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Electric-field driven stability control of skyrmions in an ultrathin transition-metal film

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npj Computational Materials 2022年第1期8卷 992-1000页

作者： Souvik Paul Stefan heinze Peter Grünberg Institut and Institute for Advanced Simulation Forschungszentrum Jülich and JARA52425JülichGermany Institute of Theoretical Physics and Astrophysics Christian-Albrechts-Universität zu KielLeibnizstrasse 1524098KielGermany

To realize future spintronic applications with magnetic skyrmions—topologically nontrivial swirling spin structures—it is essential to achieve efficient writing and deleting capabilities of these ***-field assisted nucleation and annihilation is a promising route,however,the understanding of the underlying microscopic mechanisms is still ***,we show how the stability of individual magnetic skyrmions in an ultrathin transition-metal film can be controlled via external electric *** demonstrate based on density functional theory that it is important to consider the changes of all interactions with electric field,i.e.,the pair-wise exchange,the Dzyaloshinskii–Moriya interaction,the magnetocrystalline anisotropy energy,and the higher-order exchange *** energy barriers for electric-field assisted skyrmion writing and deleting obtained via atomistic spin simulations vary by up to a factor of three more than the variations of the interactions calculated from *** surprising effect originates from the electric-field dependent size of metastable skyrmions at a fixed magnetic *** large changes in lifetimes allow the possibility of electric-field assisted thermally activated writing and deleting of skyrmions.

关键词： field stability film

Between fighting and tolerance： reproductive biology of wingless males in the ant Cardiocondyla venustula

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Insect Science 2017年第5期24卷 818-828页

作者： Susanne Jacobs Jurgen heinze LS ZoologielEvolutionsbiologie Universitat Regensburg Regensburg Germany

Male reproductive tactics vary widely across the species of the ant genus Cardiocondyla, from obligatory lethal combat among co-occurring males to complete mutual tolerance. The African species C. venustula Wheeler, 1908 has an intermediate phylogenetic position between taxa with fighting males and taxa with tolerant males and also shows an intermediate male behavior. Males from 2 native populations in South Africa and a population introduced to Puerto Rico attacked and killed freshly eclosing rivals but rarely engaged in deadly fights with adult competitors, Instead, several males per colony established small ＂territories＂ in their natal nests and defended them against other males. Males with a stable territory had more contact with female sexuals than nonterritorial males and more frequently engaged in mating attempts. In controlled choice experiments, female sexuals did not show any preference for particular males. We suggest that male territoriality in C. venustula is an adaptation to the seasonal production of large numbers of female sexuals by multiple mothers.

关键词： Cardiocondyla ergatoid males Formicidae male competition sexual selection territoriality

Apparent task specialization among cofounding ant queens

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Insect Science 2021年第1期28卷 278-280页

作者： Jurgen heinze Sarah Koller LS Zoologie/Evolutionsbiologie Universitat RegensburgRegensburg.Germany

Dear Editor,The establishment of a new colony is a critical phase in the life of an insect *** ant queens may avoid the high risks of solitary founding by starting new colonies together with other young queens(pleometrosis).Foundress associations may produce first workers faster and have a higher survival rate than solitary foundresses(Bernasconi&Strassmann,1999).Because cofoundresses are typically not related pleometrosis is rarely associated with a clear division of labor(Jeanson&Fewell,2008).

关键词： solitary starting faster

Degenerate slave-makers,but nevertheless slave-makers?Host worker relatedness in the ant Myrmoxenus kraussei

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Integrative Zoology 2015年第2期10卷 182-185页

作者： Masaki SUEFUJI Jürgen heinze Zoology/Evolutionary Biology University of RegensburgGermany

Socially parasitic ants of the formicoxenine genus Myrmoxenus exhibit considerable diversity in colony structure and life *** some species are active slave-makers with many workers and others are workerless‘murder-parasites,’Myrmoxenus kraussei is considered as a‘degenerate slave-maker’because of its very low worker ***,we document that Temnothorax recedens host workers in single colonies of *** from Lago di Garda,Italy,exhibit significantly more genetic diversity than workers in unparasitized *** raises the possibility that,despite its low worker numbers,*** may actively engage in slave raids in nature.

关键词： dulosis nestmate relatedness Myrmoxenus social parasitism slave-making

Microcrack Formation During Gas Metal Arc Welding of High-Strength Fine-Grained Structural Steel

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 140-148页

作者： Christoph heinze Thomas Michael Andreas Pittner Michael Rethmeier Division 9.3 "Welding Technology" BAM Federal Institute for Materials Research and TestingUnter den Eichen 8712205 BerlinGermany Joining and Coating Technology Fraunhofer-Institute for Production Systems and Design Technology IPKPascalstraβe 8-910587 BerlinGermany

The recent development of high-performance-modified spray arc processes in gas metal arc welding due to modern digital control technology and inverter power sources enables a focused spray arc, which results in higher penetration depths and welding speed. However, rnicrocracks occurred in the weld metal while approaching the process limits of the modified spray arc, represented by a 20-mm double layer DV-groove butt-weld, These cracks were detected in structural steel exhibiting a yield strength level of up to 960 MPa and are neither dependent on the used weld power source nor a consequence of the modified spray arc process itself. The metallographic and fractographic investigations of the rather exceptional fracture surface lead to the classification of the microcracks as hot cracks, The effects of certain welding parameters on the crack probability are clarified using a statistical design of experiment. However, these microcracks do not impact the design specification for toughness in the Charpy V-notch test （absorbed energy at -40 ℃ for the present material is 30 J）.

