Ultraviolet Behavior Research Articles

Constraints on Covariant Horava-Lifshitz Gravity from precision measurement of planetary gravitomagnetic field

Abstract As a generalization of Einstein’s theory, Horava-Lifshitz has attracted significant interests due to its healthy ultraviolet behavior. In this paper, we analyze the impact of the Horava-Lifshitz corrections on the gravitomagnetic field. We propose a new planetary gravitomagnetic field measurement method with the help of the space-based laser interferometry, which is further used to constrain the Horava-Lifshitz parameters. Our analysis shows that the high-precision laser gradiometers can indeed limit the parameters in Horava-Lifshitz gravity and improve the results by one or two orders when compared with the existing theories. Our novel method provides insights into constraining the parameters in the modified gravitational theory, which facilitates a deeper understanding of this complex framework and paving the way for potential technological advancements in the field.

Ultraviolet Nonlinear Optical Single Crystals of A Three‐Dimensional Chiral Covalent Framework Containing Te−O−B−O Bonds

AbstractExtending covalent organic frameworks (COFs) into crystalline carbon‐free covalent backbones is an important strategy to endow these materials with more exotic functions. Integrating metal‐free inorganic and organic components into one covalent framework is an effective way to address the issue of poor thermal/solvent stability in the field of nonlinear optics (NLO). However, constructing such structures is very challenging. Here, we linked 3‐connected nods (BO3) and 2‐connected organic building blocks (Te(Ph)2) together to produce colorless single crystals (size up to 400 μm) of a three‐dimensional (3D) chiral covalent framework (CityU‐22). The single‐crystal X‐ray diffraction (SCXRD) analysis reveals that CityU‐22 has a non‐carbon Te−O−B−O bond‐based network with the srs topology. The chiral CityU‐22 displays good stability under the treatment of different common solvents or heat (the decomposition temperature above 300 °C). Due to its non‐π‐conjugated backbone (−Te−O−B−O−), CityU‐22 shows an ultraviolet NLO behavior with a second‐harmonic generation (SHG) response similar to KH2PO4 (KDP).

Ultraviolet Nonlinear Optical Single Crystals of A Three-Dimensional Chiral Covalent Framework Containing Te-O-B-O Bonds.

Extending covalent organic frameworks (COFs) into crystalline carbon-free covalent backbones is an important strategy to endow these materials with more exotic functions. Integrating metal-free inorganic and organic components into one covalent framework is an effective way to address the issue of poor thermal/solvent stability in the field of nonlinear optics (NLO). However, constructing such structures is very challenging. Here, we linked 3-connected nods (BO3) and 2-connected organic building blocks (Te(Ph)2) together to produce colorless single crystals (size up to 400 µm) of a three-dimensional (3D) chiral covalent framework (CityU-22). The single-crystal X-ray diffraction (SCXRD) analysis reveals that CityU-22 has a non-carbon Te-O-B-O bond-based network with the srs topology. The chiral CityU-22 displays good stability under the treatment of different common solvents or heat (the decomposition temperature above 300 °C). Due to its non-π-conjugated backbone (-Te-O-B-O-), CityU-22 shows an ultraviolet NLO behavior with a second-harmonic generation (SHG) response similar to KH2PO4 (KDP).

The National Cancer Aid monitoring (NCAM-online) of ultraviolet radiation risk and protection behavior: a population-based observational trend study with four annual online survey waves

