K1 Values Research Articles

[11C]Metoclopramide PET can detect a seizure-induced up-regulation of cerebral P-glycoprotein in epilepsy patients

BackgroundP-glycoprotein (P-gp) is an efflux transporter which is abundantly expressed at the blood-brain barrier (BBB) and which has been implicated in the pathophysiology of various brain diseases. The radiolabelled antiemetic drug [11C]metoclopramide is a P-gp substrate for positron emission tomography (PET) imaging of P-gp function at the BBB. To assess whether [11C]metoclopramide can detect increased P-gp function in the human brain, we employed drug-resistant temporal lobe epilepsy (TLE) as a model disease with a well characterised, regional P-gp up-regulation at the BBB.MethodsEight patients with drug-resistant (DRE) TLE, 5 seizure-free patients with drug-sensitive (DSE) focal epilepsy, and 15 healthy subjects underwent brain PET imaging with [11C]metoclopramide on a fully-integrated PET/MRI system. Concurrent with PET, arterial blood sampling was performed to generate a metabolite-corrected arterial plasma input function for kinetic modelling. The choroid plexus was outmasked on the PET images to remove signal contamination from the neighbouring hippocampus. Using a brain atlas, 10 temporal lobe sub-regions were defined and analysed with a 1-tissue-2-rate constant compartmental model to estimate the rate constants for radiotracer transfer from plasma to brain (K1) and from brain to plasma (k2), and the total volume of distribution (VT = K1/k2).ResultsDRE patients but not DSE patients showed significantly higher k2 values and a trend towards lower VT values in several temporal lobe sub-regions located ipsilateral to the epileptic focus as compared to healthy subjects (k2: hippocampus: +34%, anterior temporal lobe, medial part: +28%, superior temporal gyrus, posterior part: +21%).Conclusions[11C]Metoclopramide PET can detect a seizure-induced P-gp up-regulation in the epileptic brain. The efflux rate constant k2 seems to be the most sensitive parameter to measure increased P-gp function with [11C]metoclopramide. Our study provides evidence that disease-induced alterations in P-gp expression at the BBB can lead to changes in the distribution of a central nervous system-active drug to the human brain, which could affect the efficacy and/or safety of drugs. [11C]Metoclopramide PET may be used to assess or predict the contribution of increased P-gp function to drug resistance and disease pathophysiology in various brain diseases.Trial registrationEudraCT 2019-003137-42. Registered 28 February 2020.

Adsorptive Removal of Bisphenol A by Polyethylene Meshes Grafted with an Amino Group-Containing Monomer, 2-(Dimethylamino)ethyl Methacrylate

The adsorptive removal of Bisphenol A (BPA) with the PE meshes photografted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was performed by varying the grafted amount, pH value, BPA concentration, and temperature, and the adsorption performance was correlated by the equilibrium, kinetic, and isotherm models. In addition, the regeneration of DMAEMA-grafted PE (PE-g-PDMAEMA) meshes was discussed from the repetitive adsorption/desorption process. The adsorption capacity had the maximum value at the grafted amount of 2.6 mmol/g and at the initial pH value of 8.0. The increase in the protonation of dimethylamino groups on grafted PDMAEMA chains and the dissociation of phenol groups of BPA present in the outer solution during the adsorption process results in the increase in BPA adsorption. The adsorption process followed the pseudo second-order equation. The BPA adsorption was enhanced by increasing the BPA concentration and the equilibrium data fit to Langmuir equation. The adsorption capacity stayed almost constant with the increase in the temperature, whereas the k2 value increased against the temperature. These results comprehensively emphasized that BPA adsorption occurred through the chemical interaction or ionic bonding of a BPA anion to a terminal protonated dimethylamino group. Desorption of BPA increased by increasing the NaOH concentration and BPA was entirely desorbed at more than 20 mM. The cycle of adsorption at pH 8.0 and desorption in a NaOH solution at 100 mM was repeated five times without loss or structural damage. These results indicate PE-g-PDMAEMA meshes can be used as a regenerative adsorbent for BPA removal from aqueous medium.

