Enthalpies of Combustion and Formation of Severely Crowded Methyl-Substituted 1,3-dioxanes. The Magnitudes of 2,4- and 4,6-diaxial Me,Me-Interactions and the Chair-2,5-twist Energy Difference.

Enthalpies of combustion of 2,2--4,6- () and 4,4,6,6-tetramethyl- () and 2,4,4,6,6- () and 2,2,4,4,6-pentamethyl-1,3-dioxanes () were determined to estimate their enthalpies of formation in the gas phase. By comparing the latter with the corresponding enthalpies estimated based on the various bond-bond interactions allowed to determine the chair-2,5-twist energy difference (Δ = 29.8 kJ mol) for since C-13 shift correlations indicate that it escapes to the 2,5-twist form where the 2-methyl groups are isoclinal and 4- and 6-methyl groups pseudoequatorial to avoid syn-axial interactions.

Overcoming discourse-linking difficulties in aphasia: The case of clitic pronouns.

The present study aims to contribute to the ongoing discussion about the impact of discourse-linking deficits on the performance of individuals with aphasia by providing new data from a set of rarely investigated constructions: sentences in which a clitic pronoun coexists alongside with the full DP it agrees with. To do so, we use data of individuals with non-fluent aphasias who need to overcome the difficulties in direct object (accusative) clitic production. This results in overproduction of non-target clitic right dislocations (RDs) and clitic doubling (CD).

Crystal structure of μ-oxalodi-hydroxamato-bis-[(2,2'-bipyrid-yl)(di-methyl sulfoxide-κO)copper(II)] bis-(perchlorate).

The centrosymmetric binuclear complex, [Cu2(C2H2N2O4)(C10H8N2)2(C2H6OS)2](ClO4)2, contains two copper(II) ions, connected through an N-deprotonated oxalodi-hydroxamic acid dianion, two terminal 2,2'-bi-pyridine ligands, and two apically coordinating dimethylsulfoxide mol-ecules. Two non-coordinating perchlorate anions assure electrical neutrality. The copper(II) ions in the complex dication [Cu2(C10H8N2)2(μ-C2H2N2O4)(C2H6SO)2](2+) are in an O2N3 square-pyramidal donor environment, the Cu-Cu separation being 5.

Tetra-kis[bis-(pyridin-2-yl)amine-κN (2)](nitrato-κO)silver(I).

In the title complex, [Ag(NO3)(C10H9N3)4], the nitrate ligand is found to be disordered over two sets of positions, with occupancy factors of 0.473 (5) and 0.527 (5).

Dark-leaved willow (Salix myrsinifolia) is resistant to three-factor (elevated CO2, temperature and UV-B-radiation) climate change.

Elevated carbon dioxide (CO2 ), temperature (T) and ultraviolet-B (UV-B) radiation may affect plant growth and secondary chemistry in different directions, but the effect of the combination of the three factors has seldom been tested. Here, we grew four dark-leaved willow (Salix myrsinifolia) clones under combinations of ambient or elevated CO2, T and UV-B radiation in top-closed chambers for 7 wk. Elevated UV-B had no effects on growth or phenolic compounds, and there were no significant interactions between UV-B, CO2 and T.

Analysis of fullerene-C60 and kinetic measurements for its accumulation and depuration in Daphnia magna.

A simple method for analyzing masses of water suspended fullerenes (nC60) in Daphnia magna by extracting to toluene and measuring by ultraviolet-vis spectrophotometry was developed. This method was used to assess bioaccumulation and depuration rates by daphnia after nC60 exposure in artificial freshwater. Accumulation was rapid during the first few hours, and based on accumulation modeling, 90% of the steady-state concentration was reached in 21 h.

Challenging power and meaning: outlining the popular epidemiology of HIV and AIDS in Rakai, Uganda, c. 1975-1990.

This article traces the historical evolution of conditions that favoured the spread of HIV in Rakai district, Uganda, and the process of evolution of the local, popular epidemiology of HIV and AIDS. It argues that the HIV epidemic was made possible by economic and social disparities, which grew more pronounced since the mid-1970s as a result of economic decline, physical insecurity, and the disbanding of public services. The local constructions of AIDS in Rakai have changed and shifted according to the progress of the epidemic, eventually challenging the initial cultural construction of the disease, based on local notions about causality between disease and morality.

Ophiostoma denticiliatum sp. nov. and other Ophiostoma species associated with the birch bark beetle in southern Norway.

Ophiostomatoid fungi were isolated from Scolytus ratzeburgi infesting Betula pendula and B. pubescens in Norway. Fungi were identified based on morphology, DNA sequence comparison for two gene regions and phylogenetic analyses.

Reversible protonation of amine-functionalized luminescent Au-Cu clusters: characterization, photophysical and theoretical studies.

