Elastic constants of biogenic calcium carbonate.

Living organisms form complex mineralized composite architectures that perform a variety of essential functions. These materials are commonly utilized for load-bearing purposes such as structural stability and mechanical strength in combination with high toughness and deformability, which are well demonstrated in various highly mineralized molluscan shell ultrastructures. Here, the mineral components provide the general stiffness to the composites, and the organic interfaces play a key role in providing these biogenic architectures with mechanical superiority. Although numerous studies employed state-of-the-art methods to measure and/or model and/or simulate the mechanical behavior of molluscan shells, our understanding of their performance is limited. This is partially due to the lack of the most fundamental knowledge of their mechanical characteristics, particularly, the anisotropic elastic properties of the mineral components and of the tissues they form. In fact, elastic constants of biogenic calcium carbonate, one of the most common biominerals in nature, is unknown for any organism. In this work, we employ the ultrasonic pulse-echo method to report the elasticity tensor of two common ultrastructural motifs in molluscan shells: the prismatic and the nacreous architectures made of biogenic calcite and aragonite, respectively. The outcome of this research not only provides information necessary for fundamental understanding of biological materials formation and performance, but also yields textbook knowledge on biogenic calcium carbonate required for future structural/crystallographic, theoretical and computational studies.

A Dual-Mode Surface Acoustic Wave Delay Line for the Detection of Ice on 64°-Rotated Y-Cut Lithium Niobate.

Ice accumulation on infrastructure poses severe safety risks and economic losses, necessitating effective detection and monitoring solutions. This study introduces a novel approach employing surface acoustic wave (SAW) sensors, known for their small size, wireless operation, energy self-sufficiency, and retrofit capability. Utilizing a SAW dual-mode delay line device on a 64°-rotated Y-cut lithium niobate substrate, we demonstrate a solution for combined ice detection and temperature measurement. In addition to the shear-horizontal polarized leaky SAW, our findings reveal an electrically excitable Rayleigh-type wave in the X+90° direction on the same cut. Experimental results in a temperature chamber confirm capability for reliable differentiation between liquid water and ice loading and simultaneous temperature measurements. This research presents a promising advancement in addressing safety concerns and economic losses associated with ice accretion.

From rectangular to diamond shape: on the three-dimensional and size-dependent transformation of patterns formed by single particles trapped in microfluidic acoustic tweezers.

Generally, the pattern formed by individual particles trapped inside a microfluidic chamber by a two-dimensional standing acoustic wave field has been considered only the result of the acoustic radiation force. Previous studies showed that particles can be trapped at the local minima and maxima of the first-order pressure and velocity fields. Thus, either a rectangular or a diamond pattern can be formed solely depending on the particle size, when the acoustic field is unchanged, and the material properties of the particles and the fluid are fixed. In this paper, we report about the co-existence of different patterns with particles of the same size. The actual shape of the patterns depends mainly on the ratio between particle diameter and wavelength. In addition, particles were found to be trapped at locations that coincide with the position of antinodes, even though the particles have a positive acoustic contrast factor. These phenomena imply that the trapping of individual particles cannot be described by the acoustic radiation force solely. Hence, further research is required, taking the viscous drag force caused by the fluid flow induced by the acoustic streaming effect into account.

Three-dimensional heating and patterning dynamics of particles in microscale acoustic tweezers.

Acoustic tweezers facilitate a noninvasive, contactless, and label-free method for the precise manipulation of micro objects, including biological cells. Although cells are exposed to mechanical and thermal stress, acoustic tweezers are usually considered as biocompatible. Here, we present a holistic experimental approach to reveal the correlation between acoustic fields, acoustophoretic motion and heating effects of particles induced by an acoustic tweezer setup. The system is based on surface acoustic waves and was characterized by applying laser Doppler vibrometry, astigmatism particle tracking velocimetry and luminescence lifetime imaging. In situ measurements with high spatial and temporal resolution reveal a three-dimensional particle patterning coinciding with the experimentally assisted numerical result of the acoustic radiation force distribution. In addition, a considerable and rapid heating up to 55 °C depending on specific parameters was observed. Although these temperatures may be harmful to living cells, counter-measures can be found as the time scales of patterning and heating are shown to be different.

