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Magnetic nanoparticles (MNPs) have been widely studied for bio-sensing applications, where suspended and immobilized MNPs can be magnetically distinguished using their different magnetic properties. We study magnetic properties of suspended and immobilized MNPs when the Néel relaxation time is much shorter than the Brownian. We show in both numerical simulation and experiment that they have different magnetic properties such as AC magnetization curves and harmonic spectra even though the dynamic behavior of both MNP types is primarily dominated by Néel relaxation. This difference is caused by the partial alignment of the easy axes in suspended MNPs when an AC magnetic field is applied. We introduce a distribution function for the angle of easy axis alignment. We also show a method to evaluate the distribution function from the measured AC magnetization curve and clarify the relationship between easy axis alignment and the AC field strength. Using the distribution function, we can quantitatively discuss the effect of easy axis alignment on the magnetic properties of suspended MNPs. The obtained results provide a basis for using MNPs in bio-sensing. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles (MNPs) have been widely studied for use in biomedical applications such as magnetic particle imaging and magnetic hyperthermia. We studied the effect of easy axis alignment on dynamic magnetization of both immobilized and suspended MNPs. For immobilized samples, easy axes of magnetization were aligned by applying a dc field during immobilization. For suspended samples, the applied ac field was set so that the alignment of the easy axes was caused by the ac field. Magnetization (M–H) curves of MNPs with different degrees of easy axis alignment were measured with an applied ac field. We found that the easy axis alignment of MNPs considerably affects their M–H curve and harmonic spectra, which indicates the importance of this alignment for their biomedical applications. The experimental results were quantitatively explained with numerical simulation that took account of easy axis alignment and core size distribution in the sample. We can express the degree of easy axis alignment using a distribution function of the easy axis angle for both immobilized and suspended cases. The distribution function will be useful for quantitatively evaluating MNP performance in biomedical applications. [ABSTRACT FROM AUTHOR]

We estimated the effective magnetic anisotropy constant K of magnetic nanoparticles (MNPs) from the temperature dependence of the coercive field Hc of the M–H curve for use in biosensing applications. For this purpose, a previous analytical expression for Hc was extended so that it can be applied to nanoparticles with a size distribution. Using the extended expression for Hc, we estimated the K value of multi-core based MNP sample that consists of crystalline aggregates of elementary particles. We prepared three MNP samples. One is Resovist, in which elementary particles and aggregates are mixed. The Resovist sample was magnetically divided into two fractions called MS1 and MS3, which included mainly aggregates and elementary particles, respectively. We discuss the K value of elementary particles and aggregates from the comparison among the three samples. It is suggested that the K value of the aggregates is much smaller than that of the elementary particles. The temperature dependence of K of the aggregates is also discussed. [ABSTRACT FROM AUTHOR]

This paper aims at investigating the efficiency of strengthening pre‐damaged circular reinforced concrete (RC) columns with Polyparaphenylene Benzobisoxazole fabric‐reinforced cementitious matrix (PBO‐FRCM). The investigated parameters were the degree of pre‐damage (non‐damaged, damaged monotonically up to yielding, or fatigue damaged), the number of PBO‐FRCM layers (0, 2, or 4), and the tie spacing (180 or 90 mm). The experimental results of testing 12 short columns under axial compression showed that PBO‐FRCM systems enhanced the capacity of the non‐damaged columns and successfully restored and further enhanced the capacity of the pre‐damaged columns. Columns strengthened with two and four PBO‐FRCM layers showed a gain in the capacity of up to 40% and 75%, respectively. Furthermore, PBO‐FRCM wrapping enhanced the ductility of both the non‐damaged and the pre‐damaged columns, in which ductility improvement was more noticeable in columns with the larger tie spacing. Finally, the theoretical load‐carrying capacity calculated using ACI 549 provisions showed a good agreement with the experimental capacity of all tested columns. [ABSTRACT FROM AUTHOR]

