Decomposition Curves Research Articles

Synthesis and characterization of amphiphilic Poly(2-hydroxyethyl acrylate-g-α-Methyl-β-Alanine) by Nitroxide-Mediated Polymerization Using “grafting through” approach

Oligomeric poly(α-methyl-β-alanine)with vinyl end-group (PmBA) was synthesized via base-catalyzed hydrogen-transfer polymerization (HTP) of molten methacrylamide (MAm) in the presence of sodium tert-butoxide (t-BuONa). The PmBA was used as a comonomer in the synthesis of amphiphilic poly(2-hydroxyethyl acrylate-g-α-methyl-β-alanine) (PHEA-g-PmBA)via nitroxide-mediated polymerization (NMP)and "grafting through" approach.The graft copolymer formation was confirmed byproton nuclear magnetic resonancespectroscopy (1H-NMR), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and static light scattering (SLS)measurements. Thermogravimetric analysis of the amphiphilicPHEA-g-PmBAexhibited a multi-step decomposition curve corresponding to the α-methyl-β-alanine and the 2-hydroxyethyl acrylate blocks at about 306, 369, and 403 °C.DSC curve of the copolymer has a baseline shift at −12.87 °C attributed to the glass transition temperature. SLS analysis of the final product resulted in a weight average molecular weight of 83.6 kDa. The spectroscopic and thermal analyses proved that amphiphilicPHEA-g-PmBA was successfully synthesized through HTP and NMP.

NiCoCr2O4 as a potential catalyst for the thermal decomposition of ammonium nitrate: a kinetic investigation

The thermal decomposition of high energetic materials plays an important role in their thermal performance. Use of the catalyst is one of the efficient ways improve the thermal performance of the high energetic materials. Therefore, in this work nickel cobalt chromite (NiCoCr2O4) prepared using precipitation approach was utilized as a catalyst for decreasing the thermal decomposition temperature and activation energy of high energetic material ammonium nitrate (AN). The results suggest that AN/NiCoCr2O4 decomposes at lower temperature (240 °C) within a short temperature range (Thermo gravimetry decomposition curve = 180–250 °C). The kinetic study was investigated using Kissinger-Akahira-Sunose (KAS) and Kissinger method (5, 10, and 15 °C min−1 heating rates). The activation energy of AN was reduced from 158.0 to 141.5 kJ mol−1 and decrease in the pre-exponential factor was observed upon addition of NiCoCr2O4. The outcome of the present work can be used to design AN based high energetic formulations containing NiCoCr2O4 catalyst with better thermal decomposition performance.

Precise Fourier parameters of Cepheid radial velocity curves: Towards refining the Hertzsprung progression models

Context. Radial velocity (RV) curves of Classical Cepheids allow precise determination of the resonant periods, which in turn help to constrain fundamental parameters of these stars. The RV curves of Cepheids are also useful for identifying their pulsation modes and for distance determination using the parallax-of-pulsation method. Aims. The primary goal of this paper is to derive precise Fourier parameters of the RV curves for fundamental and first-overtone Galactic Cepheids. Our secondary objectives are then to analyze the progression of the Fourier parameters up to the seventh harmonic, and to propose an identification of the pulsation modes of the stars. Methods. For each star, we carefully selected RV measurements available in the literature that yield the highest precision of Fourier parameters according to the procedure that follows. We performed a Fourier decomposition of the RV curves using the unweighted least-square method and the standard deviation of the fit was used to derive the uncertainty on the Fourier parameters. We corrected for zero-point differences between datasets and RV modulations caused by binary motion. Results. With this study we have more than doubled the number of Cepheids with published RV curve Fourier parameters and with their uncertainty properly estimated. Our sample includes 178 fundamental-mode and 33 first-overtone pulsators, as well as 7 additional Cepheids whose pulsation mode is uncertain or undetermined according to our criteria. For the fundamental-mode Cepheids, the precision of the obtained low-order Fourier phases and amplitudes is about seven times and 25% better, respectively, as compared to the precision achieved in previously published Fourier parameter surveys. With highly accurate RV Fourier phases ϕ21, we are able to firmly identify V495 Cyg as a new first-overtone Cepheid and we confirm the first-overtone nature of several other stars. In particular, α UMi should be firmly classified as a first-overtone pulsator. In three objects (VY Per, AQ Pup, and QZ Nor), we find significant γ-velocity variations, which for the first two objects (and possibly for QZ Nor as well) can be attributed to the spectroscopic binarity of these stars. Finally, the analysis of the fundamental mode Fourier parameters up to seventh order reveals tight progression of Fourier phases for all pulsation periods. Conclusions. We provide new precise Fourier parameters of Cepheid RV curves determined from RV measurements available in the literature together with unpublished data. The pulsation period coverage and the precision obtained, in particular for Fourier phase ϕ21, will be useful for studying the dynamics of Cepheid pulsations with the help of hydrodynamical models. Further RV measurements from modern high-resolution spectroscopic instruments will be important to improve these results.

