Emergence and intensification of dairying in the Caucasus and Eurasian steppes.

Archaeological and archaeogenetic evidence points to the Pontic-Caspian steppe zone between the Caucasus and the Black Sea as the crucible from which the earliest steppe pastoralist societies arose and spread, ultimately influencing populations from Europe to Inner Asia. However, little is known about their economic foundations and the factors that may have contributed to their extensive mobility. Here, we investigate dietary proteins within the dental calculus proteomes of 45 individuals spanning the Neolithic to Greco-Roman periods in the Pontic-Caspian Steppe and neighbouring South Caucasus, Oka-Volga-Don and East Urals regions. We find that sheep dairying accompanies the earliest forms of Eneolithic pastoralism in the North Caucasus. During the fourth millennium BC, Maykop and early Yamnaya populations also focused dairying exclusively on sheep while reserving cattle for traction and other purposes. We observe a breakdown in livestock specialization and an economic diversification of dairy herds coinciding with aridification during the subsequent late Yamnaya and North Caucasus Culture phases, followed by severe climate deterioration during the Catacomb and Lola periods. The need for additional pastures to support these herds may have driven the heightened mobility of the Middle and Late Bronze Age periods. Following a hiatus of more than 500 years, the North Caucasian steppe was repopulated by Early Iron Age societies with a broad mobile dairy economy, including a new focus on horse milking.

Time- and Spectrally-Resolved Photoluminescence Study of Alloyed CdxZn1-xSeyS1-y/ZnS Quantum Dots and Their Nanocomposites with SPIONs in Living Cells.

Magnetic-luminescent composites based on semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) can serve as a platform combining visualization and therapy. Here, we report the construction of QD-SPION nanocomposites based on synthesized SPIONs and alloyed QDs (CdxZn1-xSeyS1-y)/ZnS solubilized with L-cysteine molecules. The study of the spectral-luminescence characteristics, the kinetics of luminescence decay show the composite's stability in a solution. After incubation with HeLa cells, QDs, SPIONs, and their composites form clusters on the cell surface and associate with endosomes inside the cells. Component-wise analysis of the photoluminescence decay of cell-associated QDs/SPIONs provides information about their localization and aggregate status.

Organic aerosol compositions and source estimation by molecular tracers in Dushanbe, Tajikistan.

To elucidate the molecular composition and sources of organic aerosols in Central Asia, carbonaceous compounds, major ions, and 15 organic molecular tracers of total suspended particulates (TSP) were analyzed from September 2018 to August 2019 in Dushanbe, Tajikistan. Extremely high TSP concentrations (annual mean ± std: 211 ± 131 µg m-3) were observed, particularly during summer (seasonal mean ± std: 333 ± 183 µg m-3). Organic carbon (OC: 11.9 ± 7.0 µg m-3) and elemental carbon (EC: 5.1 ± 2.2 µg m-3) exhibited distinct seasonal variations from TSP, with the highest values occurring in winter. A high concentration of Ca2+ was observed (11.9 ± 9.2 µg m-3), accounting for 50.8% of the total ions and reflecting the considerable influence of dust on aerosols. Among the measured organic molecular tracers, levoglucosan was the predominant compound (632 ± 770 ng m-3), and its concentration correlated significantly with OC and EC during the study period. These findings highlight biomass burning (BB) as an important contributor to the particulate air pollution in Dushanbe. High ratios of levoglucosan to mannosan, and syringic acid to vanillic acid suggest that mixed hardwood and herbaceous plants were the main burning materials in the area, with softwood being a minor one. According to the diagnostic tracer ratio, OC derived from BB constituted a large fraction of the primary OC (POC) in ambient aerosols, accounting for an annual mean of nearly 30% and reaching 63% in winter. The annual contribution of fungal spores to POC was 10%, with a maximum of 16% in spring. Measurements of plant debris, accounting for 3% of POC, divulged that these have the same variation as fungal spores.

