Strong Dispersion Research Articles

First Record and Identification of a Microsporidian Pathogen, Nosema Maddoxi in the Population of Brown Marmorated Stink Bug Halyomorpha Halys (Hemiptera: Pentatomidae) in Türkiye

PurposeThe brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), is an invasive and a highly polyphagous species with a strong dispersal capacity. Unfortunately, there is currently no effective control method that can prevent or reduce the economic loss caused by this pest. Among natural enemies, microsporidia cause infections in insects so that they can generally shorten life span, reduce fertility and inhibit growth.MethodsCurrent study involved field study, light and electron microscopy and molecular phylogenic analyses of a microsporidian pathogen in the populations of H. halys in Türkiye.ResultsThe microsporidian infection were mostly observed in malpighian tubules and fatty tissue filled with high spore density. Fresh uninucleate spores are oval, measued as 3.73 × 2.01 µm in dimensions. The mature spore wall is relatively thick and measures 75–85 nm and consists of a clear endospore (40–50 nm) and an electron-dense, uniform, thin exospore (25–30 nm). The polar filament is isofilar, 85–110 mm in diameter and has 7–8 coils. It is found to be most closely related to Nosema maddoxi isolate Mn.6 isolated from H. halys in Georgia in phylogenetic tree.ConclusionThe spore morphology and structural features of the isolate from H. halys identify it as Nosema maddoxi. The phylogenetic analyses confirm both light and electron microscopic observations. This is the first microsporidian record from H. halys and also from the order Hemiptera in Türkiye. It is also confirmed that the invasive pest, H. halys carries its natural pathogen, N. maddoxi to new geographical locations during its distribution.

Using slow light to enable laser frequency stabilization to a short, high-Q cavity.

State-of-the-art laser frequency stabilization is limited by miniscule length changes caused by thermal noise. In this work, a cavity-length-insensitive frequency stabilization scheme is implemented using strong dispersion in a 21 mm long cavity with a europium-ion-doped spacer of yttrium orthosilicate. A number of limiting factors for slow light laser stabilization are evaluated, including the inhomogeneous and homogeneous linewidth of the ions, the deterioration of spectral windows, and the linewidth of the cavity modes. Using strong dispersion, the cavity modes were narrowed by a factor 1.6 × 105, leading to a cavity linewidth of 3.0 kHz and a Q factor of 1.7 × 1011. Frequency stabilization was demonstrated using a cavity mode in a spectral transparency region near the center of the inhomogeneous profile, showing an overlapping Allan deviation below 6 × 10-14 and a linear drift rate of 3.66 Hz s-1. Considering improvements that could be implemented, this makes the europium-based slow light laser frequency reference a promising candidate for ultra-precise tabletop frequency stabilization.

Mitigating chromatic aberration in wide-field pancake VR optics through the integration of diffractive optical elements

With the rise of the metaverse, the development of virtual reality headsets has gained significant attention in recent years. The optical architecture of VR head-mounted devices has undergone numerous transformations, with pancake optics becoming the mainstream configuration. Compared to traditional refractive designs, Pancake optics offer advantages such as compact size, high resolution, and wide viewing angle. Its catadioptric layout significantly reduces module thickness, while reflective surfaces provide greater optical power, achieving high resolution and a broad field of view. However, full-color VR headsets typically suffer from severe chromatic aberration at large viewing angles. This study adopts a two-element aspheric pancake design, incorporating a kinoform-type diffractive optical element. Due to the strong negative dispersion of the DOE, our hybrid diffractive-refractive pancake system with an FOV of 106° significantly improves lateral color shift. In the 450 to 650 nm wavelength, the multicolor root-mean-square spot radius is reduced from 142 to 30 µm. This result demonstrates that the DOE-enhanced design successfully improves full-color resolution across the entire FOV. We present simulation results for both designs with and without DOE, validating the effectiveness of our approach. This paper proposes an optical design method that includes first-order calculations and DOE principles, detailing generating the DOE profile. This innovative design not only achieves a technical breakthrough but also shows significant performance improvements in quantitative data, providing a crucial reference for the future optical design of VR headsets and laying a solid foundation for the further development of VR technology.

Recovery and Degradation Drive Changes in the Dispersal Capacity of Stream Macroinvertebrate Communities.

