Temporal associations in fig-wasp-ant interactions: diel and phenological patterns

In a complex multitrophic plant-animal interaction system in which there are direct and indirect interactions between species, comprehending the dynamics of these multiple partners is very important for an understanding of how the system is structured. We investigated the plant Ficus racemosa L. (Moraceae) and its community of obligatory mutualistic and parasitic fig wasps (Hymenoptera: Chalcidoidea) that develop within the fig inflorescence or syconium, as well as their interaction with opportunistic ants. We focused on temporal resource partitioning among members of the fig wasp community over the development cycle of the fig syconia during which wasp oviposition and development occur and we studied the activity rhythm of the ants associated with this community. We found that the seven members of the wasp community partitioned their oviposition across fig syconium development phenology and showed interspecific variation in activity across the day-night cycle. The wasps presented a distinct sequence in their arrival at fig syconia for oviposition, with the parasitoid wasps following the galling wasps. Although fig wasps are known to be largely diurnal, we documented night oviposition in several fig wasp species for the first time. Ant activity on the fig syconia was correlated with wasp activity and was dependent on whether the ants were predatory or trophobiont-tending species; only numbers of predatory ants increased during peak arrivals of the wasps.

Structural studies of analgesics and their interactions. XII. Structure and interactions of anti-inflammatory fenamates. A concerted crystallographic and theoretical conformational study

A theoretical conformational analysis of fenamates, which are N-arylated derivatives of anthranilic acid or 2-aminonicotinic acid with different substituents on the aryl (phenyl) group, is reported. The analysis of these analgesics, which are believed to act through the inhibition of prostaglandin biosynthesis, was carried out using semi-empirical potential functions. The results and available crystallographic observations have been critically examined in terms of their relevance to drug action. Crystallographic studies of these drugs and their complexes have revealed that the fenamate molecules share a striking invariant feature, namely, the sixmembered ring bearing the carboxyl group is coplanar with the carboxyl group and the bridging imino group,the coplanarity being stabilized by resonance interactions and an internal hydrogen bond between the imino and carboxyl groups. The results of the theoretical analysis provide a conformational rationale for the observed invariant coplanarity. The second sixmembered ring, which provides hydrophobicity in a substantial part of the molecule, has limited conformational flexibility in meclofenamic, mefenamic and flufenamic acids. Comparison of the conformational energy maps of these acids shows that they could all assume the same conformation when bound to the relevant enzyme. The present study provides a structural explanation for the difference in the activity of niflumic acid, which can assume a conformation in which the whole molecule is nearly planar. The main role of the carboxyl group appears to be to provide a site for intermolecular interactions in addition to helping in stabilizing the invariant coplanar feature and providing hydrophilicity at one end of the molecule. The fenamates thus provide a good example of conformation- dependent molecular asymmetry.

Study Of The Hvdc-Torsional Interactions Through Digital Dynamic Simulation

This paper presents the detailed dynamic digital simulation for the study of phenomenon of torsional interaction between HVDC-Turbine generator shaft, dynamics using the novel converter model presented in [ 1 ] The system model includes detailed representation of the synchronous generator and the shaft dynamics, the ac and dc network transients. The results of a case study indicate the various factors that influence the torsional interaction.

Theoretical studies on alpha-helix--DNA interactions

The interaction energies between (Ala)10 and alpha-helix fragment and different nucleotide sequences in right-handed B-form have been optimized using semi-empirical potential energy functions. The energies are calculated for two different orientations of the alpha-helix, viz., when the alpha-helix axis taken in the N----C direction is (i) parallel and (ii) antiparallel to the 5'-3' ascending strand of DNA, proximal to it. When both the DNA molecule as well as the alpha-helix are treated as rigid molecules it is found that a polyalanine alpha-helix has slightly more favourable contacts when it is in the proximity of a four nucleotide sequence of 5'-(N-A-T-N)-3' type, where N is either a purine or a pyrimidine. However, when the two interacting molecules are allowed to undergo local structural variations then the interaction energy appears to be independent of the base sequence confirming the non-specific nature of these interactions.

