issue in the foraging swallowtail butterfly Papilio xuthus, which we trained to associate a target presented on a monitor with a food reward. We then tracked the animal\u27s flight in real-time, allowing us to manipulate the size and/or position of the target in a closed-loop manner to create the illusion that it is situated either above or below the monitor surface. Butterflies are less attracted to (i.e. slower to approach) targets that appear, based on motion parallax, to be more distant. Furthermore, we found that the number of abortive descent manoeuvres performed prior to the first successful target approach varies according to the depth of the virtual target, with expansion and parallax cues having effects of opposing polarity. However, we found no evidence that Papilio modulate the kinematic parameters of their descents according to the apparent distance of the target. Thus, we argue that motion parallax is used to identify a proximal target object, but that the subsequent process of approaching it is based on stabilising its edge in the 2D space of the retina, without estimating its distance

Reducing driving forces for pressed-in piles

Pile jacking techniques use static loading to install sheet piles with minimal environmental effects, such as noise and ground vibrations, which are often associated with other methods of driven piling. This paper describes a series of 20g centrifuge tests conducted to investigate two methods of reducing the large driving forces that can be associated with jacked sheet piles in stiff clay. In practice, pre-auguring at the clutch positions and water jetting techniques are routinely carried out prior to the installation of sheet piling in order to reduce the driving forces. However, these methods are known to contribute to ground movements and can detract from the advantages of jacked sheet piles. The tests involved driving model sheet piles, which were modified either by installing driving shoes to the base of the pile, or by ribbing the profile of the pile shaft. The driving forces of the modified piles were compared with those of a plain pile. The tests showed that the use of driving shoes and ribs can lead to the reduction of driving forces at greater depth

Corrigendum to “The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica” [Earth and Planetary Science Letters 469 (2017) 42–52]

No abstract available

Swarming populations of Salmonella represent a unique physiological state coupled to multiple mechanisms of antibiotic resistance

Salmonella enterica serovar Typhimurium is capable of swarming over semi-solid surfaces. Although its swarming behavior shares many readily observable similarities with other swarming bacteria, the phenomenon remains somewhat of an enigma in this bacterium since some attributes skew away from the better characterized systems. Swarming is quite distinct from the classic swimming motility, as there is a prerequisite for cells to first undergo a morphological transformation into swarmer cells. In some organisms, swarming is controlled by quorum sensing, and in others, swarming has been shown to be coupled to increased expression of important virulence factors. Swarming in serovar Typhimurium is coupled to elevated resistance to a wide variety of structurally and functionally distinct classes of antimicrobial compounds. As serovar Typhimurium differentiates into swarm cells, the pmrHFIJKLM operon is up-regulated, resulting in a more positively charged LPS core. Furthermore, as swarm cells begin to de-differentiate, the pmr operon expression is down-regulated, rapidly reaching the levels observed in swim cells. This is one potential mechanism which confers swarm cells increased resistance to antibiotics such as the cationic antimicrobial peptides. However, additional mechanisms are likely associated with the cells in the swarm state that confer elevated resistance to such a broad spectrum of antimicrobial agents

Involvement of Noradrenergic Neurotransmission in the Stress- but not Cocaine-Induced Reinstatement of Extinguished Cocaine-Induced Conditioned Place Preference in Mice: Role for β-2 Adrenergic Receptors

The responsiveness of central noradrenergic systems to stressors and cocaine poses norepinephrine as a potential common mechanism through which drug re-exposure and stressful stimuli promote relapse. This study investigated the role of noradrenergic systems in the reinstatement of extinguished cocaine-induced conditioned place preference by cocaine and stress in male C57BL/6 mice. Cocaine- (15 mg/kg, i.p.) induced conditioned place preference was extinguished by repeated exposure to the apparatus in the absence of drug and reestablished by a cocaine challenge (15 mg/kg), exposure to a stressor (6-min forced swim (FS); 20–25°C water), or administration of the α-2 adrenergic receptor (AR) antagonists yohimbine (2 mg/kg, i.p.) or BRL44408 (5, 10 mg/kg, i.p.). To investigate the role of ARs, mice were administered the nonselective β-AR antagonist, propranolol (5, 10 mg/kg, i.p.), the α-1 AR antagonist, prazosin (1, 2 mg/kg, i.p.), or the α-2 AR agonist, clonidine (0.03, 0.3 mg/kg, i.p.) before reinstatement testing. Clonidine, prazosin, and propranolol failed to block cocaine-induced reinstatement. The low (0.03 mg/kg) but not high (0.3 mg/kg) clonidine dose fully blocked FS-induced reinstatement but not reinstatement by yohimbine. Propranolol, but not prazosin, blocked reinstatement by both yohimbine and FS, suggesting the involvement of β-ARs. The β-2 AR antagonist ICI-118551 (1 mg/kg, i.p.), but not the β-1 AR antagonist betaxolol (10 mg/kg, i.p.), also blocked FS-induced reinstatement. These findings suggest that stress-induced reinstatement requires noradrenergic signaling through β-2 ARs and that cocaine-induced reinstatement does not require AR activation, even though stimulation of central noradrenergic neurotransmission is sufficient to reinstate