Reaction of the polymeric alkynyl complexes (AuC(2)C(6)H(4)R)(n) (R = 4-NH(2) and 3-NH(2)) with the diphosphine PPh(2)C(6)H(4)PPh(2) in the presence of Cu(+) ions gave two novel heterometallic aggregates [{Au(3)Cu(2)(C(2)C(6)H(4)R)(6)}Au(3)(PPh(2)C(6)H(4)PPh(2))(3)](PF(6))(2) (R = 4-NH(2) (2), 3-NH(2) (3)). The compounds obtained were characterized by NMR spectroscopy and ESI-MS measurements. The solid-state structure of their 4-NMe(2) congener 1 is reported.

Near-ambient ozone concentrations reduce the vigor of Betula and Populus species in Finland.

In this review the main growth responses of Finnish birch (Betula pendula, B. pubescens) and aspen species (Populus tremula and P. tremuloides x P.

Synthesis, photophysical and theoretical studies of luminescent silver(I)-copper(I) alkynyl-diphosphine complexes.

The novel heterometallic aggregates [Ag(8)Cu(2)(C(2)C(6)H(4)X)(6)(PPh(2)C(6)H(4)PPh(2))(6)][PF(6)](4) (X = H, 1; OMe, 2; NMe(2), 3) were prepared by the self-assembly reactions starting from simple precursors. These compounds consist of the central [Ag(6)Cu(2)(C(2)C(6)H(4)X)(6)](2+) clusters capped by two tripodal fragments [Ag(diphosphine)(3)](+). The solid state structures of complexes 1 and 3 have been determined by X-ray crystallographic studies, and NMR spectroscopy confirmed that the compounds remain intact in solution.

Rational reductive fusion of two heterometallic clusters: formation of a highly stable, intensely phosphorescent Au-Ag aggregate and application in two-photon imaging in human mesenchymal stem cells.

An unprecedented Au-Ag alkynyl-diphosphine aggregate, obtained via CO-reduction of a mixture of simple reagents, exhibits intense room-temperature phosphorescence free from O(2) quenching, and serves as an excellent phosphorescence dye suited for both one- and two-photon imaging in human stem cells.

Glucosylthioureidocalix[4]arenes: Synthesis, conformations and gas phase recognition of amino acids.

The gas-phase recognition of native amino acids and the conformational properties of three glucosylthioureidocalix[4]arenes () were studied theoretically and experimentally using ab initio calculations, ESI-FTICR,(1)H and (13)C NMR MS. The conformational and complexation properties of the glucocalixarenes were dependent on the number of glucose units at the upper rim and the length of the alkyl chains at the lower rim of the calixarene skeleton. ESI-MS experiments showed the compounds to form 1 : 1 complexes with the amino acids, with a marked preference for amino acids containing an aromatic nucleus and an additional H-bonding group in their side chain (Trp, Tyr, Phe >> Ser, Leu and Asp).

Distinguishing between deterministic and stochastic pulse broadening.

Two mechanisms can cause similar broadening of pulses in a pulse train: variable temporal/spectral phase in a train of identical pulses (a deterministic mechanism) and partial correlations between different frequency components of the pulses (a stochastic mechanism). We discuss methods to distinguish between these two fundamentally different mechanisms. We show that their roles can be separated, at least for an important class of fields known as Gaussian Schell-model pulses, using time-resolved intensity measurements of pulses passing through Michelson's interferometer.

Hydrogen bonding in phosphonate cavitands: investigation of host-guest complexes with ammonium salts.

The H-bonding in alkylammonium complexes of phosphonate cavitands were studied by mass spectrometric methods and theoretical calculations. The alkylammonium ions included primary, secondary, and tertiary methyl- and ethylammonium ions. Their complexation with mono-, tetra-, and two di-phosphonate cavitands, which differ according to the number and position of H-bond acceptor P = O groups, was evaluated by using different competition experiments, energy-resolved CID, gas-phase H/D-exchange, and ligand-exchange reactions, together with ab initio theoretical optimization of the complexes.

Predicting the bioavailability of sediment-associated spiked compounds by using the polyoxymethylene passive sampling and tenax extraction methods in sediments from three river basins in Europe.

This study presents the bioavailability of four spiked compounds to Lumbriculus variegatus, in sediment samples from three river basins in Europe: the Elbe, the Llobregat, and the Scheldt. Twenty sediment samples differing in physical and chemical properties were spiked with chlorpyrifos, pyrene, tetrachloribiphenyl, and tetrabromo diphenyl ether. The main focus of this study was to compare the suitability of two chemical approaches-the rapidly desorbing fraction method based on the Tenax extraction and the freely dissolved chemical concentration method based on polyoxymethylene passive sampling-for predicting the bioavailability of sediment-associated hydrophobic compounds.

Cross-spectral purity of electromagnetic fields.

