Role of the electron spin in determining the coherence of the nuclear spins in a quantum dot

A huge effort is underway to develop semiconductor nanostructures as low-noise qubits. A key source of dephasing for an electron spin qubit in GaAs and in naturally occurring Si is the nuclear spin bath. The electron spin is coupled to each nuclear spin by the hyperfine interaction. The same interaction also couples two remote nuclear spins via a common coupling to the delocalized electron. It has been suggested that this interaction limits both electron and nuclear spin coherence, but experimental proof is lacking. We show that the nuclear spin decoherence time decreases by two orders of magnitude on occupying an empty quantum dot with a single electron, recovering to its original value for two electrons. In the case of one electron, agreement with a model calculation verifies the hypothesis of an electron-mediated nuclear spin-nuclear spin coupling. The results establish a framework to understand the main features of this complex interaction in semiconductor nanostructures.

Switching adsorption and growth behavior of ultrathin [C2C1Im][OTf] films on Au(111) by Pd deposition

Combining in vacuo deposition of ultrathin ionic liquid (UTIL) films with angle-resolved X-ray photoelectron spectroscopy (ARXPS), we demonstrate that by deposition of submonolayer amounts of Pd onto Au(111) the initial growth mode of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C₂C₁Im][OTf]) can be switched from three-dimensional (3D) to two-dimensional (2D) growth, that is, from non-wetting to wetting. On clean Au(111), pronounced 3D growth occurs on top of an initially formed 2D wetting layer with cations and anions next to each other in a checkerboard arrangement. After pre- or postdeposition of only 0.7 ML Pd, two-dimensional layer-by-layer growth is found, which is attributed to strong attractive interactions between [C₂C₁Im][OTf] and surface Pd. For Pd post deposition onto the IL, the ARXPS data revealed particularly strong interactions between the dialkylimidazolium cation and Pd atoms, which considerably reduce the regular surface alloying of Pd with the Au substrate stabilizing Pd at the metal surface. In the context of heterogeneous catalysis using the SCILL (solid catalyst coated with ionic liquid layer) concept, these results directly provide a possible explanation on the molecular level for the beneficial influence of the IL layer in case of heterogeneous metal alloy catalysts.

Time reproduction deficits in essential tremor patients

BACKGROUND

Although motor symptoms predominate in essential tremor, increasing evidence indicates additional cognitive deficits. According to the pivotal role of cognitive functioning for temporal information processing and acknowledging the relevance of temporal information processing for movement coordination, we investigated whether essential tremor patients exhibit time reproduction deficits.

METHODS

A total of 24 essential tremor patients and 24 healthy controls performed sub- and suprasecond visual duration reproduction tasks of 500 to 900 milliseconds and 1.6 to 2.4 seconds, respectively. To differentiate deficient time processing from motor or other cognitive dysfunctions, the average temporal reproduction errors were correlated with tremor severity, immediate and delayed word-list recall performance, and verbal fluency.

RESULTS

Essential tremor patients significantly underreproduced sub- and suprasecond time intervals longer than 800 milliseconds. Moreover, time compression correlated significantly with semantic verbal fluency and word-list retrieval performance, but not with tremor severity.

CONCLUSION

Data suggest impaired temporal processing in essential tremor, corroborating evidence for specific cognitive deficits. © 2016 International Parkinson and Movement Disorder Society.

Impulsivity is Associated with Increased Metabolism in the Fronto-Insular Network in Parkinson's Disease

Various neuroimaging studies demonstrated that the fronto-insular network is implicated in impulsive behavior. We compared glucose metabolism (as a proxy measure of neural activity) among 24 patients with Parkinson’s disease (PD) who presented with low or high levels of impulsivity based on the Barratt Impulsiveness Scale 11 (BIS) scores. Subjects underwent 18-fluorodeoxyglucose positron emission tomography (FDG-PET) and the voxel-wise group difference of FDG-metabolism was analyzed in Statistical Parametric Mapping (SPM8). Subsequently, we performed a partial correlation analysis between the FDG-metabolism and BIS scores, controlling for covariates (i.e., age, sex, severity of disease and levodopa equivalent daily doses). Voxel-wise group comparison revealed higher FDG-metabolism in the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and right insula in patients with higher impulsivity scores. Moreover, there was a positive correlation between the FDG-metabolism and BIS scores. Our findings provide evidence that high impulsivity is associated with increased FDG-metabolism within the fronto-insular network in PD.

