Large Temperature Research Articles

Precise Tailoring of Unprecedent Layered Perovskite-type Heterostructure Ferroelectric via Chemical Molecular Scissor.

Precise stacking of distinct two-dimensional (2D) rigid slabs to build heterostructures has renewed the portfolio of 2D materials, e.g., magic-angle graphene, due to the emergence of exotic physical properties. Recently, single-crystal heterostructures of layered perovskites have emerged as an exciting branch, while it remains scarce to achieve strong ferroelectricity in this new heterostructure family. Here, we present the first ferroelectric of 2D perovskite heterostructures as single crystal, (EA3Pb2Br7)EA4Pb3Br10 (1, EA = ethylamine), by precisely tailoring inorganic sheets via a chemical molecular scissor. It has notable ferroelectricity of large spontaneous polarization (Ps ~ 5.0 μC/cm²) and high Curie temperature (Tc ~ 375 K). Structurally, its inorganic framework adopts a unique 2D heterostructure that contains two different rigid slabs of {EA3Pb2Br7}n and {EA4Pb3Br10}n. This motif is self-assembled by layer-by-layer clipping of rigid prototype sheets, using extra neopentylamine as a molecular chemical scissor. Unlike epitaxial growth, such a molecule-level stacking facilitates the growth of heterostructure single crystals. Combining its strong ferroelectricity and inherent anisotropy, crystal-based device of 1 exhibits an ultrahigh polarized-light sensitivity up to ~37 in self-powered mode, being the highest level of 2D perovskite ferroelectric family. Our work will facilitate the further development of ferroelectric materials for optoelectronic device applications.

Cold suppresses virus accumulation and alters the host transcriptomic response in the turnip mosaic virus ̶ Arabidopsis halleri system.

Since plant viruses cause lifelong infections, virus-plant interactions are exposed to large temperature fluctuations in evergreen perennials. In such circumstances, virus-plant interactions are expected to change significantly between the warm and cold seasons. However, few studies have investigated the effects of cold temperatures on virus-plant interactions. Here, we show that in a persistent infection system of the turnip mosaic virus (TuMV) -Arabidopsis halleri, cold temperatures lead to slow viral replication/spreading within the host, slow attenuation of host symptoms, and slow cold-specific transcriptomic responses. Many differentially expressed genes (DEGs) were detected between virus-inoculated and mock-inoculated plants under warm and cold conditions; however, the sets of DEGs and response timings were temperature-dependent. Under cold temperatures, the expression of photosynthesis-related genes decreased in the early stages of infection. However, it recovered to the same level as that in uninfected plants in the later stages. In contrast, the transcriptomic changes under warm conditions suggest that viral infections cause auxin-signaling disruption. These responses coincided with the inhibition of host growth. We identified 6 cold- and 38 warm-specific DEGs, that changed their expression in response to TuMV infection under more than half of the conditions for either cold or warm temperatures. Further validation of the putative relationships between transcriptomic and phenotypic responses of the host is required. Our findings on temperature-dependent host responses at both symptomatic and transcriptomic levels help us understand how warm and cold temperatures affect virus-plant interactions in seasonal environments.

Near-field-driven thermal phonon lasing.

The extreme electromagnetic near-field environment of nanoplasmonic resonators and metamaterials can give rise to unprecedented electromagnetic heating effects, enabling large and manipulable temperature gradients on the order of 101-102 K/nm. In this Letter, by interfacing traditional semiconductor quantum dots with industry-grade plasmonic transducer technology, we demonstrate that the near-field-induced thermal gradient can facilitate the requisite population inversion for coherent phonon amplification and lasing at the nanoscale. Our detailed analysis uncovers both the characteristics and parameter sensitivity of inversion and relaxation oscillations in the system, thereby unveiling hitherto unexplored opportunities for leveraging plasmonic near-field effects in the context of quantum thermodynamics and phononics.

