Hard and Easy Instances of L-Tromino Tilings

We study tilings of regions in the square lattice with L-shaped trominoes. Deciding the existence of a tiling with L-trominoes for an arbitrary region in general is NP-complete, nonetheless, we identify restrictions to the problem where it either remains NP-complete or has a polynomial time algorithm. First, we characterize the possibility of when an Aztec rectangle and an Aztec diamond has an L-tromino tiling. Then, we study tilings of arbitrary regions where only $180^\circ$ rotations of L-trominoes are available. For this particular case we show that deciding the existence of a tiling remains NP-complete; yet, if a region does not contains certain so-called "forbidden polyominoes" as sub-regions, then there exists a polynomial time algorithm for deciding a tiling.Comment: Full extended version of LNCS 11355:82-95 (WALCOM 2019

A new generalized paucituberculatan marsupial from the oligocene of Bolivia and the origin of 'shrew-like' opossums

Insights into the origin of 'shrew-like' oposssums of South America are gained thanks to a new fossil from the Oligocene Salla Beds in Bolivia. The specimen described here consists of a partial rostrum, palate and postcanine teeth, and shows several generalized features (cranial and dental) in the context of the Paucituberculata. On this basis we recognize Evolestes hadrommatos gen. et sp. nov. In order to evaluate the affinities of the new taxon, we performed a phylogenetic analysis including representatives of the Caenolestidae, Pichipilus and allies (not regarded here as caenolestids), Palaeothentidae, and Abderitidae, with three outgroups. Evolestes is the basalmost 'caenolestoid', and provides clues to the morphological changes involved in the origin of caenolestids.Facultad de Ciencias Naturales y Muse

A new generalized paucituberculatan marsupial from the oligocene of Bolivia and the origin of 'shrew-like' opossums

Insights into the origin of 'shrew-like' oposssums of South America are gained thanks to a new fossil from the Oligocene Salla Beds in Bolivia. The specimen described here consists of a partial rostrum, palate and postcanine teeth, and shows several generalized features (cranial and dental) in the context of the Paucituberculata. On this basis we recognize Evolestes hadrommatos gen. et sp. nov. In order to evaluate the affinities of the new taxon, we performed a phylogenetic analysis including representatives of the Caenolestidae, Pichipilus and allies (not regarded here as caenolestids), Palaeothentidae, and Abderitidae, with three outgroups. Evolestes is the basalmost 'caenolestoid', and provides clues to the morphological changes involved in the origin of caenolestids.Facultad de Ciencias Naturales y Muse

Kinematic and kinetic patterns related to free-walking in Parkinson's disease

The aim of this study is to compare the properties of free-walking at a natural pace between mild Parkinson’s disease (PD) patients during the ON-clinical status and two control groups. In-shoe pressure-sensitive insoles were used to quantify the temporal and force characteristics of a 5-min free-walking in 11 PD patients, in 16 young healthy controls, and in 12 age-matched healthy controls. Inferential statistics analyses were performed on the kinematic and kinetic parameters to compare groups’ performances, whereas feature selection analyses and automatic classification were used to identify the signature of parkinsonian gait and to assess the performance of group classification, respectively. Compared to healthy subjects, the PD patients’ gait pattern presented significant differences in kinematic parameters associated with bilateral coordination but not in kinetics. Specifically, patients showed an increased variability in double support time, greater gait asymmetry and phase deviation, and also poorer phase coordination. Feature selection analyses based on the ReliefF algorithm on the differential parameters in PD patients revealed an effect of the clinical status, especially true in double support time variability and gait asymmetry. Automatic classification of PD patients, young and senior subjects confirmed that kinematic predictors produced a slightly better classification performance than kinetic predictors. Overall, classification accuracy of groups with a linear discriminant model which included the whole set of features (i.e., demographics and parameters extracted from the sensors) was 64.1

