Using a magnetic Frederiks transition technique, we measure the temperature and concentration dependences of splay K1, twist K2, and bend K3 elastic constants for the lyotropic chromonic liquid ...crystal sunset yellow formed through noncovalent reversible aggregation of organic molecules in water. K1 and K3 are comparable to each other and are an order of magnitude higher than K2. At higher concentrations and lower temperatures, K1 and the ratios K1/K3 and K1/K2 increase, which is attributed to elongation of self-assembled lyotropic chromonic liquid crystal aggregates, a feature not found in conventional thermotropic and lyotropic liquid crystals formed by covalently bound units of a fixed length.
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We report on measurements of magnetic-field induced nematic order in the bent-core liquid crystal 4-chlororesorcinol bis4-(4-n-dodecyloxybenzoyloxy) benzoate. Using the 31 T solenoid at the National ...High Magnetic Field Laboratory, we have observed, at temperatures less than 1 degrees above the clearing point, a first-order transition to the nematic phase. The critical magnetic field at which this occurs increases with temperature. We discuss these results within the context of both Maier-Saupe and Landau-de Gennes mean-field models for the nematic-isotropic transition. The implications of possible tetrahedratic order are also discussed. To our knowledge, this is the first observation of such a magnetic-field induced transition in a thermotropic liquid crystal; the reasons for which this behavior is now attainable are discussed.
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Purpose. To develop a mathematical model and propose an algorithm for analyzing and evaluating the impact on the digital economy and forming the method for choosing the factors of the external and ...internal impact which require institutional management measures. Methodology. Special and general methods of scientific knowledge are used: mathematical methods – for developing a model for assessing the effects on the digital economy and choosing institutional management measures; methods of analytical research – to distinguish groups of factors; the method of analysis and synthesis – when determining the most important factors and groups of influence and developing a management algorithm. Findings. Factors influencing the directions of investment in digital technologies for mass and corporate consumers and a significant difference in the amount of financing according to them have been identified. The possibility of a decrease in the level of competitiveness of the country due to the inadequacy of investing in digital technologies for the corporate sector is indicated. Management actions to increase investment in digital technologies for the corporate sector are recommended. Originality. The mathematical model and algorithm have been developed for the analysis and assessment of impacts on the digital economy and the formation of a method for selecting impact factors that require management measures. Using a mathematical model, the area of investing in the development of the digital economy was analyzed and management proposals for this area were developed. Practical value. The developed mathematical model for the analysis and assessment of impacts on the digital economy and the algorithm for monitoring, analysis and management of impacts can be implemented for scientific and practical purposes.
The COVID-19 pandemic poses unique challenges for vulnerable populations, including patients undergoing maintenance hemodialysis (HD). This study explores the relationship between baseline intact ...parathyroid hormone (iPTH) levels and COVID-19 severity, post-acute hospitalization, and mortality rates in HD patients. Methods. A multicenter retrospective cohort study was conducted across multiple centers, encompassing 142 patients undergoing HD treatment in three regions of Ukraine. The study spanned from March 2020 to May 2022. Baseline iPTH levels, demographic characteristics, and relevant clinical indicators were systematically recorded. Key endpoints included the severity of COVID-19, post-acute hospitalization, and mortality rates. Results. Of the initially eligible 165 patients, 23 were excluded, resulting in a final cohort of 142 patients. During the acute phase of COVID-19, distinct patterns emerged in terms of hospitalization rates, oxygen support requirements, and mortality. Lower iPTH levels were significantly associated with severe COVID-19-associated pneumonia (p < 0.0001). A 20-month follow-up revealed a significant association between serum iPTH concentration <174 pg/mL and increased rates of post-acute COVID-19 hospitalization HR 6.3 (95% CI 2.9; 13.7) and all-cause mortality HR 34.3 (95% CI 6.9; 74.5). Conclusion. This multicenter retrospective study suggests potential links between baseline iPTH levels and COVID-19 outcomes in patients undergoing HD. Serum iPTH concentration ≤174 pg/mL was significantly associated with increased post-acute hospitalization and mortality rate in our patient cohort. The findings emphasize the need for further research to elucidate underlying mechanisms and establish the prognostic value of iPTH in this specific patient population.
The present study aimed to assess the impact of post-COVID syndrome on the oxidative status and activity of paraoxonase 1 (PON-1), myeloperoxidase (MPO), and leukocyte elastase in the blood of ...patients undergoing hemodialysis (HD).
