High-amplitude Oscillations Research Articles

Study on reduction of pressure oscillation in low-velocity steam jet condensation

To mitigate the high-amplitude pressure oscillations generated during the steam low-speed jet condensation process and reduce the risk of dynamic load damage to the suppression pool and its adjacent facilities, this study designed a temperature-rising cylinder scheme based on the characteristics of low-speed steam jet condensation pressure oscillation and studied the mitigation effect of this scheme through experiments. The experimental results showed that this scheme could effectively reduce the time of low-velocity steam jet condensation in the high-amplitude pressure oscillation region. For instance, at a steam mass flow rate of 30 kg/m2s, the time was reduced from 6300 s to 700 s, which significantly improves the safety of the pool and nearby facilities. Moreover, the scheme does not affect the suppression ability of the pool and can ensure the long-term effective operation of the suppression system.

Theory of Magnetic Switchbacks Fully Supported by Parker Solar Probe Observations

Magnetic switchbacks are rapid high-amplitude reversals of the radial magnetic field in the solar wind that do not involve a heliospheric current sheet crossing. First seen sporadically in the 1970s in Mariner and Helios data, switchbacks were later observed by the Ulysses spacecraft beyond 1 au and have been recently discovered to be a typical component of solar wind fluctuations in the inner heliosphere by the Parker Solar Probe spacecraft. While switchbacks are now well understood to be spherically polarized Alfvén waves thanks to Parker Solar Probe observations, their formation has been an intriguing and unsolved puzzle. Here we provide a simple yet predictive theory for the formation of these magnetic reversals: the switchbacks are produced by the distortion and twisting of circularly polarized Alfvén waves by a transversely varying radial wave propagation velocity. We provide an analytic expression for the magnetic field variation, establish the necessary and sufficient conditions for the formation of switchbacks, and show that the proposed mechanism works in a realistic solar wind scenario. We also show that the theoretical predictions are in excellent agreement with observations, and the high-amplitude radial oscillations are strongly correlated with the shear of the wave propagation speed. The correlation coefficient is around 0.3–0.5 for both encounter 1 and encounter 12. The probability of this being a lucky coincidence is essentially zero with p-values below 0.1%.

Investigation of the wake flow and the oscillation process of two free-to-rotate tandem cylinders due to a flow disturbance

This paper presents an exploratory analysis of the oscillation process of a set of two circular cylinders (D = 25 mm) mounted with a fixed pitch-to-diameter ratio P/D = 1.26 and attached to a free-to-rotate circular table submitted to a turbulent crossflow in a wind tunnel. Measurements were performed with hot wire anemometers placed in the wake of the cylinders synchronized with a high-speed digital camera. Flow visualizations with static cylinders in a water channel were performed to investigate the wake formation around the cylinders. The analysis of the results was made through Fourier and wavelet transforms. The main objective is to address the observed phenomenon with its causing physical mechanism. Wind tunnel results showed that, depending on the imposed mean flow velocity, the set starts oscillating with a low steady amplitude. When the flow is disturbed, an increase in the oscillation amplitude is observed, remaining in this steady regime even after removing the disturbance. Although the interaction between the flow and cylinder set generates two stable states, the properties of the oscillation phenomena (frequency and amplitude) remained the same, pointing out an intrinsic property of the dynamical system. The vortex shedding is identified to be the primary mechanism responsible for initiating the small amplitude oscillation, while the flow passing through the gap between the cylinders is the cause of the high amplitude oscillation. The flow visualization corroborated the wake analysis described in the wind tunnel experiments. No evidence of coherence between the vortex shedding from the first cylinder and the oscillation process was identified. Considering the results in the present work, the configuration analyzed may work as a vortex-shedding suppressor.

Stochastic gene expression and environmental stressors trigger variable somite segmentation phenotypes

Mutations of several genes cause incomplete penetrance and variable expressivity of phenotypes, which are usually attributed to modifier genes or gene-environment interactions. Here, we show stochastic gene expression underlies the variability of somite segmentation defects in embryos mutant for segmentation clock genes her1 or her7. Phenotypic strength is further augmented by low temperature and hypoxia. By performing live imaging of the segmentation clock reporters, we further show that groups of cells with higher oscillation amplitudes successfully form somites while those with lower amplitudes fail to do so. In unfavorable environments, the number of cycles with high amplitude oscillations and the number of successful segmentations proportionally decrease. These results suggest that individual oscillation cycles stochastically fail to pass a threshold amplitude, resulting in segmentation defects in mutants. Our quantitative methodology is adaptable to investigate variable phenotypes of mutant genes in different tissues.

