Decreasing Temperature Research Articles

Exceptional tensile ductility and strength of a BCC structure CLAM steel with lamellar grains at 77 kelvin

The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.

Assessing the reliability of species distribution models under changing environments: a case study on cetaceans in the North-East Atlantic

1.Species Distribution Models (SDMs) assume stable relationships between species and their environment from which predictions are made. These relationships are likely to vary with changing environments, and predictions might depend more on modelling choices than on empirical data. Reliability assessments of predictions are necessary to support policy-making.2.We identified environmental extrapolations among potential predictions of cetaceans’ distribution from 2005 to 2020 in the North-East Atlantic and calculated the percentages of calibration data with similar environments (nearby data), supporting these predictions. Thus, the assessment of reliability is generic, as evaluated before model fitting.3.Predictions on continental shelves were extensively supported by the calibration data and were more reliable throughout the year than predictions on continental slopes and abyssal plains, which were more supported in summer. Predictions off Portugal were particularly uncertain due to the lack of surveys in this region of deep, warmer waters with seamounts.4.The high effort between May and July led to a southern winter shift of nearby data, following the decrease in temperatures. A large part of the predictions between December and April was extrapolated due to the low coverage of the winter primary productivity drops, spring peaks and cold waters. They were based on data collected during other seasons and regions, and given the large spatial extent of the area, and the seasonality and regionality of the cetacean distributions, reliable winter predictions might be restricted to geographic areas where winter surveys took place. These predictions are more uncertain and warrant caution.5.Synthesis and applications: extrapolations and nearby data highlighted environmental gaps to predict cetacean distributions in the North-East Atlantic, which could be covered by future surveys. This informs model users of regions and periods when predictions reliability becomes uncertain. SDMs are invaluable tools for supporting conservation applications and, despite the warnings that have been issued, the degree of information available for predicting distribution is still rarely reported. We recommend adding this assessment as routine information on the reliability of predictions.

Coupling effects of loading rate and temperature on mode I dynamic fracture characteristics of ductile cast iron

Engineering structures made of ductile cast iron (DCI) have a potential risk of failure due to extreme service environments such as high velocity impacts and sub-zero temperatures. Therefore, it is of great importance to investigate the dynamic fracture behavior of DCI under the coupling effect of rate and temperature. In this paper, two sets of impact velocities (5 m/s and 13.5 m/s), and four sets of temperatures (20 °C, −40 °C, −60 °C, and −80 °C) were specially designed to investigate the coupling effect on the mode I dynamic fracture toughness (DFT). The results show that DFT is positively correlated with impact velocity at 20 °C, −40 °C and −60 °C. However, at −80 °C, the rate effect is reversed. Moreover, DFT decreases with decreasing temperature regardless of impact velocity. With microscopic analysis, the phenomenon of ductile–brittle transition (DBT) was observed in the failure of the material, and it’s verified by dynamic tensile tests. The ductile–brittle transition temperature (DBTT) of DCI is determined as −39.7 °C by comparing the DFT with the strain energy density (SED) characterization method.

Controlling the heating wall temperature during melting via electric field

Thermal energy storage technology utilizing phase change materials (PCMs) is extensively applied in thermal management and energy storage. The inclination angle (θ) plays a critical factor in the phase change melting processes in practical implementations. However, the precise experimental velocity fields of liquid PCM and the impact of active regulation technology on the heating wall temperature at various angles remain unclear. Herein, a transparent melting experiment platform was established to measure velocity, and adjust θ and manipulate input electric voltage. Results from Particle Image Velocimetry indicated that the installation angle significantly impacts natural convection in the convection-dominated melting regime. The liquid fraction decreased from 73.5 % (when θ = 90°) to 54.4 % (when θ = 150°) due to reduced thermal energy absorption, as input energy was stored as sensible heat on the copper wall. The electrohydrodynamic (EHD) effect mitigated thermal resistance between the heater and the melt front, increasing melt thickness. EHD flow exhibited limited ability to regulate heating wall temperature under strong natural convection, with a 6.5 % decrease observed under +20 kV conditions. As natural convection rates decreased, the decrease rate of heating wall temperature increased to 10.7 %. The EHD effect demonstrated a heightened capability in enhancing heat transfer melting with increasing θ, leading to an increase in temperature difference from 3.3 °C to 5.3 °C under the +15 kV input voltage. These findings suggest that the electric field is an efficacious method for controlling the heating wall temperature at different inclination angles during the melting process.

