313 research outputs found
Pneumatic Metering of Hardwood Tree Seeds
A commercial, no-till row planter was extensively modified for use in direct seeding of hardwood tree species in surface mine reclamation. A pneumatic seed metering system was designed, fabricated, and mounted on the planter frame.
The metering device was tested under laboratory conditions which simulated varying terrain slope and field speed with seeds of various hardwood tree species. Metering efficiencies of 97% were achieved for pin oak seeds at 3.2 km/hr (2.0 m/h) and 50% slope. For red oak, 97% efficiency was achieved for 50% slope at 4.0 km/h (2.5 mph). Unsatisfactory metering was noted during tests of larger seeds, namely bur oak and black walnut.
The planter performed satisfactorily in field tests on a regraded sandstone/shale strip mine spoil material with an established vegetative cover. The metering device delivered approximately 95% of expected seed density when operated on a mild slope (≤ 10%) at a relatively slow speed 2.4 km/hr (or 1.5 miles/hr) using red oak seed. Penetration problems encountered in these tests were rectified by installing a 117 cm (46 in.) parabolic ripper tine
Effects of Mergers and Core Structure on the Bulk Properties of Nearby Galaxy Clusters
We use morphological measurements and the scatter of clusters about observed
and simulated scaling relations to examine the impact of merging and
core-related phenomena on the structure of galaxy clusters. All relations
constructed from emission-weighted mean temperature and intracluster medium
mass, X-ray luminosity, isophotal size, or near-IR luminosity show a separation
between cool core (CC) and non-cool core (NCC) clusters. We attribute this
partially to a temperature bias in CC clusters, and partially to other cool
core-related structural changes. We attempt to minimize CC/NCC separation in
scaling relations by applying a uniform scale factor to CC cluster temperatures
and determining the scale factor for each relation that minimizes the
separation between CC and NCC populations, and by introducing central surface
brightness as a third parameter in relations. The latter approach reduces
scatter in relations more than temperature scaling. We compare the scatter
within subsamples split by CC/NCC and morphological merger indicators. CC
clusters and clusters with less substructure generally exhibit higher scatter
about relations. The larger structural variations in CC clusters exit well
outside the core, suggesting that a process more global than core radiative
instability is at work. Simulations without cooling mechanisms also show no
correlation between substructure and larger scatter about relations, indicating
that any merger-related scatter increases are subtle. The results indicate that
cool core related phenomena, not merging processes, are the primary contributor
to scatter in scaling relations. Our analysis does not appear to support the
scenario in which clusters evolve cool cores over time unless they experience
major mergers. (Abridged)Comment: 18 pages, 17 figures; minor changes to text to match accepted
version. To appear in Ap
Use of genome sequencing to investigate the molecular basis of bacteriaphage interaction of the Escherichia coli O157 typing phages and the elucidation of the biological and public health significance of phage type
Background
Shiga toxin producing Escherichia coli (STEC) O157 causes severe gastrointestinal
disease and haemolytic uremic syndrome, and has a major impact on public health
worldwide with regular outbreaks and sporadic infection. Phage typing, i.e. the
susceptibility of STEC O157 strains to a bank of 16 bacteriophages, has been used in the UK to differentiate STEC O157 for the past 25 years and the phage type (PT)
can be an epidemiological marker of strains associated with severe disease or
associated with cases that occur from foreign travel. However, little is known
about the molecular interactions between the typing phages (TP) and STEC O157.
The aims of this thesis were to use whole genome sequencing to elucidate the
genetic basis for phage typing of STEC O157 and through this understand genetic
differences between strains relevant to disease severity and epidemiology.
Results
Sequencing the STEC O157 TPs revealed that they were clustered into 4 groups
based on sequence similarity that corresponded with their infectivity. Long read
sequencing revealed microevolutionary events occuring in STEC O157 genomes
over a short time period (approximately 1 year), evidenced by the loss and gain of
prophage regions and plasmids. An IncHI2 plasmid was found responsible for a
change in Phage Type (PT) from PT8 to PT54 during two related outbreaks at the
same restaurant. These changes resulted in a strain (PT54) that was fitter under
certain growth conditions and associated with a much larger outbreak (140 as
opposed to 4 cases). TraDIS (Transposon directed Insertion site sequencing) was
used to identify 114 genes associated with phage sensitivity and 44 genes involved
in phage resistance, emphasising the complex nature of identifying specific
genetic markers of phage susceptibility or resistance. Further work is required to
prove their phage-related functions but several are likely to encode novel phage
receptors. Deletion of a Stx2a prophage from a PT21/28 strain led to a strain that
typed as PT32, supporting the concept that the highly pathogenic PT21/28 lineage
I strains emerged from Stx2c+ PT32 strains in the last two decades by acquisition
of Stx2a-encoding prophages.
