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Charge transfer has proven to be an important mechanism in DNA photochemistry. In particular, guanine (dG) plays a major role as an electron donor, but the photophysical dynamics of dG‐containing charge‐transfer states have not been extensively investigated so far. Here, we use UV pump (266 nm) and picosecond IR probe (∼5–7 μm) spectroscopy to study ultrafast dynamics in dG‐containing short oligonucleotides as a function of sequence and length. For the pure purine oligomers, we observed lifetimes for the charge‐transfer states of the order of several hundreds of picoseconds, regardless of the oligonucleotide length. In contrast, pyrimidine‐containing dinucleotides d(GT) and d(GC) show much faster relaxation dynamics in the 10 to 30 ps range. In all studied nucleotides, the charge‐transfer states are formed with an efficiency of the order of ∼50 %. These photophysical characteristics will lead to an improved understanding of DNA damage and repair processes., Studying the photophysical dynamics of dG‐containing oligonucleotides by time‐resolved IR spectroscopy showed transient absorption changes pointing to excitation decay and vibrational cooling within a few picoseconds. On the 10‐500 picosecond time range transient charge‐transfer states were identified which are efficiently formed in these oligomers. The known reactivity and the high formation yield make charge‐transfer states important promoters for secondary reactions in DNA.

Endocrine-active substances can adversely impact the aquatic ecosystems. A special emphasis is laid, among others, on the effects of estrogens and estrogen mimicking compounds. Effect-based screening methods like in vitro bioassays are suitable tools to detect and quantify endocrine activities of known and unknown mixtures. This study describes the validation of the Arxula-Yeast Estrogen Screen (A-YES®) assay, an effect-based method for the detection of the estrogenic potential of water and waste water. This reporter gene assay, provided in ready to use format, is based on the activation of the human estrogen receptor alpha. The user-friendly A-YES® enables inexperienced operators to rapidly become competent with the assay. Fourteen laboratories from four countries with different training levels analyzed 17β-estradiol equivalent concentrations (EEQ) in spiked and unspiked waste water effluent and surface water samples, in waste water influent and spiked salt water samples and in a mixture of three bisphenols. The limit of detection (LOD) for untreated samples was 1.8 ng/L 17β-estradiol (E2). Relative repeatability and reproducibility standard deviation for samples with EEQ above the LOD (mean EEQ values between 6.3 and 20.4 ng/L) ranged from 7.5 to 21.4% and 16.6 to 28.0%, respectively. Precision results are comparable to other frequently used analytical methods for estrogens. The A-YES® has been demonstrated to be an accurate, precise and robust bioassay. The results have been included in the ISO draft standard. The assay was shown to be applicable for testing of typical waste water influent, effluent and saline water. Other studies have shown that the assay can be used with enriched samples, which lower the LOD to the pg/L range. The validation of the A-YES® and the development of a corresponding international standard constitute a step further towards harmonized and reliable bioassays for the effect-based analysis of estrogens and estrogen-like compounds in water samples.

Ecotoxicological screening of surface waters can involve multiple analyses using multiple bioassay and chemical analytical methods that require enriched samples to reach low concentrations. Such broad screening of the same sample necessitates sufficient sample volume-typically several liters-to produce a sufficient amount of enriched sample. Often, this is achieved by performing parallel solid-phase extractions (SPE) where extracts are combined into a pool-this is a laborious process. In this study, we first validated our existing SPE method for the chemical recovery of an extended set of compounds. We spiked four estrogenic compounds and 11 herbicides to samples from independent rivers (1 L) and wastewater treatment plant effluents (0.5 L). Then, we investigated the effect of increased sample loading of the SPE cartridges on both chemical and biological recoveries by comparing the validated volumes with four times larger sample volumes (i.e., 4 L river water and 2 L effluent). Samples were analyzed by LC-MS/MS and three bioassays: an estrogen receptor transactivation assay (ERα-CALUX), the combined algae test, and a bacterial bioluminescence inhibition assay. Our existing SPE method was found to be suitable for enriching the extended set of estrogens and herbicides in river water and effluents with near to perfect chemical recoveries (~ 100%), except for the herbicide metribuzin (46 ± 19%). In the large volume river and effluent samples, the biological activities and concentrations of the spiked compounds were between 87 and 104% of those measured with the lower sample loading, which is adequate. In addition, the ratio between the large and original volume SPE method for the non-target endpoint (bacterial bioluminescence inhibition) was acceptable (on average 82 ± 9%). Results indicate that our current water extraction method can be applied to up to four times larger sample volumes, resulting in four times more extract volumes, without significant reductions in recoveries for the tested estrogens and herbicides. Graphical abstract ᅟ.

The decay of electronically excited states of thymine (Thy) and thymidine 5′-monophosphate (TMP) was studied by time-resolved UV/vis and IR spectroscopy. In addition to the well-established ultrafast internal conversion to the ground state, a so far unidentified UV-induced species is observed. In D2O, this species decays with a time constant of 300 ps for thymine and of 1 ns for TMP. The species coexists with the lowest triplet state and is formed with a comparably high quantum yield of about 10% independent of the solvent. The experimentally determined spectral signatures are discussed in the light of quantum chemical calculations of the singlet and triplet excited states of thymine.

UV-induced formation of the cyclobutane pyrimidine dimer (CPD) lesion is investigated by stationary and time-resolved photosensitization experiments. The photosensitizer 2'-methoxyacetophenone with high intersystem crossing efficiency and large absorption cross-section in the UV-A range was used. A diffusion controlled reaction model is presented. Time-resolved experiments confirmed the validity of the reaction model and provided information on the dynamics of the triplet sensitization process. With a series of concentration dependent stationary illumination experiments, we determined the quantum efficiency for CPD formation from the triplet state of the thymine dinucleotide TpT to be 4 ± 0.2%.

International audience; The 12C+12C fusion reaction is one of the most important for nuclear astrophysics since it determines the carbon ignition in stellar environments. Two experiments which make use of the gamma-particle coincidence technique to measure the 12C+12C S-factors at deep sub barrier energies are discussed. Results are presented showing a decrease of the S-factor below Ec.m. = 3 MeV.