Particle size control and performance analysis of the ammonium perchlorate-based molecular perovskite energetic material

To solve the problem of high mechanical sensitivity and difficulty in coating caused by large crystal particles of ammonium perchlorate-based molecular perovskite energetic material (H2dabco)[NH4(ClO4)3] (DAP-4), we conducted research on the particle size regulation and performance of it. Firstly, we determined the solubility of DAP-4 in six commonly used organic solvents using a static method. And based on this data, an UDAP-4 (D50 = 6.19 μm) was successfully prepared. The characterization results of UDAP-4 revealed that UDAP-4 exhibits a decrease in thermal decomposition peak temperature (Tp) by 19 °C compared to the raw material, along with an 87.92kJ/mol reduction in activation energy (Ea). The studies on different particle sizes indicate that UDAP-4 maintains good thermal stability while significantly enhancing safety performance. UDAP-4 shows an over 20J increase in impact sensitivity, and a 12N increase in minimum frictional load. And the smaller the particle size, the lower the sensitivity. These findings provide a reference for further secure applications of DAP-4 in an academic context.

Effect of Framework and Complementarity Determining Region H1 Charge on the human VH-B1a Domain Expression, Folding, Stability, and Solubility

Many difficulties related to using antibodies in diagnostic and therapeutic applications can sometimes be circumvented by using smaller, less complex single domain antibodies based on variable heavy chain (VH) domain constructs such as camelid VHH domains. However, VH domains have their own limitations, including an increased tendency to aggregate. VH domains often contain hydrophobic residues within their complementarity-determining regions (CDRs) that facilitate binding to target antigens but can also mediate VH domain aggregation, which is a concern for therapeutic applications since this can trigger immune responses. In this study, we engineered the human VH-1Ba domain to improve its stability and solubility by introducing charged amino acids in the VH domain framework region and CDRH1. We followed two strategies to improve the stability and solubility of VH domains. First, we introduced positive and negatively charged amino acids in the framework region of an autonomous human VH domain (VH-B1a) and observed the effect of framework net charge on VH domain refolding, stability, and solubility. Introducing positive charge into the VH-B1a framework increased its thermostability but slightly lowered its refolding ability and solubility. We were not able to obtain correctly folded negatively charged (-VH) VH domains. Second, we introduced a series of positive and negatively charged amino acids in the CDRH1 loop of near-neutral (VH-B1a) and positively charged (+VH) VH domains, and observed their effect on expression, refolding, stability, and solubility. For both the VH-B1a and +VH domains, we observed a decrease in melting temperature (Tm) and room temperature solubility as more negative or positive charged amino acids were added to the CDRH1. The VH-B1a domain had higher room temperature solubility for negative and slightly positive CDRH1 net charges. The +VH domain had higher Tms for all CDRH1 net charges and was better able to tolerate the adverse effects of adding positive charge to CDRH1. We observed a similar response in refolding and solubility of VH-B1a and +VH in response to changes in CDRH1 net charge after temperature-induced denaturation for negative and neutral CDRH1s. We observed a positional effect with a single Lys (31K) and double Lys (31, 32KK) substitutions in CDRH1, which promoted VH-B1a aggregation and was partially overcome by the +VH domain. In summary, this study provides information for designing VH domains with improved biophysical properties and a +VH domain that will be useful for applications where positive surface charge and CDRH1 are desirable.

