35 research outputs found
The sparse Blume-Emery-Griffiths model of associative memories
We analyze the Blume-Emery-Griffiths (BEG) associative memory with sparse
patterns and at zero temperature. We give bounds on its storage capacity
provided that we want the stored patterns to be fixed points of the retrieval
dynamics. We compare our results to that of other models of sparse neural
networks and show that the BEG model has a superior performance compared to
them.Comment: 23 p
Gradation of Algebras of Curves by the Winding Number
We construct a new grading on the Goldman Lie algebra of a closed oriented
surface by the winding number. This grading induces a grading on the HOMFLY-PT
skein algebra and related algebras. Our work supports the conjectures of B.
Cooper and P. SamuelsonComment: Changed acknowledgments and Definition 2.
Equity Crowdfunding: How Dynamic Capabilities matters for the implementation of a successful project
Purpose: The aim of this article is to introduce a new dimension of analysis as driver for equity crowdfunding campaign success. This new dimension is the firm, considered under a dynamic capabilities lens. The article tries to analyse if and why firms with more dynamic capabilities are more likely to succeed in an equity crowdfunding campaign.
Design/methodology/approach: The paper will be conceptual due to the novelty of his purpose. It develop hypothesis matching two topics, the dynamic capability theory and the topic exploring the determinant of crowdfunding campaign success.
Findings: Dynamic capabilities could be an important driver for equity crowdfunding campaign success. Different capabilities have different role in an equity crowdfunding campaign process. Dynamic capabilities play an important role in the design of equity crowdfunding campaign.
Research limitation/implication: The main limitation is due to the conceptual nature of this article. This is a first attempt to provide theoretical foundation of the link dynamic capabilities/equity crowdfunding campaign. Future researcher could find empirical evidence of this link through case study or quantitative analysis of successful equity crowdfunding campaign.
Practical implication: Managers of firms interested in promoting an equity crowdfunding campaign could find interesting practical implication. Before promote the campaign they must develop dynamic capabilities in order to have more probability of success.
Originality/value: This is the first attempt of putting together dynamic capabilities and equity crowdfunding. In addition this paper provide a new theoretical model that facilitate the interpretation of equity crowdfunding even allowing the introduction of a new dimension of analysis, the firm. This new model is based on the cycle firm-campaign-crowd
Uranyl and/or Rare-Earth Mellitates in Extended Organic–Inorganic Networks: A Unique Case of Heterometallic Cation–Cation Interaction with U<sup>VI</sup>O–Ln<sup>III</sup> Bonding (Ln = Ce, Nd)
A series of uranyl and lanthanide (trivalent Ce, Nd)
mellitates
(<i>mel</i>) has been hydrothermally synthesized in aqueous
solvent. Mixtures of these 4f and 5f elements also revealed the formation
of a rare case of lanthanide–uranyl coordination polymers.
Their structures, determined by XRD single-crystal analysis, exhibit
three distinct architectures. The pure lanthanide mellitate Ln<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>(<i>mel</i>) possesses
a 3D framework built up from the connection of isolated LnO<sub>6</sub>(H<sub>2</sub>O)<sub>3</sub> polyhedra (tricapped trigonal prism)
through the mellitate ligand. The structure of the uranyl mellitate
(UO<sub>2</sub>)<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>(<i>mel</i>)·11.5H<sub>2</sub>O is lamellar and consists of 8-fold coordinated
uranium atoms linked to each other through the organic ligand giving
rise to the formation of a 2D 3<sup>6</sup> net. The third structural
type, (UO<sub>2</sub>)<sub>2</sub>Ln(OH)(H<sub>2</sub>O)<sub>3</sub>(<i>mel</i>)·2.5H<sub>2</sub>O, involves direct oxygen
bondings between the lanthanide and uranyl centers, with the isolation
