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151.
Preparation of Nanosized Hematite Particles by Mechanical Activation of Goethite Samples 总被引:4,自引:0,他引:4
Jan ubrt Luis A. Pérez-Maqueda Jose M. Criado Concepción Real Jaroslov Boháek Eva Veerníková 《Journal of the American Ceramic Society》2000,83(2):294-298
Nanosized single crystals of hematite with a very narrow particle size distribution were prepared by mechanical activation of two different goethite samples. Both goethite samples transformed completely into hematite after 70 h grinding time. Transmission electron microscopy showed that the final particles were spherical in shape and of ∼17 nm average particle size. This particle size was coincident with that estimated from specific surface measurements, indicating that the hematite samples consisted of nonporous and nonaggregated particles. The crystallite size, calculated from the broadening of the XRD peaks, in the hematite samples indicated that particles consisted of single crystals. No influence of the precursor was observed in the products, so both goethite samples yielded identical rounded single crystals with a narrow particle size distribution. 相似文献
152.
Yixuan Jia Christoph A. Spiegel Alexander Welle Stefan Heißler Elaheh Sedghamiz Modan Liu Wolfgang Wenzel Maximilian Hackner Joachim P. Spatz Manuel Tsotsalas Eva Blasco 《Advanced functional materials》2023,33(39):2207826
Manufacturing programmable materials, whose mechanical properties can be adapted on demand, is highly desired for their application in areas ranging from robotics, to biomedicine, or microfluidics. Herein, the inclusion of dynamic and living bonds, such as alkoxyamines, in a printable formulation suitable for two-photon 3D laser printing is exploited. On one hand, taking advantage of the dynamic covalent character of alkoxyamines, the nitroxide exchange reaction is investigated. As a consequence, a reduction of the Young´s Modulus by 50%, is measured by nanoindentation. On the other hand, due to its “living” characteristic, the chain extension becomes possible via nitroxide mediated polymerization. In particular, living nitroxide mediated polymerization of styrene results not only in a dramatic increase of the volume (≈8 times) of the 3D printed microstructure but also an increase of the Young's Modulus by two orders of magnitude (from 14 MPa to 2.7 GPa), while maintaining the shape including fine structural details. Thus, the approach introduces a new dimension by enabling to create microstructures with dynamically tunable size and mechanical properties. 相似文献
153.
Reverse osmosis (RO) treatment has been found to be effective for a wide range of organics but generally small, polar, uncharged molecules such as N-nitrosodimethylamine (NDMA) can be poorly rejected. The rejection of seven N-nitrosoalkylamines with molecular masses in the range of 78-158Da, including NDMA, N-nitrosodiethylamine (NDEA), N-nitrosomethylethylamine (NMEA), N-nitrosodipropylamine (NDPA), N-nitrosodibutylamine (NDBA), N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip) by three commercial brackish-water reverse osmosis membranes was studied in flat-sheet cells under cross-flow conditions. The membranes used were ESPA3 (Hydranautics), LFC3 (Hydranautics) and BW-30 (Dow/Filmtec), commonly used in water reuse applications. The effects of varying ionic strength and pH, dip-coating membranes with PEBAX 1657, a hydrophilic polymer, and artificial fouling with alginate on nitrosamine rejection were quantified. Rejection in deionized (DI) water increased with molecular mass from 56 to 70% for NDMA, to 80-91% for NMEA, 89-97% for NPyr, 92-98% for NDEA, and to beyond the detection limits for NPip, NDPA and NDBA. For the nitrosamines with quantifiable transmission, linear correlations (r(2)>0.97) were found between the number of methyl groups and the log(transmission), with factor 0.35 to 0.55 decreases in transmission per added methyl group. A PEBAX coating lowered the ESPA3 rejection of NDMA by 11% but increased the LFC3 and BW30 rejection by 6% and 15%, respectively. Artificially fouling ESPA3 membrane coupons with 170g/m(2) alginate decreased the rejection of NDMA by 18%. A feed concentration of 100mM NaCl decreased rejection of NDMA by 15% and acidifying the DI water feed to pH=3 decreased the rejection by 5%, whereas increasing the pH to 10 did not have a significant (p<0.05) effect. 相似文献
154.
Petr Kovaricek Peter Nadazdy Eva Pluharova Alica Brunova Riyas Subair Karol Vegso Valentino Libero Pio Guerra Oleksandr Volochanskyi Martin Kalbac Alexander Krasnansky Pallavi Pandit Stephan Volker Roth Alexander Hinderhofer Eva Majkova Matej Jergel Jianjun Tian Frank Schreiber Peter Siffalovic 《Advanced functional materials》2021,31(13):2009007
2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices. 相似文献
155.