关键词： High-strength low-alloy steel Welding Fracture Design of experiments Microcracking

When invasive ants meet: effects of outbreeding on queen performance in the tramp ant Cardiocondyla itsukii

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Insect Science 2019年第2期26卷 333-340页

作者： Jurgen heinze Sabine Frohschammer Abel Bernadou LS Zoologie/Evolutionsbiologie Universitat Regensburg Regensburg Germany

Most disturbed habitats in the tropics and subtropics harbor numerous species of invasive ants, and occasionally the same species has been introduced repeatedly from multiple geographical sources. We examined how experimental crossbreeding between sexuals from different populations affects the fitness of queens of the tramp ant Cardiocondyla itsukii, which is widely distributed in Asia and the Pacific Islands. Eggs laid by queens that mated with nestmate males had a higher hatchi ng rate than eggs laid by queens mated to males from neighboring (Hawaii x Kauai) or distant introduced populations (Hawaii/Kauai x Okinawa). Furthermore, inbreeding queens had a Ion ger lifespan and produced a less female-biased offspring sex ratio than queens from allopatric mating. This suggests that the genetic divergence between different source populations may already be so large that in case of multiple invasions eventual crossbreeding might negatively affect the fitness of tramp ants.

关键词： Cardiocondyla longevity outbreeding depression reproductive success tramp ants

Sperm traits differ between winged and wingless males of the ant Cardiocondyla obscurior

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Integrative Zoology 2016年第6期11卷 427-432页

作者： Alexandra SCHREMPF Astrid MOSER Jacques DELABIE Jürgen heinze Zoology/Evolutionary Biology University of RegensburgRegensburgGermany Myrmecological Laboratory Cocoa Research Center CEPLACItabunaBrazil

Size and shape of sperm cells vary tremendously throughout the animal *** adaptive significance of this variation is not fully *** addition to sperm-female interactions and the environmental conditions,the risk of sperm competition might affect number,morphology and other“quality”traits of *** the male-diphenic ant Cardiocondyla obscurior,winged sneaker males have limited sperm number,because their testes degenerate shortly after adult emergence,as is typical for males of social *** contrast,wingless fighter males continuously replenish their sperm supply due to their exceptional lifelong spermatogene*** winged males usually have to compete with several other winged males for virgin queens,wingless males are able to monopolize queens by killing all other ***,this presents a unique system to investigate how alternative reproductive tactics and associated physiology affect sperm morphology and *** found that sperm-limited males invest into sperm number instead of sperm *** in sperm length is smaller in winged males,probably reflecting that they have to compete with several other ***,sperm viability is equally high in both male phenotypes.

关键词： alternative reproductive tactic social insect sperm length sperm viability

Cuticular hydrocarbons in two parapatric species of ants and their hybrid

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Integrative Zoology 2011年第3期6卷 259-265页

作者： Mohamed EL-SHEHABY Mohamed Sayed SALAMA Elisabeth BRUNNER Jürgen heinze Biologie I University of RegensburgRegensburgGermany Department of Entomology Ain Shams UniversityCairoEgypt

Discrimination between nestmates and non-nestmates in social insects is thought to rely on the pattern of cuticular *** investigated the cuticular hydrocarbon profiles of 2 parapatric sibling ant species,Temnothorax nylanderi(Förster,1850)and Temnothorax crassispinus(Karavaiev,1926),and their *** found that although the profiles show considerable similarities,a discriminant analysis based on the relative peak areas of cuticular hydrocarbons separates the 3 *** profiles of hybrids were not consistently intermediate between those of the paternal species,suggesting either non-additive interactions among the parental biosynthetic pathways or systematic differ-ences in environment-derived odor cues.

关键词： colony odor cuticular hydrocarbons hybridization Temnothorax

Soil temperature modifies effects of soil biota on plant growth

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Journal of Plant Ecology 2017年第5期10卷 808-821页

作者： Johannes heinze Sabine Gensch Ewald Weber Jasmin Joshi Department of Biodiversity Research/Botany Institute of Biochemistry and BiologyUniversity of PotsdamMaulbeerallee 1D-14469 PotsdamGermany Berlin-Brandenburg Institute of Advanced Biodiversity Research(BBIB) Altensteinstr.614195 BerlinGermany

Aims Plants directly and indirectly interact with many abiotic and biotic soil *** so far mostly focused on direct,indi-vidual abiotic or biotic effects on plant growth,but only few studies tested the indirect effects of abiotic soil factors on plant ***,we investigated how abiotic soil conditions affect plant performance,via changes induced by soil *** In a full-factorial experiment,we grew the widespread grass Dactylis glomerata either with or without soil biota and investigated the impact of soil temperature,fertility and moisture on the soil biota effects on plant *** measured biomass production,root traits and colonization by arbuscular mycorrhizal fungi as well as microbial *** Findings We found significant interaction effects between abiotic soil con-ditions and soil biota on plant growth for fertility,but especially for soil temperature,as an increase of 10°c significantly changed the soil biota effects on plant growth from positive to ***,if tested individually,an increase in soil temperature and fertility per se positively affected plant biomass production,whereas soil biota per se did not affect overall plant growth,but both influenced root *** affecting soil microbial activ-ity and root architecture,soil temperature might influence both mutualistic and pathogenic interactions between plants and soil *** soil temperature effects should be considered in soil feedback studies to ensure greater transferability of results from artificial and experimental conditions to natural environmental conditions.

关键词： plant-soil interaction soil biota abiotic soil factors root traits plant growth