Resonance Instrument Research Articles

Bridging the buzz: In vivo EPR imaging unlocking the secrets of honey bee health.

Honey bees play a pivotal role in shaping ecosystems and sustaining human health as both pollinators and producers of health-promoting products. However, honey bee colony mortality is on the rise globally, driven by various factors, including parasites, pesticides, habitat loss, poor nutrition, and climate change. This has far-reaching consequences for the environment, economy, and human welfare. While efforts to address these issues are underway, the current progress in electron paramagnetic resonance (EPR) instrumentation affords using the immense potential of this magnetic resonance technique to study small samples such as honey bees. This paper presents the pioneering 2D in vivo EPR imaging experiment on a honey bee, revealing the ongoing redox-status of bees' intestines. This way, by monitoring the spatio-temporal changes of the redox-active spin-probes' EPR signal, it is possible to gain access to valuable information on the course of ongoing bees' pathologies and the prospect of following-up on the efficiency of applied therapies. Employing a selection of diverse spin-probes could further reveal pH levels and oxygen concentrations in bee tissues, allowing a noninvasive assessment of bee physiology. This approach offers promising strategies for safeguarding pollinators and understanding their biology, fostering their well-being and ecological harmony.

Insights into Photopolymerization at the Nanoscale Using Surface Plasmon Resonance Imaging.

Near-field photopolymerization (NFPP) driven by surface plasmon resonance has attracted increasing attention in nanofabrication. This interest comes from the nanometer-scale control of polymer thickness, due to the confinement of the evanescent wave within a highly restricted volume at the surface. In this study, a novel approach using a multi-spectral surface plasmon resonance instrument is presented that gives access to real-time images of polymer growth during NFPP with nanometer sensitivity. Using the plasmonic evanescent wave for both polymerization and real-time sensing, the influence of irradiance, concentration of dye, and initiator are investigated on the threshold energy and kinetics of NFPP. How oxygen inhibition in the near field strongly affects photopolymerization is highlighted, more than in the far field.

Underway measurement of cyanobacterial microcystins using a surface plasmon resonance sensor on an autonomous underwater vehicle

AbstractFreshwater cyanobacterial harmful algal blooms (CHABs) are a well‐known global public health threat. Monitoring and early detection of CHAB toxins are currently accomplished using labor‐intensive sampling techniques and subsequent shore‐based analyses, with results typically reported 24–48 h after sample collection. We have developed and implemented an uncrewed, autonomous mobile sampler‐analytical system capable of conducting targeted in situ toxin measurements in < 2 h. A surface plasmon resonance (SPR) instrument was combined with the environmental sample processor (ESP) to fully automate detection and quantification of particle‐associated cyanobacterial microcystins (pMC). This sensor‐sampler system was integrated with a long‐range autonomous underwater vehicle (LRAUV) and deployed in western Lake Erie for field trials in the summer of 2021. The LRAUV was remotely piloted to acquire samples at selected locations within and adjacent to a CHAB. Sixteen pMC measurements ranging from 0.09 to 0.55 μg/L lake water were obtained over a 14‐day period without recovery of the LRAUV. The SPR/ESP/LRAUV system complements existing satellite, aerial, and manual sampling CHAB survey techniques, and could be used to enhance predictive models that underpin bloom and toxicity forecasts. This system is also extensible to detection of other algal toxins in freshwater and marine environments, with its near real‐time assessment of bloom toxin levels potentially offering additional socioeconomic benefits and public health protection in a variety of settings.

A multi-technique based analytical platform for characterization and identification of a newly emerged steroid 6β-chlorotestosterone and its in-vivo epimeric metabolites

