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Technologically advanced aircraft rely on robust and responsive logistics systems to ensure a high state of operational readiness. This paper fills a critical gap in the literature for combat models by closely relating effectiveness of the logistics system to determinants of success in combat. We present a stochastic diffusion model of an aerial battle between Blue and Red forces. The number of aircraft of Blue forces aloft and ready to be aloft on combat missions is limited by the maximum number of assigned aircraft, the reliability of aircraft subsystems, and the logistic system's ability to repair and replenish those subsystems. Our parsimonious model can illustrate important trade‐offs between logistics decision variables and operational success. [ABSTRACT FROM AUTHOR]

Studies during the past 50 years demonstrate the importance of chromosome abnormalities to the occurrence of early pregnancy loss in humans. Intriguingly, there appears to be considerable variation in the rates of chromosome abnormality, with more recent studies typically reporting higher levels than those reported in early studies of spontaneous abortions. We were interested in examining the basis for these differences and accordingly, we reviewed studies of spontaneous abortions conducted in our laboratories over a 40-year-time span. Our analyses confirm a higher rate of abnormality in more recent series of spontaneous abortions, but indicate that the effect is largely, if not entirely, attributable to changes over time in the maternal age structures of the study populations. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This article describes the Distributed Interaction Campaign Model (DICM), an exploratory campaign analysis tool and asset allocation decision-aid for managing geographically distributed and swarming naval and air forces. The model is capable of fast operation, while accounting for uncertainty in an opponent's plan. It is intended for use by commanders and analysts who have limited time for model runs, or a finite budget. The model is purpose-built for the Pentagon's Office of Net Assessment, and supports analysis of the following questions: What happens when swarms of geographically distributed naval and air forces engage each other and what are the key elements of the opponents' force to attack? Are there changes to force structure that make a force more effective, and what impacts will disruptions in enemy command and control and wide-area surveillance have? Which insights are to be gained by fast exploratory mathematical/computational campaign analysis to augment and replace expensive and time-consuming simulations? An illustrative example of model use is described in a simple test scenario. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 562-576, 2016 [ABSTRACT FROM AUTHOR]

This study describes the characteristics of karyotypes leading to phenotypic Down syndrome (trisomy 21) in 29,256 cases diagnosed between 1989 and 2009 in England and Wales included in the National Down Syndrome Cytogenetic Register (NDSCR). The frequency of occurrence of the different karyotypes, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Nearly 97% of all cases were free trisomy 21; 2.9% contributory trisomy 21, 0.3% double or triple aneuploidies; 1% of all were mosaics. Mean maternal age of free trisomy 21 cases was 35 years, 54% were male, and 1% of mothers had recurrences. Free trisomy 21 mosaics had a lower mean maternal age (33 years), a lower proportion of males (39.5%), and 2.5% of mothers had recurrences. The majority of contributory translocations were Robertsonian or rea (21;21). Their mothers were younger, particularly those of Robertsonian translocations (28 years). Of the Robertsonian der (14;21) translocations of known parental origin, 54% were de novo, 41% maternal and 5% paternal and 15.8% of mothers of those of maternal origin had recurrences. Multiple aneuploidies have the highest proportion of males (67%), highest proportion of mosaics (40%), a mean maternal age of 37 years, and no mothers had a recurrence. The size of this national register allowed the frequency of occurrence of the rarer karyotypes of Down syndrome to be estimated and their epidemiology described. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Aim To review systematically the neurodevelopmental characteristics of individuals with sex chromosome trisomies (SCTs). Method A bibliographic search identified English-language articles on SCTs. The focus was on studies unbiased by clinical referral, with power of at least 0.69 to detect an effect size of 1.0. Results We identified 35 articles on five neonatally identified samples that had adequate power for our review. An additional 11 studies were included where cases had been identified for reasons other than neurodevelopmental concerns. Individuals with an additional X chromosome had mean IQs that were within broadly normal limits but lower than the respective comparison groups, with verbal IQ most affected. Cognitive outcomes were poorest for females with XXX. Males with XYY had normal-range IQs, but all three SCT groups (XXX, XXY, and XYY) had marked difficulties in speech and language, motor skills, and educational achievement. Nevertheless, most adults with SCTs lived independently. Less evidence was available for brain structure and for attention, social, and psychiatric outcomes. Within each group there was much variation. Interpretation Individuals with SCTs are at risk of cognitive and behavioural difficulties. However, the evidence base is slender, and further research is needed to ascertain the nature, severity, and causes of these difficulties in unselected samples. [ABSTRACT FROM AUTHOR]

An age-replacement policy may be used to minimize the cost of replacement and repair of a system whose rate of repairable failures increases with age. In this paper we model the failure times before replacement of one such system-a pump used on a submarine-by a non-homogeneous Poisson process having log-linear hazard rate which is a function of age. Maximum likelihood is used to estimate model parameters. A renewal-reward process is used to obtain estimates of log-run average costs of age-replacement policies. It should be noted that the policy obtained does not recognize possible between-submarine differences but does acknowledge that noise from a submarine pump is not to be tolerated. [ABSTRACT FROM AUTHOR]