Untersuchung schneller Strukturänderungen mit Hilfe ultrakurzer Röntgenimpulse

Im ersten Teil dieser Arbeit wird der Aufbau einer Laser-Plasma basierten Röntgenquelle diskutiert. Die Quelle wurde entwickelt, um zeitaufgelöste Röntgenbeugungsexperimente mit fs-Zeitau ösung durchführen zu können. Aus der Anwendung heraus ergeben sich eine Vielzahl von Konstruktionskriterien, die die Quelle zu erfüllen hat. Das Laserplasma wird auf einem umlaufenden Titandraht erzeugt, und zwar mit Hilfe des 10-Hz-Titan-Saphir-Lasersystems des Instituts für Laser- und Plasmaphysik der Universität Essen. Zur Erzeugung der Ti-K(alpha)-Röntgenstrahlung bei einer Energie von 4,5 keV werden die Laserimpulse auf den Draht fokussiert und Intensitäten von maximal 1018 W/cm2 erzielt. Die Elektronen werden im Fokus direkt vom Laserfeld beschleunigt und erzeugen bei der Wechselwirkung mit dem Material charakteristische, inkohärente Röntgenstrahlung in Form von sehr kurzen Röntgenblitzen. Die Impulsdauer der so erzeugten Strahlung liegt weit unterhalb einer Pikosekunde. Zur Detektion der Röntgenstrahlung wird eine gekühlte, röntgenempfindliche CCD-Kamera verwendet. Im zweiten Teil der Arbeit wird demonstriert, wie die inkohärente Röntgenstrahlung mittels eines torisch gebogenen Röntgenspiegels { bestehend aus Si (311) { auf eine zu untersuchenden Probe fokussiert werden kann. Mit dem gebogenen Kristall konnte die Strahlung der Ti-K(alpha)-Quelle auf ca. 80 Mikrometer fokussiert werden. Gegenüber Experimenten mit unfokussierter Strahlung wird dadurch eine Verbesserung des Röntgen flusses um zwei Größenordnungen erreicht. Die fokussierten Röntgenimpulse stehen dann den eigentlichen Anwendungen zur Verfügung. So konnten Anrege-Abfrage-Experimente realisiert werden, die zeitaufgelöste Braggbeugung auf einer fs-Zeitskala demonstrieren. Bei dieser Technik wird ein Teil des Laserimpulses zur optischen Anregung einer Probe abgespalten und zeitlich zum röntgenerzeugenden Laserimpuls verzögert. Mit der zeitlich exakt synchronisierten Röntgenstrahlung kann der zeitliche Verlauf der Beugungsintensität verfolgt werden. Mit dieser Methode konnte der direkte Übergang eines laserbestrahlten Materials von der Fest- in die Flüssigphase auf einer fs-Zeitskala beobachtet werden. Als Proben wurden dünne, einkristalline Ge-Schichten (111) auf einem Si-Substrat (111) verwendet. Es wurde nachgewiesen, dass es sich bei dem beobachteten Schmelzvorgang um einen nicht-thermischen, durch elektronische Hochanregung ausgelösten Phasenübergang handelt, und beobachtet, dass der Phasenübergang von der Fest- in die Flüssigphase innerhalb von 300 fs stattfindet. Durch Entfalten der Messdaten kann die Länge des Röntgenimpulses auf ca. 250-300 fs abgeschätzt werden. Aus der Winkelverschiebung der Beugungsprofile lassen sich Drücke, Temperaturen sowie die thermische Expansion des Materials abschätzen. In einem weiteren zeitaufgelösten Experiment wurde die kohärente A1g-Phononenmode durch Röntgenbeugung verfolgt. Die Kristallschwingung lässt sich durch einen kurzen Laserimpuls anregen. Die Effizienz der Braggbeugung wird durch das Phonon moduliert. Durch Berechnung des Strukturfaktors als Funktion der Auslenkung des Phonons lassen sich die Amplituden durch die Braggbeugung messen. Es wurden Experimente in den Beugungsrichtungen (111) und (222) durchgeführt. Beide Richtungen zeigen übereinstimmend eine Phononenfrequenz von ungefähr 2,1 THz. Bei massiver Anregung entstehen Amplituden von 10% des nächsten Nachbarabstandes.Die Stärke der Amplitude erfüllt das Lindemann-Kriterium für die Schmelzschwelle. Aus den Winkelverschiebungen konnte eine Temperatur abgeschätzt werden, die über dem Schmelzpunkt von Bi liegt. Die Messdaten beider Experimente dokumentieren erstmals die Beobachtung schneller Strukturänderungen mit Hilfe zeitaufgelöster Röntgenbeugungsexperimente mit subfs-Zeitauflösung

