Tracer Material Research Articles

Evaluation of leaf deposit quality between electrostatic and conventional multi-row sprayers in a trellised vineyard

Spray application technologies for specialty crops have developed considerably in recent years with regard to improved control, reduced cost, and ability to avoid environmental contamination. For example, new developments in electrostatic sprayers have been progressively introduced as an alternative for vineyard spray applications. This study investigated the efficiency of this emerging technology in a Spanish trellis vineyard. First, a complete characterization of an electrostatic sprayer was conducted under laboratory conditions. The liquid flow rate was measured using different restrictor configurations to obtain the outgoing air velocities in the diffusers. Second, field trials were conducted in a vineyard testing, two forward speeds (5.9 and 4.7 km h−1, resulting in volume rates of 60 and 75 l ha−1, respectively) and the activated or deactivated electrostatic system. Tartrazine was used as a tracer material to evaluate the spray quality over the canopy. These results were compared with similar trials using a standard multi-row sprayer with orientable outputs at 5.9 km h−1 and 190 l ha−1. The results indicated that activated electrostatic treatments resulted in a greater amount of deposition on vegetation than the other trials. The activated system also produced a significant correlation between leaf deposition and forward speed (p ≤ 0.05). The most homogeneous results were achieved by the activated electrostatic sprayer at 5.9 km h−1 and the reference sprayer. These results suggest that electrostatic sprayers could save up to 68% of applied volume with similar or better deposition of the liquid and achieve homogeneity over the whole canopy.

3D Printed Anatomical Model of a Rat for Medical Imaging

Abstract For medical research, approximately 115 million animals are needed every year. Rodents are used to test possible applications and procedures for the diagnosis of anatomical and physiological diseases. However, working with living animals increases the complexity of an experiment. Accurate experimental planning is essential in order to fulfill the 3R rules (replace, reduce and refine). Especially in tracer-based imaging modalities, such as magnetic particle imaging (MPI), where only nanoparticles give a positive contrast, the anatomical structure of the rodent is not visible without co-registration with another imaging modality. This leads to problems in the experimental planning, as parameters, such as field of view, rodent position and tracer concentration, have to be determined without visual feedback. In this work, a 3D CAD rat model is presented, which can be used to improve the experiment planning and thus reduce the number of animals required. It was determined using an anatomy atlas and 3D printed with stereolithography. The resulting model contains the most important organs and vessels as hollow cavities. By filling these with appropriate tracer materials, the phantom can be used in different imaging modalities such as MPI, magnetic resonance imaging (MRI) or computed tomography (CT). In a first MPI measurement, the phantom was filled with superparamagnetic nanoparticles. Finally, a successful visualization of all organs and vessels of the phantom was possible. This enables the planning of the experiment and the optimization of experimental parameters for a region of interest, where certain organs in a living animal are localized.

Sentinel lymph node biopsy in the management of conjunctival melanoma: current insights.

Purpose: To evaluate the role of sentinel lymph node biopsy (SLNB) in conjunctival melanoma (CM).Methods: This article provides a review of the literature from PUBMED.Results: Data on SLNB in the management of CM are scarce and only two relatively large cohorts have been reported. Although indication criteria for SLNB vary slightly, positive findings can be expected in 11%–13% of CM cases, including small tumors. False negative SLNB findings are rare (<10%). Failure to identify SLNB has been attributed to the surgical learning curve and recurrent tumors with scar tissue impeding spread of the tracer material. Reported 5-year survival rate following CM management including SLNB, is up to 79%, but there are no comparative cohort studies proving the assumed benefit. Adverse events reported were non-severe and transient.Conclusion: Patients can potentially benefit from SLNB and the procedure can be offered to eligible patients. However, there is not enough evidence to support SLNB as a mandatory part of CM management.

