696 research outputs found
High level dietary inclusion of monosodium glutamate lowers daily sperm production and efficiency in cocks
No full textIn a 16-week feeding trial, an investigation was carried out with 240 sexually matured cocks of twenty 24 weeks of age to assess the daily sperm production (DSP) and sperm production efficiency (SPE) of cocks fed dietary monosodium glutamate (MSG) at varied inclusion levels (0.00, 0.25, 0.50, 0.75, 1.00 and 1.25 g/kg diet designated diets A, B, C, D, E and F, respectively). The cocks were weighed (1888.33 ± 44.10 kg) and allotted to the 6 treatment diets. Each treatment was replicated 5 times with 8 cocks/ replicate in a completely randomized design. At the end of the feeding trial, 2 cocks per replicate (i.e. 4 cocks per treatment) were humanely sacrificed and their reproductive tracts dissected. The testes were carefully sampled, weighed and processed for estimation of DSP and SPE using both histological and homogenate methods of analyses. Results showed that the inclusion of MSG at 1.25 g/kg significantly reduced the DSP under the two estimation methods (P<0.05). The SPE was equally significantly lowered at 0.75 g MSG/kg diet and above when determined using the homogenate method. It was also observed that MSG at 1.00 g/kg diet and above lowered the DSP and SPE when determined histometrically. A high positive correlation was established between the DSP and the testicular volume of the cocks. However, the paired testicular sperm reserves were not significantly influenced (P≥0.05). Sperm reserves in both testicles of the cocks fed diets B and C were similar to the control. This study therefore, suggests that MSG has a potential to significantly reduce the reproductive potentials of cocks when administered in excess of 0.75 g/kg diet.
DOI: http://dx.doi.org/10.5281/zenodo.396902
Cocks n' hens
No full textcockThis is the local term for the common soft shelled clam, Mya arenaria, which is quite common in the area. Those clams are edible, and were formaly eaten quite often., but npw seems to have lost popularity, although a few people still eat them. The clam is oval in shape and chalky white in colour, being quite fragile as well. I have gone digging for them at the sandy beaches where they abound, and have talked with several who regard a meal of them as a real delicacy. The word itself is used commonly in the Grand Bank area among people of all ages and occupations. I have also heard my grandmother, Mrs. Maude Baker, from Burin, P. Bay, use it also. When showing her my collections of shells this summer she spotted specimens of the soft shell clams and immediately commented, "Huh, what you wouldn' collect! I've seen thousands of them cocks 'n hens on the lamwash in Burin Bay".Used I and SupUsed I1Not Usedcock and hen, glam, cock caplin, cock indianChecked by Jordyn Hughes on Mon 13 Jun 201
On the behavior of a three-dimensional fractional viscoelastic constitutive model
No full textIn this paper a three-dimensional isotropic fractional viscoelastic model is examined. It is shown that if different time scales for the volumetric and deviatoric components are assumed, the Poisson ratio is time varying function; in particular viscoelastic Poisson ratio may be obtained both increasing and decreasing with time. Moreover, it is shown that, from a theoretical point of view, one-dimensional fractional constitutive laws for normal stress and strain components are not correct to fit uniaxial experimental test, unless the time scale of deviatoric and volumetric are equal. Finally, the model is proved to satisfy correspondence principles also for the viscoelastic Poisson’s ratio and some issues about thermodynamic consistency of the model are addressed
The characterization of post-mortem sperm of local chicken cocks in Eastern Algeria
No full textThe present aimed to investigate for the first time the characteristics and conservation of post-mortem sperm, obtained from epididymis and the vas deferens of 18 pairs of adult local chicken cocks from the east of Algeria (age, 12-24 months, body weight 1.50-2.53 kg). And compare the sperm quality at the epididymis and the vas deferens levels, the efficacy of two post-mortem sperm retrieval techniques, the flushing and float-out methods in the collection of local chicken cock’s sperm, and the effects of conservation in situ at different temperatures (2h and 24h at 20°C and after refrigeration at 4°C for 24h). The quality was significantly higher (0.13±0.05ml vs 0.72±0.12ml) in the vas deferens compared to the epididymis, whereas spermatozoa abnormalities and chromatin quality did not differ in both the epididymis and vas deferens. No significant difference was observed between the flushing and float-out methods. Concentration (3.33±1.63 million sperm vs 1.75±0.76 million sperm), initial motility (77.50±6.89% vs 75.83±8.61%), viability (75±10.39% vs 74.67±10.15%) and abnormality (30.33±4.68% vs 30.33±4.68%), only the volume was significantly higher (0.72±0.12ml vs 0.17±0.08ml). However, the effects of conservation in situ, at 25°C and 4°C for 24h, showed a significant difference for viability and motility of the spermatozoa recovered from vas deferens, and no significant difference for abnormality and acrosome integrity. Therefore, it can be concluded that good quality semen samples can be collected from the vas deferens with the flushing method, and semen of Algerian local cocks can be preserved at 20°C for 24h
On the numerical implementation of a 3D fractional viscoelastic constitutive model
No full textThe aim of this paper is the implementation of a 3D fraction al viscoelastic constitutive law in a user material subroutine (UMAT) in the finite element software Abaqus. Essential to the implementation of the model is access to the strain history at each Gauss point of each element in a constructive manner. Details of the UMAT and comparison with some analytical results are presented in order to show that the fractional viscoelastic constitutive law has been successfully implemented
A theoretical study of creep deformation mechanisms of Type 316H stainless steel at elevated temperatures
