Modal Characterization Research Articles

Mode couplings in multiplex electromechanical structures

Mode couplings associated with elastic wave propagation through three-dimensional multiplex structures, as manifested by asymmetric eigenmodes and dissipation, determine the efficiency of electromechanical structures. As a result, it is critical to predict electroelastic symmetric modes such as thickness expander and radial modes, as well as asymmetric flexural modes, while accounting for material losses. Multiplex electromechanical structures include multi-layered through-wall ultrasound power transfer (TWUPT) systems. Physical processes that support TWUPT include vibrations at a transmitting/acoustic source element, elastic wave propagation through a barrier and coupling layers, piezoelectric transduction of elastic vibrations at a receiving element, and spatial resonances of the transmitting and receiving elements. We investigate mode couplings in an optimized modal TWUPT system, including their physical origins, models used to describe them, and regimes of weak and strong couplings. The system layout optimization is defined in terms of size (volume), operating frequency, and matching circuit load optimization. A computational model is developed and utilized in conjunction with experimental modal characterization to highlight the impact of eigenmode features on optimization results. Several behavioral modes are identified and analyzed. The interaction of symmetric radial and asymmetric flexural modes causes the system damping to increase and the device's overall efficiency to decrease. The electromechanical coupling factor value is likewise reduced as a result of this. Such occurrences are explained by the flow of energy between modes as they interact. The present work also proposes design guidelines to improve the performance of TWUPT systems based on exploiting inherent physical phenomena.

Modal Characterization of Manual Wheelchairs

Manual wheelchair (MWC) users are exposed to whole-body vibrations (WBVs) during propulsion. Vibrations enter the MWC structure through the wheels’ hub, propagate according to the MWC dynamical response, and finally reach the user’s body by the footrest, seat, backrest, and handrims. Such exposure is likely to be detrimental to the user’s health and a source of discomfort and fatigue which could, in daily life, impact users’ social participation and performance in sports. To reduce WBV exposure, a solution relies on MWC dynamical response modelling and simulation, where the model could indeed be used to identify parameters that improve the MWC dynamic. As a result, it is necessary to first assess the MWC dynamical response. In this approach, experimental modal analyses were conducted on eleven MWCs, including daily and sport MWCs (tennis, basketball, and racing). Through this procedure, modal properties (i.e., modal frequencies, damping parameters, and modal shapes) were identified for each MWC part. The results pointed out that each MWC investigated, even within the same group, revealed specific vibration properties, underlining the difficulty of developing a single vibration-reducing system for all MWCs. Nevertheless, several common dynamical properties related to MWC comfort and design were identified.

Experimental Modal Analysis and Characterization of Additively Manufactured Polymers.

Modern 3D printed components are finding applications in dynamic structures. These structures are often subject to dynamic loadings. To date, research has mostly focused on investigating the mechanical properties of these 3D printed structures with minimum attention paid to their modal analysis. This work is focused on performing experimental modal analysis of 3D printed structures. The results show that the adhesion type has the most significant impact on the vibration response and parameters obtained from the modal analysis. The average dynamic modulus, natural frequency, and damping coefficient increased by approximately 12.5%, 5.5%, and 36%, respectively, for the specimens printed using skirt adhesion compared to those printed using raft adhesion. SEM analysis suggests that the 3D printed specimens with skirt adhesion yielded flattened layers, while raft adhesion resulted in rounded layers. The flattened layers of the specimens with skirt adhesion are likely an indication of an enhanced heat transfer between the 3D printer bed and the specimen. The printed specimens with skirt adhesion are in direct contact with the printer bed during the printing process. This enhances the heat transfer between the specimen and the printer bed, causing the layers to flatten out. The enhanced heat transfer yields a better inter-layer diffusion, resulting in improved physical bonding at the layers’ interface. The improved bonding yields higher stiffnesses and natural frequencies. For the specimens with skirt adhesion, the improved heat transfer process is also likely responsible for the enhanced damping properties. The strengthened inter-layer bonding at the layer–layer interface provides better energy dissipation along the contact lines between the layers.