Apparent thermal conductivity of photoluminescent C-dot nanofluid

Carbon nanodots (C-dots) are nanometer-sized particles of amorphous carbon that form highly stable water-based suspension if given the right surface treatment. Their size, stability and unique photoluminescent properties make them attractive candidates for tracer materials for use in heat transfer experiments. Here we measure the effective thermal conductivity of water containing 1.5 g/L (0.077% volume fraction) of fluorescent green carbon nanodots. In conflict with empirical predictions from nano-fluid literature but consistent with predictions from classical theories applied to nanofluid thermal conductivity enhancement, the results show no measurable difference between the thermal conductivity of the colloid and deionized water. This finding adds confirmation to the value of photoluminescent carbon nanodots for use as a water tracer in bench-top heat transfer experiments.

Discriminating nanoparticle core size using multi-contrast MPI

Magnetic particle imaging (MPI) is an imaging modality that detects the response of a distribution of magnetic nanoparticle tracers to alternating magnetic fields. There has recently been exploration into multi-contrast MPI, in which the signal from different tracer materials or environments is separately reconstructed, resulting in multi-channel images that could enable temperature or viscosity quantification. In this work, we apply a multi-contrast reconstruction technique to discriminate between nanoparticle tracers of different core sizes. Three nanoparticle types with core diameters of 21.9 nm, 25.3 nm and 27.7 nm were each imaged at 21 different locations within the scanner field of view. Multi-channel images were reconstructed for each sample and location, with each channel corresponding to one of the three core sizes. For each image, signal weight vectors were calculated, which were then used to classify each image by core size. With a block averaging length of 10 000, the median signal-to-noise ratio was 40 or higher for all three sample types, and a correct prediction rate of 96.7% was achieved, indicating that core size can effectively be predicted using signal weight vector classification with close to 100% accuracy while retaining high MPI image quality. The discrimination of the core size was reliable even when multiple samples of different core sizes were placed in the measuring field.

A novel characterization technique for superparamagnetic iron oxide nanoparticles: The superparamagnetic quantifier, compared with magnetic particle spectroscopy.

Superparamagnetic iron oxide nanoparticles (SPIONs) are used as a tracer material in sentinel node biopsies. The latter is a procedure to analyze if cancer cells have spread to lymph nodes, helping to personalize patient care. To predict SPION behavior in vivo, it is important to analyze their magnetic properties in biological environments. The superparamagnetic quantifier (SPaQ) is a new device to measure the dynamic magnetization curve of SPIONs. The magnetization curve was measured for two types of SPIONs: Resovist and SHP-25. We used three techniques: Vibrating Sample Magnetometry (VSM), Magnetic Particle Spectroscopy (MPS), and our new SPaQ. Furthermore, AC susceptibility (ACS) measurements were performed as part of the evaluation of the three techniques. SPaQ and VSM results were found to be similar. Measurement results were nearly identical in both directions, indicating minor hysteresis. However, in MPS measurements, a clear hysteresis loop was observed. Furthermore, the ACS measurements showed a pronounced Brownian maximum, indicating an optimal response for an AC frequency below 10 kHz for both particle systems. Both the SPaQ and MPS were found to be superior to VSM since measurements are faster, can be performed at room temperature, and are particularly sensitive to particle dynamics. The main difference between the SPaQ and MPS lies in the excitation sequence. The SPaQ combines an alternating magnetic field that has a low amplitude with a gradual DC offset, whereas MPS uses only an alternating field that has a large amplitude. In conclusion, both the SPaQ and MPS are highly suited to improve understanding SPION behavior, which will lead to the radical improvement of sentinel node biopsy accuracy.

