Optimal design of piezoelectric actuators for shunt damping techniques

In vibration control with piezoceramics, a high coupling of the piezoelement with the structure is desired. A high coupling improves the damping performance of passive techniques like shunt damping. The coupling can be influenced by a the material properties of the piezoceramics, but also by the placement within the structure and the size of the transducer. Detailed knowlegde about the vibration behavior of the structure is required for this. This paper presents an in-depth analysis of the optimal shape of piezoelectric elements. General results for one-dimensional, but inhomogeneos strain distribution are provided. These results are applied to the case of a longitudinal transducer and a bending bimorph. It is obtained that for maximum coupling, only a certain fracture of the volume should be made of piezoelectric material

Minocycline is cytoprotective in human corneal endothelial cells and induces anti-apoptotic B-cell CLL/lymphoma 2 (Bcl-2) and X-linked inhibitor of apoptosis (XIAP)

Introduction Loss of corneal endothelial cells (CECs) is one major factor limiting transplant clarity and survival after keratoplasty. Amongst other factors, apoptosis due to cellular stress is responsible for these problems. This study investigates the possible anti-apoptotic and cytoprotective effects of minocycline on a human corneal endothelial cell line (HCEC-SV40) cultured under oxidative stress and with transforming growth factor beta (TGF-beta). Methods CECs were treated with 1-150 mM minocycline. Cell viability and the median inhibitory concentration (IC(50)) were evaluated after 48 h and after H(2)O(2) treatment (tetrazolium dye reduction assay and liveedead assay). Expression of B-cell CLL/lymphoma 2 (Bcl-2) and X-linked inhibitor of apoptosis (XIAP) and their mRNA were assessed by reverse transcriptase (RT)-PCR and western blot analysis after treatment with minocycline alone and consecutive incubation with 200 mM H(2)O(2) and TGF-beta 2. A quantitative detection of histone-associated DNA fragmentation by ELISA was performed. Results Minocycline concentrations from 1-50 mM showed no toxic effects on CECs. Pre-treatment with 10-40 mM minocycline led to an increase in viability after H(2)O(2) treatment. In addition, minocycline pretreatment attenuated the increase of histone-associated DNA fragmentation after treatment with H(2)O(2) and TGF-beta 2 significantly. When CECs were treated with minocycline and then consecutively with H(2)O(2) or TGF-beta 2, RT-PCR and western blot analysis yielded an overexpression of Bcl-2 and XIAP. Conclusion In this study minocycline prevented apoptotic cell death in cultured CECs in vitro. Our results suggest that minocycline might offer cytoprotective properties that might help to prevent loss of corneal endothelial cells in vivo

On the maximum damping performance of piezoelectric switching techniques

Synchronized switch damping on inductor offers a high damping performance in a broad frequency range. It consists of an inductor and resistor in a serial configuration, which are connected and disconnected from the piezoceramics in an alternating manner by a switch. When the switch is triggered by the vibration itself, it adapts to different excitation frequencies especially in the low frequency range. This article presents a detailed study of the damping performance of the synchronized switch damping on inductor technique. Calculations are performed in a normalized way. The optimal tuning of synchronized switch damping on inductor network parameters is derived, and the corresponding maximum damping performance is obtained. The results are further compared to standard linear inductance-resistance networks. For a validation of the theoretical results, measurements on a clamped beam test rig are performed. Therefore, the synchronized switch damping on inductor circuit is realized as a synthetic impedance in a DSpace environment. The measurement results are in good agreement with the theoretical calculations. © The Author(s) 2012

A new solution for the determination of the generalized couplingcoefficient for piezoelectric systems

Recently, novel damping devices based on shunted piezoceramics have been investigated. Piezoceramics are therefore embedded into the mechanical structure and convert some part of the kinetic vibration energy into electrical energy. Subsequently, this energy is dissipated in the electrical network that is connected at the electrodes of the piezoceramics. The network is designed with the aim to maximize the dissipation, which results in a damping effect on the mechanical system. Alternatively, the converted energy can be stored and utilized to power electronic devices like sensors for health monitoring, called Energy Harvesting. In both cases, the converted energy and the damping performance depend on the so called generalized electromechanical coupling coefficient K. It is therefore crucial to maximize this factor. Besider the piezoelectric material properties, the coupling coefficient also depends on the vibration mode of the piezoceramics. Only for a constant mechanical strain distribution in the whole volume the generalized coupling coefficient K is equal to the material coupling k. In all other cases, K is smaller than k. This publication presents a general derivation of the generalized coupling coefficient K for an arbitrary, uniaxial deformation of the piezoceramics, which is based on the potential energy stored in the piezoceramics. The general result is applied to a piezoelectric bending bimorph and verified by a finite element model

