Correction: Composition-dependent charge transfer and phase separation in the V1-xRexO2 solid solution.

Correction for 'Composition-dependent charge transfer and phase separation in the V1-xRexO2 solid solution' by D. Mikhailova, et al., Dalton Trans., 2017, 46, 1606-1617.

Composition-dependent charge transfer and phase separation in the V1-xRexO2 solid solution.

The substitution of vanadium in vanadium dioxide VO2 influences the critical temperatures of structural and metal-to-insulator transitions in different ways depending on the valence of the dopant. Rhenium adopts valence states between +4 and +7 in an octahedral oxygen surrounding and is particularly interesting in this context. Structural investigation of V1-xRexO2 solid solutions (0.01 ≤ x ≤ 0.30) between 80 and 1200 K using synchrotron X-ray powder diffraction revealed only two polymorphs that resemble VO2: the low-temperature monoclinic MoO2-type form (space group P21/c), and the tetragonal rutile-like form (space group P42/mnm). However, for compositions with 0.03 < x ≤ 0.15 a phase separation in the solid solution was observed below 1000 K upon cooling down from 1200 K, giving rise to two isostructural phases with slightly different lattice parameters. This is reflected in the appearance of two metal-to-insulator transition temperatures detected by magnetization and specific heat measurements. Comprehensive X-ray photoelectron spectroscopy studies showed that an increased amount of Re leads to a change in the Re valence state from solely Re6+ at a low doping level (≤3 at% Re) via mixed-valence states Re4+/Re6+ for at least 0.03 < x ≤ 0.10, up to nearly pure Re4+ in V0.70Re0.30O2. Thus, compositions V1-xRexO2 with only one valence state of Re in the material (Re6+ or Re4+) can be obtained as a single phase, while intermediate compositions are subjected to a phase separation, presumably due to different valence states of Re.

Homogeneity of lithium distribution in cylinder-type Li-ion batteries.

Spatially-resolved neutron powder diffraction with a gauge volume of 2 × 2 × 20 mm(3) has been applied as an in situ method to probe the lithium concentration in the graphite anode of different Li-ion cells of 18650-type in charged state. Structural studies performed in combination with electrochemical measurements and X-ray computed tomography under real cell operating conditions unambiguously revealed non-homogeneity of the lithium distribution in the graphite anode. Deviations from a homogeneous behaviour have been found in both radial and axial directions of 18650-type cells and were discussed in the frame of cell geometry and electrical connection of electrodes, which might play a crucial role in the homogeneity of the lithium distribution in the active materials within each electrode.

New lithium copper borates with BO3 triangles: Li6CuB4O10, Li3CuB3O7, Li8Cu7B14O32, and Li2Cu9B12O28.

Crystal structures of three new lithium copper borates, Li3CuB3O7, Li8Cu7B14O32, and Li2Cu9B12O28, and a new Li6CuB4O10 polymorph were solved by single-crystal X-ray diffraction. In all of the structures, the boron cations form BO3 triangles, which are connected with each other and with copper polyhedra only via corners in Li6CuB4O10 and Li3CuB3O7 and via both corners and edges in Li8Cu7B14O32 and Li2Cu9B12O28. The Li3CuB3O7 and Li8Cu7B14O32 compounds were synthesized as pure samples with only trace amounts of impurities; hence, their magnetic properties could be investigated and analyzed in terms of underlying magnetic couplings. Other compositions always represented multiphase mixtures. Li3CuB3O7 features infinite Cu,O chains formed by Cu2O6 units consisting of edge-shared CuO4 squares. Together with two apical oxygen atoms with long interatomic Cu-O distances of 2.7-2.8 Å, the Cu2O6 units form chains extended along the a axis. These pseudochains are responsible for strong anisotropic thermal expansion behavior. The temperature dependence of the magnetization between 4 and 380 K for Li3CuB3O7 could be fit well by a spin-dimer model. The magnetic susceptibility of Li8Cu7B14O32 showed a more complex temperature dependence, with two different Curie-Weiss regimes in the temperature range of 2-380 K.

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture.

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.

XPS investigations of electrolyte/electrode interactions for various Li-ion battery materials.

