Physical properties of new ordered bimetallic phases M0.25Cd0.75PS3 (M = ZnII, NiII, CoII, MnII)

Four bimetallic phases of the thiophosphate family have been synthesized by the cationic exchange reaction using a freshly prepared K0.5Cd0.75PS3 precursor phase and methanolic solutions of nitrates of the divalent cations ZnII, NiII, CoII, and MnII. All the materials were characterized by FTIR, PXRD, SEM-EDXS and (in the case of the diamagnetic compounds) by solid state NMR. For the K0.5Cd0.75PS3 precursor, the X-ray powder diffraction data suggest a modification of the structure, while solid state NMR results confirm that this phase possesses an ordered arrangement of Cd vacancies. The cationic exchange reaction achieves a complete removal of potassium ions (no potassium detected by SEM-EDXS) and re-occupation of the vacancies by divalent cations. Therefore, the obtained compounds have an average composition of M0.25Cd0.75PS3 (M = ZnII, NiII, CoII, MnII) and possess an ordered distribution of the substituent cations. Even with the paramagnetic substitution level of 25%, antiferromagnetic behaviour is present in the phases with MnII, CoII and NiII, as evidenced by dc susceptibility and in the case of the MnII substituted phase by EPR. The cooperative magnetic interactions confirm the conclusion that the paramagnetic ions adopt an ordered arrangement. The analysis by broad band impedance spectroscopy allows to attribute the conductivity in these materials to charge movements in the layers due to the difference in electronegativity of the metal ions. Zn0.25Cd0.75PS3 is the phase that shows the highest conductivity values. Finally, the band gap energies of the bimetallic phases tend to be lower than those of the single-metal phases, probably due to an overlap of the band structures.

Strong intermolecular antiferromagnetic verdazyl-verdazyl coupling in the solid state

Strong magnetic couplings are generally observed intramolecularly in organic diradicals or in systems in which they are promoted by crystal engineering strategies involving, for example, transition metal ligation. We herein present a strong intermolecularly coupling verdazyl radical in the solid state without the use of such design strategies. The crystal structure of an acetylene-substituted verdazyl radical shows a unique antiparallel face-to-face orientation of the neighboring verdazyl molecules along with verdazyl-acetylene interactions giving rise to an alternating antiferromagnetic Heisenberg chain. Single crystal structural data at 80, 100, 173, and 223 K show that one of the π-stacking distances depends on temperature, while heat capacity data indicate the absence of a phase transition. Based on this structural input, broken symmetry DFT calculations predict a change from an alternating linear Heisenberg chain with two comparable coupling constants J₁ and J₂ at higher temperatures towards dominant pair interactions at lower temperatures. The predicted antiferromagnetic coupling is confirmed experimentally by magnetic susceptibility, solid-state EPR and NMR spectroscopic results.

Iridium(iii) hydrido complexes for the catalytic dehydrogenation of hydrazine borane

A series of POCOP iridium hydride complexes with differently substituted aryl backbones catalyse the selective release of one equivalent of hydrogen from hydrazine borane.

P-O-B(3) linkages in borophosphate glasses evidenced by high field (11)B/(31)P correlation NMR

The long-standing debate about the presence of P-O-B(3) linkages in glasses has been solved by high-field scalar correlation NMR. Previously suggested by dipolar NMR methods, the presence of such species has been definitively demonstrated by (11)B((31)P) J-HMQC NMR techniques. The results indicate that borophosphate networks contain P-O-B(3) bonds and thus present a higher degree of atomic homogeneity than previously thought.

NMR-Untersuchungen über molekulare Bewegungsprozesse in Phenylensulfiden

Internal motion in poly (p-phenylene sulfides) and in some low-molecular phenylene sulfides has been studied using NMR relaxation and broad line techniques. The relaxation rates T1 -1 in the laboratory frame at 30 or 15 MHz, and T1e -1 in the rotating frame at 45 kHz, and the second moments (or local fields or linewidths) have been measured over an extended range of temperatures for five different materials. For the polymers, the most important process has an activation energy of approximately 40 kJ/mole; it is ascribed to reorientational random oscillations of the phenylene groups, and it depends upon the detailed polymer structure. The origin of further processes of motion observed with activation energies of 20 and 11 kcal/mole is discussed. The rather narrow lines which occur in the NMR spectra at temperatures well above the glass transition are explained by the mobile fraction of chains of the non-crystalline regions.

