scholarly journals A Time Series Analysis of Major Indexes Using GARCH Model with Regime Shifts

2017 ◽  
Vol 8 (4) ◽  
pp. 127 ◽  
Author(s):  
S. Aun Hassan
Keyword(s):  
Time Series ◽  
Garch Model ◽  
Regime Shifts ◽  
Sums Of Squares ◽  
Conditional Heteroskedasticity ◽  
Exogenous Shocks ◽  
Time Periods ◽  
Icss Algorithm ◽  
Cumulative Sums ◽  
Over Time

There has always been a great interest in learning about changes in the volatility patterns of stocks and other time series due to exogenous shocks. Researchers and investors have also been curious to study the effect of unanticipated shocks on persistence of volatility over time. This paper studies three major indexes and utilizes the Iterated Cumulative Sums of Squares (ICSS) algorithm to capture time periods of sudden changes in volatility. The findings suggest that persistence of shocks to volatility is not as high as generally perceived. Volatility persistence declines significantly when regime shifts are combined with a Generalized Autoregressive Conditional Heteroskedasticity (GARCH) model. This paper provides important implications for investors and financial researchers.

scholarly journals Structured and Systematic Team and Procedure Training in Severe Trauma: Going from ‘Zero to Hero’ for a Time-Critical, Low-Volume Emergency Procedure Over Three Time Periods

2021 ◽  
Vol 45 (5) ◽  
pp. 1340-1348
Author(s):  
Maryam Meshkinfamfard ◽  
Jon Kristian Narvestad ◽  
Johannes Wiik Larsen ◽  
Arezo Kanani ◽  
Jørgen Vennesland ◽  
...  
Keyword(s):  
Injury Severity ◽  
Trauma System ◽  
Severe Trauma ◽  
Emergency Procedure ◽  
Emergency Thoracotomy ◽  
Severity Scores ◽  
Time Periods ◽  
Low Volume ◽  
Time Critical ◽  
Over Time

Abstract Background Resuscitative emergency thoracotomy is a potential life-saving procedure but is rarely performed outside of busy trauma centers. Yet the intervention cannot be deferred nor centralized for critically injured patients presenting in extremis. Low-volume experience may be mitigated by structured training. The aim of this study was to describe concurrent development of training and simulation in a trauma system and associated effect on one time-critical emergency procedure on patient outcome. Methods An observational cohort study split into 3 arbitrary time-phases of trauma system development referred to as ‘early’, ‘developing’ and ‘mature’ time-periods. Core characteristics of the system is described for each phase and concurrent outcomes for all consecutive emergency thoracotomies described with focus on patient characteristics and outcome analyzed for trends in time. Results Over the study period, a total of 36 emergency thoracotomies were performed, of which 5 survived (13.9%). The “early” phase had no survivors (0/10), with 2 of 13 (15%) and 3 of 13 (23%) surviving in the development and mature phase, respectively. A decline in ‘elderly’ (>55 years) patients who had emergency thoracotomy occurred with each time period (from 50%, 31% to 7.7%, respectively). The gender distribution and the injury severity scores on admission remained unchanged, while the rate of patients with signs on life (SOL) increased over time. Conclusion The improvement over time in survival for one time-critical emergency procedure may be attributed to structured implementation of team and procedure training. The findings may be transferred to other low-volume regions for improved trauma care.

A Contextual Evaluation of Composite Forecasts of Annual Earnings

2016 ◽  
Vol 19 (03) ◽  
pp. 1650014 ◽  
Author(s):  
Pieter T. Elgers ◽  
May H. Lo ◽  
Wenjuan Xie ◽  
Le Emily Xu
Keyword(s):  
Time Series ◽  
Firm Size ◽  
Predictive Accuracy ◽  
Relative Accuracy ◽  
Regulation Fair Disclosure ◽  
Fair Disclosure ◽  
Time Periods ◽  
Time Specific ◽  
Annual Earnings ◽  
The Impact

This study addresses the impact of firm- and time-specific attributes on the accuracy of composite forecasts of annual earnings, constructed from time-series, price-based, and analysts' forecasts. The attributes examined include firm size, analysts' coverage, and time periods pre-dating and following the implementation of regulation fair disclosure. Our results indicate that the relative accuracy of the composite forecasts is time-specific. In the pre-regulation fair disclosure period, composite forecasts significantly outperform each of the three individual forecast sources. Moreover, the extent of improvement in accuracy of composite forecasts is significantly higher for the smaller and lightly-covered firms. Collectively, these results suggest that the predictive accuracy of composite forecasts is contextual.

