Gradient Ratio Research Articles

Further investigation of the irreversible floc breakup in flocculation kinetics modelling

Abstract Recent research has shown that the equilibrium between aggregation and breakup in flocculation kinetics modelling may not hold due to irreversible floc breakup. This work investigated the influence of the coagulant/particle ratio and average velocity gradient () in the occurrence of this phenomenon with a different water matrix than previous research. Jar test assays were conducted with low (≈15 NTU), medium (≈50 NTU) and high (≈100 NTU) turbidity synthetic raw water, using alum as coagulant and kaolin as primary particles. Results were analyzed using Argaman and Kaufman's model and values for KA (aggregation constant) and KB (breakup coefficient) were determined with the evolutionary convergence method. Model fitting was satisfactory when the Al/particle ratio varied between 10 and 27 mg Al3+/g. Outside this range, residual turbidity increased after equilibrium, attributed to the irreversible floc breakup process and not adequately described by the model. A two-factor analysis of variance (ANOVA) was conducted, and the results indicated a plausible correlation between pKA (–log KA) and Al/particle ratio. As for pKB (–log KB), the results indicated a possible correlation with both Al/particle ratio and . The results suggest that the irreversible floc breakup may occur regardless of the water matrix composition.

Combined Effects of Artificial Surface and Urban Blue-Green Space on Land Surface Temperature in 28 Major Cities in China

The two most common land cover types in urban areas, artificial surface (AS) and urban blue-green space (UBGS), interact with land surface temperature (LST) and exhibit competitive effects, namely, heating and cooling effects. Understanding the variation of these effects along the AS ratio gradient is highly important for the healthy development of cities. In this study, we aimed to find the critical point of the joint competitive effects of UBGS and AS on LST, and to explore the variability in different climate zones and cities at different development levels. An urban land cover map and LST distribution map were produced using Sentinel-2 images and Landsat-8 LST data, respectively, covering 28 major cities in China. On this basis, the characteristics of water, vegetation, and LST in these cities were analyzed. Moreover, the UBGS (water or vegetation)–AS–LST relationship of each city was quantitatively explored. The results showed that UBGS and AS have a competitive relationship and jointly affect LST; this competition has a critical point (threshold). When the proportion of UBGS exceeds this value, UBGS replaces AS as the dominant variable for LST, bringing about a cooling effect. In contrast, when AS dominates LST, it causes a warming effect. The critical points between AS and water and between AS and vegetation in 28 major cities in China were 80% and 70%, respectively. The critical point showed an obvious zonal difference. Compared with cities in subtropical and temperate climate regions, the critical point of arid cities is higher, and UBGS exhibited better performance at alleviating the urban thermal environment. The critical point of cities with higher development levels is lower than that of cities with lower development levels. Even areas with relatively low AS coverage are prone to high temperatures, and more attention should be paid to improving the coverage of UBGS. Our research results provide a reference for the more reasonable handling of the relationship between urban construction, landscape layout, and temperature control.

Probing the electron-to-proton mass ratio gradient in the Milky Way with Class I methanol masers

ABSTRACT We estimate limits on non-universal coupling of hypothetical hidden fields to standard matter by evaluating the fractional changes in the electron-to-proton mass ratio, μ = me/mp, based on observations of Class I methanol masers distributed in the Milky Way disc over the range of the Galactocentric distances $4 \lesssim R \lesssim 12$ kpc. The velocity offsets ΔV = V44 − V95 measured between the 44- and 95-GHz methanol lines provide, so far, one of the most stringent constraints on the spatial gradient kμ ≡ d(Δμ/μ)/dR < 2 × 10−9 kpc−1 and the upper limit on Δμ/μ <2 × 10−8, where Δμ/μ = $(\mu _{\rm \scriptscriptstyle obs}-\mu _{\rm \scriptscriptstyle lab})/\mu _{\rm \scriptscriptstyle lab}$. We also find that the offsets ΔV are clustered into two groups which are separated by $\delta _{\scriptscriptstyle \Delta V} = 0.022 \pm 0.003$ km s−1 (1σ confidence level). The grouping is most probably due to the dominance of different hyperfine transitions in the 44- and 95-GHz methanol maser emission. Which transition becomes favoured is determined by an alignment (polarization) of the nuclear spins of the four hydrogen atoms in the methanol molecule. This result confirms that there are preferred hyperfine transitions involved in the methanol maser action.

