Electromechanical Reciprocity Applied to the Sensing Properties of Guided Elastic Wave Transducers.

Guided elastic wave (GEW) transducers for structural health monitoring (SHM) can act as transmitters (senders) and receivers (sensors). Their performance in both cases depends on the structure to which they are coupled. Therefore, they must be characterized as system transducer- structure. The characterization of the transducer-structure as transmitter using a Scanning Laser Doppler Vibrometer (SLDV) is straightforward, whereas its characterization as receiver is non-trivial. We propose to exploit electromechanical reciprocity, which is an identity between the transfer functions of electrical-to-mechanical and mechanical-to-electrical conversions. For this purpose, the well-known electromechanical reciprocity theorem was adapted to the following situation: The two reciprocal states are "electrical excitation and detection of the surface velocity at point P" and "mechanical excitation at P and measurement of the electrical quantities". According to the derived formulas, the quantities on the mechanical and electrical sides must be chosen appropriately to ensure reciprocity as well as that the corresponding transfer functions are equal. We demonstrate the reciprocity with experimental data for correctly chosen transfer functions and show the deviation in reciprocity for a different choice. Furthermore, we propose further applications of electromechanical reciprocity.

In vivo Histology of the Cornea - from the "Rostock Cornea Module" to the "Rostock Electronic Slit Lamp" - a Clinical "Proof of Concept" Study. / In-vivo-Histologie der Hornhaut ­ vom "Rostocker Cornea Modul" zur "Rostocker Elektronischen Spaltlampe" ­ eine klinische "Proof-of-Concept"-Studie.

INTRODUCTION: Confocal in vivo microscopy is an established method in ophthalmology research. As it requires contact coupling and calibration of the instruments is suboptimal, this method has been only rarely used in clinical routine work. As a result of close collaboration between physicists, information scientists and ophthalmologists, confocal laser scanning microscopy (CLSM) of the eye has been developed in recent years and a prototype can now be used in patients. The present study evaluates possible clinical uses of this method. MATERIAL AND METHODS: The essential innovations in CLSM are (1) a newly designed coupling element with superficial adaptation to corneal curvature and (2) the use of a dual computerised piezo drive for rapid and precise focusing. In post-processing and after elastic imaging registration of the individual images parallel to the surface, it is also possible to produce sagittal sections resembling a split lamp and with resolution in the micrometer range. The concept was tested on enucleated pig bulbi and tested on normal volunteers and selected patients with diseases of the cornea. RESULTS: Simultaneous imaging in planes parallel to the surface and in sagittal planes provided additional information that can help us to understand the processes of wound healing in all substructures of the cornea and the role of immune competent cells. Possible clinical uses were demonstrated in a volunteer with healthy eyes and several groups of patients (keratoconus after CXL, recurrent keratitis, status after PRK). These show that this new approach can be used in morphological studies at cellular level in any desired and appropriate test plane. CONCLUSIONS: It could be shown that this new concept of CLSM can be used clinically. It can provide valuable and novel information to both preclinical researchers and to ophthalmologists interested in corneal disease, e.g. density of Langerhans cells and epithelial stratification in ocular surface diseases.

A computerized spatial orientation test.

In three experiments, we compared performance on a paper-based perspective-taking task (the Spatial Orientation Test [SOT]; Hegarty & Waller, 2004) with performance on a computer-based version of the task. The computer-based version automates scoring angular errors, allows for different stimulus orders to be given to each participant, and allows for different testing time limits. In Experiment 1, the two media used different objects and mirror-image stimulus arrays in the two versions to mitigate the effects of memory for specific objects or responses. In Experiments 2 and 3, the two media used identical objects (also in a mirrored arrangement), to provide a more equivalent between-media comparison. We also substituted new objects for objects in the original version that had an inherent front/back (e.g., a car) and/or that were animate; directional or animate objects may add variance that is unrelated to perspective-taking ability. Experiment 3 used clarified instructions and a sample size sufficient to examine relatively small differences between the media as well as sex differences. Overall, the computer-based version produced performance that was similar to that of the paper-based version in terms of the rank-order of the participants. The new computer and paper versions of the SOT also had similar correlations with the Money Road Map test and the Santa Barbara Sense of Direction questionnaire, adding support to the claim that the computerized SOT is tapping into the same skill as the paper-based version. We provide a Java version of the new SOT, along with pdf files of instructions and practice stimuli, on the Open Science Framework website.

Improved SH0 Guided Wave Transducers Based on Piezoelectric Fiber Patches.