Theoretical investigation of Rayleigh-type surface acoustic waves with high electromechanical coupling coefficient in c-axis-tilted ScAlN film/3C-SiC substrate structure

Surface acoustic wave (SAW) resonators are essential components of mobile communication technology. Advanced performance SAW resonators are needed to support beyond fifth-generation mobile communication technology, which aims to achieve unprecedentedly high data rates and low latency using wide frequency bands in the RF spectrum. This study theoretically investigates the propagation characteristics of a non-leaky Rayleigh-type SAW (RSAW) propagating in a c-axis-tilted ScAlN film/3C-SiC substrate structure. By appropriately selecting the c-axis tilt angle and the film thickness of the ScAlN film, a high electromechanical coupling coefficient (K2) value was obtained in the second-mode RSAW (Sezawa wave). The maximum K2 value for the Sezawa wave was 8.03%, with a phase velocity of 7456 m/s and a power flow angle of 0° under the structural conditions where the K2 value was maximized. These properties offer significant advantages for achieving wide frequency bands, high operating frequencies, and ease of design for SAW resonators. The structural conditions under which good propagation characteristics were obtained in the Sezawa waves were found to coincide with the conditions that maximize the electromechanical coupling coefficient of the quasi-longitudinal wave in the ScAlN film, and a significant increase in the shear vertical component of Sezawa wave particle displacement was observed. Additionally, ScAlN films with a 40% Sc concentration can be fabricated using sputtering and molecular beam epitaxy. Recent advancements have reported the production of high-quality 3C-SiC wafers and large 3C-SiC film/silicon wafers. Therefore, the c-axis-tilted ScAlN film/3C-SiC substrate structure shows great potential as a candidate for next-generation SAW resonators.

Association between Tomographic Characteristics of Pterygium and Preoperative Anterior and Posterior Topography Measured by Anterior Segment Optical Coherence Tomography.

Background: The utilities of anterior segment optical coherence tomography (AS-OCT) for characterization, differential diagnosis, postoperative monitoring, and evaluation/comparison of surgical techniques in pterygium are described. Through AS-OCT, it is also possible to study the corneal astigmatic effect of pterygium. Our purpose is to study the associations between the anatomical characteristics of pterygium and the corneal topography through AS-OCT. Methods: Fifty eyes with primary pterygium in a tertiary hospital were evaluated before surgery by measuring 10 anatomical variables of pterygium and 13 topographic variables using AS-OCT (Casia 2; Tomey Corp., Nagoya, Japan). Statistical analysis was used to study the association between them. Results: Pterygium classified as flat pattern exhibited lower preoperative values of flat keratometry (K1), real flat keratometry (K1r), average keratometry (AvgK), and real average keratometry (AvgKr) compared to nodular ones. The flat pattern showed greater cylinder (CYL) and real cylinder (CLYr) values. The horizontal corneal invasion proportionally increased CYL and CYLr. Overall, larger anatomical pterygium measurements (limbus thickness (LimbusT), central pterygium thickness (CentreT), head pterygium thickness (HeadT), epithelial thickness at 1 mm (EpitT1mm), stromal thickness at 1 mm (stromT1mm), total thickness at 1 mm (TotalT1mm), total thickness at 2 mm (TotalT2mm), and total thickness at 3 mm (TotalT3mm)) resulted in lower anterior K1, K1r, AvgK, and AvgKr, and posterior K1 and AvgK values. CentreT was greater in astigmatisms against the rule than in oblique ones. Conclusions: This study demonstrates associations between preoperative topography and the NF (nodular or flat) classification of pterygium and its anatomical measurements assessed by AS-OCT.

Study on Safety Tunneling Technology of Secondary Outburst Elimination by CO2 Gas Fracturing in High-Outburst Coal Seam

The No. 3 coal seam in the Yuxi Coal Mine has a measured maximum gas content of 25.59 m3/t, along with a maximum gas pressure of 2.9 MPa, indicating its high risk to gas and outbursts. To mitigate outburst risks of the coal seam, the 1301 working face has been implemented with gas pre-drainage measures by grid boreholes from underlying roadways. After one year of extraction, it was confirmed that the gas content at all 33 test sites was below 8 m3/t, meeting the outburst prevention standards. However, during subsequent coal tunnel excavation, the gas desorption index K1 value frequently exceeded the standard, resulting in numerous occurrences of abnormal gas emission or small-scale outbursts. To tackle the challenges associated with safe excavation following the first-round regional outburst prevention measures, a research and industrial trial of CO2 gas fracturing (CO2-Frac) technology for secondary outburst prevention and rapid excavation was completed. The results show that the dual-hole and high-pressure (185 MPa) CO2-Frac considerably contributes to outburst prevention. K1 exceedances per hundred meters of tunnel excavations were from an average of 2.54 without CO2-Frac to an average of 0.28 after the new technology was implemented, leading to an eight-fold reduction. Additionally, the monthly excavation footage increased from an average of 81.64 m without CO2-Frac to an average of 162.42 m with CO2-Frac, resulting in a two-fold improvement. The dual-hole and high-pressure CO2-Frac is an advanced technology for safe and efficient excavation for secondary outburst elimination in highly outburst-prone coal seams in the Yuxi Coal Mine, with potential for widespread application in similar coal seam conditions.

