Three-dimensional nanotube arrays for solar energy harvesting and production of solar fuels

Over the past decade extensive research has been carried out on photovoltaic semiconductors to provide a solution towards a renewable energy future. Fabricating high-efficiency photovoltaic devices largely rely on nanostructuring the photoabsorber layers due to the ability of improving photoabsorption, photocurrent generation and transport in nanometer scale. Vertically aligned, highly uniform nanorods and nanowire arrays for solar energy conversion have been explored as potential candidates for solar energy conversion and solar-fuel generation owing to their enhanced photoconversion efficiencies. However, controlled fabrication of nanorod and especially nanotube arrays with uniform size and shape and a pre-determined distribution density is still a significant challenge. In this research work, we demonstrate how to address this issue by fabricating nanotube arrays by confined electrodeposition on lithographically patterned nanoelectrodes defined through electron beam as well as nanosphere photolithography. This simple technique can lay a strong foundation for the study of novel photovoltaic devices because successful fabrication of these devices will enhance the ability to control structure-property relationships. The nanotube patterns fabricated by this method could produce an equivalent amount of photocurrent density produced by a thin film like device while having less than 10% of semiconducting material coverage. This project also focused on solar fuel generation through photoelectrocatalytic water splitting for which efficient electrocatalysts were developed from non-precious elements. Lastly, a protocol was developed to disperse these electrocatalysts into a butadiene based polymeric catalytic ink and further processing to yield free-standing catalytic film applicable for water electrolysis”--Abstract, page iv

Multidimensional Imaging of Density Driven Convection in a Porous Medium

Carbon dioxide (CO2) sequestration is a climate change mitigation technique which relies on residual and solubility trapping in injection locations with saline aquifers. The dissolution of CO2 into resident brines results in density-driven convection which further enhances the geological trapping potential. We report on the use of an analogue fluid pair to investigate density-driven convection in 3D in an unconsolidated bead pack. X-ray computed tomography (CT) is used to image density-driven convection in the opaque porous medium non-invasively. Two studies have been conducted that differ by the Rayleigh number (Ra) of the system, which in this study is changed by altering the maximum density difference of the fluid pair. We observe the same general mixing pattern in both studies. Initially, many high density fingers move downward through the bead pack and as time progresses these coalesce and form larger dominate flow paths. However, we also observe that a higher Rayleigh number leads to the denser plume moving faster towards the bottom of the system. Due to the finite size of the system, this in turn leads to early convective shut-down

Multidimensional observations of dissolution-driven convection in simple porous media using X-ray CT scanning

We present an experimental study of dissolution-driven convection in a three-dimensional porous medium formed from a dense random packing of glass beads. Measurements are conducted using the model fluid system MEG/water in the regime of Rayleigh numbers, Ra=2000−5000. X-ray computed tomography is applied to image the spatial and temporal evolution of the solute plume non-invasively. The tomograms are used to compute macroscopic quantities including the rate of dissolution and horizontally averaged concentration profiles, and enable the visualisation of the flow patterns that arise upon mixing at a spatial resolution of about (2×2×2)mm3. The latter highlights that under this Ra regime convection becomes truly three-dimensional with the emergence of characteristic patterns that closely resemble the dynamical flow structures produced by high-resolution numerical simulations reported in the literature. We observe that the mixing process evolves systematically through three stages, starting from pure diffusion, followed by convection-dominated and shutdown. A modified diffusion equation is applied to model the convective process with an onset time of convection that compares favourably with the literature data and an effective diffusion coefficient that is almost two orders of magnitude larger than the molecular diffusivity of the solute. The comparison of the experimental observations of convective mixing against their numerical counterparts of the purely diffusive scenario enables the estimation of a non-dimensional convective mass flux in terms of the Sherwood number, Sh=0.025Ra. We observe that the latter scales linearly with Ra, in agreement with both experimental and numerical studies on thermal convection over the same Ra regime

The concurrent association of inflammatory polymyositis and Crohn’s ileo-colitis in a Sri Lankan man: a case report of a rare association and literature review