The decay of triplet states and the formation of cyclobutane pyrimidine dimers (CPDs) after UV excitation of the all-thymine oligomer (dT)18 and the locked dinucleotide TLpTL were studied by nanosecond IR spectroscopy. IR marker bands characteristic for the CPD lesion and the triplet state were observed from ∼1 ns (time resolution of the setup) onward. The amplitudes of the CPD marker bands remain constant throughout the time range covered (up to 10 μs). The triplet decays with a time constant of ∼10 ns presumably via a biradical intermediate (lifetime ∼60 ns). This biradical has often been invoked as an intermediate for CPD formation via the triplet channel. The present results lend strong support to the existence of this intermediate, yet there is no indication that its decay contributes significantly to CPD formation.

Animal, 6 (2), ISSN:1751-7311, ISSN:1751-732X

Absorption of UV-radiation in nucleotides initiates a number of photophysical and photochemical processes, which may finally cause DNA damage. One major decay channel of photoexcited DNA leads to reactive charge transfer states. This study shows that these states trigger self-repair of DNA photolesions. The experiments were performed by UV spectroscopy and HPLC on different single and double stranded oligonucleotides containing a cyclobutane pyrimidine dimer (CPD) lesion. In a first experiment we show that photoexcitation of adenine adjacent to a CPD has no influence on this lesion. However, excitation of a guanine (G) adenine (A) sequence leads to reformation of the intact thymine (T) bases. The involvement of two bases for the repair points to a long-living charge transfer state between G and A to be responsible for the repair. The negatively charged A radical anion donates an electron to the CPD, inducing ring splitting and repair. In contrast, a TA sequence, having an inverted charge distribution (T radical anion, A radical cation), is not able to repair the CPD lesion. The investigations show that the presence of an adjacent radical ion is not sufficient for repair. More likely it is the driving power represented by the oxidation potential of the radical ion, which controls the repair. Thus, repair capacities are strongly sequence-dependent, creating DNA regions with different tendencies of self-repair. This self-healing activity represents the simplest sequence-dependent DNA repair system.

The breakup reaction 9Be(4He, 3α)n was measured using an array of four double-sided silicon strip detectors at beam energies of 22 and 26 MeV. Excited states in 9Be up to 12 MeV were populated and reconstructed through the measurement of the charged reaction products. It is proposed that limits on the spins and parities of the states can be derived from the way that they decay. Various breakup paths for excited states in 9Be have been explored including the 8Be(g.s.) + n, 8Be(2+) + n and 5He(g.s.) + 4He channels. By imposing the condition that the breakup proceeded via the 8Be ground state, clean excitation spectra for 9Be were reconstructed. The remaining two breakup channels were found to possess strongly-overlapping kinematic signatures and more sophisticated methods (referenced) are required to completely disentangle these other possibilities. Emphasis is placed on the development of the experimental analysis and the usefulness of Monte-Carlo simulations for this purpose.

A systematic measurement of the $(\ensuremath{\alpha},\ensuremath{\gamma})$ reaction for all the stable nickel isotopes has been performed using the $\ensuremath{\gamma}$-summing technique. For two of the isotopes, $^{60}\mathrm{Ni}$ and $^{61}\mathrm{Ni}$, the $\ensuremath{\alpha}$-capture cross sections have been experimentally measured for the first time. For $^{58,62,64}\mathrm{Ni}$, the current measurement is in excellent agreement with earlier results found in the literature, and additionally extends the energy range of the measured cross sections up to 8.7 MeV. The data provided a tool for testing the cross section predictions of Hauser-Feshbach calculations. The experimental results were compared to the cross sections calculated with the talys 1.6 code and commonly used databases non-smoker and bruslib. For each of the investigated isotopes a combination of input parameter for talys was identified that best reproduces the experimental data, and recommended reaction rate has been calculated. Additionally, a set of inputs for Hauser-Feshbach calculations was given that, simultaneously for all the isotopes under consideration, reproduces the experimental data within the experimental uncertainties.

UV-induced Dewar lesion formation is investigated in single- and double-stranded oligonucleotides with ultrafast vibrational spectroscopy. The quantum yield for the conversion of the (6–4) lesion to the Dewar isomer in DNA strands is reduced by a factor of 4 in comparison to model dinucleotides. Time resolved spectroscopy reveals a fast process in the excited state with spectral characteristics of bases which are adjacent to the excited (6–4) lesion. These kinetic components have large amplitudes and indicate that an additional quenching channel acts in the stranded DNA systems and reduces the Dewar formation yield. Presumably relaxation evolves via a charge transfer to the neighboring guanine and the paired cytosine participates in a double-stranded oligomer. Changes in the decay of the relaxed excited electronic state of the (6–4) chromophore point to modifications in the excited state energy landscape which may lead to an additional reduction of the Dewar formation yield.