Deep brain stimulation and cognitive decline in Parkinson's disease: The predictive value of electroencephalography

Some Parkinson's disease (PD) patients treated with subthalamic nucleus deep brain stimulation (STN-DBS) develop new-onset cognitive decline. We examined whether clinical EEG recordings can be used to predict cognitive deterioration in PD patients undergoing STN-DBS. In this retrospective study, we used the Grand Total EEG (GTE)-score (short and total) to evaluate pre- and postoperative EEGs. In PD patients undergoing STN-DBS (N = 30), cognitive functioning was measured using Mini-Mental State Test and DemTect before and after surgery. Severity of motor impairment was assessed using the Unified Parkinson's Disease Rating Scale-III. Patients were classified into patients with or without cognitive decline after STN-DBS surgery. Epidemiological data, pre- and postoperative EEG recordings as well as neuropsychological and neurological data, electrode positions and the third ventricle width were compared. A logistic regression model was used to identify predictors of cognitive decline. Motor deficits significantly improved from pre- to post-surgery, while the mean GTE-scores increased significantly. Six patients developed cognitive deterioration 4-12 months postoperatively. These patients had significantly higher preoperative GTE-scores than patients without cognitive deterioration, although preoperative cognitive functioning was comparable. Electrode positions, brain atrophy and neurological data did not differ between groups. Logistic regression analysis identified the GTE-score as a significant predictor of postoperative cognitive deterioration. Data suggest that the preoperative GTE-score can be used to identify PD patients that are at high risk for developing cognitive deterioration after STN-DBS surgery even though their preoperative cognitive state was normal.

Multi-Wavelength Photoacoustic Visualization of High Intensity Focused Ultrasound Lesions

High intensity focused ultrasound (HIFU) thermal therapies are limited by deficiencies in existing image-guidance techniques. Previous studies using single-wavelength photoacoustic (PA) imaging have demonstrated that HIFU lesions generate contrast with respect to native tissues but have not sufficiently assessed lesion extent. The purpose of this study is to demonstrate feasibility of characterization of in vitro HIFU ablation lesion dimensions using 3D multi-wavelength PA imaging. Fresh porcine cardiac and liver tissue samples were embedded in agar phantoms and ablated using a 2.5 MHz small-animal HIFU system. Both 2D and 3D multi-wavelength photoacoustic-ultrasonic (PAUS) scans were performed in the near-infrared (NIR) range to characterize the change in the absorption spectrum of tissues following ablation and were compared to stained gross pathology to assess treatment margins and lesion extent. Comprehensive 2D multi-wavelength PA imaging yielded a spectrum in ablated tissue that did not display the characteristic local maximum in the optical absorption spectrum of deoxy-hemoglobin (Hb) near 760 nm. Two-dimensional tissue characterization map (TCM) images reconstructed from 3D TCM volumes reliably characterized lesion area and showed >70% area agreement with stained gross pathology. In addition, tissue samples were heated via water bath and concurrently interrogated with 2D PAUS imaging. PA signal exhibited an initial amplitude increase across all wavelengths, corresponding to an initial temperature increase, before then exhibiting a spectral change. This study suggests that multi-wavelength PA imaging has potential to obtain accurate characterization of HIFU lesion extent and may be better suited to guide HIFU ablation therapies during clinical treatments than single-wavelength methods.

