Changes In Relaxation Times Research Articles

Volumetric assessment and longitudinal changes of subcortical structures in formalinized Beagle brains.

High field MRI is an advanced technique for diagnostic and research purposes on animal models, such as the Beagle dog. In this context, studies on neuroscience applications, e.g. aging and neuro-pathologies, are currently increasing. This led to a need for reference values, in terms of volumetric assessment, for the structures typically involved. Nowadays, several canine brain MRI atlases have been provided. However, no reports are available regarding the measurements’ reproducibility and little is known about the effect of formalin on MRI segmentation. Here, we assessed the segmentation variability of selected structures among operators (two operators segmented the same data) in a sample of 11 Beagle dogs. Then, we analyzed, for one Beagle dog, the longitudinal volumetric changes of these structures. We considered four conditions: in vivo, post mortem (after euthanasia), ex vivo (brain extracted and studied after 1 month in formalin, and after 12 months). The MRI data were collected with a 3 T scanner. Our findings suggest that the segmentation procedure was overall reproducible since only slight statistical differences were detected. In the post mortem/ ex vivo comparison, most structures showed a higher contrast, thereby leading to greater reproducibility between operators. We observed a net increase in the volume of the studied structures. This could be justified by the intrinsic relaxation time changes observed because of the formalin fixation. This led to an improvement in brain structure visualization and segmentation. To conclude, MRI-based segmentation seems to be a useful and accurate tool that allows longitudinal studies on formalin-fixed brains.

Age-Dependent Changes in Knee Cartilage T1 , T2 , and T1p Simultaneously Measured Using MRI Fingerprinting.

Magnetic resonance fingerprinting (MRF) techniques have been recently described for simultaneous multiparameter cartilage mapping of the knee although investigation of their ability to detect early cartilage degeneration remains limited. To investigate age-dependent changes in knee cartilage T1 , T2 , and T1p relaxation times measured using a three-dimensional (3D) MRF sequence in healthy volunteers. Prospective. The study group consisted of 24 healthy asymptomatic human volunteers (15 males with mean age 34.9 ± 14.4 years and 9 females with mean age 44.5 ± 13.1 years). A 3.0 T gradient-echo-based 3D-MRF sequence was used to simultaneously create proton density-weighted images and T1 , T2 , and T1p maps of knee cartilage. Mean global cartilage and regional cartilage (lateral femur, lateral tibia, medial femur, medial tibia, and patella) T1 , T2 , and T1ρ relaxation times of the knee were measured. Kruskal-Wallis tests were used to compared cartilage T1 , T2 , and T1ρ relaxation times between different age groups, while Spearman correlation coefficients was used to determine the association between age and cartilage T1 , T2 , and T1ρ relaxation times. The value of P < 0.05 was considered statistically significant. Higher age groups showed higher global and regional cartilage T1 , T2 , and T1ρ . There was a significant difference between age groups in global cartilage T2 and T1ρ but no significant difference (P=0.13) in global cartilage T1. Significant difference was also present between age groups in cartilage T2 and T1ρ for medial femur cartilage and medial tibia cartilage. There were significant moderate correlations between age and T2 and T1ρ for global cartilage (R2 =0.63-0.64), medial femur cartilage (R2 =0.50-0.56), and medial tibia cartilage (R2 =0.54-0.66). Cartilage T2 and T1p relaxation times simultaneously measured using a 3D-MRF sequence in healthy volunteers showed age-dependent changes in knee cartilage, primarily within the medial compartment.

Physics-based nozzle design rules for high-frequency liquid metal jetting

We present physics-based nozzle design rules to achieve high-throughput and stable jetting in drop-on-demand liquid metal 3D printing. The design rules are based on scaling laws that capture the change in the meniscus oscillation relaxation time with geometric characteristics of the nozzle's inner profile. These characteristics include volume, cross-sectional area, and inner surface area of the nozzle. Using boundary layer theory for a simple geometry, we show that the meniscus settles faster when the ratio of inner surface area to volume is increased. High-fidelity multiphase flow simulations verify this scaling. We use these laws to explore several design concepts with parameterized classes of shapes that reduce the meniscus relaxation time while preserving desired droplet specifications. Our findings enable exploration of nozzle concepts that can achieve optimal performance by increasing the ratio of the circumferential surface area to the bulk volume to the extent that is allowable by manufacturing constraints.

