Controlling the Shape and Chirality of an Eight-crossing Molecular Knot

<p>The knotting of biomolecules impacts their function, and enables them to carry out new tasks. Likewise, complex topologies underpin the operation of many synthetic molecular machines. The ability to generate and control more complex knotted architectures is essential to endow these machines with more advanced functions. Here we report the synthesis of a molecular knot with eight crossing points, consisting of a single organic loop woven about six templating metal centres, <i>via</i> one-pot self-assembly from a simple pair of dialdehyde and diamine subcomponents and a single metal salt. The structure and topology of the knot were established by NMR spectroscopy, mass spectrometry and X-ray crystallography. Upon demetallation, the purely organic strand relaxes into a symmetric conformation, whilst retaining the topology of the original knot. This knot is topologically chiral, and may be synthesised diastereoselectively through the use of an enantiopure diamine building block.<b></b></p>

Controlling the Shape and Chirality of an Eight-crossing Molecular Knot

<p>The knotting of biomolecules impacts their function, and enables them to carry out new tasks. Likewise, complex topologies underpin the operation of many synthetic molecular machines. The ability to generate and control more complex knotted architectures is essential to endow these machines with more advanced functions. Here we report the synthesis of a molecular knot with eight crossing points, consisting of a single organic loop woven about six templating metal centres, <i>via</i> one-pot self-assembly from a simple pair of dialdehyde and diamine subcomponents and a single metal salt. The structure and topology of the knot were established by NMR spectroscopy, mass spectrometry and X-ray crystallography. Upon demetallation, the purely organic strand relaxes into a symmetric conformation, whilst retaining the topology of the original knot. This knot is topologically chiral, and may be synthesised diastereoselectively through the use of an enantiopure diamine building block.<b></b></p>

Contrast-tuneable microscopy for single-shot real-time imaging

A novel real image in-line laser holography has enabled a tuneable image contrast, edge sharpness, and visualization of sub-wavelength structures, using a simple pair of filters and large-diameter lenses that can incorporate higher-order scattered beams. Demonstrated also are the accuracy in object sizing and the ease of imaging along the focal depth, based on a single-shot imaging via holographic principle. In addition, the use of broad, collimated laser beam for irradiation has led to a wider field of view, making it particularly useful for an extensive monitoring of, and sweeping search for, cells and microbial colonies and for the real-time imaging of cancer-cell dynamics.

Semi-Supervised Text Simplification with Back-Translation and Asymmetric Denoising Autoencoders

Text simplification (TS) rephrases long sentences into simplified variants while preserving inherent semantics. Traditional sequence-to-sequence models heavily rely on the quantity and quality of parallel sentences, which limits their applicability in different languages and domains. This work investigates how to leverage large amounts of unpaired corpora in TS task. We adopt the back-translation architecture in unsupervised machine translation (NMT), including denoising autoencoders for language modeling and automatic generation of parallel data by iterative back-translation. However, it is non-trivial to generate appropriate complex-simple pair if we directly treat the set of simple and complex corpora as two different languages, since the two types of sentences are quite similar and it is hard for the model to capture the characteristics in different types of sentences. To tackle this problem, we propose asymmetric denoising methods for sentences with separate complexity. When modeling simple and complex sentences with autoencoders, we introduce different types of noise into the training process. Such a method can significantly improve the simplification performance. Our model can be trained in both unsupervised and semi-supervised manner. Automatic and human evaluations show that our unsupervised model outperforms the previous systems, and with limited supervision, our model can perform competitively with multiple state-of-the-art simplification systems.

Zero-Hopf Bifurcation in the Generalized Stretch-Twist-Fold Flow

A zero-Hopf equilibrium in a three-dimensional system is an isolated equilibrium point which has a zero eigenvalue and a simple pair of purely imaginary eigenvalues. In general, for such an equilibrium, there is no theory for finding when some periodic solutions are bifurcated by perturbing the parameters of the system. In this work, we describe the values of the parameters for which a zero-Hopf equilibrium occurs at the equilibrium points in the generalized stretch-twist-fold flow. Thus, only one condition for parameters of the generalized stretch-twist-fold flow introduced in a system (Eq. 1) is found for which the equilibrium point is a zero-Hopf equilibrium. For this condition, we use the averaging method to provide the existence of a periodic solution, which bifurcates from the zero-Hopf equilibrium point. The main result in this paper is Theorem 1, which gives a periodic solution of the generalized stretch-twist-fold flow.

Multivariate Joint Probability Function of Earthquake Ground Motion Prediction Equations Based on Vine Copula Approach

In the structural earthquake engineering, a single parameter is often not sufficient enough to depict the severity of ground motions, and it is thus necessary to use multiple ones. In this sense, the correlation among multiple parameters is generally considered as an importance issue. The conventional approach for developing the correlation is based on regression analysis, along with simple pair copula approaches proposed in recent years. In this study, an innovative mathematical technique—vine copula—is firstly introduced to develop the empirical model for the multivariate dependence of pseudospectral accelerations (PSAs), which are the most commonly used earthquake ground motion parameters. This advancement not only offers a more flexible way of describing nonlinear dependence among multivariate PSAs from the marginal distribution functions but also highlights the extreme dependence. The results can be conventionally acquired in the ground motion selection and seismic risk and loss assessment based on multivariate parameters.

Potent and selective in vitro and in vivo antiproliferative effects of metal–organic trefoil knots

A set of metal–organic trefoil knots (M-TKs) generated by metal-templated self-assembly of a simple pair of chelating ligands were well tolerated in vitro by non-cancer cells but were significantly more potent than cisplatin in both human cancer cells––including those resistant to cisplatin––and in zebrafish embryos.