Identification of the Molecular Basis of Morphological Variation in Avian Beaks

Vertebrates, particularly birds, show extremely variable species-specific morphology in craniofacial structures. Cranial neural crest cells give rise to all the cartilage and bone of the face, and transplantation experiments have shown that these cells contain species-specific patterning information. First, I employed custom cross-species microarrays to analyze the spectrum of developmental signaling pathway and transcription factor gene expression changes in neural crest cells of the developing beaks for the chicken, duck, and quail, both before and after morphological variation is evident. I found that neural crest cells have established a species-specific gene expression profile that predates morphological variation. In addition to expression changes in the Bmp and Calmodulin pathways, previously associated with morphological variation in Darwin\u27s finches, I observed dramatic changes in a number of Wnt signaling components in the broad-billed duck. Second, given that deletion of the microRNA processing gene DICER in neural crest cells results in loss of nearly all facial structures, I utilized high-throughput sequencing to describe the microRNAs that are expressed and/or differentially expressed among the same neural crest samples used for the microarray analysis. In remarkable contrast to relatively unchanged pattern of transcription factor gene expression, microRNA expression is highly dynamic during stages when avians acquire species-specific morphology. The microRNA expression profiles also suggest that the transition from multipotent, proliferative neural crest cells into cells differentiating to form the tissues of the face may be delayed in the duck relative to the chicken and quail. This prolonged period of proliferation in duck neural crest may contribute to the increase in beak size and width of the adult duck bill versus the chicken beak. Finally, I illustrate examples of how these genomic data sets can initiate new avenues of investigation and testable hypotheses. I found that the Wnt pathway acts upstream of the Bmp pathway and induces regional changes in growth of the developing beak. I also correlate changes in expression of miR-222 in the frontonasal prominence with alterations in protein: but not mRNA) levels of one of its target genes, the cell cycle regulator p27(KIP1). I then identified seven mature microRNAs that appear to be specific to the avian lineage. Using PCR, I confirmed that two of these, miR-2954 and miR-2954*, are conserved across the avian lineage, from ratites to songbirds

Growth of Sr1-xCaxRuO3 thin films by metalorganic aerosol deposition

We report the growth of thin films of Sr1-xCaxRuO3 on SrTiO3 and MgO substrates by metalorganic aerosol deposition. The structure and microstructure is characterized by X-ray diffraction and room-temperature scanning tunnelling microscopy (STM), respectively. STM indicates in-plane epitaxy and a small surface roughness for films on SrTiO3. The high-quality of the films is supported by large residual resistivity ratios up to 29.Comment: 4 Pages, 2 Figures, submitted to Proceedings of ICM 2009 (Karlsruhe

Powder Deposition and Sintering for a Two-Powder Approach to Solid Freeform Fabrication

A two-powder approach is presented where Fused Deposition modeling (FDM) is used to create a thin shell in the shape of the part to be fabricated. The shell is filled with powder of the part material and surrounded by a support powder that has a high sintering temperature. Upon compressing and sintering the shelVpowder system in a uniaxial hot press, the polymer shell burns out and the support powder compresses the part powder. The part powder consolidates into the desired part while the support material remains in powder form and can be easily removed. This paper presents results ofinitial experimental studies.Mechanical Engineerin

Variable Powder Flow Rate Control in Laser Metal Deposition Processes

This paper proposes a novel technique, called Variable Powder Flow Rate Control (VPFRC), for the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to adjust the powder flow rate to maintain a uniform powder deposition per unit length even when disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the powder delivery system motor and the powder transport system (i.e., five–meter pipe, powder dispenser, and cladding head) are first constructed. A general tracking controller is then designed to track variable powder flow rate references. Since the powder flow rate at the nozzle exit cannot be directly measured, it is estimated using the powder transport system model. The input to this model is the DC motor rotation speed, which is estimated on–line using a Kalman filter. Experiments are conducted to examine the performance of the proposed control methodology. The experimental results demonstrate that VPFRC is successful in maintaining a uniform track morphology, even when the motion control system accelerates and decelerates.Mechanical Engineerin

Fabrication of X-Graded H13 and Cu Powder Mix Using High Power Pulsed Nd:YAG Laser

The manufacturing of Functionally Graded Material (FGM) parts using Solid Free Form manufacturing technologies has been carried out since early 1980. At present, most of the powder manufacturing techniques are being focused on layering powder with different powder blend compositions with Z gradients (graded in direction of layer build). Although, there are a few researchers working on multi powder feeder and deposition system, the study of laser fusion of the deposited powder (by a powder deposition system) is minimum or not known to date. Consequently, the manufacturing of functionally graded structures is still geometry limited. This work was focused on the manufacturing of X-graded (graded along the powder bed plane) specimens with H13 tool steel and Cu mix. Five bimodal powder blends were used with a multi-container feed hopper to spread powder layers for the selective laser fusion of the powder. The powder was fused using a high power Nd:YAG pulsed laser using a specific scanning strategy to reduce porosity. Specimens were produced with graded Cu within the H13 matrix. The specimens were analysed for dimensional accuracy, microstructure, porosity, cracks and micro hardness of the FGM.Mechanical Engineerin

