This study investigates the surface complexity of the Protonilus Mensae region in the northern hemisphere of Mars using an integrated approach based on fractal dimension (FD) and lacunarity analysis. Digital elevation model (DEM) data derived from the Mars Orbiter Laser Altimeter (MOLA), with a spatial resolution of 463 m, were analyzed using Python-based algorithms. Surface roughness was analyzed using a variogram-based fractal method. The results show that the topography of Protonilus Mensae exhibits fractal behavior, with FD values ranging from 2.11 to 2.70 and a mean value of 2.35. Spatial patterns of FD reveal predominantly low to moderate surface complexity. Lacunarity analysis was employed to characterize spatial heterogeneity and the distribution of topographic gaps. (Lacunarity means empty spaces (gaps) in DEM with similar fractal dimensions but different surface view.) The results show a strong dependence of lacunarity on elevation, with maximum heterogeneity occurring at intermediate elevations associated with fretted (not smooth) terrain. Lower and higher elevations exhibit reduced lacunarity. The combined fractal and lacunarity results suggest that the present-day morphology of Protonilus Mensae represents a degraded landscape shaped by a balance between roughness-enhancing processes and smoothing processes. This integrated quantitative approach provides new insights into the geomorphological evolution of not flat terrains on Mars.
The increasing prevalence of antimicrobial resistance has intensified the search for safe and effective alternatives to conventional antimicrobial agents, including natural compounds. L-malic acid, a naturally occurring in fruits and plant tissues, has attracted interest in this respect. The present study evaluated the in vitro antimicrobial activity of a formulation containing L-malic acid against reference strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans using a suspension assay. The tested formulation comprised 60% (w/w) L-malic acid, 30% (w/w) starch, and 10% (w/w) organosilica, obtained from product IONSIEVE MALOX®. The formulation was evaluated at nominal L-malic acid concentrations of 1, 2, and 3 mg·L-1 and exposure times of 1, 4, and 24 h using final inoculum levels of 5×10² or 1×10² CFU/mL. Under the tested conditions, the formulation reduced the number of recoverable cells of all examined microorganisms in a concentration-, time-, and inoculum-dependent manner. At 3 mg·L-1, no recoverable E. coli cells were detected after 1 h at 5×10² CFU/mL, whereas C. albicans reached undetectable levels after 4 h and P. aeruginosa and S. aureus after 24 h. At 1×10² CFU/mL no recoverable C. albicans cells were detected after 1 h, while in the other tested microorganisms - after 4 h. The formulations at 1 and 2 mg·L-1 also reduced recoverable counts of all tested strains, although with weaker early effects. These findings indicate that, under in vitro suspension-test conditions, L-malic acid exhibited significant antimicrobial activity against the tested bacterial and yeast strains and merit further investigation under application-relevant conditions.
MCNP6 computer code is used to model HTR-10 core reactor. UO2 fuel is used. We predict the Flux and power distribution for normal core loaded by UO2 fuel pebbles of the reference HTR-10 reactor. The MCNP model consisted of the reactor structure which included the graphite reflector, the borated carbon bricks surrounding it and the pebble-bed core. The results show an analogue between the thermal neutron flux distribution and the power distribution, where the thermal neutrons are responsible for causing the fission, and hence power generation. The thermal neutron flux and power generation have its maximum value at the core center and decreases as we move away from the center to core boundary. The thermal flux is increased near the reflector because the neutron reflector scatters back (or reflects) into the core many neutrons that would otherwise escape. The neutrons reflected back into the core are available for chain reaction (reflector savings).
This study investigates the potential of taro (Colocasia esculenta L.) peel, a significant agricultural waste, as a raw material for high-quality solid fuel briquettes. To optimize characteristics, briquettes were pre-treated by oven-drying (90ºC-120ºC, 30-60 min) and assessed via proximate analysis, DSC, and Ignition Rate testing. Results confirmed successful property upgrades, identifying 120ºC for 45 minutes as optimal for energy concentration. This condition yielded the highest Fixed Carbon (55.08%) and total thermal output (1,689.176 J/g by DSC), plus the maximum Ignition Rate (0.0008778 g/second), confirming superior combustion kinetics. The 120ºC variant's superior energy content and confirmed thermal stability (onset 206.840ºC) establish it as the most promising fuel. Findings validate the technical feasibility of transforming taro peel waste into an energy-dense solid fuel, demonstrating a viable strategy for sustainable waste management and renewable energy generation.
