The evolution of a citation network topology: The development of the journal Scientometrics

By mapping the electronic database containing all papers in Scientometrics for a 26-year period (1978-2004), we uncover the topological measures that characterize the network at a given moment, as well as the time evolution of these quantities. The citation network of the journal displays the characteristic features of a “small-world” network of local dense clusters of highly specialized literature. These clusters, however, are efficiently connected into a large single component by a small number of “hub” papers that allow short-distance connection among increasingly large numbers of papers. The patterns of evolution of the network toward this “small-world” are also explored

Synthesis and Structures of Dinuclear Aluminum Complexes Based on Bis(β‐diketiminate) Ligands

A series of ten dinuclear aluminum alkyl complexes based on rigid, semirigid, and flexible bis(β‐diketiminate) ligands (NacNac) has been obtained from the reaction of trimethylaluminum and the corresponding bis(β‐diketimine)s. All compounds were fully characterized using NMR and IR spectroscopy and elemental analysis. The molecular structures of five compounds have been investigated by means of single‐crystal X‐ray diffraction analysis.image John Wiley & Sons, Ltd

C-N coupling in the gas-phase reactions of ammonia and [M(CH)](+) (M = Ni, Pd, Pt): a combined experimental/computational exercise

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Electrospray ionization (ESI) of methanolic solutions of monomeric nickel(II) acetate, [Ni(CH3COO)2], and tetrameric platinum(II) acetate, [Pt4(CH3COO)8], leads to the formation of the corresponding methylidyne complexes [M(CH)]+ (M = Ni, Pt), which react with ammonia under C–N coupling. While the product couples M/[CH4N]+ and [M(CH2N)]+/H2 are observed for both metals, hydrogen-atom expulsion to generate [M(CHNH2)]+/H is only observed in the case of the nickel-containing system, and the proton transfer leading to M/[NH4]+ is limited to platinum. Attempts to conduct related experiments with [Pd(CH)]+/NH3 failed. The mechanisms that explain the experimentally observed reaction channels have been investigated computationally using the B3LYP functional for all metals of the nickel group (M = Ni, Pd, Pt). In line with labeling experiments using the reaction pairs [M(CD)]+/NH3 and [M(CH)]+/ND3 (M = Ni, Pt), two different mechanistic scenarios of the dehydrogenation process are operative for the Ni and Pt systems, respectively.DFG, EXC 314, Unifying Concepts in Catalysi

simpleISM—A straight forward guide to upgrade from confocal to ISM

Resolution in a confocal laser scanning microscopes (CLSM) can be improved if the pinhole is closed. But closing the pinhole will deteriorate the signal to noise ratio (SNR). A simple technique to improve the SNR while keeping the resolution same by upgrading the system to an image scanning microscope. In this paper, we explain in detail, based on an Olympus Fluoview 300 system, how a scanning microscope can be upgraded into an image scanning microscope (ISM) using a simple camera-based detector and an Arduino Due providing a galvo driving and camera synchronization signals. We could confirm a resolution improvement as well as superconcentration and made the interesting observation of a reduced influence of laser fluctuations

A molecular aluminium fulleride

Funding: The project was financially supported by the Deutsche Forschungsgemeinschaft (DFG, KR4782/3-1), the EPSRC (PhD studentship for S. R. L.; EP/N509759/1), and the Chemnitz University of Technology.The reaction of alumylene [(Dippnacnac)Al] (1) with C60 fashions the first example of a structurally characterised aluminium-fulleride complex, [{(Dippnacnac)Al}3C60] (2), in which the Al centres are covalently bound to significantly elongated 6:6 bonds. Hydrolysis of 2 yields C60H6 and the reaction of 2 with [{Mesnacnac)Mg}2] cleaved the Al fragments by affording the fulleride [{Mesnacnac)Mg}6C60].PostprintPeer reviewe

