Pulse Amplitude Research Articles

PAR2 Participates in the Development of Cough Hypersensitivity in Guinea Pigs by Regulating TRPA1 Through PKC

Objective: This study was conducted to validate the involvement of the PAR2-PKC-TRPA1 pathway in cough hypersensitivity (CHS) development. Methods: Guinea pigs were divided into a blank control, a citric acid-induced enhanced cough model, and drug intervention groups. The effects of the drugs on capsaicin-induced cough responsiveness in a cough model were observed. The effects of individual and combined treatments (including PAR2 agonists, TRPA1 agonists, PAR2 antagonists, TRPA1 antagonists, PKC agonists, and PKC antagonists) on PAR2, phospho-PKC (pPKC), and TRPA1 expression in bronchial tissues and the vagus ganglion (jugular and nodose) in the cough model and control groups were assessed. Additionally, whole-cell patch-clamp recordings were conducted to evaluate the effects of the drugs on vagus ganglion neuron electrophysiological activity. Results: ① Both PAR2 antagonists and TRPA1 antagonists significantly reduced cough frequency in guinea pigs with a cough, and the PAR2 antagonist inhibited coughing induced by the TRPA1 agonist. ② Western blotting and multiplex immunohistochemistry (mIHC) indicated that PAR2, pPKCα, PKCα, and TRPA1 expression in bronchial and vagus ganglion tissues was elevated in the cough model compared with the control, with TRPA1 expression being regulated by PAR2 and PKC being involved in this regulatory process. ③ Whole-cell patch-clamp recordings demonstrated that TRPA1 agonists induced an inward current in nodose ganglion neurons, which was further amplified by PAR2 agonists; this amplification effect was blocked by PKC antagonist. Additionally, PAR2 antagonists inhibited the inward current induced by TRPA1 agonists. ④ At various concentrations, including the optimal antitussive concentration, PAR2 antagonists did not significantly affect pulse amplitude, arterial oxygen saturation, heart rate, body temperature, or respiratory rate in guinea pigs. Conclusion: PAR2 regulates TRPA1 through PKC in cough syndrome (CHS) pathogenesis, making targeting PAR2 a safe and effective therapeutic strategy for CHS.

NO3--N pulse supply caused by biodegradable plastics exacerbates Trifolium repens L. invasion.

The exacerbation of plant invasion by microplastics attracted widespread attention. Pulse resource hypothesis is popular theory to elucidate plant invasion. Our previous work demonstrated biodegradable microplastics (BMPs) could increase the arbuscular mycorrhizal fungi (AMF) colonization rate. Reportedly, AMF can enhance rhizobia colonization. Therefore, we infer the coexistence of BMPs with legumes may lead to an increased colonization of rhizobia with negative feedback regulation of N fixation. This could result in NO3--N pulse supply, thereby exacerbating plant invasion. Subsequently, a 60-day pot experiment was conducted using Trifolium repens L. as invasive plant and Oxalis corniculata L. as native plant, with 1% or 5% wt BMPs. AMF colonization, BMPs degradation, NO3--N content and pulse supply, rhizobia colonization, relative competitive intensity, replacement diagrams and NO3--N utilization were determined. The mechanism was clarified through heat map and structural equation model. The results reveal the greater the NO3--N consumption by BMPs, the more AMF promoted rhizobia colonization in T. repens, thereby the larger the pulse amplitude of NO3--N supply, then, the higher the NO3--N utilization rate of T. repens. It exacerbates T. repens invasion. This study clarifies effects of BMPs on rhizobia's N fixation, and enriches the evidence on mechanism of BMPs exacerbating plant invasion.

Harmful effects of the semiconductor copper tungstate (CuWO4) on multiple photosynthetic parameters of the green microalga Raphidocelis subcapitata.