Association Between Biochemical Joint Tissue Response To Loading And Femoral Cartilage Composition After Knee Surgery

Serum cartilage oligomeric matrix protein (sCOMP) is used to measure acute biochemical joint tissue response to loading. Greater delayed sCOMP post-loading is linked to femoral cartilage thinning over 5 years. It remains unclear if sCOMP response to loading is associated with early femoral cartilage compositional changes linked to osteoarthritis development. PURPOSE: The purpose of this cross-sectional study was to estimate the associations between changes in sCOMP after a standardized walking protocol and femoral cartilage composition in individuals with anterior cruciate ligament reconstruction (ACLR). METHODS: Serum was collected before, immediately after, and 3.5 hours after a standardized 3,000 step walking protocol conducted at each participant’s self-selected speed (speed = 1.2 ± 0.1 m/s). sCOMP changes were calculated as the difference in concentrations from before to immediately and 3.5 hours after walking. Enzyme-linked immunosorbent assays were used to assess sCOMP (mean intra-assay variability = 15%). T1ρ relaxations times were collected bilaterally using magnetic resonance imaging and weightbearing portions of the cartilage were segmented into medial (MFC) and lateral (LFC) femoral condylar regions. Regional interlimb ratios were calculated by dividing mean T1ρ relaxation times in the ACLR limb by the non-injured limb. Greater T1ρ interlimb ratios were interpreted as lower proteoglycan density (worse cartilage composition) in the ACLR relative to the non-injured limb. Linear regressions were used to determine the association between change in sCOMP and T1ρ relaxation times after controlling for sex and months since surgery. RESULTS: 19 participants (9 male/10 female, 20.5 ± 4.1 years old, 24.8 ± 3.1 kg/m2 BMI, 7.3 ± 1.5 months since surgery) completed the study. Greater LFC T1ρ interlimb ratios were associated with greater increases in COMP at 3.5 hours (∆R2 = 0.28, p = 0.03), but not immediately (∆R2 = 0.08, p = 0.32) after walking. Associations between MFC T1ρ interlimb ratios and changes in sCOMP after walking were not statistically significant (p = 0.57-0.82). CONCLUSIONS: Delayed increases in sCOMP concentrations after walking may be more closely linked to deleterious cartilage metabolism and may be a better marker of early degenerative changes in knee joint health than acute changes.

Water proton NMR relaxation revisited: Ultrahighly diluted aqueous solutions beyond Avogadro’s limit prepared by iterative centesimal dilution under shaking cannot be considered as pure solvent

• Ultramolecular dilutions prepared according to homeopathic pharmacopoeia differ from solvent and from simply diluted samples. • Evidence for an unexpected gradual increase of correlation times of water with dilution in ultrahighly diluted solutions. • Evidence for solute-induced nanostructures in aqueous high dilutions growing with dilution. • Nanostructures result from nucleation between the solute, nanobubbles and elements coming from the medium during preparation. • Nanostructures in ultrahigh dilutions, even ultramolecular, enhance leaching processes in glass containers. The biological activity of ultrahigh dilutions (HDs) as used in homeopathy, especially those beyond Avogadro's limit, is still controversial and an intriguing problem for scientists. Homeopathic remedies are mostly prepared by iterative centesimal dilution under vigorous shaking, called dynamization. Cn corresponds to a dilution factor of 10 -2n , and C12 (10 -24 ) to the theoretical limit of molecular presence. Since the 1990 s, NMR relaxation of water protons has emerged as a potent tool for investigating HDs. This article reviews studies of high methodological quality by five independent teams over more than two decades. They demonstrate an increase in T1 and T1/T2, with a decrease in T2, although less constant, in dynamized aqueous HDs. No variation was observed in the similarly treated solvent controls. The phenomenon seems to be common, regardless of solute, dissolved oxygen, material used (glass or plastic), method of shaking, frequency from 0.02 to 600 MHz. Strikingly, the changes in relaxation times increased gradually with dilution, even in the C12-C30 ultramolecular range and they totally vanished after a heating–cooling cycle directly applied on the sealed NMR tubes. The results were interpreted in terms of increasing correlation times of water, greater than 10 −8 s, resulting from the formation of growing solute-induced nanostructures involving nanobubbles and various elements coming from the medium, the atmosphere and the container. Another unexpected result was that HDs were able to enhance some leaching processes in glass containers.

