Wave guide branchings (n-port) types of representation of linear, time-independent and sourceless n-ports

The wave representation and scattering matrix of n-ports is discussed. This representation is particularly suited to the treatment of microwave switching

Relationship between hatchling length and weight on later productive performance in broilers

Hatchling length and weight are used as tools to measure hatchling quality. However, the relationship between these parameters and later performance are not well known. This review evaluates the relationship between hatchling length or weight and slaughter weight, breast meat yield and feed conversion ratio (FCR) in both male and female broilers. Datasets from two trials were compared. In the first, hatchling length and weight of 100 male and 100 female broilers were measured and body weight and breast meat yield were determined at 38 days of age. In experiment 2, hatchling length of 187 female and 230 male broilers was measured and body weight was determined at 21 and 42 days of age. Feed intake was determined between 21 and 42 days of age. In both experiments, male broilers showed a positive relationship between hatchling length and slaughter weight or breast meat yield, but no relationship was found with hatchling weight. The relationship between hatchling length and performance in female broilers differed between the two experiments. In female broilers, a negative relationship between hatchling weight and breast meat yield was found. No relationship between hatchling length and FCR in both male and female broilers was found. From this limited dataset, it can be concluded that hatchling length seems to be a better parameter to predict subsequent chick performance, excluding FCR, than hatchling weight, but gender needs to be taken into accoun

The chicken embryo and its micro environment during egg storage and early incubation

When egg storage periods are prolonged (>7 days), hatchability and chick quality declines. The reason for this decline has been investigated, but is still not completely understood. At oviposition the developmental stage of the chicken embryo varies and so do the total number of viable cells. During storage, changes can occur in the embryo. Embryo viability at the end of storage seems to be dependent on the number of viable cells and the developmental stage of the embryo at oviposition. When the hypoblast is completely formed (during the quiescent developmental stage), the embryo seems to be more able to endure prolonged storage periods than embryos that are less or more advanced. During storage, changes also occur in egg characteristics such as albumen viscosity, albumen pH and yolk pH. There appears to be an interaction between albumen pH and embryo viability during early incubation and perhaps also during storage. An albumen pH of 8.2 seems to be optimal for embryo development. Albumen pH may influence embryo viability, but embryo viability may in turn, affect albumen pH. It has been hypothesised that an embryo in which the hypoblast is completely formed is better able to provide an effective barrier between the internal embryo and the exterior (yolk and albumen) and/or is better able to produce sufficient amount of carbon dioxide, which will reduce the pH level in the micro environment of the embryo to the optimal pH of 8.2. It appears that, to maintain hatchability and chick quality after prolonged storage periods, embryonic development should be advanced to the stage in which the hypoblast is completely formed or the atmosphere during storage and early incubation should be altered in such a way that albumen pH is maintained at the optimal level of 8.2

Meeting embryonic requirements of broilers throughout incubation: a review

During incubation of chicken embryos, environmental conditions, such as temperature, relative humidity, and CO2 concentration, must be controlled to meet embryonic requirements that change during the different phases of embryonic development. In the current review, the effects of embryo temperature, egg weight loss, and CO2 concentration on hatchability, hatchling quality, and subsequent performance are discussed from an embryonic point of view. In addition, new insights related to the incubation process are described. Several studies have shown that a constant eggshell temperature (EST) of 37.5 to 38.0 degrees C throughout incubation results in the highest hatchability, hatchling quality, and subsequent performance. Egg weight loss must be between 6.5 and 14.0% of the initial egg weight, to obtain an adequate air cell size before the embryo internally pips. An increased CO2 concentration during the developmental phase of incubation (first 10 days) can accelerate embryonic development and hatchability, but the physiological mechanisms of this acceleration are not completely understood. Effects of ar increased CO2 concentration during late incubation also need further investigation. The preincubation warming profile, thermal manipulation, and in ovo feeding are new insights related to the incubation process and show that the optimal situation for the embryo during incubation highly depends on the conditions of the eggs before (storage duration) and during incubation (environmental conditions) and on the conditions of the chickens after hatching (environmental temperature)

Thermoelastic properties of salt hydrates and implications for geological structures

This thesis reports the results of neutron diffraction studies and first principles ab initio simulations of two salt hydrates in the Na2SO4 – H2O and MgSO4 – H2O systems, namely mirabilite (Na2SO4·10H2O) and meridianiite (MgSO4·11H2O). Neutron diffraction experiments of deuterated mirabilite were carried on the High Resolution Powder Diffractometer (HPRD) at the ISIS spallation neutron source to measure its thermal expansion from 4.2 - 300 K and its incompressibility from 0 – 0.55 GPa. A detailed analysis of both the thermal expansion and incompressibility data is presented including determination of the thermal expansion tensor and elastic strain tensor. First principles ab initio calculations were also carried out on both materials to complement the experimental studies and to extend the study to higher pressures outside the experimental range. Mirabilite was simulated from 0 – 61 GPa; at least two new phases were detected resulting from first-order phase transformations. Meridianiite was simulated from 0 – 11GPa; this material shows one transition to a higher pressure phase (probably second-order).Finally, a simple model has been developed, incorporating the density of mirabilite determined in the experiments, to study the size and ascent speed of diapiric salt hydrate structures as they interact with, and travel through, a more viscous overburden layer within the upper crust of Earth, Mars and Ganymede, a large icy satellite of Jupiter