347 research outputs found

    Movement and predation: a catch-and-release study on the acoustic tracking of bonefish in the Indian Ocean

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    Tourism generated through bonefish (Albula spp.) fishing contributes to the economies of many isolated tropical islands and atolls. However, little research has been conducted on bonefish in the Indian Ocean. This study aimed to contribute to the understanding of bonefish ecology in the Indian Ocean by quantifying the spatial and temporal movements of Albula glossodonta at a near-pristine and predator-rich atoll in the Seychelles; however, to achieve this, an analysis to identify the occurrence of possible post-release predation bias was first necessary. An acoustic telemetry study was initiated at the remote St. Joseph Atoll, within an array of 88 automated data-logging acoustic receivers. Thirty bonefish were surgically implanted with Vemco V13 acoustic transmitters and tracked for one year. Only 10% of the tagged bonefish were detected for longer than two weeks. A comparison of the final 100 h of movement data from fish detected for less than two weeks to the movement data of the fish detected for longer periods revealed distinct differences in area use and significant differences in the average daily distance moved, speed of movement and frequency of detections. This suggested that mortality in the form of post-release predation was at least 43% of tagged fish. The three surviving bonefish were tracked for 210 to 367 days. These individuals remained in the atoll and showed high use of the marginal habitats between the shallow sand flats and the lagoon. A generalised linear mixed model identified that water temperature, diel cycle and tide were significant predictors of bonefish presence in the lagoon. The high post-release mortality highlights that catch-and-release is likely not as benign as previously believed and management and policy should be adjusted accordingly

    Infrared imagery and radiometry Summary report

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    Thermal properties of infrared transmissio

    Finite Element Modelling and Experimental Validation of the Enamel Demineralisation Process at the Rod Level

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    In the past years, a significant amount of effort has been directed at the observation and characterisation of caries using experimental techniques. Nevertheless, relatively little progress has been made in numerical modelling of the underlying demineralisation process. The present study is the first attempt to provide a simplified calculation framework for the numerical simulation of the demineralisation process at the length scale of enamel rods and its validation by comparing the data with statistical analysis of experimental results. FEM model was employed to simulate a time-dependent reaction-diffusion equation process in which H ions diffuse and cause demineralisation of the enamel. The local orientation of the hydroxyapatite crystals was taken into account. Experimental analysis of the demineralising front was performed using advanced high-resolution synchrotron X-ray micro-Computed Tomography. Further experimental investigations were conducted by means of SEM and STEM imaging techniques. Besides establishing and validating the new modelling framework, insights into the role of the etchant solution pH level were obtained. Additionally, some light was shed on the origin of different types of etching patterns by simulating the demineralisation process at different etching angles of attack. The implications of this study pave the way for simulations of enamel demineralisation within different complex scenarios and across the range of length scales. Indeed, the framework proposed can incorporate the presence of chemical species other than H ions and their diffusion and reaction leading to dissolution and re-precipitation of hydroxyapatite. It is the authors\u2019 hope and aspiration that ultimately this work will help identify new ways of controlling and preventing caries

    Synchrotron X-ray quantitative evaluation of transient deformation and damage phenomena in a single nickel-rich cathode particle

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    The performance and durability of Ni-rich cathode materials are controlled in no small part by their mechanical durability, as chemomechanical breakdown at the nano-scale leads to increased internal resistance and decreased storage capacity. The mechanical degradation is caused by the transient lithium diffusion processes during charge and discharge of layered oxide spherical cathode micro-particles, leading to highly anisotropic incompatible strain fields. Experimental characterisation of the transient mechanisms underlying crack and void formation requires the combination of very high resolution in space (sub-micron) and time (sub-second) domains without charge interruption. The present study is focused on sub-micron focused operando synchrotron X-ray diffraction and in situ Ptycho-Tomographic nano-scale imaging of a single nano-structured LiNi0.8Co0.1Mn0.1O2 core-shell particle during charge to obtain a thorough understanding of the anisotropic deformation and damage phenomena at a particle level. Preferential grain orientation within the shell of a spherical secondary cathode particle provides improved lithium transport but is also associated with spatially varying anisotropic expansion of the hexagonal unit cell in the c-axis and contraction in the a-axis. These effects were resolved in relation to the grain orientation, and the link established with the nucleation and growth of intergranular cracks and voids that causes electrical isolation of active cathode material. Coupled multi-physics Finite Element Modelling of diffusion and deformation inside a single cathode particle during charge and discharge was validated by comparison with experimental evidence and allowed unequivocal identification of key mechanical drivers underlying Li-ion battery degradation

    Avaliação e caracterização da coleção de trabalho de pimenta longa na Embrapa Acre.

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    A pimenta longa é uma planta nativa do Estado do Acre, considerada de grande valor econômico devido ao alto teor de safrol presente no óleo essencial extraído de suas folhas e ramos finos. O safrol é utilizado na indústria química para a fabricação de inseticidas biodegradáveis e cosméticos. Estudos de prospecção identificaram duas espécies, Piper hispidinervum e Piper aduncum, muito semelhantes botanicamente, porém com diferenças no teor de safrol do óleo essencial. A Piper hispidinervum apresenta altos teores de safrol (superiores a 90%) enquanto a Piper aduncum, teores de safrol menores que 10%. O objetivo desse trabalho foi avaliar caracteres morfológicos das espécies Piper hispidinervum e P. aduncum, visando sugerir alguns descritores morfológicos para essas espécies

    Sniff nasal inspiratory pressure in patients with moderate-to-severe chronic obstructive pulmonary disease: learning effect and short-term between-session repeatability

