Acoustic Microscopy Using Amplitude and Phase Measurements

We have built a low-frequency scanning acoustic microscope (SAM) that measures both amplitude and phase. The majority of SAMs simply measure the amplitude of the reflected signal. Measuring the phase gives a great deal more information. For one thing, the phase is very sensitive to height variations. Measuring the phase also gives us the ability to do signal processing on the resulting images, such as removing the effects of surface features from defocused images of subsurface defects

Detection of Delaminations Located at Ceramic/Metal Jointed Interface by Scanning Acoustic Microscopy

Since ceramic/metal joints currently play an important role of the structural parts for applications in electrical, electronic or aerospace industries, techniques must be developed for evaluating the integrity of these joints. Such techniques as collimated X-ray beam radiography [1], indentation fracture, and laser speckle imaging have been developed with limited success. No truly nondestructive techniques for evaluating joint strength have been established to date. If a conventional C-scan mode apparatus could be applied directly for detecting a defect such as a delamination on a joint interface, it might be an attractive solution in terms of visualizing the defect as a first step in the evaluation. The shape of the standard specimen of the ceramic/metal joint is essentially a rectangular bar. When the C-scan mode apparatus is used to visualize the jointed interface, an acoustic wave is required to be incident from the ceramic side of the specimen. When considering the attenuation of an ultrasonic wave in the frequency range from 10 to 100 MHz and the thickness of the ceramic portion of the specimen, the wave may not reach the interface, or the wave reflected from the interface may not be detected. When using frequencies lower than 10 MHz, the interface may be imaged, but with limited resolution. Moreover, the contrast may be poor because of water diffusing into the crack in the surface of the specimen. When a conventional A-mode apparatus such as a digital oscilloscope is used to obtain quantitative data, reflected waveforms might be collected. However, the data might not be good enough to analyze details of a defect, such as caused by a fracturing process. Recent studies have shown that delaminations at a ceramic/metal joint, such as a Si3N4/Cu/Steel joint, originate along the periphery of the interface [2]

A Waveguide Based Acoustic Microscope with Application to the Evaluation of Bone

A new ultrasonic scanning system has been developed which is capable of accurate velocity measurements with high spatial resolution. This performance is achieved while using relatively low frequencies to minimize the cost of the instrument. A waveguide detector is used in place of the normal focused ultrasonic transducer. The waveguide receiver makes it possible to provide the needed spatial resolution without limitations imposed by the finite aperture of the transducer. An increase in the complexity of the signal processing required and reduced throughput of the instrument results from this approach. However, these disadvantages are amply compensated by the ability to investigate materials with high attenuation and low wave velocities. These measurements are not possible with traditional acoustic microscopes

The effects of varying protein and energy intakes on the growth and body composition of very low birth weight infants

<p>Abstract</p> <p>Objective</p> <p>To determine the effects of high dietary protein and energy intake on the growth and body composition of very low birth weight (VLBW) infants.</p> <p>Study design</p> <p>Thirty-eight VLBW infants whose weights were appropriate for their gestational ages were assessed for when they could tolerate oral intake for all their nutritional needs. Thirty-two infants were included in a longitudinal, randomized clinical trial over an approximate 28-day period. One control diet (standard preterm formula, group A, n = 8, 3.7 g/kg/d of protein and 129 kcal/kg/d) and two high-energy and high-protein diets (group B, n = 12, 4.2 g/kg/d and 150 kcal/kg/d; group C, n = 12, 4.7 g/kg/d and 150 kcal/kg/d) were compared. Differences among groups in anthropometry and body composition (measured with bioelectrical impedance analysis) were determined. An enriched breast milk group (n = 6) served as a descriptive reference group.</p> <p>Results</p> <p>Groups B and C displayed greater weight gains and higher increases in fat-free mass than group A.</p> <p>Conclusion</p> <p>An intake of 150 kcal/kg/d of energy and 4.2 g/kg/d of protein increases fat-free mass accretion in VLBW infants.</p

Three Drosophila Hox Complex microRNAs Do Not Have Major Effects on Expression of Evolutionarily Conserved Hox Gene Targets during Embryogenesis

The discovery of microRNAs has resulted in a major expansion of the number of molecules known to be involved in gene regulation. Elucidating the functions of animal microRNAs has posed a significant challenge as their target interactions with messenger RNAs do not adhere to simple rules. Of the thousands of known animal microRNAs, relatively few microRNA:messenger RNA regulatory interactions have been biologically validated in an normal organismal context. Here we present evidence that three microRNAs from the Hox complex in Drosophila (miR-10-5p, miR-10-3p, miR-iab-4-5p) do not have significant effects during embryogenesis on the expression of Hox genes that contain high confidence microRNAs target sites in the 3′ untranslated regions of their messenger RNAs. This is significant, in that it suggests that many predicted microRNA-target interactions may not be biologically relevant, or that the outcomes of these interactions may be so subtle that mutants may only show phenotypes in specific contexts, such as in environmental stress conditions, or in combinations with other microRNA mutations

The Crest Phenotype in Chicken Is Associated with Ectopic Expression of HOXC8 in Cranial Skin

The Crest phenotype is characterised by a tuft of elongated feathers atop the head. A similar phenotype is also seen in several wild bird species. Crest shows an autosomal incompletely dominant mode of inheritance and is associated with cerebral hernia. Here we show, using linkage analysis and genome-wide association, that Crest is located on the E22C19W28 linkage group and that it shows complete association to the HOXC-cluster on this chromosome. Expression analysis of tissues from Crested and non-crested chickens, representing 26 different breeds, revealed that HOXC8, but not HOXC12 or HOXC13, showed ectopic expression in cranial skin during embryonic development. We propose that Crest is caused by a cis-acting regulatory mutation underlying the ectopic expression of HOXC8. However, the identification of the causative mutation(s) has to await until a method becomes available for assembling this chromosomal region. Crest is unfortunately located in a genomic region that has so far defied all attempts to establish a contiguous sequence