Doping athletes tend to use new and non-approved drugs in an attempt to circumvent the dope test. Recently, a package of unknown drug was obtained from black market claiming to contain steroid-like compound, which could not be readily identified due to the lack of commercially available reference standards. In order to characterize and identify the chemical structure of the unknown compound, ultra performance liquid chromatography high resolution mass spectrometry (UPLC-HRMS), high performance liquid chromatography tandem quadrupole mass spectrometry (HPLC-MS/MS), gas chromatography tandem quadrupole mass spectrometry (GC–MS/MS) and nuclear magnetic resonance (NMR) instruments were applied in this work. Based on the combined data, the unknown compound was identified as 6β-chlorotestosterone. The aim of this study was to find urinary metabolic biomarkers of 6β-chlorotestosterone for clinical research and doping control analysis. Ten in-vivo metabolites including four phase I metabolites and six phase II metabolites were characterized and potentially identified. The detailed structure of the phase I metabolite was successfully obtained by GC–MS/MS analysis of trimethylsilylation (TMS) released upon dissolution, overcoming the absence of useful fragment ions to demonstrate the structure of sulfate metabolites. Two strategies including metabolic mechanisms and retention time variation of steroids were introduced to determine and distinguish 3α/β- and 5α/β- epimeric metabolites. A comprehensive evaluation was conducted on time of appearance and detection of each metabolite. The sulfate metabolite 6β-chloro-5β-androstan-17-one-3β-O-sulfate (S1) could be detected up to 12 days after oral administration, which was considered to be the long term biomarker for 6β-chlorotestosterone abuse in clinical research and doping control analysis.

Thermal and Mechanical Investigations of (Bi, Pb)-2212 Superconductor Added with Different Oxide Nanoparticles

Abstract The current study reports the synthesis of nano-(CdO)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy, nano-(Cd0.95Mn0.05O)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy, and nano-(Cd0.95Fe0.05O)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy composites, with x = 0.00, 0.01, 0.02, 0.05, and 0.10 wt. %, respectively, using the classical solid-state reaction technique. X-ray powder diffraction (XRD) confirmed the formation of an orthorhombic structure of the (Bi, Pb)-2212 as the major phase. Thermogravimetric analysis was utilized to evaluate the thermal stability of the pure sample throughout the different stages of phase formation and the effect of nanoparticle addition. The weight loss/gain from the three additions is related to the excess of oxygen, as confirmed via iodometric titration analysis and from the findings of oxygen diffusion energy. Room temperature Vickers microhardness (HV) measurements were conducted at various applied loads (0.49–9.8 N). Based on the Vickers microhardness (HV) measurements, the optimum addition of nanoparticles for increasing the microhardness of the (Bi, Pb)-2212 phase was at x = 0.05 wt. % for all superconducting composites. Iron doped Cadmium Oxide (CdFeO) nanoparticles have the greatest enhancement on the Vicker hardness values (HV) at the plateau region. Furthermore, various mechanical parameters for potential applications, such as elastic modulus (E), yield strength (Y), and fracture toughness (K) of the samples under study, were consequently extracted from HV as a function of nanoparticle addition. Moreover, CdFeO addition outperformed CdO and Manganese doped Cadmium Oxide (CdMnO) addition in improving the parameters of E, Y, K, and B, which display better ductility and an enhanced capacity to resist indentation fractures and facilitate (Bi-2212) manufactured in the form of round wires that can be used in high magnetic field magnets, nuclear magnetic resonance instruments, and large hadron colliders. Different models were theoretically used to analyze the measured HV data in the plateau limit regions. The indentation-induced cracking model offered the most accurate theoretical model at the plateau limit region based on Vickers microhardness (HV) observations.

Label-free and early detection of HER2 breast cancer biomarker based on UiO-66-NH2 modified gold chip (Au/UiO-66-NH2) using surface plasmon resonance technique

Breast cancer is one of the leading causes of cancer death for women worldwide. This cancer occurs when the breast cells grow abnormally and spread uncontrolled. Although there are several treatments, including chemotherapy, radiation, and surgery in a clinical setting to cure cancer, these treatments cannot provide a 100 % success rate in eliminating cancer, mainly due to the late diagnosis of the disease. Thus, early detection is the key to provide better breast cancer treatment and a higher chance for survival. Herein, simple and sensitive biosensor by combining the emerging multifunctional materials of metal-organic frameworks (MOFs) with a label-free surface plasmon resonance (SPR) instrument was developed. Two types of stable Zirconium (Zr)-based MOFs, namely Zr benzene dicarboxylic acid (Zr-BDC or UiO-66) and Zr 2-amino-benzene dicarboxylic acid (Zr-BDC-NH2 or UiO-66-NH2) were synthesized using the solvothermal method. X-ray diffractometer (XRD) and fourier transform infra red (FTIR) confirmed the formation of the prepared UiO-66 and UiO-66-NH2. The electron microscopy and nitrogen adsorption desorption isotherm characterization reveal that the MOFs have a cubic crystal structure with a high surface area of 672.4 m2/g for UiO-66 and 286.1 m2/g for UiO-66-NH2. The MOFs are then functionalized on the SPR gold (Au) chip surface to serve as a matrix of Human Epidermal Growth Factor Receptor 2(HER2) antibody receptors. Interestingly, the functionalized SPR biosensors could detect the HER2 protein target with high sensitivity in the ng/mL range and a remarkable detection limit, which is 0.457 ng/mL for UiO-66-NH2. This LOD value is significantly lower than clinical concentrations of HER2 proteins in human blood (∼15 ng/mL), which indicate that the biosensor can offer the capability of early detection test.