Individual element sensitivity for stellar evolutionary isochrones

ABSTRACT Stellar evolution calculations with variable abundance ratios were used to gauge the effects on temperatures, luminosities, and lifetimes in various phases. The individual elements C, N, O, Mg, Si, and Fe were included. Most of the effect relevant to integrated light models is contained in the temperature variable, as opposed to the time-scale or luminosity. We derive a recipe for including abundance-sensitive temperature effects that is applicable to existing isochrone grids. The resultant enhanced isochrones are incorporated into composite stellar population models and compared with galaxy data from the Sloan Digital Sky Survey. A severe oxygen–age degeneracy is apparent, 2–3 Gyr per 0.1 dex in [O/R], where R represents a heavy element such as Fe. Over the range of early-type galaxy velocity dispersion, the spans of all abundance ratios are reduced but the age range increases and becomes systematically older. Allowing Fe-peak elements the freedom to vary accentuates this increase of age span. Overall, these results sharpen the age–mass correlation known as downsizing but decrease the steepness of abundance ratio gradients. Both of these observations, in turn, imply a more robust contribution from gas-free mergers in the histories of typical elliptical galaxies.

On the Synergy of SMAP and AMSR2 for Estimating Snow Depth on Arctic Sea Ice

The objective of this letter is to extend the commonly used gradient ratio (GR) method for Arctic sea ice snow depth estimation by combining brightness temperatures from the Soil Moisture Active Passive (SMAP) and the Advanced Microwave Scanning Radiometer 2 (AMSR2). The L band (1.4 GHz) channel from SMAP together with higher frequencies (i.e., 6.9, 10.7, 18.7, and 36.5 GHz) from AMSR2 were used to calculate GRs, which were then used to derive empirical snow depth retrieval algorithms based on 5 years of Operation IceBridge (OIB) snow depth measurements acquired on Arctic sea ice during springtime. Results show that the gradient ratio GR(1/19) at vertical polarization is suitable for snow depth estimation over both first-year ice (FYI) and multi-year ice (MYI) and could achieve the best performance with correlation <i>r</i> and root mean square distance (RMSD) values being -0.80 and 5.95 cm, respectively. More importantly, there exists a one-to-one relationship between snow depth and GR(1/19) independent of sea ice types, which is an advantage of the GR(1/19) over the previous GR(7/19).

Crack free metal printing using physics informed machine learning

Process parameters and thermophysical and mechanical properties of alloys affect cracking which remains a major challenge in metal printing. Cracks occur because of multiple mechanisms and currently, there is no unified mitigation strategy. Here we evaluate the effects of variables related to the physics of cracking computed by a mechanistic model and independent experimental data using machine learning to prevent cracking. The computed solidification stress, the ratio of the vulnerable and relaxation times, ratio of the temperature gradient to solidification growth rate, and cooling rates and experimental data are used to generate a cracking susceptibility index that predicts crack formation before printing. Computed values of these four variables when used in a decision tree, support vector machines, and logistic regression can predict crack formation with exceptional accuracy. Information gain, information gain ratio, and Gini index-based feature selection calculations provide the same comparative influence of these four variables. Results are presented as easy-to-use cracking susceptibility maps. Our approach can help in process optimization, designing new alloys, and solving problems in manufacturing beyond metal printing.

MBG/ PGA-PCL composite scaffolds provide highly tunable degradation and osteogenic features