Methods. In this cross-sectional cohort study, 290 patients undergoing HD were included. The oxidative status was assessed based on the levels of blood malondialdehyde (MDA), ceruloplasmin, thiol compounds (SH-groups), and the serum activities of myeloperoxidase (MPO), paraoxonase-1 (PON-1), and elastase were determined.
Results. It was found that HD patients exhibited an elevation in oxidative processes, characterized by increased blood concentrations of MDA, MPO, elastase activity, and a decrease in the levels of SH-groups and arylesterase activity of PON-1. Patients with post-COVID syndrome showed further increases in MPO activity and a decrease in arylesterase activity of PON-1. Additionally, a statistically significant elevation in the MPO/PON-1 ratio was observed in HD patients with post-COVID syndrome compared to the control group and patients examined before the onset of the pandemic (p < 0.0001). The MPO/PON-1 ratio exhibited a direct correlation with serum MDA levels (p < 0.0001) and inversely correlated with the concentration of ceruloplasmin (p = 0.0008). The MPO/PON-1 value surpassing 9.06 units was identified as a predictive marker for PCS, demonstrating a specificity of 68.4% and a sensitivity of 88.5%.
Conclusions. Our study highlights a significant impact of post-COVID syndrome on oxidative processes in HD patients, as evidenced by elevated MDA levels and MPO activity, along with reduced levels of antioxidants and arylesterase activity of PON-1. The MPO/PON-1 ratio emerges as a promising predictive marker for post-COVID syndrome, underlining its potential clinical relevance in identifying at-risk patients.
pathophysiology of long-COVID sequelae in the general population of SARS-CoV-2-infected patients has been shown to be strongly influenced by oxidative stress. However, the potential role of oxidative ...stress in the development of long-COVID sequelae in hemodialysis patients (HD) has never been investigated.
The present study aimed to evaluate the oxidative status of HD patients 3.5 months after SARS-CoV-2 infection in relation to the presence of long-COVID sequelae and the severity of the acute phase COVID-19.
Methods. This cross-sectional cohort study included 63 HD patients with a median age of 55 (43-62.5) years and a dialysis vintage of 42 (25-73) months who had been infected with COVID-19 at least 3 months before recruitment. Patients were divided into two groups according to the occurrence of long-COVID sequelae: Group 1 included 31 (49.2%) HD patients with sequelae, while Group 2 included 32 (50.8%) fully recovered individuals. At 3.5 (3.2-4.6) months after the acute phase of COVID-19, malondialdehyde (MDA) and erythrocyte levels (MDAe), sulfhydryl groups (SH -groups), serum catalase activity, transferrin, and ceruloplasmin were measured. A comparison of the obtained data was performed using the Student’s test or the Mann-Whitney test according to the data distribution. A correlation was evaluated with the Spearman test.
Results. HD patients with persistent long-COVID sequelae had significantly higher concentrations of MDAs (p = 0.002), MDAe (p = 0.0006), and CTs (p = 0.02), and lower serum levels of SH-groups (p = 0.03) and ceruloplasmin (p = 0.03) compared with Group 2. The concentration of most studied indicators of pro- and antioxidant status did not depend on the severity of the acute phase COVID-19, and only catalase activity was statistically significantly related to the need for hospitalization (r = 0.59; p = 0.001), oxygen support (r = 0.44; p = 0.02), and the percentage of lung injury according to computed tomography (p = 0.03). Although the serum concentration of transferrin did not differ between the studied groups, the individual analysis showed that its value was statistically higher in HD patients with severe COVID-19 even 3.5 months after infection (p < 0.0001).
Conclusions. Long-term COVID-19 sequelae in HD patients are associated with oxidative stress. High levels of catalase activity and serum transferrin 3.5 months after COVID-19 may be a consequence of the severe course of the acute phase of the disease. The obtained data suggest that the use of antioxidants may be one of the possible strategies to treat the long-term consequences of COVID in HD patients.
A decline in high-density lipoprotein (HDL) has been observed in the general population of COVID-19 infected patients. However, little research has been devoted to this topic in hemodialysis (HD) ...patients and there is a general lack of data on the association between the baseline HDL level and COVID-19 outcomes in HD patients. The present study aimed to assess the association between baseline HDL levels and the risk of developing severe outcomes of COVID-19 infection in HD patients.
