Atomic-scale study of the amorphous-to-crystalline phase transition mechanism in GeTe thin films

The underlying mechanism driving the structural amorphous-to-crystalline transition in Group VI chalcogenides is still a matter of debate even in the simplest GeTe system. We exploit the extreme sensitivity of ⁵⁷Fe emission Mössbauer spectroscopy, following dilute implantation of ⁵⁷Mn (T½ = 1.5 min) at ISOLDE/CERN, to study the electronic charge distribution in the immediate vicinity of the ⁵⁷Fe probe substituting Ge (Fe_Ge), and to interrogate the local environment of Fe_Ge over the amorphous-crystalline phase transition in GeTe thin films. Our results show that the local structure of as-sputtered amorphous GeTe is a combination of tetrahedral and defect-octahedral sites. The main effect of the crystallization is the conversion from tetrahedral to defect-free octahedral sites. We discover that only the tetrahedral fraction in amorphous GeTe participates to the change of the Fe_Ge-Te chemical bonds, with a net electronic charge density transfer of  ~ 1.6 e/a₀ between Fe_Ge and neighboring Te atoms. This charge transfer accounts for a lowering of the covalent character during crystallization. The results are corroborated by theoretical calculations within the framework of density functional theory. The observed atomic-scale chemical-structural changes are directly connected to the macroscopic phase transition and resistivity switch of GeTe thin films.

Fe charge state adjustment in ZnO upon ion implantation

The influence of the ion implantation process on the charge state of dilute (57)Fe impurities implanted as radioactive (57)Mn in ZnO is investigated by (57)Fe emission Mössbauer spectroscopy. One sample is additionally implanted with stable (23)Na impurities. Both Fe(2+) and Fe(3+) charge states are observed, and the Fe(3+)/Fe(2+) ratio is found to increase with the fluence of both (57)Mn/(57)Fe and (23)Na ions, demonstrating that the build-up of Fe(3+) is not related to the chemical nature of the implanted ions. The results are interpreted in terms of radiation damage induced changes of the Fermi level, and illustrate that the Fe(3+)/Fe(2+) ratio can be adjusted by ion implantation. The spin-lattice relaxation time for Fe(3+) in ZnO is found to be independent of the implantation fluence, and is evidently an intrinsic property of the system.

Magnetism at single isolated iron atoms implanted in graphite

Mössbauer spectra obtained after implantation of 57Fe into highly oriented pyrolytic graphite (HOPG) show a combined magnetic and quadrupole interaction with a magnetic hyperfine field Bhf = 32.6 T at 14 K. Though magnetic effects in nominally diamagnetic HOPG have been reported recently, no experiment has previously shown the existence of magnetism at the atomic scale. The results suggest that magnetic ordering occurs by coupling of the Fe magnetic moment to structural and/or electronic magnetic defects induced by the probe atoms' implantation damage.

Endometrial effects of exemestane compared to tamoxifen within the TEAM trial: Results of a prospective randomized study

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Background: A prospective open label randomized multicenter substudy was performed in the German TEAM Trial Group to compare the effects of the irreversible aromatase antagonist Exemestane (EXE) and the ER agonist/antagonist Tamoxifen (TAM) on the endometrium during adjuvant treatment for postmenopausal estrogen receptor positive breast cancer. Methods: Transvaginal Ultrasound Scans (TVS) were performed at baseline, 6 and 12 months of treatment if no proliferation >5mm was present, and in 3 months intervals if endometrial thickness exceeded 5mm. Intent-to-treat analysis was performed based on 158 patients. Primary endpoint was the time interval from randomization to the earliest occurrence of endometrial hyperplasia > 10mm. Secondary endpoints were the time from randomization to endometrial hyperplasia > 5mm and the time interval from randomization to vaginal bleeding. Analysis of Time to Event Curves was performed by Kaplan-Meier method, analysis of differences between treatments by two-sided Logrank test and Cox Proportional Hazards. Differences in frequency were compared by Fisher‘s Exact Test. Results: 65 patients were available for analysis in the TAM arm, 78 in the EXE arm. Both groups were comparable regarding age, height, tumor grade,and stage. Median follow-up was 727 (EXE) and 526 days (TAM). In this time period, there were no (EXE) vs. 11 (TAM) cases of endometrial hyperplasia >10mm (p<0.0001), 11 (EXE) vs. 34 (TAM) patients with hyperplasia >5mm (p< 0.006). In total, endometrial hyperplasia was observed 11 times in the EXE arm vs. 45 times in the TAM arm (p<0.0001). Time to endometrial hyperplasia was significantly longer in the EXE group (p<0.0001); HR was 0.160 indicating an 84% risk reduction of hyperplasia in the EXE group. Increase in endometrial thickness from baseline to 6mo. was 2.94mm (EXE) vs. 5.41mm(TAM), from baseline to 12 mo 2.64mm vs. 6.0 mm respectively (p<0.0006). Only 1 patient underwent histological sampling in the EXE group (no hyperplasia) vs. 18 in the TAM subset. Conclusions: In a TEAM subprotocol, irreversible inactivation of aromatase by EXE resulted in significantly less endometrial proliferation than TAM during adjuvant therapy of receptor positive postmenopausal breast cancer.