It remains a challenge to achieve satisfactory balance between biodegradability and osteogenic capacity in biosynthetic bone grafts. In this study, we aimed to address this challenge by incorporating mesoporous bioactive glass (MBG) into poly(caprolactone-co-glycolide) (PGA-PCL) at gradient ratios. MBG/PGA-PCL (PGC/M) scaffolds with MBG incorporation ratio at 0, 10%, 25% and 40% (PGC/M0-40) were synthesized using a modified solvent casting-particulate leaching method, and their physiochemical and biological properties were comprehensively evaluated. PGC/M scaffolds exhibited highly perforated porous structure with a large-pore size of 300–450 μm, with ordered MBGs of around 6.0 nm mesopores size uniformly dispersed. The increase in MBG incorporation ratio significantly improved the scaffold surface hydrophilicity, apatite-formation ability and pH stability, increased the weight loss rate while insignificantly influenced the molecular chains degradation of PGA-PCL component, and facilitated the attachment, spreading, viability and proliferation of rat bone marrow stromal cells (rBMSCs) on scaffolds. Moreover, rBMSCs cultured on PGC/M10-40 scaffolds demonstrated enhanced ALP activity and osteogenesis-related gene expression in a MBG dose-dependent manner as compared with those cultured on PGC/M0 scaffolds. When implanted to the rat cranial bone defect, PGC/M25 and PGC/M40 scaffolds induced significantly better bone repair as compared to PGC/M0 and PGC/M10 scaffolds. Besides, the biodegradability of PGC/M scaffolds correlated with the MBG incorporation ratio. These data suggested this novel PGC/M scaffolds as promising bone repair biomaterial with highly tunable hydrophilicity, bioactivity, cytocompatibility, osteogenic activity as well as biodegradability.

A deep learning approach to retrieve cold-season snow depth over Arctic sea ice from AMSR2 measurements

Snowpack on sea ice can adjust changes in sea ice conditions and plays a vital role in the Earth's climate system. Snow depth, an important parameter of snowpack, is a necessary variable for retrieving sea ice thicknesses based on satellite altimeter data. Here, regression analysis (RA) is used to determine the best gradient ratio (GR) combination of brightness temperatures for estimating snow depths, and the RA model is proposed. Based on the RA model, one additional deep learning model is built, namely, the 5-variable long short-term memory (5VLSTM) model (or the RA-5VLSTM model). Meanwhile, an additional neural network model is built for comparisons, namely, the 5-variable genetic wavelet neural network (5VGWNN) model (or the RA-5VGWNN model). Using Operation IceBridge (OIB) and ice mass balance buoy (IMB) data, these three models, plus three existing algorithms, are compared to assess their performances in estimating snow depth. The results show that the RA-5VLSTM model performed pretty well among the six algorithms, with an RMSE of 7.16 cm. The RA-5VLSTM model, a robust approach, was less influenced by the uncertainty in the input data. From January to April during 2012–2020, the average monthly snow depth in the Beaufort Sea and the Chukchi Sea mainly showed a downward trend, while an upward trend was observed in the Central Arctic in most months. Variations in snow depth in the Central Arctic were mainly affected by the autumn 2-m air temperature (T2m) and the sea surface temperature (SST). Variations in snow depth in the Chukchi Sea were mainly affected by the autumn sea ice velocity.

Dairy Methane Emissions in California's San Joaquin Valley Inferred With Ground‐Based Remote Sensing Observations in the Summer and Winter

AbstractThe dairy industry in the San Joaquin Valley (SJV) is one of California’s largest methane (CH4) sources. Reducing dairy emissions is a priority for the state’s climate change plans. Observations of current dairy CH4 emissions are key to monitoring actions taken toward this goal. To help support this, we present new ground‐based measurements of atmospheric column‐averaged CH4 mixing ratio (XCH4) gradients across a group of 600 dairies in the central SJV using EM27/SUN solar spectrometers. We used measurements from the 2019 summer and 2020 winter seasons for a top‐down emission inversion based on the WRF‐STILT model. Our top‐down estimates of the region’s dairy emissions range from 90% to 183% of the current CALGEM inventory’s emissions of 277 Gg/yr. In contrast to the strong temperature dependence found by earlier dairy CH4 emission studies, we also find that our top‐down emissions during the winter measurement days are comparable to the summer measurement days, possibly due to seasonal changes in dairy management practices and meteorological conditions. Furthermore, we find significant interday variability in our measurements and find that our emission estimates overlap with earlier top‐down studies and bottom‐up inventories in this region. Our study demonstrates how analysis of ground‐based remotely sensed CH4 gradient observations can help improve our understanding of CH4 sources at scales relevant to mitigation policy. It also reflects the need for long‐term monitoring of CH4 emissions in the region and at individual facilities to better understand their emissions.

