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61.
Michelle Chan Alexandra Capek Daniel A. Brill Simon J. Garrett 《Surface and interface analysis : SIA》2014,46(7):433-441
The dark gray corrosion layer (patina) formed on the surface of a polished low tin bronze alloy following exposure to a deoxygenated and saturated aqueous solutions of H2S has been characterized by X‐ray photoelectron spectroscopy, scanning electron microscopy‐energy dispersive spectroscopy and X‐ray diffraction. The system represents a model for bronze corrosion in reducing conditions where sulfate‐reducing bacteria in soils or deoxygenated seawater may generate H2S during respiration. The initial surface was dominated by metallic copper together with Sn, Pb and Zn oxides and hydroxides. Surface enrichment of Pb and Zn was noted because of a smearing effect during polishing. At least some of the lead was crystalline. In contrast, the corrosion layer formed by H2S(aq) exposure was dominated by polycrystalline Cu2S (low and high chalcocite) and smaller concentrations of CuSO4 · nH2O. This surface was enriched with Zn as Zn(OH)2. Lead was present as redeposited PbS (galena) crystallites in at least two different morphologies. Unlike bronzes exposed to oxidizing conditions, which develop protective SnO2 layers, the H2S(aq)‐exposed surface was considerably depleted in Sn. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
62.
63.
Agus R. Poerwoprajitno Dr. Lucy Gloag Dr. John Watt Steffen Cychy Dr. Soshan Cheong Dr. Priyank V. Kumar Dr. Tania M. Benedetti Chen Deng Dr. Kuang-Hsu Wu Dr. Christopher E. Marjo Dr. Dale L. Huber Dr. Martin Muhler Prof. Dr. J. Justin Gooding Prof. Dr. Wolfgang Schuhmann Prof. Dr. Da-Wei Wang Prof. Dr. Richard D. Tilley 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15615-15620
64.
Michelle P. van der Helm Chang-Lin Wang Bowen Fan Mariano Macchione Eduardo Mendes Rienk Eelkema 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20785-20792
Signal transduction in living systems is the conversion of information into a chemical change, and is the principal process by which cells communicate. In nature, these functions are encoded in non-equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. However, man-made catalytically controlled networks are rare. We incorporated catalysis into an artificial fuel-driven out-of-equilibrium CRN, where the forward (ester formation) and backward (ester hydrolysis) reactions are controlled by varying the ratio of two organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. This fuel-driven strategy was expanded to a responsive polymer system, where transient polymer conformation and aggregation are controlled through fuel and catalyst levels. Altogether, we show that organocatalysis can be used to control a man-made fuel-driven system and induce a change in a macromolecular superstructure, as in natural non-equilibrium systems. 相似文献
65.
Víctor Sánchez Marlon Rodrigues Garcia Michelle Barreto Requena Renan Arnon Romano Leonardo de Boni Francisco E. G. Guimarães Sebastião Pratavieira 《Photochemistry and photobiology》2020,96(6):1208-1214
Photodynamic procedures have been used in many applications, ranging from cancer treatment to microorganism inactivation. Photodynamic reactions start with the activation of a photosensitizing molecule with light, leading to the production of cytotoxic molecules that promote cell death. However, establishing the correct light and photosensitizer dosimetry for a broadband light source remains challenging. In this study, we proposed a theoretical mathematical model for the photodegradation of protoporphyrin IX (PpIX), when irradiated by multi-wavelength light sources. The theoretical model predicts the experimental photobleaching (temporal change in PpIX concentration) of PpIX for different light sources. We showed that photobleaching occurs independently of the light source wavelengths but instead depends only on the number of absorbed photons. The model presented here can be used as an important mathematical approach to better understand current photodynamic therapy protocols and help achieve optimization of the doses delivered. 相似文献
66.
