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21.
Petruleviciene Milda Parvin Maliha Savickaja Irena Gece Gintare Naujokaitis Arnas Pakstas Vidas Pilipavicius Jurgis Gegeckas Audrius Gaigalas Gediminas Juodkazyte Jurga 《Journal of Solid State Electrochemistry》2022,26(4):1021-1035
Journal of Solid State Electrochemistry - Light-assisted electrochemical processes have the potential to replace energy-intensive electrosynthesis technologies, especially in the area of strong... 相似文献
22.
Judzentiene A Butkiene R Budiene J Tomi F Casanova J 《Natural product communications》2012,7(2):227-230
For the first time, the chemical composition of the seed essential oil of Rhododendron tomentosum was determined. Forty-seven compounds were identified, comprising 91.7% of the total oil. Palustrol (38.3%) and ledol (27.0%) were the predominant constituents. Some constituents, such as beta-pinene oxide, iso-menthyl acetate, nerolidyl acetate, cadalene and guaiazulene were characteristic only for the seeds and were identified for the first time in Rh. tomentosum oils. For comparison purposes, the essential oil isolated from the shoots of the same plant were analyzed [GC(FID) in combination with RIs, GC-MS and 13C NMR]. More than a half of the oil was comprised of ledol (36.5%) and palustrol (21.0%). Quantitative analysis of ascaridol, a heat-sensitive compound, was carried out by 13C NMR spectroscopy. Indeed, ascaridol undergoes partial thermal isomerization to iso-ascaridol during GC analyses. 相似文献
23.
Effect of amorphous precipitated silica on the properties and structure of poly(p-phenylene sulfide)
T. Jesionowski K. Bula J. Jurga A. Krysztafkiewicz 《Colloid and polymer science》2001,279(10):983-989
Using a precipitation technique, silicas were obtained from sodium metasilicate solution employing an acidic agent. Alcohol
solutions were used in the process of production of highly dispersed silicas, which resulted in partial blocking of the silica
surface silanol groups. Moreover, studies on morphology and microstructure using transmission electron microscopy and scanning
electron microscopy were performed. The size distributions of primary particles and aggregate and agglomerate structures were
determined using a ZetaPlus instrument using the dynamic light scattering method. The structure and molecular dynamics of
the nanocomposite, consisting of poly (p-phenylene sulfide) (PPS) and of the precipitated silica, were studied using atomic force microscopy and nuclear magnetic
resonance. It was proved that during annealing the fragmentation of PPS agglomerates takes place. This phenomena probably
resulted from repulsion forces existing between agglomerates and aggregates. Fragmentation in the polymer network probably
resulted from repulsion forces between agglomerates and smaller aggregates.
Received: 7 November 2000 Accepted: 5 April 2001 相似文献
24.
In this study we demonstrate the applicability of nuclear magnetic resonance (NMR) microimaging in examining the efficiency of grafting coniferous plants. Grafting is a method of propagating plants. It is used mainly in gardening. In some cases it is the only possible way to propagate certain varieties (e.g., apple varieties). The biology of grafting is not well investigated yet. Therefore we have decided to take advantage of the magnetic resonance imaging techniques in order to estimate which of the commonly used grafting methods gives the best quality unions. Results of our experiment indicate that the quality of union depends very much on the grafting method. NMR images give more information about the graft than microscopic images. We hope that our technique can select the best way to prepare plants for grafting and indicate average time of union process. 相似文献
25.
S. Glowinkowski S. Jurga W. Suchanski E. Szczesniak 《Solid state nuclear magnetic resonance》1997,7(4):313-317
Spin-lattice relaxation times T1 and T1ρ as well as 1H NMR spectra have been employed to study the dynamics of the glass-forming di-isobutyl phthalate in the temperature range extending from 100 K, through the glass transition temperature Tg, up to 340 K. Below Tg NMR relaxation is governed by local dynamics and may be attributed to rotation of methyl groups at low temperatures and to motion of isobutyl groups in the intermediate temperature interval. Above Tg the main relaxation mechanism is provided by overall molecular motion. The observed relaxation behavior is explained by motional models assuming asymmetrical distributions of correlation times. The motional parameters obtained from Davidson-Cole distribution, which yields the best fit of the data at all temperatures are given. 相似文献
26.
