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1.
BMC Med Educ ; 24(1): 619, 2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38840140

ABSTRACT

INTRODUCTION/AIM: Radiological imaging is crucial in modern clinical practice and requires thorough and early training. An understanding of cross-sectional imaging is essential for effective interpretation of such imaging. This study examines the extent to which completing an undergraduate ultrasound course has positive effects on the development of visual-spatial ability, knowledge of anatomical spatial relationships, understanding of radiological cross-sectional images, and theoretical ultrasound competencies. MATERIAL AND METHODS: This prospective observational study was conducted at a medical school with 3rd year medical students as part of a voluntary extracurricular ultrasound course. The participants completed evaluations (7-level Likert response formats and dichotomous questions "yes/no") and theoretical tests at two time points (T1 = pre course; T2 = post course) to measure their subjective and objective cross-sectional imaging skills competencies. A questionnaire on baseline values and previous experience identified potential influencing factors. RESULTS: A total of 141 participants were included in the study. Most participants had no previous general knowledge of ultrasound diagnostics (83%), had not yet performed a practical ultrasound examination (87%), and had not attended any courses on sonography (95%). Significant subjective and objective improvements in competencies were observed after the course, particularly in the subjective sub-area of "knowledge of anatomical spatial relationships" (p = 0.009). Similarly, participants showed improvements in the objective sub-areas of "theoretical ultrasound competencies" (p < 0.001), "radiological cross-section understanding and knowledge of anatomical spatial relationships in the abdomen" (p < 0.001), "visual-spatial ability in radiological cross-section images" (p < 0.001), and "visual-spatial ability" (p = 0.020). CONCLUSION: Ultrasound training courses can enhance the development of visual-spatial ability, knowledge of anatomical spatial relationships, radiological cross-sectional image understanding, and theoretical ultrasound competencies. Due to the reciprocal positive effects of the training, students should receive radiology training at an early stage of their studies to benefit as early as possible from the improved skills, particularly in the disciplines of anatomy and radiology.


Subject(s)
Clinical Competence , Education, Medical, Undergraduate , Students, Medical , Ultrasonography , Humans , Prospective Studies , Male , Female , Educational Measurement , Young Adult , Adult , Curriculum
2.
Diagnostics (Basel) ; 14(7)2024 Apr 08.
Article in English | MEDLINE | ID: mdl-38611692

ABSTRACT

Prior to the curative resection of colorectal carcinoma (CRC) or pancreatic ductal adenocarcinoma (PDAC), the exclusion of hepatic metastasis using cross-sectional imaging is mandatory. The Doppler perfusion index (DPI) of the liver is a promising method for detecting occult liver metastases, but the underlying visceral duplex sonography is critically viewed in terms of its reproducibility. The aim of this study was to investigate systematically the reproducibility of the measured variables, the calculated blood flow, and the DPI. Between February and September 2023, two examinations were performed on 80 subjects within a period of 0-30 days and at two previously defined quality levels, aligned to the German standards of the DEGUM. Correlation analyses were carried out using Pearson's correlation coefficient (PCC) and the intraclass correlation coefficient (ICC). The diameters, blood flow, and DPI showed a high degree of agreement (PCC of 0.9 and ICC of 0.9 for AHP). Provided that a precise standard of procedure is adhered to, the Doppler examination of AHC, AHP, and PV yields very reproducible blood flows and DPI, which is a prerequisite for a comprehensive investigation of its prognostic value for the prediction of metachronous hepatic metastasis in the context of curatively treated CRC or PDAC.