In the condensed excitonic phase of intermediate valent TmSe0.45Te0.55 the heat conductivity and the thermal diffusivity have been obtained between 300 K and 1.5 K and between ambient pressure and 17 kbar (1.7 GPa), as a first experiment of its kind. Pressure and temperature are used to navigate in three different phases of the material, the intermediate valent semiconducting phase, the condensed excitonic phase and the intermediate valent metallic phase. In the condensed excitonic phase the heat conductivity λ increases strongly below about 20 K, suggesting a superfluid phase for the lowest temperatures. In a solid under equilibrium conditions this has never been seen before. Also the thermal diffusivity a strongly increases below 20 K, giving evidence for second sound. The quotient λ/ρa represents the specific heat, which thus can be calculated, for the first time as a function of pressure and for a large temperature range. When entering the condensed excitonic phase under pressure and from high temperatures (100 K–250 K), the Dulong-Petit value of the specific heat drops precipitously to about half its value. Also this phenomenon is unprecedented. In addition the longitudinal sound velocity has been measured under pressure and as a function of temperature. Entering the excitonic phase the sound velocity drastically increases by about a factor two. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The fate of immobilized N in soils is one of the great uncertainties in predicting C sequestration at increased CO2 and N deposition. In a dual isotope tracer experiment ( 13 C, 15 N) within a 4-year CO2 enrichment ( 1200ppmv) study with forest model ecosystems, we (i) quantified the effects of elevated CO2 on the partitioning of N; (ii) traced immobilized N into physically separated pools of soil organic matter (SOM) with turnover rates known from their 13 C signals; and (iii) estimated the remobilization and thus, the bio-availability of newly sequestered C and N. (1) CO2 enrichment significantly decreased NO3 concentrations in soil waters and export from 1.5m deep lysimeters by 30‐80%. Consequently, elevated CO2 increased the overall retention of N in the model ecosystems. (2) About 60‐80% of added 15 NH4 NO3 were retained in soils. The clay fraction was the greatest sink for the immobilized 15 N sequestering 50‐60% of the total new soil N. SOM associated with clay contained only 25% of the total new soil C pool and had small C/N ratios (o13), indicating that it consists of humified organic matter with a relatively slow turn over rate. This implies that added 15 N was mainly immobilized in stable mineral-bound SOM pools. (3) Incubation of soils for 1 year showed that the remobilization of newly sequestered N was three to nine times smaller than that of newly sequestered C. Thus, inorganic inputs of N were stabilized more effectively in soils than C. Significantly less newly sequestered N was remobilized from soils previously exposed to elevated CO2. In summary, our results show firstly that a large fraction of inorganic N inputs becomes effectively immobilized in relative stable SOM pools and secondly that elevated CO2 can increase N retention in soils and hence it may tighten N cycling and diminish the risk of nitrate leaching to groundwater.

Carbon sequestered in biomass is not necessarily stored infinitely, but is exposed to human or natural disturbances. Storm is the most important natural disturbance agent in Swiss forests. Therefore, if forests are taken into account in the national carbon budget, the impact of windthrow on carbon pools and fluxes should be included. In this article the forest scenario model MASSIMO and the soil carbon model YASSO were applied to assess the effect of forest management and an increased storm activity on the carbon sequestration in Swiss forests. First, the soil model was adapted to Swiss conditions and validated. Second, carbon fluxes were assessed applying the two models under various forest management scenarios and storm frequencies. In particular, the influence of clearing after a storm event on the carbon budget was analyzed. The evaluation of the model results showed that the soil model reliably reproduces the amount of soil carbon at the test sites. The simulation results indicated that, within the simulated time period of 40 years, forest management has a strong influence on the carbon budget. However, forest soils only react slightly to changes in the above-ground biomass. The results also showed that a storm frequency increase of 30% has a small impact on the national carbon budget of forests. To develop effective mitigation strategies for forest management, however, longer time periods must be regarded.

We show by femtosecond IR-spectroscopy that excited states in oligonucleotides decay with high yields by charge transfer to delocalized charged radicals. For the 6-4 lesion, charge transfer protects the DNA from Dewar formation.

To determine the relationship between phloem transport and changes in phloem water content, we measured temporal and spatial variations in water content and sucrose, glucose and fructose concentrations in phloem samples and phloem exudates of 70- and 30-year-old Norway spruce trees (Picea abies (L.) Karst.). Large temporal and spatial variations in phloem water content (1.4-2.6 mg mg(dw)(-1)) and phloem total sugar concentration (31-70 mg g(dw)(-1)) paralleled each other (r(2) = 0.83, P0.0001 for the temporal profile and r(2) = 0.96, P0.008 for the spatial profile), indicating that phloem water content depends on the total amount of sugar to be transferred. Changes in phloem water content were unrelated to changes in bark thickness. Maximum changes in phloem water content calculated from dendrometer readings were only 8-11% of the maximum measured changes in phloem water content, indicating that reversible changes in bark thickness did not reflect changes in internal water relations. We also studied the relationship between xylem sap velocity and changes in bark thickness in 70-year-old trees during summer 1999 and winter 1999-2000. Sap flow occurred sporadically throughout the winter, but there was no relationship between bark shrinkage or swelling and sap velocity. In winter, mean daily xylem sap velocity was significantly correlated with mean daily vapor pressure deficit and air temperature (P0.0001, in both cases). Changes in bark thickness corresponded with both short- and long-term changes in relative humidity, in both winter and summer. Under controlled conditions at0 degrees C, changes in relative humidity alone caused changes in thickness of boiled bark samples. Because living bark of Norway spruce trees contains large areas with crushed and dead sieve cell zones-up to 24% of the bark is air-filled space-we suggest that this space can compensate for volume changes in living phloem cells independently of total tissue water content. We conclude that changes in bark thickness are not indicative of changes in either phloem water capacitance or xylem sap flow.

UV excitation of the DNA single strand (dT)18 leads to electronically excited states that are potential gateways to DNA photolesions. Using time-resolved infrared spectroscopy we characterized a species with a lifetime of ∼100 ps and identified it as a charge separated excited state between two thymine bases.

Excited-state dynamics are essential to understanding the formation of DNA lesions induced by UV light. By using femtosecond IR spectroscopy, it was possible to determine the lifetimes of the excited states of all four bases in the double-stranded environment of natural DNA. After UV excitation of the DNA duplex, we detected a concerted decay of base pairs connected by Watson–Crick hydrogen bonds. A comparison of single- and double-stranded DNA showed that the reactive charge-transfer states formed in the single strands are suppressed by base pairing in the duplex. The strong influence of the Watson–Crick hydrogen bonds indicates that proton transfer opens an efficient decay path in the duplex that prohibits the formation or reduces the lifetime of reactive charge-transfer states.

Base stacking in DNA is related to long-living excited states whose molecular nature is still under debate. To elucidate the molecular background we study well-defined oligonucleotides with natural bases, which allow selective UV excitation of one single base in the strand. IR probing in the picosecond regime enables us to dissect the contribution of different single bases to the excited state. All investigated oligonucleotides show long-living states on the 100-ps time scale, which are not observable in a mixture of single bases. The fraction of these states is well correlated with the stacking probabilities and reaches values up to 0.4. The long-living states show characteristic absorbance bands that can be assigned to charge-transfer states by comparing them to marker bands of radical cation and anion spectra. The charge separation is directed by the redox potential of the involved bases and thus controlled by the sequence. The spatial dimension of this charge separation was investigated in longer oligonucleotides, where bridging sequences separate the excited base from a sensor base with a characteristic marker band. After excitation we observe a bleach of all involved bases. The contribution of the sensor base is observable even if the bridge is composed of several bases. This result can be explained by a charge delocalization along a well-stacked domain in the strand. The presence of charged radicals in DNA strands after light absorption may cause reactions--oxidative or reductive damage--currently not considered in DNA photochemistry.

