Wyniki wyszukiwania - Biblioteka Nauki

1

O protokóle Ekerta w kryptografii kwantowej

100%

Czajkowski R. , Nowakowski W.

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2010

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tom Vol. 51, nr 3

126-127

PL

W artykule podano ogólne informacje o zastosowaniu zjawiska EPR w kryptografii kwantowej (protokół Ekerta).

EN

General information about EPR and Ekert algorithm application in quantum cryptography is given.

2

Wolne rodniki w dymie tytoniowym – metody analizy i znaczenie biomedyczne

94%

Kośmider L. , Knysak J. , Gawron M. , Czogała J. , Goniewicz M. Ł.

Medycyna Środowiskowa - Environmental Medicine

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2013

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tom 16

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nr 3

7-14

EN

Free radicals, i.e. atoms or groups of atoms containing one or more unpaired electrons, are significant constituents of tobacco smoke that contribute to its toxic properties. Radicals are generated during complex pyrolysis and combustion reactions in burning a cigarette cone. It has been shown that some free radicals found in tobacco smoke have relatively long half-time life (over 5 mins). We have reviewed modern analytical methods used for identification and quantitative analysis of free radicals in tobacco smoke, particularly the electron paramagnetic resonance combined with a spin-trapping approach. We also discussed the role of free radicals in etiology of respiratory and cardiovascular conditions among smokers. Finally, we reviewed biochemical mechanisms of various pathological conditions, including disturbances in lipid peroxidation, activity modification of lecithin-cholesterol acyltransferase and level high density lipoprotein, hyperactivity to substance P, and inactivation of neutral endopeptidase, that are thought to be contributed by free radicals from tobacco smoke.

PL

Wolne rodniki – atomy lub grupy atomów, zawierające jeden lub więcej niesparowanych elektronów, są jednym z wielu czynników odpowiedzialnych za toksyczne właściwości dymu tytoniowego. Rodniki powstają w wyniku procesów spalania oraz procesów pirolizy, zachodzących w stożku żarzenia w trakcie wypalania papierosa. Niektóre rodniki występujące w dymie tytoniowym mają względnie długi okres półtrwania (ponad 5 min.). W niniejszej pracy omówiono nowoczesne metody analityczne służące do identyfikacji i ilościowej analizy wolnych rodników w próbkach dymu tytoniowego, ze szczególnym uwzględnieniem elektronowego rezonansu paramagnetycznego, w połączeniu z metodą pułapkowania spinowego. W pracy dokonano przeglądu istniejących poglądów na temat roli wolnych rodników w etiologii określonych chorób układu krążenia i układu oddechowego u palaczy, a także potencjalnych mechanizmów biochemicznych odpowiedzialnych za różne stany patologiczne (zaburzenia procesów peroksydacji lipidów, modyfikacje struktury i aktywności acylotransferazy lecytyna:cholesterol i poziomu lipoproteiny wysokiej gęstości, nadwrażliwość na substancję P i inaktywację obojętnej endopeptydazy).

3

Effect of microwave power on EPR spectra of natural and synthetic dental biocompatible materials

94%

Adamczyk J. , Ramos P. , Pilawa B.

Nukleonika

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2015

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tom 60

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nr 3

449-453

EN

Paramagnetic centers in the two exemplary synthetic and natural dental biocompatible materials applied in implantology were examined by the use of an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra were measured in the range of microwave power 2.2–70 mW. The aims of this work were to compare paramagnetic centers concentrations in different dental biocompatible materials and to determine the effect of microwave power on parameters of their EPR spectra. It is the very first and innovatory examination of paramagnetic centers in these materials. It was pointed out that paramagnetic centers existed in both natural (~1018 spin/g) and synthetic (~1019 spin/g) dental biocompatible materials, but the lower free radical concentration characterized the natural sample. Continuous microwave saturation of EPR spectra indicated that faster spin-lattice relaxation processes existed in synthetic dental biocompatible materials than in natural material. Linewidths (ΔBpp) of the EPR spectra of the natural dental material slightly increased for the higher microwave powers. Such effect was not observed for the synthetic material. The broad EPR lines (ΔBpp): 2.4 mT, 3.9 mT, were measured for the natural and synthetic dental materials, respectively. Probably strong dipolar interactions between paramagnetic centers in the studied samples may be responsible for their line broadening. EPR spectroscopy is the useful experimental method in the examination of paramagnetic centers in dental biocompatible materials.

4

Growth and EPR properties of ErVO4single crystals

94%

Leniec G. , Kaczmarek S. M. , Berkowski M. , Głowacki M. , Skibiński T. , Bojanowski B.