A piezoelectric fiber patch (PFP) is a transducer type that is suitable for guided-wave-based structural health monitoring (SHM) due to its light, thin, and flexible characteristics. In our previous work, a PFP-based transducer design for selective excitation of the zero-order shear horizontal wave mode (SH0) was introduced (shear horizontal PFP (SHPFP)). In this work, two modified SH0 wave PFP transducer designs are proposed: the rounded corner design and the dual design. The degree of improvement is determined by a numerical simulation and the dual design-the design with the most promise-is experimentally realized. Laser Vibrometry measured the generated wave field, confirming the results from the simulation. The new designs can generate an almost pure SH0 wave. The dual design has a very strong directivity that is useful for several guided-wave-based SHM applications. The conclusions on the design's properties as a transmitter are also valid for its properties as a sensor due to the reciprocity of piezoelectric transducers.

Evaluation of different diagnostic tools for the detection and identification of Riemerella anatipestifer.

Riemerella anatipestifer (RA) is an important avian pathogen with considerable impact on poultry production worldwide. However, the diagnosis of RA infections may be difficult, mainly due to problems with unequivocal differentiation of RA from other Flavobacteriaceae and a lack of standardized methods and reagents. The aim of the present study was therefore to complement the routine diagnostic strategies for RA by design and evaluation of alternative diagnostic tools. We designed and validated a new RA-specific polymerase chain reaction assay, which proved to be a valuable tool for the identification of RA isolates as well as for rapid and sensitive RA detection directly from diagnostic samples. Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry fingerprinting of whole bacterial cells was also demonstrated to identify RA isolates efficiently. Furthermore, this method may also provide opportunities for RA subtyping. In our study, a stable subcluster was formed by the mass spectroscopy profiles of a group of RA isolates originating from turkey flocks in northern Germany, suggesting an epidemiological relationship of these isolates. Serotyping is a further important measure to characterize RA isolates. We tested a set of commercially available anti-RA sera with RA serotype reference strains and field isolates to allow comparison between these sera and reference sera. In summary, this report contributes to the improvement of present microbiological and molecular strategies for the diagnosis of RA infections by providing new tools as well as enhanced knowledge on existing methods.

On the reproducibility of extrusion-based bioprinting: round robin study on standardization in the field.

The outcome of three-dimensional (3D) bioprinting heavily depends, amongst others, on the interaction between the developed bioink, the printing process, and the printing equipment. However, if this interplay is ensured, bioprinting promises unmatched possibilities in the health care area. To pave the way for comparing newly developed biomaterials, clinical studies, and medical applications (i.e. printed organs, patient-specific tissues), there is a great need for standardization of manufacturing methods in order to enable technology transfers. Despite the importance of such standardization, there is currently a tremendous lack of empirical data that examines the reproducibility and robustness of production in more than one location at a time. In this work, we present data derived from a round robin test for extrusion-based 3D printing performance comprising 12 different academic laboratories throughout Germany and analyze the respective prints using automated image analysis (IA) in three independent academic groups. The fabrication of objects from polymer solutions was standardized as much as currently possible to allow studying the comparability of results from different laboratories. This study has led to the conclusion that current standardization conditions still leave room for the intervention of operators due to missing automation of the equipment. This affects significantly the reproducibility and comparability of bioprinting experiments in multiple laboratories. Nevertheless, automated IA proved to be a suitable methodology for quality assurance as three independently developed workflows achieved similar results. Moreover, the extracted data describing geometric features showed how the function of printers affects the quality of the printed object. A significant step toward standardization of the process was made as an infrastructure for distribution of material and methods, as well as for data transfer and storage was successfully established.

Nonlinear interaction of Rayleigh waves in isotropic materials: Numerical and experimental investigation.

Surface treatment intensity monitoring is still an open and challenging nondestructive testing problem. For the estimation of residual stress with ultrasonic measurements, local linear and nonlinear elastic constants are needed as input. In this paper, nonlinear elastic-wave interactions (also called wave mixing or scattering) - namely, the generation of secondary ultrasonic waves in a nonlinear medium - are considered as a prospective means for near-surface nonlinear elastic parameter evaluation. The allowed interactions between bulk and surface waves, as well as the dependence of the scattering efficiency on the frequency and angle between source waves, were investigated through an analytical model, then compared with FEM simulations and experimental results. Finally, possible future steps for the development of the applied methods for the determination of near-surface higher-order elastic constants are discussed. In addition, several problem-relevant data processing procedures are presented.