Bactericidal Activity of Multilayered Hybrid Structures Comprising Titania Nanoparticles and CdSe Quantum Dots under Visible Light.

Titania nanoparticle/CdSe quantum dot hybrid structures are a promising bactericidal coating that exhibits a pronounced effect against light-sensitive bacteria. Here, we report the results of a comprehensive study of the photophysical properties and bactericidal functionality of these hybrid structures on various bacterial strains. We found that our structures provide the efficient generation of superoxide anions under the action of visible light due to electron transfer from QDs to titania nanoparticles with ~60% efficiency. We also tested the antibacterial activity of hybrid structures on five strains of bacteria. The formed structures combined with visible light irradiation effectively inhibit the growth of Escherichia coli, Bacillus subtilis, and Mycobacterium smegmatis bacteria, the last of which is a photosensitive causative agent model of tuberculosis.

The influence of thermal treatment conditions (solvothermal versus microwave) and solvent polarity on the morphology and emission of phloroglucinol-based nitrogen-doped carbon dots.

The optical properties of chemically synthesized carbon dots (CDs) can be widely tuned via doping and surface modification with heteroatoms such as nitrogen, which results in a range of potential applications. Herein, two most commonly used synthesis approaches, namely, solvothermal and microwave-assisted thermal treatments, have been used for the preparation of CDs from phloroglucinol using three different nitrogen containing solvents, namely, ethylenediamine, dimethylformamide, and formamide. Based on the analysis of the morphology and optical properties, we demonstrate the tenability of the CD appearance from amorphous or well-carbonized spherical particles to onion-like ones, which is controlled by solvent polarity, whereas the thermal treatment conditions mostly influence the degree of N-doping and the nature of emissive centers of CDs formed. The findings of this study expand the toolkit of the available CDs with variable morphology and energy structure.

Diet and subsistence in Bronze Age pastoral communities from the southern Russian steppes and the North Caucasus.

The flanks of the Caucasus Mountains and the steppe landscape to their north offered highly productive grasslands for Bronze Age herders and their flocks of sheep, goat, and cattle. While the archaeological evidence points to a largely pastoral lifestyle, knowledge regarding the general composition of human diets and their variation across landscapes and during the different phases of the Bronze Age is still restricted. Human and animal skeletal remains from the burial mounds that dominate the archaeological landscape and their stable isotope compositions are major sources of dietary information. Here, we present stable carbon and nitrogen isotope data of bone collagen of 105 human and 50 animal individuals from the 5th millennium BC to the Sarmatian period, with a strong focus on the Bronze Age and its cultural units including Maykop, Yamnaya, Novotitorovskaya, North Caucasian, Catacomb, post-Catacomb and late Bronze Age groups. The samples comprise all inhumations with sufficient bone preservation from five burial mound sites and a flat grave cemetery as well as subsamples from three further sites. They represent the Caucasus Mountains in the south, the piedmont zone and Kuban steppe with humid steppe and forest vegetation to its north, and more arid regions in the Caspian steppe. The stable isotope compositions of the bone collagen of humans and animals varied across the study area and reflect regional diversity in environmental conditions and diets. The data agree with meat, milk, and/or dairy products from domesticated herbivores, especially from sheep and goats having contributed substantially to human diets, as it is common for a largely pastoral economy. This observation is also in correspondence with the faunal remains observed in the graves and offerings of animals in the mound shells. In addition, foodstuffs with elevated carbon and nitrogen isotope values, such as meat of unweaned animals, fish, or plants, also contributed to human diets, especially among communities living in the more arid landscapes. The regional distinction of the animal and human data with few outliers points to mobility radii that were largely concentrated within the environmental zones in which the respective sites are located. In general, dietary variation among the cultural entities as well as regarding age, sex and archaeologically indicated social status is only weakly reflected. There is, however, some indication for a dietary shift during the Early Bronze Age Maykop period.

Toward Bright Red-Emissive Carbon Dots through Controlling Interaction among Surface Emission Centers.

