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101.
Steven Spoljaric Arto Salminen Nguyen Dang Luong Jukka Seppälä 《Cellulose (London, England)》2013,20(6):2991-3005
Nanofibrillated cellulose (NFC) was compounded with poly(acrylic acid) (PAA) via solvent casting. Nanocomposite films were thermally-crosslinked to allow the formation of ester bonds between NFC and PAA, as confirmed by 13CNMR and infrared spectroscopy. The network morphology of the cellulose nanofibrils was left intact by the introduction of PAA and crosslinking. Water absorption and swelling was diminished by the introduction of crosslinking, due to the reduced number of vacant hydroxyl and carboxyl groups available to interact with water molecules. Crosslinking with PAA increased the activation energy required for thermal degradation. PAA effectively reinforced NFC, increasing Young’s modulus, tensile strength and glass transition temperature. Crosslinking imparted restraints on segmental motion of polymer chains, further enhancing the thermomechanical properties and retaining elasticity. Wet-strength properties were enhanced due to the reduced hydrophilicity of crosslinked nanocomposite films. 相似文献
102.
N. Kodiah Beyeh Altti Ala‐Korpi Mario Cetina Arto Valkonen Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15144-15150
N‐Alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra‐ and intermolecular hydrogen bonds that leads to cavitand‐like structures. Depending on the upper‐rim substituents, self‐inclusion was observed in solution and in the solid state. The self‐inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self‐included dimers spontaneously reorganize to 1:1 host–guest complexes. These host compounds show an interesting ability to bind a series of N‐alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C?O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl?) and ammonium (NH2+) cations of the hosts, and also through CH ??? π interactions between the hosts and guests. The self‐included and host–guest complexes were studied by single‐crystal X‐ray diffraction, NMR titration, and mass spectrometry. 相似文献
103.
Ryszard Gawinecki Branko Stanovnik Arto Valkonen Erkki Kolehmainen Borys Ośmiałowski Robert Dobosz Anna Zakrzewska 《Structural chemistry》2009,20(4):655-662
15N NMR chemical shifts of the exo- and endocyclic nitrogen atoms show how efficient is the ground-state intramolecular charge
transfer between these sites in 4-dimethylamino-1-methylpyridinium cation (increased contribution of the quinoid resonance
form results in a shielding and deshielding effect of their NMR signals, respectively). As it was anticipated, insertion of
vinylene and/or 1,4-phenylene spacers to the cation considerably hinders the ground-state charge transfer. This hypothesis
is further supported by an analysis of the C–NMe2 bond lengths (X-ray data show that spacers elongate this bond). The selected valence angles in the compounds studied are
also linearly dependent on δ(15Nendo) and δ(15Nexo) values. Although the correlation coefficient for the δ(15Nendo) versus δ(15Nexo) dependence is equal to 0.983, decrease of the net charge on one nitrogen atom is not compensated entirely by its increase
on another nitrogen atom. This shows that exocyclic nitrogen atom is not the only acceptor of the positive charge in the molecule.
The natural population analysis shows that the positive charge is transferred not only to the exocyclic N but also to, e.g.,
1- and N-methyl C as well as to C3 and C5 atoms in pyridine ring. Ground-state charge transfer through the p-phenylene moiety was found to be less effective than through the trans-vinylene bridge.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
104.
Petri Lehikoinen Juha Mallat Petri Piironen Arto Lehto Jussi Tuovinene Antti V. Räisänen 《International Journal of Infrared and Millimeter Waves》1996,17(5):807-818
A planar single-ended GaAs Schottky diode mixer has been designed, built, and tested at 119 GHz. The mixer front end includes also a waveguide filter for image rejection, and a temperature compensated ring filter. Measurements at room temperature showed a conversion loss of 7 dB and a noise temperature of 900 K (SSB). At 100 K the measured noise temperature of the mixer was 500 K (SSB). 相似文献
105.
Juha Mallat Arto Lehto Jussi Tuovinen 《International Journal of Infrared and Millimeter Waves》1994,15(9):1497-1506
The differential phase measurement method has been improved to need the use of only one power meter instead of three power meters. This enables accurate antenna phase pattern measurements with a simplified set-up, accompanied by the reduction in cost. All advantages of the differential phase measurement method are still also available, e.g. there is no need to phase lock oscillators or to use rotary joints. The measurement results for an antenna at 110 GHz are presented. A good agreement with earlier data was obtained. 相似文献
106.
We discuss problems related to devising a secret balloting system with the following properties: (1) all eligible voters and they only may vote, (2) all ballots are secret, i.e. do not reveal the identity of the voter, (3) all voters may check whether their ballots have been correctly assigned, (4) the voters may revise their ballots within a predetermined time, and (5) errors in ballot assignment can be corrected within a predetermined time. 相似文献
107.
We have resolved and characterized three forms of human and rat hepatic class III alcohol dehydrogenase. Separations were carried out in narrow immobilized pH gradients. Both in humans and rats the three forms were visualized by enzyme staining with cinnamol, but not with ethanol. They were insensitive to the inhibitory effect of pyrazole. The isoelectric points were approximately from 6.3-6.4, from 5.9-6.0 and 5.6. Each electroeluted enzyme extract, purified further by analytical isoelectric focusing over the pH range from 5-6 or 6-7, revealed a single band by enzyme and silver staining and by Western blotting followed by avidin-biotin staining. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate of each extract revealed a single molecular mass species corresponding to class III alcohol dehydrogenase (ADH). All forms of class III alcohol dehydrogenase were recognized by antisera raised against total class III ADH. 相似文献
108.
109.
Arto Salomaa 《Discrete Mathematics》1974,9(1):71-77
An algorithm is presented for deciding whether or not a given regular set is a UL-language. 相似文献
110.
Louhivuori M Otten R Lindorff-Larsen K Annila A 《Journal of the American Chemical Society》2006,128(13):4371-4376
The discovery of dilute liquid crystalline media to align biological macromolecules has opened many new possibilities to study protein and nucleic acid structures by NMR spectroscopy. We inspect the basic alignment phenomenon for an ensemble of protein conformations to deduce relative contributions of each member to the residual dipolar coupling signals. We find that molecular fluctuations can affect the alignment and discover a resulting emphasis of certain conformations. However, the internal fluctuations are largely uncorrelated with those of the alignment, implying that proteins have liquidlike molecular surfaces. Furthermore, we consider the implications of a dynamic bias to structure determination using data from the weak alignment method. 相似文献