Analysis of MO Ground States of Benzenoid Hydrocarbons in Terms of BORT Resonance Structures

In order to determine the most important resonance structures in the description of benzenoid hydrocarbons, Hückel and Pariser-Parr- Pople ground states of all such hydrocarbons with up to five benzene rings were analyzed in terms of BORT resonance structures. Due to the exponential increase of the number of resonance structures with the size of a benzenoid molecule, we used an approximate optimization procedure based on the greedy algorithm. The analysis of cumulative contributions of various sequences of resonance structures to the MO ground states of the considered ben- zenoids reveals that, besides the Kekulé structures, Claus structures are also very important in the description of these systems. The relative importance of Claus structures can be attributed to the local benzene-like character of these 7t-electron systems, and to the fact that benzene ground state is exactly represented as a linear combination of the two Kekulé and one Claus structures. The relative importance of other types of structures is generally much smaller. The real contribution of these other structures is somewhat obscured due to their large number and nonorthogonality

Cattle Overwintering Areas in Middle-European Conditions - Important “Point” Sources Of Nitrous Oxide Emissions

Nitrous oxide (N2O) emissions in grazed grasslands are strongly influenced by animal excreta (Fowler et al., 1997). In addition, soil compaction caused by animal traffic significantly influences soil physical conditions and thus directly or indirectly impacts on the microbial processes producing N2O. In the Czech Republic pastures are mostly located in hilly and mountain areas. During the growing season, cattle are typically grazing, while during the winter the animals are concentrated near the animal house on a relatively small plot called an overwintering area . The objective of this study was to estimate the fluxes of N2O from a typical overwintering area, where the combined effects of soil compaction and deposition of urine and dung occur

Rotating Gliding Arc: Innovative Source for VOC Remediation

The large-scale plasma treatment of waste gas in industrial or municipal conditions requires high efficiency of plasma conversion process at high processing speed, i.e., large volumetric flow. The integration of the plasma unit into existing systems puts demands on the pipe-system compatibility and minimal pressure drop due to adoption of plasma processing step. These conditions are met at the innovative rotating electrode gliding arc plasma unit described in this article. The system consists of propeller-shaped high voltage electrode inside grounded metallic tube. The design of HV electrode eliminates the pressure drop inside the air system, contrary the plasma unit itself is capable of driving the waste gas at volumetric flow up to 300 m3/hr for 20 cm pipe diameter. In the article the first results on pilot study of waste air treatment will be given for selected volatile organic compounds together with basic characteristic of the plasma unit used

Insect herbivory and herbivores of Ficus species along a rain forest elevational gradient in Papua New Guinea

Classic research on elevational gradients in plant–herbivore interactions holds that insect herbivore pressure is stronger under warmer climates of low elevations. However, recent work has questioned this paradigm, arguing that it oversimplifies the ecological complexity in which plant–insect herbivore interactions are embedded. Knowledge of antagonistic networks of plants and herbivores is however crucial for understanding the mechanisms that govern ecosystem functioning. We examined herbivore damage and insect herbivores of eight species of genus Ficus (105 saplings) and plant constitutive defensive traits of two of these species, along a rain forest elevational gradient of Mt. Wilhelm (200–2,700 m a.s.l.), in tropical Papua New Guinea. We report overall herbivore damage 2.4% of leaf area, ranging from 0.03% in Ficus endochaete at 1,700 m a.s.l. to 6.1% in F. hombroniana at 700 m a.s.l. Herbivore damage and herbivore abundances varied significantly with elevation, as well as among the tree species, and between the wet and dry season. Community‐wide herbivore damage followed a hump‐shaped pattern with the peak between 700 and 1,200 m a.s.l. and this pattern corresponded with abundance of herbivores. For two tree species surveyed in detail, we observed decreasing and hump‐shaped patterns in herbivory, in general matching the trends found in the set of plant defenses measured here. Our results imply that vegetation growing at mid‐elevations of the elevational gradient, that is at the climatically most favorable elevations where water is abundant, and temperatures still relatively warm, suffers the maximum amount of herbivorous damage which changes seasonally, reflecting the water availability