This study investigated the efficiency of strengthening low-strength RC short columns with fiber-reinforced cementitious matrix (FRCM). Twelve columns were cast with concrete with a compressive strength of 18 MPa. All columns had a reinforcement ratio of 1.5%. The investigated parameters were the column cross section (square or circular), the spacing between the ties (90 and 180 mm) selected based on the columns' dimensions, and the number of FRCM layers used in wrapping the columns [zero, two, and four layers of paraphenylene-ben-zobisoxazole (PBO) FRCM]. All columns had a clear height of 800 mm and were tested monotonically until failure. Results showed that for columns wrapped with two PBO-FRCM layers, using a tie spacing of 90 mm eliminated the effect of varying the cross section. However, circular columns showed a higher increase in capacity than square columns for a tie spacing of 180 mm, where the increase was 40%. For all columns wrapped with four PBO-FRCM layers, the cross-section shape was the sole influence on ultimate capacity, where circular columns noticeably showed a more improved capacity. Also, column load–strain relationships were only influenced by the tie spacing. All strengthened columns showed improved ductility with the increase in PBO-FRCM layers. Using existing design provisions, the theoretical capacity of the columns was calculated, and results showed that the code underestimates ultimate capacity, where the theoretical capacities were lower than the experimental ones by 5%–20%. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental and analytical study of the fatigue performance of reinforced concrete beams strengthened with externally post-tensioned carbon-fibre-reinforced polymer (CFRP) tendons. Two loading conditions prior to strengthening the beams were investigated: in-service loading and overloading. A total of 18 beams were tested to failure: three under monotonic loading and fifteen under fatigue loads. The CFRP tendons were post-tensioned to 40% of their ultimate capacity. The results demonstrated that overloading the beams had no discernable effect on the fatigue life of the strengthened beams. The strain-reduction approach for unbonded steel tendons was modified to account for using CFRP tendons and for the permanent deformations resulting from the overloading process. The loading history of the beams prior to and after post-tensioning was incorporated into a strain-life fatigue model to predict the fatigue life of the strengthened beams. Key words: concrete beams, overloading, damage, post-tensioning, fatigue, fiber-reinforced polymer, strain life. Cet article presente les resultats d'une etude experimentale et analytique de la resistance a la fatigue de poutres en beton arme renforcees d'une armature externe post tensionnee en polymeres renforces de fibres de carbone (<< PRFC >>). Deux conditions de chargement avant le renforcement des poutres ont ete examinees : en service et en surcharge. Dix-huit poutres ont ete mises a l'epreuve jusqu'a defaillance, trois sous un chargement monotone et 15 sous des charges de fati gue. Les armatures en << PRFC >> ont ete post tensionnees a 40 % de leur capacite maximale. Les resultats ont montre que la surcharge des poutres n'avait aucun effet evident sur la duree de vie en fatigue des poutres renforcees. L'approche de reduction des contraintes pour les armatures en acier non adherentes a ete modifiee pour tenir compte de l'utilisation d'armatures en << PRFC >> et des deformations permanentes decoulant du processus de surcharge. L'historique des chargements des poutres avant et apres le post-tensionnement a ete incorpore dans un modele de fatigue contrainte-duree de vie afin de predire la duree de vie en fatigue des poutres renforcees. Mots-cles : poutres en beton, surcharge, dommage, post-tensionnement, fatigue, polymere renforce de fibres, contrainteduree de vie. [Traduit par la Redaction], Introduction and background Strengthening of reinforced concrete structures can be achieved by various techniques, usually governed by the type of the structure and its functionality. External posttensioning is a proven [...]

