4,358 research outputs found
The rise of a native sun coral species on southern Caribbean coral reefs
In contrast with a general decline of Caribbean reef corals, a previously rare sun coral is increasing in abundance within shallow coral communities on Curaçao. This azooxanthellate scleractinian was identified as Cladopsammia manuelensis, which has an amphiâAtlantic distribution. Over the last decade, C. manuelensis has increased abundance along the leeward coast of Curaçao (southern Caribbean) between depths of 4 and 30 m. This species was initially not noticed because it resembles the invasive coral Tubastraea coccinea, which was introduced to Curaçao from the IndoâPacific around 1940. However, in contrast to T. coccinea, C. manuelensis was previously only present on deeper reef sections (>70 m) of Caribbean reefs. Our observations illustrate how the sudden increase in abundance of a previously unnoticed, apparently cryptogenic species could result from natural dynamics on presentâday reefs, but also could easily be mistaken for an invasive species. The finding that deep reef sections can harbor species capable of colonizing shallower reef zones highlights the importance of thorough inventories of reef communities across large depth ranges, which can help us to discriminate between range increases of native species and the arrival of invasives
Automated computational analysis reveals structural changes in the enteric nervous system of nNOS deficient mice
Neuronal nitric oxide synthase (nNOS) neurons play a fundamental role in inhibitory neurotransmission, within the enteric nervous system (ENS), and in the establishment of gut motility patterns. Clinically, loss or disruption of nNOS neurons has been shown in a range of enteric neuropathies. However, the effects of nNOS loss on the composition and structure of the ENS remain poorly understood. The aim of this study was to assess the structural and transcriptional consequences of loss of nNOS neurons within the murine ENS. Expression analysis demonstrated compensatory transcriptional upregulation of pan neuronal and inhibitory neuronal subtype targets within the Nos1â/â colon, compared to control C57BL/6J mice. Conventional confocal imaging; combined with novel machine learning approaches, and automated computational analysis, revealed increased interconnectivity within the Nos1â/â ENS, compared to age-matched control mice, with increases in network density, neural projections and neuronal branching. These findings provide the first direct evidence of structural and molecular remodelling of the ENS, upon loss of nNOS signalling. Further, we demonstrate the utility of machine learning approaches, and automated computational image analysis, in revealing previously undetected; yet potentially clinically relevant, changes in ENS structure which could provide improved understanding of pathological mechanisms across a host of enteric neuropathies
A New Look at Mode Conversion in a Stratified Isothermal Atmosphere
Recent numerical investigations of wave propagation near coronal magnetic
null points (McLaughlin and Hood: Astron. Astrophys. 459, 641,2006) have
indicated how a fast MHD wave partially converts into a slow MHD wave as the
disturbance passes from a low-beta plasma to a high-beta plasma. This is a
complex process and a clear understanding of the conversion mechanism requires
the detailed investigation of a simpler model. An investigation of mode
conversion in a stratified, isothermal atmosphere, with a uniform, vertical
magnetic field is carried out, both numerically and analytically. In contrast
to previous investigations of upward-propagating waves (Zhugzhda and Dzhalilov:
Astron. Astrophys. 112, 16, 1982a; Cally: Astrophys. J. 548, 473, 2001), this
paper studies the downward propagation of waves from a low-beta to high-beta
environment. A simple expression for the amplitude of the transmitted wave is
compared with the numerical solution.Comment: 14 pages, 6 figure
First-order thermal correction to the quadratic response tensor and rate for second harmonic plasma emission
Three-wave interactions in plasmas are described, in the framework of kinetic
theory, by the quadratic response tensor (QRT). The cold-plasma QRT is a common
approximation for interactions between three fast waves. Here, the first-order
thermal correction (FOTC) to the cold-plasma QRT is derived for interactions
between three fast waves in a warm unmagnetized collisionless plasma, whose
particles have an arbitrary isotropic distribution function. The FOTC to the
cold-plasma QRT is shown to depend on the second moment of the distribution
function, the phase speeds of the waves, and the interaction geometry. Previous
calculations of the rate for second harmonic plasma emission (via Langmuir-wave
coalescence) assume the cold-plasma QRT. The FOTC to the cold-plasma QRT is
used here to calculate the FOTC to the second harmonic emission rate, and its
importance is assessed in various physical situations. The FOTC significantly