BackgroundUltraviolet (UV) radiation is the most important risk factor for skin cancer development. Sunlight is the main source of UV radiation in the general population. In addition, tanning beds are a source of artificial UV radiation. Since the incidence of skin cancer is increasing worldwide, it is necessary to monitor UV-related risk behaviors such as intentional indoor and outdoor tanning, as well as sun protection behavior in the general population and specific subgroups and settings. This is the aim of the National Cancer Aid Monitoring online (NCAM-online), a continuation and further development of the NCAM.MethodsThe NCAM-online is a longitudinal trend study consisting of four annual survey waves. Each year, 4,000 individuals aged 16–65 years living in Germany will be surveyed using online questionnaires. Each year, intentional indoor and outdoor tanning will be assessed. In addition, varying specific topics regarding skin cancer prevention, such as the utilization of skin cancer screening, will be addressed in the questionnaires.DiscussionThe findings of the NCAM-online will provide an important basis for the German Cancer Aid and Working Group on Dermatologic Prevention (Arbeitsgemeinschaft Dermatologische Prävention, ADP) to develop targeted prevention campaigns and projects aimed at preventing skin cancer. The explorative nature of the NCAM-online allows for the identification of new potential starting points for prevention and education. In addition, the longitudinal design allows for a description of the trend in the prevalence of intentional tanning. For tanning bed use, representative trend data from 2012 are available for Germany, to which NCAM-online will add annual data until 2027.

The Unruh–DeWitt model and its joint interacting Hilbert space

In this work we make the connection between the Unruh–DeWitt (UDW) particle detector model applied to quantum field theory in curved spacetimes and the rigorous construction of the spin-boson (SB) model. With some modifications, we show that existing results about the existence of a SB ground state can be adapted to the UDW model. In the most relevant scenario involving massless scalar fields in (3+1)-dimensional globally hyperbolic spacetimes, where the UDW model describes a simplified model of light–matter interaction, we argue that common choices of the spacetime smearing functions regulate the ultraviolet behaviour of the model but can still exhibit infrared (IR) divergences. In particular, this implies the well-known expectation that the joint interacting Hilbert space of the model cannot be described by the tensor product of a two-dimensional complex Hilbert space and the Fock space of the vacuum representation. We discuss the conditions under which this problem does not arise and the relevance of the operator-algebraic approach for better understanding of particle detector models and their applications.Our work clarifies the connection between obstructions due to Haag’s theorem and IR bosons in the SB models, and paves the way for more rigorous study of entanglement and communication in the UDW framework involving multiple detectors.

Study on multifunctional resistive switching and UV light detection characteristics in p-PEDOT:PSS/i-BFO/n-ZnO hybrid structures

The present research work based on the newly prepared organic-inorganic hybrid heterostructure will be exploited to develop a multifunctional device including non-volatile resistance switching memory devices, and ultraviolet (UV) light detection behavior for the first time based on p-PEDOT:PSS/i-BFO/n-ZnO junctions. Using a spray pyrolysis technique, n-type zinc oxide (ZnO) and i-type bismuth ferrite (BiFeO3) thin film layers were prepared on the clean glass substrates at temperature 673 K. Using a spin coater method, the p-PEDOT:PSS were grown upon a bismuth ferrite (BiFeO3) thin film with a constant spin velocity of 2000 rpm and heated at 363 K. The current (I)–voltage (V), photoresponse characteristics and resistive switching (RS) behavior of the fabricated p-PEDOT:PSS/i-BFO/n-ZnO hybrid devices were carried out. The device shows high photoresponsivity (R) of 0.001 285 A W−1 and fast photoresponse switching speed with the measured rise and fall time of 493 and 970 ms respectively. Based on the electrical properties, a conductive filament formation/rupture mechanism is proposed to explain the observed RS characteristics.

The force-force correlator at the hard thermal scale of hot QCD

High-energy particles traversing the Quark-Gluon plasma experience modified (massive) dispersion, although their vacuum mass is negligible compared to the kinetic energy. Due to poor convergence of the perturbative series in the regime of soft loop momenta, a more precise determination of this effective mass is needed. This paper continues our investigation on the factorisation between strongly-coupled infrared classical and perturbative ultraviolet behavior. The former has been studied non-perturbatively within EQCD by determining a non-local operator on the lattice. By computing the temperature-scale contribution to the same operator in 4D QCD at next-to-leading order (NLO), we remove the ultraviolet divergence of the EQCD calculation with an opposite infrared divergence from the hard thermal scale. The result is a consistent, regulator-independent determination of the classical contribution where the emergence of new divergences signals sensitivities to new regions of phase space. We address the numerical impact of the classical and NLO thermal corrections on the convergence of the factorised approach and on the partial applicability of our results to calculations of transport coefficients.

