Identification Of Critical Periods Research Articles

A Pattern New in Every Moment: The Temporal Clustering of Markets for Crude Oil, Refined Fuels, and Other Commodities

The identification of critical periods and business cycles contributes significantly to the analysis of financial markets and the macroeconomy. Financialization and cointegration place a premium on the accurate recognition of time-varying volatility in commodity markets, especially those for crude oil and refined fuels. This article seeks to identify critical periods in the trading of energy-related commodities as a step toward understanding the temporal dynamics of those markets. This article proposes a novel application of unsupervised machine learning. A suite of clustering methods, applied to conditional volatility forecasts by trading days and individual assets or asset classes, can identify critical periods in energy-related commodity markets. Unsupervised machine learning achieves this task without rules-based or subjective definitions of crises. Five clustering methods—affinity propagation, mean-shift, spectral, k-means, and hierarchical agglomerative clustering—can identify anomalous periods in commodities trading. These methods identified the financial crisis of 2008–2009 and the initial stages of the COVID-19 pandemic. Applied to four energy-related markets—Brent, West Texas intermediate, gasoil, and gasoline—the same methods identified additional periods connected to events such as the September 11 terrorist attacks and the 2003 Persian Gulf war. t-distributed stochastic neighbor embedding facilitates the visualization of trading regimes. Temporal clustering of conditional volatility forecasts reveals unusual financial properties that distinguish the trading of energy-related commodities during critical periods from trading during normal periods and from trade in other commodities in all periods. Whereas critical periods for all commodities appear to coincide with broader disruptions in demand for energy, critical periods unique to crude oil and refined fuels appear to arise from acute disruptions in supply. Extensions of these methods include the definition of bull and bear markets and the identification of recessions and recoveries in the real economy.

Maturation of the digestive system of Downs herring larvae (Clupea harengus, Linnaeus, 1758): identification of critical periods through ontogeny

Digestive system functionality is a key process linked to larval recruitment and survival. However, little is known about organ development and enzyme maturation of the digestive system of North Sea Atlantic herring (Clupea harengus). In this study, herring larvae were reared at 13 °C from hatching to 69 day post hatch, covering four developmental stages: (1) yolk sac (8–9 mm), (2) pre-flexion (9–14 mm), (3) flexion (12–18 mm) and (4) post-flexion stages (15–30 mm). Combined histological (semi-quantitative scoring) and enzyme analyses (pancreatic and intestinal) showed that developmental stages are strongly linked to physiological changes. The larvae lack a functional stomach and use the intestine as the primary site of digestion which is mainly supported by pancreatic enzyme activity. The intestine acquired adult enzymatic digestive features with a functional brush border at the end of the flexion stage and pyloric ceca started to develop during the post-flexion stage. The transition from pre-flexion to flexion stage and the end of the post-flexion stage are energetically taxing periods as indicated by a reduced number and size of liver vacuoles. Based on these findings, we consider these moments as critical periods, where herring larvae could be dramatically affected by suboptimal feeding conditions in the field. This implies that pre-flexion stage larvae with low or no liver reserves may not be able to proceed to the next developmental stage. Hence, the level of energy storage in first-feeding larvae needs to be examined for its use as a field indicator of survival and development.

Spring weather conditions influence breeding phenology and reproductive success in sympatric bat populations.

Climate is known to influence breeding phenology and reproductive success in temperate-zone bats, but long-term population level studies and interspecific comparisons are rare. Investigating the extent to which intrinsic (i.e. age), and extrinsic (i.e. spring weather conditions), factors influence such key demographic parameters as the proportion of females becoming pregnant, or completing lactation, each breeding season, is vital to understanding of bat population ecology and life-history traits. Using data from 12 breeding seasons (2006-2017), encompassing the reproductive histories of 623 Myotis daubentonii and 436Myotis nattereri adult females, we compare rates of recruitment to the breeding population and show that these species differ in their relative sensitivity to environmental conditions and climatic variation, affecting annual reproductive success at the population level. We demonstrate that (1) spring weather conditions influence breeding phenology, with warm, dry and calm conditions leading to earlier parturition dates and advanced juvenile development, whilst cold, wet and windy weather delays birth timing and juvenile growth; (2) reproductive rates in first-year females are influenced by spring weather conditions in that breeding season and in the preceding breeding season when each cohort was born. Pregnancy and lactation rates were both higher when favourable spring foraging conditions were more prevalent; (3)reproductive success increases with age in both species, but at different rates; (4) reproductive rates were consistently higher, and showed less interannual variation, in second-year and older M.daubentonii (mean 91.55%±0.05 SD) than M.nattereri (mean 72.74%±0.15 SD); (5) estimates of reproductive success at the population level were highly correlated with the size of the juvenile cohort recorded each breeding season. Improving understanding of the influence of environmental conditions, especially extreme climatic fluctuations, and the identification of critical periods (i.e. spring for reproductive female bats in temperate zones), which have disproportionate and lasting impacts on breeding phenology and reproductive success at a population level, is critical for improving predictions of the likely impact of climate change on bat populations.