Nukleonika

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2015

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tom 60

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nr 3

405-410

EN

Single crystals of ErVO4 were grown by the Czochralski method under ambient pressure in a nitrogen atmosphere. Obtained crystals were transparent with strong pink coloring. Electron paramagnetic resonance (EPR) spectra were recorded as a function of the applied magnetic field. Temperature and angular dependences of the EPR spectra of the samples in the 3–300 K temperature range were analyzed applying both Lorentzian––Gauss approximation for diluted medium and Dyson for dense magnetic medium. EPR-NMR program was done to find local symmetry and spin Hamiltonian parameters of erbium ions.

5

Dyson line and modified Dyson line in the EPR measurements

94%

Popovych V. , Bester M. , Stefaniuk I. , Kuzma M.

Nukleonika

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2015

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tom 60

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nr 3

385-388

EN

The difficulty in determining the electron paramagnetic resonance (EPR) line parameters of ferromagnetic semiconductors has been addressed. For these materials, the resonance line is very broad and lies at low resonance field, so that only a part of the line can be detected experimentally. Moreover, the line is of asymmetric (Dysonian) shape as described by the line shape parameter α. We have compared values of line parameters derived by computer fitting of the whole experimental EPR line to the Dyson function (or modified Dyson function) with the values obtained by applying this procedure to the left and the right half of the line.

6

Electronic properties of M2InV3O11 (M(II) = Zn(II) and Co(II)) compounds

94%

Guskos N. , Glenis S. , Karkas K. , Zolnierkiewicz G. , Bosacka M.

Materials Science Poland

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2013

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tom Vol. 31, No. 1

25-28

EN

The electronic properties of multicomponent vanadate oxides M2InV3O11 (M(II) = Zn(II) and Co(II)) were investigated by electrical resistivity and electron paramagnetic resonance (EPR) measurements. Replacement of non-magnetic Zn(II) cations with magnetic Co(II) ions resulted in a significant drop in the electrical conductivity and an increase in the activation energy. The EPR spectroscopy revealed the presence of VO2+ vanadyl ions in both compounds, while the presence of divalent cobalt ions was identified in the Co2InV3O11 oxide at low temperatures. The concentration of VO2+ vanadyl ions was found to be about one order higher for the vanadate oxide without magnetic ions. It is suggested that the increased concentration of VO2+ ions could be responsible for the enhanced conductivity of Zn2InV3O11.

7

Synthesis and Properties of a Trinuclear Copper(II) Complex with Trithiocyanurate Bridge

94%

Kopel P. , Čermáková S. , Dolezal K. , Kalińska B. , Bieńko A. , Mroziński J.

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2007

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tom Vol. 81, nr 3

327-335

EN

Mixed-ligand trinuclear Cu(II) complex involving trithiocyanurate(3-) anion (ttc3-) and N,N,N',N' , N'-pentamethyldiethylenetriamine (pmdien) in the coordination sphere of composition [Cu3(pmdien)3(mi-ttc)](ClO4)3 has been prepared. The complex has been characterized by EA, IR, UV-Vis, and mass spectroscopy. We can assume, that the complex is trinuclear with central atoms connected by trithiocyanurate(3-) bridges. Each central atom is in deformed trigonal bypiramidal arrangement formed by chelating S,N atoms of ttc(3-) and by three N atoms of pmdien. Temperature dependence of magnetic susceptibility and EPR spectroscopy have also been employed to characterize the compound. Magnetic susceptibility measurements over the 1.8-300 K temperature range revealed antiferromagnetic interactions among central atoms. The antitumor activity in vitro against G-361 (human malignant melanoma), HOS (human osteogenic sarcoma), K-562 (human chronic myelogenous leukaemia) and MCF-7 (human breast adenocarcinoma) tumor cell lines have been tested but unfortunately the complexes showed no cytotoxic activity against the four cell lines.

8

Microwave saturation of EPR spectra of oxidised coal

94%

Pilawa B. , Więckowski A. , Pietrzak R. , Wachowska H.

