Terms Of K2 Research Articles

The effect of various thermochemical methods on the production of biochar and removal of 2‐naphthol orange from wastewater

AbstractBACKGROUNDThermochemical conversion methods are essential processes frequently used in the production of biochar and the type chosen affects the properties of biochar. In this study, 2‐naphthol orange was removed from synthetic wastewater using biochar adsorbents produced from pelletized furniture sawdust by thermochemical techniques (torrefaction, pyrolysis and gasification) at various durations (0.5–5 h) and temperatures (200–900 °C).RESULTSThe adsorbent produced via torrefaction at 200 °C in 1 h exhibited the best removal performance. For furniture waste biochar (FWB), the optimum conditions for 2‐naphthol orange options were initial concentration 35 mg L−1, pH 2.0, contact duration 2 h, agitation speed 200 rpm, temperature 30 °C, 1.0 g L−1 of biochar and ‐ 50‐mesh biochar size. The Langmuir isotherm and Pseudo‐second‐order models showed the highest coefficients of determination (R2 = 0.9947 and 0.9978, respectively). The terms of qm (mg g−1) and KL were found to be 230.45 and 0.28, respectively, from the Langmuir isotherm. Conversely, the terms of qe (mg g−1) and k2 [g (mg.min)−1] were found to be 29.27 and 0.00486, respectively, from the pseudo‐second‐order model. According to the long‐stability experiment, the selected adsorbent of 200–1 (biochar from torrefaction) remained more stable after 10 cycles of adsorption.CONCLUSIONIt was found that the torrefaction process provides significant advantages owing to the removal efficiencies of 2‐naphthol orange dye and the fact that biochar production is easier and more economical at low temperatures. © 2023 Society of Chemical Industry.

Nutrient management in maize (Zea mays) under shifting cultivation for higher productivity and sustainability in North-East India

A participatory field experiment was conducted during the rainy (kharif) season of 2015 and 2016 at farmer’s land of Meghalaya, to identify suitable maize (Zea mays L.) varieties and nutrient-management practices for higher maize productivity under shifting cultivation (jhum). The experiment was laid out in a factorial randomized block design with treatment combination of 3 maize cultivars, viz. ‘JKMH 502’ (Hybrid), ‘RCM 61A’ (Composite) and ‘Saru Bhoi’ (Local), and 5 nutrient-management practices, viz. N1, farmers’ practice (no manure or fertilizer application); N2 , 50% of recommended dose of fertilizer (RDF) (40, 20 and 20 kg N, P2 O5 and K2 O/ha) + FYM 2 t/ha + 500 kg lime/ha in furrow; N3 , fertilizer + FYM (50% N from each source to supply 40, 20 and 20 kg N, P2 O5 and K2 O/ha) + 500 kg lime/ha in furrow; N4 , maize + groundnut (Arachis hypogaea L.) intercropping (4 : 2 ratio) with N3 ; and N5, foliar spray of diammonium phosphate (DAP) @ 2% at 30 and 60 days after sowing (DAS) with N1 . Among the cultivars, the composite cultivar ‘RCM 61A’ produced higher number of rows/cob (13), seeds/cob (271.2), seed weight/cob (67.2 g) and test weight (247.4 g) than hybrid and local cultivars. However, among the nutrient-management practices, N2 treatment resulted in significantly higher grain yield, straw yield and harvest index than N1. The soil fertility in terms of SOC, available N, P2 O5 and K2 O were significantly higher under treatment N4 . Thus, cultivation of maize composite (‘RCM 61A’) and adoption of maize + groundnut intercropping (4 : 2 ratio) along with application of fertilizer + FYM (50% N from each for total supply of 40, 20 and 20 kg N, P2 O5 and K2 O/ha + 500 kg lime) is a profitable practices for improving maize productivity in jhum lands and sustaining soil health.