Effects of water sprays on hydrogen autoignition in heated air

The effects of water mist with different diameters and mass loadings on hydrogen auto-ignition in air with elevated temperatures and pressures are studied. It is shown that smaller droplets with larger mass loading are the most effective in inhibiting the auto-ignition process. Under elevated initial pressures and temperatures, the role of water mist in impacting auto-ignition is minimal, primarily because the ignition delay is substantially shorter than the droplet evaporation duration. As the initial temperature decreases, there exists a temperature value below which water mist markedly extends the ignition delay time, even escalating it by up to two orders of magnitude or causing a complete suppression of ignition. The rate of production for important radicals was analyzed. The data indicates that the evaporation of the water mist lowers the initial temperature, leading to a reduction in the rate of the temperature-sensitive fast chain branching reaction. In contrast, the third body reaction that generates HO2 is not sensitive to temperature. Meanwhile, the introduction of H2O results in an earlier activation of the third body reactions. Consequently, the production of HO2 is enhanced, emphasizing the role of subsequent slow chain propagation reactions that generate OH, thereby extending the ignition delay. By deactivating the mass transfer between two phases and introducing artificial species, it is evident that water vapor dilution and thermal effects predominantly influence the ignition delay, while its role as a direct reactant is minimal.

Net primary productivity of paleo-peatlands linked to deep-time glacial periods in the late Carboniferous and early Permian icehouse interval

Peatlands, an important organic carbon reservoir, play a crucial role in the global carbon cycle. The carbon accumulation of peatlands, reflected by net primary productivity (NPP), can have an impact on global carbon cycling and climate change. The late Carboniferous - early Permian is an icehouse period, during which numerous thick coal beds were accumulated in the North China Block (NCB) located within a low-latitude area, providing an opportunity for studying the carbon cycling under the glacial and interglacial climates. In this study, spectral analysis was performed on the natural gamma-ray (GR) logs of the Benxi, Taiyuan and Shanxi formations of the late Carboniferous to early Permian in a borehole section located within the Ordos Basin in western NCB. Cyclic signals related to astronomical orbital parameters were identified, including long eccentricity (~405 kyr), short eccentricity (~125 kyr and ~ 95 kyr), and obliquity (~35.5kyr). A floating astronomical time scale was established by using the long eccentricity signal, and this time scale was further used to constrain the durations of the accumulation of coal-forming paleo-peatlands. The paleo-peatland for the C8 + 9 coal seam (9 m thick) of the Taiyuan Formation lasted approximately 203 kyr, and the paleo-peatland for the C5 coal seam (4 m thick) of the Shanxi Formation lasted approximately 46 kyr. Using this timeframe and an estimation of carbon loss during coalification, the carbon accumulation rates of the late Carboniferous - early Permian low-latitude peatlands are calculated to be 104.7 ± 14.9 g·C·m−2·a−1for the C8+9 coal seam and 192.6 ± 11.6 g·C·m−2·a−1for the C5 coal seam. The NPP of the paleo-peatlands, which deducts a part of carbon loss caused by the loss of CO2 and CH4, can be calculated from the carbon accumulation rates. The calculated average NPP of the paleo-peatlands for the C8+9 seam was 199 ± 28 g·C·m−2·a−1, and that of the C5 seam was 366 ± 22 g·C·m−2·a−1. In combination of the absolute time scale calibrated by high-precision UPb dates from Palougou section in western NCB, the depositional time of the investigated strata was constrained to be from 300.1 ± 0.5 Ma to 294.3 ± 0.5 Ma. The coal seams of the late Carboniferous to early Permian in the NCB corresponds to interglacial interval around ~298 Ma. The peatland with a lower NPP corresponds to the warming stage and the peatland with a higher NPP corresponds to the cooling stage. This implies that a lower NPP of paleo-peatland tend to be less efficient in carbon storage, and could not reduce the atmospheric CO2 substantially. In contrast, a higher NPP of paleo-peatland tend to accelerate carbon fixation, leading to temperature decrease and the termination of interglacial interval in early Permian. The results of this study could provide insights into the relationship between the development of paleo-peatlands and the record of the paleoclimates during the same period, and could be helpful for the prediction of future climate change.