Freshwater ecosystems face significant threats, including pollution, habitat loss, invasive species, and climate change. To address these challenges, management strategies and restoration efforts have been broadly implemented. Across Europe, such efforts have resulted in overall improvements in freshwater biodiversity, but recovery has stalled or failed to occur in many localities, which may be partly caused by the limited dispersal capacity of many species. Here, we used a comprehensive dataset comprising 1327 time series of freshwater macroinvertebrate communities ranging from 1968 to 2021 across 23 European countries to investigate whether dispersal capacity changes with the ecological quality of riverine systems. Sites experiencing improvements in ecological quality exhibited a net gain in species and tended to have macroinvertebrate communities containing species with stronger dispersal capacity (e.g., active aquatic and aerial dispersers, species with frequent propensity to drift, and insects with larger wings). In contrast, sites experiencing degradation of ecological quality exhibited a net loss of species and a reduction in the proportion of strong dispersers. However, this response varied extensively among countries and local sites, with some improving sites exhibiting no parallel gains in macroinvertebrates with higher dispersal capacity. Dispersal capacity of the local species pool can affect the success of freshwater ecosystem restoration projects. Management strategies should focus on enhancing landscape connectivity to create accessible "source" areas and refugia for sensitive taxa, especially as climate change reshapes habitat suitability. Additionally, biodiversity initiatives must incorporate adaptive decision-making approaches that account for the site-specific responses of macroinvertebrate communities to changes in ecological quality.

Understanding and quantifying the impact of solute-solvent van der Waals interactions on the selectivity of asymmetric catalytic transformations.

The majority of enantioselective organocatalytic reactions occur in apolar or weakly polar organic solvents. Nevertheless, the influence of solute-solvent van der Waals forces on the relative kinetics of competitive pathways remains poorly understood. In this study, we provide a first insight into the nature and strength of these interactions at the transition state level using advanced computational tools, shedding light into their influence on the selectivity. In addition, we introduce a series of computational tools tailored for detailed exploration of the role of the organic solvent across diverse research disciplines. As a case study, we selected a highly relevant asymmetric organocatalytic transformation catalyzed by a chiral Brønsted acid. Our analysis reveals that strong dispersion interactions exist between the transition state and the solvent, predominantly involving specific groups of the catalyst rather than being uniformly distributed around the solute. Short-range repulsion between the transition state and the solvent often counteracts the effect of these dispersion forces on the transition state energy, resulting in a minimal overall influence of solute-solvent van der Waals forces on enantioselectivity. However, for certain geometric configurations of the transition states, the effect these interactions remains significant, favoring specific reaction channels. These results suggest that integrating solvent structural and electronic information into catalyst design strategies could offer new avenues for tuning selectivity of organocatalytic processes.

Frequency-dependent breakdown of backward volume spin-wave soliton formation

This study investigates the propagation characteristics of spin waves in an yttrium iron garnet waveguide using a vector network analyzer and a real-time oscilloscope. We confirm the propagation of backward volume magnetostatic spin waves in the linear regime. Solitary spin-wave formation was observed, and the transition from linear to nonlinear response was verified by establishing a threshold power. In the nonlinear regime, collision experiments between two spin waves were conducted, revealing a dependence of attenuation on the input carrier frequency. A comparison with the transmission loss curve confirms the correlation between attenuation and the position of “frequency regions with strong dispersion.” Notably, only within a specific frequency range among these regions do the colliding spin waves maintain their shapes and momenta, passing through each other without dissipation. This remarkable phenomenon is crucial for dissipation-free information transfer. Our findings offer valuable insights into spin-wave behavior, particularly for developing spin-wave-based logic and long-distance magnonic soliton information transfer.

Efficient Simultaneous Second Harmonic Generation and Dispersive Wave Generation in Lithium Niobate Thin Film

AbstractLithium niobate thin film (LNTF) is a promising platform for ultra‐low loss nonlinear integrated photonics. Here, the simultaneous generation of second harmonic wave (SHW) and dispersive wave (DW) are demonstrated in a single LNTF under the pump of a femtosecond pulse laser, with a conversion efficiency exceeding 25%. The second harmonic generation (SHG) uses the modal phase matching mechanism based on the second‐order nonlinear effect, while the DW generation is based on the perturbations of soliton dynamics caused by self‐phase modulation and higher‐order dispersion. Notably, significant and symmetrical SHW and DW patterns are observed, which exhibit strong spatial dispersion properties. A comprehensive analysis of the phase‐matching conditions are conducted for SHG and DW generation and provide a clear elucidation of the spectral properties of different regions of the emitted light patterns. Additionally, the evolution of the pump light in LNTF is thoroughly investigated, and the solutions of the generalized Schrödinger equation are in good agreement with these experimental results. This work sheds new light on the rich physics of nonlinear optical interactions on LNTF, and by utilizing the synergistic effect of second‐order and third‐order nonlinear effects, this study anticipates achieving efficient and high energy on‐chip broadband frequency conversion and supercontinuum generation across octaves.