A note on eigenvalue bounds for non‐compact manifolds

AbstractIn this article we prove upper bounds for the Laplace eigenvalues below the essential spectrum for strictly negatively curved Cartan–Hadamard manifolds. Our bound is given in terms of k2 and specific geometric data of the manifold. This applies also to the particular case of non‐compact manifolds whose sectional curvature tends to , where no essential spectrum is present due to a theorem of Donnelly/Li. The result stands in clear contrast to Laplacians on graphs where such a bound fails to be true in general.

Strehl Ratio and Myopia in Chinese Adolescents: The Tuyou County Pediatric Eye (TYPE) Study

AimTo investigate the relationships between property of the visual quality, Strehl ratio (SR) and the degree of myopia.MethodsA total of 444 anatomically normal eyes of 222 adolescents were enrolled in the TYPE study. Based on spherical equivalent (SE), subjects were divided into four groups: emmetropia/control (SE: +0.75 to −0.75 D), low myopia (SE: −0.75 to −3.00D), moderate myopia (SE: −3.00 to −5.00D), high myopia (SE: <−5.00D). Axial length (AL) was measured. SR was attained with an OPD-III SCAN and calculated under a 3 mm pupil diameter.ResultsThe overall SR (mean ± SD) was 0.40 ± 0.08. Among all included eyes, the SR in eyes with the emmetropia, low myopia, moderate myopia and high myopia was 0.80 ± 0.11, 0.31 ± 0.04, 0.21 ± 0.11, and 0.11 ± 0.02, respectively. Furthermore, the K2 in eyes with the emmetropia, low myopia, moderate myopia and high myopia was 43.83±1.50, 43.96±1.37, 43.4±5.52, and 45.16±1.43, respectively. Significant differences were detected within the four groups in terms of SR and K2 (P < 0.001). Multiple regression analysis confirmed that AL negatively affected SR independently (P < 0.001).ConclusionOur findings provide a useful basis for the conclusion that myopia affects visual quality SR in Chinese adolescents. Besides, when performing visual quality SR, axial length must be taken into consideration, as it will influence SR.

Effectiveness and agreement of 3 optical biometers in measuring axial length in the eyes of patients with mature cataracts.

To evaluate the effectiveness and agreement of 3 optical biometers in measuring axial length (AL) and biometric parameters in the eyes of patients with mature cataracts. Oftalmosalud Instituto de Ojos, Peru. Prospective, comparative study. Eyes with mature cataracts were examined. Three consecutive scans were performed with each device: the IOLMaster 700, the Galilei G6, and the Pentacam AXL. The following parameters were recorded: AL, anterior flat keratometry (K1), steep K (K2), anterior astigmatism, mean K (Km), anterior chamber depth (ACD), central corneal thickness (CCT), and lens thickness. Agreement between devices was assessed using the coefficient of correlation of concordance (CCC). Forty-five eyes were included. After 3 attempts, the acquisition success rates in measuring mature cataracts were 84.4% (38/45), 42.2% (19/45), and 37.7% (17/45) for the IOLMaster, the Galilei, and the Pentacam, respectively. Significant differences were found between the Pentacam and the IOLMaster in terms of AL, K2, and CCT. Significant differences were found in terms of K1, K2, Km, ACD, and CCT between the Pentacam and the Galilei; and significant differences were found in AL, K1, Km, and ACD between the Galilei and the IOLMaster (P < .05 all). Good correlations were found between devices (>0.90) in terms of keratometries and AL. The IOLMaster 700 had the highest AL acquisition success rate when compared with the Pentacam AXL and Galilei G6. Good agreement between devices was found in terms of AL and K readings.

Anterior Segment Analysis and Evaluation of Corneal Biomechanical Properties in Children with Joint Hypermobility.

