Stable and metastable patterns in chromonic nematic liquid crystal droplets forced with static and dynamic magnetic fields

Spherical confinement of nematic liquid crystals leads to the formation of equilibrium director field configurations that include point and line defects. Driving these materials with flows or dynamic fields often results in the formation of alternative metastable states. In this article, we study the effect of magnetic field alignment, both under static and dynamic conditions, of nematic gems (nematic droplets in coexistence with the isotropic phase) and emulsified nematic droplets of a lyotropic chromonic liquid crystal. We use a custom polarizing optical microscopy assembly that incorporates a permanent magnet whose strength and orientation can be dynamically changed. By comparing simulated optical patterns with microscopy images, we measure an equilibrium twisted bipolar pattern within nematic gems that is only marginally different from the one reported for emulsified droplets. Both systems evolve to concentric configurations upon application of a static magnetic field, but behave very differently when the field is rotated. While the concentric texture within the emulsified droplets is preserved and only displays asynchronous oscillations for high rotating speeds, the nematic gems transform into a metastable untwisted bipolar configuration that is memorized by the system when the field is removed. Our results demonstrate the importance of boundary conditions in determining the dynamic behavior of confined liquid crystals even for configurations that share similar equilibrium bulk structures

A proposal to assess the conservation status of roadsides in southeastern Buenos Aires

Los bordes de caminos rurales (BCR) son elementos clave para conservar la biodiversidad y los servicios ecosistémicos en los paisajes agrícolas. Su restauración y manejo requieren de protocolos sencillos que valoren (diagnostiquen) su estado de conservación y funcionalidad ecológica. En este trabajo elaboramos un índice del valor de conservación (IVC) de los BCR por medio de la construcción de un árbol de decisiones realizado a partir de la consulta a expertos. El índice, que puede asumir valores entre 4 y 30, evalúa el estado de conservación y la funcionalidad ecológica de los BCR según 11 atributos relacionados principalmente con la estructura de la vegetación. El IVC fue aplicado a 30 BCR del sudeste bonaerense (Argentina). Sus valores oscilaron entre 4 y 29. Los BCR cultivados fueron los de menor valor. Los BCR con IVC más alto (>21) se caracterizaron por la mayor riqueza de especies nativas, entomófilas y de valor cultural, la mayor cobertura de especies nativas y pastos perennes, la menor cobertura de malezas y especies invasoras, y la presencia de al menos una especie vulnerable y/o fitotelmata. Este índice representa una primera contribución aplicable al diagnóstico del estado de conservación de los BCR a través de la identificación de atributos claves de la estructura de la vegetación sugeridos por expertos. Además, el índice provee información relativamente sintética sobre el estado de los BCR, los que, pese a sus múltiples funciones ecológicas, rara vez son tenidos en cuenta para su conservación dentro de la planificación territorial.Rural roadsides (RRS) are key elements for conserving biodiversity and ecosystem services in agricultural landscapes. Their restoration and management require simple protocols to assess (diagnose) their conservation status and ecological functionality. We elaborated a conservation value index (CVI) of RRS by constructing a decision tree based on the experts’ opinion. The index, which can range between 4 and 30, evaluates the conservation status and ecological functionality of RRS according to 11 attributes related to vegetation structure. The CVI was applied to 30 RRS in southeastern Buenos Aires (Argentina). Values ranged from 4 to 29, being the cropped RRS those with the lowest value. The RRS with the highest CVI (>21) were those characterized by higher richness of native, entomophily and cultural value species, higher coverage of native species and perennial grasses, lower coverage of weeds and invasive species, and presence of at least a vulnerable and/or phytotelmata species. This index represents a first contribution applicable to the diagnosis of the conservation status of RRS through the identification of key attributes of vegetation structure suggested by experts. In addition, the index provides relatively synthetic information about the status of RRS, which in spite of their multiple ecological functions are seldom taken into account for their conservation within territorial planning

Una propuesta para valorar el estado de conservación de los bordes de caminos rurales en el sudeste bonaerense

Herrera, Lorena P. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce (EEA Balcarce). Balcarce, Buenos Aires, Argentina.Sabatino, Malena C. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce (EEA Balcarce). Balcarce, Buenos Aires, Argentina.Jaimes, Florencia R. Instituto Nacional de Tecnología Agropecuaria (INTA). Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce (EEA Balcarce). Balcarce, Buenos Aires, Argentina.Poggio, Santiago L. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Producción Vegetal. Buenos Aires, Argentina.403-414Los bordes de caminos rurales (BCR) son elementos clave para conservar la biodiversidad y los servicios ecosistémicos en los paisajes agrícolas. Su restauración y manejo requieren de protocolos sencillos que valoren (diagnostiquen) su estado de conservación y funcionalidad ecológica. En este trabajo elaboramos un índice del valor de conservación (IVC) de los BCR por medio de la construcción de un árbol de decisiones realizado a partir de la consulta a expertos. El índice, que puede asumir valores entre 4 y 30, evalúa el estado de conservación y la funcionalidad ecológica de los BCR según 11 atributos relacionados principalmente con la estructura de la vegetación. El IVC fue aplicado a 30 BCR del sudeste bonaerense (Argentina). Sus valores oscilaron entre 4 y 29. Los BCR cultivados fueron los de menor valor. Los BCR con IVC más alto (mayor a 21) se caracterizaron por la mayor riqueza de especies nativas, entomófilas y de valor cultural, la mayor cobertura de especies nativas y pastos perennes, la menor cobertura de malezas y especies invasoras, y la presencia de al menos una especie vulnerable y/o fitotelmata. Este índice representa una primera contribución aplicable al diagnóstico del estado de conservación de los BCR a través de la identificación de atributos claves de la estructura de la vegetación sugeridos por expertos. Además, el índice provee información relativamente sintética sobre el estado de los BCR, los que, pese a sus múltiples funciones ecológicas, rara vez son tenidos en cuenta para su conservación dentro de la planificación territorial