The dark side of global sourcing: a systematic literature review and research agenda

Purpose: The purpose of this paper is to present a systematic review of the literature concerning the negative aspects of global sourcing (GS). It complements prior research on the positive aspects of GS, advances theoretical understanding of the phenomenon, and suggests an agenda for future research. Design/methodology/approach: The sourcing, international business and supply chain management literature is systematically reviewed and findings from 83 previous studies are investigated. Findings: Research on the downsides of GS has intensified over the last decade, but the related knowledge has been very fragmented and oftentimes latent. This literature review extracts knowledge around 28 antecedents to GS downsides from the literature and illustrates their potential harmful effects along operational and financial performance dimensions. Findings suggest that future research should focus more on the effects of decision-making biases and the effects of firm-internal barriers. The dynamic and hidden costs of GS should also be scrutinized in more depth. Originality/value: This study is the first systematic literature review of the downsides of GS. It facilitates a more balanced and nuanced picture of GS to help managers make better-informed GS decisions. The review also offers a holistic research framework that opens up avenues for much-needed research into the “dark side” of GS

Historizing international organizations and their communication – institutions, practices, changes

The Thematic Section focuses on a topic that has thus far received little attention from communication and media researchers: the history of international organizations and their communication. Since the second half of the 19th century, for numerous and diverse areas of social life, globally active international organizations of varying degrees of institutionalization and scope, both non-governmental and intergovernmental, have been founded and have dedicated themselves to the global challenges of the first modern age (Herren, 2009). The most famous of these is certainly the League of Nations, which was established in 1919 as the predecessor institution of the United Nations

Neue digitale Formate für die Kommunikation von CO2-Einsparungspotentialen für Deutschland

KlimakommunikationDer durch den Menschen verursachte Klimawandel ist eine der drängendsten Herausforderungen der Gegenwart. Die Helmholtz-Gemeinschaft leistet wichtige Beiträge um die Ursachen der klimatischen Veränderung einzudämmen und Anpassungsmöglichkeiten zu finden. Mit der Helmholtz-Klima- Initiative konzentriert sich die Forschung auf die beiden Schwerpunkte „Vermeidung von Emissionen“ und „Anpassung an Klimafolgen“. In Netto-Null-2050, Cluster I der Helmholtz-Klima- Initiative, werden Strategien und Wege zur Minderung von Kohlenstoff Emissionen wissenschaftlich untersucht und bewertet. Im Clusters I werden zwei Formate entwickelt, mit denen die komplexen Ergebnisse der Forschung verständlich gezeigt werden können. Mit dem web-basierten Netto-Null- Atlas wird der Nutzer zu verschiedenen Methoden und Technologien zur CO2-Verminderung, sowie zu möglichen Reduzierungspfaden informiert. Die native Boden-Kohlenstoff-App ermöglicht Akteuren in der Landwirtschaft, Potentiale für Klimaschutz durch landwirtschaftliche Managementmethoden abzuschätzen. Mit dem Landoberflächenmodell CLM werden Zukunftsszenarien simuliert, die über cloud-basierte, modell-gesteuerte Workflows in der App dargestellt werden. Beide Formate haben das Ziel die Nutzer in Entscheidungen und bei der Entwicklung von Strategien zu unterstützen. Wichtige Ziele während der Arbeit an den Produkten sind u.a. eine gute Verständlichkeit, Transparenz und eine angemessene Informationsaufbereitung. Dabei werden beispielsweise im Atlas verschiedene Abstraktionslevel eingeführt, die den Nutzern mit sehr unterschiedlichem Vorwissen und Informationsbedarf Erkenntnisgewinne ermöglichen. Daneben ergibt sich unter dem Aspekt der Transparenz z.B. die Frage, wie in der App mit der Thematik „Unsicherheiten“ umgegangen werden kann. Der Beitrag stellt die beiden Disseminations-Produkte sowie die Herausforderungen und Lösungsansätze aus der Entwicklungsarbeit vor

Faecal Escherichia coli as biological indicator of spatial interaction between domestic pigs and wild boar (Sus scrofa) in Corsica