Phenological Analysis of Grasses (Poaceae) in Comparison with Aerobiological Data in Moscow (Russia).

Grasses (Poaceae) produce large amounts of pollen and are among the main causes of pollinosis worldwide. Despite their morphological similarity, pollen grains of different grass species may have different allergenicities. Therefore, quantification of the roles of individual species in airborne pollen is an important task. There are very few studies on this topic, and none of them have been conducted in a temperate continental climate. Our study was carried out for three years (2020-2022) in the urban territory of Moscow (Russia) and aimed to understand what grass species contribute the most to the total pollen load of the atmosphere. The comparison of aerobiological and phenological data was based on calculating the phenological index, which is a combination of phenological parameters, pollen productivity of individual species, and their abundance. Our data showed that the decomposition of pollination curves based on the phenological index was sometimes very efficient but not always possible in temperate continental climates. The main reasons for disagreement between aerobiological and phenological data were weather conditions and lawn mowing. Not all grasses were equally important as sources of allergenic pollen. The greatest contribution to the pollen load at the beginning of the season in Moscow was made by Dactylis glomerata, and to a lesser extent by Phleum pratense and Festuca pratensis. These are the most common species, which are widespread throughout Europe. The contribution of minor components is insignificant.

Decomposition behavior of GaN under solid and ambient N2 pressure

We investigated the decomposition behavior of GaN crystals under high N2 and solid pressures using a belt-type high-pressure apparatus. The decomposition curve of GaN under solid pressure showed a considerably moderate increase compared to that under a N2 pressure. Such difference was attributed to the N2 dissolution in the Ga melt, where a high N2 pressure creates a supersaturated GaN state, which effectively prevent its decomposition. Conversely, under a solid pressure, the increase in the GaN decomposition temperature followed a common change in enthalpy, which is consistent with its typical thermodynamic behavior. The decomposition behavior of GaN under a solid pressure demonstrated its successful high-temperature annealing using a belt-type high-pressure apparatus. Therefore, this study provides valuable insights into the thermodynamic stability of GaN under different pressures, which is critical for optimizing high-performance GaN-based devices.

Synthesis of benzoic acid from catalytic co-pyrolysis of waste wind turbine blades and biomass and their kinetic analysis

This work aims to study the catalytic co-pyrolysis of waste wind turbine blades (WTB: consists of fiberglass/unsaturated polyester resin) and woody biomass (WB) over ZSM-5 and Y-type zeolite catalysts for the production of benzoic acid. The experiments were performed on an equal combination of WTB and WB (WTB/WB) and a fixed amount of catalyst (50 wt%) using a thermogravimetric (TG) analyser at 10, 20 and 30 °C/min. The evolved products from the catalytic co-pyrolysis process were recognized using TG-FTIR and GC/MS. The kinetic and thermodynamic characteristics of catalytic co-pyrolysis was studied using various linear and nonlinear approaches. Also, the decomposition curves were predicted mathematically using an artificial neural network algorithm. The results revealed that the mixture was decomposed in the presence of both catalysts in the form of dual decomposition peaks at 361–374 °C and 428–443 °C, respectively. Based on TG-FTIR results, the CO stretching and carbon dioxide clusters were their main functional groups. While the GC-MS analysis revealed that the released vapours were completely free of toxic styrene (the main compound of resin) and the catalytic co-pyrolysis treatment succeeded in converting it into highly abundant benzoic acid, especially at 10 °C/ min, with an estimated 71.4 % (ZSM-5) and 64 % (Y-type). Whereas the activation energy was estimated at 262–295 kJ/mol (ZSM-5) and 319–357 kJ/mol (Y-type) with almost similar reaction complexity when compared to the case of absence of catalysts. Finally, the developed ANN algorithm showed high efficiency in predicting TG decomposition zones for both WTB/WB mixtures over zeolite catalysts with R2 more than 0.99. These results demonstrate that WB and zeolite catalysts can be used for upgrading the pyrolysis oil of WTB and eliminate its toxic styrene and convert it into benzoic acid and other aromatic hydrocarbons compounds (such as benzene, alanine, and 2-Propanamine).

