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This work addresses the anatomy of a 2D polymer formation; that is, we identify, localize, and describe the various processes required to obtain such a macromolecule in a singlecrystal-to-single-crystal reaction. It contains aspects of lattice, local and integral strain, and the distribution of strain in the crystal and assembles the various bits and pieces to a full-scale mechanistic picture providing experimental evidence for why the polymerization avoids phase segregation and why the crystals do not shatter as a result. While lattice strain is investigated by Bragg scattering, most of the paper revolves around diffuse scattering and its analysis with the three-dimensional difference pair distribution function (3D-Delta PDF). Local and integral strain and the spatial distribution of all strains, which are fundamental issues in an endeavor to unravel the polymerization mechanism, are deciphered. These investigations use monomer crystals at three different polymerization conversions (0%, 22%, and 44%) to account for eventual mechanistic changes when oligomers start to prevail. The paper provides answers to how strain management is achieved by the crystal leading to an unprecedented level of insight into chemical reactions in crystals. First, it provides a comprehensive molecular-scale picture on how local strain is buffered during polymerization, and second, it gives an understanding of how the reactivity of the growth pairs is preserved despite the strong displacements observed in the average structure. The paper reaches out to chemists and therefore restricts crystallographic nomenclature to a minimum. ISSN:1520-5835 ISSN:0024-9297

2D polymer sheets with six positively charged pyrylium groups at each pore edge in a stacked single crystal can be transformed into a 2D polymer with six pyridines per pore by exposure to gaseous ammonia. This reaction furnishes still a crystalline material with tunable protonation degree at regular nano‐sized pores promising as separation membrane. The exfoliation is compared for both 2D polymers with the latter being superior. Its liquid phase exfoliation yields nanosheet dispersions, which can be size‐selected using centrifugation cascades. Monolayer contents of ≈30 % are achieved with ≈130 nm sized sheets in mg quantities, corresponding to tens of trillions of monolayers. Quantification of nanosheet sizes, layer number and mass shows that this exfoliation is comparable to graphite. Thus, we expect that recent advances in exfoliation of graphite or inorganic crystals (e.g. scale‐up, printing etc.) can be directly applied to this 2D polymer as well as to covalent organic frameworks., Angewandte Chemie. International Edition, 59 (14), ISSN:1433-7851, ISSN:1521-3773, ISSN:0570-0833

Covalent long-range ordered (crystalline) sheets called 2D polymers have recently been synthesized by irradiating single crystals of suitably packed monomers. To have such an action proceed successfully, billions of bond formation processes have to be mastered exclusively in two dimensions within 3D crystals. This raises questions as to how to elucidate the mechanism of these unusual polymerizations as well as their entire strain management. The article will show that single crystal X-ray diffraction based on both Bragg and diffuse scattering are powerful techniques to achieve such goal. The very heart of both techniques will be explained and it will be shown what can be safely concluded with their help and what not. Consequently, the reader will understand why some crystals break during polymerization, while others stay intact. This understanding will then be molded into a few guidelines that should help pave the way for future developments of 2D polymers by those interested in joining the effort with this fascinating and emerging class of 2D materials., Chemical Society Reviews, 49 (15), ISSN:0306-0012, ISSN:1460-4744

