Electrical Resistivity Measurements of Powder Metal Compacts

This work, as it was originally planned, was the arranging of an apparatus whereby electrical resistivity measurements could be made on powder compacts. It was also to include measurements on a series of copper-nickel compacts both before and after sintering

Professional Action Sport Athletes’ Experiences with and Attitudes Toward Concussion: A Phenomenological Study

This study examined the lived experiences and subsequent attitudes of freestyle BMX and motocross athletes relative to suffering concussions. Eleven professional athletes were interviewed using a semi-structured protocol. All cited a significant personal history with concussion and those personal accounts, along with their observations of others who experienced similar head injuries, shaped the athletes’ attitudes towards concussion. Both intrinsic and extrinsic factors contributed to each athlete’s acceptance of concussion risk inherent in their respective sport. Generally, athletes accepted concussion risk as part of their sport, but were largely unfamiliar with what concussion was and what long-term effects could result from a history of concussion. Additionally, athletes knew of no concussion protocols or guidelines in their sport and cited an overall lack of organized medical care accessible to them on an ongoing basis, as is the case with mainstream sports

Effect of Decellularization Protocol on the Mechanical Behavior of Porcine Descending Aorta

Enzymatic-detergent decellularization treatments may use a combination of chemical reagents to reduce vascular tissue to sterilized scaffolds, which may be seeded with endothelial cells and implanted with a low risk of rejection. However, these chemicals may alter the mechanical properties of the native tissue and contribute to graft compliance mismatch. Uniaxial tensile data obtained from native and decellularized longitudinal aortic tissue samples was analyzed in terms of engineering stress and fit to a modified form of the Yeoh rubber model. One decellularization protocol used SDS, while the other two used TritonX-100, RNase-A, and DNase-I in combination with EDTA or sodium-deoxycholate. Statistical significance of Yeoh model parameters was determined by paired t-test analysis. The TritonX-100/EDTA and 0.075% SDS treatments resulted in relatively variable mechanical changes and did not effectively lyse VSMCs in aortic tissue. The TritonX-100/sodium-deoxycholate treatment effectively lysed VSMCs and was characterized by less variability in mechanical behavior. The data suggests a TritonX-100/sodium-deoxycholate treatment is a more effective option than TritonX-100/EDTA and SDS treatments for the preparation of aortic xenografts and allografts because it effectively lyses VSMCs and is the least likely treatment, among those considered, to promote a decrease in mechanical compliance

Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes

Employing spectra obtained with the new Keck I HIRES near-UV sensitive detector, we have performed a comprehensive chemical composition analysis of the binary blue metal-poor star CS29497-030. Abundances for 29 elements and upper limits for an additional seven have been derived, concentrating on elements largely produced via neutron-capture nucleosynthesis. Included in our analysis are the two elements that define the termination point of the slow neutron-capture process, lead and bismuth. We determine an extremely high value of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the single-feature result obtained in previous studies. We also detect Bi for the first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with those predicted from the most recent FRANEC calculations of the slow neutron-capture process in low-mass AGB stars. We find that the neutron-capture elemental abundances of CS29497-030 are best explained by an AGB model that also includes very significant amounts of pre-enrichment of rapid neutron-capture process material in the protostellar cloud out of which the CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and ``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can be further constrained by the abundance of the light odd-element [Na/Fe] which is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to appear in ApJ Letters; additional jpeg figure available at ftp://www.astro.caltech.edu/users/iii/cs2949703

Caking behaviour of food powder binary mixes containing sticky and non-sticky powders

Caking of food powders is highly undesirable. Many food powders are powder ingredient mixes and there is little work reported on the caking of food powder mixes. This study focusses on the caking of food powder binary mixes consisting of a “sticky” powder (whey permeate WP or maltodextrin MD) and a “non-sticky” powder (salt, flour or paprika). The powders were exposed to 76% relative humidity to make the WP and MD sticky. Force-displacement testing coupled with visual assessment of 2 particles in contact using a microscope were used to investigate the caking behaviour of the binary mixes. A “sticky” powder mass fraction of at least 20% was required to initiate caking and formation of weak cakes. Increasing percentage “sticky” powder fraction above the initial caking percentage resulted in progressively stronger cakes, however the rate of this progression was much less for the stickiest MD powder. The “non-sticky” powders and how they interacted with the “sticky” powders influenced the caking behaviour of the mix. For example, salt formed the strongest cakes in the WP mixes but formed the weakest in the MD mixes. Ability of a “sticky” powder to deform and flow influenced caking behaviour

Integrating serological and genetic data to quantify cross-species transmission: brucellosis as a case study

Epidemiological data are often fragmented, partial, and/or ambiguous and unable to yield the desired level of understanding of infectious disease dynamics to adequately inform control measures. Here, we show how the information contained in widely available serology data can be enhanced by integration with less common type-specific data, to improve the understanding of the transmission dynamics of complex multi-species pathogens and host communities. Using brucellosis in Northern Tanzania as a case-study, we developed a latent process model based on serology data obtained from the field, to reconstruct Brucella transmission dynamics. We were able to identify sheep and goats as a more likely source of human and animal infection than cattle; however, the highly cross-reactive nature of Brucella spp. meant that it was not possible to determine which Brucella species (B. abortus or B. melitensis) is responsible for human infection. We extended our model to integrate simulated serology and typing data, and show that although serology alone can identify the host source of human infection under certain restrictive conditions, the integration of even small amounts (5%) of typing data can improve understanding of complex epidemiological dynamics. We show that data integration will often be essential when more than one pathogen is present and when the distinction between exposed and infectious individuals is not clear from serology data. With increasing epidemiological complexity, serology data become less informative. However, we show how this weakness can be mitigated by integrating such data with typing data, thereby enhancing the inference from these data and improving understanding of the underlying dynamics

Application of broadband acoustic resonance dissolution spectroscopy (BARDS) to the gas release behaviour during rehydration of milk protein isolate agglomerates

peer-reviewedThe BARDS technique was applied in this study to acoustically assess the rehydration behaviour of milk protein isolate (MPI) agglomerates and to compare with regular MPI powder. The results showed that BARDS has potential to monitor the rehydration behaviour of agglomerates. The greater porosity (>70%) of agglomerated powders introduced more compressible gas into the water. The BARDS profile showed that there was faster initial gas release from the agglomerates, indicating better wetting and dispersion ability of the agglomerates with shorter tM (time of maximum gas volume in solution). At 0.10% powder addition, agglomerated MPI reached tM within 109 s, which was significantly less than the control MPI at 140 s. MPI with lactose binder (MPI-L) had a tM of 80 s at 0.10% powder addition and, larger size MPI-L had a tM of 60 s. At 0.20% and 0.30% powder addition, more time was required to wet and disperse the powders

The Rise of the s-Process in the Galaxy

From newly-obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is predominantly made by the s-process in the solar system, while Eu owes most of its solar system abundance to the r-process. The changing ratio of these elements in stars over a wide metallicity range traces the changing contributions of these two processes to the Galactic abundance mix. Large s-process abundances can be the result of mass transfer from very evolved stars, so to identify these cases, we also report carbon abundances in our metal-poor stars. Results indicate that the s-process may be active as early as [Fe/H]=-2.6, alalthough we also find that some stars as metal-rich as [Fe/H]=-1 show no strong indication of s-process enrichment. There is a significant spread in the level of s-process enrichment even at solar metallicity.Comment: 64 pages, 15 figures; ApJ 2004 in pres