Directional Dependence Research Articles

Emergence of high-mass stars in complex fiber networks (EMERGE). IV. Environmental dependence of the fiber widths

Despite their variety of scales throughout the interstellar medium, filaments in nearby low-mass clouds appear to have a characteristic width of sim 0.1 pc from the analysis of Herschel observations. The validity and origin of this characteristic width, however, has been a matter of intense discussions during the last decade. We made use of the EMERGE Early ALMA Survey comprising seven targets among low- (OMC-4 South, NGC 2023), intermediate- (OMC-2, OMC-3, LDN 1641N), and high-mass (OMC-1, Flame Nebula) star-forming regions in Orion, which include different physical conditions, star formation histories, mass, and density regimes. All targets were homogeneously surveyed at high-spatial resolution (4.5 or sim 2000 au) in N$_2$H$^+$ (1$-$0) using a dedicated series of ALMA+IRAM-30m observations, and previous works identified a total of 152 fibers throughout this sample. Here, we aim to characterise the variation in the fiber widths under the different conditions explored by this survey. We characterised the column density and temperature radial profiles of fibers using the automatic fitting routine FilChap, and systematically quantified its main physical properties (i.e. peak column density, width, and temperature gradient). The Orion fibers show a departure from the isothermal condition with significant outward temperature gradients with $ T_ K > 30$ K pc$^ $. The presence of such temperature gradients suggests a change in the equation of state for fibers. By fitting their radial profiles, we report a median full width at half maximum ($FWHM$) of $ 0.05$ pc for the Orion fibers, with a corresponding median aspect ratio of $ Along with their median, the $FWHM$ values for individual cuts are consistently below the proposed characteristic width of 0.1 pc. More relevantly, we observe a systematic variation in these fiber $FWHM$ between different regions in our sample. We also find a direct inverse dependence of the fiber $FWHM$ on their central column density, $N_0$, above $ $ cm$^ $, which agrees with the expected $N_0-FWHM$ anti-correlation predicted in previous theoretical studies. Our homogeneous analysis returns the first observational evidence of an intrinsic and systematic variation in the fiber widths across different star-forming regions. While sharing comparable mass, length, and kinematic properties in all of our targets, fibers appear to adjust their $FWHM$ to their density and to the pressure in their host environment.

A phase‐field framework for stress corrosion cracking prediction in elastoplastic metallic materials

AbstractTo capture the stress corrosion cracking (SCC) in metallic materials, a phase‐field framework considering localized plastic deformation and stress states is established. A new function of critical energy release rate is proposed to describe the degradation of cracking resistance of materials in the SCC process. This proposed framework can reproduce SCC results consistent with experimental observations in C‐ring steel SCC tests, especially capturing the directionally characteristic of the cracks. Furthermore, the influences of localized plastic deformation and stress states on the SCC process are studied. This novel phase‐field framework can capture (1) the influences of coupled electricity, mechanics to the SCC mechanisms; (2) the contribution of plastic strain energy as the driving force for the phase‐field; (3) the potential and preferential crack initiation and propagation morphology within the complex stress and strain domain; and (4) the dependence of SCC rate and propagation direction on stress state and localized plastic deformation.

Synergy of Experiment and Broadened Exploration of Ab Initio Calculations for Understanding of Lanthanide-Pentacyanidocobaltate Molecular Nanomagnets and Their Optical Properties.

We present a synergistic experimental-theoretical methodology for the investigation of lanthanide-based single-molecule magnets (SMMs), demonstrated using the example of novel heterometallic molecules incorporating Nd3+/Ce3+ ions combined with three different, rarely explored, pentacyanidocobaltate(III) metalloligands, [CoIII(CN)5(azido/nitrito-N/iodido)]3-. The theoretical part of our approach broadens the exploration of ab initio calculations for lanthanide(III) complexes toward the convenient simulations of such physical characteristics as directional dependences of Helmholtz energy, magnetization, susceptibility, and their thermal and field evolution, as well as light absorption and emission bands. This work was conducted using newly designed SlothPy software (https://slothpy.org). It is introduced as an open-source Python library for simulating various physical properties from first-principles based on results of electronic structure calculations obtained within popular quantum chemistry packages. The computational results were confronted with spectroscopic and ac/dc-magnetic data, the latter analyzed using previously designed relACs software. The combination of experimental and computational methods gave insight into phonon-assisted magnetic relaxation mechanisms, disentangling them from the temperature-independent quantum tunneling of magnetization and emphasizing the role of local-mode processes. This study provides an understanding of the changes in lanthanide(III) magnetic anisotropy introduced with pentacyanidocobaltates(III) modifications, theoretically exploring also potential applications of reported compounds as anisotropy switches or optical thermometers.

