Enhacement in the dymanic response of a viscoelastic fluid flowing through a longitudinally vibrating tube

We analyzed effects of elasticity on the dynamics of fluids in porous media by studying a flow of a Maxwell fluid in a tube, which oscillates longitudinally and is subject to oscillatory pressure gradient. The present study investigates novelties brought about into the classic Biot's theory of propagation of elastic waves in a fluid-saturated porous solid by inclusion of non-Newtonian effects that are important, for example, for hydrocarbons. Using the time Fourier transform and transforming the problem into the frequency domain, we calculated: (A) the dynamic permeability and (B) the function $F(\kappa)$ that measures the deviation from Poiseuille flow friction as a function of frequency parameter $\kappa$. This provides a more complete theory of flow of Maxwell fluid through the longitudinally oscillating cylindrical tube with the oscillating pressure gradient, which has important practical applications. This study has clearly shown transition from dissipative to elastic regime in which sharp enhancements (resonances) of the flow are found

A Pluralistic Theory of Wordhood

What are words and how should we individuate them? There are two main answers on the philosophical market. For some, words are bundles of structural-functional features defining a unique performance profile. For others, words are non-eternal continuants individuated by their causal-historical ancestry. These conceptions offer competing views of the nature of words, and it seems natural to assume that at most one of them can capture the essence of wordhood. This paper makes a case for pluralism about wordhood: the view that there is a plurality of acceptable conceptions of the nature of words, none of which is uniquely entitled to inform us as to what wordhood consists in

Investigation of photoplethysmographic signals in neonatal and paediatric patients

Pulse oximeters are widely used in paediatric intensive care but they have some severe limitations. The technique relies on the presence of adequate peripheral arterial pulsations, which are detected as photoplethysmographic signals (PPG). When peripheral perfusion is poor as in states of hypovolaemia, hypothermia and vasoconstriction oxygenation readings become extremely unreliable. Hence, pulse oximetry becomes unreliable in a significant group of children just at the time when accurate readings are most needed. To overcome this limitation, the oesophagus has been investigated as a potential measurement site on the hypothesis that perfusion may well be better preserved at this central site. Studies on adult patients have shown that measurable PPG signals at red and infrared wavelengths can be detected within the whole depth of the oesophagus. A new system to investigate the quality of oesophageal PPG signals is being constructed with the aim of developing a neonatal and paediatric oesophageal pulse oximeter

Bilingual Learning for Second and Third Generation Children

Throughout the English-speaking world, children from bilingual backgrounds are being educated in mainstream classrooms where they have little or no opportunity to use their mother tongue. Second and third generation children, in particular, are assumed to be learning sufficiently through English only. This study investigated how British Bangladeshi children, learning Bengali in after-school classes but mostly more fluent in English than in their mother tongue, responded when able to use their full language repertoire within the mainstream curriculum. Through action research with mainstream and community language class teachers, bilingual literacy and numeracy tasks were devised and carried out with pupils aged seven to eleven in two East London primary schools. The bilingual activities were videorecorded and analysed qualitatively to identify the strategies used. The following cognitive and cultural benefits of bilingual learning discovered by researchers in other contexts were also found to apply in this particular setting: conceptual transfer, enriched understanding through translation, metalinguistic awareness, bicultural knowledge and building bilingual learner identities. The findings suggest that second and third generation children should be enabled to learn bilingually, and appropriate strategies are put forward for use in the mainstream classroom

From Bengali to English: sequential bilingualism of a second-generation British Bangladeshi

The paper discusses sequential language acquisition of the researcher's daughter Safa who transformed from a monolingual Bengali speaker to an almost monolingual English speaker in a few months after moving to the UK. Safa was born in Bangladesh and was a monolingual Bengali speaker until she was three years and nine months when the family moved to the UK. Unlike most research on sequential bilingualism, Safa's transition from Bengali to English went through a period of an invented language, which she developed and used for a few months. Safa then underwent language shift as Bengali became her passive language. Safa's loss of fluency in Bengali was mainly due to the absence of Bengali linguistic environment, because her family lived outside the community. Safa's mother's indifference to Bangladeshi ethnicity and her parents’ positive attitude towards Britishness meant that her decline in Bengali did not cause them much concern. Despite the lack of proficiency in Bengali, Safa still retains a strong ethnic Bangladeshi identity. Tabors and Snow’s four-stage developmental process of sequential second-language acquisition has been applied to find the similarities and differences in Safa's case, while language maintenance and shift theories have contributed to the analysis of the process of her language shift

Compound specific trends of chemical defences in Ficus along an elevational gradient reflect a complex selective landscape

