On the incorporation of iron into hexagonal barium titanate: II. Magnetic moment, electron paramagnetic resonance (EPR) and optical transmission

Systematic measurements of the magnetic moment in dependence on temperature and magnetic field of hexagonal 6H-BaTiO3 + 0.04 BaO + x/2 Fe2O3 (0.005 ⩽ x ⩽ 0.05) ceramics were performed to study the influence of Fe ions on the magnetic properties. While the samples show Curie-Weiss paramagnetism for Fe concentrations ⩽1.0 mol%, antiferromagnetic interactions become manifest for 2.0 and 5.0 mol% iron. With increasing Fe content the antiferromagnetic interaction, which is assumed to be caused by a superexchange mechanism [Formula: see text], becomes stronger. At external magnetic fields smaller than 1 T a further, ferromagnetic interaction between Fe3+ ions is detected below 200 K. The interactions between Fe3+ ions in the samples with 2.0 and 5.0 mol% iron are also manifest in the EPR spectra by numerous lines with low intensity. Q-band EPR investigations of 5.0 mol% Fe doped single crystals confirm the existence of only one type of Fe3+-VO associates in the samples.

On the incorporation of iron into hexagonal barium titanate: I. electron paramagnetic resonance (EPR) study

Electron paramagnetic resonance (EPR) investigations of BaTiO₃  +  0.04 BaO  +  x/2 Fe₂O₃ (0.007  ⩽  x  ⩽  0.05) ceramics and BaTi_0.98Fe_0.02O₃ single crystals were performed to study the incorporation of Fe ions in the hexagonal 6H-BaTiO₃ lattice and their defect properties. The samples were characterized by x-ray diffraction and wavelength-dispersive x-ray electron probe microanalysis. EPR spectra were recorded both in X- and Q-bands at room temperature. Angle-dependent single crystal EPR investigations and simulations of the ceramic powder EPR spectra revealed three different centers, which can be attributed to Fe³⁺ ions incorporated on crystallographically different Ti sites. Only one of them was already known before. Two spectra with axial symmetry belong to isolated Fe³⁺ ions incorporated at Ti(1) sites (exclusively corner-sharing oxygen octahedra) and Ti(2) sites (face-sharing octahedra). The difference of their spectral parameters arises from the different trigonal distortions of the two types of octahedra. The third spectrum has orthorhombic symmetry and is caused by Fe³⁺ centers associated with a nearest-neighbor charge-compensating oxygen vacancy. A model for the location of this associate is proposed.

[Pedicled vascularized bone graft for scaphoid reconstruction after Zaidemberg]

BACKGROUND

Nonunion of the scaphoid as a result of proximal fractures, failed surgical reconstruction, and especially avascular fragment necrosis are possible indications of vascularized bone grafts. Various techniques of vascularized (pedicled and free) grafts have been described. Pedicled grafts from the direct vicinity of the wrist provide several benefits. Harvest-site morbidity is reduced and preserved graft perfusion, without the need for blood vessel anastomosis, may lead to an improved consolidation.

METHODS

A common pedicled vascularized bone graft for reconstruction of the scaphoid was first described by C. Zaidemberg and colleagues in 1991. We describe 49 consecutive patients, who underwent vascularized bone-grafting, pedicled on the 1.2 intercompartmental, supraretinacular artery in a modified technique based on Zaidemberg's description. The fixation of the bone graft was performed by Kirschner wires.

RESULTS

A consolidation was detected in 37 cases, and 9 cases showed a persistent nonunion (3 patients did not follow up). According to the classification of Herbert, 44 patients had a nonunion grade D2 or higher, of which 36 patients showed a bony consolidation (8 non-consolidated). Complications occurred in individual cases (1x intraoperative fracture of the radius, 4x transient irritations of the superficial branch of the radial nerve). A loss in the range of motion of the affected wrist was frequent. An indication for a pedicled graft was seen if the preoperative contrast-enhanced MRI showed an impaired perfusion of scaphoid fragments.

