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Schlichting H.E.,University of California at Los Angeles | Schlichting H.E.,California Institute of Technology | Warren P.H.,University of California at Los Angeles | Yin Q.-Z.,UCD
Astrophysical Journal

The final stage of terrestrial planet formation consists of the clean-up of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the high eccentricities and inclinations of the terrestrial planets to circular and coplanar orbits after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred for the terrestrial planets and the Moon suggest that a total of about 0.01 M⊕ of chondritic material was delivered as "late veneer" by planetesimals to the terrestrial planets after the end of giant impacts. Here, we combine these two independent lines of evidence for a leftover population of planetesimals and show that: (1) a residual population of small planetesimals containing 0.01 M⊕ is able to damp the high eccentricities and inclinations of the terrestrial planets after giant impacts to their observed values. (2) At the same time, this planetesimal population can account for the observed relative amounts of late veneer added to the Earth, Moon, and Mars provided that the majority of the accreted late veneer was delivered by small planetesimals with radii ≲ 10 m. These small planetesimal sizes are required to ensure efficient damping of the planetesimal's velocity dispersion by mutual collisions, which in turn ensures sufficiently low relative velocities between the terrestrial planets and the planetesimals such that the planets' accretion cross sections are significantly enhanced by gravitational focusing above their geometric values. Specifically, we find that, in the limit that the relative velocity between the terrestrial planets and the planetesimals is significantly less than the terrestrial planets' escape velocities, gravitational focusing yields a mass accretion ratio of Earth/Mars (ρ⊕/ρmars) (R⊕/Rmars)4 17, which agrees well with the mass accretion ratio inferred from HSEs of 12-23. For the Earth-Moon system, we find a mass accretion ratio of 200, which, as we show, is consistent with estimates of 150-700 derived from HSE abundances that include the lunar crust as well as the mantle component. We conclude that small residual planetesimals containing about 1% of the mass of the Earth could provide the dynamical friction needed to relax the terrestrial planet's eccentricities and inclinations after giant impacts, and also may have been the dominant source for the late veneer added to Earth, Moon, and Mars. © 2012. The American Astronomical Society. All rights reserved.. Source

Dulgheru P.,Free University of Colombia | Sullivan J.A.,UCD
Topics in Catalysis

A series of rare earth (RE) (La, Nd, Pr) ceria zirconia materials were analysed for their soot combustion activity in air and in NO/O2. The materials were characterised using DRIFT spectroscopy. In general the presence of the RE dopant increases the activity of undoped Ce x Zr 1-x O2. The La and Pr doped catalysts showed increased low temperature activity in the presence of NO/O2 while the effect was less pronounced in case of Nd - doped samples. FTIR data has shown that the catalysts interact differently to NO/O2 mixtures in that they do not form significant quantities of adsorbed nitrite-type species. We postulate that this species is a precursor to NO2 formation which in turn increases soot combustion. © 2013 Springer Science+Business Media New York. Source

The improved survival for bulky cervical cancers (> 4cm) reported with combination platinum based chemoradiation (1999) prompted a move away from surgery as these cases frequently received adjuvant radiotherapy and were exposed to the morbidity of multimodality treatment. The period pre-1999 (Group 1) was compared with post-1999 (Group 2) when chemoradiation was the preferred treatment for bulky operable cervical cancer. Significantly more cases were treated surgically among Group 1 compared with Group 2 (79% vs. 62%; P < 0.001). Switching from surgery to radiotherapy improved survival in both treatment categories (73% vs. 78% and 37% vs. 44%, respectively) but with no improvement in overall survival (70%/ov.s 70%). Survival (86%) was similar in both groups among surgically treated women with tumors < 4 cm, but significantly more in Group 2 with negative nodes received postoperative adjuvant chemoradiotherapy (Groups 1 vs. 2; 16% vs.37.5%: P < 0.001) and overall the surgically treated patients received more not less multimodality treatment (46.5% vs. 59%; P = 0.7). Source

