Sound strategy: acoustic aposematism in the bat–tiger moth arms race

The night sky is the venue for an ancient arms race. Insectivorous bats with their ultrasonic sonar exert an enormous selective pressure on nocturnal insects. In response insects have evolved the ability to hear bat cries, to evade their hunting maneuvers, and some, the tiger moths (Arctiidae), to utter an ultrasonic reply. We here determine what it is that tiger moths say to bats. We chose four species of arctiid moths, Cycnia tenera, Euchaetes egle, Utetheisa ornatrix, and Apantesis nais, that naturally differ in their levels of unpalatability and their ability to produce sound. Moths were tethered and offered to free-flying naïve big brown bats, Eptesicus fuscus. The ability of the bats to capture each species was compared to their ability to capture noctuid, geometrid, and wax moth controls over a learning period of 7 days. We repeated the experiment using the single arctiid species E. egle that through diet manipulation and simple surgery could be rendered palatable or unpalatable and sound producing or mute. We again compared the capture rates of these categories of E. egle to control moths. Using both novel learning approaches we have found that the bats only respond to the sounds of arctiids when they are paired with defensive chemistry. The sounds are in essence a warning to the bats that the moth is unpalatable—an aposematic signal.Electronic Supplementary Material  Supplementary material is available for this article at     

Complex performance of novel CoNiMnB electrodeposits in alkaline borohydride solutions

The complex performance of newly synthesized CoNiMnB electrodeposits in base-stabilized sodium borohydride solutions was examined. The rate of hydrogen generation due to borohydride hydrolysis was determined at different temperatures. Activation energy of approximately 33 kJ/mol was estimated, which is lower than the values reported for other catalysts. At electrochemical conditions, there is a competition between borohydride hydrolysis and electrooxidation reactions. The electrooxidation of borohydride takes place with low overpotentials at relatively high current densities. The long-term discharge at galvanostatic conditions as well as possibilities for partial storage of generated hydrogen indicates potentials for application of studied electrodeposits as anode material in direct borohydride fuel cells (DBFC).     

Catalytic activity of NiW electrodeposits

NiW systems are known as one of the best catalysts for various desulfurization processes. In this study, we examined catalytic properties of NiW electrodeposits, produced from two different electrolytes, towards sulfide ion oxidation in alkaline solution. Despite the big difference in morphology and structure of both materials, they exhibit almost the same catalytic activity for the examined reaction. A possible explanation of this experimental fact is that the overall reaction is controlled by the transport of oxygen through the catalyst samples.     

Interdisciplinary studies on the technical and economic feasibility of deep underground coal gasification with CO<Subscript>2</Subscript> storage in bulgaria

This paper presents the outcome of a feasibility study on underground coal gasification (UCG) combined with direct carbon dioxide (CO₂) capture and storage (CCS) at a selected site in Bulgaria with deep coal seams (>1,200 m). A series of state-of-the-art geological, geo-mechanical, hydrogeological and computational models supported by experimental tests and techno-economical assessments have been developed for the evaluation of UCG-CCS schemes. Research efforts have been focused on the development of site selection requirements for UCG-CCS, estimation of CO₂ storage volumes, review of the practical engineering requirements for developing a commercial UCG-CCS storage site, consideration of drilling and completion issues, and assessments of economic feasibility and environmental impacts of the scheme. In addition, the risks of subsidence and groundwater contamination have been assessed in order to pave the way for a full-scale trial and commercial applications. The current research confirms that cleaner and cheaper energy with reduced emissions can be achieved and the economics are competitive in the future European energy market. However the current research has established that rigorous design and monitor schemes are essential for productivity and safety and the minimisation of the potential environmental impacts. A platform has been established serving to inform policy-makers and aiding strategies devised to alleviate local and global impacts on climate change, while ensuring that energy resources are optimally harnessed.     

Integrating GIS and high resolution orthophoto images for the development of a geomorphic shoreline classification and risk assessment—a case study of cliff/bluff erosion along the Bulgarian coast

This paper demonstrates the effectiveness of integrating GIS and modern spatial data for the development of a detailed geomorphic classification of the Bulgarian Black Sea coast. This classification is important for the precise measurement of various natural and technogenous (engineered) coastline types and serves as a basis for identification of the areas with high exposure to different coastal hazards. To illustrate potential uses of this simple methodology, a map of the potential coastal erosion/cliff retreat hazard for the Bulgarian coast was produced from this GIS database. Several types of data were used: high resolution orthophoto, topographical maps in 1:5,000 scale and geological maps. Geomorphic classification utilized both geomorphological and engineering criteria. A total of 867 segments were delineated along the coast. Four hundred sixty five were classified as natural landforms (cliffs, beaches, river mouths) with a total length of 362,62 km and 402 were indicated as technogenous segments (port and coast-protection structures, artificial beaches) with a total length of 70 km. Based on the geologic materials present at each segment and cliff height, the cliffed portions of the Bulgarian coast were classified for expected erosion rates, and therefore, hazard vulnerability: low hazard (volcanic type cliff); moderate hazard (limestone type cliff) and high hazard (loess and clayey types cliff). This “predictive model” was then compared to a previously published field study of coastal erosion rates to validate the model. As a result, a new high quality, but qualitative data for Bulgarian coastal bluff/cliff erosion were obtained, incorporated and analyzed in GIS.     

Effectiveness of tiger moth (Lepidoptera, Arctiidae) chemical defenses against an insectivorous bat (Eptesicus fuscus)

Summary. Adult tiger moths exhibit a wide range of palatabilities to the insectivorous big brown bat Eptesicus fuscus. Much of this variation is due to plant allelochemics ingested and sequestered from their larval food. By using a comparative approach involving 15 species from six tribes and two subfamilies of the Arctiidae we have shown that tiger moths feeding on cardiac glycoside-containing plants often contain highly effective natural feeding deterrents. Feeding on pyrrolizidine alkaloid-containing plants is also an effective deterrent to predation by bats but less so than feeding on plants rich in cardiac glycosides. Moths feeding on plants containing iridoid glycosides and/or moths likely to contain biogenic amines were the least deterrent. By manipulating the diet of several tiger moth species we were able to adjust their degree of palatability and link it to the levels of cardiac glycosides or pyrrolizidine alkaloids in their food. We argue that intense selective pressure provided by vertebrate predators including bats has driven the tiger moths to sequester more and more potent deterrents against them and to acquire a suite of morphology characteristics and behaviors that advertise their noxious taste.     

Linking atmospheric circulation to daily precipitation patterns over the territory of Bulgaria

An eight states non-homogeneous hidden Markov model is developed for linking daily precipitation amounts data at a network of 32 stations broadly covering the territory of Bulgaria to large-scale atmospheric patterns. At each site a 40-year record 1960?C2000 of daily October?CMarch precipitation amounts is modeled. The atmospheric data consists of daily sea-level pressure, geopotential height at 500 and 850?hPa, air temperature at 850?hPa and relative humidity at 700 and 850?hPa on a 2.5?×?2.5 grid based on NCEP-NCAR reanalysis data set covering the Europe-Atlantic sector 30W?C60E, 20N?C70N for the same period. The first 30?years data are used for model fitting purposes while the remaining 10?years are used for model evaluation. Detailed model validation is carried out on various aspects. The proposed model reproduces well the rainfall statistics for the observed and reserved data whereas the identified states are found to be physically interpretable in terms of regional climatology.