48674 research outputs found
Sort by
Theorizing temporary organizing to foster true cross fertilization: Focus on projects, processes and practices
No full textExtant scholarship in project studies is calling for fertilizing across disciplines to pave the way to stronger theorizing. This essay responds to this call by spurring a debate on how to theorize temporary organizing in new and creative ways — both broadly and with a particular focus on projects, arguably the most prevalent form of such organizing. We propose addressing projects and other forms of temporary organization as processual, practice-based phenomena that provide ample opportunities to foster cross-fertilization, in particular between the related disciplines of organization and project studies. To this end, we argue that theoretical advancements in a discipline can occur on a spectrum—ranging from leveraging reference theories from related fields (a top-down approach) to developing home-grown theories grounded in empirical research (a bottom-up approach). This spectrum serves as the foundation for this essay, as we develop this processual, practice-based perspective to project studies by illustrating how (1) reference theories from organization studies such as practice-driven institutionalism generate new insights on temporary organizing and (2) home-grown theories of temporary organizing generated by studying projects and other forms of temporary organization may have theoretical and practical implications beyond project studies
Complete protection of NIR-luminescent molecular rubies from oxygen quenching in air by L-arginine-mediated silica nanoparticles
No full textThe application of emerging luminophores such as near-infrared (NIR) emissive complexes based on earth-abundant chromium as central ion and triplet-triplet annihilation upconversion (TTA-UC) systems in air as optical reporters for bioimaging or photonic materials for energy conversion requires simple and efficient strategies for their complete protection from luminescence quenching by oxygen. Therefore, we explored the influence of sol–gel synthesis routes on the oxygen protection efficiency of the resulting core and core/shell silica nanoparticles (SiO2 NPs), utilizing the molecular ruby-type luminophores CrPF6 ([Cr(ddpd)2](PF6)3; ddpd = N,N'-dimethyl-N,N'-dipyridin-2-ylpyridin-2,6-diamine) and CrBF4 ([Cr(ddpd)2](BF4)3) with their oxygen-dependent, but polarity-, proticity-, viscosity-, and concentration-independent luminescence as optical probes for oxygen permeability. The sol–gel chemistry routes we assessed include the classical Stöber method and the underexplored L-arginine approach, which relies on the controlled hydrolysis of tetraethoxysilane (TEOS) in a biphasic cyclohexane/water system with the catalyst L-arginine. As demonstrated by luminescence measurements of air- and argon-saturated dispersions of CrPF6- and CrBF4-stained SiO2 NPs of different size and particle architecture, utilizing the luminescence decay kinetics of argon-saturated solutions of CrPF6 and CrBF4 in acetonitrile (ACN) as benchmarks, only SiO2 NPs or shells synthesized by the L-arginine approach provided complete oxygen protection of the CrIII complexes under ambient conditions. We ascribe the different oxygen shielding efficiencies of the silica networks explored to differences in density and surface chemistry of the resulting nanomaterials and coatings, leading to different oxygen permeabilities. Our L-arginine based silica encapsulation strategy can open the door for the efficient usage of oxygen-sensitive luminophores and TTA-UC systems as optical reporters and spectral shifters in air in the future
Event-based analysis of weather-related fire brigade operations in the response area of the dispatch center Allgäu
