919 research outputs found
MSC-derived exosomes inhibit proliferation and migration of SVEC cells <i>in vitro</i>.
No full text<p>(A) 2.0×10<sup>3</sup> SVEC cells were incubated with the conditioned media from 4T1 cells that were treated with various concentrations of MSC-derived exosomes or carrier control (PBS). Cell proliferation rates were determined by an EZ-Cytox cell viability assay kit. (B) SVEC cells transwell migration assay was performed in the presence of the conditioned media from 4T1 cells that were treated with various concentrations of MSC-derived exosomes or carrier control (PBS) in the lower chambers. Serum-starved SVEC cells were added to the upper chamber and incubated for 24 h to allow cell migration through the membrane. The membranes were stained with crystal violet and cell migration was analyzed by Image J. (C) SVEC cells were scratched and incubated with the conditioned media from 4T1 cells stimulated with MSC-derived exosomes (100 μg/ml) or vehicle control (PBS) for 24 h. In order to neutralize VEGF derived from 4T1 cells, anti-VEGF antibodies (20 μg/ml) were added to the conditioned media. Photographs were taken immediately and 24 h after wounding (data not shown) and analyzed by Studio Lite, version 1.0. (D) SVEC cells were serum-starved for 24 h and 2×10<sup>4</sup> SVEC cells were seeded in a Matrigel-coated well. The cells were treated with conditioned media collected from 4T1 cells stimulated with MSC-derived exosomes (100 μg/ml) or carrier control (PBS) for 24 h and viewed under a microscope. The values are presented as the mean ± SD; n = 3 for each group. Significant differences were evaluated using an unpaired two-tailed Student's t-test. *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001 compared with control.</p
Manipulated wettability of a superhydrophobic quartz crystal microbalance through electrowetting
No full textThe liquid phase response of quartz crystal microbalances (QCM) with a thin coating (~9 µm) of epoxy resin with and without a carbon nanoparticles top layer is reported. The nanoparticles convert the epoxy surface to a superhydrophobic one with a high static contact angle (~151º-155º) and low contact angle hysteresis (~1º-3.7º) where droplets of water are in the suspended Cassie-Baxter state. The frequency decrease of the fully immersed QCM with the superhydrophobic surface is less than with only epoxy layer, thus indicating a decoupling of the QCM response. A wettability transition to a liquid penetrating into the surface roughness state (for droplets a high contact angle hysteresis Wenzel state) was triggered using a molarity of ethanol droplet test (MED) and electrowetting; the MED approach caused some surface damage. The electrowetting induced transition caused a frequency decrease of 739 Hz at a critical voltage of ~100 V compared to the QCM in air. This critical voltage correlates to a contact angle decrease of 26º and a high contact angle hysteresis state in droplet experiments. These experiments provide a proof-of-concept that QCMs can be used to sense wetting state transitions and not only mass attachments or changes in viscosity-density products of liquids
Hydrogen production through water splitting at low temperature over Fe3O4 pellet: Effects of electric power, magnetic field, and temperature
No full textThis paper aims to propose an innovative breakthrough methodology for hydrogen production through water splitting over Fe3O4 pellet at low temperature (T = 250 °C; 290 °C; 310 °C). In order to achieve this goal, the effects of magnetic field (B = 0 mT; 25.4 mT; 35.1 mT; 48.3 mT) and of electric power (P = 5 W; 12 W; 20 W) on reactive medium performance were investigated. Results show that production of hydrogen was mainly influenced by electric power applied and magnetic field, since the higher the magnetic field and the electric power the higher the production of hydrogen, while the temperature showed a secondary effect; however, feasible production of hydrogen was achieved at a temperature close to 300 °C
Andrew Curran : Sublime disorder. Physical monstrosity in Diderot's universe. (SVEC 2001 : 01)
No full textBarroux Gilles. Andrew Curran : Sublime disorder. Physical monstrosity in Diderot's universe. (SVEC 2001 : 01). In: Dix-huitième Siècle, n°34, 2002. Christianisme et Lumières, sous la direction de Sylviane Albertan-Coppola et Antony McKenna. p. 668
Shear stress diminishes ACE expression and signaling in Human Safenous Vein Endothelial Cells (SVEC).