Methods. A total of 428 HD patients aged 55 (44-64) years and a dialysis vintage of 44 (21-76.6) months were enrolled in this multicenter propensity-score matched case-control study. After propensity-score matching (1 :1), 142 COVID-19 infected HD patients were compared with 142 HD patients who had never been infected with COVID-19. Propensity scores were estimated with MedCalc software based on potential confounding variables (age, diabetes, dialysis vintage and cardiovascular events). Baseline HDL levels were obtained from electronic health records of the patients (the last measurements were carried out before the COVID-19 onset). The endpoints of the study were COVID-19-related hospitalization, oxygen maintenance, and death.
The data were presented as the median and the interquartile ranges Me (Q25-Q75) and compared using the Mann-Whitney or Kruskal-Wallis tests, as appropriate. The Spearmen correlation test was used to assess the association between HDL and other markers. The multivariate logistic regression and the receiver operating characteristic (ROC) analyses were performed to evaluate the ability of HDL for predicting the severity of COVID-19 infection. The Cox regression analysis was used to determine the association between HDL and COVID-19-associated mortality.
Results. Among 142 patients infected with COVID-19, 40 patients (28%) patients were hospitalized, 34 patients (24%) needed oxygen supplements and 16 patients (11.3%) died. The baseline HDL level was significantly lower in the COVID-19 patients compared with the non-infected patients (1.22 (0.97-1.59) vs 1.52 (1.08-1.85) mmol/L, p = 0.011). Moreover, the baseline HDL level was significantly negatively associated with CT findings of pulmonary involvement (r = -0.76, p < 0.0001) and had a strong inverse correlation with serum C-reactive protein (r = -0.42, p = 0,0002) and D-dimer (r = -0.65, p < 0.0001). The multivariate logistic regression analysis demonstrated that HD patients with HDL concentration <1.22 mmol/l have 3 times higher risk of COVID-19 infection (OR 2.8; 95% CI 1.2; 6.5, p = 0.003). In the Cox regression analysis adjusted for the patients’ age, diabetic status, dialysis vintage and cardiovascular events, low HDL level (<1.22 mmol/L) was found to be associated with COVID-19-related mortality in the HD patients (χ2 = 9.2, p = 0.002).
Conclusions. Baseline low HDL-C level was independently associated with COVID-19 morbidity, severity and mortality in HD patients.
The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously ...formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments.
COPD is multifactorial disease, in which hereditary predisposition and environmental factors (including work conditions) play an important role. Among the genes associated with possible ...predisposition to COPD development a group of genes with the expression impacting the activity of “proteolysis-antiproteolysis – MMP2, MM9, TIMP2, A2M, ELN is considered. The main group of 72 underground coal miners with COPD (mean age 53,7±5,8 years, mean work experience – 21,8±4,8 years), and control group of 79 healthy miners (mean age – 48,2±5,6 years, mean work experience – 20,2±4,5 years) were examined. Polymorphism of genes with out bronchopulmonary pathology MMP9, α2M was revealed using PCR with electroforetic detection in agarosegel. Polymorphism of genes TIMP2, MMP2, ELN was revealed using PCR with fluorescent detection (RealTime PCR). By the data of molecular-genetic research among miners with COPD of occupational etiology (main group) and miners without it (control group) there was estabkished a reliable difference for the genotypes: MMP9*СС,TIMP2*GG; MMP9*СС,MMP2*CC,TIMP2*G/G,α2M*IIe/IIe,ELN*Gly/Gly; MMP9*СС,MMP2*CТ,TIMP2*G/G,α2M*IIe/Val,ELN*Gly/Gly; MMP9*СС,MMP2*CС,TIMP2*G/G,α2M*IIe/Val,ELN*Ser/Se; MMP9*СТ,MMP2*CC,TIMP2*G/G,α2M*IIe/IIe,ELN*Gly/Ser. These genotypes are associated with resistance for COPD development in underground coal miners ofUkraine. The obtained results testify to the participation of genes encoding protein synthesis of the system "proteolysantiproteolysis": MMP2, MMP9, TIMP2, A2M, ELN in the formation of genetic predisposition and resistance to the development of COPD of professional etiology in miners, which reveals new opportunities in the prevention of this disease in workers subject to the high concentrations of coal-rock dust.
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Correction for 'Peculiarities of the magneto-optical response in dispersions of anisometric pigment nano-particles' by A. Eremin
et al.
,
RSC Adv.
, 2016,
6
, 80666-80669.
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