Records |
Author |
Newman, M.E.J. |
Title |
Mixing patterns in networks |
Type |
Journal Article |
Year |
2003 |
Publication |
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics |
Abbreviated Journal |
Phys Rev E Stat Nonlin Soft Matter Phys |
Volume |
67 |
Issue |
2 Pt 2 |
Pages |
026126 |
Keywords |
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Abstract |
We study assortative mixing in networks, the tendency for vertices in networks to be connected to other vertices that are like (or unlike) them in some way. We consider mixing according to discrete characteristics such as language or race in social networks and scalar characteristics such as age. As a special example of the latter we consider mixing according to vertex degree, i.e., according to the number of connections vertices have to other vertices: do gregarious people tend to associate with other gregarious people? We propose a number of measures of assortative mixing appropriate to the various mixing types, and apply them to a variety of real-world networks, showing that assortative mixing is a pervasive phenomenon found in many networks. We also propose several models of assortatively mixed networks, both analytic ones based on generating function methods, and numerical ones based on Monte Carlo graph generation techniques. We use these models to probe the properties of networks as their level of assortativity is varied. In the particular case of mixing by degree, we find strong variation with assortativity in the connectivity of the network and in the resilience of the network to the removal of vertices. |
Address |
Department of Physics, University of Michigan, Ann Arbor, MI 48109-1120, USA |
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ISSN |
1539-3755 |
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PMID:12636767 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
5215 |
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Author |
McGuigan, M.P.; Wilson, A.M. |
Title |
The effect of gait and digital flexor muscle activation on limb compliance in the forelimb of the horse Equus caballus |
Type |
Journal Article |
Year |
2003 |
Publication |
The Journal of Experimental Biology |
Abbreviated Journal |
J Exp Biol |
Volume |
206 |
Issue |
Pt 8 |
Pages |
1325-1336 |
Keywords |
Animals; Biomechanics; Forelimb/anatomy & histology/*physiology; Gait/*physiology; Horses/anatomy & histology/*physiology; Muscle Contraction/*physiology; Running |
Abstract |
A horse's legs are compressed during the stance phase, storing and then returning elastic strain energy in spring-like muscle-tendon units. The arrangement of the muscle-tendon units around the lever-like joints means that as the leg shortens the muscle-tendon units are stretched. The forelimb anatomy means that the leg can be conceptually divided into two springs: the proximal spring, from the scapula to the elbow, and the distal spring, from the elbow to the foot. In this paper we report the results of a series of experiments testing the hypothesis that there is minimal scope for muscle contraction in either spring to adjust limb compliance. Firstly, we demonstrate that the distal, passive leg spring changes length by 127 mm (range 106-128 mm) at gallop and the proximal spring by 12 mm (9-15 mm). Secondly, we demonstrate that there is a linear relationship between limb force and metacarpo-phalangeal (MCP) joint angle that is minimally influenced by digital flexor muscle activation in vitro or as a function of gait in vivo. Finally, we determined the relationship between MCP joint angle and vertical ground-reaction force at trot and then predicted the forelimb peak vertical ground-reaction force during a 12 m s(-1) gallop on a treadmill. These were 12.79 N kg(-1) body mass (BM) (range 12.07-13.73 N kg(-1) BM) for the lead forelimb and 15.23 N kg(-1) BM (13.51-17.10 N kg(-1) BM) for the non-lead forelimb. |
Address |
Structure and Motion Laboratory, Veterinary Basic Sciences, The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK. m.p.mcguigan@leeds.ac.uk |
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0022-0949 |
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PMID:12624168 |
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Equine Behaviour @ team @ |
Serial |
3655 |
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Author |
Barker, S.C. |
Title |
The Australian paralysis tick may be the missing link in the transmission of Hendra virus from bats to horses to humans |
Type |
Journal Article |
Year |
2003 |
Publication |
Medical Hypotheses |
Abbreviated Journal |
Med Hypotheses |
Volume |
60 |
Issue |
4 |
Pages |
481-483 |
Keywords |
Animals; Chiroptera; *Disease Transmission; Ecology; Hendra Virus/*pathogenicity; Horses; Humans; Models, Theoretical; Polymerase Chain Reaction; Ticks/*virology |
Abstract |