Loss ofDiel Circadian Clock Gene Cycling Is a Part ofGrape Berry Ripening.

Diel cycles of gene expression are thought to adapt plants to 24-h changes in environmental conditions. The circadian clock contributes to this process, but less is known about circadian programs in developing reproductive organs. While model plants and controlled conditions have contributed greatly to our knowledge of circadian clock function, there is a need to better understand its role in crop plants under field conditions with fluctuating light and temperature. In this study, we investigated changes in the circadian clock during the development of grape berries of Vitis vinifera L. We found that the transcripts of circadian clock homologs had high-amplitude oscillations prior to, but not during, ripening. As ripening progressed, the amplitude and rhythmicity of the diel oscillations decreased until most transcripts tested had no significant fluctuation over the 24-h cycle. Despite this loss of rhythmicity, the majority of circadian clock genes investigated were expressed at or near their abundance at the nadir of their pre-ripening oscillation although the berries remained transcriptionally active. From this, it can be concluded that cycling of the canonical circadian clock appears unnecessary for berry ripening. Our data suggest that changes in circadian clock dynamics during reproductive organ development may have important functional consequences.

Parametric resonance: a risk to be avoided or an opportunity to be exploited? A case for a 2:1 wave energy converter

Accurate models for wave energy converters are paramount for appropriate and effective assessment of the system behaviour under operational conditions; if such models are also computationally efficient, they can be used for control and design applications. Crucially, the underlying design and working principle can be substantially modified only at early development stages and typically based on fast mathematical models with several iterations; since such models are often linear or weakly-nonlinear, complex nonlinear phenomena are rarely embedded into holistic design tools or optimization schemes. A secondary consequence is that nonlinearities are dealt with at a later verification and assessment stage and are typically a burden or an issue to limit. The aim of this paper is to highlight how nonlinearities can actually be a beneficial resource to be exploited and leveraged, rather than a bother. To do so, a computationally efficient nonlinear model is used, able to articulate relevant phenomena at a convenient computational time. The system under analysis is a prismatic floating wave energy converter and the nonlinear model implements an analytical formulation of Froude-Krylov forces computed on the instantaneous wetted surface; this modelling approach is able to articulate a 2:1 parametric resonance which, when activated under certain conditions, is a type of instability able to amplify the amplitude of motion. Note that the 2:1 proportionality refers to the ratio between wave and natural frequencies of the system. Therefore, this paper embeds parametric resonance into the notional design of a wave energy converter purposely designed to experience and take advantage of such an instability. Results are promising, since a substantial amplification is achieved in the 2:1 region, whereas similar or higher oscillation amplitude is obtained in the 1:1 region.

Phase change-driven photoacoustic oscillations induced by periodic irradiation

The photo-acoustic effect is a well-documented phenomenon in which the periodic irradiation of an absorbing media produces an acoustic wave, modulated by thermal expansion. However, little is known about the effect imparted by phase change on this mode of energy conversion, nor has it been considered as a potential method of power production. Herein, we report high-amplitude photo-acoustic oscillations, of up to 145 dB, induced upon irradiation of a water film on the wall of an acoustic loop resonator. While the driving power is quite low (∼4 W), the photo-acoustic oscillations are shown to be significantly amplified by the introduction of phase change in the acoustic cycle. A reduced-order model is formulated and is able to recover key characteristics of the acoustic oscillations, in reasonable agreement with experimental results, and confirms the underlying mechanism of pressure modulation by the phase change. The results presented here can potentially pave the way to improved, solar-driven acoustic energy conversion devices.