On the Mediterranean island of Corsica, cohabitation between sympatric domestic pigs and Eurasian wild boar (Sus scrofa) is common and widespread and can facilitate the maintenance and dissemination of several pathogens detrimental for the pig industry or human health. In this study, we monitored a population of free-ranging domestic pigs reared in extensive conditions within a 800-ha property located in Central Corsica which was frequently visited by a sympatric population of wild boar between 2013 and 2015. We used GPS collars to assess evidence of a spatially shared environment. Subsequently, we analysed by PFGE of XbaI-restricted DNA if those populations shared faecal Escherichia coli clones that would indicate contact and compared these results with those collected in a distant (separated by at least 50 km) population of wild boar used as control. Results showed that one of eight wild boars sampled in the study area shed E. coli XbaI clones identical to clones isolated from domestic pig sounders from the farm, while wild boar populations sampled in distant parts of the study area shared no identical clone with the domestic pigs monitored. Interestingly, within the sampled pigs, two identical clones were found in 2013 and in 2015, indicating a long-time persisting colonization type. Although the method of isolation of E. coli and PFGE typing of the isolates requires intensive laboratory work, it is applicable under field conditions to monitor potential infectious contacts. It also provides evidence of exchange of microorganisms between sympatric domestic pigs and wild boar populations. (Résumé d'auteur

Tools and opportunities for African swine fever control in wild boar and feral pigs : a review

DATA AVAILABILITY : All data used are already included in this manuscript.SUPPLEMENTARY MATERIAL : APPENDIX S1: complete list of references from literature review. APPENDIX S2: additional tables providing further details about EFSA reports, primary research in African swine fever (ASF), checklist for preparedness in the event of ASF (strengths and weakness). APPENDIX S3: detailed information on the point introductions in Czech Republic, Belgium and Italy.The native Eurasian wild boar (Sus scrofa) is a relevant wildlife host for African swine fever (ASF) virus, contributing to infection maintenance and spread and representing a challenge for disease control. Combining published scientific evidence with expert opinion, we provide an updated global overview of ASF control in wild boar and feral pigs in different epidemiological scenarios. We synthesize current knowledge on key background aspects of wild boar ecology and management and on ASF epidemiology in wild boar and their relative, the feral pig. We propose that establishing a proper surveillance and monitoring scheme is a requisite for disease control in wildlife and that ASF and wild boar should be monitored in an integrated way, considering the changes in the host population as well as the spatial spread and temporal distribution of disease indicators, to make possible a critical assessment of the impact of interventions. The main body of the manuscript reviews the intervention options and ASF control attempts and their outcomes in different epidemiological situations from peacetime to endemicity. Current ASF control in wild boar relies on three essential tools: carcass destruction, wild boar culling, and fencing. The experience gained since the onset of the ongoing ASF pandemic shows that certain combinations of interventions can slow down ASF spread and eventually succeed in ASF eradication in wild boar, at least after point introductions. Several strengths and weaknesses of these strategies are identified.The Università Degli Studi di Torino-Dipartimento di Scienze Veterinarie and from University of Castilla-La Mancha through a Margarita Salas.http://link.springer.com/journal/10344hj2024Veterinary Tropical DiseasesSDG-03:Good heatlh and well-bein

Research priorities to fill knowledge gaps on ASF seasonality that could improve the control of ASF

The European Commission requested EFSA to provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: i) the patterns of seasonality of ASF in wild boar and domestic pigs in the EU; ii) the ASF epidemiology in wild boar; iii) ASF virus (ASFV) survival in the environment and iv) ASF transmission by vectors. In this Scientific Opinion, the first research domain on ASF seasonality is addressed. Therefore, five research objectives were proposed by the working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the five research objectives, only two were prioritised and elaborated into a general protocol/study design research proposal, namely: 1) to monitor the herd incidence of ASF outbreaks in EU Member States (MS) and 2) to investigate potential (seasonal) risk factors for ASF incursion in domestic pig herds of different herd types and/or size. To monitor the incidence in different pig herd types, it is advised to collect, besides ASF surveillance data, pig population data describing at least the following parameters per farm from the first moment of incursion in an affected MS: the numbers of pigs (e.g. number of breeding pigs sows and boars, weaners and fatteners) and the location and the type of farm (including details on the level of biosecurity implemented on the farm and the outdoor/indoor production). We suggest collecting data from all ASF‐affected MS through the SIGMA data model, which was developed for this purpose. To investigate potential risk factors for ASF incursion in domestic pig herds, we suggest a matched case–control design. Such a study design can be run either retrospectively or prospectively. The collected data on the pig herds and the ASF surveillance data in the SIGMA data model can be used to identify case and control farms.info:eu-repo/semantics/publishedVersio

