Kuwait Journal of Science最新文献

We explore the destruction of the Kondo interaction due to a random magnetic field. Using entanglement measures, the Kondo length and the impurity entropy are analyzed. We identify a critical magnetic field amplitude $h_c$ at which the destruction happens. We find that $h_c$ scales with the Kondo temperature of the model.

Intense mesoscale eddy activity has been observed off the southern Java coast (SJC), yet its impact on local ecosystems remains largely unknown. To investigate this, we examined remotely sensed altimetry, chlorophyll-a (Chl-a), and sea surface temperature (SST) data, focusing on their response to eddies in the region. Our eddy detection and tracking analysis revealed a unique cyclonic frontal eddy near the SJC coast and a large anticyclonic eddy offshore, active from July to September 2019. The cyclonic frontal eddy induced water transport through eddy filaments, upwelled subsurface cold water, and enhanced Chl-a concentrations by horizontally entraining Chl-a-rich shelf water offshore. The anticyclonic eddy then contributed to further distributing this enriched water southward. The mean cross-shelf transport associated with the frontal eddy was estimated at 1.80–2.33 Sv offshore, exporting approximately 1.87–2.40 × 10³ tons of Chl-a to the Indian Ocean during its lifetime. Additionally, the spatial cross-correlation analysis of zonal and meridional wind stress with Chl-a revealed relatively high correlation values (0.6–1) and short lag times (<5 days) in offshore areas, indicating that the role of wind in the Chl-a advection cannot be ignored. We propose a three-stage mechanism to explain the presence of high Chl-a offshore:1) Wind-driven upwelling intensifies coastal nutrients, elevating Chl-a concentrations in coastal waters, 2) Frontal cyclonic eddy facilitates the retention and offshore export of these upwelling-enriched waters. and 3) Anticyclonic eddy advects these nutrient-rich waters further south. The combination of enhanced coastal upwelling and eddies can explain nutrient-rich coastal waters in offshore regions.

This research focused on the synthesis of biphasic titania nanowires from commercially available anatase titania via hydrothermal method to improve its antimicrobial activity. The electron microscope scanning (SEM) showed that the titania nanowires structures were successfully synthesized with width varying from 17 to 96 nm and length from 0.7 to 8 μm. The titania nanowires have biphasic structure of brookite and anatase, as observed from the X-ray diffraction pattern. The band gap was calculated from the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) spectra at 3.3eV, which is between the range of pure anatase and pure brookite band gap. The crystallite size of the titania nanowires was calculated using the Scherer equation and showed a much smaller crystallite size compared to commercial titania. The antimicrobial activity of the titania nanowires was then investigated against gram-negative and gram-positive bacteria. They exhibited improved antimicrobial activity against the Gram-negative Pseudomonas aeruginosa and Escherichia coli along with Gram-positive Bacillus subtilis. Interestingly, their inhibition zone was comparable to the antibiotic tetracycline. Meanwhile, the commercial titania did not show any antimicrobial activity on any tested bacterial strains. The improved antimicrobial activity of the titania nanowires was attributed to its biphasic phase, small particle size, and its one-dimensional morphology.

In this paper, we are interested in the order estimation of an autoregressive model using the information criterion developed by El Matouat and Hallin (1996), which is based on stochastic complexity. This criterion is a generalization of the Hannan and Quinn criterion and provides a convergence of the model order estimator, but it depends on a parameter that is sensitive to the sample size. In order to select the exact order of the candidate model, we propose a method for identifying the values of this parameter from the sample using the information contained in sub-samples of increasing size. To study the performance of the proposed method in comparison with the usual criteria, we simulated samples from autoregressive models on which we applied our procedure. Simulation results support the relevance of our procedure when compared to the Akaike criterion, the Hannan and Quinn criterion, and the Schwarz criterion.

