Impact of pressure dissipation on fluid injection into layered aquifers

Carbon dioxide (CO2) capture and subsurface storage is one method for reducing anthropogenic CO2 emissions to mitigate climate change. It is well known that large-scale fluid injection into the subsurface leads to a buildup in pressure that gradually spreads and dissipates through lateral and vertical migration of water. This dissipation can have an important feedback on the shape of the CO2 plume during injection, and the impact of vertical pressure dissipation, in particular, remains poorly understood. Here, we investigate the impact of lateral and vertical pressure dissipation on the injection of CO2 into a layered aquifer system. We develop a compressible, two-phase model that couples pressure dissipation to the propagation of a CO2 gravity current. We show that our vertically integrated, sharp-interface model is capable of efficiently and accurately capturing water migration in a layered aquifer system with an arbitrary number of aquifers. We identify two limiting cases --- `no leakage' and `strong leakage' --- in which we derive analytical expressions for the water pressure field for the corresponding single-phase injection problem. We demonstrate that pressure dissipation acts to suppress the formation of an advancing CO2 tongue during injection, resulting in a plume with a reduced lateral extent. The properties of the seals and the number of aquifers determine the strength of pressure dissipation and subsequent coupling with the CO2 plume. The impact of pressure dissipation on the shape of the CO2 plume is likely to be important for storage efficiency and security

Prediction and causal inference in the transition from acute to chronic low back pain

The overarching aim of this thesis was to enhance our understanding of the neurobiological risk factors associated with the transition from acute to chronic Low back pain (LBP). To achieve this aim, the Understanding persistent Pain Where it ResiDes (UPWaRD) study was conducted. In this thesis, six chapters describe the background, methods, and results of the UPWaRD study. Chapter 2 describes the protocol, published ‘a priori’ for developing a multivariable prediction model, including candidate predictors selected from the neurobiological (e.g. sensorimotor cortical excitability assessed by sensory and motor evoked potentials, Brain Derived Neurotrophic Factor [BDNF] genotype), psychological (e.g. depression and anxiety), symptom-related (e.g. LBP history) and demographic domains. Chapter 3 builds on the study protocol in the form of a cohort profile, describing baseline characteristics of 120 people experiencing an acute LBP episode and 57 pain-free control participants that form the UPWaRD cohort. Chapter 4 reports the results of the multivariable prediction model developed in 120 people experiencing acute LBP. To further understand the importance of these prognostic factors we developed a causal model of chronic LBP using directed acyclic graphs. The methodology and statistical analysis plan for drawing causal inferences, thus transparently reporting our causal assumptions, are reported in Chapter 5. Chapter 6 then provides the first evidence that low sensory cortex excitability during an acute LBP episode is a causal mechanism underpinning the development of chronic LBP. Finally, in Chapter 7, we report the results of a proteomic analysis, using hydrophobic interaction chromatography and electrospray ionization tandem mass spectrometry. Taken together this thesis makes an extensive and original contribution to our understanding of neurobiological risk factors involved in the transition from acute to chronic LBP. Not only is the inclusion of neurobiological prognostic factors in multivariable clinical prediction models a promising direction for future research that aims to identify people at high risk of poor outcome, but low sensory cortex excitability during acute LBP may be a promising causal mechanism that future treatments could target during acute LBP in the hope of expediting recovery and preventing the development of chronic LBP. Further, this thesis provides some of the earliest evidence to suggest sex-specific differential expression of proteins, measured from human serum, contributes to recovery status at three-month follow-up. This work provides foundational evidence for future research exploring strategies targeting distinct immune system processes in males and females that may interfere with the transition from acute to chronic LBP

Chiral Perturbation Theory Analysis of the Baryon Magnetic Moments

Nonanalytic $m_q^{1/2}$ and $m_q\ln m_q$ chiral corrections to the baryon magnetic moments are computed. The calculation includes contributions from both intermediate octet and decuplet baryon states. Unlike the one-loop contributions to the baryon axial currents and masses, the contribution from decuplet intermediate states does not partially cancel that from octet intermediate states. The fit to the observed magnetic moments including $m_q^{1/2}$ corrections is found to be much worse than the tree level SU(3) fit if values for the baryon-pion axial coupling constants obtained from a tree level extraction are used. Using the axial coupling constant values extracted at one loop results in a better fit to the magnetic moments than the tree level SU(3) fit. There are three linear relations amongst the magnetic moments when $m_q^{1/2}$ corrections are included, and one relation including $m_q^{1/2}$, $m_q\ln m_q$ and $m_q$ corrections. These relations are independent of the axial coupling constants of the baryons and agree well with experiment.Comment: (16 pages, 2 figures; uses harvmac and uufiles), CERN-TH.6735/92, UCSD/PTH 92-3