For future Li-ion battery applications the search for both new design concepts and materials is necessary. The electrodes of the batteries are always in contact with electrolytes, which are responsible for the transport of Li ions during the charging and discharging process. A broad range of materials is considered for both electrolytes and electrodes so that very different chemical interactions between them can occur, while good cycling behavior can only be obtained for stable solid-electrolyte interfaces. X-ray photoelectron spectroscopy (XPS) was used to study the most relevant interactions between various electrode materials in contact with different electrolyte solutions. It is shown how XPS can provide useful information on reactivities and thus preselect suitable electrode/electrolyte combinations, prior to electrochemical performance tests.

Oxygen nonstoichiometry of tetragonal La2-xSr(x)CuO4-δ (x = 0.15-1.2) and in situ XPS studies at elevated temperatures.

The peculiarities of oxygen nonstoichiometry (δ) in tetragonal La(2-x)Sr(x)CuO(4-δ) solid solution with x(Sr) = 0.15-1.2 were studied by XRD, NPD, in situ high-temperature XPS, and chemical analysis. Temperature dependences of oxygen nonstoichiometry, δ = δ(T), were obtained for different Sr contents at 1 bar of O(2). Two types of charge compensation during replacement of lanthanum by strontium are discussed: an increase of the average copper oxidation state and a formation of oxygen vacancies. The average copper oxidation state V(Cu) exhibits a maximum of 2.32 at x(Sr) = 0.6, while δ increases with x(Sr). Oxygen vacancies are unambiguously located on the 4c site ({CuO(2)} plane) for compositions with different strontium contents, which electronic state is described by the O 2p core electron peak at about 531 eV. Thermal stability of the solid solution in a vacuum is associated with the extraction of practically the entire oxygen from CuO(2) layers and the formation of Cu(+) at least in the near-surface region. The higher average copper oxidation state after synthesis in the Sr-rich phases in comparison with the Sr-poor compositions prevents oxygen removal and the formation of Cu(+) and, therefore, stabilizes the structure during heating in a vacuum.

The role of oxygen stoichiometry on phase stability, structure, and magnetic properties of Sr2CoIrO(6-δ).

The phase stability, crystal structure, and magnetic properties of perovskite-like nonstoichiometric Sr(2)CoIrO(6-δ) were studied. Oxygen deficiency can be well controlled and reversibly varied up to δ = 0.33. A single phase exists at least for partial oxygen pressures between 10(-5) and 1 bar at 1273 K, followed by phase decomposition at higher temperature with the elimination of metallic Ir and the formation of a new phase with approximately Sr(3)CoIrO(6) composition crystallizing in K(4)CdCl(6) structure type. The structural features of Sr(2)CoIrO(6-δ) are dependent on both temperature and oxygen content and were determined by synchrotron and neutron powder diffraction. Both the increasing amount of oxygen vacancies at constant temperature and increasing temperature at constant oxygen content result in the same higher crystal symmetry of Sr(2)CoIrO(6-δ): (1) The oxygen-stoichiometric phase Sr(2)CoIrO(6.00) is monoclinic (I2/m or P2(1)/n) at room temperature but cubic (Fm-3m) for Sr(2)CoIrO(5.67). (2) A sequence of phase transitions [Formula: see text] was observed for Sr(2)CoIrO(6.00) in air. All Sr(2)CoIrO(6-δ) compositions show weak ferromagnetism at low temperature with a canted but predominantly antiferromagnetic ground state. The magnetic ordering temperature decreases monotonously with increasing oxygen deficiency, while pronounced extrema are observed for the paramagnetic moment and the Curie-Weiss temperature at an oxygen deficiency δ ≈ 0.10, which corresponds to the P2(1)/n ↔ I2/m phase transformation.

Polymorphism of K(2)Co(2)Mo(3)O(12): variations in the packing schemes and changes in molybdenum coordination under high pressure.

Within systematic studies on the K-Co-Mo-O system so-called high-temperature and high-pressure modifications of K2Co2Mo3O12 were found. The Birch-Murnaghan fits for the ambient-conditions modification alpha (Z = 4) and the high pressure phase II (Z = 8) lead to V0 = 1193.09 (4) A3, K =30.8 (8) GPa, K'0= 5.4 (4) and V0 = 2170 (10) A3, K =51 (2) GPa with K'0 fixed at 4.0, respectively. The high-pressure phase transition is denoted as pseudoreconstructive [Wiesmann et al. (1997). J. Solid State Chem. 132, 88-97], because some [MoO4] tetrahedra turn into edge-sharing pairs of [MoO5] pyramids or face-sharing pairs of [MoO6] octahedra. The new phases are presented and compared with the alpha phase.

