Microstructure Profiles Research Articles

Shear Instability and Turbulent Mixing by Kuroshio Intrusion Into the Changjiang River Plume

AbstractShear instability is a dominant mechanism for mixing in the stratified oceans and coastal seas. For the first time, we present fine‐scale, direct measurements of shear instabilities in the bottom front generated by the Kuroshio intrusion into the Changjiang (Yangtze) river plume. Shear instabilities were identified using a shipboard echo‐sounder and the resulting turbulent mixing was quantified using a turbulence microstructure profiler. The shear instabilities generate vigorous turbulent mixing with dissipation rate and vertical diffusivity up to O (10−4 m2 s−3) and O (10−1 m2 s−1), respectively, comparable to values associated with shear instabilities observed in river plumes and western boundary currents but several orders of magnitude larger than typical values in the open ocean. The enhanced turbulence may contribute significantly to mixing between the Kuroshio water and coastal water and thereby alter the coastal biogeochemistry cycles.

Fabrication of Microstructured Hydrogels via Dehydration for On-Demand Applications.

Microstructured hydrogels show promising applications in various engineering fields from micromolds to anisotropic wetting surfaces and microfluidics. Although methods like molding by, e.g., casting as well as 3D printing are developed to fabricate microstructured hydrogels, developing fabrication methods with high controllability and low-cost is an on-going challenge. Here, a method is presented for creating microstructures through the dehydration of double network hydrogels. This method utilizes common acrylate monomers and a mask-assisted photopolymerization process, requiring no complex equipment or laborious chemical synthesis process. The shape and profile of microstructures can be easily controlled by varying the exposure time and the mask used during photopolymerization. By altering the monomer and the mask used for fabricating the second network hydrogel, both convex and concave microstructures can be produced. To showcase the utility of this method, the patterned hydrogel is utilized as a mold to fabricate a polydimethylsiloxane microlens array via soft lithography for imaging application. In addition, a patterned hydrogel surface exhibiting obvious anisotropic wetting properties and open microfluidic devices which can achieve fast directional superspreading within milliseconds are also fabricated to demonstrate the versatility of the method for different engineering fields.

Transretinal puncture with a 41G cannula for posterior residual subretinal fluid in fovea-off retinal detachments treated by vitrectomy VS fluid tolerance VS other conventional drainage techniques: a comparative study.

To compare functional and anatomical outcomes between posterior drainage of residual fluid using a 41G cannula, fluid tolerance (R-SRF), and conventional complete drainage methods, including removal through peripheral retinal breaks (PRB), perfluorocarbon liquid (PFCL), and posterior retinotomy (PR). In this retrospective, multicenter study, we evaluated cases for visual acuity (VA) at 3 months of follow-up. Secondary outcomes included surgical success, postoperative metamorphopsia, shifts, full-thickness folds (FTF), optical coherence tomography (OCT) parameters, and safety. Subgroup analyses were also conducted. VA did not differ significantly between the three main groups. Subgroup analyses revealed worse VA for PR with 1.131 LogMAR (20/270 in Snellen conversion, p=0,002), with significantly more grade C proliferative vitreoretinopathy (PVR, 40.0%, p=0,003). R-SRF tended to offer better secondary outcomes, without statistical significance except for postoperative epiretinal membrane (ERM, 30.8%, p=0,041). Subgroup analyses found significantly more shifts with PFCL (91,7%, p=0,036). No cases of postoperative FTF or macular holes were observed with the 41G. Our study introduced the 41G technique, indicating favourable outcomes for fovea-off retinal detachments. Nevertheless, fluid tolerance appeared to be the best option, offering a cost-effective and faster method, with an optimal microstructural profile and VA comparable to that of complete drainage techniques.