The Combined Link of the Indian Ocean Dipole and ENSO with the North Atlantic–European Circulation during Early Boreal Winter in Reanalysis and the ECMWF SEAS5 Hindcast

Abstract During early boreal winter, the extratropical atmospheric circulation is influenced by Rossby waves propagating from the Indian Ocean toward the North Atlantic–European (NAE) regions, resulting in a North Atlantic Oscillation (NAO)-like pattern. The mechanisms driving these teleconnections are not well understood and are crucial for improving model skills. This study investigates these mechanisms using the ERA5 dataset and tests the predictive capabilities of the ECMWF SEAS5, exploring potential reasons for a weak model response. Linear regression methods are employed to examine the extratropical links with the Indian Ocean dipole (IOD), both in isolation and in combination with El Niño–Southern Oscillation (ENSO). Our findings demonstrate a connection between October IOD sea surface temperature anomalies and December Indian Ocean precipitation patterns. Furthermore, a correlation between the October IOD and December NAO time series suggests a link between the IOD and NAE circulation. The early winter European response to a positive IOD is characterized by a north–south precipitation dipole and a large positive surface air temperature anomaly. Positive feedback from transient eddy forcing reinforces the wavenumber-3-like propagation across extratropical regions, with ENSO playing a minor role compared to the IOD. This phenomenon is particularly evident in regions such as the North Pacific and North Atlantic, where wave energy propagation is intensified. Although SEAS5 replicates the NAO response, its magnitude is significantly weaker. The model struggles to simulate the delayed rainfall dipole response to the IOD accurately and shows structural discrepancies compared to reanalysis data.

Microstructural Characteristics of Damaged Hot Dry Rock Flow Network Stimulated by Cryogenic Liquid Nitrogen Shock.

Hot dry rock (HDR) geothermal development faces challenges due to the difficulty of stimulating fluid flow and heat-exchange fracture channels within deep, low-porosity, and low-permeability reservoirs. A liquid nitrogen cyclic cold shock method was proposed, using liquid nitrogen as a fracturing fluid. The large temperature difference between the liquid nitrogen and the hot rock induces thermal stress, forming a complex pore-fracture network. In this study, HDR samples at various temperatures were subjected to 5 cycles of liquid nitrogen cold shock. Pore-fracture structures of the damaged cores were tested by low-field nuclear magnetic resonance and X-ray microscopy. Results showed temperature-dependent changes in porosity: at 200 and 300 °C, small-size pores rose, with maximum porosities of 3.13% and 3.37%; at 400-500 °C, large-size pores rose, with porosities reaching 4.59% and 12.76%. Different pore types exhibited distinct responses: mesopores are the most sensitive to temperature shock, micropores responded to the early damage stage, and macropores only responded under high-temperature differences and multiple cycles. Multifractal analysis revealed increased heterogeneity and concentration in pore distribution with damage escalation. The slice porosity, fractal box dimension, and probability entropy demonstrated exponential growth. Results indicate that temperature difference is the main controlling factor of pore damage in HDR, and cyclic shock can also contribute to continuous pore development. There is a high correlation between pore-fracture parameters and multifractal parameters, allowing the multifractal to reflect a more complex pore-fracture structure quantitatively.

An Eco‐Friendly and Multifunctional Textile Integrating Radiative Heating and Cooling for Large‐Temperature‐Variation Personal Thermal Management

AbstractRadiative heating or cooling textiles offer a sustainable means for personal thermal management (PTM). However, textiles that can realize efficient PTM under both large indoor and outdoor temperature variations are still lacking. Herein, guided by a heat transfer model, an eco‐ and user‐friendly bilayer textile (i‐textile) integrating radiative heating and cooling is developed. The i‐textile is composed of an MXene layer and a cellulose acetate (CA) layer with asymmetrical spectral characteristics. This textile provides heating when the MXene layer faces outward and cooling by wearing the textile inside out when the CA layer faces outward, thus enabling a decreased skin temperature variation range (7.3 and 6.8 °C lower than those when wearing cotton textiles) under large temperature variations indoors (12.6 °C) and outdoors (19.6 °C), respectively. Moreover, the i‐textile presents excellent wearability (breathability and washing resistance), recyclability, and biodegradability and can save≈30% of the building heating and cooling energy if widely deployed in China.