No full textExtreme Wettersituationen führen immer wieder zu einem abrupten Anstieg eingehender Notrufe in Leitstellen der Feuerwehren. Datenbasierte Vorhersagemodelle für wetterbedingte Feuerwehreinsätze könnten dem Führungspersonal in der Leitstelle dabei helfen, präventive Maßnahmen besser zu planen und umzusetzen. Für die Entwicklung solcher Modelle ist wichtig, die relevante Wettergefahren und deren Auswirkungen auf das Einsatzgeschehen zu kennen. Deshalb wurde eine ereignisbasierte Analyse wetterbedingter Feuerwehreinsätze im Zuständigkeitsgebiet der Leitstelle Allgäu durchgeführt. Diese Analyse liefert wertvolle Einblicke in die Häufigkeit und Eigenschaften von Ereignissen mit erhöhtem Einsatzaufkommen. Z.B. stehen Gewittersituationen im Zusammenhang mit 26% der analysierten Ereignisse und führen oft zu einer hohen stündlichen Einsatzzahl innerhalb kurzer Zeit. Im Vergleich dazu verteilen sich Einsätze bei großflächige Stürme und Starkregen auf längere Zeiträume. Auf Grundlage der Ergebnisse wird im nächsten Schritt die Entwicklung von Modellen zur Einsatzvorhersage durchgeführt.Extreme weather conditions repeatedly lead to a sudden increase in incoming emergency calls at fire brigade dispatch centers. Data-driven prediction models for weather-related fire brigade operations could support command staff in planning and implementing preventive measures more effectively. For the development of such models, it is essential to identify the relevant weather hazards and their impacts on operational activity. Therefore, an event-based analysis of weather-related fire brigade operations in the response area of the Allgäu Dispatch Center was conducted. This analysis provides valuable insights into the frequency and characteristics of events associated with increased operational demand. For example, thunderstorm situations account for 26% of the analyzed events and often result in a high hourly number of operations within short time periods. In comparison, large-scale storms and heavy rainfall also high numbers of operations, but these are distributed over longer periods of time. Based on these results, the next step will be the development of models for operation forecasting
Unveiling single-particle composition, size, shape, and mixing state of freshly emitted Icelandic dust via electron microscopy analysis
No full textIceland is a significant high-latitude dust source area. Airborne Icelandic dust influences the climate system by interacting with radiation, clouds, and biogeochemical cycles; it also affects snow and ice albedo and air quality. These impacts are sensitive to the dust’s mineralogical, chemical, and physical properties. However, comprehensive measurements and analyses of Icelandic dust particles remain limited. This study examines dust samples collected during a field campaign in the Dyngjusandur desert (August–September 2021) using active and passive aerosol sampling. Over 190 000 individual particles, ranging from 0.1 to 120 µm, were analyzed for their chemical and physical properties using computer-controlled scanning electron microscopy/energy-dispersive X-ray spectroscopy (ccSEM/EDX). Results show heterogeneity in particle size, shape, and composition. The most abundant particle type was medium-Al mixed particles, likely glass-like, comprising 35 %–92 % of the aerosol volume. Sulfate particles, suggesting volcanic contributions, were detected in some samples. Iron (Fe)- and titanium (Ti)-rich particles made up 3.3 % and 6 % of the aerosol volume, respectively, mainly in the size fraction <1 µm. The median aspect ratio ranged from 1.37 to 1.53, increasing with particle size. Our findings highlight key differences in Icelandic dust compared to Saharan dust, including higher iron and titanium content and a lack of potassium in Icelandic dust. Additionally, Icelandic dust shows a size-dependent increase in aspect ratio, unlike Saharan dust, which remains constant. These observations can improve model simulations that account for the effect of high-latitude dust in the Earth system
Subdiffusion from competition between multi-exponential friction memory and energy barriers
