time invariance
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2022 ◽  
Vol 204 ◽  
pp. 111173
Author(s):  
Ryo Yamada ◽  
Mikihiro Kudo ◽  
Geunwoo Kim ◽  
Tomohiro Takaki ◽  
Yasushi Shibuta ◽  
...  

Author(s):  
Liao Zhu ◽  
Robert A. Jarrow ◽  
Martin T. Wells

This paper tests a multi-factor asset pricing model that does not assume that the return’s beta coefficients are constants. This is done by estimating the generalized arbitrage pricing theory (GAPT) using price differences. An implication of the GAPT is that when using price differences instead of returns, the beta coefficients are constant. We employ the adaptive multi-factor (AMF) model to test the GAPT utilizing a Groupwise Interpretable Basis Selection (GIBS) algorithm to identify the relevant factors from among all traded exchange-traded funds. We compare the performance of the AMF model with the Fama–French 5-factor (FF5) model. For nearly all time periods less than six years, the beta coefficients are time-invariant for the AMF model, but not for the FF5 model. This implies that the AMF model with a rolling window (such as five years) is more consistent with realized asset returns than is the FF5 model.


2021 ◽  
Author(s):  
Nicholas S Bland

Rhythmic modulation of brain activity by transcranial alternating current stimulation (tACS) can entrain neural oscillations in a frequency- and phase-specific manner. However, large stimulation artefacts contaminate concurrent 'online' neuroimaging measures, including magneto- and electro-encephalography (M/EEG) — restricting most analyses to periods free from stimulation ('offline' aftereffects). While many published methods exist for removing artefacts of tACS from M/EEG recordings, they universally assume linear artefacts: either time-invariance (i.e., an artefact is a scaled version of itself from cycle to cycle) or sensor-invariance (i.e., artefacts are scaled versions of one another from sensor to sensor). However, heartbeat and respiration both nonlinearly modulate the amplitude and phase of these artefacts, predominantly via changes in scalp impedance. The spectral symmetry this introduces to the M/EEG spectra may lead to false-positive evidence for entrainment around the frequency of tACS, if not adequately suppressed. Good electrophysiological evidence for entrainment therefore requires that tACS artefacts are fully accounted for before comparing online spectra to a control (e.g., as might be observed during sham stimulation). Here I outline an approach to linearly solve templates for tACS artefacts, and demonstrate how event-locked perturbations to amplitude and phase can be introduced from simultaneous recordings of heartbeat and respiration — effectively forming time-varying models of tACS artefacts. These models are constructed for individual sensors, and can therefore be used in contexts with few EEG sensors and with no assumption of artefact collinearity. I also discuss the feasibility of this approach in the absence of simultaneous recordings of heartbeat and respiration traces.


2021 ◽  
pp. 1-13
Author(s):  
Montserrat Alegret ◽  
Ana Espinosa ◽  
Gemma Ortega ◽  
Alba Pérez-Cordón ◽  
Ángela Sanabria ◽  
...  

Background: Over the last decade, teleneuropsychology has increased substantially. There is a need for valid neuropsychological batteries to be administered home-to-home. Since 2006, the neuropsychological battery of Fundació ACE (NBACE) has been administered face-to-face in our clinical settings. Recently, we adapted the NBACE for teleneuropsychology use to be administered home-to-home (NBACEtn). Objective: The aims of the present study are: 1) to determine the home-to-home NBACE equivalence compared to its original face-to-face version; and 2) to examine home-to-home NBACE discriminant capacity by differentiating among cognitively healthy, mild cognitive impairment, or mild dementia subjects and comparing it with the face-to-face version. Methods: Data from 338 individuals assessed home-to-home (NBACEtn) were contrasted with 7,990 participants assessed with its face-to-face version (NBACE). Exploratory and confirmatory factorial structure, and invariance analysis of the two versions of the battery were performed. Results: Exploratory and confirmatory factor analysis supported the four-factor model (attention, memory, executive, and visuospatial/constructional functions). Configural, metric, and scalar measurement invariance was found between home-to-home and face-to-face NBACE versions. Significant differences in most of the neuropsychological variables assessed were observed between the three clinical groups in both versions of administration. No differences were found between the technological devices used by participants (computer or tablet and mobile devices). Conclusion: For the first time, invariance analysis findings were addressed by determining a teleneuropsychological battery’s equivalence in comparison with its face-to-face version. This study amplifies the neuropsychological assessment’s applicability using a home-to-home format, maintaining the original measure’s structure, interpretability, and discriminant capacity.


2021 ◽  
Vol 123 ◽  
pp. 104048
Author(s):  
Geir B. Asheim ◽  
John M. Hartwick ◽  
Tapan Mitra

2021 ◽  
Author(s):  
Liao Zhu ◽  
Robert A. Jarrow ◽  
Martin T. Wells
Keyword(s):  

2020 ◽  
Vol 63 (6) ◽  
Author(s):  
Pier Luigi Bragato ◽  
Carla Barnaba ◽  
Chiara Scaini ◽  
Monica Sugan

We considered the mortality data of the earthquakes which occurred in Italy since 1800 and investigated their spatial-temporal characteristics. For this purpose, we developed a log-linear regression model relating the number of deaths to the magnitude of the earthquakes and analyzed the distribution of the residuals from the model. We found that, for fixed magnitude, the mortality of the earthquakes of the last decades is almost identical to that of the 19th century despite the fact that the population is decreasing in the small municipalities with high seismic hazard. There is also a geographical divide: for the same magnitude, an earthquake in southern Italy causes 2.9 times the number of victims than in northern Italy. The gap is partially justified by the higher population density in the seismic areas of southern Italy, while it does not seem to depend on seismological factors (seismic source, regional attenuation and site effects). The north/south divide increases to a factor of 8.3 for the earthquakes occurring between 00:00 and 05:00 a.m., when most people are sleeping and rely almost entirely on the strength of their houses for survival. We suggest that differences in the quality and maintenance level of the residential buildings are the primary factors determining this geographic divide, supported by data from a survey taken in 1934 and from the last general national census of 2011. Our results indicate that the situation of residential buildings in Italy requires a strict application of the seismic regulations as well as their extension to stimulate the correct maintenance and retrofitting of the existing buildings.


Religions ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 577 ◽  
Author(s):  
Michael Ackert ◽  
Elena Prutskova ◽  
Ivan Zabaev

Since the end of the Soviet Union, Christian Orthodoxy has regained importance in Russian society. Considering the religious dynamics in the decades after 1990, scholars working in the field have been debating about a reliable measuring tool for religiosity. The present study provides a validation of two short forms of the Centrality of Religiosity Scale (CRS), the CRS-5, and CRSi-7 in Russia, as well as its corresponding translated items. Therefore, data from two large-scale sociological surveys from 2008 (N = 894) and 2019 (N = 1768) were used. A multigroup confirmatory factor analysis with restrictions on the variance and covariance structure of the model shows good results in terms of absolute, parsimony, and relative model fit for the CRS-5 and CRSi-7. Moreover, the models indicate time-invariance, which is a consistent psychometric characteristic of both short forms. The time-invariance is accompanied by the good internal consistency of the scales: The CRS-5 with α=0.85 and the CRSi-7 with α=0.84. The results of the analysis encourage the use of the CRS-5 and the CRSi-7 for research on religiosity in Russia. While the CRS-5 is especially suitable for the Orthodox-dominated religious landscape, the CRSi-7 should be used if non-monotheistic private religious practice and religious experience are the focus of the scientific investigation.


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