Values Of Relaxation Time Research Articles

Analysis of Discrete Velocity Models for Lattice Boltzmann Simulations of Compressible Flows at Arbitrary Specific Heat Ratio

This paper is devoted to the comparison of discrete velocity models used for simulation of compressible flows with arbitrary specific heat ratios in the lattice Boltzmann method. The stability of the governing equations is analyzed for the steady flow regime. A technique for the construction of stability domains in parametric space based on the analysis of eigenvalues is proposed. A comparison of stability domains for different models is performed. It is demonstrated that the maximum value of macrovelocity, which defines instability initiation, is dependent on the values of relaxation time, and plots of this dependence are constructed. For double-distribution-function models, it is demonstrated that the value of the Prantdl number does not seriously affect stability. The off-lattice parametric finite-difference scheme is proposed for the practical realization of the considered kinetic models. The Riemann problems and the problem of Kelvin–Helmholtz instability simulation are numerically solved. It is demonstrated that different models lead to close numerical results. The proposed technique of stability investigation can be used as an effective tool for the theoretical comparison of different kinetic models used in applications of the lattice Boltzmann method.

Native T2 Predicts Myocardial Inflammation Irrespective of a Patient's Volume Status.

Myocardial inflammation and edema are major pathological features in myocarditis. Myocardial tissue water content and myocardial edema can be quantified via T2 mapping. Thus, cardiac magnetic resonance (CMR) is the noninvasive gold standard for diagnosing myocarditis. Several studies showed an impact of short-term volume changes on T2 relaxation time. Plasma volume status (PVS) is a good surrogate parameter to quantify a patient's volume status, and it is simple to use. The aim of this study was to determine the effect of PVS on the diagnostic value of T2 relaxation time in myocardial inflammation. Between April 2017 and December 2022, patients who were indicated for cardiac CMR were included in our prospective clinical registry. Patients with myocardial inflammation and those with unremarkable findings were analyzed in the present study. A blood sample was drawn, and PVS was calculated. Patients were separated into PVS tertiles to explore a possible nonlinear dose-response relationship. Logistic regression analysis was used to determine whether T2 is an independent predictor of myocardial inflammation. A total of 700 patients (47.43% female) were eligible for analysis. Of these, 551 patients were healthy (78.7%), while 149 (21.3%) showed signs of myocardial inflammation. The T2 relaxation time was elevated in patients with myocardial inflammation (40 ms [IQR 37-42 ms] vs. 38.0 ms [IQR 36-39 ms], p < 0.001). PVS showed no difference between the groups (-12.94 [IQR -18.4--7.28] vs.-12.19 [IQR -18.93--5.87], p = 0.384). T2 showed a clear dose-response relationship with PVS, with increasing T2 values along the PVS tertiles. In spite of this, T2 was found to be an independent marker of myocardial inflammation in logistic regression (OR T2 1.3 [95% CI 1.21-1.39], p < 0.001), even after adjusting for PVS (OR T2 [adj. PVS] 1.31 [95% CI 1.22-1.40], p < 0.001). Despite a dose-response relationship between T2 and the volume status, T2 was found to be an independent indicator of myocardial inflammation.

A New Model for Solving Hydrological Connectivity Inside Soils by Fast Field Cycling NMR Relaxometry

In this paper, a new quantitative approach for estimating the structural and functional connectivity inside soil by Fast Field Cycling (FFC) NMR relaxometry is presented, tested by measurements carried out in three samples with different texture characteristics. Measurements by FFC NMR relaxometry have been carried out using water-suspended samples and Proton Larmor frequencies (νL) ranging in the 0.015–35 MHz interval. Two non-degraded soil samples, with different textural characteristics, and a degraded soil collected in a badland area, were analyzed. For a given soil and any applied Proton Larmor frequency, the distribution of the longitudinal relaxation times, T1, (i.e., relaxogram) measured by FFC NMR has been integrated, and the resulting S-shaped curve (i.e., relaxogram integration curve) was represented, for the first time, by Gumbel’s diagram. This new representation of the relaxogram integration curve, transforming the S-shaped curve into a straight line, allowed for distinguishing three linear components, corresponding to three different relaxation time ranges, characterized by three different slopes. Two points, identified by the abrupt slope changes of the relaxogram integration curve plotted in Gumbel’s diagram, are used to identify two characteristic values of relaxation time, T1A and T1B, which define three well-known pore size classes (T1 &lt; T1A micro-pores, T1A &lt; T1 &lt; T1B meso-pores, and T1 &gt; T1B macro-pores). The relaxogram integration curve allowed for calculating the non-exceeding empirical cumulative frequency, F(T1), corresponding to the characteristic T1A and T1B values. The analysis demonstrated that the relaxogram can be used to determine the pore-size ranges of each investigated sample. Finally, using the slope values of the three components of the relaxogram integration curve, a new definition of the Structural Connectivity Index, SCI, and Functional Connectivity Index, FCI, was proposed.

