Effective Temperature Research Articles

Keldysh Field Theory of Dynamical Exciton Condensation Transitions in Nonequilibrium Electron-Hole Bilayers.

Recent experiments have realized steady-state electrical injection of interlayer excitons in electron-hole bilayers subject to a large bias voltage. In the ideal case in which interlayer tunneling is negligibly weak, the system is in quasiequilibrium with a reduced effective band gap. Interlayer tunneling introduces a current and drives the system out of equilibrium. In this work we derive a nonequilibrium field theory description of interlayer excitons in biased electron-hole bilayers. In the large bias limit, we find that p-wave interlayer tunneling reduces the effective band gap and increases the effective temperature for intervalley excitons. We discuss possible experimental implications for InAs/GaSb quantum wells and transition metal dichalcogenide bilayers.

STUDY ON THE INFLUENCE OF RATING CHARGE ON TEMPERATURE AND PHASE BEHAVIOR OF STABILIZED MATRIX WAX-BASED THERMAL STORAGE

The rating charge characteristic is crucial for the heat energy storage, particularly for low-temperature system which uses paraffin wax. The influence of different rating charge causes severe temperature fluctuation, which is undesirable for the heat system. It is affected by unstable phase transformation, reducing the heat distribution and makes the average rating charge insufficient. In this work, the fluctuation can be minimized by adding polyethylene plastic as phase stabilizer for the wax. The polyethylene is added by ratio of weight of 15% from the total mass of 134 grams. Each material is mixed in the liquid state, stirred and molded into the apparatus. The phase transition evaluation is performed, showing the mixture indicates an additional transition peak after the principal phase transformation, ranging between 15.26 °C – 19.34 °C (melting) and 11.98 °C – 9.45 °C (freezing). The steady operation makes the lowest rating variation is only 0.3 °C/min, which is obtained by the mixture of wax and polyethylene. In the same rating charge, the wax has rating variation of 2.9 °C/min, signifying the effect of unsteady melting transition. It clearly demonstrates the addition of polyethylene for the mixture promotes a better phase transformation under various rating charge, maintaining the effective temperature distribution for the heat storage.

Migration and Evolution of giant ExoPlanets (MEEP). I. Nine Newly Confirmed Hot Jupiters from the TESS Mission

Hot Jupiters were many of the first exoplanets discovered in the 1990s, but in the decades since their discovery the mysteries surrounding their origins have remained. Here we present nine new hot Jupiters (TOI-1855 b, TOI-2107 b, TOI-2368 b, TOI-3321 b, TOI-3894 b, TOI-3919 b, TOI-4153 b, TOI-5232 b, and TOI-5301 b) discovered by NASA’s TESS mission and confirmed using ground-based imaging and spectroscopy. These discoveries are the first in a series of papers named the Migration and Evolution of giant ExoPlanets survey and are part of an ongoing effort to build a complete sample of hot Jupiters orbiting FGK stars, with a limiting Gaia G-band magnitude of 12.5. This effort aims to use homogeneous detection and analysis techniques to generate a set of precisely measured stellar and planetary properties that is ripe for statistical analysis. The nine planets presented in this work occupy a range of masses (0.55M J < MP < 3.88M J) and sizes (0.967R J < RP < 1.438R J) and orbit stars that have an effective temperature in the range of 5360 K < T eff < 6860 K with Gaia G-band magnitudes ranging from 11.1 to 12.7. Two of the planets in our sample have detectable orbital eccentricity: TOI-3919 b ( e=0.259−0.036+0.033 ) and TOI-5301 b ( e=0.33−0.10+0.11 ). These eccentric planets join a growing sample of eccentric hot Jupiters that are consistent with high-eccentricity tidal migration, one of the three most prominent theories explaining hot Jupiter formation and evolution.

Evaluation of the Physicochemical and Microbiological quality of Strawberry pulp in a Moroccan Food Industry Company

The present work was undertaken within a Moroccan agri-food production company to evaluate and monitor the physicochemical (pH, Brix degrees, etc.) and microbiological parameters of strawberry pulp destined for export and other companies. After pasteurization, these analyses were carried out on the raw material and the strawberry pulp. The results showed that the physicochemical and microbiological parameters studied met standards, with a total absence of pathogenic microorganisms. The ultimate aim of the present study is to find pasteurization conditions that are effective against all pathogens while maintaining the organoleptic quality of the finished product. Moreover, consequently, to reduce energy losses within this company. To this end, we have shown that the effective pasteurization temperature is 85°C/7.5 min or 89°C/4.6min.

