Dynamic Resonance Research Articles

Balanced GHM Mutiwavelet Transform based Contrast Enhancement Technique for Dark Images using Dynamic Stochastic Resonance

Balanced GHM Mutiwavelet Transform based Contrast Enhancement Technique for Dark Images using Dynamic Stochastic Resonance

Dynamic Resonance of Adjacent Twin Flickering (Non-premixed) Flames

Dynamic Resonance of Adjacent Twin Flickering (Non-premixed) Flames

Distribution of water in the pores of periodic mesoporous organosilicates - a proton solid state MAS NMR study.

Solid state proton (1H) magic angle spinning (MAS) NMR has been employed to study the distribution of confined water in ethane substituted periodic mesoporous organosilicate (PMOE) materials. Proton spectra acquired at different hydration levels are analysed and interpreted in terms of water clusters of various sizes and distributions of water layers on the pore surface. For comparison, we also performed similar experiments on SBA-15. The formation of larger clusters at lower hydration suggests that the pores of PMOE are getting filled with water at lower hydration levels than those in SBA-15. For PMOE, the simultaneous presence of two major resonances in the ranges 3.6-4.1 ppm and 4.4-5.2 ppm and their behaviour upon hydration imply a water layer distribution that is the sum of two contributions, corresponding to fully filled and partially filled pores or pore segments. Furthermore, the behaviour mentioned above suggests that both radial and axial filling mechanisms play a significant role in the hydration process. For SBA-15, as a function of hydration, we observed a smooth variation in the proton chemical shift of the main dynamic resonance. In accordance with previous studies, this is attributed to the gradual increase in the average thickness of water layers with an increase in hydration, and to a pore filling mechanism that is predominantly radial.

Apparent diffusion coefficient map based radiomics model in differentiating benign from malignant entity in breast imaging-reporting and data system 4 breast lesions

Objective To investigate the diagnostic values of radiomics model based on ADC map in differentiating benign from malignant lesions in suspicious breast findings with MRI breast imaging reporting and data system (BI-RADS) category 4. Methods Eighty eight patients (36 benign and 52 malignant) with diagnosis of MRI BI-RADS 4 in our hospital from December 2014 to December 2015 were retrospectively enrolled in this study. All the patients were proved by pathology and examined by sequence of T1WI, T2WI, DWI and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), and then were further sub-categorized into BI-RADS 4A, BI-RADS 4B, or BI-RADS 4C based on DCE-MRI sequence. Thus positive predictive value (PPV) of each sub-category were calculated and ROC were used to describe its efficiency in differential diagnosis. Radiomics features based on ADC map were generated automatically from Analysis-Kinetics (GE Healthcare). Sixty three of the 88 cases randomized-selected by computer were used to establish forecasting models and other 25 cases for validation. Kruskal-Wallis test and Spearman were introduced to reduce radiomics features that were highly correlated with others. Logistic linear regression (LLR) model was constructed based on the selected features by 'glm’ function in R software and then verified by 10-fold cross validation (repeat 10 times). ROC was curved to determine the diagnostic accuracy of the model. Results The PPV of BI-RADS 4A,4B,4C were 16.7% (2/12) ,59.6% (28/47) ,75.9% (22/29) respectively. Area under curve (AUC) of ROC was 0.650, sensitivity and specificity were 76.9% and 45.9% respectively. Three hundred and ninety six radiomics features were extracted automatically by software and 5 features (size zone variability, difference entropy, zone percentage, intensity variability and inverse difference moment) were left after redundancy reduction step. Cross-validation showed the accuracy of Logistic regression model was 80.0% (20/25), AUC was 0.790, sensitivity and specificity were 81.3% and 77.8% when cut-off was 0.45. Conclusion The radiomics model could provide important reference for differentiation between benign and malignant lesions in suspicious BI-RADS 4 findings. Key words: Breast neoplasms; Magnetic resonance imaging; Radiomics

Assessing the influence of isoflurane anesthesia on cardiac metabolism using hyperpolarized [1-13 C]pyruvate.

