Approximate acoustic boundary conditions in the time-domain using volume penalization.

This paper presents an immersed boundary method for modeling complex impedance boundary conditions in wave-based finite-difference time-domain simulations. The fully parallelizable and physically motivated Brinkman method allows for the representation of complex geometries on simple Cartesian grids as porous material by introducing a friction term and an effective volume. The parameters are specified using blending functions, enabling impedance boundary conditions without the need for grid fitting or special boundary treatment. Representative acoustic configurations are analyzed to assess the method. In detail, acoustic materials on and in front of a rigid wall, a reacting surface as well as fully reflecting walls are examined. Comparison with analytical solutions shows satisfactory agreement of the resulting impedances in the range from 20 Hz up to 4 kHz. The method is derived for the (non-)linear Euler equations and the acoustic wave equation. An extensive stability analysis is carried out.

Directional sound source modeling using the adjoint Euler equations in a finite-difference time-domain approach.

An adjoint-based approach for synthesizing complex sound sources by discrete, grid-based monopoles in finite-difference time-domain simulations is presented. Previously, Stein, Straube, Sesterhenn, Weinzierl, and Lemke [(2019). J. Acoust. Soc. Am. 146(3), 1774-1785] demonstrated that the approach allows one to consider unsteady and non-uniform ambient conditions such as wind flow and thermal gradient in contrast to standard methods of numerical sound field simulation. In this work, it is proven that not only ideal monopoles but also realistic sound sources with complex directivity characteristics can be synthesized. In detail, an oscillating circular piston and a real two-way near-field monitor are modeled. The required number of monopoles in terms of the sound pressure level deviation between the directivity of the original and the synthesized source is analyzed. Since the computational effort is independent of the number of monopoles used for the synthesis, also more complex sources can be reproduced by increasing the number of monopoles utilized. In contrast to classical least-square problem solvers, this does not increase the computational effort, which makes the method attractive for predicting the effect of sound reinforcement systems with highly directional sources under difficult acoustic boundary conditions.

Adjoint-based optimization of sound reinforcement including non-uniform flow.

The determination of optimal geometric arrangements and electronic drives of loudspeaker arrays in sound reinforcement applications is an ill-posed inverse problem. This paper introduces an innovative method to determine complex driving functions, also considering complex environmental conditions. As an alternative to common frequency domain methods, the authors present an adjoint-based approach in the time domain: Acoustic sources are optimized in order to generate a given target sound field. Instead of the Helmholtz equation, the full non-linear Euler equations are considered. This enables an easier treatment of non-uniform flow and boundary conditions. As proof of concept, a circular and a linear monopole array are examined. For the latter, the environmental conditions include wind and thermal stratification. For all examples, the method is able to provide appropriate driving functions.

Pramipexole in routine clinical practice: a prospective observational trial in Parkinson's disease.

OBJECTIVE: The mixed dopamine D2/D3 receptor agonist pramipexole is effective as monotherapy in early Parkinson's disease and as adjunctive therapy in advanced disease. Clinical trials suggest that the benefits of pramipexole may extend beyond the relief of motor symptoms (akinesia, rigidity and tremor at rest) to amelioration of depressive symptoms in Parkinson's disease. The aim of this study was to confirm the beneficial effects of pramipexole on the core symptoms of Parkinson's disease (with a focus on tremor), as well as to assess its antidepressant activity, during routine clinical practice. The study also aimed to demonstrate the practicability of the Snaith-Hamilton Pleasure Scale (SHAPS-D), the Tremor Impact Scale (TIS) and the Short Parkinson's Evaluation Scale (SPES) under conditions of routine clinical practice. STUDY DESIGN: This was a prospective observational study. PATIENTS: Data for 657 outpatients with Parkinson's disease were collected from German hospitals and specialist practices. The majority of patients were in Hoehn & Yahr stage II or III and were receiving levodopa. METHODS: Pramipexole (Sifrol) was initiated at a dosage of 0.375 mg/day (using a three-times-daily schedule) and titrated upwards, as required, at weekly intervals over a 4-week period to a maximum dosage of 4.5 mg/day (three times daily). Clinical evaluation was performed at baseline, at the end of the titration phase and at the end of maintenance therapy. Patients were assessed via the German questionnaire versions of the physician-assessed SPES, the self-evaluated TIS and the SHAPS-D. Changes in scale scores were evaluated nonparametrically, using the Wilcoxon-matched pairs test. Cronbach's alpha was used as a measure for item consistency. RESULTS: Pramipexole significantly improved SPES subscores for motor symptoms, complications of therapy, psychological status and activities of daily living. Pramipexole also reduced the detrimental effect of tremor on activities of daily living and social interactions, as assessed by patients via the TIS. As indicated by the results of the SHAPS-D questionnaire, pramipexole significantly reduced anhedonia in patients who had associated depression. Internal consistency of SPES subscales was found to be unaltered between the initial evaluation and follow-up. Likewise, internal consistency for TIS and SHAPS-D was demonstrated. Pramipexole was well tolerated and accepted by the vast majority of physicians and patients. CONCLUSION: In addition to ameliorating the core symptoms of akinesia and rigidity in Parkinson's disease, pramipexole improves tremor and depressive symptoms in routine clinical practice. The SPES, TIS and SHAPS-D were found to be useful instruments with validity in this study.

Dementia in idiopathic Parkinson's syndrome.

Approximately 25% of patients with idiopathic Parkinson's disease (IPD) later develop dementia, with the typical characteristics as detailed in ICD-10 and DSM-IV. Differential diagnosis has to exclude dementia due to Lewy bodies, subcortical vascular encephalopathy and subcortical dementia due to progressive supranuclear paralysis or corticobasal degeneration. Several studies showed promising results for cholinesterase inhibitors such as donepezile, rivastigmine and galantamine. The demented Parkinsonian patients then present with improvement in cognitive function while motor skills do not deteriorate.