Laser Additive Manufacturing Process of a Mixture of Iron and Nickel Powders

Laser-based powder bed additive manufacturing (AM) of metal powders uses pre-alloyed powder, which limits the alloys available for processing. Other processes using metal powders such as powder metallurgy (PM) (press and sinter and MIM (Metal Injection Molding)) and welding use elemental powder mixtures to produce a wide variety of alloy compositions. This study tests the ability of laser AM to produce a homogeneous alloy from a mixture of powders.Mechanical Engineerin

Analysis of the NASA shuttle hypervelocity impact database

A statistical analysis of the NASA Space Shuttle Hypervelocity Impact Database to find correlations between meteoroid and orbital debris (M/OD) impacts on the shuttle orbiter fleet and specific mission parameters; Inclination, Altitude, Duration and Year. M/OD impact data, regardless of location, particle type or mission was examined first, followed by the subcategories of Window data, Radiator data, Reinforced Carbon-Carbon (RCC) data, and Flexible Reusable Surface Insulation (FRSI) data. In an effort to characterize and evaluate the meteoroid and orbital debris (M/OD) environment in low earth orbit, post-flight surveys of the shuttle orbiters are conducted to identify damage caused by hypervelocity impacts from M/OD. Survey analysis determines whether the impactor was a naturally occurring meteoroid or man-made orbital debris, as well as the impactor's size and impact velocity. From the post-flight survey data, calculations on the number of impacts from specific particle diameters or specific particle materials are made and compared to mission parameters to help engineers design spacecraft for better mission efficiency by reducing the effects of M/OD impacts. This thesis analyzes the NASA Space Shuttle Hypervelocity Impact Database, using regression analysis software, to find correlations between M/OD impacts on the shuttle orbiter fleet and mission parameters to draw conclusions on what is influencing vehicle damage.http://archive.org/details/analysisofnasash109456265Lieutenant, United States NavyApproved for public release; distribution is unlimited

Structural disorder, magnetism, and electrical and thermoelectric properties of pyrochlore Nd2Ru2O7

Polycrystalline Nd2Ru2O7 samples have been prepared and examined using a combination of structural, magnetic, and electrical and thermal transport studies. Analysis of synchrotron X-ray and neutron diffraction patterns suggests some site disorder on the A-site in the pyrochlore sublattice: Ru substitutes on the Nd-site up to 7.0(3)%, regardless of the different preparative conditions explored. Intrinsic magnetic and electrical transport properties have been measured. Ru 4d spins order antiferromagnetically at 143 K as seen both in susceptibility and specific heat, and there is a corresponding change in the electrical resistivity behaviour. A second antiferromagnetic ordering transition seen below 10 K is attributed to ordering of Nd 4f spins. Nd2Ru2O7 is an electrical insulator, and this behaviour is believed to be independent of the Ru-antisite disorder on the Nd site. The electrical properties of Nd2Ru2O7 are presented in the light of data published on all A2Ru2O7 pyrochlores, and we emphasize the special structural role that Bi3+ ions on the A-site play in driving metallic behaviour. High-temperature thermoelectric properties have also been measured. When considered in the context of known thermoelectric materials with useful figures-of-merit, it is clear that Nd2Ru2O7 has excessively high electrical resistivity which prevents it from being an effective thermoelectric. A method for screening candidate thermoelectrics is suggested.Comment: 19 pages, 10 figure

Biophysical Characterization of Fluorotyrosine Probes Site-Specifically Incorporated into Enzymes:

Fluorinated tyrosines (F[subscript n]Y's, n = 2 and 3) have been site-specifically incorporated into E. coli class Ia ribonucleotide reductase (RNR) using the recently evolved M. jannaschii Y-tRNA synthetase/tRNA pair. Class Ia RNRs require four redox active Y's, a stable Y radical (Y·) in the β subunit (position 122 in E. coli), and three transiently oxidized Y's (356 in β and 731 and 730 in α) to initiate the radical-dependent nucleotide reduction process. F[subscript n]Y (3,5; 2,3; 2,3,5; and 2,3,6) incorporation in place of Y₁₂₂-β and the X-ray structures of each resulting β with a diferric cluster are reported and compared with wt-β2 crystallized under the same conditions. The essential diferric-F[subscript n]Y· cofactor is self-assembled from apo F[subscript n]Y-β2, Fe ²⁺, and O₂ to produce ∼1 Y·/β2 and ∼3 Fe ³⁺ /β2. The F[subscript n]Y· are stable and active in nucleotide reduction with activities that vary from 5% to 85% that of wt-β2. Each F[subscript n] Y·-β2 has been characterized by 9 and 130 GHz electron paramagnetic resonance and high-field electron nuclear double resonance spectroscopies. The hyperfine interactions associated with the 19 F nucleus provide unique signatures of each F[subscript n]Y· that are readily distinguishable from unlabeled Y·'s. The variability of the abiotic F[subscript n]Y pK a 's (6.4 to 7.8) and reduction potentials (-30 to +130 mV relative to Y at pH 7.5) provide probes of enzymatic reactions proposed to involve Y·'s in catalysis and to investigate the importance and identity of hopping Y·'s within redox active proteins proposed to protect them from uncoupled radical chemistry.National Institutes of Health (U.S.) (Grant GM29595)National Science Foundation (U.S.) (Grant 0645960

Methods for broad-scale plant phenology assessments using citizen scientists’ photographs

© 2020 Barve et al. Applications in Plant Sciences is published by Wiley Periodicals, Inc. on behalf of the Botanical Society of America Premise: Citizen science platforms for sharing photographed digital vouchers, such as iNaturalist, are a promising source of phenology data, but methods and best practices for use have not been developed. Here we introduce methods using Yucca flowering phenology as a case study, because drivers of Yucca phenology are not well understood despite the need to synchronize flowering with obligate pollinators. There is also evidence of recent anomalous winter flowering events, but with unknown spatiotemporal extents. Methods: We collaboratively developed a rigorous, consensus-based approach for annotating and sharing whole plant and flower presence data from iNaturalist and applied it to Yucca records. We compared spatiotemporal flowering coverage from our annotations with other broad-scale monitoring networks (e.g., the National Phenology Network) in order to determine the unique value of photograph-based citizen science resources. Results: Annotations from iNaturalist were uniquely able to delineate extents of unusual flowering events in Yucca. These events, which occurred in two different regions of the Desert Southwest, did not appear to disrupt the typical-period flowering. Discussion: Our work demonstrates that best practice approaches to scoring iNaturalist records provide fine-scale delimitation of phenological events. This approach can be applied to other plant groups to better understand how phenology responds to changing climate

Scientific Evaluation of Nanomaterials of TiO{sub 2} and Related Derivatives in a Variety of Applications

Altair Nanotechnolgies, Inc. (Altair) has performed and hereby reports on research and development of novel nanomaterials for applications in 1) advanced power storage devices, 2) sensors for chemical, biological and radiological agents and on an 3) investigation into mechanisms of living cell-nanoparticle interactions that will allow predictions of health and safety issues and potentially result in novel agents for remediation of chemical and biological hazards. The project was organized around four distinct objectives. Two of the objectives are focused on developments designed to dramatically improve the performance of rechargeable Li-Ion batteries. These efforts are based on extensions of Altair's proprietary TiO{sub 2} nanoparticles and nanoparticle aggregates in the form of lithium titanate spinel, lithium manganates and lithium cobaltates. A third objective leverages the core Altair nanomaterials technology to develop a unique (nanosensor) platform for the error-free, "lab on a chip" detection of chemical, biological and radiological agents for hazardous materials remediation and threat detection. The innovative approach taken by the Altair/Western Michigan team develops individual nanosensor elements built upon a construct that includes a target-specific receptor molecule coupled through a signal transducing nanomolecule to a gold, TiO{sub 2} or SiO{sub 2} nanoparticle coated with a high density of strongfluorescing molecules for signal amplification The final objective focuses on interaction mechanisms between cells and nanoparticles with the goal of understanding how specific chemical and physical properties of these nanoparticles influence that interaction. The effort will examine a range of microbes that have environmental or societal importance

A population of large neurons in laminae III and IV of the rat spinal cord that have long dorsal dendrites and lack the neurokinin 1 receptor