Comparison of the IOL Master and Pentacam in the measurement of anterior segment parameters in patients with high myopia and cataracts

This study aimed to compare the differences between the Zeiss IOL Master and Oculus Pentacam in keratometry and central anterior chamber depth (ACD) measurements in patients with high myopia and cataracts. Between January 2019 and December 2020, 89 patients (103 eyes) with cataracts and high myopia who underwent preoperative cataract evaluation at Nanchang First Hospital were selected for retrospective analysis. Keratometry (K1, K2) and ACD were measured with the IOL Master and Pentacam. Paired t-tests were performed to compare the differences, while the Bland-Altman method was used to evaluate the agreement. The K1 value was (43.15±2.44) D for the IOL Master and (42.98±2.47) D for the Pentacam, and the difference between the two instruments was statistically significant (P<0.01). The K2 value was (44.55±2.63) D for the IOL Master and (44.32±2.55) D for the Pentacam. The ACD was (3.44±0.33)mm for the IOL Master and (3.39±0.36)mm for the Pentacam. There were statistically significant differences between the two instruments in both keratometry and ACD (P<0.01). The absolute values of the maximum difference between the two instruments for K1 and K2 were 1.1 and 1.07; thus, the consistency of the two instruments with respect to this measurement was poor. However, the absolute value of the maximum difference between the two instruments for ACD was 0.34, so the consistency of the two instruments in relation to this measurement was good. Both the IOL Master and the Pentacam can be used in the measurement of keratometry and ACD in patients with high myopia and cataracts, but the keratometry measurements should be compared in clinical application.

Noninvasive quantification of [18F]SynVesT-1 binding using simplified reference tissue model 2.

[18F]SynVesT-1, a positron emission tomography (PET) radiotracer for the synaptic vesicle glycoprotein 2A (SV2A), demonstrates kinetics similar to [11C]UCB-J, with high brain uptake, fast kinetics fitting well with the one-tissue compartment (1TC) model, and excellent test-retest reproducibility. Challenges arise due to the similarity between k2 and [Formula: see text] (efflux rate of the reference region), when applying the simplified reference tissue model (SRTM) and related methods in [11C]UCB-J studies to accurately estimate [Formula: see text]. This study evaluated the suitability of these methods to estimate [18F]SynVesT-1 binding using centrum semiovale (CS) or cerebellum (CER) as reference regions. Seven healthy participants underwent 120-min PET scans on the HRRT scanner with [18F]SynVesT-1. Six participants underwent test and retest scans. Arterial blood sampling and metabolite analysis provided input functions for the 1TC model, serving as the gold standard for kinetic parameters values. SRTM, coupled SRTM (SRTMC) and SRTM2 estimated were applied to estimate [Formula: see text](ref: CS) and DVRCER(ref: CER) values. For SRTM2, the population average of [Formula: see text] was determined from the 1TC model applied to the reference region. Test-retest variability and minimum scan time were also calculated. The 1TC k2 (1/min) values for CS and CER were 0.031 ± 0.004 and 0.021 ± 0.002, respectively. Although SRTMC [Formula: see text] was much higher than 1TC [Formula: see text], SRTMC underestimated BPND(ref: CS) and DVRCER by an average of 3% and 1% across regions, respectively, due to similar bias in k2 and [Formula: see text] estimation. SRTM underestimated BPND(ref: CS) by an average of 3%, but with the CER as reference region, SRTM estimation was unstable and DVRCER underestimation varied by region (mean 10%). Using population average [Formula: see text] values, SRTM2 BPND and DVRCER showed the best agreement with 1TC estimates. Our findings support the use of population [Formula: see text] value in SRTM2 with [18F]SynVesT-1 for the estimation of [Formula: see text] or DVRCER, regardless of the choice of reference region.