No full textSubdiffusion is a hallmark of complex systems, ranging from protein folding to transport in viscoelastic media. However, despite its pervasiveness, the mechanistic origins of subdiffusion remain contested. Here, we analyze both Markovian and non-Markovian dynamics, in the presence and absence of energy barriers, in order to disentangle the distinct contributions of memory-dependent friction and energy barriers to the emergence of subdiffusive behavior. Focusing on the mean squared displacement (MSD), we develop an analytical framework that connects subdiffusion to multi-scale memory effects in the generalized Langevin equation (GLE), and derive the subdiffusive scaling behavior of the MSD for systems governed by multi-exponential memory kernels. We identify persistence and relaxation timescales that delineate dynamical regimes in which subdiffusion arises from either memory or energy barrier effects. By comparing analytical predictions with simulations, we confirm that memory dominates the overdamped dynamics for barrier heights up to approximately 2 kBT, a regime recently shown to be relevant for fast-folding proteins. Overall, our results advance the theoretical understanding of anomalous diffusion and provide practical tools that are broadly applicable to fields as diverse as molecular biophysics, polymer physics, and active matter systems
Sonication-assisted emulsification: Analyzing different polymers in aqueous systems for microparticle preparation by the double emulsion technique
No full textSonication-assisted emulsification has emerged as a powerful technique for the preparation of microparticles in various fields, including pharmaceuticals, cosmetics, and food science. This study aims to investigate the impact of different polymers in an aqueous system on the preparation of microparticles by the double emulsion technique. By understanding the factors that affect emulsification and stability, we can optimize the production of microparticles with desired characteristics. This study discusses the mechanism behind sonication-assisted emulsification, the various polymers used, and the analysis of particle size, morphology, and stability. The microparticle were prepared with a water-in-oil-in-water (W/O/W) solvent evaporation method, for various polymers (including EC 4 cp, Eudragit® RS 100, Eudragit® RL 100, PLGA (RG503H) and PCL) that solvent used dichloromethane. The particle size/distribution of the emulsion droplets/hardened microparticles was monitored using FBRM. The morphology of polymeric microparticles was characterized using scanning electron microscopy (SEM). The transformation of the emulsion droplets into solid microparticles occured within the first 11.5, 20, 26, 30.5 and 56 min when EC 4 cp, Eudragit® RS 100, Eudragit® RL 100, PLGA (RG503H) and PCL were used respectively. The square weighted mean chord length of PCL microparticles was smallest, but the chord count was not the highest. The chord length distribution (CLD) measured by FBRM showed that a larger mean particle size gave longer CLD and a lower peak of particle number. SEM data revealed that the morphology of microparticles was influenced by the type of polymer. Sonicator helped in emulsification of polymeric system in aquous. FBRM can be employed for online monitoring of the shift in the microparticle CLD and detect transformation of emulsion droplets into solid microparticles during the solvent evaporation process. The microparticle CLD and transformation process were strongly influenced by polymer type
Ferrocene-Based Ozonide: [CpFeCpCH2NMe3]O3·1.47 NH3, Synthesis and Crystal Structure Analysis
No full textThe highly reactive ozonide anion could be stabilized for the first time with a ferrocene-based cation resulting in the title compound [CpFeCpCH2NMe3]O3·1.47 NH3. The target compound was thoroughly characterized by X-ray diffraction [P21/c a = 1778.33(8) pm, b = 811.70(4) pm, c = 1111.71(5) pm, β = 91.715(2)°, R = 0.0325, 40301 reflections]. Additionally, infrared spectroscopy as well as quantum chemical calculations of the embedded anion were carried out to further characterize the compound and investigated the O-O bond lengths and O-O-O bond angles of the ozonide anion
Funktionalisierung von Hämoglobin-Mikropartikeln als Medikamententransporter für ein spezifischeres und effektiveres Targeting von Krebszellen