Winter cover crops grown in low altitude condition

The purpose of the study was to evaluate dry matter phytomass production, percentage of soil cover, and dry matter phytomass decomposition curve of cover crops in single and mix cultivation, in a low-altitude subtropical environment. The study was conducted in Santa Maria - RS, in agricultural years 2019/2020 and 2021/2022. The experimental design used was randomized blocks, with ten treatments and four replications. The experiments were conducted with four winter cover crops: White oat (WO), black oat (BO), forage turnip (FT), and common vetch (CV), in single cultivation and as a mix of cover plants. For the total production of dry matter phytomass, the FT and BO+CV+FT treatments stand out which present the highest averages between the experimental years, with values ​​4365.32 and 4109.87 kg ha-1. FT in single cultivation has a high potential for soil coverage in periods of 45 DAS, and the common vetch crop showed greater soil coverage in the late period, with 84% coverage at 90 days after sowing. The BO and WO treatments showed greater maintenance of dry phytomass in soil cover at the end of the 150-day period, presenting values greater than 40% of the initial volume of dry phytomass present in the production system. Recommending the exclusive cultivation of the species that meets the rural producer's objective.

Assessment of chemical degradation of epoxy resin binder used in the service of the Qin terracotta warriors

Since the Qin terracotta warriors were unearthed, polyamide 650 cross-linked E-44 epoxy resin binder has been employed to bond and restore them. In this paper, the chemical aging of the binders service in indoor natural environment during the past 30 years in the terracotta warriors was studied by means of infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results indicated that the binders did not emerge the characteristic peak of carbonyl stretching vibration at 1700 cm−1 in the IR spectra of all determined binders, and their thermal decomposition curves did not emerge any abnormal changes, and the thermal decomposition mainly occurred above 300 °C. There are evident ceramic grains attached to the surface of the binders being peeled off for sampling. These results that the binders service in the Qin terracotta warriors did not exhibit an observable chemical aging and still has strong adhesion. Generally, discrepancies were observed between natural aging and accelerated artificial aging due to the ineffectiveness of the latter to reproduce the effects of complex weather conditions. Compared to artificially accelerated aging, the evaluation results in a long-term natural aging of the binder which is used for restoration of the life-size Qin terracotta warriors, providing in the present investigation, are more reliable in terms of predicting the safety of restored terracotta warriors.

Exploring the nature of dark matter with the extreme galaxy AGC 114905

i ) morphology, remains somewhat uncertain. We present unmatched ultra-deep optical imaging of AGC 114905 reaching surface brightness limits $ r,lim 32$ mag/arcsec$^2$ ($3 10 arcsec times 10 arcsec) obtained with the 10.4 m Gran Telescopio Canarias. With the new imaging, we characterise the galaxy's optical morphology, surface brightness, colours, and stellar mass profiles in great detail. The stellar disc has a similar extent to the i disc, presents spiral arms-like features, and shows a well-defined edge. Stars and gas have a similar morphology, and crucially, we find an inclination of $31 in agreement with the previous determinations. We revisit the rotation curve decomposition of the galaxy, and we explore different mass models in the context of CDM, self-interacting dark matter (SIDM), fuzzy dark matter (FDM) or Modified Newtonian dynamics (MOND). We find that the last does not fit the circular speed of the galaxy, while CDM only does so with dark halo parameters rarely seen in cosmological simulations. Within the uncertainties, SIDM and FDM remain feasible candidates to explain the observed kinematics of AGC 114905.