Model analysis of gas residence time in an ironmaking blast furnace

Gas residence time distribution (RTD) is an effective and convenient indicator for evaluating the performance of complex multiphase chemical reactors including ironmaking blast furnaces (BFs). However, in the open literature, there lacks the systematic RTD research for BFs. In this study, an integrated mathematical model is developed for describing the gas RTD of a BF. The model combines a steady multi-fluid model for describing the in-furnace state of flow and thermo-chemical behavior of gas-solid-liquid phases and a transient model for describing the dynamic behavior of tracer materials. The results show that the gas flow field inside the BF is quite complex, resulting from many factors such as furnace geometry and coupled thermo-chemical behaviors of other phases. The tail of gas RTD curve resulted from the lagging phenomenon of tracer flow inside BFs, is captured. The gas RTD is discussed by using mean residence time, dispersion of molecules distribution, cumulative distribution function and residence time intensity function. Under the given BF conditions, mean residence time and space time of gas fluids are predicted as 13.5 s and 16.3 s, respectively. The existence of stagnant flow in the BF can be both derived and directly identified. Moreover, it is indicated the gas flow patterns in the BF are composed of piston-type flow, stagnant flow and limited mixing flow. This study provides a cost-effective tool for better understanding BF gas flow dynamics and optimizing BF operations.

Magnetic SERS Composite Nanoparticles for Microfluidic Oil Reservoir Tracer Detection and Nanoprobe Applications

Composite magnetic nanoparticles are designed and synthesized with different morphologies as surface-enhanced Raman scattering (SERS) substrates or SERS-active particles. Through the incorporation of a magnetic functionality, we provide a means to concentrate SERS-active nanoparticles in a low-volume microfluidic channel where the detected entity is now either a flowing analyte (e.g., tracer or chemical) or SERS-active particles contained in a target reservoir fluid. This collection strategy allows for detection using small amounts of material and can be optimized to provide selectivity for trace-level materials detection at the wellsite. We also demonstrate low-concentration detection of dye molecules used for reservoir tracer materials by optimizing the fluid flow rate and the intensity of the magnetic field. Thus, we developed an efficient magnetic SERS microfluidic detection platform for in situ monitoring trace level of analyte molecules. The integration of SERS with microfluidic systems also can extend the application of Raman detection in biomedical research and microreactor monitoring where low volumes of expensive samples make traditional detection methods ineffective or cost prohibitive.

Material Flow in Lap Joint of Dissimilar Metallic Foils by Friction Stir Diffusion Bonding with Micro Indentation

Friction stir diffusion bonding (FSDB) has been applied to lap dissimilar foils joints of aluminum alloy on top of commercial purity (CP) titanium. FSDB of the foils was successfully performed through stirring only the upper aluminum foil by the air spindle with an extremely-high rotation speed of 105,000 rpm. By using smooth surface of the tool tip, FSDB with micro indentation less than or equal 10μm could be carried out to improve the surface condition of the joint and the indentation depth required for joining was reduced. The material flow of the upper aluminum alloy foil in the FSDB was investigated by deposited platinum-palladium as the tracer material on the surface of the lower titanium foil. Then it was confirmed that the vestiges of vigorous stirring appeared in the region given at a distance from tool center while little vestiges was found in the other region. These regions seemed to be bounded by a radius of about 0.6 mm from the tool center. Moreover, the bonding strength distribution as a function of the distance from the tool center was likely correspondent to the stirring state.

Effect of material properties on the residence time distribution (RTD) characterization of powder blending unit operations. Part II of II: Application of models

Residence time distribution (RTD) modeling can aid the understanding and characterization of macro-mixing in continuous powder processing unit operations by relating observed behavior to quantitative model parameters. This article is the second part of the work done to characterize the effect of material properties on the measurement of RTDs in continuous powder processing operations. The goal of this paper is to examine the behavior of the RTD given different sets of tracer material properties. Tracer addition methods are discussed within the framework of their mathematical representation. The two most widely used RTD models in powder systems in the literature, the axial dispersion and the tank-in-series model, are presented and used to describe the experimental data. The RTD model parameters (e.g., Peclét number, number of tanks in series, and residence times) were regressed from the experimental data and compared using one-way ANOVA to determine the effects of materials properties on RTD. A model independent approach using a Multivariate Analysis of Variance (MANOVA) was also applied to compare the results with the model dependent method. Lastly, examples of how the RTD models can aid process design and understanding were described using both continuous and discrete convolution. The RTD models and their regressed coefficients were used to predict the mixing outputs of a semi-random input and the impact of disturbances on the process.

