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1

Impact of Extra Nitrogen on Ecological Stoichiometry of Alpine Grasslands on Tibetan Plateau : Meta-Analysis

Zhang H. R., Sun W., Li S. W., Han F. S., Yu C. Q., Zhang X. Z., Wang J. S., He Y. T., Zhong Z. M.

Polish Journal of Ecology

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2018

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Vol. 66, nr 4

315--324

EN

The general impact of extra nitrogen on ecological stoichiometry was examined in alpine grasslands on the Tibetan Plateau. Extra nitrogen increased the ratio of nitrogen to phosphorus (N:P ratio) in leaves and aboveground parts of plants by 43.4% and 32.7%, respectively. In contrast, extra nitrogen reduced the ratio of carbon to nitrogen (C:N ratio) in leaves by 30.6%. Extra nitrogen decreased soil C:N ratio by 9.1% in alpine meadows, but increased soil C:N ratio by 3.4% in alpine steppes. Extra urea had a stronger positive impact on aboveground vegetation N:P ratio than did extra ammonium nitrate. Extra urea rather than ammonium nitrate decreased aboveground vegetation C:N ratio and soil C:N ratio. The impact of extra nitrogen on aboveground vegetation N:P ratio was positively correlated with latitude, mean annual temperature and precipitation, nitrogen application rate and accumulated amount, but negatively correlated with elevation, duration and aboveground vegetation N:P ratio of the control plots. The impact of extra nitrogen on leaves N:P ratio was positively correlated with nitrogen application rate and accumulated amount. The impact of extra nitrogen on leaves C:N ratio was positively correlated with latitude, but negatively correlated with mean annual temperature and precipitation, nitrogen application rate, accumulated amount, duration and leaves C:N ratio of the control plots. Therefore, nitrogen enrichment caused by human activities will most likely alter element balance and alpine plants from nitrogen limitation to phosphorus limitation. This effect may weaken with time, and increase with climatic warming, increased precipitation and nitrogen input rate.

2

The effect of polyacrylic acid on the surface properties of calcite and fluorite aiming at their selective flotation

Zhang C., Gao Z., Hu Y., Sun W., Tang H., Yin Z., He J., Guan Q., Zhu Y.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

868--877

EN

In this study, the polyacrylic acid (PAA) was studied as a selective depressant for calcite in the selective flotation of fluorite and calcite, and the implications of this process for the separation of fluorite ore were studied using micro-flotation tests, and the results were analyzed with Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses. The flotation tests indicated that the preferential adsorption of PAA onto calcite rather than sodium oleate (NaOl) could selectively depress the flotation of calcite, allowing its separation from fluorite at pH 7. The zeta potential of calcite became more negative with the addition of PAA rather than with NaOl. However, the characteristic features of PAA adsorption were not observed for fluorite, suggesting that NaOl preferentially adsorbed on the surface of fluorite, or that PAA could be replaced by NaOl on the fluorite surface. FT-IR and XPS analysis were utilized to obtain a better understanding of the mechanism by which PAA was more strongly adsorbed on the calcite surface than NaOl. This was revealed to occur through chemical bonding between the carboxyl group of PAA and the hydroxyl groups of the Ca species on the calcite surface, modifying the structure of the adsorbed layer. A possible adsorption mechanism, along with a postulated adsorption mode for the surface interaction between PAA and calcite, is proposed.

3

The least eigenvalue of the graphs whose complements are connected and have pendent paths

Wang C., Yu G., Sun W., Cao J.

Journal of Artificial Intelligence and Soft Computing Research

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2018

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Vol. 8, No. 4

303--308

EN

The adjacency matrix of a graph is a matrix which represents adjacent relation between the vertices of the graph. Its minimum eigenvalue is defined as the least eigenvalue of the graph. Let Gn be the set of the graphs of order n, whose complements are connected and have pendent paths. This paper investigates the least eigenvalue of the graphs and characterizes the unique graph which has the minimum least eigenvalue in Gn.

4

Three-dimensional simulation of the fracture system distribution in formation rock based on fractal method

Li W., Zhao H., Liu M., Li S., Sun W., Wang L.