The semiconductor copper tungstate (CuWO4) may end up in aquatic ecosystems since it has the potential for water decontamination. The toxic effects of CuWO4 are totally unknown for eukaryotic organisms. In view of this, we aimed to evaluate the toxicity of CuWO4 particles (size of 161.5 nm) on the cosmopolitan green microalga Raphidocelis subcapitata (a standardized test-organism for ecotoxicological assays), analyzing the growth and multiple photosynthetic parameters obtained by pulse amplitude modulated (PAM) fluorometry. At 1.2 mg l-1, the growth was affected, and there was an increase in reactive oxygen species (ROS) after 72 h The effective efficiency (ɸM') of photosystem II (PSII) was affected at 13.1 mg l-1, while the efficiency of the oxygen-evolving complex (OEC), responsible for the water-splitting process, decayed at 5.6 mg l-1. According to quenching parameters, energy allocated to photosynthetic processes (qP) decreased, indicating a malfunctioning of the PSII. We also observed a 50 % increase in the non-regulated energy dissipation by heat and fluorescence (Y(NO)), and a 50 % decrease in the regulated energy dissipation (NPQ), suggesting difficulties for algae to cope with light. Rapid light curves (RLC) were the second most sensitive parameter, as we observed a decay of the relative maximum electron transport rate (rETRmax) at 2.8 mg l-1. Therefore, since the microalga R. subcapitata was affected by concentrations up to 1.2 mg l-1 (0.01 mg l-1 dissolved Cu), it is important to evaluate carefully the use of CuWO4 to decontaminate natural waters, considering the protection of the aquatic biota.

Numerical simulation of surface charge accumulation under negative discharge of different humidities and pressures

The surface discharge phenomenon of polymers severely limits their applications in electrical and electronic devices, especially in complex environments. In this study, a drift-diffusion model based on a hydrodynamic approach was developed to investigate the influence of humidity and gas pressure on the negative surface discharge. The results indicate that the discharge pattern did not change under different humidity conditions. The increased humidity accelerated the formation of discharges and increased the discharge pulse current. In particular, as the humidity increased, tiny pulses occurred at the tail of the first pulse, and the number of tiny pulses increased. The appearance of these tiny pulses changed the surface charge distribution from a “ring-like” distribution to a “spot-like” distribution. Meanwhile, the accumulation of surface charges significantly distorted the spatial electric field distribution and suppressed the electron multiplication stage of the subsequent discharges, thus reducing the current in the Trichel pulse discharge stage. It is precisely because the discharge is stronger under high humidity, resulting in more surface charges accumulating on the surface, which is in keeping with the experimental results. The measured charges at different humidities show a similar distinct spot-like distribution, illustrating a constant pattern of discharge. All these results demonstrated the correctness and applicability of the simulation. The surface discharge under different pressures exhibited some similarities with the case of different humidity levels. As the pressure increased, the number of discharge current pulses and the pulse amplitude decreased, resulting in a decrease in the surface charge density.

Energy‐Efficient Online Training with In Situ Parallel Computing on Electrochemical Memory Arrays

The rapid development of deep learning enables significant breakthroughs for intelligent edge‐terminal devices. However, neural network training for edge computing is currently overly dependent on cloud service platforms, resulting in low adaptivity for fast‐changing real‐world environments. The training energy efficiency is also strictly constrained by the traditional Von‐Neumann architecture with separate memory and processing units. To improve the adaptability and energy efficiency of edge‐terminal devices, a fully parallel online neural network training scheme based on electrochemical random‐access memory (ECRAM) arrays is proposed and validated. By exploiting the intrinsic linearity and nonlinearity functionalities of ECRAMs brought by varying numbers and amplitudes of programming pulses, a physical implementation of in situ multiplication using pulse‐based training is achieved, realizing fully parallel in situ computation and storage of outer product between two vectors. It can not only greatly accelerate the computation of weight gradients in neural network training but also significantly reduce the time complexity, latency, and energy overheads associated with data handling compared to traditional hardware implementations for this task. The ECRAM‐based online training system reduces the energy overhead of the training process by 30× when compared to the same training process executed on traditional computing hardware.

A NiAl-layered double hydroxides memristor with artificial synapse function and its Boolean logic applications.

In the era of artificial intelligence, there has been a rise in novel computing methods due to the increased demand for rapid and effective data processing. It is of great significance to develop memristor devices capable of emulating the computational neural network of the brain, especially in the realm of artificial intelligence applications. In this work, a memristor based on NiAl-layered double hydroxides is presented with excellent electrical performance, including analog resistive conversion characteristics and the effect of multi-level conductivity modulation. In addition, the device's conductance can be continuously adjusted by varying pulse width, interval, and amplitude. The successful replication of synaptic features has been achieved. In order to implement the functions of "NOT," "AND," and "OR," a logic gate is constructed using two synaptic devices. The confirmation of the potential use of synaptic devices in brain-like computing was demonstrated. In addition, it demonstrates the potential of these devices in supporting computing models beyond von Neumann architecture.

Humic substances modulate bacterial communities and mitigate adverse effects of temperature stress in coral reef organisms.

