437 research outputs found
Desiccation, thermal stress and associated mortality in Drosophila fruit flies induced by neuropeptide analogue treatment
Drosophila suzukii is a serious pest of soft fruit worldwide. With the global over-dependence on broad-spectrum pesticides, a strong imperative exists for more environmentally friendly and targeted methods of control. One promising avenue involves employing synthetic neuropeptide analogues as insecticidal agents to reduce pest fitness. Neuropeptides, central to the regulation of physiological and behavioural processes, play a vital role in cold and desiccation survival. Building upon this, the current study investigated the effects of biostable kinin, the cardioacceleratory peptide CAP2b and pyrokinin (PK) analogues (the latter of which have previously displayed cross-talk with the capa receptor), on desiccation, starvation and cold stress tolerance of the pest, D. suzukii, and the closely related non-pest, D. melanogaster. Results demonstrated analogues of the superfamily (CAP2b and PK derived) significantly impacted survival of the target insect under conditions of desiccation stress. However, these peptides enhanced desiccation stress survival in relation to controls, suggesting that they may act as antagonists of the capa signalling pathway in the Malpighian tubules. Of particular note was the ability of analogues 1895 (2Abf-Suc-FGPRLa) and 1902 (2Abf-Suc-FKPRLa) to impact D. suzukii but not D. melanogaster. A focus on native Drosophila CAP2b/PK and kinin sequences in analogue development may yield pure agonists with diuretic action that may reduce desiccation stress survival in the pest flies. In highlighting the PRXamide neuropeptide superfamily more generally, and the structures of promising analogues more specifically, this research will feed the evolution of next-generation analogues and drive forward the development of neuropeptidomimetic-based agents
Fetal liver blood flow distribution: role in human developmental strategy to prioritize fat deposition versus brain development
Among primates, human neonates have the largest brains but also the highest proportion of body fat. If placental nutrient supply is limited, the fetus faces a dilemma: should resources be allocated to brain growth, or to fat deposition for use as a potential postnatal energy reserve? We hypothesised that resolving this dilemma operates at the level of umbilical blood distribution entering the fetal liver. In 381 uncomplicated pregnancies in third trimester, we measured blood flow perfusing the fetal liver, or bypassing it via the ductus venosus to supply the brain and heart using ultrasound techniques. Across the range of fetal growth and independent of the mother's adiposity and parity, greater liver blood flow was associated with greater offspring fat mass measured by dual-energy X-ray absorptiometry, both in the infant at birth (r = 0.43, P<0.001) and at age 4 years (r = 0.16, P = 0.02). In contrast, smaller placentas less able to meet fetal demand for essential nutrients were associated with a brain-sparing flow pattern (r = 0.17, p = 0.02). This flow pattern was also associated with a higher degree of shunting through ductus venosus (P = 0.04). We propose that humans evolved a developmental strategy to prioritize nutrient allocation for prenatal fat deposition when the supply of conditionally essential nutrients requiring hepatic inter-conversion is limited, switching resource allocation to favour the brain if the supply of essential nutrients is limited. Facilitated placental transfer mechanisms for glucose and other nutrients evolved in environments less affluent than those now prevalent in developed populations, and we propose that in circumstances of maternal adiposity and nutrient excess these mechanisms now also lead to prenatal fat deposition. Prenatal developmental influences play important roles in the human propensity to deposit fa
Speech-Language Pathology Provision During the COVID-19 Pandemic for Children Born With Cleft Palate in the United Kingdom:Parent/Caregiver Perspectives and Experiences
Mass transfer in eccentric binaries: the new Oil-on-Water SPH technique
To measure the onset of mass transfer in eccentric binaries we have developed
a two-phase SPH technique. Mass transfer is important in the evolution of close
binaries, and a key issue is to determine the separation at which mass transfer
begins. The circular case is well understood and can be treated through the use
of the Roche formalism. To treat the eccentric case we use a newly-developed
two phase system. The body of the donor star is made up from high-mass "water"
particles, whilst the atmosphere is modelled with low-mass "oil" particles.
