Lower Residual Mass Research Articles

Retention force, translucency, and microstructural properties of translucent temporary luting cements: An in vitro study

The aim of the study was to investigate the retention behaviour (pull-off force include adhesive remnant index = ARI) as well as translucency of various temporary luting cements and use microstructure elucidation methods to formulate explanatory approaches to their mode of action.The retention force of the temporary luting cements Provicol QM Plus (P+), Provicol QM Aesthetic (Pae), Bifix Temp (BiT), and as a reference a glass ionomer cement Meron (M) with a direct (Structur 3/S3) or an indirect (Structure CAD/SCAD) resin-based composite restauration was investigated after accelerated aging (thermocycling). Additional investigation of the physical properties was performed regarding to translucency and surface free energy. The microstructure was evaluated by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and micro X-ray computed tomography.All tested temporary luting cements showed different pull-off forces in the range between 3.0 and 16.8 N in combination with S3 or SCAD after thermocycling. Only BiT with S3 showed pull-off forces of 129.2 N and complete retention on the restoration (ARI = 0), which was significant (p < .001) to all other samples. High translucency (BiT > Pae > M > P+) was observed for materials with lower crystalline content and low residual mass (usally resulting from higher organic content). M showed the highest surface free energy with a predominantly polar fraction, while BiT had a predominantly dispersive fraction. The highest porosity was observed in the coronal region of the restoration.The results suggest that translucency of temporary luting cements can be increased with higher organic and lower cryristall content. All combinations of cements and temporary restorations (direct/indirect; with the exception of BiT/S3) showed pull-off forces below 17 N (equivalent to a weight force of ∼1.7 kg), which allows manual detachment of the restoration by the dentist.

Comprehensive Evaluation of the Combustion Kinetic Characteristics of Owukpa Coal

Coal is a cheap and widely abundant fossil fuel that currently accounts for a significant share (35–40%) of the global energy mix. As a result, coal-fired electricity has catalyzed rapid socioeconomic growth and sustainable development worldwide. With the rapidly growing global energy demands, emerging economies like Nigeria need to address their widespread energy crises. Coal utilization for power generation is proposed as a panacea for the persistent power shortages, blackouts, and load shedding typically experienced in Nigeria. However, coal-fired power generation in Nigeria requires a comprehensive examination of the fuel properties, energy recovery potential, and emissions profiles of coal feedstocks, which is currently lacking in the literature. Therefore, this paper presents the comprehensive physicochemical, microstructure, mineralogical and thermal fuel properties of Owukpa (WKP) coal to evaluate its potential for future energy recovery and industrial applications. The results demonstrated that it contains high combustible elements, heating value (26.7 MJ/kg), and low potential for NOx and SOx emissions. Microstructural and mineralogical analyses revealed a mix of coarse-grained particles indicating the occurrence of carbonaceous and aluminosilicate minerals such as quartz, and kaolinite. Thermal properties of WKP revealed its low-rank coal (LRC) properties such as high thermal reactivity, which resulted from high mass loss (93.69 to 95.87%) and low residual mass (6.31 to 4.13%) during multiple heating rate TGA combustion. Kinetic analysis revealed that WKP is considerably reactive due to its low activation energy (Ea) and frequency factor (A), which ranged from Ea = 28.86 to 57.29 kJ/mol, whereas the A = 5.97 to 9.86 min–1 computed at high correlation R2 values of 0.97 to 1.0. The results showed that Owukpa (WKP) is a low-rank coal (LRC) with potential for electricity generation and other industrial applications.

N‐Alkoxy Carboxamide Stabilized Tin(II) and Germanium(II) Complexes for Thin‐Film Applications

A new series of germanium (1–5) and tin (6–10) complexes were successfully synthesized by employing N‐alkoxy‐functionalized carboxamides as stabilizing ligands, and these complexes could potentially serve as precursors for thin‐film applications. All of the complexes were characterized by FTIR and NMR spectroscopy as well as elemental and thermogravimetric (TG) analyses. The single‐crystal X‐ray diffraction studies of 5 and 10 revealed that they crystalize in the monoclinic space group P2(1)/c as monomers. The metal centers in these complexes are coordinated to four oxygen atoms and display distorted trigonal‐bipyramidal geometries. The thermogravimetric analysis and volatility studies of the complexes demonstrated the good volatilities and stabilities of 2–4 and 6–9. Among these complexes, Ge(mdpa)2 (3, mdpaH = N‐methoxy‐2,2‐dimethylpropanamide) and Sn(edpa)2 (9, edpaH = N‐ethoxy‐2,2‐dimethylpropanamide) exhibited excellent physicochemical properties with clean single‐step curves and low residual masses in their TG analyses.