Thermal-optical mechanical waves of the microelongated semiconductor medium with fractional order heat time derivatives in a rotational field

Outlined here is an innovative method for characterizing a layer of microelongated semiconductor material under excitation. Fractional time derivatives of a heat equation with a rotational field are used to probe the model during photo-excitation processes. Micropolar-thermoelasticity theory, which the model implements, introduces the microelongation scalar function to characterize the processes occurring inside the microelements. When the microelongation parameters are considered following the photo-thermoelasticity theory, the model investigates the interaction scenario between optical-thermo-mechanical waves under the impact of rotation parameters. During electronic and thermoelastic deformation, the key governing equations have been reduced to dimensionless form. Laplace and Fourier's transformations are used to solve this mathematical problem. Isotropic, homogeneous, and linear microelongated semiconductor medium's general solutions to their respective fundamental fields are derived in two dimensions (2D). To get complete solutions, several measurements must be taken at the free surface of the medium. As an example of numerical modeling of the important fields, we will use the silicon (Si) material’s physicomechanical characteristics. Several comparisons were made using different values of relaxation time and rotation parameters, and the results were graphically shown.

Tissue Doppler Echocardiography As A Predictor Of Early Subclinical Right Ventricular Diastolic Dysfunction In Asthmatic Children.

To assess the effect of asthma in children on systolic and diastolic functions of the heart, and to explore the relationship between the two. The case-controlstudy was conducted at Kafrelsheikh University Hospital, Egypt, from September 2019 to May 2022, and comprised asthmatic children of either gender aged 5-15 years and healthy controls matched for age and gender. The participants were subjected to detailed history, complete examination, spirometry evaluation and conventional and tissue Doppler echocardiography. Myocardial performance index was calculated and compared. Data was analysed using SPSS 22. Of the 120 subjects, 60(50%) were cases; 33(55%) boys and 27(45%) girls with mean age 9.4±2.9 years(range: 5-15 years). The remaining 60(50%)subjects were controls; 34(56.6%) boys and 26(43.3%) girls with mean age 9.7±2.9 years (range: 5-15 years). Left ventricular dimensions, estimated pulmonary artery pressure, and right ventricular dimensions showed no significant inter-group differences (p>0.05), but right ventricular end diastolic diameter was significantly higher in the cases than the controls (p=0.046). Tissue Doppler showed that lateral annular peak Ê, Â, isovolumetric relaxation time and myocardial performance index values were significantly different between the groups (p<0.05). Tissue Doppler echocardiography could detectsubtle right ventricular diastolic dysfunction in asthmatic children even with no clinical symptoms and normal findings on conventional echocardiography.

Effects of different ratios of mannitol to sorbitol on the functional properties of sweet potato starch films

Sorbitol as a plasticizer is easily crystallized from starch film, resulting in the reduction in plasticizing effect. To improve the plasticizing performance of sorbitol in starch films, mannitol, an acyclic hexahydroxy sugar alcohol, was used to cooperate with sorbitol. The effects of different ratios of mannitol (M) to sorbitol (S) as a plasticizer on mechanical properties, thermal properties, water resistance and surface roughness of sweet potato starch films were investigated. The results showed that the surface roughness of starch film with M:S (60:40) was the smallest. The number of hydrogen bonds between plasticizer and starch molecule was proportional to the mannitol content starch film. With the decrease of mannitol contents, the tensile strength of starch films gradually decreased except for M:S (60:40). Moreover, the transverse relaxation time value of starch film with M:S (100:0) was the lowest, indicating that it had the lowest degree of freedom of water molecules. Starch film with M:S (60:40) is the most effective in delaying the retrogradation of starch film. This study offered a new theoretical basis that different ratios of mannitol to sorbitol improve different performances of starch films.