Optimization of low-velocity impact behavior of FML structures at different environmental temperatures using taguchi method and grey relational analysis

Carbon fiber-reinforced Aluminum Laminate (CARALL) is a new generation of Fibre Metal Laminate (FML) material. This study investigates the low-velocity impact behavior of CARALL structures at different environmental temperatures (−40°C, 23°C, and 80°C). Two different groups of CARALL composite structures with varying fiber orientations were produced by hot pressing in a 3/2 arrangement: C1 (Al/0°90°/Al/90°0°/Al) and C2 (Al/0°0°/Al/0°0°/Al). Low-velocity impact tests were conducted at 23 J, 33 J, and 48 J energy levels using a Ø20 mm spherical impactor tip. The area of damage was detected by ultrasonic C-Scan. In addition, analysis of variance (ANOVA) was applied to reveal the influential parameters and their effect levels. After conducting experiments using the Taguchi L18 test set, it was observed that the C2-coded specimen yielded better results in terms of maximum peak load, maximum displacement, and damage area. While the decrease in temperature increased the damage and maximum peak load, the increase in temperature did not cause a significant change in the maximum peak load. The primary damage mechanisms observed in damage investigations were matrix cracks and delamination between composite layers. Although delamination is present between the Al/CFRP layer, it is not significant. According to ANOVA results, impact energy was the most effective parameter for maximum impact force, maximum displacement, and damage area, with contribution rates of 81%, 74%, and 76%, respectively. The optimal experimental conditions (23°C temperature and 23 J impact energy with the C1-coded sample) were determined using grey relational analysis based on principal component analysis.

Synthesis and magnetic properties of NiCo2O4urchin-like nanofibers.

Single-phase NiCo2O4 (NCO) nanoparticles (NPs) with an average particle size of 12 (± 3.5) nm were successfully synthesized as aggregates in urchin-like nanofibers via a hydrothermal route. Magnetization data measured as functions of temperature and magnetic field suggest a superparamagnetic-like behavior at room temperature, a ferrimagnetic transition around a Curie temperature TC ~200 K, and a spin blocking transition at a blocking temperature TB ~90 K, as observed at a field of 100 Oe. The spin blocking nature has been investigated by analyses of the field-dependence of TB in the static magnetization and its frequency-dependence in the ac susceptibility data measured in zero-field cooling regime, both indicate a low-temperature spin glass-like state. Below TB, the coercivity increases monotonically up to 1.7 kOe with decreasing temperature down to 5 K. Our results indicate that the magnetic behavior of NCO NPs, which is mainly determined by the cations' ratio, oxidation states, and site-occupancy, can be controlled by a synthesis in appropriate particle size and morphology.

Investigating the Impact of Nano‐Metal Oxides (Copper and Iron) on the Thermal Decomposition Behavior of Advanced Propellants with Nitrocellulose/Polyurethane Binders

AbstractThis research delves into the combined effects of green nano metal oxides (copper and iron) and polyurethane (PU) modification on the thermal degradation kinetics of propellant based on solid ammonium nitrate composite modified simple base (CMSB). Surface modification of ammonium nitrate particles was achieved through repeated spray coating, ensuring effective catalyst binding. The formulated compositions of propellants underwent thorough thermal characterization, including thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. TG analysis revealed a significant decrease in the propellant's thermal degradation temperature, attributed to AN modification with nano metal oxides (nMOs) and the use of PU/NC as a binder. Isoconversional kinetic methods (It‐KAS, It‐FWO, and VYA/CE) were employed for further analysis, allowing prediction of kinetic parameters. Additionally, kinetic analysis results allowed calculation of the critical ignition temperature. The thermokinetic results underscore the substantial impact of nMOs particles and PU modification regarding the reactivity and catalytic performance of propellant containing ammonium nitrate, leading to a noteworthy reduction in activation energy and critical ignition temperature. Furthermore, modifying the binder with nitrocellulose and incorporating nanoparticles significantly reduces ignition delay and combustion duration while increasing flame intensity in CMDB solid propellants, enhancing overall combustion efficiency.

Multiorgan ultrastructural changes in rats induced in synthetic torpor

Torpor is a state used by several mammals to survive harsh winters and avoid predation, characterized by a drastic reduction in metabolic rate followed by a decrease in body temperature, heart rate, and many physiological variables. During torpor, all organs and systems must adapt to the new low-energy expenditure conditions to preserve physiological homeostasis. These adaptations may be exploited in a translational perspective in several fields. Recently, many features of torpor were shown to be mimicked in non-hibernators by the inhibition of neurons within the brainstem region of the Raphe Pallidus. The physiological resemblance of this artificial state, called synthetic torpor, with natural torpor has so far been described only in physiological terms, but no data have been shown regarding the induced morphological changes. Here, we show the first description of the ultrastructural changes in the liver, kidney, lung, skeletal muscle, and testis induced by a 6-hours inhibition of Raphe Pallidus neurons in a non-hibernating species, the rat.