Study of radiation-induced structural changes in the near-surface layer of ZrO2 ceramics caused by He2+ irradiation

Abstract The aim of this study is to determine changes in the near-surface layer of ZrO2 ceramics caused by irradiation with low-energy He2+ ions, as well as the associated formation of defects and structural deformations. During the experimental work conducted, it was established that the accumulation of deformation-structural distortions is of two stage nature, having a direct dependence on irradiation fluence and, therefore, on atomic displacement value. It was determined that at small atomic displacement values (less than 10 dpa), the main mechanisms of structural distortions are caused by tensile residual stresses, the value of which is less than 0.1 GPa. At the same time, the deformation distortion of chemical bonds has a pronounced anisotropy associated with a more pronounced distortion of the Zr–OI chemical bonds, the distortion of which results in the formation of vacancy defects in the form of VO. During determination of alterations in optical characteristics depending on the atomic displacement value, it was found that the dominant role at small values of dpa (less than 10 dpa) is played by point defects, which influence the formation of obstacles in the form of absorbing centers. In this case, an increase in the irradiation fluence above 1017 ion/cm2 results in a growth in the linear refractive index, the change of which has a direct correlation with the value of residual stresses in the damaged layer. Certain dependencies of changes in structural features and their relationship with deformation distortions, as well as the accumulation of vacancy defects, can subsequently be used to predict the potential of using these ceramics as materials for new generation nuclear reactors.

Visceral pleura mechanics: Characterization of human, pig, and rat lung material properties

Pulmonary air leaks are amongst the most common complications in lung surgery. Lung sealants are applied to the organ surface and need to synchronously stretch with the visceral pleura, the layer of tissue which encompasses the lung parenchymal tissue. These adhesives are commonly tested on pig and rat lungs, but applied to human lungs. However, the unknown mechanics of human lung visceral pleura undermines the clinical translatability of such animal-tested sealants and the absence of how pig and rat lung visceral pleura compare to human tissues is necessary to address. Here we quantify the biaxial planar tensile mechanics of visceral pleura from healthy transplant-eligible and smoker human lungs for the first time, and further compare the material behaviors to pig and rat lung visceral pleura. Initial and final stiffness moduli, maximum stress, low-to-high strain transition, and stress relaxation are analyzed and compared between and within groups, further considering regional and directional dependencies. Visceral pleura tissue from all species behave isotropically, and pig and human visceral pleura exhibits regional heterogeneity (i.e. upper versus lower lobe differences). We find that pig visceral pleura exhibits similar initial stiffness moduli and regional trends compared to human visceral pleura, suggesting pig tissue may serve as a viable animal model candidate for lung sealant testing. The outcomes and mechanical characterization of these scarce tissues enables future development of biomimetic lung sealants for improved surgical applications. Statement of significanceSurgical lung sealants must synchronously deform with the underlying tissue and with each breath to minimize post-operative air leaks, which remain the most frequent complications of pulmonary intervention. These adhesives are often tested on pig and rat lungs, but applied to humans; however, the material properties of human lung visceral pleura were previously unexplored. Here, for the first time, the mechanics of human visceral pleura tissue are investigated, further contrasting rarely acquired donated lungs from healthy and smoking individuals, and additionally, comparing biaxial planar material characterizations to animal models often employed for pulmonary sealant development. This fundamental material characterization addresses key hindrances in the advancement of biomimetic sealants and evaluates the translatability of animal model experiments for clinical applications.

Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images

We present the deepest wide-field 115–166 MHz image at sub-arcsecond resolution spanning an area of 2.5° × 2.5° centred at the ELAIS-N1 deep field. To achieve this, we improved the direction-independent (DI) and direction-dependent (DD) calibrations for the International LOw Frequency ARray (LOFAR) Telescope. This enhancement enabled us to efficiently process 32 h of data from four different 8-h observations using the high-band antennas (HBAs) of all 52 stations, covering baselines up to approximately 2000 km across Europe. The DI calibration was improved by using an accurate sky model and refining the series of calibration steps on the in-field calibrator, while the DD calibration was improved by adopting a more automated approach for selecting the DD calibrators and inspecting the self-calibration on these sources. For our brightest calibrators, we also added an additional round of self-calibration for the Dutch core and remote stations in order to refine the solutions for shorter baselines. To complement our highest resolution at 0.3″, we also made intermediate resolution wide-field images at 0.6″ and 1.2″. Our resulting wide-field images achieve a central noise level of 14 μJy beam−1 at 0.3″, doubling the depth and uncovering four times more objects than the Lockman Hole deep field image at comparable resolution but with only 8 h of data. Compared to LOFAR imaging without the international stations, we note that due to the increased collecting area and the absence of confusion noise, we reached a point-source sensitivity comparable to a 500-h ELAIS-N1 6″ image with 16 times less observing time. Importantly, we have found that the computing costs for the same amount of data are almost halved (to about 139 000 CPU h per 8 h of data) compared to previous efforts, though they remain high. Our work underscores the value and feasibility of exploiting all Dutch and international LOFAR stations to make deep wide-field images at sub-arcsecond resolution.

Physical properties and anisotropy of sandstone during freeze-thaw cycle under unidirectional constraint

To investigate the evolution of physical properties of sandstone under unidirectional constraint during freeze-thaw cycles, an experimental device was specifically designed. Unidirectional constraint freeze-thaw tests were performed on sandstone specimens. The study analyzed variations in the dry mass, saturated mass, and longitudinal wave velocity of the sandstone both before and after undergoing freeze-thaw cycles, as well as examining the evolution of resistivity throughout the process. Results revealed that an increase in the number of freeze-thaw cycles leads to a gradual increase in the saturated mass of sandstone, while its dry mass consistently decreases, irrespective of whether it is subjected to constraint or not. The change rates of both dry mass and saturated mass were found to be significantly lower under unidirectional constraint compared to that without constraint. With more freeze-thaw cycles, a decline in longitudinal wave velocity was noted. Under unconstrained conditions, no significant direction dependence in longitudinal wave velocity was detected. However, under unidirectional constraint, there was a smaller decrease in the longitudinal wave velocity along the direction of constraint compared to other directions. This indicates that constraint mitigates frost heave damage. In the temperature rise and maintenance stages, resistivity initially dropped, then increased prior to stabilizing at a constant value. Conversely, in temperature decrease and maintenance stages, resistivity first rose, then dipped before ultimately rising again. Temperature primarily influenced resistivity by affecting the ion movement velocity within pore water and the connectivity of the conductive network.

Variation in microstructural features of melt-pool structure in laser powder bed fused Al–Fe–Cu alloy at elevated temperatures

The present study was undertaken to understand the effect of annealing on the microstructural features of the melt-pool structure and the associated multiscale mechanical properties of the Al–2.5%Fe–2%Cu alloy manufactured by laser powder bed fusion (LPBF). Microstructural characterizations and tensile tests were conducted for the LPBF-built specimen and those subsequently annealed at various temperatures ranging from 200 to 500 °C. Nanoindentation hardness mapping was used to evaluate the mechanical inhomogeneity of the melt-pool structure and its changes by annealing at different temperatures. The LPBF-manufactured sample exhibited a melt-pool structure containing numerous particles of the Al23CuFe4 phase (oC28, orthorhombic structure) formed because of local melting and rapid solidification during the LPBF process. The relatively coarsened cellular structure localized along the melt-pool boundary resulted in local soft regions. The local vulnerability contributed to the direction dependence of the tensile ductility. A slight variation was observed in the inhomogeneous microstructure of the samples annealed at 200 or 300 °C. The formation of numerous Al23CuFe4 nanoprecipitates in the α-Al supersaturated solid solution prevented strength loss after post-heat treatments. In addition, considerable coarsening of the intermetallic phase after annealing at 500 °C eliminated the melt-pool structure. The tensile performance of the specimens demonstrated a ductile fracture mode, wherein ductile fracture occurred in the α-Al matrix with low hardness while the harder θ-Al13Fe4 stable phase was embedded within it. The anisotropy in the mechanical properties was less pronounced owing to the significant microstructural changes.