3.
Diagnostics (Basel) ; 13(24)2023 Dec 08.
Article in English | MEDLINE | ID: mdl-38132206

ABSTRACT

BACKGROUND: Handheld ultrasound (HHUS) devices have chiefly been deployed in emergency medicine, where they are considered a valid tool. The data situation is less clear in the case of internal questions in abdominal sonography. In our study, we investigate whether HHUS devices from different manufacturers differ in their B-scan quality, and whether any differences are relevant for the significance of an internal ultrasound examination. METHOD: The study incorporated eight HHUS devices from different manufacturers. Ultrasound videos of seven defined sonographic questions were recorded with all of the devices. The analogue recording of the same findings with a conventional high-end ultrasound (HEUS) device served as an evaluation criterion. Then, the corresponding findings were played side by side and evaluated by fourteen ultrasound experts using a point scale (5 points = very good; 1 point = insufficient). RESULTS: The HHUS devices achieved relatively good results in terms of both the B-scan quality assessment and the ability to answer the clinical question, regardless of the manufacturer. One of the tested HHUS devices even achieved a significantly (p < 0.05) higher average points score in both the evaluation of B-scan quality and in the evaluation of clinical significance than the other devices. Regardless of the manufacturer, the HHUS devices performed best when determining the status/inferior vena cava volume and in the representation of ascites/free fluid. CONCLUSION: In various clinical abdominal sonography questions, HHUS systems can reliably reproduce findings, and are-while bearing their limitations in mind-an acceptable alternative to conventional HEUS systems. Irrespective of this, the present study demonstrated relevant differences in the B-scan quality of HHUS devices from different manufacturers.

4.
Med Ultrason ; 25(3): 288-295, 2023 Sep 29.
Article in English | MEDLINE | ID: mdl-37778022

ABSTRACT

AIMS: A meaningful sonographic examination is decisively dependent on the B-scan quality of the ultrasound device. When selecting a suitable ultrasound device, B-scan quality should be an important purchase criterion. Although there is no generally accepted method to measure B-scan quality, we tried to evaluate comparable sonography devices from different manufacturers regarding B-scan quality. MATERIAL AND METHODS: We systematically assessed the B-scan quality in ultrasound devices of seven different manufacturers from the mid-price segment. All 7 ultrasound units tested had comparable equipment features and the purchase value of approximately $20,000. We recorded video sequences and compared B-mode image quality. We used both physiological sectional images and pathological findings from abdominal ultrasound. RESULTS: We identified three ultrasound units that scored significantly better in measuring the B-scan quality than the other devices. The Canon Xario 200, the General Electric Logiq P7 and the Mindray DC70 (in alphabetical order) were the units that outperformed all others.The differences identified were found to be statistically significant. A subgroup analysis showed that the contrasts in quality were more pronounced in near-field examinations than in examinations with greater penetration depth. CONCLUSIONS: There are considerable qualitative discrepancies in B-scan ultrasound devices despite being similar in terms of equipment and price. Our findings show that these differences are statistically detectable and likely clinically relevant.


Subject(s)
Physical Examination , Humans , Ultrasonography/methods
5.
Diagnostics (Basel) ; 13(20)2023 Oct 20.
Article in English | MEDLINE | ID: mdl-37892093

ABSTRACT

BACKGROUND: ultrasound diagnostics have a broad spectrum of applications, including among diseases of the musculoskeletal system. Accordingly, it is important for the users to have a well-founded and up-to-date education in this dynamic examination method. The right balance between online and in-class teaching still needs to be explored in this context. Certifying institutions are currently testing digitally transformed teaching concepts to provide more evidence. METHODS: this study compared two musculoskeletal ultrasound blended learning models. Model A was more traditional, with a focus on in-person teaching, while Model B was more digitally oriented with compulsory webinar. Both used e-learning for preparation. Participants completed evaluations using a seven-point Likert scale, later converted to a 0-1 scale. Digital teaching media (e-learning) were used for preparation in both courses. RESULTS: the analysis included n = 41 evaluations for Model A and n = 30 for Model B. Model B received a better overall assessment (median: 0.73 vs. 0.69, p = 0.05). Model B also excelled in "course preparation" (p = 0.02), "webinar quality" (p = 0.04), and "course concept" (p = 0.04). The "gain of competence" (p = 0.82), "learning materials" (p = 0.30), and "tutor quality" (p = 0.28) showed no significant differences. CONCLUSION: participants favorably assessed blended learning in ultrasound teaching. Certifying institutions should consider accrediting models that combine digital methods (e.g., internet lectures/webinars) and materials (e.g., e-learning) with hands-on ultrasound training. Further research is needed to validate these subjective findings for a stronger evidential basis.

