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571.
Blazej Scheibe Ewa Borowiak-Palen Ryszard J. Kalenczuk 《Journal of nanoparticle research》2011,13(11):5769-5780
This study presents the approach to the purification and subsequent metallic/semiconductive (M/S) fractionation of single-walled
carbon nanotubes (SWCNTs) with diameter from 1.04 to 1.60 nm produced via laser ablation. SWCNTs were purified through 3-fold
refluxing processes in nitric acid followed by the multiple washings with sodium hydroxide and hydrochloric acid. The purified-annealed
SWCNTs sample was divided into seven batches. One batch was dispersed in acetone as a reference sample. Each of the remaining
batches were dispersed in one of the following surface agents: sodium dodecyl sulfate, sodium cholate acid (SCA), sodium deoxycholate,
cetrimonium bromide, cetylpyridinium chloride, and benzalkonium chloride (BKC). SWCNT suspensions were fractionated via free
solution electrophoresis technique. The recovered fractions from electrode and control areas were analyzed via optical absorption
spectroscopy in UV–Vis–NIR range to evaluate the efficiency of the separation process. Raman spectroscopy was applied to analyze
the purity of the samples. The catalyst content was estimated by atomic absorption spectroscopy. The morphology of the investigated
samples was observed via high-resolution transmission electron microscopy. This contribution clearly shows that among the
investigated surfactants there are two promising candidates (SCA and BKC) which can efficiently enrich the bulk sample in
one electronic type of carbon nanotubes when FSE is applied. 相似文献
572.
Ryszard Piasecki 《Physica A》2008,387(22):5333-5341
The statistical measure of spatial inhomogeneity for n points placed in χ cells each of size k×k is generalized to incorporate finite size objects like black pixels for binary patterns of size L×L. As a function of length scale k, the measure is modified in such a way that it relates to the smallest realizable value for each considered scale. To overcome the limitation of pattern partitions to scales with k being integer divisors of L, we use a sliding cell-sampling approach. For given patterns, particularly in the case of clusters polydispersed in size, the comparison between the statistical measure and the entropic one reveals differences in detection of the first peak while at other scales they well correlate. The universality of the two measures allows both a hidden periodicity traces and attributes of planar quasi-crystals to be explored. 相似文献
573.
Mateusz Krzyzosiak Zheyu Huang Shiping Feng Ryszard Gonczarek 《Physica C: Superconductivity and its Applications》2010,470(7-8):407-414
Within the framework of the kinetic energy driven superconductivity, the electromagnetic response in cuprate superconductors is studied in the linear response approach. The kernel of the response function is evaluated and employed to calculate the local magnetic field profile, the magnetic field penetration depth, and the superfluid density, based on the specular reflection model for a purely transverse vector potential. It is shown that the low temperature magnetic field profile follows an exponential decay at the surface, while the magnetic field penetration depth depends linearly on temperature, except for the strong deviation from the linear characteristics at extremely low temperatures. The superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance is addressed and an approximation for the dressed current vertex, which does not violate local charge conservation is proposed and discussed. 相似文献
574.
Ryszard Gonczarek Mateusz Krzyzosiak Adam Gonczarek Lucjan Jacak 《Frontiers of Physics》2018,13(2):137403
We evaluate some thermodynamic quantities and characteristic ratios that describe low- and high-temperature s-wave superconducting systems. Based on a set of fundamental equations derived within the conformal transformation method, a simple model is proposed and studied analytically. After including a one-parameter class of fluctuations in the density of states, the mathematical structure of the s-wave superconducting gap, the free energy difference, and the specific heat difference is found and discussed in an analytic manner. Both the zero-temperature limit T = 0 and the subcritical temperature range T ? Tc are discussed using the method of successive approximations. The equation for the ratio R1, relating the zero-temperature energy gap and the critical temperature, is formulated and solved numerically for various values of the model parameter. Other thermodynamic quantities are analyzed, including a characteristic ratio R2, quantifying the dynamics of the specific heat jump at the critical temperature. It is shown that the obtained model results coincide with experimental data for low-Tc superconductors. The prospect of application of the presented model in studies of high-Tc superconductors and other superconducting systems of the new generation is also discussed. 相似文献
575.
Biochemical speciation analysis by hyphenated techniques 总被引:3,自引:0,他引:3
The elucidation of mechanisms that govern the essentiality and toxicity of trace elements in living organisms is critically dependent upon the possibility of the identification, characterization and determination of chemical forms of these elements involved in life processes. The recent progress and the state-of-the-art of biochemical species-selective trace element analysis are critically evaluated with particular emphasis on the use of techniques combining the high selectivity of high performance liquid chromatography (HPLC) with the elemental or molecular specificity of mass spectrometry [using inductively coupled plasma (ICP) or electrospray ionization (ESI)]. The potential and limitations of hyphenated techniques as a tool for speciation of metals and metalloids in biological materials is discussed using a number of examples drawn from the latest research in the authors’ laboratory. 相似文献
576.