Efecto de la salinidad de una solución nutritiva en la papaya Maradol

Papaya (Carica papaya L.) is a crop of great economic importance. It is the fourth most produced tropical fruit in the world. The most substantial problems faced during its production are pests and diseases, which is why it has been planted under greenhouse conditions. However, it is required that the plants not be of great height not to need tall greenhouses. Therefore, this research aims to evaluate to the salinity effect and identify nutritive solutions that reduce plant height. The experimental design was completely randomized with four treatments and ten replications. The treatments were four concentrations of Steiner nutrient solution (50 %, 100 %, 150 %, and 200 %) in whose composition are anions (phosphate, nitrate, and sulfate) and cations (potassium, calcium, and magnesium), thus generating electrical conductivity of 1.0, 2.0, 3.0, and 4.0 dS/m, respectively. The variables evaluated were plant height, number of leaves, stem diameter, foliar area, chlorophyll a and b concentration, proline content, and foliar nutrient concentration. The nutrients comprise nitrogen, phosphorus, potassium, calcium, and magnesium. The analysis of variance indicated significant differences in all variables except magnesium concentration. As salinity increased, plant height, number of leaves, stem diameter, leaf area, phosphorus, potassium, and calcium decreased, but chlorophyll a and b concentration, proline content, and nitrogen increased. We conclude that Steiner nutrient solution with 4.0 dS/m (200 %) can reduce plant height  to grow it in greenhouses.La papaya (Carica papaya L.) es un cultivo de gran importancia económica, siendo la cuarta fruta tropical más producida en el mundo. Los problemas más fuertes que enfrenta su producción son la presencia de plagas y enfermedades, por lo que se ha optado por realizar su plantación en condiciones de invernadero. Sin embargo, se requiere que las plantas no sean de mucha altura o que los invernaderos sean muy altos. Por lo anterior, esta investigación tuvo como objetivo evaluar el efecto de salinidad para identificar soluciones nutritivas que permitan reducir la altura de la planta. El diseño experimental fue completamente al azar con cuatro tratamientos y diez repeticiones. Los tratamientos fueron cuatro concentraciones de solución nutritiva Steiner (50 %, 100 %, 150 % y 200 %) en cuya composición se encuentran aniones (fosfato, nitrato y sulfato) y cationes (potasio, calcio y magnesio), lo que genera conductividad eléctrica de 1,0, 2,0, 3,0 y 4,0 dS/m, respectivamente. Se evaluaron las variables altura de la planta, número de hojas, diámetro del tallo, área foliar, concentración de clorofila a y b, contenido de prolina y concentración foliar de nutrientes. Los nutrientes fueron nitrógeno, fósforo, potasio, calcio y magnesio. El análisis de varianza indicó diferencias significativas en todas las variables excepto en la concentración de magnesio. A medida que aumentó la salinidad, disminuyó la altura de la planta, el número de hojas, el diámetro del tallo y el área foliar, la concentración de fósforo, potasio y calcio, pero aumentó la concentración de clorofila a y b, el contenido de prolina y de nitrógeno. Se concluyó que la solución nutritiva Steiner con 4,0 dS/m (200 %), se puede utilizar para reducir la altura de la planta con el fin de cultivarla en invernadero

Inflammatory Animal Model for Parkinson's Disease: The Intranigral Injection of LPS Induced the Inflammatory Process along with the Selective Degeneration of Nigrostriatal Dopaminergic Neurons

We have developed an animal model of degeneration of the nigrostriatal dopaminergic neurons, the neuronal system involved in Parkinson's disease (PD). The implication of neuroinflammation on this disease was originally established in 1988, when the presence of activated microglia in the substantia nigra (SN) of parkinsonians was reported by McGeer et al. Neuroinflammation could be involved in the progression of the disease or even has more direct implications. We injected 2 μg of the potent proinflammatory compound lipopolysaccharide (LPS) in different areas of the CNS, finding that SN displayed the highest inflammatory response and that dopaminergic (body) neurons showed a special and specific sensitivity to this process with the induction of selective dopaminergic degeneration. Neurodegeneration is induced by inflammation since it is prevented by anti-inflammatory compounds. The special sensitivity of dopaminergic neurons seems to be related to the endogenous dopaminergic content, since it is overcome by dopamine depletion. Compounds that activate microglia or induce inflammation have similar effects to LPS. This model suggest that inflammation is an important component of the degeneration of the nigrostriatal dopaminergic system, probably also in PD. Anti-inflammatory treatments could be useful to prevent or slow down the rate of dopaminergic degeneration in this disease