Nerve agent exposure and physiological stress alter brain microstructure and immune profiles after inflammatory challenge in a long-term rat model of Gulf War Illness

Gulf War Illness (GWI) is a disorder experienced by many veterans of the 1991 Gulf War, with symptoms including fatigue, chronic pain, respiratory and memory problems. Exposure to toxic chemicals during the war, such as oil well fire smoke, pesticides, physiological stress, and nerve agents, is thought to have triggered abnormal neuroinflammatory responses that contribute to GWI. Previous studies have examined the acute effects of combined physiological stress and chemical exposures using GWI rodent models and presented findings related to neuroinflammation and changes in diffusion magnetic resonance imaging (MRI) measures, suggesting a neuroimmune basis for GWI. In the current study, using ex vivo MRI, cytokine mRNA expression, and immunohistological analyses of brain tissues, we examined the brain structure and immune function of a chronic rat model of GWI. Our data showed that a combination of long-term corticosterone treatment (to mimic high physiological stress) and diisopropyl fluorophosphate exposure (to mimic sarin exposure) primed the response to subsequent systemic immune challenge with lipopolysaccharide resulting in elevations of multiple cytokine mRNAs, an increased activated glial population, and disrupted brain microstructure in the cingulate cortex and hippocampus compared to control groups. Our findings support the critical role of neuroinflammation, dysregulated glial activation, and their relationship to disrupted brain microstructural integrity in the pathophysiology of GWI and highlight the unique consequences of long-term combined exposures on brain biochemistry and structural connectivity.

Effect of Scanning Speed on Microstructure Profile of Selective Laser Melted Stainless Steel 316L

Effect of Scanning Speed on Microstructure Profile of Selective Laser Melted Stainless Steel 316L

Effect of turbulent mixing on the formation of intermediate nepheloid layer over the northern continental slope of the Andaman sea

An intermediate nepheloid layer (INL) serves as an important conduit for the cross-slope transport of particulate matter, including organic carbon, biological nutrients and other lithogenic minerals. Despite extensive reports on the substantial sediment influx from the Ayeyarwady River into the northern continental slope of the Andaman Sea (AS), the transport route and fate of these river-borne sediments remain poorly understood, due to lack of in situ observations of turbid INL over the slope. In this study, we present direct evidence of an INL over the northern continental slope of the AS during the winter of 2019/2020, accompanied by enhanced mid-water turbulent mixing. Mooring measurements reveal energetic internal tides with high-mode vertical structure in the study region; and beam-like structures of internal tides are observed, which could be responsible for the enhanced mid-water turbulent mixing coinciding with the INL. Moreover, available microstructure profiles reveal energetic turbulent mixing with bottom-intensified turbulent diffusivity over the study area. Numerical experiments suggest that inhomogeneous distribution of turbulent mixing over the continental slope could induce local convergence of the upwelling transport in the upslope direction, resulting in an intrusion from the boundary to the interior and consequently promoting the INL formation. The discovery of the INL and its mixing-driven generation mechanism provide new insights into sediment transport dynamics over the northern continental slope of the AS.

Structural evolution in desalting Merluccius hubbsi fillets: comparative analysis of varied salting techniques

SummaryThis study investigates the reversible and irreversible structural changes in proteins induced by different salting methods (brining, mixed salting, and dry salting) during the desalting process of Merluccius hubbsi fillets. We focused on mass changes, water content, and NaCl content, employing mathematical models for kinetic analysis and sorption isotherms. Image analysis was utilised to examine tissue microstructure and texture profile analysis assessed the mechanical properties. Our results indicate that salting methods significantly influence mass changes and yield during desalting. Specifically, brining led to the highest weight gain due to controlled salt absorption and enhanced water retention. The Peleg model accurately described NaCl and water content dynamics during desalting. Microscopic analysis revealed substantial structural alterations, while mechanical properties showed significant differences; dry and mixed salting methods caused notable tissue damage and protein denaturation. These findings provide valuable insights for enhancing salting processes and improving the quality of desalted seafood products.

BundleAGE: Predicting White Matter Age using Along-Tract Microstructural Profiles from Diffusion MRI.

Brain Age Gap Estimation (BrainAGE) is an estimate of the gap between a person's chronological age (CA) and a measure of their brain's 'biological age' (BA). This metric is often used as a marker of accelerated aging, albeit with some caveats. Age prediction models trained on brain structural and functional MRI have been employed to derive BrainAGE biomarkers, for predicting the risk of neurodegeneration. While voxel-based and along-tract microstructural maps from diffusion MRI have been used to study brain aging, no studies have evaluated along-tract microstructure for computing BrainAGE. In this study, we train machine learning models to predict a person's age using along-tract microstructural profiles from diffusion tensor imaging. We were able to demonstrate differential aging patterns across different white matter bundles and microstructural measures. The novel Bundle Age Gap Estimation (BundleAGE) biomarker shows potential in quantifying risk factors for neurodegenerative diseases and aging, while incorporating finer scale information throughout white matter bundles.