Archives of Mining Sciences

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2018

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Vol. 63, no. 2

425--436

EN

During exploitation process of fractured reservoir, the complex distribution of natural fracture system may lead to a series of accidents, such as sand plug and multi fracture extension in hydraulic fracturing operation. Considering the difficulties of numerical analysis on formation rock mass fracture system distribution, three-dimensional geometry model of a single fracture formation is proposed in this paper, and fractal geometry method is introduced to build the three-dimensional fractal description model of formation fracture system distribution. On this basis, the effects of fractal parameters on natural fracture porosity, permeability and other properties are analyzed. The results show that: First, the number and propagation of natural fracture are controlled by the fractal dimension, the number of groups and the initial quantity. Second, the fractal dimension of natural fracture distribution has an obvious effect on natural fracture porosity and permeability. Third, porosity and permeability of natural fracture distribution both experience exponential growth as fractal dimension increases. Fourth, when the fractal dimension remains constant, the porosity and permeability of natural fractures both increase with the fracture scale.

PL

W trakcie eksploatacji złoża zalęgającego w spękanych warstwach i pokładach złożony system naturalnych spękań prowadzić może do licznych incydentów, np. powstawania zatorów piaskowych lub nadmiernego rozszerzenia spękań w trakcie szczelinowania hydraulicznego. Z uwagi na trudności związane z analizą numeryczną rozkładu spękań skał macierzystych, w pracy zaproponowano trójwymiarowy model geometryczny pojedynczego pęknięcia z wykorzystaniem metod geometrii fraktalnej do opracowania trójwymiarowego modelu opisującego powstawanie układu spękań i ich rozkład. Na tej podstawie przeanalizowano wpływ parametrów fraktalnych na naturalną porowatość pękniętych skał, ich przepuszczalność oraz pozostałe właściwości. Wyniki badań wskazują że, po pierwsze, liczba i tempo propagacji naturalnych spękań uzależnione są od wymiarów fraktalnych, liczby grup i wielkości początkowej. Po drugie, wymiary fraktalne naturalnego systemu spękań skał mają zdecydowany wpływ na porowatość i przepuszczalność. Po trzecie, porowatość i przepuszczalność naturalnych systemów pęknięć wykazują wzrost w miarę wzrastania wymiarów fraktalnych. Po czwarte, gdy wymiary fraktalne pozostają niezmienne, zarówno porowatość i przepuszczalność naturalnych spękań rosną wraz ze skalą fraktali.

5

Formation mechanism and control methods of inhomogeneous deformation during hot rough rolling of aluminum alloy plate

Hao P., He A., Sun W.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 1

245--255

EN

The inhomogeneous deformation which appears in hot rough rolling of aluminum alloy plate, reduces rolling output and negatively affects the rolling process. To study the formation mechanism of the inhomogeneous deformation, a finite element model for the five-pass hot rough rolling process of aluminum alloy plate is built. Results show that inhomogeneous deformation distribution in thickness direction causes two bulges at head and tail ends, as indicated by the analysis of the equivalent plastic strain distribution and deformation. However, formation mechanism of the inhomogeneous deformation at head end differs from that at tail end. Changing the end shape and angular rolling are adopted for decreasing the length and width of the crocodile mouth. It can be found that the crocodile mouth can be improved effectively by increasing the central bump length and the rotation angles through simulation and experiments. Then, the combination effect of two methods is simulated and results show that the combination effect is better than respectively using of each method. In addition, combination of two methods can avoid the restricted conditions for respectively using of each method.

6

Reverse flotation of ultrafine magnetic concentrate by using mixed anionic/cationic collectors

Lu D., Hu Y., Li Y., Jiang T., Sun W., Wang Y.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