Chromatic confocal displacement measurement using a double-sided phase diffractive lens

A chromatic confocal displacement measurement (CCDM) system using a double-sided phase diffractive lens (DPDL) is demonstrated. The DPDL is designed to produce a strong dispersion, minimize the optical structure and reduce the difficulty of fabrication and assembly, in addition to reducing the weight and size of the probe of the CCDM. A CCDM experimental system was set up based on the DPDL, and the results of the measurement experiments show that the axial measurement range of the CCDM system reaches 9.463 mm in the working wavelength range (500-700 nm), the relative error is less than 0.022% and the axial resolution near the designed focal length is better than 0.5 µm.

Evaluation and modeling of velocity dispersion and frequency-dependent attenuation in gas hydrate-bearing sediments

Wave velocity and attenuation of gas hydrate-bearing samples are often extrapolated from ultrasonic to lower seismic/sonic frequencies, but the impact of measurement frequency on these properties is rarely studied. This study evaluates velocity dispersion and frequency-dependent attenuation in gas hydrate-bearing sediments (GHBS) by comparing vertical seismic profile (VSP) and sonic logging data from the Nankai Trough and Mallik field. We also employ rock physics modeling to simulate the velocity dispersion and frequency-dependent attenuation at both sites. The results show strong velocity dispersion and frequency-dependent attenuation in the Nankai Trough, attributed to thin, low-saturation hydrate intervals. In contrast, the Mallik field exhibits weak dispersion and frequency dependence, likely due to thick, highly saturated hydrate layers. A compilation of global hydrate reservoir attenuations indicates frequency dependence, with a peak in the sonic logging range, likely due to pore-scale hydrate effects. These findings emphasize the necessity of considering the effect of measurement frequency when performing time-to-depth conversion for seismic data based on the sonic velocity at higher frequencies, particularly for thin and lowly saturated hydrate layers, thereby improving the accuracy of hydrate reservoir characterization.

Molecular Mechanism of Physical and Mechanical Improvement in Graphene/Graphene Oxide-Epoxy Composite Materials.

The performance provided by graphene (Gr) and graphene oxide (GO) additives can be improved by achieving strong adhesion and uniform dispersion in the epoxy resin matrix. In this study, molecular modeling and simulation of DGEBA/DETA based epoxy nanocomposites containing Gr and GO additives were performed. Density functional theory and molecular dynamics simulations were used to investigate interfacial interaction energies and Young's Modulus. Improvement in the interaction energies was studied by controlling the epoxy:hardener ratio, type and the number of oxygen-containing functional groups on the GO, the mass percentage of Gr/GO filler in the epoxy matrix, size and dispersion of GO in the cell. It was demonstrated that functional groups with up to 10 % oxygen content in GO significantly increase interfacial interaction energy for large size Gr/GO. Increasing DETA type amine ratio in the preparation of epoxy polymers increases the interaction energy for high oxygen content while decreasing the interaction energy for low oxygen content in GO for small size GO with edge functional groups. The performance of material dramatically decreased even at high DETA hardener and high GO mass percentages when the aggregation factor of Gr/GO was included in simulations that explain lower Gr/GO percentages in the experimental studies.

Full waveform inversion of surface wave based on instantaneous frequency

Abstract Surface wave has many advantages, such as low attenuation, high signal-to-noise ratio, strong anti-interference ability and dispersion characteristics in layered media. It is widely used in engineering measurement and nondestructive testing. However, the applicability and reliability of surface wave processing methods are severely restricted by velocity inversion or strong heterogeneity of the medium. To overcome these shortcomings, in recent years, scholars have studied full-wave inversion methods including data preprocessing, wave field forward, gradient calculation, and inversion optimization to avoid any assumptions about underground complexity. However, the classical waveform difference mismatch function is apt to fall into a local minimum, which leads to the non-convergence of inversion. At the same time, the existence of surface waves greatly increases the non-linearity of full waveform inversion. Even small perturbations, especially in the S wave velocity structure, can cause dispersion for uniform backgrounds. To overcome this difficulty, a mismatch function based on instantaneous frequency is proposed and the adjoint wave equation is derived. Taking a layered model as an example, the effectiveness of the method is verified.