Magnetically induced currents and magnetic response properties of molecules

The magnetically induced currents in organic monoring and multiring molecules, in Möbius shaped molecules and in inorganic all-metal molecules have been investigated by means of the Gauge-including magnetically induced currents (GIMIC) method. With the GIMIC method, the ring-current strengths and the ring-current density distributions can be calculated. For open-shell molecules, also the spin current can be obtained. The ring-current pathways and ring-current strengths can be used to understand the magnetic resonance properties of the molecules, to indirectly identify the effect of non-bonded interactions on NMR chemical shifts, to design new molecules with tailored properties and to discuss molecular aromaticity. In the thesis, the magnetic criterion for aromaticity has been adopted. According to this, a molecule which has a net diatropic ring current might be aromatic. Similarly, a molecule which has a net paratropic current might be antiaromatic. If the net current is zero, the molecule is nonaromatic. The electronic structure of the investigated molecules has been resolved by quantum chemical methods. The magnetically induced currents have been calculated with the GIMIC method at the density-functional theory (DFT) level, as well as at the self-consistent field Hartree-Fock (SCF-HF), at the Møller-Plesset perturbation theory of the second order (MP2) and at the coupled-cluster singles and doubles (CCSD) levels of theory. For closed-shell molecules, accurate ring-current strengths can be obtained with a reasonable computational cost at the DFT level and with rather small basis sets. For open-shell molecules, it is shown that correlated methods such as MP2 and CCSD might be needed to obtain reliable charge and spin currents. The basis set convergence has to be checked for open-shell molecules by performing calculations with large enough basis sets. The results discussed in the thesis have been published in eight papers. In addition, some previously unpublished results on the ring currents in the endohedral fullerene Sc3C2@C80 and in coronene are presented. It is shown that dynamical effects should be taken into account when modelling magnetic resonance parameters of endohedral metallofullerenes such as Sc3C2@C80. The ring-current strengths in a series of nano-sized hydrocarbon rings are related to static polarizabilities and to H-1 nuclear magnetic resonance (NMR) shieldings. In a case study on the possible aromaticity of a Möbius-shaped [16]annulene we found that, according to the magnetic criterion, the molecule is nonaromatic. The applicability of the GIMIC method to assign the aromatic character of molecules was confirmed in a study on the ring currents in simple monocylic aromatic, homoaromatic, antiaromatic, and nonaromatic hydrocarbons. Case studies on nanorings, hexaphyrins and [n]cycloparaphenylenes show that explicit calculations are needed to unravel the ring-current delocalization pathways in complex multiring molecules. The open-shell implementation of GIMIC was applied in studies on the charge currents and the spin currents in single-ring and bi-ring molecules with open shells. The aromaticity predictions that are made based on the GIMIC results are compared to other aromaticity criteria such as H-1 NMR shieldings and shifts, electric polarizabilities, bond-length alternation, as well as to predictions provided by the traditional Hückel (4n+2) rule and its more recent extensions that account for Möbius twisted molecules and for molecules with open shells.

Prediction of protein-protein interactions in dengue virus coat proteins guided by low resolution cryoEM structures

Background: Dengue virus along with the other members of the flaviviridae family has reemerged as deadly human pathogens. Understanding the mechanistic details of these infections can be highly rewarding in developing effective antivirals. During maturation of the virus inside the host cell, the coat proteins E and M undergo conformational changes, altering the morphology of the viral coat. However, due to low resolution nature of the available 3-D structures of viral assemblies, the atomic details of these changes are still elusive. Results: In the present analysis, starting from C alpha positions of low resolution cryo electron microscopic structures the residue level details of protein-protein interaction interfaces of dengue virus coat proteins have been predicted. By comparing the preexisting structures of virus in different phases of life cycle, the changes taking place in these predicted protein-protein interaction interfaces were followed as a function of maturation process of the virus. Besides changing the current notion about the presence of only homodimers in the mature viral coat, the present analysis indicated presence of a proline-rich motif at the protein-protein interaction interface of the coat protein. Investigating the conservation status of these seemingly functionally crucial residues across other members of flaviviridae family enabled dissecting common mechanisms used for infections by these viruses. Conclusions: Thus, using computational approach the present analysis has provided better insights into the preexisting low resolution structures of virus assemblies, the findings of which can be made use of in designing effective antivirals against these deadly human pathogens.