Assessment of fetal cardiac functions in pregnant women with asthma.

This study aims to investigate the effects of maternal asthma on fetal cardiac functions. The study was planned with 30 pregnant women who presented to a tertiary health center and were diagnosed with asthma and 60 healthy controls with similar gestational ages. The fetal echocardiographic assessment was assessed between 33 and 35weeks of gestation with pulsed-wave Doppler (PW), M-mode, and tissue Doppler imaging (TDI). Fetal cardiac functions were compared between maternal asthma and the control group. Cardiac functions were assessed according to the duration of maternal asthma diagnosis, as well. Early diastolic function parameters, tricuspid E wave (p=.001), and tricuspid E/A ratio (p=.005) were significantly lower in the group with maternal asthma. Tricuspid annular plane systolic excursion (TAPSE) and measurements of mitral annular plane systolic excursion (MAPSE) values were statistically lower in the study group than in the control group; p=.010 and p=.012, respectively. Parameters assessed with TDI (E', A', S', E/E', and MPI' of tricuspid valves) and global cardiac function parameters assessed with PW like myocardial performance index (MPI) and left cardiac output (LCO) were similar between groups (p>.05). Although, MPI did not change between groups, and the isovolumetric relaxation time (IVRT) value was prolonged in maternal asthma cases (p=.025). We found that maternal asthma disease causes alteration in fetal diastolic and early systolic cardiac functions, but the global fetal cardiac function does not change. Diastolic heart function values also varied with the duration of maternal asthma. Prospective studies are needed to compare fetal cardiac functions with additional patient groups according to disease severity and type of medical treatment.

Nonstationary thermophysical characterization of exfoliated graphite with carbon nanotubes composites

The sheet samples of thermally exfoliated graphite (TEG)–carbon nanotubes (CNT) composites (TEG-CNT-cs) were obtained by persulphate oxidation using chemical (CO) and electrochemical (anode) oxidation (ECAO). Electron microscopy reveals multi-layered structures of few-layer graphene nanosheets with folded and tubular-like fragments. The effective thermal diffusivity values were estimated by nonstationary photo-pyroelectric thermophysical characterization using the heat pulse and thermowave modulation methods. Comparison with other carbon (C-) based thermal management materials shows that TEG-CNT-cs exhibit thermal diffusivity, effusivity, and conductivity comparable with those of actual C–polymer- and C–C-composites. For TEG-CNT-cs, evaluated values of phonon mean free path (MFP) and relaxation time (RT) are in the ranges estimated for defective graphene. The values of diffusivity and effusivity, MFP, and RT are lower for denser TEG-CNT-cs obtained by ECAO and are higher for less dense TEG-CNT-cs obtained by CO. The obtained diffusivity and effusivity values designate TEG-CNT-cs as suitable thermal management materials.

Investigation of structural, microstructural and electrical characteristics of hydrothermally synthesized Li0.5-0.5xCoxFe2.5-0.5xO4, (0.0 ≤ x≤ 0.4) ferrite nanoparticles

Lithium Ferrite is one of the fascinating materials because of its numerous applications in the electronic industry, defense, and environment. Herein, we report the synthesis of cobalt-doped Lithium nano ferrites (Li0.5-0.5xCoxFe2.5-0.5xO4, with x = 0.0, 0.1, 0.2, 0.3, 0.4) by employing the Hydrothermal approach. The X-Ray diffraction (XRD) pattern shows the formation of cubic spinel ferrite structure where crystallite size is observed to decrease from 86 nm to 44 nm whereas, lattice parameter increases from 8.354 Å to 8.397 Å with the increase in Co2+ ions concentration. The reduction in crystallite size is coupled to a rise in the lattice stain, which changes from 0.00131 to 0.00253 during the duration of the study. Rietveld refinement is performed to know the phase purity of prepared nanoferrites. Scanning electron microscopy (SEM) micrographs show the development of grains with irregular shapes and clearly visible grain boundaries. The grain size ranges from 210 to 702 nm. Complex Impedance Spectroscopy (CIS) shows the compositional dependence of Z′ and Z″ with respect to frequency. The Cole-Cole plot shows the formation of single semi-circular arc that describes the dominance of grain. The electrical parameters from CIS plot show that the values of grain resistance (Rg), relaxation time (τg) and grain conductivity (σg) ranges from 33.542 Ω to 17.459 Ω, 0.816×10−4 s to 1.226×10−4 s and 5.57 S/cm to 16.12 S/cm, respectively. The ac conductivity rises as the doping level rises, and the fact that there is a wide range of conductivity values show that all of the samples exhibit non-Debye behaviour.