Isoflurane is a frequently used anesthetic in small-animal dissolution dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) studies. Although the literature suggests interactions with mitochondrial metabolism, the influence of the compound on cardiac metabolism has not been assessed systematically to date. In the present study, the impact of low versus high isoflurane concentration was examined in a crossover experiment in healthy rats. The results revealed that cardiac metabolism is modulated by isoflurane concentration, showing increased [1-13 C]lactate and reduced [13 C]bicarbonate production during high isoflurane relative to low isoflurane dose [average differences: +16% [1-13 C]lactate/total myocardial carbon, -22% [13 C]bicarbonate/total myocardial carbon; +51% [1-13 C]lactate/[13 C]bicarbonate]. These findings emphasize that reproducible anesthesia is important when studying cardiac metabolism. As the depth of anesthesia is difficult to control in an experimental animal setting, careful study design is required to exclude confounding factors.

In vivo redox metabolic imaging of mitochondria assesses disease progression in non-alcoholic steatohepatitis

Given the rising incidence of non-alcoholic fatty liver disease (NAFLD) in both adults and children, the development of a non-invasive diagnostic method for assessing disease progression to non-alcoholic steatohepatitis (NASH) has become an important research goal. Currently available non-invasive imaging technologies are only able to assess fat accumulation in the liver. Therefore, these methods are not suitable for a precise diagnosis of NASH. The standard diagnostic technique for NASH, liver biopsy, has several drawbacks, including the higher risk of complications that accompanies invasive procedures. Here, we demonstrated that in vivo mitochondrial redox metabolism was dramatically altered at an early stage, before histopathological changes, and NASH could be accurately diagnosed by in vivo dynamic nuclear polarization-magnetic resonance imaging, with carbamoyl-PROXYL as a molecular imaging probe. In addition, this technique was feasible for the diagnosis of NASH compared with histopathological findings from biopsies. Our data reveal a novel method for monitoring the dynamics of redox metabolic changes in NAFLD/NASH.

Mechanical Design Considerations of an “Ironless,” High-Specific-Power Electric Machine

This paper describes the mechanical design considerations for a 1 MW, 14 000 rpm motor which achieves a specific power of at least 13 kW/kg. This is enabled through an “ironless,” inside out, Halbach array permanent magnet, high frequency, and airgap or slotless configuration. The “ironless” design creates mechanical challenges because thin radial builds which reduce weight also typically reduce structural stability and vibrational damping. Structural deformation challenges include radial expansion and static bending. Vibrational issues include stator resonance mode excitation as well as rotor dynamic resonance excitation. The mechanical challenges were studied with analytical calculations and high-fidelity finite-element analysis. These analyses drove design refinements to mitigate these challenges. The rotor has then been tested to verify these analysis results.

In-depth study of intra-Stark spectroscopy in the x-ray range in relativistic laser–plasma interactions

Intra-Stark spectroscopy (ISS) is the spectroscopy within the quasistatic Stark profile of a spectral line. The present paper advances the ISS-based study of the relativistic laser–plasma interaction from our previous paper (Oks et al 2017 Opt. Express 25 1958). By improving the experimental conditions and the diagnostics, it provides an in-depth spectroscopic study of the simultaneous production of the Langmuir waves and of the ion acoustic turbulence at the surface of the relativistic critical density. It demonstrates a reliable reproducibility of the Langmuir-wave-induced dips at the same locations in the experimental profiles of Si XIV Ly-beta line, as well as of the deduced parameters (fields) of the Langmuir waves and ion acoustic turbulence in several individual 1 ps laser pulses and of the peak irradiances of 1–3 × 1020 W cm−2. Besides, this study employs for the first time the most rigorous condition of the dynamic resonance, on which the ISS phenomenon is based, compared to all previous studies in all kinds of plasmas in a wide range of electron densities. It shows how different interplays between the Langmuir wave field and the field of the ion acoustic turbulence lead to distinct spectral line profiles, including the disappearance of the Langmuir-wave-induced dips.

Evaluation of shear piezoelectric coefficient d15 of piezoelectric ceramics by using piezoelectric cantilever beam in dynamic resonance

ABSTRACTA novel method for characterization on the shear piezoelectric coefficient of piezoelectric ceramics was proposed. A shear-mode piezoelectric cantilever with coplanar electrode structure was fabricated via arranging two PZT-51 elements poled opposite in series connection, and a principle model based on Timoshenko beam theory was proposed to establish the relationship between peak-to-peak output voltage and frequency. The measured values are in good agreement with the results simulated by finite element method (FEM) with maximum relative error less than 4.5%. It is reliable and convenient for the proposed method to characterize the shear piezoelectric coefficient of piezoelectric ceramics.