Accelerated aging behavior of degradable and non-degradable microplastics via advanced oxidation and their adsorption characteristics towards tetracycline

The increasing global utilization of biodegradable plastics due to stringent regulations on traditional plastics has caused a significant rise in microplastic (MPs) pollution in aquatic ecosystems from biodegradable products. However, the environmental behavior of biodegradable MPs remains inadequately elucidated. This study explored the aging processes of polylactic acid (PLA) and polystyrene (PS) under a heat-activated potassium persulfate (K2S2O8) system, as well as their adsorption characteristics towards tetracycline (TCs). In comparison to PS, the surface structure of PLA experienced more pronounced changes over aging, exhibiting evident pits, cracks, and fragmentation. The carbonyl index (CI) and oxygen/carbon ratio (O/C) of PS displayed exponential growth over time, whereas the values for PLA showed linear and exponential increases, respectively. The adsorption capacity of TCs by PS and PLA aged for 6 days increased from 0.312 mg‧g−1 and 0.457 mg‧g−1for original PS and PLA, respectively, to 0.372 mg‧g−1 and 0.649 mg‧g−1. Meanwhile, the adsorption rate (k2 values) for TCs decreased by 42.03 % for PS and 79.64 % for PLA compared to their initial values. The findings indicated that biodegradable PLA-MPs may exhibit higher tetracycline carrying capacities than PS, potentially increasing environmental and organismal risks, particularly in view of aging effects.

Numerical and Experimental Approach to Evaluate Microplastic Transport in Saturated Porous Media

Under varying flow rate conditions, the transport and retention of polydisperse microplastics (MPls), with an average particle size of 16 ± 6 µm, were investigated in saturated porous media. First-order reversible and irreversible kinetic sorption models were used to describe the sorption kinetics. Sensitivity analyses provided insight into the effects of each sorption parameter. Both numerical modeling and experimental measurements were utilized to evaluate the retention rates of sand filters. The influence of flow rate on sorption was reflected in variations in the distribution coefficient (Kd), the mass transfer coefficient (β), and the irreversible sorption rate (K1). Lower flow rates were associated with higher Kd and β values, indicating increased sorption and reduced mass transfer rates. An increase in Kd resulted in a more gradual sorption process, with a decrease in peak concentration, whereas changes in β had a comparatively smaller impact on sorption rate and peak concentration. Lower K1 values were linked to higher peak concentrations and decreased retention efficiency. Numerical modeling revealed retention rates of 28 ± 1% at a flow rate of 31 mL min−1 and 17 ± 1% at 65 mL min−1. The introduction of MPls into saturated sand environments modifies the transport dynamics within the medium. Consequently, these alterations affect the hydrological characteristics of porous media, impacting groundwater quality and agricultural output. The mean absolute error (MAE) of 6% between the modeled and observed retention rates indicated a high level of accuracy. This study underscores the importance of examining retention efficiency and the accuracy of numerical models in understanding MPl transport in porous media.

Phytochemical preparation of Zinc Stannate nanoparticles by using lemon and grapefruit peels for removal of cadmium ions

The synthesis of Zinc Stannate (Zn2SnO4) nanoparticles may be achieved by utilizing lemon and grapefruit peels, as indicated by the results of this study. This analysis outlines a sustainable, cost-effective, and readily available approach. The Zn2SnO4 nanoparticles were generated biologically and were discovered to have a cubic crystalline structure, as established by structural analysis using Rietveld refinement. TEM microstructural examinations revealed that Zn2SnO4 nanoparticles exhibit a homogeneous distribution and possess an average diameter of around 21 nm. The Zn2SnO4 nanoparticles have an optical energy band gap of 3.05 eV and demonstrate a UV region peak, which showed that Zn2SnO4 nanoparticles were being formed. More precisely, the pH of the solution greatly affects the absorption of Cd2+ ions. Kinetic analysis involves the use of two types of models: pseudo-first-order and pseudo-second-order. The previous model yields an R2 value of 0.9031 and a rate constant (k1) of 0.41 × 10−2 min−1. However, the pseudo-second-order model provides a better match, as seen by its very high R2 value of 0.9932 and rate constant (k2) value of 4.4 × 10−3 g.(mg.min)−1. In addition, isotherm modeling shows that the experimental data closely match the Freundlich isotherm model.