Delayed sedimentary response of the Huanghe alluvial plain to climate change inferred from source variations of the Xiashu loess since ∼1 Ma

Large river systems are reactive or buffered to large climate oscillations on orbital timescales, depending on whether their sedimentary response time is shorter or longer than the period of these climate oscillations. Estimating the sedimentary response time of large river systems is essential for understanding their sensitivity to climate change and their corresponding ability to reshape themselves, but few studies have estimated the sedimentary response time of real large river systems by geologic records. Provenance analysis of the Xiashu loess in China since ∼1 Ma provides the opportunity to estimate the sedimentary response time of the adjacent Huanghe (Yellow River). Here, we conducted the first provenance analysis of such a Xiashu loess section, using measured data of element contents, Nd isotopes, and grain-size compositions. The results reveal changes in loess provenance at ∼0.3 Ma and ∼0.07 Ma. The provenance changes were caused by the expansion of the Huanghe alluvial plain at ∼0.3 Ma and its contraction at ∼0.07 Ma. The expansion and contraction can be attributed to the delayed sedimentary response of the Huanghe alluvial plain to the Mid-Pleistocene Transition and the Mid-Brunhes Transition, respectively. Therefore, the sedimentary response time of the Huanghe alluvial plain is estimated to be ∼0.4 Ma, which is much longer than the duration of the high-amplitude Quaternary climate oscillations on orbital timescales. Our findings support that the Huanghe and similar large rivers are buffered to these climate oscillations. The alluvial plains of the Huanghe and similar rivers may play a key role in delaying and reducing the impacts of future climate change on the land surface.

Transcrustal magma plumbing process in the Cenozoic Dali potassic lamprophyre dyke formation in the southeastern Tibet Plateau

(Ultra-)potassic lamprophyres are volumetrically rare, but are widely distributed in diverse geological settings and extensively applied to trace the mantle source and melting processes. However, it is still debatable whether the lamprophyre formation involved transcrustal magmatic processes. In this study, we describe the diverse zoning patterns and textures of clinopyroxene (Cpx) from a Cenozoic potassic lamprophyre dyke in southeastern Tibet Plateau. Three types of Cpx macrocrysts with normal- and reverse oscillatory zoning and sieved textures, and Cpx microcrysts from Cpx–Phl nodules are recognized. The Cpx macrocrysts have highly variable Mg# (62–89) and chemical compositions. Their oscillatory-zoned mantle has alternating coarse layers or closely-packed layers, with distinct resorption surface shown in backscattered electron (BSE) images. High-amplitude oscillation of Mg# (±5 to ±12), Al, Cr and Sr at the boundary layers of mantle may reflect multiple magma mixing/recharge events. In contrast, low-amplitude and high-frequency oscillation of Mg# (varying from < ±3) across the closely-packed layers could be attributed to local magma mixing or kinetic effect at the crystal-melt interface. The sieved domains occur in the Cpx macrocrystic core with spongy space and linking the external groundmass by cracks, and have major and minor compositions and 87Sr/86Sr ratios similar to those of the rims. This indicates that the sieved domains are probably originated from dissolution of the Cpx macrocrysts by groundmass melt and later reprecipitation. The estimated pressure and temperature for the Cpx macrocryst high-Mg# cores and low Mg# rims are 580–1160 MPa (avg. 919 MPa) and 30–1270 MPa (avg. 681 MPa), and 1116–1266 °C (avg. 1216 °C) and 955–1215 °C (avg. 1110 °C), respectively, suggesting polybaric differentiation or Cpx-saturated magmas. The estimated pressure and temperature for the reverse-zoned Cpx marcocryst cores are 450–1310 MPa (avg. 953 MPa) and 1097–1209 °C (avg. 1166 °C), respectively, indicating that they are likely formed in equilibrium with a more evolved magma batch, and then were entrapped by more primitive mantle-derived potassic magmas during magma upwelling. The La/Yb and Dy/Yb modelling of equilibrium melts suggest that magmas of the Cpx–Phl nodules and their lamprophyre host were derived from similar mantle sources. Therefore, the complex zoning patterns and compositions of Cpx macrocrysts could indicate transcrustal magmatic processes in the potassic lamprophyre dyke formation.