M14 - SPECIFIC ASD PHENOTYPES ARE MODULATED BY DISTINCT GENETIC VARIANTS CONVERGING AT NETWORK LEVEL

Background Autism spectrum disorders (ASD) are a group of genetically and phenotypically heterogeneous neurodevelopmental disorders. Common genetic variants are currently estimated to account for over 50% of ASD liability, and are also suggested to contribute to phenotypic variability. Only few studies have reported association of genetic variants with quantitative ASD phenotypes and it is unclear if different phenotypic aspects of the disorder have a distinct etiology. Here, we aim at discovering associations of common variants with ASD related phenotypes. To interpret the findings in their biological context we mapped significant variants to their genes and tested for enriched pathways and networks implicated in brain development. Methods We investigated phenotype and genotype data of 637 German trios with ASD and of the Autism Genome Project cohort (2004 families). Both cohorts were harmonized and quality checked at phenotypic (Autism Diagnostic Interview Revised, ADI-R items) and genotypic (Illumina Microarrays) level. We performed factor analysis of 28 single items of the ADI-R used in the diagnostic algorithm. To increase genetic resolution and the number of overlapping variants between the two datasets we imputed common variants with a MAF>0.05 using the “1000 Genomes” data as reference. SNPs significantly associated with the phenotype were identified using regression models corrected for ancestry, gender and IQ. Significant variants identified in both, the German and the AGP cohort, were subjected to GO-term, KEGG, and pathway enrichment analysis. Gene-regulatory modules implicated in brain development were defined by weighted gene co-expression analysis using publicly available transcriptome data of the developing human brain (brainspan.org) and tested for enrichment with the associated gene sets. Results We extracted 5 factors of the ADI-R items labeled as joint attention, social interaction and communication, non-verbal communication, repetitive sensory-motor behavior and compulsion and restricted interests. Of the 7.5M variants with a MAF > 0.05 available after imputation and quality check over 500 were associated nominally significant and replicated with each factor respectively. Analysis of the underlying genes showed that the associated GO-terms were specific for each factor and reflected directly linked biological processes such “sensory processing” for repetitive sensory-motor behavior. Finally, we present developmental time-frames specifically enriched for associated gene-sets. Discussion Our findings suggest that each ASD related phenotype is underlying a specific genetic etiology. The identification of critical periods during development further allows understanding the effects of genetic variants at specific brain-developmental and brain-regional networks. These findings thus provided a deeper insight into the complex genetic architecture of ASD and increased our understanding of mechanisms modulating ASD phenotypes

Associations of Maternal and Paternal Blood Pressure Patterns and Hypertensive Disorders during Pregnancy with Childhood Blood Pressure.

BackgroundHypertensive disorders in pregnancy may affect the cardiovascular risk of offspring. We examined the associations of maternal blood pressure throughout pregnancy and hypertensive disorders in pregnancy with childhood blood pressure of offspring. Specific focus was on the comparison with paternal blood pressure effects, the identification of critical periods, and the role of birth outcomes and childhood body mass index in the observed associations.Methods and ResultsThis study was embedded in a population‐based prospective cohort study among 5310 mothers and fathers and their children. We measured maternal blood pressure in each trimester of pregnancy and paternal blood pressure once. Information about hypertensive disorders in pregnancy was obtained from medical records. We measured childhood blood pressure at the median age of 6.0 years (95% range 5.7–8.0 years). Both maternal and paternal blood pressure were positively associated with childhood blood pressure (all P<0.05), with similar effect estimates. Conditional regression analyses showed that early, mid‐, and late‐pregnancy maternal blood pressure levels were all independent and positively associated with childhood blood pressure, with the strongest effect estimates for early pregnancy. Compared with children of mothers without hypertensive disorders in pregnancy, children of mothers with hypertensive disorders in pregnancy had higher diastolic blood pressure by a standard deviation score of 0.13 (95% CI 0.05–0.21). The observed associations were not materially affected by birth outcomes and childhood body mass index.ConclusionsBoth maternal and paternal blood pressure affects childhood blood pressure, independent of fetal and childhood growth measures, with the strongest effect of maternal blood pressure in early pregnancy.