Settling Decisions and Heterospecific Social Information Use in Shrikes

Animals often settle near competitors, a behavior known as social attraction, which belies standard habitat selection theory. Two hypotheses account for these observations: individuals obtain Allee benefits mediated by the physical presence of a competitor, or they use successfully settled individual as a source of information indicating the location of high quality habitat. We evaluated these hypotheses experimentally in two species of shrikes. These passerine birds with a raptor-like mode of life impale prey to create larders that serve as an indicator of male/habitat quality. Thus, two forms of indirect information are available in our system: a successfully settled shrike and its larder. Typically these two cues are associated with each other, however, our experimental treatment created an unnatural situation by disassociating them. We manipulated the presence of larders of great grey shrikes and examined the settling decisions of red-backed shrikes within and outside the great grey shrike territories. Male red-backed shrikes did not settle sooner on plots with great grey shrikes compared to plots that only contained artificial larders indicating that red-backed shrikes do not use the physical presence of a great grey shrike when making settling decisions which is inconsistent with the Allee effect hypothesis. In contrast, for all plots without great grey shrikes, red-backed shrikes settled, paired and laid clutches sooner on plots with larders compared to plots without larders. We conclude that red-backed shrikes use larders of great grey shrikes as a cue to rapidly assess habitat quality

Measured and Simulated Nitrous Oxide Emissions from Ryegrass- and Ryegrass/White Clover-Based Grasslands in a Moist Temperate Climate

There is uncertainty about the potential reduction of soil nitrous oxide (N2O) emission when fertilizer nitrogen (FN) is partially or completely replaced by biological N fixation (BNF) in temperate grassland. The objectives of this study were to 1) investigate the changes in N2O emissions when BNF is used to replace FN in permanent grassland, and 2) evaluate the applicability of the process-based model DNDC to simulate N2O emissions from Irish grasslands. Three grazing treatments were: (i) ryegrass (Lolium perenne) grasslands receiving 226 kg FN ha−1 yr−1 (GG+FN), (ii) ryegrass/white clover (Trifolium repens) grasslands receiving 58 kg FN ha−1 yr−1 (GWC+FN) applied in spring, and (iii) ryegrass/white clover grasslands receiving no FN (GWC-FN). Two background treatments, un-grazed swards with ryegrass only (G–B) or ryegrass/white clover (WC–B), did not receive slurry or FN and the herbage was harvested by mowing. There was no significant difference in annual N2O emissions between G–B (2.38±0.12 kg N ha−1 yr−1 (mean±SE)) and WC-B (2.45±0.85 kg N ha−1 yr−1), indicating that N2O emission due to BNF itself and clover residual decomposition from permanent ryegrass/clover grassland was negligible. N2O emissions were 7.82±1.67, 6.35±1.14 and 6.54±1.70 kg N ha−1 yr−1, respectively, from GG+FN, GWC+FN and GWC-FN. N2O fluxes simulated by DNDC agreed well with the measured values with significant correlation between simulated and measured daily fluxes for the three grazing treatments, but the simulation did not agree very well for the background treatments. DNDC overestimated annual emission by 61% for GG+FN, and underestimated by 45% for GWC-FN, but simulated very well for GWC+FN. Both the measured and simulated results supported that there was a clear reduction of N2O emissions when FN was replaced by BNF

Community structure of insect herbivores is driven by conservatism, escalation and divergence of defensive traits in Ficus

Escalation (macroevolutionary increase) or divergence (disparity between relatives) in trait values are two frequent outcomes of the plant-herbivore arms race. We studied the defences and caterpillars associated with 21 sympatric New Guinean figs. Herbivore generalists were concentrated on hosts with low protease and oxidative activity. The distribution of specialists correlated with phylogeny, protease and trichomes. Additionally, highly specialised Asota moths used alkaloid rich plants. The evolution of proteases was conserved, alkaloid diversity has escalated across the studied species, oxidative activity has escalated within one clade, and trichomes have diverged across the phylogeny. Herbivore specificity correlated with their response to host defences: escalating traits largely affected generalists and divergent traits specialists; but the effect of escalating traits on extreme specialists was positive. In turn, the evolution of defences in Ficus can be driven towards both escalation and divergence in individual traits, in combination providing protection against a broad spectrum of herbivores

