Showing papers by "Bulgarian Academy of Sciences published in 2022"

Coastal sea level monitoring in the Mediterranean and Black seas

Abstract: Abstract. Employed for over a century, the traditional way of monitoring sea level variability by tide gauges – in combination with modern observational techniques like satellite altimetry – is an inevitable ingredient in sea level studies over the climate scales and in coastal seas. The development of the instrumentation, remote data acquisition, processing, and archiving in the last decades has allowed the extension of the applications to a variety of users and coastal hazard managers. The Mediterranean and Black seas are examples of such a transition – while having a long tradition of sea level observations with several records spanning over a century, the number of modern tide gauge stations is growing rapidly, with data available both in real time and as a research product at different time resolutions. As no comprehensive survey of the tide gauge networks has been carried out recently in these basins, the aim of this paper is to map the existing coastal sea level monitoring infrastructures and the respective data availability. The survey encompasses a description of major monitoring networks in the Mediterranean and Black seas and their characteristics, including the type of sea level sensors, measuring resolutions, data availability, and existence of ancillary measurements, altogether collecting information about 240 presently operational tide gauge stations. The availability of the Mediterranean and Black seas sea level data in the global and European sea level repositories has been also screened and classified following their sampling interval and level of quality check, pointing to the necessity of harmonization of the data available with different metadata and series in different repositories. Finally, an assessment of the networks' capabilities for their use in different sea level applications has been done, with recommendations that might mitigate the bottlenecks and ensure further development of the networks in a coordinated way, a critical need in the era of human-induced climate changes and sea level rise.

Antioxidant Defense during Recovery of Resurrection Plant Haberlea rhodopensis from Drought- and Freezing-Induced Desiccation

Abstract: In this study, the contribution of nonenzymatic (ascorbate, glutathione) and enzymatic antioxidants (superoxide dismutase, catalase, glutathione reductase, glutathione S-transferase) in the first hours of recovery of the resurrection plant Haberlea rhodopensis from drought- and freezing-induced desiccation was assessed. The initial stage of recovery after desiccation is critical for plants, but less investigated. To better understand the alterations in the activity of antioxidant enzymes, their isoenzyme patterns were determined. Our results showed that ascorbate content remained high during the first 9 h of rehydration of desiccated plants and declined when the leaves' water content significantly increased. The glutathione content remained high at the first hour of rehydration and then strongly decreased. The changes in ascorbate and glutathione content during recovery from drought- and freezing-induced desiccation showed great similarity. At the beginning of rehydration (1-5 h), the activities of antioxidant enzymes were significantly increased or remained as in dry plants. During 7-24 h of rehydration, certain differences in the enzymatic responses between the two plant groups were registered. The maintenance of a high antioxidant activity and upregulation of individual enzyme isoforms indicated their essential role in protecting plants from oxidative damage during the onset of recovery.

Recovery of a Cubic Non-linearity in the Wave Equation in the Weakly Non-linear Regime

Abstract: We study the inverse problem of recovery a compactly supported non-linearity in the semilinear wave equation $$u_{tt}-\Delta u+ \alpha (x) |u|^2u=0$$ , in two and three dimensions. We probe the medium with complex-valued harmonic waves of wavelength h and amplitude $$h^{-1/2}$$ , then they propagate in the weakly non-linear regime; and measure the transmitted wave when it exits $${{\,\mathrm{supp}\,}}\alpha $$ . We show that one can extract the Radon transform of $$\alpha $$ from the phase shift of such waves, and then one can recover $$\alpha $$ . We also show that one can probe the medium with real-valued harmonic waves and obtain uniqueness for the linearized problem.

Intensity-based dynamic speckle method using JPEG and JPEG2000 compression

Abstract: Statistical processing of speckle data enables observation of the speed of processes. In intensity-based pointwise dynamic speckle analysis, a map related to speed's spatial distribution is extracted from a sequence of speckle patterns formed on an object under coherent light. Monitoring of time evolution of a process needs storage, transfer, and processing of a large number of images. We have proposed lossy compression of these images using JPEG and JPEG2000 formats. We have compared the maps computed from noncompressed and decompressed synthetic and experimental images, and we have proven that both compression formats can be applied in the dynamic speckle analysis.

Hemorheological and microvascular disturbances in patients with type 2 diabetes mellitus

Abstract: BACKGROUND: In the blood vessels the impaired hemorheological parameters in patients with type 2 diabetes mellitus (T2DM) could lead to elevated flow resistance, increased forces at the endothelial wall and to microvascular disturbances. OBJECTIVE: The aim of the study is to investigate the hemorheological variables and the changes of the skin blood flow responses to cold stress in T2DM patients. METHODS: The basic hemorheological parameters: hematocrit (Ht), fibrinogen (Fib), whole blood viscosity (WBV) and plasma viscosity (PV) were examined in 20 patients with T2DM and a control group of 10 healthy age and sex matched controls. The mechanisms of vascular tone regulation were investigated using the wavelet analysis of the skin temperature oscillations (WAST). The degrees of the microvascular tone changes were determined during a cold test in the endothelial (0.02–0.0095 Hz), neurogenic (0.05– 0.02 Hz) and myogenic (0.05– 0.14 Hz) frequency ranges. RESULTS: Significant increase of Fib and WBV in the patients in comparison to controls was found. The mean values of the amplitudes of the skin temperature (ST) pulsations decreased significantly during the cold stress only in the endothelial frequency range for the diabetic patients. CONCLUSIONS: The results of our study reveal parallel impairment of the blood rheological parameters and the cutaneous microcirculation in T2DM patients.