Soil contains the major part of carbon in terrestrial ecosystems, but the response of this carbon to enriching the atmosphere in CO 2 and to increased N deposition is not completely understood. We studied the effects of CO 2 concentrations at 370 and 570 μmol CO 2 mol -1 air and increased N deposition (7 against 0.7 g N m -2 year -1 ) on the dynamics of soil organic C in two types of forest soil in model ecosystems with spruce and beech established in large open-top chambers containing an acidic loam and a calcareous sand. The added CO 2 was depleted in 13 C and thus the net input of new C into soil organic carbon and the mineralization of native C could be quantified. Soil type was the greatest determining factor in carbon dynamics. After 4 years, the net input of new C in the acidic loam (670 ± 30 g C m -2 ) exceeded that in the calcareous sand (340 ± 40 g C m -2 ) although the soil produced less biomass. The mineralization of native organic C accounted for 700 ± 90g C m -2 in the acidic loam and for 2800 ± 170 g C m -2 in the calcareous sand. Unfavourable conditions for mineralization and a greater physico-chemical protection of C by clay and oxides in the acidic loam are probably the main reasons for these differences. The organic C content of the acidic loam was 230 g C m -2 more under the large than under the small N treatment. As suggested by a negligible impact of N inputs on the fraction of new C in the acidic loam, this increase resulted mainly from a suppressed mineralization of native C. In the calcareous sand, N deposition did not influence C concentrations. The impacts of CO 2 enrichment on C concentrations were small. In the uppermost 10 cm of the acidic loam, larger CO 2 concentrations increased C contents by 50-170 g C m -2 . Below 10cm depth in the acidic loam and at all soil depths in the calcareous sand, CO 2 concentrations had no significant impact on soil C concentrations. Up to 40% of the 'new' carbon of the acidic loam was found in the coarse sand fraction, which accounted for only 7% of the total soil volume. This suggests that a large part of the CO 2 -derived 'new' C was incorporated into the labile and easily mineralizable pool in the soil.

The epithelial Na+ channel (ENaC) absorbs Na+ across the apical membrane of epithelia. The activity of ENaC is controlled by its interaction with Nedd4; mutations that disrupt this interaction increase Na+ absorption, causing an inherited form of hypertension (Liddle's syndrome). Nedd4 contains an N-terminal C2 domain, a C-terminal ubiquitin ligase domain, and multiple WW domains. The C2 domain is thought to be involved in the Ca2+-dependent localization of Nedd4 at the cell surface. However, we found that the C2 domain was not required for human Nedd4 (hNedd4) to inhibit ENaC in both Xenopus oocytes and Fischer rat thyroid epithelia. Rather, hNedd4 lacking the C2 domain inhibited ENaC more potently than wild-type hNedd4. Earlier work indicated that the WW domains bind to PY motifs in the C terminus of ENaC. However, it is not known which WW domains mediate this interaction. Glutathione S-transferase-fusion proteins of WW domains 2-4 each bound to alpha, beta, and gammaENaC in vitro. The interactions were abolished by mutation of two residues. WW domain 3 (but not the other WW domains) was both necessary and sufficient for the binding of hNedd4 to alphaENaC. WW domain 3 was also required for the inhibition of ENaC by hNedd4; inhibition was nearly abolished when WW domain 3 was mutated. However, the interaction between ENaC and WW domain 3 alone was not sufficient for inhibition. Moreover, inhibition was decreased by mutation of WW domain 2 or WW domain 4. Thus, WW domains 2-4 each participate in the functional interaction between hNedd4 and ENaC in intact cells.

In this study, we investigated the dynamics of dissolved inorganic and organic nitrogen (N) in throughfall, in soil solutions of Gleysols, and in outflows from experimental sub-catchments as well as from a headwater catchment in Switzerland. Additionally, we studied the effect of increased N deposition on dissolved N by applying 3 g NH 4 NO 3 –N m −2 year −1 to soil plots and to one of the sub-catchments. Dissolved organic N (DON) was the dominant form of total dissolved N (TDN) in the soil and surface waters. The proportion of DON in TDN increased from the throughfall down to the subsoil, which indicates that the retention of DON was lower than that of inorganic N. Concentrations of DON in the subsoil were higher under reducing than under oxidising conditions. In the soil solution and in the runoff from all catchments, nitrate and DON displayed inverse seasonal patterns with concentrations of NO 3 − being highest in late winter and those of DON being maximal in summer and fall. This difference shows that during periods of increased biological activity, NO 3 − was retained in the forest ecosystem while the production of DON was stimulated. Concentrations of both NO 3 − and DON were negatively correlated with the amount of throughfall. In the outflow of the headwater catchment, however, the concentration–discharge relationship was negative for NO 3 − , but positive for DON. The reason for this difference appeared to be the larger contribution of topsoil water at high flow, which was poor in NO 3 − and rich in DON. Experimentally increasing the N deposition increased NO 3 − leaching significantly, but had no effects on DON leaching and on DON export from the catchments. In conclusion, our results show that the dynamics of dissolved organic and inorganic N are controlled by different factors.

• The effects of nitrogen dioxide (NO2) exposure are reported on the physiology, morphology and carbon partitioning of hybrid poplar clone cuttings (Populus ×euramericana) grown under high and low soil nitrogen supply. • Plants were exposed to filtered air or NO2-enriched air (80–135 nl l−1) over 12 wk growth in phytotrons. Stable isotope analysis, combined with CO2 and H2O gas exchange measurements, biomass analysis and morphological development, was used to assess the integrated long-term effects of NO2. • NO2 had no toxic effects. A reduced 15N-isotope ratio indicated incorporation of NO2 while nitrate reductase activity in leaves was stimulated. The two nitrogen sources had differential effects on water use efficiency (WUE): NO2 exposure increased long-term WUE; soil N supply decreased WUE; a result not detectable using growth and short-term gas exchange experiments. Plants benefited from airborne NO2, increasing CO2 assimilation rate and biomass; both N sources increased shoot production at the expense of root growth. NO2 exposure induced leaf formation with reduced stomatal density and increased leaf area. • NO2 exposure might be beneficial although the reduced root: shoot biomass could have a detrimental effect on nutrient balance and drought resistance.