Synthetic single-crystal samples of the monoclinic pyroxene-type compounds LiScGe{sub 2}O{sub 6} and NaScGe{sub 2}O{sub 6} have been investigated by means of in-situ high-pressure Raman spectroscopy and X-ray diffraction techniques. Crystal-structure investigations at hydrostatic high-pressure conditions were carried out in addition to 10{sup −4} GPa measurements using the diamond-anvil cell technique up to ∼9.5 GPa. Both samples, LiScGe{sub 2}O{sub 6} (space group P2{sub 1}/c, a=9.9999(8) A, b=9.1040(2) A, c=5.4610(2) A, β=109.240(2)° at 10{sup −4} GPa) and NaScGe{sub 2}O{sub 6} (space group C2/c, a=10.1678(5) A, b=9.1583(5) A, c=5.5672(3) A, β=107.257(3)° at 10{sup −4} GPa), did not undergo any compression-induced change of symmetry as confirmed by single-crystal diffraction patterns. Series of high-pressure Raman spectra confirm the absence of any symmetry-related structural phase transition with band positions shifting in a smooth fashion on increasing pressure. High-precision lattice parameters, as determined from X-ray diffraction profile analyzes, were used to monitor both the compressibilities of lattice directions and the evolution of the unit-cell volume with pressure. The experimental data was fitted using a third-order Birch–Murnaghan equation-of-state approach and parameterized fits yield V{sub 0}=469.60(11) A{sup 3}, K{sub 0}=85.6(1.3) GPa and K′=5.9(4) for LiScGe{sub 2}O{sub 6} and V{sub 0}=495.95(19) A{sup 3}, K{sub 0}=79(3) GPa and K′=3.9(1.1) for NaScGe{submore » 2}O{sub 6}. The systematic comparison of volume properties and compression behavior shows that both pyroxene-type compounds follow established trend lines with similar slopes in comparing volumes versus bulk moduli, and confirm that the position of trend lines in this systematics describing variations with M1 critically depend on the type of M2 and T cations, independent on the space-group symmetry. - Graphical abstract: Polyhedral model of the LiScGe{sub 2}O{sub 6} crystal structure at 9.51 GPa. Red and blue: crystallographic distinctive germanium-tetrahedral chains; Green: scandium-octahedral chains; Purple: lithium atoms. - Highlights: • High-quality high-pressure data of previously uninvestigated germanate compounds. • Results confirmed through complementing sXRD with Raman spectroscopy. • Comparison and relation of high-pressure pyroxene-type compounds.« less

Two-dimensional single-crystal-to-single-crystal polymerization and depolymerization are described in detail. The results are based on in-house and synchrotron X-ray diffraction experiments conducted on several samples at 100 K and room temperature. The reactions are associated with considerable molecular motions of all components (monomer, template and incorporated solvent molecules), which can be as large as 1 Å. Continuous polymerization leads to a gradual gap opening between the emerging two-dimensional polymer layers, which allows for increased mobility of the solvent molecules. The positional flexibility of both the solvents and the weakly bound templates buffers the local strain induced by polymerization through a complex chain of movements. As a consequence, the accumulated global strain remains small enough to essentially preserve the single-crystalline state in the course of a complete polymerization/depolymerization cycle. The unit-cell parameters evolve in an unusual way. The a and c axes of the trigonal lattice slightly increase during polymerization, even though van der Waals interactions are replaced by shorter covalent bonds and the involved molecules shrink. However, the c axis experiences a significant drop of more than 1 Å during the first depolymerization step. Progressive depolymerization expands the c axis again, but it does not quite reach the value of the fresh crystal. These effects can be explained by local strain formation and compensation mechanisms and by annealing effects during heat-induced depolymerization. An interesting side effect of the polymerization is the reorientation of incorporated solvent molecules, which give the crystal a tunable dipole moment. Of particular importance for the understanding of two-dimensional polymers is the evolution of the connectivity between molecules during polymerization and depolymerization. Combining reaction kinetics with structural information, such as the polymerization-induced displacement of reactive sites, allowed for the development of a propagation model, in which both polymerization and depolymerization proceed in a self-impeding fashion. This model is supported by Monte Carlo simulations.

The acid-assisted wet-chemical and the adhesive-tape induced micromechanical exfoliation of differently sized single crystals of a 2D polymer (approx. 20 μm and 100 μm) is shown to result in thin sheet stacks. Tuning of the thickness is achieved via duration and frequency of the exfoliation, respectively. A color code is established that correlates interference colors of sheet stacks on SiO2(300 nm)/Si as observed under an optical microscope with their thicknesses measured by atomic force microscopy. This facilitates reliable monitoring of the exfoliation and quick identification of sheet stacks of a desired thickness. Furthermore, high resolution atomic force microscopy is applied to investigate the surfaces of starting crystals and both wet-chemically and micromechanically exfoliated sheet stacks aiming at exploring whether exfoliation proceeds with preservation of surface periodicity and with a low frequency of sheet rupturing. These investigations also aimed at uncovering possible point defects and domain (grain) boundaries in the surfaces. It appears that all investigated objects have a high molecular scale perfection and that both exfoliation methods proceed mild enough to largely preserve the molecular structure of the 2D polymer including the not covalently bonded template molecules being part of the crystal packing.