724--736

EN

Compared to reverse cationic flotation, the advantages of reverse anionic flotation include relatively lower sensitivity to slimes and lower reagent cost. Besides, anionic collectors were found to have excellent capability of selectively separating an ultrafine magnetite ore. Addition of a small amount of cationic collector into the anionic collector as the collector mixture can improve the metallurgical results of removing silicates in reverse flotation. In this paper, NaOL and DDA were used for reverse flotation of the ultrafine magnetic concentrate. The separation performance of the collector mixture was investigated at different ratios of NaOL and DDA. The results showed that a better separation performance was obtained for the collector mixture than for NaOL alone. There was an optimal molar ratio between NaOL and DDA equal to 10:1. In the flotation system with the presence of the collector mixture, the good selectivity was found when starch was used as a depressor for magnetite and CaO was used as an activator for quartz. The influences of starch and CaO dosages on the separation performance of magnetite, quartz and chlorite had been investigated through micro-flotation tests. The infrared spectral analysis showed stretching vibration peaks of chemical adsorption of the collector mixture on the magnetite surface. The peaks were not present when starch was used as the depressor for magnetite. The closed flotation tests on the magnetic concentrate with the particle size of -25 μm were performed in the laboratory. The Fe concentrate assaying 64.52 % was obtained with Fe recovery of 80.66%, for the Fe content of feed equal to 52.98%.

7

Hydrochloric acid leaching for upgrading flotation concentrate from a low-grade bauxite ore

Guan C., Chen L., Zheng Y., Sun W., Zheng Y.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

1038--1046

EN

Bauxite is the major raw material for alumina production, and its Al2O3 grade improvement or desilication is a necessary process for production of high-grade alumina concentrates from bauxite ores. In practice, flotation presents an effective method for the processing of such ores. However, it is not sufficient to produce a concentrate product with high Al2O3 grade from the ores with a single flotation process, especially from these containing abundant carbonate minerals. In this investigation, hydrochloric acid leaching was used to remove dolomite impurity from the flotation concentrate of a bauxite ore, to improve its Al2O3 grade and Al2O3/SiO2 (A/S) ratio. Effects of three dominant parameters on the leaching performance, that is leaching time, leaching temperature and hydrochloric acid concentration, were investigated in details. When these parameters were optimized, the aluminum concentrate assaying 67.41% Al2O3 with 66.84% recovery and 7.44 A/S ratio was obtained from the bauxite ore assaying 42.94% Al2O3 with 2.48 A/S ratio. It was concluded that hydrochloric acid leaching proved an effective method for upgrading of flotation concentrate from a low-grade bauxite ore containing carbonate minerals.

8

An improved Otsu method for oil spill detection from SAR images

Yu F., Sun W., Li J., Zhao Y., Zhang Y., Chen G.

Oceanologia

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2017

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No. 59 (3)

311--317

EN

In recent years, oil spill accidents have become increasingly frequent due to the development of marine transportation and massive oil exploitation. At present, satellite remote sensing is the principal method used to monitor oil spills. Extracting the locations and extent of oil spill spots accurately in remote sensing images reaps significant benefits in terms of risk assessment and clean-up work. Nowadays the method of edge detection combined with threshold segmentation (EDCTS) to extract oil information is becoming increasingly popular. However, the current method has some limitations in terms of accurately extracting oil spills in synthetic aperture radar (SAR) images, where heterogeneous background noise exists. In this study, we propose an adaptive mechanism based on Otsu method, which applies region growing combined with both edge detection and threshold segmentation (RGEDOM) to extract oil spills. Remote sensing images from the Bohai Sea on June 11, 2011 and the Gulf of Dalian on July 17, 2010 are utilized to validate the accuracy of our algorithm and the reliability of extraction results. In addition, results according to EDCTS are used as a comparator to further explore validity. The comparison with results according to EDCTS using the same dataset demonstrates that the proposed self-adapting algorithm is more robust and boasts high-accuracy. The accuracy computing by the adaptive algorithm is significantly improved compared with EDCTS and threshold method.

9

The Soil Drying Along the Increase of Warming Masks the Relation between Temperature and Soil Respiration in an Alpine Meadow of Northern Tibet

Shen Z.-X., Wang J.-W., Sun W., Li S.-W., Fu G., Zhang X.-Z., Zhang Y.-J., Yu C.-Q., Shi P.-L., He Y.-T.

