891 research outputs found
Analysing the bioactive makeup of demineralised dentine matrix on bone marrow mesenchymal stem cells for enhanced bone repair
Dentine matrix has proposed roles for directing mineralised tissue repair in dentine and bone; however,
the range of bioactive components in dentine and specific biological effects on bone-derived mesenchymal
stem cells (MSCs) in humans are less well understood. The aims of this study were to further elucidate the
biological response of MSCs to demineralised dentine matrix (DDM) in enhancing wound repair responses
and ascertain key contributing components. Dentine was obtained from human teeth and DDM proteins
solubilised with ethylenediaminetetraacetic acid (EDTA). Bone marrow derived MSCs were commercially
obtained. Cells with a more immature phenotype were then selected by preferential fibronectin adhesion
(FN-BMMSCs) for use in subsequent in vitro assays. DDM at 10 μg/mL reduced cell expansion, attenuated
apoptosis and was the minimal concentration capable of inducing osteoblastic differentiation. Enzyme-linked
immunosorbent assay (ELISA) quantification of growth factors indicated physiological levels produced the
above responses; transforming growth factor β (TGF-β1) was predominant (15.6 ng/mg DDM), with relatively
lower concentrations of BMP-2, FGF, VEGF and PDGF (6.2-4.7 ng/mg DDM). Fractionation of growth factors
from other DDM components by heparin affinity chromatography diminished osteogenic responses. Depletion
of biglycan from DDM also attenuated osteogenic potency, which was partially rescued by the isolated
biglycan. Decorin depletion from DDM had no influence on osteogenic potency. Collectively, these results
demonstrate the potential of DDM for the delivery of physiological levels of growth factors for bone repair
processes, and substantiate a role for biglycan as an additional adjuvant for driving osteogenic pathways
The COVID-19 pandemic and children’s engagement with learning in rural Sierra Leone
The COVID-19 pandemic caused worldwide educational disruption. This paper addresses a gap in the literature relating to the impact of the pandemic on learning experiences of children in rural communities in the Global South, particularly in earlier years of schooling. Children in these communities are at considerable disadvantage in comparison to their urban peers due to poor school infrastructure and challenges in recruitment and retention of teachers. Drawing on a mixed-methods study of primary school children, their teachers and families in rural Sierra Leone, both during and immediately after school closures, the paper highlights how primary schools and their communities responded to the pandemic and how this influenced children’s engagement with their learning. While national planning focused on pandemic control measures and provision of some remote learning support, findings highlight challenges for poor rural communities in accessing basic learning supports and the consequent disruption to children’s education
Probabilistic Models to Describe the Dynamics of Migrating Microbial Communities
In all but the most sterile environments bacteria will reside in fluid being transported through conduits and some of these will attach and grow as biofilms on the conduit walls. The concentration and diversity of bacteria in the fluid at the point of delivery will be a mix of those when it entered the conduit and those that have become entrained into the flow due to seeding from biofilms. Examples include fluids through conduits such as drinking water pipe networks, endotracheal tubes, catheters and ventilation systems. Here we present two probabilistic models to describe changes in the composition of bulk fluid microbial communities as they are transported through a conduit whilst exposed to biofilm communities. The first (discrete) model simulates absolute numbers of individual cells, whereas the other (continuous) model simulates the relative abundance of taxa in the bulk fluid. The discrete model is founded on a birth-death process whereby the community changes one individual at a time and the numbers of cells in the system can vary. The continuous model is a stochastic differential equation derived from the discrete model and can also accommodate changes in the carrying capacity of the bulk fluid. These models provide a novel Lagrangian framework to investigate and predict the dynamics of migrating microbial communities. In this paper we compare the two models, discuss their merits, possible applications and present simulation results in the context of drinking water distribution systems. Our results provide novel insight into the effects of stochastic dynamics on the composition of non-stationary microbial communities that are exposed to biofilms and provides a new avenue for modelling microbial dynamics in systems where fluids are being transported
P19-45. Development of a therapeutic HIV vaccine comprised of autologous dendritic cells loaded with a mixture of lipopeptide HIV antigens
Impact of hiatal hernia on histological pattern of non-erosive reflux disease
