Morphological study of the organization behavior of rod-coil copolymers and their blends in thin solid films

A detailed study of the self-assembly ability of triblock coil-rod-coil copolymers containing a rigid di(styryl)-anthracene segment covalently linked to oxadiazole-based blocks and their binary blends with oxadiazole-based homopolymers is presented here. The self-organized microdomains seem to pack into a fascinating ordered hexagonal structure obtained at a critical concentration without any significant influence of the sample preparation method, based on evidence obtained by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence microscopy studies. The compatibilization efficiency of these coil-rod-coil copolymers in polymer blends composed of an electron-accepting polyoxadiazole and a luminescent polyanthracene-based pair was studied by atomic force microscopy (AFM). The common feature of all observed morphologies is the compatibilizing function of the rod-coil molecule, which intercalates between the incompatible domains to prevent the formation of well-defined phase separated nanostructured surfaces.     

Novel rectangular [Fe4(mu4-OHO)(mu-OH)(2)](7+) versus "butterfly" [Fe4(mu3-O2](8+) core topology in the Fe(III)/RCO2(-)/phen reaction systems (R = Me,Ph; phen = 1,10-phenanthroline): preparation and properties of [Fe4(OHO)(OH)(2)(O2CMe)(4)(phen)(4)](ClO4)(3), [Fe4O2(O2CPh)(7)(phen)(2)](ClO4), and [Fe4O2(O2CPh)(8)(phen)(2)

The preparations, X-ray structures, and detailed physical characterizations are presented for three new tetranuclear Fe(III)/RCO(2)(-)/phen complexes, where phen = 1,10-phenanthroline: [Fe(4)(OHO)(OH)(2)(O(2)CMe)(4)(phen)(4)](ClO(4))(3).4.4MeCN.H(2)O (1.4.4MeCN.H(2)O); [Fe(4)O(2)(O(2)CPh)(7)(phen)(2)](ClO(4)).2MeCN (2.2MeCN); [Fe(4)O(2)(O(2)CPh)(8)(phen)(2)].2H(2)O (3.2H(2)O). Complex 1.4.4MeCN.H(2)O crystallizes in space group P2(1)/n, with a = 18.162(9) A, b = 39.016(19) A, c = 13.054(7) A, beta = 104.29(2) degrees, Z = 4, and V = 8963.7 A(3). Complex 2.2MeCN crystallizes in space group P2(1)/n, with a = 18.532(2) A, b = 35.908(3) A, c = 11.591(1) A, beta = 96.42(1) degrees, Z = 4, and V = 7665(1) A(3). Complex 3.2H(2)O crystallizes in space group I2/a, with a = 18.79(1) A, b = 22.80(1) A, c = 20.74(1) A, beta = 113.21(2) degrees, Z = 4, and V = 8166(1) A(3). The cation of 1 contains the novel [Fe(4)(mu(4)-OHO)(mu-OH)(2)](7+) core. The core structure of 2 and 3 consists of a tetranuclear bis(mu(3)-O) cluster disposed in a "butterfly" arrangement. Magnetic susceptibility data were collected on 1-3 in the 2-300 K range. For the rectangular complex 1, fitting the data to the appropriate theoretical chi(M) vs T expression gave J(1) = -75.4 cm(-1), J(2) = -21.4 cm(-1), and g = 2.0(1), where J(1) and J(2) refer to the Fe(III)O(O(2)CMe)(2)Fe(III) and Fe(III)(OH)Fe(III) pairwise exchange interactions, respectively. The S = 0 ground state of 1 was confirmed by 2 K magnetization data. The data for 2 and 3 reveal a diamagnetic ground state with antiferromagnetic exchange interactions among the four high-spin Fe(III) ions. The exchange coupling constant J(bb) ("body-body" interaction) is indeterminate due to prevailing spin frustration, but the "wing-body" antiferromagnetic interaction (J(wb)) was evaluated to be -77.6 and -65.7 cm(-1) for 2 and 3, respectively, using the appropriate spin Hamiltonian approach. M?ssbauer spectra of 1-3 are consistent with high-spin Fe(III) ions. The data indicated asymmetry of the Fe(4) core of 1 at 80 K, which is not detected at room temperature due to thermal motion of the core. The spectra of 2 and 3 analyze as two quadrupole-split doublets which were assigned to the body and wing-tip pairs of metal ions. (1)H NMR spectra are reported for 1-3 with assignment of the main resonances.     

Synthesis of N-acyl-2-pyrrolidinones from the corresponding N-acyl-GABA derivatives

In this work, the synthesis of 1-(pyridine-3-carbonyl)pyrrolidin-2-one ( 1a ) and 1-(2-propyl-1-pentanoyl)pyrrolidin-2-one ( 1b ) by cyclization of the corresponding GABA derivatives, is reported. Two different methods are developed. For the synthesis of 1a , the parent molecule 4-[(pyridine-3-carbonyl)-amino]butanoic acid ( 2a ) is treated first with thionyl chloride and then with triethylamine. The second derivative, 1b , is produced by an intramolecular dehydration of 4-(2-propylpentanoylamino)butanoic acid ( 2b ) using an acid catalyst.     