Quadrupole-Central-Transition 23Na, 39K, 87Rb NMR Studies of Alkali Metal Ions under Different Molecular Tumbling Conditions: A Simple Model to Treat Chemical Exchange Involving Quadrupolar Nuclei.

We report a new NMR method for treating two-site chemical exchange involving half-integer quadrupolar nuclei in a solution. The new method was experimentally verified with extensive 23Na (I = 3/2), 39K (I = 3/2), and 87Rb (I = 3/2) NMR results from alkali metal ions (Na+, K+, and Rb+) in a solution over a wide range of molecular tumbling conditions. In the fast-motion limit, all allowed single-quantum NMR transitions for a particular quadrupolar nucleus are degenerate giving rise to one Lorentzian signal. In the slow-motion regime, although the NMR signal from quadrupolar nuclei should in principle exhibit a multi-Lorentzian line shape, only the quadrupole central transition (QCT) is often detectable in practice. In all the cases studied in this work, we found that alkali metal ions undergo fast exchange between free and bound states. Using the new theoretical method, we were able to interpret the experimental transverse relaxation data (i.e., line widths) obtained for 23Na, 39K, and 87Rb NMR signals including QCT signals over a large temperature range and extract information about ion-binding dynamics in different chemical environments. This work fills a gap in the literature where a unified approach for treating NMR transverse relaxation data for quadrupolar nuclei over the entire range of motion has been lacking. Our results suggest that the new approach is applicable in the study of alkali metal ion binding to biological macromolecules.

A theoretical kinetic study of the methane’s hydrogen abstraction by chlorine at a large temperature range

A theoretical kinetic study of the methane’s hydrogen abstraction by chlorine at a large temperature range

Is SiC a Predominant Technology for Future High Power Electronics?: A Critical Review

: Due to the magnificent properties of Silicon Carbide (SiC), such as high saturation drift velocity, large operating temperature, higher cut-off and maximum frequency (fT and fmax), high thermal conductivity and large breakdown voltages (BV), it is desirable for high power electronics. With the latest advancements in semiconductor materials and processing technologies, diverse high-power applications such as inverters, power supplies, power converters and smart electric vehicles are implemented using SiC-based power devices. Especially, SiC MOSFETs are mostly used in high-power applications due totheir capability to achieve lower switching loss, higher switching speed and lower ON resistance than the Si-based (Insulated gate bipolar transistor) IGBTs. In this paper, a critical study of SiC MOSFET architectures, emerging dielectric techniques, mobility enhancement methods and irradiation effects are discussed. Moreover, the roadmap of Silicon Carbide power devices is also briefly summarized.

Revealing formation mechanism of end of process depression in laser powder bed fusion by multi-physics meso-scale simulation

ABSTRACT Unintended end-of-process depression (EOPD) commonly occurs in laser powder bed fusion (LPBF), leading to poor surface quality and lower fatigue strength, especially for many implants. In this study, a high-fidelity multi-physics meso-scale simulation model is developed to uncover the forming mechanism of this defect. A defect-process map of the EOPD phenomenon is obtained using this simulation model. It is found that the EOPD formation mechanisms are different under distinct regions of process parameters. At low scanning speeds in keyhole mode, the long-lasting recoil pressure and the large temperature gradient easily induce EOPD. While at high scanning speeds in keyhole mode, the shallow molten pool morphology and the large solidification rate allow the keyhole to evolve into an EOPD quickly. Nevertheless, in the conduction mode, the Marangoni effects along with a faster solidification rate induce EOPD. Finally, a ‘step’ variable power strategy is proposed to optimise the EOPD defects for the case with high volumetric energy density at low scanning speeds. This work provides a profound understanding and valuable insights into the quality control of LPBF fabrication.

Study on the cooling strategy of night ventilation tunnels in long-term subway operation (ISHVAC 2023)

The continuous increase of the ambient temperature in the subway tunnel not only increases the energy consumption of the air conditioning but also makes of the air conditioning condenser of the train less efficient. In this paper, the thermal environment of a long-term operating subway system tunnel in Shanghai, China is taken as the research object, and the night ventilation cooling strategy in non-air-conditioning season is proposed. CHAMPS-BES software was used to establish a soil model surrounding the subway tunnel to explore the effect of night ventilation. The temperature decay of the interval tunnel was simulated in the hottest month from December to March, with a large temperature difference between day and night, and in May and June, with a close distance to the hottest month. The results show that if the night ventilation is turned on for two months, the most suitable months to choose for cooling tunnel air during the summer are January and February, with reductions of 0.46, 0.48, and 0.39 °C, respectively. While if the night ventilation is turned on for three months, the most suitable months are January, February, and March, with temperature reductions of 0.60, 0.63, and 0.54 °C, respectively.

A Quantum Chemistry Insight into the Potential Role of the Singlet Oxygen-Acetone System as a Source for Production of Stable Secondary Organic Aerosols through a Multiwell Multipath Reaction.

The high abundance of acetone ((CH3)2C═O), which makes it a good candidate for oxygenated molecules, and the high reactivity of oxygen atoms in the first excited state O(1D) are two well-known facts in the chemistry of the atmosphere. In this research, we prove that the singlet oxygen and acetone system is capable of proceeding through multiwell multipath reactions, leading to the production of several organic aerosols. Hence, the nature of species released by the (CH3)2C═O + O(1D) reaction to air can be clarified by profound attention to the possible routes. To verify this, the singlet potential energy surface (PES) of the acetone + O(1D) reaction is investigated by using various validated quantum chemistry approaches, especially the high-cost BD(TQ) method. By the carefully chosen theoretical methods, we forecast all possible multistep routes with high accuracy for the production of possible adducts in reliable conditions. Also, we use the kinetic results of the well-proven theories (TST and RRKM) to show the importance and atmospheric relevance of the simulated reactions. So, the rate constants of the (CH3)2C═O + O(1D) reaction channels are computed at a large temperature range employing precise energetics and partition functions to show which products have a high percentage of yield. Moreover, the competitive canonical unified statistical (CCUS) model is utilized to show whether pressure influences the products generated by barrierless reactions. In addition, the thermodynamic functions of stationary points (at 298 K) and the rate constants of the found reaction routes demonstrate that the reaction adducts are very stable, so the reverse reactions have less importance compared to the forward reactions. In summary, this study illustrates how designed reaction routes could play a vital role in secondary aerosol formation in the atmosphere.

Facile Synthesis of Functional Polytrithiocarbonates from Multicomponent Tandem Polymerizations of CS2, Thiols, and Alkyl Halides.

Polytrithiocarbonates have attracted significant attention recently because of their good thermal stability, light refractivity, crystallinity, and mechanical properties; however, the exploration of their structures and functionalities has been limited by their synthetic approaches. Multicomponent polymerization featuring simple monomers, mild conditions, diversified product structures, and high efficiency could provide a powerful and versatile tool to synthesize various polytrithiocarbonates from commercially available monomers. Herein, a robust and efficient multicomponent tandem polymerization (MCTP) of CS2, dithiols, and alkyl halides was developed in DMF with K2CO3 at room temperature in air to synthesize 12 polytrithiocarbonates with diversified and systematically tuned structures, high molecular weights (Mns up to 37900 g/mol), and high yields (up to 93%). Depending on the different polymer backbone structures, amorphous polytrithiocarbonates showed excellent breaking elongations, and crystallinic polytrithiocarbonates possessed a large process temperature window (about 200 °C) and good mechanical performance (σB of 23.6 MPa and εB of 858%), whose tensile strength could be dramatically enhanced to 87.5 MPa after uniaxial extension deformation. The upper critical solution temperature (UCST) in organic solvents, together with nonconventional luminescence, were observed for the crystallinic polytrithiocarbonates, even without any aromatic ring. This efficient, robust, mild, and economic MCTP of CS2 thus opened up an avenue for the facile construction of polytrithiocarbonates with structural diversity, bringing modulable mechanical, thermal, luminescent, and thermal-responsive properties, which would greatly broaden the scope of structures and applications of sulfur-containing polymers.

Thermodynamic modeling and analysis of cascade heat pump enhanced by vapor injection for steam production

ABSTRACT The cascade heat pump (CHP) system shows significant potential in generating high-temperature steam by upgrading the ambient heat, whose energy efficiency is constrained by the large temperature difference between the air source and terminal output. This paper integrates vapor injection (VI) technology into both low-temperature and high-temperature stages of CHP system. A thermodynamic model of the vapor injection cascade heat pump (VI-CHP) system is constructed utilizing Aspen Hysys. Furthermore, the effects of intermediate temperature, VI separators’ temperatures, evaporator superheat and condenser subcooling on COP are analyzed. Simulation results demonstrated that the VI-CHP with dual-stage VI effectively enhances efficiency, reaching a nominal COP of 2.17, which indicates 8.6% improvement over the CHP system without VI. This paper analyzes the variation of system operation at intermediate temperatures from 45°C to 65°C, low-temperature flasher outlet steam temperatures from 33°C to 45°C, high-temperature flasher outlet steam temperatures from 74°C to 86°C, and superheat and subcooling degrees from 0°C to 10°C. Sensitivity analysis shows that maximum COP can attain 2.67 under the specified operational parameters. Finally, the impact of separators’ temperatures on the exergy efficiency is discussed. It is revealed that the exergy efficiency of the proposed system can reach 2.67.

Research on the low-temperature performance of basalt fiber- rubber powder modified asphalt mixtures under freeze-thaw in large temperature differences region

Accurately assessing the low-temperature performance of asphalt materials is important for asphalt pavements in cold regions with large temperature differences. This study investigates the effects of freeze-thaw cycles on the low-temperature performance of basalt fiber-rubber powder composite modified asphalt mixtures (BRMAM). The influence of basalt fibers content on the mechanical properties of asphalt binder was characterized through basic property tests and bending beam rheometer (BBR) assessments. A freeze-thaw cycle process was designed to stimulate the more realistic climate. The deterioration of low-temperature performance and freeze-thaw damage mechanism were analyzed by the splitting tensile test, three-point bending test and semi-circular bending (SCB) test. Methods suitable for evaluating BRMAM’s low-temperature performance were compared and explored. The results indicate that when fiber content was about 0.3%, the reinforcement effect of basalt fibers on asphalt material was more pronounced. As freeze-thaw cycles progress, the impact of frost heave force on the cracking resistance significantly increases, while the influence degree gradually decreases. Excess fibers reduced the interfacial bond between rubber powder modified asphalt and aggregate. When fiber content is between 0.2 and 0.4%, BRMAM demonstrates optimal low-temperature performance and the least sensitivity to freeze-thaw cycles. After 30 cycles, the TSR of BRMAM with 0.3% basalt fiber even reached 47.6%.

Impurity effects on kinetic ballooning instability in high q regions of tokamak plasmas