Optical Modulation of MoTe2/Ferroelectric Heterostructure via Interface Doping.

Optical modulation through interface doping offers a convenient and efficient way to control ferroelectric polarization, thereby advancing the utilization of ferroelectric heterostructures in nanoelectronic and optoelectronic devices. In this work, we fabricated heterostructures of MoTe2/BaTiO3/La0.7Sr0.3MnO3 (MoTe2/BTO/LSMO) and demonstrated opposite ultraviolet (UV) light-induced polarization switching behaviors depending on the varied thicknesses of MoTe2. The thickness-dependent band structure of MoTe2 film results in interface doping with opposite polarity in the respective heterostructures. The polarization field of BTO interacts with the interface charges, and an enhanced effective built-in field (Ebi) can trigger the transfer of massive UV light-induced carriers in both MoTe2 and BTO films. As a result, the interplay among the contact field of MoTe2/BTO, the polarization field, and the optically excited carriers determines the UV light-induced polarization switching behavior of the heterostructures. In addition, the electric transport characteristics of MoTe2/BTO/LSMO heterostructures reveal the interface barrier height and Ebi under opposite polarization states, as well as the presence of inherent in-gap trap states in MoTe2 and BTO films. These findings represent a further step toward achieving multifield modulation of the ferroelectric polarization and promote the potential applications in optoelectronic, logic, memory, and synaptic ferroelectric devices.

All‐Solution‐Processed InGaO/PbI2 Heterojunction for Self‐Powered Omnidirectional Near‐Ultraviolet Photodetection and Imaging

AbstractThe persistent photocurrent (PPC) and high carrier concentration are challenging the ultraviolet photodetection behaviors of amorphous InGaO films. Herein, InGaO/PbI2 heterojunction is constructed by an all‐solution synthesis process to set up a built‐in electric field at the heterojunction interface, which is aimed at the inhibition of PPC, suppression of dark current, and promotion of photogenerated carrier separation. With an optimized In content of 90%, the as‐fabricated InGaO/PbI2 heterojunction photodetector exhibits excellent self‐powered near‐ultraviolet photodetection behaviors with high Ilight/Idark ratio of 104, ultralow dark current of 10−13 A and fast response times of 0.8/0.6 ms. Additionally, benefiting to the all‐solution synthesis process and amorphous characteristic, InGaO/PbI2 heterojunction can be implanted onto any useful substrates to achieve the specific function of photodetection. The as‐fabricated InGaO/PbI2 heterojunction flexible self‐powered photodetector exhibits outstanding mechanical flexibility, bending endurance, and photoelectric stability. When the InGaO/PbI2 heterojunction is implanted onto the transparent substrate, it demonstrates excellent omnidirectional self‐powdered photodetection performance and imaging capability. All results promise all‐solution‐processed InGaO for next‐generation advanced optoelectronics.

A 9 Month Hubble Space Telescope Near-UV Survey of M87. I. Light and Color Curves of 94 Novae, and a Redetermination of the Nova Rate* * This paper is respectfully dedicated to Jay Gallagher and the late Art Code, who first characterized the striking ultraviolet behavior of a nova a half-century ago.