The effects of salt-curing and salting procedures on the microstructure of cod (Gadus morhua) muscle
Kristin Anna Thorarinsdottir Sigurjon Arason Sjofn Sigurgisladottir Valur N. Gunnlaugsson Jonina Johannsdottir Eva Tornberg 《Food chemistry》2011
The aim of this study was to investigate the effects of salting and different pre-salting procedures (injection and brining versus brining only) on the microstructure and water retention of heavy salted cod products. Salting resulted in shrinkage of fibre diameter and enlargement of inter-cellular space. Water was expelled from the muscle and a higher fraction became located in the extra-cellular matrix. These changes were suggested to originate from myofibrillar protein aggregation and enzymatic degradation of the connective tissue. During rehydration, the muscle absorbed water again and the fibers swelled up to a similar cross-sectional area as in the raw muscle. However, the inter-cellular space remained larger, resulting in a higher water content of the muscle in the rehydrated stage. The effects of different salting procedures were strongest after salting. At that stage of the process, the inter-cellular space tended to be larger in the injected and brined muscle than in the brined only. 相似文献
156.
This study compares the citations characteristics of researchers in engineering disciplines with other major scientific disciplines,
and investigates variations in citing patterns within subdisciplines in the field of engineering. Utilizing citations statistics
including Hirsch’s (Proc Natl Acad Sci USA 102(46):16569–16572, 2005) h-index value, we find that significant differences in citing characteristics exist between engineering disciplines and
other scientific fields. Our findings also reveal statistical differences in citing characteristics between subdisciplines
found within the same engineering discipline. 相似文献
157.
Ivan Ostrovský Eva Pavlíková Jaroslav Blaško Renáta Górová Róbert Kubinec Milan Margetín Ladislav Soják 《International Dairy Journal》2009,19(9):545-549
The profile variations of approximately 70 fatty acids (FAs) in milk of ewes consuming total mixed rations (TMR) and grazing natural pasture were determined. Milk of ewes grazing pasture in May and September in the Slovak Republic contained 3-times more conjugated linoleic acid (CLA) (P < 0.001) and trans-vaccenic acid (TVA) (P < 0.001), and 2-times more α-linolenic acid (ALA) (P < 0.001) than that of ewes fed TMR. A doubling of the CLA and TVA contents of milk of ewes fed with TMR was achieved by changing to meadow hay containing a higher ALA content. Less availability of vegetation and lower ALA pasture content in summer (P < 0.001) caused a 2-fold decrease (P < 0.001) of CLA and TVA contents when compared with data obtained in May. With grass re-growth and an increase in pasture ALA content in September, the CLA and TVA contents rose to values similar to those obtained in May (P > 0.05). No significant differences in the FA composition in milk of ewes grazing on summer pasture at higher altitude were observed. 相似文献
158.
Currently the Journal Impact Factors (JIF) attracts considerable attention as components in the evaluation of the quality
of research in and between institutions. This paper reports on a questionnaire study of the publishing behaviour and researchers
preferences for seeking new knowledge information and the possible influence of JIF on these variables. 54 Danish medical
researchers active in the field of Diabetes research took part. We asked the researchers to prioritise a series of scientific
journals with respect to which journals they prefer for publishing research and gaining new knowledge. In addition we requested
the researchers to indicate whether or not the JIF of the prioritised journals has had any influence on these decisions. Furthermore
we explored the perception of the researchers as to what degree the JIF could be considered a reliable, stable or objective
measure for determining the scientific quality of journals. Moreover we asked the researchers to judge the applicability of
JIF as a measure for doing research evaluations. One remarkable result is that app. 80% of the researchers share the opinion
that JIF does indeed have an influence on which journals they would prefer for publishing. As such we found a statistically
significant correlation between how the researchers ranked the journals and the JIF of the ranked journals. Another notable
result is that no significant correlation exists between journals where the researchers actually have published papers and
journals in which they would prefer to publish in the future measured by JIF. This could be taken as an indicator for the
actual motivational influence on the publication behaviour of the researchers. That is, the impact factor actually works in
our case. It seems that the researchers find it fair and reliable to use the Journal Impact Factor for research evaluation
purposes. 相似文献
159.
立面、周边环境以及对所在街区的一系列回应,是玛丽蒂姆酒店的设计要点。这个占地约1.2万m2的酒店基地紧邻文化中心(Kulturforum)和著名的文物保护建筑贝壳屋(Shellhaus,建筑师:Emil Fahrenkamp),且距国家美术馆和波茨坦广场不远。 相似文献
160.
Gordon Rugg Malcolm Eva Atiya Mahmood Nazia Rehman Stephanie Andrews & Sarah Davies 《Information Systems Journal》2002,12(3):215-229
Abstract. Eliciting information about organizational culture is an important part of system analysis and design. However, eliciting knowledge of this sort is difficult. Laddering is an established technique that is particularly suitable for eliciting information about goals and for eliciting explanations, which are important issues when investigating organizational culture. This paper describes the method, its strengths and limitations, its use in several case studies and its relation to other elicitation techniques. Recommendations for further work are given. 相似文献