Dynamics of shear-thinning suspensions of core-shell structured latex particles

The rheological behavior and microstructure of shear-thinning suspensions of core-shell structured carboxylated latex particles were examined. The steady shear viscosity of the suspension increased with increasing dissociation of the carboxyl groups or increasing particle concentration, however the critical shear stress sigma(c) and inter-particle distance xi of the microstructure did not change. With increasing particle diameter, sigma(c) increased and xi decreased. These results were consistent with a Brownian hard sphere model, in which competition exists between the bulk mass transfer due to the applied field and diffusion of the particles. We confirmed that sigma(c) depends on xi, as expressed by sigma(c) = 3kT/4pi xi3. This relationship is consistent with the dynamics of a Brownian hard sphere model with particle diameter xi. Thus the dynamics of shear-thinning suspensions of core-shell particles can be explained by a Brownian thermodynamic model.     

Reaction of Ketones with 1,4-Diaza-1,3-diene Zirconium and Hafnium Complexes: First Example of a 1,3-Dipolar Cycloaddition Reaction of 1,4-Diaza-1,3-diene Complexes of Early Transition Metals

The novel complexes M[O(R)PhCH{CH=N(tBu)}N(tBu)](2) [M = Zr, R = Me (4a), R = Ph (4b) and M = Hf, R = Me (5a), R = Ph (5b)] have been prepared in almost quantitative yield by reaction of (tBu-DAD)(2)Zr (1) and (tBu-DAD)(2)Hf (2) [tBu-DAD = (tBu)N=CHCH=N(tBu)] with 2 equiv of the ketones MeCOPh (3a) or PhCOPh (3b). The reaction proceeds via a 1,3-dipolar cycloaddition of the C=O bond across the M-N-C unit of the DAD complexes. The molecular structures of the complexes 4a and 5b have been determined by a single-crystal X-ray diffraction study (4a, triclinic, space group P&onemacr;; a = 10.395(2) ?, b = 10.865(2) ?, c = 16.842(3) ?, alpha = 93.80(3) degrees, beta = 99.84(3) degrees, gamma = 106.12(3) degrees, V = 1787.4(6) ?(3), Z = 2, R1 = 0.035 (wR2 = 0.101) for 6963 reflections with I > 2sigma(I); 5b, monoclinic, space group P2(1)/c, a = 19.961(4) ?, b = 10.482(2) ?, c = 20.150(4) ?, beta = 91.30(1) degrees, V = 4215(1) ?(3), Z = 4, R1 = 0.036 (wR2 = 0.097) for 4650 reflections with I > 2sigma(I)). The metal atoms in 4a and 5b adopt a pseudooctahedral coordination sphere consisting of four nitrogen and two oxygen atoms. The distortion is a consequence of the [2.2.1] bicyclic structure of the newly formed tridentate ligands which are not able to span three regular octahedral positions.     

Structure-dependent dc conductivity and relaxation time in the Debye-Stokes-Einstein equation

The basis for a modification of the Debye-Stokes-Einstein (DSE) equation between the dc conductivity, sigma(dc), and dielectric relaxation time, tau, has been examined by using broad-band dielectric spectroscopy of LiClO4 solutions in 5-methyl-2-hexanol and 1-propanol and of pure liquids. According to the DSE equation, the log sigma(dc)-log tau plots should have a slope of -1. We find that sigma(dc) begins to depend upon the structure of an electrolytic solution when a variation of solvent's equilibrium dielectric permittivity, epsilon(s), with temperature causes the ion population to vary. As a consequence of this intrinsic dependence, the log sigma(dc)-log tau plots do not obey the DSE equation. Inclusion of the effect of change in epsilon(s) on the DSE equation may be useful in analyzing the measured quantities in terms of Brownian diffusion of both ions and molecules in ultraviscous liquids. Proton translocation along a hydrogen bond contributes little to sigma(dc), which appears to be predominantly determined by the ion population in the two alcohols and the solutions. The effect is briefly discussed in the potential energy landscape paradigm of structure fluctuations, and it is suggested that the high-frequency shear modulus measurements of ionic solutions would help reveal the temperature-dependent deviation from the DSE equation.     