Physiologic systems dynamics, coupling and network interactions across the sleep-wake cycle

Abstract: We review recent progress in understanding fundamental aspects of physiologic regulation during wake and sleep based on modern data-driven, analytic, and computational approaches with focus on the complex dynamics of individual physiological systems, their transient forms of coupling, and the role of network interactions among physiological systems in generating states and functions at the integrated organism level. The presented empirical findings indicate that sleep-wake and circadian cycles do not simply modulate basic physiologic functions by generating rhythms with a fixed periodicity but influence physiological systems dynamics simultaneously over a broad range of time scales. Furthermore, transitions across physiologic states are characterized by modulation in the strength of physiologic coupling and by hierarchical reorganization in the network of interactions among physiological systems, indicating high-network flexibility in response to change in physiologic regulation. We underscore the importance of novel, integrative approaches to investigate physiological dynamics of individual systems across multiple scales and to quantify emergent global behaviors of networks of physiologic interactions to comprehensively understand physiologic state and function.

Neuromodulatory Mechanisms of a Memory Loss-Preventive Effect of Alpha-Lipoic Acid in an Experimental Rat Model of Dementia

Abstract: This study evaluates some of the neuromodulatory mechanisms of the memory loss preventive effect of alpha-lipoic acid (ALA) in a scopolamine (Sco)-induced rat model of Alzheimer's disease (AD) type dementia. Our results confirmed that Sco administration induces significant memory impairment, worsens exploratory behaviour and habituation, increases acetylcholinesterase (AChE) activity, and induces pathological monoamine content changes in the prefrontal cortex and hippocampus. ALA administration largely prevented Sco-induced memory impairment. It also improved exploratory behaviour and preserved habituation, and it decreased AChE activity, reversing it to control group levels, and corrected aberrant monoamine levels in the prefrontal cortex and hippocampus. According to the data available, this is the first time that ALA-induced changes in AChE and monoamine levels in the prefrontal cortex and hippocampus (brain structures related to learning and memory) have been demonstrated in a Sco-induced rat model of AD type dementia.

How Important are Small Lotic Habitats of the Western Balkans for Local Mayflies

Abstract: Mayflies are amphibious insects which represent an important link in food and energy transfer from aquatic to terrestrial habitats. They constitute a large proportion of the aquatic ecosystems’ biomass. Although our knowledge about mayfly (bio)diversity in the Balkan Peninsula is still far from complete, more extensive systematic studies have been conducted within the last decade. In this chapter we explore development of mayfly research in the area of the Western Balkans, mayfly species richness in various small lotic habitats, including springs, streams and rivers, and determine the importance of such habitats for conservation of local mayflies. We discuss the value of mayflies as bioindicators of freshwater ecosystems’ health, as well as the influences of various anthropogenic activities on mayfly assemblages in small lotic habitats of the Western Balkans. Moreover, we present current gaps in research and we give recommendations for future directions of mayfly research in the area of the Western Balkans.

First-line Anti-GD2 Therapy Combined With Consolidation Chemotherapy in 3 Patients With Newly Diagnosed Metastatic Ewing Sarcoma or Ewing-like Sarcoma

Abstract: Despite multimodal therapy, the prognosis of patients with metastatic Ewing sarcoma (ES) remains poor, with new treatments urgently needed. The disialoganglioside GD2, a well-established tumor-associated antigen, is expressed in 40% to 90% of ES cells, making it a suitable therapeutic target. Here we report 3 cases with newly diagnosed, metastatic, GD2-positive ES or Ewing-like sarcoma treated with the anti-GD2 antibody dinutuximab beta in addition to standard chemotherapeutic regimens. Treatment was well-tolerated, and all patients achieved complete remission, without evidence of relapse. First-line anti-GD2 immunotherapy in patients with metastatic, GD2-positive ES or Ewing-like sarcoma represents a promising therapeutic option that warrants further clinical evaluation.

Research of gear drives

Abstract: Abstract Worm gear drives possess important advantages such as: compact design, high power density due to a high gear ratio within a single gear stage. However, these gear drives often show high sliding speeds within the tooth contact, resulting in relative low efficiency coefficient in the meshing. Therefore, an exact calculation regarding efficiency in the meshing and load capacity is important during the beginning stage of the machine design process. Currently, no calculation method is available to analyze worm gears considering efficiency in meshing and contact strength. The objective of the research implemented was to analyze extensively the meshing efficiency and the contact stress behavior of various geometry designs of worm gears drives. Optimization research has been implemented considering the criteria mentioned. All calculations and theoretical analysis have been implemented for different center distances, different modules, gear ratios and rotational speeds of the worm shaft. Simulation results are shown and discussed. Important conclusions and recommendations are suggested.

Study of a system for creating a statistical model of the electroless plating of Cu-Ni-P alloys

Abstract: The electroless plating method is the most convenient for the metallisation of dielectrics. During this statistical study of the process, complex relationships were found between the composition of the electrolyte and the deposition regime. The complexity of this technology is an important multifactorial object of the study. An adequate linear regression model for electroless deposition of Cu-Ni-P alloy coatings was obtained by conducting a planned factorial experiment. It allows predicting the thickness of the electroless deposited alloy coating based on certain values of the input parameters (concentrations of copper sulphate, nickel sulphate and sodium hypophosphite) in the studied factor space, as well as further optimisation of the process.