The development of the nanomaterials with the advanced functional characteristics is a challenging task because of the growing demand in the market of the optoelectronic devices, biodegradable ...plastics, and materials for energy saving and energy storage. Nanocellulose is comprised of the nanosized cellulose particles, properties of which depend on characteristics of plant raw materials as well as methods of nanocellulose preparation. In this study, the effect of the mechanochemical treatment of bleached softwood sulfate pulp on the optical and mechanical properties of nanocellulose films was assessed. It was established that the method of the subsequent grinding, acid hydrolysis and ultrasound treatment of cellulose generated films with the significant transparency in the visible spectral range (up to 78 % at 600 nm), high Young’s modulus (up to 8.8 GPa), and tensile strength (up to 88 MPa) with increased ordering of the packing of the cellulose macromolecules. Morphological characterization was done using the dynamic light scattering (DLS) analyzer and transmission electron microscopy (TEM). The nanocellulose particles had an average diameter of 15–30 nm and a high aspect ratio in the range 120–150. The crystallinity was increased with successive treatments as shown by the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. The thermal degradation behavior of cellulose samples was explored by thermal gravimetric analysis (TGA).
Crown ethers are unique compounds with exceptional ion binding properties. We investigate the 18-crown-6 ether molecule binding selectivity for a set of alkali ions (K+, Rb+, Cs+). We employ ...combination of umbrella sampling technique with the weighted histogram analysis method to derive free energies of ion-ether association. The obtained results are in a good agreement with experimental values available and represent the ion selectivity feature of the 18-crown-6 ether.
A comparative assessment of the accuracy of determining the density and viscosity has been carried out for diisopropyl ether using the method of classical molecular dynamics using three potentials. ...The accuracy of determining the viscosity coefficients when using equilibrium and nonequilibrium calculation methods was also investigated.
The spectral and kinetic properties of luminescence of fluorozirconate glasses 57ZrF
4
⋅33BaF
2
⋅ 6CeF
3
⋅4AlF
3
doped with 2–4 mol % of manganese ions have been studied. It has been demonstrated ...that increasing the doping ion concentration from 2 to 4 mol % is accompanied by the red shift of the
4
T
1
(
G
) →
6
A
1
band of Mn
2+
luminescence from 570 to 580 nm. The red shift is associated with an increase (with increasing concentration) in the number of Mn
2+
–Mn
2+
pairs, which give a longer wavelength luminescence than individual Mn
2+
ions. Analysis of the Mn
2+
luminescence kinetics showed no appreciable concentration quenching of Mn
2+
luminescence at doping concentrations up to 4 mol %. It has been shown that these glasses exhibiting broadband luminescence in the orange region of the spectrum have potential for practical application in white LEDs.
Display omitted
•Accurate carbohydrates MD model is required for food and pharmaceutical industries.•Sucrose has four stable conformations in the solution, which confirm previous data.•Equation of ...state and transport coefficients are well reproduced by the model.•Boundary condition in Stokes-Einstein formula is changed at 40% sugar concentration.
In this work, we study the applicability of the equilibrium molecular dynamics methods for the prediction of solution structure, equation of state and transport properties of sucrose aqueous solution for various concentrations and temperatures. The OPLS-AA force field with 1.14*CM1A charge corrections is used to describe the interactions in the model. We analyze the prediction power of the model against the experimental data and simulation results, obtained previously in CHARMM, OPLS-AA, GLYCAM06 and their modifications. The glycosidic linkage conformations of sucrose in solution are found. Their independence from the sugar concentration and the appearance of the conformation region at temperatures from 283 K to 308 K are observed. Sucrose solution densities are calculated for different sugar concentrations and temperatures. The obtained viscosities and sucrose diffusion coefficients match the experimental data at low sucrose concentrations, and diverge within 41% from the experiment as the concentration increases. The change of boundary condition in Stokes–Einstein formula is observed with an increase of the sucrose concentration above 40%.
The temperature dependence of density is calculated for an aqueous solution of sucrose by the molecular dynamics method. The coefficients of viscosity and diffusion are also obtained in the 273–343 K ...range of temperatures. The hydrodynamic radius of a sucrose molecule in an aqueous solution is calculated. The obtained data are compared with the experimental results.