M87 has been monitored with a cadence of 5 days over a span of 9 months through the near-ultraviolet (NUV; F275W) and optical (F606W) filters of the Wide Field Camera 3 (WFC3) of the Hubble Space Telescope. This unprecedented dataset yields the NUV and optical light and color curves of 94 M87 novae, characterizing the outburst and decline properties of the largest extragalactic nova dataset in the literature (after M31 and M81). We test and confirm nova modelers’ prediction that recurrent novae cannot erupt more frequently than once every 45 days, show that there are zero rapidly recurring novae in the central ∼1/3 of M87 with recurrence times <130 days, demonstrate that novae closely follow the K-band light of M87 to within a few arcsecs of the galaxy nucleus, show that nova NUV light curves are as heterogeneous as their optical counterparts, and usually peak 5–30 days after visible light maximum, determine our observations’ annual detection completeness to be 71%–77%, and measure the rate R nova of nova eruptions in M87 as yr−1. The corresponding luminosity-specific classical nova rate for this galaxy is . These rates confirm that ground-based observations of extragalactic novae miss most faint, fast novae and those near the centers of galaxies. An annual M87 nova rate of 300 or more seems inescapable. A luminosity-specific nova rate of ∼7–10/yr/1010 L ⊙,K in all types of galaxies is indicated by the data available in 2023.

Towards a bound on the Higgs mass in causal set quantum gravity

In the Standard Model of particle physics, the mass of the Higgs particle can be linked to the scale at which the Standard Model breaks down due to a Landau pole/triviality problem: for a Higgs mass somewhat higher than the measured value, the Standard Model breaks down before the Planck scale. We take a first step towards investigating this relation in the context of causal set quantum gravity. We use a scalar-field propagator that carries the imprints of spacetime discreteness in a modified ultraviolet behavior that depends on a nonlocality scale. We investigate whether the modification can shift the scale of the Landau pole in a scalar field theory with quartic interaction. We discover that the modifications speed up the onset of the Landau pole considerably, so that the scale of new physics occurs roughly at the nonlocality scale. Our results call into question, whether a separation between the nonlocality scale and the discreteness scale, which is postulated within causal set quantum gravity, and which has been argued to give rise to phenomenological consequences, is in fact achievable. Methodologically, our paper is the first to apply continuum functional Renormalization Group techniques in the context of a causal-set inspired setting.

Accelerated ultraviolet aging behavior and numerical simulation of ramie/carbon fiber reinforced polyethylene terephthalate glycol hybrid composites

Multi-fibers reinforced polymer hybrid composites can be designed to achieve excellent comprehensive performance through maximizing fibers physical and chemical properties. The accelerated ultraviolet (UV) aging behavior and mechanical degradation of natural ramie fiber (R) and carbon fiber (C) reinforced polyethylene terephthalate glycol (PETG) hybrid composites were investigated to broaden the industrial applications and understand the performance of ramie plant fiber products. The results show that the color and thermal properties of PETG matrix after UV aging have changed. The flexural properties of R/C laminated composites vary with the material types and layup sequences. The flexural modulus of the unaged [C/R/C/R]s and [C/C/R/R]s composites increase 1.2 and 1.0 times as compared with the unaged [R/C/R/C]s and [R/R/C/C]s. After 28 days of UV aging, the flexural strength retention rates of the [R/R/R/R]s, [R/R/C/C]s, [R/C/R/C]s, [C/R/C/R]s, [C/C/R/R]s and [C/C/C/C]s composites were 77.1 %, 79.2 %, 78.8 %, 81.7 %, 83 % and 87.4 %, respectively. The fracture strains of the R/C composites increase significantly after UV aging. The multiscale finite element model of the R/C composites is established to study the UV aging mechanism and predict the mechanical degradation. The knowledge gained in this work will be beneficial for the design and engineering application of plant fiber reinforced polymer hybrid composite materials.