Associations of Cerebral Blood Flow Patterns With Gray and White Matter Structure in Patients With Temporal Lobe Epilepsy.

Neuroimaging studies in patients with temporal lobe epilepsy (TLE) show widespread brain network alterations beyond the mesiotemporal lobe. Despite the critical role of the cerebrovascular system in maintaining whole-brain structure and function, changes in cerebral blood flow (CBF) remain incompletely understood in the disease. Here, we studied whole-brain perfusion and vascular network alterations in TLE and assessed its associations with gray and white matter compromises and various clinical variables. We included individuals with and without pharmaco-resistant TLE who underwent multimodal 3T MRI, including arterial spin labelling, structural, and diffusion-weighted imaging. Using surface-based MRI mapping, we generated individualized cortico-subcortical profiles of perfusion, morphology, and microstructure. Linear models compared regional CBF in patients with controls and related alterations to morphological and microstructural metrics. We further probed interregional vascular networks in TLE, using graph theoretical CBF covariance analysis. The effects of disease duration were explored to better understand the progressive changes in perfusion. We assessed the utility of perfusion in separating patients with TLE from controls using supervised machine learning. Compared with control participants (n = 38; mean ± SD age 34.8 ± 9.3 years; 20 females), patients with TLE (n = 24; mean ± SD age 35.8 ± 10.6 years; 12 females) showed widespread CBF reductions predominantly in fronto-temporal regions (Cohen d -0.69, 95% CI -1.21 to -0.16), consistent in a subgroup of patients who remained seizure-free after surgical resection of the seizure focus. Parallel structural profiling and network-based models showed that cerebral hypoperfusion may be partially constrained by gray and white matter changes (8.11% reduction in Cohen d) and topologically segregated from whole-brain perfusion networks (area under the curve -0.17, p < 0.05). Negative effects of progressive disease duration further targeted regional CBF profiles in patients (r = -0.54, 95% CI -0.77 to -0.16). Perfusion-derived classifiers discriminated patients from controls with high accuracy (71% [70%-82%]). Findings were robust when controlling for several methodological confounds. Our multimodal findings provide insights into vascular contributions to TLE pathophysiology affecting and extending beyond mesiotemporal structures and highlight their clinical potential in epilepsy diagnosis. As our work was cross-sectional and based on a single site, it motivates future longitudinal studies to confirm progressive effects, ideally in a multicentric setting.

Evaluation of ultrasound-assisted tomato sour soup marination on beef: Insights into physicochemical, sensory, microstructural, and flavour characteristics

This study evaluated the quality attributes of tomato sour soup marinade and investigated the effects of ultrasound-assisted marination on the physicochemical properties, microstructure, texture, sensory quality, and flavour profile of beef. The results showed that tomato sour soup significantly increased the marinade absorption rate and improved beef tenderloin’s physicochemical properties, texture, and flavour attributes compared to static brine (P < 0.05), with organic acids playing an essential role in the marinade tenderisation process. Compared to static sour soup marination, ultrasound treatment significantly accelerated the marination process, reducing beef’s shear force, hardness, and chewiness while increasing its tenderness. Microstructural observations revealed that sour soup marination induced a fragmented and irregular muscle fibre structure. Furthermore, sour soup marination significantly increased the relative concentrations of volatile flavour compounds, including alkanes, organic sulphides, alcohols, aldehydes, and aromatic compounds. Appropriate ultrasound treatment positively affects the texture and flavour characteristics of beef marinated with tomato sour soup, and the optimal approach was 320 W ultrasound treatment for 60 min. Overall, tomato sour soup improved beef’s textural and flavour attributes, while ultrasound-assisted marination is an effective processing method to improve the quality of meat products.

