Recent publications
The cryopreservation of human spermatozoa is an integral part of cryobiology, aiming to support the in-vitro fertilization. The latter relies on the availability of as much as possible reproductively active spermatozoa, whose number after thawing decreases due to the accompanied freezing injury and the cytotoxicity of cryoprotectants. An innovative option to circumvent these obstacles is to make the freezing interface non-wettable, by coating it with rapeseed oil soot possessing intrinsic cryoprotective properties, delaying the ice formation and possibly providing identical rates of intracellular dehydration and extracellular crystallization. It may mean that this technique can reduce or avoid the need of harmful cryoprotective agents, but to reach such a developmental stage, the synergistic effect of certified cryoprotectants and cooling velocities on the efficiency of soot-mediated sperm cryopreservation must be clarified. With the intention to address this research gap, we reveal that the slow freezing/thawing of distinct mixtures of three cryoprotectants (SpermFreeze™, CryoSperm™ and DMSO) and the human semen of nine patients equalizes the percent of survived spermatozoa, but declines their curvilinear velocity. At instant freezing (~7-20 s) and slow thawing, via specially-designed soot fabric-coated sheet metal cryoboxes, the inclusion of 10 % DMSO is noxious, but the post-thaw motility reaches 74-100 % independently of the cryoprotective solutes. These surprising findings are ascribed to the formation of a quasivitrified semen, whose complete freezing ensures a fraction of extracellular ice matching that from the equilibrium phase diagram , eluding the osmotic shocks and paving the path for future replacement of the classic vitrification.
Exposure to metal nanoparticles (NPs) is known to induce inflammatory responses in various tissues, thus limiting their therapeutic potential. NOD-like receptor protein 3 (NLRP3) inflammasome activation is an essential component of innate immunity playing a significant role in inflammation and development of inflammatory diseases. Therefore, the objective of the present review was to summarize data on the role of NLRP3 inflammasome in proinflammatory effects induced by metal NPs, and to discuss the underlying molecular mechanisms, including its dependence on the physical and chemical properties of metal NPs. Titanium, zinc, silver, aluminum, iron, cobalt, nickel, vanadium, and tungsten nanoparticles, as well as metal-based quantum dots have all been shown to induce NLRP3 inflammasome activation in vitro in macrophages and monocytes, dendritic cells, keratinocytes, hepatocytes, enterocytes, microglia, astrocytes, lung epithelial cells, endotheliocytes, as well as certain types of cancer cells. In vivo studies confirmed the role of NLRP3 pathway activation in development of colitis, pulmonary inflammation, liver damage, osteolysis, and neuroinflammation induced by various metal nanoparticles. Briefly, particle endocytosis with subsequent lysosomal damage, induction of ROS formation, K⁺ efflux, increased intracellular Ca²⁺ levels, and NF-κB pathway activation results in NLRP3 inflammasome complex assembly, caspase-1 activation, and cleavage of pro-IL-1β and pro-IL-18 to mature proinflammatory cytokines, while gasdermin D cleavage induces pyroptotic cell death. Moreover, small-sized and rod-shaped metal NPs exert a more profound stimulatory effect on NLRP3 inflammasome activation, but contrary findings have also been reported. Taken together, it is concluded that NLRP3 inflammasome may mediate both adverse proinflammatory effects of metal nanoparticles, as well as their beneficial effect when used as antitumor agents.
The new lithium niobate-tantalate hybrid optical material platform can be used for special tasks in integrated photonics: waveguides, periodical poling, modulators and sensors. A comparison of structure and optical characteristics was performed between optical waveguides obtained by annealed proton exchange in lithium niobate (LN) and mixed lithium niobate-tantalate (LNT) solid solutions. The prism coupling method, IR-spectroscopy and X-ray diffraction were used to study the annealed proton exchange waveguides. The calculated increment of refractive index after proton exchange was 0.129 for LNT compared to 0.112 for LN. This unusual high increase of the refractive index of LNT is likely due to the presence of both compressive and tensile deformations of the crystal lattice of LNT as a result of proton exchange. The results of IR-spectroscopy indicate a more intense proton exchange in mixed crystals, which leads to greater structural disorder, in contrast to LN. The diffusion coefficients are higher for LNT unlike LN crystals and annealing relaxation of crystal lattice stresses is faster, subsequently. This is the first report on using proton exchange technology for optical waveguides fabrication in LNT solid solutions.