Analysis of Energy Characteristics of Rice and Coffee Husks Blends

Production of first generation biofuels using food crops is under criticism over sustainability issues on food security. Tanzania is showing active interest in developing second generation biofuels to deal with some of such issues, especially from the feedstock point of view. This paper reports work done to determine energy characteristics of rice and coffee husks. The results show that coffee husks have better energy quality than rice husks, while heating values of coffee are 18.34 MJ/kg and 13.24 MJ/kg for rice husk. Thermogravimetric analysis made for coffee husks blended rice husks at a ratio of 75 : 25% vol. show better material degradation characteristics yielding low residual mass of 23.65%, compared to 26.50% of char and ash remaining in pure rice husks. Derivative thermogravimetric analysis shows comparable hemicellulose degradation peak values of −11.5 and −11.2 and cellulose −3.20 and −2.90 in pure coffee and rice husks, respectively. In coffee and rice husks blends, substantial reductions of hemicellulose and cellulose peaks were observed. Use of coffee and rice husks blends applying high temperature gasification would reduce the latter’s flammability, while increasing its flame retention characteristics, hence offering opportunities for production of clean syngas in a sustainable manner.

Calling, Courtship, and Condition in the Fall Field Cricket, Gryllus pennsylvanicus

Theoretically, sexual signals should provide honest information about mating benefits and many sexually reproducing species use honest signals when signalling to potential mates. Male crickets produce two types of acoustic mating signals: a long-distance mate attraction call and a short-range courtship call. We tested whether wild-caught fall field cricket (Gryllus pennsylvanicus) males in high condition (high residual mass or large body size) produce higher effort calls (in support of the honest signalling hypothesis). We also tested an alternative hypothesis, whether low condition males produce higher effort calls (in support of the terminal investment hypothesis). Several components of long-distance mate attraction calls honestly reflected male body size, with larger males producing louder mate attraction calls at lower carrier frequencies. Long-distance mate attraction chirp rate dishonestly signalled body size, with small males producing faster chirp rates. Short-range courtship calls dishonestly reflected male residual mass, as chirp rate and pulse rate were best explained by a curvilinear function of residual mass. By producing long-distance mate attraction calls and courtship calls with similar or higher effort compared to high condition males, low condition males (low residual mass or small body size) may increase their effort in current reproductive success at the expense of their future reproductive success, suggesting that not all sexual signals are honest.

Tactical versus continuous stocking in perennial ryegrass-subterranean clover pastures grazed by sheep in south-western Victoria. 1. Stocking rates and herbage production

A 4-year field experiment was carried out in south-western Victoria to determine whether tactical stocking might improve perennial ryegrass (Lolium perenne L.) persistence and prime lamb production, compared with the more common practice of year-around continuous stocking. Tactical stocking consisted of variable length summer, autumn and winter rotations and continuous stocking in spring. The 2 grazing strategies were compared on 2 contrasting pastures: an upgraded pasture, sown with newer cultivars of perennial ryegrass and subterranean clover (Trifolium subterraneum L.) with 26 kg phosphorus/ha.year, and a more typical naturalised perennial ryegrass pasture receiving 6 kg phosphorus/ha.year. Paddocks were grazed by Border Leicester x Merino ewes, which were mated to a terminal sire to lamb in September. The effects of the grazing systems and pasture treatments on herbage production and stocking rate are presented in this paper. Herbage production was similar between the treatments, but tactical stocking significantly increased herbage mass during the growing season (P&lt;0.05) compared with continuous stocking. In spring each year, the herbage mass generally exceeded 3000 kg dry matter/ha in tactically stocked paddocks and averaged 500–900 kg dry matter/ha higher than the mass on continuously stocked paddocks. This enabled the year-round stocking rate to be increased by an average of 9% over the 4 years of the experiment. We considered that the stocking rates could not be further increased, despite the higher herbage mass in spring, as stock reduced the dry herbage to a low residual mass by the opening rains in autumn. In contrast, stocking rates averaged 51% higher on the upgraded pasture compared with the typical pasture over the 4 years of the experiment. This indicates that pasture improvement and soil fertility status have a much greater impact on productivity than changes to grazing method. However, tactical stocking was able to increase the sustainability of prime lamb production on upgraded pastures in a dry summer climate, by maintaining herbage cover on the paddocks over the summer–autumn period.