703 research outputs found
New conception of the function of the general vasodilator reflexes
A survey of the literature regarding the vasodepressor
and cardiodepressor reflexes is given.
Evidence is put forward that the impulses which
arise from the cardioaortic and carotid sinus regions
control not only the normal vagus restraint of the
heart but also the capacity of the circulation. Loss
of these impulses not only causes cardiac acceleration
but results in an increased return of venous blood
to the heart.
It is shown that conditions which are believed
to be produced in exercise and which are known to
reduce the vagus restraint of the heart at the same
time reduce the effect of the carotid sinus impulses
upon the vessels.
The view is therefore put forward that an
important function of the vasodepressor reflxes
is to control the capacity of the circulation in
order to provide a reserve of blood for use in
physical exercise, just as is provided a cardiac
reserve to deal with such blood maintained by
similar reflex mechanisms.
The possible clinical significance of the
findings is indicated, and a bibliography of the
literature referred to in the text is given
Implementation of the FAA research and development electromagnetic database
The Idaho National Engineering Laboratory (INEL) has been assisting the FAA in developing a database of information about lightning. The FAA Research and Development Electromagnetic Database (FRED) will ultimately contain data from a variety of airborne and ground-based lightning research projects. An outline of the data currently available in FRED is presented. The data sources which the FAA intends to incorporate into FRED are listed. In addition, it describes how the researchers may access and use the FRED menu system
Children's informal learning at home during COVID-19 lockdown
The national COVID-19 lockdown during school Term 1 2020 provided a unique context to investigate childrenâs experiences of informal, everyday learning in their household bubble. In Terms 3 and 4, 178 children in Years 4â8 from 10 primary schools agreed to participate in a group art-making activity and an individual interview about their experiences. The research adopted a strengths-based approach on the basis that most children are capable actors in their social worlds. This report documents childrenâs accounts of the multiple ways in which they negotiated the novel experience of forced confinement over a period of several weeks with family and whÄnau. The report is rich with childrenâs own accounts of their everyday living and learning during lockdown. To foreground childrenâs descriptions and explanations of their lockdown experience in this way is an acknowledgement of their right to express their views on matters of interest to them in their lives, and to have those views listened to, and acted on, by adults. Similarly, the approach reflects a growing educational research interest in student voice: enabling children to articulate their experiences so that adults can use this knowledge to better respond to and support childrenâs learning aspirations and needs. This research report does not speak for all children or all childrenâs experiences. Nevertheless, it does provide valuable insights about the phenomenon of childrenâs informal and everyday learning during lockdown, gained from a group of children for whom it was a mostly positive experience, and through which they learned much about themselves as persons and as members of a family and whÄnau. Several months after the event, children in this study were able and willing to recall their experiences of learning during lockdown. They could identify social, cultural, and historical dimensions of their learning at home. Some children were able to recount rich, detailed stories about their lockdown experience and the ways in which they organised their days and activities. For some others, their days were largely shaped for them by family and whÄnau members, but even so, the children were able to explain what they enjoyed, or did not, and why. Variations in childrenâs learning across the group highlighted the complexity of learning that each child experienced, and the importance of having social relations, environments, and contexts that encourage and support their learning. Children demonstrated an understanding and appreciation of the value of this learning.falsehttp://www.nzcer.org.nz/research/publications/learning-during-lockdownNew Zealand Council for Educational Researc
Stable Determination of the Electromagnetic Coefficients by Boundary Measurements
The goal of this paper is to prove a stable determination of the coefficients
for the time-harmonic Maxwell equations, in a Lipschitz domain, by boundary
measurements
Inverse Transport Theory of Photoacoustics
We consider the reconstruction of optical parameters in a domain of interest
from photoacoustic data. Photoacoustic tomography (PAT) radiates high frequency
electromagnetic waves into the domain and measures acoustic signals emitted by
the resulting thermal expansion. Acoustic signals are then used to construct
the deposited thermal energy map. The latter depends on the constitutive
optical parameters in a nontrivial manner. In this paper, we develop and use an
inverse transport theory with internal measurements to extract information on
the optical coefficients from knowledge of the deposited thermal energy map. We
consider the multi-measurement setting in which many electromagnetic radiation