Expedition Anthropocene

Viele Gigabyte gesammelter Daten, verschiedenartigste Eindrücke und Erfahrungen, festgehalten in Fotografien und Audioaufnahmen, und vor allem die Erkenntnis, was Wissenschaft heute leisten kann und leisten muss: Damit reist die Expedition Anthropozän der Jungen Akademie im März 2020 zurück nach Deutschland. Zuvor untersuchen siebzehn Tage lang die Wissenschaftler*innen Miriam Akkermann, Martin-Immanuel Bittner, Christian Hof, Robert Kretschmer, Dirk Pflüger und Ricarda Winkelmann als interdisziplinäres Forschungsteam die Auswirkungen des Anthropozäns in verschiedenen Höhenlagen Ecuadors. Im Fokus der Expedition stehen die folgenden Fragen: Wie verändert der vom Menschen verursachte Klimawandel die belebte und unbelebte Umwelt? Und wie kann der Mensch seiner Verantwortung als geologische Einflussgröße gerecht werden? Diese Fragen führen das Team von der Großstadt über Gletscher in der dünnen Luft es Hochgebirges bis in den artenreichen Nebelwald Ecuadors. Es sind intensive, zum Teil auch von Strapazen und Regenwetter geprägte Tage. Die ungewöhnliche Konstellation von Fachgebieten – von der Musikwissenschaft bis zur Informatik – und Methoden – von Eiskernbohrungen bis zu Klangaufnahmen – erfordert Kooperation, Flexibilität und Anpassung an das übergeordnete Ziel. Nur so wird die Expedition der Komplexität des Themas gerecht – und es ist anzunehmen, dass sich auch die Herausforderungen des globalen Klimawandels nur durch Interdisziplinarität bewältigen lassen werden. Das Anthropozän betrifft alle Menschen, weltweit. Mit dem vorliegenden Dokumentationsband machen die Wissenschaftler*innen ihre Forschung in Ecuador und die daraus gewonnenen Erkenntnisse einem breiten Publikum zugänglich. Die Gliederung des Bandes folgt chronologisch den auf der Expedition beforschten Klimazonen und Siedlungsräumen. Texte, Bilder und weitere Medien laden dazu ein, mitzureisen: Wissenschaftliche Praxis mitzuerleben, beeindruckende Landschaften, Tiere und Pflanzen zu entdecken – und dem Anthropozän dort zu begegnen, wo seine Auswirkungen bereits deutlich spürbar sind.With many gigabytes of collected data, a wide variety of impressions and experiences captured in photographs and audio recordings, and above all the realisation of what science can and must achieve today the Expedition Anthropocene of Die Junge Akademie traveled back to Germany in March 2020. The scientists Miriam Akkermann, Martin-Immanuel Bittner, Christian Hof, Robert Kretschmer, Dirk Pflüger and Ricarda Winkelmann had spent seventeen days as an interdisciplinary research team investigating the effects of the Anthropocene age at various altitudes in Ecuador. The expedition focused on the following questions: How is human-induced climate change altering the living and non-living worlds? And how can humans fulfil their responsibility as a significant influencing factor capable of demarcating an entire geological age? These questions took the team all the way from cities to glaciers in the thin air of the high mountains and to the species-rich cloud forests of Ecuador. It was an intensive trip, and some days were marked by exertion and rainy weather. The unusual constellation of disciplines – from musicology to computer science – and methods – from ice core drilling to sound recording – require cooperation, flexibility and adaptation to the overall goal. Only in this way could the expedition do justice to the complexity of the topic – and it is fair to assume that the challenges of global climate change can likewise only be overcome by means of an interdisciplinary approach. The Anthropocene affects all people, worldwide. In this documentary volume, the scientists make their research in Ecuador and the insights gained from it accessible to a broad audience. The structure of the volume chronologically follows the climatic zones and settlement areas explored on the expedition. Texts, pictures and other media invite you to be part of the journey: to experience scientific practice, to discover impressive landscapes, animals and plants – and to encounter the Anthropocene where its effects are already clearly noticeable

