Motorised momentum exchange space tethers : the dynamics of asymmetrical tethers and some recent new applications

This paper reports on a first attempt to model the dynamics of an asymmetrical motorised momentum exchange tether for spacecraft payload propulsion, and it also provides some interesting summary results for two novel applications for motorised momentum exchange tethers. The asymmetrical tether analysis is very important because it represents the problematic scenario when payload mass unbalance intrudes, due to unexpected payload loss or failure to retrieve. Mass symmetry is highly desirable both dynamically and logistically, but it is shown in this paper that there is still realistic potential for mission rescue should an asymmetry condition arise. Conceptual designs for tethered payload release from LEO and lunar tether delivery and retrieval are also presented as options for future development

Assessing the Oxidative Degradation of N-methyl Pyrrolidone (NMP) in Microelectronic Fabrication Processes by using a Multi-platform Analytical Approach

During the construction of recording head devices, corrosion of metal features and subsequent deposition of corrosion by-products have been observed. Previous studies have determined that the use of N-methylpyrrolidone (NMP) may be a contributing factor. In this study, we report the use of a novel multiplatform analytical approach comprising of pH, liquid chromatography/UV detection (LC/UV), inductively coupled plasma optical emission spectroscopy (ICP-OES), and LC/mass spectrometry (LC/MS) to demonstrate that reaction conditions mimicking those of general photoresist removal processes can invoke the oxidation of NMP during the photolithography lift-off process. For the first time, we have confirmed that the oxidation of NMP lowers the pH, facilitating the dissolution of transition metals deposited on wafer substrates during post-mask and pre-lift-off processes in microelectronic fabrication. This negatively impacts upon the performance of the microelectronic device. Furthermore, it was shown that, by performing the process in an inert atmosphere, the oxidation of NMP was suppressed and the pH was stabilized, suggesting an affordable modification of the photolithography lift-off stage to enhance the quality of recording heads. This novel study has provided key data that may have a significant impact on current and future fabrication process design, optimization, and control. Results here suggest the inclusion of pH as a key process input variable (KPIV) during the design of new photoresist removal processes

Engineered basement membranes:from in vivo considerations to cell-based assays

International audienceImprovements in the physiological relevance of cell-based assays have been enabled by the development of various interdisciplinary methods. However, due to their complexity, in vivo structures such as basement membranes (BMs), which regulate the phenotype of adherent cells, are still difficult to mimic in vitro. The reconstruction of a physiologically relevant BM is crucially important to develop cell-based assays with the capacity for drug screening and disease modelling. Here, we review the biophysical and biochemical properties of BMs in vivo and their interactions with neighbouring cells. We discuss the current methods used to mimic BM functions in cell-based assays according to the type of targeted applications. In doing so, we examine the advantages and limitations of each method as well as exploring approaches to improve the physiological relevance of engineered or cell-derived BMs in vitro

Counting the Acid Sites in a Commercial ZSM-5 Zeolite Catalyst

This work was funded by Johnson Matthey plc. through the provision of industrial CASE studentships in partnership with the EPSRC (AZ (EP/N509176/1), APH (EP/P510506/1)). Experiments at the ISIS Neutron and Muon Source were made possible by beam time allocations from the Science and Technologies Facilities Council.45,46 Resources and support were provided by the UK Catalysis Hub via membership of the UK Catalysis Hub consortium and funded by EPSRC grants EP/R026815/1 and EP/R026939/1Peer reviewedPublisher PD

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Mechanistic studies and high throughput kinetic experimentation in homogeneous catalysis

This thesis presents original work in the field of Physical Organic Chemistry. The use of kinetic profiling as a mechanistic probe is central to the body of work undertaken, with established kinetic analysis protocols employed and innovative kinetic profiling techniques explored.Chapter two is concerned with the mechanism of palladium catalysed carbene insertion cross-coupling reactions. These transformations represent a versatile, and rapidly evolving, synthetic strategy; yet the mechanism underpinning such reactions is only vaguely captured. Adhering to a kinetics first approach, Variable Time Normalization Analysis was used to determine the empirical rate equation in the preparation of stereodefined (E)-1,1,2-diarylacrylates. Suggesting the existence of a single turnover-determining intermediate and inhibition of the catalytic cycle by the phosphine ligand, operando NMR spectroscopy was employed and verified the existence of three off-cycle palladium-phosphine turnover-determining intermediates, two of which were further supported by HRMS analysis, along with various parasitic phosphine-containing by-products. These empirical insights guided the development of a theoretical catalytic cycle which identified a unique mechanism of stereoselectivity, where pendant migrating groups are responsible for high levels of counter-intuitive product formation originating from the migratory insertion step.Chapter three realizes Simulated Progress Kinetic Analysis as a viable method of kinetic profiling, negating intrinsic reaction time as a barrier to efficient workflows in kinetic experimentation. Differential rate data was obtained directly using this technique in tandem with an automated flow chemistry platform, where liquid-liquid segmented flow was paramount to the success of this technology. Insights comparable to those established in the literature regarding the organocatalytic aldol reaction were replicated under non-steady-state conditions, where catalyst deactivation remained operative, and successful findings at multiple levels of experimental data density were achieved. A first-of-its-kind, quasi high throughput, kinetic experimentation campaign explored chemical space in the transformation, with all findings being consistent with the accepted mechanistic model for familial reactions, and experimentation completed in a fraction of the time, material, and labour that would be typically demanded for such endeavors. Whilst promising, the limitations of this technique were considered, with many of them attributed to current hardware limitations in chemical robotics and process analytical technologies. Collectively, this platform serves as a promethean approach to truly high throughput kinetic experimentation and is capable of accessing an unprecedented degree of experimentation.<br/