On One Generalization of Newton's Law of Gravitation

A statement is formulated which leads to the general formula for the force of interaction between two bodies. The distance between their centers of inertia varies with time. According to the third Kepler's law, the well-known Newton's law of gravitation follows from the formula. Some examples are presented and discussed     

Normal- and Reversed-Phase Behaviour of 16,17-Secoestrone Derivatives on Cyanopropyl-Bonded Silica Gel

The retention behaviour of a number of 16,17-secoestrone derivatives has been studied by LC and HPTLC on a polar cyanopropyl-bonded stationary phase using non-aqueous and aqueous-organic mobile phases. The retention behaviour has been discussed in terms of nature of the solute, eluent and stationary phase. The correlation between retention constants of 16,17-secoestrone derivatives obtained from reversed-phases and commercially available ACD log P software (Advanced Chemistry, Toronto, Canada) has also been examined.     

ICP-AES analysis of metal content in shell of mussel Mytilus galloprovincialis from Croatian coastal waters

Metal content in samples of shell of mussel Mytilus galoprovincialis was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficiency of conversion of crude samples into solution by acid digestion in an open plate and in a microwave oven was examined by use of certified reference material of marine sediment and laboratory made standards of calcite and aragonite. Influence of high Ca content matrix on emission intensities of Al, Ba, Cd, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr and Zn was observed as depression of emission signal for most of the measuring elements, ranging from 0.8% to 8%. Greater values were noted at Ba and Ni emission lines. Enhancement of signals was observed for Na and Mg lines. The determination of As, Sb, Se and Sn was performed by HG/ICP-AES. The greater abundance of Sn was found in samples collected near the Al-processing industry centre. No detectable concentrations of As, Sb, and Se were found in shell samples. Results of ICP-AES metal analysis showed that samples collected near harbours, city waste or sewage outlets, and chemical industry centres indicate the certain level of contamination. It is shown that shell analysis provides useful data in determination of marine environment status.     

Chiral Hexa‐ and Nonamethylene‐Bridged Bis(L‐Leu‐oxalamide) Gelators: The First Oxalamide Gels Containing Aggregates with a Chiral Morphology

Chiral amino acid‐ and amino alcohol‐oxalamides are well‐known as versatile and efficient gelators of various lipophilic and polar organic solvents and water. To further explore the capacity of the amino acid/oxalamide structural fragment as a gelation‐generating motif, the dioxalamide dimethyl esters 1₆Me and 1₉Me , and dicarboxylic acid 2₆OH / 2₉OH derivatives containing flexible methylene bridges with odd ( 9 ; n=7) and even ( 6 ; n=4) numbers of methylene groups were prepared. Their self‐assembly motifs and gelation properties were studied by using a number of methods (FTIR, ¹H NMR spectroscopy, CD, TEM, DSC, XRPD, molecular modeling, MMFF94, and DFT). In contrast to the previously studied chiral bis(amino acid or amino alcohol) oxalamide gelators, in which no chiral morphology was ever observed in the gels, the conformationally more flexible 1₆Me , 1₉Me , 2₆OH , and 2₉OH provide gelators that are capable of forming diverse aggregates of achiral and chiral morphologies, such as helical fibers, twisted tapes, nanotubules, straight fibers, and tapes, in some cases coexisting in the same gel sample. It is shown that the differential scanning calorimetry (DSC)‐determined gelation enthalpies could not be correlated with gelator and solvent clogP values. Spectroscopic results show that intermolecular hydrogen‐bonding between the oxalamide units provides the major and self‐assembly directing intermolecular interaction in the aggregates. Molecular modeling studies reveal that molecular flexibility of gelators due to the presence of the polymethylene bridges gives three conformations ( zz , p1 , and p2 ) close in energy, which could form oxalamide hydrogen‐bonded layers. The aggregates of the p1 and p2 conformations tend to twist due to steric repulsion between neighboring iBu groups at chiral centers. The X‐ray powder diffraction (XRPD) results of 1₆Me and 1₉Me xerogels prove the formation of p1 and p2 gel aggregates, respectively. The latter results explain the formation of gel aggregates with chiral morphology and also the simultaneous presence of aggregates of diverse morphology in the same gel system.     

