328 research outputs found
Immunisation against gonadotrophin-releasing hormone (GnRH) reduces agonistic behaviours in male rangeland goats
Rangeland goat bucks were used to evaluate the efficacy of a commercially available anti-gonadotrophin-releasing hormone vaccine, Improvac (Zoetis Australia, West Ryde, NSW, Australia). The hypothesis tested was that immunisation would suppress testosterone secretion by the testis and agonistic behaviour between male goats. We also compared intervals of 2 and 4 weeks between primary and booster immunisations and monitored responses over a 2-month period. The 45 goats were split into three groups (n = 15): one group receiving the vaccination booster on Day 14, one group receiving the vaccination booster on Day 28, and the Control group receiving sterile saline injections. Body mass, body condition score and scrotal circumference were measured fortnightly, and blood was collected at 2-week intervals and analysed for testosterone concentration. Behavioural interaction tests of 2-min duration were also conducted fortnightly. There was a significant decrease in paired testicular circumference (P < 0.05) and testosterone concentration (P < 0.01) in both vaccination groups by the end of the experiment at Day 60, compared with the Control group. Agonistic interactions measured at Day 60 were significantly reduced in both vaccination groups (P < 0.05) compared with the Control group. These results support the efficacy of Improvac in reducing agonistic behaviours in rangeland goat bucks and suggest that the use of the vaccine may assist in reducing social stress and possible injury in groups of confined male goats
A New Approach to Assess the Gastrocnemius Muscle Volume in Rodents Using Ultrasound; Comparison with the Gastrocnemius Muscle Index
Introduction: The purpose of this study was to determine the reliability and validity of a new non-invasive ultrasound technique to measure gastrocnemius muscle atrophy after nerve denervation in an animal model. Methods: In sixteen rodents an eight mm sciatic nerve gap was created. In the following 8 weeks, each week, two rodents were euthanized and the gastrocnemius muscle was examined using two different ultrasound systems and two investigators. The standardized ultrasound measurement protocol consisted of identifying pre-defined anatomical landmarks: 1) the fibula, 2) the fibular nerve, and 3) the junction between the most distal point of the semitendinosus muscle and gastrocnemius muscle. Consequently, we measured the muscle thickness as the length of the line between the fibula and the junction between the two muscles, perpendicular to the fibular nerve. After the ultrasound recording, the muscle mass was determined. Results: A steep decline of muscle weight of 24% was observed after one week. In the following weeks, the weight further decreased and then remained stable from 6 weeks onwards, resulting in a maximal muscle weight decrease of 82%. The correlation coefficient was >0.96 between muscle diameter and weight using both ultrasound systems. The inter-rater reliability was excellent for both devices on the operated side (ICC of 0.99 for both ultrasound systems) and good for the non-operated site (ICC's: 0.84 & 0.89). The difference between the muscle mass ratio and the muscle thickness ratio was not more than 5% with two outliers of approximately 13%. Discussion: We have developed an innovative, highly reliable technique for quantifying muscle atrophy after nerve injury. This technique allows serial measurements in the same animal over time. This is a significant advantage compared to the conventional technique for quantifying muscle atrophy, which requires sacrificing the animal
Instability of generalised AdS black holes and thermal field theory
We study black holes in AdS-like spacetimes, with the horizon given by an
arbitrary positive curvature Einstein metric. A criterion for classical
instability of such black holes is found in the large and small black hole
limits. Examples of large unstable black holes have a B\"ohm metric as the
horizon. These, classically unstable, large black holes are locally
thermodynamically stable. The gravitational instability has a dual description,
for example by using the version of the AdS/CFT
correspondence. The instability corresponds to a critical temperature of the
dual thermal field theory defined on a curved background.Comment: 1+16 pages. 1 figure. LaTeX. Minor clarification
Clouds, shadows, or twilight? Mayfly nymphs recognise the difference
1. We examined the relative changes in light intensity that initiate night-time locomotor activity changes in nymphs of the mayfly, Stenonema modestum (Heptageniidae). Tests were carried out in a laboratory stream to examine the hypothesis that nymphs increase their locomotion in response to the large and sustained reductions in relative light intensity that take place during twilight but not to short-term daytime light fluctuations or a minimum light intensity threshold. Ambient light intensity was reduced over a range of values representative of evening twilight. Light was reduced over the same range of intensities either continuously or in discrete intervals while at the same time nymph activity on unglazed tile substrata was video recorded.