Cation size effects in mixed-ion metaphosphate glasses: structural characterization by multinuclear solid state NMR spectroscopy

Metaphosphate glasses with two monovalent species A(1-x)B(x)PO3 (0 ≤x≤ 1) show mixed-ion effects (MIE) in the dc conductivities and glass transition temperatures, which are strongly dependent on the cation size mismatch between the two mobile species. In the present contribution, mixed-ion metaphosphate glasses based on the cation combinations Cs-Li, Rb-Li, and Cs-Ag, exhibiting particularly large size mismatches, are analyzed by (31)P, (87)Rb, (109)Ag and (133)Cs NMR to determine possible correlations between this mismatch and some of the structural properties critical to the development of the MIE: the local environments around the mobile species and their spatial distribution relative to each other. The results are compared with those obtained in the Na-Ag metaphosphate series, which serves as a reference system, with minimized cation mismatch MIE. The local coordination environments of the Ag(+), Rb(+) and Cs(+) ions follow analogous compositional trends as previously observed in Na-based mixed-ion metaphosphate glasses: for a given cation species A, the average A-O distance shows an expansion/compression when this cation is replaced by a second species B with smaller/bigger ionic radius, respectively. This compositional differentiation of the structural sites for the mobile species may contribute to the MIE. Concerning the relative spatial distribution of the mobile ions, results from (7)Li-(133)Cs (SEDOR) experiments indicate a random mixture of Cs and Li in Cs-Li metaphosphate glasses. While this result is in agreement with one of the fundamental hypotheses of the models proposed to describe the MIE, it is at variance with the observation of various partial cation segregation phenomena observed in Na-based mixed alkali glasses. This result suggests that cation size mismatch is not the decisive parameter in determining segregation or non-statistical mixing of cations in the glass. In the Cs-Ag and Na-Ag glasses, (109)Ag spin-echo NMR reveals a progressive slowing down of the Ag(+) diffusion dynamics as this species is replaced by Cs(+) or Na(+). The substitution by the bigger Cs(+) ion causes a strong reduction in Ag(+) mobility suggesting the existence of separated diffusion pathways for these cations. In contrast, substitution by the similarly-sized Na(+) causes a much weaker mobility reduction consistent with the existence of Ag-Na cooperative hopping.

Direct correlation between nonrandom ion hopping and network structure in ion-conducting borophosphate glasses

We present temperature-dependent conductivity spectra of sodium borophosphate glasses with a varying borate/phosphate ratio but a constant sodium oxide content which can be mapped into time-dependent mean square displacements. For the first time, we show that characteristic lengths of ion transport derived thereof are directly linked to features of network structure, viz., the number of boron oxide tetrahedra. Our results also shed light on the mixed network former effect.

[Quality management in a combined clinic - the quality management system according to DIN EN ISO 9001 of the The German Association of Spa Accommodation Resorts e. V. (VdKB)]

The implementation of a quality system in health care organizations offers huge potentials for improvement and development. But the realization of such systems necessitates high investments, which small companies and family businesses often are unable to raise. The German Association of Spa Accommodation Resorts (VdKB) commissioned two consultants to develop a reasonably priced implementation concept of a DIN EN ISO 9001 quality system specially adjusted to small companies and family businesses in medical spa and rehabilitation services, which was successfully accredited in May 2003. This paper describes fundamental requirements in combine management systems, considers the pros and cons of management combines and demonstrates the practical realization of combine requirements on the example of the VdKB-combine system.

