Plants as transmission channels for insect vibrational songs

Summary The vibrational songs of several species of cydnid bugs and small cicadas (leafhoppers and planthoppers) living on various types of plants are recorded by means of laser vibrometry. The recorded vibrational songs are analysed with respect to amplitude, frequency spectrum and structure in the time domain (Figs. 2–5).The emission of vibrational songs from singing insects on plants is simulated. A small magnet is glued to the surface of the plant and moved by means of an electromagnet about one cm away (Fig. 1). The vibrations are recorded by means of laser vibrometry. The propagation velocity of the vibrations increases with the square root of frequency, i.e. in the way expected for bending waves.The mechanical properties of plants ranging from soft bean plants to stiff reeds and maples are measured. The results are used for calculating the theoretical propagation velocities of bending waves. The measured and the calculated values are rather close (Table 1). Although the mechanical properties of the plants studied vary widely, the propagation velocities at a certain frequency are of the same order of magnitude (Table 1).In all the plants studied, only little vibrational energy is lost by friction at frequencies below some kHz. Communication by means of bending waves is possible over distances of some meters. The bending waves are reflected with little loss of energy both from the root and from the top of the plant. The vibration signals may therefore travel up and down the plant several times before decaying completely (Fig. 7). The vibration at a certain spot on the plant depends not only on the distance to and nature of the emitter, but also on the modes of vibration of the plant. The amplitude of vibration does not decrease monotonically with distance from the emitter (Fig. 6).These filtering properties of the plants mean that it is essentially impossible to predict which frequencies in the signals will be amplified or attenuated in the plant at the location of the receiving animal. The vibrational signals recorded from the animals cover wide frequency bandwidths. The signals are therefore well adapted to the filtering properties of the plants, but the signals of the species studied here do not appear to be particularly adapted to specific properties of the host plants.The muscular power needed for communication by means of various types of vibrational signals is calculated. The result of this calculation supports the conclusion that the signals recorded here are carried by means of bending waves.The communication strategies open to small insects are considered. Vibrational signals appear to be an efficient means of communication, but only certain types of signals are suited, because the plants cause a considerable distortion of the signals. One kind of distortion, the dispersive property, may — in theory — be used by the listening animals to obtain information about the direction and distance to the singing animals.Dedicated to Dr. F. ossiannilsson, whose pioneering studies led to the suggestion that small insects may use plants as transmission channels for their songs     

Aerosols: unexpected disequilibrium phenomena between airborne radio activities of lead-210 and its progenies bismuth-210 and polonium-210

For the first time, concentrations of the long lived radon progenies ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po were measured in the mine atmosphere of the so called "healing gallery" in Badgastein, Austria, a region famous for its radioactive springs. These investigations were performed in order to study the radioactive equilibrium between the ²¹⁰Pb-²¹⁰Bi and the ²¹⁰Pb-²¹⁰Po pairs so as to gain more information about the aerosol-forming processes in the mine. The particle size distribution of the aerosols was determined under different ventilation conditions. Six-stage and eight-stage cascade impactors with working ranges from 0.15 to5 µm and from 0.063 to 8 µm, respectively, were used to collect the mine aerosols. These samples were analysed in the laboratory and measured by liquid scintillation spectrometry. The most surprising results were found under full ventilation, when the total activity concentrations of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po were 4.6, 2.0 and 16.5 mBq/m³, respectively. In this case ²¹⁰Po/²¹⁰Pb activity ratios ranged between 1.8ǂ.3 and 4.3ǂ.3. These unexpected results were confirmed by the eight-stage impactor samples. For the smallest particles, between 0.062 and 0.125 µm, an even higher value of 7.5 was observed. As outside sources could be excluded, such ²¹⁰Po enrichments must occur during the aerosol-forming process itself inside the mine.     

Review of The Kyoto Protocol by M. Grubb,C. Vrolijk and D. Brack, 1999

Mitigation and Adaptation Strategies for Global Change -     

Influence of air flow rate on emission of DEHP from vinyl flooring in the emission cell FLEC: Measurements and CFD simulation

The emission of di-(2-ethylhexyl)phthalate (DEHP) from one type of vinyl flooring with ～15% (w/w) DEHP as plasticizer was measured at 22 °C in five FLECs + one blank FLEC (Field and Laboratory Emission Cell). Initially, the flow through all FLECs was 450 ml min^?1. After 689 days the flows were changed to 1000 ml min^?1, 1600 ml min^?1, 2300 ml min^?1, and 3000 ml min^?1, respectively, in four FLECs, and kept at 450 ml min^?1 in one FLEC. Air samples were collected from the effluent air at regular intervals. After 1190 days the experiments were terminated and the interior surfaces of all six FLECs were rinsed with methanol to estimate the internal surface concentrations of DEHP. The DEHP air concentration and specific emission rate (SER) at steady state was estimated for the five different flow rates. The steady-state concentrations decreased slightly with increasing air flow with only the two highest flow rates resulting in significantly lower concentrations. In contrast, the SERs increased significantly. Despite large variation, the internal surface concentrations appeared to decrease slightly with increasing FLEC flow. Computational fluid dynamic (CFD) simulations suggest that the interior gas and surface concentrations were roughly uniform for the low flow case (450 ml min^?1), under which, the partitioning between the FLEC internal surface and chamber air was examined. Although paired t-tests showed no difference between CFD and experimental results for DEHP air concentrations and SERs at steady-state conditions, CFD indicated that the experimental DEHP surface concentrations in the FLECs were underestimated. In conclusion, the experiments showed that the emission of DEHP from vinyl flooring is subject to “external” control and that the SER is strongly and positively dependent on the air exchange rate. However, the increased SER almost compensates for the decrease in gas-phase concentration caused by the increased air exchange.     

Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants in air and seawater of the European Arctic

The spatial distribution of polybrominated diphenyl ethers (PBDEs) and several alternative non-PBDE, non-regulated brominated flame retardants (BFRs) in air and seawater and the air-seawater exchange was investigated in East Greenland Sea using high-volume air and water samples. Total PBDE concentrations (Ó₁₀PBDEs) ranged from 0.09 to 1.8 pg m⁻³ in the atmosphere and from 0.03 to 0.64 pg L⁻¹ in seawater. Two alternative BFRs, Hexabromobenzene (HBB) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), showed similar concentrations and spatial trends as PBDEs. The air-seawater gas exchange was dominated by deposition with fluxes up to −492 and −1044 pg m⁻² day⁻¹ for BDE-47 and DPTE, respectively. This study shows the first occurrence of HBB, DPTE and other alternative flame retardants (e.g., pentabromotoluene (PBT)) in the Arctic atmosphere and seawater indicating that they have a similar long-range atmospheric transport potential (LRAT) as the banned PBDEs.     

Effects of cyanobacterium Fischerella ambigua isolates and cell free culture media on zebrafish (Danio rerio) embryo development

The toxic effects of several species of fresh water cyanobacteria, notably Microcystis species and associated toxins, the microcystins, Anabaena species (anatoxin), Nodularia sp. (nodularin), and Cylindrospermopsis raciborskii (cylindrospermopsin), are well known. Little, however, is known about the effects of secondary metabolites other than alkaloids. Early life stage tests with zebrafish (Danio rerio) were used to detect bioactive properties of compounds released by healthy cyanobacteria (Fischerella ambigua), particularly on the early developmental stages of fish. This approach, using F. ambigua is probably most valuable as it shows the toxicity of healthy growing cyanobacteria. The effects of cyanobacterial secondary metabolites on the embryonic stages of fish are of considerable interest as many aquatic creatures, particularly fish, are unable to avoid the potential toxins that may be released by undesirable algal blooms or as a result of allelopathic effects. In the current study, the zebrafish (D. rerio) was used as a model experimental system to investigate the effects of ambigols A and C, tjipanazole D and C, 2,4-dichlorobenzoic acid, cell free culture media, and media extracts of a terrestrial/fresh water strain of the cyanobacterium F. ambigua on embryo development. Fish embryo tests performed with the cell free culture medium showed that after 3h of exposure to undiluted culture medium all fish embryos died. At a tenfold dilution the process of epiboly (formation of the gastrula) was retarded in all embryos, lesions were observed, and their general development was significantly arrested, finally followed by death. The same tests performed with extracts (dichloromethane, n-butanol, and residual cell free culture medium) of the cell free culture medium, ambigol A, ambigol C, 2,4-dichlorobenzoic acid and tjipanazole D showed only ambigol A to have an influence on zebrafish development at concentrations>or=1 mg/l (2.06 microM). After 55 h all embryos showed pectoral oedema, irregularly shaped fin folds, bent tails, and unusual circular neoplasms in the dorsal tail fin fold. Due to the high concentration of ambigol A used in this assay these effects were considered to be of minor importance when compared to those of the culture medium.     

Operating problems in anaerobic digestion plants resulting from nitrogen in MSW

Organic waste and municipal solid waste usually contain considerable amounts of different nitrogen compounds, which may inhibit anaerobic degradation processes and cause problems in the downstream and peripheral devices. This refers particularly to the different process stages of anaerobic digestion, to wastewater treatment, and to exhaust air treatment. Neither the knowledge about nitrogen problems nor the technologies for elimination of nitrogen compounds from the wastewater or the exhaust air of anaerobic digestion can be regarded as state-of-the-art. Most of the technologies in question have already been applied in other areas, but are barely tested for application in anaerobic digestion plants. The few performance data and experiences at hand were mainly derived from pilot and demonstration facilities. In this paper, the problem of nitrogen will be discussed in detail according to the separate problem fields based on the authors' experience, as well as on the basis of a review of the relevant literature. Furthermore, possible solutions will be proposed and the need for further research and development will be formulated.