Effects of Exidia yadongensis polysaccharide as emulsifier on the stability, aroma, and antioxidant activities of fat-free stirred mango buffalo yogurt

Because of the poor stability and rheological properties of fat-free stirred yogurt fortified with fruit pulp, new functional polysaccharides as a natural emulsifier, which can increase viscosity in the aqueous phase, may be needed. This study aimed to evaluate the effects of Exidia yadongensis polysaccharide (EYP) as emulsifier on the stability, aroma, and antioxidant activities of mango buffalo yogurt at 4 °C for 25 days. The yogurt with 15 g/L EYP gave a higher content of 215 g/L total solids, 11.3 g/L exopolysaccharides, 0.10 g/L total polyphenols, 630.5 g/L water-holding capacity, and 11.43 g/kg total free amino acids, and maintained better texture, DPPH scavenging activity of 54.05 % and OH scavenging rates of 67.16 %. Moreover, the EYP exhibited the expected ability to weaken postacidification, syneresis, and growth of microorganism, and greatly promote the textural, rheological properties, suspension stability, microstructure, and aroma profiles of stirred mango-flavored buffalo yogurt (p < 0.05). In addition, the addition of 15 g/L EYP can inhibit protein degradation and improve the stability of secondary structure of the protein complex in mango yogurt during 25 days of storage. Therefore, EYP (15 g/L) could be used as natural positive functional factors and emulsifiers in such fat-free stirred yogurt industry.

Spatiotemporal analysis of microstructure, sensory attributes, and full-spectrum metabolomes reveals the relationship between bitterness and nootkatone in Alpinia oxyphylla miquel fruit peel and seeds

The Alpinia oxyphylla fruit (AOF) is a popular condiment and traditional Chinese medicine in Asia, known for its neuroprotective compound nootkatone. However, there has not been a comprehensive study of its flavor or the relationship between sensory and bioactive compounds. To address this issue, we examined AOF’s microstructure, flavor, and metabolomic profiles during fruit maturation. The key markers used to distinguish samples included fruit expansion, testa pigmentation, aril liquefaction, oil cell expansion, peel spiciness, aril sweetness, and seed bitterness. A full-spectrum metabolomic analysis, combining a nontargeted metabolomics approach for volatile compounds and a widely targeted metabolomics approach for nonvolatile compounds, identified 1,448 metabolites, including 1,410 differentially accumulated metabolites (DAMs). Notably, 31 DAMs, including nootkatone, were associated with spicy peel, sweet aril, and bitter seeds. Correlational analysis indicated that bitterness intensity is an easy-to-use biomarker for nootkatone content in seeds. KEGG enrichment analysis linked peel spiciness to phenylpropanoid and capsaicin biosynthesis, seed bitterness to terpenoid (especially nootkatone) biosynthesis, and aril sweetness to starch and sucrose metabolism. This investigation advances the understanding of AOF’s complex flavor chemistry and underlying bioactive principle, encapsulating the essence of the adage: “no bitterness, no intelligence” within the realm of phytochemistry.

Differences in cortical microstructure according to body mass index in neurologically healthy populations using structural magnetic resonance imaging

Associations between brain structure and body mass index (BMI) are increasingly gaining attention. Although BMI-related regional alterations in brain morphology have been previously reported, the effect of BMI on the microstructural profiles, which provide information on the proxy of neuronal density within the cortex, is unexplored. In this study, we investigated the links between cortical layer-specific microstructural profiles and BMI in 302 neurologically healthy young adults. Using the microstructure-sensitive proxy based on the T1-and T2-weighted ratio, we estimated microstructural profile covariance (MPC) by calculating linear correlations of cortical depth-wise intensity profiles between different brain regions. Then, low-dimensional gradients of the MPC matrix were estimated using dimensionality reduction techniques, and the gradients were associated with BMI. Significant effects in the heteromodal association areas were observed. The BMI-gradient association map was related to the geodesic distance along the cortical surface, curvature, and sulcal depth, suggesting that the microstructural alterations occurred along the cortical topology. The BMI-gradient association map was further linked to cognitive states related to negative emotions. Our findings may provide insights into understanding the atypical cortical microstructure associated with BMI.