Accumulation Radiocesium (137cs) By Plants of the Dnipro River’s Floodplain Ecosystems after Chernobyl Contamination

The analysis of radiocesium (137Cs) accumulation by plants of forest, marsh, meadow, psamophytic, and ruderal communities in the Dnipro River floodplain (Ukraine) was carried out. The species specificity of radiocesium accumulation by plants of specific biotopes and the direct dependence of the plant accumulation coefficient on the density of biotope contamination with radionuclides were confirmed. Differences in different radiocesium accumulation by plants of different ecosystems are probably related to the fact that the bioavailability of radiocesium strongly depends on soil properties. In the analyzed statistical model, the processes of accumulation and dissipation of 137Cs are significant.

Attracting doctors to rural areas under the state program: performance indices

Introduction.The implementation of the state program “Zemsky Doctor” is one of the effective mechanisms to attract medical personnel to medical institutions located in rural areas. The purpose of the study. To analyze the indices for attracting doctors to medical institutionsss located in rural areas of the Russian Federation during Federal Research Institute for Health Organization and Informatics the period from 2015 to 2022 within the framework of the state program “Zemsky Doctor”. Materials and methods. The study used statistical data on eighty two subjects of the Russian Federation based on operational documented inquiries for the period from 2015 to 2022. Analytical and statistical methods were used in the research process. Descriptive statistics and correlation analysis was conducted using the Statistica package version 13.3. Results. During the study period, more than 33,000 physicians of various specialties were attracted and employed in rural areas. The index of the number of doctors attracted to rural areas under the program from 2015 to 2022 increased by 32.2%, from 0.9 to 1.19 per 10,000 rural population. When analyzing this index by regions of the Russian Federation, significant differences were revealed. Research limitations. The research materials are limited by the results of the analysis of quantitative data obtained as a result of an operational request to the subjects of the Russian Federation and statistical data of the forms of federal statistical observation. Conclusion. The study revealed the regions with the lowest level of the indice of physician supply also to have a low index of the number of doctors recruited under the program. The results of correlation analysis showed that in most of the Russian regions there is a direct dependence of the index of physician supply on the results of the implementation of the program “Zemsky Doctor”. The results of the program implementation have a significant impact on the staffing of medical organizations located in rural areas.

Magnetic field enhanced laser absorption on a metallic surface incorporated with shape-dependent nanostructures

Abstract This communication proposes an analytical model to investigate the nanoparticle-based nonlinear absorption phenomenon associated with an obliquely incident p-polarized laser beam on a metallic surface. In this scheme, the surface is ingrained with noble-metal spherical nanoparticles and cylindrical nanoparticles in the presence of an external static magnetic field. The absorption of laser energy in the presence of nanoparticles (NPs) is attributed to surface plasmon resonance and enhanced magnetic-field effects. The absorption phenomenon is significantly enhanced by the incorporation of nanostructures and a magnetic field. The ellipticity characterizing parameter, which significantly influences the resonant frequency of different nanometric structures, has also been analysed and discussed. The effects of varying the magnetic field intensity, incident angle, size, and spacing of the NP were examined to determine their influence on the anomalous absorption of the laser. Furthermore, a direct dependency was found between the absorption coefficient and transmission coefficient of the incident laser, as well as the dimensions of the NPs. Several applications have direct relevance to this study, including biosensors such as DNA sensors and immunosensors, photothermal therapy, photoacoustic imaging, optoelectronic devices, solar cells, and surface-enhanced Raman spectroscopy.

Controlled electrodeposition of cobalt nanowires usingiRcompensation and their electron transport properties.