Objectives:To compare anterior segment parameters and biomechanical analysis of the cornea in children with joint hypermobility (JH) and healthy children.Materials and Methods:Cross-sectional case-control study. Fifty eyes of 25 children with JH were compared with 74 eyes of 37 healthy age- and sex-matched controls in terms of refractive, anterior segment topographic, and corneal biomechanical measurements. Axial length (AL) was measured with a Nidek AL-Scan biometry device; corneal-compensated intraocular pressure (IOPcc), Goldmann-correlated IOP (IOPg), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured with a Reichert ocular response analyzer (ORA). Central corneal thickness (CCT), anterior chamber depth (ACD), K1/K2 values, iris diameter, and anterior chamber volume (ACV) were measured with a Sirius topography device.Results:Mean age in the JH group was 10.56±4.03 years, while that of the control group was 11.27±2.59 years (p=0.23). Spherical equivalent was -0.22±1.02 diopter (D) in the JH group and -0.12±1.12 D in the control group (p=0.60); CCT was 23.01±0.82 µm in the JH group and 23.17±0.82 µm in the control group (p=0.33). There were no significant differences between the two groups in terms of age, sex, IOP, IOPcc, IOPg, CH, CRF, AL, K1, K2, iris diameter, ACD, and ACV.Conclusion:JH, which causes increased flexibility of the joints, was concluded not to cause a significant change in the corneal biomechanical markers of CRF and CH or in anterior segment topographic parameters.

Corneal Topographic Changes after Subscleral Trabeculectomy

Background: Glaucoma is a cause of permanent blindness and occurs most often in older adults. Although glaucoma can be initially managed by conservative treatments, trabeculectomy, initially described by has traditionally been considered the “gold standard” for filtration surgery. Aim of the study: is to investigate the effect of trabeculectomy on corneal topography, anterior chamber depth, and aberrations by a SIRIUS topography. Patients and methods: The present study was a prospective cohort study including 30 eyes of patients who were scheduled to undergo trabeculectomy at Ophthalmology Department of Al Azhar university hospital during the period from January 2018 to August 2019. Results: In the present study, we compared included eyes according to site of flap midway (between K1&K2) versus vertical flap (on K). We found no statistically significant differences between studied groups in terms of K1 (p =0.29), K2 (p =0.33), and astigmatism values (p =0.38).In our study,there was statistically significant difference between pre and postoperative values of ACD (p < 0.001). Eyes showed statistically significant decrease in ACD postoperatively. Conclusion: Trabeculectomy surgery can cause changes in keratometry values, aberrations and ACD. These changes can be significant enough to affect visual acuity, the accuracy of IOL power calculation, and refractive outcomes after combined or future cataract surgery. Keywords:Glaucoma,Corneal Topographic Changes, SubscleralTrabeculectomy

Corneal endothelial morphology and anterior segment parameters in children with type 1 diabetes mellitus.

To compare the corneal endothelial morphology and anterior segment parameters in type 1 diabetes mellitus children (T1DM) and healthy controls. This cross-sectional prospective study included 56 patients with T1DM and 50 eyes of 50 age-matched controls. Endothelial morphology was analyzed with EM-3000 specular microscopy, and anterior parameters were analyzed with Sirius Scheimpflug topography. Endothelial cell density (ECD), coefficient of variation (CV) of cell area, central corneal thickness (CCT), anterior chamber depth (ACD), iridocorneal angle (ICA), K1 and K2, pupillary diameter (PD), horizontal visible iris diameter (HVID), duration of T1DM, and HbA1c levels were noted. The mean age of the T1DM group was 14.3 ± 3.2 years, compared to 13.2 ± 3.7 years in the healthy group (p = 0.140). The mean duration of diabetes mellitus was 4.5 ± 3.5 years. The mean HbA1c was 9.5 ± 1.9% (minimum 6%, maximum 14%). The mean values of CCT were 556 ± 30 μm and 536 ± 36 μm in T1DM and healthy groups, respectively (p = 0.003). The mean values of ACD were 3.69 ± 0.31 mm and 3.83 ± 0.27 mm in T1DM and healthy groups, respectively (p = 0.02). The mean values of PD were 4.29 ± 1.2 mm and 5.17 ± 1.36 mm in T1DM and healthy groups, respectively (p = 0.001). There was no statistically significant difference between groups in terms of ECD, CV, ICA, K1, K2, and HVID (p > 0.05). Type 1 diabetes mellitus children have thicker corneas, shallower anterior chamber depth, and smaller pupillary diameter than healthy subjects.