of a heterometallic dinuclear motif. The 9-fold coordinated Ln cation,
LnO<sub>5</sub>(OH)(H<sub>2</sub>O)<sub>3</sub>, is linked to the
7-fold coordinated uranyl (UO<sub>2</sub>)O<sub>4</sub>(OH) (pentagonal
bipyramid) via one μ<sub>2</sub>-hydroxo group and one μ<sub>2</sub>-oxo group. The latter is shared between the uranyl bonding
(UO = 1.777(4)/1.779(6) Å) and a long Ln–O bonding
(Ce–O = 2.822(4) Å; Nd–O = 2.792(6) Å). This
unusual linkage is a unique illustration of the so-called cation–cation
interaction associating 4f and 5f metals. The dinuclear motif is then
further connected through the mellitate ligand, and this generates
organic–inorganic layers that are linked to each other via
discrete uranyl (UO<sub>2</sub>)O<sub>4</sub> units (square bipyramid),
which ensure the three-dimensional cohesion of the structure. The
mixed U–Ln carboxylate is thermally decomposed from 260 to
280 °C and then transformed into the basic uranium oxide (U<sub>3</sub>O<sub>8</sub>) together with U–Ln oxide with the fluorite
structural type (“(Ln,U)O<sub>2</sub>”). At 1400 °C,
only fluorite type “(Ln,U)O<sub>2</sub>” is formed with
the measured stoichiometry of U<sub>0.63</sub>Ce<sub>0.37</sub>O<sub>2</sub> and U<sub>0.60</sub>Nd<sub>0.40</sub>O<sub>2−δ</sub>
Series of Mixed Uranyl–Lanthanide (Ce, Nd) Organic Coordination Polymers with Aromatic Polycarboxylates Linkers
Three series of mixed uranyl-lanthanide (Ce or Nd) carboxylate
coordination polymers have been successfully synthesized by means
of a hydrothermal route using either conventional or microwave heating
methods. These compounds have been prepared from mixtures of uranyl
nitrate, lanthanide nitrate together with phthalic acid (<b>1</b>,<b>2</b>), pyromellitic acid (<b>3</b>,<b>4</b>), or mellitic acid (<b>5</b>,<b>6</b>) in aqueous solution.
The X-ray diffraction (XRD) single-crystal revealed that the phthalate
complex (UO<sub>2</sub>)<sub>4</sub>O<sub>2</sub>Ln(H<sub>2</sub>O)<sub>7</sub>(1,2-bdc)<sub>4</sub>·NH<sub>4</sub>·<i>x</i>H<sub>2</sub>O (Ln = Ce(<b>1</b>), Nd(<b>2</b>); <i>x</i> = 1 for <b>1</b>, <i>x</i> = 0 for <b>2</b>), is based on the connection of tetranuclear uranyl-centered
building blocks linked to discrete monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub> via the organic species to generate
infinite chains, intercalated by free ammonium cations. The pyromellitate
phase (UO<sub>2</sub>)<sub>3</sub>Ln<sub>2</sub>(H<sub>2</sub>O)<sub>12</sub>(btec)<sub>3</sub>·5H<sub>2</sub>O (Ce(<b>3</b>), Nd(<b>4</b>)) contains layers of monomeric uranyl-centered
hexagonal and pentagonal bipyramids linked via the carboxylate arms
of the organic molecules. The three-dimensionality of the structure
is ensured by the connection of remaining free carboxylate groups
with isolated monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub>. The network of the third series (UO<sub>2</sub>)<sub>2</sub>(OH)Ln(H<sub>2</sub>O)<sub>7</sub>(mel)·5H<sub>2</sub>O (Ce(<b>5</b>), Nd(<b>6</b>)) is built up from dinuclear uranyl
units forming layers through connection with the mellitate ligands,
which are further linked to each other through discrete monomers LnO<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>. The thermal decomposition of
the various coordination complexes led to the formation of mixed uranium-lanthanide
oxide, with the fluorite-type structure at 1500 °C (for <b>1</b>, <b>2</b>) or 1400 °C for <b>3</b>–<b>6</b>. Expected U/Ln ratio from the crystal structures were observed
for compounds <b>1</b>–<b>6</b>
Series of Mixed Uranyl–Lanthanide (Ce, Nd) Organic Coordination Polymers with Aromatic Polycarboxylates Linkers
Three series of mixed uranyl-lanthanide (Ce or Nd) carboxylate
coordination polymers have been successfully synthesized by means
of a hydrothermal route using either conventional or microwave heating
methods. These compounds have been prepared from mixtures of uranyl
nitrate, lanthanide nitrate together with phthalic acid (<b>1</b>,<b>2</b>), pyromellitic acid (<b>3</b>,<b>4</b>), or mellitic acid (<b>5</b>,<b>6</b>) in aqueous solution.
