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61.
Development and Validation of an Artificial Mechanical Skin Model for the Study of Interactions between Skin and Microneedles 下载免费PDF全文
Sahan A. Ranamukhaarachchi Thomas Schneider Sarah Lehnert Lisa Sprenger Jonathon R. Campbell Iman Mansoor Jacqueline C. Y. Lai Kimit Rai Jan Dutz Urs O. Häfeli Boris Stoeber 《大分子材料与工程》2016,301(3):306-314
Microneedles are small needle‐like structures that are almost invisible to the naked eye. They have an immense potential to serve as a valuable tool in many medical applications, such as painless vaccination. Microneedles work by breaking through the stratum corneum, the outermost barrier layer of the skin, and providing a direct path for drug delivery into the skin. A lot of research has been presented over the past two decades on the applications of microneedles, yet the fundamental mechanism of how they interact, pressure, and penetrate the skin in its native state is worth examining further. As such, a major difficulty with understanding the mechanism of microneedle–skin interaction is the lack of an artificial mechanical human skin model to use as a standardized substrate. In this research news, the development of an artificial mechanical skin model based on a thorough mechanical study of fresh human and porcine skin samples is presented. The artificial mechanical skin model can be used to study the mechanical interactions between microneedles and skin, but not diffusion of molecules across skin. This model can assist in improving the performance of microneedles by enhancing the reproducibility of microneedle depth insertions for optimal drug delivery and biosensing.
62.
Sedi Helsper Wesam A. Hatem Lisa Young Zane Wilhelm Matthew W. Liberatore 《Journal of the American Oil Chemists' Society》2022,99(7):613-619
Demand for biodiesel has increased due to being a more environmentally-friendly fuel. Cold weather operation of biodiesel is challenging due to fatty acid methyl ester (FAME) content in biodiesel. Saturated FAMEs crystallize at relatively high temperatures, increase the viscosity of biodiesel, and can clog fuel lines. Here, several factors altered crystallization temperature (CT) of FAMEs, including composition, shear rate, and cooling rate. The crystallization of pure and binary mixtures of methyl palmitate, methyl myristate, and methyl stearate were studied under shear flow and static conditions. Static phase CTs of pure methyl palmitate, methyl myristate, and methyl stearate were 26, 14, and 35°C, respectively. In binary mixtures, CTs were depressed up to 7°C, which agreed with freezing point depression theory. Increasing shear rate up to 100 s−1 decreased CT by 2°C compared to static conditions. Decreasing cooling rate from 1 to 0.1°C/min increased CT less than 2°C. Overall, FAME composition altered CT more than shear flow or cooling rate for pure and binary mixtures of three FAMEs. 相似文献
63.
Sheng Yan Lok Yan Yim Rachel Chun Yee Tam Albert Chan Liwei Lu Chak Sing Lau Vera Sau-Fong Chan 《International journal of molecular sciences》2016,17(8)
Systemic lupus erythematosus (SLE) is a chronic multi-organ autoimmune disease characterized by hyperactivated immune responses to self-antigens and persistent systemic inflammation. Previously, we reported abnormalities in circulating and bone marrow (BM)-derived plasmacytoid dendritic cells (pDCs) from SLE patients. Here, we aim to seek for potential regulators that mediate functional aberrations of pDCs in SLE. BM-derived pDCs from NZB/W F1 mice before and after the disease onset were compared for toll-like receptor (TLR) induced responses and microRNA profile changes. While pDCs derived from symptomatic mice were phenotypically comparable to pre-symptomatic ones, functionally they exhibited hypersensitivity to TLR7 but not TLR9 stimulation, as represented by the elevated upregulation of CD40, CD86 and MHC class II molecules upon R837 stimulation. Upregulated induction of miR-155 in symptomatic pDCs following TLR7 stimulation was observed. Transfection of miR-155 mimics in pre-symptomatic pDCs induced an augmented expression of Cd40, which is consistent with the increased CD40 expression in symptomatic pDCs. Overall, our results provide evidence for miR-155-mediated regulation in pDC functional abnormalities in SLE. Findings from this study contribute to a better understanding of SLE pathogenesis and ignite future interests in evaluating the molecular regulation in autoimmunity. 相似文献
64.
Chalco Vera Jorge Portocarrero Rocio Piñeiro Gervasio Acreche Martín M. 《Nutrient Cycling in Agroecosystems》2022,122(1):41-57
Nutrient Cycling in Agroecosystems - Nitrogen (N) fertilization strategies focused on increasing nitrogen use efficiency (NUE) and decreasing nitrous oxide (N2O) emissions are important for... 相似文献
65.
Synthesis and antiproliferative activity of some ellipticine-like 11H-pyrido[a]carbazole derivatives
Some modified 11H-pyrido[a]carbazoles (11H-PyC) and their corresponding tetrahydro derivatives (11H-THPyC) were prepared. A common multistep pathway characterized by conventional reactions, including a Fischer-indole-type synthesis, yielded the tetracyclic compounds. To improve cytotoxicity, 11H-PyC and 11H-THPyC derivatives were endowed with a diethylaminoethyl side chain. The antiproliferative activity was assessed in three human tumor cell lines, and a number of derivatives showed a cytotoxic effect in agreement with their capacity to form a molecular intercalative complex with DNA and to interfere with the relaxation activity of DNA topoisomerase II. In contrast, three derivatives that exhibited significant antiproliferative efficacy, showed no inhibition of topoisomerase II, thus suggesting an unexpected and novel mode of action for these ellipticine-like compounds independent of topoisomerase II activity. 相似文献
66.
