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121.
Marián Masár Pavol Kruk Milan Luc Róbert Bodor Ladislav Danč Peter Troška 《Electrophoresis》2013,34(3):432-440
Adsorption processes on a PMMA chip linked with CZE separations of a group of 13 aliphatic and aromatic mono‐ and di‐amines were studied. Due to the lack of chromophores within aliphatic amines, contact conductivity detection implemented directly onto the chip was used for monitoring of cationic CZE separations. To prevent an adsorption of studied amines to the chip channels, the surface of PMMA chip was modified by dynamic coating. Different surface modifiers, such as aliphatic oligoamines (diethylenetriamine and triethylenetetramine), were added to the BGE solutions filling the chip channels. The effect of various concentrations of surface modifiers on peak profiles and separation parameters of amines was monitored. Of these, mainly, aliphatic di‐amines and aromatic mono‐amines adversely affected the CZE resolution of a whole group of analytes by their strong adsorption to the chip channels. A propionate BGE with pH 3.2 containing 100 μM triethylenetetramine and 25 mM 18‐crown‐6‐ether was found suitable for CZE resolution of 12 from a total of 13 amines studied. Simple dynamic modification of the surface of PMMA chip enabled fast (analysis time lasted 9 min), sensitive (sub‐μM LODs reached) and reproducible (1–3% RSD of the peak areas) CZE analysis of the aliphatic and aromatic amines. 相似文献
122.
Using controlled radical polymerization to confirm the lower critical solution temperature of an N‐(alkoxyalkyl) acrylamide polymer in aqueous solution 下载免费PDF全文
Xeniya Savelyeva Lucia Li Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2015,53(1):59-67
N‐(3‐Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide‐mediated polymerization (NMP) and reversible addition–fragmentation chain‐transfer polymerization (RAFT). CRP was expected to yield well‐defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropanoic acid) and SG1 ([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, ? ~ 1.5–1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, , versus conversion, X, plots, low ? ~ 1.2–1.4 and the ability to form block copolymers using N,N‐diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with = 13.7–25.3 kg mol?1) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 °C depending on solution concentration (ranging from 1 to 3 wt %). The and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)‐b‐poly(DEAAM) block copolymer ( = 22.3 kg mol?1, ? = 1.41, molar composition FDEAAM = 0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 °C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV–Vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 59–67 相似文献
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124.
A set of original, analytical equations useful for theoretical calculation of the electron paramagnetic resonance (EPR) signal intensity are presented for the multitude of sample shapes, which range from point-like, line-like, planar, rectangular, cubical, circular, cylindrical, spherical to an irregularly shaped sample. The samples can be situated at any available position within the prescribed part of the microwave cavity (a central cylinder of diameter 11 mm and length 23.5 mm, in either a Bruker single TE102 or double TE104 rectangular cavity, with the modulation coils situated in the left and right side cavity walls, which is connected to a X-band, field-modulated CW Bruker EPR spectrometer). The theoretical computations of EPR signal intensity can be used in the computer simulations in which: (i) the EPR signal intensity profiles are constructed; (ii) the optimal sample positions in the cavity to give a maximum value of signal intensity are found; (iii) the errors associated with sample positioning within the cavity when compared to a second sample of a different size, shape or position are studied. 相似文献
125.
Milan Kracalik Stephan Laske Andreas Witschnigg Clemens Holzer 《Macromolecular Symposia》2012,311(1):33-40
Summary: Recycled PET as well as ABS - organomodified montmorillonite nanocomposites were prepared via melt compounding in a counter-rotating twin screw extruder. The topological changes in polymer matrices as dependency on clay modification have been evaluated from dynamic experiments in the shear flow using low amplitude oscillatory measurements. Flow characteristics of all studied organoclay nanocomposites showed shear-thinning behavior at low frequencies. Filling of PET with some organoclays led to degradation reactions, which were reflected by lower magnitudes of viscosity and storage modulus in the range of higher frequencies as compared to unfilled polymer matrix. On the contrary, no degradation during the processing of different organoclays with recycled ABS has been observed. 相似文献
126.
Vít Kremláček Erik Kertész Prof. Zoltán Benkő Milan Erben Robert Jirásko Prof. Aleš Růžička Prof. Roman Jambor Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13096-13097
Invited for the cover of this issue are Zoltán Benkő, Libor Dostál and co-workers at the University of Pardubice and the Budapest University of Technology and Economics. The image depicts signs for the two different pathways representing the two differing reaction types which were clearly observed for 2,1-benzazaphosphole. Read the full text of the article at 10.1002/chem.202101686 . 相似文献
127.