Open Chemistry

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2007

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tom 5

|

nr 1

330-340

EN

Microwave saturation of multi-component EPR spectra of oxidized lignite Mequinenza (Spain) with a carbon content of 65.1 wt % and with a high sulphur content of 10.3 wt % was studied. The coal was oxidized with nitric acid (NHO3), peroxyacetic acid (PAA), and in O2/Na2CO3 system. Three different groups of paramagnetic centres exist in the coal samples analyzed. The EPR spectrum of the demineralised coal was a superposition of broad Gauss (ΔB pp = 0.75 mT), broad Lorentz 1 (ΔB pp = 0.42 mT) and narrow Lorentz 3 lines (ΔB pp = 0.08 mT). The three EPR components with linewidths: 0.58–0.77 mT (Gauss line), 0.30–0.39 mT (Lorentz 1 line) and 0.05–0.06 mT (Lorentz 3 line) were recorded for the oxidized coal. The g-values were obtained for the samples studied in the ranges 2.0043–2.0046 (Gauss lines), 2.0035–2.0038 (Lorentz 1 lines) and 2.0032–2.0034 (Lorentz 3 lines). The broad Gauss and Lorentz 1 lines saturate at low microwave powers. The narrow Lorentz 3 lines of demineralised coal were not saturated at microwave power from the range considered. After the coal oxidation with HNO3, PAA and in O2/Na2CO3 system, the microwave saturation of the narrow Lorentz 3 lines was also observed, which indicated a degradation of the multi-ring aromatic structures upon oxidation. [...]

9

Stereochemistry of New Nitrogen Containing Aldehydes : V. Novel Synthesis and Spectroscopic Studies of Some Quinoline Schiff Bases Complexes

94%

El-Sonbati A. , El-Bindary A.

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2000

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tom Vol. 74, nr 5

621-630

EN

The synthesis of several new coordination compounds of Copper(II), nickel(II), cobalt(II), manganese(II), iron(II), tin(II), mercuryl(II), dioxouranium(VI) and iron(III) are described. The ligands and the complexes have been characterized by elemntal analyses, together with magnetic susceptibility measurements.

10

Growth and EPR properties of KSm(WO4)2 and KEr(WO4)2 single crystals

94%

Leniec G. , Skibiński T. , Kaczmarek S. , Iwanowski P. , Berkowski M.

Open Physics

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2012

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tom 10

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nr 2

500-505

EN

Growth conditions and electron paramagnetic resonance investigations of two well oriented KSm(WO4)2 and KEr(WO4)2 single crystals have been presented and discussed. Hyperfine structure of Sm3+ ion was detected and analyzed for angular and temperature dependences. EPR spectra of KEr(WO4)2 and its angular dependence showed the presence of 5 magnetically nonequivalent Er centers in the crystal. A change in the type of magnetic interactions was analyzed using mixed (Gaussian and Lorentzian) fits of the EPR spectra.

11

EPR and optical properties of KYb(WO4)2 and KTb0.2Yb0.8(WO4)2 single crystals

94%

Kaczmarek S. , Macalik L. , Fuks H. , Leniec G. , Skibiński T. , Hanuza J.

Open Physics

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2012

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tom 10

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nr 2

492-499

EN

Well oriented KYb(WO4)2 and KTb0.2Yb0.8(WO4)2 single crystals have been investigated for their magnetic and optical properties using the Raman and EPR techniques. The registered EPR signal is dominated by three lines ascribed to ytterbium ions: one main and two satellites. Tb ions, although non-paramagnetic, distinctly modify magnetic properties of the KYb(WO4)2 single crystal. Basic parameters of the spin Hamiltonian, including Zeeman and hyperfine terms (g and A matrices) as well the spatial orientation between principal and crystallographic axes systems were determined for both crystals.

12

A single crystal EPR study of {CuCl(C6H9N3O3)2xH2O}2Cl2

94%

Wojakowska H. , Januszczyk M. , Pietrzak J.

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2000

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tom Vol. 48, No. 2

117-123

EN

Single crystal of the [CuCl(C6H9N3O3)2 o H2O}2C12 was studied by EPR in 9.4 GHz at room temperature. The components of the g tensor were found to be gc* = 2.241, 0j = 2.094 and ga = 2.062. Since the local symmetry at the cupric ion site is no lower than rhombic, the EPR results were interpreted in terms of the theory for axial symmetry (4 + 1). A consistent explanation of the EPR and optical data is discussed. A comparison of experimental and theoretical resonance line widths suggests that the magnetic system is zero dimensional and the dominant superexchange interaction involves next-nearest neighbour Cu(II) ions.

13

X-Ray and EPR study on copper (II) complexes with an enamine ligand

94%

Ahmedova A. , Vaz M. , Ciattini S. , Gochev G. , Caneschi A. , Mitewa M.

