Places in Information Science Purves, Ross S.; Winter, Stephan; Kuhn, Werner
Journal of the Association for Information Science and Technology,
November 2019, Letnik:
70, Številka:
11
Journal Article
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Human spatial concepts, such as the concept of place, are not immediately translatable to the geometric foundations of spatial databases and information systems developed over the past 50 years. ...These systems typically rest on the concepts of objects and fields, both bound to coordinates, as two general paradigms of geographic representation. The match between notions of place occurring in everyday where questions and the data available to answer such questions is unclear and hinders progress in place‐based information systems. This is particularly true in novel application areas such as the Digital Humanities or speech‐based human–computer interaction, but also for location‐based services. Although this shortcoming has been observed before, we approach the challenges of relating places to information system representations with a fresh view, based on a set of core concepts of spatial information. These concepts have been proposed in information science with the intent of serving human–machine spatial question asking and answering. Clarifying the relationship of the notion of place to these concepts is a significant step toward geographically intelligent systems. The main result of the article is a demonstration that the notion of place fits existing concepts of spatial information, when these are adequately exploited and combined.
Despite the vast number of polyoxometalate clusters now known, an ongoing and important challenge is to understand causality in the assembly of “complex” clusters at a mechanistic level, since this ...is the only way the rational, targeted synthesis of new compounds will ever be achieved. Often, the complexity of the reactions themselves makes such investigations near impossible, as very small changes can often make dramatic differences. Herein, we explore a very simple A + B binary synthetic system that gives rise to the facile assembly of two isomeric anions, FeIII(H2O)2{γ-FeIIISiW9O34(H2O)}211– (1) and FeIII(H2O)2{γ-FeIII 2SiW8O33(H2O)2}{γ-SiW10O35}11– (2), which can be formed as individual and dimeric species (3) and (4). Furthermore, the simple binary nature of this synthetic system allowed its investigation by a comprehensive time-resolved ESI-MS analysis, yielding unprecedented mechanistic information regarding the initial interactions and reorganizations of the {γ-SiW10} precursor in the presence of Fe2+.
The reactions of γ-SiW10O368– represent one of the most important synthetic gateways into a vast array of polyoxotungstate chemistry. Herein, we set about exploring the transformation of the lacunary ...polyoxoanion β2-SiW11O398– into γ-SiW10O368– using high-resolution electrospray mass spectrometry, density functional theory, and molecular dynamics. We show that the reaction proceeds through an unexpected {SiW9} precursor capable of undertaking a direct β → γ isomerization via a rotational transformation. The remarkably low-energy transition state of this transformation could be identified through theoretical calculations. Moreover, we explore the significant role of the countercations for the first time in such studies. This combination of experimental and the theoretical studies can now be used to understand the complex chemical transformations of oxoanions, leading to the design of reactivity by structural control.
The design of highly flexible framework materials requires organic linkers, whereas inorganic materials are more robust but inflexible. Here, by using linkable inorganic rings made up of tungsten ...oxide (P
W
O
) building blocks, we synthesized an inorganic single crystal material that can undergo at least eight different crystal-to-crystal transformations, with gigantic crystal volume contraction and expansion changes ranging from -2,170 to +1,720 Å
with no reduction in crystallinity. Not only does this material undergo the largest single crystal-to-single crystal volume transformation thus far reported (to the best of our knowledge), the system also shows conformational flexibility while maintaining robustness over several cycles in the reversible uptake and release of guest molecules switching the crystal between different metamorphic states. This material combines the robustness of inorganic materials with the flexibility of organic frameworks, thereby challenging the notion that flexible materials with robustness are mutually exclusive.
