Machine intelligence for nerve conduit design and production

Nerve guidance conduits (NGCs) have emerged from recent advances within tissue engineering as a promising alternative to autografts for peripheral nerve repair. NGCs are tubular structures with engineered biomaterials, which guide axonal regeneration from the injured proximal nerve to the distal stump. NGC design can synergistically combine multiple properties to enhance proliferation of stem and neuronal cells, improve nerve migration, attenuate inflammation and reduce scar tissue formation. The aim of most laboratories fabricating NGCs is the development of an automated process that incorporates patient-specific features and complex tissue blueprints (e.g. neurovascular conduit) that serve as the basis for more complicated muscular and skin grafts. One of the major limitations for tissue engineering is lack of guidance for generating tissue blueprints and the absence of streamlined manufacturing processes. With the rapid expansion of machine intelligence, high dimensional image analysis, and computational scaffold design, optimized tissue templates for 3D bioprinting (3DBP) are feasible. In this review, we examine the translational challenges to peripheral nerve regeneration and where machine intelligence can innovate bottlenecks in neural tissue engineering

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Numerical Simulations

This book will interest researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modeling and computer simulation. Although it represents only a small sample of the research activity on numerical simulations, the book will certainly serve as a valuable tool for researchers interested in getting involved in this multidisciplinary field. It will be useful to encourage further experimental and theoretical researches in the above mentioned areas of numerical simulation

Reactive inkjet of quantum dot-silicone composites

There is a need for high-resolution and high-sensitivity temperature sensing in fields such as micro/nanoelectronics, integrated photonics, and biomedicine; however, non-invasive integrated sensing is difficult and expensive to achieve in miniaturised devices, as fabrication is greatly complicated by multi-step processes, heat treatments, and material compatibility. Inkjet printing (IJP) is a direct writing technique in the material jetting AM category that is effective for maskless multi-material printing with <50 µm resolution, which enables production of end-use devices and could simplify sensor integration. Existing inkjet-printed temperature sensors comprise simple circuit devices, which use the change in the electrical resistance of a sensing area to measure temperature. While current examples are well-suited to wearable sensors, they do not achieve the spatial and thermal resolutions desired for printed devices such as microfluidics. Development of inks for luminescence nanothermometry would enable inkjet-printable sensing geometries for planar and 3D thermal imaging with submicron and subdegree resolutions. Silicones are polymers suitable for optical sensing due to their ultraviolet (UV) and thermal stability, optical transparency, and high refractive indices. Composite inks for luminescence nanothermometry can be formulated with quantum dots (QDs), fluorescent semiconductor nanocrystals with intrinsic, reversible temperature quenching. Printable optical sensing materials would enable in situ temperature monitoring for applications and geometries that are otherwise impossible to monitor by conventional means. This thesis describes the development of the first inkjet-printable QD-silicone composite, and the first ink for luminescence thermometry, for integrated optical sensing; these may also have use in lighting applications . 2-part addition cure silicone inks and 1-part UV cure silicone inks were explored and QD-silicone composites were synthesised; inkjet printing of an addition cure QD-composite was demonstrated. Printing of reactive addition cure inks, where Ink A contained crosslinker and Ink B contained catalyst, was demonstrated using drop-on-drop IJP with the smallest average drop diameters reported for silicone IJP to date (33 36 µm). To overcome poor contact pinning, a pinned grid strategy was used for single printhead IJP and a line-by-line strategy for dual printhead IJP. Curing was the greatest challenge in reactive inkjet of QD-silicone composites, as labile ligands on the QDs poisoned the platinum catalyst despite low QD loading (0.005 wt% QD-Ink A). PtCl2 catalyst was added at low loading to enable curing and to explore the interactions between QDs and the catalyst. However, quenching was observed, with 70% decrease in emission intensity as PtCl2 concentration doubled; it was theorised that the QDs and catalyst competed for ligands, leading to metal-induced aggregation. Printing of fluorescent QD-silicone composites was demonstrated on a single printhead system using a pinned grid strategy; inks with no PtCl2 had stronger fluorescence but did not cure, highlighting their greater vulnerability to delays or fluctuations in heating. Novel UV curable silicone inks were formulated for inkjet using a high throughput screening method. Two photoinitiators (PIs) were trialled: DMPA (2,2-dimethoxy-2-phenylacetophenone) and TPO (phenylbis(2,4,6-trimethylbenzoyl)-phosphine oxide). DMPA was associated with rapid loss of fluorescence in QD-silicones, whereas quenching was not observed with TPO. Detachment of passivating ligands followed by photo-oxidation was suggested as a mechanism: TPO radicals are more susceptible to recombination with oxygen radicals than DMPA derived radicals, which might result in better shielding of the QD surface. Printing of 1 wt% TPO silicone inks without quantum dots was carried out under nitrogen to prevent oxygen inhibition. Jetting was demonstrated with 34-42 µm average drop diameter on silanised glass slides, while printing of continuous films was demonstrated on glass slides coated in a release agent. The temperature sensing performance of novel QD-silicone composites was assessed via fluorescence spectroscopy and imaging. 100 nm diameter QD clusters were observed in transmission electron microscopy and micron-scale QD aggregates in optical microscopy. QD emission appeared to be largely unchanged by immobilisation in silicone, although QD aggregation was expected to reduce photostability of the composite. Intensity- and spectral shift-based optical thermometry was demonstrated using well-plate reading and confocal laser scanning microscopy. Emission sensitivity at 627 nm was found to be approximately -0.7 to -1.2 % °C-1 between 30 50 °C and spectral sensitivity 0.07 to 0.08 nm °C-1, in agreement with other values in QD-sensing literature. Intensity decreased between thermal cycles of the same sample, although values at 60 °C were unchanged, while spectral shift appeared repeatable without redshift. Overall, fluorescent QD-silicone composites were produced via IJP for the first time and were shown to have temperature-sensitive emission. These materials are suitable for inkjet-printable devices with embedded optical temperature sensors using luminescence nanothermometry