DISCUSSION

The more advanced the changes in MRI, the more frequently treatment failed. The vascularized bone graft from the dorsal distal radius described by C. Zaidemberg et al. is one of several ways to address a circulation-impaired nonunion of the scaphoid.

Human phosphodiesterase 4D7 (PDE4D7) expression is increased in TMPRSS2-ERG-positive primary prostate cancer and independently adds to a reduced risk of post-surgical disease progression

Background:

There is an acute need to uncover biomarkers that reflect the molecular pathologies, underpinning prostate cancer progression and poor patient outcome. We have previously demonstrated that in prostate cancer cell lines PDE4D7 is downregulated in advanced cases of the disease. To investigate further the prognostic power of PDE4D7 expression during prostate cancer progression and assess how downregulation of this PDE isoform may affect disease outcome, we have examined PDE4D7 expression in physiologically relevant primary human samples.

Methods:

About 1405 patient samples across 8 publically available qPCR, Affymetrix Exon 1.0 ST arrays and RNA sequencing data sets were screened for PDE4D7 expression. The TMPRSS2-ERG gene rearrangement status of patient samples was determined by transformation of the exon array and RNA seq expression data to robust z-scores followed by the application of a threshold >3 to define a positive TMPRSS2-ERG gene fusion event in a tumour sample.

Results:

We demonstrate that PDE4D7 expression positively correlates with primary tumour development. We also show a positive association with the highly prostate cancer-specific gene rearrangement between TMPRSS2 and the ETS transcription factor family member ERG. In addition, we find that in primary TMPRSS2-ERG-positive tumours PDE4D7 expression is significantly positively correlated with low-grade disease and a reduced likelihood of progression after primary treatment. Conversely, PDE4D7 transcript levels become significantly decreased in castration resistant prostate cancer (CRPC).

Conclusions:

We further characterise and add physiological relevance to PDE4D7 as a novel marker that is associated with the development and progression of prostate tumours. We propose that the assessment of PDE4D7 levels may provide a novel, independent predictor of post-surgical disease progression.

Defect properties of cobalt-doped hexagonal barium titanate ceramics

X-ray diffraction (XRD) patterns, electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) and the magnetic susceptibility of BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.001 ⩽ x ⩽ 0.02) ceramics were studied to investigate the incorporation of Co ions in the BaTiO3 lattice and their valence states as well as the development of the hexagonal phase (6H modification) in dependence on doping level x and sintering temperature Ts. At Ts = 1400 °C the 6H modification begins to occur at a nominal Co concentration x of about 0.001 and for x > 0.005 the samples are completely hexagonal at room temperature. Two different EPR spectra were observed in the 6H modification of BaTiO3, which were both assigned to paramagnetic Co(2+) ions located at the two crystallographically non-equivalent Ti sites in 6H-BaTiO3. The EPR g tensor values as well as the molar paramagnetic susceptibility, measured in the temperature range 5 K-300 K at a magnetic field of 9 T, were analyzed in the framework of the ligand field theory using the program CONCORD. The combination of EPR and magnetic measurements reveals that in air-sintered 6H BaTiO3, the incorporated Co occurs as a mixture of paramagnetic Co(2+) and diamagnetic Co(3+) ions, whereas in samples annealed in reducing atmosphere the majority of Co is in the divalent state. The occurrence of Co(4+) can be excluded for all investigated samples. The sample color caused by Co(2+) and Co(3+) ions is beige/light yellow and dark grey/black, respectively. The majority of the Co(2+) ions substitutes Ti in the exclusively corner-sharing oxygen octahedra possessing nearly cubic symmetry. The corresponding ligand field parameter [Formula: see text] amounts to about -28 000 cm(-1) (Wybourne notation, 10Dq ≈ 20 000 cm(-1)). In the reduced samples nearly 5% of the detected Co(2+) ions occupy the Ti site in the face-sharing oxygen octahedra, which are significantly trigonally distorted. The negative sign of the obtained ligand field parameter [Formula: see text] ≈ -7300 cm(-1) reflects a compression of this octahedron in direction of the hexagonal c-axis.