Sharmaine B. Luk Adrien Métafiot Judith Morize Emmanuel Edeh Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2021,59(19):2140-2153
Ambient pressure chemical hydrogenation using p-toluene sulfonyl hydrazide (TSH) via thermal diimide formation (N2H2) permitted reduction of double bonds of poly(myrcene) (poly[Myr]) and poly(farnesene) (poly[Far]). Both pendent and backbone double bonds in poly(Myr) (Mn = 56 kg/mol) and poly(Far) (Mn = 62 kg/mol) synthesized by conventional free radical polymerization were hydrogenated to almost completion. Furthermore, TSH semi-batch addition efficiently hydrogenated double bonds, while avoiding undesired autohydrogenation of diimides that occurred in batch mode. Thermal stability improved for hydrogenated poly(Myr) and poly(Far), where temperature at 10% weight loss (T10%) increased from 188 to 404°C for poly(Myr) and from 310 to 379°C for poly(Far). Tgs of poly(Myr) and poly(Far) also increased by about 10–25°C, indicating increased stiffness after hydrogenation. Finally, viscosities of poly(Myr) and poly(Far) were also increased after hydrogenation, and a greater increase was observed for poly(Myr) (by two orders of magnitude from 102 to 104 Pa s) due to its Mn being much higher than its entanglement molecular weight. Poly(Far) viscosity only increased by 1.5 times after hydrogenation (~104 Pa s), comparable to the poly(Myr) after hydrogenation, suggesting unsaturated poly(Far) was more entangled than unsaturated poly(Myr) because of its longer side chains. 相似文献
128.
Dean P Lim YL Valavanis A Kliese R Nikolić M Khanna SP Lachab M Indjin D Ikonić Z Harrison P Rakić AD Linfield EH Davies AG 《Optics letters》2011,36(13):2587-2589
We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures. 相似文献
129.
This work presents a systematic theoretical study on Cu(I) and Cu(II) cations in variable hydrogen sulfide-aqua-ammine ligand fields. These ligands model the biologically most common environment for Cu ions. Molecular structures of the complexes were optimized at the density functional theory (DFT) level. Subsequent thorough energy analyses revealed the following trends: (i) The ammine complexes are the most stable, followed by those containing the aqua and hydrogen sulfide ligands, which are characterized by similar stabilization energies. (ii) The most preferred Cu(I) coordination number is 2 in ammine or aqua ligand fields. A qualitatively different binding picture was obtained for complexes with H(2)S ligands where the 4-coordination is favored. (iii) The 4- and 5-coordinated structures belong to the most stable complexes for Cu(II), regardless of the ligand types. Vertical and adiabatic ionization potentials of Cu(I) complexes were calculated. Charge distribution (using the natural population analysis (NPA) method) and molecular orbital analyses were performed to elucidate the nature of bonding in the examined systems. The results provide in-depth insight into the Cu-binding properties and can be, among others, used for the calibration of bioinorganic force fields. 相似文献
130.
Tauqeer Ahmad Yasir Ayesha Khan Milan Skalicky Allah Wasaya Muhammad Ishaq Asif Rehmani Naeem Sarwar Khuram Mubeen Mudassir Aziz Mohamed M. Hassan Fahmy A. S. Hassan Muhammad Aamir Iqbal Marian Brestic Mohammad Sohidul Islam Subhan Danish Ayman EL Sabagh 《Molecules (Basel, Switzerland)》2021,26(9)
Soil salinity disrupts the physiological and biochemical processes of crop plants and ultimately leads to compromising future food security. Sodium nitroprusside (SNP), a contributor to nitric oxide (NO), holds the potential to alleviate abiotic stress effects and boost tolerance in plants, whereas less information is available on its role in salt-stressed lentils. We examined the effect of exogenously applied SNP on salt-stressed lentil plants by monitoring plant growth and yield-related attributes, biochemistry of enzymes (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) amassing of leaf malondialdehyde (MDA) and hydrogen peroxide (H2O2). Salinity stress was induced by NaCl application at concentrations of 50 mM (moderate salinity) and 100 mM (severe salinity), while it was alleviated by SNP application at concentrations of 50 µM and 100 µM. Salinity stress severely inhibited the length of roots and shoots, the relative water content, and the chlorophyll content of the leaves, the number of branches, pods, seeds, seed yield, and biomass per plant. In addition, MDA, H2O2 as well as SOD, CAT, and POD activities were increased with increasing salinity levels. Plants supplemented with SNP (100 µM) showed a significant improvement in the growth- and yield-contributing parameters, especially in plants grown under moderate salinity (50 mM NaCl). Essentially, the application of 100 µM SNP remained effective to rescue lentil plants under moderate salinity by regulating plant growth and biochemical pathways. Thus, the exogenous application of SNP could be developed as a useful strategy for improving the performance of lentil plants in salinity-prone environments. 相似文献