Magnetotransport properties of oxidized iron thin films

6 pages, 7 figures, 1 table.-- PACS number(s): 75.70.Ak, 73.50.Jt, 73.61.AtWe report results of electrical resistivity, Hall effect, and anisotropic magnetoresistance (AMR) measurements performed on thin films (~80 nm) of naturally oxidized iron in the 5 to 300 K temperature range, and in magnetic fields up to 5 T. The films were grown at low temperatures. We find that the resistivity, coercive field, as well as the magnetoresistance of the films are affected by growth conditions, particularly by the substrate temperature which controls the size and shape of crystalline grains. We used AMR as a probe for magnetization reversal studies in our films. We find that the coercive fields vary as as in systems of weakly interacting ensembles of magnetic nanoparticles even though dipole-dipole interactions may well play a significant role.We acknowledge support from Ministerio de Ciencia y Tecnología of Spain through Grants No. MAT02/166 and MAT2003/01880.Peer reviewe

Magnetotransport properties of oxidized iron thin films

6 pages, 7 figures, 1 table.-- PACS number(s): 75.70.Ak, 73.50.Jt, 73.61.AtWe report results of electrical resistivity, Hall effect, and anisotropic magnetoresistance (AMR) measurements performed on thin films (~80 nm) of naturally oxidized iron in the 5 to 300 K temperature range, and in magnetic fields up to 5 T. The films were grown at low temperatures. We find that the resistivity, coercive field, as well as the magnetoresistance of the films are affected by growth conditions, particularly by the substrate temperature which controls the size and shape of crystalline grains. We used AMR as a probe for magnetization reversal studies in our films. We find that the coercive fields vary as as in systems of weakly interacting ensembles of magnetic nanoparticles even though dipole-dipole interactions may well play a significant role.We acknowledge support from Ministerio de Ciencia y Tecnología of Spain through Grants No. MAT02/166 and MAT2003/01880.Peer reviewe

The spliceosome-activating complex: molecular mechanisms underlying the function of a pleiotropic regulator

Correct interpretation of the coding capacity of RNA polymerase II transcribed eukaryotic genes is determined by the recognition and removal of intronic sequences of pre-mRNAs by the spliceosome. Our current knowledge on dynamic assembly and subunit interactions of the spliceosome mostly derived from the characterization of yeast, Drosophila, and human spliceosomal complexes formed on model pre-mRNA templates in cell extracts. In addition to sequential structural rearrangements catalyzed by ATP-dependent DExH/D-box RNA helicases, catalytic activation of the spliceosome is critically dependent on its association with the NineTeen Complex (NTC) named after its core E3 ubiquitin ligase subunit PRP19. NTC, isolated recently from Arabidopsis, occurs in a complex with the essential RNA helicase and GTPase subunits of the U5 small nuclear RNA particle that are required for both transesterification reactions of splicing. A compilation of mass spectrometry data available on the composition of NTC and spliceosome complexes purified from different organisms indicates that about half of their conserved homologs are encoded by duplicated genes in Arabidopsis. Thus, while mutations of single genes encoding essential spliceosome and NTC components lead to cell death in other organisms, differential regulation of some of their functionally redundant Arabidopsis homologs permits the isolation of partial loss of function mutations. Non-lethal pleiotropic defects of these mutations provide a unique means for studying the roles of NTC in co-transcriptional assembly of the spliceosome and its crosstalk with DNA repair and cell death signaling pathways

Uses, cultural significance, and management of peatlands in the Peruvian Amazon: Implications for conservation

Tropical peatlands play an important role in the global carbon cycle by acting as significant carbon stores. South America's largest peatland complex is located in the Loreto Region of the Peruvian Amazon. Here we present the first study of human relations with these peatlands, including their uses, cultural significance and current management, as well as implications for conservation, based on qualitative research with people living in two riverine rural communities. Our results indicate that peatlands are culturally ambiguous spaces, used mainly for hunting, palm fruit harvesting, and timber, but feared due to the dangers of getting lost, sinking into the ‘sucking’ ground, and being attacked by anacondas and/or mythical creatures. While the difficult terrain and remoteness of peatlands have thus far acted as natural barriers to their destruction through conversion to different land uses, overuse of natural resources is nevertheless a significant concern for people living in the peat-dominated landscape of the Peruvian Amazon, mixed with frustration about the lack of outside support to foster environmental conservation and economic opportunities. We explore how evaluations of the present situation differ across one indigenous and one mestizo community. We identify a range of nascent peatland conservation strategies, including seedling planting to regrow valuable (palm) trees, and the climbing of palm trees for harvesting fruit as opposed to felling them. We argue that peatland conservation could be combined with the development of sustainable management strategies, but that this would require sustained engagement by outside organisations with rapidly growing local communities in these areas.NERC; Scottish Funding Counci

Can environmental DNA be used to detect first arrivals of the cane toad, Rhinella marina, into novel locations?