ATOMIX benchmark datasets for dissipation rate measurements using shear probes

Turbulent mixing in the ocean, lakes and reservoirs facilitates the transport of momentum, heat, nutrients, and other passive tracers. Turbulent fluxes are proportional to the rate of turbulent kinetic energy dissipation per unit mass, ε. A common method for ε measurements is using microstructure profilers with shear probes. Such measurements are now widespread, and a non-expert practitioner will benefit from best practice guidelines and benchmark datasets. As a part of the Scientific Committee on Oceanographic Research (SCOR) working group on “Analysing ocean turbulence observations to quantify mixing” (ATOMIX), we compiled a collection of five benchmark data of ε from measurements of turbulence shear using shear probes. The datasets are processed using the ATOMIX recommendations for best practices documented separately. Here, we describe and validate the datasets. The benchmark collection is from different types of instruments and covers a wide range of environmental conditions. These datasets serve to guide the users to test their ε estimation methods and quality-assurance metrics, and to standardize their data for archiving.

Probing white matter microstructure in youth with chronic pain and its relation to catastrophizing using neurite orientation dispersion and density imaging.

Chronic pain is common in young people and can have a major life impact. Despite the burden of chronic pain, mechanisms underlying chronic pain development and persistence are still poorly understood. Specifically, white matter (WM) connectivity has remained largely unexplored in pediatric chronic pain. Using diffusion-weighted imaging, this study examined WM microstructure in adolescents (age M = 15.8 years, SD = 2.8 years) with chronic pain (n = 44) compared with healthy controls (n = 24). Neurite orientation dispersion and density imaging modeling was applied, and voxel-based whole-white-matter analyses were used to obtain an overview of potential alterations in youth with chronic pain and tract-specific profile analyses to evaluate microstructural profiles of tracts of interest more closely. Our main findings are that (1) youth with chronic pain showed widespread elevated orientation dispersion compared with controls in several tracts, indicative of less coherence; (2) signs of neurite density tract-profile alterations were observed in several tracts of interest, with mainly higher density levels in patients; and (3) several WM microstructural alterations were associated with pain catastrophizing in the patient group. Implicated tracts include both those connecting cortical and limbic structures (uncinate fasciculus, cingulum, anterior thalamic radiation), which were associated with pain catastrophizing, as well as sensorimotor tracts (corticospinal tract). By identifying alterations in the biologically informative WM microstructural metrics orientation dispersion and neurite density, our findings provide important and novel mechanistic insights for understanding the pathophysiology underlying chronic pain. Taken together, the data support alterations in fiber organization as a meaningful characteristic, contributing process to the chronic pain state.

Reinterpretation of the Thorpe Length Scale

Abstract In 1977, S. A. Thorpe proposed a method to estimate the dissipation rate ε of turbulence kinetic energy (TKE) in an overturning turbulent layer in a lake, by sorting the observed (unstable) density profile to render it stable and thus deriving a length scale LT named after him, from the resulting vertical displacements of water parcels. By further proposing that this purely empirical scale (with no a priori physical basis, unlike many other turbulence length scales) is proportional to the Ozmidov scale LO, definable only for stably (not unstably or neutrally) stratified flows, he was able to extract ε. The simplicity of the approach that requires nothing but CTD (Conductivity, Temperature and Depth) casts in water bodies, including lakes and oceans, made it attractive, until microstructure profilers were developed and perfected in later decades to actually make in-situ measurements of ε. Since equivalent microstructure devices are not available for the atmosphere, Thorpe technique has been resurrected in recent years for application to the atmosphere, using potential temperature profiles obtained from high vertical resolution radiosondes. Its popularity and utility have increased lately, in spite of unresolved issues related to the validity of assuming LT is proportional to LO. In this study, we touch upon these issues and offer an alternative interpretation of the Thorpe length scale as indicative of the turbulence velocity scale σK, which allows Thorpe sorting technique to be applied to all turbulent flows, including those generated by convection.

