7,358 research outputs found

    Fluid effects in model granular flows

    Get PDF
    Pore fluid plays a crucial role in many granular flows, especially those in geophysical settings. However, the transition in behaviour between dry flows and fully saturated flows and the underlying physics that relate to this are poorly understood. In this paper, we report the results of small-scale flume experiments using monodisperse granular particles with varying water content and volume in which the basal pore pressure, total pressure, flow height and velocity profile were measured at a section. We compare the results with theoretical profiles for granular flow and with flow regimes based on dimensional analysis. The runout and the centre of mass were also calculated from the deposit surface profiles. As the initial water content by mass was increased from zero to around 10%, we first observed a drop in mobility by approximately 50%, as surface tension caused cohesive behaviour due to matric suction. As the water content was further increased up to 45%, the mobility also increased dramatically, with increased flow velocity up to 50%, increased runout distance up to 240% and reduced travel angle by up to 10° compared to the dry case. These effects can be directly related to the basal pore pressure, with both negative pressures and positive pore pressures being measured relative to atmospheric during the unsteady flow. We find that the initial flow volume plays a role in the development of relative pore pressure, such that, at a fixed relative water content, larger flows exhibit greater positive pore pressures, greater velocities and greater relative runout distances. This aligns with many other granular experiments and field observations. Our findings suggest that the fundamental role of the pore fluid is to reduce frictional contact forces between grains thus increasing flow velocity and bulk mobility. While this can occur by the development of excess pore pressure, it can also occur where the positive pore pressure is not in excess of hydrostatic, as shown here, since buoyancy and lubrication alone will reduce frictional forces

    American Literatures After 1865

    Get PDF
    This work was created as part of the University Libraries’ Open Educational Resources Initiative at the University of Missouri–St. Louis. A web version of this text can be found at https://umsystem.pressbooks.pub/ala1865/. This book is an anthology of American Literatures After 1865, a new revision of the open educational resource entitled Writing the Nation: A Concise Introduction to American Literature 1865 to Present. It contains works that have been newly introduced to the public domain and provides direct links to reading materials that can be borrowed for free from Archive.org

    Parameters Spring Issue 2023

    Get PDF

    Pendjur for Baba

    Get PDF
    Senior Project submitted to The Division of Languages and Literature of Bard College

    A Russian Gil Blas, or The Adventures of Prince Gavrilo Simonovich Chistyakov

    Get PDF
    Although Vasily Trofimovich Narezhny (1780-1825) is generally considered to be one of the pioneers of the modern novel in Russia, his works have yet to be sufficiently recognized for their many artistic merits. He receives little critical attention in most histories of the rise of the novel in early nineteenth-century Russia. Born in Ukraine, but educated in Moscow, Narezhny wrote lengthy satirical novels imbued with a sardonic tone and an earthy brand of realism that tended to offend the refined aesthetic sensibilities of many contemporary followers of Nikolai Karamzin and his dominant school of literary Sentimentalism during the early years of the nineteenth century. Moreover, as I have argued elsewhere (see The Russianization of Gil Blas, 1986), Narezhny\u27s reworking of his putative model, Alain-René Lesage\u27s extremely popular Histoire de Gil Blas de Santillane (1715-1735), was mistaken for an imitation of this very tame and light-hearted French roman de moeurs. Soviet scholars, as a rule, failed to recognise it for its bold attempt to revive the genre of picaresque fiction that had flourished two centuries earlier, during the so-called Spanish Golden Age, through works written by such native novelists as Mateo Alemån, Francisco Gómez de Quevedo, and the anonymous author of Lazarillo de Tormes. Following the example of these enterprising literary forerunners in Spain, Narezhny sought to depict, in a highly satirical manner, the adventures of a lowborn rogue, Prince Gavrilo Chistyakov (he\u27s an impoverished prince in name only), who lives by his wits in a sinful and morally bankrupt Russian society that is filled with hypocrisy, deception, and falsehood. The tsarist censors, deeply offended by the sharp social criticism to be found in A Russian Gil Blas, refused to allow Narezhny\u27s novel to be published when it was submitted to them to consider for publication in 1815. Indeed, his novel would only see the light of day during the Soviet period (in 1938, to be exact), when it was hailed as a realistic satire of life in Russia under corrupt tsarist rule. It is my hope that this English-language translation of Narezhny\u27s Rossisskii Zhilblaz will enable, among others, American and British readers who cannot read Russian to become acquainted at last with this rollicking novel written by a pioneering Russian writer who has dwelled for far too long -- and far too unfairly -- in relative obscurity