Characterization and quantitative understanding of subthreshold swing of Si metal–oxide–semiconductor field effect transistors at cryogenic temperatures

The temperature and drain current (ID) dependencies of sub-threshold swing (SS) values of Si n- and p-channel metal–oxide–semiconductor field effect transistors (MOSFETs) with different substrate impurity concentrations ranging from the 1015 to 1018 cm−3 ranges are systematically and experimentally evaluated at cryogenic temperatures. It is found that SS of p-channel MOSFETs tends to increase with decreasing temperature, which contrasts with saturation of SS of n-MOSFETs at cryogenic temperatures, well reported by many previous works. To explain these SS behaviors quantitatively, we employ a density-of-state (DOS) model with tail states consisting of localized states in a deep energy range and mobile states in a shallow energy range, which are attributable to potential fluctuations caused by substrate impurities. It is shown that this model can quantitatively explain the temperature and ID dependencies of SS of both n-MOSFETs and p-MOSFETs. Then, we are assuming that the Si p-MOSFET has a higher density of localized states than the n-MOSFET. Thus, the increase in SS of the p-MOSFETs with decreasing temperature is explained by an increase in the density of localized states at the Fermi level with decreasing temperature, because the density of localized states increases with elevating the Fermi level position in the employed DOS model.

Study on Mechanism of Microstructure Refinement by Ultrasonic Cavitation Effect

During the solidification process of the alloy, the temperature lies in the range between the solid-phase line and the liquidus. Dendrite growth exhibits high sensitivity to even slight fluctuations in temperature, thereby significantly influencing the tip growth rate. The increase in temperature can result in a reduction in the rate of tip growth, whereas a decrease in temperature can lead to an augmentation of the tip growth rate. In cases where there is a significant rise in temperature, dendrites may undergo fracture and subsequent remelting. Within the phenomenon of ultrasonic cavitation, the release of internal energy caused by the rupture of cavitation bubbles induces a substantial elevation in temperature, thereby causing both dendrite remelting and fracture phenomena. This serves as the main mechanism behind microstructure refinement induced by ultrasonic cavitation. Although dendrite remelting and fracture exert significant influences on the solidification process of alloys, most studies primarily focus on microscopic characterization experiments, which fail to unveil the transient evolution law governing dendrite remelting and fracture processes. Numerical simulation offers an effective approach to address this gap. The existing numerical models primarily focus on predicting the dendrite growth process, while research on remelting and fracture phenomena remains relatively limited. Therefore, a dendrite remelting model was established by incorporating the phase field method (PFM) and finite element difference method (FDM) into the temperature-induced modeling, enabling a comprehensive investigation of the entire process evolution encompassing dendrite growth and subsequent remelting.

Heatwave-amplified atmospheric oxidation in a multi-province border area in Xuzhou, China

Ozone formation is closely tied to emissions of precursors, meteorological conditions, and atmospheric chemistry. In June 2024, Xuzhou City, located at the intersection of Jiangsu, Shandong, Henan, and Anhui provinces in East China, experienced a series of ozone pollution events. The continuous pollution episodes were characterized by consistently high levels of ozone, with daytime peaks reaching 130 ppb. By combining observations of atmospheric oxidation and the use of the Observation-Based Model model, it was determined that the pollution was the result of a “heatwave-ozone” co-occurring extreme event triggered by elevated temperatures, low humidity, and intense radiation. The heatwave led to increased emissions of VOCs from both natural and human-related sources, with more pronounced contribution from Bio-alkenes and OVOCs. This, in turn, resulted in higher levels of oxidizing agents and ozone formation potential, exacerbating the co-occurrence of heatwaves and ozone extremes. Sensitivity tests on enhanced controls showed that reducing NOx had a significant adverse effect on ozone levels, whereas reducing VOCs had positive benefits, particularly for controlling alkenes. Despite ongoing reductions in anthropogenic VOCs, the elevated temperatures led to an increase in natural VOCs emissions. On average, a 1°C temperature decrease could reduce the reactivity ratio of VOCs to NOx (VOCR/NOxR) by 0.12, thereby enhancing the advantages of emission reductions. Therefore, implementing measures to alleviate extreme heatwaves, such as limiting high-energy consumption and inducing artificial rainfall, can simultaneously reduce the intensity and reactivity of VOC emissions, aiding in the effective implementation of ozone pollution control policies.

