High strength steel in fire

High-performance materials are necessary to meet the future demands of the construction industry, which is strongly influenced by a growing population and depletion of natural resources. Sustainable development is central to research and development into innovative structural materials, and requires solutions to be economically viable whilst equally providing a positive contribution towards environmental and social factors. High strength steels (HSS) have the potential to contribute towards such demands by reducing the weight of structures when employed in appropriate applications. Lighter structures require smaller foundations, shorter transportation and construction times and also lower CO2 emissions. A particular challenge related to the use of HSS in structures include increased likelihood of stability issues resulting from the reduction in section thickness, and limiting deflection and vibration criteria are also more likely to be critical. Nevertheless, when used appropriately, they can provide a sustainable solution. Their use in structural applications is further hindered by a lack of performance data and design guidance under fire conditions. This paper compares the mechanical properties, particularly strength and stiffness of HSS (yield strengths between 460-700 MPa) and mild steel (yields between 235-460 MPa) at elevated temperatures, through a critical review of published literature. Various alloying and processing routes used to achieve high yield strength are assessed. At the same time, the review considers available information on the strengthening mechanisms that can be utilised to retain the strength and/or stiffness of the material in the event of a fire. Using the information gathered, an extensive testing programme is developed which will enable design guidance for the fire design of HSS structures to be proposed.Engineering and Physical Sciences Research Council, TW

New ages from Sehonghong rock shelter: Implications for the late Pleistocene occupation of highland Lesotho

Sehonghong rock shelter is situated in the eastern Lesotho highlands, a climatically extreme region of southern Africa. The site is one of a handful in southern Africa that preserves human occupations before, during, and after the Last GlacialMaximum(LGM). The site's long and well-preserved sequence makes it relevant to addressing questions of human mobility, subsistence, and technology in relation to broader environmental change. Here we present a Bayesian-modelled radiocarbon chronology for the LGM and terminal Pleistocene occupations at Sehonghong. Our model incorporates previously published radiocarbon dates and new accelerator mass spectrometry ages. We also present archaeological evidence to test the hypothesis that Sehonghong was occupied in a series of punctuated events, and that some of these occupations were more intensive than others. Previous chronological and archaeological data were insufficient for testing these hypotheses. The new dates and archaeological data confirmthat the sitewas occupied intensively in the early LGMand immediately thereafter. The site was otherwise occupied sporadically.We find that greater site occupation density is not always correlated with intensified use of local resources as measured by increased bipolar reduction and fish consumption. The new dates further confirm that Sehonghong contains some of the oldest evidence for systematic freshwater fishing in southern Africa. The availability of fish, a high fat protein source, probably stimulated human occupation, however sporadic, of suchmontane environments during cooler and drier periods. These findings suggest behavioural variability in response to shifting mobility and subsistence strategies. Our brief discussion informs upon huntergatherer occupation of southern Africanmontane environments more broadly and human behavioural variability during the LGM

Sparrowhawk movement, calling, and presence of dead conspecifics differentially impact blue tit (Cyanistes caeruleus) vocal and behavioral mobbing responses

Funding: UK NERC (NE/J018694/1), Royal Society (RG2012R2), M.J. Murdock Charitable Trust (2014199), University of St Andrews 600th Year Scholarship, University of St Andrews St Leonard's Fee Scholarship.Many animals alter their anti-predator behavior in accordance to the threat level of a predator. While much research has examined variation in mobbing responses to different predators, few studies have investigated how anti-predator behavior is affected by changes in a predator’s own state or behavior. We examined the effect of sparrowhawk (Accipiter nisus) behavior on the mobbing response of wild blue tits (Cyanistes caeruleus) using robotic taxidermy sparrowhawks. We manipulated whether the simulated predator moved its head, produced vocalizations, or held a taxidermy blue tit in its talons. When any sparrowhawk model was present, blue tits decreased foraging and increased anti-predator behavior and vocalizations. Additionally, each manipulation of the model predator’s state (moving, vocalizing, or the presence of a dead conspecific) impacted different types of blue tit anti-predator behavior and vocalizations. These results indicate that different components of mobbing vary according to the specific state of a given predator—beyond its presence or absence—and suggest that each might play a different role in the overall mobbing response. Last, our results indicate that using more life-like predator stimuli—those featuring simple head movements and audio playback of vocalizations—changes how prey respond to the predator; these ‘robo-raptor’ models provide a powerful tool to provide increased realism in simulated predator encounters without sacrificing experimental control.Publisher PDFPeer reviewe

