Cellulose Nanocrystals (CNCs) Induced Crystallization of Polyvinyl Alcohol (PVA) Super Performing Nanocomposite Films

This study is aimed to explore the properties of cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) composite films with and without 1,2,3,4‐butane tetracarboxylic acid (BTCA), a nontoxic crosslinker. CNC and CNC‐PVA nanocomposite films are prepared using solution‐casting technique. Differential scanning calorimetry (DSC) analyses show that crosslinking increased the glass transition temperature but reduced the melting temperature and crystallinity. Furthermore, high CNC concentrations in the PVA matrix interfere with PVA crystallinity, whereas in specific ratio between CNC and PVA, two different crystalline structures are observed within the PVA matrix. Film surfaces and fracture topographies characterized using scanning electron microscope indicate that at certain CNC‐PVA ratios, micron‐sized needle‐like crystals have formed. These crystalline structures correlate with the remarkable improvement in mechanical properties of the CNC‐PVA nanocomposite films, that is, enhanced tensile strain and toughness to 570% and 202 MJ m^?3, respectively, as compared to pristine PVA. BTCA enhances the tensile strain, ultimate tensile stress, toughness, and modulus of CNC films compared to pristine CNC films. Water absorption of crosslinked CNC and CNC‐PVA nanocomposite films is significantly reduced, while film transparency is significantly improved as a function of PVA and crosslinker content. The presented results indicate that CNC‐PVA nanocomposite films may find applications in packaging, and though materials applications.     

Fast screening of operational aqueous samples by gross alpha and beta counting with LSC systems

At nuclear installations a large number of samples is used to control operational tasks and health physics parameters. A fast screening process can be applied to provide immediate indication on possible contamination, and liquid scintillation counting (LSC) is the preferred method. Many LSC systems, which do not perform pulse shape analysis, are still in use. A screening procedure for these systems is presented based on three windows analysis. It may greatly reduce work and time, compared to using a proportional counter system, besides providing more accurate results.     

Electronic Structure Engineering of Carbon Nitride Materials by Using Polycyclic Aromatic Hydrocarbons

The design of charge separation sites under illumination in semiconductors is a standing challenge for their utilization as photo(electro)catalysts. Here, the synthesis of modified carbon nitride materials (CNs) with donor–acceptor (D–A) domains, with altering electronic structure, is reported. To do so, new monomers based on polycyclic aromatic hydrocarbons (PAH)-substituted 1,3,5-triazine were designed, which were then embedded within cyanuric acid–melamine supramolecular assemblies to form CN precursors. The conjugation degree of PAHs was systematically changed, from single benzene ring up to pyrene unit, elucidating the role of the conjugation degree on the morphology, structure and electronic properties as well as photo(electro)catalytic activity. The careful design of the D–A sites results in excellent photocatalytic activity as well as long-term stability for the hydrogen evolution reaction. Moreover, PAH–CNs films exhibit enhanced charge separation, optical absorption, electrochemical surface area and electronic conductivity, leading to an outstanding photoelectrochemical (PEC) activity compared to pristine CN.     

Brillouin zone spectroscopy of nonlinear photonic lattices

We present a novel, real-time, experimental technique for linear and nonlinear Brillouin zone spectroscopy of photonic lattices. The method relies on excitation with random-phase waves and far-field visualization of the spatial spectrum of the light exiting the lattice. Our technique facilitates mapping the borders of the extended Brillouin zones and the areas of normal and anomalous dispersion within each zone. For photonic lattices with defects (e.g., photonic crystal fibers), our technique enables far-field visualization of the defect mode overlaid on the extended Brillouin zone structure of the lattice. The technique is general and can be used for photonic crystal fibers as well as for periodic structures in areas beyond optics.     

Nondiffracting beams in periodic media

We identify nondiffracting beams in two-dimensional periodic systems, exhibiting symmetry properties and phase structure characteristic of the band(s) they are associated with.     

Synthesis of Carbon–Nitrogen–Phosphorous Materials with an Unprecedented High Amount of Phosphorous toward an Efficient Fire‐Retardant Material

Phosphorus incorporation into carbon can greatly modify its chemical, electronic, and thermal stability properties. To date this has been limited to low levels of phosphorus. Now a simple, large‐scale synthesis of carbon–nitrogen–phosphorus (CNP) materials is reported with tunable elemental composition, leading to excellent thermal stability to oxidation and fire‐retardant properties. The synthesis consists of using monomers that are liquid at high temperatures as the reaction precursors. The molten‐state stage leads to good monomer miscibility and enhanced reactivity at high temperatures and formation of CNP materials with up to 32 wt % phosphorus incorporation. The CNP composition and fire‐retardant properties can be tuned by modifying the starting monomers ratio and the final calcination temperature. The CNP materials demonstrate great resistance to oxidation and excellent fire‐retardant properties, with up to 90 % of the materials preserved upon heating to 800 °C in air.     

Sigmatropic 1.5-hydrogen shift and concomitant cyclopropane bond cleavage on thermolysis of trans-1-isopropenyl-4-methylene spiro[2.x]alkanes into 1-methylene-(3′-methylbut-2′-enyl)-cycloalk-2-enes

Thermolysis of several trans-1-isopropenyl-4-methylene-spiro[2.x]- alkanes (x = 4,5) in xylene solution at 130° causes quantitative rearrangement to 1-methylene-2-(3′-methylbut-2′-enyl)cycloalkanes ($\text{3}$ – $\text{4}$).     

A heterometric micro-determination of lead with sodium diethyldithiocarbamate

The reaction between lead and sodium diethyldithiocarbamate is studied hcterometrically. The influence of the milieu, conditions of acidity and of different complexing agents, was studied. 0.02–0.04 mg lead per ml of solution can be determined either alone or in the presence of large excesses of other metals. A titration is carried out at 20°C in 8–15 minutes with an error of 0.0–1.0%. The analysed solution may contain ~ 99.5% of the following cations: Ca⁺². Sr⁺², Ba⁺², Mg⁺² Zn⁺², Mn⁺², Ni⁺², Co⁺², Al⁺³, Cr⁺³, Fe⁺³, Cd⁺². Cu⁺², Sb⁺³, Hg⁺², Ag⁺.