3,092 research outputs found
Placental composition and surface area but not vascularization are altered by maternal protein restriction in the rat
No full textAmino acids are essential nutrients for foetal growth and development, and maternal protein restriction decreases foetal growth despite increasing placental size. To determine if placental structure is altered so as to impair function despite increased size, the effect of maternal protein restriction on the composition and vascularization of the placenta in the rat was determined.
Pregnant rats were randomized to receive either a normal protein (20 per cent) or an isocaloric low (8 per cent) protein diet. Placentae were studied at day 18 of gestation. Tissue sections were stained with biotinylatedBandeiraea simplicifolia (BS-1) lectin to allow identification of foetal capillaries, and analysed using stereological techniques.
Protein restriction increased total placental volume, but decreased the proportion of the placental volume composed of labyrinth. Consequently the total volumes of labyrinthine tissue and of foetal and maternal blood space were not different between the two groups.
Protein restriction increased the surface area density and total surface area of the materno-foetal interface, but did not alter foetal capillary surface area, diameter or length.
This study found that maternal protein restriction is associated with an increase in placental size, and that this enlargement is accompanied by increases in some, but not all, structural crelates of function
Effects of maternal iron restriction on placental vascularization in the rat
No full textTo investigate the effects of maternal iron deficiency and anaemia on the placenta the composition and vascularization of the placental labyrinth was investigated in iron-restricted rats. Rats in the experimental groups were placed on iron-restricted diets either 1 or 2 weeks before mating and continued on these diets throughout gestation. Placentae were studied at day 21 of gestation. Tissue sections were stained with lectin to allow identification of fetal capillaries and analyzed using stereological techniques. Capillary surface area density and total capillary surface area were decreased in both iron-restricted groups compared with the control group. Capillary length density was decreased in both iron-restricted groups compared with the control group. Total capillary length was significantly reduced in the 1-week, but not in the 2-week, iron-restricted group compared with the control group. Endothelial cell volume was increased in both iron-restricted groups compared to the controls. There were no significant differences in the volume of fetal capillaries, the volume of the maternal blood spaces or the surface area of the maternal–fetal interface between the control and iron-restricted groups. Labyrinthine volume, labyrinthine tissue volume and the surface area of the maternal fetal interface were increased in the 2-week group when compared with the 1-week group. These changes in placental vascularization may contribute to the fetal growth retardation observed in iron-restricted litters
Visual signals and children's communication: negative effects on task outcome
No full textPrevious research has found that young children fail to adapt to audio-only interaction (e.g. Doherty-Sneddon & Kent, 1996), and perform difficult communication tasks better face-to-face. In this new study, children aged 6- and 10 year-olds were compared in face-to-face and audio-only interaction. A problem-solving communication task involving description of abstract stimuli was employed. When describing the abstract stimuli both groups of children showed evidence of face-to-face interference rather than facilitation. It is concluded that, contrary to previous research, for some communication tasks access to visual signals (such as facial expression and eye gaze) may hinder rather than help children’s communication
R.M. Simmons presentation, Rena Smart book review
No full textR.M. Simmons of the Gospel Music Workshop of America gives a presentation on the African influence in the African American religious experience. He explains how African slaves brought to America their concept of music (utilitarian concept of music). Simmons further discusses the fusion between the utilitarian concept and the Western concept of religion resulting in spirituals. He also describes hymn categories in early forms of formal African American worship experiences. Simmons takes questions from the audience among which is Dr. Riggins Earl Jr. Video concludes with a book review on Christian Theology and Ethics by Rena Smart.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the National Endowment for Humanities - Humanities Collections and Reference Resources Implementation Project Grant in supporting the processing and digitization of a number of its major archival collections as part of the project: Spreading the Word: Expanding Access to African American Religious Archival Collections at the Atlanta University Center Robert W. Woodruff Library.</em
Velocity-Gradient Probability Distribution Functions in a Lagrangian Model of Turbulence
No full textThe Recent Fluid Deformation Closure (RFDC) model of lagrangian turbulence is recast in path-integral language within the framework of the Martin-Siggia-Rose functional formalism. In order to derive analytical expressions for the velocity-gradient probability distribution functions (vgPDFs), we carry out noise renormalization in the low-frequency regime and find approximate extrema for the Martin-Siggia-Rose effective action. We verify, with the help of Monte Carlo simulations, that the vgPDFs so obtained yield a close description of the single-point statistical features implied by the original RFDC stochastic differential equations
January 28, 1906 Page one Many shocking details in the wreck of the steamer Valencia Master of Slocum gets ten years
No full textCousins, James; Jorgenson, C.P.; Sullivan, D.S.; Nelson, Walter; Connors, Frank; Ross, Charles; Greggy, Harry; Erickson, Gus; Inglehorn, O.W.; Nelson, R.M.; Doherty, M.; Grifenstan, A.F.; Bunker, F.S.; Willis, Alfred; Van Schalck, Willliam;steamer Valencia; cutter Grant; steamer Queen; cruiser Philadelphia; tug Czar; steamer Salvor; steamship Slocum
Efficient waveguide power combiners at mm-wave frequencies