Filtration performance of non- woven geotextiles with internally-stable and -unstable soils under dynamic loading

In many applications, geotextiles are subjected to dynamic loading conditions, for example, below roads and railways, for which a Gradient Ratio (GR) test is often used to assess filtration compatibility of soil-geotextile systems. This paper presents results from GR filtration tests with internally-stable and -unstable soils under dynamic loading conditions. In the tests, four non-woven geotextiles were used with varying types of soils under a hydraulic gradient of 5. Test results were interpreted in terms of GR values, permeability values, and mass and gradation characteristics of the soil before/after testing as well as the particles passing through the geotextiles. The test results show that the dynamic loading resulted in an increase of soil migration within the soil as well as an increase in the quantity of soil passing through the geotextiles. The available criteria for evaluating the internal stability of soils are evaluated based on the experimental data. Based on the test results, improvements to filter retention design criteria are suggested which take into account the internal stability of soils under dynamic loading.

Structure function, coherence length, and angle-of-arrival variance for Gaussian beam propagation in turbulent waters.

Wave structure function, coherence length, and angle-of-arrival variance are derived analytically for a Gaussian beam propagating in an underwater turbulent medium. The recently introduced oceanic turbulence optical power spectrum model [J. Opt. Soc. Am. A37, 1614 (2020)JOAOD60740-323210.1364/JOSAA.399150] is used, and results are obtained for the case of large separations. The effect of temperature, salinity, rates of dissipation of mean-squared temperature and energy, temperature-salinity gradient ratio, wavelength, and aperture diameter, is presented. Further, a Gaussian beam is compared with the plane and spherical waves in terms of their effect on wave structure function, coherence length, and angle-of-arrival fluctuations. The presented results can be beneficial to set the parameters of imaging and communication systems using a Gaussian beam in an underwater turbulent medium and can be used for the optimization of the design of these systems.

Myocardial strain measured via two-dimensional speckle-tracking echocardiography in a family diagnosed with arrhythmogenic left ventricular cardiomyopathy

BackgroundArrhythmogenic cardiomyopathy is a myocardial disorder characterized by ventricular arrhythmias, right and/or left ventricular involvement, and fibrofatty infiltrations in the myocardium. We report a family diagnosed with arrhythmogenic left ventricular cardiomyopathy (ALVC) and depict their echocardiographic characteristics.Methods and resultsFifteen family members were divided into three groups based on whether they carried the TMEM43 mutation and had been diagnosed with ALVC. Eight of them had TMEM43 mutations, and four were diagnosed with ALVC according to the Padua criteria. Only the proband experienced sudden cardiac death and had a dilated left ventricle. Left ventricular ejection fraction was reduced in two patients; however, left ventricular global longitudinal strain was depressed in three patients. Low QRS voltages in limb leads were evident in three patients, and five patients had frequent ventricular premature contractions. Late gadolinium enhancement was evident in three patients. Left ventricular layer-specific strain showed that the transmural strain gradient ratio was increased in patients diagnosed with ALVC, and it was elevated in the genotype-positive and phenotype-negative groups compared with healthy individuals.ConclusionGlobal left ventricular longitudinal strain better evaluated left ventricular function than left ventricular ejection fraction. The transmural strain gradient ratio was elevated in patients diagnosed with ALVC, suggesting that it was useful for the evaluation of ALVC.

Effects of Selection of Inlet Perturbations, Multiphase and Turbulence Equations on Slug Flow Characteristics Using Altair® AcuSolve™

Selection of inlet perturbations, multiphase equations, and the turbulence equation may affect the development of slug flow using computational fluid dynamic simulation tools. The inlet perturbation, such as sinusoidal and random perturbations, play an essential role in inducing slug formation. Multiphase equations such as volume of fluid and level set methods are used to track and capture the gas-liquid immiscible interface. Similarly, turbulence equations such as Spalart Allmaras (SA), Detached Eddy Simulations (DES), k-omega, and k-epsilon can be used to predict the evolution of turbulence within the flow. At present, no direct comparison is available in the literature on the selection of (i) types of inlet perturbations, (ii) the choice of multiphase equations, and (iii) the turbulence equation on the development of slug flow using the Altair computational package. This article aims to compare the effects of the selection of inlet perturbations, multiphase models and turbulence equations on slug flow characteristics using Altair® AcuSolve™. The findings by Altair® simulation were compared to published experimental data and simulation works using ANSYS and STAR-CCM+. The slug flow characteristics of interest include slug morphology, a body length-to-diameter ratio, velocity, frequency, and pressure gradient. It was found that the slug flow could be developed for all combinations of settings. Although level set approach in Altair® can track fluid motion successfully, it has a limitation in modelling the convective transport of the multiphase mixture well, unlike ANSYS and STAR-CCM+. Compared to the standard level set method, the coupling of back-and-forth error compensation and correction with the level set function helps to capture the internal boundary more accurately by reducing errors caused by numerical diffusion in the transport of the level set. It was revealed that the Spalart Allmaras turbulence equation could mimic published experimental result better than DES as it produced the closest slug translational velocity. Since the frequency of the slugs for the developed models showed a good agreement with the published data, the models could be sufficient for the investigation of fluid-structure interaction.

