Strongly Correlated Exciton-Magnetization System for Optical Spin Pumping in CrBr3 and CrI3 .

Ferromagnetism in van der Waals systems, preserved down to a monolayer limit, attracted attention to a class of materials with general composition CrX3 (X=I, Br, and Cl), which are treated now as canonical 2D ferromagnets. Their diverse magnetic properties, such as different easy axes or varying and controllable character of in-plane or interlayer ferromagnetic coupling, make them promising candidates for spintronic, photonic, optoelectronic, and other applications. Still, significantly different magneto-optical properties between the three materials have been presenting a challenging puzzle for researchers over the last few years. Herewith, it is demonstrated that despite similar structural and magnetic configurations, the coupling between excitons and magnetization is qualitatively different in CrBr3 and CrI3 films. Through a combination of the optical spin pumping experiments with the state-of-the-art theory describing bound excitonic states in the presence of magnetization, we concluded that the hole-magnetization coupling has the opposite sign in CrBr3 and CrI3 and also between the ground and excited exciton state. Consequently, efficient spin pumping capabilities are demonstrated in CrBr3 driven by magnetization via spin-dependent absorption, and the different origins of the magnetic hysteresis in CrBr3 and CrI3 are unraveled.

Universal tight binding model for chemical reactions in solution and at surfaces. I. Organic molecules.

As is now well established, a first order expansion of the Hohenberg-Kohn total energy density functional about a trial input density, namely, the Harris-Foulkes functional, can be used to rationalize a non self consistent tight binding model. If the expansion is taken to second order then the energy and electron density matrix need to be calculated self consistently and from this functional one can derive a charge self consistent tight binding theory. In this paper we have used this to describe a polarizable ion tight binding model which has the benefit of treating charge transfer in point multipoles. This admits a ready description of ionic polarizability and crystal field splitting. It is necessary in constructing such a model to find a number of parameters that mimic their more exact counterparts in the density functional theory. We describe in detail how this is done using a combination of intuition, exact analytical fitting, and a genetic optimization algorithm. Having obtained model parameters we show that this constitutes a transferable scheme that can be applied rather universally to small and medium sized organic molecules. We have shown that the model gives a good account of static structural and dynamic vibrational properties of a library of molecules, and finally we demonstrate the model's capability by showing a real time simulation of an enolization reaction in aqueous solution. In two subsequent papers, we show that the model is a great deal more general in that it will describe solvents and solid substrates and that therefore we have created a self consistent quantum mechanical scheme that may be applied to simulations in heterogeneous catalysis.

Universal tight binding model for chemical reactions in solution and at surfaces. II. Water.

A revised water model intended for use in condensed phase simulations in the framework of the self consistent polarizable ion tight binding theory is constructed. The model is applied to water monomer, dimer, hexamers, ice, and liquid, where it demonstrates good agreement with theoretical results obtained by more accurate methods, such as DFT and CCSD(T), and with experiment. In particular, the temperature dependence of the self diffusion coefficient in liquid water predicted by the model, closely reproduces experimental curves in the temperature interval between 230 K and 350 K. In addition, and in contrast to standard DFT, the model properly orders the relative densities of liquid water and ice. A notable, but inevitable, shortcoming of the model is underestimation of the static dielectric constant by a factor of two. We demonstrate that the description of inter and intramolecular forces embodied in the tight binding approximation in quantum mechanics leads to a number of valuable insights which can be missing from ab initio quantum chemistry and classical force fields. These include a discussion of the origin of the enhanced molecular electric dipole moment in the condensed phases, and a detailed explanation for the increase of coordination number in liquid water as a function of temperature and compared with ice--leading to insights into the anomalous expansion on freezing. The theory holds out the prospect of an understanding of the currently unexplained density maximum of water near the freezing point.

Universal tight binding model for chemical reactions in solution and at surfaces. III. Stoichiometric and reduced surfaces of titania and the adsorption of water.

We demonstrate a model for stoichiometric and reduced titanium dioxide intended for use in molecular dynamics and other atomistic simulations and based in the polarizable ion tight binding theory. This extends the model introduced in two previous papers from molecular and liquid applications into the solid state, thus completing the task of providing a comprehensive and unified scheme for studying chemical reactions, particularly aimed at problems in catalysis and electrochemistry. As before, experimental results are given priority over theoretical ones in selecting targets for model fitting, for which we used crystal parameters and band gaps of titania bulk polymorphs, rutile and anatase. The model is applied to six low index titania surfaces, with and without oxygen vacancies and adsorbed water molecules, both in dissociated and non-dissociated states. Finally, we present the results of molecular dynamics simulation of an anatase cluster with a number of adsorbed water molecules and discuss the role of edge and corner atoms of the cluster.

Pharmacokinetics of enrofloxacin in lactating sheep.