6.
J Cancer Res Clin Oncol ; 149(15): 14465-14470, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37515612

ABSTRACT

Immune-related adverse events (irAEs) induced by immune checkpoint inhibitors (ICIs) in mono- or combination therapy may be acute or delayed, partly arising long after termination of treatment. They may be reversible or persistent. Treatment duration with ICIs is usually one year in the adjuvant setting of solid tumors, and until progression or inacceptable toxicity in metastatic disease. In the case of a response in the palliative setting, a patient may be on treatment for many years, based on individual decision making. Thus, every patient is at risk of experiencing clinically highly relevant side effects for a very long time when she/he may be transferred between many sectors of acute medicine including intensive care units (ICUs) until later rehabilitation procedures and observation by general practitioners. While actively treating oncologists in hospitals and outpatient departments have already covered a long (and partly harmful) learning curve, most physicians in other sectors like ICUs or rehabilitation hospitals have not seen many patients and these dangerous side effects to a larger extent, and thus have not trained their awareness and clinical knowledge. In most cases, irAEs appeared before the admission of the patients to their institutions, and they are only asked to control preexisting medications. Only intersectoral education and communication can help to safely overcome this gap and lag time until all medical specialties have gained sufficient experience and gone through their learning processes.

7.
Drug Metab Dispos ; 51(3): 403-412, 2023 03.
Article in English | MEDLINE | ID: mdl-36460476

ABSTRACT

Bifunctional antibody (BfAb) therapeutics offer the potential for novel functionalities beyond those of the individual monospecific entities. However, combining these entities into a single molecule can have unpredictable effects, including changes in pharmacokinetics that limit the compound's therapeutic profile. A better understanding of how molecular modifications affect in vivo tissue interactions could help inform BfAb design. The present studies were predicated on the observation that a BfAb designed to have minimal off-target interactions cleared from the circulation twice as fast as the monoclonal antibody (mAb) from which it was derived. The present study leverages the spatial and temporal resolution of intravital microscopy (IVM) to identify cellular interactions that may explain the different pharmacokinetics of the two compounds. Disposition studies of mice demonstrated that radiolabeled compounds distributed similarly over the first 24 hours, except that BfAb accumulated approximately two- to -three times more than mAb in the liver. IVM studies of mice demonstrated that both distributed to endosomes of liver endothelia but with different kinetics. Whereas mAb accumulated rapidly within the first hour of administration, BfAb accumulated only modestly during the first hour but continued to accumulate over 24 hours, ultimately reaching levels similar to those of the mAb. Although neither compound was freely filtered by the mouse or rat kidney, BfAb, but not mAb, was found to accumulate over 24 hours in endosomes of proximal tubule cells. These studies demonstrate how IVM can be used as a tool in drug design, revealing unpredicted cellular interactions that are undetectable by conventional analyses. SIGNIFICANCE STATEMENT: Bifunctional antibodies offer novel therapeutic functionalities beyond those of the individual monospecific entities. However, combining these entities into a single molecule can have unpredictable effects, including undesirable changes in pharmacokinetics. Studies of the dynamic distribution of a bifunctional antibody and its parent monoclonal antibody presented here demonstrate how intravital microscopy can expand our understanding of the in vivo disposition of therapeutics, detecting off-target interactions that could not be detected by conventional pharmacokinetics approaches or predicted by conventional physicochemical analyses.


