249 research outputs found
The ‘insider/outsider’ dilemma of ethnography: Working with young children and their families in cross-cultural contexts
No full textIn this article we unravel the difficulty of being researchers in the homes and classrooms of children and
their families whose origins are, for one of us, very different and, for the other, very similar to our own.
We first situate our work within theories of early socialization and literacy teaching which underpin our
understanding of how young children in cross-cultural contexts learn. We then turn to the question of
working with the families and teachers of these children which poses dilemmas not explained by the theories
presented. We illustrate these through a series of vignettes typifying both the ‘Outsider’ and the ‘Insider’ role.
The stories highlight paradigmatic moments of complexity, clashes or collusion which we unpick in terms of
their generalizability for others working in the field. Finally, we extend theories of dialogue in our search for
a methodology for collaborative work in future cross-cultural ethnographic studies
Comprehensive thermal characterization using ruby R fluorescence lines of sapphire and GaNE(2)-high Raman mode from Raman spectra in high-power flip-chip InGaN/GaN LEDs
No full textA comprehensive temperature characterization method based on the GaNE(2)-high Raman mode and sapphire ruby R fluorescence lines from Raman spectra was developed to analyse the thermal distribution and heat transfer process of high-power flip-chip InGaN/GaN LEDs (FC LEDs). Our analysis demonstrated that in addition to the known problem that the edges of mesa were always the hottest point of FC LEDs, which was due to the current crowding effect, a noteworthy temperature difference was first observed between the sapphire substrate and n-GaN when the injection current was above 300 mA. A 'heat reservoir' was suggested to occur at the interface between the sapphire and n-GaN due to poor thermal conductivity of sapphire when a large amount of heat from the hottest spot cannot be effectively transferred to the Si mount via the active region under high injection currents
TWO-PHOTON ABSORPTION AS A QUENCHING MECHANISM FOR STIMULATED RAMAN SCATTERING OF LASER RADIATION
No full textAuthor Institution: Electro-Optical Systems IncorporatedThis work was supported in part by the Air Force Avionics Laboratory, Research and Technology Division, Air Force Systems Command, U. S. Air Force. J. A. Giordmaine and J. A. Howe, Phys. Rev. Letters 11, 207 (1963). M. El-Sayed, F. M. Johnson and J. A. Duardo, J. Chem, Phys., to be published. J. A. Duardo and F. M. Johnson, J. Chem, Phys., to be published.Most investigations of stimulated Raman scattering involve the use of giant-pulsed ruby laser radiation . With the exception of the materials commonly used as scattering samples are free of absorption at wavelengths corresponding to two-photon energies () of this excitation source. However, when the second harmonic radiation () of the giant-pulsed neodymium laser is used, two-photon absorption becomes energetically possible for seattering materials such as benzene, and its substituted derivatives, and the alkyl Theoretical and experimental evidence will be presented which tends to confirm that, for those systems in which the selection rules for two-photon absorption are satisfied, two-photon absorption can occur to such an extent that it completely quenches the SRS process. On the other hand, for some materials which are transparent at , e.g., hexane, cyclohexane, acetonitrile, there is evidence that the radiation is more efficient than the radiation in the production of SRS
Writing and the rights of reality: usurpation and potentiality in Derrida, Plato, Nietzsche, and Beckett
No full textThe thesis critically evaluates Jacques Derrida's conferral of the rights of reality on writing, focussing on his theory of an arche-text in light of the speculative nature of this theory. The theory is initially considered in the context of Derrida's elucidation of the usurpatory status of writing within the Platonic and Nietzschean texts. This consideration reveals an admission of writing's usurpatory status by both writers while at the same time demonstrating their awareness of the intrinsically speculative nature of this view, the significance of writing lying in its ability to exteriorise the radically indeterminate status of consciousness m relation to reality rather than its ability to displace consciousness or reality The analyses, therefore, not only bring the Derridean hypothesis of a repressive or phonocentric metaphysical episteme into question but also exhibit the historical and philosophical role of potentiality in relation to writing, writing's ultimate significance lying in its capacity to exteriorise our existence as a mode of potentiality. Accordingly, in the second half of the thesis the Derridean theory of writing is countered with a specifically Aristotelian theory of the text as it is exhibited in the prose of Samuel Beckett, an author whose significance lies in his close alignment with Derridean theory within contemporary criticism. It is demonstrated that this identification has obviated an awareness of the significance of potentiality within the Beckettian text, his work consequently being appraised in the previously neglected context of Aristotelian metaphysics
ON THE PRODUCTION OF COHERENT RADIATION THROUGH STIMULATED RAMAN SCATTERING AND NONLINEAR FREQUENCY MIXING TECHNIQUES.