Modification of Poly(3-Hydroxybutyrate) with a Linear Polyurethane Modifier and Organic Nanofiller—Preparation and Structure–Property Relationship

The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health hazard of all living organisms. Moreover, most of the synthetic polymers used are made from petrochemical feedstocks from non-renewable resources. The use of petrochemical raw materials also causes degradation of the natural environment. A potential solution to these problems is the use of biopolymers. Biopolymers include biodegradable or biosynthesizable polymers, i.e., obtained from renewable sources or produced synthetically but from raw materials of natural origin. One of them is the poly(3-hydroxybutyrate) (P3HB) biopolymer, whose properties are comparable to PP. Unfortunately, it is necessary to modify its properties to improve its processing and operational properties. In the work, hybrid polymer nanobiocomposites based on P3HB, with the addition of chain, uncross-linked polyurethane (PU) and layered aluminosilicate modified with organic salts (Cloisite®30B) were produced by extrusion process. The introduction of PU and Cloisite®30B to the polymer matrix (P3HB) influenced the processing parameters beneficially and resulted in a decrease in the extrusion temperature of more than 10 °C. The influence of the simultaneous addition of a constant amount of PU (10 m/m%) and the different amounts of nanoadditives (1, 2 and 3 m/m%) on the compatibility, morphology and static mechanical properties of the resulted nanobiocomposites were examined. The component interactions by Fourier transformation infrared spectroscopy (FTIR) analysis, nano- and microscale structure studies using small-angle X-ray scattering (SAXS) and morphology by scanning electron microscopy (SEM) were carried out, and the hardness and tensile strength of the obtained polymer nanobiocomposites were determined. FTIR analysis identified the compatibility of the polyester matrix, PU, and organomodified montmorillonite, the greatest being 3 m/m% Cloisite30B content. The addition of PU to the polyester elasticizes the material and decreases the material’s strength and ductility. The presence of nanoclay enhanced the mechanical properties of nanobiocomposites. The resulting nanobiocomposites can be used in the production of short-life materials applied in gardening or agriculture.

Thermal-Gas-Elastic Coupling Modeling and Performance Analysis of Foil Cylindrical gas Film Seal Considering Speed Slip, Temperature Jump and Shaft Misalignment

Abstract The Compliant foil cylindrical gas film seal is an advanced sealing technology designed for high-speed and high-temperature conditions in a jet engine. Its design involves using a compliant foil to create a cylindrical sealing surface, achieving adaptive sealing in environments with high pressure differences and rotational speeds. For high-speed and high-temperature operation, a speed slip flow model was established by considering film slip flow, wall temperature jump, foil deformation, and gas viscosity-temperature thermal effects. The variations in the lubrication performance of the foil cylindrical gas film seal with changes in shaft misalignment directions, misalignment angles, and operating parameters were investigated. The speed slip leads to a decrease in gas film lift and an increase in leakage. The wall temperature jump phenomenon caused by speed slip leads to a 2.56% decrease in film temperature. The shaft misalignment angles on the high-pressure and low-pressure sides have different impacts on the flow field, with film pressure and temperature differing by 66.78% and 11.19%, respectively.