Effects of Thermo-Chromic materials (TCMs) on the performance of asphalt pavement with phase change materials (PCMs)

Temperature regulation is crucial for the longevity of pavements. Thermo-Chromic Materials (TCMs) is proposed for effective temperature regression in pavements with Phase Change Materials (PCMs). In this paper, the performance of asphalt pavements in a typical year is investigated with Abaqus, including the peak temperature, the variation of surface temperature and the properties of PCMs before and after the adoption of TCMs. The incorporation of PCMs resulted in a reduction of peak pavement temperatures by 1.3 °C, while the addition of TCMs further decreased temperatures by 38.5 °C. By comparison with the results with and without PCMs as well as with and without TCMs, it is concluded that both PCMs and TCMs may reduce the peak temperature of asphalt pavements. However, TCMs may further regress the peak temperature but does not result in the time delay of peak temperature, as PCMs does. The peak temperature positively correlates with the variation of surface temperature. Nevertheless, although only four types of correlation between the temperature property of TCMs and that of PCMs are involved, the profile or status of PCMs is much more complicatedly influenced after the adoption of TCMs, indicating the interaction between TCMs and PCMs. More time of PCMs is in the phase of solid, due to the modulation of solar radiation. As far as the peak temperature is considered, it is also possible to reduce the amount of PCMs applied in pavements, with the adoption of TCMs. According to the results in this paper, the application of TCMs in an asphalt pavement with PCMs may be an effective way to reduce the peak temperature, to regress the daily variation degree as well as to improve the performance of PCMs.

Helium in Exoplanet Exospheres: Orbital and Stellar Influences

Searches for helium in the exospheres of exoplanets via the metastable near-infrared triplet have yielded 17 detections and 40 nondetections. We performed a comprehensive reanalysis of published studies to investigate the influence of stellar X-ray and extreme-ultraviolet (XUV) flux and orbital parameters on the detectability of helium in exoplanetary atmospheres. We identified a distinct “orbital sweet spot” for helium detection, 0.03 to 0.08 au from the host star, where the majority of detections occurred. This sweet spot is influenced by the stellar luminosity and planet size. Notably, a lower ratio of XUV flux to mid-UV flux is preferred for planets compared to nondetections. We also found that helium detections occur for planets around stars with effective temperatures of 4400–6500 K (i.e., spectral type K and G stars), with a sharp gap between 5400 and 6000 K, where no detections occur. We also report an upper-limit efficiency of 6% for energy-limited atmospheric escape from our analysis. Additionally, our analysis of the cumulative XUV flux versus escape velocity shows planets with helium detections above the “cosmic shoreline,” where atmospheres are not thought to be present, suggesting the shoreline needs revision. The unexpected trends revealed in our meta-analysis can contribute to a better understanding of star–planet interaction and exosphere evolution.

Topological Learning Approach to Characterizing Biological Membranes.

Biological membranes play key roles in cellular compartmentalization, structure, and its signaling pathways. At varying temperatures, individual membrane lipids sample from different configurations, a process that frequently leads to higher-order phase behavior and phenomena. Here, we present a persistent homology (PH)-based method for quantifying the structural features of individual and bulk lipids, providing local and contextual information on lipid tail organization. Our method leverages the mathematical machinery of algebraic topology and machine learning to infer temperature-dependent structural information on lipids from static coordinates. To train our model, we generated multiple molecular dynamics trajectories of dipalmitoyl-phosphatidylcholine membranes at varying temperatures. A fingerprint was then constructed for each set of lipid coordinates by PH filtration, in which interaction spheres were grown around the lipid atoms while tracking their intersections. The sphere filtration formed a simplicial complex that captures enduring key topological features of the configuration landscape using homology, yielding persistence data. Following fingerprint extraction for physiologically relevant temperatures, the persistence data were used to train an attention-based neural network for assignment of effective temperature values to selected membrane regions. Our persistence homology-based method captures the local structural effects, via effective temperature, of lipids adjacent to other membrane constituents, e.g., sterols and proteins. This topological learning approach can predict lipid effective temperatures from static coordinates across multiple spatial resolutions. The tool, called MembTDA, can be accessed at https://github.com/hyunp2/Memb-TDA.