No full text<p>(A) ACE protein expression downregulation, (B) ACE phosphorylation on Ser<sup>1270</sup>, and (C) p-JNK in response to laminar shear stress. SVEC were exposed to 18 h of laminar shear stress (15 dyne/cm<sup>2</sup>; SS 18 h). Each bar represents mean ± SEM of 5 separate experiments. *p<0.05 vs static control (CTRL).</p
Analytical Model of Enhanced H2 Production from Water Vapor in Bulk Iron Oxide Pellets Using Lorentz Forces
No full textThe analytical model of the effect of Lorentz forces on enhancing, by 2 orders of magnitude, hydrogen production from water molecules in bulk iron oxide pellets is studied in this paper. This model is verified by experimental data. Dropping water molecules on the surface of an iron oxide pellet results in releasing oxygen ions, due to the existing dangling bonds at relatively elevated temperatures. These ions can be directed from the surface inward, toward the bulk of the iron oxide, due to Lorentz forces perpendicular to the surface of the magnetic pellet, thus permitting new oxygen ions to be released from water molecules. These Lorentz forces are generated by the interaction between an in-plane magnetic induction of proper orientation and an in-plane applied electric field. The oxygen ion mobilization is enabled due to the substantial amount of oxygen vacancies in the bulk of the iron oxide and is being analytically modeled as a drift-diffusion mechanism, dominated by a Lorentz force-driven drift. This process remains active as long as the paths of oxygen ion mobilization toward the inner part of the iron oxide pellet are active. The same effect should also occur in other nonstoichiometric metal oxides, provided that proper Lorentz forces are applied on the corresponding oxygen ion carriers
Boosting Techniques for Nonlinear Time Series Models
No full textMany of the popular nonlinear time series models require a priori the choice of parametric functions which are assumed to be appropriate in specific applications. This approach is used mainly in financial applications, when sufficient knowledge is available about the nonlinear structure between the covariates and the response. One principal strategy to investigate a broader class on nonlinear time series is the Nonlinear Additive AutoRegressive (NAAR) model. The NAAR model estimates the lags of a time series as flexible functions in order to detect non-monotone relationships between current observations and past values.
We consider linear and additive models for identifying nonlinear relationships. A componentwise boosting algorithm is applied to simultaneous model fitting, variable selection, and model choice. Thus, with the application of boosting for fitting potentially nonlinear models we address the major issues in time series modelling: lag selection and nonlinearity. By means of simulation we compare the outcomes of boosting to the outcomes obtained through alternative nonparametric methods. Boosting shows an overall strong performance in terms of precise estimations of highly nonlinear lag functions. The forecasting potential of boosting is examined on real data where the target variable is the German industrial
production (IP). In order to improve the model's forecasting
quality we include additional exogenous variables. Thus we address the second major aspect in this paper which concerns the issue of high-dimensionality in models. Allowing additional inputs in the model extends the NAAR model to an even broader class of models, namely the NAARX model. We show that boosting can cope with large models which have many covariates compared to the number of observations
Development of imidazotetrazines for the treatment of glioblastoma & as synthetic precursors to diazo species
No full textGlioblastoma multiforme (GBM), a grade IV astrocytoma, is the most prevalent, aggressive, and deadly form of malignant brain tumor with only 10% of patients surviving five years. The current standard treatment for GBM patients is bulk surgical resection and radiotherapy with concomitant and adjuvant temozolomide (TMZ), a small molecule DNA alkylating agent. The antitumor effect of TMZ is ultimately mediated through methylation of the O6-position of guanine and subsequent mismatch repair (MMR)-dependent cell death. Although TMZ was first synthesized in 1984 and has been FDA approved for two decades, certain key derivatives have been inaccessible due to synthetic challenges, precluding a broad exploration of the link between imidazotetrazine structure and biological activity. Novel synthetic strategies provided access to several new classes of C8-substituted imidazotetrazines and an evaluation of their aqueous stabilities enabled the derivation of a predictive model for imidazotetrazine hydrolytic stability based on the Hammett constant of the C8 substituent. Promising compounds modified at the C8 position were identified and found to have appropriate hydrolytic stability, enhanced blood-brain barrier permeability, lower hematological toxicity profiles, and superior activity relative to TMZ in a mouse model of GBM.
Despite its widespread use, certain GBM patient populations do not respond to TMZ therapy. Expression of O6-methylguanine DNA methyltransferase (MGMT) and loss of MMR function are the primary clinical modes of resistance to TMZ. Imidazotetrazine analogs modified at the N3 position were designed to deliver alternative DNA adducts that were irremovable by MGMT. An analog bearing a propargyl group at N3 demonstrated MGMT-independent activity in GBM cells in culture. Tuning the stability with an electron-donating chloro substituent at the C8 position produced novel dual-substituted imidazotetrazine CPZ, which displayed anticancer activity irrespective of MGMT expression and MMR status.
Imidazotetrazines such as TMZ are precursors to alkyl diazoniums, used therapeutically to alkylate DNA and elicit an anticancer effect. Given their stability as prodrugs and the reactivity of the species released, imidazotetrazines were repurposed into synthetic surrogates for diazomethane and other diazoalkanes. TMZ was employed to conduct esterifications and metal-catalyzed cyclopropanations, with methyl ester formation from a wide variety of substrates proving efficient and operationally simple. As a commercially available solid that is non-explosive and non-toxic, TMZ should find broad utility as a synthetic replacement for diazomethane.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01The student, Riley Svec, accepted the attached license on 2020-04-14 at 17:59.The student, Riley Svec, submitted this Dissertation for approval on 2020-04-14 at 18:07.This Dissertation was approved for publication on 2020-04-16 at 13:46.DSpace SAF Submission Ingestion Package generated from Vireo submission #14980 on 2020-08-25 at 17:40:15Made available in DSpace on 2020-08-27T00:49:56Z (GMT). No. of bitstreams: 3
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