Conclusions
This body of work has highlighted the complexity of bacteriophage interaction and
investigated the genetic basis for susceptibility and resistance in E. coli. The
grouping of the TPs showed that resistance or susceptibility to all members of a
typing group was likely to be caused by one mechanism. IncHI2 was identified as
one of the markers for the PT54 phenotype. The Stx2a prophage region was
associated with the switch from PT32 to PT21/28, although PT32 strains
containing both Stx2a and Stx2c-encoding prophages have been isolated and can
provide insights into phage variation underpinning the susceptibility to the
relevant typing phages. The TraDIS results indicated that susceptibility or
resistance was governed by multiple genetic factors and not controlled by a single
gene. The significance of LPS for initial protection from phage adsorption was
evident and a number of novel genes controlling phage susceptibility and
resistance identified including the Sap operon and stringent starvation protein A
respectively. While SNP-based typing provides an excellent indication of the
evolution and relatedness of strains, phage typing can provide real insights into
short term evolution of the bacteria as PTs can be altered by mobile elements
such as prophages and plasmids. This study has shown that, although complex,
genetic determinants for PT can be mined from the genome and allow us to
understand the evolution of this zoonotic pathogen between host species and
during outbreaks
Adaptive divergence despite strong genetic drift: genomic analysis of the evolutionary mechanisms causing genetic differentiation in the island fox (\u3ci\u3eUrocyon littoralis\u3c/i\u3e)
The evolutionary mechanisms generating the tremendous biodiversity of islands have long fascinated evolutionary biologists. Genetic drift and divergent selection are pre- dicted to be strong on islands and both could drive population divergence and specia- tion. Alternatively, strong genetic drift may preclude adaptation. We conducted a genomic analysis to test the roles of genetic drift and divergent selection in causing genetic differentiation among populations of the island fox (Urocyon littoralis). This species consists of six subspecies, each of which occupies a different California Chan- nel Island. Analysis of 5293 SNP loci generated using Restriction-site Associated DNA (RAD) sequencing found support for genetic drift as the dominant evolutionary mech- anism driving population divergence among island fox populations. In particular, pop- ulations had exceptionally low genetic variation, small Ne (range = 2.1–89.7; median = 19.4), and significant genetic signatures of bottlenecks. Moreover, islands with the lowest genetic variation (and, by inference, the strongest historical genetic drift) were most genetically differentiated from mainland grey foxes, and vice versa, indicating genetic drift drives genome-wide divergence. Nonetheless, outlier tests identified 3.6–6.6% of loci as high FST outliers, suggesting that despite strong genetic drift, divergent selection contributes to population divergence. Patterns of similarity among populations based on high FST outliers mirrored patterns based on morphology, providing additional evidence that outliers reflect adaptive divergence. Extremely low genetic variation and small Ne in some island fox populations, particularly on San Nicolas Island, suggest that they may be vulnerable to fixation of deleterious alleles, decreased fitness and reduced adaptive potential
Optoelectronic and Excitonic Properties of Oligoacenes: Substantial Improvements from Range-Separated Time-Dependent Density Functional Theory
The optoelectronic and excitonic properties in a series of linear acenes
(naphthalene up to heptacene) are investigated using range-separated methods
within time-dependent density functional theory (TDDFT). In these rather simple
systems, it is well-known that TDDFT methods using conventional hybrid
functionals surprisingly fail in describing the low-lying La and Lb valence
states, resulting in large, growing errors for the La state and an incorrect
energetic ordering as a function of molecular size. In this work, we
demonstrate that the range-separated formalism largely eliminates both of these
errors and also provides a consistent description of excitonic properties in
these systems. We further demonstrate that re-optimizing the percentage of
Hartree-Fock exchange in conventional hybrids to match wavefunction-based
benchmark calculations still yields serious errors, and a full 100%
Hartree-Fock range separation is essential for simultaneously describing both
of the La and Lb transitions. Based on an analysis of electron-hole transition
density matrices, we finally show that conventional hybrid functionals
overdelocalize excitons and underestimate quasiparticle energy gaps in the
acene systems. The results of our present study emphasize the importance of
both a range-separated and asymptotically-correct contribution of exchange in
TDDFT for investigating optoelectronic and excitonic properties, even for these
simple valence excitations.Comment: Accepted by the Journal of Chemical Theory and Computatio
A study of association between common variation in the growth hormone-chorionic somatomammotropin hormone gene cluster and adult fasting insulin in a UK Caucasian population