The pharmacokinetics of enrofloxacin (ENR) was investigated after its intravenous (iv) and intramuscular (im) administration in six healthy lactating sheep. After iv ENR injection (as a bolus), the elimination half-life (t(1/2beta)), the volume of distribution (Vd(area)), and the area under the concentration vs. time curve (AUC) were 3.30 (0.36)h, 2.91 (0.17)l/kg and 4.19 (0.18) microg h/ml, respectively. The maximum milk concentrations of ENR (C(max)), the area under the milk concentration vs. time curve (AUC(milk)) and the ratio AUC(milk)/AUC(serum) were 2.38 (0.14)microg/ml, 23.76 (2.21) microg h/ml and 5.62 (0.30), respectively. After im administration of ENR the t(1/2beta), C(max), time of C(max) (t(max)) and absolute bioavailability (F(abs)) were 3.87 (0.10)h, 0.74 (0.07) microg/ml, 0.83 (0.12)h and 75.35%, respectively. The C(max), AUC(milk) and the ratio AUC(milk)/AUC(serum) were 1.94 (0.13) microg/ml, 24.81 (2.25) microg h/ml and 8.15 (0.96), respectively.

Interspecies comparisons of plasma half-life of trimethoprim in relation to body mass.

The relationship between body mass and plasma half-life of trimethoprim was studied in 10 different species of animals and man using published data. Log half-life was positively and significantly correlated to log body mass based on individual measurements in herbivorous animals (n = 23, P < 0.01), in herbivorous animals+pigs (n = 29, P < 0.01), in ungulates (n = 27, P < 0.01), in ruminants (n = 16, P < 0.01) and in non-herbivorous mammals, except pigs (n = 6, P < 0.05). The correlation was described by the allometric equations: t 1/2 beta = 27 W0.26 in herbivorous animals and t 1/2 beta = 125 W0.32 in non-herbivorous animals except pigs.

Species specific pharmacokinetics of rolitetracycline.

Comparative studies on some selected pharmacokinetic parameters of rolitetracycline (effective antimicrobial activity levels) in sheep, pigs, rabbits, chickens and pigeons were carried out after intravenous administration of the drug at a dose of 5 mg/kg. The results revealed that a two-compartment open model was usually optimal. Interspecies differences in the rate (alpha) and the volume of distribution (Vda), the area under the serum concentration time curve (AUC) and the total body clearance (ClB) were small. The values of the elimination half-life (t1/2 beta) found in sheep, pigs, rabbits, chickens and pigeons were 1.51, 3.06, 2.18, 4.33 and 2.51 h respectively. These results and data in mice, rabbits and man taken from literature were analysed to determine any correlation to body mass (W). The log of the elimination half-life values (log t1/2 beta) of rolitetetracycline revealed a significant correlation with log values of (W) between animal species. This relationship was described by the equation t1/2 beta = 1.27.W0.29 (r = 0.93, P < 0.01, n = 5) for mammal species and t1/2 beta = 1.81.W0.24 (r = 0.78, P < 0.05, n = 7) for mammal and bird species.

Interspecies variations in plasma half-life of ampicillin, amoxycillin, sulphadimidine and sulphacetamide related to variations in body mass.

The relationships between the half-lives during the elimination phase (t1/2 minutes) of ampicillin, amoxycillin, sulphadimidine and sulphacetamide and body mass (W, kg) between species of mammals and birds were examined using data from the authors' experiments and collected from the literature. Linear regression of the log half-lives of ampicillin, amoxycillin and sulphadimidine following intravenous injection on the log body mass for a variety of species of mammals and birds revealed significant correlations (r = 0.7709, n = 8, r = 0.7712, n = 8, r = 0.7749, n = 10). The interspecies relationships were described by the allometric equations t1/2 = 31.3 W0.16, t1/2 = 32.7 W0.12 and t1/2 = 129.2 W0.28, respectively. These equations may be of value for estimating dose intervals in species for which no relevant pharmacokinetic data are available.

Interspecies differences in the pharmacokinetics of kanamycin and apramycin.

Comparative studies on some selected pharmacokinetic parameters for kanamycin in sheep, goats, rabbits, chickens and pigeons, and for apramycin in sheep, rabbits, chickens and pigeons were carried out after intravenous administration of the two drugs at a dose of 10 mg/kg. The results revealed that a two-compartment open model was most suitable for kanamycin, while for apramycin a one-compartment open model was usually optimal. The log distribution rate constant (alpha) of kanamycin was significantly correlated to the log of the body mass (r = 0.919, n = 5, p < 0.05). Interspecies differences in the apparent volume of distribution (Vda) of kanamycin were small. These differences were larger for apramycin, as were the variations in the area under the serum concentration-time curve (AUC) and in the total body clearance (ClB) of both kanamycin and apramycin, both having almost a threefold difference depending on the species but without any correlation to body mass. The values of the log half-life of kanamycin in the mammals in this study and also those from data in the literature revealed a significant correlation with log body mass between animal species according to the equation: t1/2 beta = 38.47W0.21 (r = 0.7648, n = 10, p < 0.05).