Physical insights from a penetration depth model of optically pumped NMR

A model of optically pumped NMR (OPNMR) behavior in GaAs that connects the photon energy dependence of the OPNMR signal intensity for (69)Ga with different polarizations of light has been developed. Inputs to this model include experimental conditions--external magnetic field (B(0)), temperature (T), and optical pumping parameters (tau(L), laser helicity)--as well as parameters that arise from sample-specific characteristics--electron spin lifetime (T(1e)), electron lifetime (tau(e)), electron-nuclear correlation time (tau(c)), and sample thickness (z). These various inputs affect the profile of the OPNMR signal intensity as a function of photon energy (E) in a predictable manner. Therefore, the profile can serve as a composite fingerprint by which individual parameters can be inferred when not known. Characteristics of the profile include the photon energy for maximum OPNMR signal intensity and the intensity ratio between sigma(+) and sigma(-) light.     

Ph3PAuX和Ph3AsAuX(X=Cl,Br)的最低三重激发态

分子水平上的激发态理论研究能够用来解释分子材料的多色发光机理. 采用单组态相互作用方法, 计算研究了四种二配位的Au(I)配合物Ph3PAuCl, Ph3PAuBr, Ph3AsAuCl和Ph3AsAuBr的分子结构限制的三重激发态(T1a)和分子结构松弛的三重激发态(T1b)的分子结构与光物理性质. 由于θ(PAuX)/θ(AsAuX)从180°扭曲到120°左右, T1b态的能量在单线态组态相互作用(CIS)水平上降低了0.805-1.124 eV, 在密度泛函理论(DFT)水平上降低了0.820-0.947 eV. 自然键轨道电荷布居数分析表明, 在T1a态中两个单电子主要分布在一个苯基上, 而在T1b态中两个单电子分布在PAuX/AsAuX 上. 因此, 在晶体中观察到的较高能磷光归属于T1a态的苯基之间的3π*→1π电子跃迁, 而较低能磷光主要起源于T1b态的Au 的3σ*→1σ电子跃迁.     

Phase behavior of semiflexible polymer chains

Monte Carlo simulations were performed on semiflexible polymer chains with the goal of delineating their isotropic-nematic (IN) and gas-liquid coexistence envelopes. The chain monomers are spherical beads that interact via a square-well potential with all other beads. Bonded beads are connected by strings chosen so that bond length varies between 1.01sigma and 1.05sigma (where sigma is the hard sphere diameter). The stiffness of the molecules is controlled via a potential between beads separated by two bonds; this potential restricts the distance between these beads to be between 2.02sigma and 2.1sigma. The vapor-liquid coexistence and IN coexistence curves are obtained using computer simulations. An IN transition is found for 10相似文献   

Analysis of variance in determinations of equivalence volume and of the ionic product of water in potentiometric titrations

Homogeneous sets of data from strong acid-strong base potentiometric titrations in aqueous solution at various constant ionic strengths have been analysed by statistical criteria. The aim is to see whether the error distribution matches that for the equilibrium constants determined by competitive potentiometric methods using the glass electrode. The titration curve can be defined when the estimated equivalence volume VEM, with standard deviation (s.d.) sigma (VEM), the standard potential E(0), with s.d. sigma(E(0)), and the operational ionic product of water K(*)(w) (or E(*)(w) in mV), with s.d. sigma(K(*)(w)) [or sigma(E(*)(w))] are known. A special computer program, BEATRIX, has been written which optimizes the values of VEM, E(0) and K(*)(w) by linearization of the titration curve as a Gran plot. Analysis of variance applied to a set of 11 titrations in 1.0M sodium chloride medium at 298 K has demonstrated that the values of VEM belong to a normal population of points corresponding to individual potential/volume data-pairs (E(i); v(i)) of any titration, whereas the values of pK(*)(w) (or of E(*)(w)) belong to a normal population with members corresponding to individual titrations, which is also the case for the equilibrium constants. The intertitration variation is attributable to the electrochemical component of the system and appears as signal noise distributed over the titrations. The correction for junction-potentials, introduced in a further stage of the program by optimization in a Nernst equation, increases the noise, i.e., sigma(pK(*)(w)). This correction should therefore be avoided whenever it causes an increase of sigma(pK(*)(w)). The influence of the ionic medium has been examined by processing data from acid-base titrations in 0.1M potassium chloride and 0.5M potassium nitrate media. The titrations in potassium chloride medium showed the same behaviour as those in sodium chloride medium, but with an s.d. for pK(*)(w) that was smaller and close to the expected instrumental noise, whereas the titrations in nitrate medium had a high noise level and even the determination of VEM was less certain. Procedures are also proposed for obtaining reference sets of data and checking the conformity of the solutions and apparatus to the chosen reference.     