BACKGROUND: Reduced growth during infancy is associated with adult insulin resistance. In a UK Caucasian cohort, the CSH1.01 microsatellite polymorphism in the growth hormone-chorionic somatomammotropin hormone gene cluster was recently associated with increases in adult fasting insulin of approximately 23 pmol/l for TT homozygote males compared to D1D1 or D2D2 homozygotes (P = 0.001 and 0.009; n = 206 and 92, respectively), but not for females. TT males additionally had a 547-g lower weight at 1 year (n = 270; P = 0.008) than D2D2 males. We sought to replicate these data in healthy UK Caucasian subjects. We genotyped 1396 subjects (fathers, mothers and children) from a consecutive birth study for the CSH1.01 marker and analysed genotypes for association with 1-year weight in boys and fasting insulin in fathers. RESULTS: We found no evidence for association of CSH1.01 genotype with adult male fasting insulin concentrations (TT/D1D1 P = 0.38; TT/D2D2 P = 0.18) or weight at 1 year in boys (TT/D1D1 P = 0.76; TT/D2D2 P = 0.85). For fasting insulin, our data can exclude the previously observed effect sizes as the 95 % confidence intervals for the differences observed in our study exclude increases in fasting insulin of 9.0 and 12.6 pmol/l for TT relative to D1D1 and D2D2 homozygotes, respectively. Whilst we have fewer data on boys' 1-year weight than the original study, our data can exclude a reduction in 1-year weight greater than 557 g for TT relative to D2D2 homozygotes. CONCLUSION: We have not found association of the CSH1.01 genotype with fasting insulin or weight at 1 year. We conclude that the original study is likely to have over-estimated the effect size for fasting insulin, or that the difference in results reflects the younger age of subjects in this study relative to those in the previous study
Altered Gene Synchrony Suggests a Combined Hormone-Mediated Dysregulated State in Major Depression
Coordinated gene transcript levels across tissues (denoted “gene synchrony”) reflect converging influences of genetic, biochemical and environmental factors; hence they are informative of the biological state of an individual. So could brain gene synchrony also integrate the multiple factors engaged in neuropsychiatric disorders and reveal underlying pathologies? Using bootstrapped Pearson correlation for transcript levels for the same genes across distinct brain areas, we report robust gene transcript synchrony between the amygdala and cingulate cortex in the human postmortem brain of normal control subjects (n = 14; Control/Permutated data, p<0.000001). Coordinated expression was confirmed across distinct prefrontal cortex areas in a separate cohort (n = 19 subjects) and affected different gene sets, potentially reflecting regional network- and function-dependent transcriptional programs. Genewise regional transcript coordination was independent of age-related changes and array technical parameters. Robust shifts in amygdala-cingulate gene synchrony were observed in subjects with major depressive disorder (MDD, denoted here “depression”) (n = 14; MDD/Permutated data, p<0.000001), significantly affecting between 100 and 250 individual genes (10–30% false discovery rate). Biological networks and signal transduction pathways corresponding to the identified gene set suggested putative dysregulated functions for several hormone-type factors previously implicated in depression (insulin, interleukin-1, thyroid hormone, estradiol and glucocorticoids; p<0.01 for association with depression-related networks). In summary, we showed that coordinated gene expression across brain areas may represent a novel molecular probe for brain structure/function that is sensitive to disease condition, suggesting the presence of a distinct and integrated hormone-mediated corticolimbic homeostatic, although maladaptive and pathological, state in major depression
Integrative genomic analysis implicates limited peripheral adipose storage capacity in the pathogenesis of human insulin resistance.
Insulin resistance is a key mediator of obesity-related cardiometabolic disease, yet the mechanisms underlying this link remain obscure. Using an integrative genomic approach, we identify 53 genomic regions associated with insulin resistance phenotypes (higher fasting insulin levels adjusted for BMI, lower HDL cholesterol levels and higher triglyceride levels) and provide evidence that their link with higher cardiometabolic risk is underpinned by an association with lower adipose mass in peripheral compartments. Using these 53 loci, we show a polygenic contribution to familial partial lipodystrophy type 1, a severe form of insulin resistance, and highlight shared molecular mechanisms in common/mild and rare/severe insulin resistance. Population-level genetic analyses combined with experiments in cellular models implicate CCDC92, DNAH10 and L3MBTL3 as previously unrecognized molecules influencing adipocyte differentiation. Our findings support the notion that limited storage capacity of peripheral adipose tissue is an important etiological component in insulin-resistant cardiometabolic disease and highlight genes and mechanisms underpinning this link.This study was funded by the UK Medical Research Council through grants MC_UU_12015/1, MC_PC_13046, MC_PC_13048 and MR/L00002/1. This work was supported by the MRC Metabolic Diseases Unit (MC_UU_12012/5) and the Cambridge NIHR Biomedical Research Centre and EU/EFPIA Innovative Medicines Initiative Joint Undertaking (EMIF grant 115372). Funding for the InterAct project was provided by the EU FP6 program (grant LSHM_CT_2006_037197). This work was funded, in part, through an EFSD Rising Star award to R.A.S. supported by Novo Nordisk. D.B.S. is supported by Wellcome Trust grant 107064. M.I.M. is a Wellcome Trust Senior Investigator and is supported by the following grants from the Wellcome Trust: 090532 and 098381. M.v.d.B. is supported by a Novo Nordisk postdoctoral fellowship run in partnership with the University of Oxford. I.B. is supported by Wellcome Trust grant WT098051. S.O'R. acknowledges funding from the Wellcome Trust (Wellcome Trust Senior Investigator Award 095515/Z/11/Z and Wellcome Trust Strategic Award 100574/Z/12/Z)
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