Temperature Td Research Articles

Polymer Biodegradation in Aquatic Environments: A Machine Learning Model Informed by Meta-Analysis of Structure-Biodegradation Relationships.

Polymers are widely produced and contribute significantly to environmental pollution due to their low recycling rates and persistence in natural environments. Biodegradable polymers, while promising for reducing environmental impact, account for less than 2% of total polymer production. To expand the availability of biodegradable polymers, research has explored structure-biodegradability relationships, yet most studies focus on specific polymers, necessitating further exploration across diverse polymers. This study addresses this gap by curating an extensive aerobic biodegradation data set of 74 polymers and 1779 data points drawn from both published literature and 28 sets of original experiments. We then conducted a meta-analysis to evaluate the effects of experimental conditions, polymer structure, and the combined impact of polymer structure and properties on biodegradation. Next, we developed a machine learning model to predict polymer biodegradation in aquatic environments. The model achieved an Rtest2 score of 0.66 using Morgan fingerprints, detailed experimental conditions, and thermal decomposition temperature (Td) as the input descriptors. The model's robustness was supported by a feature importance analysis, revealing that substructure R-O-R in polyethers and polysaccharides positively influenced biodegradation, while molecular weight, Td, substructure -OC(═O)- in polyesters and polyalkylene carbonates, side chains, and aromatic rings negatively impacted it. Additionally, validation against the meta-analysis findings confirmed that predictions for unseen test sets aligned with established empirical biodegradation knowledge. This study not only expands our understanding across diverse polymers but also offers a valuable tool for designing environmentally friendly polymers.

Ultrasonication modifies the structural, thermal and functional properties of pumpkin seed protein isolate (PSPI).

Protein isolates from pumpkin seeds were prepared and then treated with high-intensity ultrasound (HIUS) using a probe-based method. The impact of ultrasonication on the physicochemical, molecular, and thermal properties of these isolates were analyzed and compared to untreated controls. Results showed significant improvements (p≤0.05) in color (L*, a*, b* values), solubility, emulsification capacity, and stability, as well as a reduction in molecular weight, indicating enhanced functionality of the pumpkin seed protein isolates (PSPIs) after HIUS treatment. However, HIUS treatment decreased the denaturation temperature (Td), denaturation enthalpy (ΔH), thermal stability, and particle size of the isolates. With treatment durations ranging from 5 to 20min, Td dropped from 67.31°C to 56.38°C, and ΔH declined from 45.78 to 35.43J/g, likely due to structural and conformational modifications from ultrasonic-induced molecular bond disruptions. The greatest reduction in particle size, from 117.46μm to 85.26μm, was observed after 20min of ultrasonication. X-ray diffraction (XRD) analysis showed two distinct diffraction peaks at 2θ=10° and 2θ=20°, indicating altered crystallite sizes post-ultrasound treatment. Ultrasonication induced structural and conformational changes in the pumpkin seed protein isolates, as confirmed by SDS-PAGE and weight loss analyses. Alterations in the SDS-PAGE profile and reduced weight loss were associated with improved solubility and enhanced thermal and functional properties in the treated pumpkin seed protein isolates. This emphasizes the potential of PSPI to increase their value-added potential through ultrasonication.

Large switchable polarization and piezoelectricity in multiferroic BiFeO3-Bi0.5K0.5TiO3-based single crystals

We report the structural, ferroelectric (FE), piezoelectric, and converse magnetoelectric (ME) effects in a series of Cr/Mn doped BiFeO3-Bi0.5K0.5TiO3-based (BF-BKT) single crystals. The Cr and Mn co-doped BF-BKT crystal (i.e., CrMn04) shows a large switchable polarization of 12ΔP ∼ 59.4 μC/cm2 and large-signal piezoelectric coefficient d33* at room temperature, and nearly thermally stable piezoelectric coefficient of d33 ∼ 212 pC/N below depolarization temperature Td ∼ 358.7 °C. A high DC resistivity of ρ > ∼1.0 × 105 Ω cm for T < ∼346.5 °C was also observed in CrMn04 crystal. All samples exhibit coexistent antiferromagnetic and FE orders and evident electric control of magnetism. The simultaneous existence of good performance of ferroelectricity, piezoelectricity, and converse ME effects in especially the CrMn04 crystal suggests its potential application in multi-functional devices.