Anomalous thermal expansion in rare-earth gallium perovskites: a comprehensive powder diffraction study.

Crystal structures of rare-earth gallium perovskites LaGaO(3), PrGaO(3), NdGaO(3) and Pr(1-x)Nd(x)GaO(3) (x = 0.25, 0.50, 0.75) solid solutions were investigated in the temperature range 12-300 K by high-resolution powder diffraction using synchrotron or neutron radiation. The previously reported negative thermal expansion in the b direction of the PrGaO(3) lattice has been found to be persistent in Pr(1-x)Nd(x)GaO(3) solid solutions and its magnitude has been revealed as proportional to the amount of praseodymium. Evaluation of the obtained temperature evolution of cell dimensions indicated a weak anomalous behaviour of the b lattice parameter in NdGaO(3), and its origin is supposed to be the same as in PrGaO(3), i.e. a coupling of the crystal electric field levels with phonon excitations of about 23-25 meV energy. The performed bond length analysis revealed an anomalous behaviour of both LnO(12) (Ln-rare-earth) and GaO(6) coordination polyhedra, which can be a structural manifestation of anomalous thermal expansion in the considered compounds.

Quasi in situ XPS investigations on intercalation mechanisms in Li-ion battery materials.

New concepts for Li-ion batteries are of growing interest for high-performance applications. One aim is the search for new electrode materials with superior properties and their detailed characterization. We demonstrate the application of X-ray photoelectron spectroscopy (XPS) to investigate electrode materials (LiCoO(2), LiCrMnO(4)) during electrochemical cycling. The optimization of a "quasi in situ" analysis, by transferring the samples with a transport chamber from the glove box to the XPS chamber, and the reliability of the experiments performed are shown. The behavior of characteristic chemical species at the electrodes and the changes in oxidation states of LiCrMnO(4) during cycling is discussed. The formation of Cr(6+) is suspected as a possible reason for irreversible capacity loss during charging up to complete Li deintercalation (approximately 5.2 V).

Magnetic structure of the kagome mixed compound (Co(0.5)Ni(0.5))(3)V(2)O(8).

We report the magnetic structure of (Co(0.5)Ni(0.5))(3)V(2)O(8) (CNVO) deduced by single crystal neutron diffraction. This compound exhibits features which differ from that of its parent compounds, which are absolutely collinear along the a axis for Co(3)V(2)O(8) (CVO) or exhibit magnetic moments predominantly in the a-b plane with small components along c in the case of Ni(3)V(2)O(8) (NVO). The averaged magnetic moments of the statistically distributed Ni(2+) and Co(2+) ions in CNVO are oriented in the a-c plane and form loops of quasiferromagnetically coupled spins. These loops are connected along the a axis and separated along the c axis by cross-tie spins forming a quasiferromagnetic wave with the upper part of the respective neighbouring loops. The magnetic moments are sinusoidally modulated by the propagation vector k = (0.49,0,0) with an average amplitude of 1.59(1) µ(B) for a magnetic ion on a cross-tie site and 1.60(1) µ(B) for the spine site. In addition to neutron diffraction, specific heat and magnetization data, which confirm that the only magnetic phase transition above 1.8 K is the onset of antiferromagnetic order at T(N) = 7.4(1) K, are presented.

The short- and long-term implications of maternal obesity on the mother and her offspring.

Obesity's increasing prevalence has reached epidemic proportions in the USA, with close to one-third of the adult population affected in 2000. Additionally, there is increasing prevalence of obesity in other industrialised areas of the world such as Europe. Of potentially more concern is the potential risks associated with obesity and related metabolic complications in the developing world. The maternal, fetal, peripartum and neonatal complications of obesity in pregnancy have far-reaching implications for both mother and offspring. Of alarming interest is the increasing rate of obesity among adolescents and the cycle of obesity in future generations it portends. The purpose in this review is to briefly review the maternal perinatal morbidities associated with maternal pregravid obesity. Additionally, we will review evidence of both short- and long-term effect of maternal obesity on the in utero environment as it relates to fetal growth, neonatal body composition and adolescent obesity.