Unusual Transport and Impact of Nonparabolic Electronic Band Structure on the Thermoelectric Performance in n‐Type In4Se3‐Based Thermoelectric Materials

Unusual thermoelectric (TE) transport in n‐type In4Se3 has been reported in the context of first‐principles electronic structure calculation and Boltzmann transport theory. The density of states (DOS) shows certain peaks due to a nontopological Mexican hat and parabolic capping around the edges of Kane bands. The effect of such hard shifts of bands shows anomalously high Seebeck coefficient (S = 550 μV K−1 at ≈1017 cm−3) at room temperature due to very slow decreasing S and rapidly increasing DOS effective mass with carrier concentration compared to that obtained from Kane and parabolic band model. The best TE performance is predicated in Kane transport region (≈1018 cm−3) over the wide range of temperature, 300–700 K. The calculated values of relaxation time (≈10−14 s at 660 K), electrical conductivity, power factor and figure of merit in iodine‐doped sample and those obtained from the rigid band model of pure sample show excellent agreement with the reported experimental results.

Numerical investigation of a novel method of laser assisted cryopreservation of biological tissue considering non-fourier heat conduction

The present article proposes a numerical model for a novel laser assisted cryopreservation through vitrification of biological tissue. A two-dimensional numerical model is developed considering the non-Fourier heat conduction. The Finite Volume Method is used for discretization of the governing differential equation while the Tri-diagonal Matrix Algorithm (TDMA) is used for solving the resulting discretized algebraic equation in order to obtain the temperature distribution inside the tissue domain. The existing enthalpy method is modified considering the thermal relaxation time to capture the freezing front. With the increase in thermal relaxation time value, rate of heat transfer and rise in temperature during laser heating decreases and rate of heat loss during freezing also decreases. This reduces the length up to which vitrification is achieved. So, a proper size of the tissue is to be chosen to achieve the desired freezing rate. This length may vary based on the laser parameters and the thermal relaxation time. However, the validity of the present study may be examined experimentally in real ambient conditions before application in tissue preservation.

Investigation of the Dielectric Properties of the Insulating Gas of Commercial Gas-Filled Surge Arresters

Based on the experimental results of dynamic breakdown voltage and electrical breakdown time delay, the dielectric properties of insulating gas commercial gas-filled surge arresters were analyzed. Data for dynamic breakdown voltage obtained by the method of stepwise increase of voltage whose rise rates ranged from 1 to 10 V/s. It is shown that these values of voltage rise rate do not have a significant effect on the value of dynamic breakdown voltage. In order to monitor the processes caused by electrical breakdown on the dielectric properties of insulating gas of these components the electrical breakdown time delay was a measure for different values of relaxation time and applied voltage. It has been shown that the presence of positive ions, which are formed during breakdown and subsequent self-sustaining discharge with recombination time of about 1 ms, has a significant effect on the reduction the dielectric resistance of insulating gas. It has also been shown that the applied voltage whose values are close to DC-spark over-voltage has a significant effect on the delay response of these components.

