Journal of Mathematical and Fundamental Sciences
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Discretization and Associated Asymptotic Behavior for the Lax Equation with Skew-symmetry
Full text linkThe computation of matrix eigenvalues is vital for understanding various scientific phenomena. The QR method, which is based on the QR factorization of a matrix, is a common approach in numerical linear algebra. In integrable systems, the one-step process of the QR method is related to the time evolution of the Lax equation. In this paper, we clarify the relationship between the QR method, which incorporates an origin shift parameter, and the Lax equation with skew-symmetry. Furthermore, we show the asymptotic convergence of discretization based on matrix factorization of the Lax equation with skew-symmetry as discrete time approaches infinity
Bauxitization and REE Redistribution in Weathered I-type Granite Profile of Gunung Kijang, Bintan Island
Full text linkWeathering is often linked to economic mineral enrichment, including nickel, bauxite, and rare earth elements (REE). The exposed granitic rocks on Bintan Island, Riau Islands Province, belong to the Southeastern Asian Eastern Granite Province. This study examines the bauxitization process and REE distribution across weathered granite horizons in the Gunung Kijang area. Major oxides were analyzed using X-ray fluorescence, while trace and rare earth elements were determined by inductively coupled plasma–mass spectrometry. The trace element composition and metaluminous nature of the parent granite confirm its I-type classification. Kaolinization and bauxitization were observed in the weathered layers, with Al₂O₃ and Fe₂O₃T contents ranging from 25.21–46.50% and 6.99–8.76%, respectively. Total REE content in the weathered horizons (up to 76 ppm) is lower than in the parent rock (214 ppm). Nevertheless, the soft, near-surface materials offer potential for future REE utilization. Clay minerals are the main REE hosts, while the enrichment from the C-horizon upward is influenced by higher organic matter near the surface. Similar Eu and Ce anomaly patterns indicate minimal feldspar in the original granite or limited feldspar breakdown during weathering
An Algorithm to Construct a Tridiagonal Matrix Factored by Bidiagonal Matrices with Prescribed Eigenvalues and Specified Entries
Full text linkThis paper presents an algorithm to construct a tridiagonal matrix factored by bidiagonal matrices with prescribed eigenvalues and specified matrix entries. The proposed algorithm addresses inverse eigenvalue problems (IEPs) constrained by LR decomposition. Using techniques from discrete soliton theory, we derive recurrence relations that connect matrix entries and eigenvalues. The algorithm systematically computes unknown entries in the matrix from given spectrum data and partial matrix information. Several examples, including cases with real, complex, and multiple eigenvalues, demonstrate the efficiency of the proposed algorithm. Additionally, we provide conditions under which the algorithm successfully solves the IEP
Penta- and Tetra-cyclic Triterpenoids from Aglaia cucullata Stembark and Cytotoxicity against Cancer and Normal Cells
Full text linkThree triterpenoid compounds, belonging to the penta- and tetracyclic groups, were successively isolated from the stembark of Aglaia cucullata and identified as b-amyron (1), dammaradienon (2), and cabralealactone (3). After extensive extraction, chromatographic separation and purification, compounds 1 to 3 were gained. Spectroscopic analysis in addition to HRMS, FTIR, 1D and 2D NMR analysis were utilized to determine the chemical structure. After that, compounds 1 to 3 were tested against breast cancer, melanoma as well as normal kidney cells (MCF-7, B16-F10, and CV-1, respectively). The resulted cytotoxicity test revealed that compound 1 had the best cytotoxicity against all cells compared with the other isolated compounds. This result suggests that the pentacyclic triterpenoid core in compound 1 increases cytotoxicity compared with a tetracyclic skeleton
The Impact of Convective Available Potential Energy (CAPE) on Spatio-Temporal Variations of Indonesian Extreme Rainfall
Full text linkAtmospheric instability frequently influences the distribution of precipitation and is closely associated with atmospheric dynamics and thermodynamics. An increase in convective available potential energy (CAPE) has the potential to result in the development of convective clouds, which could contribute to extreme rainfall. This study used rainfall data from Asian Precipitation–Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) and CAPE data from the European Centre for Medium-Range Weather Forecasts. We defined extreme rainfall trends by applying the Expert Team on Climate Change Detection and Indices (ETCCDI), which include the number of days with precipitation greater than the 95th percentile (R95P), consecutive dry days (CDD), consecutive wet days (CWD), the number of days with precipitation greater than 10 mm (R10mm), the number of days with precipitation greater than 20 mm (R20mm), and the Simple Daily Intensity Index (SDII). Using Mann-Kendall statistics, we found that the trend of extreme rainfall in Indonesia from 1983 to 2007 was predominantly characterized by the extreme category, as indicated by the increasing CDD indices. During the MAM-SON seasons, the CAPE had a substantial contribution to the extreme rainfall in Indonesia. The CAPE exhibited a significant positive (negative) correlation with the CWD and R10mm (CDD) indices
Sedimentary Facies, Palynology, and Organic Geochemistry of Eocene Kalumpang Formation in Lariang and Karama Areas, West Sulawesi, Indonesia
