3,907 research outputs found
Mapping biodiversity value worldwide: combining higher-taxon richness from different groups
Maps of large-scale biodiversity are urgently needed to guide conservation, and yet complete enumeration of organisms is impractical at present. One indirect approach is to measure richness at higher taxonomic ranks, such as families. The difficulty is how to combine information from different groups on numbers of higher taxa, when these taxa may in effect have been defined in different ways, particularly for more distantly related major groups. In this paper, the regional family richness of terrestrial and freshwater seed plants, amphibians, reptiles and mammals is mapped worldwide by combining: (i) absolute family richness; (ii) proportional family richness; and (iii) proportional family richness weighted for the total species richness in each major group. The assumptions of the three methods and their effects on the results are discussed, although for these data the broad pattern is surprisingly robust with respect to the method of combination. Scores from each of the methods of combining families are used to rank the top five richness hotspots and complementary areas, and hotspots of endemism are mapped by unweighted combination of range-size rarity scores
Rota's basis conjecture for paving matroids
Rota conjectured that, given n disjoint bases of a
rank-n matroid M, there are n disjoint transversals of these bases
that are all bases of M. We prove a stronger statement for the
class of paving matroids
Quartet compatibility and the quartet graph
A collection P of leaf-labelled trees is compatible if there exists a single leaf-labelled tree that displays each of the trees in P. Despite its
difficulty, determining the compatibility of P is a fundamental task in evolutionary
biology. Attractive characterizations in terms of chordal graphs have
been previously given for this problem as well as for the problems of (i) determining
if there is a unique tree that displays each of the trees in P, that is
'P is definitive and (ii) determining if there is a tree that displays P and has
the property that every other tree that displays P is a refinement of it, that is
'P identifies a leaf-labelled tree. In this paper, we describe new characterizations
of each of these problems in terms of edge colourings. Furthermore, for
an arbitrary leaf-labelled tree 'T, we also determine the minimum number of
'quartets' required to identify 'T, thus correcting a previously published result
Use of Desulfovibrio and Escherichia coli Pd-nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil
BACKGROUND Desulfovibrio spp. biofabricate metallic nanoparticles (e.g. ‘Bio-Pd’) which catalyse the reduction of Cr(VI) to Cr(III) and dehalogenate polychlorinated biphenyls (PCBs). Desulfovibrio spp. are anaerobic and produce H2S, a potent catalyst poison, whereas Escherichia coli can be pre-grown aerobically to high density, has well defined molecular tools, and also makes catalytically-active ‘Bio-Pd’. The first aim was to compare ‘Bio-Pd’ catalysts made by Desulfovibrio spp. and E. coli using suspended and immobilised catalysts. The second aim was to evaluate the potential for Bio-Pd-mediated dehalogenation of PCBs in used transformer oils, which preclude recovery and re-use.\ud
RESULTS Catalysis via Bio-PdD. desulfuricans and Bio-PdE. coli was compared at a mass loading of Pd:biomass of 1:3 via reduction of Cr(VI) in aqueous solution (immobilised catalyst) and hydrogenolytic release of Cl- from PCBs and used transformer oil (catalyst suspensions). In both cases Bio-PdD. desulfuricans outperformed Bio-Pd E. coli by ~3.5-fold, attributable to a ~3.5-fold difference in their Pd-nanoparticle surface areas determined by magnetic measurements (Bio-PdD. desulfuricans) and by chemisorption analysis (Bio-PdE. coli). Small Pd particles were confirmed on D. desulfuricans and fewer, larger ones on E. coli via electron microscopy. Bio-PdD. desulfuricans-mediated chloride release from used transformer oil (5.6 0.8 g mL-1 ) was comparable to that observed using several PCB reference materials. \ud
CONCLUSIONS At a loading of 1:3 Pd: biomass Bio-PdD. desulfuricans is 3.5-fold more active than Bio-PdE. coli, attributable to the relative catalyst surface areas reflected in the smaller nanoparticle sizes of the former. This study also shows the potential of Bio-PdD. desulfuricans to remediate used transformer oil
Is there an integrative center in the vertebrate brain-stem? A robotic evaluation of a model of the reticular formation viewed as an action selection device
Neurobehavioral data from intact, decerebrate, and neonatal rats, suggests that the reticular formation provides
a brainstem substrate for action selection in the vertebrate central nervous system. In this article, Kilmer,
McCulloch and Blum’s (1969, 1997) landmark reticular formation model is described and re-evaluated, both in
simulation and, for the first time, as a mobile robot controller. Particular model configurations are found to
provide effective action selection mechanisms in a robot survival task using either simulated or physical robots.