Kinetics of Carbon Dioxide (CO2) with DiethylenetriamineinNon-aqueous Solvents Using Stopped-flow Technique

In this work, the reaction kinetics of carbon dioxide (CO2) with diethylenetriamine (DETA)in methanol and ethanol systems were measured using the stopped flow technique over a temperature range of 293-313K in terms of pseudo first-order rate constant (k0). Concentration in the range of 10 to 50mol/m3 for diethylenetriamine were studied. The experimental data show that the pseudo first-order rate constants (k0) increase with the increase of both amine concentration and temperature. The zwitterion mechanism and the termolecular mechanism were used to representthe data for DETAinmethanol and ethanol systems with excllent ADDs of 3.5%, 2.4%, respectively. In comparison with EDA and AEEA in terms of k2, DETA exhibits a better reaction kinetics performance for capturingCO2. Those results will be useful in finding an efficient method for the removal of CO2 from industrial gases.

Reaction Kinetics of Carbon Dioxide (CO2) with Diethylenetriamine and 1-Amino-2-propanol in Nonaqueous Solvents Using Stopped-Flow Technique

In this work, the reaction kinetics of carbon dioxide (CO2) with diethylenetriamine (DETA) and 1-amino-2-propanol (1-AP) in methanol and ethanol systems were measured using the stopped flow technique over a temperature range of 293–313 K in terms of pseudo-first-order rate constant (k0). Concentration in the range of 10 to 50 mol/m3 for diethylenetriamine, and 20 to 100 mol/m3 for 1-amino-2-propanol were studied. The experimental data show that the pseudo-first-order rate constants (k0) increase with the increase of both amine concentration and temperature. The zwitterion mechanism and the termolecular mechanism were used to represent the data for DETA in methanol and ethanol systems with excellent ADDs of 3.5% and 2.4%, respectively, and 1-AP in methanol and ethanol systems with excellent ADDs of 2.4% and 2.6%, respectively. In comparison with EDA and AEEA in terms of k2, DETA exhibits a better reaction kinetics performance for capturing CO2. Those results will be useful in finding an efficient method fo...

Simulation of Asphaltene Aggregation and Related Properties Using an Equilibrium-Based Mathematical Model

Aggregation of asphaltenes was simulated using a mathematical model based on the following consecutive equilibrium: nA⇄K1An and mA+An⇄K2An+m, where A, An, An+m, K1, K2 represent asphaltenes, n aggregates, n + m aggregates, and equilibrium constants, respectively. A mass balance lead to a n + m polynomial in C (C0, n, m, K1, K2, M), where C is the concentration of free solute (monomer), M is the monomer molecular mass, and C0 is the total monomer concentration added to solution. Using numerical methods, this polynomial was solved in terms of C0, K1, and K2 for given values of n, m, and M. Selection of n = 3, m = 5, and M = 800 g L–1 was consistent with data in the literature, and determination of K1 and K2 was achieved by fitting to experimental data from ultrasound velocity, thermal diffusion [thermal lens and dual-beam photothermal reflection (DBPR)], and self-diffusion coefficient techniques. The good fittings found suggest that asphaltene aggregation is adequately described by the present model. A procedure based on the present model was employed to simulate the stepwise adsorption of asphaltenes at the toluene/glass interface. The above sequential equilibrium is discussed in terms of aggregation of the toluene-insoluble asphaltene fraction molecules (A1TM, first equilibrium), followed by incorporation into aggregates of toluene-soluble fraction molecules (A2TM, second equilibrium). This sequential scheme is proposed as a means to keep fraction A1 as nanoaggregates (first step), which, were it not by the presence of A2 (second step), would lead to phase separation. The formation of small aggregates at very low concentrations, predicted by the model, is consistent with the very low solubility of the A1 fraction. When the above mathematical model is combined with the Hansen solubility parameter (HSP) method, it is concluded that asphaltenes form stable colloid solutions in toluene and similar solvents where A1 is insoluble. In other words, for these colloidal solutions, interfacial tension would be zero.

