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    拉

    拉脱维亚大学

    University of Latvia
    院校EST. 1919
    1.5万论文总数
    20.1万引用总数

    论文量&引用量时间轴

    机构学者

    论文(10000)

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    1The Study of Thermal Degradation and Treatment Strategies for Enhanced Electrical Performance in PEO/PEDOT:PSS Composite Polymers
    Oskars Bitmets,Kaspars Pudzs, Ciro Federico Tipaldi, Bejan Hamawandi, Renate Celmodejeva

    The electrical properties of PEDOT:PSS are constrained by the morphology of the polymer chains and the insulating effects of PSS. Enhancing these characteristics can lead to a substantial improvement in electrical conductivity. In this work, a composite polymer was prepared from PEDOT:PSS (PH1000) and PEO (MW = 1 000 000). The electrical properties of drop casted polymer films show a strong dependence on PEO concentration in the composite material. The highest electrical conductivity of 21391 Sm−1 was achieved at a 70% PEO concentration after thermally treating the film at 200°C for 25 min in ambient atmosphere. Furthermore, the electrical conductivity was improved to 57507 Sm−1, before thermal treatment, by adding 15% of DMSO to the composite polymer. Infrared spectroscopy and EDX measurements indicate to PSS removal during the thermal treatment. Scanning electron microscopy and Raman spectroscopy measurements were performed to gain an insight into the potential structural changes.

    2027Synthetic Metals(2027)
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    2Excitation-selective Coexistence of Upconversion and Persistent Luminescence in Pr3+-doped Eulytite-Type Phosphates Towards Advanced Anti-Counterfeiting
    Guna Doke,Andris Antuzevics,Didzis Salnajs, Nadiia Rebrova, Alexander Grippa,Przemyslaw J. Deren,Aldona Beganskiene,Aleksej Zarkov

    This work demonstrates the excitation-selective coexistence of blue-light-driven UVC upconversion (UC), X-ray-induced optical luminescence (XRL), and persistent luminescence (PersL) within a single Pr3+-doped host lattice. Pr3+-doped Ba3Lu(PO4)3 and Sr3Lu(PO4)3 phosphors exhibit multiple excitation-dependent luminescence modes and are studied as multifunctional materials for advanced anti-counterfeiting. When excited with blue light (444 nm), they efficiently produce blue-to-UVC upconversion via an excited-state absorption mechanism, while direct ultraviolet and visible excitation trigger characteristic Pr3+ photoluminescence. X-ray irradiation induces intense blue-red optical luminescence, followed by long-lasting red persistent luminescence detectable for several hours at room temperature. Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) measurements were employed to elucidate the nature of charge trapping processes that produce persistent emission. The TSL glow curves of all samples are dominated by a semi-broadband peak around 70 degrees C, indicative of a quasi-continuous distribution of trapping states. Tmax-Tstop experiments combined with initial rise analysis reveal trap depths between 0.9-1.15 eV, supporting effective room-temperature PersL. EPR spectroscopy identifies radiation-induced phosphorus-related radical centers and shallow traps, which most likely correspond to F+-type centers, with thermal stability matching TSL results. These findings highlight the potential of Pr3+-doped eulytite-type phosphates as versatile, multi-level luminescent platforms for advanced anti-counterfeiting and encryption solutions.

    2026JOURNAL OF MATERIALS CHEMISTRY C(2026)引用:50
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    3Transgenerationally Inherited Incisor Aberration Mediated by Stress in Two Isolated Populations of Microtus Hartingi Vole
    Larisa Kaija,Tanya A. Zorenko

