Saddlepoint approximation to functional equations in queueing theory and insurance mathematics

2010 Fall.Includes bibliographical references.We study the application of saddlepoint approximations to statistical inference when the moment generating function (MGF) of the distribution of interest is an explicit or an implicit function of the MGF of another random variable which is assumed to be observed. In other words, let W (s) be the MGF of the random variable W of interest. We study the case when W (s) = h{G (s) ; λ}, where G (s) is an MGF of G for which a random sample can be obtained, and h is a smooth function. If Ĝ (s) estimates G (s), then Ŵ (s) = h{Ĝ (s) ; λ̂} estimates W (s). Generally, it can be shown that Ŵ (s) converges to W (s) by the strong law of large numbers, which implies that F̂ (t), the cumulative distribution function (CDF) corresponding to Ŵ (s), converges to F (t), the CDF of W, almost surely. If we set Ŵ* (s) = h{Ĝ* (s) ; λ̂}, where Ĝ* (s) and λ̂* are the empirical MGF and the estimator of λ from bootstrapping, the corresponding CDF F̂* (t) can be used to construct the confidence band of F(t). In this dissertation, we show that the saddlepoint inversion of Ŵ (s) is not only fast, reliable, stable, and accurate enough for a general statistical inference, but also easy to use without deep knowledge of the probability theory regarding the stochastic process of interest. For the first part, we consider nonparametric estimation of the density and the CDF of the stationary waiting times W and Wq of an M/G/1 queue. These estimates are computed using saddlepoint inversion of Ŵ (s) determined from the Pollaczek-Khinchin formula. Our saddlepoint estimation is compared with estimators based on other approximations, including the Cramér-Lundberg approximation. For the second part, we consider the saddlepoint approximation for the busy period distribution FB (t) in a M/G/1 queue. The busy period B is the first passage time for the queueing system to pass from an initial arrival (1 in the system) to 0 in the system. If B (s) is the MGF of B, then B (s) is an implicitly defined function of G (s) and λ, the inter-arrival rate, through the well-known Kendall-Takács functional equation. As in the first part, we show that the saddlepoint approximation can be used to obtain F̂B (t), the CDF corresponding to B̂(s) and simulation results show that confidence bands of FB (t) based on bootstrapping perform well

Cross-Education Balance Effects After Unilateral Rehabilitation in Individuals With Chronic Ankle Instability: A Systematic Review

Objective: To conduct a systematic review of existing literature on cross-education balance effects after unilateral training in the population with chronic ankle instability (CAI). Data Sources: PubMed, SPORTDiscus, CINAHL Plus. Study Selection: To be included in the systematic review, studies were required to have been published in English, included participants with CAI, had participants undergo a unilateral therapeutic exercise for the lower extremity, and measured balance performance of the untrained lower extremity before and after the intervention. Data Extraction: The certainty of evidence in each included study was assessed via the Downs and Black checklist. A score of 24 to 28 indicated excellent or very low risk of bias; 19 to 23, good or low risk of bias; 14 to 18, fair or moderate risk of bias; and poor or high risk of bias. We extracted information from each study regarding design, participant characteristics, inclusion criteria, independent and dependent variables, intervention, and results. Baseline and postintervention balance performance data for participants\u27 untrained limbs were used to calculate the Hedges g effect sizes and 95% CIs. Data Synthesis: Our search returned 6 studies that met the inclusion criteria. The articles\u27 risk of bias ranged from high to low (11–19). In 4 of 5 studies that examined unilateral balance training, the authors reported a cross-education effect. In the lone study that examined resistance training at the ankle joint, a cross-education effect was also present. Several cross-education effects were associated with large effect sizes. This systematic review was limited by a small number of studies that varied in methods and quality. Conclusions: Our results suggest that unilateral therapeutic exercise can improve balance performance of the untrained limb of individuals with CAI. More work is needed to determine which training protocols are most effective for generating a cross-education effect

Korea's Participation in Global Value Chains: Measures and Implications

This paper measures the extent to which South Korea participated in global value chains (GVCs) from 1995 through 2011 and scrutinizes the consequences of such participation on the Korean economy. To this end, the World Input Output Database is utilized to calculate GVC income, GVC employment, and value-added exports created by Korean and foreign industries. Our findings show that Korea radically internationalized its production activities during the sample period, widening the gap between gross exports and value-added exports.We also document that Korea’s participation in GVCs has changed the value-added and employment structures in domestic industries in accordance with their comparative advantages while exacerbating the degree of wage inequality

Did China Tire Safeguard Save U.S. Workers?

It has been well documented that trade adjustment costs to workers due to globalization are significant and that temporary trade barriers have been progressively used in many countries, especially during periods with high unemployment rates. Consequently, temporary trade barriers are perceived as a feasible policy instrument for securing domestic jobs in the presence of increased globalization and economic downturns. However, no study has assessed whether such temporary barriers have actually saved domestic jobs. To overcome this deficiency, we evaluate the China-specific safeguard case on consumer tires petitioned by the United States. Contrary to claims made by the Obama administration, we find that total employment and average wages in the tire industry were unaffected by the safeguard using the ‘synthetic control’ approach proposed by Abadie et al. (2010). Further analysis reveals that this result is not surprising as we find that imports from China are completely diverted to other exporting countries partly due to the strong presence of multinational corporations in the world tire market

The Influence of Lumbopelvic Function on Perceived Ankle Function in Individuals with Chronic Ankle Instability

