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121.
A reversible, displacive, pressure-induced structural phase transition has been found to occur in nickel monophosphide NiP at approximately 3.5 GPa by means of in situ synchrotron single-crystal X-ray diffraction. The new phase, with Pearson symbol oC56, assumes an orthorhombic structure with Cmc21 space group and unit cell parameters a=23.801(2) Å, b=5.9238(6) Å, and c=4.8479(4) Å at 5.79 GPa. The high-pressure phase is a superstructure of the ambient, oP16 phase with multiplicity of 3.5. The phosphorous sublattice gradually converts from the net of isolated P2 dimers found in the ambient NiP, towards zig-zag polymeric P∞ chains found in MnP-type structures. The transformation involves development of triatomic phosphorous clusters and interconnected Ni slabs with diamondoid topology. The high-pressure phase, which represents intermediate polymerization step, is a commensurately modulated superstructure of the NiAs aristotype. The phase transformation in NiP bears resemblance to the effect of successive substitution of Si or Ge in place of P found in the series of stoichiometric inhomogeneous linear structures in ternary NiP1−xSix and NiP1−xGex systems. 相似文献
122.
Adaptive memory programming: local search parallel algorithms for phylogenetic tree construction 总被引:1,自引:0,他引:1
Jacek Blazewicz Piotr Formanowicz Pawel Kedziora Pawel Marciniak Przemyslaw Taront 《Annals of Operations Research》2011,183(1):75-94
One of the most important aspect of molecular and computational biology is the reconstruction of evolutionary relationships.
The area is well explored after decades of intensive research. Despite this fact there remains a need for good and efficient
algorithms that are capable of reconstructing the evolutionary relationship in reasonable time. 相似文献
123.
Przemyslaw Gawel Cagatay Dengiz Dr. Aaron D. Finke Dr. Nils Trapp Prof. Dr. Corinne Boudon Dr. Jean‐Paul Gisselbrecht Prof. Dr. François Diederich 《Angewandte Chemie (International ed. in English)》2014,53(17):4341-4345
A versatile, two‐step synthesis of highly substituted, cyano‐functionalized diaryltetracenes has been developed, starting from easily accessible tetraaryl[3]cumulenes. This unprecedented transformation is initiated by [2+2] cycloaddition of tetracyanoethylene (TCNE) to the proacetylenic central double bond of the cumulenes to give an intermediate zwitterion, which after an electrocyclization cascade and dehydrogenation yields 5,5,11,11‐tetracyano‐5,11‐dihydrotetracenes in a one‐pot procedure. A subsequent copper‐assisted decyanation/aromatization provided the target 5,11‐dicyano‐6,12‐diaryltetracene derivatives. All of the postulated structures were confirmed by X‐ray crystallography. The new chromophores are thermally highly stable and feature promising fluorescence properties for potential use in optoelectronic devices. They are selective chemosensors for CuI ions, which coordinate to one of the CN substituents and form a 1:1 complex with an association constant of Ka=1.5×105 L mol?1 at 298 K. 相似文献
124.
125.
Simultaneous speciation analysis of inorganic nitrogen with the use of ion chromatography in highly salinated environmental samples
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Iwona Kurzyca Przemyslaw Niedzielski Marcin Frankowski 《Journal of separation science》2016,39(18):3482-3487
We present the development of a method for the simultaneous determination of inorganic nitrogen species in oxidized (NO2–, NO3–) and reduced (NH4+) forms using ion chromatography with diode‐array detection (205, 208, and 425 nm, respectively). The oxidized forms were determined directly after the separation in the anion exchanger, while the reduced form was determined in the column hold‐up time after derivatization with the Nessler reagent. The use of an appropriate modifier (Seignette reagent) and mobile phase (NaCl) enabled the determination of inorganic nitrogen species in highly salinated environmental samples (water, sediments). Moreover, low detection limits were obtained of 0.04 mg/L for NH4+ and 0.006 and 0.005 mg/L for NO2– and NO3–, respectively. The analysis of environmental samples indicated NH4+ contents of up to 1161 ± 47 mg/kg and NO3– of up to 148 ± 6 mg/kg for sediment samples, as well as the NH4+ concentrations of up to 0.98 ± 0.10 mg/L, NO2– of up to 24 ± 1 mg/L and NO3– of up to 20 ± 1 mg/L for water samples. 相似文献
126.