New Routes to Synthetically Useful, Sterically Encumbered Arylaluminum Halides and Hydride Halides

The synthesis and structural characterization of the compounds MesAlCl(2)(THF) (1), MesAlCl(2) (2), MesAl(H)Cl(THF) (3a), MesAl(H)Cl (4a), and (MesAlH(2))(2) (5) (Mes = 2,4,6-t-Bu(3)C(6)H(2)(-)) are described as well as those for two compounds 3b and 4b that are analogs of 3a and 4a but have H:Cl ratios that are less than 1:1. All compounds were characterized by (1)H, (13)C NMR, and IR spectroscopy, and 1, 2, 3a, and 4b were additionally characterized by X-ray crystallography. Compound 1 is best synthesized by the reaction of [(THF)(2)LiH(3)AlMes](2) (6) with 6 equiv of Me(3)SiCl. A more conventional route involving the addition of (THF)(2)LiMes to 2 equiv of AlCl(3) in toluene usually affords a mixture of 1 and AlCl(3).THF. Recrystallization of 1 from n-hexane results in a species that has less than 1 equiv of THF per MesAlCl(2). The THF free complex 2 may be obtained in quantitative yield by heating 1 for 20 min at 90 degrees C under reduced pressure. Compound 3a may be obtained by treating a 1:1 mixture of MesLi(THF)(2) and LiAlH(4) with 2 equiv of Me(3)SiCl or by the addition of slightly less than 4 equiv of Me(3)SiCl to 6. The THF can be removed from 3a by sublimation to give 4a. The related compounds 3b and 4b, which display an aluminum-bound H:Cl ratio that is deficient in H, can be obtained by reactions with slightly more than 2 equiv of Me(3)SiCl. Crystal data at 130 K with Cu Kalpha (lambda = 1.541 78 ?) radiation: 1, C(22)H(37)AlCl(2)O, a = 11.889(3) ?, b = 9.992(3) ?, c = 19.704(5) ?, orthorhombic, space group Pca2(1), Z = 4, R = 0.068 for 1556 (I > 2sigma(I)) data; 2, C(18)H(29)AlCl(2), a = 12.147(5) ?, b = 18.042(6) ?, c = 17.771(7) ?, beta = 95.77(3) degrees, monoclinic, space group P2(1)/n,Z = 8, R = 0.032 for 4610 (I > 2sigma(I)) data; 3a, C(22)H(38)AlClO, a = 16.887(7) ?, b = 16.333(6) ?, c = 8.739(3) ?, beta = 101.41(3) degrees, monoclinic, space group P2(1)/c, Z = 4, R = 0.073 for 2752 (I > 2sigma(I)) data; 4b, C(18)H(29.64)AlCl(1.36), a = 12.077(3) ?, b = 17.920(3) ?, c = 17.634(5) ?; beta = 95.21(2) ?, monoclinic, space group P2(1)/n,Z = 8, R = 0.070 for 4261 (I > 2sigma(I)) data.     

Effect of local background intensities in the normalization of cDNA microarray data with a skewed expression profiles

Normalization of the data of cDNA microarray is an obligatory step during microarray experiments due to the relatively frequent non-specific errors. Generally, normalization of microarray data is based on the null hypothesis and variance model. In the Yang's model (Yang et al., 2001), at least two types of noises are included. The one is additive noise and the other is multiplicative noise. Usually, background is considered as one of additive noise to the signal and the variation between the signal pixels is the representative multiplicative noise. In this study, the relation between the signal (spot intensity minus background intensity) and background was observed and the influence of background on normalization as a representative additive factor was investigated. Although the relation has not been considered as a factor affecting the normalization, it could improve the accuracy of microarray data when the normalization was carried out considering signal/background ratio. The background dependent normalization decreased the number of genes whose expression levels were changed significantly and it could make their distribution more consistent through the whole range of signal intensities. In this study, printing pin dependent normalization was also carried out regarding the printing pin as a representative multiplicative noise. It improved the distribution of spots in the Cy3-Cy5 scatter plot, but its effect was slight. These studies suggest that there are some influences of the signals on the local backgrounds and they must be considered for the normalization of cDNA microarray data.     