Isolated vertebral fractures give elevated serum protein S-100B levels

<p>Abstract</p> <p>Background</p> <p>Serum protein S-100B determinations have been widely proposed in the past as markers of traumatic brain injury and used as a predictor of injury severity and outcome. The purpose of this prospective observational case series was therefore to determine S-100B serum levels in patients with isolated injuries to the back.</p> <p>Methods</p> <p>Between 1 February and 1 May 2008, serum samples for S-100B analysis were obtained within 1 hour of injury from 285 trauma patients. All patients with a head injury, polytrauma, and intoxicated patients were excluded to select isolated injuries to the spine. 19 patients with isolated injury of the back were included. Serum samples for S-100B analysis and CT spine were obtained within 1 hours of injury.</p> <p>Results</p> <p>CT scans showed vertebral fractures in 12 of the 19 patients (63%). All patients with fractures had elevated S-100B levels. Amongst the remaining 7 patients without a fracture, only one patient with a severe spinal contusion had an S-100B concentration above the reference limit. The mean S-100B value of the group with fractures was more than 4 times higher than in the group without fractures (0.385 vs 0.087 μg/L, p = 0.0097).</p> <p>Conclusion</p> <p>Our data, although limited due to a very small sample size, suggest that S-100B serum levels might be useful for the diagnosis of acute vertebral body and spinal cord injury with a high negative predictive power. According to the literature, the highest levels of serum S-100B are found when large bones are fractured. If a large prospective study confirms our findings, determining the S-100B level may contribute to more selective use of CT and MRI in spinal trauma.</p

A Planar Five‐Membered Aromatic Ring Stabilized by Only Two π‐Electrons

Many chemicals known today are partially or fully aromatic, since a ring framework experiences additional stabilization through the delocalization of π‐electrons. While aromatic rings with equal numbers of π‐electrons and ring atoms such as benzene are particularly stable, those with the minimally required two π‐electrons are very rare and yet remain limited to three‐ and four‐membered rings if not stabilized in the coordination sphere of heavy metals. Here we report the facile synthesis of a dipotassium cyclopentagallene, a unique example of a five‐membered aromatic ring stabilized by only two π‐electrons. Single‐crystal X‐ray diffraction revealed a planar Ga5 ring with almost equal gallium–gallium bond lengths, which together with computational and spectroscopic data confirm its aromatic character. Our results prove that aromatic stabilization goes far beyond what has previously been assumed as minimum π‐electron count in a five‐atom ring fragment.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Verband der Chemischen Industrie http://dx.doi.org/10.13039/100007215Peer Reviewe

Nucleophilic Magnesium Silanide and Silaamidinate Derivatives

Density functional theory (DFT) calculations demonstrate that the previously reported reaction of [(BDI)Mgn-Bu] (BDI = HC{(Me)CN-Dipp}2; Dipp – 2,6-di-iso-propylphenyl) with the silaborane, Me2PhSi-Bpin, provides the magnesium silanide derivative, [(BDI)MgSiMe2Ph], through the intermediacy of a short lived silyl-pinacolato-organoborate species. The nucleophilic character of the resultant silanide anion is assayed through a series of reactions with RN=C=NR (R = i-Pr, Cy, t-Bu) and p-tolN=C=Np-tol. When performed in a strict 1:1 stoichiometry, all four reactions result in silyl addition to the carbodiimide carbon center and formation of the corresponding beta-diketiminato magnesium sila-amidinate complexes. Although performance of the reaction of [(BDI)MgSiMe2Ph] with two equivalents of p-tolylcarbodiimide also results in the formation of a sila-amidinate anion, the second equivalent is observed to engage with the nucleophilic gamma-methine carbon of the BDI ligand to provide a tripodal di-imino-iminoamidate ligand. This behaviour is judged to be a consequence of the enhanced electrophilicity of the N-aryl substituted carbodiimide reagent, a viewpoint supported by a further reaction with the N-isopropyl sila-amidinate complex, [(BDI)Mg(i-PrN)2CSiMe2Ph]. This latter reaction not only provides an identical di-imino-iminoamidate ligand but also results in twofold insertion of p-tolN=C=Np-tol into a Mg-N bond between the magnesium center and the sila-amidinate anion