Synthesis and Properties of Thermostable Energetic Benzotriazines.

In an effort to balance energy and molecular stability effectively, several energetic compounds (3-6) based on benzotriazine were designed and synthesized. These structures were comprehensively characterized using NMR, IR, and elemental analysis, with compounds 3, 5, and 6 further confirmed by single-crystal X-ray diffraction. Notably, 3-amino-5,7-dinitrobenzo[e][1,2,4]triazine 1-oxide (5), which features a face-to-face crystal stacking arrangement, exhibits good detonation velocity (Dv = 8050 m/s), a high thermal decomposition temperature (Td = 290 °C), and low sensitivities (impact sensitivity >40 J, friction sensitivity >360 N). The preparation of compound 5 was further optimized by using a commercially available flow microreactor system, achieving an improved yield of 62%. Overall, the comprehensive properties of compound 5 make it a promising candidate for heat-resistant explosive applications.

Analysis of pyroelectric properties in quenched NBT-BT composition

Quenching has recently demonstrated its efficacy in elevating the ferroelectric to relaxor phase transition temperature (TFR) in 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-6BT). Consequently, the current investigation comprehensively examines the pyroelectric properties of quenched NBT-6BT. The pyroelectric coefficient is measured using the Byer-Roundy method, incorporating a strategic approach to mitigate the risk of overestimation by implementing cyclic heating and cooling. Quenching enhances the depolarization temperature (Td) by approximately 40 °C, quantified through the temperature-dependent pyroelectric current density (Ip). The maximum pyroelectric current (52nA) and voltage (200V) responses to thermal cycling (15s heating/cooling) were observed in quenched NBT-6BT. The voltage sensitivity figures of merit were equivalent for both furnace-cooled and quenched NBT-6BT. The assessment of pyroelectric energy storage involved charging a 48 nF capacitor in 180s, resulting in a maximum voltage of 38V. The outcomes strongly endorse the quenched NBT-6BT as an efficient pyroelectric material, showcasing promising attributes for applications in sensing and energy harvesting across a broad temperature range.

The role of extraction method to collagen substrates in enzymolysis of type I collagenase

Collagens are ubiquitous biomaterials in animal tissues whose characteristic triple-helical structure can only be hydrolyzed under physiological conditions by a few specific proteases. At present, information on the differences of collagenase hydrolysis behavior to collagen substrate caused by extraction methods is still lacking. Acid-relaxed extracted collagen (ARC) and acetic acid-pepsin extracted collagen (APC) were obtained from bovine hide by acetic acid and acetic acid-pepsin extraction method, respectively. The enzymolysis behavior of type I collagenase on ARC and APC were investigated by means of fluorescence spectra, UV spectra, and determination the release of hydrolysates into the supernatant. The results revealed that APC showed a lower molecular weight, a higher pI (5.59) and denaturation temperature (Td = 66.9 °C) than that of ARC (pI = 4.67, Td = 57.8 °C). Moreover, APC demonstrated greater resistance to type I collagenase than ARC. The cleavage on the non-helical terminal domains by pepsin might play the role in the better thermal stability, the higher pI, and the more collagenase resistance of APC than ARC. The findings of this work should provide new insights into collagenase hydrolysis behavior and facilitate targeted utilization of collagen extracted by various method.