Perceived functional impairments measured via patient-reported outcomes (PROs) are associated with reduced postural control ability in CAI patients. Furthermore, hip and trunk neuromuscular impairments are critical factors that can cause decreased postural stability in those with CAI. Identifying the relevance between reduced lumbopelvic function and impaired sensory-perceptual outcomes might direct clinicians to novel methods for CAI patients to improve postural control ability and perceived ankle function. Therefore, the aim of this study was to examine the relationship between tests of lumbopelvic function and PROs in individuals with CAI. Thirty-three individuals with CAI underwent assessment of transversus abdominis and lumbar multifidus muscle contractility using diagnostic ultrasound; lumbopelvic stability via the unilateral hip bridge, trunk flexion endurance, Biering-Sorensen, and side plank tests; and isometric hip extension, abduction, and external rotation strength via hand-held dynamometry. We assessed PROs including the Foot and Ankle Ability Measure (FAAM-ADL and FAAM-Sport), the Tampa Scale of Kinesiophobia-11 and Fear-Avoidance Beliefs Questionnaire, and the Self-Efficacy of Balance Scale. Pearson product moment correlations and Separate backward linear regression analyses were used to identify the relationship between lumbopelvic function and PROs’ scores. Alpha was set a priori at P2=0.20, P2=0.29, Phttps://digitalcommons.odu.edu/gradposters2021_healthsciences/1006/thumbnail.jp

Profiling age-related epigenetic markers of stomach adenocarcinoma in young and old subjects

The purpose of our study is to identify epigenetic markers that are differently expressed in the stomach adenocarcinoma (STAD) condition. Based on data from The Cancer Genome Atlas (TCGA), we were able to detect an age-related difference in methylation patterns and changes in gene and miRNA expression levels in young (n = 14) and old (n = 70) STAD subjects. Our analysis identified 323 upregulated and 653 downregulated genes in old STAD subjects. We also found 76 miRNAs with age-related expression patterns and 113 differentially methylated genes (DMGs), respectively. Our further analysis revealed that significant upregulated genes (n = 35) were assigned to the cell cycle, while the muscle system process (n = 27) and cell adhesion-related genes (n = 57) were downregulated. In addition, by comparing gene and miRNA expression with methylation change, we identified that three upregulated genes (ELF3, IL1??, and MMP13) known to be involved in inflammatory responses and cell growth were significantly hypomethylated in the promoter region. We further detected target candidates for age-related, downregulated miRNAs (hsa-mir-124-3, hsa-mir-204, and hsa-mir-125b-2) in old STAD subjects. This is the first report of the results from a study exploring age-related epigenetic biomarkers of STAD using high-throughput data and provides evidence for a complex clinicopathological condition expressed by the age-related STAD progression. © the authors, publisher and licensee Libertas Academica Limitedopen

Phylogenetic analysis of ABCG subfamily proteins in plants: functional clustering and coevolution with ABCGs of pathogens

ABCG subfamily proteins are highly enriched in terrestrial plants. Many of these proteins secrete secondary metabolites that repel or inhibit pathogens. To establish why the ABCG subfamily proteins proliferated extensively during evolution, we constructed phylogenetic trees from a broad range of eukaryotic organisms. ABCG proteins were massively duplicated in land plants and in oomycetes, a group of agronomically important plant pathogens, which prompted us to hypothesize that plant and pathogen ABCGs coevolved. Supporting this hypothesis, full‐size ABCGs in host plants (Arabidopsis thaliana and Glycine max) and their pathogens (Hyaloperonospora arabidopsidis and Phytophthora sojae, respectively) had similar divergence times and patterns. Furthermore, generalist pathogens with broad ranges of host plants have diversified more ABCGs than their specialist counterparts. The hypothesis was further tested using an example pair of ABCGs that first diverged during multiplication in a host plant and its pathogen: AtABCG31 of A. thaliana and HpaP802307 of H. arabidopsidis. AtABCG31 expression was activated following infection with H. arabidopsidis, and disrupting AtABCG31 led to increased susceptibility to H. arabidopsidis. Together, our results suggest that ABCG genes in plants and their oomycete pathogens coevolved in an arms race, to extrude secondary metabolites involved in the plant's defense response against pathogens.11Ysciescopu

Regulation of BRCA1 stability through the tandem UBX domains of isoleucyl-tRNA synthetase 1

Aminoacyl-tRNA synthetases possess unique domains. In this study the structure of the vertebrate IARS1 and EARS1 complex reveals that vertebrate IARS1 protects the DNA repair factor BRCA1 from proteolytic degradation via its UBX-fold domain. Aminoacyl-tRNA synthetases (ARSs) have evolved to acquire various additional domains. These domains allow ARSs to communicate with other cellular proteins in order to promote non-translational functions. Vertebrate cytoplasmic isoleucyl-tRNA synthetases (IARS1s) have an uncharacterized unique domain, UNE-I. Here, we present the crystal structure of the chicken IARS1 UNE-I complexed with glutamyl-tRNA synthetase 1 (EARS1). UNE-I consists of tandem ubiquitin regulatory X (UBX) domains that interact with a distinct hairpin loop on EARS1 and protect its neighboring proteins in the multi-synthetase complex from degradation. Phosphomimetic mutation of the two serine residues in the hairpin loop releases IARS1 from the complex. IARS1 interacts with BRCA1 in the nucleus, regulates its stability by inhibiting ubiquitylation via the UBX domains, and controls DNA repair function