1,253 research outputs found
Cusp relation for the Pauli potential
In orbital-free density functional theory, only a Schrödinger-like equation has to be solved for the square root of the electron density. In this equation, however, there is an extra potential in addition to the Kohn-Sham potential, the so-called Pauli potential. Cusp relations are now presented for this Pauli potential for spherically symmetric systems.</p
Flexibility of the quasi-non-uniform exchange-correlation approximation
In our previous study [Phys. Rev. B 86, 201104 (2012).] we introduced the so-called quasi-non-uniform gradient-level exchange-correlation approximation (QNA) and demonstrated its strength in producing highly accurate equilibrium volumes for metals and their alloys within density-functional theory. In this paper we extend the scheme to include the accuracy of the bulk modulus as an additional figure of merit and show that this scheme is flexible enough to allow the computation of accurate equilibrium volumes and bulk moduli at the same time. The power and feasibility of this scheme is demonstrated on NiAl and FeV binary alloys.</p
Chikungunya virus infections in Finnish travellers 2009-2019 : Infection Ecology & Epidemiology
ABSTRACT The mosquito-borne chikungunya virus (CHIKV) causes an acute febrile illness with rash, joint and muscle pain.A realtime RT-PCR assay for CHIKV detecting non-structural protein (nsP2; CHIKV nsP2-RT-qPCR) was set up. All the serodiagnosed CHIKV cases detected during 2009-2019 in Finland were screened with the assay, followed by isolations attempts and sequencing using Sanger and next generation sequencing (NGS). To validate the assay external and in-house quality control samples were used and all were correctly identified. Specificity of the assay was 100%. Assay was sensitive to detect CHIKV RNA in dilution of 10-8.During years 2009-2019 34 patients were diagnosed for acute CHIKV infection. Twelve out of 34 cases were positive by CHIKV nsP2-RT-qPCR.Two CHIKV isolations succeeded from two individuals infected originally in Thailand, 2019. From 12 CHIKV nsP2-RT-qPCR positive samples, five (42%) CHIKVs were successfully sequenced. In this study, CHIKVs from year 2019 clustered with CHIKV ECSA-lineage forming sub-cluster with strains from ones detected in Bangladesh 2017, and the ones from Jamaica (2014) within Asian lineage showing highest similarity to strains detected in Caribbean outbreak 2013-15.  Majority of the CHIKV infections detected in Finland originates from Asia and virus lineages reflect the global circulation of the pathogen.Peer reviewe
Segregation, precipitation, and \alpha-\alpha' phase separation in Fe-Cr alloys: a multi-scale modelling approach
Segregation, precipitation, and phase separation in Fe-Cr systems is
investigated. Monte Carlo simulations using semiempirical interatomic
potential, first-principles total energy calculations, and experimental
spectroscopy are used. In order to obtain a general picture of the relation of
the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and
interface regions several complementary methods has to be used. Using Exact
Muffin-Tin Orbitals method the effective chemical potential as a function of Cr
content (0-15 at.% Cr) is calculated for a surface, second atomic layer and
bulk. At ~10 at.% Cr in the alloy the reversal of the driving force of a Cr
atom to occupy either bulk or surface sites is obtained. The Cr containing
surfaces are expected when the Cr content exceeds ~10 at.%. The second atomic
layer forms about 0.3 eV barrier for the migration of Cr atoms between bulk and
surface atomic layer. To get information on Fe-Cr in larger scales we use
semiempirical methods. Using combined Monte Carlo molecular dynamics
simulations, based on semiempirical potential, the precipitation of Cr into
isolated pockets in bulk Fe-Cr and the upper limit of the solubility of Cr into
Fe layers in Fe/Cr layer system is studied. The theoretical predictions are
tested using spectroscopic measurements. Hard X-ray photoelectron spectroscopy
and Auger electron spectroscopy investigations were carried out to explore Cr
segregation and precipitation in Fe/Cr double layer and Fe_0.95Cr_0.05 and
Fe_0.85Cr_0.15 alloys. Initial oxidation of Fe-Cr was investigated
experimentally at 10^-8 Torr pressure of the spectrometers showing intense
Cr_2O_3 signal. Cr segregation and the formation of Cr rich precipitates were
traced by analysing the experimental spectral intensities with respect to
annealing time, Cr content, and kinetic energy of the exited electron.Comment: 16 pages, 14 figures, 52 reference
Unrelated Helpers in a Primitively Eusocial Wasp: Is Helping Tailored Towards Direct Fitness?
The paper wasp Polistes dominulus is unique among the social insects in that nearly one-third of co-foundresses are completely unrelated to the dominant individual whose offspring they help to rear and yet reproductive skew is high. These unrelated subordinates stand to gain direct fitness through nest inheritance, raising the question of whether their behaviour is adaptively tailored towards maximizing inheritance prospects. Unusually, in this species, a wealth of theory and empirical data allows us to predict how unrelated subordinates should behave. Based on these predictions, here we compare helping in subordinates that are unrelated or related to the dominant wasp across an extensive range of field-based behavioural contexts. We find no differences in foraging effort, defense behaviour, aggression or inheritance rank between unrelated helpers and their related counterparts. Our study provides no evidence, across a number of behavioural scenarios, that the behaviour of unrelated subordinates is adaptively modified to promote direct fitness interests
Magnetic origin of the chemical balance in alloyed Fe-Cr stainless steels: First-principles and Ising model study
Iron-chromium is the base material for most of the stainless steel grades. Recently, new insights into the origins of fundamental physical and chemical characteristics of Fe-Cr based alloys have been achieved. Some of the new results are quite unexpected and call for further investigations. The present study focuses on the magnetic contribution in the atomic driving forces related to the chemical composition in Fe-Cr when alloyed with Al, Ti, V, Mn, Co, Ni, and Mo. Using the ab initio exact muffin-tin orbitals method combined with an Ising-type spin model, we demonstrate that the magnetic moment of the solute atoms with the induced changes in the magnetic moments of the host atoms form the main factor in determining the mixing energy and chemical potentials of low-Cr Fe-Cr based alloys. The results obtained in the present work are related to the designing and tuning of the microstructure and corrosion protection of low-Cr steels. (C) 2014 Elsevier B. V. All rights reserved.</p
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