Polymorphism of dinitro[tris(2‐aminoethyl)amine]cobalt(III) chloride

Three polymorphs of bis(nitrito‐κN)[tris(2‐aminoethyl)amine‐κ⁴N,N′,N′′,N′′′]cobalt(III) chloride, [Co(NO₂)₂(C₆H₁₈N₄)]Cl, have been structurally characterized in the 100–300 K temperature range. Two orthorhombic polymorphs are related by a solid‐state enantiotropic order–disorder k2 phase transition at ca 152 K. The third, monoclinic, polymorph crystallizes as a nonmerohedral twin. In the structure of the high‐temperature (300 K) orthorhombic polymorph, the Co^III complex cation resides on a crystallographic mirror plane, whereas the Cl⁻ anion occupies a crystallographic twofold axis. In the unit cell of the monoclinic polymorph, the cationic Co^III complex is in a general position, whose charge is balanced by two halves of two Cl⁻ anions, each residing on a crystallographic twofold axis.     

The interplay of solvation,molecular conformation and supramolecular assembly in 1,1′‐({[(ethane‐1,2‐diyl)dioxy](1,2‐phenylene)}bis(methanylylidene))bis(thiosemicarbazide) and its N,N‐dimethylformamide disolvate

The wide diversity of applications of thiosemicarbazones and bis(thiosemicarbazones) has seen them used as anticancer and antitubercular agents, and as ligands in metal complexes designed to act as site‐specific radiopharmaceuticals. Molecules of 1,1′‐({[(ethane‐1,2‐diyl)dioxy](1,2‐phenylene)}bis(methanylylidene))bis(thiosemicarbazide) {alternative name: 2,2′‐[ethane‐1,2‐diylbis(oxy)]dibenzaldehyde bis(thiosemicarbazide)}, C₁₈H₂₀N₆O₂S₂, (I), lie across twofold rotation axes in the space group C2/c, with an O—C—C—O torsion angle of −59.62 (13)° and a trans‐planar arrangement of the thiosemicarbazide fragments relative to the adjacent aryl rings. The molecules of (I) are linked by N—H...S hydrogen bonds to form sheets containing R²₄(38) rings and two types of R²₂(8) ring. In the N,N‐dimethylformamide disolvate, C₁₈H₂₀N₆O₂S₂·2C₃H₇NO, (II), the independent molecular components all lie in general positions, but one of the solvent molecules is disordered over two sets of atomic sites having occupancies of 0.839 (3) and 0.161 (3). The O—C—C—O torsion angle in the ArOCH₂CH₂OAr component is −75.91 (14)° and the independent thiosemicarbazide fragments both adopt a cis‐planar arrangement relative to the adjacent aryl rings. The ArOCH₂CH₂OAr components in (II) are linked by N—H...S hydrogen bonds to form deeply puckered sheets containing R²₂(8), R²₄(8) and two types of R²₂(38) rings, and which contain cavities which accommodate all of the solvent molecules in the interior of the sheets. Comparisons are made with some related compounds.     

Crystal structure of twinned (η5-C5(CH3)4CF3) (η5-C5(CH3)5)Ru

The substituted sandwich complex crystallizes in monoclinic space groupP2₁/m withZ=2. Twinning to the (001) direction with the special conditionc ^*/4a ^* = cos ^* causes systematic superposition of the reciprocal lattices of both domains and results in an apparent unit cell with double volume and the reflection condition (2h)kl, l=2n. The structure solution was obtained with the subset of intensity data for the predominant individuum and converged atR = 0.040,R _w =0.046 for 832 independent observations and 122 variables. The molecules show disorder with respect to the crystallographic mirror plane. The structure is closely related to that of decamethylruthenocene.     

Neutron diffraction studies of Gd2Zr2O7 pyrochlore

The structure of Gd₂Zr₂O₇ pyrochlore over the temperature range 4-300 K has been refined from powder neutron diffraction data. The sample was enriched in ¹⁶⁰Gd to avoid the high neutron absorption of naturally occurring Gd. The diffraction pattern showed well resolved superlattice reflections indicative of the pyrochlore structure and no evidence is found for anion-disorder from the structural refinements.     