The responses of nitrogen transformations and nitrate (NO_3 -) leaching to experimentally increased N deposition were studied in forested sub-catchments (1500 m2) with Gleysols in Central Switzerland. The aim was toinvestigate whether the increase in NO3 - leaching,due to elevated N deposition, was hydrologically driven orresulted from N saturation of the forest ecosystem.Three years of continuous N addition at a rate of 30 kgNH4NO3-N ha-1 yr-1 had no effects on bulksoil N, on microbial biomass N, on K2SO4-extractableN concentrations in the soil, and on net nitrification rates.In contrast, N losses from the ecosystem through denitrification and NO3 - leaching increased significantly. Nitrate leaching was 4 kg N ha-1yr-1at an ambient N deposition of 18 kg N ha-1 yr-1.Leaching of NO3 - at elevated N deposition was 8 kg Nha-1 yr-1. Highest NO3 - leaching occurredduring snowmelt. Ammonium was effectively retained within theuppermost centimetres of the soil as shown by the absence ofNH4 + in the soil solution collected with microsuction cups. Quantifying the N fluxes indicated that 80% ofthe added N were retained in the forest ecosystem.Discharge and NO3 - concentrations of the outflow from the sub-catchments responded to rainfall within 30 min. The water chemistry of the sub-catchment outflow showed thatduring storms, a large part of the runoff from this Gleysol derived from precipitation and from water which had interactedonly with the topsoil. This suggests a dominance of near-surface flow and/or preferential transport through this soil. The contact time of the water with the soil matrix wassufficient to retain NH4 +, but insufficient for a complete retention of NO3 -. At this site with soilsclose to water saturation, the increase in NO3 - leaching by 4 kg N ha-1 yr-1 through elevated N inputsappeared to be due to the bypassing of the soil and the rootsystem rather than to a soil-internal N surplus.

The epithelial Na(+) channel (ENaC) is comprised of three homologous subunits (alpha, beta, and gamma). The channel forms the pathway for Na(+) absorption in the kidney, and mutations cause disorders of Na(+) homeostasis. However, little is known about the mechanisms that control the gating of ENaC. We investigated the gating mechanism by introducing bulky side chains at a position adjacent to the extracellular end of the second membrane spanning segment (549, 520, and 529 in alpha, beta, and gammaENaC, respectively). Equivalent "DEG" mutations in related DEG/ENaC channels in Caenorhabditis elegans cause swelling neurodegeneration, presumably by increasing channel activity. We found that the Na(+) current was increased by mutagenesis or chemical modification of this residue and adjacent residues in alpha, beta, and gammaENaC. This resulted from a change in the gating of ENaC; modification of a cysteine at position 520 in betaENaC increased the open state probability from 0. 12 to 0.96. Accessibility to this side chain from the extracellular side was state-dependent; modification occurred only when the channel was in the open conformation. Single-channel conductance decreased when the side chain contained a positive, but not a negative charge. However, alterations in the side chain did not alter the selectivity of ENaC. This is consistent with a location for the DEG residue in the outer vestibule. The results suggest that channel gating involves a conformational change in the outer vestibule of ENaC. Disruption of this mechanism could be important clinically since one of the mutations that increased Na(+) current (gamma(N530K)) was identified in a patient with renal disease.

The objectives of this study were to estimate how soil type, elevated N deposition (0.7 vs. 7 g N m−2y−1) and tree species influence the potential effects of elevated CO2 (370 vs. 570 μmol CO2 mol−1) on N pools and fluxes in forest soils. Model spruce-beech forest ecosystems were established on a nutrient-rich calcareous sand and on a nutrient-poor acidic loam in large open-top chambers. In the fourth year of treatment, we measured N concentrations in the soil solution at different depths, estimated N accumulation by ion exchange resin (IER) bags, and quantified N export in drainage water, denitrification, and net N uptake by trees. Under elevated CO2, concentrations of N in the soil solution were significantly reduced. In the nutrient-rich calcareous sand, CO2 enrichment decreased N concentrations in the soil solution at all depths (−45 to −100%). In the nutrient-poor acidic loam, the negative CO2 effect was restricted to the uppermost 5 cm of the soil. Increasing the N deposition stimulated the negative impact of CO2 enrichment on soil solution N in the acidic loam at 5 cm depth from −20% at low N inputs to −70% at high N inputs. In the nutrient-rich calcareous sand, N additions did not influence the CO2 effect on soil solution N. Accumulation of N by IER bags, which were installed under individual trees, was decreased at high CO2 levels under spruce in both soil types. Under beech, this decrease occurred only in the calcareous sand. N accumulation by IER bags was negatively correlated with current-years foliage biomass, suggesting that the reduction of soil N availability indices was related to a CO2-induced growth enhancement. However, the net N uptake by trees was not significantly increased by elevated CO2. Thus, we suppose that the reduced N concentrations in the soil solution at elevated CO2 concentrations were rather caused by an increased N immobilisation in the soil. Denitrification was not influenced by atmospheric CO2 concentrations. CO2 enrichment decreased nitrate leaching in drainage by 65%, which suggests that rising atmospheric CO2 potentially increases the N retention capacity of forest ecosystems.

DEG/ENaC Na(+) channels have diverse functions, including Na(+) absorption, neurotransmission, and sensory transduction. The ability of these channels to discriminate between different ions is critical for their normal function. Several findings suggest that DEG/ENaC channels have a pore structure similar to K(+) channels. To test this hypothesis, we examined the accessibility of native and introduced cysteines in the putative P loop of ENaC. We identified residues that span a barrier that excludes amiloride as well as anionic and large methanethiosulfonate reagents from the pore. This segment contains a structural element ((S/G)CS) involved in selectivity of ENaC. The results are not consistent with predictions from the K(+) channel pore, suggesting that DEG/ENaC Na(+) channels have a novel pore structure.