Macroscopic Disk Rotation by Means of Surface Acoustic Waves.

It is shown experimentally that a flat piezoelectric disk poled perpendicular to its surface and suspended on a thin thread can be rotated about 50° by two surface acoustic waves (SAWs) intentionally excited with different amplitudes and propagating in the opposite directions. The excitation of such counter-propagating SAWs with different amplitudes is based on the nonsymmetrical interdigital transducer with different angular width electrodes located along the disk radius. The angular width of each of the two electrodes per angular period is not change along the disk radius. Such a ring unidirectional transducer realized on one of the disk surfaces is used for the excitation of SAWs. Hereby, the flat surface of the disk allows one to create any transducer pattern using conventional technology. The other disk surface can be free or covered by the silver layer.

Cognitive remediation therapy in anorexia nervosa-A randomized clinical trial.

Objective: Especially for adult patients with anorexia nervosa (AN), treatment response is generally low to moderate. The present study aimed to evaluate the efficacy of cognitive remediation therapy (CRT) as adjunctive treatment for AN regarding clinical and cognitive outcomes. Method: In this randomized controlled superiority trial, 167 adult and adolescent (≥17 years) patients with AN were randomly allocated (1:1) to 10 weekly sessions of group therapy of either CRT (n = 82) or art therapy (ART; n = 85) as an adjunct to inpatient treatment-as-usual (TAU). Outcomes were assessed at baseline, end-of-treatment (10 weeks), and 6-month follow-up. Change in body mass index (BMI), eating disorder psychopathology, and health-related quality of life (QoL) from baseline to 6-month follow-up served as primary outcomes. Improvements in motivation to change and several indices of set-shifting and central coherence between baseline and end-of-treatment and between baseline and 6-month follow-up served as secondary outcomes. Analysis was by intention to treat. Results: Treatment groups did not differ regarding change in BMI, eating disorder psychopathology, and health-related QoL from baseline to 6-month follow-up. Likewise, groups neither differed regarding improvements in these outcomes between baseline and end-of-treatment nor in motivation to change, set-shifting, and central coherence at any time, except for greater short-term improvements in one measure of set-shifting in the CRT group. Conclusions: CRT as an adjunct to inpatient TAU for AN was not efficacious in improving clinical and cognitive outcomes. The results do not support routine employment of CRT in inpatient treatment for AN. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Microwave Acoustic Attenuation in CTGS Single Crystals.

This article presents a study of special material properties of the single crystalline material Ca3TaGa3Si2O14 (CTGS = Catangasite). The comparatively highly ordered crystal structure and acceptable piezoelectric strength make it a candidate for microacoustic applications under extreme conditions. Obviously, low-loss dynamic behavior is typical for this crystal which consequently enables high-temperature use. As a particular challenge, the behavior at gigahertz frequencies is investigated here. For that, High overtone Bulk Acoustic wave Resonator (HBAR) type measurements in the range of 1-6 GHz are performed. The selection of five distinctive propagation directions for exclusively pure or quasi-longitudinal modes enables to derive the dynamic viscosities from the quality factors of HBAR results. The observed frequency dependences exhibit Akhiezer behavior as the predominant loss mechanism in the cases examined.

Antimicrobial peptides in patients with anorexia nervosa: comparison with healthy controls and the impact of weight gain.