The present study aims at investigating, for the first time, the formation of tetrahedral intermediates during the equilibrium mechanism of D-glucaric acid in water. In this work, carried out at B3LYP/6-31+G(d,p) computational level in vacuum and using the polarizable continuum model, two systems are proposed and simulated: the first describes an intramolecular proton transfer, and the second requires the intervention of solvent molecules for the proton transfer. The second system, simulated in vacuum, indicates greater ease in establishing this equilibrium due to a significant reduction in angular tensions. Also, the idea of a tetrahedral intermediate carrying two geminal diol groups constitutes a favorable hypothesis due to the low energy barriers calculated as well as a better structural flexibility generated following the equilibrium of the tetrahedral intermediates between them. Experimental confirmation of the presence of such a powerful tetrahedral intermediate would be a considerable advance in resolving the equilibrium mechanisms of D-glucaric acid.

Hydroxyapatite (HAp) is a versatile material with wide-ranging applications, including its utility as an adsorbent. However, its brittleness and limited adsorption capacity pose challenges, prompting the incorporation of chitosan (CTS) fillers to enhance mechanical strength and adsorption properties. The hydroxyapatite/chitosan (HAp/CTS) composite was synthesized via the in-situ method, utilizing natural sources such as calcium ions from cuttlefish bones and chitosan extracted from shrimp shells. Various chitosan concentrations (10, 20, 30, 40, and 50 wt%) were explored in the synthesis process, with the optimal adsorption of Rhodamine B dye observed at a 30% concentration, yielding 0.1832 mg/g. Validation of the HAp/CTS composite synthesis was achieved through X-ray diffraction, revealing the presence of CTS at a new peak at 2θ of 19.23°, while infrared spectroscopy confirmed absorption bands for both HAp and CTS. Additionally, scanning electron microscopy-energy dipersive spectroscopy (SEM-EDS) investigations revealed irregular shapes with agglomeration, resulting in a Ca/P ratio of 1.80 for the HAp/CTS composite. The HAp/CTS-30% composite demonstrated efficient Rhodamine B dye adsorption following the Freundlich isotherm equation, pseudo-second-order adsorption kinetics, and exhibited good reusability. These findings suggest that the HAp/CTS composite could serve as a promising, cost-effective solution for treating industrial wastewater.

In this study, the effects of various light treatments, growth regulators and culture media (agar-solidified and liquid) on in vitro propagation of Alternanthera reineckii Briq. Were evaluated. In in vitro experiments were used red, blue, and white LEDs alone and various combinations of red and blue LEDs. Different levels of 6-benzylaminopurine (BAP) and Kinetin (KIN), ranging from 0.25 mg/L to 1 mg/L, were introduced into the solid and liquid Murashige and Skoog (MS) basal medium. In solid culture, the highest number of shoots per explant (16.67 shoots/explant) was observed when utilizing a proportion of 1:2 red/blue LEDs in MS medium supplemented with 1 mg/L BAP. On the other hand, in the liquid culture, 15.13 shoots/explant were obtained with 1 mg/L BAP under a 2:1 red/blue LEDs configuration. During the experiments involving KIN, 10.42 shoots/explant were observed in the solid culture conditions with 1 mg/L of KIN under a lighting configuration of 1:2 red/blue LEDs. On the other hand, a total of 10.62 shoots/explant was attained in the liquid MS medium with 0.50 mg/L of KIN under a lighting configuration of 2:1 red/blue LEDs. As a result, LED lights were found to be better than fluorescent lights for multiple propagations of A. reineckii. Moreover, higher shoot numbers and longer shoots were achieved with red and blue LED light combinations.

