1,131 research outputs found
On the kinematics of the neutron star low mass X-ray binary Cen X-4
We present the first determination of the proper motion of the neutron star
low mass X-ray binary {Cen X-4} measured from relative astrometry of the
secondary star using optical images at different epochs. We determine the
Galactic space velocity components of the system and find them to be
significantly different from the mean values that characterize the kinematics
of stars belonging to the halo, and the thin and the thick disc of the Galaxy.
The high metallicity of the secondary star of the system rules out a halo
origin and indicates that the system probably originated in the Galactic disc.
A statistical analysis of the galactocentric motion revealed that this binary
moves in a highly eccentric () orbit with an inclination of
to the Galactic plane. The large Galactic space velocity
components strongly support that a high natal kick as a result of a supernova
explosion could have propelled the system into such an orbit from a birth place
in the Galactic disc. The high Li abundance in the secondary, comparable to
that of stars in star forming regions and young stellar clusters like the
Pleiades, may suggest a relatively recent formation of the system. Following
the orbit backwards in time, we found that the system could have been in the
inner regions of the Galactic disc 100--200 Myr ago. The neutron star
might have formed at that moment. However, we cannot rule out the possibility
that the system formed at a much earlier time if a Li production mechanism
exists in this LMXB.Comment: 6 pages, 4 figures, accepted for publication in A&
Rotational Broadening and Doppler Tomography of the Quiescent X-Ray Nova Centaurus X-4
We present high and intermediate resolution spectroscopy of the X-ray nova
Centaurus X-4 during its quiescent phase. Our analysis of the absorption
features supports a K3-K5V spectral classification for the companion star,
which contributes approximately 75 % of the total flux at Halpha. Using the
high resolution spectra we have measured the secondary star's rotational
broadening to be V_rot*sin(i) = 43 +/- 6 km/s and determined a binary mass
ratio of q=0.17 +/- 0.06. Combining our results for K_2 and q with the
published limits for the binary inclination, we constrain the mass of the
compact object and the secondary star to the ranges 0.49 < M_1 < 2.49 Msun and
0.04 < M_2 < 0.58 Msun. A Doppler image of the Halpha line shows emission
coming from the secondary star, but no hotspot is present. We discuss the
possible origins of this emission.Comment: 10 pages, 4 figures, accepted by MNRA
The Impact of Range Improvement on the Economic Success and Survivability of Ranches in the Eastern Rolling Plains of Texas.
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Regeneration of multiple shoots from transgenic potato events facilitates the recovery of phenotypically normal lines: assessing a cry9Aa2 gene conferring insect resistance
Associations between neighbourhood and household environmental variables and fruit consumption : exploration of mediation by individual cognitions and habit strength in the GLOBE study
Objective The present study examined associations of several home and neighbourhood environmental variables with fruit consumption and explored whether these associations were mediated by variables derived from the Theory of Planned Behaviour (TPB) and by habit strength.Design Data of the Dutch GLOBE study on household and neighbourhood environment, fruit intake and related factors were used, obtained by self-administered questionnaires (cross-sectional), face-to-face interviews and audits.Setting The city of Eindhoven in the NetherlandsSubjects Adults (n 333; mean age 58 years, 54 % female).Results Multiple mediation analyses were conducted using regression analyses to assess the association between environmental variables and fruit consumption, as well as mediation of these associations by TPB variables and by habit strength. Intention, perceived behaviour control, subjective norm and habit strength were associated with fruit intake. None of the neighbourhood environmental variables was directly or indirectly associated with fruit intake. The home environmental variable ‘modelling behaviour by family members’ was indirectly, but not directly, associated with fruit intake. Habit strength and perceived behaviour control explained most of the mediated effect (71·9 %).Conclusions Modelling behaviour by family members was indirectly associated with fruit intake through habit strength and perceived behaviour control. None of the neighbourhood variables was directly or indirectly, through any of the proposed mediators, associated with adult fruit intake. These findings suggest that future interventions promoting fruit intake should address a combination of the home environment (especially modelling behaviour by family members), TPB variables and habit strength for fruit intake
Toward a formalized account of attitudes: The Causal Attitude Network (CAN) Model
This article introduces the Causal Attitude Network (CAN) model, which conceptualizes attitudes as networks consisting of evaluative reactions and interactions between these reactions. Relevant evaluative reactions include beliefs, feelings, and behaviors toward the attitude object. Interactions between these reactions arise through direct causal influences (e.g., the belief that snakes are dangerous causes fear of snakes) and mechanisms that support evaluative consistency between related contents of evaluative reactions (e.g., people tend to align their belief that snakes are useful with their belief that snakes help maintain ecological balance). In the CAN model, the structure of attitude networks conforms to a small-world structure: evaluative reactions that are similar to each other form tight clusters, which are connected by a sparser set of "shortcuts" between them. We argue that the CAN model provides a realistic formalized measurement model of attitudes and therefore fills a crucial gap in the attitude literature. Furthermore, the CAN model provides testable predictions for the structure of attitudes and how they develop, remain stable, and change over time. Attitude strength is conceptualized in terms of the connectivity of attitude networks and we show that this provides a parsimonious account of the differences between strong and weak attitudes. We discuss the CAN model in relation to possible extensions, implication for the assessment of attitudes, and possibilities for further study
Restless quiescence: thermonuclear flashes between transient X-ray outbursts
For thermonuclear flashes to occur on neutron-star surfaces, fuel must have
been accreted from a donor star. However, sometimes flashes are seen from
transient binary systems when they are thought to be in their quiescent phase,
during which no accretion, or relatively little, is expected to occur. We
investigate the accretion luminosity during several such flashes, including the
first-ever and brightest detected flash from Cen X-4 in 1969. We infer from
observations and theory that immediately prior to these flashes the accretion
rate must have been between about 0.001 and 0.01 times the equivalent of the
Eddington limit, which is roughly 2 orders of magnitude less than the peak
accretion rates seen in these transients during an X-ray outburst and 3-4
orders of magnitude more than the lowest measured values in quiescence.