Nitrogen (N) was added over two years to a spruce-dominated (Picea abler) montane forest at Alptal, central Switzerland. A solution of ammonium nitrate (NH4NO2) was frequently sprinkled on the forest floor (1500 m2) to simulate an additional input of 30 kg N ha−1 yr−1 over the ambient 12 kg bulk inorganic N deposition. The added nitrogen was labelled with 15NH4 15NO3 during the first year. Results are compared to a control plot.

In the present study the effect of the opioid heptadecapeptide nociceptin, also termed orphanin FQ, an endogenous ligand for the orphan receptor named ORL1 (opioid receptor-like 1) receptor, was investigated on [3H]noradrenaline release induced by electrical field stimulation (24 pulses at 0.4 Hz, 200 mA, 0.3 ms duration) in the rat tail artery in the absence and presence of an alpha2-adrenoceptor antagonist, rauwolscine 3 microM. Nociceptin inhibited the electrically-evoked tritiated noradrenaline release in a concentration-dependent manner from rat tail arteries. This inhibitory effect of nociceptin was enhanced in the presence of the alpha2-adrenoceptor antagonist rauwolscine (maximum inhibition by 25% and 50% in the absence and presence of rauwolscine, respectively). At a supramaximal concentration (10 microM), the inhibitory action of DAGO, a selective micro-opioid receptor agonist, was less pronounced than that of nociceptin. The inhibitory effect of nociceptin was counteracted by naloxone benzoylhydrazone (3 microM) which by itself did not change the stimulation-evoked noradrenaline overflow. Naloxone (10 microM), a non-selective opioid receptor antagonist, did not affect the inhibitory effect of nociceptin whereas it abolished that of DAGO. In conclusion, these results suggest that nociceptin modulates noradrenergic neurotransmission by acting on prejunctional ORL1 receptors located on nerve terminals innervating the rat tail artery. They also demonstrate that prejunctional ORL1 receptors interact with prejunctional alpha2-adrenoceptors. The physiological significance of this phenomenon remains to be determined.

In a FACE experiment, one year old alder, ash, beech, and oak seedlings were planted together in tubs containing calcareous sandy alluvial soil with or without a slow release NPK-fertilizer, and exposed to ambient and elevated CO 2 concentrations (360 and 600 μl mol −1 ) for 20 weeks. In addition to the fertilizer, all tubs received 15 N-ammonium nitrate as a marker. Elevated CO 2 significantly increased biomass production in alder, but had no effect on oak and ash. In beech, due to disease and mortality in all treatments, any possible effects were obscured. The addition of fertilizer had no effect on biomass production in alder, but increased production in oak and ash significantly. In oak a treatment synergism may be present. The non-appearance of a synergistic CO 2 and fertilizer effect in alder may be explained by a fertilizer induced reduction of the N-fixing root-nodule biomass concurrent with a switch of the N-assimilation from atmospheric N to soil N supply, as the δ 15 N measurements in the leaves of alder as opposed to oak indicate. Although elevated CO 2 resulted in a significant biomass increase in alder, it did not lead to an appreaciable increase in the proportional presence of the species as measured on total plant biomass in the tub. Increasing the nutrient supply in the soil, however, did lead to appreciable gains in the proportional presence of oak and ash.

Two small experimental headwater catchments (approx. 1500 m 2 ) were set up in an alpine spruce forest in the Alptal valley (central Switzerland). They are located at an altitude of 1200 m and receive an average of 2300 mm precipitation a year. The site is moderately impacted by atmospheric nitrogen deposition (12 kg N ha −1 yr −1 bulk deposition of inorganic N). Two different gley soils occur as patches atop a Flysch substratum. The spatial heterogeneity of the soil is related with both the microtopography of the site and the vegetation. The catchments were made by digging 80-cm deep trenches into the shallow gleyic soils. Because of the low permeability of the clay-rich subsoil, these trenches collect the lateral water flow generated in the plots. The catchments were equipped with gauging stations (V-notch weirs) and automatic runoff-proportional water samplers. Meteorological parameters, deposition, water and solute discharge were monitored during one year. A correct water balance was obtained from the experimental catchments. The leaching of inorganic nitrogen was estimated to be 4 kg N ha −1 yr −1 , mainly as nitrate. It is, however, not clear if this nitrate is leached because the ecosystem is nitrogen saturated (N in surplus of the maximal ecosystem retention). Quick preferential water flow occurs through the soil, and this may prevent nitrate from rain or snowmelt to be removed by the soil matrix before entering the water runoff pathways. Both mini-catchments showed similar biogeochemical cycles, especially for nitrogen. The time series obtained will be used as reference period for a paired-catchment experiment simulating an increased nitrogen (ammonium nitrate) deposition.

The impact of air pollutants on trees has been a research interest for decades. Nevertheless, uncertainty exists about the potential effects of the pollutant concentrations occurring at present, for example, in Central Europe. This uncertainty results from an incomplete understanding of the mechanisms by which air pollutants and other environmental factors influence woody plants. This review presents examples of the mechanisms of ozone and NO2 impacts at low concentrations on birch and poplar. The question of whether the responses found in the ecophysiology and structural differentiation of the trees reflect acclimation to these pollutants rather than injury is given particular attention. An attempt to interpret the response of carbon allocation to ozone and NO2 by one explanatory model is presented. The capacity of air pollutants to change carbon allocation may affect interspecific competition and, by this, the species composition and the dynamics in the development of forest ecosystems.

A systematic study of the radiative proton capture reaction for all stable nickel isotopes is presented. The results were obtained using 2.0 - 6.0 MeV protons from the 11 MV tandem Van de Graaff accelerator at the University of Notre Dame. The \gamma-rays were detected by the NSCL SuN detector utilising the \gamma-summing technique. The results are compared to a compilation of earlier measurements and discrepancies between the previous data are resolved. The experimental results are also compared to the theoretical predictions obtained using the NON-SMOKER and SMARAGD codes. Based on these comparisons an improved set of astrophysical reaction rates is proposed for the (p,\gamma) reactions on the stable nickel isotopes as well as for the 56Ni(p,\gamma)57Cu reaction.