Subjectively perceived personality and mood changes associated with subthalamic stimulation in patients with Parkinson's disease

BACKGROUND

Clinical and ethical implications of personality and mood changes in Parkinson's disease (PD) patients treated with subthalamic deep brain stimulation (STN-DBS) are under debate. Although subjectively perceived personality changes are often mentioned by patients and caregivers, few empirical studies concerning these changes exist. Therefore, we analysed subjectively perceived personality and mood changes in STN-DBS PD patients.

METHOD

In this prospective study of the ELSA-DBS group, 27 PD patients were assessed preoperatively and 1 year after STN-DBS surgery. Two categories, personality and mood changes, were analysed with semi-structured interviews. Patients were grouped into personality change yes/no, as well as positive/negative mood change groups. Caregivers were additionally interviewed about patients' personality changes. Characteristics of each group were assessed with standard neurological and psychiatric measurements. Predictors for changes were analysed.

RESULTS

Personality changes were perceived by six of 27 (22%) patients and by 10 of 23 caregivers (44%). The preoperative hypomania trait was a significant predictor for personality change perceived by patients. Of 21 patients, 12 (57%) perceived mood as positively changed. Higher apathy and anxiety ratings were found in the negative change group.

CONCLUSIONS

Our results show that a high proportion of PD patients and caregivers perceived personality changes under STN-DBS, emphasizing the relevance of this topic. Mood changed in positive and negative directions. Standard measurement scales failed to adequately reflect personality or mood changes subjectively perceived by patients. A more individualized preoperative screening and preparation for patients and caregivers, as well as postoperative support, could therefore be useful.

Decision-making under risk is improved by both dopaminergic medication and subthalamic stimulation in Parkinson's disease

Inconsistent findings regarding the effects of dopaminergic medication (MED) and deep brain stimulation (DBS) of the subthalamic nucleus (STN) on decision making processes and impulsivity in Parkinson's disease (PD) patients have been reported. This study investigated the influence of MED and STN-DBS on decision-making under risk. Eighteen non-demented PD patients, treated with both MED and STN-DBS (64.3±10.2years, UPDRS III MED off, DBS off 45.5±17.1) were tested with the Game of Dice Task (GDT) which probes decision-making under risk during four conditions: MED on/DBS on, MED on/DBS off, MED off/DBS on, and MED off/DBS off. Task performance across conditions was compared analyzing two GDT-parameters: (i) the "net score" indicating advantageous decisions, and (ii) the patient's ability to use negative feedback. Significantly higher GDT net scores were observed in Med on in contrast to Med off conditions as well as in DBS on versus DBS off conditions. However, no effect of therapy for the patient's ability to make use of negative feedback could be detected. The data suggest a positive influence of both MED and STN-DBS on making decisions under risk in PD patients, an effect which seems to be mediated by mechanisms other than the use of negative feedback.

Hypomania and mania related to dopamine replacement therapy in Parkinson's disease

OBJECTIVES

To investigate hypomania and mania related to dopamine replacement therapy (DRT) in Parkinson's disease (PD).

METHODS

We recruited 108 non-demented PD patients without deep brain stimulation from a movement disorders in and outpatient clinic. Forty-five age- and gender-matched controls were also included. Disease characteristics, cognitive functioning, comorbid psychiatric diseases, dopaminergic and psychiatric medication were evaluated. Diagnosis of DRT-related hypomania and mania was based on DSM-IV-TR criteria with supplementary assessment of two mania self-rating scales. First, patients and controls were compared. Patients with DRT-related hypomania or mania were then compared to the remaining patients. A binary logistic regression analysis was performed to identify correlates of DRT-related hypomania.

RESULTS

Patients scored significantly higher on mania self-rating scales than controls. Twelve patients (11.1%) had DRT-related hypomania and six patients (5.6%) had DRT-related mania. Both groups had significantly higher self-rating mania-scores than patients without these mood states. DRT-related hypomania was significantly related to younger age, younger age at PD onset, dyskinesias, higher levodopa equivalent daily dose, dopamine dysregulation, and amantadine treatment. In contrast, DRT-related mania was significantly associated with hallucinations and delusions, history of levodopa-induced psychosis, quetiapine treatment, higher depression and daily levodopa dose, and cognitive deficits. Regression analysis revealed dopamine dysregulation, dyskinesias, amantadine treatment, and younger age at PD onset as significant correlates of DRT-related hypomania.