patterns are used to probe the domain of interest. By developing an expansion
of the measurement operator into singular components, we show that the spatial
variations of the intrinsic attenuation and the scattering coefficients may be
reconstructed. We also reconstruct coefficients describing anisotropic
scattering of photons, such as the anisotropy coefficient in a
Henyey-Greenstein phase function model. Finally, we derive stability estimates
for the reconstructions
Hyperglycaemia and lipid differentially impair mouse oocyte developmental competence
Maternal diabetes and obesity are characterised by elevated blood glucose, insulin and lipids, resulting in upregulation of specific fuel-sensing and stress signalling pathways. Previously, we demonstrated that, separately, upregulation of the hexosamine biosynthetic pathway (HBP; under hyperglycaemic conditions) and endoplasmic reticulum (ER) stress (due to hyperlipidaemia) pathways reduce blastocyst development and alter oocyte metabolism. In order to begin to understand how both glucose and lipid metabolic disruptions influence oocyte developmental competence, in the present study we exposed mouse cumulusâoocyte complexes to hyperglycaemia (30 mM) and/or lipid (40 ÎźM) and examined the effects on embryo development. The presence of glucosamine (GlcN; a hyperglycaemic mimetic) or increased lipid during in vitro maturation severely perturbed blastocyst development (P < 0.05). Hyperglycaemia, GlcN and hyperglycaemia + lipid treatments significantly increased HBP activity, increasing total O-linked glycosylation (O-GlcNAcylation) of proteins (P < 0.0001). All treatments also induced ER stress pathways, indicated by the expression of specific ER stress genes. The expression of genes encoding the HBP enzymes glutamine:fructose-6-phosphate amidotransferase 2 (Gfpt2) and O-linked β-N-acetylglucosaminyltransferase (Ogt) was repressed following lipid treatment (P < 0.001). These findings partially implicate the mechanism of O-GlcNAcylation and ER stress as likely contributors to compromised fertility of obese women.Siew L. Wong, Linda L. Wu, Rebecca L. Robker, Jeremy G. Thompson and Melanie L. Sutton McDowal
Fluctuations and differential contraction during regeneration of Hydra vulgaris tissue toroids
We studied regenerating bilayered tissue toroids dissected from Hydra
vulgaris polyps and relate our macroscopic observations to the dynamics of
force-generating mesoscopic cytoskeletal structures. Tissue fragments undergo a
specific toroid-spheroid folding process leading to complete regeneration
towards a new organism. The time scale of folding is too fast for biochemical
signalling or morphogenetic gradients which forced us to assume purely
mechanical self-organization. The initial pattern selection dynamics was
studied by embedding toroids into hydro-gels allowing us to observe the
deformation modes over longer periods of time. We found increasing mechanical
fluctuations which break the toroidal symmetry and discuss the evolution of
their power spectra for various gel stiffnesses. Our observations are related
to single cell studies which explain the mechanical feasibility of the folding
process. In addition, we observed switching of cells from a tissue bound to a
migrating state after folding failure as well as in tissue injury.
We found a supra-cellular actin ring assembled along the toroid's inner edge.
Its contraction can lead to the observed folding dynamics as we could confirm
by finite element simulations. This actin ring in the inner cell layer is
assembled by myosin- driven length fluctuations of supra-cellular
{\alpha}-actin structures (myonemes) in the outer cell-layer.Comment: 19 pages and 8 figures, submitted to New Journal of Physic
Extending prematuration with cAMP modulators enhances the cumulus contribution to oocyte antioxidant defence and oocyte quality via gap junctions
First published online: February 22, 2016Study question: Can bovine oocyte antioxidant defence and oocyte quality be improved by extending the duration of pre-in vitro maturation (IVM) with cyclic adenosine mono-phosphate (cAMP) modulators? Summary answer: Lengthening the duration of cAMP-modulated pre-IVM elevates intra-oocyte reduced glutathione (GSH) content and reduces hydrogen peroxide (H2O2) via increased cumulus cell-oocyte gap-junctional communication (GJC), associated with an improvement in subsequent embryo development and quality. What is known already: Oocytes are susceptible to oxidative stress and the oocyteâs most important antioxidant glutathione is supplied, at least in part, by cumulus cells. A temporary inhibition of spontaneous meiotic resumption in oocytes can be achieved by preventing a fall in cAMP, and cyclic AMP-modulated pre-IVM maintains cumulus-oocyte GJC and improves subsequent embryo development. Study design, size, duration: This study consisted of a series of 10 experiments using bovine oocytes in vitro, each with multiple replicates.Arange of pre-IVM durations were examined as the key study treatments which were compared with a control. The study was designed to examine if one of the oocyteâs major antioxidant defences can be enhanced by pre-IVM with cAMP modulators, and to examine the contribution of cumulus-oocyte GJC on these processes. Participants/materials, setting, methods: Immature bovine cumulus-oocyte complexes were treated in vitro without (control) or with the cAMP modulators; 100 mM