Hendra virus is a new virus of the family Paramyxoviridae. This virus was first detected in Queensland, Australia, in 1994; although, it seems that the virus has infected fruit-eating bats (flying-foxes) for a very long time. At least 2 humans and 15 horses have been killed by this virus since it first emerged as a virus that may infect mammals other than flying-foxes. Hendra virus is thought to have moved from flying-foxes to horses, and then from horses to people. There is a reasonably strong hypothesis for horse-to-human transmission: transmission of virus via nasal discharge, saliva and/or urine. In contrast, there is no strong hypothesis for flying-fox-to-human transmission. I present evidence that the Australian paralysis tick, Ixodes holocyclus, which has apparently only recently become a parasite of flying-foxes, may transmit Hendra virus and perhaps related viruses from flying-foxes to horses and other mammals. |
Address |
Department of Microbiology and Parisitology, Institute for Molecular Biosciences, ARC Special Research Center for Functional and Applied Genomics, The University of Queensland, Brisbane, Australia. s.barker@imb.uq.edu.au |
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ISSN |
0306-9877 |
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Notes |
PMID:12615503 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
2641 |
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Author |
Adolphs, R. |
Title |
Cognitive neuroscience of human social behaviour |
Type |
Journal Article |
Year |
2003 |
Publication |
Nature Reviews. Neuroscience |
Abbreviated Journal |
Nat Rev Neurosci |
Volume |
4 |
Issue |
3 |
Pages |
165-178 |
Keywords |
Cognition; Emotions; Humans; Models, Psychological; *Social Behavior |
Abstract |
We are an intensely social species--it has been argued that our social nature defines what makes us human, what makes us conscious or what gave us our large brains. As a new field, the social brain sciences are probing the neural underpinnings of social behaviour and have produced a banquet of data that are both tantalizing and deeply puzzling. We are finding new links between emotion and reason, between action and perception, and between representations of other people and ourselves. No less important are the links that are also being established across disciplines to understand social behaviour, as neuroscientists, social psychologists, anthropologists, ethologists and philosophers forge new collaborations. |
Address |
Deparment of Neurology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242, USA. ralph-adolphs@uiowa.edu |
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ISSN |
1471-003X |
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Notes |
PMID:12612630 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
4706 |
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Author |
Gulotta, M.; Rogatsky, E.; Callender, R.H.; Dyer, R.B. |
Title |
Primary folding dynamics of sperm whale apomyoglobin: core formation |
Type |
Journal Article |
Year |
2003 |
Publication |
Biophysical Journal |
Abbreviated Journal |
Biophys J |
Volume |
84 |
Issue |
3 |
Pages |
1909-1918 |
Keywords |
Animals; Apoproteins/*chemistry; Crystallography/*methods; Horses; Myocardium/chemistry; Myoglobin/*chemistry; Protein Conformation; *Protein Folding; Species Specificity; Structure-Activity Relationship; Temperature; Whales |
Abstract |
The structure, thermodynamics, and kinetics of heat-induced unfolding of sperm whale apomyoglobin core formation have been studied. The most rudimentary core is formed at pH(*) 3.0 and up to 60 mM NaCl. Steady state for ultraviolet circular dichroism and fluorescence melting studies indicate that the core in this acid-destabilized state consists of a heterogeneous composition of structures of approximately 26 residues, two-thirds of the number involved for horse heart apomyoglobin under these conditions. Fluorescence temperature-jump relaxation studies show that there is only one process involved in Trp burial. This occurs in 20 micro s for a 7 degrees jump to 52 degrees C, which is close to the limits placed by diffusion on folding reactions. However, infrared temperature jump studies monitoring native helix burial are biexponential with times of 5 micro s and 56 micro s for a similar temperature jump. Both fluorescence and infrared fast phases are energetically favorable but the slow infrared absorbance phase is highly temperature-dependent, indicating a substantial enthalpic barrier for this process. The kinetics are best understood by a multiple-pathway kinetics model. The rapid phases likely represent direct burial of one or both of the Trp residues and parts of the G- and H-helices. We attribute the slow phase to burial and subsequent rearrangement of a misformed core or to a collapse having a high energy barrier wherein both Trps are solvent-exposed. |
Address |
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA. gulotta@aecom.yu.edu |
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0006-3495 |
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Notes |
PMID:12609893 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
3783 |
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Author |
Johnson, D.D.P.; Stopka, P.; Knights, S. |
Title |
Sociology: The puzzle of human cooperation |
