Regions Of Mass Loss Research Articles

Dynamical Interactions and Mass Loss within the Uranian System

The origin and evolution of planetary rings and moons remains an active area of study, particularly as they relate to the impact history and volatile inventory of the outer solar system. The Uranian system contains a complex system of rings that are coplanar with the highly inclined planetary equator relative to the orbital plane. Uranus also harbors five primary regular moons that play an important role in the distribution of material that surrounds the planet. Here we present the results of a dynamical simulation suite for the Uranian system, intended to explore the interaction between the five primary regular moons and particles within the system. We identify regions of extreme mass loss within 40 planetary radii of Uranus, including eccentricity excitation of particle orbits at resonance locations that can promote moonlet formation within the rings. We calculate a total dynamical particle mass-loss rate of 35% within 0.5 × 106 yr and 40% mass loss within 107 yr. We discuss the implications for postimpact material, including dynamical truncation of stable ring locations and/or locations of moon formation promoted by dynamical excitation of ring material.

The luminous type IIn supernova SN 2017hcc: Infrared bright, X-ray, and radio faint

ABSTRACT We present multiwavelength observations of supernova (SN) 2017hcc with the Chandra X-ray telescope and the X-ray telescope onboard Swift (Swift-XRT) in X-ray bands, with the Spitzer and the TripleSpec spectrometer in near-infrared (IR) and mid-IR bands and with the Karl G. Jansky Very Large Array (VLA) for radio bands. The X-ray observations cover a period of 29 to 1310 d, with the first X-ray detection on day 727 with the Chandra. The SN was subsequently detected in the VLA radio bands from day 1000 onwards. While the radio data are sparse, synchrotron-self absorption is clearly ruled out as the radio absorption mechanism. The near- and the mid-IR observations showed that late time IR emission dominates the spectral energy distribution. The early properties of SN 2017hcc are consistent with shock breakout into a dense mass-loss region, with $\dot{M} \sim 0.1$ M⊙ yr−1 for a decade. At few 100 d, the mass-loss rate declined to ∼0.02 M⊙ yr−1, as determined from the dominant IR luminosity. In addition, radio data also allowed us to calculate a mass-loss rate at around day 1000, which is two orders of magnitude smaller than the mass-loss rate estimates around the bolometric peak. These values indicate that the SN progenitor underwent an enhanced mass-loss event a decade before the explosion. The high ratio of IR to X-ray luminosity is not expected in simple models and is possible evidence for an asymmetric circumstellar region.

Desorption Behavior and Thermogravimetric Analysis of Bio-Hardeners

In this work, the thermal degradation and drying of bio-hardeners are investigated. Four bio-hardeners based on exudates of Senegalia senegal, Vachellia nilotica, Vachellia seyal, and Acacia Siebteriana were analyzed by FTIR and thermogravimetric analysis, and a desorption study was also conducted. The analysis by infrared spectroscopy indicates the existence of oligomers of different types all giving 5-hydroxy-2-hydroxymethylfuran and 2, 5-dihydroxymethylfuran which are then the real hardening molecules. The pyrolysis of these extracts reveals three main regions of mass loss, a first region is located between 25°C and 110°C reflecting the loss of water from the adhesive and the formation of some traces of volatile organic compounds such as CO2 and CO, a second zone characterized by the release of CO, CO2 and CH4 gases with peaks between 110° and 798.8°C. At the end of the analysis, about 22% of the initial mass remains undecomposed, this mass corresponds to the rigid segments of the bio-hardener which are not completely decomposed.