BACKGROUND: Hiatus hernia (HH) has major pathophysiological effects favoring gastroesophageal reflux and hence contributing to esophageal mucosa injury, especially in patients with severe gastroesophageal disease. However, prospective studies investigating the impact of HH on the esophageal mucosa in non-erosive reflux disease (NERD) are lacking. This study evaluated the association between the presence of (HH) and the histological findings in symptomatic patients with NERD. METHODS: Fifty consecutive patients with gastroesophageal reflux disease (GERD) were enrolled. After conventional endoscopy, Lugol solution was applied and biopsy specimens were obtained. Histological parameters including basal zone hyperplasia, papillary length and cellular infiltration were evaluated. The chi-square test with Yates' correlation was used for comparing discrete parameters between groups. However, Fisher's exact probability test was used where the expected frequencies were lower than 5. Wilcoxon's test for unpaired samples was preferred in cases of semi-quantitative parameters. RESULTS: The presence of HH along with more severe findings (0.01 <P < 0.05) was confirmed in 18 patients. NERD was observed in 29 (58%) patients. Basal zone hyperplasia and loss of glycogen accompanied HH in all cases, and the correlation was significant in NERD (P < 0.001). The remaining histological patterns were similar between erosive reflux disease and NERD in the presence of HH. CONCLUSION: The presence of HH is correlated with more severe endoscopy findings, and predisposes for severe histological abnormality in cases of NERD
Electronic Structure Control of Sub-nanometer 1D SnTe via Nanostructuring within Single-Walled Carbon Nanotubes
Nanostructuring, e.g., reduction of dimensionality in materials, offers a viable route toward regulation of materials electronic and hence functional properties. Here, we present the extreme case of nanostructuring, exploiting the capillarity of single-walled carbon nanotubes (SWCNTs) for the synthesis of the smallest possible SnTe nanowires with cross sections as thin as a single atom column. We demonstrate that by choosing the appropriate diameter of a template SWCNT, we can manipulate the structure of the quasi-one-dimensional (1D) SnTe to design electronic behavior. From first principles, we predict the structural re-formations that SnTe undergoes in varying encapsulations and confront the prediction with TEM imagery. To further illustrate the control of physical properties by nanostructuring, we study the evolution of transport properties in a homologous series of models of synthesized and isolated SnTe nanowires varying only in morphology and atomic layer thickness. This extreme scaling is predicted to significantly enhance thermoelectric performance of SnTe, offering a prospect for further experimental studies and future applications
On multicasting nested message sets over combination networks
In this paper, we study delivery of two nested message sets over combination networks with an arbitrary number of receivers, where a subset of receivers (public receivers) demand only the lower priority message and a subset of receivers (private receivers) demand both the lower and the higher priority messages. We give a complete rate region characterization over combination networks with three public and many private receivers, where achievability is through linear coding. Our encoding scheme is general and characterizes an achievable region for arbitrary number of public and private receivers
Active site isolation in bismuth-poisoned Pd/SiOâ‚‚ catalysts for selective hydrogenation of furfural
Active site isolation in furfural (FA) hydrogenation was studied by poisoning a Pd catalyst with bismuth. A solution of FA in water was hydrogenated over a 5 wt% Pd/SiO₂ catalyst in a batch reactor at various reaction temperatures and pressures. Furfuryl alcohol (FAL) was an intermediate product which was further hydrogenated into tetrahydrofurfuryl alcohol (TFAL) or cyclopentanone (CPA) and cyclopentanol (CPOL). While application of hydrogen pressure above 30 bar had little effect on the hydrogenation kinetics, a reaction temperature affected product distribution and the main product changed from TFAL (at 50 °C) to FAL (100 and 150 °C). Poisoning the catalyst with Bi decreased the number of available active sites but had little effect on the turn-over frequencies, most likely because of the absence of electronic effects of Bi on Pd nanoparticles. The main reaction product over the Bi-poisoned catalyst was FAL with no FA oligomerisation products. At a reaction temperature of 150 °C, CPA was formed with a 57% yield. Considering that Bi preferentially poisons step sites of Pd, the comparison of the product distribution between the Pd and Pd-Bi catalyst as well as the literature data for the alloy Pd-Cu catalysts indicates that the active site isolation observed in the Pd-Bi catalysts is responsible for the increasing FAL and CPA selectivities and elimination of oligomer by-products
Linear and Helical Cesium Iodide Atomic Chains in Ultranarrow Single-Walled Carbon Nanotubes: Impact on Optical Properties
One-dimensional (1D) atomic chains of CsI were previously reported in double-walled carbon nanotubes with ∼0.8 nm inner diameter. Here, we demonstrate that, while 1D CsI chains form within narrow ∼0.73 nm diameter single-walled carbon nanotubes (SWCNTs), wider SWCNT tubules (∼0.8–1.1 nm) promote the formation of helical chains of CsI 2 × 1 atoms in cross-section. These CsI helices create complementary oval distortions in encapsulating SWCNTs with highly strained helices formed from strained Cs2I2 parallelogram units in narrow tubes to lower strain Cs2I2 units in wider tubes. The observed structural changes and charge distribution were analyzed by density-functional theory and Bader analysis. CsI chains also produce conformation-selective changes to the electronic structure and optical properties of the encapsulating tubules. The observed defects are an interesting variation from defects commonly observed in alkali halides as these are normally associated with the Schottky and Frenkel type. The energetics of CsI 2 × 1 helix formation in SWCNTs suggests how these could be controllably formed
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