Signature of High-amplitude Pulsations in Seven δ Sct Stars via TESS Observations

The regular behavior of the pulsations of high-amplitude δ Sct (HADS) stars gives a greater chance to investigate the interiors of stars. We analyzed seven HADS stars showing peak-to-peak amplitudes of more than 0.3 mag that were newly observed by TESS. We obtained that TIC 374753270, TIC 710783, and TIC 187386415 pulsate in fundamental radial mode; also, TIC 130474019 and TIC 160120432 show double radial modes. On the other hand, TIC 148357344 and TIC 278119167 demonstrate triple-mode behavior. Our analysis shows that these seven stars are close to the red edge of the (inside) instability strip in the Hertzsprung–Russell diagram. The fundamental mode of these seven targets follows the period–luminosity (PL) relation for δ Sct stars. However, TIC 278119167 deviates slightly from the fundamental PL relation. The double-mode and triple-mode HADS stars (TIC 130474019, TIC 160120432, TIC 148357344, and TIC 278119167) are in agreement with the period ratio ranges (fundamental to first and second overtones). Using the information of 176 HADS stars (Netzel and Smolec), we find a scaling relation ( [Fe/H]∝log(M7.95±0.15L−1.83±0.11P00.79±0.14Teff0.047±0.02 )) between the metallicity ([Fe/H]) and mass (M), luminosity (L), effective temperature (T eff), and the fundamental period (P0). We estimate the metallicity of the seven newly identified HADS stars ranging from −0.62 to 0.37 dex.

Stellar spectral template library construction based on generative adversarial networks

Stellar spectral template libraries play an important role in the automated analysis of stellar spectra. Synthetic template libraries cover a very large parameter space but suffer from poor matching with observed spectra. In this study, we propose a synthetic-to-observed spectral translation (SOST) method based on generative adversarial networks. The SOST method is able to calibrate synthetic spectra by converting them to the corresponding observed spectra. We applied this method to Kurucz synthetic spectra and observed spectra data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). After that, we constructed a stellar spectral library with uniform and broad parameter distributions using the SOST-corrected Kurucz synthetic spectra. Our stellar spectral template library contains 2431 spectra spanning a parameter space of 3500–8000 K for effective temperature (Teff), 0.0–5.0 dex for surface gravity (log g), and −2.0–0.5 dex for metallicity ([Fe/H]). The spectra in the library have a resolution of R ∼ 1800 and cover the wavelength range 3900–8700 Å. In order to verify the accuracy of this template library, we used the template library and the template-matching algorithm to derive the parameters of the PASTEL database. Compared to measurements using the original synthetic template library, the accuracies of the three parameters, Teff, log g, and [Fe/H], are improved, from 140 K, 0.31 dex, and 0.21 dex to 121 K, 0.26 dex, and 0.13 dex, respectively. In addition, we re-parameterised more than six million stellar spectra released by LAMOST DR8.

Research and development of corrosion monitoring sensor for bridge cable using electrical resistance probes technique

A cable corrosion monitoring sensor with a temperature compensation probe has been designed and manufactured to monitor the corrosion of high-strength steel wires in the transition zone between the cable body and the anchorage. The influence of temperature and tensile force on the resistance of steel wires was thoroughly investigated. Reliability tests were conducted on the temperature compensation probe, along with salt spray corrosion tests on the corrosion sensor. The research results demonstrated that, compared to the temperature sensor, temperature compensation probe can better reflect the actual temperature of the corrosion sensor and provide effective temperature compensation for the corrosion sensor. Moreover, the developed corrosion sensor can effectively reflect the mass loss rate of the corrosion probe. The sensor is capable of detecting a corrosion level as low as 0.02 % of the complete steel wire mass, which corresponds to an average corrosion depth of 0.412 μm.

Temperature analysis and prediction for road-rail steel truss cable-stayed bridges based on the structural health monitoring