Relatively weak red photoluminescence of carbon dots (CDots) is a major challenge on the way to their successful implementation in biological and optoelectronic devices. We present a theoretical analysis of the interaction among the surface emission centers of CDots, showing that it may determine efficiency of the red photoluminescence of CDots. Based on the previous experimental studies, it is assumed that the optical response of the CDots is determined by the molecule-like subunits of polycyclic aromatic hydrocarbons (PAHs) attached to the CDots' surface. Three characteristic types of coupling of these PAH subunits are considered: non-interacting monomers, noncovalently bound dimers, and covalently bound dimers with two, three, or four carbon linkers. We demonstrate that the CDots' photoluminescence broadens, redshifts, and weakens by 2 orders of magnitude when the free monomers are substituted by the covalently bridged centers. These and other results of our study show that the realization of CDots with many weakly interacting surface emission centers may constitute an efficient way to achieve their efficient red photoluminescence, which is highly desirable for biological and optoelectronic applications.

Investigation of Magnetic Circular Dichroism Spectra of Semiconductor Quantum Rods and Quantum Dot-in-Rods.

Anisotropic quantum nanostructures have attracted a lot of attention due to their unique properties and a range of potential applications. Magnetic circular dichroism (MCD) spectra of semiconductor CdSe/ZnS Quantum Rods and CdSe/CdS Dot-in-Rods have been studied. Positions of four electronic transitions were determined by data fitting. MCD spectra were analyzed in the A and B terms, which characterize the splitting and mixing of states. Effective values of A and B terms were determined for each transition. A relatively high value of the B term is noted, which is most likely associated with the anisotropy of quantum rods.

Emergence of human-adapted Salmonella enterica is linked to the Neolithization process.

It has been hypothesized that the Neolithic transition towards an agricultural and pastoralist economy facilitated the emergence of human-adapted pathogens. Here, we recovered eight Salmonella enterica subsp. enterica genomes from human skeletons of transitional foragers, pastoralists and agropastoralists in western Eurasia that were up to 6,500 yr old. Despite the high genetic diversity of S. enterica, all ancient bacterial genomes clustered in a single previously uncharacterized branch that contains S. enterica adapted to multiple mammalian species. All ancient bacterial genomes from prehistoric (agro-)pastoralists fall within a part of this branch that also includes the human-specific S. enterica Paratyphi C, illustrating the evolution of a human pathogen over a period of 5,000 yr. Bacterial genomic comparisons suggest that the earlier ancient strains were not host specific, differed in pathogenic potential and experienced convergent pseudogenization that accompanied their downstream host adaptation. These observations support the concept that the emergence of human-adapted S. enterica is linked to human cultural transformations.

Influence of the solvent environment on luminescent centers within carbon dots.

Carbon dots (CDs) are luminescent nanomaterials, with potential use in bioimaging and sensorics. Here, the influence of the surrounding solvent media on the optical properties of CDs synthesized from the most commonly employed precursors, namely citric acid and ethylenediamine, is investigated. The position of optical transitions of CDs can be tuned by the change of pH and solvent polarity. The most striking observation is related to the interaction of CDs with chlorine containing solvents, which results in resolving a set of narrow peaks within both the absorption and PL bands, similar to those observed for polycyclic aromatic hydrocarbons or organic dyes. We assume that the chlorine containing molecules penetrate the surface layers of CDs, which results in an increase of the distance between the luminescent centers; this correlates well with an enhanced D-band in their Raman spectra. A model of CDs composed of a matrix of hydrogenated amorphous carbon with the inclusions of sp2-domains formed by polycyclic aromatic hydrocarbons and their derivatives is suggested; the latter are stacked ensembles of the luminophores and are considered as the origin of the emission of CDs.

Investigation of AgInS2/ZnS Quantum Dots by Magnetic Circular Dichroism Spectroscopy.