We report an approach to synthesize molecular tungsten‐oxide‐based pentagonal building blocks, in a new {W21O72} unit, and show how this leads to a family of gigantic molecular architectures ...including H12W48O16428− {W48}, H20W56O19024− {W56}, and H12W92O31158− {W92}. The {W48} and {W56} clusters are both dimeric species incorporating two {W21} units and the {W56} species is the first example of a molecular metal oxide cluster containing a chiral “double‐stranded” motif which is stable in solution as confirmed by mass spectrometry. The {W92} anion having four {W21} units is one of the largest transition metal substituted isopolyoxotungstates known.
High nuclearity isopolyoxotungstates (isoPOTs) of formulae H12W48O16428−, H20W56O19024− and H12W92O31158− are made of unique {W21O72} building units containing pentagonal {W(W5)}, {W(W4)}, and {W(W3)} motifs. The growth of these {W21O72} building blocks allows for the formation of large isoPOTs with chiral features.
Lacunary polyoxometalates of low nuclearity are difficult to synthesize in isolation. We report the facile synthesis of six {M2(B-β-SiW8O31)2} clusters (M = Co/Mn/Ni/Zn/Cu(2+), Fe(3+)) that can be ...employed as building blocks for the formation of larger architectures. We show for the first time that such {B-β-SiW8O31} lacunae are capable of reorganizing into larger Keggin lacunary species even in the absence of an external source of tungstate. We hypothesize, based on electrospray ionization mass spectrometry evidence obtained, not only that such a transformation is only possible via an initial decomposition of the {SiW8} precursor into a {SiW6}-based intermediate but also that it is this {SiW6} species that acts as the template for the growth of the larger fragments.
We report a {Cu
} embedded within a {W
} cluster containing four cubane-like Cu
O
units within an isopolyoxotungstate (isoPOT) in a {Na
Cu
(H
W
O
) (CH
COO)(OH)
}
·88H
O (1) and a polyanion ...Cu-linked {W
} chain Na
Cu
(H
W
O
)(CH
COO)(OH)·26H
O (2). Electronically, the redox properties show that both compounds 1 and 2 undergo irreversible reductions resulting in the demetalation of the compounds, whilst the magnetic behavior of 1 and 2 shows a weak antiferromagnetic and a stronger ferromagnetic coupling, respectively.
Two near isomeric clusters containing a novel {Mn8W4} Keggin cluster within a W36Mn10Si4O136(OH)4(H2O)824− cluster are reported: K10Li14 W36Si4O136MnII10(OH)4(H2O)8 (1) and ...K10Li13.5Mn0.25W36Si4O136MnII10(OH)4(H2O)8 (1′). Bulk characterization of the clusters has been carried out by single crystal X‐ray structure analysis, ICP‐MS, TGA, ESI‐MS, CV and SQUID‐magnetometer analysis. X‐ray analysis revealed that 1′ has eight positions within the central Keggin core that were disordered W/Mn whereas 1 contained no such disorder. This subtle difference is due to a differences is how the two clusters assemble and recrystallize from the same mother liquor and represents a new type of isomerism. The rapid recrystallization process was captured via digital microscopy and this uncovered two “intermediate” types of crystal which formed temporarily and provided nucleation sites for the final clusters to assemble. The intermediates were investigated by single crystal X‐ray analysis and revealed to be novel clusters K4Li22W36Si4Mn7O136(H2O)8⋅56 H2O (2) and Mn2K8Li14W36Si4Mn7O136(H2O)8⋅45 H2O (3). The intermediate clusters contained different yet related building blocks to the final clusters which allowed for the postulation of a mechanism of assembly. This demonstrates a rare example where the use X‐ray crystallography directly facilitated understanding the means by which a POM assembled.
Nanoassembly: Assembly isomers of a {Mn8W4} Keggin cluster within a W36Mn10Si4O136(OH)4(H2O)824− cluster are reported. The clusters are formed through the aggregation of new {γ‐SiMnW9} fragments in a tetrahedral fashion. Investigation of the crystal growth of these clusters revealed two intermediate clusters, which unveiled a mechanism of formation (see scheme). Physical analysis of the magnetic and solution behaviour of the isomers is also reported.
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