Investigating the influence of stereochemistry upon the properties of thermoplastic polymers

The diverse mechanical and thermal property requirements of modern society have largely been satisfied by polymer materials in the last century. Most materials are almost exclusively synthesized from crude oil derivatives and lack end of life degradation in reasonable time frames, leading to environmental pollution fears. The development of polymers to replace polyolefins will rely on sustainably derived feedstocks from nature. However, extensive study is still required to design degradable polymers from these biosourced derivatives that can mechanically compete with petrol-plastics. Our historical focus on polyolefins revealed that control of the simplest stereo-centres offers extensive manipulation of bulk properties. Derivatives from nature are typically rich in stereochemistry and have unique 3D structures that can be exploited in polymer materials. The goal of this thesis was to understand how stereochemistry within the backbone of linear polymers can be leveraged to manipulate thermal and mechanical properties of synthetic thermoplastics. Initially a platform to incorporate the desired stereo-center was developed based upon the thiol-ene “Click” reaction. Multiple types of stereoisomerism were incorporated into polyesters and polyurethanes at varying ratios that enabled the tuning of thermal and mechanical properties. Importantly, the presence of crystallinity within one stereoisomer vs the other led to the largest property change, but if both were amorphous or crystalline the manipulations were modest. These findings lay down the framework for predicting and designing better thermoplastics. However, a future focus into stereochemistry will be crucial to unlocking the full potential of bio-sourced derivatives

Interaction of charge transfer fluorescence probe with non-ionic surfactants: Estimation of physico-chemical properties and association constant

Fluorescence behavior of intramolecular charge transfer probe trans-ethyl-p-(dimethylamino) cinnamate (EDAC) is extremely sensitive to the local environment. This study explores the interaction of EDAC with several Igepal, Brij and Tween series of non-ionic surfactants by steady state and picoseconds time-resolved fluorescence spectroscopy. The physico-chemical properties, like critical micelle concentration and micropolarity of the micellar media surrounding the probe were determined. In most of the cases, the observed values were in good agreement with the data reported in the literature. Results obtained from time-resolved fluorescence experiments show a substantial reduction in total non-radiative decay rate of the probe in micellar medium compared to that in aqueous phase. This indicates preferential association of the probe inside the micellar core. The association constant of the probe-micelle interaction was also evaluated in different cases

Cation Exchange in Smectites as a New Approach to Mineral Carbonation

Mineral carbonation of alkaline mine residues is a carbon dioxide removal (CDR) strategy that can be employed by the mining industry. Here, we describe the mineralogy and reactivity of processed kimberlites and kimberlite ore from Venetia (South Africa) and Gahcho Kué (Canada) diamond mines, which are smectite-rich (2.3–44.1 wt.%). Whereas, serpentines, olivines, hydrotalcites and brucite have been traditionally used for mineral carbonation, little is known about the reactivity of smectites to CO2. The smectite from both mines is distributed as a fine-matrix and is saponite, Mx/mm+Mg3(AlxSi4−x)O10(OH)2·nH2O, where the layer charge deficiency is balanced by labile, hydrated interlayer cations (Mm+). A positive correlation between cation exchange capacity and saponite content indicates that smectite is the most reactive phase within these ultramafic rocks and that it can be used as a source of labile Mg2+ and Ca2+ for carbonation reactions. Our work shows that smectites provide the fast reactivity of kimberlite to CO2 in the absence of the highly reactive mineral brucite [Mg(OH)2]. It opens up the possibility of using other, previously inaccessible rock types for mineral carbonation including tailings from smectite-rich sediment-hosted metal deposits and oil sands tailings. We present a decision tree for accelerated mineral carbonation at mines based on this revised understanding of mineralogical controls on carbonation potential

LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Ex vivo drug sensitivity screening predicts response to temozolomide in glioblastoma patients and identifies candidate biomarkers

Background: Patient-derived glioma stem-like cells (GSCs) have become the gold-standard in neuro-oncological research; however, it remains to be established whether loss of in situ microenvironment affects the clinically-predictive value of this model. We implemented a GSC monolayer system to investigate in situ-in vitro molecular correspondence and the relationship between in vitro and patient response to temozolomide (TMZ). Methods: DNA/RNA-sequencing was performed on 56 glioblastoma tissues and 19 derived GSC cultures. Sensitivity to TMZ was screened across 66 GSC cultures. Viability readouts were related to clinical parameters of corresponding patients and whole-transcriptome data. Results: Tumour DNA and RNA sequences revealed strong similarity to corresponding GSCs despite loss of neuronal and immune interactions. In vitro TMZ screening yielded three response categories which significantly correlated with patient survival, therewith providing more specific prediction than the binary MGMT marker. Transcriptome analysis identified 121 genes related to TMZ sensitivity of which 21were validated in external datasets. Conclusion:GSCs retain patient-unique hallmark gene expressions despite loss of their natural environment. Drug screening using GSCs predicted patient response to TMZ more specifically than MGMT status, while transcriptome analysis identified potential biomarkers for this response. GSC drug screening therefore provides a tool to improve drug development and precision medicine for glioblastoma.</p