Kinetic and thermodynamic analyses of date palm surface fibers pyrolysis using Coats-Redfern method

This study presents the thermo-kinetics and thermodynamic analyses of date palm surface fibers (DPSFs) using thermogravimetric analysis. DPSFs were heated non-isothermally from 20 to 800 OC at a ramp rate of 10 OC/min in nitrogen atmosphere. Thermogravimetric analysis indicated that there have been two stages for pyrolysis of DPSFs. Kinetic and thermodynamic parameters have been calculated for the second stage which is further subdivided into two mass-loss regions. The low-temperature stable components were decomposed in a temperature range of 270–390 OC and high-temperature stable components were degraded in a temperature range of 390–600 OC. The Coats–Redfern integral method was employed with 21 different kinetic models from four major solid-state reaction mechanisms. Among all models, the two diffusion models: Ginstling–Brounshtein and Ginstling diffusion were the best fitted models with highest regression coefficient values (R2 > 0.99) in both mass-loss regions. For mass-loss regions: I (270–390 OC) and II (390–600 OC), the activation energy values were found to be 96–98 and 113–114 kJ/mol, respectively. Thermodynamic parameters (ΔH, ΔG, ΔS) were calculated using kinetic data. The findings reported herein are helpful in characterizing date palm fibers as a source of energy, designing reactors, producing chemicals, and understanding the properties of surface fibers for making composites.

Oxidation kinetics of graphite nanoparticles with copper oxide as oxygen carrier

The oxidation characteristics of graphite with copper oxide nanoparticles as oxidizer mixed in stoichiometric proportion were studied using a thermogravimetric analyzer. Progress of reactions was followed by measuring the mass loss, evolved gas analysis, and energy-dispersive X-ray spectroscopy. The samples were heated from room temperature conditions to 975 °C at four different heating rates of 5, 10, 15, and 20 °C min -1. The exhaust gas composition was quantified using a non-dispersive infrared analyzer. Experimental results indicate that the system requires a critical CO concentration buildup before the combustion process accelerates. The carbon dioxide production begins and peaks later than carbon monoxide. A total of three peaks occur in both carbon monoxide and carbon dioxide evolution. An Arrhenius dependence for the peak separation times with respect to the starting peak or trough temperature was observed. This work experimentally identifies the various regimes of oxidation chemistry for this fuel oxidizer combination over the entire combustion process via the trajectory of CO and CO2 evolution with temperature. The paths in this trajectory are then mapped onto the mass loss profiles. Modulated TGA experiments were also conducted to obtain the activation energy during the combustion process that shows overlapping mass loss regions. This activation energy is obtained over a wide range of temperatures using this model free-approach. The activation energies obtained using the modulated TGA experiments were also compared to those obtained using the Flynn–Wall–Ozawa method. This work provides new insights into the oxidation kinetics of graphitic carbon with solid copper oxide as an oxidizer.

Pyrolysis characteristics of cellulosic biomass in the presence of alkali and alkaline-earth-metal (AAEM) oxalates

The pyrolysis characteristics including reaction kinetics and products distribution of cellulose pyrolysis in the presence of AAEM oxalates were preliminarily studied by using the TG and PY-GC/MS analysis. In general, the main mass loss region took place at 300–400 °C and the maximum mass loss temperature was about 380 °C. The activation energy Ea of cellulose pyrolysis (159 kJ/mol) was decreased in the presence of AAEM oxalates (K2C2O4—123 kJ/mol, MgC2O4—151 kJ/mol and CaC2O4—138 kJ/mol). The major pyrolytic components were classified into furans, anhydrosugars, acids, esters, alcohols, aldehydes, pyrans, ketones, hydrocarbons and phenols, etc. The presence of AAEM oxalates promoted the generation of ketones. In particular, K2C2O4 and MgC2O4 showed a high selectivity (relative content: > 30%) on the production of ketones. As a good candidate of MgO, MgC2O4 or MgCO3 has a high potential for both gas upgrading and porous carbon production in biomass pyrolysis.