Dynamic responses of a conceptual two-dimensional airfoil in hypersonic flows with random perturbations

This paper investigates a conceptual pitch–plunge airfoil in hypersonic flows with both structural and aerodynamic nonlinearity, meanwhile the effects of irregular fluctuations in the flow and external random loads modeled as a Gaussian white noise are considered. The dynamic responses of the airfoil model especially the bifurcation behaviors are analyzed via the harmonic balance method for the deterministic case. We found the airfoil system undergo both subcritical and supercritical Hopf bifurcations. Subsequently, the effects of stochasticity on the dynamical behaviors of the hypersonic airfoil system are explored in the regimes of subcritical and supercritical Hopf bifurcations depending on the system parameters. Several interesting phenomena are triggered under random perturbations such as intermittency and stochastic transition between the low-amplitude oscillation state and the undesirable high-amplitude oscillation state. These dynamics are further characterized via the probability density function and time history. This work will provide new insights into the safety and reliability design of hypersonic aircraft.

Benthic Foraminiferal Response to the Aptian−Albian Carbon Cycle Perturbation in the Atlantic Ocean

Abstract A planktic foraminiferal mass extinction, coeval with the major carbon cycle perturbation of Oceanic Anoxic Event (OAE) 1b, occurred at the Aptian−Albian boundary interval (AABI). However, the scarcity of high-resolution records across the AABI hampers an assessment of the impacts of OAE 1b on deep-water benthic foraminiferal assemblages. Here we present high-resolution benthic foraminiferal census counts at Deep Sea Drilling Project (DSDP) Site 511 (southern South Atlantic Ocean) and Ocean Drilling Program (ODP) Site 1049 (western subtropical North Atlantic Ocean) over the AABI. Our records at these bathyal sites provide conclusive evidence that there was no benthic foraminiferal extinction at the Aptian−Albian boundary, although marked reorganizations of relative abundances occurred. During the latest Aptian, cyclic increases in the abundance of infaunal species at both sites point to repeated pulses of reduced bottom water oxygenation and increased organic carbon flux to the ocean floor. Additionally, agglutinated and weakly calcified benthic foraminiferal species were relatively abundant during the latest Aptian, suggesting deep-water carbonate ion depletion in the Atlantic Ocean, although we did not identify signs of carbonate dissolution at these relatively shallow sites. At Site 511, abundances of infaunal foraminifera increased in tandem with the negative carbonate carbon isotope (δ13Ccarb) excursion of the Kilian sub-event within OAE 1b, suggesting decreased bottom water ventilation and increased organic carbon flux to the ocean floor during the sub-event. Bottom water ventilation and carbonate ion saturation improved during the earliest Albian in the Atlantic Ocean, followed by high-amplitude oscillations, as suggested by abundance trends of heavily calcified epifaunal foraminifera at Sites 511 and 1049.

Lock-on to quasi-periodic flow transformation for a rotationally oscillating cylinder due to gust impulse

A computational study is conducted to analyze the effects of an upstream gust impulse on lock-on flow of a cylinder, which is rotationally oscillating. Reynold numbers of 100, 110, and 120 and three discrete oscillation conditions based on rotational oscillation amplitudes are considered. The current solution scheme is validated for the cases of stationary and rotationally oscillating cylinders in a uniform flow. The oscillation Strouhal forcing frequency is varied with a resolution of 0.0001 for lock-on to quasi-periodic flow boundary identification. Flows are categorized as either lock-on or quasi-periodic based on frequency analysis of lift. Furthermore, three different gust impulses for each Reynolds number are selected by associating gust Strouhal frequency to natural shedding Strouhal frequency, whereas the Prandtl number is 7. These gust impulses were introduced in lock-on flow near lock-on to quasi-periodic flow boundary. Analysis of lift, drag, and vorticity contours confirms that the lock-on flow is transformed into quasi-periodic flow in conditions of high oscillation amplitude and low gust frequency. This transformation is observed to persist for four descending values of rotational oscillation Strouhal forcing frequency at the upper lock-on boundary.