Moving table magnetic particle imaging: a stepwise approach preserving high spatio-temporal resolution.

Magnetic particle imaging (MPI) is a highly sensitive imaging method that enables the visualization of magnetic tracer materials with a temporal resolution of more than 46 volumes per second. In MPI, the size of the field of view (FoV) scales with the strengths of the applied magnetic fields. In clinical applications, those strengths are limited by peripheral nerve stimulation, specific absorption rates, and the requirement to acquire images of high spatial resolution. Therefore, the size of the FoV is usually a few cubic centimeters. To bypass this limitation, additional focus fields and/or external object movements can be applied. The latter approach is investigated. An object is moved through the scanner bore one step at a time, whereas the MPI scanner continuously acquires data from its static FoV. Using a 3-D phantom and dynamic 3-D in vivo data, it is shown that the data from such a moving table experiment can be jointly reconstructed after reordering the data with respect to the stepwise object shifts and heart beat phases.

Colloidal solution of luminescent ZnO quantum dots embedded silica as nano-tracers for remote sensing applications

The deployment of traditional radioactive isotopes as tracers has the drawback of environmental concerns. In this study, we investigated alternative luminescent zinc oxide quantum dots embedded silica (ZnO@SiO2) nanoparticles as tracers for oil reservoir applications. ZnO quantum dots (QDs) were prepared via solgel process having an average diameter of ~5 nm. For the encapsulation of these ZnO QDs, tetraethyl orthosilicate (TEOS) was utilized to synthesize hydrophilic ZnO@SiO2 nanoparticles (H-NPs), while dimethyldiethoxysilane (DMDES) in combination with TEOS was used to prepare partially hydrophobic ZnO@SiO2 (PH-NPs). The fluorescence of bare ZnO QDs was compared to that of silica-coated ZnO@SiO2 NPs in various solvents. The effects of cetyltrimethylammonium bromide (CTAB) surfactant and silica coatings on the fluorescence of ZnO QDs were investigated by photoluminescence spectroscopy. The fluorescence and structural properties of ZnO@SiO2 nano-tracers were examined in highly saline water and at elevated temperature to mimic the oil reservoir environment. The significant improvement in fluorescence emission stability was achieved for PH-NPs in harsh conditions, which advocates their potential use as a tracer material for oil exploration.

A decade of fluvial morphodynamics: relocation and restoration of the Inde River (North-Rhine Westphalia, Germany)

BackgroundRelocations and restorations do not only change the ecological passability and sediment continuity of a river but also its flow behavior and fluvial morphodynamics. Sediment transport processes and morphological development can be assessed with field measurements, also taking the transport of sediment-bounded contaminants as a tracer material for fluvial morphodynamics into account. The objective of this study was to determine the morphological development of the Inde River (a tributary of the Rur River in North-Rhine Westphalia, Germany) towards its pre-defined guiding principle after a relocation and restoration in 2005 AD.MethodsThe fluvial morphodynamics of the Inde River were analyzed over a period of almost 15 years taking sediment samples, analyzing echo soundings of the river’s bathymetry and determining the heavy metal content of the sediment as a tracer material for the morphological development.ResultsThe results show that the relocation and restoration of the Inde River initiates new hydrodynamic processes, which cause morphological changes of the river widths, meander belts and channel patterns. The riverbed of the new Inde River has incised into the ground due to massive erosion, which has led to increased fine sediment transport in the downstream direction. The reasons for and consequences of this fine sediment transport are discussed and correlated to the sediment continuity of a river.ConclusionsOverall, the new Inde River has reached its goal of being a natural river as a consequence of the relocation and restoration and has adapted its new conditions towards a dynamic morphological equilibrium.