BAKIR ASETAT MONOHİDRATIN (Cu(CH3COO)2.H2O) TERMAL BOZUNMASINDAN BAKIR OKSİT (CuO) SENTEZİ

The synthesis of copper oxide (CuO) via the thermal decomposition of copper (II) acetate monohydrate (Cu(CH 3 COO) 2 .H 2 O) in air atmosphere was investigated at TG-DTG/DSC apparatus with the heating rate of 10°C min -1 under non-isothermal conditions from 25 to 900°C. It was seen from TG-DTG/DSC analyzes that the thermal decomposition process consists of three main steps (two mass-loss regions and a tiny mass-gain region). The obtained products at 200, 300, 400°C temperatures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy disperse spectroscopy (EDS) analysis. The XRD results show that the CuO nanoparticles having the monoclinic crystal structure. The SEM images showed that CuO nanoparticles were spherical in shape. The size of CuO nanoparticles decreased with an increase in annealing temperature.

Investigation of the oxidation behavior of a Turkey coal at low temperature by TGA, FTIR and BET analysis

ABSTRACT The mechanism and kinetics of the Tavşanlı (Turkey)-coal oxidation at low-temperature before ignition was investigated in this study. FTIR, BET analysis were used to determine the changes in the structure of coal at this temperature range. The gas products released during oxidation was monitored by TG-FTIR apparatus at a heating rate of 5°C min−1. The kinetics parameters of the oxidation process at the low-temperature were determined by thermal analysis apparatus. TG data taken in air atmosphere at heating rates of 1°C, 2.5°C, 5°C, and 10°C min−1 were plotted at non-isothermal heating program. For the kinetics analysis, the low-temperature oxidation region was divided into two regions, corresponding temperature ranges of which were 25–150°C and 150 ~ 250°C, respectively. It was seen that the mass-gain in coal between 150°C~250°C was due to the accumulation of -C = O functional groups in the coal structure. It was observed that the mass-loss region at 25–150°C is best described by F2: [(1-α)−1–1] model and the mass-gain region at 150 ~ 250°C is R3: [1-(1-α)1/3] model. The activation energies, pre-exponential factors of the regions were calculated by using Ortega method. It was found 49.9 and 74.5 kJmol−1, respectively.

Chemical characterization and antioxidant of polysaccharide extracted from Dioscorea bulbifera

The air yam (Dioscorea bulbifera) is an unconventional vegetable that produces a reserve stem, which has polysaccharides in its composition. These biopolymers, in turn, have aroused industrial interest due to many of their properties and applications in several areas, such as agro-food, chemical, pharmaceutical, textile, metallurgical, oil, among others. The objective of this work is to characterize the polysaccharide present in the raw and pre-purified air yams, as well as to verify its potential antioxidant capacity. The FTIR analysis showed in the two samples, a characteristic OH band at approximately 3250 cm−1, which is characteristic of polysaccharides. Through the SEM it was possible to analyze the morphology of the samples and verify that they are composed of films or “sheets” without measurable format. Furthermore, by XRD the samples were found to be an amorphous material, with peaks of crystallinity being observed at approximately 21.54° and 23.62° 2θ. Thermal analysis indicates that the NDP sample presents three regions of mass loss, the first one running up to 100 °C and may be associated with water loss; the second occurs from 150 °C, and occurs in several steps that can be visualized by DTG, and the third from 550 °C. The organic matter present in the sample was about 84%. The DP (Dialysed Polysaccharide) sample, in turn, also presented three regions of mass loss, the first one occurring up to 150 °C, the second from 175 °C and the third, from 425 °C. All these mass losses occur in only one stage. The organic matter present in the sample was approximately 80%. The samples presented potential antioxidant activity when analyzed by DPPH, ABTS, FRAP, OH radical removal, H2O2 removal and reducing power. The obtained results are very important, as they reveal information about the chemical characteristics and potential bioactivity of the dialysed and non-dialysed polysaccharide of D. bulbifera.

