1,234 research outputs found
Solar Wind and its Evolution
By using our previous results of magnetohydrodynamical simulations for the
solar wind from open flux tubes, I discuss how the solar wind in the past is
different from the current solar wind. The simulations are performed in fixed
one-dimensional super-radially open magnetic flux tubes by inputing various
types of fluctuations from the photosphere, which automatically determines
solar wind properties in a forward manner. The three important parameters which
determine physical properties of the solar wind are surface fluctuation,
magnetic field strengths, and the configuration of magnetic flux tubes.
Adjusting these parameters to the sun at earlier times in a qualitative sense,
I infer that the quasi-steady-state component of the solar wind in the past was
denser and slightly slower if the effect of the magneto-centrifugal force is
not significant. I also discuss effects of magneto-centrifugal force and roles
of coronal mass ejections.Comment: 6 pages, 1 figure, Earth, Planets, & Space in press (based on 5th
Alfven Conference) correction of discussion on a related pape
Plasma density gradients at the edge of polar ionospheric holes: the presence and absence of phase scintillation
Polar holes were observed in the high-latitude ionosphere during a series of multi-instrument case studies close to the Northern Hemisphere winter solstice in 2014 and 2015. These holes were observed during geomagnetically quiet conditions and under a range of solar activities using the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR) and measurements from Global Navigation Satellite System (GNSS) receivers. Steep electron density gradients have been associated with phase scintillation in previous studies; however, no enhanced scintillation was detected within the electron density gradients at these boundaries. It is suggested that the lack of phase scintillation may be due to low plasma density levels and a lack of intense particle precipitation. It is concluded that both significant electron density gradients and plasma density levels above a certain threshold are required for scintillation to occur
A cross-sectional survey of cardiovascular health and lifestyle habits of hospital staff in the UK: Do we look after ourselves?
Background: A high prevalence of stress-related disorders is well known among healthcare professionals. We set out to assess the prevalence of cardiovascular risk factors and compliance with national dietary and physical activity recommendations in NHS staff in the UK with comparison between clinical and non-clinical staff, and national surveys. Design: A multi-centre cross-sectional study. Methods: A web-based questionnaire was developed to include anonymised data on demographics, job role, cardiovascular risk factors and diseases, dietary habits, physical activity and barriers towards healthy lifestyle. This was distributed to staff in four NHS hospitals via emails. Results: A total of 1158 staff completed the survey (response rate 13%) with equal distribution between the clinical and non-clinical groups. Most staff were aged 26–60 years and 79% were women. Half of the staff were either overweight or obese (51%) with no difference between the groups (P = 0.176), but there was a lower prevalence of cardiovascular risk factors compared to the general population. The survey revealed a low compliance (17%) with the recommended intake of five-a-day portions of fruit and vegetables, and that of moderate or vigorous physical activity (56%), with no difference between the clinical and non-clinical staff (P = 0.6). However, more clinical staff were exceeding the alcohol recommendations (P = 0.02). Lack of fitness facilities and managerial support, coupled with long working hours, were the main reported barriers to a healthy lifestyle. Conclusions: In this survey of UK NHS staff, half were found to be overweight or obese with a lower prevalence of cardiovascular risk factors compared to the general population. There was a low compliance with the five-a-day fruit and vegetables recommendation and physical activity guidelines, with no difference between the clinical and non-clinical staff
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Indole: An evolutionarily conserved influencer of behavior across kingdoms
Indole is a key environmental cue that is used by many organisms. Based on its biochemistry, we suggest indole is used so universally, and by such different organisms, because it derives from the metabolism of tryptophan, a resource essential for many species yet rare in nature. These properties make it a valuable, environmental cue for resources almost universally important for promoting fitness. We then describe how indole is used to coordinate actions within organisms, to influence the behavior of conspecifics and can even be used to change the behavior of species that belong to other kingdoms. Drawing on the evolutionary framework that has been developed for understanding animal communication, we show how this is diversely achieved by indole acting as a cue, a manipulative signal, and an honest signal, as well as how indole can be used synergistically to amplify information conveyed by other molecules. Clarifying these distinct functions of indole identifies patterns that transcend different kingdoms of organisms
Risk factors for race-day fatality in flat racing Thoroughbreds in Great Britain (2000 to 2013)
A key focus of the racing industry is to reduce the number of race-day events where horses die suddenly or are euthanased due to catastrophic injury. The objective of this study was therefore to determine risk factors for race-day fatalities in Thoroughbred racehorses, using a cohort of all horses participating in flat racing in Great Britain between 2000 and 2013. Horse-, race- and course-level data were collected and combined with all race-day fatalities, recorded by racecourse veterinarians in a central database. Associations between exposure variables and fatality were assessed using logistic regression analyses for (1) all starts in the dataset and (2) starts made on turf surfaces only. There were 806,764 starts in total, of which 548,571 were on turf surfaces. A total of 610 fatalities were recorded; 377 (61.8%) on turf. In both regression models, increased firmness of the going, increasing racing distance, increasing average horse performance, first year of racing and wearing eye cover for the first time all increased the odds of fatality. Generally, the odds of fatality also increased with increasing horse age whereas increasing number of previous starts reduced fatality odds. In the ‘all starts’ model, horses racing in an auction race were at 1.46 (95% confidence interval (CI) 1.06–2.01) times the odds of fatality compared with horses not racing in this race type. In the turf starts model, horses racing in Group 1 races were at 3.19 (95% CI 1.71–5.93) times the odds of fatality compared with horses not racing in this race type. Identification of novel risk factors including wearing eye cover and race type will help to inform strategies to further reduce the rate of fatality in flat racing horses, enhancing horse and jockey welfare and safety