No significant financial relationships to disclose.

Cyclandelate in the treatment of patients with mild to moderate primary degenerative dementia of the Alzheimer type or vascular dementia: experience from a placebo controlled multi-center study

A 24-week, double-blind, multi-center, randomised parallel group study compared the efficacy and safety of 800 mg bid cyclandelate with placebo in patients with mild to moderate dementia of primary degenerative or vascular origin. A total of 196 patients entered the study, 147 patients completed treatment in adherence with the protocol. Primary outcome measures were the cognitive score of the Alzheimer's Disease Assessment Scale (ADAS-Cog), the subscale Instrumental Activities of Daily Living of the Nurses' Observation Scale for Geriatric Patients (NOSGER-IADL) and the Clinical Global Impressions of Change (CGI-C). Safety assessments included adverse events, vital signs, ECG and clinical laboratory parameters. The primary efficacy results based on a multi-level responder analysis including ADAS-Cog, NOSGER-IADL and CGI-C failed to demonstrate statistical superiority of cyclandelate in comparison to placebo. The direction of changes favored cyclandelate in each of the variables, but the differences to placebo were small and varied considerably between patients and centers. Retrospective exploratory analyses suggested that efficacy of cyclandelate might be dependent on the severity of the disease. The treatment effects in favor of cyclandelate were statistically significant in the subgroup of moderately impaired patients (MMSE at baseline <18) for ADAS-Cog (delta = -4.0 points, p = 0.015) and CGI-C (delta = -0.4 points, p = 0.043) but not for NOSGER-IADL (delta = -1.6 points, p = 0.059). When patients were stepwise selected for the severity of the disease according to ADAS-Cog at baseline (>15, >20, >25 points), statistical significance was reached for ADAS-Cog and NOSGER-IADL beginning with the step ADAS-Cog >20 points: delta ADAS-Cog = -3.9 points, p = 0.044; delta NOSGER-IADL = -1.0, p = 0.023. The treatment differences increased further with the step ADAS-Cog >25 points: delta ADAS-Cog = -7.0 points, p = 0.008; delta NOSGER-IADL = -1.7, p = 0.003. Treatment differences in CGI-C increased marginally with the stepwise selection but did not reach statistical significance. The drug was safe and well tolerated.

Neuropsychometric tests in cross sectional and longitudinal studies - a regression analysis of ADAS - cog, SKT and MMSE

INTRODUCTION

In clinical and drug studies, different neuropsychometric tests are used. So far, no empirical data have been published to compare studies using different tests. The purpose of this study was to calculate a regression formula allowing a comparison of cross-sectional and longitudinal data from three neuropsychometric tests that are frequently used in drug studies (Alzheimer's Disease Assessment Scale, ADAS-cog; Syndrom Kurz Test, SKT; Mini Mental State Examination, MMSE).

METHOD

177 patients with dementia according to ICD10 criteria were studied for the cross sectional and 61 for the longitudinal analysis. Correlations and linear regressions were calculated between tests. Significance was proven with ANOVA and t-tests using the SPSS statistical package.

RESULTS

Significant Spearman correlations and slopes in the regression occurred in the cross sectional analysis (ADAS-cog-SKT r(s) = 0.77, slope = 0.45, SKT-ADAS-cog slope = 1.3, r2 = 0.59; ADAS-cog-MMSE r2 = 0.76, slope = -0.42, MMSE-ADAS-cog slope = -1.5, r2 = 0.64; MMSE-SKT r(s) = -0.79, slope = -0.87, SKT-MMSE slope = -0.71, r2 = 0.62; p<0.001 after Bonferroni correction; N = 177) and in the longitudinal analysis (SKT-ADAS-cog, r(s) = 0.48, slope = 0.69, ADAS-cog-SKT slope = 0.69, p<0.001, r2 = 0.32, MMSE-SKT, r(s) = 0.44, slope = -0.41, SKT-MMSE, slope = -0.55, p<0.001, r2 = 0.21).