Elevational gradients affect the production of plant secondary metabolites through changes in both biotic and abiotic conditions. Previous studies have suggested both elevational increases and decreases in host-plant chemical defences. We analysed the correlation of alkaloids and polyphenols with elevation in a community of nine Ficus species along a continuously forested elevational gradient in Papua New Guinea. We sampled 204 insect species feeding on the leaves of these hosts and correlated their community structure to the focal compounds. Additionally, we explored species richness of folivorous mammals along the gradient. When we accounted for Ficus species identity, we found a general elevational increase in flavonoids and alkaloids. Elevational trends in non-flavonol polyphenols were less pronounced or showed non-linear correlations with elevation. Polyphenols responded more strongly to changes in temperature and humidity than alkaloids. The abundance of insect herbivores decreased with elevation, while the species richness of folivorous mammals showed an elevational increase. Insect community structure was affected mainly by alkaloid concentration and diversity. Although our results show an elevational increase in several groups of metabolites, the drivers behind these trends likely differ. Flavonoids may provide figs with protection against abiotic stressors. In contrast, alkaloids affect insect herbivores and may provide protection against mammalian herbivores and pathogens. Concurrent analysis of multiple compound groups alongside ecological data is an important approach for understanding the selective landscape that shapes plant defences

Pyrethroid treatment of cattle for tsetse control: Reducing its impact on dung fauna

Background: African trypansomiases of humans and animals can be controlled by attacking the vectors,various species of tsetse fly. Treatment of cattle with pyrethroids to kill tsetse as they feed is the most cost-effective method. However, such treatments can contaminate cattle dung, thereby killing the fauna which disperse the dung and so play an important role in soil fertility. Hence there is a need to identify cost-effective methods of treating cattle with minimal impact on dung fauna. Methodology/Principal Findings: We used dung beetles to field bioassay the levels of dung contamination following the use of spray and pour-on formulations of deltamethrin, applied to various parts of the body of cattle in Zimbabwe. Results suggested that dung was contaminated by contact with insecticide on the body surface as the cattle defecated, and by ingestion of insecticide as the cattle licked themselves. Death of dung beetles was reduced to negligible levels by using only the spray and applying it to the legs and belly or legs alone, i.e., places where most tsetse feed. Conclusion/Significance: The restricted applications suitable for minimising the impact on dung fauna have the collateral benefits of improving the economy and convenience of cattle treatments for tsetse control. The demonstration of collateral benefits is one of the surest ways of promoting environmentally friendly procedures

Compound Specific Trends of Chemical Defences in Ficus Along an Elevational Gradient Reflect a Complex Selective Landscape

Elevational gradients affect the production of plant secondary metabolites through changes in both biotic and abiotic conditions. Previous studies have suggested both elevational increases and decreases in host-plant chemical defences. We analysed the correlation of alkaloids and polyphenols with elevation in a community of nine Ficus species along a continuously forested elevational gradient in Papua New Guinea. We sampled 204 insect species feeding on the leaves of these hosts and correlated their community structure to the focal compounds. Additionally, we explored species richness of folivorous mammals along the gradient. When we accounted for Ficus species identity, we found a general elevational increase in flavonoids and alkaloids. Elevational trends in non-flavonol polyphenols were less pronounced or showed non-linear correlations with elevation. Polyphenols responded more strongly to changes in temperature and humidity than alkaloids. The abundance of insect herbivores decreased with elevation, while the species richness of folivorous mammals showed an elevational increase. Insect community structure was affected mainly by alkaloid concentration and diversity. Although our results show an elevational increase in several groups of metabolites, the drivers behind these trends likely differ. Flavonoids may provide figs with protection against abiotic stressors. In contrast, alkaloids affect insect herbivores and may provide protection against mammalian herbivores and pathogens. Concurrent analysis of multiple compound groups alongside ecological data is an important approach for understanding the selective landscape that shapes plant defences

Language policy and orthographic harmonization across linguistic, ethnic and national boundaries in Southern Africa

Drawing on online and daily newspapers, speakers' language and writing practices, official government documents and prescribed spelling systems in Southern Africa, the paper explores the challenges and possibilities of orthographic reforms allowing for mobility across language clusters, ethnicity, regional and national borders. I argue that this entails a different theorisation of language, and for orthographies that account for the translocations and diasporic nature of late modern African identities and lifestyles. I suggest an ideological shift from prescriptivism to practice-orientated approaches to harmonisation in which orthographies are based on descriptions of observable writing practices in the mobile linguistic universe. The argument for orthographic reforms is counterbalanced with an expose on current language policies which appear designed for an increasing rare monoglot 'standard' speaker, who speaks only a 'tribal' language. The implications of the philosophical challenges this poses for linguists, language planners and policy makers are thereafter discussed.IS