Experimental Investigation on the Effect of Salt Solution on the Soil Freezing Characteristic Curve for Expansive Soils

With the development of the Belt and Road Initiative in China, high-speed railways are booming and inevitably pass through seasonal frost regions. In Nanyang basin, due to seasonal changes, railway subgrades will undergo frost heaving and thawing subsidence. The freezing characteristics of the soil are characterized by the freezing characteristic curve, and the important factors affecting the freezing characteristic curve are the content of expansive clay minerals in the soil and the salt solution. Therefore, three soil samples with different montmorillonite contents were saturated with salt solutions of different concentrations, and the freezing temperature of the soil samples was controlled by a cold bath. After the temperature equilibrium, the frozen stable soil samples were put into a nuclear magnetic resonance instrument to test the unfrozen water content, and the relationship between the freezing temperature and the unfrozen water content of expansive soil under different salt solution concentrations was obtained. Additionally, a unified model was used to simulate the test results. The results show that SFCC shifts to the left, that is, the sodium chloride salt solution reduces the freezing point of the soil sample so that it has more unfrozen water at the same temperature. At the same time, the soil’s freezing characteristic curves are closely related to content of expansive clay minerals in the soil. The more expansive clay mineral content, the greater the corresponding unfrozen water content. These results provide some basic insights for improving the frost heave and thaw subsidence problems of railway subgrades in seasonal permafrost regions, which will have a positive impact on promoting the management and rational application of land resources and the promotion of sustainable development.

The Effect of Thermal Maturity on the Pore Structure Heterogeneity of Xiamaling Shale by Multifractal Analysis Theory: A Case from Pyrolysis Simulation Experiments

Shale oil and gas, as source-reservoir-type resources, result from organic matter hydrocarbon generation, diagenesis, and nanoscale pore during the evolution processes, which are essential aspects of shale gas enrichment and reservoir formation. To investigate the impact of diagenetic hydrocarbons on shale pore heterogeneity, a thermal simulation of hydrocarbon formation was conducted on immature shale from the Middle Proterozoic Xiamaling Formation in the Zhangjiakou area, covering stages from mature to overmature. Nuclear magnetic resonance (NMR) instruments analyzed the microstructure of the thermally simulated samples, and the multifractal model quantitatively assessed pore development and heterogeneity in the experimental samples. The results reveal that the quartz and clay mineral contents show alternating trends with increasing temperature. Organic matter dissolution intensifies while unstable mineral content decreases, promoting clay mineral content development. Pyrolysis intensity influences Total Organic Carbon (TOC), which reduces as hydrocarbons are generated and released during simulation. Porosity exhibits a decreasing–increasing–decreasing trend during thermal evolution, peaking at high maturity. At maturity, hydrocarbon generation obstructs pore space, resulting in higher levels of bound fluid porosity than those of movable fluid porosity. Conversely, high maturity leads to many organic matter micropores, elevating movable fluid porosity and facilitating seepage. Shale pore heterogeneity significantly increases before 450 °C due to the dissolution of pores and the generation of liquid and gas hydrocarbons. In the highly overmature stage, pore heterogeneity tends to increase slowly, correlated with the generation of numerous micro- and nano-organic matter pores.