EPR-Untersuchungen an Schwefelradikalen in Ultramarinen

Künstliche Ultramarine werden mit Hilfe der EPR im X- und Q-Band untersucht. Es wird gezeigt, daß der Paramagnetismus durch 4 Schwefelradikale, die durch die chemische Behandlung mit NaCN abgebaut werden können, entsteht.

Notizen: Cyclopentadienyl-eisen-dicarbonyl-quecksilber

Nach Aufklärung des schwarzbraunen Mono-cyclopentadienyl-metall-carbonyls des Eisens als dimeres, diamagnetisches [(C5H5)Fe(CO)2]2 gelang dessen reduktive Aufspaltung mittels Na-Amalgam in Methanol zu gelbem [(C5H5)Fe(CO)2]--Anion. Dieses ließ sich als in Wasser schwerlösliches, gelbes Hg[(C5H5)Fe(CO)2]2 ausfällen. Beim Ansäuern konnte kein stabiles freies Hydrid gefaßt werden.

Paramagnetic resonance study of nickel ions in hexagonal barium titanate

X-ray diffraction patterns and electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) of BaTiO(3) + 0.04 BaO + xNiO (0.001 ≤ x ≤ 0.02) ceramics were studied to investigate the incorporation of Ni ions and their valence states as well as the development of the hexagonal phase (6H modification) of Ni-doped material with respect to doping level x and sintering temperature T(s). The 6H modification begins to occur at a nominal Ni concentration of between x = 0.005 and 0.01 and its percentage increases with increasing sintering temperature. Ni-doped BaTiO(3) with x = 0.02 sintered at T(s) = 1400 °C is completely hexagonal. In the 3C modification, present in as-sintered ceramics with low nominal Ni concentrations, only one type of Ni EPR spectrum was observed. By comparing its principal values of the g tensor with data of single-crystal measurements the clear assignment of this spectrum to Ni(+) ions is possible. Two different EPR spectra with orthorhombic g tensors are observed in the as-sintered samples with hexagonal crystal structure. These spectra were assigned to Ni(3+) ions with the electron spin S = 1/2 (electron configuration 3d(7), strong crystal field) substituted at Ti lattice sites corresponding to the different distorted octahedra of the hexagonal modification. Measurements of the concentration reveal that only 5% of the doping material is in the state Ni(3+). No EPR spectra of Ni(2+) ions have been detected in either 3C or 6H modification in as-sintered ceramics. Therefore, we suppose that the main part of nickel is substituted as Ni(4+) ions on Ti(4+) lattice sites. After heat treatment of the samples in H(2)/Ar atmosphere a single-line spectrum with g = 2.21 ± 0.01 at room temperature has been observed which is assigned to metallic Ni or antiferromagnetically coupled Ni(2+) ions in secondary phases segregated at grain boundaries or triple points.

The Jahn-Teller effect in Cr5+ -doped PbTiO3: a multi-frequency electron paramagnetic resonance study

Electron paramagnetic resonance (EPR) spectra of Cr5+ defects incorporated on Ti(4+) sites in powdered ceramics of PbTiO3 were investigated in the temperature range 50-400 K at 9 GHz (X), 34 GHz (Q) and 94 GHz (W band). The [Formula: see text] Jahn-Teller effect stabilizes the vibronic ground state of the 3d(1) electron of the Cr(5+) ion and leads to a tetragonally distorted defect- O6 octahedron with the point symmetry D(4h). The spontaneous electrical polarization present in the ferroelectric phase of PbTiO3 appears as a further perturbation producing an additional g-tensor contribution by the quadratic field effect. Its symmetry is dependent on the orientation of the electrical polarization with respect to the Jahn-Teller distortion axis, the tetragonal axis of the defect- O6 octahedron. If the polarization of a domain is anti- or parallel to this axis, the local tetragonal symmetry of the Cr5+ ion persists whereas it is reduced by a perpendicular orientation. Anisotropic EPR spectra of tetragonally and orthorhombic distorted Cr(5+)O6(12-) are detected at low temperatures. Increasing the temperature, the peaks of the two spectra are broadened and a motionally averaged isotropic spectrum appears at 200 K.