Subject(s)
Antibodies, Monoclonal , Liver , Rats , Mice , Animals , Tissue Distribution , Antibodies, Monoclonal/pharmacokinetics , Liver/metabolism , Kidney
8.
Diagnostics (Basel) ; 14(1)2023 Dec 26.
Article in English | MEDLINE | ID: mdl-38201363

ABSTRACT

BACKGROUND: the use of handheld ultrasonography (HHUS) devices is well established in prehospital emergency diagnostics, as well as in intensive care settings. This is based on several studies in which HHUS devices were compared to conventional high-end ultrasonography (HEUS) devices. Nonetheless, there is limited evidence regarding potential variations in B-scan quality among HHUS devices from various manufacturers, and regarding whether any such differences hold clinical significance in intensive care medicine settings. METHODS: this study included the evaluation of eight HHUS devices sourced from diverse manufacturers. Ultrasound videos of five previously defined sonographic questions (volume status/inferior vena cava, pleural effusion, pulmonary B-lines, gallbladder, and needle tracking in situ) were recorded with all devices. The analogue recording of the same pathologies with a HEUS device served as gold standard. The corresponding findings (HHUS and HEUS) were then played side by side and evaluated by sixteen intensive care physicians experienced in sonography. The B-scan quality and the clinical significance of the HHUS were assessed using a five-point Likert scale (5 points = very good; 1 point = insufficient). RESULTS: both in assessing the quality of B-scans and in their ability to answer clinical questions, the HHUS achieved convincing results-regardless of the manufacturer. For example, only 8.6% (B-scan quality) and 9.8% (clinical question) of all submitted assessments received an "insufficient" rating. One HHUS device showed a significantly higher (p < 0.01) average points score in the assessment of B-scan quality (3.9 ± 0.65 points) and in the evaluation of clinical significance (4.03 ± 0.73 points), compared to the other devices. CONCLUSIONS: HHUS systems are able to reliably answer various clinical intensive care questions and are-while bearing their limitations in mind-an acceptable alternative to conventional HEUS devices. Irrespective of this, the present study was able to demonstrate relevant differences in the B-scan quality of HHUS devices from different manufacturers.

9.
Nanoscale ; 13(30): 13158, 2021 Aug 14.
Article in English | MEDLINE | ID: mdl-34477799

ABSTRACT

Correction for 'Structural insights into fusion mechanisms of small extracellular vesicles with model plasma membranes' by Fabio Perissinotto et al., Nanoscale, 2021, 13, 5224-5233, DOI: .


Subject(s)
Extracellular Vesicles , Cell Membrane
10.
Nanoscale ; 13(10): 5224-5233, 2021 Mar 18.
Article in English | MEDLINE | ID: mdl-33687046

ABSTRACT

Extracellular vesicles (EVs) are a potent intercellular communication system. Such small vesicles transport biomolecules between cells and throughout the body, strongly influencing the fate of recipient cells. Due to their specific biological functions they have been proposed as biomarkers for various diseases and as optimal candidates for therapeutic applications. Despite their extreme biological relevance, their mechanisms of interaction with the membranes of recipient cells are still hotly debated. Here, we propose a multiscale investigation based on atomic force microscopy, small angle X-ray scattering, small angle neutron scattering and neutron reflectometry to reveal structure-function correlations of purified EVs in interaction with model membrane systems of variable complex compositions and to spot the role of different membrane phases on the vesicle internalization routes. Our analysis reveals strong interactions of EVs with the model membranes and preferentially with the borders of protruding phase domains. Moreover, we found that upon vesicle breaking on the model membrane surface, the biomolecules carried by/on EVs diffuse with different kinetics rates, in a process distinct from simple fusion. The biophysical platform proposed here has clear implications on the modulation of EV internalization routes by targeting specific domains at the plasma cell membrane and, as a consequence, on EV-based therapies.


