First record of the Balkan-Anatolian crested newt (Triturus ivanbureschi Arntzen & Wielstra, 2013) on the territory of the Nature Park “Shumensko plato”

In a four-year monitoring period, numerous permanent and temporary water basins on the territory of the Habitat Protected Site BG0000382 and the Nature Park “Shumensko Plato” (NE Bulgaria) were identified as possible habitats for amphibians. We inspected the water bodies for presence of Urodelas, included in the inventory documentation of the protected territories. Despite intense field surveys and use of traps, we were able only recently to identify one specimen of the Balkan-Anatolian crested newt. This is the first official record of the species for the protected site

Ten millennia of hepatitis B virus evolution

Hepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between ~10,500 and ~400 years ago. We date the most recent common ancestor of all HBV lineages to between ~20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for ~4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic

Emergence and dispersal of snakes after syntopic hibernation

A communal hibernaculum situated in Southwestern Bulgaria and its adjacent area (4 km in diameter) was studied. Seven snake species used this hibernating den, Malpolon insignitus, Dolichophis caspius, Platyceps najadum, Elaphe quatuorlineata, Telescopus fallax, Vipera ammodytes and Xerotyphlops vermicularis. The emergence of the snakes was related to the rise of daily temperatures. Malpolon insignitus emerged from hibernation earlier in the spring than the other species, and most individuals were the first to leave the hibernaculum. There was a temporal segregation among the basking area in early spring, between the latter species and D. caspius, which were the two most abundant species. These two species also used the same area of the hibernaculum, in contrast to P. najadum and E. quatuorlineata, which used a different area. After spring dispersal, M. insignitus and D. caspius used the same microhabitats during the rest of the active period. The earlier emergence of M. insignitus (and earlier departure from the site) probably reduces the competition for basking sites. The early departure of the species may give advantage in the competition for optimal microhabitats with D. caspius

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

A series of OLED-relevant compounds, consisting of 1,3,5-triazine core linked to various aromatic arms by amino group, has been synthesized and characterized. The studied compounds exist in solution as a mixture of two conformers, a symmetric propeller and asymmetric conformer, in which one of the aromatic arms is rotated around the C-N bond. At temperatures below −40 °C, the VT NMR spectra in DMF-d7 are in a slow exchange regime, and the signals of two conformers can be elucidated. At temperatures above 100 °C, the VT NMR spectra in DMSO-d6 are in a fast exchange regime, and the averaged spectra can be measured. The ratio of symmetric and asymmetric conformers in DMF-d7 varies from 14:86 to 50:50 depending on the substituents. The rotational barriers of symmetric and asymmetric conformers in DMF-d7 were measured for all compounds and are in the interval from 11.7 to 14.7 kcal/mol. The ground-state energy landscapes of the studied compounds, obtained by DFT calculations, show good agreement with the experimental rotational barriers. The DFT calculations reveal that the observed chemical exchange occurs by the rotation around the C(1,3,5-triazine)-N bond. Although some of the compounds are potentially tautomeric, the measured absorption and emission spectra do not indicate proton transfer neither in the ground nor in the excited state

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

A series of OLED-relevant compounds, consisting of 1,3,5-triazine core linked to various aromatic arms by amino group, has been synthesized and characterized. The studied compounds exist in solution as a mixture of two conformers, a symmetric propeller and asymmetric conformer, in which one of the aromatic arms is rotated around the C-N bond. At temperatures below −40 °C, the VT NMR spectra in DMF-d7 are in a slow exchange regime, and the signals of two conformers can be elucidated. At temperatures above 100 °C, the VT NMR spectra in DMSO-d6 are in a fast exchange regime, and the averaged spectra can be measured. The ratio of symmetric and asymmetric conformers in DMF-d7 varies from 14:86 to 50:50 depending on the substituents. The rotational barriers of symmetric and asymmetric conformers in DMF-d7 were measured for all compounds and are in the interval from 11.7 to 14.7 kcal/mol. The ground-state energy landscapes of the studied compounds, obtained by DFT calculations, show good agreement with the experimental rotational barriers. The DFT calculations reveal that the observed chemical exchange occurs by the rotation around the C(1,3,5-triazine)-N bond. Although some of the compounds are potentially tautomeric, the measured absorption and emission spectra do not indicate proton transfer neither in the ground nor in the excited state