In situ high-pressure investigations on norsethite, BaMg(CO3)2, have been performed in sequence of diamond-anvil cell experiments by means of single-crystal X-ray and synchrotron diffraction and Raman spectroscopy. Isothermal hydrostatic compression at room temperature yields a high-pressure phase transition at P c ≈ 2.32 ± 0.04 GPa, which is weakly first order in character and reveals significant elastic softening of the high-pressure form of norsethite. X-ray structure determination reveals C2/c symmetry (Z = 4; a = 8.6522(14) A, b = 4.9774(13) A, c = 11.1542(9) A, β = 104.928(8)°, V = 464.20(12) A3 at 3.00 GPa), and the structure refinement (R 1 = 0.0763) confirms a distorted, but topologically similar crystal structure of the so-called γ-norsethite, with Ba in 12-fold and Mg in octahedral coordination. The CO3 groups were found to get tilted off the ab-plane direction by ~16.5°. Positional shifts, in particular of the Ba atoms and the three crystallographically independent oxygen sites, give a higher flexibility for atomic displacements, from which both the relatively higher compressibility and the remarkable softening originate. The corresponding bulk moduli are K 0 = 66.2 ± 2.3 GPa and dK/dP = 2.0 ± 1.8 for α-norsethite and K 0 = 41.9 ± 0.4 GPa and dK/dP = 6.1 ± 0.3 for γ-norsethite, displaying a pronounced directional anisotropy (α: β −1 = 444(53) GPa, β −1 = 76(2) GPa; γ: β −1 = 5.1(1.3) × 103 GPa, β −1 = 193(6) GPa β −1 = 53.4(0.4) GPa). High-pressure Raman spectra show a significant splitting of several modes, which were used to identify the transformation in high-pressure high-temperature experiments in the range up to 4 GPa and 542 K. Based on the experimental series of data points determined by XRD and Raman measurements, the phase boundary of the α-to-γ-transition was determined with a Clausius–Clapeyron slope of 9.8(7) × 10−3 GPa K−1. An in situ measurement of the X-ray intensities was taken at 1.5 GPa and 411 K in order to identify the nature of the structural variation on increased temperatures corresponding to the previously reported transformation from α- to β-norsethite at 343 K and 1 bar. The investigations revealed, in contrast to all X-ray diffraction data recorded at 298 K, the disappearance of the superstructure reflections and the observed reflection conditions confirm the anticipated $$R\bar{3}m$$ space-group symmetry. The same superstructure reflections, which disappear as temperature increases, were found to gain in intensity due to the positional shift of the Ba atoms in the γ-phase.

The single-crystal-to-single-crystal (scsc) synthesis of a 2D polymer based on photochemically triggered [2 + 2]-cycloaddition is reported. Both monomer and polymer single crystals are analyzed by X-ray diffraction, which is the first case of a scsc two-dimensional polymerization based on this cycloaddition and the third ever case for a scsc synthesis of a 2D polymer. The product crystals at quantitative conversion are wet-exfoliated under mild conditions and afford countless features that are single and double layers as judged by their AFM heights of hAFM ≈ 1.2 ± 0.5 and 2.2 ± 0.5 nm, respectively. The X-ray-structure-based molecular weight of the 2D polymers and their degree of polymerization per μm2 are M = 360 MDa and Pn = 464 900, respectively. The sheet size is on the order of 5 × 5 μm2.

This work proves the existence and chemical addressability of defined edge groups of a 2D polymer. Pseudohexagonally prismatic single crystals consisting of layered stacks of a 2D polymer are used. They should expose anthracene-based edge groups at the six (100) but not at the two pseudohexagonal (001) and (001̅) faces. The crystals are reacted with the isotopically enriched dienophiles maleic anhydride and a C18-alkyl chain-modified maleimide. In both cases the corresponding Diels-Alder adducts between these reagents and the edge groups are formed as confirmed by solid state NMR spectroscopy. The same applies to a maleimide derivative carrying a BODIPY dye which was chosen for its fluorescence to be out of the range of the self-fluorescence of the 2D polymer crystals stemming from contained template molecules. If the crystals are excited at λ = 633 nm, their (100) faces and thus their rims fluoresce brightly, while the pseudohexagonal faces remain silent. This is visible when the crystals lie on a pseudohexagonal face. Lambda-mode laser scanning microscopy confirms this fluorescence to originate from the BODIPY dye. Micromechanical exfoliation of the dye-modified crystals results in thinner sheet packages which still exhibit BODIPY fluorescence right at the rim of these packages. This work establishes the chemical nature of the edge groups of a 2D polymer and is also the first implementation of an edge group modification similar to end group modifications of linear polymers.

