In his programmatic article More Is Different (1972), Nobel laureate P. W. Anderson captured the fundamental interest in quantum matter in a nutshell. The central motive in this field is emergence. In the inaugural volume of the homonymous journal, J. Goldstein defined this as "the arising of novel and coherent structures, patterns and properties during the process of self-organization in complex systems". Famously, the idea that the "the whole is greater than the sum of its parts" goes back to Aristotle's metaphysics, and it has served as a stimulating concept in 19th century biology, economics and philosophy. The study of emergence in condensed matter physics is unique in that the underlying complex systems are sufficiently "simple" to be modelled from first principles. Notably, the emergent phenomena discovered in this field, such as high-temperature superconductivity, giant magnetoresistance, and strong permanent magnetism have had an enormous impact on technology, and thus, society. Historically, there has been a distinction between materials with localized, strongly interacting (or correlated) electrons - and non-interacting, itinerant electronic states. In the last decade, several new states of matter have been discovered, which emerge not from correlations, but from peculiar symmetries (or topology) of itinerant electronic states. The term quantum materials has therefore become popular to subsume these two strands of condensed matter physics: Electronic correlations and topology. In this thesis, I report investigations of four quantum materials which each illustrate present key interests in the field: The mechanism of high temperature superconductivity, the search for materials that combine both electronic correlations and non-trivial topology and novel emergent phenomena that arise from the synergy of electronic correlations and a strong coupling of spin- and orbital degrees of freedom. The common factor and potential key to understanding these materials is magnetism. My experimental work is focused on neutron and x-ray scattering techniques, which are able to determine both order and dynamics of magnetic states at the atomic scale. I illustrate the full scope of these methods with experimental studies at neutron and synchrotron radiation facilities. This includes both diffraction and spectroscopy, of either single- or polycrystalline samples. My in-depth analysis of each dataset is aided by structural, magnetic and charge transport experiments. Thus, I provide a quantitative characterization of magnetic fluctuations in an iron-based superconductor and in two Dirac materials, and determine the magnetic order in a Dirac semimetal candidate and a complex oxide. As a whole, these results demonstrate the elegant complementarity of modern scattering techniques. Although such methods have a venerable history, they are presently developing at a rapid pace. Several results of this thesis have only been enabled by very recent instrumental advances.

Thesis (Ph.D.)--Boston University / Lutetium oxide doped with europium oxide (Lu20 3:Eu3+) has been established to be a bright, dense scintillator materi al with vast potential in both medical and high resolution X-ray imaging applications. Unfortunately its commercial viability has been restricted due to the manufacturing and post treatment costs associated with device fabrication. This research was aimed at the development of two vapor deposition techniques; chemical and physical vapor deposition (CVD and PVD), to produce coatings of Lu203:Eu3+ for various X-ray imaging applications. A customized CVD process to codeposit Lu20 3 and Eu20 3 was developed using lutetium and europium chloride (LuCb and EuCI3) precursors and reacting with carbon dioxide (C02) and hydrogen (H2) . An in depth study was performed by systematically varying the process parameters to explore the deposition kinetics and identify the rate limiting steps and their effects on the growth morphology using both cold and hot wall CVD reactors. The activation energy for the kinetically limited deposition of Lu20 3 from the LuCI3 - Ar - C02 - H2 system was identified to be approximately 170 kJ/mol , which is significantly lower than expected. The predominant growth orientations were identified to be { 111} and { 100} , depending on the deposition conditions. As the temperature is increased, the growth orientation preference decreases to produce a randomly oriented growth at 1150°C. The scintillation and X-ray imaging characteristics of a co-deposited Lu203:Eu3+ thin film with a {100} orientation were measured, confirming the feasibility and applicability of the CVD system to produce thick scintillator x-ray imaging devices. A fundamental study of the PVD process was performed by sputtering of Lu203:Eu3+ using a single target magnetron sputtering gun. Systematic vatiations of the deposition parameters were used to understand the effect of the ejected flux kinetic energies and deposition rate on the deposit density, stress, optical and scintillation properties. The deposition system was subsequently optimized for rapid, dense growth of a 10 um thick Lu203:Eu3+ coating at elevated temperatures. The X-ray imaging properties were measured and the results yielded an X-ray imaging resolution slightly better than 1 um with the potential for 0.5 um with further optimization, a level never before attained.

