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For the problem of horizontal convection the Nusselt number based on entropy production is bounded from above by
as the horizontal convective Rayleigh number
for some constant
(Siggers et al., J. Fluid Mech., vol. 517, 2004, pp. 55–70). We re-examine the variational arguments leading to this ‘ultimate regime’ by using the Wentzel–Kramers–Brillouin method to solve the variational problem in the
limit and exhibiting solutions that achieve the ultimate
scaling. As expected, the optimizing flows have a boundary layer of thickness
pressed against the non-uniformly heated surface; but the variational solutions also have rapid oscillatory variation with wavelength
along the wall. As a result of the exact solution of the variational problem, the constant
is smaller than the previous estimate by a factor of
for no-slip and
for no-stress boundary conditions. This modest reduction in
indicates that the inequalities used by Siggers et al. (J. Fluid Mech., vol. 517, 2004, pp. 55–70) are surprisingly accurate.
The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m2) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural–geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status.
OBJECTIVES/SPECIFIC AIMS: The National Institutes of Health (NIH) has provided continual support for the Georgia Clinical and Translational Science Alliance (CTSA) since 2006. An overarching goal of the Georgia CTSA is to accelerate clinical and translational research to impact health in Georgia and beyond. Toward these ends, a primary objective has been to support interdisciplinary research projects encompassing 2 or more disciplinary domains. The goal of the present study is to evaluate the degree to which interdisciplinary research projects increased in prevalence during the first decade of funding. METHODS/STUDY POPULATION: We began by using PubMed to identify all publications citing the Georgia CTSA hub (n=1865), categorizing each article as encompassing 1 or more research domain using a taxonomy derived from the Web of Science. We created 1 network for each of the 10 years with nodes representing research areas and ties between pairs of nodes representing the presence of 1 or more publication integrating both research areas. We conducted longitudinal network analyses using an approach called MCMC MLE Temporal Exponential Random Graph Models, which models the antecedents of networks over time. RESULTS/ANTICIPATED RESULTS: Supporting Georgia CTSA objectives, results suggest the probability of publications connecting multiple research areas increased over time, with substantially greater increases appearing initially as compared to later years. DISCUSSION/SIGNIFICANCE OF IMPACT: This study advances an innovative approach to modeling the system-wide impact of CTSA hub funding.
Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990–1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.
We consider the slow motion generated when a body is set into motion relative to an incompressible, inviscid, non-diffusive rotating stratified fluid, showing that there is generated in general a topographic Rossby wave which leads to non-decaying fluctuations in the lift on the obstacle and a fluctuating non-zero drag. The problem is relevant to the flow patterns and forces excited when slow oceanic flows cross bottom topography, and suggests a mechanism for slow fluctuations observed in laboratory experiments.
Major depressive disorder (MDD) is moderately heritable, however genome-wide association studies (GWAS) for MDD, as well as for related continuous outcomes, have not shown consistent results. Attempts to elucidate the genetic basis of MDD may be hindered by heterogeneity in diagnosis. The Center for Epidemiological Studies Depression (CES-D) scale provides a widely used tool for measuring depressive symptoms clustered in four different domains which can be combined together into a total score but also can be analysed as separate symptom domains.
We performed a meta-analysis of GWAS of the CES-D symptom clusters. We recruited 12 cohorts with the 20- or 10-item CES-D scale (32 528 persons).
One single nucleotide polymorphism (SNP), rs713224, located near the brain-expressed melatonin receptor (MTNR1A) gene, was associated with the somatic complaints domain of depression symptoms, with borderline genome-wide significance (pdiscovery = 3.82 × 10−8). The SNP was analysed in an additional five cohorts comprising the replication sample (6813 persons). However, the association was not consistent among the replication sample (pdiscovery+replication = 1.10 × 10−6) with evidence of heterogeneity.
Despite the effort to harmonize the phenotypes across cohorts and participants, our study is still underpowered to detect consistent association for depression, even by means of symptom classification. On the contrary, the SNP-based heritability and co-heritability estimation results suggest that a very minor part of the variation could be captured by GWAS, explaining the reason of sparse findings.
We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results were similar among boys and girls and also in MZ and DZ twins. Overall, the differences in height and BMI between first- and second-born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.
A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.