UV aging behavior evolution characterization of HALS-modified asphalt based on micro-morphological features

Abstract To clarify the effect of Hindered amine light stabilizer (HALS) on ultraviolet (UV) aging behavior of asphalt binder, the evolution history and characteristics of the UV induced micro-structure of modified asphalt were characterized. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt during UV aging. By defining the micro-structure of asphalt in aging joints induced by UV, the identification and classification of typical micro-structure are proposed. On this basis, an evaluation method based on the morphology evolution process of modified asphalt aging was proposed to quantitatively analyze the effect of HALS on the UV aging of asphalt binder. The results show that the control effect of HALS on the UV aging behavior of asphalt can be verified by SEM and AFM detection methods. At the same time, the aging interval of the asphalt modified by hindered amine was divided by the method, and it was verified that the HALS could significantly prolong the service life of the asphalt binder. The micro-morphology of asphalt binder undergoes the process of crack generation and propagation during UV aging. The micro-morphological changes of UV aged asphalt were interfered effectively by HALS, which could alleviate and control the development of UV induced micro-cracks, and promote the fusion of micro-cracks. This study provides an effective evaluation method for detecting UV aging microscopic evolution of HALS.

Fock Quantization of a Klein–Gordon Field in the Interior Geometry of a Nonrotating Black Hole

We study the canonical quantization of a scalar field in Kantowski–Sachs spacetime. For simplicity, we consider compactified spatial sections, since this does not affect the ultraviolet behavior. A time-dependent canonical transformation is performed prior to quantization. As in previously studied cases, the purpose of this canonical transformation is to identify and extract the background contribution to the field evolution which is obstructing a unitary implementation of the field dynamics at the quantum level. This splitting of the time dependence into a background piece and the part to be seen as true quantum evolution is, to a large extent, determined by the unitarity requirement itself. The quantization is performed in the usual setup of Fock representations, demanding the preservation of the spatial symmetries. Under the joint requirements of quantum unitary dynamics and compatibility with those classical symmetries, the quantization is shown to be unique, in the sense that any two representations with these properties are unitarily equivalent. This confirms the validity of our conditions as criteria to discriminate among possibly inequivalent quantum descriptions. The interest of this analysis goes beyond cosmological applications since the interior of a nonrotating black hole has a geometry of the Kantowski–Sachs type.

Nitrogen doped reduced graphene oxide: Investigations on electronic properties using X-ray and Ultra-violet photoelectron spectroscopy and field electron emission behaviour

The practice of heteroatom doping has been proven to significantly enhance the intrinsic properties of host materials. A facile, one-step process due to the thermal reduction of ammonium hydroxide-treated graphene oxide (GO) was employed to yield nitrogen (N) doped reduced graphene oxide (rGO). In-depth characterization has been performed to reveal the phase, structure, morphology, and electronic properties of as-synthesized products. It is observed that the processing temperature noticeably affects the concentration and type of doped N species. The N-doped rGO (N-rGO) prepared at 900 ℃ exhibited excellent field electron emission (FEE) performance with relatively lower values of turn-on and threshold fields ∼ 1.28 and 1.52 V/µm, defined at emission current densities of 10 and 100 µA/cm2, respectively. Furthermore, a high current density of 5.83 mA/cm2 was drawn at an applied field of 2.51 V/µm, and the emitter showed equitably current stability tested at 10 µA. The obtained results promote the N-rGO emitter, with tuned concentrations of doped N-species, as a promising candidate for practical applications in various vacuum microelectronic devices.

Ultraviolet behavior of conformally reduced quadratic gravity

Ultraviolet behavior of conformally reduced quadratic gravity

Combinatorial tuning of structure and optoelectronic properties of Zn-Ga-O thin films for deep ultraviolet photodetection

Ternary complex oxides exhibit strong compositional dependence on their structure and functionalities. While the profound impact of the cation stoichiometry on the physical properties of ZnGa2O4 is widely recognized, how it affects the ultraviolet photodetection behavior remains not clear. Here we apply a combinatorial pulsed laser deposition technique to establish graded composition in ZnxGa1-xO (0 ≤ x ≤ 1) across a 2-inch sapphire substrate. In combination with structural and optical characterizations, a systematic investigation of the compositional effect on the phase, crystallinity and bandgap for the ZnxGa1-xO system is performed, and their further impact on the photodetection performance is compared by fabricating multiple metal–semiconductor-metal (MSM) photodetectors based on the graded ZnxGa1-xO films. Decent photodetection behavior is seen for the photodetectors with x ≤ 0.33, above which the performance is largely limited by the conductive phase formation. An optimized compositional range of x = 0.18–0.27 is identified to deliver the best device performance, which includes a responsivity of 12.88 A/W and a photo-to-dark current ratio of 2.8 × 108. This slight zinc deficiency is considered beneficial for the formation of moderate level of oxygen vacancies or antisite defects that boosts carrier transport. This study sheds light on the composition-dependent evolution of structure and properties in ternary ultrawide-bandgap semiconductors for high-performance ultraviolet photodetection.