A new detection system for magnetic particles, which can operate in an unshielded environment, is developed using a fundamental mode orthogonal fluxgate gradiometer. The proposed detection system offers the advantages of cost, size, and weight reduction as compared to contamination detection systems using superconducting quantum interference device sensor. The detection system can be used to detect metallic contamination in foods or lithium ion battery production lines. The system has been investigated numerically to optimize various design parameters of the system. Experimental setup has been developed to evaluate some of the numerically predicted results. Steel balls were successfully detected down to the diameter of 50 μm. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles (MNPs) are physically immobilized in some biomedical applications. In this case, dynamic ac magnetization that determines MNPs’ performance has strong dependence on the relative direction between the magnetic easy axes of MNPs and the applied excitation field. To study this dependence, we prepared immobilized MNP samples with different degrees of easy axes’ alignment. The degree of alignment was changed by setting the strength of a dc field that is applied during the immobilization process. The magnetic properties of these samples, such as ac magnetization, coercive field, amplitude of third-harmonic signal, and hysteresis loss, are compared with those of a randomly oriented easy axes’ sample. It was shown that these values are significantly affected by the degree of easy axes’ alignment when the strength of the ac excitation field, $H_{0}$ , is relatively small. The alignment effect gradually becomes smaller when $H_{0}$ is increased. These findings are important for immobilized MNP applications in hyperthermia and magnetic particle imaging. [ABSTRACT FROM AUTHOR]

We performed three-dimensional detection of magnetic nanoparticle (MNP) samples using the combination of a field-free line (FFL) and multiple pickup coils. In this method, two-dimensional maps of the signal fields generated by the MNP samples were used to reconstruct a three-dimensional image of the MNP concentration. In the experiment, a weak field gradient of the FFL (0.06–0.13 T m−1) was used. The degradation of the imaging quality owing to the weak field gradient was compensated using ten field maps. We successfully demonstrated the three-dimensional detection of two MNP samples. The Fe content of each sample was 10 and 20 μg and the spacing for both samples was 16 mm. The results confirm the effectiveness of the present method for MNP detection using a weak field gradient. We also quantitatively discuss how the imaging quality degrades when the field gradient is decreased. [ABSTRACT FROM AUTHOR]

Highlights • Procedure for magnetic parameters evaluation of magnetic nanoparticles is presented. • Suspended sample M-H curve, immobilized sample M-H curve and AC susceptibility are used. • Parameters of Resovist MNP sample and its two fractionated samples were evaluated. • Resovist sample parameters were given by volume-weighted average of the two fractionated samples. Abstract We present a procedure for the comprehensive evaluation of parameters of magnetic nanoparticles (MNPs), such as saturation magnetization, core-size distribution, anisotropy energy constant, and characteristic time for Néel relaxation for use in biomedical applications and fundamental MNPs research. The static magnetization curve of suspended and immobilized MNP samples and the AC susceptibility of immobilized samples were used for the evaluation of these parameters. The magnetic properties reconstructed from the obtained parameters agreed with the experimental results, indicating the accuracy of the estimation procedure. Using the procedure, the parameters of the commercial Resovist MNP sample were evaluated. Then, the Resovist sample was magnetically fractionated into two MNP samples with large and small core sizes, and the parameters of the two fractionated samples were evaluated. It was demonstrated that the parameters of the Resovist sample are given by the volume-weighted average for those of the fractionated samples. [ABSTRACT FROM AUTHOR]

We studied the magnetization (M-H) curve of immobilized magnetic nanoparticles (MNPs) used for biomedical applications. First, we performed numerical simulation on the DC M-H curve over a wide range of MNPs parameters. Based on the simulation results, we obtained an empirical expression for DC M-H curve. The empirical expression was compared with the measured M-H curves of various MNP samples, and quantitative agreements were obtained between them. We can also estimate the basic parameters of MNP from the comparison. Therefore, the empirical expression is useful for analyzing the M-H curve of immobilized MNPs for specific biomedical applications. [ABSTRACT FROM AUTHOR]

This paper presents the recent development in Structural Health Monitoring (SHM) applications for monitoring the dynamic behavior of structures using the Global Positioning Systems (GPS) technique. GPS monitoring systems for real-time kinematic (RTK), precise point positioning (PPP) and the sampling frequency development of GPS measurements are summarized for time series analysis. Recent proposed time series GPS monitoring systems, errors sources and mitigation, as well as system analysis and identification, are presented and discussed. [ABSTRACT FROM AUTHOR]