Two-dimensional 109Ag NMR and random-walk simulation studies of silver dynamics in glassy silver ion conductors

By applying one- and two-dimensional 109Ag NMR, we demonstrate that silver diffusion in silver iodide/silver phosphate glasses is governed by a very broad, continuous distribution of correlation times G(lg tau). As a consequence, over a wide temperature range, the 109Ag NMR spectra can be described by a weighted superposition of a Gaussian and a Lorentzian where these line-shape components result from the slow and the fast silver ions in G(lg tau), respectively. For the 109Ag NMR two-time correlation functions F2(t), measured as a stimulated echo, a very stretched decay to F2SS(t(m)) = 0 is observed. When fitting to a Kohlrausch function, exp[-(t/tau)beta], a stretching parameter beta approximately = 0.2 is found. The temperature dependence of the mean correlation time of silver dynamics is described by an Arrhenius law where the activation energy is consistent with the one reported for the dc conductivity sigma(dc). In addition, it is shown that the effect of complex dynamical processes on NMR multi-time correlation functions can easily be calculated when performing random-walk simulations for schematic models such as the random-barrier model and the random-energy model. Based on these models it is possible to simulate various NMR observables and the mean square displacement, thus revealing the information content of multi-dimensional NMR experiments on solid ion conductors.

[Quality management in German rehabilitation clinics - a stratified representative survey]

BACKGROUND

As of January 1, 2000 rehabilitation clinics in Germany are obliged to implement and develop a quality management system.

OBJECTIVE

This study aims to depict the implementation of quality management (QM), to trace the preferred QM models, identify the reasons for and experience with the introducing quality management, and inquire into the quality tools used in rehabilitation clinics.

METHODS

Postal study of a representatively selected random sample of 298 rehabilitation clinics, stratified along the criteria state, number of beds and financially responsible agency, using six questions with nominally scaled items. Questionnaire design provided no clues as to the responding clinics. The study was designed along the Total Design Method.

RESULTS

89 % of the responding clinics have implemented a QM system, or are about to or planning to do so. Only 11 % reject quality management. 59 % implemented their system in 1998, 1999 or 2000. Among the reasons for implementing a QM system, items related to potentials of quality management predominate, whereas demands by third parties are given only very rarefy.

DISCUSSION

The response rate was 59 %, i. e., the study can be considered representative. The high share of clinics taking a positive view on quality management is however somewhat modified by the fact that 40.4 % of the clinics have adopted or are planning far traditional quality assurance methods. Whether these systems will satisfy the legal requirements in place (SGB V) is doubtful. Adjusted, responses show that 48.9 % of the clinics are running QM systems, are about to or planning to implement one.

CONCLUSIONS

Many of the responding clinics have already implemented a QM system or are about to do so. A majority of the clinics however rely on traditional quality assurance methods. Whether quality assurance will satisfy the legal requirements in place (SGB V) re an internal quality management system must be awaited.

Dipolar coupling information in multispin systems: application of a compensated REDOR NMR approach to inorganic phosphates. Rotational echo double resonance

An experimental strategy has been developed for measuring multiple dipole-dipole interactions in inorganic compounds using the technique of rotational echo double resonance (REDOR) NMR. Geometry-independent information about the dipole couplings between the observe nuclear species S (arbitrary quantum number) and the heteronuclear species I (spin-12) can be conveniently obtained from the experimental curve of DeltaS/S(0) versus dipolar evolution time by limiting the analysis to the initial data range 0 < delta S/S(0) < 0.30. Numerical simulations have been carried out on a three-spin system of type SI(2) in order to assess the effect of the I-I homonuclear dipole-dipole coupling and the influence of experimental imperfections such as finite pulse length and misadjustments of the 180 degrees pulses applied to the I-spin species. The simulations show further that within the initial data range the effects of such misadjustments can be internally compensated by a modified sequence having an additional 180 degrees pulse on the I channel in the middle of the dipolar evolution periods. Experimental (27)Al¿(31)P¿ REDOR results on the multispin systems Al(PO(3))(3), AlPO(4), [AlPO(4)](12)(C(3)H(7))(4)NF, and Na(3)PO(4) confirm the general utility of this approach. Thus, for applications to unknown systems the compensation strategy obviates calibration procedures with model compounds.

[Reform of the Law DIN EN ISO 9001:2000. Commentary on the new requirements on quality management systems]

Since January this year the German translation of the third draft to the reform of the DIN EN ISO 9000 is available. The draft reveals an approximation to the models of Business Excellence. Most important changes are a far stronger customer orientation, orientation on the processes and resource management. The norms DIN EN ISO 9002 and 9003 have been removed, ISO 8402 has been integrated in the reformed DIN EN ISO 9000. Apart from that the compatibility with other management systems has been improved. It was the aim of the reform to improve the applicability for all types of business, products and services.