Polymer-Solvent Interactions in Modified Starches Pastes-Electrokinetic, Dynamic Light Scattering, Rheological and Low Field Nuclear Magnetic Resonance Approach.

Starch paste is a very complex dispersion that cannot be clearly classified as a solution, colloid or suspension and many factors affects its properties. As these ambiguities constitute a barrier to technological development, the aim of this study was to investigate the interaction of starch macromolecules with water by analysing the results of rheological properties, low field nuclear magnetic resonance (LF NMR), dynamic light scattering (DLS) and ζ potential analyses. Starch pastes with a concentration of 1%, prepared with distilled water and buffered to pH values of 2.5, 7.0 and 9.5 were analysed. It was proved that the pH buffering substantially decreased the values of consistency index but the pH value itself was not significant. LF NMR studies indicated that the dissolution of starch in water resulted in a reduction in spin-lattice as well as spin-spin relaxation times. Moreover, changes in relaxation times followed the patterns observed in rheological studies. Electrokinetic and DLS analyses showed that potential values are primarily influenced by the properties of the starches themselves and, to a lesser extent, by the environmental conditions. The conducted research also showed complementarity and, to some extent, substitutability of the applied research methods as well as exclusion chromatography (a method not used in this work).

Local Patterns in 2-Year T1ρ and T2 Changes of Hip Cartilage Are Related to Sex and Functional Data: A Prospective Evaluation on Hip Osteoarthritis Participants.

Although T1ρ and T2 have emerged as early indicators for hip osteoarthritis (OA), there is little information regarding longitudinal changes across the cartilage in the early stages of this disease. To characterize the variability in 2-year hip cartilage T1ρ and T2 changes and investigate associations between these patterns of change and common indicators of hip OA. Prospective. A total of 25 women (age: 51.9 ± 16.3 years old; BMI: 22.6 ± 2.0 kg/m2 ) and 17 men (age: 55.8 ± 14.9 years old; body mass index (BMI): 24.4 ± 3.8kg/m2 ) who were healthy or with early-to-moderate hip OA. A 3 T MRI (GE), 3D combined T1ρ /T2 magnetization-prepared angle-modulated partitioned k-space spoiled gradient echo snapshots. Principal component (PC) analysis of Z-score difference maps of 2-year changes in hip cartilage T1ρ and T2 relaxation times, participant hip disability and osteoarthritis outcome scores (HOOS) and functional tests at 2-year follow-up. Shapiro-Wilk test, unpaired t-tests, Kruskal Wallis tests, Pearson or Spearman (ρ) correlations. Significance was set at P < 0.05. Women (-6.40 ± 14.48) had significantly lower T1ρ PC1 scores than men (10.05 ± 26.15). T1ρ PC4 was significantly correlated with HOOSsport , HOOSsymptoms , HOOSpain , HOOSadl , and HOOSqol at 2-year follow-up (ρ: [0.36, 0.50]). T1ρ PC2 and PC4 were significantly correlated with 30-second chair test (ρ=-0.39 and ρ=0.24, respectively) and side plank (ρ=-0.32 and ρ=0.21). T1ρ and T2 PC2 were significantly correlated with 40 m walk test (ρ=0.34 and ρ=0.31) and 30-second chair rise test (ρ=-0.39 and ρ=-0.32). Men exhibited accelerated T1ρ increases across the femoral cartilage compared to women, suggesting sex should be considered when evaluating early hip OA. Participants with poorer HOOS and function exhibited greater T1ρ and T2 increases in superior and anterior femoral cartilage and greater T1ρ increases in the anterior femoral cartilage. These patterns of short-term relaxometry increases could indicate hip OA progression. 2 TECHNICAL EFFICACY: Stage 3.

Association of Superficial Cartilage Transverse Relaxation Time With Osteoarthritis Disease Progression: Data From the Foundation for the National Institutes of Health Biomarker Study of the Osteoarthritis Initiative.

