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951.
Britta Fuchs Felix Schlenkrich Susanne Seyffarth Andreas Meschede Robert Rotzoll Philipp Vana Peter Gro?mann Klaus Mann Hans-Ulrich Krebs 《Applied Physics A: Materials Science & Processing》2010,98(4):711-715
Smooth poly(methyl methacrylate) (PMMA) films without any droplets were pulsed laser deposited at a wavelength of 248 nm and
a laser fluence of 125 mJ/cm2. After deposition at room temperature, the films possess low universal hardness of only 3 N/mm2. Thermal treatments up to 200°C, either during deposition or afterwards, lead to film hardening up to values of 200 N/mm2. Using a combination of complementary methods, two main mechanisms could be made responsible for this temperature induced
hardening effect well above the glass transition temperature of 102°C. The first process is induced by the evaporation of
chain fragments and low molecular mass material, which are present in the film due to the ablation process, leading to an
increase of the average molecular mass and thus to hardening. The second mechanism can be seen in partial cross-linking of
the polymer film as soon as chain scission occurs at higher temperatures and the mobility and reactivity of the polymer material
is high enough. 相似文献
952.
Ruth A. Perez Nils Rehmann Sheila Crain Patricia LeBlanc Cheryl Craft Shawna MacKinnon Kelley Reeves Ian W. Burton John A. Walter Philipp Hess Michael A. Quilliam Jeremy E. Melanson 《Analytical and bioanalytical chemistry》2010,398(5):2243-2252
The production and certification of a series of azaspiracid (AZA) calibration solution reference materials is described. Azaspiracids were isolated from contaminated mussels, purified by preparative liquid chromatography and dried under vacuum to the anhydrous form. The purity was assessed by liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The final concentration of each AZA in a CD3OH stock solution was determined by quantitative NMR spectroscopy. This solution was then diluted very accurately in degassed, high purity methanol to a concentration of 1.47?±?0.08 μmol/L for CRM-AZA1, 1.52?±?0.05 μmol/L for CRM-AZA2, and 1.37?±?0.13 μmol/L for CRM-AZA3. Aliquots were dispensed into argon-filled glass ampoules, which were immediately flame-sealed. The calibration solutions are suitable for method development, method validation, calibration of liquid chromatography or mass spectrometry instrumentation and quality control of shellfish monitoring programs. 相似文献
953.
Krishna C. Etika Florian D. Jochum Michael A. Cox Philipp Schattling Patrick Theato Jaime C. Grunlan 《Macromolecular rapid communications》2010,31(15):1368-1372
Poly(N‐ispropylacrylamide) [PNIPAM] is a widely studied polymer for use in biological applications due to its lower critical solution temperature (LCST) being so close to the human body temperature. Unfortunately, attempts to combine carbon nanotubes (CNTs) with PNIPAM have been unsuccessful due to poor interactions between these two materials. In this work, a PNIPAM copolymer with 1 mol‐% pyrene side group [p‐PNIPAM] was used to produce a thermoresponsive polymer capable of stabilizing both single and multi‐walled carbon nanotubes (MWNTs) in water. The presence of pyrene in the polymer chain lowers the LCST less than 4 °C and the interaction with nanotubes does not show any influence on LCST. Moreover, p‐PNIPAM stabilized nanotubes show a temperature‐dependent dispersion in water that allows the level of nanotube exfoliation/bundling to be controlled. Cryo‐TEM images, turbidity, and viscosity of these suspensions were used to characterize these thermoresponsive changes. This ability to manipulate the dispersion state of CNTs in water with p‐PNIPAM will likely benefit many biological applications, such as drug delivery, optical sensors, and hydrogels.
954.
Erni P Fischer P Windhab EJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10555-10563
The shear and dilatational rheology of condensed interfacial layers of the water-insoluble surfactant sorbitan tristearate at the air/water interface is investigated. A new interfacial shear rheometer allows measurements in both stress- and strain-controlled modes, providing comprehensive interfacial rheological information such as the interfacial dynamic shear moduli, the creep response to a stress pulse, the stress relaxation response to a strain step, or steady shear curves. Our experiments show that the interfacial films are both viscoelastic and brittle in nature and subject to fracture at small deformations, as was supported by in-situ Brewster angle microscopy performed during the rheological experiments. Although any large-deformation test is destructive to the sample, it is still possible to study the linear viscoelastic regime if the deformations involved are controlled carefully. Complementary results for the dilatational rheology in area step compression/expansion experiments are reported. The dilatational behavior is predominantly elastic throughout the frequency spectrum measured, whereas the layers exhibit generalized Maxwell behavior in shear mode within a deformation frequency regime as narrow as two decades, indicating the presence of additional relaxation mechanisms in shear as opposed to expansion/compression. If the transient rheological response from stress relaxation experiments is considered, then the data can be described well with a stretched exponential model both in the shear and dilatational deformations. 相似文献
955.