Two-layer elastic models for single-yeast compressibility with flat microlevers.

Unicellular organisms such as yeast can survive in very different environments, thanks to a polysaccharide wall that reinforces their extracellular membrane. This wall is not a static structure, as it is expected to be dynamically remodeled according to growth stage, division cycle, environmental osmotic pressure and ageing. It is therefore of great interest to study the mechanics of these organisms, but they are more difficult to study than other mammalian cells, in particular because of their small size (radius of a few microns) and their lack of an adhesion machinery. Using flat cantilevers, we perform compression experiments on single yeast cells (S. cerevisiae) on poly-L-lysine-coated grooved glass plates, in the limit of small deformation using an atomic force microscope (AFM). Thanks to a careful decomposition of force-displacement curves, we extract local scaling exponents that highlight the non-stationary characteristic of the yeast behavior upon compression. Our multi-scale nonlinear analysis of the AFM force-displacement curves provides evidence for non-stationary scaling laws. We propose to model these phenomena based on a two-component elastic system, where each layer follows a different scaling law..

Characterization of solid carbon from hydrocarbon pyrolysis in molten aluminum

This study analyzed the synthesized solid carbon from the pyrolysis of methane, ethane, propane, and natural gas using molten aluminum at 1000 °C. Microscopic examination revealed the formation of spherical structures and capped-carbon nanotubes with average primary particle sizes of 0.18–1.29 μm for the spheres and 0.31–0.39 μm for the capped-carbon nanotubes. Methane and ethane pyrolysis generated spherical carbon exclusively, while propane and natural gas pyrolysis produced spheres and capped-carbon nanotubes. The analysis of interlayer spacing indicated the presence of nanocrystalline properties in all carbon samples. X-ray diffraction analysis indicated broad graphitic phases in methane, ethane, and natural gas-derived carbon, and a broad and sharp graphitic carbon peak in propane-derived carbon. Raman spectroscopy confirmed the presence of graphitic structures and disorder, with capped-carbon nanotubes demonstrating more ordered structures than spheres. The thermogravimetric analysis uncovered differences in oxidation behavior, with the mixture of spherical carbon and capped-carbon nanotubes resulting from propane pyrolysis displaying superior thermal stability compared to samples composed solely of spherical carbon. Additionally, the solid carbon samples from the pyrolysis of methane, ethane, and natural gas displayed a final decomposition curve corresponding with commercial carbon black N991. The surface area analysis unveiled that carbon samples derived from ethane and natural gas exhibited surface areas that were 2.4–5.2 times larger than those of commercial carbon black N991 and graphite flakes. These findings underscore the adaptability of tailoring solid carbon materials by selecting the appropriate feed gas to suit specific applications.

Facile synthesis of lanthanum carbonate octahydrate and lanthanum oxide nanoparticles by sonochemical method: systematic characterizations