Full text linkThe Kalumpang Formation was deposited in a delta plain setting. A Middle to Late Eocene age (Proxapertites operculatus zone) was inferred from palynological analysis, with a paleoenvironment in a coastal plain setting with a strong terrestrial influence. Samples from the Kalumpang Formation indicate a marginal to early mature stage for hydrocarbon generation. It is mostly composed of gas-prone to oil and gas-prone Type III kerogen facies. The biomarker character of both the rock and oil samples suggests a terrestrial origin, with a significant contribution of estuarine or bay organic material. The oil derives from a non-carbonate lithology, while the rock samples are from carbonate/calcareous shale origin. The abundance of oleanane compound and C30 resins suggests higher plant angiosperm input of Late Cretaceous or younger age for both the rock and the oil samples. The oil seep contains more abundant oleananes compared to the carbonaceous mudstone of the Kalumpang Formation. This suggests that the oil originated from more marine facies than the rock samples, which were deposited in a delta plain setting. This study demonstrated the agreement of depositional environment interpretation and age assessment between lithofacies, palynological, and organic geochemistry analysis
Optical Spectroscopy and Photoionization Model of Planetary Nebula NGC 6572
Full text linkWe investigated NGC 6572 through optical spectroscopy to determine its kinematical and chemical properties. Two intermediate dispersion spectra (R~5000) centered around Hα and Hβ were used to derive the nebular expansion velocity from emission lines associated with Hα, Hβ, [OIII], [NII], and [SII] ions. A low dispersion spectrum (R~1000) was used to determine the nebular electron temperature, density, and chemical composition. We performed photoionization modeling to construct a self-consistent nebular model, while intermediate-resolution spectral images showed the global elliptical structure of the nebula. The expansion velocity deduced from most of the emission lines is consistent with the typical expansion velocity of planetary nebulae, i.e., around 15-20 kms-1. The nebular physical properties align well with those determined by other studies. The nebular abundances were found to be lower than the solar abundances (except for oxygen) but still comparable with the abundances derived by other researchers. The photoionization model generated spectral lines that are consistent with the lines found in the observations. Further spectroscopic observations with higher resolution and wider range at various position angles will be very useful to reveal a more complete and detailed structure of the nebula and to improve the determination of the nebular physical properties
Synthesis and Characterization of Bi2S3 Deposited on TiO2 Nanotubes (TiO2NTAs) as Photoanode in the Tandem DSSC-PEC System for Hydrogen Evolution
Full text linkTiO2NTAs is one of the most frequently used photoanodes. However, TiO2NTAs has a wide bandgap, so it is only active under UV light. Therefore, this study modified TiO2NTAs photoanode film to increase its efficiency. A simple method that successfully assists the Bi2S3 coating process on the surface of TiO2NTAs film is the Successive Ionic Layer Adsorption and Reaction (SILAR) method. In this research, modified Bi2S3 with TiO2NTAs was prepared using the SILAR method with variations of the number of synthesis cycles at 1, 2, 4, and 6. Based on the synthesis results, the number of deposition cycles greatly influences the performance of TiO2NTAs films. The synthesized TiO2NTAs/Bi2S3 results were characterized using SEM, XRD, FTIR, UV-Vis DRS, and photoelectrochemistry. The X-ray diffractogram showed that the composite compound was obtained successfully. The SEM images showed that Bi2S3 was deposited on the surface of the TiO2NTAs without blocking the nanotube holes. The constructed DSSC-PEC system could produce hydrogen with an STH (solar-to-hydrogen) efficiency of 0.02318% in an H-type reactor using anode irradiation for 6 hrs
Deformation under a Young Volcanic Covered Area in Southern Garut, Indonesia: Insight from 3D Gravity Modelling
Full text linkDestructive earthquakes are frequently related to inland active faults. In recent years, a significant number of shallow earthquakes with low magnitude have occurred in southern Garut, West Java, Indonesia. Two earthquakes, with magnitudes of M4.2 and M3.9 in 2016 and 2017, respectively, have caused significant damage and were interpreted as indications of an active fault. We used publicly available gravity data to infer the subsurface structure that may be related to recent seismic activity. We used spectral analysis and filtering techniques for the regional-residual anomaly separation and anomaly enhancement to show the basin structure in the study area. 3D gravity inversion modelling was performed to obtain the subsurface density distribution. The result indicates the sedimentary layers with a density of 2.4 to 2.5 gr/cm3 with an underlying basement with a density of 2.65 gr/cm3. An intra-basin basement high with an NE-SW trend divides the basin into two sub-basins. This local basement high can be associated with a magmatic intrusion body and a series of young volcanic bodies located at the northeastern end of the basin. Our results emphasize a possible strong interaction between the tectonic and magmatic activities in this region
Simulation of Ultra-Short Laser Pulses Propagation and Ionization in Dual-Gas-Cells to Enhance the Quasi-Phase Matching of Harmonics Generation in Plasmas
Full text linkA numerical model was designed and implemented to investigate the influence of plasma defocusing on laser characteristics. The effects of plasma defocusing were investigated by studying beam divergence, intensity reduction, and blue shifting. The diffusion of the ultra-intense laser beam in gas cells was within a Rayleigh range. Moreover, using dual-gas-cells, the impact of quasi-phase matching (QPM) on the creation of harmonic pulses in argon and hydrogen plasmas was studied. The alternating structure of argon and hydrogen gas cells showed a perfect build-up of the generated ultra-short harmonics pulses. The impact of electron density on laser diffusion and the creation of harmonic pulses were also investigated in this work. In the simulation, argon plasma with different plasma densities was used in an alternating structure to create dual-gas-cells and quasi-phase-matching. Noticeable conversion of the fundamental laser pulses to harmonics pulses was accomplished in the model by using the QPM concept