Facile Synthesis and Decomposition Kinetics of Energetic Molecular Perovskite DAP-4 Catalyzed with Copper Nanoparticles for Advanced Energetic Systems

AbstractMolecular perovskite DAP-4 (NH4)(C6H12N2)(ClO4)3 can expose high oxidizing capability, with superior decomposition enthalpy compared with ammonium perchlorate (AP). DAP-4 was developed via molecular assembly method. The potential impact of copper nanoparticles (Cu NPs) on DAP-4 thermal decomposition was evaluated. Reactive Cu NPs of 50 nm were integrated into DAP-4 structure via solvent evaporation. Uniform dispersion of Cu NPs into DAP-4 matrix was assessed using elemental mapping. Whereas AP demonstrated decomposition enthalpy of 733 J/g; virgin DAP-4 and Cu/DAP-4 nanocomposite experienced decomposition enthalpy of 3800, and 4150 J/g respectively. Cu NPs offered decrease in DAP-4 main decomposition temperature by 49 oC. Decomposition kinetics was investigated via Kissinger, and Kissinger–Akahira–Sunose (KAS). Cu/DAP-4 demonstrated apparent activation energy of 134.97 ± 3.02 kJ/mol compared with 216.32 ± 4.42 kJ/mol for virgin DAP-4. Cu NPs offered decrease in DAP-4 combustion time from 70 ms to 31 ms, with high intense combustion flame. Copper NPs experienced dramatic change in DAP-4 decomposition mechanism from F1 to F3.Copper NPs could act as efficient reactive catalyst particles; that could be oxidized to CuO with the evolution of 3700 J/g. The evolved CuO nanocatalyst could boost decomposition enthalpy.

Local and systemic photobiomodulation using a 650nm LED on skin temperature and hyperalgesia in cellulite: a randomized, placebo-controlled and double-blinded clinical trial.

Cellulite is a skin condition that significantly affects women, characterized by "holes" or depressions in the skin, affecting approximately 95% of women at some point in their lives. Cellulite often presents inflammatory symptoms such as increased skin temperature and hyperalgesia. Photobiomodulation, whether applied locally or systemically, has demonstrated important anti-inflammatory effects in various conditions. This study investigates the effects of local and systemic photobiomodulation on hip culottes temperature increases and hyperalgesia in patients with grades 2 to 4 cellulite. Cellulite assessment was carried out using detailed anamnesis, photographic records, algometry, and infrared thermography. Participants received randomized bilateral treatment with or without systemic irradiation using LED photobiomodulation on the hip culottes for four weeks, three times a week. This study aimed to evaluate the effect of photobiomodulation, especially locally applied, together or not with systemic irradiation, on cellulite hyperalgesia and skin temperature among 25 female participants. The group that received only LED treatment showed an increase in pain threshold of 8% and 20% on the right and left sides, respectively, while the group treated with LED + ILIB showed an increase in pain threshold of 32% on both sides. Local photobiomodulation produced a skin temperature decrease of 0.4°C, while the combination of local and systemic irradiation produced an average skin temperature decrease of 1.2°C. Our results clearly demonstrate a significantly beneficial effect of LED therapy for cellulite treatment, especially when administered in combination with mILIB, leading to a significant reduction of pain hypersensitivity and skin temperature, indicating a regional subcutaneous improvement of the inflammatory status.

Thickness-dependent nanoscale friction across the first-order charge density wave phase transition in 1T-TaS2

The layered charge density wave (CDW) phase transition material 1T-TaS2 has garnered significant attention due to its modulable bandgap and electrical transport properties. These unique properties make 1T-TaS2 highly promising for applications in fields such as optoelectronic devices and microstructure physics devices. In various micro-/nanodevices made from quasi-two-dimensional 1T-TaS2, it is often utilized in thin layers, making the understanding of its frictional properties crucial for practical applications. However, the layer-dependent frictional properties of 1T-TaS2 have not been thoroughly investigated. In this article, we examine the CDW phase transition between the nearly commensurate (NCCDW) and commensurate (CCDW) phases in 1T-TaS2 around 183 K using atomic force microscopy, focusing on the number of layers in the samples. Our results indicate that for thicker samples with more than approximately 17 layers, a friction peak is observed during the NCCDW–CCDW phase transition. In contrast, thinner samples do not exhibit this friction peak, and their friction continuously increases as the temperature decreases. This behavior is attributed to the suppressed NCCDW–CCDW phase transition in thinner samples. These results enhance our understanding of the frictional behavior of 1T-TaS2 in the context of micro-/nano-electromechanical systems. Furthermore, our observations offer a straightforward method to identify the NCCDW–CCDW phase transition, providing an alternative to traditional, more complex techniques such as electrical resistance measurements and Raman spectroscopy.