Spin correlations and Dzyaloshinskii-Moriya interaction in Cs2_2CuCl4_4

We report on electron spin resonance (ESR) studies of the spin relaxation in Cs$_2$CuCl$_4$. The main source of the ESR linewidth at temperatures $T \leq 150$ K is attributed to the uniform Dzyaloshinskii-Moriya interaction. The vector components of the Dzyaloshinskii-Moriya interaction are determined from the angular dependence of the ESR spectra using a high-temperature approximation. Both the angular and temperature dependence of the ESR linewidth have been analyzed using a self-consistent quantum-mechanical approach. In addition analytical expressions based on a quasi-classical picture for spin fluctuations are derived, which show good agreement with the quantum-approach for temperatures $T \geq 2J/k_{\rm B} \approx 15$ K. A small modulation of the ESR linewidth observed in the $ac$-plane is attributed to the anisotropic Zeeman interaction, which reflects the two magnetically nonequivalent Cu positions

Nitrite induced transcription of p450nor during denitrification by Fusarium oxysporum correlates with the production of N2O with a high 15N site preference

The greenhouse gas nitrous oxide (N2O) is produced in soil as a consequence of complex co-occurring processes conducted by diverse microbial species, including fungi. The fungal p450nor gene encodes a nitric oxide reductase associated with fungal denitrification. We thus hypothesized that p450nor gene expression is a marker for ongoing fungal denitrification. Specific PCR primers and quantitative PCR (qPCR) assays were developed targeting p450nor genes and transcripts. The novel PCR primers successfully amplified p450nor from pure cultures, and were used in an mRNA targeted qPCR to quantify p450nor gene transcription (i.e., gene expression) during denitrification activity in cultures of the fungal model denitrifier Fusarium oxysporum. Gene expression was induced by high (5 mM) and low (0.25 mM) nitrite concentrations. Nitrite stimulated N2O production rates by F. oxysporum, which correlated well with an up to 70-fold increase in p450nor gene expression during the first 12–24 h of anoxic incubation. The relative p450nor gene peak expression and peak N2O production rates declined 20- and 2-fold on average, respectively, towards the later phase of incubation (48–120 h). The 15N site preference of N2O (SP(N2O)) was high for F. oxysporum and independent of reaction progress, confirming the fungal origin of N2O produced. In conclusion, the developed fungal p450nor gene expression assay together with the analysis of SP(N2O) values provide a basis to improve current tools for the identification of fungal denitrification and/or N2O production in natural systems like soils

Cultivated ties and strategic communication: Do international environmental secretariats tailor information to increase their bureaucratic reputation?

The past few years have witnessed a growing interest among scholars and policy-makers in the interplay of international bureaucracies with civil society organizations, other non-profit entities, and the private sector. This article extends the state of research by investigating whether and how secretariats try to strengthen their reputation within their respective policy regimes through information provision and alliance building. Based on reputation theory, the article argues that ties cultivated with stakeholders as well as appearance and presentation of information are decisive in this regard. Methodologically, the study implements a mixed-methods design that combines a quantitative survey with social network analysis and qualitative content analysis of interviews with stakeholders within the climate and biodiversity regime. We show that the secretariats of the Convention on Biological Diversity (CBD) and the United Nations Framework Convention on Climate Change (UNFCCC) maintain relationships with a wide range of state and non-state actors to enhance their reputation. Moreover, different types of actors receive different types of information from the two secretariats studied. Our findings reveal that both secretariats use their limited resources for investing strategically into networks with different types of actors (in the broader transnational policy network), either via the tailored provision of information or through strategic networking with multipliers. They also indicate that reputation does not simply depend on characteristics of bureaucracies, but also on framework conditions and different communication strategies.info:eu-repo/semantics/acceptedVersio

Brokering climate action: the UNFCCC secretariat between parties and non-party stakeholders

Our article aims to better understand the role of the secretariat of the United Nations Framework Convention on Climate Change (UNFCCC) in the increasingly complex global climate governance structure. We employ an innovative approach to addressing this issue by systematically examining the climate secretariat’s relations with the main groups of actors involved in this policy domain, in particular with nonparty actors. In a first step, we use social network analysis (SNA) to examine the secretariat’s relations with nonparty and state stakeholders and to identify its position in the UNFCCC policy network. An understanding of where the climate secretariat stands in the global climate governance network and which actors it interacts with most allows us to draw preliminary conclusions about the ways in which it connects with other stakeholders to influence global climate policy outputs. In a second step, we conduct thirty-three semistructured interviews to corroborate the results of the SNA. Our findings lend support to the argument that the climate secretariat may gradually be moving from a rather neutral and instrumental stance to playing a proactive and influential role in international climate governance. It aims to increase its political influence by establishing strategic links to actors other than the formal negotiation parties.info:eu-repo/semantics/acceptedVersio

SPIN-MIMS simplifying the SPIN-MAS instrumentation for online measurement of 15N-abundances of ammonium, nitrite and nitrate in aqueous solutions

Common methods for measuring selectively the 15N abundances in individual N-species such as NH4+, NO2- and NO3- in samples with multiple N-species are laborious and time consuming. The SPIN-MAS technique (Stange et al. 2007) offers an automated, rapid and selective determination of 15N abundances in NH4+, NO2- and NO3- in aqueous samples. During a SPIN-MAS measurement one of three different reaction solutions is mixed with the aqueous sample in a Sample Preparation unit for Inorganic N-species (SPIN). The reaction solution is chosen in dependence on the N-species of interest. The gaseous reaction products (N2 or NO) are then conducted to a quadrupole mass spectrometer (MAS) in a helium stream. This measurement technique is not commonly used due to its complex instrumentation. The instrumentation can be significantly simplified by the use of a membrane inlet mass spectrometer (MIMS). The presented SPIN-MIMS approach relies on the use of a reaction capillary in which the sample containing the N-species of interest is mixed with the corresponding reaction solution. The mixture of reaction solution and sample is pumped from the reaction capillary directly to the membrane inlet of the mass spectrometer. The reaction products (N2 or NO) formed during the reaction of NH4+, NO2- and NO3- with the reaction solutions are passed through the gas-permeable membrane of the inlet directly into the ion source of the mass spectrometer. 15N standards with different at% 15N (NH4+, NO2- and NO3- respectively in dist. Water) were used to assess the performance of the system. Overall, SPIN-MIMS measurements showed a good agreement between measured and expected 15N abundances (range 0.36 – 10 at% 15N deviations: <0.5 at% 15N for NH4+-, <0.23 for NO2-- and <0.15 at% 15N for NO3-- standards)