No full textIn the light of rising cancer rates, the development of more effective and specific cancer therapies is essential. Protein microparticles (MPs) as drug delivery vehicles have shown many advantages such as biodegradability, non-immunogenicity and biocompatibility. They have the potential to solve common limitations in the application of anticancer drugs including poor water solubility, dose-limiting toxicity, poor targeting and anticancer drug resistance. The hemoglobin-MPs (HbMPs) were prepared using a newly developed Coprecipitation-Crosslinking-Dissolution (CCD) and one-pot method. Different approaches to improve cell targeting of the MPs, including Layer-by-Layer assembly with the oppositely charged polyelectrolytes alginate, polyethyleneimine (PEI) and human serum albumin (HSA) and functionalization with active C-end rule (CendR) peptides (P-OH) and control peptides (P-NH2) were investigated. CendR peptides bind to the NRP-1 receptor, which is overexpressed by most solid tumors. Cellular uptake was evaluated by FACS measurement and CLSM, and the metabolic effect of the MPs on the cells was assessed by CCK-8 assay. In additional experiments, the one-pot MPs were loaded with the chemotherapeutic agent doxorubicin (DOX). In NRP-1 positive PPC1 cells, LbL-assembly increased the percentage of cells with internalized HbMPs after 24h to more than 90%, compared to uncoated HbMPs which were internalized by less than 10% of cells. Additional functionalization with CendR peptides did not further increase the uptake. In NRP-1 negative M21 cells, uncoated HbMPs were taken up by 22% of the cells and LbL-coated HbMPs were taken up by about 64% of the cells after 24h. When functionalized with peptides, P-LbL-HbMPs were found in more than 90% of the M21 cells after 24h. Pre-incubation of both cell lines with Anti-NRP-1 antibodies did not influence the uptake of the MPs. None of the evaluated MPs affected cell viability or metabolic activity. Using the one-pot fabrication method, a DOX drug-loading efficiency of 77% was achieved. The increased endocytosis of MPs by the investigated cells, achieved through surface modification of the MPs, represents an important step in the development of protein MPs as drug carriers. Further experiments are necessary to confirm or refute the hypothetical mechanisms that led to the enhanced uptake of P-LbL-HbMPs in NRP-1 negative M21 cells as a result of the LbL coating.Weltweit steigende Krebsraten erfordern die Entwicklung wirksamerer und zielgerichteterer Tumortherapien. Die derzeit verfügbaren Therapieoptionen weisen zahlreiche Einschränkungen auf, wie z.B. schlechte Wasserlöslichkeit der Medikamente, dosislimitierende Toxizität, unzureichendes Zelltargeting und Arzneimittelresistenz. Die Entwicklung von Protein-Mikropartikeln (MP) als Wirkstoffträger stellt eine vielversprechende Alternative zur Überwindung dieser Herausforderungen dar. Im Vergleich zu vielen anderen Wirkstoffträgern sind Protein-MP biokompatibel, biologisch abbaubar und nicht immunogen. Die hier verwendeten Hämoglobin-MP (HbMP) wurden nach der neu entwickelten Coprecipitation-Crosslinking-Dissolution (CCD) und One-Pot Methode hergestellt. Verschiedene Methoden zur Verbesserung des Zelltargetings wurden untersucht, wie z.B. die Layer-by-Layer (LbL) Beschichtung mit den entgegengesetzt geladenen Polyelektrolyten Alginat, Polyethylenimin (PEI) und Humanes Serum Albumin (HSA) und die Funktionalisierung mit aktiven C-end rule (CendR) Peptiden. CendR-Peptide binden an den NRP-1-Rezeptor, der von vielen Tumorzellen überexprimiert wird. Die Aufnahme der MP wurde an NRP-1 positiven PPC1 Zellen und NRP-1 negativen M21 Zellen mittels FACS Messungen und CLSM untersucht und die metabolischen Effekte auf die Zellen mit dem CCK-8 Test bestimmt. In weiteren Experimenten wurden die One-Pot MP mit dem Chemotherapeutikum Doxorubicin (DOX) beladen. In PPC1 Zellen führte die LbL-Beschichtung der HbMP nach 24h zu einer Aufnahme in mehr als 90 % der Zellen, während unbeschichtete HbMP von weniger als 10% der Zellen aufgenommen wurden. Eine weitere Funktionalisierung der LbL-HbMP mit CendR-Peptiden führte zu keiner weiteren Steigerung der Aufnahme. In den M21 Zellen waren nach 24h durchschnittlich 64% der Zellen mit LbL-HbMP beladen, während die mit Peptiden