Multilayer network analysis to study complex inter-subsystem interactions in a turbulent thermoacoustic system

Thermoacoustic systems are complex systems where the interactions between the hydrodynamic, acoustic and heat release rate fluctuations lead to diverse dynamics such as chaos, intermittency and ordered dynamics. Such complex interactions cause catastrophically high-amplitude acoustic pressure oscillations and the emergence of order in the spatiotemporal dynamics, referred to as thermoacoustic instability. In this work, we use multilayer networks to study the spatial pattern of inter-subsystem interactions between the vorticity dynamics and thermoacoustic power generated due to acoustically coupled combustion in a bluff-body-stabilised turbulent dump combustor. We construct a two-layered network where the layers represent the thermoacoustic power and vorticity fields. The inter-layer links are determined using cross-variable short-window correlations between vorticity and thermoacoustic power fluctuations at any two locations in the flow field. Analysing the topology of inter-layer networks, using network properties such as degree correlations and link-rank distributions, helps us infer the spatial inhomogeneities in inter-subsystem interactions and unravel the fluid mechanical processes involved during different dynamical states. We show that, during chaotic dynamics, interactions between subsystems are non-localised and spread throughout the flow field of the combustor. During the state of thermoacoustic instability (order), we find that intense interactions occur in between regions of coherent vortex shedding and thermoacoustic power generation and we understand that these processes are strongly and locally coupled. Moreover, we discover that such dense inter-layer connections emerge in spatial pockets in the dump plane of the combustor during the state of intermittency much prior to the onset of order.

No evidence for the effect of entrainment's phase on duration reproduction and precision of regular intervals.

Perception of time is not always veridical; rather, it is subjected to distortions. One such compelling distortion is that the duration of regularly spaced intervals is often overestimated. One account suggests that excitatory phases of neural entrainment concomitant with such stimuli play a major role. However, assessing the correlation between the power of entrained oscillations and time dilation has yielded inconclusive results. In this study, we evaluated whether phase characteristics of neural oscillations impact time dilation. For this purpose, we entrained 10-Hz oscillations and experimentally manipulated the presentation of flickers so that they were presented either in-phase or out-of-phase relative to the established rhythm. Simultaneous electroencephalography (EEG) recordings confirmed that in-phase and out-of-phase flickers had landed on different inhibitory phases of high-amplitude alpha oscillations. Moreover, to control for confounding factors of expectancy and masking, we created two additional conditions. Results, supplemented by the Bayesian analysis, indicated that the phase of entrained visual alpha oscillation does not differentially affect flicker-induced time dilation. Repeating the same experiment with regularly spaced auditory stimuli replicated the null findings. Moreover, we found a robust enhancement of precision for the reproduction of flickers relative to static stimuli that were partially supported by entrainment models. We discussed our results within the framework of neural oscillations and time-perception models, suggesting that inhibitory cycles of visual alpha may have little relevance to the overestimation of regularly spaced intervals. Moreover, based on our findings, we proposed that temporal oscillators, assumed in entrainment models, may act independently of excitatory phases in the brain's lower level sensory areas.

Functional network dynamics between the anterior thalamus and the cortex in deep brain stimulation for epilepsy.

Due to its unique connectivity profile with cortical brain regions, and its suggested role in the subcortical propagation of seizures, the Anterior Nucleus of the Thalamus (ANT) has been proposed as a key Deep Brain Stimulation (DBS) target in drug-resistant epilepsy (DRE). However, the spatio-temporal interaction dynamics of this brain structure, and the functional mechanisms underlying ANT DBS in epilepsy, remain unknown. Here, we study how the ANT interacts with the neocortex in vivo in humans and provide a detailed neurofunctional characterization of mechanisms underlying the effectiveness of ANT DBS, aiming at defining intraoperative neural biomarkers of responsiveness to therapy, assessed at 6 months post-implantation as the reduction in seizure frequency. A cohort of 15 DRE (N = 6 males, age = ) patients underwent bilateral ANT DBS implantation. Using intraoperative cortical and ANT simultaneous electrophysiological recordings, we found that the ANT is characterized by high amplitude (4-8 Hz) oscillations, mostly in its superior part. The strongest functional connectivity between the ANT and the scalp EEG was also found in the band in ipsilateral centro-frontal regions. Upon intraoperative stimulation in the ANT, we found a decrease in higher EEG frequencies (20-70 Hz) and a generalized increase in scalp-to-scalp connectivity. Crucially, we observed that responders to ANT DBS treatment were characterized by higher EEG oscillations, higher power in the ANT, and stronger ANT-to-scalp θ connectivity, highlighting the crucial role of oscillations in the dynamical network characterization of these structures. Our study provides a comprehensive characterization of the interaction dynamic between the ANT and the cortex, delivering crucial information to optimize and predict clinical DBS response in patients with DRE.

