8,976 research outputs found
An analysis of HCN observations of the Circumnuclear Disk at the galactic centre
The Circumnuclear Disk (CND) is a torus of dust and molecular gas rotating
about the galactic centre and extending from approximately 1.6pc to 7pc from
the central massive black hole, SgrA*. Large Velocity Gradient modelling of the
intensities of the HCN 1-0, 3-2 and 4-3 transitions is used to infer hydrogen
density and HCN optical depth. From HCN observations we find the molecular
hydrogen density ranges from 0.1 to 2 10 cm, about an
order of magnitude less than inferred previously. The 1-0 line is weakly
inverted with line-centre optical depth approx 0.1, in stark contrast to
earlier estimates of 4. The estimated mass of the ring is approximately 3 4
10M consistent with estimates based on thermal dust
emission. The tidal shear in the disk implies that star formation is not
expected to occur without some significant triggering event.Comment: 17 pages, 8 figures, 7 tables (including 3 landscape tables generated
with 2 separate Latex files
Accretion in giant planet circumplanetary disks
During the final growth phase of giant planets, accretion is thought to be
controlled by a surrounding circumplanetary disk. Current astrophysical
accretion disk models rely on hydromagnetic turbulence or gravitoturbulence as
the source of effective viscosity within the disk. However, the
magnetically-coupled accreting region in these models is so limited that the
disk may not support inflow at all radii, or at the required rate. Here, we
examine the conditions needed for self-consistent accretion, in which the disk
is susceptible to accretion driven by magnetic fields or gravitational
instability. We model the disk as a Shakura-Sunyaev disk and calculate
the level of ionisation, the strength of coupling between the field and disk
using Ohmic, Hall and Ambipolar diffusevities for both an MRI and vertical
field, and the strength of gravitational instability. We find that the standard
constant- disk is only coupled to the field by thermal ionisation
within with strong magnetic diffusivity prohibiting accretion through
the bulk of the midplane. In light of the failure of the constant- disk
to produce accretion consistent with its viscosity we drop the assumption of
constant- and present an alternate model in which varies
radially according to the level magnetic turbulence or gravitoturbulence. We
find that a vertical field may drive accretion across the entire disk, whereas
MRI can drive accretion out to , beyond which Toomre's and
gravitoturbulence dominates. The disks are relatively hot (K),
and consequently massive ().Comment: 19 pages, 5 figures, 2 tables; accepted for publication by MNRA
Magnetic fields in gaps surrounding giant protoplanets
Giant protoplanets evacuate a gap in their host protoplanetary disc, which
gas must cross before it can be accreted. A magnetic field is likely carried
into the gap, potentially influencing the flow. Gap crossing has been simulated
with varying degrees of attention to field evolution (pure hydrodynamical,
ideal, and resistive MHD), but as yet there has been no detailed assessment of
the role of the field accounting for all three key non-ideal MHD effects: Ohmic
resistivity, ambipolar diffusion, and Hall drift. We present a detailed
investigation of gap magnetic field structure as determined by non-ideal
effects. We assess susceptibility to turbulence induced by the
magnetorotational instability, and angular momentum loss from large-scale
fields. As full non-ideal simulations are computationally expensive, we take an
a posteriori approach, estimating MHD quantities from the pure hydrodynamical
gap crossing simulation by Tanigawa et al. (2012). We calculate the ionisation
fraction and estimate field strength and geometry to determine the strength of
non-ideal effects. We find that the protoplanetary disc field would be easily
drawn into the gap and circumplanetary disc. Hall drift dominates, so that much
of the gap is conditionally MRI unstable depending on the alignment of the
field and disc rotation axes. Field alignment also influences the strong
toroidal field component permeating the gap. Large-scale magnetic forces are
small in the circumplanetary disc, indicating they cannot drive accretion
there. However, turbulence will be key during satellite growth as it affects
critical disc features, such as the location of the ice line.Comment: 14 pages, 6 figures, accepted for publication by MNRA
Food neophobia and mealtime food consumption in 4-5 year old children.
Background: Previous research has documented a negative association between maternal report
of child food neophobia and reported frequency of consumption of fruit, vegetables, and meat. This
study aimed to establish whether neophobia is associated with lower intake of these food types in
naturalistic mealtime situations.
