1,135 research outputs found
The concept of strong and weak virtual reality
We approach the virtual reality phenomenon by studying its relationship to
set theory, and we investigate the case where this is done using the
wellfoundedness property of sets. Our hypothesis is that non-wellfounded sets
(hypersets) give rise to a different quality of virtual reality than do
familiar wellfounded sets. We initially provide an alternative approach to
virtual reality based on Sommerhoff's idea of first and second order
self-awareness; both categories of self-awareness are considered as necessary
conditions for consciousness in terms of higher cognitive functions. We then
introduce a representation of first and second order self-awareness through
sets, and assume that these sets, which we call events, originally form a
collection of wellfounded sets. Strong virtual reality characterizes virtual
reality environments which have the limited capacity to create only events
associated with wellfounded sets. In contrast, the more general concept of weak
virtual reality characterizes collections of virtual reality mediated events
altogether forming an entirety larger than any collection of wellfounded sets.
By giving reference to Aczel's hyperset theory we indicate that this definition
is not empty, because hypersets encompass wellfounded sets already. Moreover,
we argue that weak virtual reality could be realized in human history through
continued progress in computer technology. Finally, we reformulate our
characterization into a more general framework, and use Baltag's Structural
Theory of Sets (STS) to show that within this general hyperset theory
Sommerhoff's first and second order self-awareness as well as both concepts of
virtual reality admit a consistent mathematical representation.Comment: 17 pages; several edits in v
catena-Poly[[[bis(N,N-dimethylformamide)iron(II)]-{μ-2,2′-bis(diphenylphosphinoyl)-N,N′-[(1R,2R)-cyclohexane-1,2-diyl]dibenzamide}] bis(perchlorate) N,N-dimethylformamide disolvate]
The title extended solid coordination compound, {[Fe(C44H40N2O4P2)(C3H7NO)2](ClO4)2·2C3H7NO}n, was crystallized unexpectedly from the reaction mixture containing the Trost ligand (1R,2R)-(+)-1,2-diaminocyclohexane-N,N′-bis(2′-diphenylphosphinobenzoyl) and Fe(ClO4)2·6H2O in a 1:1 ratio in dimethylformamide (DMF) under reflux conditions. The polymeric complex is characterized by FeII metal centers that are coordinated by two oxidized Trost ligands, each coordinated in a bidentate fashion in a square plane, along with two DMF molecules above and below the plane [average Fe—ODMF = 2.086 (4) Å], forming an overall pseudo-octahedral geometry. The Trost ligand binds adjacent FeII centers, each FeII being bound through the O atom of one of the phosphine oxides [average Fe—OPPh2 = 2.115 (4) Å] and the carbonyl O atom of the adjacent amide [average Fe—Oamide = 2.192 (3) Å]. Disorder is observed in the co-solvated solvent: there are two DMF molecules per FeII centre, which were modeled as one DMF molecule with complete occupancy and the other being modeled in two positions with equal occupancy. Disorder was also observed with one of the perchlorate anions, which was modeled in two positions with 0.75:0.25 occupancy
Benzoyldicarbonyl(η5-indenyl)ruthenium(II)
In the title molecule, [Ru(C9H7)(C7H5O)(CO)2], the dihedral angle between the mean plane of the indene ring system and the phenyl ring is 86.28 (8)°. The crystal structure is stabilized by weak intermolecular C—H⋯O and C—H⋯π(arene) interactions. The Ru—η5-cyclopentadienyl centroid bond length is 1.946 (11)
Solid Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State H-1 Nuclear Spin Relaxation
Using solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on t-butyl group and methyl group rotation in solid 1,3,5-tri-t-butylbenzene. The goal is to relate the dynamics of the t-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 K or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K) where the t-butyl groups are disordered (that is, with a rotational six-fold intermolecular potential dominating) to a triclinic phase (below 155 K) where the t-butyl groups are ordered (that is, with a rotational threefold intermolecular potential dominating). This transition shows very different DSC scans when both a 5 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the t-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the lowtemperature triclinic phase, the rotations of the t-butyl groups and their methyl group in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the t-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range
Solid Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State H-1 Nuclear Spin Relaxation
Using solid state 1H nuclear magnetic resonance (NMR) spin-lattice relaxation experiments, we have investigated the effects of several solid-solid phase transitions on t-butyl group and methyl group rotation in solid 1,3,5-tri-t-butylbenzene. The goal is to relate the dynamics of the t-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid-solid phase transition at either 268 K or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K) where the t-butyl groups are disordered (that is, with a rotational six-fold intermolecular potential dominating) to a triclinic phase (below 155 K) where the t-butyl groups are ordered (that is, with a rotational threefold intermolecular potential dominating). This transition shows very different DSC scans when both a 5 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin-lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the t-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17-23 kJ mol-1 range and the constituent methyl groups rotate with NMR activation energies in the 7-12 kJ mol-1 range. In the lowtemperature triclinic phase, the rotations of the t-butyl groups and their methyl group in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the t-butyl groups are rotating with activation energies in the 5-11 kJ mol-1 range
Eigenvector localization as a tool to study small communities in online social networks
We present and discuss a mathematical procedure for identification of small
"communities" or segments within large bipartite networks. The procedure is
based on spectral analysis of the matrix encoding network structure. The
principal tool here is localization of eigenvectors of the matrix, by means of
which the relevant network segments become visible. We exemplified our approach
by analyzing the data related to product reviewing on Amazon.com. We found
several segments, a kind of hybrid communities of densely interlinked reviewers
and products, which we were able to meaningfully interpret in terms of the type
and thematic categorization of reviewed items. The method provides a
complementary approach to other ways of community detection, typically aiming
at identification of large network modules
Carbonyl[tris(3,5-diphenylpyrazol-1-yl-κN 2)methane]copper(I) hexafluoridophosphate–dichloromethane–diethyl ether (4/3/1)
In the title compound, [Cu(C46H34N6)(CO)]PF6·0.75CH2Cl2·0.25C4H10O, the CuI atom is coordinated by three N atoms from the tridentate chelating tris(3,5-diphenylpyrazol-1-yl)methane ligand (average Cu—N distance = 2.055 Å) and the C atom from a carbon monoxide ligand in a distorted tetrahedral coordination geometry. The average N—Cu—N angle between adjacent pyrazole-ring-coordinated N atoms is 88.6°, while the average N—Cu—C angle between the pyrazole-bound N atom and the C atom of carbon monoxide is 126.3°. One of the 3-phenyl rings of the tris(pyrazolyl)methane ligand is disordered over two sites each with an occupancy factor of 0.50. The structure also exhibits disorder of the monosolvate that has been modeled with 0.75 CH2Cl2 and 0.25 Et2O occupancy
Collective emotions online and their influence on community life
E-communities, social groups interacting online, have recently become an
object of interdisciplinary research. As with face-to-face meetings, Internet
exchanges may not only include factual information but also emotional
information - how participants feel about the subject discussed or other group
members. Emotions are known to be important in affecting interaction partners
in offline communication in many ways. Could emotions in Internet exchanges
affect others and systematically influence quantitative and qualitative aspects
of the trajectory of e-communities? The development of automatic sentiment
analysis has made large scale emotion detection and analysis possible using
text messages collected from the web. It is not clear if emotions in
e-communities primarily derive from individual group members' personalities or
if they result from intra-group interactions, and whether they influence group
activities. We show the collective character of affective phenomena on a large
scale as observed in 4 million posts downloaded from Blogs, Digg and BBC
forums. To test whether the emotions of a community member may influence the
emotions of others, posts were grouped into clusters of messages with similar
emotional valences. The frequency of long clusters was much higher than it
would be if emotions occurred at random. Distributions for cluster lengths can
be explained by preferential processes because conditional probabilities for
consecutive messages grow as a power law with cluster length. For BBC forum
threads, average discussion lengths were higher for larger values of absolute
average emotional valence in the first ten comments and the average amount of
emotion in messages fell during discussions. Our results prove that collective
emotional states can be created and modulated via Internet communication and
that emotional expressiveness is the fuel that sustains some e-communities.Comment: 23 pages including Supporting Information, accepted to PLoS ON
Observation of a Distribution of Internal Transverse Magnetic Fields in a Mn12-Based Single Molecule Magnet
A distribution of internal transverse magnetic fields has been observed in
single molecule magnet (SMM) Mn12-BrAc in the pure magnetic quantum tunneling
(MQT) regime. Magnetic relaxation experiments at 0.4 K are used to produce a
hole in the distribution of transverse fields whose angle and depth depend on
the orientation and amplitude of an applied transverse ``digging field.'' The
presence of such transverse magnetic fields can explain the main features of
resonant MQT in this material, including the tunneling rates, the form of the
relaxation and the absence of tunneling selection rules. We propose a model in
which the transverse fields originate from a distribution of tilts of the
molecular magnetic easy axes.Comment: 4 page
Manageable creativity
This article notes a perception in mainstream management theory and practice that creativity has shifted from being disruptive or destructive to 'manageable'. This concept of manageable creativity in business is reflected in a similar rhetoric in cultural policy, especially towards the creative industries. The article argues that the idea of 'manageable creativity' can be traced back to a 'heroic' and a 'structural' model of creativity. It is argued that the 'heroic' model of creativity is being subsumed within a 'structural' model which emphasises the systems and infrastructure around individual creativity rather than focusing on raw talent and pure content. Yet this structured approach carries problems of its own, in particular a tendency to overlook the unpredictability of creative processes, people and products. Ironically, it may be that some confusion in our policies towards creativity is inevitable, reflecting the paradoxes and transitions which characterise the creative process
- …