Experimental Firing Test Campaign and Nozzle Heat Transfer Reconstruction in a 200 N Hybrid Rocket Engine with Different Paraffin-Based Fuel Grain Lengths

Firing test campaigns were carried out on a 200 N thrust-class hybrid rocket engine, using gaseous oxygen as an oxidizer and a paraffin-wax-based fuel. Different fuel grain lengths were adopted to extend the fuel characterization under different operating conditions, and to evaluate rocket performances and internal ballistics in the different configurations. In addition to data collected under a 220 mm propellant grain length, two further test campaigns were carried out considering 130 mm and 70 mm grain lengths. Two different injector types were adopted in the 130 mm configuration; in particular, a showerhead injection system was used with the aim to contain high-amplitude pressure oscillations observed during some firing tests in this engine configuration. Parameters such as the chamber pressure and temperature inside the graphite nozzle, space-averaged fuel regression rate and nozzle throat diameter were measured. The results allowed for the investigation of different issues related to hybrid rockets (e.g., fuel regression rate, engine performance, nozzle ablation under different conditions). The focus was mainly directed to the nozzle heat transfer, through the reconstruction of the convective heat transfer coefficient for different tests in the 70 mm grain length engine configuration. The reconstruction took advantage of the experimental data provided by the nozzle embedded thermocouple. Then, the experimental convective heat transfer coefficient was used to validate the results from some empirical correlations. The results showed significant differences between the experimental convective heat transfer coefficients when considering tests with different oxidizer mass flow rates. Furthermore, the predictions from the empirical correlations proved to be more reliable only in cases characterized by oxidizer-rich conditions.

An artificially-damped Fourier method for dispersive evolution equations

Computing solutions to partial differential equations using the fast Fourier transform can lead to unwanted oscillatory behavior. Due to the periodic nature of the discrete Fourier transform, waves that leave the computational domain on one side reappear on the other and for dispersive equations these are typically high-velocity, high-frequency waves. However, the fast Fourier transform is a very efficient numerical tool and it is important to find a way to damp these oscillations so that this transform can still be used. In this paper, we accurately model solutions to four nonlinear partial differential equations on an infinite domain by considering a finite interval and implementing two damping methods outside of that interval: one that solves the heat equation and one that simulates rapid exponential decay. Heat equation-based damping is best suited for small-amplitude, high-frequency oscillations while exponential decay is used to damp traveling waves and high-amplitude oscillations. We demonstrate significant improvements in the runtime of well-studied numerical methods when adding in the damping method.

Study on the Oscillating Phenomenon of Welding Pool with Different Penetration States in Short-Circuiting GMAW

The oscillating phenomenon of the weld pool has a direct physical correspondence with its penetration state, which has broad application prospects in the monitoring of weld penetration states. This article studied the characteristics of the oscillating phenomenon of the weld pool in short-circuiting gas metal arc welding (S-GMAW) with different penetration states based on a welding high-speed photography system. The results show that the form of the liquid bridge electric explosion impact on the weld pool is “surface impact” in S-GMAW. The oscillation frequency of the weld pool decreases as the size of the weld pool increases. Compared with the partially penetrated weld pool, the boundary conditions of the fully penetrated weld pool had different boundary conditions, resulting in higher oscillation amplitude and lower oscillation frequency. In S-GMAW, no difference in welding voltage signal, caused by the difference in amplitude of the weld pool oscillation with different penetration states, was observed.