Fishes of the Darkness : Water colour-regulated competitive interactions in humic lakes

Humic lakes are abundant in the temperate and cold regions of the Boreal Zone. High levels of water colour and strong thermal stratification of humic lakes limit the potential fish habitats and give a special role to the intraspecific and interspecific interactions. Water colour has different effects on species depending on species-specific life-history traits and trophic interactions. Fish species whose success in predation is based on visual cues are more susceptible to suffer in competition. The main aim of the thesis was to demonstrate the effects of water colour on European perch (Perca fluviatilis) in humic lakes. The contribution of water colour to diet, feeding, growth and competitive interactions of fish was studied both in laboratory and in small humic lakes with varying levels of water colour. The main findings of the thesis were that water colour has different effects on species, depending on species-specific life-history traits and trophic interactions. Water colour affected visually-oriented perch feeding and growth negatively, and the prolonged benthic feeding phase of perch resulting from the increased water colour could increase intraspecific competition in perch populations and may result in a partial bottleneck in growth for perch. Moreover, water colour may act as a proximate factor behind the population dependency of sexual growth dimorphism in perch.

Mechanical Anisotropy in Crystalline Saccharin: Nanoindentation Studies

The nanoindentation technique has been employed to relate the mechanical properties of saccharin single crystals with their internal structure. Indentations were performed on (100) and (011) faces to assess the mechanical anisotropy. The load-displacement (P-h) curves indicate significant differences in the nature of the plastic deformation on the two faces. The P-h curves obtained on the (011) plane are smooth, reflecting homogeneous plasticity. However, displacement bursts (pop-ins) are observed in the P-h curves obtained on the (100) plane suggesting a discrete deformation mechanism. Marginal differences exist in the hardness and modulus on the two faces that may, in part, be rationalized, although one notes that saccharin has a largely three-dimensional close-packed structure. The structural origins of the fundamentally different deformation mechanisms on (100) and (011) are discussed in terms of the dimensionality of the hydrogen bonding networks. Down the (100) planes, the saccharin dimers are stacked and are stabilized by nonspecific van der Wants interactions mostly between aromatic rings. However, down the (011) planes, the molecules are stabilized by more directional and cross-linked C-H ... O hydrogen bonds. This anisotropy in crystal packing and interactions is reflected in the mechanical behavior on these faces. The displacements associated with the pop-ins were found to he integral multiples oldie molecule separation distances. Nanoindentation offers an opportunity to compare experimentally, and in a quantitative way, the various intermolecular interactions that fire present in a molecular crystal.

Analysis of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl intermolecular interactions involving chlorine in substituted 2-chloroquinoline derivatives

Six crystal structures of substituted 2-chloroquinoline derivatives have been analysed to evaluate the role of Cl atom as a self recognizing unit resulting in the formation of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl interactions to generate supramolecular assembly in the solid state. The features of Type I and Type II geometries associated with Cl center dot center dot center dot Cl interactions have been analysed to show directional preferences leading to differences in the packing motifs in these crystal structures. C-H center dot center dot center dot Cl interactions are generated exclusively in structures depicting Type II Cl center dot center dot center dot Cl interaction have been observed in these structures.

Drug epidemiology, interactions and pharmacogenetics : A post-mortem database study

Use of adverse drug combinations, abuse of medicinal drugs and substance abuse are considerable social problems that are difficult to study. Prescription database studies might fail to incorporate factors like use of over-the-counter drugs and patient compliance, and spontaneous reporting databases suffer from underreporting. Substance abuse and smoking studies might be impeded by poor participation activity and reliability. The Forensic Toxicology Unit at the University of Helsinki is the only laboratory in Finland that performs forensic toxicology related to cause-of-death investigations comprising the analysis of over 6000 medico-legal cases yearly. The analysis repertoire covers most commonly used drugs and drugs of abuse, and the ensuing database contains also background information and information extracted from the final death certificate. In this thesis, the data stored in this comprehensive post-mortem toxicology database was combined with additional metabolite and genotype analyses that were performed to complete the profile of selected cases. The incidence of drug combinations possessing serious adverse drug interactions was generally low (0.71%), but it was notable for the two individually studied drugs, a common anticoagulant warfarin (33%) and a new generation antidepressant venlafaxine (46%). Serotonin toxicity and adverse cardiovascular effects were the most prominent possible adverse outcomes. However, the specific role of the suspected adverse drug combinations was rarely recognized in the death certificates. The frequency of bleeds was observed to be elevated when paracetamol and warfarin were used concomitantly. Pharmacogenetic factors did not play a major role in fatalities related to venlafaxine, but the presence of interacting drugs was more common in cases showing high venlafaxine concentrations. Nicotine findings in deceased young adults were roughly three times more prevalent than the smoking frequency estimation of living population. Contrary to previous studies, no difference in the proportion of suicides was observed between nicotine users and non-nicotine users. However, findings of abused substances, including abused prescription drugs, were more common in the nicotine users group than in the non-nicotine users group. The results of the thesis are important for forensic and clinical medicine, as well as for public health. The possibility of drug interactions and pharmacogenetic issues should be taken into account in cause-of-death investigations, especially in unclear cases, medical malpractice suspicions and cases where toxicological findings are scarce. Post-mortem toxicological epidemiology is a new field of research that can help to reveal problems in drug use and prescription practises.