forskolin (FSK) and 500 mM 3-isobutyl-1-methyxanthine (IBMX), for 0, 2, 4 or 6 h (pre-IVM phase) prior to IVM. Oocyte developmental competence was assessed by embryo development and quality post-IVM/IVF. Cumulus-oocyte GJC, intra-oocyte GSH and H2O2 were quantified at various time points during pre-IVM and IVM, in the presence and the absence of functional inhibitors: carbenoxolone (CBX) to block GJC and buthionine sulfoximide (BSO) to inhibit glutathione synthesis. Main results and the role of chance: Pre-IVM with FSK + IBMX increased subsequent blastocyst formation rate and quality compared with standard IVM (P , 0.05), regardless of pre-IVM duration. The final blastocyst yields (proportion of blastocysts/immature oocyte) were 26.3% for the control, compared with 39.2, 35.2 and 34.2%, for the 2, 4 and 6 h pre-IVM FSK + IBMXtreatments, respectively. In contrast to standard IVM (control), pre-IVM with cAMP modulators maintained open gap junctions between cumulus cells and oocytes for the duration (6 h) of pre-IVM examined, and persisted for a further 8 h in the IVM phase. Cyclic AMP-modulated pre-IVM increased intra-oocyte GSH levels at the completion of both pre-IVM and IVM, in a pre-IVM duration-dependent manner (P , 0.05), whichwas ablated when GJC was blocked usingCBX (P , 0.05). By 4 h of pre-IVM treatment with cAMP modulators, oocyte H2O2 levels were reduced compared the control (P , 0.05), although this beneficial effect was lost when oocytes were co-treated with BSO. Inhibiting glutathione synthesis with BSO during pre-IVM ablated any positive benefits of cAMP-mediated pre-IVM on oocyte developmental competence (P , 0.01). Limitations, reasons for caution: It is unclear if the improvement in oocyte antioxidant defence and developmental competence reported here is due to direct transfer of total and/or reduced glutathione from cumulus cells to the oocyte via gap junctions, or whether a GSH synthesis signal and/or amino acid substrates are supplied to the oocyte via gap junctions. Embryo transfer experiments are required to determine if the cAMP-mediated improvement in blastocyst rates leads to improved live birth rates. Wider implications of the findings: IVM offers significant benefits to infertile and cancer patients and has the potential to significantly alter ART practice, if IVM efficiency in embryo production could be improved closer to that of conventional IVF (using ovarian hyperstimulation). Pre-IVM with cAMP modulators is a simple and reliable means to improve IVM outcomes. Study funding/competing interest(s): This work was supported by grants and fellowships from the National Health and Medical Research Council of Australia (1007551, 627007, 1008137, 1023210) and by scholarships from the Chinese Scholarship Council (CSC) awarded to H.J.L. and the Japanese Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad awarded to S.S. The Fluoview FV10i confocal microscope was purchased as part of the Sensing Technologies for Advanced Reproductive Research (STARR) facility, funded by the South Australian Premierâs Science and Research Fund. We acknowledge partial support from the Australian Research CouncilCentre of Excellence for Nanoscale BioPhotonics (CE140100003).We declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.H.J. Li, M.L. Sutton-McDowall, X.Wang, S. Sugimura, J.G. Thompson, and R.B. Gilchris
Climate change decouples marine and freshwater habitats of a threatened migratory fish
Aim To assess how climate change may decouple the ecosystems used by a migratory fish, and how decoupling influences priorities for stream restoration. Location Australia. Methods We modelled changes in habitat suitability under climate change in both riverine and marine habitats for a threatened diadromous species, the Australian Grayling Prototroctes maraena, using niche models. The loss of riverine habitats for Grayling was compared with or without considering the impact of climate change on adjacent marine habitats. We also asked whether considering marine climate change changed the locations where removing dams had the greatest benefit for Grayling conservation. Results Climate change is expected to cause local extinction in both marine and river habitats regardless of whether dams are retained or removed at the trailing edge of the Grayling's range (northâeastern). Decoupling of habitats was most apparent in the eastern and southâeastern portion of the Grayling's range, where ocean warming may cause a decline in the suitability of marine habitats for larvae, while many freshwater habitats retained suitable habitat for adults. Removing dams to restore connectivity between ocean and freshwater habitats was predicted to have the greatest benefit for Grayling in southern portions of their range. Under climate change, the priorities for barrier removal gradually shift towards dams at higher elevation because of increasing suitability of freshwater habitats at higher elevations. Main conclusions Our study highlights the importance of assessing climate range shifts in multiple ecosystems for migratory species and can help inform priorities for stream restoration under a changing climate
Stability of the gauge equivalent classes in stationary transport
For anisotropic attenuating media, the albedo operator determines the
scattering and the attenuation coefficients up to a gauge transformation. We
show that such a determination is stable
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