CONCLUSIONS

The results allow calculation of ADAS-scores when SKT scores are given, and vice versa. In longitudinal studies or in the course of the disease, scores assessed with the ADAS-cog and the SKT may now be statistically compared. In all comparisons, bottom and ceiling effects of the tests have to be taken into account.

Alzheimer's Disease Assessment Scale: reliability and validity in a multicenter clinical trial

Psychometric characteristics of the Alzheimer's Disease Assessment Scale (ADAS) were examined on the basis of data from 440 patients with dementia of the Alzheimer type that were collected before treatment in a multicenter clinical drug trial. Coefficients of internal consistency of above .80 for the cognitive (ADAS-Cog) and the noncognitive section (ADAS-Noncog) indicated a high degree of homogeneity of item contents within the two assessment domains. Test-retest reliability was estimated to be .93, .98, and .96 for ADAS-Cog, ADAS-Noncog, and the total score (ADAS-Total), respectively. Reliably detectable individual changes, which were derived from the reliability estimates, were 7, 3, and 8 points for ADAS-Cog, ADAS-Noncog, and ADAS-Total, in that order. Factor analysis and correlations with MMSE, SKT, and NOSGER scores support the validity of the ADAS-Cog and ADAS-Noncog scores with regard to the cognitive and the noncognitive assessment domains. The ADAS summary scores, almost all of the cognitive items, and some of the noncognitive items discriminated significantly between stages of severity of dementia, as classified independently by MMSE and SKT scores.

A controlled study of 2 doses of idebenone in the treatment of Alzheimer's disease

Two doses of idebenone were studied in a prospective, randomized, double-blind, placebo-controlled multicentre study in patients suffering from dementia of the Alzheimer type (DAT) of mild to moderate degree. Diagnosis was based on DSM-III-R (primary degenerative dementia) and NINCDS-ADRDA criteria (probable Alzheimer's disease). A total of 300 patients were randomized to either placebo, idebenone 30 mg t.i.d. or 90 mg t.i.d. (n = 100, each) and treated for 6 months. The primary outcome measure was the total score of the Alzheimer's Disease Assessment Scale (ADAS-Total) at month 6. Secondary outcome measures were the ADAS cognitive (ADAS-Cog) and noncognitive scores (ADAS-Noncog), the clinical global response (CGI-Improvement), the MMSE, the Digit Symbol Substitution test (DSS) and several scales for the assessment of daily activities (the self- and observer-rating scales NAA and NAB of the Nuremberg Age Inventory NAI and Greene's Assessment). Safety parameters were adverse events, vital signs, ECG and clinical laboratory parameters. Clinical and psychometric evaluations were performed at baseline, and after 1, 3 and 6 months of treatment. After month 6 idebenone 90 mg t.i.d. showed statistically significant improvement in the primary efficacy variable ADAS-Total and in ADAS-Cog. An analysis of therapy responders performed for 3 outcome measures (CGI-global improvement, ADAS-Cog, ADAS-Noncog), selected to represent different domains of assessment, revealed significant superiority of idebenone 90 mg t.i.d. with respect to placebo in each of the 3 variables and in the concordance of responses across the 3 measures. Exploratory results for a subgroup of patients (ADAS-Total > or = 20) showed dose-related superiority of idebenone additionally on ADAS-Noncog and the CGI-Improvement scale. Safety results were inconspicuous for all assessments. The study results demonstrate the efficacy and safety of idebenone in the treatment of DAT patients.

Lack of interaction between diazepam and nimodipine during chronic oral administration to healthy elderly subjects

1. Nimodipine (30 mg three times daily) and diazepam (10 mg once daily), were given orally to 24 elderly healthy subjects in a randomized, non-blinded, threefold-crossover study. Each of the three treatment periods lasted 5 days separated by 2 week washout phases. 2. Plasma concentrations of nimodipine and diazepam were not affected by the combined treatment. 3. No clinically relevant changes in haemodynamics, ECG recordings, clinical chemistry or haematology were observed after all of the three treatments. The overall frequency of side effects was lowest during monotherapy with nimodipine and highest during diazepam monotherapy. 4. In the test of subjective rating of tiredness (VAS) and the Pauli calculation test, diazepam, alone and with nimodipine co-medication, produced an increase in tiredness and a clear reduction in performance and endurance. After nimodipine monotherapy an improvement was observed only in the Pauli test. Using the critical flicker fusion frequency test (CFF) significant decrements in performance were found after diazepam monotherapy only. 5. In summary, there was no evidence that either nimodipine or diazepam affected the pharmacokinetics, safety and tolerance of each other. However, the CNS-effects of diazepam were compensated partially by nimodipine.