Blends of Reverse Enteric Polymer with Enteric and pH-Independent Polymers: Mechanistic Investigations for Tailoring Drug Release

Blends of conventional reverse enteric polymer with enteric polymers result in insoluble polyelectrolyte complexes and hence cannot be used in film coatings. We report a new set of miscible blends of a new reverse enteric polymer (NREP) synthesized by us with enteric and pH-independent polymers. The nature of interactions between polymers in the blends has been established by analyzing Fourier transform infrared (FTIR) spectra. The extent of interaction has been investigated by thermal analysis and quantified in terms of parameters K1 and K2 in the Schneider equation. Based on these values, the interactions between NREP and these polymers have been ranked in the order EC (ethylcellulose) < ES (Eudragit S) < HPMCP (hydroxypropyl methylcellulose phthalate). The quantification of interactions in blends helps explain the release pattern of cefuroxime axetil (CA) at gastric pH and tailor the release of other drugs according to their pharmacokinetic characteristics. The understanding also provides a more rational approach for selection of polymers and their content in the coating compositions, rather than an empirical approach.

Efficiency of energy conversion by piezoelectrics

The efficiency of energy conversion by piezoelectric devices depends upon the quality factor Q and electromechanical coupling coefficient k2. In this study the efficiency Q and k2 are measured for a piezoelectric cantilever, a piezoelectric stack, and a micromachined piezoelectric membrane. The experimental values are compared to a model which predicts efficiency at resonance in terms of k2 and Q. Results of the experiment and model are within 2% of each other.

Temperature dependence of magnetic anisotropy in Co/Au layered structures

Abstract Second- and fourth-order K2 and K4 constants of the magnetic uniaxial anisotropy of Co/Au layered structures have been determined as a function of temperature T from ferromagnetic resonance measurements. We found that K2 of the order of 1– 2 MJ / m 3 monotonically decreases with T while K4 of the order of 10−2×K2 is independent of T. The temperature dependence of the volume K2V and the surface K2S terms of K2 are discussed.

Temperature dependence of the higher order magnetic anisotropies in Co/Au layered structures

Second- and fourth- order K2, K4 constants of the magnetic anisotropy of ultrathin (0.8–1.5 nm) Co layers in [Py/Au/Co/Au]15 multilayer structures have been determined as a function of temperature from 100 to 600 K. We found that K2 of order of 1 MJ/m3 monotonically decreases with temperature while K4 of the order of 10–2 × K2 is temperature independent. We also estimated the temperature dependence of the volume K2V and surface K2S terms of K2. K2V varies almost linearly with temperature and is at room temperature noticebly larger than the magnetocrystalline anisotropy of bulk Co. K2S is temperature independent. The results are qualitatively compared with anisotropy data of bulk Co.

Improved Signal-to-Noise Ratio in Parametric Images by Cluster Analysis

Parametric images are formed by analyzing the concentration history of every voxel in PET data sets. Because PET concentration data at the voxel level are rather noisy, noise propagation into the parametric image is often quite noticeable. To address this problem, a model-based clustering method has been developed to generate parametric images. The basic idea of the clustering method is to average over voxels whose concentration histories have the same shape. We applied the method to a two-parameter (K1,k2) compartment model of local cerebral blood flow. The statisticR=∫tC(t)dt/∫C(t)dt=∫te−k2t⊗Ca(t)dt/∫e−k2t⊗Ca(t)dtclassifies curves in terms ofk2, whereC(t) andCa(t) denote the tissue and blood concentration histories, respectively, and ⊗ is the convolution operator. Simulation studies of noise propagation in the clustering statistic showed that 30% voxel noise yielded a 2% standard deviation inR. Parametric images of blood flow and partition coefficient were computed for an O15study, with and without clustering. Cluster size affected bias, statistical precision, and computation time. With clusters of 400 voxels, the variance of the flow parameter was around 1/50 smaller with clustering, with negligible bias and a computation time of 30 s on a 64-MHz workstation for 15 × 128 × 128 images with MATLAB 5.1.