"NaB15": a new structural description based on X-ray and neutron diffraction, electron microscopy, and solid-state NMR spectroscopy

A boron-rich sodium boride, formerly known as NaB15, has been subjected to a comprehensive structural reinvestigation using X-ray single-crystal and powder diffraction, low-temperature neutron and electron diffraction, high-resolution transmission electron microscopy, and 23Na solid-state NMR spectroscopy. The results indicate that the previously published orthorhombic space group is incorrect. Consistent with all of the experimental results a modified structural description is developed in the monoclinic space group Ilml (a = 585.92(3), b= 1039.92(6), c = 833.17(5) pin, beta = 90.373(5) from powder data). Because one of the interstitial boron atom positions remains unoccupied, the accurate compositional formula is NaB145 or Na2B29.

Dephasing of spin echoes by multiple heteronuclear dipolar interactions in rotational echo double resonance NMR experiments

The application of rotational echo double resonance (REDOR) nuclear magnetic resonance (NMR) for accurate distance measurements has thus far been largely restricted to isolated heteronuclear two-spin systems. In the present paper, the informational content of REDOR curves is explored for systems characterized by multi-spin interactions. To this end, numerical REDOR simulations are presented for cases in which single observe spins S are dipolarly coupled to groups of spins I in distinct geometries. To develop the utility of REDOR for characterizing dipolar couplings in unknown and/or ill-defined geometries, the validity ranges and systematic errors of certain analytical approximations are studied. In the limit of short dipolar evolution times where 0 < deltaS/S0 < or = 0.2 to 0.3, the REDOR difference signal intensity increases approximately proportional to the square of the dipolar evolution time. Here, the curvature depends simply on the second moment M2 characterizing the overall strength of the heterodipolar coupling, irrespective of specific molecular geometries. Fitting experimental REDOR data in this manner produces slight systematic underestimates of M2. However, these errors tend to be counterbalanced by additional systematic errors made by neglecting weak couplings to more remote spins and distribution effects caused by disorder. Based on these findings, the results suggest a convenient method of obtaining site-resolved second moment information in disordered materials.

Synthesis and structural characterization of mixed aluminum-gallium-offretites

A new synthesis procedure is reported for the preparation of mixed Al,Ga-offretites over the entire solid solution range 0 < or = Ga/(Ga + Al) < or = 1. The resulting materials are characterized by X-ray powder diffraction, adsorption microcalorimetry and multinuclear solid state NMR. The 29Si MAS-NMR data are consistent with statistical occupancy of the T1 and T2 sites by aluminum and gallium, and also show no positive evidence for preferential siting effects between both framework metals. Isotropic chemical shifts and nuclear electric quadrupolar coupling constants for 27Al and 71Ga have been obtained from a field-dependent analysis of the center of gravity in the MAS-NMR spectra. H-Al,Ga-offretites produced by ammonium exchange and subsequent calcination reveal evidence of partial demetallation of the framework with formation of extra-lattice metal species.

31P to 77Se cross polarization in beta-P4Se3

Cross polarization from 31P to 77Se is demonstrated in beta-P4Se3. This material, an inorganic glass, is readily synthesized from the elements and serves as a convenient sample for setting the Hartmann-Hahn condition.

11B[27Al] and 27Al[11B] double resonance experiments on a glassy sodium aluminoborate

Cross-polarization/magic-angle spinning (CP/MAS) and rotational echo double resonance (REDOR) experiments involving two half-integer quadrupolar nuclei, 11B and 27Al, are reported, to demonstrate boron-aluminum connectivities in a model aluminoborate glass. A detailed study of the spin-lock behavior of 11B and 27Al proves to be a prerequisite for successful CP/MAS experiments. Under MAS conditions, two distinct boron sites are observed, corresponding to tetrahedral BO4/2- sites (nuclear electric quadrupole coupling constant near 0.3 MHz) and trigonal BO3/2 sites (nuclear electric quadrupole coupling constant near 2.7 MHz). The BO4/2- sites are most successfully spin-locked in the adiabatic regime at high radio frequency (RF) field strengths, whereas for the BO3/2 sites optimum spin-lock conditions are achieved in the sudden regime (low RF field strengths). These differences can be exploited for spectral editing purposes in REDOR experiments. Using corresponding T1p filters, it becomes possible to measure individual REDOR dephasing curves for both types of boron sites. The results illustrate the possible utility of heteronuclear X-Y double resonance techniques in unravelling the intermediate range order in amorphous systems containing quadrupolar nuclei.