67.
Mirna E. Sigrist Horacio R. Beldomenico Enrique E. Tarifa Carlos L. Pieck Carlos R. Vera 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(10):1256-1264
BACKGROUND: Arsenic decontamination of drinking water by adsorption is a simple and robust operation. When designing packed bed adsorbers for arsenic, the main problems are the slow diffusion kinetics of As in microporous media and the lack of simple equations for predicting the performance of the equipment. Commercial iron‐doped granular activated carbon adsorbents (Fe/GAC) for groundwater arsenic abatement were studied in this work. Basic parameters for arsenate (AsV) adsorption were measured and their performance at larger scale was simulated with an approximate analytical model. RESULTS: In the 0–300 µgAs L?1 range, the AsV adsorption isotherm on Fe/GAC was found to be approximately linear. Assuming Henry's law for adsorption and homogeneous surface diffusion with constant diffusivity for intrapellet mass transfer, an approximate model for flow and adsorption of arsenate inside packed bed adsorbers was developed, and reduced to an analytic compact solution using the quasi‐lognormal distribution (Q‐LND) approximation. The use of this model with fitted and reported parameters enabled the approximate simulation of industrial adsorbers and home point‐of‐use filters. Results show that industrial adsorbers meet the breakthrough condition with incomplete utilization of the adsorbent unless convenient process configurations are used. In point‐of‐use systems with short residence times intraparticle diffusion would drastically reduce the adsorbent performance. CONCLUSION: Assuming linear adsorption of AsV over Fe/GAC, an analytical approximate solution for flow and adsorption in packed beds can be obtained. The model seems to represent correctly the main features of industrial and home filters, however, more experimental data is necessary for scale‐up purposes. Copyright © 2011 Society of Chemical Industry 相似文献
68.
Spherical and tube‐like (TL) silica nanoparticles were melt blended with an isotactic polypropylene (PP) matrix and its effect on the isothermal spherulite growth rate was analyzed by polarized optical microscope. The addition of low amount (≈1 wt.‐%) of either 15 nm spherical or TL particles raises the spherulite growth rate and the nucleation density of spherulites. Samples prepared with silica spheres of 80 nm otherwise do not show any change in the crystallization behavior. By adding a compatibilizer, both the nucleation density and the spherulite growth rate of the pure polymer are increased. Noteworthy, although the nanoparticles do not further increase the nucleation density of the PP/compatibilizer blend, independent of its form and size, they cause a decrease in its spherulite growth rate.
69.
Zlata Hrnjak‐Murgi
elimir Jel
i Vera Kova
evi Marica Mlinac‐Miak Jasenka Jelen
i 《大分子材料与工程》2002,287(10):684-692
The compatibilizing effect of nano sized calcium carbonate filler on immiscible blends of styrene‐co‐acrylonitrile/ethylene propylene diene (SAN/EPDM) was examined. The surface energy of the calcium carbonate was modified by stearic acid. The compatibility of SAN/EPDM blends was studied by following the glass transition temperature Tg by DSC. SEM was used to observe the blend morphology and the X‐ray analyzer was used to detect the calcium from filler in samples. Mechanical properties of the blends were determined, and related to changes of polymer‐filler interactions and morphology. The results suggest that the morphology of the SAN/EPDM blends studied was affected by the reduction of surface energy of the filler.
70.
Carlos R. Vera Carlos L. Pieck Kiyoyuki Shimizu Jos M. Parera 《Applied Catalysis A: General》2002,230(1-2):137-151
An assessment of the influence of the crystal structure, surface hydroxylation state and previous oxidation/reduction pretreatments on the activity of sulfate-zirconia catalysts for isomerization of n-butane was performed using crystalline and amorphous zirconia supports. Different sulfation methods were used for the preparation of bulk and supported SO42−-ZrO2 with monoclinic, tetragonal and tetragonal+monoclinic structures. Activity was important only for the samples that contained tetragonal crystals. The catalysts prepared from pure monoclinic zirconia showed negligible activity. SO42−-ZrO2 catalysts prepared by sulfation of crystalline zirconia displayed sites with lower acidity and cracking activity than those sulfated in the amorphous state. Prereduction of the zirconia samples with H2 was found to greatly increase the catalytic activity, and a maximum rate was found at a reduction temperature of 550–600 °C, coinciding with a TPR peak supposedly associated with the removal of lattice oxygen and the creation of lattice defects. A weaker dependence of catalytic activity on the density or type of surface OH groups on zirconia (before sulfation) was found in this work.
A model of active site generation was constructed in order to stress the dependence on the crystal structure and crystal defects. Current and previous results suggest that tetragonal structure in active SO42−-ZrO2 is a consequence of the stabilization of anionic vacancies in zirconia. Anionic vacancies are in turn supposed to be related to the catalytic activity for n-butane isomerization through the stabilization of electrons from ionized intermediates. 相似文献