Numerical and experimental analysis of a vibration isolator equipped with a negative stiffness system

This paper presents a Negative Stiffness System (NSS) based on a set of two double–acting pneumatic linear actuators (PLA). The NSS is added to a system with a single degree of freedom, which consists of a sprung mass and a pneumatic spring. One end of each PLA is jointed to the sprung mass while the other end is jointed to the vibrating frame. In addition, the PLAs are symmetrically arranged so that they remain horizontal while the sprung mass is in static conditions. When the rear chamber is pressurised, the vertical component of the force applied by the PLAs will work against the pneumatic spring reducing the dynamic resonance frequency of the overall system. Experimental tests and simulations showed improvements regarding sprung mass isolation in comparison to the passive system without NSS, decreasing the resonance frequency by up to 58% and improving the vibration attenuation for different experimental excitations.

MCTDH study on the reactive scattering of the Cl + HD reaction based on the neural-networks potential energy surface

To study the dynamics resonances of the Cl + HD reaction which was proposed to proceed via abstraction mechanism with no clear resonances, we perform dynamics calculations by the multiconfiguration time-dependent Hartree (MCTDH) method based on recently developed neural-networks potential energy surface (Science347 (2015), 60). The HD molecule in v=0 (GS), v=1 (EX1), v=2 (EX2), and v=3 (EX3) states is used for the reactant. For GS, no distinctive resonance peak is found, while for EX1 two distinctive peaks at kinetics energies of 0.11 and 0.17 eV are investigated. These resonance peaks are well consistent with the previous results (Science347 (2015), 60). Moreover, the present MCTDH calculations predict well-marked resonance peaks at 0.04,0.05,0.07, and 0.10 eV for EX2 and EX3, which indicates that anticipation of the chemical bond softening model (Science327 (2010), 1501) is confirmed in this work.

Mechanism-Based and Input-Output Modeling of the Key Neuronal Connections and Signal Transformations in the CA3-CA1 Regions of the Hippocampus.

This letter examines the results of input-output (nonparametric) modeling based on the analysis of data generated by a mechanism-based (parametric) model of CA3-CA1 neuronal connections in the hippocampus. The motivation is to obtain biological insight into the interpretation of such input-output (Volterra-equivalent) models estimated from synthetic data. The insights obtained may be subsequently used to interpretat input-output models extracted from actual experimental data. Specifically, we found that a simplified parametric model may serve as a useful tool to study the signal transformations in the hippocampal CA3-CA1 regions. Input-output modeling of model-based synthetic data show that GABAergic interneurons are responsible for regulating neuronal excitation, controlling the precision of spike timing, and maintaining network oscillations, in a manner consistent with previous studies. The input-output model obtained from real data exhibits intriguing similarities with its synthetic-data counterpart, demonstrating the importance of a dynamic resonance in the system/model response around 2 Hz to 3 Hz. Using the input-output model from real data as a guide, we may be able to amend the parametric model by incorporating more mechanisms in order to yield better-matching input-output model. The approach we present can also be applied to the study of other neural systems and pathways.

Growth-Induced In-Plane Uniaxial Anisotropy in V2O3/Ni Films

We report on a strain-induced and temperature dependent uniaxial anisotropy in V2O3/Ni hybrid thin films, manifested through the interfacial strain and sample microstructure, and its consequences on the angular dependent magnetization reversal. X-ray diffraction and reciprocal space maps identify the in-plane crystalline axes of the V2O3; atomic force and scanning electron microscopy reveal oriented rips in the film microstructure. Quasi-static magnetometry and dynamic ferromagnetic resonance measurements identify a uniaxial magnetic easy axis along the rips. Comparison with films grown on sapphire without rips shows a combined contribution from strain and microstructure in the V2O3/Ni films. Magnetization reversal characteristics captured by angular-dependent first order reversal curve measurements indicate a strong domain wall pinning along the direction orthogonal to the rips, inducing an angular-dependent change in the reversal mechanism. The resultant anisotropy is tunable with temperature and is most pronounced at room temperature, which is beneficial for potential device applications.