Type |
Journal Article |
Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
Volume |
421 |
Issue |
6926 |
Pages |
911-2; discussion 912 |
Keywords |
Altruism; *Cooperative Behavior; Evolution; Humans; *Models, Biological; Punishment; Reward; Risk |
Abstract |
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Address |
Olin Institute for Strategic Studies, Harvard University, Cambridge, Massachusetts 02138, USA. dominic@post.harvard.edu |
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English |
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Edition |
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ISSN |
0028-0836 |
ISBN |
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Notes |
PMID:12606989 |
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no |
Call Number |
refbase @ user @ |
Serial |
467 |
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Author |
Touma, C.; Sachser, N.; Mostl, E.; Palme, R. |
Title |
Effects of sex and time of day on metabolism and excretion of corticosterone in urine and feces of mice |
Type |
Journal Article |
Year |
2003 |
Publication |
General and Comparative Endocrinology |
Abbreviated Journal |
Gen Comp Endocrinol |
Volume |
130 |
Issue |
3 |
Pages |
267-278 |
Keywords |
Animals; Chromatography, High Pressure Liquid; Circadian Rhythm/*physiology; Corticosterone/*metabolism/urine; Feces/*chemistry; Female; Immunoenzyme Techniques; Kinetics; Male; Mice; Mice, Inbred C57BL; Reference Values; Sex Factors; Stress/metabolism; Time Factors; Tritium |
Abstract |
Non-invasive techniques to monitor stress hormones in small animals like mice offer several advantages and are highly demanded in laboratory as well as in field research. Since knowledge about the species-specific metabolism and excretion of glucocorticoids is essential to develop such a technique, we conducted radiometabolism studies in mice (Mus musculus f. domesticus, strain C57BL/6J). Each mouse was injected intraperitoneally with 740 kBq of 3H-labelled corticosterone and all voided urine and fecal samples were collected for five days. In a first experiment 16 animals (eight of each sex) received the injection at 9 a.m., while eight mice (four of each sex) were injected at 9 p.m. in a second experiment. In both experiments radioactive metabolites were recovered predominantly in the feces, although males excreted significantly higher proportions via the feces (about 73%) than females (about 53%). Peak radioactivity in the urine was detected within about 2h after injection, while in the feces peak concentrations were observed later (depending on the time of injection: about 10h postinjection in experiment 1 and about 4h postinjection in experiment 2, thus proving an effect of the time of day). The number and relative abundance of fecal [3H]corticosterone metabolites was determined by high performance liquid chromatography (HPLC). The HPLC separations revealed that corticosterone was extensively metabolized mainly to more polar substances. Regarding the types of metabolites formed, significant differences were found between males and females, but not between the experiments. Additionally, the immunoreactivity of these metabolites was assessed by screening the HPLC fractions with four enzyme immunoassays (EIA). However, only a newly established EIA for 5alpha-pregnane-3beta,11beta,21-triol-20-one (measuring corticosterone metabolites with a 5alpha-3beta,11beta-diol structure) detected several peaks of radioactive metabolites with high intensity in both sexes, while the other EIAs showed only minor immunoreactivity. Thus, our study for the first time provides substantial information about metabolism and excretion of corticosterone in urine and feces of mice and is the first demonstrating a significant impact of the animals' sex and the time of day. Based on these data it should be possible to monitor adrenocortical activity non-invasively in this species by measuring fecal corticosterone metabolites with the newly developed EIA. Since mice are extensively used in research world-wide, this could open new perspectives in various fields from ecology to behavioral endocrinology. |
Address |
Department of Behavioral Biology, Institute of Neuro and Behavioral Biology, University of Muenster, Badestrasse 9, D-48149 Muenster, Germany. touma@uni-muenster.de |
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0016-6480 |
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PMID:12606269 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
4086 |
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Author |
Drent, P.J.; van Oers, K.; van Noordwijk, A.J. |
Title |
Realized heritability of personalities in the great tit (Parus major) |
Type |
Journal Article |
Year |
2003 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
Volume |
270 |
Issue |
1510 |
Pages |
45-51 |
Keywords |
Aggression; Animals; Animals, Domestic; Animals, Wild; *Behavior, Animal; Breeding; Exploratory Behavior; Female; *Heredity; Male; Selection (Genetics); Songbirds/*genetics/*physiology; Variation (Genetics) |