Aeronautical engineering: A continuing bibliography with indexes (supplement 270)

This bibliography lists 600 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 44)

A subject index is provided for over 5500 patents and patent applications for the period May 1969 through December 1993. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

Fire performance of residential shipping containers designed with a shaft wall system

seven story building made of shipping containers is planned to be built in Barcelona, Spain. This study mainly aimed to evaluate the fire performance of one of these residential shipping containers whose walls and ceiling will have a shaft wall system installed. The default assembly consisted of three fire resistant gypsum boards for vertical panels and a mineral wool layer within the framing system. This work aimed to assess if system variants (e.g. less gypsum boards, no mineral wool layer) could still be adequate considering fire resistance purposes. To determine if steel temperatures would attain a predetermined temperature of 300-350ºC (a temperature value above which mechanical properties of steel start to change significantly) the temperature evolution within the shaft wall system and the corrugated steel profile of the container was analysed under different fire conditions. Diamonds simulator (v. 2020; Buildsoft) was used to perform the heat transfer analysis from the inside surface of the container (where the fire source was present) and within the shaft wall and the corrugated profile. To do so gas temperatures near the walls and the ceiling were required, so these temperatures were obtained from two sources: (1) The standard fire curve ISO834; (2) CFD simulations performed using the Fire Dynamics Simulator (FDS). Post-flashover fire scenarios were modelled in FDS taking into account the type of fuel present in residential buildings according to international standards. The results obtained indicate that temperatures lower than 350ºC were attained on the ribbed steel sheet under all the tested heat exposure conditions. When changing the assembly by removing the mineral wool layer, fire resistance was found to still be adequate. Therefore, under the tested conditions, the structural response of the containers would comply with fire protection standards, even in the case where insulation was reduced.Postprint (published version

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals