Force distributions and force chains in random stiff fiber networks

We study the elasticity of random stiff fiber networks. The elastic response of the fibers is characterized by a central force stretching stiffness as well as a bending stiffness that acts transverse to the fiber contour. Previous studies have shown that this model displays an anomalous elastic regime where the stretching mode is fully frozen out and the elastic energy is completely dominated by the bending mode. We demonstrate by simulations and scaling arguments that, in contrast to the bending dominated \emph{elastic energy}, the equally important \emph{elastic forces} are to a large extent stretching dominated. By characterizing these forces on microscopic, mesoscopic and macroscopic scales we find two mechanisms of how forces are transmitted in the network. While forces smaller than a threshold $F_c$ are effectively balanced by a homogeneous background medium, forces larger than $F_c$ are found to be heterogeneously distributed throughout the sample, giving rise to highly localized force-chains known from granular media.Comment: 7 pages, 7 figures, final version as publishe

Does symmetry preclude the evolution of senescence? A comment on Pen and Flatt 2021

Funding Information: C.d.V. and H.K. were supported by Swiss National Science Foundation grant no. 310030B_182836. C.d.V. was also supported by an Academy of Finland grant (no. 340130, awarded to Jussi Lehtonen). E.Y.E. was supported by the National Institutes of Health (NIH) grant no. U54 CA217376 (awarded to Hanna Kokko) and Swiss National Science Foundation grant no. P500PB_203022.Peer reviewe

Demography can favour female-advantageous alleles

When female fecundity is relatively independent of male abundance, while male reproduction is proportional to female abundance, females have a larger effect on population dynamics than males (i.e. female demographic dominance). This population dynamic phenomenon might not appear to influence evolution, because male and female genomes still contribute equally much to the next generation. However, here we examine two evolutionary scenarios to provide a proof of principle that spatial structure can make female demographic dominance matter. Our two simulation models combine dispersal evolution with local adaptation subjected to intralocus sexual conflict and environmentally driven sex ratio biases, respectively. Both models have equilibria where one environment (without being intrinsically poorer) has so few reproductive females that trait evolution becomes disproportionately determined by those environments where females survive better (intralocus sexual conflict model), or where daughters are overproduced (environmental sex determination model). Surprisingly, however, the two facts that selection favours alleles that benefit females, and population growth is improved when female fitness is high, together do not imply that all measures of population performance are improved. The sex-specificity of the source-sink dynamics predicts that populations can evolve to fail to persist in habitats where alleles do poorly when expressed in females

Tanhuan gabron geofysikaaliset tutkimukset ja mittaustulosten mallinnus

Tiivistelmä. Keski-Lapin paleoproterosooisen liuskevyöhykkeen mafiset ja ultramafiset kivet ovat potentiaalisia Ni-Cu-Co-PGE ja V-Ti-Fe-Cr malmien suhteen. Tämän tutkielman kohteena oli Savukosken kunnassa sijaitseva Tanhuan mafinen intruusio. Tavoitteena oli luoda Tanhuan Kannusvaaran ja Markkinaselän alueella mitatun magneettisen mittausaineiston pohjalta suskeptibiliteettimalleja sekä painovoima-aineiston pohjalta tiheysmalleja 3D-inversion avulla. Malleja tulkittiin yksin ja yhdessä sekä petrofysiikan mittaustulosten kanssa. Petrofysiikan perusteella luotiin rajoittamattomien mallien lisäksi suskeptibiliteetiltaan ja tiheydeltään rajoitettuja inversiomalleja. Näin voitiin mallintaa intruusion magneettisten osien laajuutta suhteessa intruusion magnetoitumattomiin osiin. Työssä käytetyt geofysiikan ja petrofysiikan aineistot olivat peräisin GTK:lta. 3D-mallinnuksessa käytettiin Geosoft Oasis Montaj ohjelmistoa ja sen VOXI Earth Modelling lisäosaa, joka mahdollistaa potentiaalikenttien kolmiulotteisen suoran ja käänteismallinnuksen. GTK on suorittanut Tanhuan alueella vuosien 2019--2021 aikana kattavasti erilaisia geofysikaalisia mittauksia ja kairannut alueelle vuosina 2019--2020 yhteensä 14 kairanreikää. Aiheen tutkimuksille antoivat Rautaruukki OY:n vuonna 1976 magneettiseen anomaliaan kairaamat kairanreiät, joissa oli viitteitä kobolttipitoisten sulfidien ja kuparin esiintymisestä. GTK:n tutkimusten perusteella Tanhuan mafisen intruusion muodostavat erilaiset magneettiset ja magnetoitumattomat gabrot, magnetoituneet dioriittiset ja graniittiset kivet sekä niitä ympäröivät suprakrustiset kivet. Alueen kivet ovat eriasteisesti metamorfoituneet ja muuttuneet hydrotermisten prosessien vaikutuksesta, minkä takia ne ovat voimakkaasti albiittiutuneita ja biotiittiutuneita. GTK:n tutkimusten perusteella alueen kivissä esiintyy paikoin Co-Cu-(Au) mineralisaatioita, joista merkittävimmät keskittyvät oksidipitoisiin kiviin. Kannusvaaran ja Markkinaselän kairasydämistä oli tutkittu kivinäytteitä GTK:n petrofysiikan laboratoriossa. Kivinäytteistä mitattua tiheyttä, indusoitunutta magnetoitumaa (suskeptibiliteetti) ja remanenssia (jäännösmagnetoituma) havainnollistettiin tässä työssä kuvaajien avulla. Petrofysiikan mittaustulosten perusteella alueella esiintyy tiheitä gabroidisia kiviä, joiden keskitiheys on noin 3,1 g/cm³. Gabroidisista kivistä osa on hyvin magneettisia ja suskeptibiliteettien keskiarvo on noin 0,4 SI näytteillä, joiden suskeptibiliteetit ovat suurempia kuin 0,1 SI. Alueella esiintyy lisäksi alhaisemman tiheyden omaavia suprakrustisia kiviä, joiden keskitiheys on noin 2,7 g/cm³. Alueella tavataan myös gabroidisia kiviä alhaisemman tiheyden omaavia dioriittisia ja graniittisia kiviä, joiden keskitiheys on noin 2,8 g/cm³ ja, joiden suskeptibiliteettien keskiarvo on noin 0,2 SI eli ne ovat myös voimakkaasti magneettisia. Alueen kivissä on lisäksi tavattu huomattavaa remanenttia magnetoitumaa. Kivinäytteiden Königsberger:in-suhteiden (Q-suhde) keskiarvo on noin 1,7. Ilman viittä suurinta arvoa Q-suhteiden keskiarvoksi jää 0,9. Koska Tanhuan alueen gabroidisilla kivillä on suuri tiheysero verrattuna niitä ympäröiviin suprakrustisiin kivilajeihin, gabroidiset kivet näkyvät painovoimakartoissa laajoina positiivisina anomalioina suhteessa niitä tiheydeltään pienempiin kvartsiitteihin ja vulkaniitteihin. Siten painovoimamittauksissa voidaan havaita molemman tyyppiset sekä magneettiset, että ei-magneettiset gabroidiset kivet. Intruusion magnetoituneet kivet erottuvat selvästi magneettisissa lentomittauskartoissa ja systemaattisissa maanpintamittauksissa, jossa anomaliat ovat tuhansien nT luokkaa, ylittäen paikoin jopa 10 000 nT. Mallinnusten perusteella Tanhuan Kannusvaaran ja Markkinaselän alueen positiivisen painovoima-anomalian ja magneettisen anomalian aiheuttavat tiheät ja magneettiset kivilajiyksiköt, jotka osaksi leikkaavat toisiaan -- eli osa kivistä on sekä tiheitä, että magneettisia. Magneettisen ja painovoima-anomaliavyöhykkeen muodostavat pääosin kaksi pohjois-etelä(lounais)-suuntaista epäsäännöllisen muotoista magneettista ja tiheämpää osiota. Magneettisten inversiotulosten perusteella intruusion kaateet näyttävät olevan länteen päin, mutta painovoimainversiomalleissa kaateen suunta ei ole aivan yhtä selkeä. Tiheämpien kivien muodostamat yksiköt ovat laajempia suhteessa kapeampiin magneettisiin osiin. Eri mallien välillä on eroja sekä magneettisten, että painovoimainversiomallien kanssa, erityisesti syvyysulottuvuudessa. Magneettiset osat koostuvat useammasta magnetoituneesta kappaleesta, joissa suskeptibiliteetin suuruus on välillä 0,1--1,7 SI. Suskeptibiliteettimallien perusteella alueen länsipuoleinen N-S suuntainen magneettinen anomaliajakso on noin 3,0 kilometriä pitkä ja itäpuolen noin 1,5 kilometriä pitkä. Magneettisten osien maksimileveys on noin 400--500 metriä. Rajoitettu malli on yleisesti leveämpi kuin rajoittamaton suskeptibiliteettimalli. Magneettiset osiot alkavat läheltä maanpintaa ja ylettyvät pääasiassa 100--0 metriin (merenpinnan yläpuolella) ja enimmillään noin 200--300 metrin syvyyteen (merenpinnan alapuolella). Rajoittamaton suskeptibiliteettimalli jatkuu vielä syvemmälle alueen pohjoisosassa. Rajoittamattomassa tiheysmallissa tiheimmät osat erottuvat osittain erillisiksi kappaleiksi, mutta tiheydeltään rajoitetussa mallissa tiheimmät osat sulautuvat syvemmällä enemmän yhteen. Tiheysmallien perusteella alueen länsipuoleisen painovoima-anomalialähteen leveys vaihtelee noin 250--550 metrin välillä ja se on noin 2,4 kilometriä pitkä. Itäpuoleisen anomalialähteen leveys on noin 300 metriä ja se on noin 750 metriä pitkä. Tiheät osat jatkuvat pituussuunnassa mahdollisesti mallinnusalueen ulkopuolelle. Tiheysjakauma vaikuttaa jatkuvan magneettista syvemmällekin, jopa noin 500 metriin (merenpinnan alapuolella). Tiheysmallien perusteella laajempien tiheämpien yksiköiden välissä on lisäksi pari pienempää tiheämpää kappaletta. Magneettisen aineiston pohjalta lasketun pseudopainovoiman perusteella aivan tutkimusalueen kaakkoisosassa, eteläisimmän painovoimalinjan itäisessä reunassa muodostuma koostuu pääosin vain magnetoitumattomasta, mutta tiheästä osasta. Kairanrei’istä mitattuja suskeptibiliteetteja havainnollistettiin kairanreikinä yhdessä suskeptibilitettimallien kanssa. Luotujen suskeptibiliteettimallien ja kairasydämistä mitattujen suskeptibiliteettien välillä on yhteneväisyyksiä, mutta myös eroja. Suskeptibiliteetiltaan rajoitettu malli vaikuttaa korreloivan hieman paremmin kairasydänten petrofysiikan kanssa.Geophysical studies and 3D modelling on Tanhua gabbro. Abstract. ³The mafic and ultramafic rocks in the Central Lapland Greenstone Belt are potential targets for Ni-Cu-Co-PGE and V-Ti-Fe-Cr mineralizations. This thesis focuses on the Tanhua mafic intrusion located in Savukoski in the Finnish Lapland. The goal of this thesis was to create 3D-inversion models of susceptibility based on magnetic ground data and density models based on ground gravity data measured in the Tanhua Kannusvaara and Markkinaselkä area. The models were interpreted individually, together, and with petrophysical laboratory measurements. In addition to non-constrained models, constrained models were created based on the petrophysical data. The goal was to understand the extent of the magnetic parts of the intrusion in subject to the non-magnetic parts. The geophysical and petrophysical data used were provided by the GTK. Geosoft Oasis Montaj and its VOXI Earth Modelling extension, which can be used for the 3D forward and inverse modelling of potential fields, were used in the modelling. The Geological Survey of Finland has conducted extensive geophysical measurements between 2019--2021 and drilled 14 drillholes in the years 2019--2020. These investigations were motivated by drillholes drilled by Rautaruukki Oy in 1976, indicating cobalt-enriched sulfides and copper. Based on the GTK investigations, Tanhua mafic intrusion is composed of different types of magnetic and non-magnetic gabbros, magnetic dioritic and granitic rocks, with supracrustal rocks surrounding them. Rocks in the area show signs of metamorphosis and alteration due to hydrothermal processes. Hence, they are strongly albitized and biotitized. Based on the GTK investigations, some Co-Cu-(Au) mineralized zones in the rocks have been found. However, the most significant mineralizations are concentrated in the oxide-bearing rocks. Samples from the Kannusvaara and Markkinaselkä drill cores were examined by the GTK in their petrophysics