Open Chemistry

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2005

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tom 3

|

nr 1

146-156

EN

The enamine (HEAID) obtained from aniline and 2-acetyl-1,3-indandione (2AID) behaves as a bidentate ligand in coordination with copper (II) ion. Two types of crystals, apparently different in shape, were isolated and studied by single-crystal X-ray diffraction. The X-ray data for the brown rhombic crystals of compound 1 shows a mononuclear complex of Cu(II) coordinated with two EAID-anions, Cu(EAID)2. The X-ray data for the green crystals of compound 2 shows a dinuclear Cu(II) complex with two OH− groups acting as bridging ligands, [Cu2(μ-OH)2(EAID)2]. In both cases the ligand coordinates after deprotonation of the amine group.

14

Elektronowy rezonans paramagnetyczny nanokompozytów (CoFeZr)x(Al2O3)(100-x) wytwarzanych rozpylaniem jonowym

84%

Zhukowski P. , Kołtunowicz T. N. , Sidorenko J. , Fedotova J.

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2012

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tom R. 88, nr 7a

324-326

PL

W pracy przedstawiono wyniki badań metodą elektronowego rezonansu paramagnetycznego (EPR) właściwości magnetycznych nanokompozytów (CoFeZr)x(Al2O3)(100-x) wytworzonych rozpylaniem jonowym w atmosferze argonu (próbki beztlenowe) oraz argonu i tlenu (próbki tlenowe). Ustalono, że w badanych materiałach występuje pojedyncza linia EPR, parametry której Hmin, Hmax, Hg oraz czynnik g wykazują silną zależność kątową. Jest ona związana ze zmianą czynnika rozmagnesowania z kątem ustawienia próbki w stosunku do wektora natężenia pola magnetycznego. Wektor namagnesowania w próbkach beztlenowych jest większy, niż w próbkach tlenowych co jest związane z udziałem części atomów metali w związkach z tlenem. Wygrzewanie termiczne do Ta = 450°C powoduje wzrost wektora namagnesowania i czynnika g.

EN

The paper presents results of studies with the method of electron paramagnetic resonance (EPR) on properties of magnetic nanocomposites (CoFeZr)x(Al2O3)(100-x) produced by ion sputtering in an argon atmosphere (anaerobic samples) or argon and oxygen atmosphere (aerobic samples). It was found that there is a single EPR line in the material studied which parameters like Hmin, Hmax, Hg and a factor g show a strong angular dependence. It is connected with the change of the demagnetization factor according to the sample set angle relative to the vector of magnetic field strength. Magnetization vector in the anaerobic samples is larger than in aerobic samples that is connected with the participation of the certain metal atoms in compounds with oxygen. Thermal annealing up to the value of Ta = 450°C causes increase of the magnetization vector and the factor g.

15

Nowoczesne spektroskopowe techniki w badaniach artykułów spożywczych

84%

Marek D.

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2002

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tom R. 7, nr 6

12-13

PL

Starzenie się produktów spożywczych jest procesem pogarszającym walory smakowo-zapachowe, zatem również przydatność do spożycia. Powstawanie specyficznego odoru i smaku to efekt działania aldehydów, a te z kolei są wynikiem przebiegających reakcji wolnorodnikowych. To powstawanie wolnych rodników jest odpowiedzialne za psucie się żywności. Procesy te są ściśle związane z temperaturą i przebiegają bardzo wolno, gdy produkty spożywcze są przechowywane w chłodniach, a bardzo szybko w wysokich temperaturach.

16

Synthesis, characterization and spectroscopic properties of some 2-substituted 1,3-indandiones and their metal complexes

83%

Ahmedova A. , Atanasov V. , Marinova P. , Stoyanov N. , Mitewa M.

Open Chemistry

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2009

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tom 7

|

nr 3

429-438

EN

New 2-acyl-1,3-indandione derivatives, compounds 1–4, were obtained by condensation of 2-acetyl-1,3-indandione with benzaldehyde, thiophene-2-aldehyde, thiophene-3-aldehyde and furane-2-aldehyde, respectively. The structures of the newly synthesized 2-substituted 1,3-indandiones were characterized by means of spectroscopic methods (FT-IR, 1H and 13C NMR, UV-Vis and MS). Based on the obtained results it is suggested that the compounds exist in the exocyclic enolic form. Mass spectral fragmentation paths are also proposed. In order to verify the possibility for tautomerization processes of the newly synthesized compounds their absorption spectra were recorded in various solvents. Furthermore, the complexation properties of the compounds with metal(II) ions were also studied. A series of non-charged complexes with Cu(II), Cd(II), Zn(II), Co(II) and Ni(II) was isolated and analyzed by elemental analyses and IR. The paramagnetic Cu(II) complexes were studied by EPR and distorted, flattened tetrahedral structures are predicted. The other metal complexes show the presence of water molecules, most probably coordinated to the metal ion, thus forming octahedral geometry. Ultimately, the studied properties of the newly synthesized compounds, 1–4, suggest that they may find application as extracting agents for metal ions, rather than as optical sensors. [...]