Methods: One hundred and nine parents of 4–5 year olds completed questionnaires which
included a six-item version of the Child Food Neophobia Scale (CFNS). The children took part in
a series of 3 test lunch meals at weekly intervals at school at which they were presented with:
chicken, cheese, bread, cheese crackers, chocolate biscuits, grapes and tomatoes or carrot sticks.
Food items served to each child were weighed before and after the meal to assess total intake of
items in four categories: Fruit and vegetables, Protein foods, Starchy foods and Snack foods.
Pearson Product Moment Correlations and independent t tests were performed to examine
associations between scores on the CFNS and consumption during lunches.
Results: Neophobia was associated with lower consumption of fruit and vegetables, protein foods
and total calories, but there was no association with intake of starch or snack foods.
Conclusion: These results support previous research that has suggested that neophobia impacts
differentially on consumption of different food types. Specifically it appears that children who score
highly on the CFNS eat less fruit, vegetables and protein foods than their less neophobic peers.
Attempts to increase intake of fruit, vegetables and protein might usefully incorporate strategies
known to reduce the neophobic response
Development of the children's eating behaviour questionnaire
Individual differences in several aspects of eating style have been implicated in the development of weight problems in children and adults, but there are presently no reliable and valid scales that assess a range of dimensions of eating style. This paper describes the development and preliminary validation of a parent-rated instrument to assess eight dimensions of eating style in children; the Children's Eating Behaviour Questionnaire (CEBQ). Constructs for inclusion were derived both from the existing literature on eating behaviour in children and adults, and from interviews with parents. They included reponsiveness to food, enjoyment of food, satiety responsiveness, slowness in eating, fussiness, emotional overeating, emotional undereating, and desire for drinks. A. large pool of items covering each of these: constructs was developed. The number of items was then successively culled through analysis of responses from three samples of families of young children (N = 131; N = 187, N = 218), to produce a 35-item instrument with eight scales which were internally valid and had good test-retest reliability. Investigation of variations by gender and age revealed only minimal gender differences in any aspect of eating style. Satiety responsiveness and slowness in eating diminished from age 3 to 8. Enjoyment of food and food responsiveness increased over this age range. The CEBQ should provide a useful measure of eating style for research into the early precursors of obesity or eating disorders. This is especially important in relation to the growing evidence for the heritability of obesity, where good measurement of the associated behavioural phenotype will be crucial in investigating the contribution of inherited variations in eating behaviour to the process of weight gain
Reason to Ratify: The Influence of John Locke\u27s Religious Beliefs on the Creation and Adoption of the United States Constitution
The pervasive influence of Lockean religious convictions motivated the framers of the Constitution to establish a new form of government, provided the theoretical basis for the document itself, and inspired its popular ratification. Part II will lay the groundwork for this thesis by outlining Locke\u27s life and sources of his religious beliefs. Part III will undertake a more substantive examination of Locke\u27s opinions and the writings that memorialized them. Establishing how Lockean ideas of natural law, social contract, and reason are related to the inspiration, drafting, and acceptance of the Constitution takes place in Part IV, before the article\u27s conclusion in Part V
Reason to Ratify: The Influence of John Locke\u27s Religious Beliefs on the Creation and Adoption of the United States Constitution
The pervasive influence of Lockean religious convictions motivated the framers of the Constitution to establish a new form of government, provided the theoretical basis for the document itself, and inspired its popular ratification. Part II will lay the groundwork for this thesis by outlining Locke\u27s life and sources of his religious beliefs. Part III will undertake a more substantive examination of Locke\u27s opinions and the writings that memorialized them. Establishing how Lockean ideas of natural law, social contract, and reason are related to the inspiration, drafting, and acceptance of the Constitution takes place in Part IV, before the article\u27s conclusion in Part V
MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. IV. The Parent Luminosity Function of Radio-Loud Blazars
(Abridged) We use a complete sample of active galactic nuclei (AGN) selected
on the basis of relativistically beamed 15 GHz radio flux density to derive the
parent radio luminosity function (RLF) of bright radio-selected blazar cores.
