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Manipulating matter at the nanoscale creates materials endowed with unique optoelectronic and physicochemical attributes. Among the noble metals, the properties of gold in "nano" can be manipulated by varying, their shapes and sizes. Gold nanoparticles find several applications in electronics, medicine and environmental reclamation. Emphasis has been on the “green synthesis” of nanogold to mitigate the hazardous implications stemmed from conventional nanogold synthesis. However, it is not known if the in planta synthesis of nanogold particles could be “green engineered” as well for generating desirable sizes and exotic shapes. In the present study, we used inductively coupled plasma (ICP) analysis to determine the species-specific variability, if any, in uptake of gold across taxonomically diverse plant species (alfalfa, cucumber, red clover, rye grass, sunflower, and oregano). Seedlings of these species were grown in half strength Hoagland’s solution supplemented with 100 ppm potassium tetrachloroaurate (KAuCl4) for 15d under controlled growth room conditions. Significant variations were detected in the ability of different plant species in accumulating gold in the root tissues ranging from 500 ppm (ryegrass) to 2500 ppm (alfalfa). Sunflower and oregano translocated significantly higher levels of gold into their aerial tissues compared to other species. This study thus suggested differential abilities of diverse plant species in uptake of gold by roots and its mobilization to aerial parts. For further elucidation of the effects of different growth variables on in planta synthesis of different shapes and sizes of nanogold particles, alfalfa was selected due to its ability to accumulate large quantities of gold in the root tissues. Further, alfalfa was subjected to KAuCl4 (50 ppm) treatment under variable growth conditions (duration of treatment, pH, temperature and light). Temporal analysis revealed that most of the nanogold particles formed within 6 h of treatment and majority fall within the size range of 10-30 nm. Spherical nanogold particles in the size range of 1-50 nm were detected ubiquitously across different treatments. Interestingly though, a noticeable shift was apparent towards the formation of nanogold particles of exotic shapes in response to specific treatments i.e., pH 3.8 (triangular), pH 7.8 (hexagonal), 15°C (rectangular). This study thus provides empirical evidence towards in planta “green engineering” of nanogold particles of exotic shapes and variable sizes. Efforts are now underway to decipher the mechanistic details governing the acquisition, synthesis and mobilization of nanogold particles in a model plant system. Furthermore, testing the efficacy of alternative non-lignified systems (callus and in vitro germinated pollen tubes) for nanogold particle production is of great interest in that in may be conducive for the extraction of nanogold particles.

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Since the advent of Quantum Field Theory (QFT) in the late 1940's, perturbation theory has become one of the most successful means of extracting phenomenologically useful information from QFT. In the ever-increasing enthusiasm for new phenomenological predictions, the mechanics of perturbation theory itself have taken a back seat. It is in this light that this thesis aims to investigate some of the more fundamental properties of perturbation theory. In the first part of this thesis, we develop the idea, suggested by C.J.Maxwell, that at any given order of Feynman diagram calculation for a QCD observable all renormalization group (RG)-predictable terms should be resummed to all-orders. This "complete" RG-improvement (CORGI) serves to separate the perturbation series into infinite subsets of terms which when summed are renormalization scheme (RS)-invariant. Crucially all ultraviolet logarithms involving the dimensionful parameter, Q, on which the observable depends are resummed, thereby building the correct Q-dependence. We extend this idea, and show for moments of leptoproduction structure functions that all dependence on the renormahzation and factorization scales disappears provided that all the ultraviolet logarithms involving the physical energy scale Q are completely resummed. The approach is closely related to Grunberg's method of Effective Charges. In the second part, we perform an all-orders resummation of the QCD Adler D-function for the vector correlator, in which the portion of perturbative coefficients containing the leading power of b, the first beta-function coefficient, is resummed to all-orders. To avoid a renormalization scale dependence when we match the resummation to the exactly known next-to-leading order (NLO), and next-NLO (NNLO) results, we employ the Complete Renormalization Group Improvement (CORGI) approach , removing all dependence on the renormalization scale. We can also obtain fixed-order CORGI results. Including suitable weight-functions we can numerically integrate these results for the D-function in the complex energy plane to obtain so-called "contour-improved" results for the ratio R and its tau decay analogue Rr. We use the difference between the all-orders and fixed-order (NNLO) results to estimate the uncertainty in αs(M2/z) extracted from Rr measurements, and find αs(M2/z) = 0.120±0.002. We also estimate the corresponding uncertainty in a{Ml) arising from hadronic corrections by considering the uncertainty in R(s), in the low-energy region, and compare with other estimates. Analogous resummations are also given for the scalar correlator. As an adjunct to these studies we show how fixed-order contour-improved results can be obtained analytically in closed form at the two-loop level in terms of the Lambert W-function and hypergeometric functions.

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The resummation of double-logarithmic perturbative contributions produced by soft- gluon radiation (Sudakov resummation) has proved to be an important tool for enlarging the applications of perturbative QCD to a wider range of kinematical regions. In particular, a complete description of W and Z boson production at high-energy hadron colliders requires the resummation of large double logarithms that dominate the transverse momentum (p(_r)) distribution at small p(_r). This can be performed either directly in transverse momentum space or in impact parameter (Fourier transform) b space. The b space method succeeds in resumming all the leading and sub-leading logarithmic terms, but does not allow a smooth transition to fixed-order dominance at high transverse momenta. In contrast, the pr space approach experiences difficulties with resumming more sub-leading logarithms. This thesis concentrates on developing the p(_r) space formalism which completely resums the first four towers of logarithms. The number of fully resummed towers is the same as for the b space method. The results are compared, both analytically and numerically, with the original b space result as well as with results of other p(_r) space methods. Parametrization of the non-perturbative effects in p(_r) space is discussed. Given recent Tevatron data on Z boson production we find good agreement between the data and the theoretical predictions. Using the same formalism, the transverse momentum distributions are also calculated for W and Z boson production at the LHC. Finally, we discuss production of like-sign W pair production in the context of double parton scattering at the LHC.