The influence of domains on tetrahedrally coordinated Cr(5+) in ferroelectric BaTiO(3): an electron paramagnetic resonance study

Electron paramagnetic resonance (EPR) spectra of quasi-tetrahedrally coordinated Cr(5+) ions (named Cr(II)(5+) in contrast to the octahedrally coordinated Cr(I)(5+)) in powdered ceramic samples of BaTiO(3) were investigated in the temperature range 50-220 K at 9.4 and 34.0 GHz (X and Q band). At 50 K, in the ferroelectric low-temperature phase with rhombohedral symmetry, two peaks in the powder spectrum of the 1/2-spin Cr(II)(5+) centre show a frequency-dependent doublet splitting which is explained assuming the existence of two Cr(II)(5+) centres with slightly different g tensors. The spontaneous polarization in the ferroelectric domains induces changes in the peak positions in the spectra and generates alignment effects of the off-centred Cr(5+) ions. These effects are caused by the linear coupling of the electric dipole moment, associated with the off-centred Cr(5+) ion within the octahedron of surrounding O(2-) ions, and the polarization field. At 75 K a dynamic reorientation of the defect ions among the possible positions in the unit cell broadens the powder peaks. Above 150 K only an isotropic single-line spectrum is observed, the line width of which increases with rising temperature.

Jahn-Teller effect in BaTiO(3):Cr(5+): an electron paramagnetic resonance study

Electron paramagnetic resonance (EPR) spectra of Cr(I)(5+) defects incorporated on Ti(4+) sites in single-crystal and powdered ceramics of BaTiO(3) were investigated in the temperature range 50-220 K at 34 GHz (Q band). Single-crystal and powder measurements allow the unambiguous determination of the full g tensor in the ferroelectric rhombohedral phase whereas in the orthorhombic phase only the determination of the principal values of the Cr(I)(5+) g tensor was successful. The [Formula: see text] Jahn-Teller effect stabilizes the vibronic ground state of the 3d(1) electron of the Cr(I)(5+) ion and leads to a tetragonally compressed defect-O(6) octahedron with the point symmetry D(4h). The spontaneous electrical polarization present in the ferroelectric phases of BaTiO(3) appears as a further perturbation. The quadratic field effect reduces the D(4h) symmetry of the Cr(I)(5+) defect centre and produces an additional g tensor breaking the tetragonal symmetry of the Zeeman term. For symmetry reasons one of the principal axes of the rhombic g tensor must be directed along one [Formula: see text] direction. The angles of the other two principal axes with respect to the [Formula: see text] axes are dependent on the absolute value of the spontaneous polarization. The difference in the temperature behaviour of the single-crystal and powder spectra can be explained by the presence of internal stress in the grains of the ceramic samples which increases the JT energy of the 3d(1) electron.

Osteomyelitis der Mittelhand- und Handwurzelregion

AIM

Because of the low prevalence, there is poor evidence on the effective management of bone and joint infections of the carpus and metacarpus. We therefore studied the outcomes of patients undergoing surgical treatment at our department.

METHOD

We conducted a retrospective study on all patients operated on because of osteomyelitis of the carpus and metacarpus between January 1998 and June 2004. Main study endpoint were the infection control rate at end of treatment and at time of follow-up.

RESULTS

Of eleven subjects (nine men, two women) with a median age of 43 years (range, 19 to 79 years) serial débridement with temporary wound closure and surgical fixation proved successful in ten cases. We identified causative pathogens in ten cases (S. aureus: n = 3, P. aeruginosa: n = 3, mixed: n = 4) by intraoperative biopsy. Eight subjects received local or free tissue flaps. A 73 year old man died in hospital. Follow-up information was available for eight patients after a median of 19.5 months (range: 3 to 61 months). Seven of them did not show signs of recurrent infection.