An Improved HPLC Method for Simultaneous Analysis of Losartan Potassium and Hydrochlorothiazide with the Aid of a Chemometric Protocol

An experimental design method was used for fast, simple, and accurate high-performance-pressure liquid chromatograpy (HPLC) determination of losartan and hydrochlorothiazide in combined dosage forms. This method avoids the disadvantages of the traditional analytical approach, which is time-consuming, involves a large number of runs, and does not allow the determination of multiple interacting parameters. On the basis of preliminary experiments, three independent variables (methanol content, pH value of the mobile phase, and flow rate) were selected as input, and as dependent variables, five responses (retention time of hydrochlorothiazide, retention time of losartan, asymmetry of hydrochlorothiazide peak, asymmetry of losartan peak, and resolution) were chosen. A full 2³ factorial design was used to determine which factors had an effect on the studied response. Afterwards, experimental design was used to optimize these influencing parameters in the previously selected experimental domain. After optimizing the experimental conditions, a separation was conducted on a Zorbax C₈ (150 mm × 4.6 mm, 5 μm particle size) column with a mobile phase consisting of methanol–acetonitrile–acetate buffer 45:20:35 v/v/v, pH 4.8 with flow rate of 0.82 mL min^?1 and column temperature of 25 °C. The developed method was successfully applied to simultaneous separation of these active drug compounds in their commercial pharmaceutical dosage forms.     

Influence of a weak constant magnetic field on the Hβ line of a t-tube plasma

Measurements of the additional shift of the Hβ spectral line emitted by a plasma in a magnetic field are performed. The magnitudes of the shift are distinguished by good reproducibility. The magnetic field strength was 0.5 and 2.1 T. Comparison is made of the Hβ line profiles recorded in the presence of the magnetic field and without it, all other things being equal. Consideration is given to a number of possible causes of the additional shift (they include the dependence of the shift on the density of electrons, their temperature, and on the velocity of the plasma flux). The additional shift of the Hβ line in the presence of the magnetic field is qualitatively substantiated. Presented at the 1th Belorussian-Yugoslavian Symposium on the Physics and Diagnostics of Laboratory and Astrophysical Plasmas, 1–3 July, 1996, Misnk. Institute of Physics, 4, Obradović St., Novi Sad, 21000, Yugoslavia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 566–574, September–October, 1997.     

Optimization of Two Eco-Friendly Extractions of Black Medick (Medicago lupulina L.) Phenols and Their Antioxidant,Cosmeceutical, α-Glucosidase and α-Amylase Inhibitory Properties

Medicago lupulina is an ancient edible plant from the Fabaceae family. In this work, two eco-friendly methods for extraction of bioactive phenolics from M. lupulina were developed using mixtures of water with two non-toxic, skin- and environmentally-friendly polyol solvents: glycerol and polypropylene glycol. Ultrasound-assisted extractions were optimized using a Box–Behnken design. The independent variables were the concentration of organic solvent in water (X₁), extraction temperature (X₂) and time (X₃), while the response was phenolic content. The optimum conditions for extraction of polyphenols were (X₁, X₂, X₃): (45%, 70 °C, 60 min) and (10%, 80 °C, 60 min) for glycerol and polypropylene glycol extraction, respectively. The extracts prepared at optimum conditions were rich in phenolic compounds, mainly derivatives of apigenin, kaempferol, luteolin, quercetin, caffeic and ferulic acid, as well as coumestrol. Their cosmeceutical and antidiabetic activity was tested. Both extracts demonstrated notable antioxidant, anti-lipoxygenase and anti-α-amylase activity. In addition to those activities, the glycerol extract efficiently inhibited protein coagulation, elastase and α-glucosidase activity. Glycerol present in the extract displayed enzyme-inhibiting activity in several assays and supported the action of the bioactive constituents. Thus, the optimized glycerol extract is a desirable candidate for direct incorporation in antidiabetic food supplements and cosmeceutical products.     

New Experimental Data for the Validation of Radiative Heat Transfer

The numerical simulation of radiative heat transfer is now well established. Key ingredients in such a simulation model are calculated view factors that are used to describe the exchange of radiated energy between different surfaces. Several methods for the calculation of these geometrical factors are available, including Integration, Monte Carlo, and the Hemi-cube methods. Several analytical test cases are also available, such as the well-known “parallel plates” case, which allow modelers to validate their view factor routines. However, there is much less information available that combines both view factor information and heat transfer effects simultaneously.

This article describes the construction of a simple testing rig that allows experiments to be performed that combine view factor effects with measured heat transfer exchanged between surfaces only. The equipment has been used to consider simple cases, such as the parallel plates test case, and also cases where shadowing is important. The results of these experiments are presented as experimental benchmarking data for model users and developers.