CONCLUSION

DRT-related hypomania and mania are relevant comorbidities in PD. DRT-related hypomania may exist as a distinct psychiatric symptom complex in young patients with early disease onset. Different patient profiles likely underlie DRT-related hypomania and mania.

Patients' expectations of deep brain stimulation, and subjective perceived outcome related to clinical measures in Parkinson's disease: a mixed-method approach

OBJECTIVE

To study patients' expectations of subthalamic deep brain stimulation (STN-DBS) and their subjective perceived outcome, by using qualitative and quantitative methods in Parkinson's disease (PD).

METHODS

PD patients were prospectively examined before and 3 months after surgery. Semistructured interviews regarding preoperative expectations and postsurgical subjective perceived outcome were conducted. These were analysed using content analysis. For statistical analyses, patients were classified according to their subjective perceived outcome, resulting in three different subjective outcome groups (negative, mixed, positive outcome). The groups were used for multiple comparisons between and within each group regarding motor impairment, quality of life (QoL), neuropsychiatric status and cognitive functioning, using standard instruments. A logistic regression analysis was conducted to find predictors of subjective negative outcome. Receiver operating characteristic curves were used to analyse cut-off scores for predictive tests.

RESULTS

Of the 30 PD patients participating, 8 had a subjective negative outcome, 8 a mixed and 14 a positive outcome. All groups significantly improved in motor functioning. Patients with subjective negative outcome were characterised by preoperative unrealistic expectations, no postsurgical improvement in QoL, and significantly higher presurgical and postsurgical apathy and depression scores. Higher preoperative apathy and depression scores were significant predictors of negative subjective outcome. Cut-off scores for apathy and depression were identified.

CONCLUSIONS

The mixed-method approach proved useful in examining a patient's subjective perception of STN-DBS outcome. Our results show that significant motor improvement does not necessarily lead to a positive subjective outcome. Moreover, PD patients should be screened carefully before surgery regarding apathy and depression. (DRKS-ID: DRKS00003221).

Design and initial evaluation of a treatment planning software system for MRI-guided laser ablation in the brain

PURPOSE

An open-source software system for planning magnetic resonance (MR)-guided laser-induced thermal therapy (MRgLITT) in brain is presented. The system was designed to provide a streamlined and operator-friendly graphical user interface (GUI) for simulating and visualizing potential outcomes of various treatment scenarios to aid in decisions on treatment approach or feasibility.

METHODS

A portable software module was developed on the 3D Slicer platform, an open-source medical imaging and visualization framework. The module introduces an interactive GUI for investigating different laser positions and power settings as well as the influence of patient-specific tissue properties for quickly creating and evaluating custom treatment options. It also provides a common treatment planning interface for use by both open-source and commercial finite element solvers. In this study, an open-source finite element solver for Pennes' bioheat equation is interfaced to the module to provide rapid 3D estimates of the steady-state temperature distribution and potential tissue damage in the presence of patient-specific tissue boundary conditions identified on segmented MR images.

RESULTS

The total time to initialize and simulate an MRgLITT procedure using the GUI was [Formula: see text]5 min. Each independent simulation took [Formula: see text]30 s, including the time to visualize the results fused with the planning MRI. For demonstration purposes, a simulated steady-state isotherm contour [Formula: see text] was correlated with MR temperature imaging (N = 5). The mean Hausdorff distance between simulated and actual contours was 2.0 mm [Formula: see text], whereas the mean Dice similarity coefficient was 0.93 [Formula: see text].

CONCLUSIONS

We have designed, implemented, and conducted initial feasibility evaluations of a software tool for intuitive and rapid planning of MRgLITT in brain. The retrospective in vivo dataset presented herein illustrates the feasibility and potential of incorporating fast, image-based bioheat predictions into an interactive virtual planning environment for such procedures.