Updated distribution and species composition of the amphibians and reptiles along the Lower Danube, Bulgaria

In a recently published paper (Popgeorgiev et al. 2019), we compiled for the first time published and unpublished data on localities of the herpetofaunal species observed up to ca. 10 km south of the Bulgarian Danube River. Overall, we identified 687 published records belonging to 62 cells of the 10×10 km MGRS grid. Another 1918 records with real coordinates of our unpublished data from the past ca. 13 years belong to 1269 cells of the 1×1 MGRS grid. As a result, 34 native species – 15 amphibians (4 salamanders and 11 frogs) and 19 reptiles (1 turtle, 2 tortoises, 8 lizards and 8 snakes), and one invasive turtle, have been recorded; further species findings are unlikely. This study further identifies areas that are under-sampled and species such as Pelophylax lessonae that are cryptic. Our data are especially relevant concerning the high economic incentives to change the hydrology of the Danube, which will likely negatively impact the biodiversity along the river and its surrounding

Comparison of methodologies for the extraction of snakes’ (Reptilia: Serpentes) skin secretions and preliminary results on the presence of pheromones

During this preliminary study, 26 specimens from 8 different snake species were examined. Three methodologies for extraction of skin secretions by immersion of skin in n-hexane were used: immersing the whole body of live individuals for approximately 1 min in the field (n = 13), immersing the whole body of dead specimens (found freshly killed on road) for 24 h (n = 4), and soaking a shed skin for 24 h (n = 9). We did not immerse the head and tail to avoid contamination of the samples. All samples were collected during snakes’ active period (February – first half of June) and were analyzed by gas chromatography-mass spectrometry (GC/qMS). Based on the prevalence in the fraction of long-chained hydrocarbons, lipids or lipids with ketones we can separate the samples in three categories. The lipid fractions were present mainly in the shed skin samples, while the long-chained hydrocarbons dominated in the live specimens. According to the literature, ketones are the main component of the snakes’ pheromone communication. We found ketones in five samples, three live and two dead specimens, from five different species (Vipera ammodytes (Linnaeus, 1758), V. berus (Linnaeus, 1758), Dolichophis caspius (Gmelin, 1789), Natrix natrix (Linnaeus, 1758), and Platyceps najadum (Eichwald, 1831)). No ketones were found in the shed skin extracts. Ketones were found only in adults, both males and females. Presence of ketones was observed only for the period from the end of May to the beginning of June. Based on the preliminary results, we can suggest that secretion extraction from live specimens in the field could prove a valuable method in studies on snake pheromones in addition to the already developed methodologies. We speculate that the pheromones are present only in the reproductive and probably post-reproductive period. However, further research with larger sample size is required

Analyses of Skin Secretions of Vipera ammodytes (Linnaeus, 1758) (Reptilia: Serpentes), with Focus on the Complex Compounds and Their Possible Role in the Chemical Communication

Snakes rely heavily on chemical cues when foraging, searching for mates, etc. Snakes’ sex attractiveness pheromones comprise mainly heavy, semi-volatile compounds such as ketones. Here we investigated the composition of skin secretions of adult Vipera ammodytes (Linnaeus, 1758) individuals. The samples were analyzed by gas chromatography/mass spectrometry and the identification of the compounds was performed using commercial mass spectral libraries and retention times. The relative concentrations of all detected compounds were tested for significant differences between (1) male vs. female live individuals, (2) shed skin vs. live individuals, and (3) pre-reproductive vs. reproductive live individuals. We detected fifty-nine compounds of which six were ketones. Two ketones (2-pentacosanone and 2-heptacosanone) were present in many of the samples and thus may have an important role in the V. ammodytes chemical communication. We did not find significant differences between the relative concentrations of the compounds between male and female individuals (only three compounds are exceptions). Significant differences were found between extracts from shed skins and live individuals and between live pre-reproductive individuals and live reproductive individuals. The results of the study suggest that chemical communication in V. ammodytes involves less compounds in comparison to the known literature data for other species

Mapping European Association of Urology Guideline Practice Across Europe: An Audit of Androgen Deprivation Therapy Use Before Prostate Cancer Surgery in 6598 Cases in 187 Hospitals Across 31 European Countries

Peer reviewe