Complexation of 3p-C-NETA with radiometal ions: A density functional theory study for targeted radioimmunotherapy

Bifunctional chelators (BFCs) are vital in the design of effective radiopharmaceuticals, as they are able to bind to both a radiometal ion and a targeting vector. The 3p-C-NETA or 4-[2-(bis-carboxy-methylamino)-5-(4-nitrophenyl)-entyl])-7-carboxymethyl-[1,4,7]tri-azonan-1-yl acetic acid is a novel and promising BFC, developed for diagnostic and therapeutic purposes. The binding affinity between the BFC and radiometal ion significantly impacts their effectiveness. Predicting the equilibrium constants for the formation of 1:1 radiometals/chelator complexes (log K1 values) is crucial for designing BFCs with improved affinity and selectivity for radiometals. The purpose of this study is to evaluate the complexation of Ga3+, Tb3+, Bi3+, and Ac3+ radiometal ions with 3p-C-NETA using density functional theory (B3LYP and M06-HF functional) and 6-311G(d)/SDD basis sets, where the 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetracetic acid (DOTA) was employed as a benchmark. Formation of the [Ac3+(3p-C-NETA)(H2O)]- complexes is predicted to be markedly less stable compared to the other complexes, exhibiting the lowest chemical hardness and the highest chemical softness. Additionally, the chelation stability of the complexes is mainly determined by ligand-ion and ion-water interactions, which depend on the atomic charge and atomic radius of the metal ion.

Synthesis and Characterization of Silver-Modified Nanoporous Silica Materials for Enhanced Iodine Removal.

In aquatic environments, the presence of iodine species, including radioactive isotopes like 129I and I2, poses significant environmental and health concerns. Iodine can enter water resources from various sources, including nuclear accidents, medical procedures, and natural occurrences. To address this issue, the use of natural occurring nanoporous minerals, such as zeolitic materials, for iodine removal will be explored. This study focuses on the adsorption of iodine by silver-modified zeolites (13X-Ag, 5A-Ag, Chabazite-Ag, and Clinoptilolite-Ag) and evaluates their performance under different conditions. All materials were characterized using scanning electron microscopey (SEM), energy-dispersive X-ray spectroscopy (EDS), powdered X-ray diffraction (P-XRD), Fourier-transform infrared spectrometry (FTIR), and nitrogen adsorption studies. The results indicate that Chabazite-Ag exhibited the highest iodine adsorption capacity, with an impressive 769 mg/g, making it a viable option for iodine removal applications. 13X-Ag and 5A-Ag also demonstrated substantial adsorption capacities of 714 mg/g and 556 mg/g, respectively, though their behavior varied according to different models. In contrast, Clinoptilolite-Ag exhibited strong pH-dependent behavior, rendering it less suitable for neutral to slightly acidic conditions. Furthermore, this study explored the impact of ionic strength on iodine adsorption, revealing that Chabazite-Ag is efficient in low-salinity environments with an iodine adsorption capacity of 51.80 mg/g but less effective in saline conditions. 5A-Ag proved to be a versatile option for various water treatments, maintaining its iodine adsorption capacity across different salinity levels. In contrast, Clinoptilolite-Ag exhibited high sensitivity to ionic competition, virtually losing its iodine adsorption ability at a NaCl concentration of 0.1 M. Kinetic studies indicated that the pseudo-second-order model best describes the adsorption process, suggesting chemisorption mechanisms dominate iodine removal. Chabazite-Ag exhibited the highest initial adsorption rate with a k2 value of 0.002 mg g-1 h-1, emphasizing its superior adsorption capabilities. Chabazite and Clinoptilolite, naturally occurring minerals, provide eco-friendly solutions for iodine adsorption. Chabazite superior iodine removal highlights its value in critical applications and its potential for addressing pressing environmental challenges.

Effect of Si substrate conductivity on surface acoustic wave resonator

A surface acoustic wave (SAW) filter’s bandwidth and quality are determined by its resonators’ electromechanical coupling coefficient (k2) and impedance ratio (IR). Research commonly focuses on the effects of piezoelectric material and cutting direction on these parameters. This paper investigates the effect of the conductivity of the Si substrate on k2 and IR through finite element method (FEM) simulations. A new model based on the modified Butterworth-van-Dyke (MBVD) model is presented. This new model takes into account the substrate parasitic capacitance and resistance to predict resonator performance on low resistivity (LR) Si piezoelectric on insulator (POI) substrates. Both high resistivity (HR) Si and LR-Si are utilized to fabricate POI SAW resonators, which are subsequently tested. The high conductivity of the Si support layer leads to a decrease in both k2 and IR. By employing Si substrates with different resistances during fabrication, it becomes possible to manufacture resonators with varying k2 values, thus meeting diverse bandwidth requirements for filters.