BACKGROUND: Crohn’s disease is a relapsing, systemic inflammatory disease affecting the gastrointestinal tract with associated extraintestinal manifestations and immune disorders. Among the few cases reported, the association of Crohn’s disease with polymyositis varies in its complexity and severity. We report here the first known case of inflammatory polymyositis leading to rhabdomyolysis in a male patient diagnosed with Crohn’s ileocolitis. CASE PRESENTATION: A 42-year-old previously healthy man presented with acute polymyositis leading to rhabdomyolysis. The acute nature of the illness raised the suspicion of an infective, toxic, or metabolic insult, which was excluded during further investigations. Prolonged low-grade fever and raised inflammatory markers led to the suspicion of inflammatory polymyositis, which was confirmed by electromyography and muscle histology. In the absence of an infective cause, the concurrent association of prolonged diarrhea containing blood and mucous after recovery from an acute phase of myositis proved a diagnostic challenge. Ileocolonoscopy findings of extensive aphthous ulceration with skip lesions extending to the terminal ileum, and histology showing polymorph infiltration of the lamina propria, transmural involvement, and micro abscess formation was suggestive of Crohn’s disease. Sensory motor axonal peripheral neuropathy, which is another rare association of inflammatory bowel disease, was also present. CONCLUSION: An unrecognized genetic predisposition or altered gut permeability causing disruption of the gut immune barrier triggering an immune response against skeletal muscles may have contributed to this unique association. Both polymyositis and Crohn’s ileocolitis responded well to corticosteroids and azathioprine, which is supportive of their immune pathogenesis. Myositis can be considered to be a rare extraintestinal manifestation of Crohn’s disease and can be used in the differential diagnosis of corticosteroid or hypokalemia-induced myopathy in Crohn’s disease

Improvement in Performance of ZnO Based DSC Prepared by Spraying Method

This paper reports the effect of TiCl4 on the performance of ZnO based DSC. ZnO was used due to its stability against photo-corrosion  and  photochemical  properties  similar  to  TiO2.  Thin  films  of  nanocrystalline  ZnO  were  deposited  on transparent conducting oxide glass using spray  method. The ZnO  films  were treated using TiCl4. The cell’s efficiency was found to be 2.5% with TiCl4 post-treatment and 1.9% without TiCl4 post-treatment

Isaacs’ syndrome-possible etiopathogenesis and clinical aspects: a case report

Isaacs’ syndrome (IS) is a rare condition which is characterized by peripheral nerve hyperexcitability which is due to continuous motor activity. The exact etiology for this condition is unknown yet there are several etiopathologies like autoimmune, genetic, or hereditary which can be an etiology for the IS. In our case report the likely etiology is autoimmune. Its clinical feature includes fasciculation, myokymia, and hyperhidrosis. To confirm the diagnosis mostly imaging methods of examination are performed like MRI, ultrasound, and EMG. In our patient MRI and EMG examination was performed. There are no particular therapeutic treatments that can help in this condition only symptomatic treatment can be delivered. Plasma exchange has a promising outcome for a momentary. In our case report, we propose the possible etiology of the condition

Structural identifiability analysis of epidemic models based on differential equations: A Primer

The successful application of epidemic models hinges on our ability to estimate model parameters from limited observations reliably. An often-overlooked step before estimating model parameters consists of ensuring that the model parameters are structurally identifiable from a given dataset. Structural identifiability analysis uncovers any existing parameter correlations that preclude their estimation from the observed variables. Here we review and illustrate methods for structural identifiability analysis based on a differential algebra approach using DAISY and Mathematica (Wolfram Research). We demonstrate this approach through examples of compartmental epidemic models previously employed to study transmission dynamics and control. We show that lack of structural identifiability may be remedied by incorporating additional observations from different model states or fixing some parameters based on existing parameter correlations, or by reducing the number of parameters or state variables involved in the system dynamics. We also underscore how structural identifiability analysis can help improve compartmental diagrams of differential-equation models by indicating the observed variables and the results of the structural identifiability analysis