Effect of silane coupling agent on the ultraviolet weathering behavior of polylactic acid based composites

Polylactic acid (PLA) is a promising material due to its biodegradability and compatibility. However, the limited resistance to ultraviolet (UV) degradation of PLA composites hinders their use in automotive interior materials. In our previous work, we successfully prepared 3D printed filaments by combining KH550-treated micro-nano rice husk (MNRH) fibers with KH570-treated PLA, which exhibited favorable performance. This study aimed to investigate the effects of silane coupling agents, MNRH, and accelerated UV weathering time on the photodegradation behavior of 3D printed PLA-matrix composites reinforced with MNRH. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were utilized to characterize the 3D printed PLA-matrix composites. Furthermore, an exponential equation between tensile strength and UV weathering time was established, providing theoretical guidance for predicting the service life of automotive interior materials based on PLA composites. The morphological characterization experimental results indicate that with prolonged UV aging time, both PLA and RH6-KH550/KH570 composite materials transitioned from transparency to translucency. This transition can be attributed to the rupture of polylactic acid molecular chains and chemical bonds during the UV aging process. FTIR test results revealed the formation of carboxylic acid in the composite, and the reduction of C = O absorption intensity indicated that MNRH and silane coupling agents exhibited a stabilizing effect on the UV durability of the RH6-KH550/KH570 composite. TGA and DSC results indicated that KH550 and KH570 delayed the photodegradation rate of PLA-matrix composites.

Study of the ultraviolet behavior of an O(N) |ϕ→|6 theory in d=3 dimensions

We study the ultraviolet (UV) behavior of an O($N$) $|\vec \phi |^6$ theory in $d=3$ spacetime dimensions, focusing on the question of the range in $N$ over which the perturbative beta function exhibits robust evidence of a UV zero in the $|\vec \phi |^6$ coupling, $g$. The four-loop $(4\ell)$ beta function is known to have a (scheme-independent) UV zero at $g=g_{_{UV,4\ell}}$, which is reliably calculable for large $N$. For our analysis we use the six-loop beta function calculated in the minimal subtraction scheme. We find that this six-loop beta function has a UV zero, $g_{_{UV,6\ell}}$, if $N > N_c$, where $N_c \simeq 796$, and we calculate $g_{_{UV,6\ell}}$. To investigate the reliability of the result in the region of $N \gtrsim N_c$, we apply three methods: (i) calculation of the fractional difference between $g_{_{UV,4\ell}}$ and $g_{_{UV,6\ell}}$, (ii) a Pad\'e approximant, and (iii) an assessment of scheme dependence. Our results provide quantitative measures of the range of $N$ over which the six-loop beta function has a UV zero and of the $1/N$ corrections to the value of $g$ at the UV zero for large but finite $N$. If one imposes a benchmark requirement that the fractional difference between $g_{_{UV,4\ell}}$ and $g_{_{UV,6\ell}}$ must be less than 15 \%, then our results show that this requirement is satisfied for $N \gtrsim 2 \times 10^3$. The possible role of nonperturbative effects is also noted.

Effect of Organic Montmorillonite on Rheological Properties of Sasobit Warm-Mix Asphalt and Analysis of Its Ultraviolet Aging Behaviors

Effect of Organic Montmorillonite on Rheological Properties of Sasobit Warm-Mix Asphalt and Analysis of Its Ultraviolet Aging Behaviors