排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
Keller A Fritzsche M Ogaki R Bald I Facsko S Dong M Kingshott P Besenbacher F 《The Journal of chemical physics》2011,134(10):104705
The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K(+) ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle >80° is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity. 相似文献
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Bald I Dabkowska I Illenberger E Ingólfsson O 《Physical chemistry chemical physics : PCCP》2007,9(23):2983-2990
Low energy electron attachment (DEA) to hexafluoroacetone azine (HFAA) leads to a remarkable energy selective excision of CN(-) within a pronounced resonance located at 1.35 eV. The underlying dissociative electron attachment (DEA) reaction involves multiple bond cleavages and rearrangement within the neutral products. A series of further fragment ions (F(-), CF(3)(-), (CF(3))(2)C(-) and (CF(3))(2)CN(-)) are observed from resonant features above 2 eV and only (CF(3))(2)CN(-) is additionally formed within a narrow resonance below 1 eV. In contrast to CN(-) all the remaining fragment ions can be formed by simple bond cleavages with (CF(3))(2)CN(-) being the result of a symmetric decomposition of the target molecule by cleavage of the (N-N) bond with the excess charge localised on either of the identical fragments. Our ab initio calculations predict an adiabatic electron affinity of HFAA close to 2 eV with the geometry of the relaxed anion considerably distorted with respect to that of the neutral molecule. 相似文献
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Bald I Deng Z Illenberger E Huels MA 《Physical chemistry chemical physics : PCCP》2006,8(10):1215-1222
We report that 10-100 eV Ar+ ion irradiation induces severe damage to the biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose in the condensed phase on a polycrystalline Pt substrate. Ar+ ions with kinetic energies down to 15 eV induce effective decomposition of both sugar molecules, leading to the desorption of abundant cation and anion fragments, including CH3+, C2H3+, C3H3+, H3O+, CHO+, CH3O+, C2H3O+, H-, O-, and OH-, etc. Use of isotopically labelled molecules (5- 13C D-ribose and 1-D D-ribose) reveals the site specificity for some of the fragment origins, and thus the nature of the chemical bond breaking. It is found that all of the chemical bonds in both molecules are vulnerable to ion impact at energies down to 15 eV, particularly both the endo- and exocyclic C-O bonds. In addition to molecular fragmentation, several chemical reactions are also observed. A small amount of O-/O fragments abstract hydrogen to form OH-. It is found that the formation of the H3O+ ion is related to the hydroxyl groups of the sugar molecules, and is associated with additional hydrogen loss from the parent or adjacent molecules via hydrogen abstraction or proton transfer. The formation of several other cation fragments also requires hydrogen abstraction from its parent or an adjacent molecule. These fragmentations and reactions are likely to occur in a real biomedium during ionizing radiation treatment of tumors and thus bear significant radiobiological relevance. 相似文献
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We have observed reactive scattering damage to fundamental DNA building blocks by the type of hyperthermal secondary ions that are produced along heavy ion tracks in biological media. Reactions include carbon abstraction by N+, and hydrogen abstraction by O- and N+, at collision energies down to 1 eV. Our results show that localized reactive scattering by hyperthermal secondary fragments can lead to important physicochemical damage to DNA in cells irradiated by heavy ions. This suggests a fundamentally different picture of nascent DNA damage induced by heavy ion tracks, compared to conventional (x or gamma) radiation tracks. 相似文献
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Vrankić Ilko Herceg Tomislav Pejić Bach Mirjana 《Central European Journal of Operations Research》2021,29(3):1001-1019
Central European Journal of Operations Research - In this paper, we analyse the company behaviour in duopoly taking into account the most common strategies, including dominant, reactive,... 相似文献
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Marekov Ilko Tarandjiiska Roumyana Panayotova Svetlana Nikolova Nelly 《平面色谱法杂志一现代薄层色谱法》2001,14(5):384-390
JPC – Journal of Planar Chromatography – Modern TLC - A stand-alone argentation TLC (Ag-TLC) procedure has been established for rapid estimation of the authenticity and densitometric... 相似文献
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Ilko K. Ilev Hiroshi Kumagai Koichi Toyoda Deepak Uttamchandani Brian Culshaw 《Optical Review》1997,4(1):A58-A60
An alternative and simple fiber-optic backreflectance sensor method for accurate measurement of either effective focal lengths
of optical elements and short distances using a single-mode optical fiber and cw laser is presented. The method is based on
the intensity sensing of focused backreflectance laser emission and the spatial location of three specific points: the focal
point of the focusing optical element and two object points. The single-mode fiber is a key optical element and serves simultaneously
as a point laser source for testing, an object for projecting and a highly sensitive point receiver of the focused backreflectance
emission. The experimental and analytical results demonstrate the potential of the method for locating the spatial points
and determining the effective focal length with accuracies exceeding 1 μm and 0.5%, respectively, as well as for short distance
measurement with submicron accuracy. 相似文献