laboratory. In this thesis, susceptibility, remanence, and density of the drill core samples were visualized with charts. The results indicate that the average density of the gabbroic rocks in the area is approximately 3,1 g/cm³. Some of the gabbroic rocks are very magnetic, and the average susceptibility is approximately 0,4 SI for samples with susceptibilities over 0,1 SI. The supracrustal rocks in the area have much lower densities, on average approximately 2,7 g/cm³. There are also dioritic and granitic rocks in the area, which have lower densities than gabbroic rocks, on average approximately 2,8 g/cm³, but they are quite magnetic, having average susceptibilities of approximately 0,2 SI. There is also evidence of remanent magnetization in the rocks. The average Königsberger’s ratio (Q-value) of the rock samples in the area is approximately 1,7. Without the five highest samples, the average Q-value becomes approximately 0,9. Rocks in the Tanhua area have higher densities than the supracrustal rocks surrounding them, thus gabbroic rocks are seen as positive gravity anomalies relative to less dense quartzites and vulcanites. Therefore, it is possible to detect both magnetic and non-magnetic rocks with gravity measurements. Furthermore, the magnetized rocks can be detected in low-altitude airborne magnetic maps and in systematic magnetic ground surveys in which the anomalies are thousands of nT, in some parts even over 10 000 nT. Based on the modelling, the positive gravity anomaly and the magnetic anomaly in the Tanhua Kannusvaara and Markkinaselkä area is produced by dense and magnetic rock units, which partly intersect — meaning some of the rocks are magnetic and dense. The magnetic and gravity anomaly zones are composed primarily of two north--south(southwest) oriented irregularly shaped magnetic and dense sections. Based on the magnetic inversion results, the intrusion appears to dip westwards, but the dip direction is not as evident in the gravity inversion. The dense rock units seem to be wider than the magnetic rock units. The results show differences in the models, in both gravity and magnetic inversions, especially with their depth extensions. The magnetic sections appear to be composed of several separate pieces with susceptibilities between 0,1--1,7 SI. Based on the susceptibility models, the western section of the magnetic N-S anomaly is approximately 3,0 kilometers long, and the eastern section of the magnetic anomaly is approximately 1,5 kilometers long. The maximum width of the magnetic parts is approximately 400--500 meters. The constrained model is generally wider than the non-constrained susceptibility model. The magnetic sections begin close to the surface, continuing approximately to 100--0 meters (above sea level). In some parts, even approximately 200--250 meters in depth (below sea level). In the non-constrained model, the susceptibility continues even deeper in the northern part of the area. In the non-constrained model, the densest sections stand out more as individual pieces, but in the constrained model, they are more merged together. Based on the density models, the western gravity anomaly is produced by an anomalous source of varying width of 250--550 meters, and it is approximately 2,4 kilometers long. The eastern gravity anomaly is produced by an anomalous source of a width of 300 meters and is approximately 750 meters long. The dense sections may probably continue beyond the model area. The dense anomalous sources continue deeper than the magnetic parts, to 500 meters (below sea level). Based on the density inversion models, there are also a couple of smaller pieces of higher relative density. The pseudo gravity calculated from the magnetic data indicates that in the south-eastern parts of the study area, the anomalous source is composed mainly of non-magnetic but dense rock units at the eastern part of the most south line. Susceptibilities measured from the rock samples were also visualized as drill cores and inspected together with the susceptibility models. Based on the results, there appears to be some congruence with the susceptibility models and visualized drill cores but also some differences. The inversion model with the constrained susceptibility seems to be coinciding more with the drill cores