Cracking the Code of Complex Drug Modalities via Multidimensional Liquid Chromatography Coupled to Mass Spectrometry

Multidimensional liquid chromatography, coupled to mass spectrometry (MDLC–MS) is a powerful tool for the characterization of complex biopharmaceutical drug modalities, from antibody–drug conjugates to nuclear acid therapeutics like antisense oligonucleotides and small interfering RNA.

Serotonin G Protein-Coupled Receptor-Based Biosensing Modalities in Yeast.

Serotonin is a key neurotransmitter involved in numerous physiological processes and serves as an important precursor for manufacturing bioactive indoleamines and alkaloids used in the treatment of human pathologies. In humans, serotonin sensing and signaling can occur by 12 G protein-coupled receptors (GPCRs) coupled to Gα proteins. In yeast, human serotonin GPCRs coupled to Gα proteins have previously been shown to function as whole-cell biosensors of serotonin. However, systematic characterization of serotonin biosensing modalities between variant serotonin GPCRs and application thereof for high-resolution serotonin quantification is still awaiting. To systematically assess GPCR signaling in response to serotonin, we characterized reporter gene expression at two different pHs of a 144-sized library encoding all 12 human serotonin GPCRs in combination with 12 different Gα proteins engineered in yeast. From this screen, we observed changes in the biosensor sensitivities of >4 orders of magnitude. Furthermore, adopting optimal biosensing designs and pH conditions enabled high-resolution high-performance liquid chromatography-validated sensing of serotonin produced in yeast. Lastly, we used the yeast platform to characterize 19 serotonin GPCR polymorphisms found in human populations. While major differences in signaling were observed among the individual polymorphisms when studied in yeast, a cross-comparison of selected variants in mammalian cells showed both similar and disparate results. Taken together, our study highlights serotonin biosensing modalities of relevance to both biotechnological and potential human health applications.

A van Benthem Theorem for Atomic and Molecular Logics

After recalling the definitions of atomic and molecular logics, we show how notions of bisimulation can be automatically defined from the truth conditions of the connectives of any of these logics. Then, we prove a generalization of van Benthem modal characterization theorem for molecular logics. Our molecular connectives should be uniform and contain all conjunctions and disjunctions. We use modal logic, the Lambek calculus and modal intuitionistic logic as case study and compare in particular our work with Olkhovikov's work.

Reactive bisimulation semantics for a process algebra with timeouts

This paper introduces the counterpart of strong bisimilarity for labelled transition systems extended with timeout transitions. It supports this concept through a modal characterisation, congruence results for a standard process algebra with recursion, and a complete axiomatisation.

Modal characterisation of simulation relations in probabilistic concurrent games

Probabilistic game structures combine both nondeterminism and stochasticity, where players repeatedly take actions simultaneously to move to the next state of the concurrent game. Probabilistic alternating simulation and bisimulation are important tools to compare the behaviour of different probabilistic game structures. In this paper, we present a sound and complete modal characterisation of these two relations by proposing a new modal logic based on probability distributions. This logic enables a player to enforce a property in the next state or distribution. We further extend the logic with fixpoint operators, which also characterises the simulation relations. This logic can express a lot of interesting properties in practical applications. • Modal characterization for Probabilistic Alternating Simulation (and Bisimulation). • A new modal logic for probability distributions in concurrent game structures. • Extends the modal logic with fixpoint operators.