New tetrathiapentalene-derived charge transfer salts with paramagnetic transition metal complex anion: kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2)

The preparation, crystal structures, and optical and magnetic properties of two new charge-transfer salts kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) (1) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2) (2), where phen = 1,10- phenanthroline, EDDH-TTP = 2-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, and BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, are reported. Crystal data: (1) monoclinic P2(1)/a, a = 25.0752(5) A, b = 10.6732(3) A, c = 28.1601(6) A, beta = 95.195(2) degrees, Z = 4, R = 0.0585 for 6741 independent reflections with I > 3 sigma(I); (2) monoclinic P2(1)/a, a = 23.8275(4) A, b = 9.1015 (2) A, c = 27.0420(1) A, beta = 99.9297(8) degrees, Z = 4, R = 0.0530 for 4565 independent reflections with I > 2 sigma(I). The crystal structures for both compounds consist of alternating organic and inorganic layers. The organic layer in compound 1 is characterized as kappa-type, while the organic layer in 2 resembles the kappa-type but it contains orthogonal dimers and monomers, and it is therefore called kappa(21). Compound 1 shows metallic behavior down to low temperature. Salt 2 shows semiconductive behavior, which is explained as the result of either charge ordering owing to the kappa(21)-type structure or Peierls distortion due to the one-dimensional electronic nature. However, weak metallic behavior could be observed at 10 kbar above ca. 150 K and at 15 kbar above 170 K. The magnetic susceptibilities for both compounds show Curie-Weiss behavior, showing that the exchange interactions between the magnetic anions are weak. Polarized reflectance spectra of single crystals were measured over the spectral range from 650 to 7000 cm(-1). Moreover, absorption and diffusion reflectance spectra of powdered crystals dispersed in KBr (from 400 to 7000 cm(-1)) were recorded. Vibrational and electronic features are discussed.     

Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

We investigate the complexation of long thin polyelectrolyte (PE) chains with oppositely charged spheres. In the limit of strong adsorption, when strongly charged PE chains adapt a definite wrapped conformation on the sphere surface, we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and the energy of the complex. We discuss some biological applications of the obtained results. For weak adsorption, when a flexible weakly charged PE chain is localized next to the sphere in solution, we solve the Edwards equation for PE conformations in the Hulthen potential, which is used as an approximation for the screened Debye-Huckel potential of the sphere. We predict the critical conditions for PE adsorption. We find that the critical sphere charge density exhibits a distinctively different dependence on the Debye screening length than for PE adsorption onto a flat surface. We compare our findings with experimental measurements on complexation of various PEs with oppositely charged colloidal particles. We also present some numerical results of the coupled Poisson-Boltzmann and self-consistent field equation for PE adsorption in an assembly of oppositely charged spheres.     

Theory of the cooperative transition between two ordered conformations of poly(L-proline). III. Molecular theory in the presence of solvent.