We report on the systematic investigation of the pressure dependence of the transition temperature dTc/dp of YBa2Cu3Ox as a function of the oxygen content x. The samples from the 60 K plateau have shown a pressure dependence dTc/dp in the order of 0.4–0.5 K/kbar. Giant pressure effects have been found for the oxygen stoichiometries x = 6.7 − 6.8. Most astonishingly, the 90 K samples have revealed a variety of pressure effects systematically changing with the oxygen content. We have found a correlation of structural parameters and dTc/dp in the oxygen range x = 6.8 − 7.

Although increasing tropospheric ozone (O3) concentrations as well as precursor NO2 emissions and N deposition have been observed, the combination of their effects on deciduous trees is little understood. We therefore examined the growth and leaf injury response of a model tree (Populus ×euramericana (Dode) Guinier cuttings exposed before flush and until they reached a height of more than 1 m) to low and high soil N supply (105 or 315 mg N•L−1 substrate volume), to filtered air, and to filtered air with NO2 (sinusoidal daily course with a mean of 100 nL•L−1), with O3 (60 nL•L−1), or with a combination of both in climate-controlled chambers. High soil N increased total plant dry weight, leaf area, and xylem radius in plants fumigated with or without added NO2 or O3. The number of leaves increased with high soil N independent of added NO2. The stomatal density was influenced by soil N and by fumigations, but the appearance of leaf injury symptoms, leaf loss, specific leaf weight, and bark radius were not modified by the soil N regimes. NO2 alone, though applied in a sixfold ambient concentration, did not significantly increase plant growth. NO2 and O3 alone had opposite effects on specific leaf dry weight, stomatal density, and in the high fertilization regime, on the bark radius. The decrease in specific leaf dry weight and the appearance of early leaf symptoms were enhanced by NO2 added to O3. Visible leaf injury caused by O3 increased in parallel with microscopic changes in mesophyll cell walls, in the starch and protein patterns of mesophyll cells, in the bark cell content, and in the phloem sieve pores. NO2 enhanced the negative effect of O3 rather than compensated for a low soil N supply.

The elemental concentrations of K, Rb and Cs were determined in needles from individual spruce trees as a function of the needle age class. The concentrations are highest in current year's needles and decrease smoothly in older needles, approaching a constant value. Rb and Cs show similar behaviour, whereas that of K differs in so far as its relative decrease with time is less pronounced. Intra- and intersite variation of the needle concentrations are largest for Cs and smallest for K. Individual trees show a highly significant correlation between the log (Cs) and log (Rb) values. Total soil concentrations were determined at 9 sites with different parent material. Intra- and intersite variations of K are comparable for soils and for needles, whereas those for Rb and Cs are much smaller for soils than for needles. All three elements are correlated in soil samples. There is no close connection between soil and needle concentrations at the various sites. However, the results suggest that needle concentrations of Rb and Cs, but not of K, are strongly dependent on the sorption properties of the associated soils. Die K-, Rb- und Cs-Konzentrationen in Fichtennadeln (Picea abies Karst) und den dazugehorigen Boden Die Gehalte der Elemente K, Rb and Cs wurden in Nadeln unterschiedlichen Alters von einzelnen Fichten gemessen. Die Konzentrationen sind jeweils am grosten in jungen Nadeln und nehmen mit zunehmender Nadelaltersklasse sukzessive bis auf einen konstanten Wert ab. Dabei ist das Verhalten von Rb und Cs sehr ahnlich, wahrend K eine deutlich kleinere Abnahme zeigt. Die Streuung der Nadelgehalte ist am grosten fur Cs und am kleinsten fur K, und zwar sowohl zwischen Baumen auf einem Standort als auch zwischen Standortmitteln. Die Gehalte von Cs und Rb zeigen eine hochsignifikante Korrelation ihrer logarithmischen Werte. In Bodenprofilen auf 9 Standorten (uber unterschiedlichem Muttergestein) wurden die Totalgehalte von K, Rb und Cs gemessen. Diese Elemente sind in Bodenproben sowohl innerhalb eines Standortes als auch zwischen Standorten korreliert. Ihre Streuung in Bodenproben ist fur K vergleichbar mit derjenigen in Nadeln, wahrend sie fur Rb und Cs in Boden viel kleiner als in Nadeln ist. Zwischen den Nadel- und Bodengehalten besteht keine enge Beziehung. Die Ergebnisse deuten jedoch darauf hin, das die Nadelgehalte von Rb und Cs, nicht aber diejenigen von K, stark von den Adsorptionseigenschaften der jeweiligen Standortsboden abhangen.

The endogenous concentrations of Rb and Cs have been determined in needles of 56 trees (Norway spruce, Picea abies) from eight different sites. Analysis was done by instrumental neutron activation. Concentrations were found to have a very large range (3-28,000 ng Cs/g and 1-190 micrograms Rb/g). The values on a given site have a tendency toward a log-normal distribution. There is a significant correlation between Rb and Cs, but the correlation is not linear. The concentrations of both elements are a function of the needle age. They decrease smoothly, approaching a constant value, when going from needle age class 1 to 5. It is shown that one algebraic function describes this biodynamic behavior on all sites and at all concentration levels. The function and its parameters are discussed.

The endogenous concentrations of Sc, La, Ce, Sm, Eu, Tb, Yb, and Lu were determined by neutron activation analysis in up to five successive needle age classes of Norway spruce (Picea abies). Trees from nine sites over different bedrocks were sampled individually. Concentration values found are generally much lower than those reported in the literature. This is attributed to the careful removal of any aerosols or soil particles from the needle surface prior to analysis. The concentration of each element increases linearly with the needle age class, i.e., the accumulation can be characterized by just one parameter, the yearly increment. This pattern is followed at small as well as at large concentrations. The accumulation behavior of the investigated elements is identical to that of Si. The relative concentrations of the rare earth elements (REE) in the needles are similar to those in the earth crust. There are significant correlations between the individual REE and between Sc and La.