A randomised controlled trial (RCT) of high-dose v. low-dose fish oil in recent-onset rheumatoid arthritis (RA) demonstrated that the group allocated to high-dose fish oil had increased remission and decreased failure of disease-modifying anti-rheumatic drug (DMARD) therapy. This study examines the relationships between plasma phospholipid levels of the n-3 fatty acids in fish oil, EPA and DHA, and remission and DMARD use in recent-onset RA. EPA and DHA were measured in blood samples from both groups of the RCT. The data were analysed as a single cohort, and Cox proportional hazards models were used to examine relationships between plasma phospholipid (PL) EPA and DHA and various outcome measures. When analysed as a single cohort, plasma PL EPA was related to time to remission, with a one unit increase in EPA (1 % total fatty acids) associated with a 12 % increase in the probability of remission at any time during the study period (hazard ratio (HR)=1·12; 95 % CI 1·02, 1·23; P=0·02). Adjustment for smoking, anti-cyclic citrullinated peptide antibodies and ‘shared epitope’ HLA-DR allele status did not change the HR. Plasma PL EPA, adjusted for the same variables, was negatively related to time to DMARD failure (HR=0·85; 95 % CI 0·72, 0·99; P=0·047). The HR for DHA and time to remission or DMARD failure were similar in magnitude to those for EPA, but not statistically significant. Biomarkers of n-3 status, such as plasma PL EPA, have the potential to predict clinical outcomes relevant to standard drug treatment of RA patients.
For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.
Herbicides are the foundation of weed control in commercial crop-production systems. However, herbicide-resistant (HR) weed populations are evolving rapidly as a natural response to selection pressure imposed by modern agricultural management activities. Mitigating the evolution of herbicide resistance depends on reducing selection through diversification of weed control techniques, minimizing the spread of resistance genes and genotypes via pollen or propagule dispersal, and eliminating additions of weed seed to the soil seedbank. Effective deployment of such a multifaceted approach will require shifting from the current concept of basing weed management on single-year economic thresholds.
‘Uruq Bani Ma‘arid in Saudi Arabia is an Important Plant Area (IPA) in the Arabian Peninsula. This paper describes the flora of ‘Uruq Bani Ma‘arid, provides an up-to-date botanical checklist of the area, and gives background information on the geology and fauna. It designates the locality as an IPA due to the highest known levels of plant species diversity in the Empty Quarter and the presence of endemic Arabian taxa. In addition to conservation assessments, this study discusses socio-economic issues, threats to biodiversity conservation on ‘Uruq Bani Ma‘arid, and the future research required to build upon these preliminary studies. A new combination is made for Fagonia schweinfurthii.
Jabal Aja’ in Saudi Arabia is an Important Plant Area (IPA) in the Arabian Peninsula. This paper describes the flora of the Jabal Aja’ area and provides an up-to-date botanical checklist. It designates the site as an IPA due to the presence of endemic and biogeographically relict species and the function of the site as a bioclimatic refuge. In addition to these conservation assessments, this study discusses socio-economic issues, threats to biodiversity conservation on Jabal Aja’, and the future research required to build upon these preliminary studies.
The prevalence of psychological distress and common mental disorders has been shown to peak in midlife but analyses have ignored the association of poor material circumstances with prevalence. This study aimed to test the hypothesis that the midlife prevalence peak occurs only in lower-income households.
Pooled data were used from the annual Health Survey for England, a nationally representative cross-sectional study, on community-dwelling individuals aged ⩾16 years from years 1997 to 2006 (n=100 457). 12-item General Health Questionnaire scores, reported mental illness diagnoses and receipt of relevant medication were assessed in relation to household income and age. Analyses were separated by gender and adjusted for age, ethnicity, smoking, social class, education and co-morbidities.
Prevalence of psychological distress, diagnoses and treatments rose with age until early middle age and declined subsequently. In analyses conducted separately by income categories, this pattern was marked in low-income groups but absent in high-income groups. Income-related inequalities in the prevalence of psychological distress were greatest in midlife; for example, in men aged 45–54 years the odds ratio of receiving psychiatric medication in the lowest income group compared with the highest was 7.50 [95% confidence interval (CI) 4.24–13.27] and in women aged 45–54 years the odds ratio of reporting mental illness was 10.25 (95% CI 6.16–17.05).
An increased prevalence of psychological distress, common mental disorder diagnoses and treatment in midlife is not a universal phenomenon but is found only in those in low-income households. This implies the phenomenon is not inevitable but is potentially manageable or preventable.
The Farasan Archipelago in Saudi Arabia is an Important Plant Area (IPA) in the Arabian Peninsula. This paper describes the flora of the Farasan Islands and provides an up-to-date botanical checklist together with background information on the geology and fauna of the islands. It designates the locality as an IPA due to the presence of nationally and regionally rare species and the presence of good examples of mangrove vegetation, which is both regionally and globally threatened. In addition to conservation assessments, this study also examines conservation planning concerns, particularly the colonisation of the main island Farasan Al-Kabir by the invasive species Prosopis juliflora. Suggestions for conservation action are provided. A new combination is made for Tetraena boulosii.