Comparative study of pterygium excision with suture and sutureless conjunctival autograft

Introduction and aim. This is a prospective interventional study to compare corneal astigmatism before and after pterygium excision with conjunctival autograft, to determine the difference in mean corneal curvatures before and after pterygium excision, to evaluate the safety and efficacy of autologous blood technique, and sutured conjunctival autograft for primary pterygium. Material and methods. Patients were divided into group A – pterygium excision+sutured conjunctival limbal autograft and group B – pterygium excision+autologous conjunctival limbal autograft under local anesthesia. The preoperative and post operative K1 and K2 values and BCVA were noted. Results. There was statistically significant reduction in mean astigmatism at each post operative follow up in group A at 1 week (p=0.0249), 2 weeks (p=0.004), 1 month (p=0.0031) and at 3 months (p=0.0009) and similarly in group B post operative follow up at 1 week (p=0.0011), 2 weeks (p=0.0021), 1 month (p=0.0009) and at 3 months (p=0.0003). Conclusion. Pterygium surgery decreases the cylindrical error and reverts corneal curvatures to normal, thus improving subjective visual acuity. Astigmatism produced by the pterygium is reduced after surgery We found autologous conjunctival autograft is superior than sutural conjunctival autograft. Pterygium causes astigmatism depending upon the size of pterygium it should be surgically removed to prevent obstruction in the vision.

A consistent explanation of seemingly inconsistent experimental and theoretical data for N[formula omitted]O + O via MultiScale Informatics

The N2O + O reaction plays a critical role in NOx formation at high pressures and low peak temperatures, in the “dark zone” region of deflagration waves of organic energetic materials, and in N2O consumption in NH3 combustion. While the rate constant for N2O + O = NO + NO (R3) is considered reasonably well established, viewpoints regarding the rate constants for N2O + O = N2 + O2 (R2)—and even the main products of the N2O + O reaction—have not reached a consensus, with studies from the past few years continuing to reach drastically different conclusions. To date, no single model has been presented that can reproduce all key datasets on both sides of the debate. Using the MultiScale Informatics (MSI) approach, we identified a model consistent with a vast catalog of theoretical and experimental data previously used to determine rate constants for R2, R3, and other key reactions influencing experimental interpretations. Notably, this MSI model (presented herein) reproduces all experimental datasets previously used to anchor low-activation-energy k2 expressions that greatly favor R2 at intermediate temperatures. However, its kinetic parameters are also consistent with theoretical calculations that instead show high activation energy for R2 and k2 values many orders of magnitude lower—such that R3 is the main channel at essentially all temperatures. This model is also consistent with our new experimental data (presented in our companion paper) at optimally selected conditions that avoid the interpretation ambiguities that have hindered definitive conclusions from previous experimental data. The present analysis elucidates the role of secondary reactions that would have artificially inflated the apparent k2/k3 ratio previously deduced from experiments in a manner that may not have been detectable from even multi-species measurements at typical conditions—and may, therefore, explain the persistent historical difficulties in establishing the main products of N2O + O.Novelty and significance statementDespite decades of research, viewpoints regarding the rate constants for N2O + O = N2 + O2 (R2)—and even the main products of the N2O + O reaction—have not reached a consensus, with studies from the past few years still reaching drastically different conclusions. To date, no single model has been presented that can reproduce all key datasets on both sides of the debate. Here, we present a single model consistent with a vast catalog of theoretical and experimental data, including all experimental datasets previously used to anchor low-activation-energy expressions for k2 that greatly favor R2 as the main channel at intermediate temperatures—but with kinetic parameters consistent with theoretical calculations that instead show high activation energy for R2 and N2O + O = NO + NO (R3) as the main channel at essentially all temperatures.