Julia Pretula Krzysztof Kaluzynski Ryszard Szymanski Stanislaw Penczek 《Journal of polymer science. Part A, Polymer chemistry》1999,37(9):1365-1381
Polycondensation of 1,10‐decanediol with dimethyl‐H‐phosphonate taken in excess leads to oligomers with methyl‐H‐phosphonate end groups. The polytransesterification of the resulting oligomer as well as the related model reactions were studied. The synthesis of poly(decamethylene‐H‐phosphonate) was analyzed and the final product had M̄n = 1.4–1.9 104 (from end groups, vpo, and M̄n of the derived polymers). The exchange of the ester groups between two homoesters (dimethyl and diethyl phosphonates) used as models, conducted at r.t. and catalyzed by metal alkoxide provides mixed (hetero) ester in a few minutes. If the concentration of the catalyst is not high enough, then the reaction does not go to equilibrium, because the alcoholate anions are converted into the anions of monoesters of the H‐phosphonic acid, catalytically inactive at this temperature. However, these monoesters become catalytically active at higher temperature, i.e., at the conditions used for preparing higher molecular‐weight products by transesterification. The apparent rate constants (k̄) of the ester exchange catalyzed by monoester salt (modeling the propagation step in polytransesterification) were determined by two independent methods; at 130°C k̄ ∼ 1.0 · 10−2 mol−1 · L · s−1. The detailed study of the model polytransesterification, and particularly of the polymer end groups appearance and disappearance (studied by 1H‐, 13C‐, and 31P‐NMR) allowed postulation of the reaction mechanism and confirmed our previous work, describing formation at these conditions of polymers with M̄n > 104. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1365–1381, 1999 相似文献
577.
Jan Janczak Ryszard Kubiak 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(6):m237-m240
Isomorphous triclinic forms of dichloro[phthalocyaninato(2−)]tin(IV), [Sn(C32H16N8)Cl2], and dichloro[phthalocyaninato(2−)]germanium(IV), [Sn(C32H16N8)Cl2], and a monoclinic form of the latter have been obtained from the reaction of pure tin and germanium powder, respectively, with phthalonitrile under a stream of ICl vapour. All three crystal structures consist of centrosymmetric [SnPcCl2] and [GePcCl2] [Pc is phthalocyaninate(2−)] molecules, which are separated but interacting. In the triclinic forms (Sn and Ge), the Pc macrocycles are not staggered but slipped, and in the monoclinic form (Ge), the molecules are additionally inclined. In both cases, the central Sn or Ge atom is six‐coordinated by the four isoindole N atoms of the Pc macrocyclic ligand and by two Cl atoms (located trans) into a tetragonal–bipyramidal structure. The arrangement of [SnPcCl2] and [GePcCl2] molecules in the crystal structure is determined mainly by intermolecular C—H⃛Cl, π–π and van der Waals interactions. 相似文献
578.
Ryszard Szorek 《Macromolecular theory and simulations》2001,10(6):634-643
In this work a theoretical approach to dynamics of linear vinyl polymers in dilute solutions of high viscosity solvents is presented. The calculations for the relaxation time spectra, polymer intrinsic viscosity [η (ω)], complex elastic modulus G*(ω), total intrinsic viscosity [ηT (ω)] and specific heat capacity C (ω) were carried out in the non‐free‐draining limits. The relaxation time spectrum calculated for dynamics of low frequency modes exhibits a Rouse‐like character. Its position and shape corresponds to the ultrasonic relaxation time spectrum observed in the system at 106 Hz. On the other hand, the relaxation time spectrum associated with moderate frequency mode dynamics is narrower and typical for ultrasonic relaxation observed at 107 Hz. The polymer intrinsic viscosity [η (ω)] and elastic modulus G*(ω) are shown to be represented by the model within a low‐frequency range. In turn, the specific heat capacity C (ω) is displayed as a representation of the model in the acoustic region mentioned above. In the high‐frequency range the dynamics is described by the total intrinsic viscosity [ηT (ω)] tending to a plateau where the value is equal to the sum of the single‐bead intrinsic viscosity [ηN] and effective solvent viscosity [ηeff]. 相似文献
579.
Results of studies on synthesis and properties of siloxane–urethane prepolymers as well as on selected properties of moisture‐cured silicone–urethanes have already been published. In this paper, some results of investigations of the effect of chemical structure of such silicone–urethane polymers on their phase seggregation investigated using mainly (TEM) transmission electron microscopy and small‐angle x‐ray scattering (SAXS) techniques are presented. It was found in TEM studies that in silicone‐urethanes obtained by moisture‐curing of NCO‐terminated prepolymers prepared from siloxane oligomer diols (SOD) and isophoronediisocyanate (IPDI), two factors determine the morphology of samples: length of siloxane chain and NCO/OH ratio. SAXS investigations showed that these silicone–urethanes had a lamellar structure. It was found that the long period of this structure changed from 4 to 9 nanometers as the siloxane chain length increased nine times. The increase of the long period correlated with the decrease of Young's modulus of the corresponding samples. TEM investigations of silicone–urethanes obtained by moisture‐curing of NCO‐terminated prepolymers prepared from the blends of SOD and polyoxypropylenediol (PPG) revealed complex morphology which depended on the SOD/PPG ratio. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
580.
Chain transfer to macromolecules with chain scission is the most often observed “side” reaction in the polymerization of heterocyclics. In our previous works we analysed quantitatively the intramolecular chain transfer to the own macromolecule (back-biting). This paper gives a general treatment of the kinetics of polymerization with propagation and intermolecular chain transfer to macromolecules, accompanied with chain scission. The numerical solution developed allows determining the kp/ktr ratio from the dependence of m̄w/m̄n on monomer conversion. This treatment was applied to the polymerization of L,L-lactide and kp/ktr ratios were measured for covalent alcoholate active species bearing Al, Fe, Ti, Sm, and La. In this way selectivities of active species (expressed with kp/ktr) were for the first time measured and finally correlated with the atomic number of the corresponding metal atoms, related to the strength of the bond involved in the monomer addition. 相似文献