No full textIn this study, an efficient power combiner for mm-wave frequency transmitters is investigated. The combiner is based on a parallel plate waveguide (PPW) excited with multiple parallel feeds. The Doherty power combiner scheme is also integrated in the proposed concept, to increase the efficiency of the amplifiers when implementing amplitude modulation. The advantage of the proposed PPW combiner with respect to other concepts, for example, the ones based on substrate-integrated waveguide, is the wider bandwidth and the scalability to an arbitrary number of inputs. Measured results from a demonstrator realised in standard printed circuit board technology are presented. Two variations of the combiner are implemented, one terminated with a 50 Ω coaxial output, and another integrated with an antenna. In the latter case, the waveguide is folded so that both the power combiner and the antenna fit within a half wavelength size, and thus would be compatible with a dense antenna array implementation.</p
Author Correction: Global geochemical fingerprinting of plume intensity suggests coupling with the supercontinent cycle
No full textThe original version of this Article omitted from the author list the 4th and 5th authors, Grant Cox and Ross Mitchell, who were both at Curtin University. Consequently, the corrected version of the Acknowledgements removes the following from the original version: ‘and Ross Mitchell’. In addition, the following was added to the Author Contributions: ‘G.M.C. and R.M. were involved in an early attempt of this study.’. This has been corrected in both the PDF and HTML versions of the Article
Colonising "The Coral Island": A Postcolonial Reading of R.M. Ballantyne's Children's "Classic"
No full textstudent essayBeing written during the rise of the British Empire in the 1850sm R.M. Ballantyne's boys' adventure story "The Coral Island" is in many ways a product of its time, conveying imperial ideas and Victorian values to the young reader. Through his portrayal of the native inhabitants in relation to his descriptions of the three British protagonists, the author creates a stereotyped image of the natives as primitive savages. Due to the further use of a first person narrator and realist pretensions, the dated racist ideas become influential upon the reader. In spite of the fact that the novel has been considered as an entertaining children's classic by generations since its first publication, "The Coral Island" should not be classified as good children's literature today but should rather be historicised as a result of its controversial contents. By adopting a postcolonial approach and applying postcolonial theory in my analysis of R.M. Ballantyne's "The Coral Island", I have in this essay endeavoured to demonstrate in what ways the novel would prove problematic as a children's book today. In my first chapter I present the imperial ideas and Victorian values that are conveyed, whereas in my second chapter I discuss Ballantyne's stereotyping of the natives. As a result of my study of this novel, I have exemplified how the author portrays the three British boys as representative of the Victorian ideals of the time. I have also illustrated their assumed superiority over nature and their roles as colonisers. Furthermore, my analysis of "The Coral Island" has revealed how Ballantyne communicates both white superiority as well as the Western "oblibation" to civilise primitive people throug Christian conversion. Consequently, the novel promotes the ideology of its time. As a result of my findings, I would like to argue that "The Coral Island" should today be viewed as a text conveying historical ideas and values rather than as an exciting children's classic
Acoustic emmission gedrag van verschillende grondsoorten
No full textDit rapport vat de resultaten samen van de meetrapporten "Acoustic Emission" (A.E.) gedrag van verschillende grondsoorten door ing. F.M. Schenkeveld, LGM en "Acoustic emission laboratory testing of sand, clay and peat soils" door Prof. R.M. Koerner, Drexel University, U.S.A. Het onderzoek werd verricht in opdracht van het Centrum voor Onderzoek Waterkeringen (COW), in samenwerking met het Laboratorium voor Grondmechanica (LGM). Projectleider voor het COW was ir. A. Penning. Het doel van het onderzoek is de evaluatie van de "acoustic emission"-methode met betrekking tot stabiliteitsproblemen bij Nederlandse dijken. Tijdens het vooronderzoek is kontakt gelegd met Prof. R.M. Koerner (R.M.K.), Drexel University, U.S.A. Om een goede basis te geven aan het onderzoek werd met Prof. Koerner een gezamenlijk project uitgevoerd. "Acoustic Emissions" zijn spanningsgolven die gegenereerd worden in een materiaal onder spanning tijdens deformatie. Soms zijn deze spanningsgolven hoorbaar (kraken van hout), maar vaak niet vanwege de lage amplitude en hoge frequentie. Een piezoelectrische sensor wordt gebruikt om de "acoustic emissions" te detecteren. De opnemer produceert een electrisch signaal evenredig met de amplitude van de waargenomen trilling. Het signaal wordt dan versterkt, gefilterd en geteld of op een andere wijze gekwantificeerd. Achtergrondruis en andere ongewenste verstoringen worden gefilterd of apart gekwantificeerd en afgetrokken van de resultaten. De tellingen of andere bewerkte resultaten van de emissies worden dan gecorreleerd met het materiaal gedrag om empirisch de veiligheid van de onderzochte situatie te bepalen. Indien er geen acoustic emissions zijn is het materiaal in het algemeen in rust en stabiel. Evenwel als er emissies worden waargenomen is het materiaal in beweging, hetgeen uiteindelijk kan leiden tot bezwijken. De komponenten van het huidige "acoustic emission" systeem bestaan uit: een stalen staaf (om het signaal vanuit de grond naar een geschikt waarnemingspunt te brenger.) , een sensor (geofoon, versnellingsopnemer,hydrofoon of een andere opnemer die een mechanische trilling in een electrisch signaal omzet), een voorversterker (om het signaal te versterken indien een lange kabel wordt gebruikt), filters (om ongewenste gedeelten van het signaal te elimineren), een versterker (om het signaal verder te versterken voor signaalbewerking) en een signaalbewerkingssysteem. Het signaalbewerkingssysteem is over het algemeen een teller die telt als een bepaalde drempelwaarde wordt overschreden.TAW/EN
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