Forecasting VARMA processes using VAR models and subspace-based state space models

VAR modelling is a frequent technique in econometrics for linear processes. VAR modelling offers some desirable features such as relatively simple procedures for model specification (order selection) and the possibility of obtaining quick non-iterative maximum likelihood estimates of the system parameters. However, if the process under study follows a finite-order VARMA structure, it cannot be equivalently represented by any finite-order VAR model. On the other hand, a finite-order state space model can represent a finite-order VARMA process exactly, and, for state-space modelling, subspace algorithms allow for quick and non-iterative estimates of the system parameters, as well as for simple specification procedures. Given the previous facts, we check in this paper whether subspace-based state space models provide better forecasts than VAR models when working with VARMA data generating processes. In a simulation study we generate samples from different VARMA data generating processes, obtain VAR-based and state-space-based models for each generating process and compare the predictive power of the obtained models. Different specification and estimation algorithms are considered; in particular, within the subspace family, the CCA (Canonical Correlation Analysis) algorithm is the selected option to obtain state-space models. Our results indicate that when the MA parameter of an ARMA process is close to 1, the CCA state space models are likely to provide better forecasts than the AR models. We also conduct a practical comparison (for two cointegrated economic time series) of the predictive power of Johansen restricted-VAR (VEC) models with the predictive power of state space models obtained by the CCA subspace algorithm, including a density forecasting analysis.subspace algorithms; VAR; forecasting; cointegration; Johansen; CCA

Social Representations of Bogota - Colombia Inhabitants Regarding a Conditional Cash Transfer Policy

The current article shows the development of a research process whose main objective was to explain the influence of the social representations of the inhabitants of Bogotá, Colombia in the implementation of the public policy of conditional cash transfers “Más Familias en Acción.” For this aim, a qualitative study of hermeneutic design was conducted with beneficiaries of the program and non-beneficiaries, in which, through the application of semi-structured interviews, the most frequent social representations about subsidies, policies, work, education, health, among other relevant issues related to this public policy were identified and once the information was coded by using the Atlas.ti software, interpretation of results was done making possible to establish a relationship between the social representations found and the implementation of “Más Familias en Acción,” leading to the understanding of how social representations as sets of ideas, values and practices that become a social code that denominates the individual and collective reality, have influence both in the way in which the beneficiaries of the program conceive their social reality, and in the sense they give to the program, as well as in their articulation and interaction with it, enabling its implementation, which may or may not occur according to the objectives of public policy

Approaches for Removal of PAHs in Soils: Bioaugmentation, Biostimulation and Bioattenuation

Polycyclic aromatic hydrocarbons (PAHs)‐contaminated soils have been a concern during last decades; consequently, physicochemical and biological technologies have emerged and evolved with the aim of remediating them. Particularly, biological technologies are considered promising since they are low cost, safe and environmentally friendly. However, their results so far have been diverse and scattered. This chapter includes a review of the current status on bioaugmentation, biostimulation and bioattenuation techniques, which have been applied in PAHs‐contaminated agricultural soils during the last decades. Successes and failures in PAHs remediation applied at microcosm and field levels are exhibited. Furthermore, the effects of microbial inoculum, the soil organic matter and the particle size of the aggregates on the PAHs’ availability and on the subsequent microbial biodegradation are reviewed. Finally, agricultural management systems are considered in the prediction of the behaviour and the end‐point of some contaminants, as well as in the success of applying a biological technique

Enhanced near infrared optical access to the brain with a transparent cranial implant and scalp optical clearing.

We report on the enhanced optical transmittance in the NIR wavelength range (900 to 2400 nm) offered by a transparent Yttria-stabilized zirconia (YSZ) implant coupled with optical clearing agents (OCAs). The enhancement in optical access to the brain is evaluated upon comparing ex-vivo transmittance measurements of mice native skull and the YSZ cranial implant with scalp and OCAs. An increase in transmittance of up to 50% and attenuation lengths of up to 2.4 mm (i.e., a five-fold increase in light penetration) are obtained with the YSZ implant and the OCAs. The use of this ceramic implant and the biocompatible optical clearing agents offer attractive features for NIR optical techniques for brain theranostics

A PHYLOGENETIC PERSPECTIVE OF THE AVIAN TROPHIC DIVERSIFICATION: INTEGRATING PALAEONTOLOGICAL AND NEONTOLOGICAL INFORMATION