A growing number of road-rail steel truss bridges have been built worldwide in recent years. Due to the complex cross-sectional structure and increasing span length, these main girders are prone to developing uneven temperature fields and significant local thermal effects, which can lead to excessive temperature stresses and structural damage. An accurate assessment of the temperature distribution in road-rail steel truss girders is critical as it aids in the thermal response analysis of the bridge and the structural safety evaluation. The paper analyses the temperature distribution of the road-rail steel truss girder base on the light conditions and the structure of the main girder. A modified method for calculating the effective temperature (ET) and temperature difference (TD) is also proposed. Comparing with the conventional regional weighted averaging method, the modified method improves the accuracy of ET calculation by 20 %. A prediction method based on the long short-term memory (LSTM) network is proposed, which estimates ET and TD for road-rail steel truss girders based on the environment around the bridge. The deep learning-based method improves accuracy by 40 % compared with the conventional linear regression method for ET prediction. Meanwhile, the proposed method alleviates the current lack of prediction methods for TD of road-rail steel truss girders. A detailed analysis of the temperature of a road-rail steel truss bridge is also presented based on the structural health monitoring (SHM) system. A negative vertical temperature difference was observed in the fringe truss. The maximum transverse temperature difference (TTD) was much greater than the maximum vertical temperature difference (VTD). The above features deserve extra attention from bridge designers.

Estimating the Atmospheric Parameters of Early-type Stars from the Chinese Space Station Telescope (CSST) Slitless Spectra Survey

The measurement of atmospheric parameters is fundamental for scientific research using stellar spectra. The Chinese Space Station Telescope (CSST), scheduled to be launched in 2024, will provide researchers with hundreds of millions of slitless spectra for stars during a 10 yr survey. And machine learning has unparalleled efficiency in processing large amounts of data compared to manual processing. Here we studied the stellar parameters of early-type stars (effective temperature T eff > 15,000 K) based on the design indicators of the CSST slitless spectrum and the machine learning algorithm, Stellar LAbel Machine. We used the Potsdam Wolf–Rayet (POWR) synthetic spectra library for cross validation. Then we tested the reliability of machine learning results by using the Next Generation Spectrum Library (NGSL) from Hubble Space Telescope observation data. In an ideal case for full-wavelength spectra without any noise, the average absolute value of the relative deviation is 2.7% (800 K) for T eff, and 3.5% (0.11 c.g.s) for surface gravity logg . We use the spectra with the impact of interstellar extinction (AV = 0, 0.5, 1, 1.5, 2 mag) and radial velocity (RV = −50, −30, 0, 30, 50 km s−1) from the POWR library as the test set. When RV = 0 km s−1 and AV = 0 mag, the average value and standard deviation for 3 wavelength ranges (2550–4050 Å (R = 287); 4050–6300 Å (R = 232); 6300–10000 Å (R = 207)) are –66 ± 3351 K, 550 ± 3536 K, and 356 ± 3616 K for T eff, and 0.004 ± 0.224 c.g.s, –0.024 ± 0.246 c.g.s, and 0.01 ± 0.212 c.g.s for logg . When using the observed data from NGSL as the testing samples, the deviation of T eff is less than 5% (1500 K), and the deviation of logg is less than 11% (0.33 c.g.s). In addition, we also test the influence of shifting of spectra on the parameters’ accuracy. The deviation of T eff for the case with a shift of 5 Å and 10 Å are 3.6% (1100 K) and 4.3% (1300 K), respectively; the deviation of logg are 4.2% (0.13 c.g.s) and 5.1% (0.15 c.g.s). These results demonstrate that we can obtain relatively accurate stellar parameters of a population of early-type stars with the CSST slitless spectra and a machine-learning method.

Extracting the speed of sound in quark–gluon plasma with ultrarelativistic lead–lead collisions at the LHC

Ultrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark–gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we determine the speed of sound in an extended volume of quark–gluon plasma using lead–lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 0.607 nb−1. The measurement is performed by studying the multiplicity dependence of the average transverse momentum of charged particles emitted in head-on PbPb collisions. Our findings reveal that the speed of sound in this matter is nearly half the speed of light, with a squared value of 0.241±0.002(stat)±0.016(syst) in natural units. The effective medium temperature, estimated using the mean transverse momentum, is 219±8(syst)MeV . The measured squared speed of sound at this temperature aligns precisely with predictions from lattice quantum chromodynamic (QCD) calculations. This result provides a stringent constraint on the equation of state of the created medium and direct evidence for a deconfined QCD phase being attained in relativistic nuclear collisions.

Fuzzy-based thermal management control analysis of vehicle air conditioning system

Automotive air conditioning (ACC) system designers faced unique challenges in satisfying customer demands for efficient and comfortable operation across a broad temperature range. The AAC system's effective or fixed temperature setting makes this possible. Many climate control models, like the state flow switching controller in MATLAB control, must handle heating and cooling due to a single Simulink/environment software and frequently contain steady-state error (SSE). The present research proposes to design an automatic temperature control scheme and fuzzy logic control (FLC) for an automotive air-conditioned (AAC) system. In addition, it employs MATLAB Simulink/environment software to model the fuzzy control technique to analyze the AAC system's response. A simulation has been set up to evaluate the suggested system performance to match a selection of user-specified reference temperatures and compressor speeds. Compared with a PID-controlled AAC system, the proposed FLC-based system reduced the undershoot to only 2.30% from 33.30% respectively, and was robust, quicker, and better at controlling temperature.

A channel with hybrid twisted tapes for immersion cooling battery thermal management system

The promotion of transport electrification represents a pivotal strategy in addressing the energy crisis, wherein the adoption of the electric vehicles (EVs) plays a crucial role towards the realization of this goal. Immersion cooling battery thermal management systems (ICBTMS) emerge as an innovative strategy to guarantee the safe operation of the EVs. This study proposes an immersion cooling battery thermal management system with twisted tapes channel (TT-ICBTMS), offering effective temperature regulation of the battery pack. Drawing upon the experimental and simulation results associated with the high-capacity square battery, this paper selects a channel for further experimentation and simulation to elucidate the mechanisms by which various cooling methods and twisted tape configurations impact cooling efficacy. Subsequently, predicated on the comprehensive evaluation results, the channel with the hybrid twisted tapes (H-TT) is proposed. The H-TT, comprising both reverse twisted tapes (R-TT) and hollow reverse twisted tapes (HR-TT), serves to mitigate battery temperature rise, diminish pressure drop, and reduce the maximum temperature difference. This paper examines the heat transfer performance of the channel with the H-TT, revealing that, at the flow rate of 0.5 L/min and the discharge rate of 3C (Idischarge = 654 A), the maximum temperature of battery reaches merely 36.47 °C, with the maximum temperature difference of battery module being confined to 1.81 °C. Finally, a methodology employing the porous structure as the replacement for the H-TT in simulations is introduced in this study, a tactic validated through juxtaposition of experimental and simulation results, and subsequently applies this method in battery pack simulations. The simulation results demonstrate that, within the immersion cooling battery thermal management system with hybrid twisted tapes channel (H-TT-ICBTMS), the maximum temperature is confined to a mere 36.29 °C, with the maximum temperature difference limited to 2.63 °C, under the conditions of the flow rate of 22.5 L/min and the discharge rate of 3C (Idischarge = 654 A). This study posits that the H-TT-ICBTMS heralds novel thermal management paradigms for EVs.

Surface parameterisation and spectral synthesis of rapidly rotating stars. Vega as a testbed

Spectral synthesis is a powerful tool with which to find the fundamental parameters of stars. Models are usually restricted to single values of temperature and gravity, and assume spherical symmetry. This approximation breaks down for rapidly rotating stars. This paper presents a joint formalism to allow a computation of the stellar structure — namely, the photospheric radius, $R$, the effective temperature, $T_ eff $, and gravity, $g_ eff $ — as a function of the colatitude, theta , for rapid rotators with radiative envelopes, and a subsequent method to build the corresponding synthetic spectrum. The structure of the star is computed using a semi-analytical approach, which is easy to implement from a computational point of view and which reproduces very accurately the results of much more complex codes. Once $R( eff and eff are computed, the suite of codes atlas and synthe by R. Kurucz are used to synthesise spectra for a mesh of cells in which the star is divided. The appropriate limb-darkening coefficients are also computed, and the final output spectrum is built for a given inclination of the rotation axis with respect to the line of sight. All the geometrical transformations required are described in detail. The combined formalism has been applied to Vega, a rapidly rotating star almost seen pole-on, as a testbed. The structure reproduces the results from interferometric studies and the synthetic spectrum matches the peculiar shape of the spectral lines well. Contexts where this formalism can be applied are outlined in the final sections.

Effective temperatures in nonequilibrium statistical physics.

This paper summarizes two related effective-temperature analyses of nonequilibrium phenomena: first, dislocations in deforming crystals and, second, chaotic behaviors of defects in thermally driven Rayleigh-Bénard hydrodynamic systems. The results are encouraging for broader applications of this statistical concept.

Evolution of BD-14 3065b (TOI-4987b) from giant planet to brown dwarf as possible evidence of deuterium burning at old stellar ages

The present study confirms BD-14\,3065b as a transiting planet-brown dwarf in a triple-star system, with a mass near the deuterium-burning boundary. BD-14\,3065b has the largest radius observed within the sample of giant planets and brown dwarfs around post-main sequence stars. Its orbital period is 4.3 days and it transits a subgiant F-type star with a mass of $M_ odot $, a radius of $R_ odot $, an effective temperature of $T_ eff and a metallicity of $-0.34 By combining TESS photometry with high-resolution spectra acquired with the TRES and Pucheros+ spectrographs, we measured a mass of $M_p=12.37 and a radius of $R_p=1.926 Our discussion of potential processes that could be responsible for the inflated radius led us to conclude that deuterium burning is a plausible explanation for the heating taking place in BD-14\,3065b's interior. Detections of the secondary eclipse with TESS photometry enabled a precise determination of the eccentricity, $e_p=0.066 and reveal that BD-14\,3065b has a brightness temperature of $3520 130$\,K. With its unique characteristics, BD-14\,3065b presents an excellent opportunity to study its atmosphere via thermal emission spectroscopy.

A novel method of flash‐hydrolysis assisted pigment extraction (carotenoids) from microalgae biomass

AbstractThe human body can easily convert β‐carotene into retinol (a precursor of vitamin A), a significant ingredient in dietary supplements. The need for commercial natural pigment production, including β‐carotene, has led to intensive research in this area. Processing after biosynthesis is a vital stage that involves the use of nontoxic solvents, efficient mechanical disruption of cells, and the isolation of the required compounds. With the growing popularity of green extraction methods and the increasing market demand for carotenoids due to their health benefits, the use of clean, nontoxic, flash‐hydrolyzed biomass for carotenoid production presents a significant advantage. Furthermore, the remaining biomass can serve as a protein source for animal feed, thereby aligning with the principles of the biorefinery concept. In this study, our aim was to optimize the disruption of cells in two microalgal species using flash hydrolysis (FH). We applied two distinct levels of pressure and four separate temperature conditions over a brief residence time. Following this, we employed an ethanol extraction method to assess the efficiency of carotenoid pigment extraction. Flash hydrolysis is a chemical‐free subcritical water‐based continuous‐flow process, injected with wet biomass slurry at a high temperature (150–250 °C) for a very short time (8–12 s) to obtain bioproducts. In this study, we discovered that the pigment β‐carotene constituted 0.04 to 0.3% of the dry biomass in the case of Chlorella vulgaris. Bands of lutein and zeaxanthin were also observed in the thin layer chromatography (TLC) analysis of the treated slurry. This was achieved under conditions of an effective temperature of 200 °C and a pressure of 1700 psi. The Arthrospira platensis (1Tex), β‐carotene yield was 0.014 to 0.021% of dry biomass. Some lutein and zeaxanthin bands were also found in the treated slurry with an effective temperature of 150 °C and 1000 psi pressure. This study reports pigment extraction by FH for the first time. It is a viable process to scale up high‐value natural products like carotenoids from microalgae at the industrial level without adverse environmental impacts. Due to low residence time, the temperature does not have a negative effect on pigments; cell rupture was accomplished effectively using water as a solvent. A considerable amount of pigment could be recovered from microalgae at specific combinations of temperature and pressure depending on the type of cell wall that microalgae possess.

The time evolution of the ultraviolet habitable zone

ABSTRACT For stars hosting Circumstellar Habitable Zone (CHZ) exoplanets, we investigate the time evolution of their ultraviolet habitable zone (UHZ), the annular region around a star where an exoplanet could experience a suitable ultraviolet environment for the presence and emergence of life, and the possible intersection of the UHZ with the CHZ. To estimate their ultraviolet (UV) luminosity evolution, and therefore the evolution of their UHZ, we analyse Swift-UV/Optical telescope observations and adopt the near-UV luminosity evolutionary tracks derived using GALEX observations of young moving groups. We find that an intersection between CHZ and UHZ could exist (or have existed) around all stars of our sample at different epochs, except for the coldest M-dwarfs (temperature $\lesssim 2800$ K, e.g. Trappist-1). For hotter M-dwarfs the formation of ribonucleic acid precursors through cyanosulfidic chemistry triggered by near-UV radiation could occur during the first $\simeq$1–2 Gyr. The radial extension and time duration of the CHZ–UHZ intersection increase with the stellar effective temperature and the exoplanet atmospheric transmissivity at near-UV wavelengths. Within our sample, Proxima Centauri represents a golden target for the quest of life outside the Solar system because it experienced a long-lasting and more extended, compared to similar M-dwarfs, CHZ–UHZ intersection.