Spatiotemporal Analysis of Complex Emission Dynamics in Port Areas Using High-Density Air Sensor Network.

Cargo terminals, as pivotal hubs of mechanical activities, maritime shipping, and land transportation, are significant sources of air pollutants, exhibiting considerable spatiotemporal heterogeneity due to the complex and irregular nature of emissions. This study employed a high-density air sensor network with 17 sites across four functional zones in two Shanghai cargo terminals to monitor NO and NO2 concentrations with high spatiotemporal resolution post sensor data validation against regulatory monitoring stations. Notably, NO and NO2 concentrations within the terminal surged during the night, peaking at 06:00 h, likely due to local regulations on heavy-duty diesel trucks. Spatial analysis revealed the highest NO concentrations in the core operational areas and adjacent roads, with significantly lower levels in the outer ring, indicating strong emission sources and limited dispersion. Employing the lowest percentile method for baseline extraction from high-resolution data, this study identified local emissions as the primary source of NO, constituting over 80% of total emissions. Elevated background concentrations of NO2 suggested a gradual oxidation of NO into NO2, with local emissions contributing to 32-70% of the total NO2 concentration. These findings provide valuable insights into the NO and NO2 emission characteristics across different terminal areas, aiding decision-makers in developing targeted emission control policies.

Modeling Rayleigh wave in viscoelastic media with constant Q model using fractional time derivatives

The propagation of seismic waves within the near-surface weathering layers, characterized by their low-quality factors (Q), is often accompanied by strong attenuation and dispersion phenomena. Among these, the Rayleigh wave, with its sensitivity to dispersion, has proven to be a powerful tool for near-surface exploration. We propose a novel approach for simulating Rayleigh wave propagation in such low-Q media. Our method uses the time-domain fractional wave equation with memory effect, based on Kjartansson's constant-Q (CQ) model, for accurate characterization of the propagation process. To solve numerically the wave equation with the fractional derivatives, we employ a finite-difference method combined with the auxiliary differential equation-perfectly matched layer (ADE-PML) and the acoustic-elastic boundary approach (AEA). The algorithm's high computational accuracy is verified through comparison with the conventional integer-order wave equation based on the nearly constant-Q (NCQ) models in strong attenuation media. The research in this paper deepens our understanding of the propagation characteristics of Rayleigh waves in strongly weathering layers. This new method strongly supports those seismic imaging and inversion methods depending on seismic modeling, including the reverse time migration and the full waveform inversion of the internal structure of low-Q media.

Physical modeling of organics-contaminated groundwater remediation by ozone micro-nano-bubbles enhanced oxidation

Ozone micro-nano-bubbles (MNBs) enhanced oxidation is a promising in-situ remediation technology for organics-contaminated groundwater. The transport behavior of MNBs and contaminant removal effect in actual groundwater scene is not yet comprehensively understood, although one-dimensional column experiments and batch tests were conducted to investigate the migration of MNBs and contaminant degradation in previous studies. Here, a novel two-dimensional (2D) physical modeling facility was developed, which can characterize the tempo-spatial distribution of MNBs and contaminant in groundwater. The facility was used to explore the migration of MNBs under different hydraulic gradients and the removal of methyl orange, a representative organic pollutant, using ozone MNBs. The experimental results show that groundwater flow velocity has a significant influence on the migration behavior of MNBs. A model including groundwater flow, MNBs transport, and dissolved gas transport can well capture the migration and distribution of MNBs under different hydraulic gradients. The longitudinal and transverse dispersivities of the MNBs were calculated to be 1.14 cm and 0.18 cm, respectively. MNBs are able to migrate with groundwater flow to long distances and exhibit strong dispersion in the lateral and longitudinal directions. The increase in hydraulic gradient greatly enhances the transport of MNBs in groundwater and relieves the deposited MNBs on the surface of porous media. At a hydraulic gradient increasing from 0.033 to 0.1, the range of influence of MNBs increased from about 80 cm × 40 cm to 140 cm × 39 cm after 36 h of injection of oxygen MNBs water. The methyl orange in groundwater is effectively removed by ozone MNBs enhanced oxidation, showing the remarkable remediation ability of ozone MNBs. The area of influence and pollutant removal of the ozone MNBs expanded with injection, and the area of influence was approximately 48 cm × 30 cm after 48 h of treatment. We also discuss the effect of groundwater matrix on ozone MNB migration and degradation of contaminants. The 2D model tests illustrate the mechanism of MNB migration and indicate that ozone MNBs enhanced oxidation technology has great potential in the remediation of organics-contaminated groundwater.