The dorsal horn of the rat spinal cord contains a population of large neurons with cell bodies in laminae III or IV, that express the neurokinin 1 receptor (NK1r) and have long dorsal dendrites that branch extensively within the superficial laminae. In this study, we have identified a separate population of neurons that have similar dendritic morphology, but lack the NK1r. These cells also differ from the NK1r-expressing neurons in that they have significantly fewer contacts from substance P-containing axons and are not retrogradely labelled following injection of tracer into the caudal ventrolateral medulla. We also provide evidence that these cells do not belong to the postsynaptic dorsal column pathway or the spinothalamic tract. It is therefore likely that these cells do not have supraspinal projections. They may provide a route through which information transmitted by C fibres that lack neuropeptides is conveyed to deeper laminae. The present findings demonstrate the need for caution when attempting to classify neurons solely on the basis of somatodendritic morphology

The role of GDNF family ligand signalling in the differentiation of sympathetic and dorsal root ganglion neurons

The diversity of neurons in sympathetic ganglia and dorsal root ganglia (DRG) provides intriguing systems for the analysis of neuronal differentiation. Cell surface receptors for the GDNF family ligands (GFLs) glial cell-line-derived neurotrophic factor (GDNF), neurturin and artemin, are expressed in subpopulations of these neurons prompting the question regarding their involvement in neuronal subtype specification. Mutational analysis in mice has demonstrated the requirement for GFL signalling during embryonic development of cholinergic sympathetic neurons as shown by the loss of expression from the cholinergic gene locus in ganglia from mice deficient for ret, the signal transducing subunit of the GFL receptor complex. Analysis in mutant animals and transgenic mice overexpressing GFLs demonstrates an effect on sensitivity to thermal and mechanical stimuli in DRG neurons correlating at least partially with the altered expression of transient receptor potential ion channels and acid-sensitive cation channels. Persistence of targeted cells in mutant ganglia suggests that the alterations are caused by differentiation effects and not by cell loss. Because of the massive effect of GFLs on neurite outgrowth, it remains to be determined whether GFL signalling acts directly on neuronal specification or indirectly via altered target innervation and access to other growth factors. The data show that GFL signalling is required for the specification of subpopulations of sensory and autonomic neurons. In order to comprehend this process fully, the role of individual GFLs, the transduction of the GFL signals, and the interplay of GFL signalling with other regulatory pathways need to be deciphered

Measurement of sarcomere behavior at multiple locations along single permeabilized muscle fibers.

The measurement of sarcomere lengths of single muscle fibers has been limited to sampling of a single region of the fiber although repeated samplings were possible. During studies that sample only a single region of the fiber, investigators are unable to correlate the measured length changes of the sarcomeres with overall length changes of the fiber. The lack of data from multiple regions leaves several issues of muscle behavior unexplained and hinders investigations of contraction induced injury. In the present study, instrumentation was designed and tested that permits, during a single event, the measurement of sarcomere lengths in single muscle fibers at multiple regions along a fiber. Multiple regions along the fiber were sampled by translating a laser beam and sequentially recording the diffraction patterns. The laser sweep was considerably faster than the motion of the sarcomeres. Consequently, during a single sweep, a map of regional sarcomere behavior was recorded with little or no motion of the sarcomeres. Following characterization of the apparatus, measurements of the length of sarcomeres at multiple regions along passive single permeabilized fibers were obtained while the fibers were held at a constant length and during constant-velocity stretches. The results from these tests supported two hypotheses. The first, when passive fibers were subjected to repeated stretches of ∼20% strain, and returned to the initial fiber length after each stretch, the sarcomere lengths of different regions along the fiber were reproducible (less than 2% coefficient of variation), The second, when passive fibers were subjected to repeated stretches of ∼20% strain, the changes in sarcomere lengths of the different regions along the fiber during the stretch were reproducible (less than 2% coefficient of variation). Although highly reproducible, the dispersion of sarcomere lengths along the fiber indicated that certain regions of a passive fiber had a predisposition to longer resting lengths and others to shorter resting lengths. The variation in the intrinsic length of different groups of sarcomeres must be dependent upon the non-contractile elements in the fiber. During repeated stretches, reproducible behavior provides a consistent baseline for future experiments where sarcomere behavior is likely to be more variable.PhDApplied SciencesBiomedical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132692/2/9977267.pd