Trends in extreme rainfall over the past 55 years suggest springtime subhourly rainfall extremes have intensified in Mahantango Creek, Pennsylvania

Extreme short-duration rainfall is intensifying with climate warming, and growing evidence suggests that subhourly rainfall extremes are increasing faster than more widely studied durations at hourly and daily timescales. In this case study, we used 55 years (1968–2022) of 5-min precipitation data from Mahantango Creek, a long-term experimental agricultural watershed in east-central Pennsylvania, United States, to examine annual and seasonal changes in subhourly (15-min), hourly, and daily rainfall extremes. Specifically, we evaluated temporal trends in the magnitude and frequency of subhourly, hourly, and daily rainfall extremes. We then estimated apparent scaling rates between rainfall extremes and dew point temperature (Td) and compared these rates to the Clausius-Clapeyron (CC) rate (∼ 7% per °C). We also determined the coincidence of extreme rainfall trends with indicators of atmospheric instability and convective-type precipitation. Overall, we found the most significant changes in rainfall extremes at 15-min durations during the spring, with magnitudes of these subhourly extremes increasing by 0.6 to 0.9% per year, and frequencies rising by 3.4% per year. Apparent scaling rates in the spring showed that 15-min rainfall extremes transitioned from sub-CC scaling to greater than 2CC scaling when Td reached 11° C, implying a possible shift from stratiform rains to more intense convective rains above this Td threshold. Notably, trends in maximum hourly convective available potential energy (CAPE) increased during spring, as did the ratio of 15-min rainfall extremes to their corresponding daily rainfall totals. Findings indicate that convective-type precipitation may be playing an increasing role in the intensification of springtime 15-min rainfall extremes in Mahantango Creek.

Preparation of mayonnaise with excellent thermal and storage stability from egg yolk-amino acid complex: Rheology, interfacial property, microstructure and lutein delivery

In this paper, egg yolk-amino acid (betaine or proline) complex was prepared at different pasteurization temperatures (68, 72 and 76 °C). Then complexes were applied to stabilized mayonnaise emulsion system. The results demonstrated that liquid egg yolk (LEY) protein structure gradually aggregated, molecular flexibility increased by 5 %, interfacial tension and intermolecular force enhanced remarkably with growth of pasteurization temperature. Compared with LEY, egg yolk-amino acid complex exhibited a more flexible structure with lower interfacial tension and superior molecular wettability. Complexes stabilized mayonnaise emulsion displayed excellent rheological property, homogeneous droplet distribution, smaller average particle size and higher (about 10 °C) thermal denaturation temperature (Td). In terms of thermal stability, oil binding capacity (OBC) of heated betaine mayonnaise (HBM) and heated proline mayonnaise (HPM) was approximately 20 % higher than that of heated control mayonnaise (HCM). Notably, the group of HBM thermal stability was generally excellent. During storage, mayonnaise might be an intermediate unstable state before emulsion breakage. In vitro digestion results illustrated that bioaccessibility of lutein delivered by BM-72 and PM-72 was 48.9 % and 37.0 % higher than CM-72, respectively. The results will provide reference for preparation of mayonnaise by egg yolk-amino acid complex as a carrier to deliver fat-soluble substances to improve bioaccessibility.

Thermoanalytical study of protein state during rehydration and rehydration kinetics in osmotically dehydrated pork meat (Longissimus dorsi): Insights from Peleg and Weibull models

Osmotically dehydrated pork meat (Longissimus dorsi), in the molasses, was used in the aim to study the protein state during rehydration. Protein state and rehydration kinetics are crucial for obtaining the desired meat product quality. The thermoanalytical techniques were employed to follow protein state and kinetics of rehydration. Obtained kinetic parameters were Peleg's rate constant (k1), 34.43, 6.23, and 10.15 (min (kg d.m.)(kg water)−1) and Peleg's capacity constant (k2), 0.726, 1.243, and 0.860 at 20, 30, and 40 °C, respectively. Parameters of Weibull's model, α, β (min), at 20 °C were 34.4; 0.86, at 30 °C were 6.24; 1.24, at 40 °C were 10.15; 0.86. From obtained enthalpies (ΔHd) and temperatures (Td) of meat proteins denaturation, it was found that proteins were partly denatured and gradually lost their structure and thermal stability during rehydration. Rehydration kinetic parameters indicated that most efficient rehydration was found to be at the 40 °C.

