3 results
Joint inversion of tectonic stress and magma pressures using dyke trajectories
- F. Maerten, L. Maerten, R. Plateaux, P. H. Cornard
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- Journal:
- Geological Magazine / Volume 159 / Issue 11-12 / November 2022
- Published online by Cambridge University Press:
- 23 August 2022, pp. 2379-2394
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In volcano-tectonic regions, dyke propagation from shallow magmatic chambers is often controlled by the interaction of the local and regional stress fields. The variations of the stress fields result from a combination of factors including the regional tectonic stress, the geometry of pressurized magma chambers, the layering and the pre-existing discontinuities (e.g. fractures). In this contribution, we describe and apply a new multiparametric inversion technique based on geomechanics that can invert for both the far field stress attributes and the internal pressure of magma chambers or stocks, constrained by observed dyke or eruptive fissure orientations. This technique is based on the superposition principle and uses linear elastic models that can be solved using many types of numerical methods. For practical reasons, we chose a 3D boundary element method (BEM) for a heterogeneous elastic half-space, where magma chambers are modelled as pressurized cavities. To verify this approach, the BEM solution has been validated against the known 3D analytical solution of a pressurized cylindrical cavity. Then the effectiveness of this technique and its practical use is demonstrated through application to natural examples of dyke network development around two different volcanic systems, the Spanish Peaks (USA) and the Galapagos Islands (Ecuador). Results demonstrate that regional stress characteristics as well as the internal pressure of magma chambers can be estimated from observed radial and circumferential dyke patterns and some knowledge of magma chamber geometry.
Effects of semi-group housing and floor type on pododermatitis, spinal deformation and bone quality in rabbit does
- S. Buijs, K. Hermans, L. Maertens, A. Van Caelenberg, F. A. M. Tuyttens
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The most common housing system for reproduction rabbits, individual cage housing on a wire floor, is increasingly scrutinized because of its potential detrimental impact on animal welfare. We compared three types of housing: (1) individual cage housing on a wire floor (3952 cm2/doe, maximum roof height 63 cm, one 1000 cm2 plastic footrest/doe), (2) semi-group housing on a wire floor (5000 cm2/doe, roofless, one 1000 cm2 plastic footrest/doe) and (3) the same semi-group housing, but with a fully plastic slatted floor. In all housing systems, does had free access to an elevated platform. In the semi-group housing pens, four does were housed communally during 21 days of the reproduction cycle (to allow more space for locomotion and to increase opportunities for social contact), and individually during the other 21 days of the cycle (to minimize doe–doe and doe–kit aggression that peaks around kindling). In all, 24 Hycole does were included per system. The does entered the experiment at 203 days of age (after their first parity). The experiment consisted of four reproductive cycles, ending at 369 days of age. Pododermatitis was scored in cycles 1, 2 and 4. At the end of the 4th cycle the does were euthanized and X-rays were taken to assess spinal deformation. Tibia and femur length, width and cortical thickness were determined and bone strength was assessed using a shear test, as a measure of bone quality. Although severe pododermatitis was absent, the prevalence of plantar hyperkeratosis (hair loss and callus formation) at the end of the 4th cycle was much greater on the wire floor (65% and 68% for semi-group housing and individual cages, respectively) than on the plastic floor (5%, P<0.0001), even though the wire floors were equipped with a plastic footrest known to decrease hyperkeratosis. In contrast to our expectations, semi-group housing did not affect the prevalence of spinal deformations (P>0.10), but in line with our expectations bone quality was affected favourably by semi-group housing. The tibial cortex (and to a lesser extent the femoral cortex) was thicker in semi-group housing than in individual cages (1.45, 1.46 and 1.38 mm for semi-group housing on wire, semi-group housing on plastic and individual housing on wire, respectively, P=0.045). What this increase in cortical thickness means in terms of doe welfare requires further study, as it may reflect an increase in activity resulting either from increased space for locomotion, or from fleeing aggressive pen mates.
Effect of nursing by two does on the performance of sucking and growing rabbits
- Zs. Szendrö, T. Gyarmati, L. Maertens, E. Biró-Németh, I. Radnai, G. Milisits, Zs. Matics
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- Journal:
- Animal Science / Volume 74 / Issue 1 / February 2002
- Published online by Cambridge University Press:
- 18 August 2016, pp. 117-125
- Print publication:
- February 2002
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Five hundred and eighty-four Pannon White kits of 73 newborn litters were submitted to one of five treatments. Control litters (SS) were nursed once a day for 35 days post partum (traditional method of nursing). DD litters were raised by two does and the kits were nursed both in the morning and in the evening until day 35 post partum. DS litters were nursed twice a day for 23 days, and then once a day until weaning at 35 days. Part of the DS litters were nursed at 08:00 and 20:00 h (i.e. every 12 h, DS12), the rest were nursed at 08:00 and at 16:00 h (DS8). Kits of the fifth treatment (D0) were nursed twice a day until day 23, and then immediately weaned.
Rabbit kits that were nursed twice a day (DD, DS12, DS8, D0) consumed on average 1·89 more milk compared with SS individuals until day 23 (overall treatment effect P < 0·001). The 21-day body weight of these young was 1·7 times greater than that of the SS kits (overall P < 0·001). D0 rabbits were weaned early and their growth curve showed a slight break at this point. However, they compensated for this lag by the end of the fattening period. SS rabbits and DD ones were respectively the first and the last to start consuming solid food. The food consumption of DS rabbits was similar to that of DD until day 23 and from then until day 35 it was not significantly different from that of SS. After having been weaned on day 23, D0 kits consumed only very small quantities of pellets for 2 days. Afterwards their food intake increased abruptly. Rabbits that were nursed twice a day (DD, DS12, DS8 and D0) consumed more food as compared with the SS individuals throughout the total period of fattening (157 v. 137 g/day; P < 0·05). The weight at 10 weeks of age was 2·49 v. 2·88 kg (overall P < 0·001), respectively for SS and doublenursed (DD, DS, D0) rabbits. Nursing twice a day did not affect dressing proportion but the proportion of the carcass in the front part of the body decreased slightly (318 v. 323 g/kg; P < 0·05) while that in intermediate part increased (321 v. 307 g/kg; P < 0·05). Nevertheless, rabbits that were nursed twice a day had more (P < 0·05) perirenal + scapular fat and produced heavier livers. Total fat content of the empty body, however, was not significantly higher, with the one exception of the DD rabbits which had higher levels than any other group. The results of our experiment show clearly that the growth potential of rabbit kits is strongly limited by the milk availability during the first weeks post partum.