An investigation of factors influencing adolescent health behaviour

In this study, the Ajzen and Fishbein model, developed from their theory of reasoned action, was applied to the investigation of factors influencing adolescent health behaviour. This model proposes that intentions (by extension, behaviour) are explained by a weighted combination of evaluated beliefs about that behaviour (i.e. attitudes) and motivation to comply with the wishes of significant referents concerning that behaviour (i.e. perceived social pressures). Recent innovations in Health Education in schools seem implicitly to be based on this rationale. They seek to establish beliefs leading to good health behaviour and to develop in pupils the confidence to act in accordance with these beliefs in the face of possible contrary social pressures. Questionnaires for measuring adolescents' intentions, beliefs and perceptions of social pressures concerning drinking alcohol, smoking cigarettes, keeping fit and diet were developed through a series of pilot trials, adapting the approaches suggested by Ajzen and Fishbein and subsequent workers. The reliability of these measures was shown to be satisfactory. Face and content validity were ensured during development: convergent and discriminant validity were evident, post hoc. The criterion-related validities of the scales were established, demonstrating the internal and external validity of the model itself. A representative sample of pupils aged 11 to 18 years, from Berkshire secondary schools, completed these questionnaires. The amount of variance in intentions explained by the weighted combination of the variance in beliefs and social pressures was statistically significant for all the topics and similar in magnitude to that frequently reported in attitude-behaviour studies with adolescents. It was lower, however, than that reported by researchers using the Ajzen and Fishbein model with adults. Reasons for this short-fall are considered: the unsuitability of the model for use with adolescents; the incorporation of constant and random error in the data; and the use of short scales. Finally, the implications of the results for Health Education programmes are considered

Large-amplitude, short-wave peristalsis and its implications for transport

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow is often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: Fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a nonlinear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate unidirectionally along a tube without the need for a structurally fixed flow direction

Coral reef communities, habitats and substrates in and near Sanctuary Zones of Ningaloo Marine Park

As Australia's longest fringing reef, Ningaloo Reef lies close to the mainland of northwest Australia in an area of high tourism potential. The establishment of Sanctuary Zones in and around the northern Ningaloo Marine Park has necessitated improvements in understanding of the biodiversity and distribution of habitats and substrates in the reef lagoon, its seaward barrier and the adjacent shelf environments. Using a combination of video transects in forereef to shelf environments, GPS controlled ground-truthing of colour satellite images and aerial photography for shallow lagoon settings, sixteen habitat types were identified and mapped regionally. Lagoon substrates described in previous reconnaissance were mapped here in greater detail, and some of the first data on poorly known forereef and shelf communities has been analysed from the video transects. There is a strong correlation between reef morphology, inherited substrate type and coral communities across reef lagoons and their associated barriers, where an energy gradient controlled by wave driven and tidal circulation in reef flat and lagoon environments is reflected in the distribution and cover of robust to more delicate coral communities. Morphological controls are less distinct in island-associated habitats, where increased turbidity, differing wave energy and more variable topography result in higher substrate variability and increasing soft coral communities. The data obtained in this study provide a background for management of biodiversity and monitoring of future impacts in some of the Sanctuary Zones likely to experience increased use in the northern Ningaloo Reef

Why Are You So Slimy?

The epithelium of vertebrates is a complex tissue that houses a large variety of cells with different functions. One of its most important functions is protection and in many cases this function is achieved by exuding copious amounts of mucous that fight off diseases, harmful toxins and overall protect the species from external invaders. Mucous, made of mucin, is produced by specialized epithelial cells called goblet cells. Among vertebrates’, fishes are perhaps one of the major groups known to produce mucous, particularly stingrays. The Atlantic stingray, Dasyatis sabina is one of the few cartilaginous fishes known to inhabit both freshwater areas and saltwater areas. It has been suggested by that mucous production varies significantly among freshwater and saltwater populations. In this study we aim to characterize the epithelium of freshwater vs saltwater D. sabina by quantifying (if any) variations on goblet cells density among different populations (freshwater vs salt water). This study will contribute to a much-needed characterization of stingray epithelia that may be used as a baseline anatomical framework in future studies and will contribute to the limited epithelium related literature among lower vertebrates. In addition, this study will contribute to our understanding of the morphological bases for the differential mucous production among this populations to ultimately relate this to ecosystem differences and environmental issues including water pollution

The Role of the Pericardium in the Valveless, Tubular Heart of the Tunicate, \u3cem\u3eCiona savignyi\u3c/em\u3e

Tunicates, small invertebrates within the phylum Chordata, possess a robust tubular heart which pumps blood through their open circulatory systems without the use of valves. This heart consists of two major components: the tubular myocardium, a flexible layer of myocardial cells that actively contracts to drive fluid down the length of the tube; and the pericardium, a stiff, outer layer of cells that surrounds the myocardium and creates a fluid-filled space between the myocardium and the pericardium. We investigated the role of the pericardium through in vivo manipulations on tunicate hearts and computational simulations of the myocardium and pericardium using the immersed boundary method. Experimental manipulations reveal that damage to the pericardium results in aneurysm-like bulging of the myocardium and major reductions in the net blood flow and percentage closure of the heart\u27s lumen during contraction. In addition, varying the pericardium-to-myocardium (PM) diameter ratio by increasing damage severity was positively correlated with peak dye flow in the heart. Computational simulations mirror the results of varying the PM ratio experimentally. Reducing the stiffness of the myocardium in the simulations reduced mean blood flow only for simulations without a pericardium. These results indicate that the pericardium has the ability to functionally increase the stiffness of the myocardium and limit myocardial aneurysms. The pericardium\u27s function is likely to enhance flow through the highly resistive circulatory system by acting as a support structure in the absence of connective tissue within the myocardium

Large Amplitude, Short Wave Peristalsis and Its Implications for Transport

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow is often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: Fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a nonlinear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate unidirectionally along a tube without the need for a structurally fixed flow direction

Less-structured time in children's daily lives predicts self-directed executive functioning.

Executive functions (EFs) in childhood predict important life outcomes. Thus, there is great interest in attempts to improve EFs early in life. Many interventions are led by trained adults, including structured training activities in the lab, and less-structured activities implemented in schools. Such programs have yielded gains in children's externally-driven executive functioning, where they are instructed on what goal-directed actions to carry out and when. However, it is less clear how children's experiences relate to their development of self-directed executive functioning, where they must determine on their own what goal-directed actions to carry out and when. We hypothesized that time spent in less-structured activities would give children opportunities to practice self-directed executive functioning, and lead to benefits. To investigate this possibility, we collected information from parents about their 6-7 year-old children's daily, annual, and typical schedules. We categorized children's activities as "structured" or "less-structured" based on categorization schemes from prior studies on child leisure time use. We assessed children's self-directed executive functioning using a well-established verbal fluency task, in which children generate members of a category and can decide on their own when to switch from one subcategory to another. The more time that children spent in less-structured activities, the better their self-directed executive functioning. The opposite was true of structured activities, which predicted poorer self-directed executive functioning. These relationships were robust (holding across increasingly strict classifications of structured and less-structured time) and specific (time use did not predict externally-driven executive functioning). We discuss implications, caveats, and ways in which potential interpretations can be distinguished in future work, to advance an understanding of this fundamental aspect of growing up

A Rac1-independent role for P-Rex1 in melanoblasts

No abstract available