Slow release bolus for small ruminants: in vitro release of tetracycline compared with serum concentrations of the antibiotic in sheep.

Two formulations of slow release boluses for small ruminants containing tetracycline hydrochloride in a compressed form were investigated in vitro and in vivo in adult sheep. An in vitro dissolution test was used for the preliminary selection of the 2 boluses. It was shown that the non-cumulative kinetics of tetracycline release in vitro were predictive of the tetracycline serum levels in sheep treated orally with the 2 boluses. The maximum concentrations revealed by the in vitro and in vivo curves were obtained at almost the same Tmax and, in vivo, the therapeutic serum levels were maintained for about 5 days. It is concluded that an in vitro approach is of value in predicting the kinetic profiles of a long-acting tetracycline bolus in sheep.

[Subchronic toxicity of apramycin in pigs]. / Subkhronichna toksichnost na apramitsina pri praseta.

Use was made of four groups of six pigs each, weighing 40 to 50 kg to follow up the toxicity of Pharmachim's apramycin in the form of water-soluble powder of apramycin sulfate, given at the rate of (nil), 300, 500, and 1,000 mg per liter of drinking water in the course of 35 days. It was found that such treatment did not lead to changes in the general status of the animals. On the contrary, apramycin sulfate stimulated growth and improved feed conversion. In concentrations of up to 300 mg/l the preparation did not produce an essential effect on the clinico-laboratory indices, and did not lead to toxic alterations of the viscera. In concentrations of 500 and 1,000 mg/l and extending the period to more than 15 days an occasional drop of the percent of lobular neutrophilic leukocytes and rise of the percent of lymphocytes in the blood might occur. This could lead to dystrophic processes in the liver and to negligible changes of the same character in both the kidneys and the heart.

[Chronic 90-day toxicity of apramycin in chickens]. / Prouchvane vurkhu khronichnata 90-dnevna toksichnost na apramitsina pri pileta.

Investigations were carried out on 72 2-day-old broilers, divided into four groups (one control group--27 broilers and 3 experimental groups--15 broilers in each), treated with apramycin sulphate (AS), which was added to the food in concentration 0, 330, 1000 and 1600 mg/kg (corresponding to 0, 50, 150 and 250 mg/kg m.), in the course of 90 days. It was established that dose of 50 mg/kg m. AS does not causes toxic activities. With doses of 50, 150 and 250 mg/kg m. AS causes reduction of the degree of the pseudo-eosinophilic cells and increase of the percentage of leucocytes--in range similar to the physiological variations, contributes to stimulate the growth and the feed conversion. With doses of 150 and 250 mg/kg m. AS causes reduction of the content of haemoglobin and reduction of the number of erythrocytes; causes dystrophic changes in the internal organs.

[Preclinical research on drug forms containing rifamycin SV intended for intramammary use]. / Predklinichni izsledvaniia vurkhu lekarstveni formi, sudurzhashti rifamitsin SV, prednaznacheni za intramamarna upotreba.

It was established, that LD50 of rifamycin SV--sodium salt, produced by the Research Institute on Microbiological Industry--Razgrad (People's Republic of Bulgaria)--RM, at p.o. applying on albino mice, albino rats and broilers is correspondingly greater than 4100.0 mg/kg m., greater than 5740.0 mg/kg m. and 1951.6 (1355.5 divided by 2810.1) mg/kg m. and at s. c. introducing into albino mice--815.9 (756.9 divided by 879.9) mg/kg m. From the prepared on the basis of RM-4 intramammary medicaments--RM-1, RM-2 and RM-3 for lactating cows and RM-4 for cows in the dry period, a good bearing have RM-1, RM-3 and RM-4. RM-1, RM-2 and RM-3, applied intracisternally a single time on lactating cows, and RM-4 on cows in the dry period, create antimicrobial levels with duration correspondingly 168, 72 and 48 h, and 35 days. RM almost does not penetrate in the neighbouring not treated quarters. Appropriate medicament for the lactating cows with average duration of emission is RM-3 (term of action 96 h) and for cows in the dry period RM-4 when applied 35 days before the calving.

[Effect of feed antibiotics on ampicillin pharmacokinetics in chickens]. / Vliianie na niakoi nutritivni antibiotitsi vurkhu farmakokinetikata na ampitsilina pri pileta.