Polish Journal of Ecology

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2016

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Vol. 64, nr 1

125--129

EN

A warming experiment with two magnitudes was performed in an alpine meadow of Northern Tibet since late June, 2013. Open top chambers (OTCs) with two top diameters (0.60 m and 1.00 m) were used to increase soil temperature. Soil respiration (Rs) was measured during the growing season in 2013–2014. The OTCs with top diameters of 1.00 m and 0.60 m increased soil temperature by 1.30 and 3.10oC, respectively, during the whole study period, but decreased soil moisture by 0.02 and 0.05 m3 m-3, respectively. However, the two patters of OTCs did not affect Rs . These results implied that a higher warming did not result in a higher Rs but a greater soil drying. Therefore, a higher warming may not cause a higher soil respiration, which was most likely due to the fact that a higher warming may result in a greater soil drying.

10

Study on pre-concentration efficiency of wolframite from tungsten ore using gravity and magnetic separations

Lu D., Wang Y., Jiang T., Sun W., Hu Y.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

718--728

EN

Pre-concentration is effectively applied in recovering wolframite from tungsten ore, due to its benefits of further upgrading tungsten ore and improving separation efficiency. The most important pre-concentration techniques for tungsten ore include gravity separation and magnetic separation, based on the fact that there are appreciable differences, between the desired wolframite and the gangue minerals, in density and magnetic susceptibility. This study investigated the separation efficiency of gravity pre-concentration (Falcon Concentrator) and high-gradient magnetic pre-concentration (SLon VPHGMS) for the beneficiation of a Canada tungsten ore. It is a low-grade type of ore with high silica and arsenic content, and an average content of WO3 is about 0.45%. The optimum conditions for different operational parameters of two pre-concentration separators were studied on this low-grade material. The results presented in this paper suggested that although both pre-concentration techniques were effective for producing pre-concentrates containing high WO3, magnetic pre-concentration showed significantly better separation efficiency. Over 90% of the feed was rejected as the final tailings, meanwhile, over 85% of arsenic minerals were removed with tailings, while the WO3 loss was less than 15%.

11

Nonlinear inverse solution by the look-up table method for Risley-prism-based scanner

Li A., Sun W., Gao X.

Optica Applicata

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2016

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Vol. 46, nr 4

501--515

EN

A pair of rotation Risley prisms can perform superior optical pointing and tracking functions with large visual field and high accuracy. Crucial to the function implementation are the nonlinear inverse solutions to the double-prism orientation angles for tracking a given target trajectory. In the paper, a novel look-up table method is proposed to solve this problem. Because there are two groups of solutions to the rotation angles achieved from an arbitrary target point, a "jump" phenomenon occurs and generates the discontinuous curves of multi-group rotation angle solutions. According to the mapping relation between the coordinate values of the target point and the corresponding rotation angles of two prisms, we can establish the continuous solution curves by adding constraints and employing an optimization algorithm. Experimental results validate the obtained inverse solutions applicable to scan a trajectory close to the given one within an error threshold. The proposed look-up table method can provide foundation for the continuous control of the Risley-prism-based scanner in its inverse applications.Keywords: Risley prism, look-up table method, inverse solution, scanner.

12

A scheme of resource allocation and stability for peer-to-peer file-sharing networks

Li S., Sun W., E C. G., Shi L.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 3

707--719

EN

Peer-to-peer (P2P) networks offer a cost-effective and easily deployable framework for sharing content. However, P2P file-sharing applications face a fundamental problem of unfairness. Pricing is regarded as an effective way to provide incentives to peers to cooperate. In this paper we propose a pricing scheme to achieve reasonable resource allocation in P2P file-sharing networks, and give an interpretation for the utility maximization problem and its sub-problems from an economic point of view. We also deduce the exact expression of optimal resource allocation for each peer, and confirm it with both simulation and optimization software. In order to realize the optimum in a decentralized architecture, we present a novel price-based algorithm and discuss its stability based on Lyapunov stability theory. Simulation results confirm that the proposed algorithm can attain an optimum within reasonable convergence times.

13

Interannual Variation of the Growing Season Maximum Normalized Difference Vegetation Index, MNDVI, and Its Relationship with Climatic Factors on the Tibetan Plateau

Wang S.-H., Sun W., Li S.-W., Shen Z.-X., Fu G.