Clinical observations show that patients with anorexia nervosa (AN) are surprisingly free from infectious diseases. There is evidence from studies in Drosophila melanogaster that starvation leads to an increased expression of antimicrobial peptides (AMPs). AMPs are part of the innate immune system and protect human surfaces from colonization with pathogenic bacteria, viruses and fungi. We compared the expression of AMPs between patients with AN and healthy controls (HC) and investigated the influence of weight gain. Using a standardized skin rinsing method, quantitative determination of the AMPs psoriasin and RNase 7 was carried out by ELISA. Even though non-significant, effect sizes revealed slightly higher AMP concentrations in HC. After a mean weight gain of 2.0 body mass index points, the concentration of psoriasin on the forehead of patients with AN increased significantly. We could not confirm our hypotheses of higher AMP concentrations in patients with AN that decrease after weight gain. On the contrary, weight gain seems to be associated with increasing AMP concentrations.

Approach and avoidance bias for thin-ideal and normal-weight body shapes in anorexia nervosa.

OBJECTIVE: The two studies aimed to examine implicit affective evaluations of thin-ideal and normal-weight body shapes in women with anorexia nervosa (AN), taking identification with body shapes into account. METHOD: In study 1, approach-avoidance bias for thin-ideal and normal-weight bodies was assessed in 40 women with AN and 40 healthy women by using an Approach-Avoidance Task and female avatar bodies with a standard face as stimuli. In study 2, 39 women with AN and 38 healthy women underwent a similar task but identification with bodies was manipulated by presenting bodies once with the participant's own face and once with another woman's face. RESULTS: In study 1, patients with AN did not differ from healthy participants in their automatic approach-avoidance tendencies towards thin-ideal and normal-weight bodies. In study 2, no definite approach bias for a thin self and no avoidance bias for thin other women or for a normal-weight self were found. However, as compared to healthy women, those with AN showed a less positive implicit evaluation of thin other women, and an implicit preference for thin bodies depicted as themselves over thin bodies depicted as another woman. CONCLUSIONS: The findings suggest that intra-sexual competition for being slim is increased in AN.

Improving emotion recognition in anorexia nervosa: An experimental proof-of-concept study.

OBJECTIVE: Previous research has found increasing evidence for difficulties in emotion recognition ability (ERA) and social cognition in anorexia nervosa (AN), and recent models consider these factors to contribute to the development and maintenance of the disorder. However, there is a lack of experimental studies testing this hypothesis. Therefore, the present proof-of-concept study examined whether ERA can be improved by a single session of a computerized training in AN, and whether this has short-term effects on eating disorder symptoms. METHOD: Forty inpatients (22.20 ± 7.15 years) with AN were randomly assigned to receive a single session of computerized training of ERA (TERA) or a sham training (training the recognition of different types of clouds). ERA, self-reported eating disorder symptoms, and body mass index (BMI) were assessed within 3 days before and after training. RESULTS: After training, both groups showed improved ERA, reduced self-reported eating disorder symptoms, and an increased BMI. As compared to patients in the control group, patients who received TERA showed greater improvements in ERA and self-reported eating disorder symptoms. DISCUSSION: ERA can be effectively trained in patients with AN. Moreover, short-term improvements in self-reported eating disorder symptoms provide tentative support for the hypothesis that difficulties in ERA contribute to the maintenance of AN, and that specific trainings of ERA hold promise as an additional component in AN treatment. Future studies are needed to replicate these findings in larger samples, and to investigate long-term effects and transfer into real-world settings.

Transport and Electromechanical Properties of Ca3TaGa3Si2O14 Piezoelectric Crystals at Extreme Temperatures.

Transport mechanisms in structurally ordered piezoelectric Ca3TaGa3Si2O14 (CTGS) single crystals are studied in the temperature range of 1000-1300 °C by application of the isotope 18O as a tracer and subsequent analysis of diffusion profiles of this isotope using secondary ion mass spectrometry (SIMS). Determined oxygen self-diffusion coefficients enable calculation of oxygen ion contribution to the total conductivity, which is shown to be small. Since very low contributions of the cations have to be expected, the total conductivity must be dominated by electron transport. Ion and electron conductivities are governed by different mechanisms with activation energies (1.9±0.1) eV and (1.2±0.07) eV, respectively. Further, the electromechanical losses are studied as a function of temperature by means of impedance spectroscopy on samples with electrodes and a contactless tone-burst excitation technique. At temperatures above 650 °C the conductivity-related losses are dominant. Finally, the operation of CTGS resonators is demonstrated at cryogenic temperatures and materials piezoelectric strain constants are determined from 4.2 K to room temperature.