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios

We document the first occurrence of Sigmodontinae (Mammalia, Rodentia, Cricetidae) from the Pliocene of northern South America, from the San Gregorio Formation of northwestern Venezuela. The recovered isolated molars are identified as Oligoryzomys sp. and Zygodontomys sp., two currently widespread sigmodontines in South America. These records constitute the oldest representatives of these genera, potentially new species, and the first Pliocene occurrence for Oryzomyini and the whole subfamily outside Argentina. Hypotheses on the historical biogeography of sigmodontines have been constructed almost exclusively using genetic data and the fossils we report provide a new kind of evidence. The occurrence of Oligoryzomys sp. and Zygodontomys sp. in Venezuela provides novel information for the diversification models suggested for Oligoryzomys, by supporting a potential eastern corridor of open environments from northern to southern South America. The presence of sigmodontines from the locality home of the new reports, Norte Casa Chiguaje, is consistent with the palaeoenvironmental conditions originally proposed for it based on mammals and botanical records, being characterized as mixed open grassland/forest areas surrounding permanent freshwater systems. The new sigmodontine evidence is used to discuss the putative scenarios of the ancient evolution of the subfamily in South America, favouring a model in which open areas (savannahs) to the east of the Andes played crucial role aiding or obstructing Late Miocene-Pliocene sigmodontine dispersion southwards

Treadmill exercise activates subcortical neural networks and improves walking after a stroke

BACKGROUND AND PURPOSE: Stroke often impairs gait thereby reducing mobility and fitness and promoting chronic disability. Gait is a complex sensorimotor function controlled by integrated cortical, subcortical, and spinal networks. The mechanisms of gait recovery after stroke are not well understood. This study examines the hypothesis that progressive task-repetitive treadmill exercise (T-EX) improves fitness and gait function in subjects with chronic hemiparetic stroke by inducing adaptations in the brain (plasticity).METHODS: A randomized controlled trial determined the effects of 6-month T-EX (n=37) versus comparable duration stretching (CON, n=34) on walking, aerobic fitness and in a subset (n=15/17) on brain activation measured by functional MRI.RESULTS: T-EX significantly improved treadmill-walking velocity by 51% and cardiovascular fitness by 18% (11% and -3% for CON, respectively; P<0.05). T-EX but not CON affected brain activation during paretic, but not during nonparetic limb movement, showing 72% increased activation in posterior cerebellar lobe and 18% in midbrain (P<0.005). Exercise-mediated improvements in walking velocity correlated with increased activation in cerebellum and midbrain.CONCLUSIONS: T-EX improves walking, fitness and recruits cerebellum-midbrain circuits, likely reflecting neural network plasticity. This neural recruitment is associated with better walking. These findings demonstrate the effectiveness of T-EX rehabilitation in promoting gait recovery of stroke survivors with long-term mobility impairment and provide evidence of neuroplastic mechanisms that could lead to further refinements in these paradigms to improve functional outcomes

Sistemas conversacionales aplicados a la gobernanza

Un chatbot es un sistema inteligente conversacional capaz de simular y procesar una conversación humana de forma escrita o hablada, permitiendo a sus usuarios interactuar con servicios digitales como si estuvieran tratando con otra persona real. Estos pueden ser tan sencillos como un pequeño programa que responde preguntas con una línea de texto, como un gran y sofisticado asistente digital que aprende y relaciona conceptos a partir de la información que recibe y procesa logrando altos niveles de personalización e “inteligencia”. El chatbot propuesto será capaz de responder consultas y entregar formularios a los interesados en los cursos y trabajos disponibles de la oficina de empleo local en Caleta Olivia utilizando lenguaje natural ameno y sencillo de seguir, también tomando en cuenta posibles reconocimientos erróneos de intenciones y pudiendo aprender de ellos.Red de Universidades con Carreras en Informátic

An exceptionally well-preserved skeleton of Palaeothentes from the Early Miocene of Patagonia, Argentina: new insights into the anatomy of extinct paucituberculatan marsupials

International audienc

A new generalized paucituberculatan marsupial from the oligocene of Bolivia and the origin of 'shrew-like' opossums

Insights into the origin of 'shrew-like' oposssums of South America are gained thanks to a new fossil from the Oligocene Salla Beds in Bolivia. The specimen described here consists of a partial rostrum, palate and postcanine teeth, and shows several generalized features (cranial and dental) in the context of the Paucituberculata. On this basis we recognize Evolestes hadrommatos gen. et sp. nov. In order to evaluate the affinities of the new taxon, we performed a phylogenetic analysis including representatives of the Caenolestidae, Pichipilus and allies (not regarded here as caenolestids), Palaeothentidae, and Abderitidae, with three outgroups. Evolestes is the basalmost 'caenolestoid', and provides clues to the morphological changes involved in the origin of caenolestids.Facultad de Ciencias Naturales y Muse