271 research outputs found
The evolving low-cost business model: Network implications of fare bundling and connecting flights in Europe
In a context of limited organic growth, some low-cost airlines have considered business strategies that are changing two key principles of the low-cost airline business model: fare unbundling and point-to-point operations. Using a multivariate analysis we identify the influence of several route characteristics on the share that European pure low-cost and hybrid low-cost carriers have on the routes they operate. Results show that, from a network perspective, the distance between the archetypical low-cost carrier business model and the adapted low-cost carrier business model with a hybrid approach is widening. Differences are also clear between hybrids offering connecting services and hybrids offering fare bundling. The results are also important from an airport policy perspective, since secondary airports and legacy airports in transition could be able to reduce the gap between them and the main hub airports
Bad Habits: Policy Confounding and Out-of-Trajectory Generalization in RL
Reinforcement learning agents may sometimes develop habits that are effective
only when specific policies are followed. After an initial exploration phase in
which agents try out different actions, they eventually converge toward a
particular policy. When this occurs, the distribution of state-action
trajectories becomes narrower, and agents start experiencing the same
transitions again and again. At this point, spurious correlations may arise.
Agents may then pick up on these correlations and learn state representations
that do not generalize beyond the agent's trajectory distribution. In this
paper, we provide a mathematical characterization of this phenomenon, which we
refer to as policy confounding, and show, through a series of examples, when
and how it occurs in practice
Effects of Crime Type and Location on Park Use Behavior
Crime and the fear of crime can be a barrier to park use, and locations of crimes can have varied effects. Unsafe areas in or around the park, around the residence, or along the route to the park can alter park use behavior. Our study aimed to examine associations between objective measures of types and location of crimes and park use behaviors. In 2013 we surveyed a sample (N = 230) of residents in Greensboro, North Carolina, about park use, with responses matched to objective crime and spatial measures. We measured all crimes and violent crimes near home, near the closest park, and along the shortest route between home and park. By using ordered and binary logistic modeling, we examined the relationships between the locations of crime and park use and duration of park visit, park rating, and never visiting parks. Additional models included distance to the closest park. Increased crime in parks and near home was associated with fewer park visits. Greater violent crime in all locations was related to fewer park visits. Park ratings were lower for parks with high violent crime rates. Given the importance of parks as settings for outdoor recreation and physical activity, crime may have a detrimental effect on physical activity and, therefore, public health
The average mixing matrix signature
Laplacian-based descriptors, such as the Heat Kernel Signature and the Wave Kernel Signature, allow one to embed the vertices of a graph onto a vectorial space, and have been successfully used to find the optimal matching between a pair of input graphs. While the HKS uses a heat di↵usion process to probe the local structure of a graph, the WKS attempts to do the same through wave propagation. In this paper, we propose an alternative structural descriptor that is based on continuoustime quantum walks. More specifically, we characterise the structure of a graph using its average mixing matrix. The average mixing matrix is a doubly-stochastic matrix that encodes the time-averaged behaviour of a continuous-time quantum walk on the graph. We propose to use the rows of the average mixing matrix for increasing stopping times to develop a novel signature, the Average Mixing Matrix Signature (AMMS). We perform an extensive range of experiments and we show that the proposed signature is robust under structural perturbations of the original graphs and it outperforms both the HKS and WKS when used as a node descriptor in a graph matching task
Dendrimers as Carrier Protein Mimetics for IgE Antibody Recognition. Synthesis and Characterization of Densely Penicilloylated Dendrimers
The synthesis of benzylpenicilloyl-containing dendrimers has been achieved by a convenient procedure involving quantitative functionalization of the terminal amino groups of the three Starbust PAMAM generations used (G n ; n ) 0, 1, 2). All these densely penicilloylated dendrimers (G n P) exhibit similar, simple NMR spectroscopic data suggesting highly symmetric structures and a monodisperse nature, and the results obtained from MALDI-TOF-MS demonstrate their exact chemical composition. The use of PAMAM dendrimers has allowed us to synthesize, for the first time, carrier benzylpenicilloyl conjugates (G n P) of precisely defined chemical structure. The attempts to synthesize G 2 P show that forced experimental conditions are not always useful for the functionalization of the dendrimer, especially in introducing bulky groups. The initial results with sera from patients with different RAST levels were positive and thus suggestive that inhibition occurs, so recognition exists; we can therefore conclude that the hapten-carrier (dendrimer) conjugates studied mimic recognition with natural hapten-carrier (protein) conjugates
Red de coordinación de la implantación del primer curso del Grado en IngenierÃa en Sonido e Imagen
El profesorado de la red docente realizó durante el curso 2009/10 un proyecto para la planificación de las asignaturas del primer curso del Grado en IngenierÃa en Sonido e Imagen de la Escuela Politécnica Superior, y nos toca ahora la puesta a punto del primer curso del Grado. En el marco creado por los nuevos estudios dentro del EEES, el proyecto tiene como objetivo principal es el seguimiento, coordinación, evaluación, y mejora de la planificación realizada el curso anterior ya con las nuevas experiencias.Los autores desean agradecer las ayudas institucionales recibidas tanto por parte de la Universidad de Alicante y la Escuela Politécnica Superior (a través del instituto de Ciencias de la Educación y del Vicerrectorado de Planificación Estratégica y Calidad) y el Grupo de Innovación Tecnológica y Educativa de la Universidad de Alicante (GITE-09006-UA)
Microbial Dysbiosis in Colorectal Cancer (CRC) Patients
The composition of the human intestinal microbiota is linked to health status. The aim was to analyze the microbiota of normal and colon cancer patients in order to establish cancer-related dysbiosis
Health-seeking behaviour and beliefs around sore throat in The Gambia: A qualitative study.
Group A Streptococcus (Strep A) bacteria causes a broad spectrum of diseases. The most common manifestations of Strep A infection are sore throat and pus-producing skin infections such as impetigo. Complications of Strep A infection can lead to inflammation in the bones, muscles, joints, and internal organs causing acute rheumatic fever and rheumatic heart disease (RHD). In The Gambia, the RHD burden is thought to be very high. However, epidemiological data is minimal, and Strep A control programmes do not exist. This study aimed to explore common beliefs and practices related to sore throats among primary caregivers of children, and healthcare providers in a community with a high Strep A disease burden. Four informal conversations with providers and fifteen semi-structured interviews with caregivers were conducted in the peri-urban area of Sukuta, The Gambia. Sampling was purposive and gradual, beginning from households identified to have recently experienced sore throat through a parallel cohort study. Themes explored in qualitative analysis included: sore throat causal attributions and diagnoses, care practises, health-seeking behaviour, and perceived barriers to using the biomedical sector. We found that sore throats were typically perceived to affect one child in a family, disproportionately or exclusively. Sore throats were rarely perceived as life-threatening, and awareness of links between sore throat and ARF or RHD was not reported among caregivers or providers in this study population. Most cases of sore throat were initially managed at home using traditional medicine which delayed resort to antibiotics, though in two instances of severe pain with the presence of exudate, fear that the child's life was at risk prompted care-seeking through the formal health system. Our findings can inform the development of tailored strategies to increase community knowledge of the potential long-term consequences of sore throats and appropriate care-seeking, alongside improvements in the health system, to prevent Strep A sequelae effectively
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