Preparation, crystal structure and magnetic properties of the high-pressure phase MnReO4 with a wolframite-type structure.

The ternary oxide MnReO(4), manganese rhenium oxide, has been synthesized under a high pressure of 5.5 GPa at 1473 K and its crystal structure has been determined by single-crystal X-ray diffraction. MnReO(4) crystallizes in a wolframite-type structure with average bond lengths of Re-O = 1.935 and Mn-O = 2.160 A that are in good agreement with the ionic radii of Re(6+) and Mn(2+). The magnetic properties of MnReO(4) have been studied by SQUID measurements, revealing magnetic ordering below 275 (10) K and a weak ferromagnetic component of the ordered magnetic structure.

The impact of chorionicity on umbilical cord acid-base values in twin gestations.

OBJECTIVE: To evaluate the impact of chorionicity on inter-twin differences in acid-base status at birth. METHODS: Records for twin pregnancies delivered at > or = 24 weeks' gestation from 1 January 1990 to 31 June 2000 were reviewed. Collected data included maternal demographics, gestational age, fetal presentation, anesthesia, delivery mode, inter-twin interval, umbilical artery (UA) and venous (UV) acid-base values, Apgar scores and birth weights. The influence of chorionicity on umbilical cord biochemistry was evaluated. (p < 0.05 was considered significant.) RESULTS: Analysis was carried out in 87 twin pairs (29 monochorionic, MC; and 58 dichorionic, DC). MC and DC twins were similar in maternal age (25.5 vs. 28.2 years), estimated gestational age (33.7 vs. 33.6 weeks), Cesarean delivery (55.2 vs. 52.6%), delivery interval (10 vs. 5 min) and respective birth weights (twin A, 1882 vs. 1981; and twin B, 1828 vs. 1872 g). MC first twins had a higher UA pH (7.31 +/- 0.05 vs. 7.26 +/- 0.08; p = 0.0005) than DC first twins. MC first and second twins had higher UA and UV bicarbonate levels than their DC counterparts (DeltapH = 21.7 +/- 5.1 vs. 18.5 +/- 3.1 mmol/l and 22.0 +/- 3.5 vs. 19.6 +/- 2.5 mmol/l, respectively; p = 0.003). MC twins were more discordant in UA pH than DC twins (DeltapH = 0.043 +/- 0.09 vs. 0.003 +/- 0.07; p = 0.009). MC and DC twins had a similar venous pH (DeltapH = 0.01 +/- 0.06 vs. 0.02 +/- 0.06; p = 0.5). CONCLUSIONS: There is a significant association between placental chorionicity and umbilical cord biochemistry in twins. Although it is possible that the mechanism of this finding is related to placental angioarchitecture, it is unlikely to be a result of simple mixing of blood volumes between twins. The physiology of underlying processes requires further study.

Structural investigation of the Na-Fe-Mo-O system.

Four new crystalline structures within the Na-Fe-Mo-O system are reported: sodium tetrairon pentamolydate (1), NaFe(4)(MoO(4))(5), alpha-sodium diiron trimolybdate (2), alpha-NaFe(2)(MoO(4))(3), beta-sodium diiron trimolybdate (3), beta-NaFe(2)(MoO(4))(3), trisodium diiron trimolybdate (4), Na(3)Fe(2)(MoO(4))(3). All these structures belong to orthomolybdate class of compound and are described as networks of [FeO(6)] octahedra and [MoO(4)] tetrahedra. They are compared with each other and with other related structures.

Are maternal and sonographic factors associated with the detection of a fetal echogenic cardiac focus?