From their origin in the Middle Jurassic until the present, birds have undergone one of the most important evolutionary radiations among vertebrates, with the development of great species-level diversity and the occupation of a broad spectrum of ecological niches. Since dietary shifts involve a series of morphophysiological adjustments and reflect the use of the resources, diet represents a key ecological and evolutionary parameter to understand the history of bird clades. This study combines neontological and paleontological dietary information in a phylogenetic context, aiming the understanding the role of feeding habits in bird evolution and their potential relationship with past ecological and evolutionary events. Our findings point towards an omnivorous ancestral diet for the avian clade, which is consistent with dietary information, dental structure and life style of the first birds, such as Archaeopteryx. Our results also show dietary shifts in avian evolutionary history. Faunivores predominate in the avian history, while herbivorous lineages underwent adaptive radiations possibly related to transformation of ecosystems and their plant assemblages worldwide such as the development of the angiosperms during the Cretaceous or the development of grassy environments in the Oligocene. Faunivorous and herbivorous clades arose basically through diversification within lineages, while omnivores evolved due to transitions into the strategy. The capacity to specialize and generate new trophic niches allowed faunivores and herbivores to diversify more than omnivores. Nevertheless, despite this relatively low diversification, the omnivorous strategy appears to be key to the primary processes of bird radiation and fundamental in the evolutionary success of birds.Peer reviewe

A contact domain method for large deformation frictional contact problems. Part 1: Theoretical basis

In the first part of this work, the theoretical basis of a frictional contact domain method for two-dimensional large deformation problems is presented. Most of the existing contact formulations impose the contact constraints on the boundary of one of the contacting bodies, which necessitates the projection of certain quantities from one contacting surface onto the other. In this work, the contact constraints are formulated on a so-called contact domain, which has the same dimension as the contacting bodies. This contact domain can be interpreted as a fictive intermediate region connecting the potential contact surfaces of the deformable bodies. The introduced contact domain is subdivided into a non-overlapping set of patches and is endowed with a displacement field, interpolated from the displacements at the contact surfaces. This leads to a contact formulation that is based on dimensionless, strain-like measures for the normal and tangential gaps and that exactly passes the contact patch test. In addition, the contact constraints are enforced using a stabilized Lagrange multiplier formulation based on an interior penalty method (Nitsche method). This allows the condensation of the introduced Lagrange multipliers and leads to a purely displacement driven problem. An active set strategy, based on the concept of effective gaps as entities suitable for smooth extrapolation, is used for determining the active normal stick and slip patches of the contact domain

Perceived attachment and problematic smartphone use in young people: mediating effects of self-regulation and prosociality

Background: Problematic use of smartphones is a challenge facing societies around the world. This phenomenon has been associated with negative socialization experiences through the impact they have on how the youth relates to their environment. This study was designed to examine parental and peer attachment, self-efficacy and prosocial reasoning as predictors of different attitudes towards online communication and problematic smartphone use. Method: 561 youth aged 14-20 years (Mage= 17.82; SD= 1.64; 67.7% Female) participated in an online survey. Results: Results indicated that an increase in self-efficacy or prosocial reasoning is correlated with a decrease in problematic smartphone use and attitudes towards online communication aimed at avoiding reality or constructing a more comfortable parallel social reality. Attachment to parents and peers had direct and indirect effects on problematic smartphone use and attitudes toward online communication through youth personal and social adjustment. Conclusions: Attachment plays a relevant role in the symptoms reduction of smartphone addiction and attitudes to online communication in youth, through its impact on self-efficacy perceptions and prosocial reasoning

Could people with stereo-deficiencies have a rich 3D experience using HMDs?

People with stereo-deficiencies usually have problems for the perception of depth using stereo devices. This paper presents a study that involves participants who did not have stereopsis and participants who had stereopsis. The two groups of participants were exposed to a maze navigation task in a 3D environment in two conditions, using a HMD and a large stereo screen. Fifty-nine adults participated in our study. From the results, there were no statistically significant differences for the performance on the task between the participants with stereopsis and those without stereopsis. We found statistically significant differences between the two conditions in favor of the HMD for the two groups of participants. The participants who did not have stereopsis and could not perceive 3D when looking at the Lang 1 Stereotest did have the illusion of depth perception using the HMD. The study suggests that for the people who did not have stereopsis, the head tracking largely influences the 3D experience

Multi-target Attachment for Surgical Instrument Tracking

The pose estimation of a surgical instrument is a common problem in the new needs of medical science. Many instrument tracking methods use markers with a known geometry that allows for solving the instrument pose as detected by a camera. However, marker occlusion happens, and it hinders correct pose estimation. In this work, we propose an adaptable multi-target attachment with ArUco markers to solve occlusion problems on tracking a medical instrument like an ultrasound probe or a scalpel. Our multi-target system allows for precise and redundant real-time pose estimation implemented in OpenCV. Encouraging results show that the multi-target device may prove useful in the clinical settin