No full text F. M. Johnson and J. A. Duardo, Laser Focus, June (1967). J. A. Duardo, L. Nugent, and F. M. Johnson, J. Chem. Phys. (May 1, 1967). F. M. Johnson, J. A. Duardo, and G. L. Clark, Appl. Phys. Letter 10, 157 (1967). J. A. Duardo, L. Nugent, and F. M. Johnson, Applied Optics (to be published).Author Institution: Electro-Optical Systems, Inc.; Oak RidgeThe phenomena of stimulated Raman scattering (SRS) and frequency mixing in nonlinear optical crystals can potentially be used to great advantage in molecular spectroscopy investigations, since they result in the production of pulsed, intense, coherent, collimated radiation at discrete wavelengths. In most instances, SRS has been produced by using either 6943\AA ruby laser or neodymium laser radiation. On the other hand, the so-called second harmonic radiation of these laser sources, at 3472\AA and 5290\AA, respectively, would provide a more useful set of discrete SRS wavelengths, i.e., ``laser-like'' radiation in the ultraviolet spectral region where the electronic absorption bands of a great number of molecules are located. However, few experiments of SRS involving the second-harmonic of giant-pulsed laser radiation have been reported. The reasons for this are discussed and experimental techniques which can be used to overcome some of the limitations inherent in the production of SRS spectra of second harmonic radiation are described. In addition, recent experimental which are pertinent to the production of coherent radiation at discrete wavelengths throughout the UV, visible and IR spectral regions are reviewed. This work was supported in part by the Air Force Avionics Laboratory, Research and Technology Division under Contract No. AF 33(615)-3669, and NASA/Electronics Research Center under Contract No. NASI-2137, and Edgewood Arsenal, U.S. Army, under Contract No. DA-04-495-AMC-1218(A)
Modulation of host intestinal epithelium by gastrointestinal nematode secreted extracellular vesicles
No full textHelminths have co-evolved alongside their hosts for millions of years and haveadapted eloquent mechanisms that allow them to reside in the host withoutcausing significant pathology, or elimination. The ability of these parasites tomanipulate their specialised host is reflected by their continued persistence asa global health concern, with ~1 billion people infected with soil transmittedhelminths (STHs). Helminth infections have long been associated with reducedallergic and autoimmune diseases leading to the hypothesis that helminthsuppress the host immune system, and this has been confirmed in both animalmodels and controlled human infection studies. Many studies have shown thatmany suppressive effects of infection on the host immune system can beattributed to helminth excreted/secreted products (ES). A small but growing listof individual molecules from helminth ES have been characterised, and themechanism of action elucidated. For example, multiple helminth species havebeen identified to secrete TGFβ mimic proteins that can bind host TGFβreceptor and induce T-regulatory (Treg) immunosuppressive cells. However,the full repertoire of helminth secreted molecules that modulate the host ishypothesised to be far from complete.
Our lab discovered the presence of extracellular vesicles (EVs) within ES fromthe mouse infective helminth Heligmosomoides polygyrus bakeri (H. bakeri).EVs are lipid bilayer enclosed nanoparticles that carry proteins, lipids andnucleic acids and are released ubiquitously by all cells and organisms studiedto date. In mammalian systems EVs provide a mechanism of communicationbetween near or distal cells. In the context of host-pathogen dynamics it isproposed that EVs could play a role in enabling parasites to condition theirenvironment during infection. There is mounting evidence of host-parasite EVmediated modulation occurrence between plants and colonising fungal cells,bacteria and mammalian host cells, and several parasites and theirmammalian hosts including several helminth species.