The X-ray diffraction (XRD) single-crystal revealed that the phthalate
complex (UO<sub>2</sub>)<sub>4</sub>O<sub>2</sub>Ln(H<sub>2</sub>O)<sub>7</sub>(1,2-bdc)<sub>4</sub>·NH<sub>4</sub>·<i>x</i>H<sub>2</sub>O (Ln = Ce(<b>1</b>), Nd(<b>2</b>); <i>x</i> = 1 for <b>1</b>, <i>x</i> = 0 for <b>2</b>), is based on the connection of tetranuclear uranyl-centered
building blocks linked to discrete monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub> via the organic species to generate
infinite chains, intercalated by free ammonium cations. The pyromellitate
phase (UO<sub>2</sub>)<sub>3</sub>Ln<sub>2</sub>(H<sub>2</sub>O)<sub>12</sub>(btec)<sub>3</sub>·5H<sub>2</sub>O (Ce(<b>3</b>), Nd(<b>4</b>)) contains layers of monomeric uranyl-centered
hexagonal and pentagonal bipyramids linked via the carboxylate arms
of the organic molecules. The three-dimensionality of the structure
is ensured by the connection of remaining free carboxylate groups
with isolated monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub>. The network of the third series (UO<sub>2</sub>)<sub>2</sub>(OH)Ln(H<sub>2</sub>O)<sub>7</sub>(mel)·5H<sub>2</sub>O (Ce(<b>5</b>), Nd(<b>6</b>)) is built up from dinuclear uranyl
units forming layers through connection with the mellitate ligands,
which are further linked to each other through discrete monomers LnO<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>. The thermal decomposition of
the various coordination complexes led to the formation of mixed uranium-lanthanide
oxide, with the fluorite-type structure at 1500 °C (for <b>1</b>, <b>2</b>) or 1400 °C for <b>3</b>–<b>6</b>. Expected U/Ln ratio from the crystal structures were observed
for compounds <b>1</b>–<b>6</b>
Series of Mixed Uranyl–Lanthanide (Ce, Nd) Organic Coordination Polymers with Aromatic Polycarboxylates Linkers
Three series of mixed uranyl-lanthanide (Ce or Nd) carboxylate
coordination polymers have been successfully synthesized by means
of a hydrothermal route using either conventional or microwave heating
methods. These compounds have been prepared from mixtures of uranyl
nitrate, lanthanide nitrate together with phthalic acid (<b>1</b>,<b>2</b>), pyromellitic acid (<b>3</b>,<b>4</b>), or mellitic acid (<b>5</b>,<b>6</b>) in aqueous solution.
