Projections to the preoptic area from the paraventricular nucleus, acuate nucleus and the bed nucleus of the stria terminalis are unlikely to be involved in stress-induced suppression of GnRH secretion in sheep

Stress compromises reproductive function and the major physiological system activated during stress is the hypothalamo-pituitary-adrenal axis. Corticotrophin-releasing hormone and arginine vasopressin (AVP), which are produced in neurones of the paraventricular nucleus (PVN), drive the hypothalamo-pituitary-adrenal axis and are also implicated in the suppression of the reproductive axis. We used retrograde tracing and Fos labelling to map the projections from the PVN to the preoptic area (POA) where most gonadotrophin releasing hormone (GnRH) neurones are found. Fluorogold (FG) injections were made into the POA of gonadectomised male and female sheep (n = 5/sex), the animals were stressed and the brains recovered for histochemistry. All animals responded to stress with an increase in the number of Fos-labelled nuclei in the PVN. Few retrogradely labelled cells of the PVN were activated by stress. Dual labelling showed that very few FG-labelled cells also stained for corticotrophin-releasing hormone, none for AVP or enkephalin. Dual labelling for FG and Fos in the bed nucleus of the stria terminalis (BNST) and the arcuate nucleus showed that no FG-labelled cells in the BNST and only few in the ARC were activated by stress. No sex differences were observed in the activation of FG-labelled cells in any of the nuclei examined. We conclude that, although cells of the PVN, BNST and/or arcuate nucleus may affect reproduction via the GnRH cells of the POA, this is unlikely to involve direct input to the POA. If cells of these regions are involved in GnRH suppression during stress, this may occur via interneuronal pathways.

Dynamic characteristics and efficiency of a fluidized bed heat treatment process

The dynamic characteristics of gas bubbles in fluidized beds are important to determine the heat and mass transfer rates at component surfaces and the treated profiles of components. They also have great impact on the components’ structural, mechanical and physical properties. However, it has been very difficult to monitor those characteristics dynamically. In this paper, a specifically designed fluidized bed was introduced to facilitate the capturing of its dynamic characteristics and a new video image processing and analysis algorithm was developed. The algorithm is robust and adaptive in terms of locating both bubbles and components in beds with a single or multiple components. It has many advantages in dynamic characterization of gas bubbles and monitoring component treatment. By using this algorithm, the properties of gas bubbles over any period of time can be accurately obtained. This technology will provide a potential on-line dynamic monitoring and quality control system for the chemical heat treatment processes with fluidized beds.

Computational simulation of gas flow and heat transfer near immersed object in fluidised bed

To improve the understanding of the heat transfer mechanism and find a reliable and simple heat-transfer model, the gas flow and heat transfer between fluidised beds and immersed object surfaces was numerically simulated based on a double particlelayer and porous medium model. The velocity field and temperature distribution of gas were discussed to analyse the heat transfer process.

Heat and mass transfer in fluidised-bed heat-treatment furnaces

The mechanisms of heat and mass transfers between heat-treatment fluidised beds and immersed workpiece were studied by using computational simulation and experimental validation. A model called Double Particle-layer and Porous Medium was developed to simulate the gas flow and heat transfer between fluidised beds and immersed workpiece.

Fluidised bed nitrocarburising of tool steels

The work examines how ferritic nitrocarburising, a common heat treatment process for steels, can be adapted to the fluidised bed furnace. The effect of fluidising powder contamination on repeatability, composition of the reactive gas mixture, the development of nitrocarburised tool steel microstructure and resulting wear properties were investigated.

Pulse-lavage brushing followed by hydrogen peroxide-gauze packing for bone-bed preparation in cemented total hip arthroplasty : a bovine model

To compare the effectiveness of pulse-lavage brushing followed by hydrogen peroxide-gauze packing with either technique alone or normal-saline irrigation in bone-bed preparation for cemented total hip arthroplasty. 44 fresh-frozen ox femoral canals were prepared for cemented total hip arthroplasty using 4 techniques: normal-saline irrigation, pulse-lavage brushing, hydrogen peroxide-soaked gauze packing, and a combination of the latter 2 techniques. The maximum tensile pull-out force required to separate the prosthesis from the femoral canal was measured as an indicator of the strength of the cement-bone interface. The mean pull-out force to separate the prosthesis from the femoral canal was significantly higher in specimens prepared with pulse-lavage brushing followed by hydrogen peroxide-soaked gauze packing or pulse-lavage brushing alone than those prepared with normal-saline irrigation or hydrogen peroxide-soaked gauze packing alone 300(p<0.001). Pulse-lavage brushing is more effective at cleansing the femoral canal and increasing mechanical strength at the cement-bone interface than preparation with normal-saline irrigation or hydrogen peroxide-soaked gauze packing.

Surface alloying of metals using fluid bed reactor

The use of fluidised bed reactors for surface alloying is reviewed. Research at Deakin has includes the use of chemical vapour deposition to form chromium rich layers on ferrous substrates, including stainless and tool steel grades. These layers can be modified to carbide or nitride if required by the end application. The deposition of aluminium and silicon has also been successfully achieved.

Surface modification for enhanced corrosion resistance using fluid bed reactor chemical vapour deposition (FBR-CVD)

The use of materials with otherwise desirable mechanical properties is often problematic in practice as a result of corrosion. Susceptibility may arise for a number of reasons, including an electrochemically heterogeneous surface or destabilisation of a passive film. These shortcomings have historically been overcome through the use of various coatings or claddings. However, a more robust surface layer with enhanced corrosion resistance could possibly be produced via local surface alloying using a fluidised bed. A fluidised bed treatment allows a surface to be alloyed, producing a distinct surface layer up to tens of microns thick. Surface alloying additions can be selected on the basis of whether they are known or suspected to enhance the corrosion resistance of a particular material, whilst at a minimum, surface alloying likely provides a more electrochemically homogeneous surface. Electrochemical evaluations using potentiodynamic polarisations in NaCl electrolytes have shown chromised plain carbon and stainless steel surfaces have decreased rates of corrosion, decreased passive current densities, and ennobled pitting potentials relative to untreated specimens.

Mathematical modelling of deep bed filtration

Numerous mathematical models have been developed to evaluate both initial and transient stage removal efficiency of deep bed filters. Microscopic models either using trajectory analysis or convective-diffusion equations were used to compute the initial removal efficiency. These models predicted the removal efficiency under favorable filtration conditions quantitatively, but failed to predict the removal efficiency under unfavorable conditions. They underestimated the removal efficiency under unfavorable conditions. Thus, semi-empirical formulations were developed to compute initial removal efficiencies under unfavorable conditions. Also, correction for the adhesion of particles onto filter grains improved the results obtained for removal efficiency from the trajectory analysis. Macroscopic models were used to predict the transient stage removal efficiency of deep bed filters. O’Melia and Ali’s model assumed that the particle removal is due to filter grains as well as the particles that are already deposited onto the filter grain. Thus, semi-empirical models were used to predict the ripening of filtration. Several modifications were made to the model developed by O’Melia and Ali to predict the deterioration of particle removal during the transient stages of filtration. Models considering the removal of particles under favorable conditions and the accumulation of charges on the filter grains during the transient stages were also developed. This paper evaluates those models and their applicability under different operating conditions of filtration.