17

Effect of microwave power on EPR spectra of thermally sterilizedeucerinum anhydricum

83%

Ramos P. , Pepliński P. , Pilawa B.

Nukleonika

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2015

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tom 60

|

nr 3

439-442

EN

Free radicals formed during thermal sterilization of eucerinum anhydricum – the pharmaceutical base were examined by an X-band (9.3 GHz) spectrometer. Eucerinum anhydricum was sterilized at different physical conditions according to the Polish Pharmacopeia norms. The samples were heated at temperatures: 160°C (120 min), 170°C (60 min), and 180°C (30 min). The aim of this study is to compare free radical concentration and effect of microwave power on EPR spectra of eucerinum anhydricum base thermally sterilized at different temperatures and periods of time. The effect of time storage on the free radicals in the heated samples was tested. Free radical concentrations in the sample stored 15 min strongly decreased with the increasing of sterilization temperature, probably as the result of recombination. Storage caused strong decrease of free radical concentrations in the samples, probably as the result of interactions with oxygen. It was observed to be independent of sterilization conditions from 2 days of storage and longer. Because of the lowest free radical concentration, for eucerinum anhydricum thermal sterilization at 180°C for 30 min is recommended. The sterilized samples should be stored at inert atmosphere without oxygen molecules. Fast spin-lattice relaxation processes existed in sterilized eucerinum anhydricum. The character of changes of amplitudes and linewidths of EPR lines with increasing of microwave power was the same for different storage times. The parameters of thermal sterilization and storage time influenced free radical concentration in eucerinum anhydricum, but magnetic spin-lattice interactions were unchanged. The usefulness of EPR spectroscopy in optimization of thermal sterilization process of eucerinum anhydricum was confirmed.

18

Synthesis, characterization, catalytic and antimicrobial studies of ruthenium(III) complexes

83%

Thilagavathi N. , Jayabalakrishnan C.

Open Chemistry

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2010

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tom 8

|

nr 4

842-851

EN

Ru(III) complexes of the type [RuXB(L)2] have been prepared by the reaction of 3,4-dihydropyrimidin-2(1H)-ones/thiones (HL1–HL4) with the precursors of the type [RuX3B3] where X=Cl or Br; B=PPh3 or AsPh3 and L is the deprotonated ligand. The synthesized complexes were characterized by physico-chemical methods, electrochemical and magnetic moment data. The catalytic efficiency of the complexes were examined in the oxidation of alcohols and antimicrobial studies were also carried out. [...]

19

Oxovanadium(IV) complexes of bromo-and methoxy substituted N1,N4-diarylidene-S-methylthiosemicarbazones

83%

Demirci T. , Köseoğlu Y. , Güner S. , Ülküseven B.

Open Chemistry

|

2006

|

tom 4

|

nr 1

149-159

EN

Four new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations. The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis, conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g‖ < g⊥ < ge = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The EPR spectra recorded from solution forms almost have isotropic character.

20

Callitriche cophocarpa - a new rich source of active phenolic compounds

83%

Augustynowicz J. , Długosz-Grochowska O. , Kostecka-Gugała A. , Leja M. , Kruczek M. , Świderski A.

Open Chemistry

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2014

|

tom 12

|

nr 4

519-527

EN

This study was focused on the analysis of the contents (by HPLC-DAD) and antioxidant activity of phenolic compounds of aquatic higher plant Callitriche cophocarpa. The novelty of the work was: 1) the study of the species which is almost unknown in the context of investigations of bio-active compounds and, 2) the application of a unique L-band electron resonance spectroscopy (L-band EPR) to measure antioxidant activity of samples. The results were compared with those obtained for microalgae Chlorella and Spirulina which are widely distributed as the diet supplements. The obtained results are very promising with respect to the freeze-dried material of Callitriche, which revealed both high level of phenolic compounds (33 mg g−1 dry weight) and antioxidant activity (0.14 g of reduced DPPH· g−1 dry weight). An isoform of sinapic acid appeared to be the main fraction in this sample. The average content of the total phenolic compounds in Callitriche freeze-dried samples was ca. 43 or 25 times higher than in the case of the Chlorella or Spirulina samples, respectively. These samples showed also 16 times lower scavenging activity in relation to freeze-dried Callitriche material.