Carbofuran pesticide is used to control insects in agriculture and acts as a contaminant that pollutes aquatic ecosystems, exerting harmful effects on fish health. The present study was conducted to evaluate the ameliorative effects of moringa leaf powder after fish being exposed to carbofuran on hematobiochemical and histological changes, oxidative and antioxidative mechanisms in the soft tissues of rohu Labeo rohita. Fish were divided into three groups (A, B, and C). Group A treated as control while groups B and C were exposed to two sublethal doses (0.32 and 0.84 mg/L) of carbofuran for 28 days. At day 28, ten fish were removed from the high dose group and transferred to carbofuran-free freshwater (group D) for recovery responses. Results revealed that concentrations of hemoglobin (HGB), red blood cells (RBCs), high-density lipoprotein (HDL), low-density lipoprotein (LDL), albumin, globulin, total proteins, triiodothyronine (T₃), thyroxin (T₄) and blood urea nitrogen (BUN) significantly decreased. White blood cells (WBCs), triglycerides, cholesterol, very low-density lipoprotein (VLDL), alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood glucose, thyroid stimulating hormone (TSH), urea, and creatinine levels were elevated significantly in carbofuran exposed fish. Results showed a significant rise in oxidative stress content (TBARS and ROS), and a decline in the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione (GSH) in the brain, kidney, liver, and gills of exposed fish. Histological alterations showed deleterious effects on different organs in carbofuran-exposed fish. After the recovery period, all parameters were recovered to some extent. The results of this study indicated that carbofuran is harmful to fish even at low doses. Therefore, extreme care should be taken to prevent the drainage of carbofuran into water bodies.

This study put forward Melaleuca cajuputi leaves to prepare activated carbon using H₃PO₄ as an activating agent and examined the aqueous solution of benzene, toluene, ethylbenzene and xylene (BTEX). The surface functional group, surface morphology, and surface area were identified by employing Fourier transform infrared spectra, field emission scanning microscopy, and Brunauer-Emmett-Teller to characterize the properties of the produced activated carbon; others include pH, moisture content, and yield percentage. The activated carbon's performance was assessed using batch adsorption experiment. 50 mg/L of BTEX disintegrates in purified water to form the standard solution and is stored at 4 °C. The study examined the effects of time spent in contact, dosage of the adsorbent and initial concentration. The results show that Melaleuca cajuputi activated carbon (MCAC2) has the optimum surface area 128 m²/g and performs very effectively as a BTEX adsorbent. According to the BTEX adsorption data, MCAC2 has 94% elimination effectiveness at 50 mg/L after 30 min of contact. To further adapt the experimental information for BTEX adsorption onto the MCAC2, Freundlich, Langmuir, and pseudo-first-order and pseudo-second-order models were used. The findings fitted pseudo-second-order with optimal values of R² = 0.979, and the isotherm model adsorption fitted Langmuir model with values of R² = 0.992 The finding reveals that Melaleuca cajuputi leaves are useful material for producing adsorbents, and successful testing outcomes demonstrate that M. cajuputi leaves products serves as a vital organic absorbent in the decomposition of BTEX.

In recent years, carbon nanotubes have been extensively explored based on numerous applications in fields such as carbon nanotube based electrodes, super capacitors, nanowires, sensors, coating with polymers, biomedical, and mechanical applications. Keeping in view the significance of carbon nanotubes in the heat transfer process in micro-electrochemical systems, this study is conducted to examine the heat transfer attributes of the carbon nanotubes using the mixture base working fluid. The focus of this investigation is to elaborate the consequence of higher chemical reactions on the bioconvective flow of carbon nanotubes. Additionally, modified Buongiorno's nanofluid model has been used, which undertakes thermophoresis and Brownian motion effects. Heated boundary condition has also been incorporated with the migration of motile microorganisms. The hybrid nanofluid mechanism has been followed in this work. Carbon nanotubes of single-layer and multi-layer have been used simultaneously with different working fluids, such as ethylene glycol (EG) and ethylene glycol/water (EG-water). Non-dimensional flow model equations have been tackled with the bvp-4c package. The obtained outcomes have been presented for distinct profiles and tabulated data sets for the surface skin friction and heat transfer coefficient. It has been observed that when the level of Brownian motion increases, the velocity profile decreases abruptly for SWCNT-MWCNT/EG as compared to SWCNT-MWCNT/EG-water hybrid nanofluid. Opposite behavior has been seen with raising values of magnetization. High Prandtl number decrease thermal boundary layer thickness for both types of hybrid nanofluids. The motile microorganism profile expands by raising the level of bioconvective Lewis number. Moreover, the outcomes of drag force and Nusselt number have been compared, and good agreement has been found.