Charting the main sequence of star-forming galaxies out to redshifts z ≲ 5.7

We present a new determination of the star-forming main sequence (MS), obtained through stacking 100k K-band-selected galaxies in the far-infrared (FIR) Herschel and James Clerk Maxwell Telescope (JCMT) imaging. By fitting the dust emission curve to the stacked FIR photometry, we derive the IR luminosities (LIR), and hence the star formation rates (SFRs) out to z ≲ 5.7. The functional form of the MS is found, with the linear SFR-M* relation that flattens at high stellar masses and the normalization that increases exponentially with redshift. We derive the corresponding redshift evolution of the specific star formation rate (sSFR) and compare our findings with the recent literature. We find our MS to be exhibiting slightly lower normalization at z ≲ 2 and to flatten at somewhat larger stellar masses at high redshifts. By deriving the relationship between the peak dust temperature (Td) and redshift, where Td increases linearly from ∼20 K at z = 0.5 to ∼50 K at z = 5, we conclude that the apparent inconsistencies in the shapes of the MS are most likely caused by the different dust temperatures assumed when deriving SFRs in the absence of FIR data. Finally, we investigate the derived shape of the star-forming MS by simulating the time evolution of the observed galaxy stellar mass function (GSMF). While the simulated GSMF is in good agreement with the observed one, some inconsistencies persist. In particular, we find the simulated GSMF to be slightly overpredicting the number density of low-mass galaxies at z ≳ 2.

Sustainable recovery of monomers from PET and PC waste via Thermocatalytic depolymerization for synthesis of polycarbonates and co-polycarbonates

The increasing global demand for sustainable plastics recycling methods has propelled the research and development of innovative depolymerization processes. The Thermocatalytic depolymerization (TCDP) of polyethylene terephthalate (PET) and polycarbonate (PC) has been performed at 200 ℃. Ethylene glycol (EG) is used as a reactant and as well a polymer bond-cleaving agent and Yttrium Oxide (Y2O3) is used as an effective catalyst. Y2O3 acted as a dual role during depolymerization reaction, which converts EG into cyclic ethylene oxide (CEO) and as well as to break the ester and carbonate bonds in the polymer structure of PET and PC respectively. The TCDP reaction conditions were optimized and the maximum quantity of Bis(2-hydroxyethyl) terephthalate (BHET) (80%) and (Bisphenol A (BPA)) (83%) has been recovered by TCDP reaction of PET and PC respectively. The polycarbonate and co-polycarbonate (Co-PC) were synthesized using recovered BPA and BHET with triphosgene via polycondensation reaction. The structure of monomers and polymers was confirmed by existing analytical (FTIR, NMR, XRD and GPC) techniques. The thermal properties of PC and Co-PC were performed by TG analysis. The TGA results reveal that the degradation temperature (Td) of PC and Co-PC are observed at 420.5 and 442.8 °C respectively, which shows that the Td of Co-PC has been increased by 22 ℃ than PC. The TCDP process is an effective method to recover specific value-added products from waste plastics, which could be made into a new versatile material for different applications. This research finding will provide a new direction to convert plastic waste into useful chemicals, which could reduce waste plastic and their carbon footprint and contribute to a more sustainable future by reusing plastic materials and achieving a circular economy.

Colossal Dielectric Constant of Nanocrystalline/Amorphous Homo-Composite BaTiO3 Films Deposited via Pulsed Laser Deposition Technique.

We report the pulsed laser deposition (PLD) of nanocrystalline/amorphous homo-composite BaTiO3 (BTO) films exhibiting an unprecedented combination of a colossal dielectric constant (εr) and extremely low dielectric loss (tan δ). By varying the substrate deposition temperature (Td) over a wide range (300-800 °C), we identified Td = 550 °C as the optimal temperature for growing BTO films with an εr as high as ~3060 and a tan δ as low as 0.04 (at 20 kHz). High-resolution transmission electron microscopy revealed that the PLD-BTO films consist of BTO nanocrystals (~20-30 nm size) embedded within an otherwise amorphous BTO matrix. The impressive dielectric behavior is attributed to the combination of highly crystallized small BTO nanograins, which amplify interfacial polarization, and the surrounding amorphous matrix, which effectively isolates the nanograins from charge carrier transport. Our findings could facilitate the development of next-generation integrated dielectric devices.