The X-ray diffraction (XRD) single-crystal revealed that the phthalate
complex (UO<sub>2</sub>)<sub>4</sub>O<sub>2</sub>Ln(H<sub>2</sub>O)<sub>7</sub>(1,2-bdc)<sub>4</sub>·NH<sub>4</sub>·<i>x</i>H<sub>2</sub>O (Ln = Ce(<b>1</b>), Nd(<b>2</b>); <i>x</i> = 1 for <b>1</b>, <i>x</i> = 0 for <b>2</b>), is based on the connection of tetranuclear uranyl-centered
building blocks linked to discrete monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub> via the organic species to generate
infinite chains, intercalated by free ammonium cations. The pyromellitate
phase (UO<sub>2</sub>)<sub>3</sub>Ln<sub>2</sub>(H<sub>2</sub>O)<sub>12</sub>(btec)<sub>3</sub>·5H<sub>2</sub>O (Ce(<b>3</b>), Nd(<b>4</b>)) contains layers of monomeric uranyl-centered
hexagonal and pentagonal bipyramids linked via the carboxylate arms
of the organic molecules. The three-dimensionality of the structure
is ensured by the connection of remaining free carboxylate groups
with isolated monomeric units LnO<sub>2</sub>(H<sub>2</sub>O)<sub>7</sub>. The network of the third series (UO<sub>2</sub>)<sub>2</sub>(OH)Ln(H<sub>2</sub>O)<sub>7</sub>(mel)·5H<sub>2</sub>O (Ce(<b>5</b>), Nd(<b>6</b>)) is built up from dinuclear uranyl
units forming layers through connection with the mellitate ligands,
which are further linked to each other through discrete monomers LnO<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>. The thermal decomposition of
the various coordination complexes led to the formation of mixed uranium-lanthanide
oxide, with the fluorite-type structure at 1500 °C (for <b>1</b>, <b>2</b>) or 1400 °C for <b>3</b>–<b>6</b>. Expected U/Ln ratio from the crystal structures were observed
for compounds <b>1</b>–<b>6</b>
Uranyl–Pyromellitate Coordination Polymers: Toward Three-Dimensional Open Frameworks with Large Channel Systems
Five coordination polymers based on uranyl–pyromellitates
have been hydrothermally synthesized, and their single-crystal XRD
structures have been analyzed. These different compounds, obtained
with different ammonia concentrations, exhibit either three-dimensional
(3D) or two-dimensional (2D) networks. Complex <b>1</b>, (UO<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec)·H<sub>2</sub>O, is a quite compact 3D structure containing isolated 7-fold
coordinated uranyl cations linked through the pyromellitate (noted
btec) and encapsulating free water species. Phase (NH<sub>4</sub>)[(UO<sub>2</sub>)<sub>2</sub>(OH)(H<sub>2</sub>O)(btec)]·1.75H<sub>2</sub>O (<b>2</b>) offers a second 3D architecture built up from
dinuclear 7-fold coordinated uranyl units and mononuclear 8-fold coordinated
uranyl units linked through the organic ligands. This framework is
slightly more open because narrow one-dimensional (1D) channels trapping
water species are visible. Phase <b>3</b>, (NH<sub>4</sub>)<sub>2</sub>[(UO<sub>2</sub>)<sub>6</sub>O<sub>2</sub>(OH)<sub>4</sub>(btec)<sub>1.5</sub>]·11H<sub>2</sub>O, consists of large 1D
lozenge-shaped channels (8.2 Å × 8.6 Å) delimited by
infinite ribbons (composed of 7-fold coordinated uranyl polyhedra
sharing edges) and pyromellitate ligands. Ammonium cations as well
as water molecules are trapped within the channels. The fourth compound,
(NH<sub>4</sub>)<sub>6</sub>[(UO<sub>2</sub>)<sub>3</sub>(btec)<sub>3</sub>]·12H<sub>2</sub>O (<b>4</b>), is lamellar with
sheets containing 8-fold coordinated uranyl centers linked through
the btec molecules, which have two nonbonded carboxylate functions
interacting with the intercalated ammonium cations. Compound <b>5</b> also consists of a layered structure, (UO<sub>2</sub>)<sub>3</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec), with uncommon
trinuclear building blocks containing 7-fold (×2) and 8-fold
(×1) coordinated uranyl centers, linked through the btec molecules.