Simulation Study of Transient Eddy Current Effect in 3T Animal Gradient Coil

In the process of high-field magnetic resonance imaging (MRI), the eddy current modeling and simulation of the cold screen and metal parts are not highly accurate. To solve this problem, this paper uses the target field method to design a 3T animal gradient coil model. To get more realistic simulation results, a complex model including a gradient system, cryogenic vessel, cold screen, epoxy resin, and temperature holes was constructed. The model was refined using the finite element method, and the effects of eddy currents induced by the gradient coil on the cylindrical cryogenic container and cold screen in the superconducting magnetic resonance instrument under the state of multi-physical field coupling were simulated. The model effectively reflects the transient eddy current distributions on the cold screen and cryogenic vessel in the MRI system and their time-dependent temperature rise effects.

Investigating the Impact of Aqueous Phase on CO2 Huff ‘n’ Puff in Tight Oil Reservoirs Using Nuclear Magnetic Resonance Technology: Stimulation Measures and Mechanisms

Summary CO2 huff ‘n’ puff is a promising enhanced oil recovery (EOR) technique for tight/shale reservoirs, also enabling CO2 geological storage. However, the effectiveness of this method can be significantly affected by the aqueous phase resulting from connate water and hydraulic fracturing. The mechanism underlying the influence of the aqueous phase on oil recovery during CO2 huff ‘n’ puff, as well as the corresponding stimulation methods in such scenarios, remain unclear and warrant further study. To investigate this, we utilized a nuclear magnetic resonance (NMR) instrument to track the movement of fluids during CO2 huff ‘n’ puff under water invasion conditions. The impact of the invaded aqueous phase on oil recovery was examined, and the impact of different treatment parameters was explored. The results show that the aqueous barrier formed by water invasion alters the pathway of CO2 diffusion to matrix oil. This alteration leads to a diminished concentration of CO2 in the oil phase, which, in turn, results in a substantial reduction in oil recovery. Consequently, the performance of CO2 huff ‘n’ puff is highly sensitive to the water phase. Nevertheless, the oil recovery dynamics in cyclic CO2 huff ‘n’ puff under water invasion exhibit distinctive patterns compared with those without water invasion. These differences manifest as notable low oil recovery in the first cycle, followed by a rapid increase in the second cycle. This behavior primarily arises from the expulsion of a significant portion of the invaded water from the macropores after the first cycle. However, the effectiveness of this mechanism is limited in micropores due to the challenging displacement of trapped water in such pores. Raising the injection pressure mainly boosts oil recovery in macropores, with minimal response in micropores. Yet, the achievement of miscibility does not lead to a substantial improvement in the CO2 huff ‘n’ puff performance, primarily due to the constraints imposed by the limited CO2 dissolution through molecular diffusion Additionally, we have proposed three stimulation mechanisms achieved by lengthening the soaking time under water invasion conditions. First, the prolonged soaking time increases the concentration of CO2 molecules that diffuse into the matrix oil. Second, it promotes the imbibition of the trapped water on the fracture surface into the deeper matrix to alleviate water blockage. Finally, the invaded water in macropores displaces oil in micropores by capillary force during the soaking period.

Chemical Exposure Highlighted without Any A Priori Information in an Epidemiological Study by Metabolomic FT-ICR-MS Fingerprinting at High Throughput and High Resolution.

Epidemiological studies aim to assess associations between diseases and risk factors. Such investigations involve a large sample size and require powerful analytical methods to measure the effects of risk factors, resulting in a long analysis time. In this study, chemical exposure markers were detected as the main variables strongly affecting two components coming from a principal component analysis (PCA) exploration of the metabolomic data generated from urinary samples collected on a cohort of about 500 individuals using direct introduction coupled with a Fourier-transform ion cyclotron resonance instrument. The assignment of their chemical identity was first achieved based on their isotopic fine structures detected at very high resolution (Rp > 900,000). Their identification as dimethylbiguanide and sotalol was obtained at level 1, thanks to the available authentic chemical standards, tandem mass spectrometry (MS/MS) experiments, and collision cross section measurements. Epidemiological data confirmed that the subjects discriminated by PCA had declared to be prescribed these drugs for either type II diabetes or cardiac arrhythmia. Concentrations of these drugs in urine samples of interest were also estimated by rapid quantification using an external standard calibration method, direct introduction, and MS/MS experiments. Regression analyses showed a good correlation between the estimated drug concentrations and the scores of individuals distributed on these specific PCs. The detection of these chemical exposure markers proved the potential of the proposed high-throughput approach without any prior drug exposure knowledge as a powerful emerging tool for rapid and large-scale phenotyping of subjects enrolled in epidemiological studies to rapidly characterize the chemical exposome and adherence to medical prescriptions.