Anaerobic digestion (AD) is an effective biotechnological process for treatment of different agricultural, municipal and industrial wastes. However, it is a very unstable process in regard to the biogas reactors operation. This is due to the complicated interactions between different microbial species as well as of the complex transformations of the organic matter affected by a variety of environmental factors. The most common reactor type used for AD of wastewaters is the continuously stirred tank reactor (CSTR). AD is a process carried out by microorganisms that is widely used to convert various organic wastes into bioenergy (hydrogen and methane-rich biogas) and nutrient-rich digestate (natural fertilizer). AD of organic waste mixtures (AcoD) offers several advantages such as better biodegradation and process stability, while increasing biogas yield due to synergistic effects. However, the operation of effective AD and AcoD processes requires a full understanding of important operating parameters. Use of mathematical models is a powerful tool for investigations and optimisation of the AD. A large number of papers in the field of the mathematical modeling of AD are known. On the basis of such models, monitoring systems (software sensors) and automatic control of the AD processes have been theoretically developed. However, most of them are very complicated and difficult to implement in industry. Recently, artificial intelligence (AI) has emerged as an innovative approach to the computer modelling and optimization of AD and AcoD processes. Compared to conventional methods and models, AI-based algorithms have made modelling these processes much easier. Various AI algorithms, including multivariate statistical analyses, tree-based machine learning, nature-inspired optimization, support vector machine, and artificial neural networks (ANNs) have been widely used to model the AD processes. This paper reviews the current state of the art in the AD in CSTR modelling and identifies the key areas that require further research endeavours. This review discusses AI applications for AD process modeling as well. A critical comparison is made with some of the popular mathematical models and algorithms for monitoring and optimization designed on their basis. The review presents also future research directions in this area.
The forest fires are very common in the territory of Bulgaria, especially in cases of long summer droughts. They represent one of the most significant challenges in forest management, both from an economic and silvicultural perspective. The implementation of reforestation measures aimed at restoring destroyed forest ecosystems necessitates comprehensive studies on the changes in soil composition and properties. This paper presents results from a study on the dynamics of changes in the composition and properties of Cinnamonic Forest soils (Chromic Luvisols) affected by wildfires in Southwestern Bulgaria. The research examines changes in total carbon content, total nitrogen, pH levels, and the C/N ratio. The diverse nature of the factors influencing the dynamics of soil property alterations following wildfires underscores the need to investigate the consequences in each specific case of forest fire.
This study applies fractal analysis to characterize the topographic complexity of the Republic of Bulgaria using contour lines derived from a high-resolution Digital Elevation Model (DEM). The fractal dimension (FD), estimated via the box-counting method, serves as a quantitative indicator of spatial heterogeneity across different hypsometric belts and relief types. Results reveal an overall mean FD of approximately 0.784, with values increasing from lowlands through hills to mountain areas. Within the mountain belt, the low mountain zone (600–1000 m a.s.l.) exhibits the highest fractal dimension, while middle and high mountain zones show decreasing FD values. Minimum FD values display a narrow range, whereas maximum FD values fluctuate more broadly, indicating somewhat greater landscape fragmentation in certain areas. Spatial patterns of fractal dimension correspond closely with major tectonic features, including the Stara Planina mountain range and Eastern Rhodopes, where tectonic block boundaries coincide with elevated FD values. The northern part of Bulgaria, geodynamically stable, exhibits lower fractal dimensions compared to the more active southern regions. Additionally, the highest elevation areas tend to have the lowest FD values, attributed to their limited spatial extent and shorter contour line lengths. These findings contribute to a deeper geomorphological understanding of Bulgaria’s terrain and demonstrate the utility of fractal metrics in regional landscape analysis.
The creation of the three well-known companies engaged in Environmental Engineering is being tracked. The report aimed to present applications of ecological engineering methods to Regenerative Agriculture. Three examples are given: First – development of Decision Support System to help irrigated crops growers. Second - The project “Synergism – key to sustainable Agriculture” in the Institute of Soil Science, Agrotechnologies and Plant Protection, Sofia, Bulgaria. The result is development of the scientific basis of a new Innovative approach for fertilization and irrigation of agricultural crops in a changing climate for sustainable agriculture. Third - Australian Net Zero Institute and University of Sydney are examining the exploration, extraction, and processing of critical mineral resources. The medium-to long-term focus of the Net Zero Institute is on recycling critical materials in end-of-life products and substituting critical materials in new products. Results of these projects clarify the importance of ecological engineering methods for Circular Solutions in ecology.