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    Background: Sniff nasal inspiratory pressure (SNIP) is a non-invasive measure of inspiratory muscle function often used as an outcome measure in clinical studies. An initial period of familiarisation with the test is recommended to minimise the learning effect. The repeatability of SNIP in patients with chronic obstructive pulmonary disease (COPD) is currently unknown. Objectives: The aim of this study was to assess the between-session repeatability of SNIP over a 3-week period in moderate-to-severe COPD patients and compare it with that of maximal inspiratory (PImax) and expiratory pressure (PEmax). Methods: Twenty-one patients (13 males) with a mean forced expiratory volume in 1 s (FEV1) of 38% of predicted (SD: 15) and FEV1/forced vital capacity of 34.3% (SD: 10.4) performed SNIP and PImax and PEmax manoeuvres on 3 different sessions (S1, S2 and S3) 3-7 days apart. SNIP was performed at functional residual capacity (FRC), and PImax was performed at FRC and at residual volume (RV) to explore volume-dependent differences in the learning effect between sessions and PEmax from total lung capacity. Results: The intra-class correlation coefficient (ICC) for SNIP was the highest of the three measures: S1-S3 ICC (95% CI) SNIP: 0.96 (0.88-0.94); PImax at FRC 0.82 (0.63-0.92); PImax at RV: 0.89 (0.78-0.95), and PEmax: 0.96 (0.92-0.98), and had the lowest mean change between sessions [mean S2 - S1: 2.1(p = 0.4) and S3 - S2: -0.3 (p = 0.9)]. Conclusions: SNIP is repeatable over a period of 3 weeks in medically stable, moderate-to-severe COPD patients. In our study, 2 sessions were adequate to learn how to perform the test

    Versatile Coordination of Cyclopentadienyl-Arene Ligands and Its Role in Titanium-Catalyzed Ethylene Trimerization

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    Cationic titanium(IV) complexes with ansa-(η5-cyclopentadienyl,η6-arene) ligands were synthesized and characterized by X-ray crystallography. The strength of the metal-arene interaction in these systems was studied by variable-temperature NMR spectroscopy. Complexes with a C1 bridge between the cyclopentadienyl and arene moieties feature hemilabile coordination behavior of the ligand and consequently are active ethylene trimerization catalysts. Reaction of the titanium(IV) dimethyl cations with CO results in conversion to the analogous cationic titanium(II) dicarbonyl species. Metal-to-ligand backdonation in these formally low-valent complexes gives rise to a strongly bonded, partially reduced arene moiety. In contrast to the η6-arene coordination mode observed for titanium, the more electron-rich vanadium(V) cations [cyclopentadienyl-arene]V(NiPr2)(NC6H4-4-Me)+ feature η1-arene binding, as determined by a crystallographic study. The three different metal-arene coordination modes that we experimentally observed model intermediates in the cycle for titanium-catalyzed ethylene trimerization. The nature of the metal-arene interaction in these systems was studied by DFT calculations.

    Coexistence of OSA may compensate for sleep related reduction in neural respiratory drive in patients with COPD

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    Background The mechanisms underlying sleep-related hypoventilation in patients with coexisting COPD and obstructive sleep apnoea (OSA), an overlap syndrome, are incompletely understood. We compared neural respiratory drive expressed as diaphragm electromyogram (EMGdi) and ventilation during stage 2 sleep in patients with COPD alone and patients with overlap syndrome. Methods EMGdi and airflow were recorded during full polysomnography in 14 healthy subjects, 14 patients with OSA and 39 consecutive patients with COPD. The ratio of tidal volume to EMGdi was measured to indirectly assess upper airway resistance. Results Thirty-five patients with COPD, 12 healthy subjects and 14 patients with OSA completed the study. Of 35 patients with COPD, 19 had COPD alone (FEV1 38.5%±16.3%) whereas 16 had an overlap syndrome (FEV1 47.5±16.2%, AHI 20.5±14.1 events/hour). Ventilation (VE) was lower during stage 2 sleep than wakefulness in both patients with COPD alone (8.6±2.0 to 6.5±1.5 L/min, p<0.001) and those with overlap syndrome (8.3±2.0 to 6.1±1.8 L/min). Neural respiratory drive from wakefulness to sleep decreased significantly for patients with COPD alone (29.5±13.3% to 23.0±8.9% of maximal, p<0.01) but it changed little in those with overlap syndrome. The ratio of tidal volume to EMGdi was unchanged from wakefulness to sleep in patients with COPD alone and healthy subjects but was significantly reduced in patients with OSA or overlap syndrome (p<0.05). Conclusions Stage 2 sleep-related hypoventilation in COPD alone is due to reduction of neural respiratory drive, but in overlap syndrome it is due to increased upper airway resistance

    Does the engineering culture in UK higher education advance women’s careers?

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    Current research suggests that increases in the number of women studying engineering and related courses have not been matched by a similar increase in women engineering professionals. This suggests that although women are attracted to engineering, their experiences in higher education (HE) discourage them from pursuing their chosen career path. The paper explores whether the masculine culture of the engineering sector permeates the culture and curriculum in engineering HE, and if it does, what impact this has on women engineering students. This is achieved through semi-structured, qualitative interviews with a range of female engineering students from both the pre and post 1992 university sectors. Findings indicate that while women are not deterred from pursuing their chosen engineering career, the culture and structure of the engineering education system has been designed for a male audience. This suggests that engineering HE does not benefit most female students to the same extent as male students. It is recommended that HE engineering must review its structure, culture, practices and curriculum if it is to retain female engineering graduates and to attract more women into the sector. This paper fulfils an identified gap in research on women in engineering and will be of interest to university engineering departments and faculties and the Engineering Council, as well as to those in the fields of social policy, education and equal opportunities
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