To study whether layer-specific cartilage transverse relaxation time (T2) and/or longitudinal change is associated with clinically relevant knee osteoarthritis (OA) disease progression. The Foundation for the National Institutes of Health Biomarker Consortium was a nested case-control study on 600 knees from 600 Osteoarthritis Initiative participants. Progressor knees had both medial tibiofemoral radiographic joint space width (JSW) loss (≥0.7 mm) and a persistent increase in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score (≥9 on a 0-100 scale) at 24-48 months from baseline (n=194). Multiecho spin-echo (MESE) magnetic resonance images (MRIs) for cartilage T2 analysis had been acquired in the right knees only (97 progressor knees). These were compared to 104 control knees without JSW or pain progression. Fifty-three knees had JSW progression, and 57 pain progression only. Cartilage thickness segmentations obtained from double-echo steady-state MRI were matched to MESE MRI to extract superficial and deep femorotibial cartilage T2. Superficial medial femorotibial compartment (MFTC) T2 at baseline was the primary, and change in deep MFTC T2 between baseline and 12 months was the secondary analytic outcome of this post hoc exploratory study. Baseline superficial MFTC T2 was significantly elevated in progressor knees (adjusted mean 47.2 msec [95% confidence interval (95% CI) 46.5, 48.0]) and JSW progression only knees (adjusted mean 47.3 msec [95% CI 46.3, 48.3]), respectively, versus non-progressor knees (45.8 msec [95% CI 45.0, 46.5]) after adjustment for age, sex, body mass index, WOMAC pain score, and medial joint space narrowing grade (analysis of covariance). Change in T2 was not significantly associated with case status. Baseline superficial, but not deep, medial cartilage T2 is associated with clinically relevant disease progression in knee OA.

Worse Tibiofemoral Cartilage Composition Is Associated with Insufficient Gait Kinetics After ACL Reconstruction.

Greater articular cartilage T1ρ magnetic resonance imaging relaxation times indicate less proteoglycan density and are linked to posttraumatic osteoarthritis development after anterior cruciate ligament reconstruction (ACLR). Although changes in T1ρ relaxation times are associated with gait biomechanics, it is unclear if excessive or insufficient knee joint loading is linked to greater T1ρ relaxation times 12 months post-ACLR. The purpose of this study was to compare external knee adduction (KAM) and flexion (KFM) moments in individuals after ACLR with high versus low tibiofemoral T1ρ relaxation profiles and uninjured controls. Gait biomechanics were collected in 26 uninjured controls (50% females; age, 22 ± 4 yr; body mass index, 23.9 ± 2.8 kg·m -2 ) and 26 individuals after ACLR (50% females; age, 22 ± 4 yr; body mass index, 24.2 ± 3.5 kg·m -2 ) at 6 and 12 months post-ACLR. ACLR-T1ρ High ( n = 9) and ACLR-T1ρ Low ( n = 17) groups were created based on 12-month post-ACLR T1ρ relaxation times using a k-means cluster analysis. Functional analyses of variance were used to compare KAM and KFM. ACLR-T1ρ High exhibited lesser KAM than ACLR-T1ρ Low and uninjured controls 6 months post-ACLR. ACLR-T1ρ Low exhibited greater KAM than uninjured controls 6 and 12 months post-ACLR. KAM increased in ACLR-T1ρ High and decreased in ACLR-T1ρ Low between 6 and 12 months, both groups becoming more similar to uninjured controls. There were scant differences in KFM between ACLR-T1ρ High and ACLR-T1ρ Low 6 or 12 months post-ACLR, but both groups demonstrated lesser KFM compared with uninjured controls. Associations between worse T1ρ profiles and increases in KAM may be driven by the normalization of KAM in individuals who initially exhibit insufficient KAM 6 months post-ACLR.

In vivo fluid transport in human intervertebral discs varies by spinal level and disc region.

BackgroundThe lumbar discs are large, dense tissues that are primarily avascular, and cells residing in the central region of the disc are up to 6–8 mm from the nearest blood vessel in adults. To maintain homeostasis, disc cells rely on nutrient transport between the discs and adjacent vertebrae. Thus, diminished transport has been proposed as a factor in age‐related disc degeneration.MethodsIn this study, we used magnetic resonance imaging (MRI) to quantify diurnal changes in T2 relaxation time, an MRI biomarker related to disc hydration, to generate 3D models of disc fluid distribution and determine how diurnal changes in fluid varied by spinal level. We recruited 10 participants (five males/five females; age: 21–30 years; BMI: 19.1–29.0 kg/m2) and evaluated the T2 relaxation time of each disc at 8:00 AM and 7:00 PM, as well as degeneration grade (Pfirrmann). We also measured disc height, volume, and perimeter in a subset of individuals as a preliminary comparison of geometry and transport properties.ResultsWe found that the baseline (AM) T2 relaxation time and the diurnal change in T2 relaxation time were greatest in the cranial lumbar discs, decreasing along the lumbar spine from cranial to caudal. In cranial discs, T2 relaxation times decreased in each disc region (nucleus pulposus [NP], inner annulus fibrosus [IAF], and outer annulus fibrosus [OAF]), whereas in caudal discs, T2 relaxation times decreased in the NP but increased in the AF.ConclusionsFluid transport varied by spinal level, where transport was greatest in the most cranial lumbar discs and decreased from cranial to caudal along the lumbar spine. Future work should evaluate what level‐dependent factors affect transport.