Geochemistry and accumulation of the ultra-deep Ordovician oils in the Shunbei oilfield, Tarim Basin: Coupling of reservoir secondary processes and filling events

Ultra-deep (7300 m–8900 m) condensed and volatile oil reservoirs have been discovered in the Ordovician reservoirs of the Shunbei oilfield, in the Tarim Basin. This study describes the petroleum accumulation process in the Shunbei oilfield by combining an analysis of its geochemical characteristics with seismic section observations and an analysis of petroleum filling events. Geochemical techniques are used to determine the sources, maturity, secondary processes, accumulation periods, and timing of petroleum filling. Analysis of fluid inclusion homogenization temperatures and burial-thermal histories indicates distinct petroleum filling events. Specifically, the north sub-section of the No. 5 fault zone experienced two petroleum filling periods during the late Caledonian and Indosinian epochs while the No. 1 fault zones and the mid-south sub-sections of the No. 5 fault zones experienced three distinct filling periods, encompassing the late Caledonian, Indosinian, and Himalayan periods. The CO2 concentrations and δ13CCO2 values suggest the presence of secondary microbial gases, primarily thermogenic gases. Gas component analysis reveals a transition from kerogen degradation gas to oil cracking gas from north to south. The detection of intact n-alkanes and compounds of the 25-norhopanes series in oil samples suggests a mixture of early biodegradable oil with late fresh oil in the area. Seismic sections reveal diabase intrusions with strong axial reflections. Local hydrothermal activities during the Permian era rapidly cracked saturated hydrocarbon biomarkers, forming polycyclic aromatic hydrocarbons in the oil. Hydrothermal activity in the south sub-section of the No. 5 fault zone depleted the hydrocarbon-generating capacity of the underlying source rocks. Petroleum charged during the Indosinian period likely originated from potential petroleum reservoirs in the Cambrian system. This explains the comparatively low temperature of the SHB57X reservoir (163.32 °C) and the lack of strong hydrothermal activity in the late stage, but no biomarkers of the second-stage charged oil have been detected. Biomarker detection and gas genesis in the mid-south sub-section of the No. 5 fault zone and in the No. 1 fault zone suggest weak or no hydrothermal activity, with Cambrian source rocks maintaining their hydrocarbon generation capacity. Gas filling in the Himalayan period caused evaporative fractionation in the original reservoirs, resulting in a disproportionate (2-MH+2,3-DMP)/(3-MH+2,4-DMP), producing high K1 values in the light hydrocarbons in the present petroleum reservoirs. Differences in gas charging events in the Himalayan period led to the present distribution of petroleum phases.

Comparative Analysis of Keratometric and Pachymetry Values From Corneal Topography Scans: A Comparison Between Pentacam and Galilei.

Objective The objective of this study was to compare K1, K2, Kmax, and pachymetry values from Pentacam and Galilei scans of corneal topography in order to assess their correlation and interchangeability in clinical practice. Methodology A total of 34 patients (68 eyes) were enrolled in the study. Corneal topography was performed using Pentacam and Galilei devices on the same day. K1, K2, Kmax, and pachymetry readings were obtained from the scans and analyzed using paired t-tests and Bland-Altman plots. Results There were minimal differences in clinical settings between Pentacam and Galilei for K1, K2, Kmax (>0.75 D), and pachymetry values (>15 um). However, there was a statistically significant difference found between Kmax and pachymetry, making their interchangeability questionable. Conclusion Pentacam and Galilei demonstrate a good correlation between corneal keratometric values (K1, K2, and Kmax) and pachymetry values in clinical settings, and they should be used interchangeably with caution.

Axial length and keratometry characteristics of patients undergoing cataract surgery in Saudi Arabia.

Cataract surgery is one of the most successful surgical procedures, mainly due to the recent developments in surgical instruments and intraocular lens (IOL) measurements. Understanding the nature of axial length (AL) and keratometry readings (K) in patients with cataracts has significant implications for accurate postoperative IOL size selection. This study aimed to measure AL and K in patients undergoing cataract surgery in Saudi Arabia. This retrospective study included patients who underwent cataract surgery in Madinah, Saudi Arabia. The medical records of adult patients between May 2022 and May 2023 were reviewed, and those with a history of retinal detachment, refractive surgery, or trauma were excluded. The AL and K readings were obtained from the patient's IOL master results. A total of 691 eyes from 451 patients were included in the analysis. The mean age was 64.54 years old. Most of the patients were women (55%). The mean AL, K1, and K2 values were 23.27, 43.42, and 44.69, respectively. Linear regression analysis was used to measure the relationship between AL and K, revealing an inverse relationship in our findings. As AL increased by one unit, the mean K was estimated to decrease by 0.548, with a 95% confidence interval. Our results demonstrated an inverse relationship between AL and K, implying that when AL increases, K decreases, or the corneal curvature becomes flat. Further studies are needed to investigate the biomechanical mechanisms underlying this relationship.