A. Woźniak-Braszak M. Szostak K. Jurga J. Jurga A. Piekarz M. Baranowski 《Applied magnetic resonance》2005,29(2):221-229
The aim of the work was to examine molecular dynamics of a series of poly(ethylene 2,6-naphthalate)-polycarbonate blends with
changing weight ratio of copolymers by off-resonance nuclear magnetic resonance technique. It was shown that this technique
provides information about the correlation times of the internal motions. The spectral density function amplitudes were estimated
on the basis of the dispersion of the spin-lattice relaxation time off-resonanceT
lpoff. The measurements were performed for two series of blends which had been injection moulded with and without compatibilizer.
The new polymer materials were also characterized using differential scanning calorimetry. Samples obtained after injection
moulding and annealing became amorphous, which indicates that a reaction of transesterification process between the two polymers
occurred. 相似文献
27.
Farhod Nozirov Zbigniew Fojud Jacek Klinowski Stefan Jurga 《Solid state nuclear magnetic resonance》2002,21(3-4)
Solid poly[(R)-3-hydroxybutyric] acid was examined by high-resolution 13C MAS NMR, differential scanning calorimetry and infrared spectroscopy. The 13C methyl group resonance consists of three components: the rigid amorphous phase, the crystalline phase and the mobile amorphous phase. Spectral deconvolution, using the Lorentz function, reveals the relative amounts as 62% crystalline and 38% amorphous at 333 K, and 42% crystalline, 40% pure amorphous and 18% β-orthorhombic at 413 K. NMR indicates a large difference in molecular mobility between the crystalline and amorphous regions of the sample. Infrared spectroscopy shows that the stretching at 1725 cm−1 (characteristic of the α-form) comes from the crystalline region, and the bands at 1744 cm−1 (characteristic of the β-form) and 1800 cm−1 come from the amorphous region. 相似文献
28.
Ali Mohammad Pourbagher-Shahri Tahereh Farkhondeh Marjan Talebi Dalia M. Kopustinskiene Saeed Samarghandian Jurga Bernatoniene 《Molecules (Basel, Switzerland)》2021,26(15)
Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes. 相似文献
29.
Solid poly[(R)-3-hydroxybutyric] acid was examined by high-resolution 13C MAS NMR, differential scanning calorimetry and infrared spectroscopy. The 13C methyl group resonance consists of three components: the rigid amorphous phase, the crystalline phase and the mobile amorphous phase. Spectral deconvolution, using the Lorentz function, reveals the relative amounts as 62% crystalline and 38% amorphous at 333 K, and 42% crystalline, 40% pure amorphous and 18% β-orthorhombic at 413 K. NMR indicates a large difference in molecular mobility between the crystalline and amorphous regions of the sample. Infrared spectroscopy shows that the stretching at 1725 cm−1 (characteristic of the -form) comes from the crystalline region, and the bands at 1744 cm−1 (characteristic of the β-form) and 1800 cm−1 come from the amorphous region. 相似文献
30.
I. Gnatyuk G. Puchkovska I. Chashechnikova F. Nozirov S. Jurga B. Peplinska 《Journal of Molecular Structure》2004,700(1-3):183-189
It has been found that the main mechanism of 1H protons spin–lattice relaxation of bulk 5CB at 200 MHz is its intramolecular motion, namely, the reorientation of CH2 and CH3 groups of its alkyl chain. Activation parameters of such motions have been estimated.
Drastic decrease in proton spin–lattice relaxation times at the nematic-to-isotropic phase transition can be explained by the activation of molecular translational diffusion and reorientations around long and short molecular axes of bulk 5CB.
Our NMR analysis revealed the slowing-down of molecular dynamics of confined 5CB molecules and their fragments. This can be explained by the interaction of some part of 5CB molecules with the surface active Si(Al)–OH centers of MCM matrix via hydrogen bonds of Si(Al)–OHN≡C-type. 相似文献