RESUMO

Semen deposition through the cervix into the uterus is a difficult technique in ewes and represents the main limiting factor for insemination in this species. The objective of this study was to evaluate the pregnancy rate achieved with a new transcervical insemination method in comparison with conventional cervical and laparoscopic intrauterine techniques. A total of 586 multiparous Corriedale ewes were synchronized for fixed time artificial insemination (FTAI) performed by cervical, transcervical, or intrauterine route at 46-50 h or 52-56 h after progesterone device removal in a 3 × 2 factorial design. Pregnancy rate was affected by the insemination technique and by the moment of FTAI (P < 0.05), without interaction (P= NS). Overall, the fertility was improved as semen deposition was deeper and insemination was delayed. For transcervical insemination, pregnancy rate was intermediate (42.3%; P= NS) between cervical and intrauterine route (36.0% and 50.2%; P < 0.05), and was greater for those ewes inseminated beyond 4 cm into the cervix (60.0% versus 35.1% for insemination beyond or within 4 cm into the cervix, respectively; P < 0.05). Semen deposition beyond 4 cm into the cervix was achieved only in 28.8% of the females receiving transcervical insemination. This method was more time-consuming than cervical or laparoscopic insemination (11.4 ± 1.6 versus 85.5 ± 7.5 and 56.8 ± 5.6 ewes inseminated per hour, respectively; P < 0.05). In summary, greater pregnancy rate using FTAI is obtained when semen is placed into the uterus, which was achieved in all females only through laparoscopy. Further improvements are required for transcervical insemination to be applied in large-scale FTAI programs in Corriedale ewes.

Assuntos

RESUMO

The aim of this research was to analyze temporal auditory processing and phonological awareness in school-age children with benign childhood epilepsy with centrotemporal spikes (BECTS). Patient group (GI) consisted of 13 children diagnosed with BECTS. Control group (GII) consisted of 17 healthy children. After neurological and peripheral audiological assessment, children underwent a behavioral auditory evaluation and phonological awareness assessment. The procedures applied were: Gaps-in-Noise test (GIN), Duration Pattern test, and Phonological Awareness test (PCF). Results were compared between the groups and a correlation analysis was performed between temporal tasks and phonological awareness performance. GII performed significantly better than the children with BECTS (GI) in both GIN and Duration Pattern test (P < 0.001). GI performed significantly worse in all of the 4 categories of phonological awareness assessed: syllabic (P = 0.001), phonemic (P = 0.006), rhyme (P = 0.015) and alliteration (P = 0.010). Statistical analysis showed a significant positive correlation between the phonological awareness assessment and Duration Pattern test (P < 0.001). From the analysis of the results, it was concluded that children with BECTS may have difficulties in temporal resolution, temporal ordering, and phonological awareness skills. A correlation was observed between auditory temporal processing and phonological awareness in the suited sample.

Assuntos

RESUMO

The pressure dependences of the structural, thermoelastic and vibrational properties of SnO2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl2-type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO2. A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure P(c). A zone-center phonon of B1g symmetry in the rutile phase involves such rotation and softens on approaching Pc. It becomes an Ag mode which stabilizes with increasing pressure in the CaCl2 phase. This behavior, together with the softening of the shear modulus (C11-C12)/2 related to the orthorhombic distortion, allows a precise determination of a value for Pc. An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B(1g) mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model.

RESUMO

In this work, we study theoretically the elastic properties of the orthorhombic (Pnma) high-pressure phase of IV-B group oxides: titania, zirconia and hafnia. By means of the self-consistent SIESTA code, pseudopotentials, density functional theory in the LDA and GGA approximations, the total energies, hydrostatic pressures and stress tensor components are calculated. From the stress-strain relationships, in the linear regime, the elastic constants C(ij) are determined. Derived elastic constants, such as bulk, Young's and shear modulus, Poisson coefficient and brittle/ductile behavior are estimated with the polycrystalline approach, using Voigt-Reuss-Hill theories. We have found that C(11), C(22) and C(33) elastic constants of hafnia and zirconia show increased strength with respect to the experimental values of the normal phase, P 2(1)/c. A similar situation applies to titania if these constants are compared with its normal phase, rutile. However, shear elastic constants C(44), C(55) and C(66) are similar to the values found in the normal phase. This fact increases the compound anisotropy as well as its ductile behavior. The dependence of unit-cell volumes under hydrostatic pressures is also analyzed. P-V data, fitted to third-order Birch-Murnaghan equations of state, provide the bulk modulus B(0) and its pressure derivatives B'(0). In this case, LDA estimations show good agreement with respect to recent measured bulk moduli of ZrO(2) and HfO(2). Thermo-acoustic properties, e.g. the propagation speed of transverse, longitudinal elastic waves together with associated Debye temperatures, are also estimated.

RESUMO

The SIESTA approach based on pseudopotentials and a localized basis set is used to calculate the electronic, elastic and equilibrium properties of P 21/c, Pbca, Pnma, Fm3m, P42nmc and Pa3 phases of HfO2. Using separable Troullier-Martins norm-conserving pseudopotentials which include partial core corrections for Hf, we tested important physical properties as a function of the basis set size, grid size and cut-off ratio of the pseudo-atomic orbitals (PAOs). We found that calculations in this oxide with the LDA approach and using a minimal basis set (simple zeta, SZ) improve calculated phase transition pressures with respect to the double-zeta basis set and LDA (DZ-LDA), and show similar accuracy to that determined with the PPPW and GGA approach. Still, the equilibrium volumes and structural properties calculated with SZ-LDA compare better with experiments than the GGA approach. The bandgaps and elastic and structural properties calculated with DZ-LDA are accurate in agreement with previous state of the art ab initio calculations and experimental evidence and cannot be improved with a polarized basis set. These calculated properties show low sensitivity to the PAO localization parameter range between 40 and 100 meV. However, this is not true for the relative energy, which improves upon decrease of the mentioned parameter. We found a non-linear behaviour in the lattice parameters with pressure in the P 21/c phase, showing a discontinuity of the derivative of the a lattice parameter with respect to external pressure, as found in experiments. The common enthalpy values calculated with the minimal basis set give pressure transitions of 3.3 and 10.8 GPa for [Formula: see text] and [Formula: see text], respectively, in accordance with different high pressure experimental values.