Vacuum powder injector and method of impregnating fiber with powder

A method and apparatus uniformly impregnate stranded material with dry powder such as low solubility, high melt flow polymer powder to produce, for example, composite prepregs. The stranded material is expanded in an impregnation chamber by an influx of air so that the powder, which may enter through the same inlet as the air, penetrates to the center of the stranded material. The stranded material then is contracted for holding the powder therein. The stranded material and powder may be pulled through the impregnation chamber in the same direction by vacuum. Larger particles of powder which do not fully penetrate the stranded material may be combed into the stranded material and powder which does not impregnate the stranded material may be collected and reused

Computer Generation of Metal Components by Simultaneous Deposition of Mould, Cores and Part

A new solid freeforming method based on co-delivery of mould powder materials and part powder materials using vibration-controlled, dry powder valves is presented in this paper. Thin layers of stainless steel powder are delivered to the forming area according to the cross-section of the CAD file to produce the component. Mould powder which has low sinterability is delivered to the non-forming areas of the same layer. All powders are delivered by computer-controlled, acoustic powder valves. The flow rate and switching of the valves provides the composition and shape control during fabrication. The stacked layers of loose powder are then sintered in a conventional furnace. The mould materials are removed after sintering. This method avoids the high thermal stress problem in selective laser sintering, avoids high capitalisation, makes use of conventional furnaces and allows for the incorporation of three dimensional function gradients. Test pieces including step wedge and Spierpinski’s cube were fabricated. Advantages, limitations and problems are discussed.Mechanical Engineerin

Optimization of Powder Layer Density in Selective Laser Sintering

An important parameter for the overall quality of SLS parts is the density of powder layers before sintering. Previous studies have shownthatthe control of powder particle shape and size distribution can increase the density of non-packed powder beds. However, these studies concerned beds several orders of magnitude larger than the SLS layers. The purpose ofthis study. is to determine if,and to what extent, the density of thin powder layers can be ineteased. Experiments show that the density of thin layers increases from 53% to 63% when adding 30% fine powder to the coarse powder,/with a coarse-to-fine ratio of 1:10. Compared with the bulk experiments, this density improvement method is less efficient, because the particles do not arrange as efficiently, and the wall effects can become predominant.Mechanical Engineerin

The effect of cheese powder in the functional properties of croissant pastry : a thesis presented in partial fulfilment of the requirements of the degree of Master of Technology in Food Technology at Massey University

The increasing use of cheese powder as an ingredient used by food manufactures can be related to the changing consumer needs, identifying new consumer preferences, marketing and obtaining an acceptable capital return. Cheese powder have been used in bakery products to improve their functional properties and impart flavour. Therefore, the development of cheese flavoured croissants was chosen to increase the utilization of cheese powder in the formulation croissant pastry. For this reason, the New Zealand Dairy Board (NZDB) predicted a brighter future for this type of dairy ingredient because of its dual acceptability of providing important functional characteristics and its cost advantage over other dairy products. The addition of cheese powder to croissant pastry resulted in affecting the dough's physical properties and baking characteristics; i.e, increasing the dough elongational viscosity, decreasing the farinograph absorption values, decreasing the specific volume of baked croissants, and croissant firmness results indicating significant differences as a function of time for storage. Cheese croissants containing ten percent level of Cheddar-20 cheese powder was found to be the only one to have statistically significant differences in most of the attributes compared to CP1 and CP2 cheese powder when used in the formulation. Ten percent level of cheddar-20 cheese powder received the highest score and preferred by 77.8% of the panellists. Therefore, the ten percent of cheddar-20 cheese powder level was chosen for further development including the determination of the new cheese powder mixing method with its time-temperature relationship and evaluation of the market trial. The new cheese powder mixing method (3% cheese powder mixed with dry ingredients, and 7% used to produce cheese paste) during which the paste was applied over the laminated dough and the cheese powder combined with the dry ingredients improved the cheese croissant quality characteristics when compared to the other mixing method (total 10% cheese powder mixed with other dry ingredients). The baking time-temperature relationship of the new cheese powder mixing method was twenty seven minutes at 275°F which gave the best quality characteristics for high volume, a golden brown crust colour and flaky texture. This method received the highest scores and the most acceptable cheese croissant by the panellists. The market evaluation results indicated that 87% of potential consumers preferred the cheese croissants. The total sales potential indicated to be approximately 2.000 tonnes/annum of finished product with a population of ten percent of the market share. The estimated net present value over five year product life was $3,206,000

Spiral Growth Manufacturing (SGM) – A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting

Spiral growth manufacturing is a new innovative powder based rapid manufacturing technique. The innovation exists in the methodology in which powder layers are deposited. Unlike other pre-placed powder systems, the deposited layers move relative to the location at which they are processed. This is made possible by a rotating build drum into which powder is deposited, in spiralled layers, from a stationary hopper. With this configuration powder can be continuously deposited and levelled and simultaneously processed, eliminating delays in the build cycle. Stainless steel and cobalt-chrome powder is selectively melted using a 100W flash lamp pumped Nd:YAG laser. This paper reports on factors affecting build rate and on build strategies for creating a number of axis-symmetric thin and thick walled cylinders. Experimental results suggest that build rate for thin walled structures bonded to a substrate will ultimately be governed by tangential movements of the powder particles when frictional forces are not sufficient to accelerate the particles along a curved path, provided that enough laser power is available for melting. Even melt pool balling, which is evident when melting one layer at high speeds, diminishes in multiple layer builds due to re-melting and infilling.Mechanical Engineerin