Abstract This study could present the size and morphology of two synthesized nanoparticles (NPs) by observing their smallest possible dimensions. Lanthanum carbonate nanoparticles were synthesized by sonochemical method through the interaction of lanthanum acetate hydrate and sodium carbonate in an aqueous medium with a probe sonicator. After rigorous washing followed by drying, the La2(CO3)3·8H2O(S1) NPs were calcined at a temperature of 600 °C to obtain lanthanum oxide nanoparticles (S2). Both NPs were characterised through various instrumental techniques. PXRD study showed orthorhombic with space group of Pccn (56) and hexagonal phases with space group of P 3 ‾ m 1 $P\overline{3}m1$ (164) for S1 and S2 respectively whose morphology and elemental analysis were studied through FESEM and EDX. High resolution TEM image of La2(CO3)3·8H2O and La2O3 showed spherical shapes of the nanoparticles. Further study of XPS and FTIR conveyed detailed information of both nanoparticles whose TGA-DSC showed three step decomposition curves. The size and morphology of the synthesized nanoparticles have been found to have a distinct morphology and are found comparatively smaller in size than those observed in the earlier reported works (Table 1 Table 1: Comparative study of synthesized lanthanum carbonate and lanthanum oxide NPs with various techniques applied by other researchers. Sl. no. Name of NPs Methods Conditions Size of NP Reference 1 La2(CO3)3·8H2O Sonochemical method Time: 25 min XRD: Pccn (56) a = 8.9840 Å b = 9.5800 Å c = 17.0000 Å This work Temperature: 301 K Size: 24.102 nm Starting materials:(a) La(CH3COO)2: 0.050 M(b) Na2CO3:0.050 M TEM: Size: 4–30 nm La2(CO3)3 Reverse micelles Time: 1 h XRD: Size: nanoparticles absent [20] Temperature: 303 K Starting materials:(a) Triton X-100(b) Cyclohexane(c) n-butylalcohol(d) La(NO3)3(aq) e) NaCO3(aq) La2(CO3)3·8H2O Hydrothermal Time: 2–5 days XRD: Pccn a = 8.984 Å b = 9.580 Å c = 17.00 Å [21] Temperature: 773 K Size: nanoparticles absent Prepared by slow hydrolysis of La(CCl3COO)3 La2(CO3)3·1.4H2O Hydrothermal Time: 1 h 30 min Structure unknown [22] Temperature: 368 K Starting material:(a) La2O3 (b) HNO3 (c) Urea La2(CO3)3·1.7H2O Sonochemical Time: 30 min XRD: a = 8.990 Å c = 9.675 Å [23] Temperature: not specified Size: not specified (a) La(OAC)3 (b) Na2CO3 TEM: Size: 25–35 nm Concentration:(a) La(OAC)3: 0.051 M(b) Na2CO3: 0.251 M La2(CO3)3·5H2O Hydrothermal Time: XRD: Pbca a = 9.0167 Å b = 12.842 Å c = 9.6331 Å [24] Temperature: Size: not specified Starting materials:(a) La2O3 (b) HCl(c) Na2CO3 La2(CO3)3·3.4H2O Hydrothermal Time: 3–4 h XRD: P21212 a = 9.57 Å b = 12.65 Å c = 8.94 Å [25] Temperature: 298–308 K Size: not specified Starting materials:(a) LaCl3 (b) NH4HCO3 2 La2O3 Thermal decomposition Time: 2 h P3m1 a = 3.973 Å b = 3.9373 Å c = 6.129 Å [26] Temperature: 1073 K Size: 15 nm Starting material: La(OH)3 nanorods TEM: Size: 23 nm La2O3 Thermal decomposition Time: 2 h XRD: a = 11.347 Å [23] Temperature: 873 K Size: 30 nm Starting material:La2(CO3)3·1.7H2O TEM: Size: 30 nm La2O3 Thermal decomposition Time: not specified Not specified [27] Temperature: 1198 K Starting material:(a) La(NO3)3·9H2O(b) NH4HCO3 La2O3 Thermal decomposition Time: 4 h Not specified [28] Temperature: 1073 K Starting material: La(OH)3 La2O3 Thermal decomposition Time: 2 h P 3 ‾ m 1 $P\overline{3}m1$ a = 3.973 Å b = 3.9373 Å c = 6.129 Å This work Temperature: 873 K XRD: Size: 43.26 nm Starting material: La2(CO3)3·8H2O TEM: Size: 17–34 nm ).

<i>Diospyros</i> <i>crassiflora</i> (HIERN) surface and subsoil leaf litter decomposition pattern along a time gradient in a humid rainforest