Abstract |
Behaviour under conditions of mild stress shows consistent patterns in all vertebrates: exploratory behaviour, boldness, aggressiveness covary in the same way. The existence of highly consistent individual variation in these behavioural strategies, also referred to as personalities or coping styles, allows us to measure the behaviour under standardized conditions on birds bred in captivity, link the standardized measurements to the behaviour under natural conditions and measure natural selection in the field. We have bred the great tit (Parus major), a classical model species for the study of behaviour under natural conditions, in captivity. Here, we report a realized heritability of 54 +/- 5% for early exploratory behaviour, based on four generations of bi-directional artificial selection. In addition to this, we measured hand-reared juveniles and their wild-caught parents in the laboratory. The heritability found in the mid-offspring-mid-parent regression was significantly different from zero. We have thus established the presence of considerable amounts of genetic variation for personality types in a wild bird. |
Address |
Netherlands Institute of Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands. drent@cto.nioo.knaw.nl |
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0962-8452 |
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PMID:12590770 |
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no |
Call Number |
refbase @ user @ |
Serial |
591 |
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Author |
Mills, D.S.; Taylor, K. |
Title |
Field study of the efficacy of three types of nose net for the treatment of headshaking in horses |
Type |
Journal Article |
Year |
2003 |
Publication |
The Veterinary Record |
Abbreviated Journal |
Vet. Rec. |
Volume |
152 |
Issue |
2 |
Pages |
41-44 |
Keywords |
Animals; Female; Horse Diseases/pathology/*prevention & control; Horses; Male; Nose; Protective Devices/*veterinary; Seasons; Severity of Illness Index; *Stereotypic Movement Disorder; Treatment Outcome |
Abstract |
Thirty-six owners of seasonally headshaking horses took part in a trial to compare the effectiveness of three types of nose net, a traditional cylindrical net (full net) and two forms of larger mesh nets which cover only the nostrils and dorsorostral muzzle (half nets). Baseline data relating to the overall severity of the problem and 18 specific behaviours describing the nature of the problem were recorded on a check sheet by the owners. A within-subjects repeated measures design experiment, with each net used for a week before reassessment, was then used to assess the effect of the nets on the headshaking problem. Approximately 75 per cent of owners reported some overall improvement with each net; around 60 per cent recorded a 50 per cent or greater improvement and 30 per cent a 70 per cent or greater improvement. The nets significantly reduced the overall headshaking score and the following specific behaviours: up-and-down headshaking, nose flipping, acting as if a bee had flown up the nose, shaking at exercise, shaking when excited, shaking in bright sunlight or in windy conditions (P < 0.0001), striking at the face, shaking at night, rubbing the nose when moving, rubbing the nose on objects, sneezing, shaking in the rain and shaking indoors (P < 0.05). There was no evidence of a significant effect on side-to-side headshaking, shaking at rest or rubbing the nose when stationary, but the effect on snorting was uncertain. There were few significant differences between the nets, but the half nets were reported to be significantly better at controlling 'bee up the nose' behaviour. Horses more than 10 years old were reportedly less likely to show a 50 per cent or greater improvement in 'nose flipping' and 'headshaking at exercise. |
Address |
Animal Behaviour, Cognition and Welfare Group, University of Lincoln, Riseholme Park, Lincoln LN2 2LG |
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0042-4900 |
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PMID:12553579 |
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no |
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Serial |
1909 |
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Author |
Conradt, L.; Roper, T.J. |
Title |
Group decision-making in animals |
Type |
Journal Article |
Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
Volume |
421 |
Issue |
6919 |
Pages |
155-158 |
Keywords |
Animals; Behavior, Animal/*physiology; *Decision Making; Democracy; Group Processes; *Models, Biological; Population Density; Social Behavior |
Abstract |
Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans. |
Address |
School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK. l.conradt@sussex.ac.uk |
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0028-0836 |
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PMID:12520299 |
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no |
Call Number |
Equine Behaviour @ team @ |
Serial |
5136 |
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