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71.
J. U. Keller 《Adsorption》1995,1(4):283-290
The gas adsorbed on the inner surface of a highly porous material like activated carbon or zeolite can be measured by slow damped oscillations of a torsional pendulum. The physical principles and the theory of this method are outlined. Formulas are given relating the increase in mass due to adsorption to changes of the frequency and the logarithmic decrement of slow, damped rotational oscillations of the pendulum. Preliminary measurements of gas adsorption equilibria of nitrogen on activated carbon show that the ratio of the mass adsorbedm, to the mass of the adsorbentm
s
, can be determined by this method with mean absolute error |m/m
s
|0.04%.Dedicated to the memory of Joseph Kestin (1913–1993). 相似文献
72.
Yang Xin Dr. Boxuan Shen Prof. Mauri A. Kostiainen Prof. Guido Grundmeier Prof. Mario Castro Dr. Veikko Linko Dr. Adrian Keller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(33):8564-8571
The surface-assisted hierarchical assembly of DNA origami nanostructures is a promising route to fabricate regular nanoscale lattices. In this work, the scalability of this approach is explored and the formation of a homogeneous polycrystalline DNA origami lattice at the mica-electrolyte interface over a total surface area of 18.75 cm2 is demonstrated. The topological analysis of more than 50 individual AFM images recorded at random locations over the sample surface showed only minuscule and random variations in the quality and order of the assembled lattice. The analysis of more than 450 fluorescence microscopy images of a quantum dot-decorated DNA origami lattice further revealed a very homogeneous surface coverage over cm2 areas with only minor boundary effects at the substrate edges. At total DNA costs of € 0.12 per cm2, this large-scale nanopatterning technique holds great promise for the fabrication of functional surfaces. 相似文献
73.
Karl Krmer Hans U. Güdel Gerd Meyer Thorsten Heuer Norman N. Edelstein Bernd Jung Lukas Keller Peter Fischer Eugeniusz Zych Janusz Drozdzynski 《无机化学与普通化学杂志》1994,620(8):1339-1345
The ternary uranium(III) halides A2UX5 (A = K, Rb; X = Cl, Br, I) have been prepared from the binary components AX and UX3 in sealed tantalum containers. According to their Guinier X-ray powder patterns, they all crystallize with the K2PrCl5/Y2HfS5 type of structure. Lattice constants for ambient temperature are reported. Single-crystal structure refinemens were undertaken for K2UI5 and Rb2UCl5. Magnetic susceptibility data were recorded with a SQUID magnetometer from liquid helium to room temperature. One-dimensional (intrachain) and three-dimensional antiferromagnetic ordering occur at low temperatures dependent upon the U3+? U3+ distance. Absorption spectra were recorded between 4 000 and 28 000 cm?1. They show f—f transitions typical for U3+ and, depending on the halide, very strong f—d transitions above 14 000 to 15 000 cm?1, respectively. 相似文献
74.
L. Forte K. Andrieux G. Keller C. Grabielle-Madelmont S. Lesieur M. Paternostre M. Ollivon C. Bourgaux P. Lesieur 《Journal of Thermal Analysis and Calorimetry》1998,51(3):773-782
The thermotropic transitions of 1,2-dipalmitoylphosphatidylcholine (DPPC) and the structural changes of its lamellar phases have been studied between 0 and 50°C by both DSC and synchrotron small angle X-ray diffraction/scattering as a function of temperature (XRDT) and sodium taurocholate concentration [TC] in the 0–40 mM range ([DPPC]=50 mM) at pH 7.4. The existence of multiple phase transitions (up to 5 peaks within a 5°C interval) in a narrow domain of temperature between 25 and 42°C depending on the [TC]/[lipid] ratio was observed in the DSC curves. XRDT showed that at low ratios they might correspond to transitions between lamellar phases, the structural characteristics of which are given. At higher ratios a lamellar to micellar transition was observed, and the temperature at which it was observed decreased as a function of the TC content. The relationships with DPPC vesicle bilayer permeabilization and solubilization are discussed. 相似文献
75.
Vargis E Kanter EM Majumder SK Keller MD Beaven RB Rao GG Mahadevan-Jansen A 《The Analyst》2011,136(14):2981-2987
In this paper, we examine how variations in normal tissue can influence disease classification of Raman spectra. Raman spectra from normal areas may be affected by previous disease or proximity to areas of dysplasia. Spectra were acquired in vivo from 172 patients and classified into five tissue categories: true normal (no history of disease), previous disease normal (history of disease, current normal diagnosis), adjacent normal (disease on cervix, spectra acquired from visually normal area), low grade, and high grade. Taking into account the various "normal" states of the tissue before statistical analysis led to a disease classification accuracy of 97%. These results indicate that abnormal changes significantly affect Raman spectra, even when areas are histopathologically normal. The sensitivity of Raman spectroscopy to subtle biochemical differences must be considered in order to successfully implement it in a clinical setting for diagnosing cervical dysplasia and cancer. 相似文献
76.
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
77.
The measurements of oscillator strengths of hypersensitive bands for Ln(ClO4)3 (Ln Nd, Ho, Er) in different solvents are reported. The sesults are discussed within the framework of the polarizability mechanism. 相似文献
78.
Kim Kyoung Heon Tucker Melvin P. Keller Fred A. Aden Andy Nguyen Quang A. 《Applied biochemistry and biotechnology》2001,91(1-9):253-267
Two-stage dilute acid pretreatment followed by enzymatic cellulose hydrolysisis an effectivemethod for obtaining high sugar
yields from wood residuessuchassoftwood forest thinnings. In the first-stage hydrolysis step, most of the hemicellulose is
solubilized using relatively mild conditions. The soluble hemicellu losic sugars are recovered from the hydrolysateslurry
by washing with water. The washed solids are then subjected tomoresevere hydrolysis conditions to hydrolyze approx 50% of
the cellulose to glucose. The remaining cellulose can further be hydrolyzed with cellulase enzyme. Our process simulation
indicates that the amount of water used in the hemicellulose recovery step has a significan tim pact on the cost of ethanol
production. It is important to keep water usage as low as possible while mainta ining relatively high recovery of solublesugars.
To achieve this objective, a prototype pilot-scale continuous countercurrent screw extractor was evaluated for the recovery
of hemicellulose from pretreated forest thinnings. Using the 274-cm (9-ft) long extractor, solubles recoveries of 98, 91,
and 77% were obtained with liquid-to-insoluble solids (L/1S) ratios of 5.6, 3.4, and 2.1, respectively. An empirical equation
was developed to predict the performance of the screwextractor. This equation predicts that soluble sugar recovery above 95%
can be obtained with an L/IS ratio as low as 3.0. 相似文献
79.
The present paper, dealing with nylons 66, 610, and 612, is part of a study on a series of polyamides as crystallized from solution. The lath-shaped crystallization products, aggregated in the form of sheaves, possess the characteristics of chain-folded single crystals. In particular, they can be collected in the form of oriented mats which display arced X-ray reflections both in the wide- and low-angle regions. This enables the fold surfaces to be indexed as 00l. In a given polymer the long spacing has a characteristic value and for different polymers it varies in the ratio of the monomer lengths. The measured layer thickness corresponds closely to four-unit cell lengths. The fact that this holds for all three polymers implies that the fold length is determined by the number of hydrogen bonds between the stems. In view of the small value of this figure (due to the large identity period) the long period can only be apportioned between straight stems and folds in a limited number of ways which enables some concrete suggestions to be made on the possible constitution of the fold itself. On annealing, the fold length increases preferentially by factors of 2. A mechanism with general implications for the refolding behavior of polymers is proposed. 相似文献