Objective: To evaluate the effects of balance retraining in a sample of people with multiple sclerosis. Design: Randomized controlled trial. Setting: Rehabilitation unit. Subjects: A consecutive sample of 44 subjects was randomized into two experimental groups and one control group. The inclusion criteria were: ability to stand independently more than 30 seconds, ability to walk for 6 m. Interventions: Group 1 received balance rehabilitation to improve motor and sensory strategies. Group 2 received balance rehabilitation to improve motor strategy. Group 3 received treatments not specifically aimed at improving balance. Main outcome measure: Berg Balance Scale, Dynamic Gait Index and fall frequency were used to assess balance impairments. Dizziness Handicap Inventory and Activities-specific Balance Confidence were used to assess handicap and the level of balance confidence. Results: Frequency of falls post treatment was statistically different among groups (P = 0.0001); The Berg Balance Scale showed an overall statistically significant difference (P = 0.0008) among groups. Change pre—post scores were 6.7, 4.6 and 0.8 points for groups 1, 2 and 3. Dynamic Gait Index showed an overall near statistically significant difference among groups (P = 0.14), with change pre—post scores of 3.85, 1.6 and 1.75 points for groups 1, 2 and 3; after the exclusion of drop-outs a statistically significant difference was observed (P = 0.04). The self-administered tests (Activities-specific Balance Confidence and Dizziness Handicap Inventory) did not show clinically relevant improvements. Conclusions: Balance rehabilitation appeared to be a useful tool in reducing the fall rate and improving balance skills in subjects with multiple sclerosis. Exercises in different sensory contexts may have an impact in improving dynamic balance.

Nanopowders of TiO2 doped with by V, Nb, Ta were obtained by laser-induced pyrolysis. The profiles of the diffraction peaks were Fourier analysed with a single-peak method and the microstructural parameters 〈M〉 (average crystallite size) and 〈ε2〉1/2 (mean-square root microstrain) were estimated. A linear correlation between 〈ε2〉1/2〈M〉 and 1/〈M〉 was observed in both anatase and rutile phases. For a given crystallite size, the microstrains as well as the dispersion of data were larger in anatase then in rutile. Indeed, one of the factors inducing the anatase-to-rutile transformation may be the presence of larger microstrains in anatase. In rutile, the high correlation found between 〈ε2〉1/2〈M〉 and 1/〈M〉 suggests that in this phase the microstrains present in the structure are due only to the geometrical constraints of the surface. Indeed, for infinite crystallite size no microstrains are expected. In anatase, microstrains depend also on the specific cation present in the crystallite.

The kinetics of phase transitions and phase segregation induced by annealing temperature on the Ti–W–O gas-sensing layer was studied by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The main goal was to identify, on the basis of kinetics studies, structurally stable Ti–WO_3 thin film phases and compare their response to polluting gases in order to determine possible correlations between structural and electrical properties of the sensing layers.

The structural properties of Cr3C2/NiCr 75/25 coatings, prepared with the high velocity oxy-fuel (HVOF) spraying method, have been studied at room temperature by XRD techniques. The dependence of the phase composition and of the amorphous-crystalline transformations on the thermal history of the specimens have been investigated by varying the annealing temperature of the samples in the range 300-1073 K, with different annealing schedules. In parallel, a microstructural examination with SEM and EDS has been made on the starting powders and on the cross section of the coatings before and after annealing treatments. The HVOF coating evaluated in this study does not present carbides with relatively poor content of carbon as Cr7C3and Cr23C6. In all specimens Cr3C2and M3C2(M=Cr,Ni) carbides and small amount of Cr2O3were found. The results, in terms of XRD spectra, are compared with those obtained for the Cr3C2/NiCr 75/25 starting powders.

In the present contribution an X-ray diffraction (XRD) study of thin films in the Mo-Bi-O system is reported. The samples were grown by MOCVD on Al2O3 substrates. Several thin films have been grown starting from a Mo:Bi ratio in the two metallorganic precursors ranging from 6:1 to 1:1, thus obtaining films constituted by MoO3 and Mo-Bi-O layers with different thicknesses. The effect of the underlying Mo-Bi-O layer on the preferred orientation of the MoO3 layer, which is found in the samples with a high Mo:Bi ratio in the precursors, is discussed. Moreover, an equation is proposed relating the percentage of the phase constituting the film, as given by the Rietveld leastsquares procedure, and the film thickness. Thus it is shown that the growth rate of the pure MoO3 film is much higher than that of the Mo-Bi-O oxide film. A tentative explanation can be given by considering a possible growth inhibiting action by Bi in this system.