Environmental stoichiometry mediates phytoplankton diversity effects on communities' resource use efficiency and biomass

Abstract Positive biodiversity–ecosystem functioning (BEF) relationships are predicted to increase in strength when high environmental variability allows for complementarity between resource use strategies in diverse communities. This environmental variability can be represented by spatial or temporal variation in nutrient ratios, but resource use efficiency (RUE) and therefore biomass build‐up of primary producers might be restricted when nutrient ratios are highly imbalanced (i.e. limitation by one nutrient and beyond optimal ratios for growth). Although the linkages between ecosystem functioning, diversity and nutrient availability are theoretically well understood, we lack experimental evidence on how phytoplankton diversity affects resource use and biomass under variable nutrient ratios (N:P ratios). Combining a mesocosm and a microcosm experiment, we tested diversity effects on ecosystem functioning by exposing a species diversity gradient generated by the loss of rare species in a natural community to different N:P ratios (uniform vs. a gradient). The N:P supply ratio gradient also allowed us to evaluate responses across balanced and imbalanced ratios. We found that increased species diversity led to increased community RUE when supplied a gradient of N:P ratios; but restricted to the highest diversity level. However, diversity did not affect RUE under uniform nutrient ratios. The overall phytoplankton biomass and carbon:nutrient ratios responses to diversity reflected the patterns detected for RUE. Contrary to theoretical predictions, RUE was maintained under highest N:P supply ratios (extreme phosphorous limitation) suggesting that imbalanced N:P ratios do not necessarily decrease function. Thus, we showed that the nutrient context influences diversity effects on RUE and biomass. Synthesis. Overall, our results suggest that the effect of rare phytoplankton species losses on community RUE and biomass can be compensated by the persistent species when nutrient ratios are uniform, but leads to decreases in ecosystem functioning under variable nutrient ratios. This work provides a first attempt for testing interactions between the nutrient context (including concentrations and ratios) and the diversity of (natural) communities experimentally, which is conceptually understood but poorly tested for phytoplankton.

Depth Estimation of Single Defocused Images Based on Multi-Feature Fusion

Based on multi-feature fusion, this paper introduces a novel depth estimation method to suppress defocus and motion blurs, as well as focal plane ambiguity. Firstly, the node features formed by occlusion were fused to optimize image segmentation, and obtain the position relations between image objects. Next, the Gaussian gradient ratio between the defocused input image and the quadratic Gaussian blur was calculated to derive the edge sparse blur. After that, the fast guided filter was adopted to diffuse the sparse blur globally, and estimate the relative depth of the scene. Experimental results demonstrate that our method excellently resolves the ambiguity of depth estimation, and accurately overcomes the noise problem in real-time.

Bearing capacity of conical footings on clays considering combined effects of anisotropy and non-homogeneity

ABSTRACT A spudcan is one of the foundation systems widely used to support the load transferred from a jack-up platform for most offshore drilling operations. The spudcan is an axisymmetric footing with a conical shape. The study on the stability effects of anisotropic and non-homogeneous clays on the bearing capacity of this kind of footings is yet to be found in the current literature. This paper presents novel plastic solutions of the bearing capacity factor for conical footings on clays with linearly increasing anisotropic shear strength. The finite element limit analysis is employed to perform the bearing capacity solutions based on three dimensionless parameters including the cone apex angle, the strength gradient ratio, and the ratio between the undrained shear strength ratio obtained from the triaxial compression test and triaxial extension test. The proposed equations in this study provide a reliable solution to improve the current design standard for conical footings in anisotropic and non-homogeneous clays.