During H. bakeri infection host immune suppression is thought to primarilyoccur during the adult stage of infection when the parasite resides in the lumenof the duodenum in close proximity to the intestinal epithelium. The intestinalepithelium plays an integral role both in helminth detection, and in mediatingparasite clearance. Therefore, I hypothesised that adult H. bakeri EVs targetthe intestinal epithelium and directly modulate this tissue. The goal of thisthesis was to determine the role of helminth EVs in infection dynamics andhost modulation in the intestinal epithelium. I aimed to address whether H.bakeri EVs enter the intestinal epithelium, whether uptake is targeted to aspecific cell type and how these effects the function of this tissue usingintestinal organoid models.
To address these aims development and refinement of methods for high purityEV preparations and EV labelling was required in order to directly implicate H.bakeri EVs as the causative agent in host responses. In Chapter 3, I comparedvarious combinational approaches to EV isolation and improved the purity ofour EV and EV depleted HES preparations. I then assessed EV preparationsusing cryoEM which furthered our understanding of the morphology anddiversity of H bakeri secreted EVs. I trialled multiple labelling methodologiesand found a low-background labelling method that allowed high confidenceidentification of uptake for subsequent chapters. However, I later discoveredthat the majority of labelling techniques trialled had variable labelling efficiencywith low proportions of EVs labelled; this is a caveat to consider wheninterpreting results using labelled EVs.
To understand how H. bakeri EVs interact with the intestinal epithelium Ideveloped methods to grow small intestinal 2-D organoids (enteroids) whichare in vitro cultures that reconstitute the intestinal epithelium (Chapter 4). 2-Denteroids have greater cellular complexity as compared to a homogenous cellline and allow us to address the question of cell type specificity for uptake. 2-D enteroid cultures maintained cellular polarisation and differentiated into 6-7major cell types of the intestinal epithelium.
In Chapter 5, I demonstrated by using fluorescently labelled EVs that H. bakeriEVs enter organoid cells, however at a lower proportion than I see side-by-side for our cell line cultures. This led to the hypothesis that H. bakeri EVscould target specific cellular populations within the intestinal epithelium. Toidentify whether uptake of H. bakeri EVs occurs in a targeted fashion byspecific cell types I performed microscopy experiments aiming to co-localiseEVs with certain cell types. Microscopy approaches did not provide a definitiveanswer to the question of whether uptake is cell type specific. Next, I modifiedthe cellular proportion of our 2-D enteroids to identify whether this altered theproportion of EV uptake. Goblet and tuft cells are specialised cells of theepithelium that are strongly induced during helminth infection and mediatehelminth clearance; I reasoned that H. bakeri EVs may specifically enter andmodulate these cell types. Organoid cultures that were enriched in goblet andtuft cells showed no enhanced ability to take up EVs, suggesting that neithergoblet nor tuft cells are specifically targeted over other cell types; however, thisdata does not rule out that H. bakeri EVs can enter these cell types andmodulate them. Whether cell type specificity exists for the uptake of H. bakeriEVs within the intestinal epithelium remains unclear and is still an active areaof investigation.
To understand how EV treatment of 2-D enteroids altered host geneexpression in Chapter 6, I performed RNA sequencing (RNA seq) andcharacterised the transcriptional changes within 2-D enteroids to H. bakeri EVsor EV depleted ES after 24 h. Genes critical for maintenance of stem cells, cellcycle and antimicrobial defence were downregulated by H. bakeri EVs. Withinthe intestinal epithelium only a proportion of the cells are mitotic, thereforechanges in cell cycle suggest a modulation of either stem cells of Transit-amplifying (TA) cells. I also identified several changes in cell type restricted genes expressed specifically by stem cells, Paneth cells, TA cells orEnteroendocrine cells (EECs). I now hypothesise EVs specifically modify thesecell types. To define the cell type specific responses after EV or EV depletedES treatment I performed single cell RNA seq, unfortunately the quality of ourcontrol sample made interpreting these results difficult. However, these dataserve as conformation of the cellular composition of our 2-D enteroids model.