Reasonable structural models are proposed for the Cu complexes of two intercalated compounds of α-Zr(HPO4)2·H2O (α-ZrP): one with 1,10-phenanthroline (A) and the other with 2,2′-bipyridyl (B). The models are derived from considerations of the unit-cell geometry changes undergone by α-ZrP upon insertion of, first, the organic molecules and then copper, in accordance with a set of general criteria of structural analysis called the “comparison method.”

The structure of lithium zirconate (Li6Zr2O7) has been solved by the single-crystal X-ray method. Li6Zr2O7 is monoclinic, space group C2/c and cell parameters a = 10.440(4), b = 5.991(1), c = 10.204(2) Å, β = 100.25(3)°, Z = 8 (for the asymmetric unit Li3ZrO7/2). A least-squares refinement gave conventional and weighted R factors of 0.041 and 0.052, respectively. The structure is of the NaCl type and is characterized by an ordered anionic deficiency. As a consequence the coordination number of the Li atoms is 5, with the coordination geometry of a distorted square pyramid. Also, the oxygen octahedron around each Zr atom is significantly distorted. A comparison between Li6Zr2O7 and Li2ZrO3, another phase of the NaCl type, shows that the structure of the former compound is more "open" than that of Li2ZrO3 and, for this reason, a higher mobility of both the Li+ and O2- ions can be expected for the former phase. These results are in agreement with conductivity measurements.

SnO2 thin films were grown by means of the CVD technique, starting from dibutyltin diacetate as the precursory species. A good response of SnO2 thin films towards hydrogen, ethyl alcohol and especially methane was observed in the temperature range 300–300 °C. The gas sensitivity ΔG/G towards 1000 ppm of hydrogen, ethyl alcohol and methane at the temperature of 350 °C was equal to 200, 100 and 30, respectively; on the contrary, the response to CO, NOx and other hydrocarbons was almost negligible. If the temperature is augmented from 350 to 500 °C, an increase of the sensitivity to methane together with a lower sensitivity to hydrogen is observed. Therefore, the sensor selectivity to methane could be improved by pulsing the sensor operating temperature between 350 and 500 °C.

The Zr and Y coordination polyhedra, as found in the room-temperature phases of their pure oxides, are used as building blocks in modeling the structures of yttria-stabilized zirconias (YSZ). It is found that, in order to obtain the right coordination geometry, three clusters of four Zr- and Y-based building blocks can be constructed. When Y building blocks are present in a cluster they form a couple, characterized by a common structural vacancy, a neutral defect which can be defined when an oxygen is missing with respect to the case of the Zr seven coordination in monoclinic zirconia. It is shown that this model fairly well justifies the experimental results obtained by others. In conclusion, this kind of cluster modeling is proposed as a general method for solving structural problems in other mixed oxides.

AbstractThe dependence of a peak diffraction angle on the positioning of the diffracted-beam Soller-slit pack was observed and studied by discussing the determining factors. In particular, the misalignment angle between the Soller pack and the counter axis is recognized as a key factor and experiments were performed for giving a quantitative basis to this statement. An important consequence of the results of these experiments and related profile analysis is the suggestion of designing parallel-beam diffractometers with the possibility of checking and changing the position of the diffracted-beam Soller-slit packs in order to optimize the performance of the instrument.

Semiconducting samples of a Bi–Ca–Sr–Cu oxide, having a nominal composition 4:3:3:4, were prepared by melting high purity oxides of the various elements. Superconducting samples were obtained by annealing the semiconducting samples at a temperature close to the melting temperature. Electrical resistivity measurements indicated the presence of two superconducting phases, one with the onset temperature at about 110 K, the other with a significantly lower onset temperature. The presence of this second phase is proven by the x-ray powder diffraction patterns. The crystalline structures of both the semiconductor and superconductor samples have almost equal lattice parameters and are orthorhombic, but belong to different space groups: Fmmm and Bbmm, respectively. No significant amount of the 110 K superconducting phase was present in the diffraction pattern of the superconducting compound. XPS and XANES data on the Ca atom indicate that a different electronic state of Ca is present in the superconducting compound, which still contains an appreciable amount of the semiconducting phase.