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

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

Inflated Impact Factors? The True Impact of Evolutionary Papers in Non-Evolutionary Journals

Amongst the numerous problems associated with the use of impact factors as a measure of quality are the systematic differences in impact factors that exist among scientific fields. While in theory this can be circumvented by limiting comparisons to journals within the same field, for a diverse and multidisciplinary field like evolutionary biology, in which the majority of papers are published in journals that publish both evolutionary and non-evolutionary papers, this is impossible. However, a journal's overall impact factor may well be a poor predictor for the impact of its evolutionary papers. The extremely high impact factors of some multidisciplinary journals, for example, are by many believed to be driven mostly by publications from other fields. Despite plenty of speculation, however, we know as yet very little about the true impact of evolutionary papers in journals not specifically classified as evolutionary. Here I present, for a wide range of journals, an analysis of the number of evolutionary papers they publish and their average impact. I show that there are large differences in impact among evolutionary and non-evolutionary papers within journals; while the impact of evolutionary papers published in multidisciplinary journals is substantially overestimated by their overall impact factor, the impact of evolutionary papers in many of the more specialized, non-evolutionary journals is significantly underestimated. This suggests that, for evolutionary biologists, publishing in high-impact multidisciplinary journals should not receive as much weight as it does now, while evolutionary papers in more narrowly defined journals are currently undervalued. Importantly, however, their ranking remains largely unaffected. While journal impact factors may thus indeed provide a meaningful qualitative measure of impact, a fair quantitative comparison requires a more sophisticated journal classification system, together with multiple field-specific impact statistics per journal

Female Fertilization: Effects of Sex-Specific Density and Sex Ratio Determined Experimentally for Colorado Potato Beetles and Drosophila Fruit Flies

If males and females affect reproduction differentially, understanding and predicting sexual reproduction requires specification of response surfaces, that is, two-dimensional functions that relate reproduction to the (numeric) densities of both sexes. Aiming at rigorous measurement of female per capita fertilization response surfaces, we conducted a multifactorial experiment and reanalyzed an extensive data set. In our experiment, we varied the density of male and female Leptinotarsa decemlineata (Colorado potato beetles) by placing different numbers of the two sexes on enclosed Solanum tuberosum (potato plants) to determine the proportion of females fertilized after 3 or 22 hours. In the reanalysis, we investigated how the short-term fertilization probability of three Drosophila strains (melanogaster ebony, m. sepia, and simulans) depended on adult sex ratio (proportion of males) and total density. The fertilization probability of female Leptinotarsa decemlineata increased logistically with male density, but not with female density. These effects were robust to trial duration. The fertilization probability of female Drosophila increased logistically with both sex ratio and total density. Treatment effects interacted in m. sepia, and simulans. These findings highlight the importance of well-designed, multifactorial experiments and strengthen previous experimental evidence for the relevance of sex-specific densities to understanding and prediction of female fertilization probability.WKV, MEH, and HK acknowledge financial support from the Academy of Finland. GB and PM acknowledge financial support from Agriculture and Agri-Food Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Soliton-like Spin State in the A-like Phase of 3He in Anisotropic Aerogel

We have found a new stable spin state in the A-like phase of superfluid 3He confined to intrinsically anisotropic aerogel. The state can be formed by radiofrequency excitation applied while cooling through the superfluid transition temperature and its NMR properties are different from the standard A-like phase obtained in the limit of very small excitation. It is possible that this new state is formed by textural domain walls pinned by aerogel.Comment: 9 pages, 3 figures. Submitted to J. of Low Tem. Phys. (QFS2007 Proceedings