956.
Der Satz von Bell behauptet, da? die Existenz von sogenannten objektiv Einstein-lokalen verborgenen Variablen und die Quantenmechanik unvereinbar sind. Der von Bell gegebene Beweis ist rein mathematischer Natur und schlie?t eine gewisse Klasse von verborgenen Variablen aus. Bells Beweis beruht auf der nun berühmten Bellschen Ungleichung, die eng mit dem Konsistenzproblem von Wahrscheinlichkeitsverteilungen für drei Paare von Zufallsver?nderlichen verbunden ist. Ziel dieser Arbeit ist es, einen überblick über diesen Gedankenkreis zu geben, sowie eine Reihe von weiteren in der Literatur erschienenen Beweisans?tze zu analysieren und gleichzeitig zu zeigen, da? man mit diesen Beweismethoden nicht alle Einstein-lokalen verborgenen Variablen ausschlie?en kann. 相似文献
957.
Philipp Afèche 《Operations Research Letters》2003,31(5):390-400
We evaluate the delay performance of an open multi-class stochastic processing network of multi-server resources with preemptive-resume priority service. We show that the stationary distribution of aggregate queue lengths has product form. For each service class we derive explicit expressions for the following stationary performance measures: The mean and, under feedforward routing, the Laplace transform of the delay distribution at each resource. We show that these measures are the same as if the resources were operating in isolation. 相似文献
958.
Böhm O Leitsmann R Plänitz P Radehaus C Schreiber M Schaller M 《The journal of physical chemistry. A》2011,115(29):8282-8287
In this study we investigate the silylation of OH groups with different silazanes. In particular we use density functional theory and the nudged elastic band method to study the different reaction mechanisms. For the silylation reaction of hexamethyldisilazane and trimethylaminosilane with silanol, the minimum energy paths as well as the activation and reaction energies are discussed in detail. From minimum energy reaction paths we found that all studied silazanes react exothermically. Bis(dimethylamino)dimethylsilane shows the most exothermic silylation reaction with the lowest activation energies. Therefore, it is a good candidate for the chemical repair of porous films in the semiconductor k-restoring process. 相似文献
959.
Wollmann P Leistner M Stoeck U Grünker R Gedrich K Klein N Throl O Grählert W Senkovska I Dreisbach F Kaskel S 《Chemical communications (Cambridge, England)》2011,47(18):5151-5153
A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the tool in the discovery of new cobalt-based metal-organic frameworks is given. 相似文献
960.
Dr. Safak Bulut Dr. Philipp Eiden Witali Beichel Dr. John M. Slattery Dr. Tom F. Beyersdorff Dr. Thomas J. S. Schubert Prof. Dr. Ingo Krossing 《Chemphyschem》2011,12(12):2296-2310
A series of bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) with classical as well as mildly functionalized cations was prepared and their viscosities and conductivities were determined as a function of the temperature. Both were analyzed with respect to Arrhenius, Litovitz and Vogel–Fulcher–Tammann (VFT) behaviors, as well as in the context of their molecular volume (Vm). Their viscosity and conductivity are highly correlated with Vm/T or related expressions (R2≥0.94). With the knowledge of Vm of new cations, these correlations allow the temperature‐dependent prediction of the viscosity and conductivity of hitherto unknown, non‐ or mildly functionalized ILs with low error bars (0.05 and 0.04 log units, respectively). The influence of the cation structure and mild functionalization on the physical properties was studied with systematically altered cations, in which Vm remained similar. The To parameter obtained from the VFT fits was compared to the experimental glass temperature (Tg) and the Tg/To ratio for each IL was calculated using both experimental values and Angell’s relationship. With Walden plots we investigated the IL ionicity and interpreted it in relation to the cation effects on the physical IL properties. We checked the validity of these Vm/T relations by also including the recently published variable temperature viscosity and conductivity data of the [Al(ORF)4]? ILs with RF=C(H)(CF3)2 (error bars for the prediction: 0.09 and 0.10 log units, respectively). 相似文献