THE EVALUATION OF STABLE ISOTOPIC RATIOS 13C AND 15N IN HUMIC ACIDS ALONG A FEN PEAT PROFILE

Mires are known as consistent environmental archives, but humic acids are the fraction of peat that is most recalcitrant and refractory to organic matter degradation, thus data on environmental changes during mire development can be recorded into them. This work was focused on the studies of stable isotopic ratios delta carbon-13 and delta nitrogen-15, and their distribution in humic acids within fen peat layers of different depths and peat composition. The variations in delta carbon-13 reflect isotopic variations in peat-forming plants over time and can be considered as a function of photosynthetic pathway that is being used to fix carbon dioxide. At the same time, variations in delta nitrogen-15 show nitrogen fixation in peat-forming plants and can be traced along with peat decomposition degree and depth. Properties of humic acids were studied in 2018 at 3 fens located in Latvia and Southern Finland, and comparatively they show properties. The method used for the determination of stable isotopes was the isotope-ratio mass spectrometry that was performed in the Faculty of Chemistry, University of Latvia. Results on delta carbon-13 indicate signal of C3 peat-forming plants, while signal of C4 peat-forming plants is not evident, which can be explained by non-efficient carbon dioxide fixation in fen vegetation. Results on delta nitrogen-15 show variations in nitrogen fixation in fen vegetation. Data show nitrogen fixation in terrestrial plants, however significant shifts in absolute isotope values indicate dependence on variations in peat decomposition degree and botanical composition. Data suggest that differences in peat botanical composition, decomposition degree and site dependent characteristics reflect in differences in delta carbon-13 and delta nitrogen-15 variation

Investigation of mass graves in the Churchyard of St. Gertrude’s, Riga, Latvia

What determines the magnitude of attentional capture by deviant sound events? We combined the cross-modal oddballdistraction paradigm with sequence learning to address this question. Participants responded to visual targets, eachpreceded by tones that formed a repetitive cross-trial standard sequence. In Experiment 1, with the standard tone sequence…-660-440-660-880-… Hz, either the 440 Hz or the 880 Hz standard was occasionally replaced by one of two deviant tones(220 Hz and 1100 Hz), that either differed slightly (by 220 Hz) or markedly (by 660 Hz) from the replaced standard. InExperiment 2, with the standard tone sequence …-220-660-440-660-880-660-1100-… Hz, the 440 Hz and the 880 Hzstandard was occasionally replaced by either a 220 Hz or a 1100 Hz pattern deviant. In both experiments, a high-pitchdeviant was more captivating when it replaced a low-pitch standard, and a low-pitch deviant was more captivating when itreplaced a high-pitch standard. These results indicate that the magnitude of attentional capture by deviant sound eventsdepends on the discrepancy between the deviant event and the expected event, not on perceived local change

Gold nanowire synthesis by semi-immersed nanoporous anodic aluminium oxide templates in potassium dicyanoaurate-hexacyanoferrate electrolyte

Publisher Copyright: © The Institution of Engineering and Technology 2014.The synthesis reaction of potassium dicyanoaurate-hexacyanoferrate electrolyte and the pertinence of this electrolyte for gold nanowire synthesis are reported. Gold nanowires were synthesised in anodic aluminium oxide (AAO) nanopores using an improved design of the electrochemical cell. AAO templates with thick gold layers were placed on the surface of the electrolyte, thus the ends of the nanopores were opened, allowing the electrolyte to freely diffuse into the nanopores, extruding gases. The presented procedure simplifies the preparation before nanowire synthesis: AAO templates before synthesis do not need to degas and isolate themselves from contact with the electrolyte by a parafilm or a non-conductive adhesive. A considerably faster nanowire growth in the given conditions in the case of a semi-immersed AAO template when compared with the complete immersion method is reported. For comparison with literature data, gold nanowires were synthesised by the classical electrochemical cell using potassium dicyanoaurate-citrate electrolyte. Long, smooth and high purity nanowires were obtained using semi-immersed templates.publishersversionPeer reviewe

Application of electrochemical impedance for characterising arrays of Bi2S3 nanowires