    Environmental and social stress (SS) can alter phenotypic expression at both individual and population levels. We examined the effects of ancestral SS, imposed through forced polygyny, on reproductive success and maxillary incisor overgrowth in 2 isolated populations of Microtus hartingi vole: from Central Anatolia (CAP) and Eastern Rhodope (RP). In addition to ancestral SS, CAP voles were exposed to environmental stress during prenatal, lactation, and early-life periods. Under control conditions, the prevalence of incisor overgrowth was at a stable rate of similar to 16.7% in RP and occurred very rarely (0.5%) in CAP. Stress exposure markedly increased prevalence in CAP but not in RP, independent of female kinship, ancestor sex, or generation. We propose that upper incisor overgrowth arises from an interaction between genetic background and stress-sensitive regulatory mechanisms, with stress releasing cryptic genetic variation. The RP, shaped by long-term habitat fragmentation, lack of dispersal, polygyny, and possibly inbreeding, appears to exhibit compensatory stabilization of this aberration, potentially through increased stress tolerance and earlier reproductive onset. CAP, originating from more stable environments, can be considered as a model of the early stage of RP adaptation to habitat fragmentation, as their heightened stress responsiveness leads to pronounced fluctuations in incisor overgrowth levels. Together, these findings suggest that stress-induced regulatory effects can persist across generations and may contribute to population divergence.

    2026CURRENT ZOOLOGY(2026)引用:49
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    4Evaluating Greenhouse Gas Emissions in Multifunctional Grazing Systems: the Case of GrassLIFE Project in Latvia
    Janis Brizga

    This study evaluates greenhouse gas emissions associated with a multifunctional conservation-oriented grazing system in Latvia. The inventory covers methane from enteric fermentation, nitrous oxide from manure deposited on pasture, and carbon dioxide from fuel use for hay-related operations and transport within the defined system boundary. Total emissions for 2022 were estimated at 350 t CO2e and were dominated by enteric methane. Emission intensities depend strongly on the functional unit and animal pathway: annual herd-level intensities reflect marketed output in the assessment year, while lifetime-pathway results show much lower carcass-weight intensities for bulls finished at around 4 years than for breeding cows culled after long service, due to cumulative emissions over longer lifespans. The results illustrate the central trade-off in multifunctional grazing: extensive management and habitat stewardship can support biodiversity and grassland maintenance, while longer animal lifespans and lower growth rates increase product-based emission intensities. Soil organic carbon (SOC) sequestration was not credited in the footprint due to high uncertainty in short-term SOC change estimates; longer-term, stratified monitoring is required to assess sequestration dynamics and permanence. Future work should integrate quantified biodiversity and habitat-condition indicators alongside improved, regionally calibrated emission parameters to support more policy-relevant assessments of extensive multifunctional grazing systems.

    2026AGROECOLOGY AND SUSTAINABLE FOOD SYSTEMS(2026)引用:49
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    5Impacts of Felling and Forest Road Construction on Surface Water Quality in a Managed Forested Catchment in Latvia
    Zane Klavina,Ivars Klavins,Arta Bardule,Zane Libiete

    While forests are generally regarded as beneficial for water quality, forest management can significantly impact water quality, even if sustainable forest management practices are applied. Fellings alter water balance and nutrient cycling, while forest roads with impermeable surfaces fragment ecosystems and enhance runoff. Road construction often requires extensive landscape modification and material relocation, which increases substance leaching and erosion. In the present study, water quality parameters and nutrient export were monitored over eight years (2016-2023) in a forested catchment (2212 ha) and its sub-catchments. During this period, 15.8 km of forest roads were constructed, and fellings occurred across 18.8% of the catchment. Fellings increased nitrogen compound concentrations and export, with effects persisting for four-five years. Runoff patterns strongly controlled the export of total nitrogen, calcium, and dissolved organic carbon. The onset of fellings and higher felling intensities raised total suspended solids levels, though high variability masked statistical significance. Calcium and potassium concentrations also increased during periods of more intense felling, though their export patterns closely followed runoff dynamics. Road construction increased calcium and total suspended solids concentrations.

    2026SCANDINAVIAN JOURNAL OF FOREST RESEARCH(2026)引用:38
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    合作机构(100)

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    立陶宛健康科学大学合作论文 120
    波兰科学院合作论文 119

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