Vibration performance assessment of deteriorating footbridges: A study of Tunja’s public footbridges

This paper presents the results of the assessment of the dynamic characteristics and vibration performance of eight deteriorating footbridges. The bridges examined, part of the public infrastructure of the city of Tunja (Colombia), present an evident state of deterioration, showing excessive vibration under service loadings. A consistent evaluation methodology based on vibration tests and numerical analyses was implemented. After completing a deterioration assessment, an experimental modal characterization was carried out, the results of which were used to update numerical structural models. Uniform vibration tests for different pedestrian loading scenarios were conducted. Then, pedestrian crossing simulations for a typical range of walking and running frequencies were performed using a step-by-step load model with a new proposal of normalised single-footstep force functions. Results showed elevated vibrations in most of the footbridges for temporary and exceptional loading conditions, which are unsafe for some of the structures. Discomfort and deterioration were compared using a vibration discomfort index (VDI) and a deterioration index (DI). High vibration discomfort levels were found to be consistent with the degree of deterioration of the structures evaluated.

Modal identification and dynamic analysis of a 1000 years old historic minaret of Kalaa Beni-Hammad

From structural and material point of view each historic monument is a textbook case, as it differs in shape, age, material characteristics and level of preservation. New means and approaches are used for geometric and shape survey, material and modal characterization, which helps restitute detailed information regarding the structural elements of the edifices. This paper investigates a 1000 years old historic minaret having a square base of 6.50 m of side and 24.70 m height. An ambient vibration survey has been carried out and the results were used to update a Finite Element (FE) model of the minaret in two stages. First, the elastic modulus of the rubble stone masonry has been determined by matching the experimental and numerical fundamental frequency. In a second phase, a frequency response function (FRF) correlation is carried out iteratively by adjusting the damping ratios to minimize the FRF error. The elastic modulus of the rubble stone masonry is found to be in the lowest range of values given in the literature, which confirms a deteriorated quality of the material. A seismic performance of the structure has been carried out using the updated FE model subjected to a set of acceleration time histories having the mean spectrum matching a compatible site spectrum. The stress concentration zones have been determined and a steel tie system to retrofit the structure is proposed. Beside the proposed investigation framework, the characterization results are valuable facts that can be added to the available database of historic monuments.

Shack-Hartmann Wavefront Sensing of Ultrashort Optical Vortices.

Light beams carrying Orbital Angular Momentum (OAM), also known as optical vortices (OV), have led to fascinating new developments in fields ranging from quantum communication to novel light–matter interaction aspects. Even though several techniques have emerged to synthesize these structured-beams, their detection, in particular, single-shot amplitude, wavefront, and modal content characterization, remains a challenging task. Here, we report the single-shot amplitude, wavefront, and modal content characterization of ultrashort OV using a Shack-Hartmann wavefront sensor. These vortex beams are obtained using spiral phase plates (SPPs) that are frequently used for high-intensity applications. The reconstructed wavefronts display a helical structure compatible with the topological charge induced by the SPPs. We affirm the accuracy of the optical field reconstruction by the wavefront sensor through an excellent agreement between the numerically backpropagated and experimentally obtained intensity distribution at the waist. Consequently, through Laguerre–Gauss (LG) decomposition of the reconstructed fields, we reveal the radial and azimuthal mode composition of vortex beams under different conditions. The potential of our method is further illustrated by characterizing asymmetric Gaussian vortices carrying fractional average OAM, and a realtime topological charge measurement at a 10Hz repetition rate. These results can promote Shack-Hartmann wavefront sensing as a single-shot OV characterization tool.

Modal Characterization, Aerodynamics, and Gust Response of an Electroactive Membrane