Subject(s)
Extracellular Vesicles , Cell Communication , Cell Membrane , Microscopy, Atomic Force
11.
Nanoscale Adv ; 4(1): 19-25, 2021 Dec 21.
Article in English | MEDLINE | ID: mdl-36132967

ABSTRACT

The spatial confinement of atoms at surfaces and interfaces significantly alters the lattice dynamics of thin films, heterostructures and multilayers. Ultrathin films with high dielectric constants (high-k) are of paramount interest for applications as gate layers in current and future integrated circuits. Here we report a lattice dynamics study of high-k Eu2O3 films with thicknesses of 21.3, 2.2, 1.3, and 0.8 nm deposited on YSZ(001). The Eu-partial phonon density of states (PDOS), obtained from nuclear inelastic scattering, exhibits broadening of the phonon peaks accompanied by up to a four-fold enhancement of the number of low-energy states compared to the ab initio calculated PDOS of a perfect Eu2O3 crystal. Our analysis demonstrates that while the former effect reflects the reduced phonon lifetimes observed in thin films due to scattering from lattice defects, the latter phenomenon arises from an ultrathin EuO layer formed between the thin Eu2O3 film and the YSZ(001) substrate. Thus, our work uncovers another potential source of vibrational anomalies in thin films and multilayers, which has to be cautiously considered.

12.
Sci Rep ; 10(1): 13923, 2020 Aug 18.
Article in English | MEDLINE | ID: mdl-32811888

ABSTRACT

The multilayer of approximate structure MgO(100)/[nFe51Rh49(63 Å)/57Fe51Rh49(46 Å)]10 deposited at 200 °C is primarily of paramagnetic A1 phase and is fully converted to the magnetic B2 phase by annealing at 300 °C for 60 min. Subsequent irradiation by 120 keV Ne+ ions turns the thin film completely to the paramagnetic A1 phase. Repeated annealing at 300 °C for 60 min results in 100% magnetic B2 phase, i.e. a process that appears to be reversible at least twice. The A1 → B2 transformation takes place without any plane-perpendicular diffusion while Ne+ irradiation results in significant interlayer mixing.

13.
J Ultrason ; 20(80): e24-e28, 2020.
Article in English | MEDLINE | ID: mdl-32320551

ABSTRACT

Introduction: A professional and valid ultrasound examination is dependent upon an extensively experienced examiner. Recognition and classification of rare or minimally distinctive findings are a particular source of uncertainty on the part of the examiner. By creating an online-based video database of sonographic findings, we tried to share our own experience for clinical and educational purposes. Material and methods: More than a thousand video clips of documented ultrasound findings were anonymized and cut to a practicable length of between 10 and 25 sec. The findings were critically evaluated and labeled with a primary diagnosis. They were also classified by organ systems and various keywords. Results: An online portal that currently contains more than 1,000 video sequences of typical, non-typical, especially vivid or rare ultrasound findings has been created. The portal is free of charge and accessible for any Internet-capable PC. It is also optimized for use on mobile devices (smartphones, iPads, etc.). Search and location of relevant findings is performed using keywords or a diagnosis-based search function. The Internet address is www.sono.gallery. Conclusions: The video portal is a fast and universally accessible non-commercial platform. Its moving images can be used as an aid in resolving problematic differential diagnoses of typical, non-typical or especially rare ultrasound findings or in verifying one's own findings.Introduction: A professional and valid ultrasound examination is dependent upon an extensively experienced examiner. Recognition and classification of rare or minimally distinctive findings are a particular source of uncertainty on the part of the examiner. By creating an online-based video database of sonographic findings, we tried to share our own experience for clinical and educational purposes. Material and methods: More than a thousand video clips of documented ultrasound findings were anonymized and cut to a practicable length of between 10 and 25 sec. The findings were critically evaluated and labeled with a primary diagnosis. They were also classified by organ systems and various keywords. Results: An online portal that currently contains more than 1,000 video sequences of typical, non-typical, especially vivid or rare ultrasound findings has been created. The portal is free of charge and accessible for any Internet-capable PC. It is also optimized for use on mobile devices (smartphones, iPads, etc.). Search and location of relevant findings is performed using keywords or a diagnosis-based search function. The Internet address is www.sono.gallery. Conclusions: The video portal is a fast and universally accessible non-commercial platform. Its moving images can be used as an aid in resolving problematic differential diagnoses of typical, non-typical or especially rare ultrasound findings or in verifying one's own findings.

