988 research outputs found
A partial skull of Paranthropus robustus from Cooper's Cave, South Africa.
A partial hominin skull (COB 101) was identified in the fossil collections of the Transvaal Museum, Pretoria, attributed to the Cooper's Cave site in South Africa. The find represents the most complete hominin specimen recovered from localities at this site to date. COB 101 comprises the supraorbital, zygomatic, infraorbital and nasoalveolar regions of the right side, and the right upper third premolar. The specimen has undergone post-depositional distortion that resulted in the flattening of the facial structures. Here we describe and compare COB 101 with other hominin material from Africa and find that this specimen shares numerous diagnostic features with Paranthropus robustus. The discovery of COB 101 augments the number of specimens attributed to this species from other South African sites and other Cooper's Cave localities.NCS2016
On the absence of fifth-order contributions to the nucleon mass in heavy-baryon chiral perturbation theory
(New version with some expanded discussion; figures and minor typos
corrected.)
We have calculated the contribution proportional to the fifth power of the
pion mass in the chiral expansion of the nucleon mass in two flavour HBCPT.
Only one irreducible two-loop integral enters, and this vanishes. All other
corrections in the heavy-baryon limit can be absorbed in the physical
pion-nucleon coupling constant which enters in the third order term, and so
there are no contributions at fifth order. Including finite nucleon mass
corrections, the only contribution agrees with the expansion of the
relativistic one-loop graph in powers of the ration of the pion and nucleon
masses, and is only 0.3% of the third order term. This is an encouraging result
for the convergence of two-flavour heavy-baryon chiral perturbation theory.Comment: 4 pages RevTex, 4 eps figure
Temperature dependence of Andreev spectra in a superconducting carbon nanotube quantum dot
Tunneling spectroscopy of a Nb coupled carbon nanotube quantum dot reveals
the formation of pairs of Andreev bound states (ABS) within the superconducting
gap. A weak replica of the lower ABS is found, which is generated by
quasi-particle tunnelling from the ABS to the Al tunnel probe. An inversion of
the ABS-dispersion is observed at elevated temperatures, which signals the
thermal occupation of the upper ABS. Our experimental findings are well
supported by model calculations based on the superconducting Anderson model.Comment: 6 pages, 7 figure
MAPPING THE SURROUNDINGS AS A REQUIREMENT FOR AUTONOMOUS DRIVING
Motivated by the hype around driverless cars and the challenges of the sensor integration and data processing, this paper presents a model for using a XBox One Microsoft Kinect stereo camera as sensor for mapping the surroundings. Today, the recognition of the environment of the car is mostly done by a mix of sensors like LiDAR, RADAR and cameras. In the case of the outdoor delivery challenge Robotour 2016 with model cars in scale 1:5, it is our goal to solve the task with one camera only. To this end, a three-stage approach was developed. The test results show that our approach can detect and locate objects at a range of up to eight meters in order to incorporate them as barriers in the navigation process
3D techniques and fossil identification: An elephant shrew hemi-mandible from the Malapa site.
Conventional methods for extracting fossilised bones from calcified clastic sediments, using air drills or chemical preparations, can damage specimens to the point of rendering them unidentifiable. As an alternative, we tested an in silico approach that extended preparation and identification possibilities beyond those realisable using physical methods, ultimately proving to be crucial in identifying a fragile fossil. Image data from a matrix-encased hemi-mandible of a micromammal that was collected from the Plio-Pleistocene site of Malapa, Cradle of Humankind, South Africa, were acquired using microtomography. From the resultant images, a 3D rendering of the fossil was digitally segmented. Diagnostic morphologies were evaluated on the rendering for comparison with extant comparative specimens, positively identifying the specimen as an elephant shrew (Elephantulus sp.). This specimen is the first positively identified micromammal in the Malapa faunal assemblage. Cutting-edge in silico preparation technology provides a novel tool for identifying fossils without endangering bone integrity, as is commonly risked with physical preparation.NCS2016
Coupling methylammonium and formamidinium cations with halide anions: Hybrid orbitals, hydrogen bonding, and the role of dynamics
The electronic structures of four precursors for organic–inorganic hybrid perovskites, namely, methylammonium chloride and iodide, as well as formamidinium bromide and iodide, are investigated by X-ray emission (XE) spectroscopy at the carbon and nitrogen K-edges. The XE spectra are analyzed based on density functional theory calculations. We simulate the XE spectra at the Kohn–Sham level for ground-state geometries and carry out detailed analyses of the molecular orbitals and the electronic density of states to give a thorough understanding of the spectra. Major parts of the spectra can be described by the model of the corresponding isolated organic cation, whereas high-emission energy peaks in the nitrogen K-edge XE spectra arise from electronic transitions involving hybrids of the molecular and atomic orbitals of the cations and halides, respectively. We find that the interaction of the methylammonium cation is stronger with the chlorine than with the iodine anion. Furthermore, our detailed theoretical analysis highlights the strong influence of ultrafast proton dynamics in the core-excited states, which is an intrinsic effect of the XE process. The inclusion of this effect is necessary for an accurate description of the experimental nitrogen K-edge X-ray emission spectra and gives information on the hydrogen-bonding strengths in the different precursor materials
Strangeness in the Scalar Form Factor of the Nucleon
The scalar form factor of the nucleon and related physical quantities are
investigated in the framework of the semibosonized SU(3) Nambu-Jona-Lasinio
soliton model. We take into account the rotational corrections and
linear corrections. The strangeness content of the nucleon in the scalar
form factor is discussed in detail. In particular, it is found that the
corrections play an essential role of reducing the arising from the leading order and rotational contributions.
We obtain the \sigma_{\pi N} (0)=40.80\;\mbox{MeV}, \Delta \sigma =
\sigma_{\pi N} (2m^{2}_{\pi})-\sigma_{\pi N} (0) = 18.18\;\mbox{MeV} and
\langle r^2\rangle^{S}_{N} = 1.50\;\mbox{fm}^2.
The results are in a remarkable agreement with empirical data analyzed by
Gasser, Leutwyler, and Sainio~\cite{gls}.Comment: 13 pages, RevTex is used. 3 figures as uufiles are include
Proposal of a population wide genome-based testing for Covid-19
Our lives (and deaths) have by now been dominated for two years by COVID-19, a pandemic that has caused hundreds of millions of disease cases, millions of deaths, trillions in economic costs, and major restrictions on our freedom. Here we suggest a novel tool for controlling the COVID-19 pandemic. The key element is a method for a population-scale PCR-based testing, applied on a systematic and repeated basis. For this we have developed a low cost, highly sensitive virus-genome-based test. Using Germany as an example, we demonstrate by using a mathematical model, how useful this strategy could have been in controlling the pandemic. We show using real-world examples how this might be implemented on a mass scale and discuss the feasibility of this approach
Allocating the Burdens of Climate Action: Consumption-Based Carbon Accounting and the Polluter-Pays Principle
Action must be taken to combat climate change. Yet, how the costs of climate action should be allocated among states remains a question. One popular answer—the polluter-pays principle (PPP)—stipulates that those responsible for causing the problem should pay to address it. While intuitively plausible, the PPP has been subjected to withering criticism in recent years. It is timely, following the Paris Agreement, to develop a new version: one that does not focus on historical production-based emissions but rather allocates climate burdens in proportion to each state’s annual consumption-based emissions. This change in carbon accounting results in a fairer and more environmentally effective principle for distributing climate duties
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