In addition, I also utilised our 2-D organoid model to perform novel co-culturedexperiments with live adult or larval stage 4 (L4) H. bakeri and performedtranscriptional analysis of the host epithelium under these conditions. Thesedata allow us to uncouple the impact of infection with whole parasites on theintestinal epithelium from any immune driven changes in the epithelium thatoccur in vivo. These data also serve as a comparison between host effectsattributed specifically to H. bakeri EVs, and changes induced by the wholeparasite.
In summary, this thesis contributes new knowledge to our understanding of H.bakeri interactions with the intestinal epithelium in the absence of host immunedriven responses and distinguishes the role of secreted H. bakeri EVs inmodulating this tissue. I determined that H. bakeri EVs enter host epithelialcells in 2-D enteroids, but whether this is specifically targeted to certainsubpopulations remains elusive. I characterised the host gene expressionchanges upon H. bakeri EV treatment in 2-D enteroids, these findings furtherour understanding as a field of which host genes and pathways are targetedby H. bakeri. In the future, this thesis along with continued research, couldhave important implications for helminth eradication. Conversely, where H.bakeri EVs suppress specific genes or pathways involved in diseases of theintestinal epithelium such as ulcerative colitis, Crohn's disease, oradenocarcinoma, they could provide novel strategies for therapeutics
APPLICATION OF THE FREQUENCY DOUBLED Nd LASER TO TWO-PHOTON SPECTROSCOPY
No full text P.R. Monson and W.M. McClain, J. Chem. Phys. 56, 10 (1972) pp. 4817-4825.Author Institution: Department of Chemistry, University of California; Department of Chemistry, Wayne State UniversityA frequency doubled Nd oscillator-amplifier system has been constructed and applied to two-photon absorption spectroscopy. This system can, in some cases, reach higher energies than were possible with a two-photon spectrometer utilizing a ruby laser. Preliminary results on the two-photon absorption spectrum of liquid benzene will be described
A critical analysis of research related to attitudes toward low-income families and services provided by public school systems
No full textIncludes bibliographical references
COMBINATION FREQUENCY GENERATION IN RAMAN LASER EMISSION
No full textPresent address of L. J. Nugent: Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, E. Garmire, F. Pandarese and C. H. Townes, Phys, Rev, Lett. 11, 160 (1963).Author Institution: Electro-Optical Systems, Incorporated, 300 N. Halstead Street; Chemistry Division, Oak Ridge National LaboratoryIn two experiments giant-pulse ruby-excited coherent Raman emission spectra were observed from high pressure and gases. In the first experiment approximately equimolar mixtures of these gases were contained within one scattering cell. In the second experiment each gas was isolated in a separate cell and the cells were placed in series so the excitation could proceed first through one and then through the other. The spectra in both cases are essentially identical. Above an excitation threshold, characteristic stimulated Raman emission from each gas is observed at , where is the excitation frequency, in is any positive or negative integer, and is the frequency of a totally symmetric molecular vibration of molecule j. Of greater significance, however, was the presence in both cases of the combination frequencies in high intensity. In another series of experiments, Raman laser emission from the following isolated two-component series configurations also contained high intensity combination frequencies as well as the characteristic stimulated emission from each substance: , and , where the gas in each case directly followed the ruby laser, These results are examined in the light of the classical theory of stimulated Raman . The effect of molecular interactions is discussed and a mechanism which can be independent of the interactions between different molecular species is proposed for the production of the combination frequencies. Work supported in part by USA Chemical Research and Development Laboratories, Edgewood Arsenal, Md. under Contract DA-04-195-AMC-1218(A)
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