1,228 research outputs found
Group size and seasonal pattern of occurrence of humpback dolphins sousa chinensis in Algoa Bay, South Africa
The occurrence of humpback dolphins Sousa chinensis and their group size in Algoa Bay, South Africa, are described for the period May 1991–May 1994. The mean group size of dolphins was seven (ranging between 3 and 24). Group size was not affected by diurnal, tidal or lunar variability. Solitary, large individuals were commonly observed and they occasionally joined groups of other humpback dolphins. The number of sightings of humpback dolphins per unit effort and their group size varied seasonally, increasing in summer and again in late winter. These observations follow a regular seasonal fluctuation in water temperature, coincide with the dolphins’ reproductive seasonal cycle and could be related to seasonal changes in the abundance and distribution of their prey
The potential for using acoustic tracking to monitor the movement of the West Coast rock lobster Jasus lalandii
Although acoustic tracking has been used to study the movement of several species of clawed and spiny lobsters, only recent technological advances have provided sufficiently small transmitters to examine the utility of using acoustic tracking as a means to analyse the movement of relatively small spiny lobsters, such as Jasus lalandii. The effect of the transmitter on the mobility of J. lalandii was tested in aquarium experiments and was shown to have no influence on movement in three separate experiments. Thereafter, adult male rock lobsters (86–98mm carapace length) were tracked in field trials for up to 32 days at Betty's Bay (n = 4) and Hermanus (n = 5) off the Western Cape, South Africa. Tracking J. lalandii in the field using acoustic tags was successful, even in areas with dense kelp beds and rocky outcrops. The signal from the transmitters was readily detectable from the surface and subsequent use of underwater tracking equipment enabled visual confirmation of the position of the rock lobsters. Lobsters moved significantly longer distances (>45m day−1) in the first two days following tagging than during any subsequent time period (<10m day−1). This suggests that transmitter attachment and/or handling altered the movement pattern for the first 72 hours after tagging. During the period of observation, J. lalandii displayed classical nomadic behaviour
Phosphatidylinositol Transfer Protein-α in platelets is inconsequential for thrombosis yet is utilized for tumor metastasis
Platelets are increasingly recognized for their contributions to tumor metastasis. Here, we show that the phosphoinositide signaling modulated by phosphatidylinositol transfer protein type α (PITPα), a protein which shuttles phosphatidylinositol between organelles, is essential for platelet-mediated tumor metastasis. PITPα-deficient platelets have reduced intracellular pools of phosphoinositides and an 80% reduction in IP3 generation upon platelet activation. Unexpectedly, mice lacking platelet PITPα form thrombi normally at sites of intravascular injuries. However, following intravenous injection of tumor cells, mice lacking PITPα develop fewer lung metastases due to a reduction of fibrin formation surrounding the tumor cells, rendering the metastases susceptible to mucosal immunity. These findings demonstrate that platelet PITPα-mediated phosphoinositide signaling is inconsequential for in vivo hemostasis, yet is critical for in vivo dissemination. Moreover, this demonstrates that signaling pathways within platelets may be segregated into pathways that are essential for thrombosis formation and pathways that are important for non-hemostatic functions
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Converging Prefronto-Insula-Amygdala Pathways in Negative Emotion Regulation in Marmoset Monkeys
BACKGROUND: Impaired regulation of emotional responses to potential threat is a core feature of affective disorders. However, while the subcortical circuitry responsible for processing and expression of fear has been well characterized, the top-down control of this circuitry is less well understood. Our recent studies demonstrated that heightened emotionality, as measured both physiologically and behaviorally, during conditioned fear and innate/ social threat was induced, independently, by excitotoxic lesions of either the anterior orbitofrontal cortex (antOFC) or ventrolateral prefrontal cortex (vlPFC). An important outstanding question is whether the antOFC and vlPFC act on common or distinct downstream targets to regulate negative emotion.
METHODS: The question was addressed by combining localized excitotoxic lesions in the PFC of a nonhuman primate and functional neuroimaging ([F]fluorodeoxyglucose positron emission tomography) with a fear-regulating extinction paradigm. Marmoset monkeys with unilateral lesions of either the antOFC or vlPFC were scanned immediately following exposure to a fearful or safe context, and differences in [F]fluorodeoxyglucose uptake were evaluated.
RESULTS: [F]fluorodeoxyglucose uptake in the insula and amygdala of the intact hemisphere was significantly increased in response to the fearful context compared with the safe context. Such discrimination between the two contexts was not reflected in the activity of the insula-amygdala of the antOFC or vlPFC-lesioned hemisphere. Instead, uptake was at an intermediate level in both contexts.