Entropy and enthalpy of formation and migration of lattice defects in Na(I)

The self-diffusion coefficients of Na⁺ and I^?, as well as the ionic conductivity, are measured in Na(I) single crystals, pure and doped with Ca²⁺ ions. The computer analysis of the whole set of data shows that the atom transport in Na(I) is ensured essentially by the free vacancies with a very small contribution (～4%) of the vacancy pairs. The thermodynamic parameters of vacancy formation and migration are derived by taking the long range interactions into account (activity coefficients on the concentrations and relaxation factors on the mobilities). The respective entropies of Schottky defect formation, cation migration and anion migration are equal to 7.64, 3.23 and 2.91 k while the corresponding enthalpies are equal to 2.00, 0.58 and 0.77 eV.     

A proof of W. T. Gowers' theorem

W. T. Gowers' theorem asserts that for every Lipschitz function and 0$">, there exists an infinite-dimensional subspace of such that the oscillation of on is at most . The proof of this theorem has been reduced by W. T. Gowers to the proof of a new Ramsey type theorem. Our aim is to present a proof of the last result.

     

Sensitivity analysis and decomposition of unreliable production lines with blocking

The analysis of finitebuffered, unreliable production lines is often based on the method of decomposition, where the original system is decomposed into a series of twostage subsystems that can be modeled as quasi birthdeath processes. In this paper, we present methods for computing the gradients of the equilibrium distribution vector for such processes. Then we consider a specific production line with finite buffers and machine breakdowns and develop an algorithm that incorporates gradient estimation into the framework of Gershwin's approximate decomposition. The algorithm is applied to the problem of workforce allocation to the machines of a production line to maximize throughput. It is shown that this problem is equivalent to a convex mathematical programming problem and, therefore, a globally optimal solution can be obtained.     

Isomorphous replacement of M(II) ions in M(II)-Gd(III) dimers (M(II) = Cu(II), Mn(II), Ni(II), Co(II), Zn(II)): magnetic studies of the products

Complexes [M(II)Gd(III){pyCO(OEt)pyC(OH)(OEt)py}?](ClO?)?·EtOH [M(II) = Cu(II) (1), Mn(II) (2), Ni(II) (3), Co(II) (4) and Zn(II) (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate M(II) ion and one enneacoordinate Gd(III) ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}? ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2-4. Using the ? = -J?(Gd(III))?(M(II)) spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm?1 for 1, -1.7 cm?1 for 2, and -0.22 cm?1 for 3. In complex 4, the orbital contributions of Co(II) precluded the determination of the magnetic coupling. The complex follows the Curie-Weiss law with θ = -2.07 K (-1.44 cm?1).     

Quantitative combination of volumetric MR imaging and MR spectroscopy data for the discrimination of meningiomas from metastatic brain tumors by means of pattern recognition

The analysis of information derived from magnetic resonance imaging (MRI) and spectroscopy (MRS) has been identified as an important indicator for discriminating among different brain pathologies. The purpose of this study was to investigate the efficiency of the combination of textural MRI features and MRS metabolite ratios by means of a pattern recognition system in the task of discriminating between meningiomas and metastatic brain tumors. The data set consisted of 40 brain MR image series and their corresponding spectral data obtained from patients with verified tumors. The pattern recognition system was designed employing the support vector machines classifier with radial basis function kernel; the system was evaluated using an external cross validation process to render results indicative of the generalization performance to “unknown” cases. The combination of MR textural and spectroscopic features resulted in 92.15% overall accuracy in discriminating meningiomas from metastatic brain tumors. The fusion of the information derived from MRI and MRS data might be helpful in providing clinicians a useful second opinion tool for accurate characterization of brain tumors.     

Measurable events indexed by products of trees

A tree T is said to be homogeneous if it is uniquely rooted and there exists an integer b ≥ 2, called the branching number of T, such that every t ∈ T has exactly b immediate successors. A vector homogeneous tree T is a finite sequence (T ₁,...,T _d ) of homogeneous trees and its level product ?T is the subset of the Cartesian product T ₁×...×T _d consisting of all finite sequences (t ₁,...,t _d ) of nodes having common length. We study the behavior of measurable events in probability spaces indexed by the level product ?T of a vector homogeneous tree T. We show that, by refining the index set to the level product ?S of a vector strong subtree S of T, such families of events become highly correlated. An analogue of Lebesgue’s density Theorem is also established which can be considered as the “probabilistic” version of the density Halpern-Läuchli Theorem.