2. Nymphs increased their locomotor activity during darkness in response to large, sustained relative light decreases, but not in response to short-term, interrupted periods of light decrease. Nymphs did not recognise darkness unless an adequate light stimulus, such as large and sustained relative decrease in light intensity, had taken place.
3. We show that nymphs perceive light change over time and respond only after a lengthy period of accumulation of light stimulus. The response is much lengthier than reported for other aquatic organisms and is highly adaptive to heterogeneous stream environments
The orbit rigidity matrix of a symmetric framework
A number of recent papers have studied when symmetry causes frameworks on a
graph to become infinitesimally flexible, or stressed, and when it has no
impact. A number of other recent papers have studied special classes of
frameworks on generically rigid graphs which are finite mechanisms. Here we
introduce a new tool, the orbit matrix, which connects these two areas and
provides a matrix representation for fully symmetric infinitesimal flexes, and
fully symmetric stresses of symmetric frameworks. The orbit matrix is a true
analog of the standard rigidity matrix for general frameworks, and its analysis
gives important insights into questions about the flexibility and rigidity of
classes of symmetric frameworks, in all dimensions.
With this narrower focus on fully symmetric infinitesimal motions, comes the
power to predict symmetry-preserving finite mechanisms - giving a simplified
analysis which covers a wide range of the known mechanisms, and generalizes the
classes of known mechanisms. This initial exploration of the properties of the
orbit matrix also opens up a number of new questions and possible extensions of
the previous results, including transfer of symmetry based results from
Euclidean space to spherical, hyperbolic, and some other metrics with shared
symmetry groups and underlying projective geometry.Comment: 41 pages, 12 figure
Partially filled stripes in the two dimensional Hubbard model: statics and dynamics
The internal structure of stripes in the two dimensional Hubbard model is
studied by going beyond the Hartree-Fock approximation. Partially filled
stripes, consistent with experimental observations, are stabilized by quantum
fluctuations, included through the Configuration Interaction method. Hopping of
short regions of the stripes in the transverse direction is comparable to the
bare hopping element. The integrated value of compares well
with experimental results.Comment: 4 page
Multidimensional rasch models for partial credit scoring
Rasch models for partial-credit scoring are discussed
and a multidimensional version of the model is formulated.
A model may be specified in which consecutive
item responses depend on an underlying latent trait. In
the multidimensional partial-credit model, different responses
may be explained by different latent traits. Data
from van Kuyk’s (1988) size concept test and the Raven
Progressive Matrices test were analyzed. Maximum
likelihood estimation and goodness-of-fit testing are discussed
and applied to these datasets. Goodness-of-fit
statistics show that for both tests, multidimensional partial-credit models were more appropriate than the unidimensional
partial-credit model. Index terms: X2 testing,
exponential family model, multidimensional item response
theory, multidimensional Rasch model, partial-credit
models, Progressive Matrices test, Rasch model
A Burgessian critique of nominalistic tendencies in contemporary mathematics and its historiography
We analyze the developments in mathematical rigor from the viewpoint of a
Burgessian critique of nominalistic reconstructions. We apply such a critique
to the reconstruction of infinitesimal analysis accomplished through the
efforts of Cantor, Dedekind, and Weierstrass; to the reconstruction of Cauchy's
foundational work associated with the work of Boyer and Grabiner; and to
Bishop's constructivist reconstruction of classical analysis. We examine the
effects of a nominalist disposition on historiography, teaching, and research.Comment: 57 pages; 3 figures. Corrected misprint
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