PD23-03 IMPAIRED NITRIC OXIDE MECHANISMS UNDERLYING LOWER URINARY TRACT DYSFUNCTION IN AGING RATS

You have accessJournal of UrologyCME1 Apr 2023PD23-03 IMPAIRED NITRIC OXIDE MECHANISMS UNDERLYING LOWER URINARY TRACT DYSFUNCTION IN AGING RATS Daisuke Gotoh, Kenta Onishi, Yosuke Morizawa, Shunta Hori, Yasushi Nakai, Makito Miyake, Kazumasa Torimoto, Fujimoto Kiyohide, and Naoki Yoshimura Daisuke GotohDaisuke Gotoh More articles by this author , Kenta OnishiKenta Onishi More articles by this author , Yosuke MorizawaYosuke Morizawa More articles by this author , Shunta HoriShunta Hori More articles by this author , Yasushi NakaiYasushi Nakai More articles by this author , Makito MiyakeMakito Miyake More articles by this author , Kazumasa TorimotoKazumasa Torimoto More articles by this author , Fujimoto KiyohideFujimoto Kiyohide More articles by this author , and Naoki YoshimuraNaoki Yoshimura More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003296.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Nitric oxide (NO) promotes the intracellular production of cyclic guanosine monophosphate (cGMP) in smooth muscles, reduces the intracellular calcium concentration, and enhances smooth muscle relaxation. However, it remains unknown whether changes in the expression of NO-related molecules are associated with the development of lower urinary tract dysfunction (LUTD) with age. Therefore, we examined changes in bladder and urethral activities, and in NO-related molecule expression using aging rats. METHODS: Fourteen Female Sprague–Dawley rats were divided into two age groups: (A) young rats (12 weeks old, n=8) and (B) aging rats (15 months old, n=6). In both groups, 24 h voiding assay was performed, and the urodynamic parameters were evaluated using cystometry (CMG) and urethral perfusion pressure (UPP) recordings. mRNA expression levels of NO-, ischemia-, and inflammation-related markers in bladder and urethra tissues were assessed, and the cGMP level in the urethra was measured. RESULTS: There was no significant difference in the 24-h voiding assay results between the groups. In CMG, the number of non-voiding contractions (NVCs) per voiding cycle and post-void residual (PVR) were significantly higher, and voiding efficiency (VE) was significantly lower in Group B than in Group A (Figure 1A, B). In the UPP recordings, urethral pressure (UP) reduction and high frequency oscillation (HFO) amplitudes were both significantly lower in Group B than in Group A (Figure 1C, D). In molecular studies, mRNA expression levels of HIF-1α, VEGF, and TGF-β1 in the bladder were significantly higher in Group B than in Group A (Figure 2A). mRNA expression levels of NOS1 and PKG were significantly lower in Group B than in Group A (Figure 2B). In addition, the concentration of cGMP in the urethra was significantly lower in Group B than in Group A (Figure 2C). CONCLUSIONS: Aging rats would be a useful model for the study of the natural progression of age-related LUTD, for which impaired NO-mediated transmitter function is likely to be an important mechanism. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e671 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Daisuke Gotoh More articles by this author Kenta Onishi More articles by this author Yosuke Morizawa More articles by this author Shunta Hori More articles by this author Yasushi Nakai More articles by this author Makito Miyake More articles by this author Kazumasa Torimoto More articles by this author Fujimoto Kiyohide More articles by this author Naoki Yoshimura More articles by this author Expand All Advertisement PDF downloadLoading ...

Unusual nonlinear switching in branched carbon nanotube nanocomposites

In this experimental study, we investigate the nonlinear dynamic response of nanocomposite beams composed of polybutylene terephthalate (PBT) and branched carbon nanotubes (bCNTs). By varying the weight fraction of bCNTs, we obtain frequency response curves for cantilever specimens under harmonic base excitations, measuring the tip displacement via 3D scanning laser vibrometry. Our findings reveal a surprising nonlinear softening trend in the steady-state response of the cantilevers, which gets switched into hardening for higher bCNT weight fractions and increasing oscillation amplitudes. The interaction of bCNTs with the thermoplastic hosting matrix results in stick-slip hysteresis, causing a softening nonlinearity that counteracts the geometric hardening associated with the nonlinear curvature of the first mode of the cantilever. However, when the weight fraction of bCNTs is greater than 1%, the bridging of the branched CNTs leads to the formation of a strong network that contributes to the hardening response at higher oscillation amplitudes. This mechanical behavior is detected by the trend of the nonlinear harmonic spectra and the equivalent damping ratio estimated using the half-power bandwidth method. To predict the observed unusual experimental behavior, we use a nonlinear mathematical model of the nanocomposite cantilever samples derived from a 3D mesoscale hysteretic model of the PBT/bCNT material. Our results suggest that the presence of bCNTs in a thermoplastic matrix is the main driver of the highly tunable nonlinear stiffness and damping capacity of the material. The reported experimental and modeling results provide valuable insights into the nonlinear dynamic behavior of PBT/bCNT nanocomposites and have potential applications in the design of advanced materials with tailored mechanical properties.