Surface acoustic wave diffraction driven mechanisms in microfluidic systems.

Acoustic forces arising from high-frequency surface acoustic waves (SAW) underpin an exciting range of promising techniques for non-contact manipulation of fluid and objects at micron scale. Despite increasing significance of SAW-driven technologies in microfluidics, the understanding of a broad range of phenomena occurring within an individual SAW system is limited. Acoustic effects including streaming and radiation force fields are often assumed to result from wave propagation in a simple planar fashion. The propagation patterns of a single SAW emanating from a finite-width source, however, cause a far richer range of physical effects. In this work, we seek a better understanding of the various effects arising from the incidence of a finite-width SAW beam propagating into a quiescent fluid. Through numerical and experimental verification, we present five distinct mechanisms within an individual system. These cause fluid swirling in two orthogonal planes, and particle trapping in two directions, as well as migration of particles in the direction of wave propagation. For a range of IDT aperture and channel dimensions, the relative importance of these mechanisms is evaluated.

Body image related negative interpretation bias in anorexia nervosa.

A distorted body image and pronounced body dissatisfaction are hallmarks of anorexia nervosa (AN) that typically result in dietary restraint and compensatory behaviours. Cognitive biases such as negative interpretation bias are considered key maintaining factors of these maladaptive cognitions and behaviours. However, little attention has been paid to empirical tests whether negative interpretation bias exists in AN and to what degree it is associated with symptom severity. Participants in the present study were 40 women with AN and 40 healthy women with no history of an eating disorder. Body-related negative interpretation bias (i.e., a tendency to interpret ambiguous information about the own body in a negative way) was measured by a Scrambled Sentences Task. Patients with AN showed a stronger body-related negative interpretation bias than healthy controls. Within both groups, negative interpretation bias correlated strongly and positively with AN symptom severity and these effects were not moderated by levels of depressive symptoms. The findings support the idea that biased interpretation of body-related information is associated with the specific psychopathology of AN. Targeted, computerised interventions (e.g. interpretation bias modification) may help to alter these dysfunctional cognitive schemas that lie at the heart of AN.

Correction: Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.

Correction for 'Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming' by David J. Collins et al., Lab Chip, 2017, DOI: 10.1039/c7lc00215g.

3D measurement and simulation of surface acoustic wave driven fluid motion: a comparison.

The characterisation of the fluid motion induced by the acoustic streaming effect is of paramount interest for novel microfluidic devices based on surface acoustic waves (SAWs), e.g. for a detailed description of the achievable mixing efficiency and thus the design of such devices. Here, we present for the first time a quantitative 3D comparison between experimental measurements and numerical simulations of the acoustic streaming induced fluid flow inside a microchannel originating from a SAW. On the one hand, we performed fully three-dimensional velocity measurements using the astigmatism particle tracking velocimetry. On the other hand, we derived a novel streaming force approach solving the damped wave equation, which allows fast and easy 3D simulations of the acoustic streaming induced fluid flow. Furthermore, measurements of the SAW amplitude profile inside the fluid filled microchannel were performed. Based on these results, we obtained a very good agreement between the velocity measurements and the simulations of the fluid flow demonstrating the importance of comprising the actual shape of the SAW amplitude profile for quantitatively reliable simulations. It is shown that the novel streaming force approach is a valid approximation for the simulation of the acoustic streaming induced fluid flow, allowing a rapid and simple estimation of the flow field of SAW based microfluidic devices.

Selective particle and cell capture in a continuous flow using micro-vortex acoustic streaming.