SOFNet: Optical-flow based large-scale slice augmentation of brain MRI

Brain magnetic resonance imaging (MRI) data from multiple centers often exhibit variations in imaging conditions, such as the types of nuclear magnetic resonance instruments used and the presence of random noise. Additionally, discrepancies in the gap between MRI slices further complicate the usability of the data for advanced artificial intelligence (AI) analysis. Deep learning-based methods have emerged as practical solutions to address the challenge. However, existing research has largely overlooked the augmentation of brain MRI data, particularly when confronted with significant slice gaps, such as around 6 mm observed in our clinical brain MRI slices. In response to this research gap, we aim to develop novel approaches for augmenting brain MRI data, focusing on more significant slice gaps. To achieve this, we propose SOFNet, which utilizes the optical flow-based and encoder–decoder backbone. The primary objective of our model is to interpolate MRI slices while preserving feature consistency. Leveraging the optical flow method, which has exhibited exceptional performance compared to other super-resolution algorithms, our proposed approach has been evaluated on three distinct brain MRI datasets, explicitly addressing the gap between 4.2 mm and 6.0 mm. The experimental results highlight the significant enhancement in super-resolution quality achieved by SOFNet in generating adapted brain MRI data, surpassing other single-image super-resolution (SISR) methods in feature completion. To ensure the credibility of the interpolated brain MRI slices, we conducted experiments on three axes of MRI based on metrics such as peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM). These experiments demonstrate the effectiveness of our approach in transforming low-resolution MRI data into clear and reliable brain MRIs, thereby enabling improved analysis using AI techniques.

Numerical analysis and test of vibration and interference characteristics of dual U-tube Coriolis flowmeter

The Coriolis flowmeter is a resonant instrument that can be easily affected by environmental vibration interference factors. Therefore, it is necessary to study the vibration characteristics of the Coriolis flowmeter, as well as the on-site environmental interference vibrations. In this paper, a full-scale numerical model of the flowmeter, including the support pipe and flange, was established, and the vibration characteristics of the Dual U-Tube Coriolis flowmeter were analyzed using structural dynamics and fluid-structure coupling calculation methods. The first to sixth natural frequencies and vibration modes were obtained. A mass flowmeter of the same model was selected from the oil transportation station, and vibration analysis and testing were carried out on the Dual U-Tube Coriolis flowmeter. The driving frequency of the Coriolis mass flowmeter and the frequency of external interference vibration signals during the distribution process were obtained through Fast Fourier transform, which verified the correctness of the numerical calculation model. It was found that the natural frequency of the Coriolis flowmeter varies with the installation conditions, and it was pointed out that external vibration signals can interfere with the operation of the Coriolis flowmeter during field operations. This work in this paper has significant reference value for the actual field installation and noise reduction of the Coriolis mass flowmeter.

Monitoring silica core@shell nanoparticle-bacterial film interactions using the multi-parametric surface plasmon resonance technique.

In a healthcare setting, biofilms are a major source of infection and difficult to eradicate once formed. Nanoparticles (NPs) can be designed to effectively penetrate biofilms to more efficiently either deliver antibiotic drugs throughout the biofilm matrix or elicit inherent antibiofilm activity. Antibacterial cerium oxide (CeO2) NPs were employed as core material and coated with a mesoporous silica shell (MSN) to generate cerium oxide coated mesoporous silica NPs (CeO2@MSN). Detailed studies of NP-biofilm interactions are required to rationally develop NP platforms to prevent biofilm-related infections. This work developed and implemented a unique label-free analysis platform for the real-time monitoring of bacterial biofilm formation and then assessed the interactions of antibacterial NPs. An analysis platform which allows bacterial biofilms to grow and develop in situ in flow within the multi-parametric surface plasmon resonance (MP-SPR) instrument was established. This enabled simultaneous monitoring and detection of biofilm growth phases, structure, and interactions between differentially charged CeO2@MSNs and bacterial biofilms. Positively charged antibacterial NPs (polyethyleneimine functionalized CeO2@MSNs) were found to be the most efficient to penetrate the biofilm. The MP-SPR analysis platform was shown to be a powerful tool for monitoring biofilm development in real-time and to analyze biofilm properties and NP-biofilm interactions.