Electrochemical Impedance Spectroscopy (EIS) was used to characterise the electrical properties of bismuth sulphide (Bi2S3) nanowires (NWs) templated within anodic aluminium oxide (AAO) membranes. A specially engineered cell, with a nominal electrolyte volume of 0.1–0.2 ml, was used to hold and measure the electrochemical impedance of the fragile NW/AAO samples. An equivalent circuit model was developed to determine the filling density of nanowires within the porous templates. The EIS method can be utilised to probe the nanowire filling density in porous membranes over large sample areas, which is often unobtainable using electron microscopy and conductive atomic force microscopy techniques

Fibrinolytic system changes in liver surgery : A pilot observational study

Publisher Copyright: © 2018 Ozolina, Nemme, Ozolins, Bjertnæs, Vanags, Gardovskis, Viksna and Krumina.Introduction: Bleeding occurs frequently in liver surgery. Unbalance between tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) concentrations might increase bleeding. Our aim was to analyze perioperative fibrinolytic changes during liver surgery. Materials and Methods: We evaluated 15 patients for inclusion into a prospective pilot study of liver surgery. We assessed fibrinolysis by plasma PAI-1 and t-PA: before surgery (T1), before Pringle maneuver (PM;T2), at the end of surgery (T3) and 24 h postoperatively (T4), and registered demographic and laboratory data, extent and duration of surgery, hemodynamic parameters, blood loss, and transfused volumes of blood products. Data presented as mean ± SD. Significance at P < 0.05. Results: After exclusion of six patients only undergoing biopsies, we included six women and three men aged 49.1 ± 19.6 years; two patients with liver metastases of colorectal cancer and hepatocellular carcinoma, respectively, two with focal nodular hyperplasia, two with hepatic hemangioma, and one with angiomyolipoma. Six patients underwent PM. PAI-1 plasma concentration (n = 9) rose from 6.25 ± 2.25 at T1 through 17.30 ± 14.59 ng/ml at T2 and 28.74 ± 20.4 (p = 0.007) and 22.5 ± 16.0 ng/ml (p = 0.04), respectively, at T3 and T4. Correspondingly, t-PA plasma concentration (n = 9) increased from 4.76 ± 3.08 ng/ml at T1 through 8.00 ± 5.10 ng/ml (p = 0.012) at T2 and decreased to 4.25 ± 2.29 ng/ml and 3.04 ± 3.09 at T3 and T4, respectively. Plasma t-PA level at T2 was significantly different from those at T1, T3, and T4 (p < 0.004). In PM patients, t-PA levels increased from T1, peaked at T2 (p = 0.001), and subsequently decreased at T3 and T4 (p = 0.011 and p = 0.037), respectively. Mean blood loss was 1,377.7 ± 1,062.8 ml; seven patients received blood products. Patients with higher PAI-1 levels at T3 received more fresh frozen plasma (r = 0.79; p = 0.01) and red blood cells (r = 0.88; p = 0.002). Conclusions: During liver surgery, fibrinolysis increased, as evidenced by rises in plasma PAI-1and t-PA, especially after start of surgery and following PM. Transfused volumes of blood products correlated with higher plasma concentrations of PAI-1. Confirming this tendency requires a larger cohort of patients.publishersversionPeer reviewe

Bi2Se3 Nanostructured Thin Films as Perspective Anodes for Aqueous Rechargeable Lithium-Ion Batteries

Funding Information: This research was funded by the European Regional Development Fund Project (ERDF) No. 1.1.1.1/19/A/139. Y.R. acknowledges the support of post-doctoral ERDF project No. 1.1.1.2/VIAA/4/20/694. V.L. also acknowledges the support of “Strengthening of the capacity of doctoral studies at the University of Latvia within the framework of the new doctoral model”, identification No. 8.2.2.0/20/I/006. A.S. acknowledges the support from the Institute of Solid State Physics, University of Latvia, which, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. Publisher Copyright: © 2022 by the authors.In recent years, aqueous rechargeable lithium-ion batteries (ARLIBs) have attracted attention as an alternative technology for electrical storage. One of the perspective battery anode materials for application in ARLIBs is Bi2Se3, which has already shown good perspectives in the application of conventional lithium-ion batteries (LIBs) that use organic electrolytes. In this study, the electrochemical properties of Bi2Se3 thin films with two different layers on the electrode surface—the solid electrolyte interphase (SEI) and the Bi2O3 layer—were investigated. The results of this work show that the formation of the SEI layer on the surface of Bi2Se3 thin films ensures high diffusivity of Li+, high electrochemical stability, and high capacity up to 100 cycles, demonstrating the perspectives of Bi2Se3 as anode material for ARLIBs.publishersversionPeer reviewe