Flexibility and electric field sensitivity of dielectric elastomer membranes motivate the consideration of their applications in the wings of unmanned aerial vehicles. Applied electric field excitation expands the dielectric elastomer in the in-plane direction by compressing it into the thickness direction, which causes a change in the tension and ultimately affects the dynamic behavior of the elastomer. This study outlines the modal characteristics and fluid-structural dynamic behavior of the very high bond 4910 membrane, a type of dielectric elastomer, especially in an abrupt flow environment. An experimental shaker arrangement along with the digital image correlation system is used for experimental vibration testing. A finite element model is developed to study the modal characteristics and validate the experimental results. A fluid–structure interaction model of the electroactive membrane and its surrounding airflow is also developed to investigate the aerodynamic responses of the structure. Gust environments are predicted using the von Kármán and Dryden gust models, and the effect of different gust velocities on the aerodynamic lift and drag are obtained from the numerical fluid–structure interaction models. A wind tunnel, equipped with a data acquisition system, is used to study the aerodynamic responses and validate the numerical results experimentally. The modal analysis shows that the resonance frequencies decreased as the applied electric field excitation is increased. The coefficients of lift and drag fluctuate with the stochastic gust distribution, and the effects of von Kármán and Dryden gust profiles on aerodynamic characteristics are comparable. The values of the coefficients of lift and drag increase with the increase of applied voltage. The numerical results for the modal and aerodynamic responses show a good agreement with their corresponding experimental findings.

Characterization of Treatment Modalities for Patients With Syndromic Craniosynostosis in Relation to Degree of Midface Hypoplasia and Patient's Age Using Longitudinal Follow-Up Data.

The purpose of this study was to investigate the type and frequency of use of treatment modalities (Tx-Mods) in patients with syndromic craniosynostosis (SC) using longitudinal follow-up data. A total of 28 patients with SC (24 Crouzon, 2 Apert, and 2 Antley-Bixler syndromes), who were treated at the Department of Orthodontics, Seoul National University Dental Hospital, Seoul, South Korea between 1998 and 2020, was included. According to the degree of midface hypoplasia (MH) at the initial visit (T1), the patients were divided into the mild-MH (78°≤SNA < 80°, n = 8), moderate-MH (76≤SNA < 78°, n = 7), and severe-MH (SNA < 76°, n = 13) groups. T1-age and Tx-Mods, including cal-varial surgery (CALS), orthopedic treatment (OPT), fixed orthodontic treatment, and midface advancement surgery in childhood (MAS-child) and adulthood (MAS-adult), were investigated. Complexity of MAS-adult was graded as follows: 0, no surgery; 1, orthognathic surgery; 2, distraction osteogenesis (DOG); 3, combination of distraction osteogenesis and orthognathic surgery. Then, statistical analysis was performed. Percentage distribution of Tx-Mods was 71.4% in CALS, 21.4% in MAS-child, 42.9% in OPT, 100% in fixed orthodontic treatment, and 89.3% in MAS-adult. 92.9% of patients underwent MAS more than once. The number of MAS increased according to the severity of MH ( P < 0.05). The complexity of MAS-adult increased as T1-age and severity of MH increased (all P < 0.05); whereas it decreased when CALS and OPT were performed (all P < 0.05). However, MAS in childhood did not guarantee the avoidance of additional MAS in adulthood ( P > 0.05). These findings may be used as basic guidelines for successful treatment planning and prognosis prediction in patients with SC.

A study on team bisimulation and H-team bisimulation for BPP nets

A subclass of finite Petri nets, called BPP nets (acronym of Basic Parallel Processes), was recently equipped with an efficiently decidable, truly concurrent, bisimulation-based, behavioral equivalence, called team bisimilarity. This equivalence is a very intuitive extension of classic bisimulation equivalence (over labeled transition systems) to BPP nets and it is checked in a distributed manner. This paper has three goals. First of all, we provide BPP nets with various causality-based observational semantics, notably a novel semantics, called causal-net bisimilarity. Then, we define a variant semantics, called h-team bisimilarity, coarser than team bisimilarity, for which we adapt the modal logic characterization and the axiomatization of team bisimilarity. Then, we complete the study about team bisimilarity and h-team bisimilarity, by comparing them with the causality-based semantics we have introduced: the main results are that team bisimilarity coincides with causal-net bisimilarity, while h-team bisimilarity with fully-concurrent bisimilarity.

