Search

In this article, we outline a demonstration that is relatively simple to perform but whose results require a quite subtle interpretation of Faraday's Law. When a very small magnet is dropped through a coil it can tumble as it falls leading to 'spikes' in the measured emf signal. The experiment, and demonstration, can be used in an introductory laboratory module and our early evidence suggests it is useful in teaching electromagnetic induction as a covariational relation between magnetic flux and time, and particularly useful as a demonstration of EMF induced by a 'swept area'.

Paleoenvironmental archives in Arctic regions serve as sensitive recorders of past climate change where summer temperatures hover near freezing and small climate variations may exhibit strong threshold-crossing environment responses. Lake El'gygytgyn (Far East Russian Arctic) is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact at 3.58 Ma. Prior research on sediments collected from Lake El'gygytygyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (δ13C) values. Here, we investigate the abundance and carbon isotopic characteristics of lipid biomarkers recovered from Lake El'gygytygn sediments spanning marine isotope stages 1-3, to identify key sources of organic matter (OM) to lake sediments, to establish which compounds and thus OM sources drive the negative δ13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1-3, direct evidence for water column anoxia is lacking. A ~4‰ negative excursion in bulk sediment δ13C values during the local Last Glacial Maximum (LLGM) is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol δ13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative δ13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide during glaciation at Lake El'gygytgyn. [ABSTRACT FROM AUTHOR]

Susceptibility measurements performed on initial short (3-16 m) cores taken from Lake El'gygytgyn exhibited a large range in values. This observation led to the suggestion of widespread magnetite dissolution within the sediments due to anoxic conditions within the lake. Rock magnetic properties and their comparison with magnetic susceptibility, Total Organic Carbon (TOC), and bulk δ13Corg proxies in core LZ1029-7 provide an insight into the character of the magnetic minerals present within the lake and can further the understanding of processes that may be present in the newer long core sediments Susceptibility measurements (Χ) of discrete samples corroborate the two order of magnitude difference seen in previous continuous susceptibility measurements (Κ), correlating high values with interglacial periods and low values with glacial intervals. Hysteresis parameters defined the majority of the magnetic material to be magnetite of PSD size. TOC values increase while δ13Corg values decrease in one section of LZ1029-7, which is defined as the Last Glacial Maximum (LGM), and help confine the age of the core to approximately 62 kyr. Increases in TOC during the most recent glacial interval suggest increased preservation of organic carbon during these times High TOC and low magnetic susceptibility during the LGM support the theory of perennial ice cover during glacial periods, which would lead to lake stratification and therefore anoxic bottom water conditions. Low temperature magnetic measurements also confirmed the presence of magnetite, but also indicated titanomagnetite, siderite and/or rhodochrosite, and vivianite were present. The latter three minerals are found only in anoxic environments, and further support the notion of magnetite dissolution. [ABSTRACT FROM AUTHOR]

Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn basin hydrology. Compound specific hydrogen isotope ratios determined from modern vegetation are compared with modern precipitation and lake core top sediments. Multi-species net (apparent) fractionation values between source water (precipitation) and leaf wax lipids (mean value is -105±13 ‰) agree with previous results in arid environments and provide a basis for application of this proxy downcore. We conclude that although there may be some bias towards winter precipitation signal, overall leaf wax lipids record annual average precipitation within the El'gygytgyn Basin. [ABSTRACT FROM AUTHOR]

Hydrocephalus is a neurological disorder whose clinical symptoms and treatment outcome are correlated with patient age. In Wilkie et al. (2010, A theoretical study of the effect of intraventricular pulsations on the pathogenesis of hydrocephalus. Appl. Math. Comput., 215, 3181–3191), the fractional Zener model was used to investigate the role of cerebrospinal fluid pressure pulsations in the development of hydrocephalus in infants and adults. In this paper, we determine the mechanical parameters of the fractional Zener model for the infant and adult brains using age-dependent shear complex modulus data (Thibault, K. L. & Margulies, S. S. (1998) Age-dependent material properties of the porcine cerebrum: effect on pediatric inertial head injury criteria. J. Biomech., 31, 1119–1126). The displacement of brain tissue under conditions representing the onset of hydrocephalus are then calculated. The infant brain was found to produce tissue displacements that are unphysical for our model geometry and a new boundary condition is proposed to replace the stress-free outer boundary condition used in Wilkie et al. (2010). The steadystate elastic modulus is identified as the parameter of interest in the development of hydrocephalus: it is found to increase from the infant value of 621 Pa to the young adult value of 955 Pa and we hypothesize that it then decreases with age. The low steady-state elastic modulus of the infant brain (and possibly the aged brain) increases the tissue's susceptibility to large deformations and thus to the ventricular expansion characteristic of hydrocephalus. [ABSTRACT FROM PUBLISHER]

Aims and objectives. Carers' experiences of caring for a stroke survivor were explored, including reactions and changes in their lives. Method. A phenomenological approach was taken to the collection and analysis of data. Semi-structured interviews lasting an average of 43 min were carried out with nine informal carers in their own homes. All were married to someone who had survived a stroke. Results. An overarching theme emerged, entitled: 'lives turned upside-down'. It took time for participants to understand the long-term impacts of stroke. Carers experienced increased caring and domestic workloads alongside reduced participation and altered expectations of life. They found emotional and cognitive changes in their partners particularly distressing, and would have valued more information and help with adjusting to the increased emotional, physical and cognitive workload of caring. Conclusions. It is important to support carers of people who have survived a stroke in adjusting to their changed lifestyles. This may affect their quality of life as well as sustainability of caring, and requires further research. [ABSTRACT FROM AUTHOR]

Objectives. To compare mean angles of anterior pelvic tilt (APT) and variability of APT angles in elite cyclists and matched non-cyclists.Design. Observation, cross-sectional, matched pairs.Participants: Seventeen elite cyclists Australian Institute of Sport Track Cycling Squad (AISTCS) (23 +/- 4.2 years, 15 males) age and gender matched with 17 non-cyclists (23 +/- 4.1 years, 15 males).Setting: Laboratory within the University of South Australia. The APT was assessed in long-sitting position with chest as close to thighs as voluntarily possible and measured using a digital inclinometer over L5-S1 intervertebral space.Main outcome measures: APT in elite and non-cyclists. Unpaired t-tests and F-tests were used to analyze difference and variability of APT angles between groups with p