Krzysztof Czolczynski Przemyslaw Perlikowski Andrzej Stefanski Tomasz Kapitaniak 《Communications in Nonlinear Science & Numerical Simulation》2013,18(2):386-400
We consider the synchronization of a number of self-excited identical pendula hanging on the same beam which can move vertically. We identify different synchronous configurations and investigate their stability. An approximate analytical analysis of the energy balance allows to derive the synchronization conditions, phase difference between pendula and explains the observed types of synchronizations. 相似文献
127.
Vladimir P. Fonf Michael Lin Przemyslaw Wojtaszczyk 《Israel Journal of Mathematics》2010,179(1):479-491
We construct on any quasi-reflexive of order 1 separable real Banach space an equivalent norm, such that all contractions
on the space and all contractions on its dual are mean ergodic, thus answering negatively a question of Louis Sucheston. 相似文献
128.
Przemyslaw Malanowski Saskia Huijser Rolf A.T.M. van Benthem Leendert G.J. van der Ven Jozua Laven Gijsbertus de With 《Polymer Degradation and Stability》2009,94(11):2086-2094
In this paper the mechanisms of photodegradation of poly(neopentyl isophthalate) (PNI) in laboratory (Suntest XXL+, λ > 300 nm) and outdoor conditions are compared. Changes in the chemical composition were studied with ATR-FTIR, SEC and MALDI-ToF MS. Furthermore, the results were compared with data presented in our previous paper on PNI coatings that were aged in the UVACUBE (λ > 254 nm). Two main aspects of photodegradation of PNI are addressed in the present paper: the influence of different wavelengths and the comparison of laboratory and outdoor exposure regarding the mechanism of degradation. Under short (λ > 254 nm) and long (λ > 300 nm) wavelength irradiation similar products of degradation are formed. However, the presence of short wavelength radiation dramatically accelerates the overall rate of photodegradation of PNI. UV light absorption calculations confirm this experimentally found acceleration. Exposure of PNI in laboratory and outdoor conditions, both with wavelengths λ > 300 nm resulted in similar degradation products in the initial stage of ageing. 相似文献
129.
Sebastian Zurek Przemyslaw Guzik Sebastian Pawlak Marcin Kosmider Jaroslaw Piskorski 《Physica A》2012
We explore the relation between correlation dimension, approximate entropy and sample entropy parameters, which are commonly used in nonlinear systems analysis. Using theoretical considerations we identify the points which are shared by all these complexity algorithms and show explicitly that the above parameters are intimately connected and mutually interdependent. A new geometrical interpretation of sample entropy and correlation dimension is provided and the consequences for the interpretation of sample entropy, its relative consistency and some of the algorithms for parameter selection for this quantity are discussed. To get an exact algorithmic relation between the three parameters we construct a very fast algorithm for simultaneous calculations of the above, which uses the full time series as the source of templates, rather than the usual 10%. This algorithm can be used in medical applications of complexity theory, as it can calculate all three parameters for a realistic recording of 104 points within minutes with the use of an average notebook computer. 相似文献
130.
D'Silva L Ozdowy P Krajewski M Rothweiler U Singh M Holak TA 《Journal of the American Chemical Society》2005,127(38):13220-13226
We describe an NMR method that directly monitors the influence of ligands on protein-protein interactions. For a two-protein interaction complex, the size of one component should be small enough (less than ca. 15 kDa) to provide a good quality (15)N((13)C) HSQC spectrum after (15)N((13)C) labeling. The size of the second unlabeled component should be large enough so that the molecular weight of the preformed complex is larger than ca. 40 kDa. When the smaller protein binds to a larger one, broadening of NMR resonances results in the disappearance of most of its cross-peaks in the HSQC spectrum. Addition of an antagonist that can dissociate the complex would restore the HSQC spectrum of the smaller component. The method directly shows whether an antagonist releases proteins in their wild-type folded states or whether it induces their denaturation, partial unfolding, or precipitation. We illustrate the method by studying lead compounds that have recently been reported to block the MDM2-p53 interaction. Activation of p53 in tumor cells by inhibiting its interaction with MDM2 offers new strategy for cancer therapy. 相似文献