Estimating the critical and sensitive periods of investment in early childhood: A methodological note

The identification of critical periods in early human development requires statistical analyses beyond simple cross tabulation of correlations of observed variables. This paper provides an overview of different quantitative methods available for the statistical analysis of longitudinal data regarding child development, and in particular the identification of critical and sensitive periods for later abilities. It draws heavily on the work on human skill formation developed by the economist James Heckman, which treats ability as a latent variable and explains its formation through the simultaneous estimation of structural equations of investments and achieved abilities across time. We distinguish between two specifications of the ability formation function. One of them (the ‘recursive’) format explains current ability as a function of the ability and investment at the immediately preceding period. The other (the ‘non-recursive’) format explains current ability as a function of a series of past investments. In order to fully examine critical and sensitive periods of investments, the non-recursive formulation needs to be used. Furthermore, true abilities of an individual cannot be directly observed: what we observe are the test scores, for example, on reading and writing. We outline an approach, structural equation modelling, that treats actual test scores as measurements of the latent ability variable, and show how it can be used in the recursive and non-recursive formulation. In order to fully examine critical and sensitive periods of investments, we argue that the non-recursive formulation of this structural model is necessary. However, the non-recursive formulation requires more data than the recursive formulation, and to the best of our knowledge, has never been used in the identification of critical and sensitive periods in early childhood development.

Analysis of robustness in proactive scheduling: A graphical approach

Scheduling environments are generally disturbed by different types of unforeseen events, such as machine breakdowns, unavailability of tools, and arrival of urgent orders. To maintain good performances when these perturbations occur, a schedule has to be robust. These last years, robustness has become an essential issue for scheduling problems. In the related literature, the robustness of schedules is generally evaluated in a quantitative manner, using different possible measures which usually quantify the capacity of a schedule to remain efficient in unexpected conditions. In this article, robustness is addressed from a more qualitative viewpoint. Flowshop scheduling problems are emphasized upon. Instead of evaluating scheduling using a measure, two graphical representations of scheduling solutions are proposed. They provide assistance to the decision maker in understanding the consequences of possible perturbations, so that a suited decision about which solution to choose can be made. The first type of plot shows the extent to which disruptions can be admitted without any consequences on the performance criterion. It also allows the identification of critical periods, where no disruption can be admitted. The second type of plot aims at representing the consequences of disruptions, of different possible length with different possible occurrences, on the performance. An example, comparing two candidate solutions, of a flowshop problem, illustrates the benefits of this approach, which is complementary from a quantitative analysis, based on common robustness measures.

Identification of critical periods for turning broiler hatching eggs during incubation

1. Fertile hatchability was superior from a broiler breeder flock at 29 weeks of age than at 68 weeks of age because of decreased mortality at all stages of embryo development. 2. Eggs that were either turned or not turned during the 0 to 7 d, 8 to 14 d and 15 to 18 d periods in the 8 possible combinations showed that the absence of turning from 0 to 7 d of incubation caused a decrease in fertile hatchability and an increase in all stages of embryonic mortality, and an incidence of Malposition II (head in small end of shell) that was more pronounced in a 68-week-old flock than a 29-week-old flock. 3. When eggs from 33- and 35-week-old broiler breeder flocks were either turned or not turned from 0 to 2 d, 3 to 4 d, 5 to 6 d or 7 to 8 d in the 16 possible combinations, the absence of turning from 3 to 8 d, or 0 to 2 d alone or in combination with other time periods reduced fertile hatchability and increased embryonic mortality and percentage of Malposition II. 4. The most critical period for turning commercial broiler hatching eggs during incubation was from 0 to 7 d with the single most critical 2-d period being 0 to 2 d.

Effects of ethanol exposure on the embryo–fetus: experimental considerations, mechanisms, and the role of prostaglandins

The purpose of this review is to critically examine the effects of ethanol on the embryo-fetus. There has been a tremendous amount of human epidemiological and experimental animal research on the characterization of the anomalies produced by chronic prenatal ethanol exposure and the identification of critical periods of vulnerability and critical amounts of ethanol necessary to produce fetal effects and (or) abnormal development. Few studies have examined the underlying mechanism(s) of the action of ethanol, and even fewer studies have examined the effects of single-dose ethanol exposure on the embryo-fetus. In this review, the current state of knowledge of the effects of chronic use of ethanol on the embryo-fetus is summarized. The primary focus of the review is on the embryonic-fetal effects of acute ethanol exposure, with particular emphasis on the ethanol-induced suppression of fetal breathing movements, as this effect appears to be a very sensitive index of acute exposure of the near-term fetus to ethanol. Factors to be considered in the selection of experimental animals to investigate the mechanism of action of ethanol and to study the acute effects of ethanol are discussed. Postulated mechanisms of action of ethanol on the embryo-fetus are evaluated with a focus on the role of prostaglandins. Finally, future directions in this field of research are proposed.