Natural clearance of hepatitis C virus in hemophilia patients

Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Objective. The objective of this study was to investigate the prevalence of HCV (hepatitis C virus) infection in hemophilia patients in Latvia and to analyze association between natural clearance of HCV and human leukocyte antigen (HLA) class II genes. Material and methods. From 61 hemophilic patients participating in this study, 38 were adults and 23 were pediatric patients younger than 18 years. To analyze association between HLA class II alleles and natural clearance of HCV, the gene frequency was compared in hemophilia patients group and the control group of 60 healthy subjects, all men. Serum HCV RNA was qualitatively determined and HLA class II alleles were identified by polymerase chain reaction (PCR) method. Results. HCV infection is common among hemophilia patients in Latvia. Antibodies to HCV were found in 45 of 61 (74%) hemophilia patients. In 41% of hemophilia patients (18 of 44), HCV infection resolved spontaneously. Children cleared HCV more frequently than adults (7 of 11 comparing to 11 of 33, respectively; OR=3.50; P<0.05). The frequency difference was found to be statistically significant when comparing HLA alleles distribution in the sample of hemophilia patients who naturally cleared HCV (n=18) and in the control group (n=60) (corresponding frequency of HLA-DRB1*07 allele - 4 (11.11%) and 9 (1.67%); OR=7.38; P<0.05). Conclusions. Natural clearance of HCV infection is frequently found in hemophilia patients in Latvia. Children are more likely to clear virus naturally than adults. There is an association between natural clearance of HCV and HLA allele DRB1*07 in hemophilia patients.Peer reviewe

Antimicrobial and Antibiofilm Properties of Latvian Honey against Causative Agents of Wound Infections

Funding Information: The authors thank Riga Stradiņš University Department of Microbiology and Biology, Department of Pharmaceutical Chemistry for providing access to the instruments used in this research. The authors acknowledge the access to the infrastructure and expertise of the BBCE—Baltic Biomaterials Centre of Excellence (European Union’s Horizon 2020 research and innovation programme under the grant agreement No. 857287) and “Strengthening of the capacity of doctoral studies at the University of Latvia within the framework of the new doctoral model”, identification no. 8.2.2.0/20/I/006. Publisher Copyright: © 2023 by the authors.Honey is widely used in traditional medicine and modern wound healing biomaterial research as a broad-spectrum antimicrobial, anti-inflammatory and antioxidant agent. The study’s objectives were to evaluate the antibacterial activity and polyphenolic profiles of 40 monofloral honey samples collected from beekeepers in the territory of Latvia. The antimicrobial and antifungal activity of Latvian honey samples were compared with commercial Manuka honey and the honey analogue sugar solutions–carbohydrate mixture and tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, clinical isolates Extended-Spectrum Beta-Lactamases produced Escherichia coli, Methicillin-resistant Staphylococcus aureus and Candida albicans. Antimicrobial activity was evaluated with the well-diffusion method (80% honey solution w/v) and microdilution method. The honey samples with the highest antimicrobial potential were tested to prevent biofilm development and activity against a preformed biofilm. The principal component analysis of the antimicrobial properties of honey samples vs. polyphenolic profile was performed. Eleven honey samples exhibited antibacterial activity to all investigated bacteria. The antibacterial effect of the samples was most significant on the Gram-positive bacteria compared to the studied Gram-negative bacteria. Latvian honey presents promising potential for use in wound healing biomaterials, opening the possibility of achieving long-term antibacterial effects.publishersversionPeer reviewe