Effect of tracer material properties on the residence time distribution (RTD) of continuous powder blending operations. Part I of II: Experimental evaluation

Residence time distribution (RTD) models are essential to understand process dynamics and support process monitoring and control in continuous manufacturing systems. RTD models can also be used to monitor material traceability and to isolate intermediate materials or finished products when specifications are not met. However, while pharmaceutical companies are currently making extensive use of RTD approaches, standard methods for conducting, interpreting, and using RTD results in continuous pharmaceutical manufacturing have not yet been established by regulatory authorities. This paper seeks to facilitate generating such standards. We discuss in detail the assumptions and conditions that are relevant to the proper selection of tracers for RTD experiments, and demonstrate that tracer selection can have substantial impact on RTD results. We selected seven materials with a wide range of properties as tracers and a single material as our base “blend”. The experimental results led to two major conclusions: (1) materials with different mechanical properties have dissimilar mean residence times (MRT) inside the systems and (2) blend ingredients with different mechanical properties travel at different speed inside of continuous blending systems. Results further indicated there were two critical mean residence times (MRTs): that of the tracer and that of the bulk. Matching of material properties between tracers is key in order to obtain similar MRTs using a given tracer. Differences between selected tracer and bulk material properties were found to lead to differences between the bulk space time and the tracer MRT. A set of recommendations on how to select tracer materials that would help characterize accurately the RTD of a continuous flow system are presented.

Magnetic particle imaging in vascular medicine.

Magnetic particle imaging (MPI) is a new medical imaging technique that enables three-dimensional real-time imaging of a magnetic tracer material. Although it is not yet in clinical use, it is highly promising, especially for vascular and interventional imaging. The advantages of MPI are that no ionizing radiation is necessary, its high sensitivity enables the detection of very small amounts of the tracer material, and its high temporal resolution enables real-time imaging, which makes MPI suitable as an interventional imaging technique. As MPI is a tracer-based imaging technique, functional imaging is possible by attaching specific molecules to the tracer material. In the first part of this article, the basic principle of MPI will be explained and a short overview of the principles of the generation and spatial encoding of the tracer signal will be given. After this, the used tracer materials as well as their behavior in MPI will be introduced. A subsequent presentation of selected scanner topologies will show the current state of research and the limitations researchers are facing on the way from preclinical toward human-sized scanners. Furthermore, it will be briefly shown how to reconstruct an image from the tracer materials’ signal. In the last part, a variety of possible future clinical applications will be presented with an emphasis on vascular imaging, such as the use of MPI during cardiovascular interventions by visualizing the instruments. Investigations will be discussed, which show the feasibility to quantify the degree of stenosis and diagnose strokes and traumatic brain injuries as well as cerebral or gastrointestinal bleeding with MPI. As MPI is not only suitable for vascular medicine but also offers a broad range of other possible applications, a selection of those will be briefly presented at the end of the article.

Residence time distribution of a continuously-operated capsule filling machine: Development of a measurement technique and comparison of three volume-reducing inserts

This paper presents the measurement and analysis of the residence time distribution (RTD) of a tamping-pin capsule filling machine. The tamping speed and the amount of material inside the powder bowl proved to have a significant effect on the RTD. Various inserts into the powder bowl that reduce the volume and alter mixing and transport in the bowl were experimentally investigated. To obtain the RTD, a tracer-based measurement method was applied and a sophisticated data processing strategy was developed. The tracer-based method also allowed investigations of stagnant zones in the powder bowl, another important aspect in continuous manufacturing (CM). The suitability of tracer material was assessed based on a detailed characterization of bulk and tracer material. Characteristic parameters of the RTD were extracted and compared, proposing a systematic strategy for selection of a suitable insert.