Doctor of Philosophy / Department of Grain Science and Industry / Yong Cheng Shi / Wheat bran is a by-product of the wheat flour milling industry. The number of food products containing wheat bran is on the rise because it is a well-recognized good source of dietary fiber. Currently, bran is a low-value commodity used mostly in animal feed, but it has the potential for more extensive applications. To understand the functional and nutritional properties of wheat bran and better use wheat bran in food, it is critical to understand the physical structure of wheat bran. For the first time, solid-state ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS) were used to study the physical structure of wheat bran and its dissected layers. The XRD and Solid-State ¹³C CP/MAS NMR both confirmed the presence of crystalline cellulose in untreated bran, enzymatically treated bran, and dissected bran layers. Destarched and deproteinized wheat bran (DSDPB) was treated with a mixture of either 7 or 9% sodium hydroxide and 12% urea solvent and structure of the extracted polymers was investigated. Three and 6 cycle dissolution schemes, were examined involving the repeated cooling of the solvent bran mixture to -12.6 °C and then agitating it at 25 °C. When 7% NaOH/12% urea (6 cycle) was applied to DSDPB, 84.1% of the material was solubilized including 89.8% of the arabinoxylans (AX). This procedure recovered more wheat bran AX for characterization than any previous study using alkaline dissolution. Wheat bran was enzymatically and hydrothermally treated to maximize the soluble fraction. Unlike previous research, the starch and protein were kept and not removed before endoxylanase treatment. The retained protein and glucose polymers (starch, β-glucan, cellulose) could provide functional benefits in addition to the arabinoxylan and could make the process more economical. Wheat bran hydrolyzed with thermostable α-amylase, protease, and xylanase was the recommended treatment. The combined solubles had a viscosity of 23 cP (10% w/w solids) and ranged in estimated molecular weight from ~600 to 20,000. The percentage of untreated wheat bran AX that was solubilized was 50% and the percentage of AX in the solubles was 23%.

No description available.

Carboxylesterases are glycosylated general detoxification enzymes belonging to the serine esterase superfamily and play a critical role in the hydrolysis of numerous ester- and amide- containing molecules, including active metabolites, drugs and prodrugs. Three functionally active carboxyleterases have been identified in man (CES1-3), which all show differential tissue expression and critically overlapping, yet specific substrate selectivities. Elucidating the basis of their exact substrate preference would help facilitate the design of clinical prodrugs which are activated by carboxylesterases. Because of their widespread applications, carboxylesterases have attracted much attention in recent years, with CES1 being the most extensively studied human carboxylesterase to date. The work presented here addresses the structure-function relationship of the three human carboxylesterases using a combination of X-ray crystallography, kinetic analysis and biophysical techniques. Recombinant proteins were successfully produced using a mammalian expression system in high yield (5.0 – 84.0 mg/ L cell culture). Analytic ultracentrifugation and size-exclusion chromatography coupled to multi-angle laser light scattering were used to investigate the proteins in solution. These results showed CES1 exists primarily in a trimeric arrangement, whilst CES2 and CES3 are monomeric. Interestingly, atypical mechanisms of substrate inhibition, positive cooperativity and biphasic kinetics were observed for both CES1 and CES2. Three structures of CES1 were solved: wild type, an aglycosylated form and a catalytically inactive form, to 1.48, 1.86 and 2.01 Å respectively. The novel structure of CES2 was solved to 2.04 Å, which revealed that the enzyme forms a strand exchange dimer in contrast to the trimeric CES1. To summarise, this thesis documents a platform that has been generated for the production, characterisation and crystallization of human carboxylesterases. This will aid future structural work for protein ligand binding studies.

No description available.

The reaction of [MCl2(cod)] (M = Pt, Pd) with two equivalents of 2-(diphenylphosphinoamino)pyridine, Ph2PNHpy, in warm acetonitrile led to cationic complexes of the type cis-[MCl(Ph2PNHpy-P,N){Ph2PNHpy-P}][Cl] (M = Pt, Pd) which exhibit broad single 31P{1H} NMR resonances due to their dynamic pyridyl exchange behaviour in solution. A single crystal X-ray diffraction study of the platinum species confirmed the proposed structure and revealed that adjacent complex molecules were held together by hydrogen bonding to the same chloride counter-ion. The bromo- and iodo-cis[MX(Ph2PNHpy-P,N){Ph2PNHpy-P}][X] (M = Pt, Pd; X = Br, I) complexes were obtained by metathesis from the corresponding chloride complex.