23Na nuclear magnetic resonance spin echo decay spectroscopy of sodium silicate glasses and crystalline model compounds

The possibility of using Hahn spin echo decay spectroscopy for measuring 23Na-23Na dipole-dipole couplings in crystalline solids and glasses is investigated. Although the presence of nuclear electric quadrupolar splittings complicates the situation compared to the case of dipole-dipole couplings among spin-1/2 nuclei, experimentally measured second moments lie within approximately 10-20% of the calculated values, if the following conditions are fulfilled: (1) selective excitation of the central 1/2-->-1/2 transition, and (2) restriction of the analysis to short evolution times (2t1 < or = 200 microseconds). At longer evolution times, partial suppression of the spin-exchange term in the dipolar Hamiltonian due to magnetic inequivalencies between the interacting nuclei produces substantial differences between experimental and calculated spin echo decays, the extent of which depends on the compound considered. These results signify the potential utility of 23Na spin echo nuclear magnetic resonance for testing the distribution of Na-Na distances in structurally disordered solids and glasses. The method is shown to be applicable to sodium silicate glasses, where it reproduces anticipated compositional trends in 23Na-23Na couplings. Details and inherent limitations of this methodology are discussed.

Identical expression of ELAM-1, VCAM-1, and ICAM-1 in sarcoidosis and usual interstitial pneumonitis

Extravasation of leucocytes in tissues is mediated by leucocyte-endothelial cell interactions in which adhesion molecules play an important role. Until now, two pathways have been unravelled, i.e., the LFA-1/ICAM-1 and the VLA-4/VCAM-1 pathways. ELAM-1 has been shown to be involved in granulocyte accumulation and recently also in lymphocyte migration. The role of HECA-452 is under investigation. In this study we have investigated the expression of the above-mentioned adhesion molecules in lung tissue of patients with pulmonary sarcoidosis and usual interstitial pneumonitis (UIP), and in mediastinal lymph nodes of patients with sarcoidosis. ICAM-1 (CD54) was broadly distributed on the endothelium of all the vessels found in sarcoidosis and UIP. VCAM-1 was present on the endothelium of the venules, capillaries, and arterioles in both sarcoidosis and UIP. ELAM-1 reacted with endothelial cells lining venules and capillaries in chronic progressive sarcoidosis and in the active phase of UIP but not in the stationary phases of both diseases. HECA-452 activity could be detected only on high endothelial venules within sarcoid lymph nodes. In lung tissues, macrophages bearing the ICAM-1 antigen were present in sarcoid tissue but not in the interstitium and alveolar space of UIP. LFA-1 (CD11a/CD18) and VLA-4 (CD49d/CD29) were present on all leucocytes found but seemed to be more highly expressed on lymphocytes in sarcoidosis. These findings suggest that the LFA-1/ICAM-1 and VLA-4/VCAM-1 pathways are involved in leucocyte migration in both types of lung disease, while in the active phases of sarcoidosis and UIP, ELAM-1 is also involved.

Spectral editing in MAS NMR of aprotic solids. 31P-113Cd cross-polarization and heteronuclear double-quantum filtering studies in II-IV-V2 semiconductor alloys

Magic-angle-spinning NMR spectra of aprotic solids, ceramics and glasses frequently suffer from poor site resolution due to wide chemical shift distribution effects. In such cases, cross-polarization and heteronuclear double-quantum filtering experiments involving nuclei other than 1H offer unique spectral editing capabilities. The utility of such assignment techniques for examining site populations in semiconductor alloys is demonstrated for the chalcopyrite systems CdGeAs2-xPx, CdSiAs2-xPx and ZnxCd1-xGeP2. The results permit a distinction between local and non-local effects on experimental chemical shift trends and reveal that compositional dependences observed in these alloys are dominated by non-local chemical shift contributions.