Stochastic modelling of long-term persistence in streamflow sequences

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Electrical impedance measurements of the uterine cervix in pregnancy

This is the first time that electrical impedance studies have been performed on the pregnant cervix.In this thesis the following has been demonstrated:1. An inter-observer variability in resistivity readings, initially of the order of 20%, but decreasing to 1% once proficiency with the technique was established.2. An intra-observer variability in resistivity readings of less than 15% in 94% of cases using the 5.5mm probe and 90% when using the 8mm probe.3. A degree of heterogeneity in the pregnant cervix as attested to by the differences in resistivity measurements on different sites on the cervix. Some of these changes were partly due to technical difficulties. Nevertheless there appeared to be an increase in extracellular resistivity measurements between the anterior and posterior lips of the external cervical os. 4. A positive correlation between the resistivity measurements and gestational age using the 5.5mm probe. No significant correlations were identified between resistivity readings and both parity and maternal age. 5. A statistically significant difference in resistivity readings when comparing the non-pregnant and pregnant cervix. The change in readings was in a direction which reflected the increase in tissue hydration described by others. 6. A statistically significant difference between readings for ripe and unripe cervices at the time of induction of labour, with a fall in extracellular resistivity with increasing favourability as assessed by the Bishop score. This was accompanied by an increase in intracellular resistivity with increasing cervical favourability. The effect of prostaglandin administration on the pregnant cervix demonstrated a decrease in extracellular resistivity and an increase in intracellular resistivity associated with the cervical ripening process. Whilst the results were neither of statistical nor of clinical significance, they were nevertheless in the direction predicted. 7. A statistically significant correlation between extracellular resistivity and interval to delivery using the 8mm probe. 8. A new investigative modality that had high patient acceptability. To date the findings demonstrated in this thesis conceptually agree with the literature on the pregnant cervix. Thus it is imperative to continue with further studies of this new investigative modality

Synthesis and characterisation of bifunctional MRI contrast agents

Macrocyclic ligands based on cyclen form lanthanide complexes with good thermodynamic stability and kinetic inertness due to the large degree of preorganization of the ligand. Conversely, it is these favourable properties which have impeded their development as magnetopharmaceudcals as the functionalization of cyclen remains synthetically challenging. This thesis describes the development of new synthetic routes to substituted cyclen ligands, which after complexation with Gd(III), could have potential as MRI contrast agents. At present, cyclen is primarily functionalized by alkylation with halide substrates. In an attempt to prepare bifunctional ligands, cyclen was alkylated with derivatised amino acids. Elimination of the halide substrate to give the corresponding alkene was found to be a significant problem using this approach. As an alternative route to functionalized macrocycles, the Michael addition of cyclen to activated alkenes was investigated. The aza-Michael addition of cyclen to acrylamide was found to be regioselective with the tri-amide substituted cyclen (D03PAM) being the major product. Hydrolysis of D03PAM with 12M HCl gave the corresponding tri-acid substituted cyclen (D03P) in a yield of 90 %. D03P is an analogue of the important cyclen ligand, D03A, which has three acetate substituents. Trifluoromethanesulfonic acid was found to catalyse the conjugate addition of mono-N-Z-cyclen to methyl-2-acetamidoacrylate under mild conditions. This methodology of mono-Z-protecrion followed by acid-catalysed addition and deprotection offers a new and versatile route to tri-N-substituted cyclen derivatives. The addition of cyclen to ethyl-cis-B-cyanoacrylate was regioselective as addition occurred exclusively at the carbon B to the nitrile group. The ligands D03P and D03PAM were complexed with gadolinium(III) and the T1 spin-lattice relaxation times of the complexes were measured. The corresponding T1-relaxivity values (r1) of Gd(D03P) and Gd(D03PAM) were determined to be 4.0 and 4.6 mM-1s-1 (60 MHz, 25 °C), respectively. These complexes provide significantly better relaxivity values than that of the best-selling MRI contrast agent, Magnevist (Gd-DPTA), which has an value of 2.8mM-1s-1 (60 MHz, 25 °C)

Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials

Previous studies indicate that elasmobranch fishes (sharks, skates and rays) detect the Earth’s geomagnetic field by indirect magnetoreception through electromagnetic induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of elasmobranchs overall in comparison with control and procedural control hooks in the hook-and-line experiment. Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were signif icantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not. Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish (Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-and-line or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations

Galaxy Formation In The Reionization Epoch As Hinted By Wide Field Camera 3 Observations Of The Hubble Ultra Deep Field

We present a large sample of candidate galaxies at z~7--10, selected in the HUDF using the new observations made by the HST/WFC3. Our sample is composed of 20 z-dropouts, 15 Y-dropouts, and 20 J-dropouts. The surface densities of the z-dropouts are close to what predicted by earlier studies, however, those of the Y- and J-dropouts are quite unexpected. While no Y- or J-dropouts have been found at AB < 28.0 mag, their surface densities seem to increase sharply at fainter levels. While some of these candidates seem to be close to foreground galaxies and thus could possibly be gravitationally lensed, the overall surface densities after excluding such cases are still much higher than what would be expected if the luminosity function does not evolve from z~7 to 10. Motivated by such steep increases, we tentatively propose a set of Schechter function parameters to describe the LFs at z~8 and 10. As compared to their counterpart at z~7, here L* decreases by ~ 6.5x and Phi* increases by 17--90x. Although such parameters are not yet demanded by the existing observations, they are allowed and seem to agree with the data better than other alternatives. If these LFs are still valid beyond our current detection limit, this would imply a sudden emergence of a large number of low-luminosity galaxies when looking back in time to z~10, which, while seemingly exotic, would naturally fit in the picture of the cosmic hydrogen reionization. These early galaxies could easily account for the ionizing photon budget required by the reionization, and they would imply that the global star formation rate density might start from a very high value at z~10, rapidly reach the minimum at z~7, and start to rise again towards z~6. In this scenario, the majority of the stellar mass that the universe assembled through the reionization epoch seems still undetected by current observations at z~6. [Abridged]Comment: accepted for publication in Research in Astronomy and Astrophysic

COMPREHENSION OF CONVERSTATIONAL IMPLICATURE: EXAMINING EVIDENCE OF ITS SEPARABILITY AS A LISTENING SUBSKILL

Understanding the inferences that speakers rely on to communicate is a core part of listening comprehension and is, more broadly, an important aspect of communicative ability. As a result, theories of communicative language ability account for it, and language testers who try to gauge the proficiency of learners of a second language include it in their assessments. Within the field of language testing, much research has been conducted to better understand how different aspects of listening may contribute to difficulty for second-language learners. One area of investigation has been the notion of listening being separable into different subskills, such as listening for inferences as opposed to listening for specific explicit details or listening for main idea. However, there have been mixed results when attempting to determine the psychological reality of these subskills. This study attempts to clarify this question via a listening comprehension instrument that was designed specifically to assess the comprehension of conversational implicature, or pragmatic inferencing, in contrast to non-implicature, or general comprehension. This balanced instrument was administered to 255 language learners in two item formats, multiple choice and constructed response. In addition, participants were administered short-term memory and working memory measures. A variety of analyses, including item response theory (Rasch), logistic regression, and confirmatory factor analyses were used to try to attain evidence for 1) the existence of a separable listening for conversational implicature subskill and 2) the validity of assessing this subskill through a multiple-choice format. The results from the analyses generally converged to indicate that while conversational implicature contributes to difficulty, it is not a separable subskill. However, the results did show that the multiple-choice item format is a defensible method for targeting this skill. This leads to the conclusion that expending effort on assessing comprehension of conversational implicature in general language proficiency tests may not be necessary unless the test-use context places particular emphasis on this ability. Although it is an integral aspect of listening, from an assessment standpoint, performance on general listening items will likely give test users the information they need to make predictions about comprehension of conversational implicature ability

Detection of Ly\beta auto-correlations and Ly\alpha-Ly\beta cross-correlations in BOSS Data Release 9