Phenomenological theories of the form I in equilibrium to form II interconversion in poly(L-proline) have been presented by Schwarz (using the parameters s, sigma, beta', and beta' in a 2 X 2 matrix formulation) and by the present authors (using the parameters s, sigma, betaC, and betaN in a 4 X 4 matrix formulation). In addition, a molecular theory was developed to compute s, sigma, beta', and beta' under vacuum. In this paper, we take into account the effect of solvent on the parameters s, sigma, beta', and beta' of the isothermal poly(L-proline) form I in equilibrium to form II interconversion. The growth parameter is sensitive to the binding of solvent molecules to the peptide CO groups, but the nucleation parameters sigma, beta', and beta' are not affected by this type of solvent effect. The calculated values of s and sigma under vacuum are in good agreement with the corresponding values derived from experimental data. By combining the theoretical values of s, sigma, beta', and beta' under vacuum with experimentally determined equilibrium constants for the binding of alcohols to the peptide CO groups (which differ in magnitude for form I and form II), it was possible to reproduce the experimental tranistion curves satisfactorily. Alternatively, the binding constants for alcohols, obtained by combining our theoretically computed parameters under vacuum with experimental equilibrium transition curves, are in a satisfactory agreement with those evaluated independently by infrared spectral measurements of the binding of alcohols to the peptide CO groups. It is pointed out that significant errors may arise in analyzing experimental data if short chains are included with long chains in the determination of s, sigma, beta', and beta' from the equilibrium transition curves. The transition of poly(L-proline) from form II to form I when n-butyl alcohol is added to a solution of the polymer in benzyl alcohol is brought about by the slight difference in the binding free energies of both alcohols to the carbonyl groups of form II. The different binding affinities of two alcohols, ROH, to form II may arise from (a) the different hydrogen-bond strength between the alcohol and the proline carbonyl group, and (b) possible differences in nonbonded and electrostatic interactions between the R group and the binding-site environment of the proline carbonyl group. The greater binding affinity of form II (compared to form I) for given alcohol is attributed to the more open and extended conformation of form II.     

Organotransition-Metal Metallacarboranes. 46. Multidecker Sandwiches of the Cobalt Group Metals(,)(1)

The double-decker sandwich complex CpIr(2,3-Et(2)C(2)B(4)H(4)) (1a) was prepared via deprotonation of nido-2,3-Et(2)C(2)B(4)H(6) to its mono- or dianion and reaction with (CpIrCl(2))(2) in THF and isolated as a colorless air-stable solid; the B(4)-chloro derivative 1b was also obtained. Decapitation of 1a and 1b with TMEDA afforded colorless nido-CpIr(2,3-Et(2)C(2)B(3)H(5)) (2a) and its 4-chloro derivative 2b. Chlorination of 1a by Cl(2) or N-chlorosuccinimide gave the symmetrical species CpIr(2,3-Et(2)C(2)B(4)H(3)-5-Cl) (1c), which was decapped to yield nido-CpIr(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (2c). The triple-decker complexes CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)IrCp (3), an orange solid, and dark green CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)CoCp (5) were prepared from 2a and nido-CpCo(2,3-Et(2)C(2)B(3)H(5)) (4a), respectively, by deprotonation and reaction with (CpIrCl(2))(2) in THF. Reaction of the 2c(-) anion with Rh(MeCN)(3)Cl(3) gave the dark green tetradecker complex [CpIr(Et(2)C(2)B(3)H(2)-5-Cl)](2)RhH (6). In an attempt to prepare a heterotrimetallic Co-Rh-Ir tetradecker sandwich, a three-way reaction involving the deprotonated anions derived from CpCo(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (4b) and 2c with Rh(MeCN)(3)Cl(3) was conducted. The desired species CpCo(Et(2)C(2)B(3)H(2)Cl)RhH(Et(2)C(2)B(3)H(2)Cl)IrCp (7) and the tetradeckers [CpCo(Et(2)C(2)B(3)H(2)Cl)](2)RhH (8) and 6 were isolated in small quantities from the product mixture; many other apparent triple-decker and tetradecker products were detected via mass spectroscopy but were not characterized. All new compounds were isolated via column or plate chromatography and characterized via NMR, UV-visible, and mass spectroscopy and by X-ray crystal structure determinations of 1a and 3. Crystal data for 1a: space group C2/c; a = 28.890(5) ?, b = 8.511(2) ?, c = 15.698(4) ?, beta = 107.61(2) degrees; Z = 8; R = 0.049 for 1404 independent reflections having I > 3sigma(I). Crystal data for 3: space group P2(1)/c; a = 11.775(4) ?, b = 15.546(5) ?, c = 15.500(5) ?, beta = 103.16(3) degrees; Z = 4; R = 0.066 for 2635 independent reflections having I > 3sigma(I).     