Research objectives to fill knowledge gaps in African swine fever virus survival in the environment and carcasses, which could improve the control of African swine fever virus in wild boar populations

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; ii) the epidemiology of ASF in wild boar; iii) survival of ASF virus (ASFV) in the environment and iv) transmission of ASFV by vectors. In this Scientific Opinion, the third research domain on ASFV survival is addressed. Nine research objectives were proposed by the working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the nine research objectives, only one was prioritised and elaborated into a general protocol/study design research proposal, pertaining ASFV survival in feed and bedding. To investigate the survival of ASFV in feed, bedding and roughage, laboratory survival studies are proposed. To investigate possible risk mitigation measures, proof-of-concept approaches should be investigated.info:eu-repo/semantics/publishedVersio

Research priorities to fill knowledge gaps in the control of African swine fever: possible transmission of African swine fever virus by vectors

The European Commission requested that EFSA provide study designs for the investigation of four research domains according to major gaps in knowledge identified by EFSA in a report published in 2019: (i) the patterns of seasonality of African Swine Fever (ASF) in wild boar and domestic pigs in the EU; (ii) the epidemiology of ASF in wild boar; (iii) survival of ASF virus (ASFV) in the environment and (iv) transmission of ASFV by vectors. In this Scientific Opinion, the fourth research domain on ASFV transmission by vectors is addressed. Eleven research objectives were proposed by the EFSA working group and broader ASF expert networks, such as ASF stop, ENETWILD, VectorNet, AHAW network and the AHAW Panel Experts. Of the 11 research objectives, six were prioritised based on the following set of criteria: (1) the impact on ASF management; (2) the feasibility or practicality to carry out the study; (3) the potential implementation of study results in practice; (4) a possible short time-frame study (< 1 year); (5) the novelty of the study and (6) if it was a priority for risk managers. The prioritised research objectives were: (I) Studies on the potential vector fauna at the pig–wild boar interface and the feeding preference of blood-feeding potential vectors in ASF-affected areas; (II) Assessment of the efficacy of insect screens on indoor/outdoor pig holdings to prevent the entry of blood-sucking vectors (i.e. Stomoxys) in ASF endemic areas; (III) Assess the role of mechanical vectors in the virus transmission in ASF-affected areas; (IV) Distribution of the potential mechanical transmission vectors in ASF-affected areas of the EU; (V) ASFV transmission by synanthropic birds; and (VI) Assessment on the presence/absence of the soft tick Ornithodoros erraticus in ASF-affected areas in Europe. For each of the selected research objectives, a research protocol has been proposed considering the potential impact on ASF management and the period of 1 year for the research activities.info:eu-repo/semantics/publishedVersio

African swine fever and outdoor farming of pigs

This opinion describes outdoor farming of pigs in the EU, assesses the risk of African swine fewer (ASF) introduction and spread associated with outdoor pig farms and proposes biosecurity and control measures for outdoor pig farms in ASF-affected areas of the EU. Evidence was collected from Member States (MSs) veterinary authorities, farmers’ associations, literature and legislative documents. An Expert knowledge elicitation (EKE) was carried out to group outdoor pig farms according to their risk of introduction and spread of ASF, to rank biosecurity measures regarding their effectiveness with regard to ASF and propose improvements of biosecurity for outdoor pig farming and accompanying control measures. Outdoor pig farming is common and various farm types are present throughout the EU. As there is no legislation at European level for categorising outdoor pig farms in the EU, information is limited, not harmonised and needs to be interpreted with care. The baseline risk of outdoor pig farms for ASFV introduction and its spread is high but with considerable uncertainty. The Panel is 66–90% certain that, if single solid or double fences were fully and properly implemented on all outdoor pig farms in areas of the EU where ASF is present in wild boar and in domestic pigs in indoor farms and outdoor farms (worst case scenario not considering different restriction zones or particular situations), without requiring any other outdoor-specific biosecurity measures or control measures, this would reduce the number of new ASF outbreaks occurring in these farms within a year by more than 50% compared to the baseline risk. The Panel concludes that the regular implementation of independent and objective on-farm biosecurity assessments using comprehensive standard protocols and approving outdoor pig farms on the basis of their biosecurity risk in an official system managed by competent authorities will further reduce the risk of ASF introduction and spread related to outdoor pig farms.info:eu-repo/semantics/publishedVersio