The moderately salty and lightly salty lakes and marshes near the Black Sea are specific in terms of their high degree of physical alteration; intensive hydromorphological pressure ; and point-source and diffusive enrichment with biogenic, organic and inorganic compounds. Nutrients are among the most regularly measured variables in monitoring programs, providing the most complete information for long-term analysis and assessment. Nonetheless, their results need a final summary score, such as the water quality index, which assesses spatial and temporal conditions very well. In this study, we used all available data for Varna and Burgas Lakes from state monitoring for six years (2016-2021), using the parameters monitored with the greatest frequency. The aims were to trace temporal changes in the water quality parameters to determine which of the biogenic elements had the greatest significance for the variance in water quality while seeking the most contributing elements for the formation of the Canadian Council of Ministers of the Environment water quality index (CCME-WQI). The objectives were achieved via multiple factor analysis (MFA) loaded with the results for the environmental variables and the final scores of the CCME-WQI since this multivariate analysis allows simultaneous consideration of multiple data series while balancing the influence of each set of variables. MFA revealed that CCME-WQI scores were influenced solely by total phosphorus (TP) in Varna Lake, where TP was negatively correlated with total nitrogen. In Burgas Lake, TP had the greatest influence on the CCME-WQI, but in this slightly saline lake, pH and dissolved oxygen were also negatively correlated with the complex assessment scores. The approach developed in this study is simple to implement and provides information for the simultaneous use of both the CCME-WQI and the MFA, which could optimize monitoring programs by directing sampling efforts on fewer parameters that could be analyzed more often or from more sampling sites.
In [1] it was shown that the degree (vertex) spanning tree enumerator polynomial of a connected graph G is a real stable polynomial (that is, it does not vanish if all the variables have positive imaginary parts) if and only if G is a distance-hereditary graph. We prove a similar characterization for weighted graphs. With the help of this generalization, define the class of weighted distance-hereditary graphs.
Introduction
The emergence and development of LGBTQI + studies within the past few decades have faced many challenges. Although there is a growing body of scientific knowledge and courses, the most recent wave of backlash against gender and sexuality studies, known as anti-gender mobilization, has drastically threatened the advancement of the field and the well-being of scholars. Based on this, the study aims to explore the personal and professional challenges faced by scholars working on LGBTQI + topics in Europe.
Methods
This study is based on 49 self-reported online questionnaires with scholars working on LGBTQI + issues across Europe. The data was collected between February 2022 and April 2023. The submitted questionnaires were individually coded with the use of MaxQDA software.
Results
The data suggests that (1) an increasing number of scholars engage in LGBTQI+ studies as a personal reflection and deploy their knowledge in activism; (2) almost half of the participants have experienced personal and institutional challenges due to the nature of their work; (3) the anti-gender mobilizations have intensified and strengthened the “dirty work” status of LGBTQI + studies; and (4) more than half of the respondents have confirmed political hostility and public attacks towards LGBTQI + studies in their country, and one third have expressed fear of future political attack in contexts where it is not prevalent currently.
Conclusions
Researchers working on LGBTQI + topics experience personal and professional difficulties that those not involved in this type of research are less likely to experience. While the threats and difficulties at the workplace and in the institutional context have affected the well-being of the participants, there is an increasing number of people who are engaged in LGBTQI + topics due to anti-gender mobilization and political hostility.
Policy Implications
Although anti-gender mobilization has become a significant political force in the past few years, there has been no coordinated response to these threats, which attack the legitimacy of LGBTQI + studies and the well-being of scholars. An integrated response and policy implementation are crucial for the development of the field. More specifically, the following should be considered when approaching the issue systematically: (1) professional solidarity; (2) Coordinated institutional support and framework on an institutional level; (3) a common strategic plan by the major professional associations; (4) inclusion of anti-gender mobilization in the strategic policies and research priorities of EU programs and politics; and (5) reconsideration of national policies regarding the production and dissemination of scientific knowledge.
Soil contamination by heavy metals represents a critical environmental risk. Innovative and sustainable remediation strategies are urgently needed to address this global challenge. Biochar, derived from biomass pyrolysis, has gained attention as an eco-friendly material for heavy metal adsorption. However, its adsorption performance is highly dependent on the pyrolysis conditions and can be further enhanced through functionalization. In this study, wheat straw biochar was optimized for enhanced porosity, carbon content, and structural stability and further functionalized by incorporating metal–organic frameworks (MOFs) to create a high-performance nanocomposite. Three MOFs—ZIF-8, UiO-66, and MIL-100(Fe)—were evaluated for their Cu2⁺ and Pb2⁺ adsorption capacities. MIL-100(Fe) emerged as the most effective due to its high pore volume and iron-active sites. Coating biochar with MIL-100(Fe) increased its surface area sixfold, achieving 419 m²∙g⁻¹, and doubled its sorption capacity for heavy metals in soil (142 mmol·kg⁻¹ for Cu2⁺ and 156 mmol·kg⁻¹ for Pb2⁺). Advanced characterization techniques, including XAFS, XRD, and SEM–EDX, revealed that the sorption mechanisms were dominated by complexation and cation exchange, with the nanocomposite demonstrating superior metal immobilization compared to neat biochar. These findings highlight the potential of the nanocomposite as an effective amendment for reducing heavy metal toxicity in soils.