Copper Bismuth Chalcogenide Halogenides with Extensively Disordered and Mobile Copper(I) Cations

A new family of quaternary phases with the general sum formula Cu_3+δBi_5–δSe_8–2δX_2+2δ (X = Cl, Br) was discovered by slow cooling of high temperature melts. Cu_3.58(1)Bi_4.42(1)Se_6.84(2)Cl_3.16(2) (δ = 0.58) and Cu_4.52(1)Bi_3.48(1)Se_4.96(2)Br_5.04(2) (δ = 1.52) crystallize isostructural in the orthorhombic space group type Pnnm with a = 1332.3(1)/1340.2(3) pm, b = 1683.7(2)/1717.2(1) pm, and c = 406.2(1)/407.1(2) pm. The new structure type resembles in some aspects the hollandite as well as the pavonite type. A framework of face‐ and edge‐sharing anion polyhedra around Bi³⁺ cations hosts Cu⁺ cations. The characteristic motif is an infinite band of polyhedra that has the width of five polyhedra, with three octahedra being enclosed by capped trigonal prisms. The octahedrally coordinated Bi³⁺ cations are partially substituted by Cu⁺ (in octahedra faces), while Se^2– anions are replaced by X^–. The sulfide iodide Cu_3.33(2)Bi₂S_3.33(2)I_2.67(2) crystallizes in the monoclinic space group C2/m with a = 2803.6(9) pm, b = 409.9(1) pm, c = 1058.0(3) pm, and β = 110.68(2)°. Double strands of face‐sharing [BiS_1/1S_2/2I_4/4] as well as [BiS_3/3I_2/2(S_0.33/I_0.67)_2/2] polyhedra run along [010]. In between them, the Cu⁺ cations are spread over numerous closely spaced sites. They define a ladder‐shaped continuous path for ion conduction along [010].     

Exploring metabolic syndrome serum profiling based on gas chromatography mass spectrometry and random forest models

Metabolic syndrome (MetS) is a constellation of the most dangerous heart attack risk factors: diabetes and raised fasting plasma glucose, abdominal obesity, high cholesterol and high blood pressure. Analysis and representation of the variances of metabolic profiles is urgently needed for early diagnosis and treatment of MetS. In current study, we proposed a metabolomics approach for analyzing MetS based on GC–MS profiling and random forest models. The serum samples from healthy controls and MetS patients were characterized by GC–MS. Then, random forest (RF) models were used to visually discriminate the serum changes in MetS based on these GC–MS profiles. Simultaneously, some informative metabolites or potential biomarkers were successfully discovered by means of variable importance ranking in random forest models. The metabolites such as 2-hydroxybutyric acid, inositol and d-glucose, were defined as potential biomarkers to diagnose the MetS. These results obtained by proposed method showed that the combining GC–MS profiling with random forest models was a useful approach to analyze metabolites variances and further screen the potential biomarkers for MetS diagnosis.     

Influence of structure disorders and temperaturesof systems on the bio-energy transport in proteinmolecules (Ⅱ)

The influence of molecular structure disorders and physiological temperature on the states and properties of solitons as transporters of bio-energy are numerically studied through the fourth-order Runge-Kutta method and a new theory based on my paper [Front. Phys. China, 2007, 2(4): 469]. The structure disorders include fluctuations in the characteristic parameters of the spring constant, dipole-dipole interaction constant and exciton-phonon coupling constant, as well as the chain-chain interaction coefficient among the three channels and ground state energy resulting from the disorder distributions of masses of amino acid residues and impurities. In this paper, we investigate the behaviors and states of solitons in a single protein molecular chain, and in α-Helix protein molecules with three channels. In the former we prove first that the new solitons can move without dispersion, retaining its shape, velocity and energy in a uniform and periodic protein molecule. In this case of structure disorder, the fluctuations of the spring constant, dipole-dipole interaction constant and exciton-phonon coupling constant, as well as the ground state energy and the disorder distributions of masses of amino acid residues of the proteins influence the states and properties of motion of solitons. However, they are still quite stable and are very robust against these structure disorders, even in the presence of larger disorders in the sequence of masses, spring constants and coupling constants. Still, the solitons may disperse or be destroyed when the disorder distribution of the masses and fluctuations of structure parameters are quite great. If the effect of thermal perturbation of the environment on the soliton in nonuniform proteins is considered again, it is still thermally stable at the biological temperature of 300 K, and at the longer time period of 300 ps and larger spacing of 400 amino acids. The new soliton is also thermally stable in the case of motion over a long time period of 300 ps in the region of 300–320 K under the influence of the above structure disorders. However, the soliton disperses in the case of a higher temperature of 325 K and in larger structure disorders. Thus, we determine that the soliton’s lifetime and critical temperature are 300 ps and 300–320 K, respectively. These results are also consistent with analytical data obtained via quantum perturbed theory. In α-Helix protein molecules with three channels, results obtained show that these structure disorders and quantum fluctuations can change the states and features of solitons, decrease their amplitudes, energies and velocities, but they still cannot destroy the solitons, which can still transport steadily along the molecular chains while retaining energy and momentum when the quantum fluctuations are small, such as in structure disorders and quantum fluctuations of and and . Therefore, the solitons in the improved model are quite robust against these disorder effects. However, the solitons may be dispersed or disrupted in cases of very large structure disorders. When the influence of temperature on solitons is considered, we find that the new solitons can transport steadily over 333 amino acid residues in the case of motion over a long time period of 120 ps, and can retain their shapes and energies to travel forward along protein molecules after mutual collision of the solitons at the biological temperature of 300 K. Therefore, the soliton is also very robust against thermal perturbation of the α-helix protein molecules at 300 K. However, the soliton disperses in cases of higher temperatures at 325 K and in larger structure disorders. Thus, their critical temperature is about 320 K. When the effects of structure disorder and temperature are considered simultaneously, the soliton has high thermal stability and can transport for a long time along the protein molecular chains while retaining its amplitude, energy and velocity, even though the fluctuations of the structure parameters and temperature of the medium increase continually. However, the soliton disperses in the larger fluctuations of and at T=300 K, and at temperatures higher than 315 K when the fluctuations are and . This means that the critical temperature of the soliton is only 315 K in this condition. In a word, we can conclude from the above investigations that the soliton in the improved model is very robust against the structure disorders and thermal perturbation of proteins at the biological temperature of 300 K in α-helix protein molecules, and is a possible bio-energy transport carrier; the improved model is a possible candidate for the mechanism of this transport.      

