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

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

Sequential and switchable patterning for studying cellular processes under spatiotemporal control

Attachment of adhesive molecules on cell culture surfaces to restrict cell adhesion to defined areas and shapes has been vital for the progress of in vitro research. In currently existing patterning methods, a combination of pattern properties such as stability, precision, specificity, high-throughput outcome, and spatiotemporal control is highly desirable but challenging to achieve. Here, we introduce a versatile and high-throughput covalent photoimmobilization technique, comprising a light-dose-dependent patterning step and a subsequent functionalization of the pattern via click chemistry. This two-step process is feasible on arbitrary surfaces and allows for generation of sustainable patterns and gradients. The method is validated in different biological systems by patterning adhesive ligands on cell-repellent surfaces, thereby constraining the growth and migration of cells to the designated areas. We then implement a sequential photopatterning approach by adding a second switchable patterning step, allowing for spatiotemporal control over two distinct surface patterns. As a proof of concept, we reconstruct the dynamics of the tip/stalk cell switch during angiogenesis. Our results show that the spatiotemporal control provided by our “sequential photopatterning” system is essential for mimicking dynamic biological processes and that our innovative approach has great potential for further applications in cell science