Both sets of particles take part fully in SPH interactions. To test the
technique we model circular mass-transfer binaries containing a 0.6 Msun donor
star and a 1 Msun white dwarf; such binaries are thought to form cataclysmic
variable (CV) systems. We find that we can reproduce a reasonable CV
mass-transfer rate, and that our extended atmosphere gives a separation that is
too large by aproximately 16%, although its pressure scale height is
considerably exaggerated. We use the technique to measure the semi-major axis
required for the onset of mass transfer in binaries with a mass ratio of q=0.6
and a range of eccentricities. Comparing to the value obtained by considering
the instantaneous Roche lobe at pericentre we find that the radius of the star
required for mass transfer to begin decreases systematically with increasing
eccentricity.Comment: 9 pages, 8 figures, accepted by MNRA
Parent/Caregiver Views of the Effectiveness of Speech-Language Pathology for Children Born With Cleft Palate Delivered via Telemedicine During COVID-19
Period Concatenation Underlies Interactions between Gamma and Beta Rhythms in Neocortex
The neocortex generates rhythmic electrical activity over a frequency range covering many decades. Specific cognitive and motor states are associated with oscillations in discrete frequency bands within this range, but it is not known whether interactions and transitions between distinct frequencies are of functional importance. When coexpressed rhythms have frequencies that differ by a factor of two or more interactions can be seen in terms of phase synchronization. Larger frequency differences can result in interactions in the form of nesting of faster frequencies within slower ones by a process of amplitude modulation. It is not known how coexpressed rhythms, whose frequencies differ by less than a factor of two may interact. Here we show that two frequencies (gamma – 40 Hz and beta2 – 25 Hz), coexpressed in superficial and deep cortical laminae with low temporal interaction, can combine to generate a third frequency (beta1 – 15 Hz) showing strong temporal interaction. The process occurs via period concatenation, with basic rhythm-generating microcircuits underlying gamma and beta2 rhythms forming the building blocks of the beta1 rhythm by a process of addition. The mean ratio of adjacent frequency components was a constant – approximately the golden mean – which served to both minimize temporal interactions, and permit multiple transitions, between frequencies. The resulting temporal landscape may provide a framework for multiplexing – parallel information processing on multiple temporal scales
The effects of rhythm and melody on auditory stream segregation
Whilst many studies have assessed the efficacy of similarity-based cues for auditory stream segregation, much less is known about whether and how the larger-scale structure of sound sequences support stream formation and the choice of sound organization. Two experiments investigated the effects of musical melody and rhythm on the segregation of two interleaved tone sequences. The two sets of tones fully overlapped in pitch range, but differed from each other in interaural time and intensity. Unbeknownst to the listener, separately, each of the interleaved sequences was created from the notes of a different song. In different experimental conditions, the notes and/or their timing could either follow those of the songs, or they could be scrambled or, in case of timing, set to be isochronous. Listeners were asked to continuously report whether they heard a single coherent sequence (integrated) or two concurrent streams (segregated). Although temporal overlap between tones from the two streams proved to be the strongest cue for stream segregation, significant effects of tonality and familiarity with the songs were also observed. These results suggest that the regular temporal patterns are utilized as cues in auditory stream segregation and that long-term memory is involved in this process
A Far-Ultraviolet Survey of 47 Tucanae.II The Long-Period Cataclysmic Variable AKO 9
We present time-resolved, far-ultraviolet (FUV) spectroscopy and photometry
of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47
Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and He
II emission lines. The spectrum broadly resembles that of long-period,
cataclysmic variables in the galactic field.
Combining our time-resolved FUV data with archival optical photometry of 47
Tuc, we refine the orbital period of AKO 9 and define an accurate ephemeris for
the system. We also place constraints on several other system parameters, using
a variety of observational constraints. We find that all of the empirical
evidence is consistent with AKO 9 being a long-period dwarf nova in which mass
transfer is driven by the nuclear expansion of a sub-giant donor star. We
therefore conclude that AKO 9 is the first spectroscopically confirmed
cataclysmic variable in 47 Tuc.
We also briefly consider AKO 9's likely formation and ultimate evolution.
Regarding the former, we find that the system was almost certainly formed
dynamically, either via tidal capture or in a 3-body encounter. Regarding the
latter, we show that AKO 9 will probably end its CV phase by becoming a
detached, double WD system or by exploding in a Type Ia supernova.Comment: 40 pages, 11 figures, to appear in the Dec 20 issue of ApJ; minor
changes to match final published versio
Is There Enough Evidence to Support the Role of Glycosaminoglycans and Proteoglycans in Thoracic Aortic Aneurysm and Dissection?—A Systematic Review
Altered proteoglycan (PG) and glycosaminoglycan (GAG) distribution within the aortic wall has been implicated in thoracic aortic aneurysm and dissection (TAAD). This review was conducted to identify literature reporting the presence, distribution and role of PGs and GAGs in the normal aorta and differences associated with sporadic TAAD to address the question; is there enough evidence to establish the role of GAGs/PGs in TAAD? 75 studies were included, divided into normal aorta (n = 51) and TAAD (n = 24). There is contradictory data regarding changes in GAGs upon ageing; most studies reported an increase in GAG sub-types, often followed by a decrease upon further ageing. Fourteen studies reported changes in PG/GAG or associated degradation enzyme levels in TAAD, with most increased in disease tissue or serum. We conclude that despite being present at relatively low abundance in the aortic wall, PGs and GAGs play an important role in extracellular matrix maintenance, with differences observed upon ageing and in association with TAAD. However, there is currently insufficient information to establish a cause-effect relationship with an underlying mechanistic understanding of these changes requiring further investigation. Increased PG presence in serum associated with aortic disease highlights the future potential of these biomolecules as diagnostic or prognostic biomarkers.</jats:p
Tests of Spurious Transport in Smoothed Particle Hydrodynamics
We have performed a series of systematic tests to evaluate the effects of
spurious transport in three-dimensional smoothed particle hydrodynamics (SPH)
calculations. Our tests investigate (i) particle diffusion, (ii) shock heating,
(iii) numerical viscosity, and (iv) angular momentum transport. The results are
useful for quantifying the accuracy of the SPH scheme, especially for problems
where shear flows or shocks are present, as well as for problems where true
hydrodynamic mixing is relevant.
We examine the different forms of artificial viscosity (AV) which have been
proposed by Monaghan, by Hernquist & Katz, and by Balsara. For each form, our
tests suggest a single set of values for the AV parameters and
(coefficients of the linear and quadratic terms) which are appropriate in a
large number of situations. We also discuss how these parameters should be
adjusted depending on the goals of the particular application. We find that
both the Hernquist & Katz and Balsara forms introduce relatively small amounts
of numerical viscosity. Furthermore, both Monaghan's and Balsara's AV do well
at treating shocks and at limiting the amount of spurious mixing. For these
reasons, we endorse the Balsara AV for use in a broad range of applications.Comment: 49 pages, 26 figures as 30 postscript files, submitted to The Journal
of Computational Physic
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