Construction of Carbon Dioxide Responsive Graphene Point Imbibition and Drainage Fluid and Simulation of Imbibition Experiments

The global oil and gas exploration targets are gradually moving towards a new field of oil and gas accumulation with nanopore throats, ranging from millimeter scale to micro-nano pore throats. The development method of tight oil reservoirs is different from that of conventional oil reservoirs, and the development efficiency is constrained. Therefore, it is necessary to construct a nanoscale fluid with strong diffusion and dispersion and improve its permeability, suction, and displacement capabilities. Under the background of CCUS, carbon dioxide flooding is a better way to develop tight reservoirs. However, in order to solve the problem of gas channeling, this paper developed a carbon dioxide-responsive graphene point type surfactant, which has a good gas–liquid synergistic effect. At the same time, graphene nanomaterials are carbon-based and create no environmental damage in oil reservoirs. In this study, graphene quantum dots (GQDs) were prepared using the hydrothermal method, and functional graphene quantum dots (F-GQDs) responsive to carbon dioxide stimulation were synthesized by covalent grafting of amidine functional groups. By characterizing its structure and physical and chemical properties, and by conducting imbibition simulation experiments, its imbibition and drainage ability in nanopore throats is elucidated. Infrared spectrum measurement shows that after functional modification, the quantum dots exhibited new characteristic peaks at 1600 cm−1 to 1300 cm−1, considering the N-H plane-stretching characteristic peak. The fluorescence spectra showed that the fluorescence intensity of F-GQDs was increased after functional modification, which indicated that F-GQDs were successfully synthesized. Through measurements of interfacial activity and adhesion work calculations, the oil–water interfacial tension can achieve ultra-low values within the range of 10−2 to 10−3 mN/m. Oil sand cleaning experiments and indoor simulations of spontaneous imbibition in tight cores demonstrate that F-GQDs exhibit effective oil-washing capabilities and a strong response to carbon dioxide. When combined with carbon dioxide, the system enhances both the rate and efficiency of oil washing. Imbibition recovery can reach more than 50%. The research results provide a certain theoretical basis and data reference for the efficient development of tight reservoirs.

Achromatic Silicon Photonic Waveguide Lenses for Ultra‐Broadband Multimode Spot‐Size Conversion

AbstractThe rapid development of silicon photonics inspired the emergence of on‐chip geometric optics. As one of the most crucial elements, waveguide‐lenses have attracted much attention. Nevertheless, waveguide‐lenses often suffer from large chromatism due to the strong waveguide dispersion, especially for the cases with multiple guided‐modes. In this paper, achromatic waveguide‐lenses available for multimode photonics are proposed and are further utilized for realizing multimode spot size converters (MSSCs) as an example. The present MSSC shows low excess losses < 0.4 dB and low inter‐mode crosstalks <−14 dB within an ultra‐broad bandwidth of 1450–1650 nm, which is realized for the first time by comprising a positive waveguide‐lens and a negative waveguide‐lens. In addition, the present MSSC is applied successfully for realizing high‐performance multimode waveguide corner‐bends. To the best of the knowledge, the proposed MSSC is the unique one with an ultra‐compact footprint and the largest bandwidth for low crosstalks as well as low losses, indicating that on‐chip geometric optics potentially provides a new perspective for on‐chip light manipulation desired in various applications.

Crystal Structures and Piezoelectric Properties of Quenched and Slowly-Cooled BiFeO3-BaTiO3 Ceramics.

