Magnetic structure of CeRhIn_5 as a function of pressure and temperature

We report magnetic neutron-diffraction and electrical resistivity studies on single crystals of the heavy-fermion antiferromagnet CeRhIn$_{5}$ at pressures up to 2.3 GPa. These experiments show that the staggered moment of Ce and the incommensurate magnetic structure change weakly with applied pressure up to 1.63 GPa, where resistivity, specific heat and NQR measurements confirm the presence of bulk superconductivity. This work places new constraints on an interpretation of the relationship between antiferromagnetism and unconventional superconductivity in CeRhIn$_{5}$.Comment: 6 pages, 6 figures, submitted to Phys. Rev.

Cloud boundary height measurements using lidar and radar

Using only lidar or radar an accurate cloud boundary height estimate is often not possible. The combination of lidar and radar can give a reliable cloud boundary estimate in a much broader range of cases. However, also this combination with standard methods still can not measure the cloud boundaries in all cases. This will be illustrated with data from the Clouds and Radiation measurement campaigns, CLARA. Rain is a problem: the radar has problems to measure the small cloud droplets in the presence of raindrops. Similarly, few large particles below cloud base can obscure the cloud base in radar measurements. And the radar reflectivity can be very low at the cloud base of water clouds or in large regions of ice clouds, due to small particles. Multiple cloud layers and clouds with specular reflections can pose problems for lidar. More advanced measurement techniques are suggested to solve these problems. An angle scanning lidar can, for example, detect specular reflections, while using information from the radars Doppler velocity spectrum may help to detect clouds during rain.Comment: Reviewed conference contributio

Crystal and magnetic structure of the oxypnictide superconductor LaO(1-x)FxFeAs: evidence for magnetoelastic coupling

High-resolution and high-flux neutron as well as X-ray powder-diffraction experiments were performed on the oxypnictide series LaO(1-x)FxFeAs with 0<x<0.15 in order to study the crystal and magnetic structure. The magnetic symmetry of the undoped compound corresponds to those reported for ReOFeAs (with Re a rare earth) and for AFe2As2 (A=Ba, Sr) materials. We find an ordered magnetic moment of 0.63(1)muB at 2 K in LaOFeAs, which is significantly larger than the values previously reported for this compound. A sizable ordered magnetic moment is observed up to a F-doping of 4.5% whereas there is no magnetic order for a sample with a F concentration of x=0.06. In the undoped sample, several interatomic distances and FeAs4 tetrahedra angles exhibit pronounced anomalies connected with the broad structural transition and with the onset of magnetism supporting the idea of strong magneto-elastic coupling in this material.Comment: 8 pages, 7 figures, regular articl

Characterisation of Enzyme Evolution through Ancestral Enzyme Reconstruction

Through ancestral sequence reconstruction (ASR) techniques, ancient enzymes can be recreated and biochemically tested, giving insight into the enzymes’ evolutionary history. A previous study by Hobbs et al. (2012) has shown that some ancestral 3-isopropylmalate dehydrogenase (IPMDH) enzymes of the Bacillus lineage are more catalytically efficient and kinetically stable than extant counterparts. Given these characteristics, this trend raises questions as to why ancestral Bacillus IPMDH enzymes have been superseded by catalytically slower and less kinetically stable counterparts. The homology between IPMDH and the dehydrogenases of tartrate, malate and isocitrate makes IPMDH an interesting model enzyme in terms of the evolution of substrate specificity. Here, the reconstruction of a 2.7 billion year old enzyme has been attempted to extend the reconstruction of IPMDH back to the last common ancestor of the Firmicutes. This reconstruction tested the limits of ASR techniques in terms of time and levels of sequence divergence, especially for such a structurally complex enzyme. However, upon expression and purification, the enzyme was found to form an inactive, soluble aggregate. This suggests that current ASR techniques are too simplistic to reconstruct the complexity and divergence of IPMDH back as far as the last common ancestor of the Firmicutes. Enzyme evolution was investigated with ancestors from the Bacillus genus. Substrate promiscuity of ancestral enzymes was compared to a contemporary counterpart. It was concluded that the ancestral IPMDH enzymes tested do not show additional substrate promiscuity when compared to contemporary counterparts. The fitness of organisms carrying the IPMDH ancestors was assessed to establish what effects the high turnover rates and kinetic stability possessed by some ancestral IPMDH enzymes had on cells when functioning within the normal catalytic pathway for leucine. In vivo, the fastest and most kinetically stable ancestral IPMDH resulted in slower growth rates. This detrimental effect in vivo clarifies why this enzyme has been lost over evolutionary time. The X-ray crystal structure of the most recent IPMDH ancestor was also determined at 2.6 Å resolution. The structure of this ancestral IPMDH was found to be similar to other IPMDH structures, including the previously solved IPMDH from the last common ancestor of the Bacillus

Reflections on Excavating Archaeological Grey Literature: and on the Challenges in Information Extraction

The largely unpublished reports generated by commercial or “rescue” archaeology, commonly known as “grey literature” contain a great deal of untapped information, highly relevant to the research and analysis of archaeological evidence. The presentation unfolds experiences and challenges in using Natural Language Processing techniques for "unlocking" and surfacing information from unstructured textual input, delivering structured outputs which enable new information access methods, based on linking worded representations to ontological definitions and formalisations for the purposes of information retrieval from heterogeneous data sources. The role of Named Entity Recognition, Relation Extraction, Negation Detection, and Word-Sense Disambiguation is presentedin connection to a semantic annotation and automatic metadata generation endeavour, which spanned over ten years and two research projects, focusing on English, Dutch and Swedish grey literature

Knowledge Overlap in Nearshore Service Delivery

Multinational organizations now increasingly source tasks from nearshore units. While, offshore locations promise superior opportunities for cost savings and access to large scale, flexible workforces, organisations are increasingly distributing work much closer to home (Deliotte 2014). One of the biggest attractions of nearshore locations is proximity. In principle nearshore units are geographically, temporally, and culturally closer to their onshore counterparts reducing the cost and coordination effort to manage distance. Despite the anticipation that onshore units and nearshore units will operate effectively from distinctive and separate knowledge bases, they continue to be bogged down by knowledge overlaps. Knowledge overlaps (KOs) are a duplication of information and know-how of specific migrated activities that allow onshore units to retain control of nearshore units. In this paper, we draw on data from an on-going qualitative case study to demonstrate how nearshore units manage KOs and relinquish control of processes

A fish stinks from the head: Ethnic diversity, segregation, and the collapse of Yugoslavia

Demographic analysis clarifies political issues in the collapse of Yugoslavia. In most regions, 1961-1991, ethnic diversity (estimated by informational entropy) increased and segregation (estimated by Theil’s H) decreased. In a few regions there was a reversal in 1991 as migration flows or presentations of self perhaps changed in anticipation of war. The analysis strengthens refutations of the view that long standing ethnic hatreds were the root cause of the Yugoslav collapse and supports analyses that attribute collapse to general economic crisis, economic competition between regions, and failures at the peak of government.collapse of Yugoslavia, diversity, ethnic politics, ethnicity, segregation, Yugoslavia