14.
J Mech Behav Biomed Mater ; 107: 103757, 2020 07.
Article in English | MEDLINE | ID: mdl-32276188

ABSTRACT

The hierarchical and anisotropic mechanical behavior requirement of load-bearing soft tissues limits the utility of conventional elastomeric materials as a replacement for soft-tissue materials. Liquid-crystal elastomers (LCEs) have the potential to excel in this regard owing to its unique combination of mesogenic order in an elastomeric network. In this study, the mechanical behavior of the LCEs relevant to load-bearing biomedical applications was explored. LCEs with different network orientations (i.e., mesogen alignments) were investigated by fabricating the LCEs with polydomain and monodomain configurations. The polydomain and monodomain LCEs with the same degree of network crosslinking demonstrated diverse mechanical behavior, ranging from highly stiff and elastic nature to high damping capacity, depending on the loading direction with respect to the network alignment. The LCEs were also capable of matching the anisotropic mechanical behavior of an intervertebral disc. Additional studies were conducted on the in vivo biological response of LCEs upon subcutaneous implantation, as well as on the effect of the exposure to an in vitro simulated physiological environment on the mechanical behavior. The LCEs' mechanical response was negligibly affected when exposed to biomedically relevant conditions. Furthermore, the solid and porous LCEs did not show any adverse effect on the surrounding tissues when implanted subcutaneously in rats. The biological response allows for tissue ingrowth and helps illustrate their utility in implantable biological devices. Finally, the utility of LCEs to mimic the mechanical function of biological tissue such as intervertebral disc was demonstrated by fabricating a proof of concept total disc replacement device.


Subject(s)
Elastomers , Intervertebral Disc , Liquid Crystals , Animals , Porosity , Prostheses and Implants , Rats
15.
Phys Chem Chem Phys ; 22(11): 6449-6456, 2020 Mar 18.
Article in English | MEDLINE | ID: mdl-32149295

ABSTRACT

Structuring of aqueous suspensions of colloidal silica nanoparticles near an isolated planar silica-water interface is studied by specular neutron reflectivity. The reflectivity data clearly show that the suspensions develop a damped, oscillatory concentration profile in the normal direction to the interface. The wavelengths of these oscillations agree well with those independently determined by direct force measurements in the slit-geometry. The reflectivity data further demonstrate that the oscillatory structure persists over several layers and that the first particle layer is separated from the interface by a particle-free region.

16.
Nanoscale ; 11(22): 10968-10976, 2019 Jun 06.
Article in English | MEDLINE | ID: mdl-31139805

ABSTRACT

Reducing the material sizes to the nanometer length scale leads to drastic modifications of the propagating lattice excitations (phonons) and their interactions with electrons and magnons. In EuO, a promising material for spintronic applications in which a giant spin-phonon interaction is present, this might imply a reduction of the degree of spin polarization in thin films. Therefore, a comprehensive investigation of the lattice dynamics and spin-phonon interaction in EuO films is necessary for practical applications. We report a systematic lattice dynamics study of ultrathin EuO(001) films using nuclear inelastic scattering on the Mössbauer-active isotope 151Eu and first-principles theory. The films were epitaxially grown on YAlO3(110), which induces a tensile strain of ca. 2%. By reducing the EuO layer thickness from 8 nm to a sub-monolayer coverage, the Eu-partial phonon density of states (PDOS) reveals a gradual enhancement of the number of low-energy phonon states and simultaneous broadening and suppression of the peaks. These deviations from bulk features lead to significant anomalies in the vibrational thermodynamic and elastic properties calculated from the PDOS. The experimental results, supported by first-principles theory, unveil a reduction of the strength of the spin-phonon interaction in the tensile-strained EuO by a factor of four compared to a strain-free lattice.