Polish Journal of Ecology

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2015

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Vol. 63, nr 3

424--439

EN

The effects of the growing season climatic factors (i.e., temperature, precipitation, vapor pressure and relative humidity) on the growing season maximum normalized difference vegetation index (MNDVI), which can mirror the aboveground net primary production and the vegetation maximum absorbed ability of photosynthetically active radiation, were examined during the period from 2000 to 2012 on the Tibetan Plateau. The effects of climatic factors on the MNDVI changed with vegetation types, which was probably due to the fact that the changes of climatic factors differed with the type of vegetation. There was a significant increasing trend for the spatially averaged MNDVI of the vegetation area over the entire plateau. Approximately 16 and 3% of the vegetation area demonstrated a significant MNDVI increasing and decreasing trend, respectively. The MNDVI was significantly affected by relative humidity and vapor pressure, but not affected by temperature and precipitation over the entire plateau. Our findings suggested that the environmental humidity played a predominant role in affecting the variation of MNDVI over the entire Tibetan Plateau.

14

Wpływ chlorków na mikrostrukturę betonu w warunkach cyklicznego zamrażania i rozmrażania

Li M., Zhang Y., Wu Z., Qian C., Sun W.

Cement Wapno Beton

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2013

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R. 18/80, nr 2

74--80

PL

Chlorkowe sole odladzające działające w warunkach cyklicznego zamrażania i rozmrażania są przyczyną poważnych uszkodzeń betonu. W pracy badano zmiany modułu sprężystości, masy próbek i ich porowatość w oparciu o metodę ultradźwiękową, skaningową mikroskopię elektronową oraz porozymetrię rtęciową. Wyniki badań wykazują utratę masy próbek, jak również spadek modułu sprężystości ze wzrostem liczby cykli zamrażania i rozmrażania, czasu przetrzymywania w minimalnej temperaturze i zawartością soli odladzającej.

EN

Chloride deicer and freeze-thaw cycles can cause serious damage of concrete. The relative dynamic elastic modulus, weight loss and porosity were measured by using ultrasonic testing method, Scanning Electron Microscopy and Mercury Intrusion Porosimetry. The microstructure change of concrete under the action of chloride salt and freeze-thaw cycling were analyzed. The results showed that the weight loss and the relative dynamic elastic modulus are decreasing with the salt deicer use and freeze-thaw cycles.

15

NCPIE: network-coding-based cooperative peer-to-peer information exchange in wireless communications

Sun W., Zhang G., Xiao J., Liang G.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 3b

214-218

EN

In this paper, we propose a network-coding-based cooperative peer-to-peer information exchange (NCPIE) algorithm to solve peer scheduling problem in wireless communications. NCPIE can achieve lower transmission delay and higher network throughput by studying the issue of scheduling transmission opportunities among peers in wireless communications. Experimental results demonstrate the effectiveness of NCPIE is best than that of rarest first algorithm and peer-to-peer information exchange algorithm.

PL

W artykule zaproponowano algorytm NCPIE wymiany informacji w bezprzewodowych sieciach P2P. Można osiągnąć mniejsze opóźnienia transmisji i większą przepływność przez stosowanie odpowiednich harmonogramów wymiany.

16

Interval Multi-objective Optimization Design Based on Physical Programming

Zhang X., Sun W., Huo J., Ding X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 7b

379--381

EN

This paper develops a new effective and computationally-efficient approach for design optimization, hereby entitled interval physical programming optimization design. In view of the limitation that weights without physical meaning are required to be provided in traditional evaluation methods, physical programming is used in multi-objective optimization problem. Considering the uncertain factors in manufacture process and operation environment, the interval physical programming model (IPP) is improved. Decision-makers only need to set the boundary values of each preference range，thereby the interval objective of selected projects are computed with the IPP model. To address the existing problems in structure optimal design, the manufacturing tolerances of each dimension are defined as the region limits of design variables. The example of multi-objective optimization design of a pinned-pinned sandwich-beam demonstrates the effectiveness and practicality of the proposed method.

PL

W artykule zaproponowano nowy skuteczny model optymalizacji projektowania nazwany: interval physical programming optimization design. Model wykorzystuje problem optymalizacji wieloobiektowej uwzględniając niepewność w procesie produkcji i warunki środowiskowe.

17

Badania i analiza mechanizmu zapobiegającego odpryskom w betonie o wysokiej wytrzymałości za pomocą włókien polipropylenowych

Li M., Wu Z., Sun W., Qian C.