A Study of the Influence of Ion-Ozonized Water on the Properties of Pasta Dough Made from Wheat Flour and Pumpkin Powder.

Water treated with ion ozone improves the technological qualities of food products. Therefore, ion-ozonated water was used in the work, and whole-grain flour from soft wheat of the Almaly variety and pumpkin powder were used as raw materials to improve the quality and nutritional value of the pasta. This study investigated the effects of ion-ozone concentration in ion-ozonated water Cio, water temperature tw, pumpkin powder content Cpp and drying temperature td on various characteristics affecting the quality of pasta, including its organoleptic physical, chemical, and rheological properties. These characteristics were assessed by conducting multiple experiments, a total of 25 indicators were determined, such as humidity, acidity, cooking properties, deformation, and other basic quality indicators. To reduce the number of experiments and obtain a reliable assessment of the influence of individual factors on the quality indicators of pasta, methods involving the multifactorial design of experiments were applied. Data processing and all necessary calculations were carried out using the PLAN sequential regression analysis program. Consequently, our findings indicate that minimizing dry water (DM) loss in cooking water requires a dual approach: increasing ion-ozone concentration and optimizing pasta composition and drying conditions, specifically by reducing pumpkin powder content and drying temperature. As a result, it was established that to obtain high-quality pasta from whole-grain flour with high quality and rheological properties, it is necessary to use the following optimal production modes: ion-ozone concentration in ion-ozonated water Cio = 2.5 × 10-6 mg/cm3, water temperature tw = 50 °C, pumpkin powder content Cpp = 3.0%, and pasta drying temperature td = 50 °C. The resulting pasta is an environmentally friendly product with a high content of biologically active substances.

Dual Cross-Linked Networks Reinforced Polyimide Foams with Outstanding Piezoelectric Properties and Heat Resistance Performance.

The application of traditional isocyanate-based polyimide (PI) foams is highly hindered due to limited flame retardancy, poor mechanical properties, and relatively single functionality. Herein, we propose an effective method to fabricate dual cross-linked polyimide/bismaleimide (PI-BMI) foams with outstanding heat resistance and enhanced mechanical properties by incorporating bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (ME-BMI) as the interpenetrating network. The results show that the prepared PI-BMI composite foams exhibit enhanced mechanical properties with lightweight characteristics (23-80 kg·m-3). When the ME-BMI loading reached 120 wt %, the tensile and compressive strength of PI-BMI composite foam can reach 1.9 and 7.8 MPa, which are 9.6 and 63.3 times higher than that of pure PI foam, respectively. In comparison with PIF-0, the 10% heat loss temperature (Td,10%) of PIF-90 improved by 156 °C. Moreover, the PI-BMI foam piezoelectric sensor containing fluorine groups presents a short response time (14.22 ms), high sensitivity (0.266 V/N), and outstanding stability (10 000 cycles). Besides, the sensor can accurately monitor human activity in different states. This work provides a promising strategy for designing multifunctional PI foams, making them suitable for applications in aerospace and microelectronics.