Dynamic resonance and social reciprocity in language change: the case of Good morrow

Entrenchment (i.e. Langacker, 1987) does not necessarily lead to predictable behaviour. This study aims at complementing the usage-based model of language change by operationalising the role of dialogic creativity as a mechanism that can be in competition with conventionalization and grammaticalization. We provide a distinctive collexeme analysis (i.e. Hilpert, 2006) focussing on the constructionalization of the dialogic pair [A: good morrow B B: (good) morrow (A)] from the 15th up to the 18th century. After reaching the highest degree of entrenchment and automatisation, the dialogic pair will show an increasing tendency to be creatively re-modelled with ad-hoc meanings during online exchanges by means of dynamic resonance (Du Bois, 2014) and non-reciprocal behaviour. We define this creative process of large-scale alteration as entrenchment inhibition. From our data it will emerge that entrenchment inhibition is triggered by spontaneous attempts of producing a creative ‘surplus’ over the expected social reciprocity (Gouldner, 1960) of conventionalized exchanges. This tendency will be shown to be driven by marked attempts of polite and impolite behaviour.

Dynamic performance analysis of solar organic Rankine cycle with thermal energy storage

This paper discusses the dynamic performance in a small-scale solar organic Rankine cycle (SORC) with thermal energy storage (TES) considering solar disturbance. A dynamic model of SORC is developed. The factor FSR (Fluctuation Suppression Ratio) is defined to reflect the effect of TES on suppressing the dynamic impact. The dynamics of the SORC are found to contain resonance characteristics. With the interaction between solar disturbances and system thermal inertia (mainly determined by TES capacity), the energy superposition could cause dynamic resonance. In order to study the dynamic performance of the SORC, the influence factor including TES capacity, solar fluctuation (period, amplitude, average solar) and evaporation temperature were analysed, while FSR and the total system efficiency were the indicators which represent the system stability and performance respectively. The simulation result shows that within a certain solar period, there is a specific TES capacity range leading to resonance. The proper TES capacity should be selected according to local solar fluctuations to effectively suppress dynamic impact in the initial design phase.

Excitation device for high frequency vibration analysis: Design and test results

In the present paper, the design and optimization of a high frequency excitation source is presented. The device was developed for a harmonic response analysis test bench, aimed at dynamic characterization and resonance prediction of mechanical structures. A wide frequency range must be covered, depending on the analyzed structure: the range 1–10 kHz was considered in the present work. The device was designed for a test bench aimed at investigating the vibrational response of centrifugal compressor bladed wheels. A really compact solution was needed since the final test bench provides one exciter for each blade (up to 20 devices on the circumference hoop). Both contact and contactless solutions were considered, but only the contact solution was found to fulfill all the specifications. Finally, different stinger solutions were proposed and compared in the paper. The investigated solutions were: a beam stinger (diameter 1 mm); a wire stinger (diameter 0.2 mm); and a ball stinger (diameter 3 mm) with two different support solutions. Experimental tests performed on a device prototype allowed to verify the specifications fulfillment and to choose the best stinger solution for the application.

Chronologic Evaluation of Cerebral Hemodynamics by Dynamic Susceptibility Contrast Magnetic Resonance Imaging After Indirect Bypass Surgery for Moyamoya Disease.

Although indirect bypass surgery is an effective treatment option for patients with ischemic-onset moyamoya disease (MMD), the time point after surgery at which the patient's hemodynamic status starts to improve and the time point at which the improvement reaches a maximum have not been known. The objective of the present study is to evaluate the hemodynamic status time course after indirect bypass surgery for MMD, using dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI). We retrospectively analyzed the cases of 25 patients with MMD (37 sides; mean age, 14.7 years; range, 3-36 years) who underwent indirect bypass surgery and repeated DSC-MRI measurement within 6 months after the operation. The difference in the mean transit time (MTT) between the target regions and the control region (cerebellum) was termed the MTT delay, and we measured the MTT delay's chronologic changes after surgery. The postoperative MTT delay was 1.81 ± 1.16 seconds within 1 week after surgery, 1.57 ± 1.01 at weeks 1-2, 1.55 ± 0.68 at weeks 2-4, 1.32 ± 0.68 at months 1-2, 0.95 ± 0.32 at months 2-3, and 0.77 ± 0.33 at months 3-6. Compared with the preoperative value (2.11 ± 0.98 seconds), the MTT delay decreased significantly from 2 to 4 weeks after surgery (P < 0.05). The amelioration of cerebral hemodynamics by indirect bypass surgery began soon after surgery and gradually reached a maximum at 3 months after surgery. DSC-MRI detected small changes in hemodynamic improvement, which are suspected to be caused by the initiation of angiogenesis and arteriogenesis in the early postoperative period.