In this investigation we assessed the physiological reaction of hamsters in response to chemical signals from potential sexual partners, and also after a private meeting with them, which allowed us ...to ascertain the type of mating system for this species. The reception of olfactory signals led to an increase in peroxidase activity in the blood for both sexes, indicative of activity of a non-specific line of immune defense in recipients. The increase in blood cortisol level in response to the chemical signals of a partner was only observed in females. Males spent more time near samples of estrous females, with elevated levels of cortisol in the urine. In olfactory tests, an hour after grouping all the individuals in pairs there was a significant increase in blood peroxidase activity, which indicates the reaction of a non-specific link in the immune system of partners. This increase was greater in the pairs with a mutual preference. Females from these pairs demonstrated a substantial decrease in stress hormone levels in the plasma after an hour of mating in comparison to females prior to mating, and in non-preferred coupling.
Ceramic samples of Y
3
MgGa
3
SiO
12
, Y
3
MgGa
2
AlSiO
12
, and Y
3
MgGaAl
2
SiO
12
multicomponent garnets doped with 0.2 at % Cr
3+
have been obtained by high-temperature solid-state synthesis. In ...the luminescence spectra of the synthesized garnet samples, overlapping broadband luminescence is observed in the far red spectral region caused by the
4
T
2
→
4
A
2
transition in Cr
3+
ions, and a narrow band is observed in the range of 690–700 nm, corresponding to the zero-phonon line of the
2
Е →
4
A
2
transition in Cr
3+
. The narrow-band and broad-band parts of the spectra are attributed to radiation from two different types of chromium centers, which are in octahedral coordination with different distortion degrees and strength of the crystal field. This results from the presence of two ions at the octahedral position of these garnets, which differ significantly in crystal chemical properties, namely, Mg
2+
and Ga
3+
(Al
3+
). The studied phosphors, which have broadband luminescence in the phytoactive far red region of the spectrum, have the potential for use in greenhouse LED lamps.
Chromium trifluoride-doped fluoride glasses in the ZrF
4
–BaF
2
–LaF
3
–AlF
3
–NaF (ZBLAN) system with partial substitution of fluorine for chlorine have been synthesized. The spectral data obtained ...confirm that chromium ions enter the glass structure and exhibit broadband luminescence caused by the
4
T
2
→
4
A
2
transition in the Cr
3+
ion. The observed long-wavelength shift of the broadband luminescence band and Cr
3+
absorption bands in fluoride–chloride glass compared to fluoride glass corresponds to the expected behavior of the Cr
3+
luminescence and absorption spectra when fluoride ions are replaced by chloride ions, which should lead to a weakening of the strength of the crystal field acting on Cr
3+
ions. At room temperature, the luminescence of Cr
3+
ions at 888 and 908 nm is strongly quenched due to the thermally stimulated nonradiative transition from the
4
T
2
excited state to the
4
A
2
ground state.
—
Ceramic LiAl
5
O
8
lithium aluminate spinel materials doped with trivalent chromium ions have been prepared by high-temperature solid-state synthesis. The intensity, spectral shift, and width of ...two zero-phonon luminescence lines (
R
lines) due to transitions from the
2
E
excited state to the
4
A
2
ground state of Cr
3+
ions have been measured as functions of temperature in the range 80–295 K. Analysis of luminescence and luminescence excitation spectra of the ceramics points to severe local lattice distortion around the Cr
3+
ions, which shows up, in particular, as large inhomogeneous broadening of the zero-phonon Cr
3+
luminescence lines. The temperature dependences of the relative intensity, spectral shift, and width of the two zero-phonon lines can be sufficiently well described in terms of existing models for optical centers in crystals. The feasibility of using these temperature dependences for noncontact luminescence thermometry is assessed. Analysis of the data obtained in this study provides no way to uniquely identify the observed zero-phonon lines as due to transitions from two sublevels of the
2
E
state of a single type of chromium center (that is, as
R
1
and
R
2
lines) or transitions of two inequivalent chromium centers coupled by nonresonant energy transfer.
PDF