Superconducting hybrid structures based on single nanowires are a new type of nanoscale devices with peculiar transport characteristics. Control over the nanowire structure is essential for understanding hybrid electronic phenomena arising in such complex systems. In this work, we report a technique for the fabrication of cobalt nanowires by template-assisted electrodeposition usingiRcompensation, which allows revealing the fundamental dependence of the preferred direction of nanowire growth on the deposition potential. Long coarse-grained cobalt nanowires with a diameter of 70 nm have been implemented into Nb/Co/Nb hybrid structures. We demonstrate that using electrode fabrication techniques that do not contaminate the surface of the nanowire leads to a high quality of devices with low-resistance interfaces. Low-temperature resistivity of 4.94 ± 0.83µΩ cm and other transport characteristics of Co nanowires are reported. The absence of long-range superconducting proximity effect for Nb/Co/Nb systems with different nanowire length is discussed.

Insights into fatigue crack propagation behaviour of WAAM produced SS316 stainless steel: Molecular dynamics simulation and experimental analysis

The current work focuses on the crack growth mechanism / behavior of wire arc additively manufactured SS316L. Beside the experimental investigation, a molecular dynamics based polycrystalline model is developed to simulate the crack propagation under cyclic loading. The purpose of this work is to understand the crack growth behavior of wire arc additively manufactured SS316L, particularly the directional dependence of crack propagation. The experiments and molecular dynamics analysis are performed for the crack propagation along the build and traverse direction for the SS316L deposit. The experimental procedure involves fatigue crack growth rate tests, while the molecular dynamics simulations model the crack propagation in polycrystalline structures of different grain sizes. The ultimate tensile strength in build and traverse direction were 535±2 MPa and 495 ± 2 MPa, respectively. The experimental results reveal faster crack propagation along build direction in comparison to traverse direction. The values for Paris law material constants i.e. C and m are 7x10-15 and 6.78 along build direction while 8x10-14 and 6.02 along traverse direction, respectively. The crack growth along the build direction is primarily intergranular, which leads to high crack growth rate. The molecular dynamics simulations reveal the initiation and closure of secondary cracks for the traverse direction, which leads to slower crack growth rate along the traverse direction. The fractography of the fractured surfaces from fatigue crack growth rate test also indicate the formation of secondary cracks for the case of traverse direction. The molecular dynamics simulations performed with three grain sizes and thickness variation indicate the insensitivity of predicted crack growth mechanisms with respect to grain sizes used for simulations.

(Invited) Modification of Dielectric Properties of Film Dielectric Materials by Solid Solution System

Compound semiconductor based power devices such as SiC and GaN require high temperature operating passive devices such as a capacitor. SiC-based active devices can operate above 250 °C. The development of high-temperature operational passives is urgently needed to advance to the module and system level. In the case of capacitors, currently available capacitors can only operate efficiently up to 175 °C. Therefore, a thin film capacitor that can operate at high temperatures and be monolithically integrated near the active device should be developed. In this talk, I will present our achievements in the development of high-temperature operating dielectric film materials using the solid solution system. One topic is A2B2O7 pyrochlore ferroelectrics. The ferroelectric materials with the pyrochlore structure such as Sr2Nb2O7 exhibited the high dielectric constant above 100 at high and low temperature ranges. However, due to the crystallographic direction dependence of the Curie-Weiss temperature, the temperature stability of the dielectric constant from room temperature to 300 °C was not available. In order to obtain the high temperature stability of dielectric constant from room temperature to 300 °C with high dielectric constant over 100, the pyrochlore ferroelectric solid solution thin films were investigated by employing the combinatorial synthesis. Composition spread thin films of solid solution of two or three kinds of materials were deposited on substrates by physical vapor deposition technique, which provided the systematic physical properties. High-throughput combinatorial synthesis method is effective in the rapid optimization of the correlation between the crystallization and the dielectric property change behavior. For the composition spread solid solution film, the Sr- or La-containing A2B2O7 pyrochlore ferroelectrics were selected from the viewpoints of ion radios and crystallographic direction dependence of the Curie-Weiss temperature. The composition spread films were formed on a Pt/Ti/SiO2/Si substrate by combinatorial RF sputtering with stoichiometric composition targets. The X-ray fluorescence spectrum of the composition-spread film showed a linear variation of the metal composition. After deposition, the samples were annealed at different temperatures under oxygen atmosphere to reduce oxygen vacancies and improve crystallinity. The crystallization of the composition-spread solid solution thin film was confirmed by X-ray diffraction patterns, indicating the composition dependence of the crystallographic orientation. Some compositions showed high dielectric constant over 100 and high temperature stability from room temperature to 300 °C. In the presentation, the correlation between film composition, orientation and dielectric constant will be discussed in detail. In the presentation, we also introduce our achievement of the BaTiO3 based relaxor ferroelectrics and other dielectric materials development using the solid solution system. For the relaxor ferroelectrics, among the BaTiO3 based relaxor ferroelectrics, we have selected x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] . The permittivity of 400 and the stability <8% from room temperature to 400 °C were obtained, which are promising as high-temperature dielectric medium.