scholarly journals Longitudinal assessment of the bovine ocular bacterial community dynamics in calves

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Alison C. Bartenslager ◽  
Nirosh D. Althuge ◽  
John Dustin Loy ◽  
Matthew M. Hille ◽  
Matthew L. Spangler ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Community Dynamics ◽  
Bacterial Community Composition ◽  
Clinical Signs ◽  
Sampling Time ◽  
Experimental Population ◽  
Opportunistic Pathogens ◽  
Time Periods ◽  
Over Time

Abstract Background Infectious Bovine Keratoconjunctivitis (IBK), commonly known as pinkeye, is one of the most significant diseases of beef cattle. As such, IBK costs the US beef industry at least 150 million annually. However, strategies to prevent IBK are limited, with most cases resulting in treatment with antibiotics once the disease has developed. Longitudinal studies evaluating establishment of the ocular microbiota may identify critical risk periods for IBK outbreaks or changes in the microbiota that may predispose animals to IBK. Results In an attempt to characterize the establishment and colonization patterns of the bovine ocular microbiota, we conducted a longitudinal study consisting of 227 calves and evaluated the microbiota composition over time using amplicon sequence variants (ASVs) based on 16S rRNA sequencing data and culture-based approaches. Beef calves on trial consisted of both male (intact) and females. Breeds were composed of purebred Angus and composites with varying percentages of Simmental, Angus, and Red Angus breeds. Average age at the start of the trial was 65 days ±15.02 and all calves remained nursing on their dam until weaning (day 139 of the study). The trial consisted of 139 days with four sampling time points on day 0, 21, 41, and 139. The experimental population received three different vaccination treatments (autogenous, commercial (both inactivated bacteria), and adjuvant placebo), to assess the effectiveness of different vaccines for IBK prevention. A significant change in bacterial community composition was observed across time periods sampled compared to the baseline (p < 0.001). However, no treatment effect of vaccine was detected within the ocular bacterial community. The bacterial community composition with the greatest time span between sampling time periods (98d span) was most similar to the baseline sample collected, suggesting re-establishment of the ocular microbiota to baseline levels over time after perturbation. The effect of IgA levels on the microbial community was investigated in a subset of cattle within the study. However, no significant effect of IgA was observed. Significant changes in the ocular microbiota were identified when comparing communities pre- and post-clinical signs of IBK. Additionally, dynamic changes in opportunistic pathogens Moraxella spp. were observed and confirmed using culture based methods. Conclusions Our results indicate that the bovine ocular microbiota is well represented by opportunistic pathogens such as Moraxella and Mycoplasma. Furthermore, this study characterizes the diversity of the ocular microbiota in calves and demonstrates the plasticity of the ocular microbiota to change. Additionally, we demonstrate the ocular microbiome in calves is similar between the eyes and the perturbation of one eye results in similar changes in the other eye. We also demonstrate the bovine ocular microbiota is slow to recover post perturbation and as a result provide opportunistic pathogens a chance to establish within the eye leading to IBK and other diseases. Characterizing the dynamic nature of the ocular microbiota provides novel opportunities to develop potential probiotic intervention to reduce IBK outbreaks in cattle.

scholarly journals Evolutionary history of zoogeographical regions surrounding the Tibetan Plateau

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jiekun He ◽  
Siliang Lin ◽  
Jiatang Li ◽  
Jiehua Yu ◽  
Haisheng Jiang
Keyword(s):  
Tibetan Plateau ◽  
Evolutionary History ◽  
The Tibetan Plateau ◽  
Change Over Time ◽  
Deep Time ◽  
Terrestrial Vertebrates ◽  
History Of ◽  
Striking Change ◽  
Time Periods ◽  
Over Time

AbstractThe Tibetan Plateau (TP) and surrounding regions have one of the most complex biotas on Earth. However, the evolutionary history of these regions in deep time is poorly understood. Here, we quantify the temporal changes in beta dissimilarities among zoogeographical regions during the Cenozoic using 4,966 extant terrestrial vertebrates and 1,278 extinct mammal genera. We identify ten present-day zoogeographical regions and find that they underwent a striking change over time. Specifically, the fauna on the TP was close to the Oriental realm in deep time but became more similar to the Palearctic realms more recently. The present-day zoogeographical regions generally emerged during the Miocene/Pliocene boundary (ca. 5 Ma). These results indicate that geological events such as the Indo-Asian Collision, the TP uplift, and the aridification of the Asian interior underpinned the evolutionary history of the zoogeographical regions surrounding the TP over different time periods.