Speech is powerful information technology and the basis of human interaction. By emitting streams of buzzing, popping, and hissing noises from our mouths, we transmit thoughts, intentions, and knowledge of the world from one mind to another. We're accustomed to thinking of speech as an acoustic, auditory phenomenon. However, speech is also visible. Although the primary function of speech is to manipulate air in the vocal tract to produce sound, this action has an ancillary effect of changing the face's appearance. In particular, the action of the lips and jaw during speech causes constant deformation of the facial surface, generating a robust visual signal highly correlated with the acoustic one1-that is, visual speech.

In this paper we present a novel approach to generate a sequence of head motion units given some speech. The modelling approach is based on the notion that head motion can be divided into a number of short homogeneous units that can be modelled individually. The system is based on Hidden Markov Models (HMM), which are trained on motion units and act as a sequence generator. They can be evaluated by an accuracy measure. A database of motion capture data was collected and manually annotated for head motion and is used to train the models. It was found that the model is good at distinguishing high activity regions from regions with less activity with accuracies around 75 percent. Furthermore the model is able to distinguish different head motion patterns based on speech features somewhat reliably, with accuracies reaching almost 70 percent.

The goal of this project was to build a unit selection voice that could portray emotions with varying intensities. A suitable definition of an emotion was developed along with a descriptive framework that supported the work carried out. A single speaker was recorded portraying happy and angry speaking styles. Additionally a neutral database was also recorded. A target cost function was implemented that chose units according to emotion mark-up in the database. The Dictionary of Affect supported the emotional target cost function by providing an emotion rating for words in the target utterance. If a word was particularly ’emotional’, units from that emotion were favoured. In addition intensity could be varied which resulted in a bias to select a greater number emotional units. A perceptual evaluation was carried out and subjects were able to recognise reliably emotions with varying amounts of emotional units present in the target utterance.

In-situ investigations on BaMg(CO3)2 (= α-phase, space group R-3c) by means of single-crystal diffraction and Raman spectroscopy yield the existence of novel structural polymorphs at high-pressure (γ-phase, C2/c) and high-temperature (β-phase, R-3m) conditions. Isothermal hydrostatic compression at room temperature yield a high-pressure phase transition at Pc ≍ 2.3210.04 GPa, which is weakly first order in character and reveals significant elastic softening of the high-pressure form (α: K0 = 66.212.3 GPa, dK/dP = 2.011.8; γ: K0 = 41.910.4 GPa, dK/dP = 6.110.3). X-ray structure determination confirms a distorted but topologically similar crystal structure of the γ-phase, with Ba in twelve-fold and Mg in octahedral coordination together with characteristic CO3 units. Based on the experimental series of in-situ HPHT data points, the phase boundary of the α-to-γ-transition was determined with a Clausius-Clapeyron slope of 9.8(7) × 10-3 GPa K-1. In-situ measurements of the X-ray intensities carried out to identify the nature of the structural variation correspond to the previously reported transformation from α- to β-BaMg(CO3)2 at 343 K and 1 bar. The investigations revealed, in contrast to all X-ray diffraction data recorded at 298 K, the disappearance of the superstructure reflections and the observed reflection conditions confirm the anticipated R-3m space-group symmetry. The pathway of structural transformation follows a typically displacive fashion, involving exclusively positional shifts of the oxygen atoms for the α-β-transformation. In contrast, in the atomic displacement of the Ba atoms in addition to the three crystallographically independent oxygen sites is responsible for a comparably higher flexibility of the C2/c structure, which explains the origin of the remarkable elastic softening.

This paper presents a comparison between a hidden Markov model (HMM) based method and a novel artificial neural network (ANN) based method for lip synchronisation. Both model types were trained on motion tracking data, and a perceptual evaluation was carried out comparing the output of the models, both to each other and to the original tracked data. It was found that the ANN-based method was judged significantly better than the HMM based method. Furthermore, the original data was not judged significantly better than the output of the ANN method.