Melanoidin Content Determines the Primary Pathways in Glucose Dark Fermentation: A Preliminary Assessment of Kinetic and Microbial Aspects

Melanoidins are heterogeneous polymers with a high molecular weight and brown color formed during the Maillard reaction by the combination of sugars and amino acids at high temperatures with the potential to inhibit the microbial activity in bioprocesses. This study assessed the impacts of melanoidins on the kinetic of substrate conversion and production of organic acids via dark fermentation using microbial consortia as inoculum. The investigations were carried out in fed-batch reactors using synthetic melanoidins following glucose-to-melanoidin ratios (G/M; g-glucose g−1 melanoidins) of 0.50, 1.50, 1.62, 1.67, and 5.00, also considering a melanoidin-free control reactor. The results showed that melanoidins negatively impacted the kinetics of glucose fermentation by decreasing the first-order decay constant (k1): when dosing equivalent initial concentrations of glucose (ca. 3 g L−1), the absence of melanoidins led to a k1 of 0.62 d−1, whilst dosing 2 g L−1 (G/M = 1.5) and 6.0 g L−1 (G/M = 0.5) of melanoidins produced k1 values of 0.37 d−1 and 0.27 d−1, respectively. The production of butyric and acetic acids was also negatively impacted by melanoidins, whilst the lactic activity was not impaired by the presence of these compounds. Lactate production reached ca. 1000 mg L−1 in G/M = 1.67, whilst no lactate was detected in the control reactor. The presence of melanoidins was demonstrated to be a selective metabolic driver, decreasing the microbial diversity compared to the control reactor and favoring the growth of Lactobacillus. These results highlight the importance of further understanding the impacts of melanoidins on melanoidin-rich organic wastewater bioconversion, such as sugarcane vinasse, which are abundantly available in biorefineries.

Multiparameter optimization of non-thermal plasma-driven synthesis of carbohydrate-stabilized rhenium nanoparticles towards enhancement of their catalytical activity for reduction of nitroaromatic compounds

This study aims to optimize the synthesis of carbohydrate-stabilized rhenium nanoparticles (ReNPs) utilizing cold atmospheric pressure plasma (CAPP), specifically direct current atmospheric pressure glow discharge (dc-APGD), hypothesizing that controlling synthesis parameters will enhance catalytic efficiency in the reduction of nitroaromatic compounds (NACs). The dc-APGD system operated in flowing liquid cathode (FLC-dc-APGD) and flowing liquid anode (FLA-dc-APGD) modes. Design of experiments (DOE) and response surface methodology (RSM) were employed for the first time to optimize ReNPs synthesis by adjustment of the concentration of ReO4- in ReNPs precursor solution, its flow rate, as well as the discharge current. ReNPs were characterized using high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), and X-Ray photoelectron spectroscopy (XPS). In turn, optical emission spectroscopy (OES) was employed for the identification of reactive species generated in the plasma phase that contributed to the synthesis of ReNPs. The resultant sizes, surface charges, and phase compositions were linked with synthesis parameters and then with catalytic activities revealed by the variety of ReNPs. HRTEM photomicrographs showed spherical and spherical-like morphologies of the obtained ReNPs synthesized using FLC-dc-APGD and FLA-dc-APGD modes with the actual sizes of 7.28 ± 2.90 nm and 3.24 ± 0.57 nm, respectively. The optimized conditions yielded ReNPs of exceptional catalytic activity, that reduced 94.9 % (FLC-dc-APGD) and 90.5 % (FLA-dc-APGD) of 4-nitrophenol (4-NP) with the apparent rate constants (k1) 0.269 and 0.107 min−1, respectively. Further, the conversions of 90 % were achieved over FLC-dc-APGD-based ReNPs for nitrobenzene (NB), 2,4,6-trinitrophenol (2,4,6-TNP), 2,4-dinitrophenol (2,4-DNP), and 4-nitroaniline (4-NA). In these cases, the k1 values were 0.235, 0.174, 0.070, 0.001 min−1, respectively. The results allowed to find a correlation between ReNP size distribution, oxidation state, and catalytic activity that suggested a potential for tailored Re nanocatalysts in environmental remediation.