Bioconvection effect in the Carreau nanofluid with Cattaneo–Christov heat flux using stagnation point flow in the entropy generation: Micromachines level study

Abstract The addition of gyrotactic microbes in the nanoparticles is essential to embellish the thermal efficiency of many systems such as microbial fuel cells, bacteria-powered micro-mixers, micro-volumes like microfluidics devices, enzyme biosensor, and chip-shaped microdevices like bio-microsystems. This analysis investigates the second law analysis in the bioconvection flow of a Carreau nanoliquid through a convectively stretching surface. The heat transports characteristics encountered with Cattaneo–Christove heat flux and thermal radiation. The Buongiorno model is used for nanoliquid, which comprises the Brownian motion and thermophoretic. The appropriate transformation is invoked to change the system of the partial differential equation into ordinary differential equations. Afterward, these equations are classified analytically with the help of the homotopy analysis method. The influence of numerous physical variables is interpreted and elaborated via graphs. The tabular result shows the numerical consequences of different physical flow parameters. It is examined that a more significant Weissenber number We {\rm{We}} results in deprecation in the velocity field. It is appraised that the temperature profile reduces to augment the value of thermal relaxation time. Justification of the current work has existed through previous publishing results. The utilization of Carreau nanoparticles in the shear rate-dependent viscous fluid is of significant importance due to their potential to improve heat and mass transmission.

Risk factors for the recurrence of cervical cancer using MR-based T1 mapping: A pilot study.

This study aimed to identify risk factors for recurrence in patients with cervical cancer (CC) through quantitative T1 mapping. A cohort of 107 patients histopathologically diagnosed with CC at our institution between May 2018 and April 2021 was categorized into surgical and non-surgical groups. Patients in each group were further divided into recurrence and non-recurrence subgroups depending on whether they showed recurrence or metastasis within 3 years of treatment. The longitudinal relaxation time (native T1) and apparent diffusion coefficient (ADC) value of the tumor were calculated. The differences between native T1 and ADC values of the recurrence and non-recurrence subgroups were analyzed, and receiver operating characteristic (ROC) curves were drawn for parameters with statistical differences. Logistic regression was performed for analysis of significant factors affecting CC recurrence. Recurrence-free survival rates were estimated by Kaplan-Meier analysis and compared using the log-rank test. Thirteen and 10 patients in the surgical and non-surgical groups, respectively, showed recurrence after treatment. There were significant differences in native T1 values between the recurrence and non-recurrence subgroups in the surgical and non-surgical groups (P<0.05); however, there was no difference in ADC values (P>0.05). The areas under the ROC curve of native T1 values for discriminating recurrence of CC after surgical and non-surgical treatment were 0.742 and 0.780, respectively. Logistic regression analysis indicated that native T1 values were risk factors for tumor recurrence in the surgical and non-surgical groups (P=0.004 and 0.040, respectively). Compared with cut-offs, recurrence-free survival curves of patients with higher native T1 values of the two groups were significantly different from those with lower ones (P=0.000 and 0.016, respectively). Quantitative T1 mapping could help identify CC patients with a high risk of recurrence, supplementing information on tumor prognosis other than clinicopathological features and providing the basis for individualized treatment and follow-up schemes.

Theoretical study on bio-convection of micropolar fluid with an exploration of Cattaneo–Christov heat flux theory

This research explores the heat transfer rate for micropolar fluid in a channel flow. In spite of formal Fourier’s law, the Cattaneo–Christov heat flux design is implemented in energy system. Using appropriate dimensionless parameters, the guiding coupled partial differential equations that represent the fluid flow are modified into ordinary differential equations. By executing Runge–Kutta integration procedure and the shooting method, the numerical results are achieved. The impacts of thermal relaxation time and bio-convection flow of micropolar fluid are examined in this assessment. Graphical analyses are used to assess the effects of physical factors for the momentum, micro-rotation, concentration, density of micro-organisms and temperature gradient. The skin friction values, motile density number, heat and mass transfer rate are the fascinating physical quantities whose numerical data are computed and validated against different parametric values. The variational iteration method (VIM) and Adomian decomposition method are the analytical modules which have been incorporated here for solving the nonlinear systems for showing better approximity. It is found from the study that larger the thermal relaxation time values, the more likely they are to increase heat transfer, hence lowering the fluid temperature. Moreover, both Fourier and Cattaneo–Christov heat conduction module exhibit qualitatively similar influence on embedded parameters also the temperature profile diminishes for larger values of [Formula: see text]. The culminations evidently disclose that the bio-convection Peclet number and the motile microbes parameter enhance the density of motile micro-organisms. From a computational perspective, the VIM is more effective, practical and ease of use. The numerical and analytical results are compared well with the existing articles. The optimum parameter level for maximum heat transfer is considered to be [Formula: see text]. Taguchi approach was successfully used to determine the optimum design parameters for maximum heat transfer is 1.724012 for the parameters A-5:B-5:C-0.5:D-0.5:E-0.7.