Modal Characterization of Sandwich Skew Plates

Abstract The current work focuses on the experimental and finite element free vibration studies of laminated composite sandwich skew plates. The comparison was made between the experimental values obtained by the Fast Fourier transform (FFT) analyzer and a finite element solution obtained from CQUAD8 finite element of The MacNeal-Schwendler Corporation (MSC) / NASA STRucture Analysis (NASTRAN) software. The influence of parameters such as aspect ratio (AR) (a/b), skew angle (α), edge condition, laminate stacking sequence, and fiber orientation angle (θ°) on the natural frequencies of sandwich skew plates was studied. The values obtained by both the finite element and experiment approaches are in good agreement. The natural frequencies increase with an increase in the skew angle for all given ARs.

Dosimetric Evaluation in Micro-CT Studies Used in Preclinical Molecular Imaging

In microCT imaging, there is a close relationship between the dose of radiation absorbed by animals and the image quality, or spatial resolution. Although the radiation levels used in these systems are generally non-lethal, they can induce cellular or molecular alterations that affect the experimental results. Here, we describe a dosimetric characterization of the different image acquisition modalities used by the microCT unit of the Albira microPET/SPECT/CT scanner, which is a widely used multimodal imaging system in preclinical research. The imparted dose at the animal surface (IDS) was estimated based on Boone’s polynomial interpolation method and experimental measurements using an ionization chamber and thermoluminescent dosimeters. The results indicated that the imparted dose at surface level delivered to the mice was in the 30 to 300 mGy range. For any combination of current (0.2 or 0.4 mA) and voltage (35 or 45 kV), in the Standard, Good, and Best image acquisition modalities, the dose imparted at surface level in rodents was below its threshold of deterministic effects (250 mGy); however, the High Res modality was above that threshold.

Characterization of Phenotypes and Treatment Modalities in Patients With Treacher-Collins Syndrome.

The purpose of this study was to investigate the phenotypes and treatment modalities (Tx-Mod) in patients with Treacher-Collins syndrome (TCS) using a TCS severity index (TSI). The sample consisted of 14 Korean TCS patients treated at the Department of Orthodontics, Seoul National University Dental Hospital during 1998 to 2019. The TSI was calculated by adding the scores from the number of deformity-involved midface structures (eye, ear, zygoma) and the degree of mandibular hypoplasia (Pruzansky-Kaban type, gonial angle, Sella-Nasion-B point angle). The deformity-involved midface structure, degree of mandibular hypoplasia, oral manifestations, dental phenotypes, and Tx-Mod types were investigated using descriptive statistics. The TSI classified the subjects into 2 mild, 6 moderate, and 6 severe cases. The severity of ear and zygoma deformities, degree of condylar hypoplasia (Pruzansky-Kaban type), clockwise-rotated morphology (gonial angle) and retrusive position (Sella-Nasion-B point angle) of the mandible, and frequency of oral/craniofacial cleft, openbite, congenitally missing tooth and impacted tooth showed a tendency of increase from mild to severe TCS cases. After growth observation (78.6%), diverse combinations of Tx-Mods were applied except for functional appliance therapy. Surgical procedures for eye, ear, and zygoma reconstruction were performed on all patients (100%), whereas fixed orthodontic treatment, mandibular distraction osteogenesis, and orthognathic surgery were performed on 50% of patients. Surgical procedure for hearing improvement was the most frequent Tx-Mod (78.6%). The main desires of TCS patients were to obtain the facial esthetics in the midface and to improve hearing function. The TSI might provide a primary data for individualized diagnosis and treatment planning.