Single-step recovery of pectin and essential oil from lemon waste by ohmic heating assisted extraction/hydrodistillation: A multi-response optimization study

The main products obtained from citrus wastes are pectin and essential oil. In this work, ohmic heating assisted extraction/hydrodistillation (OHAE/H) was applied for the simultaneous recovery of pectin and essential oil from lemon waste. Optimum OHAE/H conditions to maximize the yield of pectin and essential oil were determined with response surface methodology. Three independent variables, namely liquid to solid ratio (w:v), extraction/hydrodistillation time (min) and voltage gradient (V/cm) were varied to obtain maximum pectin and essential oil yield. Optimum OHAE/H conditions were determined as 8.7:1 liquid to solid ratio, 58.4 min extraction/hydrodistillation time and 14.2 V/cm voltage gradient. The predicted pectin and essential oil yields at optimum conditions were 16.58 and 3.62 g/100 g lemon waste, respectively. Data analysis showed that all of the independent variables significantly affected the pectin and essential oil yield. In the verification study, close agreement was found between predicted and experimental values. Conventional heating extraction/hydrodistillation (CHE/H) were conducted to evaluate the effectivity of OHAE/H. With OHAE/H process, the yields of the pectin and essential oil were significantly increased when compared to CHE/H. Limonene concentration of the essential oil produced with OHAE/H was higher than the essential oil produced by CHE/H. Results demonstrate that the single-step OHAE/H could be an effective method for simultaneous extraction and hydrodistillation of pectin and essential oils.

Impact of the Elemental Composition of Exported Organic Matter on the Observed Dissolved Nutrient and Trace Element Distributions in the Upper Layer of the Ocean

AbstractSystematic regional variations in the ratio of nutrient depth gradients of dissolved inorganic carbon (ΔDIC):nitrate (ΔNO3):phosphate (ΔPO4) in the upper layer (300 m) of the Pacific Ocean are observed. Regional variations in the ΔDIC/ΔNO3/ΔPO4 are primarily the result of three processes, that is, the C/N/P of organic matter (OM) being exported and subsequently degraded, nitrogen fixation, and air‐sea CO2 gas exchange. The link between the observed dissolved ΔDIC/ΔNO3/ΔPO4 and the C/N/P of exported OM is established using surface layer dissolved DIC, NO3, and PO4 budgets. These budgets, in turn, provide a means to indirectly estimate the C/N/P of OM being exported from the surface layer of the ocean. The indirectly estimated C/N/P of exported OM reach maxima in the subtropical gyres at 177/22/1, that is, significantly greater than the Redfield ratio and a minimum in the equatorial ocean at 109/16/1 with both results agreeing with available observed particle C/N/P and ocean biogeochemical models. The budget approach was applied to a bioactive trace element (TE) using the measured dissolved Cadmium (Cd) to PO4 gradients to estimate the Cd/P of exported OM in the Pacific Ocean. Combining the budget method with the availability of high‐quality dissolved nutrient and TE data collected during the GOSHIP and GEOTRACES programs could potentially provide estimates of the C/N/P/TE of exported OM on global ocean scales which would significantly improve our understanding of the link between the ocean's biological pump and dissolved nutrient distributions in the upper ocean.

The Potential Role of Peritumoral Apparent Diffusion Coefficient Evaluation in Differentiating Glioblastoma and Solitary Metastatic Lesions of the Brain.