Linear Trinuclear Pt.Mo-Mo Complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CR)(2)](2) (X = Cl, Br, I; R = CH(3), C(CH(3))(3); pyphos = 6-(Diphenylphosphino)-2-pyridonate) with an Axial Interaction between the Quadruply Bonded Mo(2) Moiety and the Platinum Atom

An example of a direct axial interaction of a platinum(II) atom with a Mo(2) core through a uniquely designed tridentate ligand 6-(diphenylphosphino)-2-pyridonate (abbreviated as pyphos) is described. Treatment of PtX(2)(pyphosH)(2) (2a, X = Cl; 2b, X = Br; 2c, X = I) with a 1:1 mixture of Mo(2)(O(2)CCH(3))(4) and [Mo(2)(O(2)CCH(3))(2)(NCCH(3))(6)](2+) (3a) in dichloromethane afforded the linear trinuclear complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCH(3))(2)](2) (4a, X = Cl; 4b, X = Br; 4c, X = I). The reaction of [Mo(2)(O(2)CCMe(3))(2)(NCCH(3))(4)](2+) (3b) with 2a-c in dichloromethane afforded the corresponding pivalato complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCMe(3))(2)](2) (5a, X = Cl; 5b, X = Br; 5c, X = I), whose bonding nature is discussed on the basis of the data from Raman and electronic spectra as well as cyclic voltammograms. The linear trinuclear structures in 4b and 5a-c were confirmed by NMR studies and X-ray analyses: 4b, monoclinic, space group C2/c, a = 34.733(4) ?, b = 17.81(1) ?, c = 22.530(5) ?, beta = 124.444(8) degrees, V = 11498(5) ?(3), Z = 8, R = 0.060 for 8659 reflections with I > 3sigma(I) and 588 parameters; 5a, triclinic, space group P&onemacr;, a = 13.541(3) ?, b = 17.029(3) ?, c = 12.896(3) ?, alpha = 101.20(2) degrees, beta = 117.00(1) degrees, gamma = 85.47(2) degrees, V = 2599(1) ?(3), Z = 2, R = 0.050 for 8148 reflections with I > 3sigma(I) and 604 parameters; 5b, triclinic, space group P&onemacr;, a = 12.211(2) ?, b = 20.859(3) ?, c = 10.478(2) ?, alpha = 98.88(1) degrees, beta = 112.55(2) degrees, gamma = 84.56(1) degrees, V = 2433.3(8) ?(3), Z = 2, R = 0.042 for 8935 reflections with I > 3sigma(I) and 560 parameters; 5c, monoclinic, space group P2(1)/n, a = 13.359(4) ?, b = 19.686(3) ?, c = 20.392(4) ?, beta = 107.92(2) degrees, V = 5101(2) ?(3), Z = 4, R = 0.039 for 8432 reflections with I > 3sigma(I) and 560 parameters.     

A general approach to the analysis of errors and failure modes in the base-calling function in automated fluorescent DNA sequencing

We describe the analysis of errors and failure modes in the base-calling function in automated DNA sequencing, on instruments in which fluorescently-labeled Sanger dideoxy-sequencing ladders are detected via their times of migration past a fixed detector. A general approach entails the joint use of: (i) well-defined control samples such as M13mp18, and (ii) mathematical simulation of sequencing electropherograms, with the deliberate introduction of different types of distortion and noise. An algorithm, the electrophoretic trace simulator (ETS), is used to calculate electrophoresis traces corresponding to the output data stream of an automated fluorescent DNA sequencer. The ETS accepts a user-defined sequence of nucleotide bases (A, C, G, T) as input, and employs user-adjustable functions to compute the following critical parameters of an electropherogram: peak intensity, peak spacing, peak shape as a function of base number; background, noise, and spectral cross-talk correction (for a sequencer using multiple dyes). We use a combination of M13mp18 controls and simulated electropherograms to analyze two problems of considerable practical importance: (i) variation in electrophoretic migration rates between different lanes of a gel, and (ii) variation in signal intensity due to user-dependent loading artifacts. The issue of base-calling errors and failure modes, for electropherograms that contain noise and distortion, is addressed.     