The magnetic core-size distribution of magnetic nanoparticles (MNPs) was estimated from three independent measurements, i.e., magnetization, ac susceptibility (ACS), and magnetic relaxation (MRX). First, distribution of magnetic moment m in MNP sample was estimated by analyzing the static magnetization ( M – H) curve of the MNP sample in suspension. Next, distribution of anisotropy energy E was estimated by analyzing the ACS of immobilized MNP sample measured from 10 Hz to 1 MHz. The ACS measurement in much lower frequency range was substituted by the MRX measurement. MRX of immobilized MNP sample was measured from 2 to 10^4 s, corresponding to the frequency range from 10^-4 to 0.5 Hz in ACS measurement. The relaxation curve was analyzed using a newly developed analytical method to estimate the E distribution of the MNPs in the range of large E values. Then, the estimated distributions of m and E were transferred to the distributions of magnetic core size. Core-size distributions obtained from m and E distributions reasonably agreed with each other. Namely, we obtained similar core-size distribution from static and dynamic properties of MNP sample, confirming the validity of the present method. Therefore, the present method can be useful to estimate the core-size distribution of MNP sample. [ABSTRACT FROM AUTHOR]

A novel method for constructing an integrated gradiometer and a magnetometer is proposed based on fundamental mode orthogonal fluxgate operation. In the integrated sensor construction, the summation of both sensor head outputs is used for the magnetometer operation and the subtraction of them is used for the gradiometer operation. The baseline separation distance between the sensor heads is adjustable. The sensor heads pair can be configured either axially or in parallel. Experiments were conducted with axial configuration of 5 cm baseline to show the selective detection capability to gradient and homogeneous magnetic field. The sensing system presented can be used to measure the average and the gradient of input magnetic field and its interesting applications are the gradiometric sensing of magnetic field distribution anomalies in a relatively large homogenous magnetic field interference. [ABSTRACT FROM AUTHOR]

• Studied the effect of viscosity on the harmonic signals from magnetic nanoparticles. • First harmonic decreased with increase in viscosity while third and fifth increased. • First and third harmonics had negative correlation, whereas the third and fifth had positive correlation. • Viscosity dependences are related to co-existence of Néel and Brownian relaxation. • Proposed a method for estimation of viscosity and temperature of MNP samples. We studied the effect of viscosity on the harmonic signals of magnetic nanoparticles (MNPs) for thermometry application. Although thermometry is based on the temperature dependence of MNPs harmonic signals, they are also affected by the viscosity of the surrounding media. Therefore, we first perform numerical calculation to qualitatively show the effect of viscosity on the first (M 1), third (M 3) and fifth (M 5) harmonic signals when an excitation field with medium amplitude (3 mT) and high frequency (10 kHz) is applied. We then present the experimental results for Resovist MNPs samples when viscosity is changed from 0.89 to 5.2 mPa·s. We obtained qualitative agreement between numerical calculation and experimental results on the viscosity dependences. Next, we study the correlation between the changes in harmonic signals caused by viscosity variation. The M 1 and M 3 had negative correlation in their change, while M 3 and M 5 had positive correlation. Due to the positive correlation, the ratio M 5 / M 3 became almost independent of viscosity when appropriate amplitude and frequency were chosen for the excitation field. We also proposed a method to accurately estimate both viscosity and temperature of the MNPs sample from the measured harmonic signals even when the viscosity is not known in advance, which will be useful for precise thermometry. [ABSTRACT FROM AUTHOR]

Unlabelled: Prolonged use of opioids and benzodiazepines for the care of critically ill infants and children can generate physical dependence. We present a case of an 8-mo-old infant with Hunter's syndrome who was maintained on very large doses of fentanyl and midazolam and who could not be weaned from these drugs by conventional taper. We used dexmedetomidine, an alpha(2)-adrenergic agonist, to facilitate opioid and benzodiazepine withdrawal. A processed electroencephalogram (Bispectral Index) was used to guide the titration of dexmedetomidine in this neurologically impaired infant. This is the first report of this drug being used in an infant to manage chemical dependence withdrawal., Implications: Dexmedetomidine was used to facilitate opioid and benzodiazepine withdrawal in an 8-mo-old infant. A processed electroencephalogram (Bispectral Index) was used to guide the titration of dexmedetomidine in this neurologically impaired infant. This is the first report of dexmedetomidine use in an infant to manage chemical dependence withdrawal.