EPR and Optical Studies of Mo5+ Ions in Lithium Molybdoborate Glasses

Electron paramagnetic resonance (EPR) and optical absorption studies of Li2O–MoO3–B2O3 with varying concentrations of Li2O, MoO3 and B2O3 have been carried out at room temperature. Two series of glasses, one with constant MoO3 (CM) and another with constant borate (CB), have been investigated. Characteristic EPR spectra of Mo5+ have been observed centered around g ≅ 2.00, which are attributed to Mo5+ ion in an octahedral coordination sphere with an axial distortion. The spectra also show strong dependence on the concentration of Li2O and B2O3. Spin concentrations (N) and magnetic susceptibilities (χ) have been calculated. In the CM series, the N values decrease with increasing Li2O content up to 30 mol%, while in the CB series variation of N is found to increase initially up to 20 mol%, and with further increase in the Li2O content the N values tend to decrease. The variation of magnetic susceptibilities is almost similar to that observed with the variation of N. From the optical absorption spectra, an absorption edge (α) has been evaluated. In the CM series, the values of α show a blueshift. On the other hand, in the CB series a redshift is observed. The observed variations in spectral parameters are explained by considering the molybdoborate network. Addition of Li2O to the CM and CB series results in modification of [MoO6/2]0 → [MoOO5/2]− and [BO3/2]0 → [BO4/2]− → [BOO2/2]− groups, respectively, leading to creation of nonbridging oxygens. The optical basicity of the glasses has been evaluated in both the CM and the CB glasses. The optical basicity can be used to classify the covalent-to-ionic ratios of the glass, since an increasing optical basicity indicates decreasing covalency. It is observed that the covalency between Mo5+ ions and oxygen ligands increases in the CB series, whereas in the CM series the covalency between Mo5+ ions and oxygen ligands decreases

Optical Limiting in Single-walled Carbon Nanotube Suspensions

Optical limiting behaviour of suspensions of single-walled carbon nanotubes in water, ethanol and ethylene glycol is reported. Experiments with 532 nm, 15 nsec duration laser pulses show that optical limiting occurs mainly due to nonlinear scattering. The observed host liquid dependence of optical limiting in different suspensions suggests that the scattering originates from microbubbles formed due to absorption-induced heating.Comment: 10 pages, 5 eps figures, to appear in Chem. Phys. Let

On-site Coulomb interaction and the magnetism of (GaMn)N and (GaMn)As

We use the local density approximation (LDA) and LDA+U schemes to study the magnetism of (GaMn)As and (GaMn)N for a number of Mn concentrations and varying number of holes. We show that for both systems and both calculational schemes the presence of holes is crucial for establishing ferromagnetism. For both systems, the introduction of $U$ increases delocalization of the holes and, simultaneously, decreases the p-d interaction. Since these two trends exert opposite influences on the Mn-Mn exchange interaction the character of the variation of the Curie temperature (T$_C$) cannot be predicted without direct calculation. We show that the variation of T$_C$ is different for two systems. For low Mn concentrations we obtain the tendency to increasing T$_C$ in the case of (GaMn)N whereas an opposite tendency to decreasing T$_C$ is obtained for (GaMn)As. We reveal the origin of this difference by inspecting the properties of the densities of states and holes for both systems. The main body of calculations is performed within a supercell approach. The Curie temperatures calculated within the coherent potential approximation to atomic disorder are reported for comparison. Both approaches give similar qualitative behavior. The results of calculations are related to the experimental data.Comment: to appear in Physical Review

A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants

An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types

The shared socioeconomic pathways and their energy, land use, and greenhouse gas emissions implications: An overview

This paper presents the overview of the Shared Socioeconomic Pathways (SSPs) and their energy, land use, and emissions implications. The SSPs are part of a new scenario framework, established by the climate change research community in order to facilitate the integrated analysis of future climate impacts, vulnerabilities, adaptation, and mitigation. The pathways were developed over the last years as a joint community effort and describe plausible major global developments that together would lead in the future to different challenges for mitigation and adaptation to climate change. The SSPs are based on five narratives describing alternative socio-economic developments, including sustainable development, regional rivalry, inequality, fossil-fueled development, and a middle-of-the-road development. The long-term demographic and economic projections of the SSPs depict a wide uncertainty range consistent with the scenario literature. A multi-model approach was used for the elaboration of the energy, land-use and the emissions trajectories of SSP-based scenarios. The baseline scenarios lead to global energy consumption of 500-1100 EJ in 2100, and feature vastly different land-use dynamics, ranging from a possible reduction in cropland area up to a massive expansion by more than 700 million hectares by 2100. The associated annual CO2 emissions of the baseline scenarios range from about 25 GtCO2 to more than 120 GtCO2 per year by 2100. With respect to mitigation, we find that associated costs strongly depend on three factors: 1) the policy assumptions, 2) the socio-economic narrative, and 3) the stringency of the target. The carbon price for reaching the target of 2.6 W/m2 differs in our analysis thus by about a factor of three across the SSP scenarios. Moreover, many models could not reach this target from the SSPs with high mitigation challenges. While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quantifications span a wide range of different futures broadly representative of the current literature. This allows their subsequent use and development in new assessments and research projects. Critical next steps for the community scenario process will, among others, involve regional and sectorial extensions, further elaboration of the adaptation and impacts dimension, as well as employing the SSP scenarios with the new generation of earth system models as part of the 6th climate model intercomparison project (CMIP6)