Evolution of oxygen functionalities in graphene oxide and its impact on structure and exfoliation: An oxidation time based study

Control over oxygen functionalities is important for the realization of Graphene Oxide (GO) based applications. Evolution of oxygen functionalities with time of oxidation and its impact on GO structure, exfoliation and reduction is investigated using XRD, FTIR, XPS, TGA and AFM. The results indicate no net increase in oxygen bound carbon atoms compared to graphitic carbon within the samples studied. However the percentage contributions from each type of oxygen functionalities tend to vary as the oxidation progress. Changes in the thermogravimetric response were observed with continued oxidation that showed a change from one mass loss region to two mass loss regions. The interaction kinetics of the protective group and the spatial distribution of oxygen functionalities during graphite oxidation give key insight to the above observed properties in GO. It is also shown that the observed changes in the structure have a direct impact on the ability to exfoliate GO to single layers as well as on the reduction process to produce reduced graphene oxide (rGO). These results are significant in the scalable production of GO with controlled and consistent quality for applications in the areas such as chemical and biological sensing, water purification and development of nanocomposites.

Catchment-scale weathering fluxes in the Southern Alps, New Zealand

The dissolved and suspended sediment flux in a small headwater in the Southern Alps, New Zealand over a 16-month period showed that mass transferred as dissolved load (91 t km−2 a−1) is a significant flux relative to the suspended sediment flux (210 t km−2 a−1). Export of dissolved load occurs mostly under baseflow, with 268 t being transported over 10 discrete events, relative to a total load of 1171 t over the experimental observation period; which is equivalent to 23% of the ionic flux occurring during event flow. Storm events contribute 2420 t of suspended sediment, accounting for 90% of the total suspended sediment flux. The chemical weathering flux was 43% of the physical weathering flux, and much higher than previous estimates of 1–9% for the Southern Alps. Such a high relative rate of chemical weathering is unlikely to be indicative of the full Southern Alps extent, but suggests that in some regions of the eastern Southern Alps mass loss via chemical weathering may be a significant portion of overall flux. During storm events, temporal exhaustion of sediment occurred and inferred limited sediment source production, rather than limited connectivity with the hillslope environment. Similar supply-limitation is expressed in the ionic flux, where rainfall events do not usually express hysteretic behaviour, and event flow is dominated by a simple dilution recession.

Sensing underground coal gasification by ground penetrating radar

The paper describes the results of research on the applicability of the ground penetrating radar (GPR) method for remote sensing and monitoring of the underground coal gasification (UCG) processes. The gasification of coal in a bed entails various technological problems and poses risks to the environment. Therefore, in parallel with research on coal gasification technologies, it is necessary to develop techniques for remote sensing of the process environment. One such technique may be the radar method, which allows imaging of regions of mass loss (voids, fissures) in coal during and after carrying out a gasification process in the bed. The paper describes two research experiments. The first one was carried out on a large-scale model constructed on the surface. It simulated a coal seam in natural geological conditions. A second experiment was performed in a shallow coal deposit maintained in a disused mine and kept accessible for research purposes. Tests performed in the laboratory and in situ conditions showed that the method provides valuable data for assessing and monitoring gasification surfaces in the UCG processes. The advantage of the GPR method is its high resolution and the possibility of determining the spatial shape of various zones and forms created in the coal by the gasification process.

Crystal structure, Hirshfeld surface analysis, vibrational, thermal behavior and UV spectroscopy of (2,6-diaminopyridinium) dihydrogen arsenate

A new organic dihydrogenomonoarsenate (C5H8N3)H2AsO4 was synthesized by slow evaporation method at room temperature and characterized by X-ray single crystal diffraction. This compound crystallizes in the monoclinic system with the centro-symmetric space group P21/n. Unit cell parameters are a = 10.124 (5)Ǻ, b = 6.648 (5)Ǻ, c = 13.900 (5)Ǻ, β = 105.532° with Z = 4. The crystal structure was solved and refined to R = 0.038 with 2001 independent reflections. Hirshfeld surfaces analysis were used to visualize the fidelity of the crystal structure which has been determined by X-ray data collection on single crystals (C5H8N3)H2AsO4. Due the strong hydrogen OH⋯O bond network connecting the H2AsO4 groups, the anionic arrangement must be described as infinite (H2AsO4)nn-of dimers chains spreading, in a zig zag fashion, parallel to the b direction. The organic groups (C5H8N3)+ are anchored between adjacent polyanions through multiple hydrogen bonds NH⋯O. The thermal decomposition of precursors studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicate the existence of two mass loss regions correspond to degradation of the title compound. The existence of vibrational modes correspond to the organic and inorganic groups are identified by the infrared and Raman spectroscopy in the frequency ranges 500–4000 and 25-4000 cm−1, respectively.