Investigation of the Hydration Behavior of Different Sugars by Time Domain-NMR.

The hydration behavior of sugars varies from each other and examining the underlying mechanism is challenging. In this study, the hydration behavior of glucose, fructose, allulose (aka rare sugar), and sucrose have been explored using different Time Domain Nuclear Magnetic Resonance (TD-NMR) approaches (relaxation times, self-diffusion, and Magic Sandwich Echo (MSE)). For that purpose, the effects of different sugar concentrations (2.5%, 5%, 10%, 15%, 20%, 30%, and 40%) (w/v) and hydration at different times for 1 day were investigated by T2 relaxation times and self-diffusion coefficients. Crystallinity values of the solid and hydrated sugars were also determined with MSE. Change in T2 relaxation times with concentration showed that the fastest binding with water (parallel with the shortest T2 values) was observed for sucrose for all concentrations followed by glucose, fructose, and allulose. Furthermore, dependency of T2 relaxation times with hydration time showed that sucrose was the fastest in binding with water followed by glucose, fructose, and allulose. The study showed that allulose, one of the most famous rare sugars that is known to be a natural low-calorie sugar alternative, had the lowest interaction with water than the other sugars. TD-NMR was suggested as a practical, quick, and accurate technique to determine the hydration behavior of sugars.

In Vivo Compositional Changes in the Articular Cartilage of the Patellofemoral Joint Following Anterior Cruciate Ligament Reconstruction.

To compare T1ρ relaxation times of the medial and lateral regions of the patella and femoral trochlea at 6 and 12 months following anterior cruciate ligament reconstruction (ACLR) on the ACLR and contralateral extremity. Greater T1ρ relaxation times are associated with a lower proteoglycan density of articular cartilage. This study involved 20 individuals (11 males, 9 females; mean ± SD age 22 ± 3.9 years, weight 76.11 ± 13.48 kg, and height 178.32 ± 12.32 cm) who underwent a previous unilateral ACLR using a patellar tendon autograft. Magnetic resonance images from both extremities were acquired at 6 and 12 months post-ACLR. Voxel by voxel T1ρ relaxation times were calculated using a 5-image sequence. The medial and lateral regions of the femoral trochlea and patellar articular cartilage were manually segmented on both extremities. Separate extremity (ACLR and contralateral extremity) by time (6 months and 12 months) analysis of variance tests were performed for each region (P < 0.05). For the medial patella and lateral trochlea, T1ρ relaxation times increased in both extremities between 6 and 12 months post-ACLR (medial patella P = 0.012; lateral trochlea P = 0.043). For the lateral patella, T1ρ relaxation times were significantly greater on the contralateral extremity compared to the ACLR extremity (P = 0.001). The T1ρ relaxation times of the medial trochlea on the ACLR extremity were significantly greater at 6 (P = 0.005) and 12 months (P < 0.001) compared to the contralateral extremity. T1ρ relaxation times of the medial trochlea significantly increased from 6 to 12 months on the ACLR extremity (P = 0.003). Changes in T1ρ relaxation times occur within the first 12 months following ACLR in specific regions of the patellofemoral joint on the ACLR and contralateral extremity.

Development of a novel task-based functional magnetic resonance imaging phantom based on a bubble-compression approach.

