"Secretary in Fashion" and "Love-Letters": a study of socio-cultural and pragmatic-linguistic features in the late 17th century English language

Epistolary manuals are conspicuous historical documents for the pedagogy of letter writing; however, their actual usage as manuals by letter writers is unknown. "Secretary in Fashion" by Serre (1668), an epistolary manual, and "Love-Letters between a Nobleman and his Sister" (1684), an epistolary novel attributed to Behn, both give insights into epistolary conventions. Their inception and nature is interesting, considering their historical context. Despite the Restoration of Charles II, 17th century England was in a confused political state; as a result, texts regarding social convention or politics interested contemporary readers (the novel is inspired by a scandal of Lord Grey, an ardent Whig opposing Charles II). Past epistolary studies focus on 18th rather than 17th century manuals; the latter is typically used as supplementary information. Similarly, past epistolary fiction studies focus on 18th century texts; moreover, linguistic studies on Behn and the novel are deficient. Thus, this study addresses the research questions: 1) What are the socio-cultural and pragmaticlinguistic features represented in "Secretary in Fashion"? 2) What are the socio-cultural and pragmatic-linguistic features represented in "Love-Letters between a Nobleman and his Sister", and do any of these features correlate with the features represented in "Secretary in Fashion"? How far do the characteristic linguistic features of "Love-Letters between a Nobleman and his Sister" correlate with the practices recommended by the manual? Both texts were qualitatively analysed from an historical pragmatic perspective, which observes the potential effects of the socio-cultural and historical context. Also, as the texts concern shared discourses, comparisons were made with Gricean and Politeness Theory. The results show that the manual is a typical 17th century epistolary manual, aligning particularly with the "Academies of Complements", as it concerns the social conventions of the gentry. The novel mainly upheld instructions on form and matter; deviations occurred due to the amatory nature of some letters, and the narrative force affecting the style. Unfortunately, neither research question elucidates the actual usage of manuals. However, this study does show the epistolary practices of two writers, within specific contexts. It reveals that their 17th century English language use is affected by socialisation, in terms of social conventions concerning social rank, age, and gender; therefore, context varies language use. Also, their popularity reveals the interests of the 17th century society. Interest in epistolary-related texts, surely piques the interest of the modern reader as to why such epistolary-related texts were interesting.

Wavelengths in bioconvection patterns

Unicellular bottom-heavy swimming microorganisms are usually denser than the fluid in which they swim. In shallow suspensions, the bottom heaviness results in a gravitational torque that orients the cells to swim vertically upwards in the absence of fluid flow. Swimming cells thus accumulate at the upper surface to form a concentrated layer of cells. When the cell concentration is high enough, the layer overturns to form bioconvection patterns. Thin concentrated plumes of cells descend rapidly and cells return to the upper surface in wide, slowly moving upwelling plumes. When there is fluid flow, a second viscous torque is exerted on the swimming cells. The balance between the local shear flow viscous and the gravitational torques determines the cells' swimming direction, (gyrotaxis). In this thesis, the wavelengths of bioconvection patterns are studied experimentally as well as theoretically as follow; First, in aquasystem it is rare to find one species lives individually and when they swim they can form complex patterns. Thus, a protocol for controlled experiments to mix two species of swimming algal cells of \emph{C. rienhardtii} and \emph{C. augustae} is systematically described and images of bioconvection patterns are captured. A method for analysing images using wavelets and extracting the local dominant wavelength in spatially varying patterns is developed. The variation of the patterns as a function of the total concentration and the relative concentration between two species is analysed. Second, the linear stability theory of bioconvection for a suspension of two mixed species is studied. The dispersion relationship is computed using Fourier modes in order to calculate the neutral curves as a function of wavenumbers $k$ and $m$. The neutral curves are plotted to compare the instability onset of the suspension of the two mixed species with the instability onset of each species individually. This study could help us to understand which species contributes the most in the process of pattern formation. Finally, predicting the most unstable wavelength was studied previously around a steady state equilibrium situation. Since assuming steady state equilibrium contradicts with reality, the pattern formation in a layer of finite depth of an evolving basic state is studied using the nonnormal modes approach. The nonnormal modes procedure identifies the optimal initial perturbation that can be obtained for a given time $t$ as well as a given set of parameters and wavenumber $k$. Then, we measure the size of the optimal perturbation as it grows with time considering a range of wavenumbers for the same set of parameters to be able to extract the most unstable wavelength.