Geometrical properties of the potential energy of the soft-sphere binary mixture

We report a detailed study of the stationary points (zero-force points) of the potential energy surface (PES) of a model structural glassformer. We compare stationary points found with two different algorithms (eigenvector following and square gradient minimization), and show that the mapping between instantaneous configuration and stationary points defined by those algorithms is as different as to strongly influence the instability index K vs. temperature plot, which relevance in analyzing the liquid dynamics is thus questioned. On the other hand, the plot of K vs. energy is much less sensitive to the algorithm employed, showing that the energy is the good variable to discuss geometric properties of the PES. We find new evidence of a geometric transition between a minima-dominated phase and a saddle-point-dominated one. We analyze the distances between instantaneous configurations and stationary points, and find that above the glass transition, the system is closer to saddle points than to minima

Ultrashort Mn-Mn Bonds in Organometallic Complexes

Manganese metallocenes larger than the experimentally produced sandwiched MnBz$_2$ compound are studied using several density functional theory methods. First, we show that the lowest energy structures have Mn clusters surrounded by benzene molecules, in so-called rice-ball structures. We then find a strikingly short bond length of 1.8 {\AA} between pairs of Mn atoms, accompanied by magnetism depletion. The ultrashort bond lengths are related to Bz molecules caging a pair of Mn atoms, leading to a Mn-Mn triple bond. This effect is also found when replacing benzenes by other molecules such as borazine or cyclopentadiene. The stability of the Mn-Mn bond for Mn$_2$Bz$_2$ is further investigated using dissociation energy curves. For each spin configuration, the energy versus distance plot shows different spin minima with barriers, which must be overcome to synthesize larger Mn-Bz complexes.Comment: 9 pages, 8 figure

Quiescence: a mechanism for escaping the effects of drug on cell populations

We point out that a simple and generic strategy to lower the risk for extinction consists in the developing a dormant stage in which the organism is unable to multiply but may die. The dormant organism is protected against the poisonous environment. The result is to increase the survival probability of the entire population by introducing a type of zero reproductive fitness. This is possible, because the reservoir of dormant individuals act as a buffer that can cushion fatal fluctuations in the number of births and deaths which without the dormant population would have driven the entire population to extinction.Comment: 18 pages and 9 figure

Microencapsulation with Maillard Reaction Products to improve the oxidative stability of chia oil

The oil obtained from the seeds of chia (Salvia hispanica L.) is a valuable plant source of omega-3 polyunsaturated fatty acids (PUFA). Chia oil’s high PUFA content makes it an interesting source for enriching foods with these essential fatty acids, but the oil’s high PUFA content also makes it susceptible to oxidation. Consequently, one of the most relevant challenges is to protect the oil from oxidative deterioration.Fil: Copado, Claudia Noelia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Diehl, Bernd W. K.. Spectral Service Gmbh Laboratorium Fur Auftragsanalytik; AlemaniaFil: Ixtaina, Vanesa Yanet. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Tomás, Mabel Cristina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

Revisão e atualização da listagem de espécies de aves registradas na planície do Pantanal.

Este trabalho teve como objetivo atualizar a listagem das espécies de aves já registradas no Pantanal. Uma lista preliminar baseada em informações de literatura foi complementada com comunicações pessoais de ornitólogos que visitaram a região. Somente localidades situadas na planície inundável (de acordo com cartas do DSG em escala 1:100 000) foram consideradas. Um total de 470 espécies já foi registrado na planície, representando um aumento de cerca de 34% à riqueza de espécies anteriormente creditada a esse bioma. Deste total, 379 espécies tiveram exemplares coletados e depositados em coleções do Brasil e do exterior. Das 91 espécies restantes (registradas por observação direta, captura e/ou vocalização), 46 estão presentes em duas ou mais publicações, 26 em apenas uma e dezenove espécies resultaram de comunicações pessoais. O Pantanal não apresenta endemismos. Inventários são realizados nessa região desde o século XIX e localizam-se em pontos mais acessíveis, próximos a cidades, grandes rios ou rodovias. Grandes lacunas são evidentes no centro, em toda porção leste, no sul e na porção noroeste. Novos inventários e pesquisas em coleções de museus poderão resultar em acréscimos a esta listagem, além de confirmar ou desconsiderar registros de ocorrência duvidosa.bitstream/item/37413/1/BP39.pd

Forest and cone structure influence where crossbills forage in a managed Scots pine forest

The structure of forests is a fundamental attribute that impacts biodiversity and ecosystem services and in turn is influenced by natural disturbances and management practices. Here, we examine spatial variation in the interaction between a specialized predispersal seed predator, common crossbills (Loxia curvirostra), and Scots pine (Pinus sylvestris) in relation to forest structure and tree features in a managed Mediterranean forest. Crossbills preferred to forage in pine stands that were more open, which correspond to older stands or regeneration stands with scattered old seed trees. More open older stands with larger trees tend to produce more cones that are attractive to crossbills, although their use was also consistent with crossbills reducing their risk of predation. Within these patches, crossbills selectively foraged on trees having many small, thin-scaled cones, which require less effort and time to extract the seeds. Crossbills were apparently limited to only a very small subset of the closed Scots pine cones because they have relatively small and ineffective bills for foraging on Scots pine. Given that crossbills foraged on only a small subset of the cones within more open stands, a management strategy that would aid common crossbills is to thin middle-aged stands. This would accelerate the development of older stand structure, which would benefit crossbills by increasing the occurrence of suitably open woodlands, benefit other species that rely on older more open stand structure, and potentially decrease the vulnerability of the forest to fire and droughtWe thank C. Ferrini, E. García and P. Acebes for field assistance, P. Edelaar and R. Summers for helpful comments on the manuscript, and Centro de Montes y Aserradero de Valsaín (Organismo Autónomo de Parques Nacionales) for providing information and the LiDAR data. The REMEDINAL 3-CM research network (S2013/mae-2719) partially funded this research. ETM was supported by “Convenio Comunidad de Madrid y Universidad Autónoma de Madrid en Línea 3: Excelencia del Profesorado Universitario” during the writing and publication process

Capital Natural: fontes de bens e serviços - o caso do Pantanal.

bitstream/CPAP/56321/1/ADM094.pdfFormato eletrônico

X-ray spectra reveal the reawakening of the repeat changing-look AGN NGC 1566

We present simultaneous XMM-Newton and NuSTAR observations of the repeat changing-look AGN NGC 1566, which dramatically increased in brightness in the IR to X-ray bands in 2018. The broad-band X-ray spectrum was taken at the peak of the outburst and is typical of Seyfert 1 AGN. The spectrum shows a soft excess, Compton hump, warm absorption and reflection, ruling out tidal disruption as the cause of the outburst and demonstrating that a 'standard' accretion disk can develop very rapidly. The high resolution grating spectrum reveals that the outburst has launched a ~ 500 km/s outflow, and shows photoionised emission lines from rest-frame gas. We discuss possible mechanisms for the outburst, and conclude that it is most likely caused by a disk instability.Comment: 5 pages, 2 figures, accepted to MNRAS letter