Application of the Nicoya OpenSPR to Studies of Biomolecular Binding: A Review of the Literature from 2016 to 2022

The Nicoya OpenSPR is a benchtop surface plasmon resonance (SPR) instrument. As with other optical biosensor instruments, it is suitable for the label-free interaction analysis of a diverse set of biomolecules, including proteins, peptides, antibodies, nucleic acids, lipids, viruses, and hormones/cytokines. Supported assays include affinity/kinetics characterization, concentration analysis, yes/no assessment of binding, competition studies, and epitope mapping. OpenSPR exploits localized SPR detection in a benchtop platform and can be connected with an autosampler (XT) to perform automated analysis over an extended time period. In this review article, we provide a comprehensive survey of the 200 peer-reviewed papers published between 2016 and 2022 that use the OpenSPR platform. We highlight the range of biomolecular analytes and interactions that have been investigated using the platform, provide an overview on the most common applications for the instrument, and point out some representative research that highlights the flexibility and utility of the instrument.

Study on the Test Error of Silt Dynamic Characteristic and Its Influence on the Peak Ground Acceleration

In order to grasp the nonlinear experimental errors of dynamic shear modulus ratio (DSMR) and damping ratio (DR), as well as the current level of resonant column testing, the GZ-1 resonant column instrument was used to study the probability statistical indicators, basic laws, and the impact of experimental errors on peak acceleration of DSMR and DR of silt under 8 typical shear strains. The results show that, firstly, the DSMR and DR of silt under different shear strains obey normal distributions. Secondly, there is no significant difference between the reference range of the standard deviation of the DSMR and DR of silt and the outer envelope line. This result indicates that the dispersion of experimental errors for the same person is very small. Thirdly, in medium to hard sites, the influence of experimental errors in DSMR and DR on peak acceleration can be ignored. And the impact of DR test errors on peak acceleration should not be ignored on soft ground with a probability range exceeding 95%. Overall, the testing accuracy of the testing personnel proved to generally meet the requirements, while in other special cases, it is necessary to increase the number of parallel tests and improve the testing technology. Otherwise, it will cause certain risks to the estimation of seismic input for engineering structures. Doi: 10.28991/HIJ-2023-04-01-05 Full Text: PDF

Evolutionary Law of Pore Structure of Ion-Adsorbed Rare Earth Ore Leaching Process

In the process of ion-adsorbed rare earth (RE) ore leaching and mining, the injected chemical agent and rare earth particles have a strong chemical reaction, resulting in changes in the structure of the rare earth, and thus affecting the macroscopic mechanical properties and permeability of soil. To investigate the evolution of the pore structure during the leaching process, indoor leaching simulation experiments were used to compare and analyze the changes of Zeta potential during the leaching process with different concentrations of leaching solution, the process of the gradual change of the strong and weak combined water layer was analyzed, and a nuclear magnetic resonance (NMR) instrument was used to obtain the structural parameters such as the porosity, T2 spectrum and pore radius to analyze the evolution law of microscopic pore structure. The experimental results show that the deionized (DI) water leaching process has less effect on the pore structure of the ore body, and the pore structure inside the ore body evolves gradually from small and medium pore size pores to large pore size pores, while the pore structure of the ore body changes more during the leaching process of the MgSO4 leaching solution. In the initial leaching stage, the number of minimal pores (0–0.24 μm) and small pores (0.24–0.65 μm) of the ore body decreases rapidly, and the number of large pores (1.6–10 μm) increases. In the effective leaching stage, the number of minimal pores (0–0.24 μm), small pores (0.24–0.65 μm) and medium pores (0.65–1.6 μm) increases, while the number of large pores (1.6–10 μm) and mega pores (greater than 10 μm) decreases. At the end of leaching stage, the pore size evolves from medium pores (0.65–1.6 μm) and small pore (0.24–0.65 μm) to large pores (1.6–10 μm). Both chemical replacement reaction and solution percolation can induce changes in the pore structure of the ore body, and the influence of the chemical replacement reaction is higher than that of percolation in the leaching process. The evolution of pore structure during ion exchange is caused by the difference of ionic strength in leaching solution. RE ore particles are adsorbed or released to the solid phase, and the migration of particles leads to changes in the interface properties of RE particles, which affects the pore structural changes.