Fluorescence spectra of compounds <b>1</b>, <b>3</b>,
and <b>4</b> are also measured
Uranyl–Pyromellitate Coordination Polymers: Toward Three-Dimensional Open Frameworks with Large Channel Systems
Five coordination polymers based on uranyl–pyromellitates
have been hydrothermally synthesized, and their single-crystal XRD
structures have been analyzed. These different compounds, obtained
with different ammonia concentrations, exhibit either three-dimensional
(3D) or two-dimensional (2D) networks. Complex <b>1</b>, (UO<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec)·H<sub>2</sub>O, is a quite compact 3D structure containing isolated 7-fold
coordinated uranyl cations linked through the pyromellitate (noted
btec) and encapsulating free water species. Phase (NH<sub>4</sub>)[(UO<sub>2</sub>)<sub>2</sub>(OH)(H<sub>2</sub>O)(btec)]·1.75H<sub>2</sub>O (<b>2</b>) offers a second 3D architecture built up from
dinuclear 7-fold coordinated uranyl units and mononuclear 8-fold coordinated
uranyl units linked through the organic ligands. This framework is
slightly more open because narrow one-dimensional (1D) channels trapping
water species are visible. Phase <b>3</b>, (NH<sub>4</sub>)<sub>2</sub>[(UO<sub>2</sub>)<sub>6</sub>O<sub>2</sub>(OH)<sub>4</sub>(btec)<sub>1.5</sub>]·11H<sub>2</sub>O, consists of large 1D
lozenge-shaped channels (8.2 Å × 8.6 Å) delimited by
infinite ribbons (composed of 7-fold coordinated uranyl polyhedra
sharing edges) and pyromellitate ligands. Ammonium cations as well
as water molecules are trapped within the channels. The fourth compound,
(NH<sub>4</sub>)<sub>6</sub>[(UO<sub>2</sub>)<sub>3</sub>(btec)<sub>3</sub>]·12H<sub>2</sub>O (<b>4</b>), is lamellar with
sheets containing 8-fold coordinated uranyl centers linked through
the btec molecules, which have two nonbonded carboxylate functions
interacting with the intercalated ammonium cations. Compound <b>5</b> also consists of a layered structure, (UO<sub>2</sub>)<sub>3</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec), with uncommon
trinuclear building blocks containing 7-fold (×2) and 8-fold
(×1) coordinated uranyl centers, linked through the btec molecules.
Fluorescence spectra of compounds <b>1</b>, <b>3</b>,
and <b>4</b> are also measured
Uranyl–Pyromellitate Coordination Polymers: Toward Three-Dimensional Open Frameworks with Large Channel Systems
Five coordination polymers based on uranyl–pyromellitates
have been hydrothermally synthesized, and their single-crystal XRD
structures have been analyzed. These different compounds, obtained
with different ammonia concentrations, exhibit either three-dimensional
(3D) or two-dimensional (2D) networks. Complex <b>1</b>, (UO<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec)·H<sub>2</sub>O, is a quite compact 3D structure containing isolated 7-fold
coordinated uranyl cations linked through the pyromellitate (noted
btec) and encapsulating free water species. Phase (NH<sub>4</sub>)[(UO<sub>2</sub>)<sub>2</sub>(OH)(H<sub>2</sub>O)(btec)]·1.75H<sub>2</sub>O (<b>2</b>) offers a second 3D architecture built up from
dinuclear 7-fold coordinated uranyl units and mononuclear 8-fold coordinated
uranyl units linked through the organic ligands. This framework is
slightly more open because narrow one-dimensional (1D) channels trapping
water species are visible. Phase <b>3</b>, (NH<sub>4</sub>)<sub>2</sub>[(UO<sub>2</sub>)<sub>6</sub>O<sub>2</sub>(OH)<sub>4</sub>(btec)<sub>1.5</sub>]·11H<sub>2</sub>O, consists of large 1D
lozenge-shaped channels (8.2 Å × 8.6 Å) delimited by
infinite ribbons (composed of 7-fold coordinated uranyl polyhedra
sharing edges) and pyromellitate ligands. Ammonium cations as well
as water molecules are trapped within the channels. The fourth compound,
(NH<sub>4</sub>)<sub>6</sub>[(UO<sub>2</sub>)<sub>3</sub>(btec)<sub>3</sub>]·12H<sub>2</sub>O (<b>4</b>), is lamellar with
sheets containing 8-fold coordinated uranyl centers linked through
the btec molecules, which have two nonbonded carboxylate functions
interacting with the intercalated ammonium cations. Compound <b>5</b> also consists of a layered structure, (UO<sub>2</sub>)<sub>3</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(btec), with uncommon
trinuclear building blocks containing 7-fold (×2) and 8-fold
(×1) coordinated uranyl centers, linked through the btec molecules.
Fluorescence spectra of compounds <b>1</b>, <b>3</b>,
and <b>4</b> are also measured