The influence of unintended field retting on the physicochemical and mechanical properties of industrial hemp bast fibres

Developing hemp fibre composites for structural applications requires both reconsideration and optimisation of the transformation processes to obtain stable, high-quality fibre reinforcements. In this context, field retting remains an important issue because it is weather dependent and has not been completely mastered by the hemp industries. Retting can be achieved voluntarily to facilitate fibre separation and extraction from the stalks prior to mechanical decortication. However, retting can also be involuntary and result from climatic misfortune and unforeseeable events at the time of harvest. Therefore, this study aimed to quantify the influence of involuntary and non-controlled field retting on the physicochemical and mechanical properties of industrial hemp bast fibres. A wide spectrum of analytical techniques was applied, including colour spectrophotometry; morphological, microscopic (SEM), surface (EDX, roughness), biochemical (HPLC and pXRD) and thermogravimetric (TGA) analyses; dynamic vapour sorption; and tensile characterisation. The results indicate that retting induced a decrease in the average width of fibre elements after mechanical processing and a loss of pectic substances. We also observed a change in colour from yellow to dark grey, an increase in surface roughness and an increase in the decomposition temperature for the third mass loss region. A decrease in tensile properties at the scales of both single and technical fibres was also observed. Since no significant decrease in cellulose content was measured, this decay in mechanical performance was connected with both the significant degradation of hemicelluloses and a decrease in the fraction of crystalline cellulose that was quantified in this work.

Hybrid glacier Inventory, Gravimetry and Altimetry (HIGA) mass balance product for Greenland and the Canadian Arctic

We present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery, cryosphere-attributed mass trends derived from satellite gravimetry, and ice surface elevation trends derived from airborne and satellite altimetry. We use this algorithm to assess mass balance across Greenland and the Canadian Arctic over the Sep-2003 to Oct-2009 period at 26km resolution. We evaluate local algorithm-inferred mass balance against forty in situ point observations. This evaluation yields an RMSE of 0.15mWE/a, and highlights a paucity of in situ observations from regions of high dynamic mass loss and peripheral glaciers. We assess mass losses of 212±67Gt/a to the Greenland ice sheet proper, 38±11Gt/a to peripheral glaciers in Greenland, and 42±11Gt/a to glaciers in the Canadian Arctic. These magnitudes of mass loss are dependent on the gravimetry-derived spherical harmonic mass trend we invert. We spatially partition the transient glacier continuity equation by differencing algorithm-inferred mass balance from modeled surface mass balance, in order to solve the horizontal divergence of ice flux as a residual. This residual ice dynamic field infers flux divergence (or submergent flow) in the ice sheet accumulation area and at tidewater margins, and flux convergence (or emergent flow) in land-terminating ablation areas, which is consistent with continuum mechanics theory.

Stability and Decomposition of Ca‐Substituted Lanthanum Ferrite in Reducing Atmospheres

Calcium‐substituted lanthanum ferrites (La1−xCaxFeO3−δ x = 0, 0.1, 0.2, 0.3, 0.4) were synthesized in air and subsequently decomposed in reducing atmospheres. The partial pressure of oxygen () was controlled by varying the H2/H2O ratio by bubbling hydrogen/argon mixtures through water baths at controlled temperatures. Three regions of mass loss were identified as the was reduced, two of which were determined to be associated with decomposition reactions. Calcium was shown to decrease the thermal stability of the perovskite compound, but rather than incrementally increasing the required for decomposition proportional to calcium concentration, all samples partially decomposed at a single . The extent of the partial decomposition was dependent on the amount of calcium substitution and temperature. The perovskite phase remaining after the partial decomposition was found to fully decompose at the same oxygen partial pressure as pure lanthanum ferrite.