Analytical characterization of DNA and RNA oligonucleotides by hydrophilic interaction liquid chromatography-tandem mass spectrometry

Liquid chromatography-mass spectrometry has been widely implemented as a powerful tool for providing in-depth characterization of nucleic acid therapeutic modalities, such as anti-sense oligonucleotides and small interfering RNAs (siRNAs). In this study, we developed a generic hydrophilic interaction liquid chromatography (HILIC) hyphenated with tandem mass spectrometry method in the absence of ion-pairing reagents and demonstrated its capability as an attractive and robust alternative for oligonucleotide and siRNA analysis. HILIC separation of mixtures of unmodified and fully phosphorothioate-modified DNA oligonucleotides and their synthetic 3’ exonuclease-digested metabolites were also assessed. High-resolution mass spectrometric (HRMS) analysis was used to determine the deconvoluted masses of oligonucleotide and siRNA standards and their impurities. To enable unbiased sequence characterization with tandem mass spectrometry (MS/MS), we also optimized higher-energy C-trap dissociation (HCD) on improving the sequence coverage of DNA and RNA oligonucleotides. Lastly, we evaluated on-column sensitivity for a phosphorothioate oligonucleotide by performing targeted analysis with either targeted selected ion monitoring (tSIM) or parallel reaction monitoring (PRM). Higher on-column sensitivity of 13 ng, equivalent to 2.0 pmol, of a phosphorothioate oligonucleotide was achieved by tSIM analysis as compared to PRM analysis.

Multilevel capillary gel electrophoresis characterization of new antibody modalities

Capillary gel electrophoresis-based methods were applied to comprehensively characterize two development phase new modality monoclonal antibodies including a glycoengineered and a bispecific test compound. The samples were subjected to multilevel characterization at the intact (both by SDS-SGE and cIEF) as well as the reduced protein and the released N-glycan levels. SDS capillary gel electrophoresis analysis showed excellent separation of the light and heavy chains of both samples. The bispecific antibody required a special temperature gradient denaturation process and a longer capillary to resolve its two light chain fragments. Separation of PNGase F digested antibodies revealed migration time shifts, suggesting the presence of N-linked glycosylation on the corresponding subunits. For efficient glycan removal, the highly glycosylated glycoengineered monoclonal antibody was trypsin digested prior to the endoglycosidase treatment. The released glycans were profiled by capillary gel electrophoresis after APTS labeling and their oligosaccharide structures were identified by exoglycosidase based carbohydrate sequencing. Finally, capillary isoelectric focusing shed light on the charge heterogeneity of the test compounds, providing important complementary information. A flowchart was established for workflow optimization.

Characterization of the Signaling Modalities of Prostaglandin E2 Receptors EP2 and EP4 Reveals Crosstalk and a Role for Microtubules.

Prostaglandin E2 (PGE2) is a lipid mediator that modulates the function of myeloid immune cells such as macrophages and dendritic cells (DCs) through the activation of the G protein-coupled receptors EP2 and EP4. While both EP2 and EP4 signaling leads to an elevation of intracellular cyclic adenosine monophosphate (cAMP) levels through the stimulating Gαs protein, EP4 also couples to the inhibitory Gαi protein to decrease the production of cAMP. The receptor-specific contributions to downstream immune modulatory functions are still poorly defined. Here, we employed quantitative imaging methods to characterize the early EP2 and EP4 signaling events in myeloid cells and their contribution to the dissolution of adhesion structures called podosomes, which is a first and essential step in DC maturation. We first show that podosome loss in DCs is primarily mediated by EP4. Next, we demonstrate that EP2 and EP4 signaling leads to distinct cAMP production profiles, with EP4 inducing a transient cAMP response and EP2 inducing a sustained cAMP response only at high PGE2 levels. We further find that simultaneous EP2 and EP4 stimulation attenuates cAMP production, suggesting a reciprocal control of EP2 and EP4 signaling. Finally, we demonstrate that efficient signaling of both EP2 and EP4 relies on an intact microtubule network. Together, these results enhance our understanding of early EP2 and EP4 signaling in myeloid cells. Considering that modulation of PGE2 signaling is regarded as an important therapeutic possibility in anti-tumor immunotherapy, our findings may facilitate the development of efficient and specific immune modulators of PGE2 receptors.