Cement Wapno Beton

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2011

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R. 16/78, nr 3

129-138

PL

Jak wiadomo mikrowłókna polipropylenowe (PP) zapobiegają powstawaniu odprysków w betonach o wysokiej wytrzymałości (BWW) poddanych działaniu wysokiej temperatury. W pracy przedstawiono doświadczenia obejmujące obserwacje mikrostruktury, pomiary wytrzymałości i współczynnika przepuszczalności BWW z dodatkiem włókien polipropylenowych. Przeprowadzono także obliczenia ciśnienia pary wodnej i analizę przebiegu pola tego ciśnienia w betonie poddanego działaniu wysokiej temperatury. Wykazano, że pole ciśnienia pary występuje w betonie w wysokiej temperaturze. Ciśnienie pary zmienia się z temperaturą, położeniem w betonie i czasem, co prowadzi do utworzenia szczytowego ciśnienia w betonie. W BWW poddanym działaniu wysokiej temperatury powstają mikro-kanaliki w miejscach zajmowanych poprzednio przez włókna PP. Powoduje to wzrost porowatości i współczynnika przepuszczalności betonu co zmniejsza ciśnienie pary wodnej i zakres odprysków.

EN

It is known that polypropylene (PP) micro-fibres can restrain the spalling of high strength concrete (HSC) exposed to high temperatures. In the paper an experimental study embracing micro-structural analysis, as well as test strength and permeability coefficient measurements of HSC mixed with PP micro-fibers are presented. Moreover, the calculation of water vapour pressure and an analysis of the pressure field in concrete under high temperature are performed. It was shown that a vapour pressure field exists in concrete exposed to high temperature. The vapour pressure is changing with temperature, position and time and a peak pressure of vapour is formed in concrete. In HSC exposed to high temperature micro-channels are formed in the places previously occupied by PP micro-fibers. As the result pore volume and water permeability coefficient of concrete is increased, thereby releasing the water vapour pressure and reducing the degree of spalling.

18

Electrochemical studies of interactions of pyronine B with RNA and determination of RNA

Sun W., You J., Wang Q., Jiao K.

Chemia Analityczna

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2006

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Vol. 51, No. 4

477-488

EN

Interaction of pyronine B (PB) with yeast RNA (yRNA) has been studied by electrochemical method on a hanging mercury drop electrode (HMDE) in 0.2 mol L(-1) Britton-Robinson (B-R) buffer solution. Under selected conditions, voltammetric peak at-0.90 V (vj SCE) corresponding to reduction of PB was formed. After addition of yRNA, the height of the reduction peak of PB apparently decreased and its potential exhibited a positive shift; no new redox peaks were observed. Some electrochemical properties of PB were quantitatively determined in the absence and in the presence of yRNA. It has been found that the values of E°, ks, an, etc. changed in the presence of yRNA, which indicated the formation of electroactive PB—RNA complex. yRNA was electroinactive in the selected potential range. Consequently, redox activity of PB in PB-RNA biocomplex was lowered and the corresponding peak height was decreased, as well as the peak potential was shifted. Conditions of the binding reaction and electrochemical detection of PB have been optimised. Under optimum conditions a decrease of peak current was linearly proportional to the concentration of yRNA in the range 1.0-35.0 μg mL(-1). The corresponding regression equation is: δIp(nA) = 24.12C (μg mL(-1) + 25.27 (n = 14, r = 0.993), detection limit is 0.73 μg mL(-1)(3σ). The proposed method has been applied to the determination of yRNA in synthetic samples with satisfactory results.