funktionalisierten P-LbL-HbMP von mehr als 90% der Zellen aufgenommen wurden. Die Vorinkubation mit Anti-NRP-1 Antikörpern zeigte in beiden Zelllinien keine Auswirkung auf die Aufnahme der MP. Zudem beeinflusste keiner der untersuchten MP die Zellviabilität. Zusätzlich zu den Zellversuchen konnte mit der One-Pot-Methode eine DOX-Einschlusseffizienz von circa 77% erreicht werden. Die durch die Oberflächenmodifikation der MP erreichte Steigerung der Endozytose der MP durch die untersuchten Zellen stellt einen wichtigen Schritt in der Entwicklung von Protein-MP als Medikamententransporter dar. Weiterführende Versuche sind notwendig, um die hypothetischen Mechanismen, die zur verstärkten Aufnahme von P-LbL-HbMP in NRP-1 negativen M21 Zellen infolge der LbL-Beschichtung führten, zu bestätigen oder zu widerlegen
Die Preisfragen der französischen Akademien (1670–1794) als Medium der Wissensreflexion
No full textDie Preisfragen der französischen Akademien entwickelten sich im 18. Jahrhundert zu einem populären Medium der europäischen Gelehrtenrepublik. Durch die ungewöhnlich inklusiven Zugangsbedingungen mobilisierte der concours académique eine beträchtliche Teilnehmer*innenschaft über den herkömmlichen Gelehrtenstand hinaus. Dieses öffentlichkeitswirksame Genre erschließt die Breite des zeitgenössischen Wissenstransfers abseits der bekannten Autoren und etablierten Debattenforen.
Martin Urmann geht in seiner Studie der Frühgeschichte des concours académique seit 1670 nach und rekonstruiert die wissens- und mediengeschichtlichen Voraussetzungen dieser vielbeachteten, aber noch immer wenig erforschten Gattung. Die Preisfragenpraxis gründet tief in den Langfristtraditionen von Dialektik und Rhetorik und verbindet die frühneuzeitlichen Akademien entgegen deren historischer Selbstdarstellung mit den scholastischen Wissenstechniken an den Universitäten. Der concours académique wirft somit ein anderes Licht auf die Gelehrtenkultur der Sozietätsbewegung und legt deren agonale Wurzeln frei. Vor diesem Hintergrund wird sodann der sich wandelnde Geltungsanspruch greifbar, den die Preisfragenliteratur im Laufe des 18. Jahrhunderts bekundet. Nun werden speziell die prix d’éloquence zu einem Reflexionsmedium der prägenden epistemischen Verschiebungen innerhalb der Gelehrtenrepublik seit dem 17. Jahrhundert. Sie gehen den tiefgreifenden Veränderungen, die mit der Umstellung auf Distanzkommunikation im Medium der Schrift und mit dem Wissensmodus der Akkumulation von Fakten verbunden sind, kritisch auf den Grund
Timing and cultural-environmental context of the spread of barley to and within northern East Asia
No full textWhile the introduction of wheat into early full-scale farming systems of northern China has received much research attention over the past two decades, few studies have looked at when and how the cultivation of barley, which is better adapted to colder climates, spread across East Asia. New radiocarbon (14C) dates obtained from archaeological barley grains together with material evidence suggest that the crop was introduced to Primorye (Russia’s border region with China and North Korea) no later than the 2nd century BCE, although an earlier arrival sometime between the 4th and 3rd centuries BCE seems possible. From Primorye, the crop probably spread further eastward to Hokkaido. The combined archaeological and chronological evidence suggests that barley-cultivating cultural groups may have migrated to southern Primorye from areas to the west or from southern Liaoning/north-western Korea, which rules out a dispersal via the northern Eurasian steppes or the Japanese archipelago. We propose that a combination of cultural and climatic factors was the driving force behind this migration. While we identify the eastward expansion of the Warring State of Yan around 300 BCE as the primary driver that pushed barley-cultivating populations to migrate, it seems possible that long-term cooling and drying less favourable for farming during 1000–300 BCE added to the political unrest at the northern and eastern boundaries of the Chinese Warring States, or may even have amplified their policies of territorial expansion