3D Printing of a Polymer Bioactive Glass Composite for Bone Repair

A major limitation of synthetic bone repair is insufficient vascularization of the interior region of the scaffold. In this study, we investigated the 3D printing of adipose derived mesenchymal stem cells (AD-MSCs) with polycaprolactone (PCL)/bioactive glass composite in a single process. This offered a three-dimensional environment for complex and dynamic interactions that govern the cell’s behavior in vivo. Borate based bioactive (13-93B3) glass of different concentrations (10 to 50 weight %) was added to a mixture of PCL and organic solvent to make an extrudable paste. AD-MSCs suspended in Matrigel was extruded as droplets using a second syringe. Scaffolds measuring 10x10x1 mm3 in overall dimensions with a filament width of ~500 μm and pore sizes ranging from 100 to 200 μm were fabricated. Strut formability dependence on paste viscosity, scaffold integrity, and printing parameters for droplets of ADMSCs suspended in Matrigel were investigated

EMBEDDING TEMPERATURE SENSORS WITH THE USE OF LASER-FOILPRINTING ADDITIVE MANUFACTURING

Laser foil printing (LFP) is a metal additive manufacturing (AM) process using laser-based melting of metal foil technique. Using metal foils in AM has advantages over laser powder-feed processes, allowing for efficient heat transfer and resolving the drawbacks of powder-based AM such as potential powder inhalation health hazards, balling, spattering, and high powder costs. In this study, we demonstrate the advantage of LFP for embedding sensors into structures using 304L stainless-steel foil as the feed material and two different types of temperature sensors. The first type is a resistance temperature detector (RTD) platinum sensor (Pt 100), and the second type is a k-type thermocouple probe. A detailed study of the sensor embedment through LFP revealed that the spot-welding scanning strategy significantly improves the product quality than conventional line-welding scanning strategy. As a result of this study, the feasibility of fabricating functional parts with embedded sensors using the LFP process is demonstrated.Mechanical Engineerin

A Multisegment Dynamic Model of Ski Jumping

This paper presents a planar, four-segment, dynamic model for the flight mechanics of a ski jumper. The model consists of skis, legs, torso and head, and anns. Inputs include net joint torques that are used to vary the relative body configurations of the jumper during fiight. The model also relies on aerodynamic data from previous wind tunnel tests that incorporate the effects of varying body configuration and orientation on lift, drag, and pitching moment. A symbolic manipulation program, "Macsyma," is used to derive the equations of motion automatically. Experimental body segment orientation data during the fiight phase arc presented for three ski jumpers which show how jumpers of varying ability differ in flight and demonstrate tlie need for a more complex analytical model than that previously presented in the literature. Simulations are presented that qualitatively match the measured trajectory for a good jumper. The model can be used as a basis for the study of optimal jumper behavior in fiight which maximizes jump distance

Individually Addressed Quantum Gate Interactions Using Dynamical Decoupling

A leading approach to implementing small-scale quantum computers has been to use laser beams, focused to micron spot sizes, to address and entangle trapped ions in a linear crystal. Here we propose a method to implement individually addressed entangling gate interactions, but driven by microwave fields, with a spatial resolution of a few microns, corresponding to 10^{−5} microwave wavelengths. We experimentally demonstrate the ability to suppress the effect of the state-dependent force using a single ion, and find the required interaction introduces 3.7(4)×10^{−4} error per emulated gate in a single-qubit benchmarking sequence. We model the scheme for a 17-qubit ion crystal, and find that any pair of ions should be addressable with an average crosstalk error of approximately 10^{−5}

Investigation of Sparse-Build Rapid Tooling by Fused Deposition Modeling

This paper describes the investigation of sparse-build tooling by Fused Deposition Modeling (FDM®) aimed at rapid tooling with reduction in the amount of material. Sparse-build test coupons having ULTEM as the material and varying air gap (sparse spacing), wall thickness, and cap thickness were fabricated using the sparse and sparse-double dense build styles of the Stratasys Fortus machine. The strengths and moduli of these coupons were measured in compression and flexure tests. The strength/mass ratio and modulus/mass ratio were compared among the various coupons, as well as with solid coupons, to investigate the effects of the two build styles and the three sparse-build parameters. In addition, the effects of build direction and raster orientation were also studied.Mechanical Engineerin

OSTF1: A HD-GL2 family homeobox gene is developmentally regulated during early embryogenesis in rice

In many eukaryotic organisms, homeobox genes are important regulators that specify the cell fate and body plan in early embryogenesis. In this study, a gene designated OSTF1 (Oryza sativa transcription factor 1) encoding a homeodomain protein in rice was isolated and characterized. The encoded OSTF1, although sharing only approximately 51% sequence identity with other RD-GL2 members, contains four characteristic motifs (an N-terminal acidic region, a homeodomain, a truncated leucine zipper, and a START domain). OSTF1 was detected as a single copy gene in rice. The transcripts were absent in young panicle or mature spikelet before anthesis, but appeared very early in the pollinated grain with a transient profile. In vegetative tissues examined, expression was only detectable in root. In situ hybridization analysis on developing grains revealed that OSTF1 was strongly and uniformly expressed in the embryo at the globular stage and preferentially localized to the protoderm at 3-6 d after pollination. Expression was also detectable in the integument and throughout the endosperm. Although OSTF1 is not closely related to the remaining HD-GL2 members in sequences, this gene exhibits an analogous epidermis-p referential expression pattern

In-Situ Thermographic Inspection for Laser Powder Bed Fusion

Laser powder bed fusion is strongly influenced by the quality of the powder layer including the powder properties as well as the layer thickness. In particular, thermal stresses can produce sufficient part deformation to the point that a part interferes with the wiper. This paper investigates the use of long-wave infrared thermography to monitor the surface temperature of the build. When cold powder is spread by the wiper, heat diffuses from the underlying part through the powder. The surface temperature history is a strong function of the thermal transport properties of the powder as well as the thickness. This correlation is explored and measured experimentally. It is then used to estimate the powder layer thickness above overhanging parts. This approach is shown to capture the part distortion and predicts wiper state prior to catastrophic interaction with the part.Mechanical Engineerin

Effect of Sparse-Build Internal Structure on Performance of Fused Deposition Modeling Tools Under Pressure

Two different approaches to design a sparse-build tool for fabrication by the fused deposition modeling (FDM) process are compared. One approach uses a 2D lattice structure and the other approach is inspired by topology optimization. Ultem 9085 is used as the material, and the amount of material used to build the tool is kept constant to ensure a fair comparison. A solid tool is also included in the comparison. The performance of the tool under uniform pressure is simulated using finite element analysis (FEA) and the accuracy of the FEA results is verified by comparing them with experimentally measured data for a similar tool. The build material, support material, build time, maximum displacement, and maximum von Mises stress are compared for the three build approaches, with an emphasis on the pros and cons of each sparse-build tool with regards to performance under uniform pressure and fabrication by FDM.Mechanical Engineerin