Normal modes and discovery of high-order cross-frequencies in the DBV white dwarf GD 358
We present a detailed mode identification performed on the 1994 Whole Earth Telescope (WET) run on GD 358. The results are compared with that obtained for the same star from the 1990 WET data. The two temporal spectra show very few qualitative differences, although amplitude changes are seen in most modes, including the disappearance of the mode identified as k=14 in the 1990 data. The excellent coverage and signal-to-noise ratio obtained during the 1994 run lead to the secure identification of combination frequencies up to fourth order, i.e. peaks that are sums or differences of up to four parent frequencies, including a virtually complete set of second-order frequencies, as expected from harmonic distortion. We show how the third-order frequencies are expected to affect the triplet structure of the normal modes by back-interacting with them. Finally, a search for â„“=2 modes was unsuccessful, not verifying the suspicion that such modes had been uncovered in the 1990 data set
Genetic differentiation among host-associated Alebra leafhoppers (Hemiptera: Cicadellidae)
The limited importance ascribed to sympatric speciation pro cesses via host race formation is partially due to the few
cases of host races that have been reported among host
populations. This work sheds light on the taxonomy of Alebra
leafhoppers and examines the possible existence of host
races among host-associated populations. The species of
this genus show varying degrees of host association with
deciduous trees and shrubs and, frequently, host popu lations of uncertain taxonomic status coexist and occasion ally become pests. Allozyme electrophoresis of 21 Greek
populations including sympatric, local and geographically
distant samples collected on 13 different plant species, show
that they represent at least five species: A. albostriella
Falle´n, A. viridis (Rey) (sensu Gillham), A. wahlbergi Bo Keywords: host races; leafhoppers; sympatric speciation; sibling species; allozymes; Alebra
Introduction
Sympatric speciation is a controversial subject in evol utionary biology (see Mayr, 1963; Futuyma and Mayer,
1980; Paterson, 1981; Via, 2001). One of the reasons for
this controversy is that sympatric speciation seems to be
an extremely rare phenomenon occurring only in very
few groups of taxa, represented chiefly by phytophagous
insects (Tauber and Tauber, 1977; Menken, 1981; Wood,
1993; Emelianov et al, 1995; Via, 1999; Finchak et al, 2000;
Craig et al, 2001). The limited number of reported cases
among organisms with sexual reproduction can be at
least partially attributed to the fact that taxa undergoing
sympatric speciation events must fulfill very restrictive
biological and ecological requirements.
Most sympatric speciation models demand that there is
intraspecific genetic variation in traits that differentially
affect the fitness of individuals that colonise new habitats
or hosts (Dieckman and Doebeli, 1999; Hawthorne and
Via, 2001 but see Higashi et al, 1999 and Takimoto et al,
2000). They assume that selection acting on these traits
can prevent genetic exchange between populations
(Bush, 1975; Tauber and Tauber, 1977; Diehl and Bush,
1989). In phytophagous insects, this means that host pref erences must be genetically determined and mating
should occur on the host (Bush, 1975; Diehl and Bush,
Correspondence: D Aguin-Pombo, Department of Biology, University of
Madeira, Campus Universitario da Penteada, 9000 Funchal, Madeira,
Portugal. E-mail: aguin uma.pt
Received 12 December 2000; accepted 13 December 2001
heman and two new species. Of these, one is associated
to Quercus frainetto and other is specific to Crataegus spp.
Significant genetic differences among sympatric and local
host populations were found only in A. albostriella, between
populations on Turkey oak, beech and common alder. It is
suggested that the last two of these host populations may
represent different host races. The results show that both
the host plant and geographical distance affect the patterns
of differentiation in the genus. The formation of some spec ies seems to have been the result of allopatric speciation
events while, for others, their origin can be equally explained
either by sympatric or allopatric speciation.info:eu-repo/semantics/publishedVersio
Telomerase activity, apoptosis and cell cycle progression in ataxia telangiectasia lymphocytes expressing TCL1
Individuals affected by ataxia telangiectasia (AT) have a marked susceptibility to cancer. Ataxia telangiectasia cells, in addition to defects in cell cycle checkpoints, show dysfunction of apoptosis and of telomeres, which are both thought to have a role in the progression of malignancy. In 1-5% of patients with AT, clonal expansion of T lymphocytes carrying t(14;14) chromosomal translocation, deregulating TCL1 gene(s), has been described. While it is known that these cells can progress with time to a frank leukaemia, the molecular pathway leading to tumorigenesis has not yet been fully investigated. In this study, we compared AT clonal cells, representing 88% of the entire T lymphocytes (AT94-1) and expressing TCL1 oncogene (ATM- TCL1 +), cell cycle progression to T lymphocytes of AT patients without TCL1 expression (ATM- TCL1-) by analysing their spontaneous apoptosis rate, spontaneous telomerase activity and telomere instability. We show that in ATM- TCL1+ lymphocytes, apoptosis rate and cell cycle progression are restored back to a rate comparable with that observed in normal lymphocytes while telomere dysfunction is maintained. © 2003 Cancer Research UK
Stellar Coronal and Wind Models: Impact on Exoplanets
Surface magnetism is believed to be the main driver of coronal heating and
stellar wind acceleration. Coronae are believed to be formed by plasma confined
in closed magnetic coronal loops of the stars, with winds mainly originating in
open magnetic field line regions. In this Chapter, we review some basic
properties of stellar coronae and winds and present some existing models. In
the last part of this Chapter, we discuss the effects of coronal winds on
exoplanets.Comment: Chapter published in the "Handbook of Exoplanets", Editors in Chief:
Juan Antonio Belmonte and Hans Deeg, Section Editor: Nuccio Lanza. Springer
Reference Work
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