Search

The Ca0.6−xSr0.4HoxMnO3−δ (x = 0.05, 0.10, and 0.15) manganites with an orthorhombic crystal structure (space group Pbnm) have been produced via citrate–nitrate route in air. The electron donor holmium (Ho3+) and oxygen nonstoichiometry strongly affect the electrical conductivity (σ), Seebeck coefficient (S), thermal conductivity (κ), and thermal expansion. The increase in the absolute values of S with temperature and the decline of σ above 500 K are explained by the decrease in the concentration of Mn3+ ions due to their disproportionation into Mn2+ and Mn4+ ions. The equilibrium constant of disproportionation, the concentration and mobility of charge carriers depend on temperature and can be derived from the data for S(T) and σ(T). The formation of Mn3+ ions as a result of partial removal of oxygen from the manganites has a strong influence on their properties above 1000 K. Temperature-activated character of mobility and the values of S are consistent with the adiabatic small polaron transport mechanism in Ca0.6−xSr0.4HoxMnO3−δ. [ABSTRACT FROM AUTHOR]

The Ca0.6−xSr0.4HoxMnO3−δ (x = 0.05, 0.10, and 0.15) manganites with an orthorhombic crystal structure (space group Pbnm) have been produced via citrate–nitrate route in air. The electron donor holmium (Ho3+) and oxygen nonstoichiometry strongly affect the electrical conductivity (σ), Seebeck coefficient (S), thermal conductivity (κ), and thermal expansion. The increase in the absolute values of S with temperature and the decline of σ above 500 K are explained by the decrease in the concentration of Mn3+ ions due to their disproportionation into Mn2+ and Mn4+ ions. The equilibrium constant of disproportionation, the concentration and mobility of charge carriers depend on temperature and can be derived from the data for S(T) and σ(T). The formation of Mn3+ ions as a result of partial removal of oxygen from the manganites has a strong influence on their properties above 1000 K. Temperature-activated character of mobility and the values of S are consistent with the adiabatic small polaron transport mechanism in Ca0.6−xSr0.4HoxMnO3−δ. [ABSTRACT FROM AUTHOR]

Introduction: Deep Brain Stimulation (DBS) is an established neurosurgical treatment that can be used to alleviate symptoms in essential tremor (ET) and other movement disorders. Objective: To develop a method and software tool for prediction of effective DBS electrodes based on probabilistic stimulation maps in patients with ET treated by DBS. Methods: 34 patients (39 leads) treated with DBS in the caudal zona incerta were evaluated with the Essential Tremor Rating Scale (ETRS) at 12 months after surgery. In addition, hand tremor and hand function (ETRS items 5/6 & 11-14) were evaluated for every electrode contact during stimulation with best possible outcome without inducing side effects. Prediction of effective electrode contacts was carried out in a retrospective leave-one-out manner based on probabilistic stimulation maps (PSMs), simulated stimulation fields, and a scoring function. Electrode contacts were ranked according to their likelihood of being used in the clinical setting. Ranked electrodes contacts were compared to actual clinical settings. Results: Predictions made by the software tool showed that electrodes with a rank of 1 matched the clinically used electrode contacts in 62% of the cases. Electrode contacts with a rank of 1-2, and 1-3 matched the clinical electrode contacts in 79% and 97% of the cases, respectively. Improvement of hand tremor and hand function was 79% (SD 21%) and 77% (SD 22%) for the clinically used and the predicted electrode contacts, respectively. Conclusions: Effective electrode contacts can be predicted based on PSMs in patients treated with DBS for ET. Predictions may in the future be used to reduce the number of clinical assessments that are carried out before a satisfying stimulation setting is defined. [ABSTRACT FROM AUTHOR]

Objective: OCD is a sometimes debilitating psychiatric disease with a 2% lifetime prevalence. Up to 10% of patients do not respond to conservative treatment. For severe cases, DBS targeting the Nacc/ALIC is a viable option, receiving CE-mark in 2009. However, because of variable success rates and side effects, 8 different targets have been proposed for OCD in the last 18 years - the search for a hotspot continues. In this study, using a novel visualization software, we correlated lead position and resulting volume of tissue activated (VTA) with clinical outcome and side effects in order to narrow down the optimal target area. Methods: We analyzed data for 16 consecutive patients treated at our center over a period of 3 years with DBS of the Nacc/ALIC, following a routine targeting procedure. Based on improvement on the Yale-Brown obsessive compulsive scale (YBOCS) and clinical profit at 12 months follow up, four outcome groups were defined. Subgroups were also designated for unexpected side effects. Individual ROIs from all patient hemispheres were stacked to create a median intensity image, and then registered to the resulting intermediate to create a common anatomical space (Patient average MRI, PAM). Using the Suretune Expert Tuning Tool software (Medtronic), the location of the individual contacts used and the resulting VTA were aggregated into the PAM and probabilistic stimulation maps (PSM) were calculated. The adapting Yelnik-Bardinet atlas was aligned to the PAM as an anatomical reference. Results: The graphical analysis indicates anatomical localization to be correlating with both clinical outcome as well as sideeffects. PSM of non- and fair responders were revealed to be distinct from - but nearby to - the PSM of good and excellent responders. All patients reporting unwanted weight-gain had their active contacts clustered in a circumscript area, independent of their improvement in OCD. These patients are followed up with a multidisciplinary approach to further elucidate the underlying mechanism. Conclusion: While data and analysis is preliminary, this novel tool shows promise for correlation of lead location and clinical effect in the way that PSM suggest an area of best profit. The results also open the way for further research into the insufficiently understood side effect of weight gain through DBS in OCD. [ABSTRACT FROM AUTHOR]