Abstract The impurity effects on kinetic ballooning modes (KBMs) in high q regions of tokamak plasmas are numerically investigated, using a full gyrokinetic description for main and impurity ions. The findings indicate that the critical plasma pressure ratio β c for KBM is significantly lower (higher) than the first (second) stable threshold β MHD predicted by MHD theory. The KBM exhibits stronger extended instabilities for low q , while the instability region of KBM becomes significantly narrow for high q , resulting in a more concentrated instability window (localized in narrow medium- β region). In addition, the contributions from electromagnetic effect and Shafranov shift are identified in detail, i.e. the electromagnetic destabilizing effect is suppressed by the Shafranov shift, and strong stabilizing effect of Shafranov shift for high β e or α on KBM is pronounced. The impurity ions with negative gradient ratio L e z have stabilizing (destabilizing) effects on KBMs for high (low) q . Such distinct behaviors are demonstrated to be associated with the used parameters close to the second and first unstable α region, i.e. the instability reduces and enhances with the increase of α , respectively. Significantly, the presence of impurities, regardless of the peaking directions of their density profiles, serves to stabilize KBMs and reduce the window of extended instability for high q region, which is in significant contrast with the results for low q region. Furthermore, high concentration, steep negative gradient ratio L ez , and high mass numbers of impurity ions as well as large temperature gradient η i and η e contribute to the stabilization of KBMs and improvement of confinement in high q regions of tokamaks. The region of stabilizing effect of magnetic shear on KBM, is found not belonging to the conventional magnetic shear region, but shows strong sensitivity to q value.

The Study on the Freeze–Thaw Deterioration of Soil Sites Modified with the ZDS-2 Organosilicon Reinforcement Agent

Due to the large temperature fluctuations between day and night during the transition from winter to spring, soil sites in seasonally frozen soil areas go through repeated freeze–thaw cycles. During these cycles, the water in the soil undergoes phase transformation and migration, which changes the physical and mechanical properties of the soil and directly affects the stability and durability of the soil site. In order to explore the feasibility of using the ZDS-2 organosilicon reinforcement agent for the anti-freeze-and-thaw protection of soil sites, Qingtai site soil and the ZDS-2 organosilicon reinforcement agent were used as raw materials. The optimal ratio of modified soil samples with different freeze–thaw cycles was obtained by laboratory tests. The strengthening mechanism of the ZDS-2 organosilicon reinforcement agent under freeze–thaw cycles was revealed by a microscopic test. The test results showed that the ZDS-2 organosilicon reinforcement agent can inhibit the volume expansion of soil samples caused by the freeze–thaw cycle. After nine freeze–thaw cycles, the shear strength of the soil samples, to which 15% ZDS-2 organosilicon reinforcement agent was added, increased by 53.4% on average compared with plain soil. The highly cross-linked organic–inorganic hybrid network structure formed between the siloxane group in the ZDS-2 organosilicon reinforcement agent and the soil particles can fill the pores and form a protective layer. The experimental results provided a basis and reference for the research of freeze–thaw-resistant materials for soil sites in seasonally frozen soil areas.

Temperature Control Strategy for Hydrogen Fuel Cell Based on IPSO-Fuzzy-PID

Hydrogen fuel cell water-thermal management systems suffer from slow response time, system vibration, and large temperature fluctuations of load current changes. In this paper, Logistic chaotic mapping, adaptively adjusted inertia weight and asymmetric learning factors are integrated to enhance the particle swarm optimization (PSO) algorithm and combine it with fuzzy control to propose an innovative improved particle swarm optimization-Fuzzy control strategy. The use of chaotic mapping to initialize the particle population effectively enhances the variety within the population, which subsequently improves the ability to search globally and prevents the algorithm from converging to a local optimum solution prematurely; by improving the parameters of learning coefficients and inertia weight, the global and local search abilities are balanced at different stages of the algorithm, so as to strengthen the algorithm’s convergence certainty while reducing the dependency on expert experience in fuzzy control. In this article, a fuel cell experimental platform is constructed to confirm the validity and efficiency of the recommended strategy, and the analysis reveals that the improved particle swarm optimization (IPSO) algorithm demonstrates better convergence performance than the standard PSO algorithm. The IPSO-Fuzzy-PID management approach is capable of providing a swift response and significantly diminishing the overshoot in the system’s performance, to maintain the system’s safe and stable execution.