Viscosity quantification using multi-contrast magnetic particle imaging

Magnetic particle imaging (MPI) is a relatively new tomographic imaging technique using static and oscillating magnetic fields to image the spatial distribution of magnetic nanoparticles. The latter being the contrast MPI has been initially designed for. However, recently it has been shown that MPI can be extended to a multi-contrast method that allows one to simultaneously image the signals of different MPI tracer materials. Additionally, it has been shown that changes in the particles environment, e.g. the viscosity have an impact on the MPI signal and can potentially be used for functional imaging. The purpose of the present work is twofold. First, we generalize the MPI imaging equation to describe different multi-contrast settings in a unified framework. This allows for a more precise interpretation and discussion of results obtained by single- and multi-contrast reconstruction. Second, we propose and validate a method that allows one to determine the viscosity of a small sample from a dual-contrast reconstruction. To this end, we exploit a calibration curve mapping the sample viscosity onto the relative signal weights within the channels of the dual-contrast reconstruction. The latter allows us to experimentally determine the viscosity of the particle environment in the range of 1–51.8 mPa s with a relative methodological error of less than 6%.

Novel production method of tracer particles for residence time measurements in gas-solid processes

In order to measure the residence time distribution (RTD) in continuous gas-solid processes tracer particles are used. In this contribution, a novel production concept for magnetizable particles has been developed and optimized. The process includes coating of a fraction of the investigated bed material with a magnetizable paint in a laboratory spouted bed. The coated particles fulfill the requirements of tracer material, are resistant, harmless to health and reusable. After passing a continuously operated process, the tracer material can be separated by a magnetic rod from the sample, which allows the fast and easy calculation of the exit age distribution as demonstrated in this contribution with a horizontal fluidized bed.

Joint Reconstruction of Tracer Distribution and Background in Magnetic Particle Imaging.

Magnetic particle imaging (MPI) is a novel tomographic imaging technique, which visualizes the distribution of a magnetic nanoparticle-based tracer material. However, reconstructed MPI images often suffer from an insufficiently compensated image background caused by rapid non-deterministic changes in the background signal of the imaging device. In particular, the signal-to-background ratio (SBR) of the images is reduced for lower tracer concentrations or longer acquisitions. The state-of-the-art procedure in MPI is to frequently measure the background signal during the sample measurement. Unfortunately, this requires a removal of the entire object from the scanner's field of view (FOV), which introduces dead time and repositioning artifacts. To overcome these considerable restrictions, we propose a novel method that uses two consecutive image acquisitions as input parameters for a simultaneous reconstruction of the tracer distribution, as well as the background signal. The two acquisitions differ by just a small spatial shift, while keeping the object always within the focus of a slightly reduced FOV. A linearly interpolated background between the initial and final background measurement is used to seed the iterative reconstruction. The method has been tested with simulations and phantom measurements. Overall, a substantial reduction of the image background was observed, and the image SBR is increased by a factor of 2(7) for the measurement (simulation) data.

Quantifying soil movement by forest vehicles with corpuscular metal tracers

Bulk soil movement caused by human impact is hard to quantify. In forestry the bulk soil displacement by passage with heavy machinery is virtually unknown. We present a new method to measure such soil movement with hollow corpuscular metal tracers (16 mm pieces of thin-walled metal pipes made of iron, aluminum, copper and lead) and a metal detector. The tracers are installed minimally invasive into the soil before and located with a metal detector after logging operations. To correctly interpret these measurements it is crucial to know about the accuracy and precision of the method, especially under varying soil moisture content or if different tracer materials are present. To address these questions a series of experiments under controlled conditions on soils with differing iron oxide concentrations were conducted. Best performance on all soils showed Al-tracers, whereas Fe-tracers are limited by increasing Fe-oxide concentrations. Cu and Pb failed. Material specific detection is limited to soils poor in Fe-oxides. Tracers were accurately detectable up to 15–20 cm depth depending on soil moisture. As the signals of the metal detector leave room for interpretation handling needs individual training to obtain unbiased results. In a case study from timber harvesting operations on sloping terrain in Central Europe the tracers where successively moved by each passage of the harvesting machines. After a complete operating cycle the histogram of displacement matched a heavy tailed distribution with a median of around 10 cm and a maximum of several meters. Displacement was reduced by the use of a traction supporting winch. However uncertainty remains whether tracer displacement exactly reflects bulk soil movement.