Integral equation theory for symmetric nonadditive hard sphere mixtures

An integral equation theory is presented for the pair correlation functions and phase behavior of symmetric nonadditive hard sphere mixtures with hard sphere diameters given by sigma(A)(A)() = sigma(BB) = lambdad and sigma(AB) = d. This mixture exhibits a fluid-fluid phase separation into an A-rich phase and a B-rich phase at high densities. The theory incorporates, into the closure approximation, all terms that can be calculated exactly in the density expansion of the direct correlation functions. We find that the closure approximation developed in this work is accurate for the structure and phase behavior over the entire range of lambda, when compared to computer simulations, and is significantly more accurate than the previous theories.     

Temperature behaviour of a liquid crystal comb polymer: Light scattering and noise of the scattered light

Measurements of the intensity of the monochromatic light transmitted through and scattered by a comb polymer with a polyacrylamide main chain were performed between room temperature and the isotropization temperature of the polymer. The stationary noise of the light scattered at low angle was measured in the same temperature interval. The transmitted intensity is observed to increase strongly above the smectic S_I2-S_c2 transition, where the intensity of the light scattered at low angles is maximized. The power dissipated by the molecular fluctuations dramatically increases above the transition between the two smectic phases. The spectral density curves display a Lorentzian character only below the S_I2-S_c2 transition. At higher temperatures, a more complex frequency behaviour of the stationary noise spectra is observed. Such a behaviour is interpreted in terms of a model explicitly invoking the effect of the Brownian movement of segments of the main chain (backbone) of the polymer on the side chain fluctuations. The parameters governing the Brownian movements of both main and side chains, and their evolution with temperature, are determined and discussed in the light of a simple structural model.     

Influence of Intramolecular Coordination on the Aggregation of Sodium Phenolate Complexes. X-ray Structures of [NaOC(6)H(4)(CH(2)NMe(2))-2](6) and [Na(OC(6)H(2)(CH(2)NMe(2))(2)-2,6-Me-4)(HOC(6)H(2)(CH(2)NMe(2))(2)-2,6-Me-4)](2)

The structural characterization of two new sodium phenolate complexes, containing ortho-amino substituents, enables the influence of intramolecular coordination on the aggregation of sodium phenolate complexes to be determined. Crystals of hexameric [NaOC(6)H(4)(CH(2)NMe(2))-2](6) (1a) are monoclinic, space group P2(1)/c, with a = 11.668(4) ?, b = 18.146(4) ?, c = 14.221(5) ?, beta = 110.76(3) ?, V = 2815.5(16) ?(3), and Z = 2; R = 0.0736 for 2051 reflections with I > 2.0sigma(I). Complex 1a contains a unique Na(6)O(6) core, consisting of two face-fused cubes, with the ortho-amino substituent of each phenolate coordinating to a sodium atom. In addition, two of the phenolate ligands have an eta(2)-arene interaction with an additional sodium atom in the core. Crystals of dimeric [(NaOC(6)H(2)(CH(2)NMe(2))(2)-2,6-Me-4)(HOC(6)H(2)(CH(2)NMe(2))(2)-2,6-Me-4)](2) (2b) are triclinic, space group P&onemacr;, with a = 10.0670(8) ?, b = 10.7121(7) ?, c = 27.131(3) ?, alpha = 92.176(8) degrees, beta = 99.928(8) degrees, gamma = 106.465(6) degrees, V = 2752.1(4) ?(3), and Z = 2; R = 0.0766 for 5329 reflections with I > 2.0sigma(I). Dimeric complex 2b contains two phenolate ligands, which bridge the two sodium atoms, each coordinating with one ortho-amino substituent to a sodium atom, while the second available ortho-amino substituent remains pendant. The coordination sphere of each sodium atom is completed by a (neutral) bidentate O,N-coordinated parent phenol molecule. The second ortho-amino substituent of this neutral phenol is involved in a hydrogen bridge with its acidic hydrogen. On the basis of these two new crystal structures and previously reported solid state structures for sodium phenolate complexes, it is shown that the introduction of first one and then two ortho-amino substituents into the phenolate ligands successively lowers the degree of association of these complexes in the solid state. In this process, the basic Na(2)O(2) building block of the molecular structures remains intact.     