Phantoms used in previous functional magnetic resonance imaging (fMRI) studies have drawbacks, such as a complicated circuit and equipment use, a single signal-change rate, and T2 * values that do not correspond to those of living human brains. We aimed to develop a phantom for use in task-based fMRI studies (gradient-echo echo-planar imaging; GRE-EPI) with bioequivalent T1 and T2 * values, using an innovative method to control the rate of signal change. A gel phantom with T1 and T2 * values equivalent to that of the living brain gray matter was fixed in a 150mm diameter container, with five holes, each of which could hold a 30-ml syringe. The gel phantom contained microscopic air bubbles; this made it possible to control the percent signal change by injector-induced water pressure changes. Using this phantom, we investigated the percent signal change, derived an equation that can approximately reproduce an arbitrary percent signal change, compared different gel phantom samples, investigated the change in relaxation time and bubble size during signal change, and assessed the change in values in each sample over time. The relaxation time of the gel phantom was similar to the literature values for gray matter. The percent signal change achieved was approximately 0%-13.51% and was dependent on the water pressure change. The derived equation was y=0.000008x3 - 0.000771x2 + 0.034222x - 0.026054, with y being the percent signal change and x being the pressure in kPa; the reproducibility was high. No significant difference was detected among samples of gray matter gel phantoms (P>0.05). The change in the rate of signal change with the change in water pressure was due to the change in T2 * value with the change in bubble size. With pressure increasing from 0 to 151.7kPa, the T2 * value increased from 52ms to 85ms. The newly developed gel phantom was stable for 60 days, but its bubble size changed after 21 days. We developed a novel phantom for use in fMRI, which could reproduce minute signal changes similar to the blood-oxygen-level-dependent effect and with bioequivalent T1 and T2 * values, and used an innovative method to control the percent signal change by compressing the air contained in the phantom for validation of fMRI using GRE-EPI. This phantom reproduced the percent signal change due to changes in T2 * values, which is very similar to scanning a human body. This phantom is expected to be a powerful tool for advancing the study of task-based fMRI.

404 Can MRI Non-Invasively Measure Blood-Brain-Barrier Permeability?

Abstract Aim Blood brain barrier (BBB) integrity in neurological disease is tested with gadolinium-enhanced Magnetic Resonance Imaging (MRI). Pathology studies have shown gadolinium deposits in brains with intact BBBs, thus raising concern. We propose a novel use of Arterial Spin Labelling (ASL) –a MRI technique which ‘tags’ blood-water making it a tracer– as a safer alternative in assessing BBB permeability. ASL’s ability to capture T2 (transverse relaxation time) changes of tagged water in blood vs. in tissue (post-exchange across the BBB) supports its feasibility. Method We developed an ASL protocol and collected data from healthy volunteers (n=5) on a 3T Achieva Scanner with the parameters: echo times (TEs) 30, 40, 50, 60, 70ms; repetition time 4200ms; field of view 240x240x47mm and post label delays (PLDs) 1,000ms and 1,500ms. We calculated mean ASL signal (arb units) from the images at each TE, and then extracted T2(ms) values for each volunteer at each PLD. The primary outcome was the change in T2 across PLDs. Results Calculated mean T2s demonstrated a majority of increasing T2s across longer PLDs (n=3) with mean T2 of 55.3+5.3ms at PLD 1,000ms and 62.1+10.8ms at PLD 1,500ms. However, the results are inconclusive as the sample size precluded statistical testing. Conclusions We developed an ASL protocol that demonstrated changes in T2 of blood water with time passage, indicating water exchange through the BBB. This supports the use of ASL in assessing BBB permeability, but more wide-scale studies need to be performed.

Gold core @ platinum shell nanozyme-mediated magnetic relaxation switching DNA sensor for the detection of Listeria monocytogenes in chicken samples

Herein, an Au@Pt nanozyme-mediated magnetic relaxation switching (MRS) DNA biosensor has been developed for the rapid detection of Listeria monocytogenes. Au@Pt nanoparticle was with enhanced stability and high peroxidase activity for decomposing the hydrogen peroxide. After DNA hybridization and magnetic separation, the conjugates of MNP180-probe1-L. monocytogenes DNA-probe2-Au@Pt could adjust the hydrogen peroxide-mediated Mn(VII)/Mn(II) conversion, and thus leading to the change of the transverse relaxation time. The amount of Au@Pt was directly proportional to the concentration of L. monocytogenes. The Au@Pt nanozyme and the hydrogen peroxide-mediated Mn(VII)/Mn(II) signal conversion system contributed to the sensitivity and stability of this sensor. This sensor enabled the detection of L. monocytogenes with a LOD of 30 CFU/mL, which was 33-folds enhancement compared with that of enzyme-linked immunosorbent assay, providing a promising platform to trace the foodborne pathogen in the complex food matrix.