Long-Term Cold Acclimation Extends Survival Time at 0°C and Modifies the Metabolomic Profiles of the Larvae of the Fruit Fly Drosophila melanogaster

Drosophila melanogaster is a chill-susceptible insect. Previous studies on this fly focused on acute direct chilling injury during cold shock and showed that lower lethal temperature (LLT, approximately -5°C) exhibits relatively low plasticity and that acclimations, both rapid cold hardening (RCH) and long-term cold acclimation, shift the LLT by only a few degrees at the maximum.We found that long-term cold acclimation considerably improved cold tolerance in fully grown third-instar larvae of D. melanogaster. A comparison of the larvae acclimated at constant 25°C with those acclimated at constant 15°C followed by constant 6°C for 2 d (15°C→6°C) showed that long-term cold acclimation extended the lethal time for 50% of the population (Lt(50)) during exposure to constant 0°C as much as 630-fold (from 0.137 h to 86.658 h). Such marked physiological plasticity in Lt(50) (in contrast to LLT) suggested that chronic indirect chilling injury at 0°C differs from that caused by cold shock. Long-term cold acclimation modified the metabolomic profiles of the larvae. Accumulations of proline (up to 17.7 mM) and trehalose (up to 36.5 mM) were the two most prominent responses. In addition, restructuring of the glycerophospholipid composition of biological membranes was observed. The relative proportion of glycerophosphoethanolamines (especially those with linoleic acid at the sn-2 position) increased at the expense of glycerophosphocholines.Third-instar larvae of D. melanogaster improved their cold tolerance in response to long-term cold acclimation and showed metabolic potential for the accumulation of proline and trehalose and for membrane restructuring

Avenue foundation in extreme conditions special respect to soil quality

Quality of soil environment is an important factor which substantially influences growth of plants. Present paper deals on general features and main parts of soils. The importance of soil air content and composition of soil air together with main principles of movement of gases in soil are described. Soil aeration status, namely low oxygen concentration, both low and high carbon dioxide concentrations and higher ethylene concentrations directly influence plants. Changes in amount and composition of soil air impact a number of soil physical and chemical properties, and by this mechanism also influence plant growth and behaviour

Radar observation of the Leonids in 1998 and 1999

Results of Ondřejov radar observations of Leo nid meteor shower in 1998 and 1999 are presented. It was found that while the activity in 1998 was dominated by the long-duration echoes resulting in a low mass distribution index averaged over an interval 23 h UT November 16 to 12 h UT November 17 as $s = 1.23 \pm 0.02$ with the peak at L_{\odot} = 234\fdg633 \pm 0\fdg004. The 1999 activity culminated at L_{\odot} = 235\fdg285 \pm 0\fdg002 and was mainly due to prevailing of fainter echoes yielding a mean mass distribution index $s = 1.58 \pm 0.05$ between 23 h UT November 17 8 h UT November 18. The activity pattern in 1998 showed a multiple peak structure while the corresponding 1999 pattern showed only one distinct peak. The 1998 activity rates were lower than those in 1999 by the ratio of 2.8. Our observations indicate that the main outburst of this Leonid return occurred in 1999. The 1998 activity is characterized by a large scatter of observed hourly echo counts while the ones in 1999 possessed only one sharp maximum. The flux curve in 1998 shows multiple peak character while in 1999 the activity patterns of echoes with duration in excess of 0.4 s even though their peaks do not coincide generally with the activity maxima. The 1998 flux reached 3.34 10-12 m-2 s-1 for a limiting mass of $m_{0}= 10^{-5}$ kg while for 1999 it was determined as 37.41 10-12 m-2 s-1