Differentiating glioblastoma (GBM) and solitary metastasis is not always possible using conventional magnetic resonance imaging (MRI) techniques. In conventional brain MRI, GBM and brain metastases are lesions with mostly similar imaging findings. In this study, we investigated whether apparent diffusion coefficient (ADC) ratios, ADC gradients, and minimum ADC values in the peritumoral edema tissue can be used to discriminate between these two tumors. This retrospective study was approved by the local institutional review board with a waiver of written informed consent. Prior to surgical and medical treatment, conventional brain MRI and diffusion-weighted MRI (b = 0 and b = 1000) images were taken from 43 patients (12 GBM and 31 solitary metastasis cases). Quantitative ADC measurements were performed on the peritumoral tissue from the nearest segment to the tumor (ADC1), the middle segment (ADC2), and the most distant segment (ADC3). The ratios of these three values were determined proportionally to calculate the peritumoral ADC ratios. In addition, these three values were subtracted from each other to obtain the peritumoral ADC gradients. Lastly, the minimum peritumoral and tumoral ADC values, and the quantitative ADC values from the normal-appearing ipsilateral white matter, contralateral white matter, and ADC values from cerebrospinal fluid (CSF) were recorded. For the differentiation of GBM and solitary metastasis, ADC3 / ADC1 was the most powerful parameter with a sensitivity of 91.7% and specificity of 87.1% at the cut-off value of 1.105 (p < 0.001), followed by ADC3 / ADC2 with a cut-off value of 1.025 (p = 0.001), sensitivity of 91.7%, and specificity of 74.2%. The cut-off, sensitivity and specificity of ADC2 / ADC1 were 1.055 (p = 0.002), 83.3%, and 67.7%, respectively. For ADC3 - ADC1, the cut-off value, sensitivity, and specificity were calculated as 150 (p < 0.001), 91.7%, and 83.9%, respectively. ADC3 - ADC2 had a cutoff value of 55 (p = 0.001), sensitivity of 91.7%, and specificity of 77.4, whereas ADC2 - ADC1 had a cut-off value of 75 (p = 0.003), sensitivity of 91.7%, and specificity of 61.3%. Among the remaining parameters, only the ADC3 value successfully differentiated between GBM and metastasis (GBM 1802.50 ± 189.74 vs. metastasis 1634.52 ± 212.65, p = 0.022). The integration of the evaluation of peritumoral ADC ratio and ADC gradient into conventional MR imaging may provide valuable information for differentiating GBM from solitary metastatic lesions.

ANALYSIS OF ECHOCARDIOGRAPHIC AND MRI ANATOMICAL CHARACTERISTICS AND HEMODYNAMIC CHARACTERISTICS OF LEFT VENTRICULAR OUTFLOW TRACT STENOSIS

Objective: To analyze the anatomical morphological and hemodynamic characteristics of left ventricular outflow tract stenosis (LVOTS) by echocardiography and MRI. Methods: The Echocardiography data of 112 patients with LVOTS were retrospectively analyzed by measuring the basal interventricular septal thickness (IVST-b), the left ventricle posterior wall thickness (LVPWT), and the peak pressure gradient of LVOTS, as well as by observing the characteristics of spectral pattern and the presence of systolic anterior motion of mitral valve leaflets. A Siemens 3.0T MRI scanner was used to scan the contrast-enhanced left ventricular (LV) volume of all cases. The obtained end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) of LV were compared with the Echocardiography results. Results: The 112 patients were divided into four groups: hypertrophic obstructive cardiomyopathy (Group I, 42 cases), hypertensive left ventricular hypertrophy (Group II, 40 cases), basal septal hypertrophy in the elderly (Group III, 21 cases), and the subaortic membrane (Group IV, 9 cases). The continuous wave (CW) Doppler characteristic of Groups I, II, and III was broadsword-shaped jet, and that of Group IV was equilateral triangle-like spectrum. The IVST-b, IVST-b/LVPWT ratio and peak pressure gradient of LVOTS of Group I was significantly higher than those in Groups II and III ([Formula: see text]). The LVPWT of the first three groups was slightly correlated with the LVOTS peak pressure gradient ([Formula: see text], respectively, [Formula: see text]). There were no statistically significant differences between Echocardiography and MRI results regarding the LV EDV, ESV, SV, and EF ([Formula: see text]), and no statistically significant differences were found between Echocardiography and MRI results regarding the myocardial thicknesses of septal, anterior, lateral, and inferior walls ([Formula: see text]). The Pearson’s correlation analysis demonstrated correlations between MRI and Echocardiography results for LV EDV, ESV, SV, and EF ([Formula: see text], 0.002, 0.009, and [Formula: see text], respectively). The MRI enhancement was shown as delayed enhancement in 52 cases, localized enhancement in 8 cases, diffuse enhancement in 6 cases, and transmural enhancement in 3 cases, with abnormal enhancement lesions distributed in the area of ventricular septum free wall junctions and ventricular septum. Conclusion: Using MRI to evaluate LV function of hypertrophic cardiomyopathy is reliable and accurate. MRI enhancement can be used for the quantitative measurement of myocardial fibrosis. Echocardiography can distinguish the stenosis types of LVOTS. The IVST-b and existence of SAM may be important anatomical characteristics determining the degree of dynamic stenosis, and MRI combined with Echocardiography can provide important detailed information.