The BiFeO3-BaTiO3 (BF-BT) ceramics were here prepared through the solid-state reaction of Bi2O3, Fe2O3 and nano-sized BT powders. The crystal structures and piezoelectric properties were investigated in both quenched (AQ) and slowly cooled (SC) 0.7BF-0.3BT ceramics. Prior work has shown that rhombohedral and pseudo-cubic phases coexist in 0.7BF-0.3BT ceramics. In this work, the crystal structure of the pseudo-cubic phase was refined as a non-polar orthorhombic Pbnm phase in the SC sample and as a polar orthorhombic Pmc21 phase in the AQ sample. In addition to a sharp dielectric peak at about 620 °C, corresponding to the Curie temperature of the rhombohedral phase, a broad dielectric peak with strong frequency dispersion and a sharp frequency-independent dielectric peak were observed at around 500 °C in the SC and AQ samples, respectively. We determine that the dielectric anomalies around 500 °C were caused by a relaxor phase transition of the non-polar orthorhombic phase in the SC sample and a ferroelectric-paraelectric phase transition of the polar orthorhombic phase in the AQ sample. The AQ sample showed better ferroelectric and piezoelectric properties than the SC sample. The 0.7BF-0.3BT ceramic slowly cooled in a nitrogen atmosphere showed a well-saturated P-E curve and a similar temperature-dependent dielectric constant as the AQ sample. Our results indicate that large concentrations of oxygen vacancies produce a more distorted polar orthorhombic phase and better piezoelectric properties in the AQ sample than in the SC sample.

Tetrasodium iminodisuccinate modified montmorillonite for Pb and Cd adsorption from water: Characterization and mechanism

Heavy metal pollution is a huge hazard to the water environment and modified clay adsorbents have been widely used to remove heavy metals from water. Degradable anionic chelating agents have a greater potential for the immobilization of heavy metals, so tetrasodium iminodisuccinate (IDS) was introduced to modify montmorillonite (Mt) for Pb(II) and Cd(II) adsorption from water in this study. IDS was bound with Mt by sonication, heating, and acidity to form IDS-Mt, and characterized by XRD, FT-IR, SEM, and zeta potential analyzer. The batch adsorption experiments revealed that IDS-Mt5 had excellent adsorption capacity of Pb(II) and Cd(II) up to 214.73 mg/L and 104.07 mg/L, respectively. The adsorption process of IDS-Mt on Pb(II) and Cd(II) was consistent with the Sips model and PSO model, indicating that the adsorption was heterogeneous and chemical. The adsorption capacities of IDS-Mt in the second cycle remained above 76 % for Pb(II) and 69 % for Cd(II) of the initial ones, respectively. IDS was immobilized on the interlayer and edge surfaces of Mt through interactions or forming hydrogen bonds facilitated by ultrasonic under acidic heating conditions. Pb(II) and Cd(II) were immobilized by IDS-Mt through cation exchange, negative charge attraction at the edge surface, and IDS chelation. IDS-Mt was an excellent adsorbent with strong dispersibility and swelling properties for Pb(II) and Cd(II) removal from contaminated water. This study provides a new solution for the anionic modification of Mt and a new material for the treatment of heavy metal wastewater.

Erstnachweise und Wiederfunde verschollener Stechimmenarten (Hymenoptera Aculeata) in Schleswig-Holstein

Especially intensive collecting activities of the AG Stechimmen Schleswig-Holstein during the years 2016-2022 resulted in the discovery of 37 species of wild bees and aculeate wasps (Hymenoptera Aculeata) that were recorded for the first time in Schleswig-Holstein, Germany, as well as the rediscovery of 19 species that were considered extinct for this region. The newly discovered species are discussed regarding their known distribution in neighbouring regions. In particular, a strong northward dispersal of thermophilic species can be observed, presumably due to climate warming.

Ultraviolet astronomical spectrograph calibration with laser frequency combs from nanophotonic lithium niobate waveguides

Astronomical precision spectroscopy underpins searches for life beyond Earth, direct observation of the expanding Universe and constraining the potential variability of physical constants on cosmological scales. Laser frequency combs can provide the required accurate and precise calibration to the astronomical spectrographs. For cosmological studies, extending the calibration with such astrocombs to the ultraviolet spectral range is desirable, however, strong material dispersion and large spectral separation from the established infrared laser oscillators have made this challenging. Here, we demonstrate astronomical spectrograph calibration with an astrocomb in the ultraviolet spectral range below 400 nm. This is accomplished via chip-integrated highly nonlinear photonics in periodically-poled, nano-fabricated lithium niobate waveguides in conjunction with a robust infrared electro-optic comb generator, as well as a chip-integrated microresonator comb. These results demonstrate a viable route towards astronomical precision spectroscopy in the ultraviolet and could contribute to unlock the full potential of next-generation ground-based and future space-based instruments.