Metastable liquid lamellar structures in binary and ternary mixtures of Lennard-Jones fluids

We have carried out extensive equilibrium molecular dynamics (MD) simulations to investigate the Liquid-Vapor coexistence in partially miscible binary and ternary mixtures of Lennard-Jones (LJ) fluids. We have studied in detail the time evolution of the density profiles and the interfacial properties in a temperature region of the phase diagram where the condensed phase is demixed. The composition of the mixtures are fixed, 50% for the binary mixture and 33.33% for the ternary mixture. The results of the simulations clearly indicate that in the range of temperatures $78 < T < 102 ^{\rm o}$K, --in the scale of argon-- the system evolves towards a metastable alternated liquid-liquid lamellar state in coexistence with its vapor phase. These states can be achieved if the initial configuration is fully disordered, that is, when the particles of the fluids are randomly placed on the sites of an FCC crystal or the system is completely mixed. As temperature decreases these states become very well defined and more stables in time. We find that below $90 ^{\rm o}$K, the alternated liquid-liquid lamellar state remains alive for 80 ns, in the scale of argon, the longest simulation we have carried out. Nonetheless, we believe that in this temperature region these states will be alive for even much longer times.Comment: 18 Latex-RevTex pages including 12 encapsulated postscript figures. Figures with better resolution available upon request. Accepted for publication in Phys. Rev. E Dec. 1st issu

Moving conferences online: lessons learned from an international virtual meeting

We consider the opportunities and challenges associated with organizing a conference online, using a case study of a medium-sized (approx. 400 participants) international conference held virtually in August 2020. In addition, we present quantifiable evidence of the participants’ experience using the results from an online post-conference questionnaire. Although the virtual meeting was not able to replicate the in-person experience in some aspects (e.g. less engagement between participants) the overwhelming majority of respondents found the meeting an enjoyable experience and would join similar events again. Notably, there was a strong desire for future inperson meetings to have at least some online component. Online attendance by lower-income researchers was higher compared with a past, similarthemed in-person meeting held in a high-income nation, but comparable to one held in an upper-middle-income nation. This indicates that online conferences are not a panacea for diversity and inclusivity, and that holding in-person meetings in developing economies can be at least as effective. Given that it is now relatively easy to stream contents of meetings online using low-cost methods, there are clear benefits in making all presented content accessible online, as well as organizing online networking events for those unable to attend in person

Nuclear Translocation of b-Catenin during Mesenchymal Stem Cells Differentiation into Hepatocytes Is Associated with a Tumoral Phenotype

Wnt/b-catenin pathway controls biochemical processes related to cell differentiation. In committed cells the alteration of this pathway has been associated with tumors as hepatocellular carcinoma or hepatoblastoma. The present study evaluated the role of Wnt/b-catenin activation during human mesenchymal stem cells differentiation into hepatocytes. The differentiation to hepatocytes was achieved by the addition of two different conditioned media. In one of them, b-catenin nuclear translocation, up-regulation of genes related to the Wnt/b-catenin pathway, such as Lrp5 and Fzd3, as well as the oncogenes c-myc and p53 were observed. While in the other protocol there was a Wnt/b-catenin inactivation. Hepatocytes with nuclear translocation of b-catenin also had abnormal cellular proliferation, and expressed membrane proteins involved in hepatocellular carcinoma, metastatic behavior and cancer stem cells. Further, these cells had also increased auto-renewal capability as shown in spheroids formation assay. Comparison of both differentiation protocols by 2D-DIGE proteomic analysis revealed differential expression of 11 proteins with altered expression in hepatocellular carcinoma. Cathepsin B and D, adenine phosphoribosyltransferase, triosephosphate isomerase, inorganic pyrophosphatase, peptidyl-prolyl cis-trans isomerase A or lactate dehydrogenase b-chain were up-regulated only with the protocol associated with Wnt signaling activation while other proteins involved in tumor suppression, such as transgelin or tropomyosin b-chain were downregulated in this protocol. In conclusion, our results suggest that activation of the Wnt/b-catenin pathway during human mesenchymal stem cells differentiation into hepatocytes is associated with a tumoral phenotyp

Effect of bicarbonate on chloride-dependent transmural potential and ATPase activity in the rectal wall of Schistocerca gregaria

An activating effect of bicarbonate on the active transport of Cl- across the rectal wall of Schistocerca gregario has been found, as revealed by an increase of the transmural potential and short-circuit current. Acetazolamide, an inhibitor of both parameters, does not show this inhibitory effect, even at much higher concentrations, when added in the presence of bicarbonate. A Cl- or S O , anion dependent ATPase, different from the Na+, K+ ATPase, has also been Cound, which can be further stimulated by bicarbonate