Identification of Trueperella bernardiae isolated from peking ducks (Anas platyrhynchos domesticus) by phenotypical and genotypical investigations and by a newly developed loop-mediated isothermal amplification (LAMP) assay.

Trueperella (T.) bernardiae is a well-known bacterial pathogen in infections of humans, rarely in animals. In the present study, five T. bernardiae isolates, isolated from five Peking ducks of four different farms, were identified by phenotypic properties, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, and genotypically by sequencing the 16S ribosomal RNA (rRNA) gene, the superoxide dismutase A encoding gene sodA, and the glyceraldehyde-3-phosphate dehydrogenase encoding gene gap. In addition, the T. bernardiae isolates could be identified with a newly developed loop-mediated isothermal amplification (LAMP) assay based on the gyrase encoding housekeeping gene gyrA. All these tests clearly identified the T. bernardiae isolates to the species level. However, the detection of the specific gene gyrA with the newly designed LAMP assay appeared with a high sensitivity and specificity, and could help to identify this bacterial species in human and animal infections in future. The importance of the T. bernardiae isolates for the clinical condition of the ducks and for the problems at farm level remains unclear.

In Vivo Monitoring of Corneal Dendritic Cells in the Subbasal Nerve Plexus during Trastuzumab and Paclitaxel Breast Cancer Therapy-A One-Year Follow-Up.

Paclitaxel and trastuzumab have been associated with adverse effects including chemotherapy-induced peripheral neuropathy (CIPN) or ocular complications. In vivo confocal laser scanning microscopy (CLSM) of the cornea could be suitable for assessing side effects since the cornea is susceptible to, i.e., neurotoxic stimuli. The study represents a one-year follow-up of a breast cancer patient including large-area in vivo CLSM of the subbasal nerve plexus (SNP), nerve function testing, and questionnaires during paclitaxel and trastuzumab therapy. Six monitoring sessions (one baseline, four during, and one after therapy) over 58 weeks were carried out. Large-area mosaics of the SNP were generated, and identical regions within all sessions were assigned. While corneal nerve morphology did not cause alterations, the number of dendritic cells (DCs) showed dynamic changes with a local burst at 11 weeks after baseline. Simultaneously, paclitaxel treatment was terminated due to side effects, which, together with DCs, returned to normal levels as the therapy progressed. Longitudinal in vivo CLSM of the SNP could complement routine examinations and be helpful to generate a comprehensive clinical picture. The applied techniques, with corneal structures acting as biomarkers could represent a diagnostic tool for the objective assessment of the severity of adverse events and the outcome.

Assessment of dynamic corneal nerve changes using static landmarks by in vivo large-area confocal microscopy-a longitudinal proof-of-concept study.

Background: The purpose of the present proof-of-concept study was to use large-area in vivo confocal laser scanning microscopy (CLSM) mosaics to determine the migration rates of nerve branching points in the human corneal subbasal nerve plexus (SNP). Methods: Three healthy individuals were examined roughly weekly over a total period of six weeks by large-area in vivo confocal microscopy of the central cornea. An in-house developed prototype system for guided eye movement with an acquisition time of 40 s was used to image and generate large-area mosaics of the SNP. Kobayashi-structures and nerve entry points (EPs) were used as fixed structures to enable precise mosaic registration over time. The migration rate of 10 prominent nerve fiber branching points per participant was tracked and quantified over the longitudinal period. Results: Total investigation times of 10 minutes maximum per participant were used to generate mosaic images with an average size of 3.61 mm2 (range: 3.18-4.42 mm2). Overall mean branching point migration rates of (46.4±14.3), (48.8±15.5), and (50.9±13.9) µm/week were found for the three participants with no statistically significant difference. Longitudinal analyses of nerve branching point migration over time revealed significant time-dependent changes in migration rate only in participant 3 between the last two measurements [(63.7±12.3) and (43.0±12.5) µm/week, P<0.01]. Considering individual branching point dynamics, significant differences in nerve migration rate from the mean were only found in a few exceptions. Conclusions: The results of this proof-of-concept study have demonstrated the feasibility of using in vivo confocal microscopy to study the migration rates of corneal subbasal nerves within large areas of the central human cornea (>1 mm2). The ability to monitor dynamic changes in the SNP opens a window to future studies of corneal nerve health and regenerative capacity in a number of systemic and ocular diseases. Since corneal nerves are considered part of the peripheral nervous system, this technique could also offer an objective diagnostic tool and biomarker for disease- or treatment-induced neuropathic changes.