Microfocus X-ray tomography as a method for characterising macro-fractures on quartz backed tools

Abstract: Here we present the first assessment of microfocus X-ray tomography (micro-XCT) as an analytical technique to generate data about macro-fractures on small quartz backed tools similar to those currently held to represent the oldest known evidence for bow hunting. Our experimental results are derived from 21 replicated quartz backed tools randomly selected from a population (n=218) that were broken in a controlled hunting context. We used 3D data obtained from micro-XCT scans to identify macro-fractures and to derive more accurate measurements for these fractures. Our results demonstrate that the micro-XCT technique overcomes reflected-light challenges associated with analysing quartz through conventional macro-fracture approache s. We were able to increase the total observed macrofracture sample by 33% compared with conventional approaches using a hand-lens. Whereas macro-fracture data could be refined, the additionally gained data did not change interpretations obtained from a conventional macro-fracture analysis. It did, however, marginally change the degree of significance in differences between the different applications. During this study, we also detected micro-fracture features, such as possible fracture wings and microscopic linear impact traces (MILTs).With further studies, the morphometric traits of these micro-fracture features could be useful for distinguishing between ancient weapon-delivery systems

Phenotypic Study of Intraflagellar Transport and FLA10 in the lf4 Mutant of Chlamydomonas reinhardtII

Chlamydomonas reinhardtii is a biflagellate, unicellular green alga that serves as an ideal basic science organism (Harris, 2008a). Compared to eukaryotic primary cilia, it shares many homologous flagellar genes with humans, of which several ciliary disorders, or ciliopathies, are known to occur (Pazour, 2008). Almost all vertebrate cells possess primary cilia, but this organelle had long been thought to have no function (Pan et al., 2005). With the discovery of intraflagellar transport (IFT), the mechanism for flagellar assembly, by Kozminski and coworkers (1993), new approaches to study ciliopathies were established. To investigate how flagellar length was controlled, long-flagellar mutants lf1, lf2, lf3 and lf4 were created. Yet little phenotypically was known about lf4. To characterize the morphology of and localize IFT proteins (FLA10p and LF4p) in the lf4 mutant, this work used bright-field microscopy, immunofluorescence microscopy (IMF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The lf4 flagella were grossly longer than wild-type cells, which were observed to be most active at 36 h. The lf4 cells were most active between 24-36 h likely indicating the best time to harvest for experimentation. Using IMF, the FLA10p and LF4p localized to flagella in a punctate pattern, likely indicating IFT particles. No bulbous tips were observed in lf4, unlike the lf2 and lf3 mutants as reported by Tam and coworkers (2003; 2007). Multiple IFT particles were observed in cross-sectional and longitudinal flagellar ultrastructure of lf4 using TEM. Plus, an as yet unidentified electron-dense structure in an lf4 cross-section was observed to connect the outer doublet microtubules to the cell membrane. Quantification of IFT particles per length, area and volume of flagella were the same in wild-type and lf4, suggesting that IFT particle quantity is independent of length. Immunogold electron localization is the logical next step to further the phenotypic characterization of the lf4 mutant.Department of Biochemistry and Molecular Biolog

Interpretative tools for studying Stone Age hunting technologies: experimental archaeology, macrofracture analyses and morphometric techniques