No full textThe currently operating Generation II Advanced Gas-Cooled Reactors (AGR) in the nuclear power stations in the UK, mainly built in the 1960s and 1970s, are approaching their designed life. Besides the development of the new generation of reactors, the government is also seeking to extend the life of some AGRs. Creep and failure properties of Type 316H austenitic stainless steels used in some components of AGR at elevated temperature are under investigation in EDF Energy Ltd. However, the current empirical creep models used and examined in EDF Energy have deficiency and demonstrate poor agreement with the experimental data in the operational complex thermal/mechanical conditions. The overall objective of the present research is to improve our general understanding of the creep behaviour of Type 316H stainless steels under various conditions by undertaking theoretical studies and developing a physically based multiscale state variable model taking into account the evolution of different microstructural elements and a range of different internal mechanisms in order to make realistic life prediction. A detailed review shows that different microstructural elements are responsible for the internal deformation mechanisms for engineering alloys such as 316H stainless steels. These include the strengthening effects, associated with forest dislocation junctions, solute atoms and precipitates, and softening effects, associated with recovery of dislocation structure and coarsening of precipitates. All the mechanisms involve interactions between dislocations and different types of obstacles. Thus change in the microstructural state will lead to the change in materials' internal state and influence the mechanical/creep property. Based on these understandings, a multiscale self-consistent model for a polycrystalline material is established, consisting of continuum, crystal plasticity framework and dislocation link length model that allows the detailed dislocation distribution structure and its evolution during deformation to be incorporated. The model captures the interaction between individual slip planes (self- and latent hardening) and between individual grains and the surrounding matrix (plastic mismatch, leading to the residual stress). The state variables associated with all the microstructure elements are identified as the mean spacing between each type of obstacles. The evolution of these state variables are described in a number of physical processes, including the dislocation multiplication and climb-controlled network coarsening and the phase transformation (nucleation, growth and coarsening of different phases). The enhancements to the deformation kinetics at elevated temperature are also presented. Further, several simulations are carried out to validate the established model and further evaluate and interpret various available data measured for 316H stainless steels. Specimens are divided into two groups, respectively ex-service plus laboratory aged (EXLA) with a considerable population of precipitates and solution treated (ST) where precipitates are not present. For the EXLA specimens, the model is used to evaluate the microscopic lattice response, either parallel or perpendicular to the loading direction, subjected to uniaxial tensile and/or compressive loading at ambient temperature, and macroscopic Bauschinger effect, taking into account the effect of pre-loading and pre-crept history. For the ST specimens, the model is used to evaluate the phase transformation in the specimen head volume subjected to pure thermal ageing, and multiple secondary stages observed during uniaxial tensile creep in the specimen gauge volume at various temperatures and stresses. The results and analysis in this thesis improve the fundamental understanding of the relationship between the evolution of microstructure and the creep behaviour of the material. They are also beneficial to the assessment of materials' internal state and further investigation of deformation mechanism for a broader range of temperature and stress
A review of the changes of internal state related to high temperature creep of polycrystalline metals and alloys
No full textWhen polycrystalline metals and their alloys are used at high temperature, creep deformation leads to changes in their internal state. The change in internal state manifests itself in many ways, but the two ways that concern us in this review are (i) the creation of internal stress arising from the strain incompatibility between grains and/or the formation of cell/sub-grain structures and (ii) a change in the material resistance. This review aims to provide a clear separation of these two concepts by exploring the origin of each term and how it is associated with the creep deformation mechanism. Experimental techniques used to measure the internal stress and internal resistance over different length-scales are critically reviewed. It is demonstrated that the interpretation of the measured values requires knowledge of the dominant creep deformation mechanism. Finally, the concluding comments provide a summary of the key messages delivered in this review and highlight the challenges that remain to be addresse
The impact of golf balls on natural turf: a physical model of impact
No full textA mathematical model of impact was developed using experimental data from stroboscopic photographs of impacts of golf balls with natural turf. A vertical model of impact was first considered using the Kelvin-Voigt visco-elastic solid. The surface was modelled as having two layers, the first layer having an elastic as well as a damping component, while the second layer had only a damping component. The model was then modified for oblique impacts including the coefficient of friction to account for the effects of spin. Good agreement was found between the model and experimental data. Discrepancies were thought t be caused by the dependence of the coefficient of friction of the velocity of the ball. The model was used to predict the outcomes of 5-iron and 9-iron shots with a variety of backspins
Internal strains between grains during creep deformation of an austenitic stainless steel
No full textInternal strains that develop between grains during creep of an austenitic stainless steel were measured using in situ neutron diffraction. The secondary creep pre-strained test specimens were considered. Measurements were undertaken before, during and post creep deformation at 550 °C. There was no measurable change of internal strains between grains during in situ creep for 4 h at 550 °C. In addition, the effect of increasing/reducing temperatures in a range from 470 to 550 °C on the internal strains was measured and interpreted with respect to contributions from thermal expansion/contraction. No further internal misfit strains between grains were created when specimen crept during the dwell time at 530, 510, 490 and 470 °C. Results are discussed with respect to (i) the general structure of self-consistent models and (ii) the optimised use of neutron sources for creep studies.</p
- …