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More than half a decade of X-ray astronomy with various balloon borne and space orbiting X-ray instruments, have led to discoveries and detailed studies of X-ray binaries. An important property of X-ray binaries is intensity variations of different magnitudes in a wide range of timescales from milliseconds (quasi-periodic oscillations, millisecond pulsations), to a few weeks (orbital and super-orbital modulations) or longer (outbursts etc). In this thesis, different types of variabilities of X-ray binaries are considered in X-ray binary population studies and to investigate certain aspects of some individual systems. In Chapter 1, we provide an introduction to various types of variabilities seen in different classes of X-ray binaries. We mention in detail the various periodic and aperiodic variabilities seen in X-ray binaries. In Chapter 2, we describe, in some detail, the various X-ray all sky monitors and X-ray observatories, data from which has been utilized in the work carried out in this thesis. We also describe the various data analysis techniques that we have used. The rest of the thesis is divided into two major sections: Variability studies of indi-vidual systems and X-ray binary population studies Variability studies of individual systems In Chapter 3, we report results from an investigation of energy resolved orbital in-tensity pro les and from exhaustive orbital phase resolved spectroscopic measurements of GX 301{2 with MAXI{GSC . The orbital variation of the spectral parameters, es-pecially the relation between the equivalent width of Fe line and the column density of absorbing matter are then utilized to examine the models for the mode of accretion onto the neutron star in GX 301{2: circumstellar disk model by Pravdo & Ghosh (2001), and the accretion stream model by Leahy & Kostka (2008). A very large equivalent width of the iron line along with a small value of the column density in the orbital phase range 0.10-0.30 after the periastron passage indicates an asymmetry in the distribution of the matter around the neutron star, strongly favoring the accretion stream model by Leahy & Kostka (2008). Presence of an eclipse in an X-ray binary can be useful in determining orbital param-eters like inclination and in estimating the orbital evolution by eclipse timing method, which is reported in Chapter 4. For the HMXB system IGR J16393{4643, we found a short eclipse in the Swift{BAT light-curve and utilized it to constrain the orbital in-clination of the system. We have also studied, for the rst time, broad-band pulsation and spectral characteristic of the system with a Suzaku observation, showing sub-orbital intensity variations. For another eclipsing and non-pulsing HMXB 4U 1700{37, the orbital evolution is studied using mid-eclipse times from observations with narrow eld instruments as well as from long term light-curves of X-ray all sky monitors. The orbital period decay rate is estimated to be 5 10 7 /yr, an order slower than a previous measurement by Rubin et al.(1996). Since no pulsations are detected in this system, it is difficult to estimate its orbital parameters, especially its eccentricity. Using mid-eclipse times from 10 years of Swift{BAT data, we have independently constrained the eccentricity of the binary system. X-ray binary population studies In Chapter 5, we report results from an analysis of the 16 years light-curves of X-ray binaries in 2-10 keV energy band of RXTE{ASM , used to construct the differential and integral probability distributions of count-rates. These distributions are then employed to construct multiple snapshots of X-ray binary luminosity functions of the Milky Way instead of averaging the luminosities, an improvement over previous analysis by Grimm et al. (2002). We found that the averaged luminosities of highly variable X-ray binaries do not represent their true positions in XLFs and the variability of X-ray binaries do indeed signi cantly affect the luminosity functions. In Chapter 6, the measurements of the averaged spectra of X-ray binaries using MAXI{GSC data are reported and are used for constructing the composite X-ray spec-trum. These composite X-ray binary spectra are useful in estimating the contribution of X-ray binaries in extra-galactic SEDs constructed from the simultaneous Chandra / XMM{Newton and NuSTAR observations of these galaxies. These SEDs will also serve as a useful input in estimating the contribution of X-ray binary heating at high redshift IGM during the Epoch of Re-ionization. In Chapter 7, we summarize the main conclusions of the work carried out in this thesis and discuss some future prospects related to this thesis.