The Effect of Gadolinium-Based Contrast Agents on Longitudinal Changes of Magnetic Resonance Imaging Signal Intensities and Relaxation Times in the Aging Rat Brain.

ObjectivesThe aim of the study was to investigate the possible influence of changes in the brain caused by age on relaxometric and relaxation time–weighted magnetic resonance imaging (MRI) parameters in the deep cerebellar nuclei (DCN) and the globus pallidus (GP) of Gd-exposed and control rats over the course of 1 year.Materials and MethodsTwenty-five Wistar-Han rats were equally subdivided into 5 groups and initially received 8 injections on 4 consecutive days per week of either 3.6 mL/kg body weight saline (group I–III) or 1.8 mmol Gd/kg body weight gadobutrol (group IV) or gadodiamide (group V). T1- and T2-weighted scans, as well as relaxation maps, were acquired at 1 week (all groups); 5, 12, 20, and 26 weeks (saline II, gadobutrol, gadodiamide); and at 35, 44, and 52 weeks (saline III, gadobutrol, gadodiamide) after the last administration. Saline I was euthanized after 1 week, saline II after 26 weeks, and the remaining groups after 52 weeks. Signal intensities (SIs) were evaluated for the DCN/pons (P) and the GP/piriform cortex (PC) ratios, and relaxation times for the DCN and the GP. Brain tissue was extracted, and the gadolinium, iron, and manganese contents were quantified with inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation–ICP-MS imaging.ResultsT1-weighted SI ratios did not show any significant trend with age in any region. The between-group analysis at 52 weeks resulted in a significant difference for the DCN/P and GP/PC region ratio between gadodiamide and its comparators. T1 relaxation times dropped with increasing age in the GP with a 10% to 20% difference between first and last measurement for all groups, and in the DCN <10% with a significant decrease for the gadodiamide group only (DCN: P = 0.0158). Group-related differences were observed at the last measurement time point for T1 values between gadodiamide and saline III in the DCN (P = 0.0153) and gadodiamide and gadobutrol in the GP (P = 0.0287). Analysis of the SI ratios of the T2-weighted images revealed a significant increase for the DCN/P and a decrease for the GP/PC with increasing age for all groups and no differences at 52 weeks after the last injection between groups. T2 values of the GP showed a significant linear decrease over time for all groups (saline I–III: P = 0.0101; gadobutrol: P = 0.0001; gadodiamide: P = 0.0142) in the aging rat brain. Quantitative imaging of manganese and iron by laser ablation–ICP-MS showed a linear increase for the saline groups in the GP for both metals (Fe: P < 0.0001; Mn: P = 0.0306) and in the DCN for manganese only (P = 0.0187), but no differences between groups at 52 weeks.ConclusionsExtensive MRI evaluation did not reveal an indication of SI or relaxation time changes associated with multiple exposure to the macrocyclic-chelated GBCA gadobutrol in the DCN and the GP. With increasing age, a T1 and T2 shortening in the GP and an increase in T2-weighted SI ratio in the DCN/P, as well as a decrease in the GP/PC, were observed for all groups. Such age-related changes can potentially bias MRI results as an indicator for gadolinium presence in the brain.

Regularities of behavior of temperature dependences of resistivity of crystals of solid solutions (Bi-=SUB=-2-x-=/SUB=-Sb-=SUB=-x-=/SUB=-)Te-=SUB=-3-=/SUB=- (0&amp;lt;x&amp;lt;2)

It is shown that the change in the resistivity of crystals of solid solutions (Bi2-xSbx)Te3 (0&amp;lt;x&amp;lt;2) p-type in the temperature range preceding the onset of intrinsic conductivity is due not only to a change in the static relaxation time, the behavior of which in the temperature range from 80 to 300 K is determined mainly by carrier scattering on the vibrations of the crystal lattice, but also by changing the concentration of light holes. The latter is a consequence of the transition of charge carriers from the subzone of heavy holes to the subzone of light holes, as a result of which the concentration of light holes, which make the main contribution to electrical conductivity, decreases with increasing temperature. As a consequence, the plasmon energy proportional to the concentration of charge carriers also decreases with increasing temperature, and the energy of this transition, comparable to the plasmon energy, increases. In this regard, crystals (Bi2-xSbx)Te3 have a specific feature due to the convergence of the plasmon energy and the interband transition, which creates conditions for increasing the intensity of the electron-plasmon interaction. Keywords: thermoelectric materials, bismuth and antimony tellurides, resistivity, interband transitions, plasma of free charge carriers.