The crystal of the title compound is monoclinic (space group C2/c), with a = 22,067(17), b = 10.111 (10), c = 16.886(11) Å,β=142.95(5)°, and Z = 4. Its structure is based on the packing of SmBr3·4iPr(OH) (iPr = isopropyl) molecules. The metal atom is coordinated by three Br ions and by the oxygen atoms of the four iPr(OH) ligands. The coordination polyhedron is a distorted pentagonal bipyramid of C2 symmetry, with Sm and one of the Br atoms lying on the twofold axis of crystallographic symmetry. Polymerization experiments are reported showing that the activity of the catalytic system based on the title complex is much lower than that shown by systems based on similar Nd complexes. A possible rationalization of this fact is given in terms of the oxidation capacity of the rare-earth ions.

While the deviations from linearity of EPSILON-sin2-psi curves in the case of two welded hot-rolled C40 steel bars were being studied, this paper was prompted by the observation that, at psi = 0-degrees, the diffraction angle 2-theta depends, on phi, the inclination angle of the diffraction plane with respect to an arbitrarily chosen reference plane attached to the specimen. This result is unexpected and cannot be explained by bulk structural or microstructural factors. A surface effect is offered as a possible explanation.

The crystal structure of Cs(Mo0.95W0.05)7O21 has been determined from a single-crystal X-ray diffraction experiment. The crystal is orthorhombic (space group Pnma), with a = 17.638(5), b = 5.448(1), c = 17.945(7)Å, and Z = 4, for a formula unit Cs(Mo0.95W0.05)7O21. The intensities (I) of 1431 reflections, for which I > 3σ(I), were considered observed. The structure was solved by direct and Fourier methods and refined by least squares to a value of 0.019 for the conventional R factor. It is based on the corner sharing of molybdenum coordination polyhedra, forming chains of five very distorted “octahedra” and two terminal tetrahedra. These chains, similar to those found in the structures of γ- and η-Mo4O11, pack to form a three-dimensional network, thus generating voids in which the Cs atoms are located with a coordination number of 12.

The crystal of the title compound, trigonal (P3m1) with hexagonal parameters a = 3.744(1) and c = 12.149(3)Å, is isostructural with polytype I of ZnIn2S4, being formed by the stacking of hexagonal layers of S anions, with the cations occupying, in intermediate planes, voids of approximate Oh and Td symmetry. Single-crystal X-ray and powder neutron diffraction intensities were used as the basis for the refinement of various models of cation distribution among three different crystallographic sites. Eventually the “best” model was found to be represented by the formula (Co0.38In0.62)o (Co0.29In0.38Ga0.33)t1(Co0.33Ga0.67)t2S4, where the subscript o refers to a pseudooctahedral site and subscripts t1 and t2 refer to two different sites of approximate Td symmetry. Evidence is found for the fact that the center of gravity of the pseudooctahedral site, as determined by the neutron experiment, is different from that “observed” by X-ray diffraction and a possible explanation is presented for this fact.

This paper reports on the study of five neodymium bromide complexes of general formula NdBr3·nL prepared according to the scheme NdBr3·6H2O + 6HC(OCH3)3 → NdBr3·nCH3OH + 6HCO(OCH3) + (12 − n)CH3OH, followed by ligand exchange, leading to neodymium tribromide complexes NdBr3·nL with nL = 4iPrOH (I), 4THF (II), 4Py (III), 2THF (IV) and 2iPrOH (V) where iPr = isopropyl, THF = tetrahydrofuran and Py = pyridine. The catalytic activity of all the above complexes in the polymerization of butadiene is very high and it increases from I to III. The diffraction study of I and II shows that both molecules are monomeric (coordination number 7), indicates that the nature of the NdBr bonds is influenced by ligand substitution, and reveals that the covalent contribution is more important in II than in I. The correlation of these findings with the results obtained from the study on the activity is discussed.

The structures of the low-and high-temperature modifications of lithium orthotantalate, Li3TaO4, have been determined by neutron and X-ray diffraction methods. The low-temperature, or β, phase has symmetry C2c and lattice parameters a1 = 8.500(3), b1 = 8.500(3), c1 = 9.344(3)Å, and β = 117.05(2)°. The high-temperature, or α, phase has symmetry P2 and lattice parameters ah = 6.018(1), bh = 5.995(1), ch = 12.865(2)Å, and βh = 103.53(2)°. Both structures are ordered. The β-phase has a rock salt-type structure with a 3 : 1 ordering of the Li+ and Ta5+ ions. Its structure can be generated from the low-temperature modification by means of a complex pattern of shifts of the Ta5+ ions.