    Electrospinning nanofiber insert for anterior ocular drug delivery for cataract treatment : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

    Get PDF
    The eye is a complex visual aid (for human and animals) which gathers visual information from the surrounding physical environment. The more common vision threatening diseases that affect both anterior/posterior segment (age related macular degeneration, cataract, keratitis, glaucoma, diabetic retinopathy, retinoblastoma, allergic conjunctivitis, and ocular trauma) is a massive social and economic burden especially for less developed countries. Drug delivery to any tissue is a challenge, eye is not an exception. Barriers to ocular drug delivery are both physiological, anatomical, static, and dynamic. The current cost-effective cataract treatment option involves surgical removal of opaque or cataractous lens and replicated with artificial intraocular lens followed with topical application of corticosteroid eye drops as post-operative management. Whilst current topical drugs are easy to apply their bioavailability is impeded due to various barriers prevailing in the eye which put a strain on the cost and the duration of recovery. This has led researchers to the path of finding alternative methods of ocular drug delivery which more recently has led to the use of nanotechnology. Nanotechnology research that can transport and deliver active ingredient (AI) safely to site of action has gained importance in recent years. Ocular drug delivery with nanotechnology though can overcome some of the challenges but does have some limitations, like patient compliance and irritation. These limitations have been addressed by researchers across the globe by reducing drug particle size, using less irritable polymers and excipients, but with limited success. The research presented in this thesis approached this problem using nanofiber technology to develop solid ocular insert that would allow sustained drug delivery. Caffeine, a model drug, was used to determine the kinetics of bioactive release. Nanofiber membranes fabricated as mono-, two- or three-layered using two polymers, poly (ethylene) oxide (PEO) and poly Δ-caprolactone (PCL) and analysed for physical characteristics of fiber (mat thickness, water contact angle, tensile properties, SEM) and drug release. Results from this study shows that the thickness of mat can be increased by having additional layer (average of 46% for two- and 54% for three-layered) compared to monolayer but it is not proportionate to the extra amount of polymer. For water contact angle the results achieved for various iterations were on par with the property of the polymer, hydrophobicity (>80°) and hydrophilicity (<50°). The tensile properties (only for mono- and three-layered formulation), puncture strength and elongation at break there was no differences between the formulations for elongation at break but for puncture strength, the force required was almost double for three-layered formulation compared to control monolayer. However, it was a challenge to measure the tensile property for monolayer formulation with PEO polymer. Mucoadhesion evaluated for only three-layered nanofiber formulations containing PEO and PCL polymer shows that the force required to detach the mat from mucin tablet (used as test material) was almost double compared to the monolayer control formulations. Surface morphology (SEM) of the nanofiber mat shows heterogenous fiber diameter distribution irrespective of the polymer and number of layers. The caffeine release from monolayer was almost immediate (within 5 min) for the formulations with PEO polymer (>50%) compared to PCL polymer wherein the same release % was noticed 1h after the initiation of the experiment. The drug release from two-layered formulation was reduced by 50% when the drug was incorporated in the first layer and the second layer acted as a barrier. Unlike the two-layered formulation, same results could not be achieved from a three-layered formulation when the drug was incorporated in the third layer, there was average >70% drug released after 1h. Surface morphology of mono- and three-layered formulations exhibited the presence of caffeine crystalline structures on the surface of the fiber which probably has attributed to immediate burst release of the drug when in contact with the aqueous solution. The results from this study elucidate that mucoadhesion onto the cornea surface can be enhanced by incorporating a hydrophilic polymer into the formulation which would probably help in the retention and increase the bioavailability of the drug to the target site in the eye. The results also shows that burst release can be mitigated and sustained release achieved when there is a barrier layer to the drug as shown in the two-layered formulation where the drug release was reduced by 50% by having a barrier layer with only the hydrophobic polymer. This formulation show promise for bioactive delivery but will require further exploration and refining

    LIPIcs, Volume 274, ESA 2023, Complete Volume

    Get PDF
    LIPIcs, Volume 274, ESA 2023, Complete Volum
    • 

    corecore