Reparameterisation Invariance Constraints on Heavy Particle Effective Field Theories

Since fields in the heavy quark effective theory are described by both a velocity and a residual momentum, there is redundancy in the theory: small shifts in velocity may be absorbed into a redefinition of the residual momentum. We demonstrate that this trivial reparameterisation invariance has non-trivial consequences: it relates coefficients of terms of different orders in the $1/m$ expansion and requires linear combinations of these operators to be multiplicatively renormalised. For example, the operator $-D^2/2m$ in the effective lagrangian has zero anomalous dimension, coefficient one, and does not receive any non-perturbative contributions from matching conditions. We also demonstrate that this invariance severely restricts the forms of operators which may appear in chiral lagrangians for heavy particles.Comment: (14 pages, 0 figures), UCSD/PTH 92-1

Derivation of the Effective Pion-Nucleon Lagrangian within Heavy Baryon Chiral Perturbation Theory

We develop a method for constructing the Heavy Baryon Chiral Perturbation Theory Lagrangian (L_{HBChPT}), to a given chiral order, within HBChPT. We work within SU(2) theory, with only the pion field interacting with the nucleon. The main difficulties, which are solved, are to develop techniques for implementing charge conjugation invariance, and for taking the nucleon on shell, both within the nonrelativistic formalism. We obtain complete lists of independent terms in L_{HBChPT} through O(q^3) for off- shell nucleons. Then, eliminating equation-of-motion (eom) terms at the relativistic and nonrelativistic level (both within HBChPT), we obtain L_{HBCHPT} for on-shell nucleons, through O(q^3). The extension of the method (to obtain on-shell L_{HBChPT} within HBChPT) to higher orders is also discussed.Comment: 31 pages, LaTex; original version shortened; 2 new tables and new material on extending on-shell reduction method within HBChPT to arbitrary chiral orders, include

Chiral invariant renormalization of the pion--nucleon interaction

The leading divergences of the generating functional for Green functions of quark currents between one--nucleon states are calculated with heat kernel techniques. The results allow for a chiral invariant renormalization of all two--nucleon Green functions of the pion--nucleon system to $O(p^3)$ in the low--energy expansion.Comment: 13 pages, LaTex, 2 figures in appended postscript file, Univ. Wien preprint UWThPh-1994-

Assessment of Vadose-Zone Wells for Enhancing Groundwater Recharge in the Mississippi Delta

Current pumping rates in the Mississippi River Valley Alluvial Aquifer in the Mississippi Delta are unsustainable as they are depleting the water level in the aquifer. The following thesis is a feasibility analysis on groundwater recharge to the Mississippi River Valley Alluvial Aquifer using vadose zone wells. Two days were spent in the field at Sky Lake near Belzoni, Mississippi, collecting core soil samples, bag soil samples, and constant head hydraulic conductivity values. Numerous days were spent in the lab conducting sieve analyses, Atterberg limits, and falling head hydraulic conductivity tests. The Atterberg limit test and sieve analyses were used to create a soil profile of the investigation area, and the hydraulic conductivities were used to find the flow rate of water from the vadose zone well into the soil. Using the data, it was found that an excessive number of wells would be required to offset the historical decline for the entire Delta. A smaller target area (37.5 square miles) was examined and it was determined that a remediation process of 283 wells at 8 wells per square mile would be a reasonable scenario in offsetting the decline in this analysis. In conclusion, vadose zone wells are not a feasible option for remediation of water-level decline over the entire Delta, but can be useful on a smaller scale

Semileptonic BcB_c Decay and Heavy Quark Spin Symmetry

Semileptonic decay of the $B_c$ meson is studied in the heavy quark limit. The six possible form factors for $B_c \rightarrow B_s (B^0),B_s^* (B^{*0})$ semileptonic decay are determined by two invariant functions. Only one of these functions contributes at zero recoil, where it is calculable to lowest order in an operator product expansion in terms of the meson decay constant $f_B$ and the $B_c$ wavefunction. A similar result is found for $B_c \rightarrow D^0,D^{*0}$ and for $B_c\rightarrow\eta_c,J/\psi$ semileptonic decay for a restricted kinematic region. Semileptonic $B_c$ decay provides a means for determining the KM mixing angle $|V_{ub}|$.Comment: (12 Pages, no figures

Assessing the Suitability of Black Soldier Fly Castings Produced from Piggery Waste as a Fertilizer

Black Soldier Fly (Hermetia illucens, BSF) farming provides an alternative waste management solution on piggeries by utilising manure to produce a high protein insect meal, whilst the fly castings (frass) are a valuable fertiliser