increases the rate when the ratio of the Langmuir phase speed to the electron
thermal speed is less than about 3.Comment: 11 pages, 2 figures, submitted to Physics of Plasma
Numerical simulation of unconstrained cyclotron resonant maser emission
When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of Auroral Kilometric Radiation (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared to waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.Publisher PD
Parkinson\u27s disease and multiple system atrophy have distinct α-synuclein seed characteristics
Perspectives on next steps in classification of oro-facial pain - Part 3: biomarkers of chronic oro-facial pain - from research to clinic
The purpose of this study was to review the current status of biomarkers used in oro-facial pain conditions. Specifically, we critically appraise their relative strengths and weaknesses for assessing mechanisms associated with the oro-facial pain conditions and interpret that information in the light of their current value for use in diagnosis. In the third section, we explore biomarkers through the perspective of ontological realism. We discuss ontological problems of biomarkers as currently widely conceptualised and implemented. This leads to recommendations for research practice aimed to a better understanding of the potential contribution that biomarkers might make to oro-facial pain diagnosis and thereby fulfil our goal for an expanded multidimensional framework for oro-facial pain conditions that would include a third axis
Simulations of Electron Acceleration at Collisionless Shocks: The Effects of Surface Fluctuations
Energetic electrons are a common feature of interplanetary shocks and
planetary bow shocks, and they are invoked as a key component of models of
nonthermal radio emission, such as solar radio bursts. A simulation study is
carried out of electron acceleration for high Mach number, quasi-perpendicular
shocks, typical of the shocks in the solar wind. Two dimensional
self-consistent hybrid shock simulations provide the electric and magnetic
fields in which test particle electrons are followed. A range of different
shock types, shock normal angles, and injection energies are studied. When the
Mach number is low, or the simulation configuration suppresses fluctuations
along the magnetic field direction, the results agree with theory assuming
magnetic moment conserving reflection (or Fast Fermi acceleration), with
electron energy gains of a factor only 2 - 3. For high Mach number, with a
realistic simulation configuration, the shock front has a dynamic rippled
character. The corresponding electron energization is radically different:
Energy spectra display: (1) considerably higher maximum energies than Fast
Fermi acceleration; (2) a plateau, or shallow sloped region, at intermediate
energies 2 - 5 times the injection energy; (3) power law fall off with
increasing energy, for both upstream and downstream particles, with a slope
decreasing as the shock normal angle approaches perpendicular; (4) sustained
flux levels over a broader region of shock normal angle than for adiabatic
reflection. All these features are in good qualitative agreement with
observations, and show that dynamic structure in the shock surface at ion
scales produces effective scattering and can be responsible for making high
Mach number shocks effective sites for electron acceleration.Comment: 26 pages, 12 figure
Development for change.
Lifelong Learning Networks are concerned with bringing about change in the practices and the provision of higher education to address the issue of low progression through vocational, applied and work-based routes. MOVE Lifelong Learning Network has sought to create a step change in
lifelong learning and maximise the vocational progression opportunities for individuals within the MOVE learner constituency in the East of England. This includes: those with vocational or applied qualifications at level three
those qualifying through work-based learning routes return to study learners seeking entry into vocational programmes either directly or through Access to Higher Education provision This document describes how MOVE has strategically employed the use of development funding
to generate a critical mass of curriculum and other development activity within the region to bring about the step change in provision that is required to meet the needs of these learners. The aim is to demonstrate how targeted funding can stimulate significant innovation in the way in which higher education is delivered, in the type and range of provision that is available and in
the practices employed to promote and support progression to higher education. In addition, the document describes how such changes in provision can contribute to a more employer led approach to curriculum development. The text also includes a range of project case study examples to illustrate the qualitative impact of the development activity supported by MOVE
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