In vitro studies of the enzyme chitinase for inhibitory effect on oval fungi Sacharomyces cerevisiae and Candida albicans were performed in order to assess its prospect of practical application as an antimycotic agent. Antimycotic action against both examined species was established in studies conducted by the agar-gel diffusion method. Тhe effect enhanced with increasing the enzyme concentration (P<0.01) and the exposure time. After a two-hour exposure to chitinase of the tested oval fungi in suspensions with a density of 2x106 CFU/ml, the decrease in their quantity was average 17.5%, after 4 hours – by 32.5%, and after 24 hours – almost twice.
Information is presented on the principles of organic farming, which is based on the dynamic relationship between soil, plants, animals, humans, and the environment. The main goal of the organic farming system is to support the natural cycles of life without harming nature. The main principles for the sustainable development of organic farming and the strictly regulated forms of sustainable farming, which cover the criteria for ecological production to the highest degree, are indicated. A characteristic of organic farming is given, with the concept of soil as a biological system taking center stage. Approaches to the organic production system are presented, as well as the advantages and disadvantages of organic farming.
A large number of factories were built on the territory of Bulgaria in the 1960s and 1970s. In some areas, heavy metal pollution greatly worsened soil fertility. This is the case with the soils in the area of the Copper Mining Plant in the Srednogorie region. A significant part of the surface horizons of the soil is acidified to a very high degree and has an exchangeable acidity that is toxic to plants. Some of the studies are presented, which establish that acidification and accumulation of copper is mainly in the surface layer of the soil and in the zone of mechanical displacement up to 30 cm. Vegetation experiments were carried out with arable and subsoil from the "Gradinite" area. Indicator crops are corn, alfalfa, turnips and peas. 3 precise field experiments were also carried out, in which the influence of various land improvement agents was tested - manure, ash, phosphorization and mineral fertilization. Technological solutions have been developed to restore the fertility of contaminated soils in the area of the Copper Mining Plant in the Srednogorie region – through a combination of chemical reclamation and mechanical displacement of the layers, chemical and biological reclamation of contaminated soils and for heavily eroded and skeletal soils.
This paper addresses the design of an active Fault-Tolerant Control (FTC) strategy for Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems exhibiting time-delay characteristics. An adaptive observerbased approach is proposed using a Linear Parameter Varying (LPV) model and Unknown Input Observer (UIO) techniques to estimate actuator faults and generate residuals. The proposed method leverages Linear Matrix Inequality (LMI) conditions to ensure the stability and convergence of the observer in the presence of parameter variations and delays. The fault estimation and control law are integrated to compensate for faults such as compressor mass flow and return manifold orifice deviations. Simulation results validate the robustness and efficiency of the control strategy under various fault scenarios.
Elephants are vital to their ecosystems, acting as keystone species and ecosystem engineers that help maintain biodiversity and ecological balance. Their presence and behavior significantly influence the structure of their ecosystems. They help maintain the balance of different plant and animal species, enriching biodiversity. In the present article, the importance of elephants for nature and humans in the areas they inhabit is reviewed. The main anatomical and behavioral features of elephants and the specific care for them in zoo breeding are presented. In this aspect, a survey of the conditions and care for elephants in the zoos in Sofia and Athens was carried out. The importance of climatic factors in the respective regions was also highlighted. It was established that the conditions of breeding and care for the animals are maximally tailored to their characteristics and requirements, which is why the health status of all elephants bred in both zoos is very good. The cooperation between the zoos in Sofia and Athens is fruitful for the bringing up these exotic animals.
Forty Ross 308 hybrid broiler chickens at the age of 20 days were included in the study. They were raised under the same conditions in the vivarium of the FVM at LTU - Sofia in bird cages with 10 chicks per cage. Twenty of the chickens (experimental group) received Lavandula angustifolia Mill essential oil in the daily feed ration at a final concentration of 0.01% or an average of 5 mg per chicken, from the 20th day to the 42th day of age. Pooled faecal samples were taken from all birds in both groups on the first day, on the 15th day after their arrival (in the middle of the experimental period) and at the end of the experiment. Microbiological studies of the samples were carried out, as for the isolation of microorganisms cultures were made in elective and selective nutrient media for bacteria from different groups, as well as for fungi, and their identification was carried out biochemically with the help of polymicrotests. Intake of lavender essential oil with food resulted in a more than two-fold reduction in the number of bacterial species in their faeces from major groups including pathogenic species as well as Candida ovale fungi. These data show that lavender oil exerts a significant antimicrobial effect in vivo, as a result of which their feces contain significantly less microorganisms with pathogenic potential and, accordingly, they are much louer dangerous from an epizootological point of view than those of normally fed birds.