PL

Badano oddziaływania między pyroninąB (PB) i RNA z drożdży (yRNA) stosując wiszącą kroplową elektrodę rtęciową (HMDE, WKER) w środowisku buforu Britona-Robinsona o stężeniu 0,2 mol L(-1). W wybranych warunkach eksperymentalnych, obserwowano pik woltamperometryczny redukcji PB w potencjale -0,90 V (względem NEK). Po dodaniu do roztworu yRNA, pik PB malał, a jego potencjał przesuwał się w stronę dodatnią. Nie obserwowano powstawania nowego piku. Opisano ilościowo elektrochemiczne zachowanie PB w obecności i nieobecności yRNA. Stwierdzono niewielką zmianę wartości takich parametrów redukcji PB jak: E°, ks i αn; świadczy to o tworzeniu się elektroaktywnego kompleksu PB-RNA. Zoptymalizowano warunki powstawania kompleksu i oznaczania PB. W optymalnych warunkach obniżenie prądu piku PB zależało liniowo, w zakresie stężeń l ,0-35,0 μg mL(-1), od stężenia yRNA. Zależność tę można opisać równaniem δIp (nA) = 42,12 C(μg mL(-1) + 25,27 (n = 14, r = 0,993). Granicę wykrywalności określono jako 0,73 μg mL(-1)(3σ). Zaproponową metodę zastosowano z sukcesem do oznaczania yRNA w próbkach syntetycznych.

19

Synthesis and Magnetism of Ferromagnetically Coupled {Cu II 3 Cr III] Heterotetranuclear Complexes with N,N'-Bis(aminoalkyl)oxamidatocopper(II)

Li Y., Yan C., Xu G., Zhang G., Sun W.

Polish Journal of Chemistry

|

2005

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Vol. 79 / nr 9

1415-1424

EN

The strategy of "complex as ligand" allowed us to synthesize two new _-oxamido- bridged copper(II)-chromium(III) heterotetranuclear complexes formulated as [Cu3(oxae)3Cr](ClO4)3 (1) and [Cu3(oxpn)3Cr](ClO4)3 (2), where oxae and oxpn represent N,N_-bis(2-aminoethyl)oxamido and N,N_-bis(3-aminopropyl)oxamido dianions, respectively. Based on elemental analyses, molar conductivity and magnetic moment (room-temperature) measurements, IR, ESR and electronic spectral studies, these complexes are proposed to have oxamido-bridged structures consisting of three copper(II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment and the three copper(II) ions have a square-planar environment. The two heterotetranuclear complexes were further characterized by variable-temperature magnetic susceptibility (3~300 K) measurements and the magnetic data have been used to deduce the indicated heterotetranuclear structure. The results derived from least-squares fit of the experimental data have confirmed the ferromagnetic interaction between the adjacent copper(II) and chromium(III) ions through the oxamido-bridge within each molecule. On the basis of the spin Hamiltonian operator, H=-2J(S Cu1 . S Cr+S Cu2 . S Cr + S Cu3 . S cr) , the magnetic analyses were carried out for the two copper(II)-chromium(III) heterotetranuclear complexes and the spin-coupling constants (J) were evaluated as +13.98 cm-1 for (1) and +12.65 cm-1 for (2). The results indicate that the bridging oxamido should be able to transmit ferromagnetic interaction in the strict orthogonality [Cu3 IICrIII] system. The influence of the symmetry of the magnetic orbitals on the nature of the magnetic interaction between the paramagnetic centers is preliminarily discussed.

20

Synthesis and Magnetism of Cu(II)-Ln(III)-Cu(II) (Ln+La, Nd, Gd, Tb, Ho, Er) Trinuclear Complexes Bridged by N, N'-Bis[3-dimethylamino)propyl]oxamido

Yan C., Li L., Li Y., Zhang G., Sun W.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1425-1433

EN

Six new mi-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes described by the overall formula Cu2(dmoxpn)2Ln(NO3)3 {Ln = La, Nd, Gd, Tb, Ho, Er; dmoxpn = N,N'bis[3-(dimethylamino)propyl]oxamido dianions} have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectral studies. The variable-temperature susceptibility (4.2~300 K), ESR measurements, and studies of the Cu2(dmoxpn)2Gd(NO3)3 complex have revealed that the central gadolinium(III) and terminal copper(II) ions are ferromagnetically coupled with the exchange integral J(Cu-Gd) = +6.85 cm-1, while an antiferromagnetic coupling is detected between the terminal copper(II) ions with J'(Cu-Cu) = -0.27 cm-1, on the basis of the spin Hamiltonian operator [H=-2J(S Cu1.S Gd+S Cu2.Gd)-2J(S Cu1.S Cu2)]. A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium( III) is discussed in terms of spin polarization.