Effect of stacking fault energy on the dynamic recrystallization during hot working of FCC metals: A study using processing maps

The influence of stacking fault energy (SFE) on the mechanism of dynamic recrystallization (DRX) during hot deformation of FCC metals is examined in the light of results from the power dissipation maps. The DRX domain for high SFE metals like Al and Ni occurred at homologous temperature below 0·7 and strain rates of 0·001 s−1 while for low SFE metals like Cu and Pb the corresponding values are higher than 0·8 and 100 s−1. The peak efficiencies of power dissipation are 50% and below 40% respectively. A simple model which considers the rate of interface formation (nucleation) involving dislocation generation and simultaneous recovery and the rate of interface migration (growth) occurring with the reduction in interface energy as the driving force, has been proposed to account for the effect of SFE on DRX. The calculations reveal that in high SFE metals, interface migration controls DRX while the interface formation is the controlling factor in low SFE metals. In the latter case, the occurrence of flow softening and oscillations could be accounted for by this model.

Amino acid-lanthanide interactions, Part 2. The X-ray crystal structures of lanthanide and calcium complexes of 1-amino-cyclohexane-1-carboxylic acid (Acc6)

The structures of [Nd-2(Acc(6))(H2O)(6)](ClO4)(6) .(H2O)(6) (1) [Er-2(Acc(6))(4)(H2O)(8)](ClO4)(6) .(H2O)(11) (2) and [Ca-5(Acc(6))(12)(H2O)(6)](ClO4)(10).(H2O)(4) (3) (Acc(6) = 1-aminocyclohexane-1-carboxylic acid) have been determined by X-ray crystallography. The lanthanide complexes 1 and 2 are dimeric in which two lanthanide cations are bridged by four carboxylato groups of Acc(6) molecules. In addition, the neodymium complex (1) features the unidentate coordination of the carboxyl group of an Acc(6) molecule in place of a water molecule in the erbium complex (2). The coordination number in both 1 and 2 is eight. The calcium Acc(6) complex (3) is polymeric; three different calcium environments are observed in the asymmetric unit. Two calcium ions are hexa-coordinated and one is hepta-coordinated. Considerable differences are observed between the solid state structures of Ln(III) and Ca-II complexes of Acc(6

Synthetic studies in aromatic hemiterpenes of natural origin, Part 5: Synthesis of 6-acetyl-2,2-dimethyl-8-methoxychromene via benzylic oxidation route

The synthesis of 6-acetyl-2,2-dimethyl-8-methoxychromene (lc), a naturally occurring isomer of encecalin (la)h~s been described startilag from 2,2,6- trimethyl-8-methoxyclaromene (2e) which was obtained from creosol (4) in two steps involving condensation of the phenol with malic acid to the coumarin (3), followed by Grignard reaction with CHaMgI. The transformation of (2e) to the natural product (lc) was effeeted by oxidative dehydrogenation by DDQ of the 6-meth~r function to the formyl group (2f), Grignard reaction to the carbinol (2g) and finally its oxidation to the acetyl moiety (lc), the sequence of the essential steps schematically summarised as : Ar-CHs --* Ar-CHO --* Ar-CH (OH) CHs --* Ar---COCHs.