1,043 research outputs found
Behaviour of the smooth muscle of the cardiovascular system
This investigation was undertaken in an attempt to study the behaviour
of vascular smooth muscle at the cellular level, and in conditions as near
physiological as possible. Microelectrodes were inserted into smooth muscle
cells in the walls of small arteries and arterioles in the rat mesenteric
circulation in the intact anaesthetized rat, and the electrical activity recorded
at rest and under the influence of various physiological stimuli.Intracellular recording gave membrane potentials that were low and
variable, showing slow fluctuations at frequencies of some 9 to 12/min, and
occasional action potentials which appeared to arise from the slow waves.
Both these types of electrical activity were capable of being influenced by the
sympathetic nervous system, as shown by the effects of stimulating the
splanchnic nerves and denervating by chemical means and by cutting the nerves.
However, as it is not known whether any residual nervous activity remained
after denervation was attempted, it remains uncertain whether this electrical
activity was generated by nervous activity or by some mechanism inherent in
the smooth muscle cell itself.Propagated action potentials could not be elicited by direct electrical
stimulation of the blood vessels, and the application of a stimulating pulse
across the cell membrane into the interior of the cell did not evoke an action
potential, but this may have been due to technical limitations.It was found impossible to record for long periods with an electrode
inside a cell due to the small size and continuous movement of the cells, and
the effects of various stimulating and inhibiting agents were therefore studied
using extracellular recording methods. In general, stimulating agents such
as asphyxia, electrical stimulation of the sympathetic nerves, and local
application of adrenaline, noradrenaline, and vasopressin, increased the
electrical activity of the muscle, and inhibiting agents such as acetylcholine
and removal of the nerve supply depressed it. High concentrations of adrenaline
and noradrenaline appeared to be capable of causing the muscle cells to contract
without firing action potentials, but whether this type of contracture is a
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physiological phenomenon remains uncertain. None of these manoeuvres
had any significant effect on the frequency of the slow waves, but under the
influence of stimulating agents the percentage of waves with action potentials
increased, and spikes appeared in twos and threes.It was concluded that the technical difficulties due to the small size of
the smooth muscle cells relative to that of the penetrating electrode tip will
limit further investigation using refined techniques until the development of
methods for producing finer microelectrodes
Defining Short-Term Accommodation for Animals
Abstract The terms short-term, temporary, and transitional are related but can have different contexts and meanings for animal husbandry. The definitions and use of these terms can be pivotal to animal housing and welfare. We conducted three separate literature searches using Google Scholar for relevant reports regarding short-term, temporary, or transitional animal husbandry, and analysed key publications that stipulate relevant periods of accommodation. English Government guidance regarding acceptable short-term, temporary, or transitional accommodation for animals varies widely from 24 h, all animals at all facilities should be accommodated in conditions that are consistent with long-term housing, husbandry, and best practices
Reptile expos: an analysis and recommendations for control.
Reptile expos are typically itinerant events at which live wild-caught and/or captive-bred turtles, tortoises, crocodiles, lizards, and snakes are displayed, sold, or exchanged for pet keeping purposes. We conducted a literature review and analysis of reports regarding animal welfare and public health issues of concern associated with the display and sale of reptiles at expos in Europe and North America. We also conducted a limited survey of several relevant government authorities to briefly appraise existing situations regarding governance and law internationally, and performed a further limited examination of online advertisements in order to estimate the number of events. In addition, we conducted an analysis comparing husbandry standards for reptile expos versus other animal display or sale situations using UK formal legal guidance, which adopts the Five Welfare Needs as a basis. Finally, we also conducted a SWOT (strengths, weaknesses, opportunities, and threats) analysis of key features associated with reptile expos. We identified at least 10 animal welfare and 5 public health and safety problems as occurring and endemic to the typical operation of reptile expos. Comparisons between the ways in which animal welfare and public health issues are regarded or managed for reptile expos in relation to, for example, traditional zoos, mobile zoos, and pet sales are stark and concerning, with expos constituting the least protective and potentially most harmful situations out of all captive reptile-keeping scenarios. The lack of monitoring and control of reptile expos, combined with their frequent occurrence, strongly indicates the requirement to urgently control and prohibit these events. We recommend that where reptile expos are already essentially prohibited such bans should be immutable and not subject to any weakening provisions. Where reptile expos are permitted and/or subject to limiting conditions, or where reptile expos are not subject to limiting conditions, then our recommended 40 stipulations and overarching control principles should be applied as interim mitigating measures pending the introduction of prohibitions or âbansâ. Governments should aim to ensure that enforcement of such measures is robust
Automatic Transcription of Polyphonic Vocal Music
This paper presents a method for automatic music transcription applied to audio recordings of a cappella performances with multiple singers. We propose a system for multi-pitch detection and voice assignment that integrates an acoustic and a music language model. The acoustic model performs spectrogram decomposition, extending probabilistic latent component analysis (PLCA) using a six-dimensional dictionary with pre-extracted log-spectral templates. The music language model performs voice separation and assignment using hidden Markov models that apply musicological assumptions. By integrating the two models, the system is able to detect multiple concurrent pitches in polyphonic vocal music and assign each detected pitch to a specific voice type such as soprano, alto, tenor or bass (SATB). We compare our system against multiple baselines, achieving state-of-the-art results for both multi-pitch detection and voice assignment on a dataset of Bach chorales and another of barbershop quartets. We also present an additional evaluation of our system using varied pitch tolerance levels to investigate its performance at 20-cent pitch resolution
Pathways to economic well-being among teenage mothers in Great Britain
The present study examines pathways to independence from social welfare among 738 teenage mothers, participants of the 1970 British Cohort Study, who were followed up at age 30 years. Using a longitudinal design, a pathway model is tested, examining linkages between family social background, cognitive ability, school motivation, and individual investments in education, as well as work- and family-related roles. The most important factors associated with financial independence by age 30 are continued attachment to the labor market as well as a stable relationship with a partner (not necessarily the father of the child). Pathways to financial independence, in turn, are predicted through own cognitive resources, school motivation, and family cohesion. Implications of findings for policy making are discussed.© 2010 Hogrefe Publishing
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