Crawled News Article
Site: http://phys.org/biology-news/

Accountants everywhere would cry as their books ceased to balance. You might find yourself pausing at the supermarket wondering if you could save money by buying your milk before your toothpaste. Eurovision fans may value a 'douze points' early in the voting more than one later on. Fortunately, there is no new evidence to suggest that order matters in addition. However, researchers at UCD have recently found that order matters a surprising amount for sequence alignment, an important part of modern genetic analyses. Sequence alignment is used to understand similarities and differences between proteins found in different species. Proteins are the building blocks of life and carry out most of the functions in our cells. Consequently understanding proteins and their function is a key part of biology. We can use pairwise sequence alignment to identify which parts of a specific protein are identical between a pair of species (e.g. humans and chimps). Using multiple sequence alignment, we can identify those parts of a protein that are conserved in all mammals or in even larger groups of species. Very large sequence alignments help us understand which parts of proteins are important; if part of a protein is identical in all mammals then it's probably important and also gives us some insight into the three dimensional structure of proteins (as parts of a protein that are close together in 3D space tend to change together across species). PhD student Kieran Boyce, Dr Fabian Sieviers and Professor Des Higgins in UCD Conway Institute & Systems Biology Ireland found that for large protein sequence alignments the order in which sequences are compared matters, i.e. the alignment that you get out of a sequence alignment programme depends on the order that you input your sequences into the programme. This finding is surprising, as people have been performing sequence alignments for decades without knowing how dependent the results are on the input order. It is important because it suggests that most scientific publications that make use of large multiple sequence alignments probably have not provided sufficient information to reproduce their results. Reproducibility is an important part of science. Consequently, when performing sequence alignment, most scientists will provide details of the sequence alignment programme and the settings they used. The findings from Boyce et al suggest that the order is also an important setting that may need to be provided from now on. A question left open by the paper is how we can make sequence alignment programmes ignore order, or how we can choose the best possible ordering. Explore further: Relationships in rank and file: Better sequence searches of genes and proteins More information: Kieran Boyce et al. Instability in progressive multiple sequence alignment algorithms, Algorithms for Molecular Biology (2015). DOI: 10.1186/s13015-015-0057-1

Crawled News Article
Site: http://phys.org/biology-news/

Lions, African elephants and red deer have developed physical features that enable them to vary the pitch and frequency of their vocal signals to make their body size appear larger to attract potential sexual partners and deter rivals, according to the study published in the journal Nature Communications. Some animals have developed physical adaptations that enable them to make low-frequency (resonance) vocal sounds that usually only mammals of larger body sizes can make – thereby making themselves appear bigger to potential mates. These physical traits are often only present or are disproportionately large in males involved in trying to attract mates or deter rivals. There is particular pressure on some species of animals to have larger body sizes than their potential rivals for mating. The researchers from University College Dublin and the University of Sussex now believe that this pressure was a key factor leading to the evolution of physical adaptations in some male mammals, enabling them to exaggerate their size through their vocal signals. The researchers made the findings after they analysed the relationship between male vocal signals and the body sizes of 72 species of land-based mammals, including lions, chimpanzees and humans. Dr Benjamin Charlton, Assistant Professor, UCD School of Biology and Environmental Science and Dr David Reby, School of Psychology, University of Sussex authored the paper. "Male mammals from mating systems with strong selection pressures for large male body size produce lower call frequencies than expected for their body size i.e. they acoustically exaggerate the impression of their body size," said Benjamin Charlton, who led the research. "The study sheds light on the evolution of acoustic diversity across mammals." The two main parts of mammals' vocal signals are fundamental frequency and formant frequency. Males of species where there is pressure to have large bodies for mating and deterring rivals produce vocal signals with lower formant frequency than expected for their body size, but not fundamental frequency. Some animals, such as lions, koalas and Mongolian gazelles can produce abnormally low formant frequency for their size by extending their vocal tracts using descended and/or mobile larynges – voice box. Other mammals, such as howler monkeys and colobus monkeys possess additional resonators, while African elephants and southern elephant seals have nasal proboscises – snouts. Explore further: Why female deer like a stag to be a big noise in the forest More information: Benjamin D. Charlton et al. The evolution of acoustic size exaggeration in terrestrial mammals, Nature Communications (2016). DOI: 10.1038/ncomms12739

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