Over recent years, quantum dots (QDs) based on ternary metal dichalcogenides have attracted a lot of attention due to their unique properties and a range of potential applications. Here, we review the latest studies on the optical properties of AgInS2/ZnS QDs with emphasis on their theoretical modeling, and present our investigations of electronic transitions invisible in unstructured absorption spectra of AgInS2/ZnS QDs. The analysis of the absorption, photoluminescence excitation (PLE), and magnetic circular dichroism (MCD) spectra of hydrophobic and hydrophilic AgInS2/ZnS QDs of different sizes enables us to determine positions of electron transitions in these QDs. We demonstrate that the use of the second derivative of PLE spectra provides more unequivocal data on the position of the energy transitions compared with the second derivative of absorption spectra. Analysis of the MCD spectra reveals that the magnetic field induces energy level mixing in AgInS2/ZnS QDs in contrast to the traditional Cd-based QDs, where MCD is associated only with removing degeneracy of the excited energy level.

Amino Functionalization of Carbon Dots Leads to Red Emission Enhancement.

The availability of carbon dots (CDots) with bright red photoluminescence (PL) would significantly broaden the range of their biological and optoelectronic applications. We present a theoretical model that predicts that amino functionalization of CDots not only shifts their PL to longer wavelengths but also preserves large oscillator strengths of the fundamental radiative transitions of CDots. The model considers the optical response of amino-functionalized CDots determined by molecule-like subunits of polycyclic aromatic hydrocarbons with one, two, or three -NH2 groups at the CDots' surface; the excited state of those subunits is characterized by strong charge separation between the amino groups and CDots' carbon core. Such a separation determines the Stokes shift of the CDots' emission, which increases with the growing amount of the amino functional groups at the CDot surface. Our model explains the experimentally observed dependence of the PL spectra of CDots on the excitation wavelength, the phenomenon well documented in the literature for nitrogen-containing CDots.

Ancient human genome-wide data from a 3000-year interval in the Caucasus corresponds with eco-geographic regions.

Archaeogenetic studies have described the formation of Eurasian 'steppe ancestry' as a mixture of Eastern and Caucasus hunter-gatherers. However, it remains unclear when and where this ancestry arose and whether it was related to a horizon of cultural innovations in the 4th millennium BCE that subsequently facilitated the advance of pastoral societies in Eurasia. Here we generated genome-wide SNP data from 45 prehistoric individuals along a 3000-year temporal transect in the North Caucasus. We observe a genetic separation between the groups of the Caucasus and those of the adjacent steppe. The northern Caucasus groups are genetically similar to contemporaneous populations south of it, suggesting human movement across the mountain range during the Bronze Age. The steppe groups from Yamnaya and subsequent pastoralist cultures show evidence for previously undetected farmer-related ancestry from different contact zones, while Steppe Maykop individuals harbour additional Upper Palaeolithic Siberian and Native American related ancestry.

Multilevel Data Encryption Using Thermal-Treatment Controlled Room Temperature Phosphorescence of Carbon Dot/Polyvinylalcohol Composites.

Thermal-treatment controlled room temperature phosphorescence is realized by embedding either originally synthesized carbon dots (CDs) or 200 °C thermal-treated CDs into a polyvinylalcohol (PVA) matrix through post-synthetic thermal annealing at 200 or 150 °C. The thermal-treatment controlled phosphorescence is attributed to the transfer of photoexcitation from the excited singlet state to the triplet state through intersystem crossing, followed by radiative transition to the ground state, which is due to decrease of quenchers (oxygen) in the CDs and suppression of the vibrational dissipations through the chemical bonding of CDs in the PVA matrix. Multilevel fluorescence/phosphorescence data encryption is demonstrated based on the thermal-treatment controlled phosphorescence from CD@PVA composites.

Circular dichroism of surface complexes based on quantum dots and azo dye.

