92 research outputs found
Interactions of cross-linked and uncross-linked chitosan hydrogels with surfactants for biomedical applications
The swelling equilibrium of Chitosan and sodium tripolyphosphate (NaTPP) cross-linked chitosan hydrogels in aqueous solutions of surfactants differing in structure and hydrophobicity at 250C is reported. Anionic
surfactant sodium dodecylsulfate (SDS), the cationic surfactant hexadecyltrimethylammonium bromide (HTAB) and neutral surfactants Triton X-100 were employed. The surfactants induced abrupt change in the gel volume. The equilibrium swelling ratio first decreased sharply as the concentration of the surfactant increased and remained almost constant up to the critical micelles concentration (CMC) of the surfactants and then
increased again as the concentration increased above the CMC of the surfactants used. The equilibrium volume change of hydrogel was significantly increased from HTAB > Triton X-100 > SDS> the mixed SDS/Triton X- 100 system. A decrease in equilibrium swelling ratio of the gel in SDS/TX-100 mixtures was observed with an increase in the mole ratio of SDS. The results also revealed that cross-linking with 3% or 5% w/v NaTPP exhibited lower equilibrium swelling values. This swelling study showed that cross-linking density, surfactant type, and their respective concentrations were important parameters that could affect equilibrium swelling of chitosan gel. Structural elucidation of the nanocomposites was monitored using Infra-red Spectroscopy (IR), and X-Ray Diffractography (XRD)
Mandibular reconstruction: a new defect classification system
This paper presents a new mandibular segmental defect classification system (La-Co-CE) with a view to highlight the complexity and difficulty of the reconstruction with free autogenous bone grafts which the most frequently used method for surgeons practicing in developing countries. We submit that defect classification systems will continue to remain relevant if surgeons are to is pre-operatively classify the envisaged operative difficulty and objectively compare the outcome postoperatively
Perception of nonnative tonal contrasts by Mandarin-English and English-Mandarin sequential bilinguals
This study examined the role of acquisition order and crosslinguistic similarity in influencing transfer at the initial stage of perceptually acquiring a tonal third language (L3). Perception of tones in Yoruba and Thai was tested in adult sequential bilinguals representing three different first (L1) and second language (L2) backgrounds: L1 Mandarin-L2 English (MEBs), L1 English-L2 Mandarin (EMBs), and L1 English-L2 intonational/non-tonal (EIBs). MEBs outperformed EMBs and EIBs in discriminating L3 tonal contrasts in both languages, while EMBs showed a small advantage over EIBs on Yoruba. All groups showed better overall discrimination in Thai than Yoruba, but group differences were more robust in Yoruba. MEBsâ and EMBsâ poor discrimination of certain L3 contrasts was further reflected in the L3 tones being perceived as similar to the same Mandarin tone; however, EIBs, with no knowledge of Mandarin, showed many of the same similarity judgments. These findings thus suggest that L1 tonal experience has a particularly facilitative effect in L3 tone perception, but there is also a facilitative effect of L2 tonal experience. Further, crosslinguistic perceptual similarity between L1/L2 and L3 tones, as well as acoustic similarity between different L3 tones, play a significant role at this early stage of L3 tone acquisition.Published versio
Diversities, affinities and diasporas: a southern lens and methodology for understanding multilingualisms
We frame multilingualisms through a growing interest in a linguistics and sociology of the âsouthâ and acknowledge earlier contributions of linguists in Africa, the AmĂ©ricas and Asia who have engaged with human mobility, linguistic contact and consequential ecologies that alter over time and space. Recently, conversations of multilingualism have drifted in two directions. Southern conversations have become intertwined with âdecolonial theoryâ, and with âsouthernâ theory, thinking and epistemologies. In these, âsouthernâ is regarded as a metaphor for marginality, coloniality and entanglements of the geopolitical north and south. Northern debates that receive traction appear to focus on recent âre-awakeningsâ in Europe and North America that mis-remember southern experiences of linguistic diversity. We provide a contextual backdrop for articles in this issue that illustrate intelligences of multilingualisms and the linguistic citizenship of southern people. In these, southern multilingualisms are revealed as phenomena, rather than as a phenomenon defined usually in English. The intention is to suggest a third direction of mutual advantage in rethinking the social imaginary in relation to communality, entanglements and interconnectivities of both South and North
Speaking with a forked tongue about multilingualism in the language policy of a South African university
As part of a broader student campaign for âfree decolonized educationâ, protests
over language policies at select South African universities between 2015 and 2016
belied widespread positive appraisals of these policies, and revealed what is possibly
an internal contradiction of the campaign. The discourse prior to the protests (e.g.
âexcellent language policies but problematic implementationâ), during the protests
(e.g. silence over the role of indigenous African languages in the âAfrikaans must
fallâ versus âAfrikaans must stayâ contestations), and after the protests (e.g. English
becoming a primary medium in some institutional policy reviews) warrant attention
to critical literacy in language policy scholarship. Based on a theoretical account of
speaking with a forked tongue, this article analyzes the language policy text of one
South African university. The analysis suggests, simultaneously, why similar policies
have tended to be positively appraised, why studentsâ calls for policy revisions
were justified, but why the changes clamoured for arguably amount to complicity in
self-harm
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