Comparación entre dos ecosistemas tropoandinos: la Puna chilena y el Páramo ecuatoriano

This survey is a preliminary, comparative study of the phyto-ecologic features of two great types of ecosystems of the Andes mountain range.It deals with the Chilean "puna" in northern Chile (volcanic region of the Pallachatas, lsluga, Guallatire, and Colorado hills all of which are over 6.000 m above sea level) and the Ecuador paramos (volcanic regions of Cotopaxi and Rumiñahui in the west and the central range of the country).Numerous samples were collected in the field according to the Canfield lineal method andthe Braun-Blanquet one. The data were used to establish the frequency percentage, prevalence, covering, and importance index of shrubs and herbaceous species representative of vegetal formations. These groups were found on the vegetal range floor of the "puna"and "paramo" fover 3.000 m above sea level). They proved to have a very similar composition in gender and family but they are different at the level of species. There were only two plants. Stipa-ichu and dense Azorella which presented a high index of common representativeness in both ecosystems.This botanical variety is mainly due to the different ways that the definitive ecological factors affect the development of herbaceous species. In the "paramo", there are some factors that help the development of extensive shrub and herbaceous communities, such as, favourable exposition, high atmopheric humidity, and high rainfall. All of these help provide a high degree of cover and a dense physiognomy. Meanwhile, in the "puna" there are some factors, such as the high atmospheric dryness, low rainfall, and the existence of unfertile soils which are appropriate for the development of plants adapted to dryness, cold, and wind. They contribute to the formation of open intermediate altitude shrubs and rangelands lower in altitude than in the "paramo".The comparative tables and the vegetal profiles show the predominance of herbaceousspecies in the high mountain communities and the extense altitudinal distribution of these. Some are living close to the lower limit of the eternal snows of the volcanoes.Specific, morphological, and physiological functions of the plants would explain the greatecologic adaptability of these species to exist in mountains over 5.000 m in altitude

Strictly correlated uniform electron droplets

We study the energetic properties of finite but internally homogeneous D-dimensional electron droplets in the strict-correlation limit. The indirect Coulomb interaction is found to increase as a function of the electron number, approaching the tighter forms of the Lieb-Oxford bound recently proposed by Rasanen et al. [Phys. Rev. Lett. 102, 206406 (2009)]. The bound is satisfied in three-, two-, and one-dimensional droplets, and in the latter case it is reached exactly - regardless of the type of interaction considered. Our results provide useful reference data for delocalized strongly correlated systems, and they can be used in the development and testing of exchange-correlation density functionals in the framework of density-functional theory

Near infrared laser irradiation on single multicellular spheroids

Light is being widely used in biomedicine due to its non-invasive nature, with application in imaging techniques and as a therapeutic agent. However, several aspects of its effect on irradiated tissues still leads to discussion in the scientific community. This particularly relates to novel biological models, as is the case of 3D multicellular spheroids, which are rising as an intermediate model between in vitro monolayer cultures and small animals. The applications of these spherical cell aggregates are diverse and include tissue reconstruction, drug testing or cancer studies, to cite some. To address the effect of light on these models, we use spheroids formed by MCF-7 (adenocarcinoma) or by U-87 MG (glioblastoma) cells. After their growth, they have been irradiated individually with focused laser radiation in the near-infrared (808 nm and 1450 nm), which provokes size changes in the spheroid. Time-lapse imaging in a brightfield microscope allows to define a reduction parameter, which informs about the extent of the size change. This parameter is correlated with cell viability studies; thus, we can set a safe range of reduction in which spheroids are not damaged by irradiation, and a threshold that should be avoided to keep cell mortality low. This correlation can be used as preliminary and visual information on the survival of cells during optical experiments with 3D spheroidsBesides, we would like to mention our funding institution, Ministerio de Ciencia e Innovacion ´ de Espana ˜ (grants PID2019-105195RA-I00, PID2019-110632RB-I00, CNS2022-135495, CNS2022-135965 and TED2021-129937B-I00). P.C. thanks the regional government of Comunidad de Madrid for the Programa Investigo (Plan de Recuperacion, ´ Transformacion ´ y Resiliencia) which was developed thanks to SEPE, Ministerio de Trabajo y Economía Social and the European Union through NextGenerationE

Effect of spatial inhomogeneity on the mapping between strongly interacting fermions and weakly interacting spins

A combined analytical and numerical study is performed of the mapping between strongly interacting fermions and weakly interacting spins, in the framework of the Hubbard, t-J and Heisenberg models. While for spatially homogeneous models in the thermodynamic limit the mapping is thoroughly understood, we here focus on aspects that become relevant in spatially inhomogeneous situations, such as the effect of boundaries, impurities, superlattices and interfaces. We consider parameter regimes that are relevant for traditional applications of these models, such as electrons in cuprates and manganites, and for more recent applications to atoms in optical lattices. The rate of the mapping as a function of the interaction strength is determined from the Bethe-Ansatz for infinite systems and from numerical diagonalization for finite systems. We show analytically that if translational symmetry is broken through the presence of impurities, the mapping persists and is, in a certain sense, as local as possible, provided the spin-spin interaction between two sites of the Heisenberg model is calculated from the harmonic mean of the onsite Coulomb interaction on adjacent sites of the Hubbard model. Numerical calculations corroborate these findings also in interfaces and superlattices, where analytical calculations are more complicated.Comment: 7 pages, 6 figure