Sorafenib prevents human retinal pigment epithelium cells from light-induced overexpression of VEGF, PDGF and PlGF

Background Cumulative light exposure is significantly associated with progression of age-related macular degeneration (AMD). Inhibition of vascular endothelial growth factor is the main target of current antiangiogenic treatment strategies in AMD. However, other growth factors, such as platelet-derived growth factor (PDGF) and placenta growth factor (PlGF), have a substantial impact on development of AMD. Previous reports indicate that sorafenib, an oral multikinase inhibitor, might have beneficial effects on exudative AMD. This study investigates the effects of sorafenib on light-induced overexpression of growth factors in human retinal pigment epithelial (RPE) cells. Methods Primary human RPE cells were exposed to white light and incubated with sorafenib. Viability, expression, and secretion of VEGF-A, PDGF-BB, and PlGF and their mRNA were determined by reverse transcription-polymerase chain reactions, immunohistochemistry and enzyme-linked immunosorbent assays. Results Light exposure decreased cell viability and increased expression and secretion of VEGF-A, PDGF-BB and PlGF. These light-induced effects were significantly reduced when cells were treated with sorafenib at a dose of 1 mu g/ml. Conclusion The results show that sorafenib has promising properties as a potential antiangiogenic treatment for AMD

Study protocol - efficacy of an attachment-based working alliance in the multimodal pain treatment

Background: The concept of attachment is relevant for the onset and development of chronic pain. Insecure attachment styles negatively affect therapeutic outcome. Insecurely attached patients seem to be less able to sustain positive effects of a multimodal treatment program. However, it has never been tested before if an attachment-oriented approach can improve treatment results of insecurely attached patients in a multimodal outpatient setting. To test this assumption, we compare the short- and long-term outcomes for pain patients who will receive multidisciplinary, attachment-oriented treatment with the outcomes for patients in a control group, who will receive the multidisciplinary state-of-the-art treatment. Methods: Two patient groups (baseline, attachment intervention) are assessed before treatment, after treatment, and at a 6 month follow-up. The study is conducted in a block design: After data collection of the first block (controls) and before as well as during data collection for the second block (treatment group), the health care personnel of the outpatient pain clinic receives training on attachment theory and its use in the therapeutic context. Pain intensity as measured with visual analogue scales and physical functioning will serve as the primary outcome measures. Discussion: The design of our study allows for a continuous exchange of experienced team members, which may help bring about concrete attachment related guidelines for the enhancement of therapeutic outcome. This would be the first attempt at an attachment-oriented improvement of multimodal pain programs. Conclusion: An attachment-based approach may be a promising way to enhance long-term treatment outcomes for insecurely attached pain patients. Trial registration: DRKS00008715 (registered on the 3rd of June 2015)

A Phase III Randomized Trial of Gemcitabine–Oxaliplatin versus Carboplatin–Paclitaxel as First-Line Therapy in Patients with Advanced Non-small Cell Lung Cancer

Purpose:This phase III study compared the efficacy and tolerability of gemcitabine and oxaliplatin (GEMOX) with paclitaxel and carboplatin (PCb) in chemotherapy-naive patients with stage IIIB/IV non-small cell lung cancer.Patients and Methods:Patients aged 18 years or older were randomized to PCb (paclitaxel 225 mg/m2 followed by carboplatin area under the curve = 6 on day 1 every 3 weeks) or GEMOX (gemcitabine 1,000 mg/m2 on days 1 and 8 followed by oxaliplatin 130 mg/m2 on day 1 every 3 weeks) for up to six cycles. The primary end point was progression-free survival (PFS), with tumor response rate, overall survival (OS), and quality of life as secondary end points.Results:The study was terminated after 383 patients had been randomized (371 received treatment) as the incidence of adverse events had exceeded the protocol-specified safety threshold (≥20% in either arm). No formal statistical comparisons were conducted. Median PFS was 4.44 months and 4.67 months in the GEMOX and PCb groups, respectively. Objective response rates (complete or partial) were 15.2% and 22.4% in the GEMOX and PCb arms, respectively. Median OS was 9.90 months (GEMOX) and 9.24 months (PCb); post hoc analyses showed median OS in patients aged 70 years or older to be similar to those younger than 70 years. PFS was similar in both groups of patients with adenocarcinoma histology, although OS favored the GEMOX group. Quality of life was improved from baseline in both groups. Toxicity profiles were comparable between the groups.Conclusion:PFS, OS, and objective response rates with GEMOX were similar to PCb. Nevertheless, toxicities limit the adoption of this regimen for routine use in advanced non-small cell lung cancer