The polyether ionophore monensin A (MonH), applied as silver monensinate, reacts with caesium cations to form a dinuclear complex [Mon2Cs2] the structure of which has been solved by single‐crystal X‐ray diffraction. Two Cs⁺ ions are located in the hydrophilic cage of two ligand anions, achieving coordination number eight. In addition, the metal cations are bridged by two functional groups of monensinate A, completing the inner tenfold coordination sphere. NMR studies show that the dinuclear complex dissociates to its mononuclear counterparts in methanol solutions. Further molecular dynamics theoretical modelling of the interaction of monensinate A with alkali metal ions reveals the effect of solvent polarity on the zipping ability of the ligand. Thus, in methanol, used as an explicit solvent, potassium and rubidium cations fully occupy the cavity of the ligand, whereas the sodium monensinate exists in an “open” form, with Na⁺ ions still interacting with the monodentate carboxylate group. The replacement of methanol by the less polar chloroform induces the folding of monensinate A and the formation of “closed” structures with all group 1 metal cations. The obtained data explain the specifics in the behaviour of monensinate A caused by the environment, e. g., physical state or solvent.
Mesoporous silica (SiO2) was prepared using a simple procedure from rice husks without the application of a template. Incipient wetness impregnation method was employed to prepare magnesium-doped nickel-copper- and nickel–cobalt-containing SiO2 catalysts. The obtained materials were characterized by X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), temperature-programmed reduction (TPR-TGA), and NMR and XPS spectroscopies. The study demonstrated the significant influence of Ni and Co/Cu content, as well as the sequence of Mg promotion (before or after the nickel-copper- and nickel–cobalt-modification) on the physico-chemical properties of the catalysts. The peculiar properties of the mesoporous carrier positively influenced the formation of finely dispersed nickel and/or copper/cobalt oxide species, which were readily reducible at temperatures below 600 °C. XPS analysis revealed that the surface of Mg-doped Ni-Co supported SiO2 catalysts was rich in nickel. All the prepared catalysts were active in CO2 hydrogenation to methane. The Mg-doped Ni-Co supported SiO2 catalysts showed higher catalytic activity compared to their Mg-doped Ni-Cu counterparts. The 1.5Mg10Ni5Co/SiO2 catalyst demonstrated 82% CO2 conversion and 99.5% selectivity to methane. The activity and selectivity of this catalyst was maintained at 400 °C for a reaction time of 4 h.
Can natural language represent logically impossible circumstances? Can there be logically impossible contents? The received view on semantic content allows for logically impossible contents. Much recent work in the philosophy of language and logic meant to account for hyperintensional phenomena also assumes that the answer to both of these questions is “yes.” I want to argue that this widespread assumption is indefensible. Representing the logically impossible in language, contrary to the dominant view in semantics, is not truly possible. The main argument for this position appeals to a highly plausible and minimal condition for the possession of semantic content. I call this the negative coherence condition . Any candidate's meaningful sentence S possesses semantic content only if the content of S is logically compossible with the content of the meaning‐constituting sentences associated with each of the descriptive constituent terms of S . However, the sentences of L thought to express logically impossible contents that cannot meet the negative coherence condition on semantic content. In an intuitive sense, sentences with logically impossible contents are incoherent with the conditions of their own meaningfulness.
This study is oriented to elaborating mathematical models for the synthesis and analysis of Wildhaber-type globoid worm gear mechanisms, which are distinct within the worm gear transmission group for their integration of a cylindrical gear and a toroidal-form globoid worm. These gears mechanisms are characterized by their non-orthogonal axes of rotation, a departure from traditional designs where axes are typically perpendicular. This work focuses on developing a mathematical modeling approach that defines and studies the active tooth surfaces and the mesh region of the synthesized gear set. Special attention is given to studying the singularity of the meshed active tooth surfaces. The locations of the ordinary nodes and undercutting points and the orientation of the total circumferential velocity are determined. This modeling is essential for predicting and improving the hydrodynamic load capacity of the synthesized gear transmission. The results of this study provide valuable information into the operational advantages of the Wildhaber-type gear set, highlighting its potential as a high-power transmission application where precision and efficiency are essential.