Self-assembly of cuII and niII [2 x 2] grid complexes and a binuclear CuII complex with a new semiflexible substituted pyrazine ligand: multiple anion encapsulation and magnetic properties

With the new substituted pyrazine ligand pyrazine-2,3-dicarboxylic acid bis[(pyridin-2-ylmethyl)amide], H(2)L, a binuclear complex [Cu(2)(LH)(Cl(3))(H(2)O)].H(2)O (1) and two [2 x 2]G grid complexes, [[Cu(4)(LH)(4)](ClO(4))(4)].5CH(3)OH.4H(2)O (2) and [[Ni(4)(LH)(4)]Cl(4)].5CH(3)CN.13H(2)O (3), have been synthesized and characterized spectroscopically and crystallographically. The ligand H(2)L crystallized in the triclinic space group P1, with a = 4.9882(7) A, b = 12.079(2) A, c = 14.454(2) A, alpha = 107.08(2) degrees, beta = 98.61(2) degrees, gamma = 97.54(2) degrees, V = 808.8(2) A(3), Z = 2, R1 = 0.0747, and R(w) = 0.1829 for 1319 observed reflections [I > 2 sigma(I)]. The molecule is L-shaped with a strong intramolecular bifurcated hydrogen bond in half of the molecule. In the crystal the molecules are linked by an intermolecular hydrogen bond to form a 1D polymer. The binuclear complex [Cu(2)(LH)(Cl(3))(H(2)O)].H(2)O (1) crystallized in the monoclinic space group P2(1)/a, with a = 8.6859(7) A, b = 28.060(2) A, c = 9.5334(9) A, beta = 107.89(1) degrees, V = 2211.2(3) A(3), Z = 4, R1 = 0.039, and R(w) = 0.097 for 1408 observed reflections [I > 2 sigma(I)]. There are two independent copper atoms both having square pyramidal geometry. Both coordinate to a pyrazine, a pyridine, and an amide N atom. Two chlorines complete the coordination sphere of one of the copper atoms, while one chlorine atom and a water molecule complete the coordination sphere of the other. The copper(II) [2 x 2] grid complex [[Cu(4)(LH)(4)](ClO(4))(4)].5CH(3)OH.4H(2)O (2) crystallized in the triclinic space group P1, with a = 17.1515(14) A, b = 17.7507(13) A, c = 19.3333(15) A, alpha = 67.34(1) degrees, beta = 69.79(1) degrees, gamma = 71.50(1) degrees, V = 4980.3(7) A(3), Z = 2, R1 = 0.083, and R(w) = 0.207 for 5532 observed reflections [I > 2 sigma(I)]. The four Cu(II) atoms are octahedrally coordinated by two pyrazine, two pyridine, and two amide N atoms and occupy the corners of a [2 x 2] grid with edge lengths, Cu...Cu, varying from 7.01 to 7.39 A. The nickel(II) [2 x 2] grid complex [[Ni(4)(LH)(4)]Cl(4)].5CH(3)CN.13H(2)O (3) crystallized in the monoclinic space group C2/c, with a = 16.3388(10) A, b = 29.754(2) A, c = 20.857(1) A, beta = 101.845(1) degrees, V = 9923.6(12) A(3), Z = 4, R1 = 0.050, and wR2 = 0.101 for 3391 observed reflections [I > 2 sigma(I)]. Here the complex possesses C(2) symmetry and again each metal atom is octahedrally coordinated to two pyrazine, two pyridine, and two amide N atoms. They occupy the corners of a [2 x 2] grid with an average edge length, Ni.Ni, of 6.97 A. Of the four anions (ClO(4)(-)'s in 2 and Cl(-)'s in 3) required to equilibrate the charges in the grid complexes, two are encapsulated, one above and one below the plane of the four metal atoms. The remaining two anions are located between the "wings" of the ligands. Magnetic susceptibility measurements indicate that the binuclear complex 1 is antiferromagnetic, with a J value of -15.07 cm(-1). This is larger than the J values found for the Cu(II) (2) and Ni(II) (3) grid complexes, which were -5.87 and -2.64 cm(-1), respectively. DFT calculations have been carried out to explain the difference in the J values found for complexes 1 and 2.