We extend Mandel's scalar-wave concept of cross-spectral purity to electromagnetic fields. We show that in the electromagnetic case, assumptions similar to the scalar cross-spectral purity lead to a reduction formula, analogous with the one introduced by Mandel. We also derive a condition that shows that the absolute value of the normalized zeroth two-point Stokes parameter of two cross-spectrally pure electromagnetic fields is the same for every frequency component of the field.

To speciate, or not to speciate? Resource heterogeneity, the subjectivity of similarity, and the macroevolutionary consequences of niche-width shifts in plant-feeding insects.

Coevolutionary studies on plants and plant-feeding insects have significantly improved our understanding of the role of niche shifts in the generation of new species. Evolving plant lineages essentially constitute moving islands and archipelagoes in resource space, and host shifts by insects are usually preceded by colonizations of novel resources. Critical to hypotheses concerning ecological speciation is what happens immediately before and after colonization attempts: if an available plant is too similar to the current host(s), it simply will be incorporated into the existing diet, but if it is too different, it will not be colonized in the first place.

Aquatic environment and differentiation of vibrissae: comparison of sinus hair systems of ringed seal, otter and pole cat.

This study investigated the structure and innervation of the vibrissal systems of the pole cat (Mustela putorius), European otter (Lutra lutra) and ringed seal (Phoca hispida) in order to find adaptations to aquatic environment. The number of myelinated nerve fibers of deep vibrissal nerve (DVN) of the entire vibrissal system was considerably greater in the ringed seal (10x, aquatic mammal) and in the otter (4x, semi-aquatic mustelid) compared to the pole cat which is a terrestrial mustelid. Similarly, the number of neural end organs in the vibrissae of ringed seals was about ten times more numerous than in pole cats.

Robust sensor for turbidity measurement from light scattering and absorbing liquids.

Internationally standardized turbidity measurements for probing solid particles in liquid are problematic in the case of simultaneous light scattering and absorption. A method and a sensor to determine the turbidity in the presence of light absorption are presented. The developed sensor makes use of the total internal reflection of a laser beam at the liquid-prism interface, and the turbidity is assessed using the concept of laser speckle pattern.

Chiral differentiation of some cyclic beta-amino acids by kinetic and fixed ligand methods.

Differentiation of beta-amino acid enantiomers with two chiral centres was investigated by kinetic method with trimeric metal-bound complexes. Four enantiomeric pairs of beta-amino acids were studied: cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)- and trans-(1S,2S)-2-aminocyclopentanecarboxylic acids (cyclopentane beta-amino acids), and cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)-, and trans-(1S,2S)-2-aminocyclohexanecarboxylic acids (cyclohexane beta-amino acids). The results showed that the choice of metal ion (Cu(2+), Ni(2+)) and chiral reference compound (alpha- and beta-amino acids) had an effect on the enantioselectivity.

Sexualised space, sexual networking & the emergence of AIDS in Rakai, Uganda.

This paper argues that the outbreak of the epidemic of AIDS in Rakai, Uganda, in the early 1980s was a consequence of economic change, leading to the erosion of conventional cultural checks on juvenile, female and male sexuality and the emergence and growth of sexualised spaces and sexual networking in a few remote rural hubs of economic activity which exhibited a different sexual culture from the surrounding countryside. The trading hubs developed dense local and regional sexual networks which enabled HIV to spread quickly among the "risk groups" and local people of the busiest trading towns and villages. The high degree of sexual mixing in these hubs opened up new routes for HIV to infect the general population.

Strong fluorescence-signal gain with single-excitation-enhancing and emission-directing nanostructured diffraction grating.

A dielectric subwavelength diffraction grating structure is designed and fabricated in order to enhance fluorescence-based detection of biomolecules. Two separate phenomena, enhancement of the local energy densities of the excitation illumination and direction of the emitted signal toward the detector, are examined theoretically and experimentally. 530-fold enhancement of detected signal is achieved compared with the signal from flat surface.

Two-point Stokes parameters: interpretation and properties.

Whereas the classic Stokes parameters are measures of intensity, the recently introduced two-point Stokes parameters characterize spatial coherence. It is shown that in analogy to the Stokes parameters, the two-point parameters have a physical interpretation as sums and differences of (scalar) cross-spectral density functions of specific electric-field components. A measurement scheme and several physical consequences of the two-point parameters are discussed.

Expression of calsequestrin in atrial and ventricular muscle of thermally acclimated rainbow trout.

Calsequestrin (CASQ) is the main Ca(2+) binding protein within the sarcoplasmic reticulum (SR) of the vertebrate heart. The contribution of SR Ca(2+) stores to contractile activation is larger in atrial than ventricular muscle, and in ectothermic fish hearts acclimation to low temperatures increases the use of SR Ca(2+) in excitation-contraction coupling. The hypotheses that chamber-specific and temperature-induced differences in SR function are due to the increased SR CASQ content were tested in rainbow trout (Oncorhynchus mykiss) acclimated at either 4 degrees C (cold acclimation, CA) or 18 degrees C (warm acclimation, WA).