In the present study, we tested if terrestrially-derived humic substances (HS) could mitigate the adverse effects of elevated temperature and UVB radiation on the bacterial communities of two hard corals (Montipora digitata and Montipora capricornis), one soft coral (Sarcophyton glaucum), sediment and water. We also examined the impact of temperature, UVB radiation and HS supplementation on coral photosynthetic activity, a proxy for coral bleaching. We performed a multifactorial experiment using a randomized-controlled microcosm setup. Coral photosynthetic efficiency was measured in vivo using a pulse amplitude modulation (PAM) fluorometer. Bacterial communities were analyzed using 16s rRNA gene sequencing. Corals in HS-supplemented microcosms had significantly higher photosynthetic activities than those in microcosms subjected to elevated temperature and UVB radiation. Additionally, HS supplementation significantly influenced the composition of sediment, water and host-associated bacterial communities. Reef organisms in HS supplemented microcosms contained distinct bacterial communities enriched with groups of potentially beneficial bacteria. In the hard coral Montipora digitata, we observed an interactive effect of HS supplementation, UVB radiation, and temperature. Our findings indicate that HS significantly modulates coral reef bacterial communities and support the hypothesis that these substances contribute to improved reef resistance to the adverse effects of elevated temperature and UVB radiation.

Online Pulse Compensation for Energy Spectrum Determination: A Pole-Zero Cancellation and Unfolding Approach

Signal conditioning circuits, in particle energy spectrum determination systems, introduce shaping characteristics that affect pulse integrity. This study explores algorithms to compensate for these effects, focusing on digital signal processing for pole-zero cancellation (PZC) and unfolding techniques. The PZC algorithm successfully corrects baseline shift and pulse amplitude loss, providing significant improvements in signal fidelity. Although a digital PZC applied in streaming for high event rates was previously not feasible, this work proposes its implementation on FPGA, combining it with the unfolding method to enable online compensation and enhanced performance under various experimental conditions.

Optical semantic communication through multimode fiber: from symbol transmission to sentiment analysis

We propose and validate a novel optical semantic transmission scheme using multimode fiber (MMF). By leveraging the frequency sensitivity of intermodal dispersion in MMFs, we achieve high-dimensional semantic encoding and decoding in the frequency domain. Our system maps symbols to 128 distinct frequencies spaced at 600 kHz intervals, demonstrating a seven-fold increase in capacity compared to conventional communication encoding. We further enhance spectral efficiency by implementing 4-level pulse amplitude modulation (PAM-4), achieving 9.12 bits/s/Hz without decoding errors. Additionally, we explore the application of this system for sentiment analysis using the IMDb movie review dataset. By encoding semantically similar symbols to adjacent frequencies, the system’s noise tolerance is effectively improved, facilitating accurate sentiment analysis. This work highlights the potential of MMF-based semantic communication to enhance both capacity and robustness in optical communication systems, offering promising applications in bandwidth-constrained and noisy environments.

Characterization of RAP Signal Patterns, Temporal Relationships, and Artifact Profiles Derived from Intracranial Pressure Sensors in Acute Traumatic Neural Injury.

Current methodologies for assessing cerebral compliance using pressure sensor technologies are prone to errors and issues with inter- and intra-observer consistency. RAP, a metric for measuring intracranial compensatory reserve (and therefore compliance), holds promise. It is derived using the moving correlation between intracranial pressure (ICP) and the pulse amplitude of ICP (AMP). RAP remains largely unexplored in cases of moderate to severe acute traumatic neural injury (also known as traumatic brain injury (TBI)). The goal of this work is to explore the general description of (a) RAP signal patterns and behaviors derived from ICP pressure transducers, (b) temporal statistical relationships, and (c) the characterization of the artifact profile. Different summary and statistical measurements were used to describe RAP's pattern and behaviors, along with performing sub-group analyses. The autoregressive integrated moving average (ARIMA) model was employed to outline the time-series structure of RAP across different temporal resolutions using the autoregressive (p-order) and moving average orders (q-order). After leveraging the time-series structure of RAP, similar methods were applied to ICP and AMP for comparison with RAP. Finally, key features were identified to distinguish artifacts in RAP. This might involve leveraging ICP/AMP signals and statistical structures. The mean and time spent within the RAP threshold ranges ([0.4, 1], (0, 0.4), and [-1, 0]) indicate that RAP exhibited high positive values, suggesting an impaired compensatory reserve in TBI patients. The median optimal ARIMA model for each resolution and each signal was determined. Autocorrelative function (ACF) and partial ACF (PACF) plots of residuals verified the adequacy of these median optimal ARIMA models. The median of residuals indicates that ARIMA performed better with the higher-resolution data. To identify artifacts, (a) ICP q-order, AMP p-order, and RAP p-order and q-order, (b) residuals of ICP, AMP, and RAP, and (c) cross-correlation between residuals of RAP and AMP proved to be useful at the minute-by-minute resolution, whereas, for the 10-min-by-10-min data resolution, only the q-order of the optimal ARIMA model of ICP and AMP served as a distinguishing factor. RAP signals derived from ICP pressure sensor technology displayed reproducible behaviors across this population of TBI patients. ARIMA modeling at the higher resolution provided comparatively strong accuracy, and key features were identified leveraging these models that could identify RAP artifacts. Further research is needed to enhance artifact management and broaden applicability across varied datasets.