Chiral properties of surface complexes based on CdSe/ZnS quantum dots (QDs) and 1-(2-pyridylazo)-2-naphthol (PAN) azo dye were investigated by circular dichroism spectroscopy. The use of L-, D-cysteine (Lcys, Dcys) capping ligands allowed us to obtain water-soluble chiral QD-PAN complexes. The characterization of the complexes was performed by UV-vis, FTIR, and CD spectroscopy. Quantum chemical TDDFT calculated CD spectra reproduced the experimentally observed sign patterns, which originate from binding Lcys or Dcys and PAN molecules to the same Zn atom on the QD surface. The resulting complex is characterized by a large circular dichroism in comparison with an ordinary QD chirality induced by cysteine molecules. The pattern of CD signal is the same for Lcys and Dcys ligands in chiral QD-PAN complex.

The influence of phthalocyanine aggregation in complexes with CdSe/ZnS quantum dots on the photophysical properties of the complexes.

The formation of nonluminescent aggregates of aluminium sulfonated phthalocyanine in complexes with CdSe/ZnS quantum dots causes a decrease of the intracomplex energy transfer efficiency with increasing phthalocyanine concentration. This was confirmed by steady-state absorption and photoluminescent spectroscopy. A corresponding physical model was developed that describes well the experimental data. The results can be used at designing of QD/molecule systems with the desired spatial arrangement for photodynamic therapy.

Circular Dichroism of Electric-Field-Oriented CdSe/CdS Quantum Dots-in-Rods.

Here we report anisotropy of intrinsic chiroptical response in CdSe/CdS quantum dot-in-rod systems. These nanostructures being oriented in an external electric field demonstrate dependence of circular dichroism signal on the orientation of the nanocrystals. The type of circular polarization in these nanostructures correlates with preferential direction of linear polarization, and the degree of circular polarization is the maximal for the first circular dichroism band corresponding to the absorption band edge. We also support our experimental data with a theoretical model. Using this model, we show a direct connection between theoretically derived morphological parameters of twisting in nanocrystals lattices and calculated from experimental data parameters of circular dichroism anisotropy.

Molecular Recognition of Biomolecules by Chiral CdSe Quantum Dots.

Molecular recognition is one of the most important phenomena in Chemistry and Biology. Here we present a new way of enantiomeric molecular recognition using intrinsically chiral semiconductor nanocrystals as assays. Real-time confocal microscopy studies supported by circular dichroism spectroscopy data and theoretical modelling indicate an ability of left-handed molecules of cysteine and, to a smaller extent, histidine and arginine to discriminate between surfaces of left- and right-handed nanocrystals.

Intrinsic Chirality of CdSe/ZnS Quantum Dots and Quantum Rods.

A new class of chiral nanoparticles is of great interest not only for nanotechnology, but also for many other fields of scientific endeavor. Normally the chirality in semiconductor nanocrystals is induced by the initial presence of chiral ligands/stabilizer molecules. Here we report intrinsic chirality of ZnS coated CdSe quantum dots (QDs) and quantum rods (QRs) stabilized by achiral ligands. As-prepared ensembles of these nanocrystals have been found to be a racemic mixture of d- and l-nanocrystals which also includes a portion of nonchiral nanocrystals and so in total the solution does not show a circular dichroism (CD) signal. We have developed a new enantioselective phase transfer technique to separate chiral nanocrystals using an appropriate chiral ligand and obtain optically active ensembles of CdSe/ZnS QDs and QRs. After enantioselective phase transfer, the nanocrystals isolated in organic phase, still capped with achiral ligands, now display circular dichroism (CD). We propose that the intrinsic chirality of CdSe/ZnS nanocrystals is caused by the presence of naturally occurring chiral defects.

Energy transfer in complexes of water-soluble quantum dots and chlorin e6 molecules in different environments.

The photoexcitation energy transfer is found and investigated in complexes of CdSe/ZnS cationic quantum dots and chlorin e6 molecules formed by covalent bonding and electrostatic interaction in aqueous solution and in porous track membranes. The quantum dots and chlorin e6 molecules form stable complexes that exhibit Förster resonance energy transfer (FRET) from quantum dots to chlorin e6 regardless of complex formation conditions. Competitive channels of photoexcitation energy dissipation in the complexes, which hamper the FRET process, were found and discussed.