Donor ordering and the statistics of quantum dot level spacings and widths from full 3D self-consistent electronic structure

Using full 3D self-consistent electronic structure calculations of small (electron numberN 100) lateral quantum dots formed on GaAs–AlGaAs HEMT devices we calculate the statistics of level spacings Δε_pand tunneling coefficients Γ_pbetween leads and confined states of the dot. We employ random and ordered donor layer charge distributions, the latter generated through Monte Carlo variable range hopping simulations, as well as a homogeneous (jellium) ionic charge distribution, and examine the effects on these statistics.It has recently been argued that the statistics of the level spacings and widths follow from random matrix theory when the Hamiltonian is described by the Gaussian orthogonal ensemble (GOE) for zero magnetic fieldB, and by the Gaussian unitary ensemble (GUE) forBsufficiently large to break time reversal symmetry. Specifically it is argued that when the dot wave functions are expanded in an arbitrary basis the expansion coefficients, according to the postulate of Porter and Thomas, are uniformly distributed in Hilbert space.In our calculation we obtain statistics of level spacings and widths by generating many configurations of disordered and ordered donor charge. This corresponds to the experimental situation of thermal cycling of the device. We find that a pronounced transition occurs in the level spacing statistics between the completely disordered donor layer ensemble, which seems to be well described by random matrix theory, and the ordered ensemble which is dominated by secular variations in the coefficients. In particular, a shell structure in the levels, which results from approximate parabolicity in the self-consistent confining potential, is observed. This, and the effects of symmetry under inversion and azimuthal symmetry, are speculated to undermine level repulsion and result in Poisson statistics for the levels here at the band edge.Finally we find that distortions in the dot shape are markedly less significant in varying the widths (and level spacings) than calculations based on a hard wall potential for the dot predict. This suggests that the notion of invariant atomic structure for sufficiently small dots is not invalidated by the randomness inherent in donor positions and shape distortion but, on the contrary, a systematic study of dot structure is possible.     

Voice disorders in patients with suspected laryngo-pharyngeal reflux disease

Many symptoms have been recognized in association with laryngo-pharyngealreflux disease (LPRD), but reports of perceptual voice disorders in this condition have been lacking to date. Forty-nine patients with suspected LPRD were studied for five specific perceptual voice characteristics, and these characteristics were compared to the same characteristics in individuals who had never seen an Otolaryngologist for a voice disorder or throat problem (controls). Sixteen of the suspected LPRD patients also underwent 24-hour pH probe studies. All patients with suspected LPRD had significantly increased abnormal perceptual voice characteristics (musculoskeletal tension, hard glottal attack, glottal fry, restricted tone placement, and hoarseness) compared to the controls. Statistical objective differences between the two groups was demonstrated by the presence of increased shimmer in patients with suspected LPRD compared to controls. The differential diagnosis between functional voice disorders and LPRD may be complex, and perceptual parameters may overlap. Interdisciplinary evaluation is advocated.     

Optimal online detection of parameter changes in two linear models

Shiryaev has obtained the optimal sequential rule for detecting the instant of a distributional change in an independent sequence using the theory of optimal stopping of Markov processes. This paper considers the problem of sequential detection of certain parameter changes in two dependent sequences: an autoregressive process, and a regression model with serially correlated error terms. It is shown that the rule that is optimal in the sense of minimizing the expected positive delay is the one which declares a change to have occured as soon as the posterior probability of a change crosses a threshold. This rule also permits control of the probability of a false-declaration of change, just as in the independent sequence case.