Efficient synthesis of fluorinated triphenylenes with enhanced arene–perfluoroarene interactions in columnar mesophases

The high potential of non-covalent arene–fluoroarene intermolecular interactions in the design of liquid crystals lies in their ability to strongly promote self-assembly, improve the order and stability of the supramolecular mesophases, and enable tuneability of the optical and electronic properties, which can potentially be exploited for advanced applications in display technologies, photonic devices, sensors, and organic electronics. We recently successfully reported the straightforward synthesis of several mesogens containing four lateral aliphatic chains and derived from the classical triphenylene core self-assembling in columnar mesophases based on this paradigm. These mesogenic compounds were simply obtained in good yields by the nucleophilic substitution (SNFAr) of various types of commercially available fluoroarenes with the electrophilic organolithium derivatives 2,2'-dilithio-4,4',5,5'-tetraalkoxy-1,1'-biphenyl (2Li-BPn). In a continuation of this study, aiming at testing the limits of the reaction and providing a large diversity of structures, a structurally related series of compounds is reported here, namely 1,2,4-trifluoro-6,7,10,11-tetraalkoxy-3-(perfluorophenyl)triphenylenes (Fn). They were obtained by reacting the above mentioned 2,2’-dilithiobiphenyl derivatives with decafluorobiphenyl, C6F5–C6F5. These compounds differ from the previously reported series, 1,2,4-trifluoro-6,7,10,11-tetraalkoxy-3-aryltriphenylenes (PHn), solely by the substitution of the terminal phenyl ring with a pentafluorophenyl ring. Thus, as expected, they display a Colhex mesophase over large temperature ranges, with only small differences in the mesophase stability and transition temperatures. Furthermore, the presence of the terminal fluorophenyl group enables a subsequent second annulation, yielding a new series of extended polyaromatic mesomorphic compounds, i.e., 1,1',3,3',4,4'-hexafluoro-6,6',7,7',10,10',11,11'-octaalkoxy-2,2'-bitriphenylene (Gnm) which were found to display a Colrec mesophase. The specific nucleophilic substitution patterns of the Fn derivatives and the antiparallel stacking mode into columnar structures stabilized by arene–perfluoroarene intermolecular interactions were confirmed by the single-crystal structure of the alkoxy-free side chain analog, i.e., 1,2,4-trifluoro-3-(perfluorophenyl)triphenylene (F). UV–vis absorption and fluorescence emission spectroscopies reveal green photoluminescence with fluorescence quantum yields of up to 33% for the Fn derivatives. The J-aggregation for the inner fluorine-substituted dimers Gnm is energetically and stereoelectronically more favorable and G66 exhibits thin-film fluorescence with a large red-shift of the emission peak.

Evaluation of Cold Resistance in Alfalfa Varieties Based on Root Traits and Winter Survival in Horqin Sandy Land.

The Horqin Sandy Land in China is a key alfalfa production base, challenged by low winter temperatures and large diurnal temperature shifts, affecting alfalfa's winter survival. Alfalfa roots are the primary organs responsible for winter adaptability; consequently, by investigating the changes in the root physiology and nutritional components of alfalfa during the overwintering period, we can enhance our understanding of its mechanisms for cold resistance. Over the course of two years (2022-2023), field trials were conducted on 40 alfalfa varieties selected from both domestic and international sources for their potential cold resistance. This study assessed winter survival rates and analyzed root contents, including soluble sugars, starch, soluble proteins, and the concentrations of carbon (C), nitrogen (N), phosphorus (P) and their stoichiometric ratios. Principal component analysis, subordinate function analysis, and cluster analysis were employed for comprehensive evaluation. Biochemical markers varied significantly across varieties. The C, N, and starch contents in the roots were the main factors determining cold resistance. The varieties were categorized into four groups: Category I included five highly resistant varieties ('Baimu 202', 'WL168HQ', 'Zhongmu No. 1', 'Gongnong No. 1', and 'Legacy'); Category II consisted of six moderately resistant varieties; Category III included twenty-eight slightly resistant varieties; and Category IV contained one non-resistant variety ('3010'). This study recommends the adoption of the five varieties in Category I to enhance alfalfa cultivation in the Horqin region. This research provides valuable theoretical and practical guidance for improving the cultivation of alfalfa in the cold regions of northeastern China, supporting the development of the local livestock industry.