CONCLUSIONS: These findings demonstrate that the distinct control functions of the antOFC and vlPFC converge on the same downstream targets to promote emotion regulation, taking us closer to a mechanistic understanding of different forms of anxiety.This research was supported by a Medical Research Programme Grant (No. MR/M023990/1) from the Medical Research Council (to ACR) and was carried out within the Behavioural and Clinical Neuroscience Institute supported by a consortium award from the Wellcome Trust and the Medical Research Council
Covalent grafting of molecular catalysts on Câ‚„Nâ‚“H_{y} as robust, efficient and well-defined photocatalysts for solar fuel synthesis
The covalent attachment of molecules to 2D materials is an emerging area as strong covalent chemistry offers new hybrid properties and greater mechanical stability compared with nanoparticles. A nickel bis-aminothiophenol catalyst was grafted onto a range of 2D carbon nitrides C₄NₓH_{y} to form noble metal-free photocatalysts for H2 production. The hybrids produce H_{2} beyond 8 days with turnover numbers reaching 1360 based on nickel, a more than 3 fold higher durability than reported molecular catalyst-carbon nitride mixtures, and under longer wavelengths (>475 nm). Time-resolved spectroscopy reveals sub-microsecond electron transfer to the grafted catalyst, six orders of magnitude faster compared with similar reports of non-grafted catalysts. The photoelectrons on the catalyst have a ca. 1000 times longer half-time (7 ms) compared with bare carbon nitride (10 μs). The grafting strategy operates across a range of molecular catalyst-carbon nitride combinations, thus paving the way for robust efficient photocatalysts based on low-cost tunable components
Mathematically gifted and talented learners: Theory and practice
This is an Author's Accepted Manuscript of an article published in International Journal of Mathematical Education in Science and Technology, 40(2), 213-228, 2009, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/00207390802566907.There is growing recognition of the special needs of mathematically gifted learners. This article reviews policy developments and current research and theory on giftedness in mathematics. It includes a discussion of the nature of mathematical ability as well as the factors that make up giftedness in mathematics. The article is set in the context of current developments in Mathematics Education and Gifted Education in the UK and their implications for Science and Technology. It argues that early identification and appropriate provision for younger mathematically promising pupils capitalizes on an intellectual resource which could provide future mathematicans as well as specialists in Science or Technology. Drawing on a Vygotskian framework, it is suggested that the mathematically gifted require appropriate cognitive challenges as well as attitudinally and motivationally enhancing experiences. In the second half of this article we report on an initiative in which we worked with teachers to identify mathematically gifted pupils and to provide effective enrichment support for them, in a number of London Local Authorities. A number of significant issues are raised relating to the identification of mathematical talent, enrichment provision for students and teachers’ professional development
Dynamics in the satellite system of Triangulum: Is AndXXII a dwarf satellite of M33?
We present results from a spectroscopic survey of the dwarf spheroidal And
XXII and the two extended clusters EC1 and EC2. These three objects are
candidate satellites of the Triangulum galaxy, M33, which itself is likely a
satellite of M31. We use the DEep Imaging Multi-Object Spectrograph mounted on
the Keck-II telescope to derive radial velocities for candidate member stars of
these objects and thereby identify the stars that are most likely actual
members. Eleven most probable stellar members (of 13 candidates) are found for
AndXXII. We obtain an upper limit of sigma_v < 6.0 km s-1 for the velocity
dispersion of AndXXII, [Fe/H] ~ -1.6 for its metallicity, and 255pc for the
Plummer radius of its projected density profile. We construct a colour
magnitude diagram for AndXXII and identify both the red giant branch and the
horizontal branch. The position of the latter is used to derive a heliocentric
distance to And XXII of 853 pm 26 kpc. The combination of the radial velocity,
distance, and angular position of AndXXII indicates that it is a strong
candidate for being the first known satellite of M33 and one of the very few
examples of a galactic satellite of a satellite. N-body simulations imply that
this conclusion is unchanged even if M31 and M33 had a strong encounter in the
past few Gyr. We test the hypothesis that the extended clusters highlight
tidally stripped galaxies by searching for an excess cloud of halo-like stars
in their vicinity. We find such a cloud for the case of EC1 but not EC2. The
three objects imply a dynamical mass for M33 that is consistent with previous
estimates.Comment: 14 pages, 14 figures, revised for MNRAS publicatio
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