17.
Z Gastroenterol ; 56(12): 1491-1498, 2018 Dec.
Article in English | MEDLINE | ID: mdl-30536254

ABSTRACT

PURPOSE: The quality of an ultrasound device's B-scan mode is decisive in obtaining clear and informative images. High demands are placed upon ultrasound devices, particularly in cases where evidence of small lesions of parenchymal organs is being gathered. METHODS: We tested the quality of the B-scan mode in ultrasound devices of 7 different manufacturers. We performed ultrasound examinations of 3 predefined abdominal sections on 4 healthy subjects with 7 different ultrasound devices. Documentation was compiled digitally by recording video sequences. Any characteristics identifying the manufacturer were removed. Subsequently, the sequences were organized into corresponding pairs. The resulting 252 video pairs were shown side by side to a panel of 10 experienced ultrasound examiners who evaluated the quality of the scans by way of direct visual comparison. RESULTS: Two of the 7 devices were clearly judged to be of higher quality. In part, the differences in the overall evaluation and within the subgroups reached levels of statistical significance. The ranking of the tested devices did not correlate with their suggested retail prices. CONCLUSION: There are relevant differences in the quality of the B-scan mode of modern high-end devices. The suggested retail prices do not correlate with the B-scan quality of the ultrasound devices.


Subject(s)
Abdomen , Ultrasonography , Abdomen/diagnostic imaging , Humans , Ultrasonography/economics , Ultrasonography/instrumentation
18.
Soft Matter ; 14(29): 6024-6036, 2018 Jul 25.
Article in English | MEDLINE | ID: mdl-29974115

ABSTRACT

Two-stage thiol-acrylate Michael addition reactions have proven useful in programming main-chain liquid crystal elastomers (LCEs). However, the influence of excess acrylate concentration, which is critical to monodomain programming, has not previously been examined with respect to thermomechanical properties in these two-stage LCEs. Previous studies of thiol-acrylate LCEs have focused on polydomain LCEs and/or variation of thiol crosslinking monomers or linear thiol monomers. This study guides the design of monodomain LCE actuators using the two-stage methodology by varying the concentration of mesogenic acrylate monomers from 2 mol% to 45 mol% in stoichiometric excess of thiol. The findings demonstrate a technique to tailor the isotropic transition temperature by 44 °C using identical starting monomers. In contrast to expectations, low amounts of excess acrylate showed excellent fixity (90.4 ± 2.9%), while high amounts of excess acrylate did not hinder actuation strain (87.3 ± 2.3%). Tensile stress-strain properties were influenced by excess acrylate. Linear elastic behavior was observed parallel to the director with modulus increasing from 1.4 to 6.1 MPa. The soft elastic plateau was observed perpendicular to the director with initial modulus and threshold stresses increasing from 0.6 MPa to 2.6 MPa and 14 kPa to 208 kPa, respectively. Overall, this study examines the influence of excess acrylate on mechanical properties of LCE actuators.

19.
Sci Rep ; 7: 43114, 2017 02 22.
Article in English | MEDLINE | ID: mdl-28225031

ABSTRACT

Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

20.
Macromol Rapid Commun ; 37(23): 1912-1917, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27717085

ABSTRACT

This study explores the functionalization of main-chain nematic elastomers with a conductive metallic surface layer using a polydopamine binder. Using a two-stage thiol-acrylate reaction, a programmed monodomain is achieved for thermoreversible actuation. A copper layer (≈155 nm) is deposited onto polymer samples using electroless deposition while the samples are in their elongated nematic state. Samples undergo 42% contraction when heated above the isotropic transition temperature. During the thermal cycle, buckling of the copper layer is seen in the direction perpendicular to contraction; however, transverse cracking occurs due to the large Poisson effect experienced during actuation. As a result, the electrical conductivity of the layer reduced quickly as a function of thermal cycling. However, samples do not show signs of delamination after 25 thermal cycles. These results demonstrate the ability to explore multifunctional liquid-crystalline composites using relatively facile synthesis, adhesion, and deposition techniques.


Subject(s)
Coated Materials, Biocompatible/chemistry , Copper/chemistry , Elastomers/chemistry , Indoles/chemistry , Liquid Crystals/chemistry , Polymers/chemistry , Coated Materials, Biocompatible/chemical synthesis , Electric Conductivity , Particle Size , Surface Properties , Temperature
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