Responsive hyperbranched poly(formyl-1,2,3-triazole)s toward quadruple-modal information security protection

Science China Chemistry - Secrecy has received tremendous attention in modern information society. Innovative polymer-based fluorescent materials with multiple mode emission are quite desirable to...     

Stokes instability in inhomogeneous membranes: application to lipoprotein suction of cholesterol-enriched domains

We examine the time-dependent distortion of a nearly circular viscous domain in an infinite viscous sheet when suction occurs. Suction, the driving force of the instability, can occur everywhere in the two phases separated by an interface. The model assumes a two-dimensional Stokes flow; the selection of the wavelength at short times is determined by a variational procedure. Contrary to the viscous fingering instability, undulations of the boundary may be observed for enough pumping, whatever the sign of the viscosity contrast between the two fluids involved. We apply our model to the suction by lipoproteins of cholesterol-enriched domains in giant unilamellar vesicles. Comparison of the number of undulations given by the model and by the experiments gives reasonable values of physical quantities such as the viscosities of the domains.     

Neumann-like integrable models

A countable class of integrable dynamical systems, with four-dimensional phase space and conserved quantities in involution (Hn,In)$(H_n,I_n)$ are exhibited. For n=1$n=1$ we recover Neumann system on T^∗S²$T^{\ast }{S}^2$. All these systems are also integrable at the quantum level.     

Kinetic,isotherm, and mechanism investigations of the removal of nitrate and nitrite from water by the synthesized hydrotalcite Mg–Al

Research on Chemical Intermediates - The objective of this work is to test the effectiveness of hydrotalcite as an adsorbent for the retention of nitrate and nitrite ions and to study the influence...     

Phosphorylated cellulose for water purification: a promising material with outstanding adsorption capacity towards methylene blue

Cellulose - Enhancing the sorption properties of cellulose is a prerequisite for its efficient use in water purification as an alternative to costly activated carbon. Here, solvent-free...     

Magnetic Coupling Constants of Self‐Assembled CuII [3×3] Grids: Alternative Spin Model from Theoretical Calculations

This paper reports a theoretical analysis of the electronic structure and magnetic properties of a ferromagnetic Cu^II [3×3] grid. A two‐step strategy, combining calculations on the whole grid and on binuclear fragments, has been employed to evaluate all the magnetic interactions in the grid. The calculations confirm an S=7/2 ground state, which is in accordance with the magnetisation versus field curve and the thermal dependence of the magnetic moment data. Only the first‐neighbour coupling terms present non‐negligible amplitudes, all of them in agreement with the structure and arrangement of the Cu 3d magnetic orbitals. The results indicate that the dominant interaction in the system is the antiferromagnetic coupling between the ring and the central Cu sites (J₃=J₄≈?31 cm^?1). In the ring two different interactions can be distinguished, J₁=4.6 cm^?1 and J₂=?0.1 cm^?1, in contrast to the single J model employed in the magnetic data fit. The calculated J values have been used to determine the energy level distribution of the Heisenberg magnetic states. The effective magnetic moment versus temperature plot resulting from this ab initio energy profile is in good agreement with the experimental curve and the fitting obtained with the simplified spin model, despite the differences between these two spin models. This study underlines the role that the theoretical evaluations of the coupling constants can play on the rationalisation of the magnetic properties of these complex polynuclear systems.     

Preparation of Stereoregular Isotactic Poly(mandelic acid) through Organocatalytic Ring‐Opening Polymerization of a Cyclic O‐Carboxyanhydride

Poly(mandelic acid) (PMA) is an aryl analogue of poly(lactic acid) (PLA) and a biodegradable analogue of polystyrene. The preparation of stereoregular PMA was realized using a pyridine/mandelic acid adduct (Py?MA) as an organocatalyst for the ring‐opening polymerization (ROP) of the cyclic O‐carboxyanhydride (manOCA). Polymers with a narrow polydispersity index and excellent molecular‐weight control were prepared at ambient temperature. These highly isotactic chiral polymers exhibit an enhancement of the glass‐transition temperature (T_g) of 15 °C compared to the racemic polymer, suggesting potential future application as high‐performance commodity and biomedical materials.     

New complex macromolecular architectures based on organosilicon chemistry

Polycarbosilane networks were prepared from well-defined α, ω-difunctional oligomers: X-[Si(CH₃)₂-CH₂-CH₂]_n-X with X = H ( 1 ) and X = CH=CH₂ ( 2 ). Crosslinking reactions were performed by hydrosilylation of tetramethyltetravinylcyclotetrasiloxane (V₄) or of tetravinylsilane with SiH end groups of 1 . Hydrosilylation of Si-CH=CH₂ end groups of 2 with tetramethyltetrahydrocyclotetrasiloxane (D₄H) was also successfully tried. Some physicochemical properties of these new networks will be presented.¹⁾ Interpenetrating networks based on polysiloxanes and polycarbonates were synthesized by the in situ method: a polysiloxane bearing various proportions of room temperature crosslinkable -Si(OEt)₃ side groups was mixed with bis(allyl ethylene glycol) biscarbonate and a free-radical initiator. After the formation of the first network at room temperature, the cross-linking of the polycarbonate network was performed by raising the temperature up to 80°C. Various chemical modifications of the polysiloxane component in the IPN were performed in order to improve the degree of interpenetration as estimated from turbidity, density, refractive index and DSC measurements.²⁾     

A Comparative Study of Various Pretreatment Approaches for Bio-Ethanol Production from Willow Sawdust,Using Co-Cultures and Mono-Cultures of Different Yeast Strains

The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H₂O₂) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H₂O₂ (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H₂O₂ (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost.     

Towards a unified recurrent neural network theory: The uniformly pseudo-projection-anti-monotone net

In the past decades, various neural network models have been developed for modeling the behavior of human brain or performing problem-solving through simulating the behavior of human brain. The recurrent neural networks are the type of neural networks to model or simulate associative memory behavior of human being. A recurrent neural network (RNN) can be generally formalized as a dynamic system associated with two fundamental operators: one is the nonlinear activation operator deduced from the input-output properties of the involved neurons, and the other is the synaptic connections (a matrix) among the neurons. Through carefully examining properties of various activation functions used, we introduce a novel type of monotone operators, the uniformly pseudo-projectionanti-monotone (UPPAM) operators, to unify the various RNN models appeared in the literature. We develop a unified encoding and stability theory for the UPPAM network model when the time is discrete. The established model and theory not only unify but also jointly generalize the most known results of RNNs. The approach has lunched a visible step towards establishment of a unified mathematical theory of recurrent neural networks.