Mass-selected, cluster anion beams of Mo100±2.5 – and (MoO3)67±1.5 – were prepared with a magnetron source and soft-landed onto highly ordered pyrolytic graphite (HOPG) under UHV conditions. These two clusters were selected because they possess essentially the same masses and consequently could be soft-landed with the same low kinetic energies. The chemical composition of the deposited clusters was analyzed using in situ Auger electron spectroscopy and ex situ X-ray photoelectron spectroscopy, while their surface morphologies were characterized with in situ scanning tunneling microscopy (STM) and ex situ atomic force microscopy (AFM). Both STM and AFM results indicated a high mobility for the metal atom clusters on HOPG at room temperature. At low coverages, Mo100±2.5 clusters nucleated preferentially at step-edges. As their coverage increased, cluster aggregates formed on the terraces until a fully saturated overlayer was created. By contrast, deposited metal oxide clusters produced a stochastic array of adsorbed clusters for all coverages. Differences in the behavior of deposited Mo100±2.5 and (MoO3)67±1.5 clusters were interpreted in terms of differences in the interactions of metal and metal oxide clusters with carbonaceous substrates.
Thins films are synthesized by deposition of size-selected Mo n À cluster anions on an inert substrate. Scanning tunneling microscopy pictures indicate that the deposited material consists of individual particles with diameters corresponding to the size of the preformed clusters from the gas phase. Previous attempts to manufacture cluster materials from metals failed since these clusters coalesced at room temperature. Our data suggest the possibility to synthesize new nanomaterials from clusters of high fusing metals. This may prove to be the key to harness size-dependent and tuneable properties of clusters for creating novel classes of functional tailor-made materials. V C 2014 AIP Publishing LLC. [http://dx.
The cosmid clone, CX16-2D12, was previously localized to the centromeric region of the human X chromosome and shown to lack human X-specific alpha satellite DNA. A 1.2 kb EcoRI fragment was subcloned from the CX16-2D12 cosmid and was named 2D12/E2. DNA sequencing revealed that this 1,205 bp fragment consisted of approximately five tandemly repeated DNA monomers of 220 bp. DNA sequence homology between the monomers of 2D12/E2 ranged from 72.8% to 78.6%. Interestingly, DNA sequence analysis of the 2D12/E2 clone displayed a change in monomer unit orientation between nucleotide positions 585-586 from a "tail-to-head" arrangement to a "head-to-tail" configuration. This may reflect the existence of at least one inversion within this repetitive DNA array in the centromeric region of the human X chromosome. The DNA consensus sequence derived from a compilation of these 220 bp monomers had approximately 62% DNA sequence similarity to the previously determined gamma 8 satellite DNA consensus sequence. Comparison of the 2D12/E2 and gamma 8 consensus sequences revealed a 20 bp DNA sequence that was well conserved in both DNA consensus sequences. Slot-blot analysis revealed that this repetitive DNA sequence comprises approximately 0.015% of the human genome, similar to that found with gamma 8 satellite DNA. These observations suggest that this satellite DNA clone is derived from a subfamily of gamma satellite DNA and is thus designated gamma X satellite DNA. When genomic DNA from six unrelated males and two unrelated females was cut with SstI or HpaI and separated by pulsed-field gel electrophoresis, no restriction fragment length polymorphisms were observed for either gamma X (2D12/E2) or gamma 8 (50E4) probes. Fluorescence in situ hybridization localized the 2D12/E2 clone to the lateral sides of the primary constriction specifically on the human X chromosome.
Theory C 1000Closo-alanes (Al4H4, AlnHn+2, 4 ≤ n ≤ 8): A New Chapter in Aluminum Hydride Chemistry. -The clusters Al n (4 ≤ n ≤ 8, 0 ≤ m ≤ 10) are characterized by anion PES and DFT calculations. High HOMO-LUMO gaps and relatively low electron affinity values for Al4H4, Al4H6, and the family AlnHn+2 (5 ≤ n ≤ 8) indicate that these clusters possess substantial stability over their stoichiometric neighbors. The AlnHn+2 (5 ≤ n ≤ 8) family adopts closo-structures with two extra hydrogen atoms occupying bridging positions in agreement with the Wade's (n + 1) rule. Al 4 H 4 exhibits a closo--tetrahedral cage. -(GRUBISIC, A.; LI, X.; STOKES, S. T.; CORDES, J.; GANTEFOER, G. F.; BOWEN*, K. H.; KIRAN, B.; JENA, P.; BURGERT, R.; SCHNOECKEL, H.; J.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.