Parkinson subtypes progress differently in clinical course and imaging pattern

OBJECTIVE

To elucidate whether Parkinson's disease (PD) subtypes show a differential pattern of FP-CIT-SPECT binding during the disease course.

METHODS

We examined 27 patients (10 female, 17 male, mean age 61.68±11.24 years, 14 tremordominant, 13 akinetic-rigid) with [(123)I]FP-CIT-SPECT and clinical ratings including UPDRS III after at baseline and after a mean period of 2.47 years. Patients had been classified at baseline as tremordominant or akinetic-rigid according to a "tremor score" and "non-tremor score". These subgroups were compared for differences in disease progression. Means of clinical ratings and the quantitative analyses of FP-CIT-SPECT for ipsi- and contralateral putamen and caudate nucleus were calculated and compared between baseline and follow-up.

RESULTS

There were no statistical differences concerning age, disease duration, L-Dopa equivalent dose, disease severity (UPDRS III) or dopaminergic uptake in FP-CIT-SPECT at baseline between both subgroups. At follow-up, akinetic-rigid patients showed a distinct and statistically significant reduction of the dopaminergic uptake associated with significant progression of the clinical symptoms (UPDRS III). In contrast, in tremor patients the aggravation of clinical symptoms and dopaminergic deficit was less pronounced without statistical significance among assessments.

CONCLUSIONS

This study shows for the first time a considerable progression of clinical symptoms and in-vivo dopaminergic deficit of akinetic-rigid compared to tremordominant PD patients over time. Our data may help to improve strategic planning of further therapeutic trials and to provide a clearer prognosis for patients regarding the perspective of their disease.

Don't get the blues: conspicuous nuptial colouration of male moor frogs (Rana arvalis) supports visual mate recognition during scramble competition in large breeding aggregations

Conspicuous male colouration is expected to have evolved primarily through selection by female choice. In what way conspicuous colours could be advantageous to males scrambling for mates remains largely unknown. The moor frog (Rana arvalis) belongs to the so-called explosive breeders in which spawning period is short; intrasexual competition is strong, and males actively search and scramble for females. During breeding, male body colouration changes from a dull brown (similar to females) to a conspicuous blue, and we wanted to test if male blueness influences mating success or facilitates male mate recognition. To do so, we first measured the colour of mated and non-mated males using a spectrophotometer. In an experiment, we then analysed interactions of actual male moor frogs in natural spawning aggregations with a brown (resembling a female or a non-breeding male) and a blue model frog. Mated and non-mated males did not differ in colouration, suggesting that female choice based on colour traits was unlikely. In our behavioural experiment, male moor frogs spent significantly more time in contact and in amplexus with the brown model than with the blue model. Our results suggest that the nuptial colouration in moor frogs can act as a new type of visual signal in anurans evolved to promote instantaneous mate recognition allowing males to quickly move between rivals while scrambling for females.

[Refractory industrial production, chemical composition, synthesis processes and hygienical aspects in worker health protection]

The importance of the refractories sintering and manufacture can be better understood considering that the worldwide refractories consumption is about 2,3 kg per year/human being. The RHI Group, world leader in the refractories production, is present in Italy with the production of refractories for the steel and glass sectors in two important industrial sites, in Marone (Brescia) and in San Vito al Tagliamento (Pordenone) respectively. Describes origin, structure and characteristics of the different refractory materials, with particular focus on the different production technologies used in the manufacture of basic refractories (dolomite refractories) and mixed based on alumina, zirconia and silica. We describe the main hygienistics aspects relevant for the protection to the exposure of the workers involved in described production processes. In the production of dolomite refractories, we present the actions that have been implemented in order to reduce the exposure to the Polycyclic Aromatic Hydrocarbons (PAHs). In this process, we report the results of a decade of exposure's monitoring to polycyclic aromatic hydrocarbons in a group of refractory workers.