Dr. Abshar Hasan Dr. Kyueui Lee Dr. Kunal Tewari Prof. Lalit M. Pandey Prof. Phillip B. Messersmith Prof. Karen Faulds Dr. Michelle Maclean Dr. King Hang Aaron Lau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5789-5793
Microbial surface attachment negatively impacts a wide range of devices from water purification membranes to biomedical implants. Mimics of antimicrobial peptides (AMPs) constituted from poly(N-substituted glycine) „peptoids“ are of great interest as they resist proteolysis and can inhibit a wide spectrum of microbes. We investigate how terminal modification of a peptoid AMP-mimic and its surface immobilization affect antimicrobial activity. We also demonstrate a convenient surface modification strategy for enabling alkyne–azide „click“ coupling on amino-functionalized surfaces. Our results verified that the N- and C-terminal peptoid structures are not required for antimicrobial activity. Moreover, our peptoid immobilization density and choice of PEG tether resulted in a „volumetric“ spatial separation between AMPs that, compared to past studies, enabled the highest AMP surface activity relative to bacterial attachment. Our analysis suggests the importance of spatial flexibility for membrane activity and that AMP separation may be a controlling parameter for optimizing surface anti-biofouling. 相似文献
67.
Wenhan Xu Michelle M. S. Lee Jing‐Jun Nie Zhihan Zhang Ryan T. K. Kwok Jacky W. Y. Lam Fu‐Jian Xu Dong Wang Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2020,59(24):9610-9616
Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation‐induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far‐red/near‐infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three‐pronged PDT. 相似文献
68.
Ana Ediléia Barbosa Pereira Leal Ana Paula de Oliveira Raira Feitosa dos Santos Juliana Mikaelly Dias Soares Erica Martins de Lavor Michelle Cruz Pontes 《Natural product research》2020,34(7):995-1001
AbstractEthanol extracts of different parts of Passiflora cincinnata were obtained by maceration. The total phenolic and flavonoid contents were evaluated. The antioxidant activities were determined by β-carotene-linoleic acid bleaching test, 2,2-diphenyl-1-picrylhydrazil (DPPH), and 2,2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging. The crude ethanol stem extract showed the highest amount of total polyphenols (45.53?mg gallic acid equivalent/g) while the highest total flavonoid contents (1.42?mg of quercetin equivalent/g) were observed in the leaf extract. The lowest IC50 (25.65?μg/ml) by the DPPH method was observed for the stem extract. The ABTS method showed a significant antioxidant activity for all investigated extracts. The secondary metabolite composition of ethanol extracts was assessed by HPLC-DAD-MS/MS analysis, leading to the identification of fourteen secondary metabolites in P. cincinnata extracts. These results showed the potentiality of this species as a source of phenolic compounds and antioxidants. 相似文献
69.
Samuel W. Foster Xiaofeng Xie Michelle Pham Paul A. Peaden Leena M. Patil Luke T. Tolley Paul B. Farnsworth H. Dennis Tolley Milton L. Lee James P. Grinias 《Journal of separation science》2020,43(9-10):1623-1627
A newly developed portable capillary liquid chromatograph was investigated for the separation of various pharmaceutical and illicit drug compounds. The system consists of two high‐pressure syringe pumps capable of delivering capillary‐scale flow rates at pressures up to 10 000 psi. Capillary liquid chromatography columns packed with sub‐2 μm particles are housed in cartridges that can be inserted into the system and easily connected through high‐pressure fluidic contact points by simply applying a specific, predetermined torque rather than using standard fittings and less precise sealing protocols. Several over‐the‐counter analgesic drug separations are demonstrated, along with a simple online measurement of tablet dissolution. Twenty illicit drug compounds were also separated across six targeted drug panels. The results described in this study demonstrate the capability of this compact liquid chromatography instrument to address several important drug‐related applications while simplifying system operation, and greatly reducing solvent usage and waste generation essential for onsite analysis. 相似文献
70.
Let W be a potential on R 2 which is equivariant by the symmetry group of the equilateral triangle and has three minima. We show that the elliptic system possesses a nontrivial smooth solution U : R 2 → R 2. Here DW(U)T is the transpose of the derivative DW( U ). The natural energy of the problem is unbounded and compactness techniques cannot be applied. The proof depends on careful energy estimates and asymptotics for several one-dimensional problems and for two-dimensional problems on bounded domains. © 1996 John Wiley & Sons, Inc. 相似文献