CONCLUSION

Adhering to accepted standards of treating osteomyelitis, satisfactory control rates in carpal and metacarpal infection can be achieved while salvaging the hand.

[Diagnosis of lunotriquetral instability]

BACKGROUND

Lunotriquetral dissociation with rupture of the lunotriquetral ligament and the radiolunotriquetral and the radiodorsal ligament is usually recognized late. Cinematography, arthrography, magnetic resonance imaging and arthroscopy are the diagnostic procedures. Treatment includes nonoperative methods in the case of incomplete lesions but also closed reposition with temporary LT arthrodesis and open ligament repair. In many cases, definitive LT arthrodesis may become necessary. It is the aim to develop a diagnostic algorithm on the base of retrospective analysed data.

MATERIAL AND METHODS

From January 1998 to July 2003, 97 cinematographies of the wrist were performed, 22 with the question for a dynamic or static VISI deformity as a sign for lunotriquetral instability. This group of patients was analysed retrospectively to evaluate the diagnostic reliability. Based on these datas, a diagnostical algorithm was established for prospective investigations.

RESULTS

The combination of cinematography, arthrography and magnetic resonance imaging suspected lunotriquetral instability in ten cases so that an arthroscopy was arranged. This way LT-lesions were verified in nine cases. The mean interval between accident and first contact with our institution was five months.

CONCLUSIONS

The management of lunotriquetral injuries is complicated by the long time from trauma to definitive diagnosis. A combination of refined clinical and apparative investigations can lead to a reliable diagnosis.

Elucidation of structure and location of V(IV) ions in heteropolyacid catalysts H4PVMo11O40 as studied by hyperfine sublevel correlation spectroscopy and pulsed electron nuclear double resonance at W- and X-band frequencies

Electron spin resonance, pulsed electron nuclear double resonance (ENDOR) spectroscopy at W- and X-band frequencies, and hyperfine sublevel correlation (HYSCORE) spectroscopy have been employed to determine the location of the V(IV) ions in H4PVMo11O40 heteropolyacid catalysts. In these materials the heteropolyanions have the well-known structure of the Keggin molecule. Interactions of the unpaired electrons of the paramagnetic vanadyl ions (VO(2+)) with all relevant nuclei 1H, 31P, and 51V) could be resolved. The complete analysis of the hyperfine coupling tensor for the phosphorus nucleus in the fourth coordination sphere of the V(IV) ion allowed for the first time a detailed structural analysis of the paramagnetic ions in heteropolyacids in hydrated and dehydrated catalysts. The 31P and 1H ENDOR results show that V(IV) ions are incorporated as vanadyl pentaaqua complexes [VO(H2O)5](2+) in the void space between the heteropolyanions in the hydrated heteropolyacid. For the dehydrated H4PVMo11O40 materials the distance between the V(IV) ion and the central phosphorus atom of the Keggin molecule could be determined with high accuracy on the basis of orientation-selective 31P ENDOR experiments and HYSCORE spectroscopy. The results give a first direct experimental evidence that the paramagnetic vanadium species are not incorporated at molybdenum sites into the Keggin structure of H4PVMo11O40 and also do not act as bridges between two Keggin units after calcination of the catalyst. The vanadyl species are found to be directly attached to the Keggin molecules. The VO(2+) ions are coordinated to four or three outer oxygen atoms from one PVMo11 heteropolyanion in a trigonal-pyramidal or slightly distorted square-pyramidal coordination geometry, respectively.

[Remarks on the "pure alexia" syndrome--a case report]

The article describes a case with the "pure alexia" syndrome caused by an infarct of the arteria cerebri posterior sinistra during a diffuse cerebral vascular disease. The authors consider the alexia to be a consequence of difficulties in transcoding graphic into graphemic structures.