The Lyman-$\beta$ forest refers to a region in the spectra of distant quasars that lies between the rest-frame Lyman-$\beta$ and Lyman-$\gamma$ emissions. The forest in this region is dominated by a combination of absorption due to resonant Ly$\alpha$ and Ly$\beta$ scattering. When considering the 1D Ly$\beta$ forest in addition to the 1D Ly$\alpha$ forest, the full statistical description of the data requires four 1D power spectra: Ly$\alpha$ and Ly$\beta$ auto-power spectra and the Ly$\alpha$-Ly$\beta$ real and imaginary cross-power spectra. We describe how these can be measured using an optimal quadratic estimator that naturally disentangles Ly$\alpha$ and Ly$\beta$ contributions. Using a sample of approximately 60,000 quasar sight-lines from the BOSS Data Release 9, we make the measurement of the one-dimensional power spectrum of fluctuations due to the Ly$\beta$ resonant scattering. While we have not corrected our measurements for resolution damping of the power and other systematic effects carefully enough to use them for cosmological constraints, we can robustly conclude the following: i) Ly$\beta$ power spectrum and Ly$\alpha$-Ly$\beta$ cross spectra are detected with high statistical significance; ii) the cross-correlation coefficient is $\approx 1$ on large scales; iii) the Ly$\beta$ measurements are contaminated by the associated OVI absorption, which is analogous to the SiIII contamination of the Ly$\alpha$ forest. Measurements of the Ly$\beta$ forest will allow extension of the usable path-length for the Ly$\alpha$ measurements while allowing a better understanding of the physics of intergalactic medium and thus more robust cosmological constraints.Comment: 26 pages, 10 figures; matches version accepted by JCA

Measurements of the acid-binding capacity of ingredients used in pig diets

peer-reviewedSome feed ingredients bind more acid in the stomach than others and for this reason may be best omitted from pig starter foods if gastric acidity is to be promoted. The objective of this study was to measure the acid-binding capacity (ABC) of ingredients commonly used in pig starter foods. Ingredients were categorised as follows: (i) milk products (n = 6), (ii) cereals (n = 10), (iii) root and pulp products (n = 5), (iv) vegetable proteins (n = 11), (v) meat and fish meal (n = 2), (vi) medication (n = 3), (vii) amino acids (n = 4), (viii) minerals (n = 16), (ix) acid salts (n = 4), (x) acids (n = 10). A 0.5 g sample of food was suspended in 50 ml distilled de-ionised water with continuous stirring. This suspension was titrated with 0.1 mol/L HCl or 0.1 mol/L NaOH so that approximately 10 additions of titrant was required to reach pH 3.0. The pH readings after each addition were recorded following equilibration for three minutes. ABC was calculated as the amount of acid in milliequivalents (meq) required to lower the pH of 1 kg food to (a) pH 4.0 (ABC-4) and (b) pH 3.0 (ABC-3). Categories of food had significantly different (P < 0.01) ABC values. Mean ABC-4 and ABC-3 values of the ten categories were: (i) 623 (s.d. 367.0) and 936 (s.d. 460.2), (ii) 142 (s.d. 79.2) and 324 (s.d. 146.4), (iii) 368 (s.d. 65.3) and 804 (s.d. 126.7), (iv) 381 (s.d. 186.1) and 746 (s.d. 227.0), (v) 749 (s.d. 211.6) and 1508 (s.d. 360.8), (vi) 120 (s.d. 95.6) and 261 (s.d. 163.2), (vii) 177 (s.d. 60.7) and 1078 (s.d. 359.0), (viii) 5064 (s.d. 5525.1) and 7051 (s.d. 5911.6), (ix) 5057 (s.d. 1336.6) and 8945 (s.d. 2654.1) and (x) -5883 (s.d. 4220.5) and -2591 (s.d. 2245.4) meq HCl per kg, respectively. Within category, ABC-3 and ABC- 4 values were highly correlated: R2 values of 0.80 and greater for food categories i, iv, v, vi, vii and viii. The correlation between predicted and observed ABC values of 34 mixed diets was 0.83 for ABC-4 and 0.71 for ABC-3. It was concluded that complete diets with low ABC values may be formulated through careful selection of ingredients. The final pH to which ABC is measured should matter little as ABC-3 and ABC-4 are highly correlated

Meniscus confined fabrication of multidimensional conducting polymer nanostructures with scanning electrochemical cell microscopy (SECCM)

Scanning electrochemical cell microscopy (SECCM) is demonstrated as a new approach for the construction of extended multi-dimensional conducting polymer (polyaniline) nanostructures, making use of a mobile dual-channel theta pipette cell to control and monitor the location, rate and extent of electropolymerisation