Sodium sulfate and magnesium sulfate resistances of mortar with multi-binder systems of calcined kaolinite clay, fly ash, and limestone powder

This study aimed to assess the durability of mortars subjected to sulfate solutions (specifically Na2SO4 and MgSO4). The effectiveness of cement replacement materials (CRMs) such as calcined kaolinite clay (C), high CaO fly ash (F), and limestone powder (L) in multi-binder systems was studied. The pastes’ microstructure, phase assemblage, and elemental profiles were examined. The results showed that mortars containing calcined kaolinite clay and high CaO fly ash (C30F15) had the lowest expansion when exposed to Na2SO4 and MgSO4. This was caused by the decreased portlandite and expansive products, improved mortar’s compressive strength, and refined pore structure (smallest pore size and lowest pore volume). However, the use of the CRMs, especially when calcined kaolinite clay was combined with fly ash or limestone powder, raised the weight loss and surface deterioration of mortars in a MgSO4 solution because of the lowered pH in the pore solution and formation of MSH.

GAN-MAT: Generative adversarial network-based microstructural profile covariance analysis toolbox

Multimodal magnetic resonance imaging (MRI) provides complementary information for investigating brain structure and function; for example, an in vivo microstructure-sensitive proxy can be estimated using the ratio between T1- and T2-weighted structural MRI. However, acquiring multiple imaging modalities is challenging in patients with inattentive disorders. In this study, we proposed a comprehensive framework to provide multiple imaging features related to the brain microstructure using only T1-weighted MRI. Our toolbox consists of (i) synthesizing T2-weighted MRI from T1-weighted MRI using a conditional generative adversarial network; (ii) estimating microstructural features, including intracortical covariance and moment features of cortical layer-wise microstructural profiles; and (iii) generating a microstructural gradient, which is a low-dimensional representation of the intracortical microstructure profile. We trained and tested our toolbox using T1- and T2-weighted MRI scans of 1,104 healthy young adults obtained from the Human Connectome Project database. We found that the synthesized T2-weighted MRI was very similar to the actual image and that the synthesized data successfully reproduced the microstructural features. The toolbox was validated using an independent dataset containing healthy controls and patients with episodic migraine as well as the atypical developmental condition of autism spectrum disorder. Our toolbox may provide a new paradigm for analyzing multimodal structural MRI in the neuroscience community and is openly accessible at https://github.com/CAMIN-neuro/GAN-MAT.

CO2 and CH4 dynamics in a eutrophic tropical Andean reservoir.

We studied the dynamics of methane (CH4) and carbon dioxide (CO2) in a eutrophic tropical reservoir located in the Colombian Andes. Temporal and spatial dynamics were addressed through sampling during six field campaigns conducted throughout a two-year period. We monitored fluxes at the air-water interface, dissolved gas concentrations, physical and chemical properties of the water column, microstructure profiles of turbulence, and meteorological conditions. Throughout the study period, the reservoir was a persistent source of CH4 to the atmosphere with higher emissions occurring in the near inflow region. During periods of low water levels, both the emissions and surface concentrations of CH4 were higher and more spatially heterogeneous. The measured CO2 fluxes at the air-water interface changed direction depending on the time and location, showing alternating uptake and emissions by the water surface. Mass balances of dissolved CH4 in the surface mixed layer revealed that biochemical reactions and gas evasion were the most significant processes influencing the dynamics of dissolved CH4, and provided new evidence of possible oxic methane production. Our results also suggest that surface CH4 concentrations are higher under more eutrophic conditions, which varied both spatially and temporally.

Decomposing cortical activity through neuronal tracing connectome-eigenmodes in marmosets

Deciphering the complex relationship between neuroanatomical connections and functional activity in primate brains remains a daunting task, especially regarding the influence of monosynaptic connectivity on cortical activity. Here, we investigate the anatomical-functional relationship and decompose the neuronal-tracing connectome of marmoset brains into a series of eigenmodes using graph signal processing. These cellular connectome eigenmodes effectively constrain the cortical activity derived from resting-state functional MRI, and uncover a patterned cellular-functional decoupling. This pattern reveals a spatial gradient from coupled dorsal-posterior to decoupled ventral-anterior cortices, and recapitulates micro-structural profiles and macro-scale hierarchical cortical organization. Notably, these marmoset-derived eigenmodes may facilitate the inference of spontaneous cortical activity and functional connectivity of homologous areas in humans, highlighting the potential generalizing of the connectomic constraints across species. Collectively, our findings illuminate how neuronal-tracing connectome eigenmodes constrain cortical activity and improve our understanding of the brain’s anatomical-functional relationship.