Pseudo-extravasation rate constant of dynamic susceptibility contrast-MRI determined from pharmacokinetic first principles.

Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected. Several approaches to correct this leakage effect have been proposed throughout the years. Amongst the most popular is the Boxerman-Schmainda-Weisskoff (BSW) K2 leakage correction approach, in which the K2 pseudo-first-order rate constant quantifies the leakage. In this work, we propose a new method for the BSW leakage correction approach. Based on the pharmacokinetic interpretation of the data, the commonly adopted R2 * expression accounting for contributions from both intravascular and extravasating CR components is transformed using a method mathematically similar to Gjedde-Patlak linearization. Then, the leakage rate constant (KL ) can be determined as the slope of the linear portion of a plot of the transformed data. Using the DSC data of high-molecular-weight (~750kDa), iron-based, intravascular Ferumoxytol (FeO), the pharmacokinetic interpretation of the new paradigm is empirically validated. The primary objective of this work is to empirically demonstrate that a linear portion often exists in the graph of the transformed data. This linear portion provides a clear definition of the Gd CR pseudo-leakage rate constant, which equals the slope derived from the linear segment. A secondary objective is to demonstrate that transformed points from the initial transient period during the CR wash-in often deviate from the linear trend of the linearized graph. The inclusion of these points will have a negative impact on the accuracy of the leakage rate constant, and even make it time dependent.

A semi-analytical approach towards plane wave analysis of local resonance metamaterials using a multiscale enriched continuum description

This work presents a novel multiscale semi-analytical technique for the acoustic plane wave analysis of (negative) dynamic mass density type local resonance metamaterials with complex micro-structural geometry. A two step solution strategy is adopted, in which the unit cell problem at the micro-scale is solved once numerically, whereas the macro-scale problem is solved using an analytical plane wave expansion. The macro-scale description uses an enriched continuum model described by a compact set of differential equations, in which the constitutive material parameters are obtained via homogenization of the discretized reduced order model of the unit cell. The approach presented here aims to simplify the analysis and characterization of the effective macro-scale acoustic dispersion properties and performance of local resonance metamaterials, with rich micro-dynamics resulting from complex metamaterial designs. First, the dispersion eigenvalue problem is obtained, which accurately captures the low frequency behavior including the local resonance bandgaps. Second, a modified transfer matrix method based on the enriched continuum is introduced for performing macro-scale acoustic transmission analyses on local resonance metamaterials. The results obtained at each step are illustrated using representative case studies and validated against direct numerical simulations. The methodology establishes the required scale bridging in multiscale modeling for dispersion and transmission analyses, enabling rapid design and prototyping of local resonance metamaterials.

Transport of Liposome Encapsulated Drugs in Voxelized Computational Model of Human Brain Tumors.

There are many obstacles in the transport of chemotherapeutic drugs to tumor cells that lead to irregular and non-uniform uptake of drugs inside tumors. The study of these transport problems will help with accurate prediction of drug transport and optimizing treatment strategy. To this end, liposome mediated drug delivery has emerged as an excellent anticancer therapy due to its ability to deliver drugs at site of action and reducing the chances of side effects to the healthy tissues. In this paper, a computational fluid dynamics (CFD) model based on realistic vasculature of human brain tumor is presented. This model utilizes dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) data to account for heterogeneity in tumor vasculature. Porosity of the interstitial space inside the tumor and normal tissue is determined voxel-wise by processing the DCE-MRI images by general tracer kinetic model (GTKM). The CFD model is applied to predict transport of two different types of liposomes (stealth and conventional) in tumors. The amount of accumulated liposomes is compared with accumulated free drug (doxorubicin) in the interstitial space. Simulation results indicate that stealth liposomes accumulate more and remain for longer periods of time in tumors as compared with conventional liposomes and free drug. The present model provides us a qualitative and quantitative examination on the transport and deposition of liposomes as well as free drugs in actual human brain tumors.