Experimental studies with broiler birds revealed that medicated feed (flavophospholipol, vitamyacin A, and the A-149 antibiotic in stimulative doses), offered in the course of two weeks, led to changes in the pharmacokinetic parameters of ampicillin administered i/v (in the form of ampicillin-Na) and via the crop (in the form of ampicillin-trihydrate at 30 mg/kg). It was found that the biologic half-life of ampicillin-Na was prolonged by A-149, and was shortened by vitamicin A, and to a certain extent--by flavophospholipol; the seeming volume of distribution was shown to rise by A-149, and to a certain extent--by flavophospholipol, and was lowered by vitamycin A. The biologic half-life of ampicillin-trihydrate was prolonged by all three ergotropic agents. The systematic bioavailability of ampicillin-trihydrate rose with the use of A-149, and dropped with the use of vitamycin A, and to a lower extent--with the use of flavophospholipol. On the base of the changes established in the pharmacokinetic parameters ampicillin-trihydrate was dosed for use via the drinking water as follows: 196 mg/l simultaneously with flavophospholipol in the feed, 156 mg/l--with the use of vitamycin A, 148 mg/l--when used with the A-149 antibiotic, and 216 mg/l--when administered at no medication via the feed.

[Ergotrophic action of flavophospholipol during the fattening of geese]. / Ergotropnoto deistvie na flavofosfolipola pri ugoiavane na guski.

Experiments were carried out with a total of 144 geese of the Benkovska breed divided into 6 groups of 24 birds each. The average weight was 3.5 kg, the birds being compulsory fattened with steamed maize over an average period of 27 days. Flavophospholipol (flavofarm-NIHFI) was given at rates of 0, 4, 8, 12, and 16 ppm. The method of positive control check was employed--a group which was offered zinc-bacitracin--(bacifarmin) at 30 ppm. Under the effect of flavophospholipol the weight gain was 2.2 to 21.2 per cent higher, and the weight of the liver rose by 1.4-23.1 per cent. The intake of maize per kg of gain dropped by 2.5 to 15.7 per cent, and it was 1.8 to 16.9 per cent lower per kg of liver. When flavophospholipol was given at 16 ppm, a maximum effect was produced--21.0 percent higher gain, 23.1 per cent increase of the liver weight, 15.7 per cent drop of maize intake per kg of gain, and 16.9 per cent drop of maize intake per kg of liver. With geese that were offered bacifarmin these indices were 3.3, 11.9,, 4.8, and 10.7 per cent, respectively. The amount of flavophospholipol used correlated positively with its ergotropic effect. The liver quality with geese treated with flavophospholipol and bacifarmin was higher. No residual amounts of flavophospholipol were found in the meat, liver and viscera of the treated birds.

[Trial of trimedin action on chickens]. / Izpitvane deistvieto na trimedina pri pileta.

Investigations were carried out with a total of 421 broiler birds (four-line Cornish X Plymouth Rock hydbrids) within the age range of 2 days to 5 weeks. Determined was the acute toxicity of the combination sulfadimidine (SDM) + trimetoprim (TMP)--5 + 1 and the water-soluble formula of trimedin following the intraingluvial introduction with week-old birds. LD50 of the combinations SDM+TMP (5+1) was 3980 mg/kg (2780: 5690), and that of trimedin was 2038 mg/kg body mass. The biologic half-life of SDM ranged from 4.77 to 5.34 h, and that of TMP--from 4.81 to 5.71 h at the intraingluvial introduction of the combination SDM+TMP (5+1) at the rate of 0.06 g/kg. Demonstrated were the therapeutic levels of SDM and TMP during the whole period (10 days) of treatment with the combination SDM+TMP (5+1) given with the feed in conc. 500 ppm or at the application of trimedin alone via the drinking water in conc. 0.05%. It was found that trimedin used for 10 days with the drinking water in conc. 0.05 per cent with broilers at the experimental infection with Salmonella gallinarum-pullorum protected about 40 per cent of the birds, the latter remaining, however, carriers of the infection.

[Effect of salinomycin (K 364) on the fattening of pigs]. / Izsledvane vliianieto na salitsinomitsina (K 364) vurkhu praseta za ugoiavane.

Experiments with pigs of the White Bulgarian Improved breed of initial weight of 25 kg revealed that the oral administration of salinomycin at the rate of 50 ppm (from the beginning of treatment up to the 61st day) and 25 ppm (from the 62nd day up to the 117th day) with the feed led to the increase in weight gain by 10.9 per cent and in feed conversion by 7.4 per cent by the end of the experimental period. The effect of nutrition was manifested regularly in the course of both periods of fattening. The slaughter weight also rose under the effect of salinomycin. It should be noted that higher rates of treatment--100, resp. 50 ppm--for the respective periods led to the reduction of the stimulant action of salinomycin. Under the conditions to the investigation nitrovin did not show a clearly manifested nutrition effect.