Dysfunction of the main inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is the underlying reason behind many neurological disorders including Alzheimer’s and Huntington’s diseases, autism spectrum disorders, anxiety, depression, hypertension, and cardiovascular diseases, among others. Here, we address neurotransmitter-induced alterations of synaptosomal and model membrane electrical properties for elucidating membrane-related biophysical mechanisms of neurological disorders. We focus on membrane surface characteristics of the pinched off nerve endings synaptosomes, which for decades have been a powerful tool in neurobiology. Microelectrophoretic measurements of GABA-treated negatively charged synaptosomes from rat cerebral cortex reveal lower negative zeta potential as a result of reduced electrical charge on the membrane surface at (1–4 h) after isolation. Conversely, enhancement of the surface parameters of synaptosomes (17–22 h) post isolation is obtained due to additional negatively exposed groups on the surface of the vesicles. The electrical properties of bilayer lipid membranes are probed by electrochemical impedance spectroscopy, reporting as light increase of the membrane electrical capacitance in the presence of GABA, likely related to membrane thinning and dielectric permittivity alterations. The neurotransmitter inhibits sodium–potassium as well as the total ATPase activity and slightly enhances magnesium-ATPase of native synaptic membranes. At low (pM) GABA concentrations the activity of acetylcholinesterase (AChE) in synaptic membranes increases. AChE inhibition is reported at higher GABA concentrations. The relation between the surface electrical properties of cells and the enzymatic activity of brain ATPases and AChE, as examined here, are expected to be helpful in the elucidation of membrane-mediated molecular mechanisms relevant to neurological disorders and conditions.
Graphical Abstract
Dithienylethenes (DTE) are a rare class of photoswitches, which are capable of undergoing a fast photochemical cyclization leading to increased aromaticity of the closed isomer. At the same time in most of the tautomeric compounds the tautomeric state is strongly affected by the change in the aromaticity of the involved aromatic rings. Very recently it has been shown that the implementation of DTE moiety in salicylideneaniline leads to switching of the stable open form enol tautomer to thermodynamically stable keto tautomer upon cyclization. In the present communication we consider in depth, by using DFT and TD‐DFT methodology, the reasons for low efficiency of these new switches and further develop the idea for DTE based switching in proton cranes.
van der Waals heterostructures provide a versatile platform for tailoring electrical, magnetic, optical and spin transport properties via proximity effects. Hexagonal transition metal dichalcogenides induce valley Zeeman spin–orbit coupling in graphene, creating spin lifetime anisotropy between in-plane and out-of-plane spin orientations. However, in-plane spin lifetimes remain isotropic due to the inherent heterostructure’s three-fold symmetry. Here we demonstrate that pentagonal PdSe2, with its unique in-plane anisotropy, induces anisotropic gate-tunable spin–orbit coupling in graphene. This enables a tenfold modulation of spin lifetimes at room temperature, depending on the in-plane spin orientation. Moreover, the directional dependence of the spin lifetimes, along the three spatial directions, reveals a persistent in-plane spin texture component that governs the spin dynamics. These findings advance our understanding of spin physics in van der Waals heterostructures and pave the way for designing topological phases in graphene-based heterostructures in the strong spin–orbit coupling regime.
In this work, the characteristics of a single-dye laser (LDS 821) with gold nanorods (NRs) as scattering centers were examined to better understand how random lasers operate in the near-infrared (NIR) region. The study presents the results of using Au NRs of different sizes (22.3 nm × 7.2 nm and 18.8 nm × 6.3 nm) and various concentrations (1 and 2 × 10¹⁸ cm⁻³). Random laser emission was achieved from the dye using both sizes of the Au NRs and at both concentrations. However, using smaller Au NRs allowed reaching coherent emission with lower pumping energy than with larger particles. In addition, a higher concentration of these NRs ensured obtaining coherent emission at even lower pumping energy.
Here, we present ammonite localities of high scientific value from the Bathonian and Callovian strata of Northwest Bulgaria. A review of the available faunas was made, along with new illustrations and identifications of ammonites. These include abundant Perisphinctidae and Macrocephalitidae, but also accessory Oppeliidae, Morphoceratidae, Tulitidae, Stephanoceratidae and Haploceratidae. Some extreme rarities, such as Reineckeiidae, Kosmoceratidae, Parkinsoniidae and Peltoceratinae, and a limited number of Phylloceratina and Lytoceratina, also belong to the fossil assemblages. In addition, common bivalves, brachiopods and echinoids accompany the ammonites. The NW Bulgarian fossil sites are particularly valuable from the perspective of paleobiogeography and correlation since a number of distinctive ammonite taxa, as well as genera and species introduced on type material from these sites, have been found elsewhere in Europe and beyond. Besides, the localities offer the most comprehensive understanding of the phenomena they represent and have the potential for further multidisciplinary paleontological studies. Cultural, educational and geoconservation standards can be derived from them. By raising public awareness of the fossil sites from NW Bulgaria, this contribution will trigger institutional action to protect them.
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Sofia, Bulgaria
Head of institution
Academician Julian Revalski