The effects of endotoxin on endothelial and smooth muscle function were investigated in small femoral arteries removed from rats 4 h after intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS; 20 mg/kg) or solvent. In the absence of L-arginine in the organ bath, the sensitivity of the arteries to norepinephrine (NE) was decreased only slightly, and the relaxing effects of neither 3-morpholinosydonimine-N-ethyl-carbamide (SIN-1), a nitric oxide (NO) donor, nor acetylcholine (ACh) were modified by LPS treatment despite morphological damage to the endothelium seen with scanning electron microscopy. However, L-arginine (30 microM to 1 mM), which had no effect on control vessels, caused a rapid and stereospecific relaxation of arteries from LPS-treated rats that was abolished by both NG-nitro-L-arginine methyl ester (1 mM), a NO synthase inhibitor, and methylene blue, an inhibitor of the activation of guanylyl cyclase by NO. The relaxing effect of L-arginine was observed in the absence of endothelium, although it was significantly greater in its presence. In addition, a 30-min exposure to extracellular L-arginine (100 microM) moderately but significantly decreased the sensitivity to ACh and SIN-1 of vessels from LPS-treated but not from control rats. These results indicate that LPS treatment induced a NO synthase activity in smooth muscle cells of rat small femoral arteries and that the resulting relaxation was dependent on extracellular L-arginine in these resistance vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

The weight of the ash resulting from dry ashing spruce needles at 500° C can be predicted with good precision from the concentrations of calcium (Ca), potassium (K), magnesium (Mg), manganese (Mn), and silicon (Si) in the needles. The empirical factors associated with the individual elements are given. There is evidence that they can also be applied to leaves from other plants. The colour of the ash can be related to the Mn concentration in the needles. Dry ashing entails no losses for Ca, cobalt (Co), barium (Ba), K, rubidium (Rb), antimony (Sb), scandium (Sc), and zinc (Zn), whereas a very small loss was observed for cesium (Cs), and a very large for bromine (Br).

The anisotropic resistivity components of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ have been measured from 0 to 900 K. ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ is an underdoped, genuinely untwinned, and stoichiometric high temperature superconductor. The ${\mathrm{CuO}}_{2}$ plane resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}}$ exhibits a strong correlation with the spin dynamics, i.e., with Knight shift and spin-lattice relaxation time ${\mathit{T}}_{1}$. The resistivity along the b axis (plane plus chain) is consistent with Bloch-Gr\"uneisen theory. The cotangent of the Hall angle is quadratic in temperature above the spin gap, and linear below.

We have measured the polarized-reflectivity spectra of ${\mathrm{Y}}_{2}$${\mathrm{Ba}}_{4}$${\mathrm{Cu}}_{6+\mathit{n}}$${\mathrm{O}}_{14+\mathit{n}}$ (n=1,2) at 6 and 300 K. These substances are not twinned because of thermally stable double CuO chains instead of single chains as in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$. The light was polarized along the two plane directions a and b. We have found a strong contribution of the chain (E\ensuremath{\parallel}b) to the optical conductivity and thus an anisotropy of about 1:3. At 300 K, a flat plateau in the reflectance below 60 meV has been attributed to phonon interactions. As regards the interband transitions, the charge-transfer gap seems to be above 2.5 eV. The ir scattering rate of the charge carriers in the plane, ${\mathrm{\ensuremath{\sigma}}}^{\mathit{a}}$(\ensuremath{\omega}), is linear from 0.05 up to 0.8 eV. In the superconducting state, plasma edges have developed between 11 and 21 meV, respectively, which we assume to be determined rather by the density of superconducting carriers than by a gap. Good fits are obtained by a two-fluid model.

Contrary to the literature, the dependence on nonstoichiometry of the lattice parameters of “nearly” equilibrated 123 samples (particularly the c- and b-axis), shows strong changes of slope in the nonstoichiometric range x = 6.8–6.9. At x = 7.0-6.9 the c-axis decreases with decreasing oxygen concentration. And at x ≅ 6.9 the well known trend sets on:increase of c-axis and decrease of b-axis with decreasing oxygen content. These changes are reflected in the physical properties investigated up to now: • The dependence of Tc on hydrostatic pressure is 6.9, increases strongly in the range x = 6.9-6.8 and shows a change of slope at x = 6.8 where it has reached the value dTc/dP = 0.35 K/kbar. At x = 6.5 is dTc/dP = 0.45 K/kbar. (Also the tc as a function of nonstoichiometry shows the well known decrease at x = 6.8). • The muon spin-depolarization rate as a function of nonstoichiometry shows also an unexpected strong decrease (25%) in the range x = 7.0-6.9. This suggests that the density of the superconducting carriers decreases strongly in this range. It seems possible from the lattice parameter effects that a threshold concentration of oxygen vacancies in the chains is necessary in order that the expansion of the apical bond sets on.

The family Y 2 Ba 4 Cu 6 + n O 14 + n (n = 0,1,2) shows a wide range of the transition temperature T c . The pressure dependences of T c (dT c /dp) differ by one order of magnitude. We have shown that: 1. a) YBa 2 Cu 3 O 7 (123) has a differential dT c /dp from 0.03 K/kbar to 0.43 K/kbar, depending on the oxygen content. 2. b) YBa 2 Cu 3.5 O 7.5 (247) has a dT c /dp of 0.5 K/kbar with a leveling off of T c (p) at high pressure. 3. c) YBa 2 Cu 4 O 8 (124) has up to 18 kbar a dT c /dp of 0.57 K/kbar without a diminished pressure effect. Further, we report on the change of T c when Y is partially replaced by Sc or In. We have also investigated the 90 K compound (Y,Ba,Ca) 3 Cu 4 O 8 looking for a still high pressure dependence. We discuss the connection of dT c /dp with the strong shift of the apical oxygen towards the CuO plane at applied pressure, as detected by neutron diffraction. The n = 1 and n = 2 members have the great advantage, not to be twinned. So it was possible for the first time to resolve the anisotropy of the a- and b direction. We have measured the polarized reflectance R(ω) with respect to the a- and b direction of single crystals from 0.001 to 10 eV. The resistivity in a- and b direction ( ρ a and ρ b ) at ambient and high pressure reveals an anisotropy of a factor three and a deviation from the linear temperature behavior of ρ (T).