The role of the principle of proportionality in the development of modern constitutionalism

The article examines the formal and substantive interrelationship between the principle of proportionality and modern constitutionalism, elucidating the essence of the phenomenon of constitutionalism through its characteristics and the role of the principle of proportionality in its establishment and development. Based on the works of domestic and foreign researchers on constitutionalism, it has been assumed that the key value and feature of modern constitutionalism is the limitation of state arbitrariness, the inadmissibility of unjustified interference (restriction) of human rights and freedoms, and the partnership relations between the individual and the state. This, in turn, must be guaranteed, ensured, measured, and evaluated by specific legal instruments, one of the most important and applicable of which is the principle of proportionality. The impact of the principle of proportionality on the development of constitutionalism is analyzed through its function and purpose, demonstrating the direct dependence of the exercise of state power based on the constitution and in accordance with the principle of the rule of law on the adherence to the principle of proportionality by public administration. The provision that real constitutionalism can only be discussed when all its values are considered and protected in the process of law-making and law enforcement, not at an abstract-formal level, but in each specific case of interference (restriction) of human rights, subjected to a consistent and structured proportionality test, has received further development. It is concluded that the principle of proportionality plays a key role in the development of modern constitutionalism. Considering the contemporary challenges faced by human rights and freedoms, it has been concluded that the principle of proportionality is the safeguard intended to protect human rights and freedoms by addressing questions regarding the legitimate aim of certain state actions, the necessity of such actions, the adequacy and relevance of the means chosen by the state to achieve such an aim, the balance between the potential benefit for public interests and the extent of the restriction of rights, etc., which is a crucial factor not only in ensuring but also in developing modern constitutionalism.

Does the carbon market signal the market efficiency of clean and dirty cryptocurrencies? An analysis of quantile directional dependence

The role of the carbon market in the market efficiency of cryptocurrencies has not received much attention from scholars, despite its particular relevance for integrating environmental externalities into the theory and practice of digital financial markets. We investigate whether and how the performance of the carbon market during busts and booms affects the market efficiency of both clean and dirty cryptocurrencies. Overall, our results underscore the complex quantile dependence of cryptocurrency market efficiency on carbon market performance, highlighting significant variability in how different types of cryptocurrencies respond to carbon market. These results have significant implications for regulatory policies, investment strategies, industry practices, public perceptions, and technological advances in the pursuit of aligning cryptocurrency markets with environmental sustainability goals.

Inhomogeneous deformation in melt-pool structure of Al-Fe-Cu alloy manufactured by laser powder bed fusion

Abstract The laser powder bed fusion (L-PBF) processed Al–2.5Fe–2Cu (mass%) alloy exhibited a high tensile strength above 340 MPa and pronounced directional dependence. The sample exhibited a characteristic inhomogeneous microstructure (in melt-pool structure) arising from the local melting and rapid solidification in the L-PBF process. The coarsened cellular structure localized along the melt pool boundary resulted in the local soft regions affected by the melt pool structure. The local vulnerability contributed to the direction dependence of the tensile ductility of the specimen.