Acoustic streaming has emerged as a promising technique for refined microscale manipulation, where strong rotational flow can give rise to particle and cell capture. In contrast to hydrodynamically generated vortices, acoustic streaming is rapidly tunable, highly scalable and requires no external pressure source. Though streaming is typically ignored or minimized in most acoustofluidic systems that utilize other acoustofluidic effects, we maximize the effect of acoustic streaming in a continuous flow using a high-frequency (381 MHz), narrow-beam focused surface acoustic wave. This results in rapid fluid streaming, with velocities orders of magnitude greater than that of the lateral flow, to generate fluid vortices that extend the entire width of a 400 µm wide microfluidic channel. We characterize the forces relevant for vortex formation in a combined streaming/lateral flow system, and use these acoustic streaming vortices to selectively capture 2 µm from a mixed suspension with 1 µm particles and human breast adenocarcinoma cells (MDA-231) from red blood cells.

Anisotropy effects in the reflection of surface acoustic waves from obstacles.

The paper studies the difference between the reflection coefficients of a surface acoustic wave incident on a groove or strip along the inverse directions. This difference occurs because of the crystallographic anisotropy of the substrate and/or the asymmetry of the shape of the obstacle. The numerical computations are carried out by the finite element method. A perfectly matched layer is implemented to truncate the computational domain. Some general properties of the transmission and reflection coefficients of surface acoustic waves are also discussed.

Atomization off thin water films generated by high-frequency substrate wave vibrations.

Generating aerosol droplets via the atomization of thin aqueous films with high frequency surface acoustic waves (SAWs) offers several advantages over existing nebulization methods, particularly for pulmonary drug delivery, offering droplet sizes in the 1-5-µm range ideal for effective pulmonary therapy. Nevertheless, the physics underlying SAW atomization is not well understood, especially in the context of thin liquid film formation and spreading and how this affects the aerosol production. Here, we demonstrate that the film geometry, governed primarily by the applied power and frequency of the SAW, indeed plays a crucial role in the atomization process and, in particular, the size of the atomized droplets. In contrast to the continuous spreading of low surface energy liquids atop similar platforms, high surface energy liquids such as water, in the present case, are found to undergo transient spreading due to the SAW to form a quasisteady film whose height is determined by self-selection of the energy minimum state associated with the acoustic resonance in the film and whose length arises from a competition between acoustic streaming and capillary effects. This is elucidated from a fundamental model for the thin film spreading behavior under SAW excitation, from which we show good agreement between the experimentally measured and theoretically predicted droplet dimension, both of which consistently indicate a linear relationship between the droplet diameter and the mechanical power coupled into the liquid by the SAW (the latter captured by an acoustic Weber number to the two thirds power, and the reciprocal of the SAW frequency).

Two-finger (TF) SPUDT cells.

SPUDT cells including two fingers are only known thus far for so-called NSPUDT directions. In that case, usual solid-finger cells are used. The purpose of the present paper is to find SPUDT cell types consisting of two fingers only for pure mode directions. Two-finger (TF) cells for pure mode directions on substrates like 128°YX LiNbO(3) and YZ LiNbO(3) were found by means of an optimization procedure. The forward direction of a TF-cell SPUDT on 128°YX LiNbO(3) was determined experimentally. The properties of the new cells are compared with those of conventional SPUDT cells. The reflectivity of TF cells on 128°YX LiNbO(3) turns out to be two to three times larger than that of distributed acoustic reflection transducer (DART) and Hanma-Hunsinger cells at the same metal layer thickness.

Usage of symmetry in the simulation of interdigital transducers.

This paper discusses the application of the finite element method to the simulation of surface acoustic wave generation on piezoelectric substrates and the possibility of reducing the number of computations by taking into account the symmetry of the problem. It is shown that the computations can be performed in only one half of the structure provided that the substrate assumes particular orientations. The class of allowed orientations encompasses the majority of crystal cuts used in practice. A test computation of the electric admittance agrees well with experimental results. The perfectly matched layer method is implemented to truncate the computational domain.