Закономерности поведения температурных зависимостей удельного сопротивления кристаллов твердых растворов (Bi-=SUB=-2-x-=/SUB=-Sb-=SUB=-x-=/SUB=-)Te-=SUB=-3-=/SUB=- (0&amp;lt;x&amp;lt;2)

It is shown that the change in the resistivity of crystals of solid solutions (Bi2-xSbx)Te3 (0&lt;x&lt;2) p-type in the temperature range preceding the onset of intrinsic conductivity is due not only to a change in the static relaxation time, the behavior of which in the temperature range from 80 to 300 K is determined mainly by the scattering of carriers on oscillations crystal lattice, but also by changing the concentration of light holes. The latter is a consequence of the transition of charge carriers from the subzone of heavy holes to the subzone of light holes, as a result of which the concentration of light holes, which make the main contribution to electrical conductivity, decreases with increasing temperature. As a consequence, the plasmon energy proportional to the concentration of charge carriers also decreases with increasing temperature, and the energy of this transition, comparable to the plasmon energy, increases. In this regard, crystals (Bi2-xSbx)Te3 have a specific feature due to the convergence of the plasmon energy and the interband transition, which creates conditions for increasing the intensity of the electron-plasmon interaction. Keywords: thermoelectric materials, bismuth and antimony tellurides, resistivity, interband transitions, plasma of free charge carriers.

Use of NMR relaxometry for determination of meat properties: a brief review

Nuclear magnetic resonance spectroscopy (NMR) is a non-destructive and rapid meat analytical technique. Since meat has high proton content, the quality of fresh meat can be assessed by exciting proton spin using NMR laboratory apparatus. NMR allows the assessment of intrinsic properties including animal development stages and muscle type, as well as extrinsic factors including processing and storage conditions that affect the technological traits of meat. It can be used to determine the water-holding capacity of meat, water distribution in muscles, meat authentication, fat content, post mortem aging, rigor mortis, and changes in metabolomes, among others. Changes in NMR relaxation times are associated with the changes in muscle components and their distribution as affected by various processing conditions. Since, industrial assessment is now demanding rapidity and real-time assessment, it is therefore essential to evaluate the potential of NMR in contrast to other techniques. Therefore, this review article presents the principle of working of NMR, various methods available, quality traits of meat that can be evaluated using this technique, and a brief history. This review article will help the industry to adopt novel NMR-based meat quality assessment tools for rapid quality determinations.

Agarose and Wax Tissue-Mimicking Phantom for Dynamic Magnetic Resonance Imaging of the Liver

Objectives: Polymer phantoms can be used to simulate the properties of tissues or organs such as the liver during magnetic resonance imaging (MRI). Although there are reports of simulated liver phantoms with hepatocellular carcinoma (HCC); no studies have documented the simulating of the typical dynamic pattern. Aim: The present study aimed to investigate properties of developed phantoms with respect to the stability, including chemical, mechanical, electrical, as well as MRI properties (T1- and T2- signal intensities), in addition to simulating HCC in a dynamic way. Methods: In this study, liver parenchyma of size 23 ×18 ×13 cm was simulated using three different agarose-wax samples (agarose at concentrations of 2.5 wt%, 4.5 wt%, and 6.0 wt%) mixed with a fixed wax concentration of 2.6 wt%.. HCC samples were fabricated using polyurethane and glycerol of various diameters (0.5, 1.0, and 2.0 cm). Results: The results showed that the agarose-wax sample with a concentration of 2.5 wt% was the most stable sample among the other samples (P-value, 0.468) in mechanical and T1 and T2 intensities. It was also noted that the sample at the concentration of 4.5 wt% had the closest density value to human liver with a difference of 7.88%. Moreover, the agarose-wax sample at a concentration of 2.5 wt% had the closest compressibility and conductivity values, and T1-relaxation time compared to the human liver. However, the largest changes in relaxation times were observed in the fifth week of all samples (P-value = 0.047). The typical enhancement pattern for a simulated HCC of a minimum size, which can be measured with MRI, was 1.0 cm, using a body coil, and 0.5 cm using a head coil. Conclusions: The chemical, electrical density, compressive strength, density, and MR imaging properties of the phantom were measured and compared to those of the human body.