Vibration Suppression based on Improved Adaptive Optimal Arbitrary-Time-Delay Input Shaping

Abstract Vibration suppression is important for high-precision motion control because positioning accuracy is an essential figure of merit for a servo system. The paper presents a vibration-suppression method that is based on adaptive optimal arbitrary-time-delay (AOAT) input shaping. First, analyzing a conventional optimal-arbitrary-time-delay (OAT) input shaper yields an OAT input shaper with five pulses that completely suppresses two-mode vibrations when the natural frequency and damping ratio are exactly known. Next, embedding an adaptive algorithm in the shaper gives an AOAT that handles unknown natural frequencies and damping ratios. Note that this shaper contains five pulses that have to be updated, but the delay times of the pulses are prescribed. Then, extending the symmetry of pulse amplitudes for zero damping ratio to a nonzero case reduces the number of pulses to three. A recursive-least-squares algorithm is devised to update these parameters. This shaper features the smallest number of parameters and high robust performance. Finally, comparisons with other input-shaping methods show the effectiveness and superiority of the developed method over others.

Numerical simulation and parametric optimization of harmonic pulse water flooding technology

Pulse water injection technology is an emerging enhanced oil recovery method that improves oil-water interface and flow characteristics by periodically varying the injection rate. This study, using the TOUGH2 simulator, examines the impact of different pulse injection waveforms (sine, triangle, and square) on the recovery factor in medium to low-permeability carbonate reservoirs. It highlights that pulse water injection outperforms constant rate injection, with the triangle waveform yielding the best recovery rates. Through controlled simulations, findings indicate that increasing pulse injection time and amplitude enhances recovery and water flow. However, frequency variations in ultra-low frequency pulses have minimal effects on recovery. Additionally, the efficiency of pulse water injection is inversely related to reservoir porosity and permeability, while higher oil viscosity significantly boosts recovery efficiency. Conversely, increasing water temperature reduces dynamic viscosity, affecting the oil-water interface lag and decreasing overall displacement efficiency. The study also notes significant differences between heterogeneous and homogeneous reservoir models, emphasizing the need for future large-scale numerical modeling to consider reservoir heterogeneity. These findings provide valuable insights for optimizing pulse water injection in medium to low-permeability reservoirs, supporting practical oil field development strategies.

Plasma Humanin and Non-Coding RNAs as Biomarkers of Endothelial Dysfunction in Rheumatoid Arthritis: A Pilot Study

Background: Rheumatoid arthritis (RA) is a chronic autoimmune disorder associated with an increased risk of cardiovascular disease (CVD), largely driven by peripheral endothelial dysfunction (ED). Humanin, a mitochondrial-derived peptide, has been suggested to play a protective role in endothelial function. However, the relationship between Humanin levels and ED in RA, as well as the interaction between Humanin and non-coding RNAs such as Long Non-Coding RNA GAS5, microRNA-21 (miR-21), and microRNA-103 (miR-103), remains unclear. Objective: This study aimed to investigate the relationship between circulating Humanin levels, non-coding RNAs (GAS5, miR-21, miR-103), and endothelial dysfunction (ED) in patients with RA. Additionally, we explored the correlation between Humanin expression and specific non-coding RNAs (GAS5, miR-21, and miR-103) to better understand their potential role in vascular health. Methods: Peripheral ED was assessed using flow-mediated pulse amplitude tonometry, with Ln-RHI values <0.51 indicating dysfunction. Humanin levels, GAS5, miR-21, and miR-103 were measured in RA patients. Univariate and multivariate analyses were conducted to determine the relationship between these biomarkers and ED. Kaplan–Meier survival analysis and ROC curve analysis were used to assess the prognostic value of Humanin. Results: Higher Humanin levels were significantly associated with better endothelial function (OR = 0.9774, p = 0.0196). Kaplan–Meier analysis demonstrated that higher Humanin levels correlated with improved survival (p < 0.0001). The non-coding RNAs (GAS5, miR-21, and miR-103) did not show significant associations with ED. Conclusions: Humanin is a potential protective biomarker for endothelial dysfunction and survival in RA patients. Further research is needed to explore the interaction between Humanin and non-coding RNAs in the context of vascular health.

