Gold as intermolecular glue: a theoretical study of nanostrips based on quinoline-type monomers

A family of infinite nanostrips is computationally predicted. In it monomers of single, double or triple aromatic rings are linked to each other by strong C-Au-C, C-Au <-- N or N --> Au <-- N bonds. Depending on the geometry of the system and saturation of the bonds, these 1-D nanostrips are found to be insulators, narrow- or zero-gap semiconductors, or metals. The calculated dimerization and polymerization energies suggest clear exothermicity of formation. Varying the nitrogen content in the aromatic ring is found to little affect the geometry, and the 1-D band structure of the strips can be interpreted in a rigid-band picture. The orbital character of the states at the Fermi level has been analyzed. One of the new structures is found to be closely similar to graphene with respect to its band structure properties.     

Physicochemical Characteristics of Biochar from Waste Cricket Chitin (Acheta domesticus)

The properties of biochar (BC) from crustacean chitin are relatively well understood, while there are few studies on BC from insect chitin. This study presents the characterization and phytotoxic assessment of BC produced from crickets and cricket chitin. Cricket powder (BCCR) and cricket chitin (BCCH) were pyrolyzed at 500 °C and 700 °C. Physicochemical characteristics, N ad-/desorption, FTIR, were examined. SEM images were also performed. Regardless of the pyrolysis temperature, biochars were characterized by a densely “packed” solid surface/monolithic type with a non-porous structure (0.05–0.22 m²/g) and high content of N (9.4–11.8%). BCCHs showed a higher pH (12.2–12.4) compared to BCCR (8.7–10.8). Based on the XRD analysis, BCs were characterized by an amorphous carbon turbostratic structure and a randomly oriented graphitic-like micro-crystallite structure. FTIR spectra of BCs confirmed the presence of various O₂ and N-functional groups on the BC surface. BCCHs added to soil at rates from 0.5 to 1.5% significantly reduced the germination of Lepidium sativum. Stimulation of root elongation was also observed in the case of BCCR500 1.0% and BCCR700 1.5%. Thermal degradation of cricket powder and cricket chitin promotes the formation of organic N-containing heterocyclic rings, which lead to the production of N-doped carbons with potential uses in energy storage and the contaminations sorption.     

Intramolecular hydrogen bonds in 3-diethylaminomethyl-5-R-salicylic aldehydes

Two 3-diethylaminomethyl-5-R-salicylic aldehydes were obtained and studied in chloroform solutions by FTIR and NMR spectroscopy. The existence of an equilibrium between the structures with OHO=C and NHO intramolecular hydrogen bonds was suggested. In the case of compound 1 (R=OCH₃) the OHO=C intramolecular hydrogen bond was more favorable whereas in the case of compound 2 (R=Br) the structure with the OHN intramolecular hydrogen bond was predominant.     

Theoretical study of highly-excited states of KRb molecule

Semi-empirical adiabatic potential energy curves of highly excited states of the KRb molecule are calculated as a function of the internuclear distance R over a wide range from 3 to 150 a ₀. The diatomic molecule is treated as an effective two-electron system by using the large core pseudopotentials and core polarization potentials. All calculations are performed by using the nonrelativistic CASSCF/MRCI method with accurate basis set functions. The spectroscopic constants of the calculated electronic states agree well with experimental data, including the recent ones from Lee et al., and with available theoretical results.     

The variable, fractional-order discrete-time PD controller in the IISv1.3 robot arm control

In this paper, the discrete differentiation order functions of the variable, fractional-order PD controller (VFOPD) are considered. In the proposed VFOPD controller, a variable, fractional-order backward difference is applied to perform closed-loop, system error, discrete-time differentiation. The controller orders functions which may be related to the controller input or output signal or an input and output signal. An example of the VFOPD controller is applied to the robot arm closed-loop control due to system changes in moment of inertia. The close-loop system step responses are presented.     

Evaluation of Effectiveness of a Toothpaste Containing Tea Tree Oil and Ethanolic Extract of Propolis on the Improvement of Oral Health in Patients Using Removable Partial Dentures

The aim of this study was to evaluate the effect of toothpaste containing natural tea tree essential oil (TTO) and ethanolic extract of propolis (EEP), on microflora and selected indicators of oral health in patients using removable acrylic partial dentures. Fifty patients with varying conditions of hygiene were divided into two groups. The study group received the toothpaste with TTO and EEP, while the control group received the same toothpaste but without TTO and EEP. At the first visit, oral hygiene and hygiene of the prostheses were carried out. Control visits took place 7 and 28 days later and compared to baseline. Indexes like API (Approximal Plaque Index), mSBI (modified Sulcus Bleeding Index), OHI-s (simplified Oral Hygiene Index), and DPI (Denture Plaque Index) were assessed in three subsequent stages, and swabs were collected from floor of the mouth area to assess the microbiota. After 7 and 28 days of using the toothpaste with TTO and EEP, a statistically significant decrease of the examined indicator values were observed in the study group as compared to the values upon the initial visit. The number of isolated strains of microorganisms in the study group was decreased or maintained at the same level, whereas in the control group an increase in the number of isolated strains was observed. The observed stabilization of oral microbiota in patients from the study group confirms the beneficial activity of toothpaste containing EEP and TTO compared to the control group.     

Podand Solvents for Organic Reactions

Three tris(oxaalkyl)phenylsilanes and two tris(oxaalkyl)phosphates were used as podand solvents in kinetic studies of proton transfer reactions between C-acids: dimethyl (4-nitrophenyl)malonate or phenyl-4-nitrophenylcyanomethane and the strong base: 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). The acceptor numbers were measured for all new podand solvents. The kinetic parameters for studied reactions were obtained, discussed and compared with those of acetonitrile and OP(OEt) 3 as non-podand solvents. This study demonstrated that the second order rate constants strongly decreased and the energy barrier increased for the proton transfer reaction in podand solvents. Spectroscopic observations showed that ionic products were strongly stabilised and therefore their lifetime was relatively long. The podand solvents formed the ionic channels in which ionic products are strongly solvated.