Eradicating invasive species is difficult, but success is more likely when populations are small after arrival. The cane toad, Rhinella marina, is an invasive pest species that threatens native fauna worldwide. Increasingly, environmental DNA (eDNA) is used as a technique to monitor the presence of invasive species given its power to detect low numbers of individuals. We aimed to investigate eDNA persistence in freshwater at three different temperatures (25, 30 and 35°C) and eDNA detection thresholds for R. marina using controlled experiments in aquaria. For the latter, two water volumes and two cane toad exposure times were used (800 or 200 L volume with 5 or 30 min exposure). A 15‐ml water sample was collected from each replicated aquaria and preserved with 5 ml Longmire's buffer. Environmental DNA was extracted and four technical quantitative PCR replicates were analyzed targeting the cane toad 16S rDNA mitochondrial gene. Environmental DNA decayed rapidly in water and was reliably detected for up to 3 days after cane toad removal, regardless of the temperature treatment. Also, cane toad eDNA was detected in the water after a 5‐min initial exposure of a single individual in 800 L of water. Under the physical parameters tested here, a positive detection means that a cane toad has been in contact with the water body between 1 and 3 days prior to the sampling event. The results of the present study show the importance of eDNA for determining the presence of a species that occurs at low abundance in a small water body, such as at the onset of a cane toad invasion

Percepciones de los estudiantes sobre el Taller de Metodología de Estudio Universitario de la Facultad de Ciencias Veterinarias de la Universidad Nacional del Centro de la Provincia de Buenos Aires

Una de las estrategias implementadas en la Facultad de Ciencias Veterinarias de la Universidad Nacional del Centro de la Provincia de Buenos Aires para disminuir el desgranamiento y la deserción estudiantil durante el primer año de la carrera de Medicina Veterinaria, es el Taller de Metodología de Estudio Universitario. El objetivo de este trabajo es dar a conocer las características de dicho Taller y las percepciones de los estudiantes que participaron del mismo durante el año 2022. La adquisición y el desarrollo de técnicas de estudio es uno de los objetivos más importantes en todo proceso educativo porque contribuyen a mejorar las estrategias de aprendizaje y son la base para futuras técnicas de trabajo profesional. El Departamento de Bienestar Estudiantil de la Facultad, como estrategia de ingreso y permanencia, ofrece el Taller para estudiantes ingresantes que no lograron aprobar el primer curso de la carrera, Introducción a las Ciencias Básicas, trabajando en conjunto con docentes de las áreas que lo componen (Biología, Física, Matemática y Química). El taller tiene como fin lograr que los estudiantes adquieran y consoliden actitudes, disposiciones, capacidades, estrategias y técnicas para estudiar que les ayuden a mejorar su rendimiento académico.Especialización en Docencia Universitari

Different topologies in three manganese-μ-azido 1D compounds: magnetic behavior and DFT-quantum Monte Carlo calculations

The syntheses and structural characterization of three new monodimensional azido-bridged manganese(II) complexes with empirical formulae [Mn(N3)2(aminopyz)2]n (1), [Mn(N3)2(4-azpy)2]n (2) and [Mn(N3)2(4-Bzpy)2]n (3) (pyz = pyrazine (1,4-diazine)), 4-azpy = 4-azidopyridine and 4-Bzpy = 4-benzoylpyridine) are reported. 1 is a monodimensional compound with double EO azido bridges, 2 is an alternating monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EE and 3 is a monodimensional compound with double end-on and double end-to-end azido bridges in the sequence di-EO-di-EO-diEO-di-EO-di-EE. The magnetic properties of 1-3 are reported. Periodic DFT calculations were performed to estimate the J values and quantum Monte Carlo simulations were carried out using the calculated J values to check their accuracy in comparison with the experimental magnetic measurements. From this theoretical analysis, two appealing features of the di-EO Mn(II) compounds can be extracted: first, the exchange coupling becomes more ferromagnetic when the Mn-N-Mn bridging angle becomes larger and the spin density of the bridging nitrogen atoms has an opposite sign to that of the Mn(II) centers