Fast Hadamard-Encoded 7T Spectroscopic Imaging of Human Brain.

Background/Objectives: The increased SNR available at 7T combined with fast readout trajectories enables accelerated spectroscopic imaging acquisitions for clinical applications. In this report, we evaluate the performance of a Hadamard slice encoding strategy with a 2D rosette trajectory for multi-slice fast spectroscopic imaging at 7T. Methods: Moderate-TE (~40 ms) spin echo and J-refocused polarization transfer sequences were acquired with simultaneous Hadamard multi-slice excitations and rosette in-plane encoding. The moderate spin echo sequence, which targets singlet compounds (i.e., N-acetyl aspartate, creatine, and choline), uses cascaded multi-slice RF excitation pulses to minimize the chemical shift dispersion error. The J-refocused sequence targets coupled spin systems (i.e., glutamate and myo-inositol) using simultaneous multi-slice excitation to maintain the same TE across all slices. A modified Hadamard slice encoding strategy was used to decrease the peak RF pulse amplitude of the simultaneous multi-slice excitation pulse for the J-refocused acquisition. Results: The accuracy of multi-slice and single-slice rosette spectroscopic imaging (RSI) is comparable to conventional Cartesian-encoded spectroscopic imaging (CSI). Spectral analyses for the J-refocused studies of glutamate and myo-inositol show that the Cramer Rao lower bounds are not significantly different between the fast RSI and conventional CSI studies. Linear regressions of creatine/N-acetyl aspartate and glutamate/N-acetyl aspartate with tissue gray matter content are consistent with literature values. Conclusions: With minimal gradient demands and fast acquisition times, the 2.2 min to 9 min for single- to four-slice RSI acquisitions are well tolerated by healthy subjects and tumor patients, and show results that are consistent with clinical outcomes.

Design of spike-timing-dependent plasticity synapses based on CoPt-SOT device and its application in all-spin spiking neural network

Spintronic could be used to simulate synapses or neurons due to its multistate storage characteristics. In this work, a reliable design of all-spin spiking neural networks (SNN) based on spin–orbit torque (SOT) devices has been proposed in A1 CoPt single layer. The CoPt-SOT devices exhibited field-free SOT switching, and the magnetization reversal mechanism was inferred to be a combination of domain nucleation and domain-wall propagation as observed through magneto-optical Kerr microscopy images. Moreover, the current-induced SOT switching process of the device exhibited stable multistate magnetic switching behavior, which can be controlled by varying the amplitude and pulse width of the current pulse. Meanwhile, the spike-timing-dependent plasticity (STDP) curve was inverted when the SOT switching polarity was reversed by different magnetic fields, and the change in anomalous Hall resistances (ΔRH) in the STDP curve was linearly related to the SOT switching ratio. In addition, at the zero magnetic field, we constructed an all-spin SNN using STDP synapses and leaky integrate-and-fire neurons of CoPt-SOT devices. The handwritten digits recognition rate of this all-spin SNN network was 89.9%. These results substantiate that the CoPt single layer represents a promising hardware solution for high-performance neuromorphic computing, with applicability in the domain of SNN.

A 1 kV sub-nanosecond electrical pulse generated by a linear GaAs photoconductive semiconductor switch and its characterization

A 1 kV sub-nanosecond electrical pulse generated by a linear GaAs photoconductive semiconductor switch and its characterization

A Self-Formed Ag Nanostructure Based Neuromorphic Device Performing Arithmetic Computation and Area Integration: Influence of Presynaptic Pulsing Scheme on Mathematical Precision.