NUMERICAL SIMULATION OF THE INTERACTION OF HETEROGENEOUS DETONATION WITH THE POROUS INSERT OF DIFFERENT GEOMETRY

Numerical simulation of interaction of heterogeneous detonation with a porous insert was carried out. The mathematical model for porous inserts assumed that the porous zone was a continuous medium in the form of a grid of stationary cylinders. Main regimes and critical conditions of detonation attenuation in porous zones were obtained for micron-sized aluminum particles. Main features of the flow field in the channel were described. It was found that for micron particles in the empty space, a planar detonation wave formed. Main patterns for micron-sized combustible particles and inert porous zone were found. The critical height of the empty space without porous inserts was determined. The critical height of the empty space did not depend on the amount of open areas in the porous zone. The critical height did not depend on the width of the channel. For micron-sized particles, a physical explanation for the existence of planar detonation based on the values of thermal relaxation times is proposed.

Value of pre-/post-contrast-enhanced T1 mapping and readout segmentation of long variable echo-train diffusion-weighted imaging in differentiating parotid gland tumors

PurposeThis study aimed to explore the value of pre-/post-contrast-enhanced T1 mapping and readout segmentation of long variable echo-train diffusion-weighted imaging (RESOLVE-DWI) for the differential diagnosis of parotid gland tumors. MethodsA total of 128 patients with histopathologically confirmed parotid gland tumors [86 benign tumors (BTs) and 42 malignant tumors (MTs)] were retrospectively recruited. BTs were further divided into pleomorphic adenomas (PAs, n = 57) and Warthin’s tumors (WTs, n = 15). MRI examinations were performed before and after contrast injection to measure the longitudinal relaxation time (T1) value (T1p and T1e, respectively) and the apparent diffusion coefficient (ADC) value of the parotid gland tumors. The reduction in T1 (T1d) values and the percentage of T1 reduction (T1d%) were calculated. ResultsThe T1d and ADC values of the BTs were considerably higher than those of the MTs (all P <.05). The area under the curve (AUC) of the T1d and ADC values for differentiating between BTs and MTs of the parotid was 0.618 and 0.804, respectively (all P <.05). The AUC of the T1p, T1d, T1d%, and ADC values for differentiating between PAs and WTs was 0.926, 0.945, 0.925, and 0.996, respectively (all P >.05). The ADC and T1d% + ADC values performed better in differentiating between PAs and MTs than the T1p, T1d, and T1d% (AUC values: 0.902, 0.909, 0.660, 0.726, and 0.736, respectively). The T1p, T1d, T1d%, and T1d% + T1p values all had high diagnosis efficacy in differentiating WTs from MTs (AUC values: 0.865, 0.890, 0.852, and 0.897, respectively, all P >.05). ConclusionT1 mapping and RESOLVE-DWI can be used to differentiate parotid gland tumors quantitatively and can be complementary to each other.

Fetal left ventricular myocardial performance index measured at 11-14 weeks of gestation in fetuses with an increased nuchal translucency.

This study aimed to evaluate the effect of an increase in nuchal translucency (NT) thickness on the myocardial performance index (MPI) in fetuses without cardiac anomaly in the first trimester and to determine whether a difference in MPI between those with and without trisomy 21 in these fetuses could be determined. The study group consisted of 53 pregnancies complicated with increased NT thickness without any associated structural anomalies. Forty-six gestational age-matched pregnant women whose fetuses had normal NT thickness were enrolled as the control group. In the increased NT thickness group, the mean isovolumetric relaxation time (IRT) value (0.050 ± 0.011 s) was significantly higher and the mean ejection time (ET) value (0.149 ± 0.010 s) was significantly lower than those values in the normal NT thickness group (0.045 ± 0.005 and 0.155 ± 0.009 s, p=0.023 and p=0.009, respectively). We found a significantly higher mean left MPI value in the increased NT thickness group (0.574 ± 0.153) versus the normal NT thickness group (0.487 ± 0.107, p < 0.001). Within the increased NT thickness group, the mean left MPI value was similar in the fetuses with normal karyotype and those with trisomy 21 (p=0.419). We demonstrated a significantly greater mean MPI value in the increased NT thickness group than in the normal NT thickness group. Within the increased NT thickness group, no differences in the left MPI value in the fetuses with normal karyotype and the fetuses with trisomy 21 were found.