scholarly journals Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa

2010 ◽  
Vol 67 (6) ◽  
pp. 1185-1197 ◽  
Author(s):  
C. Fernández ◽  
S. Cerviño ◽  
N. Pérez ◽  
E. Jardim
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Reference Points ◽  
Assessment Model ◽  
Marine Science ◽  
Fishing Mortality ◽  
Change Over Time ◽  
Age Structured ◽  
Available Information ◽  
Over Time

Abstract Fernández, C., Cerviño, S., Pérez, N., and Jardim, E. 2010. Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa. – ICES Journal of Marine Science, 67: 1185–1197. A Bayesian age-structured stock assessment model is developed to take into account available information on discards and to handle gaps in the time-series of discard estimates. The model incorporates mortality attributable to discarding, and appropriate assumptions about how this mortality may change over time are made. The result is a stock assessment that accounts for information on discards while, at the same time, producing a complete time-series of discard estimates. The method is applied to the hake stock in ICES Divisions VIIIc and IXa, for which the available data indicate that some 60% of the individuals caught are discarded. The stock is fished by Spain and Portugal, and for each country, there are discard estimates for recent years only. Moreover, the years for which Portuguese estimates are available are only a subset of those with Spanish estimates. Two runs of the model are performed; one assuming zero discards and another incorporating discards. When discards are incorporated, estimated recruitment and fishing mortality for young (discarded) ages increase, resulting in lower values of the biological reference points Fmax and F0.1 and, generally, more optimistic future stock trajectories under F-reduction scenarios.

scholarly journals Phagolysosome formation in normal and colchicine-treated macrophages.

1975 ◽  
Vol 142 (4) ◽  
pp. 903-913 ◽  
Author(s):  
E L Pesanti ◽  
S G Axline
Keyword(s):  
Acid Phosphatase ◽  
Lysosomal Enzyme ◽  
Peritoneal Macrophages ◽  
Cell Type ◽  
Inert Particles ◽  
Time Periods ◽  
Mouse Peritoneal Macrophages ◽  
Over Time

Intracellular lysosomal fusion has been evaluated in cultivated mouse peritoneal macrophages by measurement of transfer of acid phosphatase to polyvinyltoluene (PVT)-containing phagolysosomes. Enzyme transfer was found to be directly and significantly related to the uptake of PVT and to be independent of time allowed for phagolysosome formation over time periods of 15 min to 18 h. In addition, the extent of transfer of lysosomal enzyme to phagolysosomes was unaffected by treatment of the cells with 10(-6) M colchicine, a dose which eradicates morphologically identifiable microtubules in this cell type within 2 h. The data indicate that intracellular fusion of lysosomes with phagosomes in the macrophage does not require formed microtubules and suggest that fusion occurs promptly after interiorization of inert particles.

Precarity Unbound

2007 ◽  
Vol 32 (3) ◽  
pp. 319-340 ◽  
Author(s):  
Nancy Ettlinger
Keyword(s):  
Everyday Life ◽  
Final Section ◽  
Multiple Scales ◽  
Bush Administration ◽  
Radical Democracy ◽  
Top Down ◽  
Hardt And Negri ◽  
Global Events ◽  
Time Periods ◽  
Over Time

Departing from tendencies to bound precarity in particular time periods and world regions, this article develops an expansive view of precarity over time and across space. Beyond effects of specific global events and macroscale structures, precarity inhabits the microspaces of everyday life. However, people attempt to disengage the stress of precarious life by constructing the illusion of certainty. Reflexive denial of precarious life entails essentialist strategies that implicitly or explicitly classify and homogenize people and phenomena, legitimize the constructed boundaries, and in the process aim at eliminating difference and possibilities for negotiation; the tension between these goals and material realities helps explain misrepresentations that can be catastrophic at multiple scales, re-creating precarity. Reactions to 9/11 by the Bush administration represent a case in point of reflexive denial of precarity through strategies that created illusions of certainty with deleterious results. Normatively, the paradox of precarious life and reflexive denials prompts questions as to how urges for certainty in the context of precarity might be constructively channeled. the author approaches this challenge in the final section by drawing from a nexus of concerns about post-Habermasian radical democracy, individual thought and feeling, and network dynamics. Whereas Hardt and Negri reverse the direction of the Foucauldian concept of biopower from top-down to bottom-up, the author draws from Foucault's concept of governmentality in relation to resistance to imagine a cooperative politics operating within as well as across scales.

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