Litter decomposition is a crucial bedrock of nutrient recycling, organic matter accumulation, soil physicochemical properties, biodiversity and life support of forest and agroforestry systems. We therefore investigated <i>Diospyros</i> <i>crassiflora</i> surface and subsoil leaf litter decomposition pattern along a duration gradient in a humid rainforest. The study was conducted in the nursery of the humid forest research station of the Forestry Research Institute of Nigeria (FRIN) in Umuahia, Abia State. One gram (1g) of <i>D.</i> <i>crassiflora</i> fresh leaf litter was placed on the surface and subsoil of 4kg of topsoil contained in 32cm x 20cm polyethene bags; there were a total of 108 bags in a completely randomized experimental design layout and the treatments were the duration gradient of litter decomposition which were: 2, 4, 6, 8, 10, 12, and 14 weeks; on each of the duration, litter was collected from nine of the polyethene bags for laboratory analysis and estimate of decomposition rate. The results showed a significantly high initial decomposition rate (3.19±0.13 %day-1; 4.28±0.03 %day-1) in the 2 week duration followed by significant continuous decline until the lowest (0.04±0.00%day-1; 0.28±0.02%day-1) in the 14 week in the surface and subsoil respectively. There was a positive correlation (r=0.80) in decomposition rate between the surface and subsoil leaf litter, which yielded a model with a significant R2 (0.64), for site-specific estimates of decomposition rate <i>D.</i> <i>crassiflora</i> leaf litter. A steeper and smoother subsoil cumulative percentage decomposition curve showed that leaf litter decomposition was significantly faster in the subsoil than surface soil.

Secrets on the rock: analysis and discussion of the Dunde Bulaq rock art site

The Altay Prefecture in Xinjiang Uyghur Autonomous Region, China, boasts an abundance source of rock art, with the Dunde Bulaq rock art complex holding paramount significance in the study of local culture. This work employs hyperspectral techniques for data collection and analysis of the Dunde Bulaq I rock art site. Signal decomposition, pigment classification/clustering, and spectral curve analysis were employed to delve deeply into the information of the rock art hyperspectral data. Furthermore, cross-validation was utilized to reveal hidden information within rock art. To comprehend these hidden information, a more profound historical tracing was conducted, employing methods such as literature retrieval and image analysis, uncovering the internal relationship between the site I and the Chemurchek culture. This provides fresh material for studying the Bronze Age cultures within the Altai region.

Selection of Effective Temperature for Thermal Regeneration of Spent Alkali-Phenolic Binder Moulding Sand.

This article presents the results of research on alkali-phenolic binders used in moulding sands. The results of the presented experiments are part of a search for the optimum conditions to implement the thermal regeneration of spent alkali-phenolic binder moulding sands. The cured binders were subjected to thermogravimetric analysis in aerobic and anaerobic atmospheres. On the basis of the resin decomposition curves, the integral polymer decomposition temperature was determined, and the required thermal regeneration temperature for the alkali-phenolic binder moulding sands that were used was determined according to a specific procedure. The spent moulding sand was subjected to roasting procedures at different temperatures in order to confirm the necessary regeneration temperatures. The effects of the procedures that were carried out were evaluated by means of weight losses and ignition losses, microscopic pictures were taken, and using scanning microscopy, an analysis of the chemical composition in the micro areas on the surfaces of the matrix grains was carried out using scanning microscopy. The indicators for the comparisons between the individual binders were also calculated from the mass losses. The research and analysis that were carried out made it possible to indicate the required temperature for the thermal regeneration of the spent alkali-phenolic binder moulding sand to reduce the involved energy expenditure. The factors that can determine the successful implementation of the process and the obtaining of the best possible grain matrix for reuse were also indicated.

Exploring the energy harvest of droplet flow over inducted film for the rainy-shiny solar panel application

An equivalent electrical circuit (EEC) based on transient pseudo-capacitive and electrostatic induction is established to understand the operating mechanism using voltage-time curve decomposition. All relative parameters including top electrode dimension and the instantaneous droplet area variation are used to demonstrate our droplet-base electricity generation (DEG) mechanism and illustrate the principle of the reverse voltage. Moreover, the Debye length concept is introduced to explain charge density at the interface between ionic droplet and the PTFE surface by various ion concentrations and valent number solutions. This work provides insightful and valuable perspective to explain the exponential decay of output voltage by instantaneous droplet area variation during leaving away from the PTFE surface. Moreover, the multi-functions of fluorinated ethylene propylene film coating on the solar panel by correct circuit design can improve 30% which is novel concept at rainy days alternated with dry ones.