Condensation in an Economic Model with Brand Competition

We present a linear agent based model on brand competition. Each agent belongs to one of the two brands and interacts with its nearest neighbors. In the process the agent can decide to change to the other brand if the move is beneficial. The numerical simulations show that the systems always condenses into a state when all agents belong to a single brand. We study the condensation times for different parameters of the model and the influence of different mechanisms to avoid condensation, like anti monopoly rules and brand fidelity.Comment: Accepted in: International Journal of Modern Physics

Investigation of on-site inter-orbital single electron hoppings in general multi-orbital systems

A general multi-orbital Hubbard model, which includes on-site inter-orbital electron hoppings, is introduced and studied. It is shown that the on-site inter-orbital single electron hopping is one of the most basic interactions. Two electron spin-flip and pair-hoppings are shown to be correlation effects of higher order than the on-site inter-orbital single hopping. It is shown how the double and higher hopping interactions can be well-defined for arbitrary systems. The two-orbital Hubbard model is studied numerically to demonstrate the influence of the single electron hopping effect, leading to a change of the shape of the bands and a shrinking of the difference between the two bands. Inclusion of the on-site inter-orbital hopping suppresses the so-called orbital-selective Mott transition.Comment: 5 pages, 3 figure

Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System

It is argued that ultracold quantum degenerate gas of ytterbium $^{173}$Yb atoms having nuclear spin $I = 5/2$ exhibits an enlarged SU$(6)$ symmetry. Within the Landau Fermi liquid theory, stability criteria against Fermi liquid (Pomeranchuk) instabilities in the spin channel are considered. Focusing on the SU$(n > 2)$ generalizations of ferromagnetism, it is shown within mean-field theory that the transition from the paramagnet to the itinerant ferromagnet is generically first order. On symmetry grounds, general SU$(n)$ itinerant ferromagnetic ground states and their topological excitations are also discussed. These SU$(n > 2)$ ferromagnets can become stable by increasing the scattering length using optical methods or in an optical lattice. However, in an optical lattice at current experimental temperatures, Mott states with different filling are expected to coexist in the same trap, as obtained from a calculation based on the SU$(6)$ Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6) symmetry-breaking patterns; v3: added further discussion on the order of the transition. Added Reference

Marginal Bone Loss and Pink Esthetic Evaluation of Narrow-Diameter Dental Implants for Single Crowns: 1-Year Prospective Clinical Study

Purpose: The aims of this study were: (1) to quantify the marginal bone loss (MBL) of 3.3-mm narrow-diameter, bone-level, titanium-zirconia (Ti-Zr) implants with two different surfaces in single restorations after a 1-year follow-up; (2) to analyze the combinations of different variables that may influence MBL; and (3) to record the Pink Esthetic Score (PES) value and its correlation with MBL. Materials and Methods: This is a prospective longitudinal clinical study with a 1-year follow-up after crown placement. Two different implant surfaces (sandblasted acid-etched and modified sandblasted acid-etched) were used. All bone-level and bone level-tapered implants had a diameter of 3.3 mm. Different healing and prosthetic abutments were used. Clinical, radiographic, and photographic records were taken 6 months and 1 year after placement of the restorations, and the survival rate, MBL, PES, clinical parameters, and biologic and/or mechanical complications were assessed. The correlations between the variables and MBL were verified. Results: A total of 30 narrow-diameter implants were placed in 30 patients; 18 implants had a sandblasted acid-etched surface, and 12 implants had a modified sandblasted acid-etched surface. The measured MBL at 1 year after implant function had a mean value of-0.36 mm, ranging from 0 mm to-1.77 mm. There was no implant loss. A statistically significant relationship was observed between implant shape (design and length), implant placement level, healing abutment, prosthetic abutment size, gingival thickness, and MBL. The mean PES values recorded at the beginning and end of the study were 7.58 and 11.37, respectively. Conclusion: Narrow-diameter implants showed reduced MBL values, with the surrounding tissues remaining stable after 1 year of follow-up. The MBL did not show different values on two implant surfaces. MBL does not seem to influence esthetic outcome. Int.Oral Maxillofaciallmplants2022;37::515-524. doi: 10.11607/jomi.905

A methodology to implement a closed-loop feedback-feedforward level control in a laboratory-scale flotation bank using peristaltic pumps

This paper describes the implementation of a level control strategy in a laboratory-scale flotation system. The laboratory-scale system consists of a bank of three flotation tanks connected in series, which mimics a flotation system found in mineral processing plants. Besides the classical feedback control strategy, we have also included a feedforward strategy to better account for process disturbances. Results revealed that the level control performance significantly improves when a feedforward strategy is considered. This methodology uses peristaltic pumps for level control, which has not been extensively documented even though: (1) peristaltic pumps are commonly used in laboratory-scale systems, and (2) the control implementation is not as straightforward as those control strategies that use valves. Therefore, we believe that this paper, which describes a proven methodology that has been validated in an experimental system, can be a useful reference for many researchers in the field.•Preparation of reagents to ensure that the froth stability of the froth layer is representative of an industrial flotation froth.•Calibration of instruments - convert the electrical signal from PLCs to engineering units.•Tuning PI parameters using SIMC rules by performing step-changes in each flotation cell