Diimide-Mediated Hydrogenation of Nitrile Butadiene Rubber

The hydrogenation of nitrile butadiene rubber (NBR) has shown great potential for improving its physical, thermal, mechanical, and chemical stability. Hydrogenation process of NBR in this work involved the utilization of diimide produced from the interaction between hydrazine hydrate (N2H4) and hydrogen peroxide (H2O2), with the addition of boric acid as a promoter. Attenuated total reflectance Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were used to evaluate the degree of hydrogenation, glass transition, thermal stability, and rubber crystallinity, respectively. The highest hydrogenation degree was 99%, which resulted in a 57% gel content. Upon hydrogenation, both the glass transition temperature (Tg) and decomposition temperature (Td) increased. The hydrogenated rubber samples generally showed an amorphous state, except for the 99% hydrogenated sample, which displayed a semi-crystalline state. However, using diimide for direct hydrogenation yields a side reaction from the free radicals in the system, which leads to gel formation. Optimization was accomplished by employing the response surface methodology (RSM), which entailed manipulating parameters such as the total solid content (TSC) of NBR, reaction time, and the mole ratio of H2O2 to N2H4, to reduce the percentage of gel content. The RSM analysis identified the optimum reaction conditions as a 1:1 mole ratio of H2O2: N2H4 and 25% TSC, with a reaction time of 8 h, which yielded 32% gel content percentage, where a mole ratio of H2O2 to N2H4 and reaction time indicated a synergistic effect, whereas TSC denoted an antagonistic effect.

Partially Bio-Based and Biodegradable Poly(Propylene Terephthalate-Co-Adipate) Copolymers: Synthesis, Thermal Properties, and Enzymatic Degradation Behavior.

A series of partially bio-based and biodegradable poly(propylene terephthalate-co-adipate) (PPTA) random copolymers with different components were prepared by the melt polycondensation of petro-based adipic acid and terephthalic acid with bio-based 1,3-propanediol. The microstructure, crystallization behavior, thermal properties, and enzymatic degradation properties were further investigated. The thermal decomposition kinetics was deeply analyzed using Friedman's method, with the thermal degradation activation energy ranging from 297.8 to 302.1 kJ/mol. The crystallinity and wettability of the copolymers decreased with the increase in the content of the third unit, but they were lower than those of the homopolymer. The thermal degradation activation energy E, carbon residue, and reaction level n all showed a decreasing trend. Meanwhile, the initial thermal decomposition temperature (Td) was higher than 350 °C, which can meet the requirements for processing and use. The PPTA copolymer material still showed excellent thermal stability. Adding PA units could regulate the crystallinity, wettability, and degradation rate of PPTA copolymers. The composition of PPTA copolymers in different degradation cycles was characterized by 1H NMR analysis. Further, the copolymers' surface morphology during the process of enzymatic degradation also was observed by scanning electron microscopy (SEM). The copolymers' enzymatic degradation accorded with the surface degradation mechanism. The copolymers showed significant degradation behavior within 30 days, and the rate increased with increasing PA content when the PA content exceeded 45.36%.

Relationship Between Greenhouse Gases Emissions with Some Meteorological Variables Over Baghdad City

When infrared radiation from the earth is emitted and back to it, the gases known as greenhouse gases can absorb this entire thermal energy, which is what causes global warming. In addition to other gases including those present on the surface of the ozone layer, nitrous oxides, and fluorinated gases, water vapour is one of the most significant greenhouse gases, albeit its impact is less. Although it is a straightforward type of atmospheric gas, greenhouse gases have a huge impact on the planet’s energy system and have been implicated in significant global climate change. The methods used in the study depend on the daily and monthly average CH4, H2O, N2O, CO2 and temperature (T) and Dewpoint temperature (Td) and relative humidity (RH) taken from the European Mediterranean Weather Forecast (ECMWF) during the year (2021) for the Baghdad region. As a result, in the Statistical analysis of air pollutants, carbon dioxide gas represents the highest correlation with heat, and this leads to high global warming, followed by ozone, methane, and water vapour.

Effects of glycation modifications of different glycosylating agents on the molecular structure and gel properties of sheep's hoof gelatin