Furthermore, three such flashes, including the one from Cen X-4, occurred
within 2 to 7 days followed by an X-ray outburst. A long-term episode of
enhanced, but low-level, accretion is predicted near the end of the quiescent
phase by the disk-instability model, and may thus have provided the right
conditions for these flashes to occur. We discuss the possibility of whether
these flashes acted as triggers of the outbursts, signifying a dramatic
increase in the accretion rate. Although it is difficult to rule out, we find
it unlikely that the irradiance by these flashes is sufficient to change the
state of the accretion disk in such a dramatic way.Comment: 9 pages, 3 figures, accepted for publication in A&A; referee comments
included plus improved text; results unchange
Do columnar defects produce bulk pinning?
From magneto-optical imaging performed on heavy-ion irradiated YBaCuO single
crystals, it is found that at fields and temperatures where strong single
vortex pinning by individual irradiation-induced amorphous columnar defects is
to be expected, vortex motion is limited by the nucleation of vortex kinks at
the specimen surface rather than by half-loop nucleation in the bulk. In the
material bulk, vortex motion occurs through (easy) kink sliding. Depinning in
the bulk determines the screening current only at fields comparable to or
larger than the matching field, at which the majority of moving vortices is not
trapped by an ion track.Comment: 5 pages, 5 figures, submitted to Physical Review Letter
Predicting the consumption of foods low in saturated fats among people diagnosed with Type 2 diabetes and cardiovascular disease: the role of planning in the theory of planned behaviour
The present study tested the utility of an extended version of the theory of planned behaviour that included a measure of planning, in the prediction of eating foods low in saturated fats among adults diagnosed with Type 2 diabetes and/or cardiovascular disease Participants (N = 184) completed questionnaires assessing standard theory of planned behaviour measures (attitude, subjective norm, and perceived behavioural control) and the additional volitional variable of planning in relation to eating foods low in saturated fats Self-report consumption of foods low insaturated fats was assessed 1 month later In partial support of the theory of planned behaviour, results indicated that attitude and subjective norm predicted intentions to eat foods low in saturated fats and intentions and perceived behavioural control predicted the consumption of foods low in saturated fats As an additional variable, planning predicted the consumption of foods low in saturated fats directly and also mediated the intention-behaviour and perceived behavioural control-behaviour relationships, suggesting an important role for planning as a post-intentional construct determining healthy eating choices. Suggestions are offered for interventions designed to improve adherence to healthy eating recommendations for people diagnosed with these chronic conditions with a specific emphasis on the steps and activities that are required to promote a healthier lifestyle. (C) 2010 Elsevier Ltd. All rights reserve
Food choice motives, attitudes toward and intention to adopt personalised nutrition
yesObjective: This study explored associations between food choice motives, attitudes towards,
5 and intention to adopt personalised nutrition in order to inform communication strategies
6 based on consumer priorities and concerns. Design and Setting: A survey was administered
7 online which included the food choice questionnaire (FCQ), and items assessing attitudes
8 towards and intention to adopt personalised nutrition. Participants: Nationally representative
9 samples were recruited in 9 EU countries (N=9381). Results: Structural equation modelling
10 indicated that the food choice motives, weight control, mood, health and ethical concern had
11 a positive association and price had a negative association with attitude towards, and
12 intention to adopt, personalised nutrition. Health was positively associated and familiarity
13 negatively associated with attitude toward personalised nutrition. The effects of weight
14 control, ethical concern, mood and price on intention to adopt personalised nutrition were
15 partially mediated by the attitude. The effects of health and familiarity were fully mediated
16 by attitude. Sensory appeal was negatively and directly associated with intention to adopt
17 personalised nutrition. Conclusion: Personalised nutrition providers may benefit from taking
18 into consideration the importance of underlying determinants of food choice, particularly
19 weight control, mood and price, in potential users when promoting services and in tailoring
20 communications that are motivationally relevant.Post peer-review accepted manuscript; changes are in red
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