A material equivalent of a biosynapse is the key to neuromorphic architecture. Here we report a self-forming labyrinthine Ag nanostructure activated with a few pulses of 0.5 V, width and interval set at 50 ms, at current compliance (ICC) of 400 nA, serving as the active material for a highly stable device with programmable volatility. Both the conductance (G) and its retention time (tr) in the potentiated state are found to vary linearly with the pulse number for pulses of positive and negative polarities, with the nonlinearity factors being noticeably small, ∼0.03 for G during potentiation and ∼0.08 during depression. This was tested for over 200 days, and the results were highly reproducible. Relying on the high linearity, arithmetic operations involving counting of positive and negative integers were realized using pulses of both polarities, often by mixing them in the feeding sequence. The observed outcomes based on G and independently from tr are highly accurate, with deviations being typically less than ∼1.5% from the expected results. Notably, the way the pulse polarities are mixed is found to have an influence, with random sequences producing relatively larger deviations in integer estimation. However, deviations decreased with higher ICC values, which promoted stronger filament formation in the percolation networks. Besides, the G and tr values were found to vary with the pulse amplitude as well, which enabled the calculation of the area under a curve. Further, the device exhibited a simulation-based image classification accuracy of 94.95%, close to the ideal value (96.05%). Simulations utilizing the finite element method have showcased the uniqueness of the labyrinthine morphology, giving rise to field intensification along potential percolative paths.

Multilevel voltage source inverter with coupled reactors using coarsely quantized pulse amplitude modulation

The paper discusses a multilevel voltage source inverter with coupled reactors (MVSI-CR). The output voltage is generated using the novel coarsely quantized pulse amplitude modulation (CQ-PAM). The AC voltage synthesis is realized by selecting and applying an appropriate collection of voltage vectors from the space-vector diagram. Integrating classical two-level inverters allows achieving modularity of the solution. The main advantage of the proposed approach is a very low switching-to-fundamental frequency ratio and a multistep quasisinusoidal output voltage. The paper includes a theoretical analysis, simulations, and laboratory test results.

Assessment of interfacial properties in a two-layered plate using quasi-static component generation during primary Lamb wave propagation.

This study delves into the feasibility of leveraging quasi-static component (QSC) generation during primary Lamb wave propagation to discern subtle alterations in the interfacial properties of a two-layered plate. Unlike the second-harmonic generation of Lamb waves, QSC generation doesn't necessitate precise phase-velocity matching but rather requires an approximate matching of group velocities to ensure the emergence of cumulative growth effects. This unique characteristic empowers the QSC-based nonlinear ultrasonic method to effectively surmount the limitations associated with inherent dispersion and multimode traits of Lamb wave propagation. Modeling the QSC generation reveals that the integrated amplitude of the QSC pulse, derived from the propagation of the primary Lamb wave tone burst, progressively amplifies with increasing propagation distance. Finite element simulations illustrate an overall decline in the efficiency of QSC generation amidst interfacial degradation. Experimental outcomes obtained via a nonlinear ultrasonic measurement-based setup vividly showcase the cumulative growth effect of QSC generation, evident with the propagation distance under approximate group velocity matching. To substantiate the influence of interfacial properties on QSC generation efficiency, varying thermal fatigue durations under cyclic temperature conditions are employed to simulate subtle changes in the two-layered plate's interfacial properties. The relative nonlinear acoustic parameter exhibits a distinctly sensitive and monotonically decreasing behavior with escalating thermal fatigue durations, corroborating the impact of alterations in interfacial properties on QSC generation efficiency. The alignment between experimental findings and numerical analysis predictions suggests that the effect of QSC generation in primary Lamb wave propagation provides a promising means for sensitively assessing the early-stage degradation of interfacial properties in layered plates.

Effects of collagen and chondroitin sulfate on relaxation at multiple magnetic field strengths.

To elucidate the connection between MRI relaxation properties of articular cartilage and tissue composition, in terms of collagen and chondroitin sulfate (CS). Additional aims were to determine the effect of different magnetic field strengths, as well as the effect of concentrations of the components on relaxation properties. A series of MRI phantoms consisting of gels containing collagen and chondroitin sulfate were prepared with final concentrations of collagen in the range 20-60 mg/g and the CS concentration in the range 0-40 mg/g. (= 1/ ) and (= 1/ ) values of the phantoms were measured at three different MRI field strengths (1.5, 3.0 and 9.4 T), (= 1/ ) values were measured at 9.4 T. Relaxation rates generally increased with increasing concentration of either of the compounds. values generally increased with CS, and at clinically used magnetic fields, namely 1.5 T and 3.0 T, with collagen concentration. At 9.4 T, values also showed an increase with collagen concentration that could not be clearly identified at lower field strengths. values increased with both collagen and CS concentration but the amplitude of the spin-lock pulse only had a limited effect on relaxation rates above 100 Hz. Our results suggest that , , and are modulated by collagen and CS concentrations, with collagen likely dominating at physiological concentrations.