Thermal Characterization and Model Free Kinetic Application on a Tar Sand Sample

In the first part of this research, kinetic software was developed for the evaluation of kinetic parameters using nonisothermal thermogravimetry data. Different computational methods were used and applied to a set of experimental and simulated data distributed in the ICTAC (International Confederation for Thermal Analysis and Calorimetry) kinetics project. The reliability of the software was verified by comparing the kinetic results and it was observed that the results were in good agreement. In the second part, developed software was applied to determine the kinetics of a tar sand sample. Therefore, experiments were performed at three different heating rates, in the temperature range of 20–900°C. Different stages of mass loss regions were observed in TG-DTG curves. Ozawa-Flynn-Wall (OFW), Kissinger, and Augis-Bennett kinetic models were used to determine the activation energy of tar sand sample and the results are discussed.

Structural determination; vibration study and thermal decomposition of [C5H6N5]2SeO4⋅2H2O

The present paper reports the chemical synthesis, structure study, thermal analysis, and vibrational properties of new hybrid compound called: bis (adeninium) selenate bihydrates. It is crystallized in the triclinic system with P-1 space group and the following parameters a=7.804(5)Å; b=9.686 (5)Å; c=11.771 (5)Å; α=84.421(5)°; ß=77.556(5)°; γ=81.186 (5)°; Z=2 and V=856.7(8)Å3.The structure is built up from tunnels containing all the components of the structure and following to the c axis, linked via three types of hydrogen bonds (NH…O, NH…N and OH…O). The thermal decomposition of precursors studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicate the existence of two mass loss region correspond to dehydration and degradation of the title compound, respectively. The existence of vibrational modes correspond to the organic and inorganic groups and water molecular are identified by the IR and Raman spectroscopy in the frequency ranges 400–4000 and 300–1600cm−1, respectively.

Mn-based borohydride synthesized by ball-milling KBH4 and MnCl2 for hydrogen storage

In this work, a mixed-cation borohydride (K2Mn(BH4)4) with P21/n structure was successfully synthesized by mechanochemical milling of the 2KBH4–MnCl2 sample under argon. The structural and thermal decomposition properties of the borohydride compounds were investigated using XRD, Raman spectroscopy, FTIR, TGA-MS and DSC. Apart from K2Mn(BH4)4, the KMnCl3 and unreacted KBH4 compounds were present in the milled 2KBH4–MnCl2. The two mass loss regions were observed for the milled sample: one was from 100 to 160 °C with a 1.6 ± 0.1 wt% loss (a release of majority hydrogen and trace diborane), which was associated with the decomposition of K2Mn(BH4)4 to form KBH4, boron, and finely dispersed manganese; the other was from 165 to 260 °C with a 1.9 ± 0.1 wt% loss (only hydrogen release), which was due to the reaction of KBH4 with KMnCl3 to give KCl, boron, finely dispersed manganese. Simultaneously, the formed KCl could dissolve in KBH4 to yield a K(BH4)xCl1−x solid solution, and also react with KMnCl3 to form a new compound K4MnCl6.

Supernova interaction with dense mass loss

AbstractSupernovae of Type IIn (narrow line) appear to be explosions that had strong mass loss before the event, so that the optical luminosity is powered by the circumstellar interaction. If the mass loss region has an optical depth >c/vs, where vs is the shock velocity, the shock breakout occurs in the mass loss region and a significant fraction of the explosion energy can be radiated. The emission from the superluminous SN 2006gy and the normal luminosity SN 2011ht can plausibly be attributed to shock breakout in a wind, with SN 2011ht being a low energy event. Superluminous supernovae of Type I may derive their luminosity from interaction with a mass loss region of limited extent. However, the distinctive temperature increase to maximum luminosity has not been clearly observed in Type I events. Suggested mechanisms for the strong mass loss include pulsational pair instability, gravity-waves generated by instabilities in late burning phases, and binary effects.