We use a maximum likelihood method to fit a beamed RLF to the observed data and
thereby recover the parameters of the intrinsic (unbeamed) RLF. We analyze two
subsamples of the MOJAVE sample: the first contains only objects of known FR II
class, with a total of 103 sources, and the second subsample adds 24 objects of
uncertain FR class for a total of 127 sources. Both subsamples exclude four
known FR I radio galaxies and two gigahertz-peaked spectrum sources. We obtain
good fits to both subsamples using a single power law intrinsic RLF with pure
density evolution function. We find that a previously reported break in the
observed MOJAVE RLF actually arises from using incomplete bins (because of the
luminosity cutoff) across a steep and strongly evolving RLF, and does not
reflect a break in the intrinsic RLF. The derived space density of the parent
population of the FR II sources from the MOJAVE sample (with L>1.3e25 W/Hz) is
approximately 1600/Gpc^3.Comment: 31 pages, 7 figures and 2 tables. Accepted for publication in ApJ.
Changes: classification of sources based on radio morphology instead of
optical classes; added the parameters of the RLF of the FR II sources; added
more explanations; added a table listing the sample sources; added 2 extra
figures related to the observed break in the RLF; updated reference
Broken Record: Revisiting the Flaws in Sony\u27s Fair Use Analysis in Light of the Grokster Decision
The impact of N-3 pufa ingestion on metabolic, molecular and epigenetic responses to a short-term high-fat diet
Obesity is widely considered a primary risk factor for type 2 diabetes (T2D). However, less is known about the early adaptive responses to short-term periods of high-fat energy excess (HFEE). Previous reports detailing whole-body adaptation to fat and energy oversupply are equivocal, perhaps, in part, owing to use of different experimental protocols, varying durations of dietary manipulation and participant cohorts with individuals of varying characteristics.
In addition to use of different dietary protocols between studies, alterations in functional end-point measures due to the type of dietary fat consumed warrants consideration. Daily n-3 PUFA intake, commonly obtained from pelagic fish oil (FO) consumption, has been shown to positively associate with insulin sensitivity in epidemiological studies and thus may be a useful dietary strategy for slowing insulin resistance development.
Chapter 2 of this thesis extends previous literature by demonstrating that 6 d HFEE (150 % habitual energy intake; 60 % of energy from fat) does not clearly alter whole- body insulin sensitivity, irrespective of FO consumption. However, investigation of metabolism at the tissue level, as presented in Chapter 3 of this thesis, offers insight into a potential tissue-specific level of regulation that precedes whole-body regulation. Skeletal muscle insulin signalling protein (e.g. protein kinase B (PKB)) activity, levels of certain ceramide species, and AMPK α2 activity were altered following HFEE and may explain the early maladaptive responses to short-term HFEE. Moreover, FO intake as 10 % of total fats mediated some of these molecular
Sophie Wardle: Ph.D. Thesis ii
responses, including PKB and AMPK α2 activity, reflecting possible functional effects of FO at the subcellular level.
Regulation of these metabolic / molecular responses at both the tissue and whole- body level can be explained, in part, by genetic predisposition, environmental influence and more recently epigenetics, including microRNAs (miRNAs). In Chapter 4, we characterised the plasma and skeletal muscle miRNA responses to HFEE and oral glucose ingestion. We demonstrate transient changes in levels of certain miRNAs following oral glucose ingestion in both tissue types and in response to HFEE in skeletal muscle. However, no significant correlations between basal plasma and skeletal muscle miRNA levels were observed, suggesting that our candidate plasma miRNAs may be co-ordinating functional changes in other tissue types. Plasma miR- 145-5p and skeletal muscle miR-204-5p predicted a significant proportion of the variance in mean whole-body insulin sensitivity change in response to HFEE. These data indicate that these miRNAs may be useful biomarkers of insulin resistance development following HFEE.
A constraint of this thesis is that all conclusions are made within the context of statistically unaltered insulin sensitivity. Therefore, future investigations of diet- induced maladaptation should consider establishing a time course of insulin resistance development in response to HFEE, or use different study populations. Populations that are more susceptible to T2D development, e.g., overweight, sedentary individuals would be of particular interest. These data would aid development of a working model of diet-induced insulin resistance that has more direct application to T2D progression and extends the data presented herein
- …