Anisotropic effects in the nondipole relativistic photoionization of hydrogen

In the nonrelativistic and dipole regime of multiphoton ionization, spherical symmetry in all but the polarization direction of the laser pulse ensures that directional dependency in the photoelectron spectra is limited to the laser polarization direction, with the final distribution exhibiting no asymmetry along the propagation direction of the laser. When relativistic effects and spatial dependency in the external potential are accounted for however, the addition of time dilation and radiation pressure both impose anisotropic effects. Previously we have found that nondipole effects induce a redshift in the photoelectron energy distribution, while conversely relativistic effects induce a blueshift, with the net effect of an apparent near-cancellation of the two. In this work we study these effects further. By examining photoelectron momentum distributions acquired from simulations with the time-dependent Dirac equation we propose explanatory models for both phenomena and present a simplified model of the shifts as a function of the angle relative to the propagation direction of the laser pulse. It is found that both nondipole and relativistic effects must be accounted for on an equal footing in order to correctly describe the photoelectron momentum distribution in the high-intensity regime.

A framework and review of evidence of the importance of coral reefs for marine birds in tropical ecosystems.

As global heating and other anthropogenic influences alter tropical marine environments, it is unclear how marine bird populations will be impacted and whether their current roles in tropical marine ecosystems will change. Although marine birds roost and breed on tropical islands in large numbers, the direct trophic interactions between these birds and their prey across the tropics are poorly documented. We present a first framework for evaluating the dependence on and contributions of marine birds to tropical coral reef ecosystems and use it to examine the evidence for different kinds of interaction, focusing primarily on avian diets. We found 34 publications between 1967 and 2023 that presented a total of 111 data sets with enough detail for quantitative dietary analysis of tropical marine birds. Only two bird species out of 37 (5.4%) had diets of >50% coral reef fishes and only one, the Pacific Reef Egret, appeared to depend almost entirely on reef-based production. Marine birds are also prey for other marine organisms, but insufficient data are available for quantitative analysis. Evidence for indirect effects of birds in tropical marine environments is stronger than for direct dependence on coral reefs, particularly in relation to nutrient concentration and the fertilisation impacts of guano on corals. Dispersal of propagules (e.g. seeds, spores, invertebrate eggs) by bathing, drinking, resting or foraging birds is under-studied and poorly documented. Although the degradation of coral reefs appears unlikely to have a significant direct impact on food availability for most marine bird populations, indirect effects involving marine birds may be disrupted by global environmental change.

Analysis of data on phytophotodermatitis caused by contact with the sap of plants of the genus Hogweed (&lt;i&gt;Heracleum&lt;/i&gt; L.)

The rapid spread of overgrowth of plants of the genus Hogweed, associated with their use as an agricultural fodder crop, is currently a serious problem for the Russian Federation. This process has a negative impact on the biodiversity of the vegetation cover, destroying natural ecosystems and causing significant economic damage. However, the active spread of hogweeds on the territory of the Russian Federation would not be so catastrophic if it were not for their aggressive properties: in contact with the skin, plant sap causes phytophotodermitis, which is a burn similar to thermal burns of I, II and III degrees. The article considers qualitative and quantitative composition of the main biologically active substances of hogweeds sap and shows that the biologically active substances causing phytophotodermatitis are furanocoumarins. It has been established that the pronounced photosensitizing activity of furanocoumarins is determined by the presence of a furan ring at positions 6,7 and 7,8 of coumarin. Such compounds include psoralen and its main derivatives: xanthotoxin, bergapten, bergamotin, imperatorin, isopimpinellin and angelicin (isopsoralen) and its main derivatives: sfondin, pimpinellin, isobergapten. Substitution of furan ring condensed with coumarin ring as well as change of its position leads to loss of photosensitizing activity. It was determined that the activity of plant sap of the genus Hogweed is in direct dependence on such factors as qualitative and quantitative content of furanocoumarins in the plant sap, the amount of sap and the area of the skin lesion zone, the time of contact of the affected skin areas with the plant sap, the intensity of ultraviolet irradiation and the time of its effect on the affected areas, as well as the peculiarities of each person (e.g., age, skin phototype). The methods of standard therapy of three clinical forms of phytophotodermatitis were analyzed. It was found that currently no specific clinical recommendations for the diagnostics and treatment of phytophotodermatitis resulting from contact with the sap of hogweeds. At the end of the article, the conclusion is formulated that one of current and promising tasks of pharmaceutical technology may be the development of drugs used in the treatment of burns caused by the sap of plants of the genus Hogweed, taking into account the mechanism of action of furanocoumarins.