Influence of chemical composition on the properties and foamability with supercritical CO2 in thermoplastic polythiourethanes

In this work, four polythiourethane films with different types of polyols and isocyanates were synthesized, characterized, and foamed. After characterization, it was also observed that the type of isocyanate has a large influence on the crystallinity and stiffness of the polymers, while the type of polyol modifies the FT-IR spectra and the decomposition curve of the material with temperature. During the foaming tests, it was observed that the polymeric foams with tolylene-2,4-diisocyanate as isocyanate were able to achieve higher values of expansion ratio, although they also suffered higher shrinkage. Moreover, these foams presented cells with higher size and heterogeneity, while the foam obtained with hexamethylene diisocyanate as isocyanate presented cells with lower size and heterogeneity but with higher cell density, proving that the selection of the isocyanate type not only has a huge influence on the properties of the polymeric material but also on the foams obtained from it.

Deconvolution of DSC peaks of high-temperature phases in an illite/smectite–CaCO3 mixture

Heat flow curves measured in differential scanning calorimetry (DSC) may contain overlapping peaks corresponding to multiple-step processes. To analyze the individual steps in such a process, a deconvolution of the overlapping peaks into the individual peaks is necessary. Using the Frazer-Suzuki function to describe asymmetric peaks, we apply a nonlinear least squares analysis to perform the decomposition of heat flow curves measured for a mixture of an illite/smectite clay with 19.6 wt.% of CaCO3. The curves contain two overlapping peaks associated with the crystallizations of gehlenite and anorthite in the temperature interval from 900 °C to 1050 °C. Several versions of the decomposition analysis may be used, depending on the number of optimized parameters. These may range from four to all eight parameters (four for either peak). We applied the versions with seven and eight fitting parameters, yielding results that are in very good agreement with the experimental data.

Variable stars in the field of the Galactic bulge globular cluster NGC 6522

We present a comprehensive analysis of the variable stars projected on the field of the Galactic bulge globular cluster NGC 6522, offering valuable insights into their characteristics. Using proper motions from Gaia-DR3, we aim to distinguish between field stars and true cluster members. For an accurate color-magnitude diagram of the member stars, we produced a differential reddening map. We detect and discuss the peculiarities of variable stars of the types RR Lyrae, type II Cepheids, Long Period Variables (LPV) and eclipsing binaries, whose light curves are available through the OGLE III and IV databases. Notably, we explore the variable V24, which shows a prominent phase modulation resulting from period changes in a time scale of 1100 days. The variable stars among the cluster members serve as indicators of the cluster metallicity and distance; these determinations are based on their light curves. With the Fourier light curve decomposition of three RRc stars, we have derived the following cluster parameters: the metallicity in the spectroscopic scale text{[Fe/H]}_{mathrm{UVES}}=-1.16 pm 0.09; and the mean distance D=8.77 pm 0.16 kpc.

Cluster analysis and forecasting of viruses incidence growth curves: Application to SARS-CoV-2

The sanitary emergency caused by COVID-19 has compromised countries and generated a worldwide health and economic crisis. To provide support to the countries' responses, numerous lines of research have been developed. The spotlight was put on effectively and rapidly diagnosing and predicting the evolution of the pandemic, one of the most challenging problems of the past months. This work contributes to the existing literature by developing a two-step methodology to analyze the transmission rate, designing models applied to territories with similar pandemic behavior characteristics. Virus transmission is considered as bacterial growth curves to understand the spread of the virus and to make predictions about its future evolution. Hence, an analytical clustering procedure is first applied to create groups of locations where the virus transmission rate behaved similarly in the different outbreaks. A curve decomposition process based on an iterative polynomial process is then applied, obtaining meaningful forecasting features. Information of the territories belonging to the same cluster is merged to build models capable of simultaneously predicting the 14-day incidence in several locations using Evolutionary Artificial Neural Networks. The methodology is applied to Andalusia (Spain), although it is applicable to any region across the world. Individual models trained for a specific territory are carried out for comparison purposes. The results demonstrate that this methodology achieves statistically similar, or even better, performance for most of the locations. In addition to being extremely competitive, the main advantage of the proposal lies in its complexity cost reduction. The total number of parameters to be estimated is reduced up to 93.51% for the short term and 93.31% for the mid-term forecasting, respectively. Moreover, the number of required models is reduced by 73.53% and 58.82% for the short- and mid-term forecasting horizons.