The model’s competence is dependent on the organization of afferents from model sensory systems, and a genetic
algorithm search identified a class of afferent configurations which have long survival times. The results support
our proposal that the reticular formation evolved to provide effective arbitration between innate behaviors
and, with the forebrain basal ganglia, may constitute the integrative, ’centrencephalic’ core of vertebrate brain
architecture. Additionally, the results demonstrate that the Kilmer et al. model provides an alternative form of
robot controller to those usually considered in the adaptive behavior literature
Efficient synthesis of an aluminum amidoborane ammoniate
A novel species of metal amidoborane ammoniate, [Al(NH2BH3)6 3-][Al(NH3)6 3+] has been successfully synthesized in up to 95% via the one-step reaction of AlH3·OEt2 with liquid NH3BH3·nNH3 (n = 1~6) at 0 °C. This solution based reaction method provides an alternative pathway to the traditional mechano-chemical ball milling methods, avoiding possible decomposition. MAS 27Al NMR spectroscopy confirms the formulation of the compound as an Al(NH2BH3)6 3- complex anion and an Al(NH3)6 3+ cation. Initial dehydrogenation studies of this aluminum based M-N-B-H compound demonstrate that hydrogen is released at temperatures as low as 65 °C, totaling ~8.6 equivalents of H2 (10.3 wt %) upon heating to 105 °C. This method of synthesis offers a promising route towards the large scale production of metal amidoborane ammoniate moieties
IDENTIFICATION OF GENES ASSOCIATED WITH QT INTERVAL USING THE 50K CARDIO-METABOLIC SNP CHIP: RESULTS FROM THE WHITEHALL II STUDY
Cascaded acceleration of proton beams in ultrashort laser-irradiated microtubes
A cascaded ion acceleration scheme is proposed by use of ultrashort
laser-irradiated microtubes. When the electrons of a microtube are blown away
by intense laser pulses, strong charge-separation electric fields are formed in
the microtube both along the axial and along the radial directions. By
controlling the time delay between the laser pulses and a pre-accelerated
proton beam injected along the microtube axis, we demonstrate that this proton
beam can be further accelerated by the transient axial electric field in the
laser-irradiated microtube. Moreover, the collimation of the injected proton
beam can be enhanced by the inward radial electric field. Numerical simulations
show that this cascaded ion acceleration scheme works efficiently even at
non-relativistic laser intensities, and it can be applied to injected proton
beams in the energy range from 1 to 100 MeV. Therefore, it is particularly
suitable for cascading acceleration of protons to higher energy.Comment: 13 pages, 4 figure
The UK Paediatric Familial Hypercholesterolaemia Register: Statin-related safety and 1-year growth data
BACKGROUND: For children with familial hypercholesterolemia (FH), UK guidelines recommend consideration of statin therapy by age 10 years and dietary and lifestyle advice to maintain an ideal body weight. OBJECTIVES: The objective of the study is to use the UK Paediatric Familial Hypercholesterolemia Register to determine: (1) the prevalence of plasma markers of liver toxicity and muscle damage in statin-treated FH children; (2) the prevalence of obesity in FH children compared to the UK general population; and (3) to compare growth rates in statin-treated and nontreated children. METHODS: Differences in registration and 1-year characteristics were compared by Mann-Whitney U tests. Age and gender body mass index percentiles were compared to UK children's growth charts. RESULTS: In 300 children (51% boys, 75% Caucasian, untreated mean [standard deviation] low-density lipoprotein cholesterol 5.50 [1.49] mmol/L), the proportion on statins varied significantly (P 15 years = 73.2%). Statin treatment reduced low-density lipoprotein cholesterol by 31% (1.84 [1.43] mmol/L), and no child showed elevated levels of markers of liver toxicity or muscle damage. At registration, 16.9% of the FH children were overweight (>85th percentile) and 11.1% were obese (>95th percentile) vs reported in 21.2% in UK non-FH children. There was no difference in annual growth rate in statin vs no-statin groups (age-adjusted weight increases 3.58 vs 3.53 kg; P = .91, height 4.45 vs 4.60 cm P = .73). CONCLUSIONS: We show no evidence for statin-related safety or growth issues, but many FH children over the age of 10 years are not on statin treatment. Fewer UK children with FH are obese compared to UK non-FH children
IL18 Haplotypes Are Associated with Serum IL-18 Concentrations in a Population-Based Study and a Cohort of Individuals with Premature Coronary Heart Disease
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