Insights into high hydrostatic pressure pre-treatment generating a more efficient catalytic mode of maltogenic α-amylase: Effect of multi-level structure on retrogradation properties of maize starch

Maltogenic α-amylase (MA) is an enzyme used to retard starch retrogradation in the baking industry. However, sometimes it exhibits low efficiency which may restrict the enzymatic application. This study investigates the effects of using High hydrostatic pressure (HHP) as a pre-treatment to promote MA catalysis. The results showed that HHP resulted in more indentations and fissures of the starch granules promoting the susceptibility of MA. While MA treatment alone introduced short malto-oligosaccharide chains with degree of polymerization (DP) 1–5, the combined HHP-MA treatment exhibited a higher proportion of DP 1–9, but a lower proportion of DP 13–24. Furthermore, when increasing the pressure, the ratio of α-1,6 to α-1,4 glycosidic bonds increased in the MA-treated starch. MA modification on the HHP-pretreated starch showed increasing gelatinization temperature and enthalpy, while it had a reverse impact on long-term retrogradation enthalpy due to the shortening of the outer chains of amylopectin. LF-NMR was applied to analyze the water mobility and compartmentalization in starch gel systems after 1- and 7-days storage. Compared with single MA-treated system, HHP-MA treated starches showed no significant changes in the value of the transverse relaxation times, but less amount of bulk water was detected due to higher amounts of soluble small oligosaccharides. In conclusion, HHP pre-treatment combined with MA could improve the water holding properties of retrograded starch gels and that HHP prior to MA catalysis provides an efficient alternative method to modify starch-based food products with anti-stalling properties.

Reference Values of Myocardial T1 Relaxation Times in Healthy Latin American Patients

Theoretical framework. Cardiac magnetic resonance imaging (CMR) is an invaluable tool for diagnosis and risk stratification in a broad spectrum of cardiac diseases. Magnetic resonance imaging techniques are increasingly complemented by mapping sequences that allow quantitative assessment of myocardial tissue with measurement of absolute relaxation times T1, T2, and T2*. The clinical utilities are diverse, among which is the quantification of edema and/or fibrosis through the estimation of the extracellular volume fraction calculated from pre-contrast, post-contrast and hematocrit T1 relaxation times. There are multiple ways to obtain T1 mapping images, among which the modified look-locker inversion recovery technique (MOLLI) stands out. However, different manufacturers have designed various methods of obtaining them with slight variability between the equipment. Aim To determine the reference values of myocardial T1 relaxation times in our population to justify their clinical interpretation in the tissue evaluation of different cardiovascular diseases. Material and method. Type of study: prospective observational and single center. Field intensity/sequence A short CMR protocol was performed in a 1.5 T resonator, using the MOLLI technique, in T1 mapping. Evaluation Global and segmental T1 values were quantified, using the American Heart Association (AHA) model, for the entire left ventricle, in three short-axis slices (basal, mid, and apical). The post processing and analysis of the data with the commercialized software, Cvi42. Results The mean global myocardial T1 value was 1069.41 ms with a SD of 38.73 msec. Among the age groups, the &lt;34-year-old group had the lowest global T1 values (1057 SD 33 msec), and the 35-year-old group -44 years obtained the highest values (1100 SD 50 msec), so no relationship was found between the linear increase in age and the variability of relaxation times. Between both sexes, men had lower global T1 values than women (1049 vs 1086). conclusions Native T1 ranges can serve as a basis for the quantitative characterization of the myocardium in the context of focal or diffuse diseases, in patients with infarcts, storage diseases, and inflammatory diseases. We are getting closer to standardizing the clinical use of these techniques by CMR. In conclusion, this analysis allows us to take another step to establish their use in the Latin American population.