In this study, we utilized sheep's hoof gelatin as a raw material to modify gelatin by non-enzymatic glycation reactions using five different monosaccharides (D-glucose, D-sorbose, D-fructose, D-ribose, and D-erythrose) and five different polysaccharides (pectin, inulin, carrageenan, xanthan gum, and konjac glucomannan) and comparatively analyzed the properties (rheological properties, textural properties, and thermal stability) of differently glycosylated sheep's hoof gelatin to determine the mechanism of different glycosylating agents on the molecular properties and gel performance of sheep's hoof gelatin. The results showed that the reactivity (DG value) and phase transition temperature (Td value) of gelatin modified with monosaccharide glycosylates were notably higher (p < 0.05) compared to those modified with polysaccharides, resulting in a micro-network structure with finer pore size. Conversely, polysaccharide glycosylation significantly enhanced the mechanical properties and rheological characteristics of gelatin (p < 0.05). The formation of a mosaic network structure in the polysaccharide-glycosylated gelatin group played a pivotal role in enhancing gel properties. Notably, the gel strength (584.62 ± 6.34 g), viscosity (η-value), and gel melting temperature (37.85 ± 0.20 °C) of the polysaccharide S-PEC were significantly higher than the other treatment groups (p < 0.05). This research not only provides a new perspective for modifying gelatin derived from sheep's hooves but also offers an important theoretical basis for the exploration and application of gelatin materials in the food industry.

Anthropogenic Climate Change and Urbanization Exacerbate Risk of Hybrid Heat Extremes in China

AbstractDry‐ and wet‐bulb temperature (Td and Tw) are usually to define heatwaves (HWs) which have been enhanced under anthropogenic climate change (ACC) and urbanization. However, responses of various types of HWs (i.e., dry HWs, only high Td; humid HWs, only high Tw; hybrid HWs, both high Td and Tw; total HWs, high Td or Tw), to ACC and urbanization remain unknown. In this study, both observations and simulations show significantly increasing occurrence probability of total HWs over China during 1971–2020, whereas this increase is mainly reflected in hybrid HWs, followed by dry HWs and humid HWs. 68.2%–93.0% of the observed increases in the above four types of HWs can be attributed to ACC; on the other hand, urbanization tends to suppress humid HWs but enhance dry HWs, as a result of contributing to the increase of hybrid HWs by 10.9%. Under future ACC, total HWs are projected to be more frequent as expected, which is mainly sourced from the increasing hybrid HWs because dry/humid HWs are projected to be steady/downward. As a consequence, urban population exposure to ACC‐induced total HWs would remarkably increase to 83.55 billion person‐days by the 2090s, 89.5% of which can be attributed to hybrid HWs. Urbanization would amplify this population exposure of ACC‐induced hybrid HWs from 74.79 billion person‐days to 110.9 billion person‐days. Our results underscore the importance of improving understanding of hybrid HWs in urban areas and developing targeted adaptation planning on a warmer planet.

Eco‐friendly synthesis of non‐isocyanate polyurea using PET and CO2 upcycling: A double green approach

AbstractFrom the perspective of sustainability, this research explored both the recycling of polyethylene terephthalate (PET) and the conversion of carbon dioxide (CO2) into polymer materials. To this end, a series of copolyurea specimens were synthesized through the polycondensation of carbon dioxide with hexamethylenediamine (HDA) and terephthalic dihydrazide (TDH), where TDH was derived from the chemical recycling of PET via the aminolysis method. FTIR spectroscopy, 1H NMR, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) characterized the products of PET recycling and synthesized copolyureas. Additionally, we sought to identify the optimal parameters for both the recycling and copolymerization processes. The results of identification analyses for both the recycling and copolymerization reactions confirmed the formation of the desired structures. An increase in the hard segment (TDH) led to discrepancies between the intended and actual monomer ratios in the synthesis, possibly due to dimethyl sulfoxide (DMSO) solubility issues or unreacted TDH. Furthermore, the TGA analysis indicated that the initial degradation temperature (Td,5%) of the copolymer increased with the proportion of aromatic rings in the hard segment, underscoring the complex interactions within the copolymer matrix affecting its thermal and structural properties. The DSC results revealed that for copolyureas with the formula HDAxTDH100–x (where x = 50, 60, 70, 80, 90), reducing the x fraction or increasing the TDH content lowered the melting temperature. Furthermore, at a high percentage of TDH, the melting point disappeared entirely due to the destruction of the crystalline structure, indicating a critical threshold where the copolymer transitions from a semi‐crystalline to an amorphous state.