Determination of copolymer compositions in polyhydroxyalkanoates using 1H benchtop nuclear magnetic resonance spectroscopy.

Continuous research into polyhydroxyalkanoates (PHAs), biodegradable polymers which can be produced by, and harvested from, various bacteria has led to more cost-effective ways of isolating and commercializing them. As bio-based polymers, PHAs can be transformed into compostable bioplastics and utilized for a variety of applications. Often isolated as copolymers, the monomeric ratio compositions of these products greatly affect both the properties and consequently, possible end uses of these products. As such, methods of reliably characterizing these ratios are important for quality control and product development purposes. Herein, we discuss how 1H benchtop nuclear magnetic resonance (NMR) instruments can be used for the determination of monomeric ratio compositions in PHAs and compare results obtained at three different NMR field strengths: 1.40 T (60 MHz), 2.35 T (100 MHz), and 9.4 T (400 MHz).

Quasi-continuous infrared matrix-assisted laser desorption electrospray ionization source coupled to a quadrupole time-of-flight mass spectrometer for direct analysis from well plates.

High-throughput screening (HTS) is a technique mostly used by pharmaceutical companies to rapidly screen multiple libraries of compounds to find drug hits with biological or pharmaceutical activity. Mass spectrometry (MS) has become a popular option for HTS given that it can simultaneously resolve hundreds to thousands of compounds without additional chemical derivatization. For this application, it is convenient to do direct analysis from well plates. Herein, we present the development of an infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source coupled directly to an Agilent 6545 for direct analysis from well plates. The source is coupled to a quadrupole time-of-flight (Q-TOF) mass spectrometer to take advantage of the high acquisition rates without sacrificing resolving power as required with Orbitrap or Fourier-transform ion cyclotron resonance (FTICR) instruments. The laser used for this source operates at 100 Hz, firing 1 pulse-per-burst, and delivers around 0.7 mJ per pulse. Continuously firing this laser for an extended duration makes it a quasi-continuous ionization source. Additionally, a metal capillary was constructed to extend the inlet of the mass spectrometer, increase desolvation of electrospray charged droplets, improve ion transmission, and increase sensitivity. Its efficiency was compared with the conventional dielectric glass capillary by measured signal and demonstrated that the metal capillary increased ionization efficiency due to its more uniformly distributed temperature gradient. Finally, we present the functionality of the source by analyzing tune mix directly from well plates. This source is a proof of concept for HTS applications using IR-MALDESI coupled to a different MS platform.

Extreme low-temperature freezing process and characteristic curve of icy lunar regolith simulant

Water distribution uniformity is an important control criterion for icy lunar regolith samples during ground simulations and is easily influenced by the sample freezing process. However, the freezing process and characteristics of icy lunar regolith are rarely studied. Therefore, to address this issue, simulated samples of icy lunar regolith with two raw material ratios, various water contents and dry densities were prepared in this study, and the unfrozen water contents of samples at different freezing temperatures were tested by nuclear magnetic resonance instrument. The freezing process of icy lunar regolith from 20 °C to −192.8 °C was analyzed based on the variation of the T2 spectrum, and the influence of initial water content and dry density of the samples on the variation rules of unfrozen water content with temperature was discussed. The results show that the freezing process includes the subcooling stage, the fast freezing stage, the slow freezing stage and the stable freezing stage. Below −80 °C, the unfrozen water content in both unsaturated and saturated samples reaches a very small order of magnitude. However, at −190 °C, unfrozen water is still present in the pores (<1 nm) of the samples. Unfrozen water can be divided into bound water, capillary water and gravity water. Unfrozen water in samples with the water content of 5 wt% and 10 wt% is mainly bound water, and water migration occurs during freezing. The solid ice formed during the freezing process of saturated samples has similar adsorption or capillary effect on unfrozen water to rock particles. A lower dry density of the sample means a higher initial freezing temperature and can more significantly promote the formation of capillary and gravity water. Finally, a new freezing characteristic model was constructed based on the linear relationship between particle and pore radii. The model well predicts the four variation stages of unfrozen water content with temperature from room temperature (20 °C) to extreme low temperature (−190 °C). And the applicability of the model was verified by quantifying the available surface permafrost data.