This dissertation contains an assessment and use of the macrofracture and morphometric methods for detecting Later Stone Age hunting weaponry. Two sets of replicated unretouched stone artefacts were trampled by cattle and humans to determine the formation of impact fractures under these, and knapping conditions. The results suggest that small frequencies (c. 3 %) of certain impact fracture types do occur on flakes subject to trampling and knapping forces. Macrofracture and morphometric data were recorded for stone artefacts (bladelets, backed artefacts and convergent pieces) from Robberg (c. 18 000 - 12 000 years ago) and Wilton (c. 8000 - 2000 years ago) Later Stone Age assemblages on the southern Cape coast. Impact fracture frequencies were similar in these two samples, but were significantly higher than in the trampling experiments. The morphometric data suggests, on average, congruence between Later Stone Age tools with impact fractures and experimental, archaeological and ethnohistoric spear and arrow tips. Based on these results it appears likely that Wilton backed artefacts, specifically segments, were used as arrowheads and it is unclear at present what weapon types were used during the Robberg phase although the use of spears seems probable

Regional variability in lithic miniaturization and the organization of technology in late glacial (~18 – 11 kcal BP) Southern Africa

Abstract: Miniaturized stone tools made by controlled fracture are reported from nearly every continent where archaeologists have systematically looked for them. While similarities in technology are acknowledged between regions, few detailed inter-regional comparative studies have been conducted. Our paper addresses this gap, presenting results of a comparative lithic technological study between Klipfonteinrand and Sehonghong – two large rockshelters in southern Africa. Both sites contain Late Glacial (~18 – 11 kcal BP) assemblages, though are located in regions with different geologies, climates and environments. Results demonstrate that lithic miniaturization manifests differently in different regions. Both assemblages provide evidence for small blade production, though key differences exist in terms of the specific technological composition of this evidence, the raw materials selected, the role played by bipolar reduction and the manner in which lithic reduction was organized. Patterned variability of this nature demonstrates that humans deployed miniaturized technologies strategically in relation to local conditions

Assessing surface movement at Stone Age open-air sites : first impressions from a pilot experiment in northeastern Botswana

Open-air sites are ubiquitous signatures on most archaeological landscapes. When they are appropriately recorded, well-preserved and are single-component occupations, they provide access to high-resolution occupation data that is often not available from rock-shelter sites. These sites are, however, commonly affected by a number of post-depositional factors that are not adequately studied in archaeology. This paper presents the results of an open-air experiment conducted in northeastern Botswana. Two surface scatters modelled on known Bushman open-air camp sites were created to investigate the taphonomic factors affecting such sites. The scattered materials at these sites included stone tools, ostrich eggshell fragments, ceramic sherds, glass beads and faunal remains. Two scatters were laid out consisting of a nested square design; one site was excavated after four months and the other after twelve. The results show little horizontal material movement at these scatters and an initial, rapid, vertical period of mobility, after which the majority of surface artefacts are protected from subsequent movement, preserving the general scatter structures. This experiment suggests that open-air sites can offer detailed spatial information relevant to human settlement structure that is often not accessible at rock-shelter sites.Palaeontological Scientific Trust, the Leakey Foundation, the Meyerstein travel grant and Mashatu Game Reserve.http://www.sahumanities.org.za/hb201

Lithic miniaturization as adaptive strategy : a case study from Boomplaas Cave, South Africa

Abstract: Lithic miniaturization is a multivariate and evolutionarily significant technological phenomenon involving backed tools, bladelets, small retouched tools, flakes, and small cores. This paper investigates the proximate causes for variability in lithic miniaturization processes during Marine Isotope Stage 2 (c. 29–12 ka) in southern Africa. We test the hypothesis that lithic miniaturization represents a form of adaptive behavior by examining its relationship to site occupation intensity and rainfall seasonality at Boomplaas Cave in South Africa. These are two widely cited explanations for shifts in the organization of huntergatherer technologies and the data required for testing them are also readily available. We combine several lithic variables, macrofauna and microfauna indicators, and other archeological data to test the hypotheses. We find evidence that demographic processes impacted choices of technology within contexts of shifting rainfall seasonality, aridity, and rapidly rising Late Glacial sea-levels. In this context, Late Glacial humans converged on a small number of high payoff strategies including technological efficiency through bipolar bladelet production, greater production of ostrich eggshell ornaments and water containers, and a reorganized subsistence strategy targeting lower yield small mammals. The results demonstrate that lithic miniaturization was a strategic choice rather than an inevitable technological outcome. The outcomes have implications for understanding global instances of lithic miniaturization and their relationship to rapidly shifting paleoenvironments