OBJECTIVE: To evaluate the influence of maternal weight and the orientation of the fetal 4-chamber heart view on the detection of a fetal echogenic cardiac focus. METHODS: In this nested case-control study, 103 women undergoing anatomic surveys at 15 to 22 weeks between January 1, 1997, and June 15, 1999, were identified as having an echogenic cardiac focus via our computerized database. A control group was selected from among the same group of patients. Data were collected from the sonography reports, prenatal records, and sonographic images of 4-chamber heart views; maternal characteristics and sonographic details were recorded, including the orientation of the 4-chamber view (apical, basilar, and right and left lateral). RESULTS: Gravidas in the echogenic cardiac focus group were more likely to be of lower weight (68.0 +/- 14.4 versus 72.9 +/- 18.3 kg; P = .04), of lower body mass index (25.5 +/- 5.3 versus 27.3 +/- 6.2 kg/m2; P = .03), of younger age (24.4 +/- 6.5 versus 26.9 +/- 6.9 years; P = .01), and African American or Asian (37.9% versus 27.2% and 9.7% versus 2%; P = .01). Cases were scanned at earlier gestational ages (18.9 +/- 1.6 versus 19.5 +/- 1.7 weeks; P = .01). The focus group was more likely to have had an apical view of the fetal heart taken (80.8% versus 51.4%; P = .0001). Controls were more likely to have had a right lateral view taken (44.6% versus 20.8%; P = .002). No significant difference was found between groups in terms of any other maternal or sonographic variable studied. CONCLUSIONS: The echogenic cardiac focus group was more likely to have a lower body mass index and to be scanned with the apical fetal heart view. The orientation of the fetal 4-chamber heart view exerted the most statistically significant influence on detection rates for the echogenic cardiac focus, implying that the more technically facile the sonographic study, the more likely an echogenic cardiac focus will be found.

Antibiotics and the management of preterm premature rupture of the fetal membranes.

Preterm premature rupture of membranes remains an important cause of preterm birth and neonatal morbidity and mortality. Although the underlying pathophysiology remains largely undefined, subclinical infection has been implicated both in the mechanism of membrane rupture and the resultant neonatal morbidity. The use of maternal systemic antibiotics reduces both neonatal and maternal morbidity in the expectant management of PPROM. Although concern persists over the development of resistant strains of organisms involved with neonatal sepsis, current data support the use of antibiotics in this setting. Further study is needed regarding the risks and benefits of additional tocolytic therapy or antenatal corticosteroids in the management of PPROM, and the predictors of successful and unsuccessful conservative management, and subclinical intrauterine infection. This will be helpful in the ultimate delineation of the optimal management scheme for PPROM.

Calcium carbonate modifications in the mineralized shell of the freshwater snail Biomphalaria glabrata.

The mineralized shell (consisting of calcium carbonate) of the tropical freshwater snail Biomphalaria glabrata was investigated with high resolution synchrotron X-ray powder diffractometry and X-ray absorption spectroscopy (EXAFS). Parts from different locations of the snail shell were taken from animals of different age grown under various keeping conditions. Additionally, eggs with ages of 60, 72, 120, and 140 hours were examined. Traces of aragonite were found as first crystalline phase in 120 h old eggs, however, Ca K-edge EXAFS indicated the presence of aragonitic structures already in the X-ray amorphous sample of 72 h age. The main component of the shell of adult animals was aragonite in all cases, but in some cases minor amounts of vaterite (below 1.5%) are formed. The content of vaterite is generally low in the oldest part of the shell (the center) and increases towards the mineralizing zone (the shell margin). In juvenile snails, almost no vaterite was detectable in any part of the shell.

Structure determination of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate by powder diffraction.

Most halogenoacetates of alkali salts readily undergo a thermally induced polymerization reaction to poly-(hydroxyacetic acid) in the solid state. The lithium salts represent a remarkable exception. The crystal structures of lithium chloroacetate, lithium bromoacetate and lithium iodoacetate were determined ab initio from synchrotron powder diffraction data. The three compounds are isostructural and differ considerably from the structures of sodium chloroacetate and silver chloroacetate, two compounds that undergo polymerization. Most likely, the strong polarizing effect of the small lithium cation is responsible for the unfavorable crystal structure in which each lithium cation is coordinated to four O atoms from four different halogenoacetate molecules. Lithium chloroacetate: a = 9.3882 (9), b = 4.8452 (4), c = 9.0119 (7) Å, beta = 94.330 (5) degrees; lithium bromoacetate: a = 9.7165 (11), b = 4.8610 (6), c = 9.0228 (11) Å, beta = 93.946 (5) degrees; lithium iodoacetate: a = 10.1812 (10), b = 4.8922 (8), c = 9.0468 (10) Å, beta = 93.251 (5) degrees, all crystallizing in space group P2(1)/c with Z = 4.