The paper presents an overview of the investigations on the electrochemically activated water solutions. The description concerns the changes in water composition and structure leading toabnormal properties of the obtained highly alkaline and acidic fractions and their influence on vitalprocesses in living mater. The destructive action of the anolyte on different bacteria and viruses hasbeen reported. Another important problem refers to the beneficial influence of catholyte on vital processes in plants and animals. Positive effect on plants growth and production has been reported by scientists from different countries. Some unpublished results are involved. Disputable problems that require further elucidation are outlined.
Photobioreactors (PBR) can be considered as a sophisticated system where many parallel physical, chemical, biochemical and other processes proceed. Many phenomena from sub-systems must be taken into account and to be described and optimized in order to improve PBRs functioning and design. In this work, the PBR behavior for removal of CO2 from biogas by microalgae is analyzed mathematically. Model describing mixing conditions of two phases (gas-liquid) in sectioned PBR is analyzed for different gas load where backflows can influence residence time of air bubbles and part of biomass in PBR sections. This will have direct impact on so call flashing light effect (FLE) inside the vessel. This phenomenon has very solid theoretical basis, which lies in the intimate metabolic mechanisms of photosynthesis and improve cell growth and utilization of CO2 from the biogas. Hence, PBR performance and design depends on optimal functioning of its sub-systems. Optimal innovative design of PBRs includes application of system analysis theory and application of different modeling approaches for simulations of different scenarios in order to minimize the time for experiments and to guarantee success of research tasks. This paper analyses the modeling procedure when worked with sectioning column PBRs and results showed some very robust findings which further were proved in Brazilian and Bulgarian laboratories. These findings can be adapted to fulfill the overall picture of integral biorefinery concept for green technologies linked with the environmental protection and ecology.
Reliable results can be produced by using the research triangulation method. Its application is illustrated with agroecology data from Bulgaria. In several agroecological, environmental and sociological studies it is convenient and necessary to compare results of multivariate analyses derived from different data on the same territory or derived from different analyses of the same data. An appropriate approach for such comparative studies is based on the so-called “Procrustes analysis”. Its application is illustrated in search of interrelations between crop yields and soil texture, and soil hydraulic properties.
Climate change is caused by the release of greenhouse gases into the atmosphere, leading to global warming. The studies conducted focus on limiting the negative effects of climate change. In this report, we will focus on some research and solutions for protecting the environment and mitigating climate change: what are the sludges from waste water treatment plants /WWTP/; why they should be treated before use; sludge use opportunities; soil changes resulting from the use of sludge as a soil improver; study of the by-product bio-slime obtained from the production of biogas from waste. In conclusion, it is noted that in our country a number of problems with various organic waste are being worked on in order to find the most efficient and rational technological solutions for their utilization and environmental protection. New technologies close the cycles of waste from production to use of its and so protect the environment and limit negative climate change.
Thus far, attempts to mitigate global warming have been based exclusively on reducing atmospheric carbon dioxide concentration. One problem with this approach is that the lifetime of CO2 in the atmosphere is very long, and the effect of reducing CO2 emissions on decreasing atmospheric temperature will only become significant after decades. In this work, I propose reducing or even halting the increase in global atmospheric temperature by removing sensible heat from the atmosphere and transferring it to other media, such as water and/or land mass. It is shown that the annual negative effect of heating ocean water will be close to non-existent. One of the main advantages is that it has an immediate effect on atmospheric temperature. The technology to realize this idea is simple, inexpensive, and relatively well-developed. It should be noted that the proposed solution to global warming is temporary and will only work for several decades. In the long term, reducing CO2 emissions should take precedence as the main method of mitigating global warming.
As a result of military operations, soils are contaminated with shell debris and shrapnel, primarily composed of iron. Therefore, there is a strong need to understand the pathways of iron transformation in soil and the role of microorganisms in this process. The aim of this study was to investigate the interaction between soil microbiomes and ferromagnetic iron fractions that simulate materials originating from shells and mines. Cultivation of microorganisms from Ukrainian chernozem under anaerobic conditions in the liquid phase revealed that introducing the microbiome along with the starch-containing substrate (potatoes) led to a 120-fold increase in the mobilization and stabilization of soluble iron compounds compared to the control. This process resulted in concentrations of soluble Fe(II) exceeding 1 g/L within 20 days, highlighting the effectiveness of microbial organic acids as chelating agents. In contrast, aerobic cultivation in soil produced the amount of soluble iron compounds comparable to the control without added iron, indicating the assimilation of chelated compounds into microbial metabolic pathways
