1,721,370 research outputs found
Computed rate coefficients and product yields for c-C[subscript 5] H[subscript 5] + CH[subscript 3] [right arrow] products
No full textUsing quantum chemical methods, we have explored the region of the C[subscript 6]H[subscript 8] potential energy surface that is relevant in predicting the rate coefficients of various wells and major product channels following the reaction between cyclopentadienyl radical and methyl radical, c-C[subscript 5]H[subscript 5] + CH[subscript 3]. Variational transition state theory is used to calculate the high-pressure-limit rate coefficient for all of the barrierless reactions. RRKM theory and the master equation are used to calculate the pressure dependent rate coefficients for 12 reactions. The calculated results are compared with the limited experimental data available in the literature and the agreement between the two is quite good. All of the rate coefficients calculated in this work are tabulated and can be used in building detailed chemical kinetic models
Intramolecular hydrogen migration in Alkylperoxy and Hydroperoxyalkylperoxy radicals: Accurate treatment of hindered rotors
No full textWe have calculated the thermochemistry and rate coefficients for stable molecules
and reactions in the title reaction families using CBS-QB3 and B3LYP/CBSB7
methods. The accurate treatment of hindered rotors for molecules having multi-
ple internal rotors with potentials that are not independent of each other can be
problematic and a simplified scheme is suggested to treat them. This is particu-
larly important for hydroperoxyalkylperoxy radicals (HOOQOO). Two new ther-
mochemical group values are suggested in this paper and with these values the
group additivity method for calculation of enthalpy as implemented in RMG gives
good agreement with CBS-QB3 predictions. The barrier heights follow the Evans-
Polanyi relationship for each type of intramolecular hydrogen migration reaction
studied
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Targeting restoration sites to improve connectivity in a tiger conservation landscape in India
Full text linkBackground Maintaining and restoring connectivity between source populations is essential for the long term viability of wide-ranging species, many of which occur in landscapes that are under pressure to meet increasing infrastructure needs. Identifying barriers in corridors can help inform conservation and infrastructure development agencies so that development objectives can be achieved without compromising conservation goals. Here, we use the tiger landscape in central India as a case study to identify barriers, associate them with existing infrastructure, and quantify the potential improvement by restoring or mitigating barriers. Additionally, we propose an approach to categorize linkages based on their current status within and between Protected Areas (PAs). Methods We generated a hybrid landuse-landcover map of our study area by merging datasets. We used least-cost methods and circuit theory to map corridors and generate linkage metrics. We mapped barriers and used the improvement score (IS) metric to quantify potential improvement by restoring or mitigating them. Based on criteria that represent the status of corridors between-PAs and populations within-PAs, we ranked linkages into one of four categories: Cat1—linkages that currently have high quality and potential for tiger connectivity and should be maintained, Cat2W—linkages where focus on habitat and tiger populations may improve connectivity, Cat2B—linkages where focus on reducing barriers between PAs may improve connectivity, and Cat3—linkages where effort is needed to both reduce barriers between PAs and improve tiger populations and habitat within PAs. We associated barriers with infrastructure and present maps to show where restoration or mitigation measures can be targeted to have the highest potential impact. Results We mapped 567 barriers within 30 linkages in this landscape, of which 265 barriers intersect with infrastructure (694 km of roads, 150 km of railway, 48 reservoirs, 10 mines) and 302 barriers are due to land-use or gaps in forest cover. Eighty-six barriers have both roads and railways. We identified 7 Cat1, 4 Cat2w, 9 Cat2b, and 10 Cat3 linkages. Eighty surface mines and thermal power plants are within 10 km of the least-cost paths, and more coal mines are closer to connectivity areas where linkages are narrow and rank poorly on both axes. Discussion We present spatial and quantitative results that can help conservation practitioners target mitigation and restoration efforts. India is on the path to rapid economic growth, with infrastructure development planned in biodiversity-rich areas. The mitigation hierarchy of avoiding, minimizing, and offsetting impacts due to proposed development projects can be applied to corridors in this landscape. Cross-sectoral cooperation at early stages of project life-cycles to site, design, and implement solutions can maintain connectivity while meeting infrastructure needs in this rapidly changing landscape
Radar and optical remote sensing for near real‐time assessments of cyclone impacts on coastal ecosystems
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Q-switching of an optical tweezer phonon laser
No full textWe theoretically investigate the active Q-switching of an optical tweezer phonon laser Pettit et al (2019 Nat. Photon. 13 402) operating in a coupled-mode configuration. One of the modes is lasing and outcouples to the second mode. The coupling is induced via asymmetric modulation of the trap potential in the transverse plane of the trapped nanoparticle. We show that a time-modulated coherent coupling between two transverse modes of oscillation of an optically levitated nanoparticle holds the key to coherent pulsed phonon transfer between them. Our analytical and numerical results on the position dynamics, phonon dynamics as well as second-order coherence confirms pulsed phonon lasing transfer between the transverse modes. Our work on Q-switched operation of the optical tweezer phonon laser enhances understanding of the analogies between optical and mechanical lasers, and is relevant to levitated phonon transport, acoustic imaging, sensing and information processing technologies.
Correction: An overview of computational tools for preparing, constructing and using resistance surfaces in connectivity research
No full textData analytics on raw material properties to accelerate pharmaceutical drug development
No full textManufacturability of active pharmaceutical ingredients (APIs) is often evaluated by an empirical approach during development due to limited material availability. This brings challenges in designing flexible yet robust manufacturing processes under highly accelerated timelines. Hence, good utilisation of a limited material dataset is key to accelerate the delivery of high quality final drug product into the market at minimum cost and maximum process capacity. In this study, we present a data-driven method to investigate a raw materials database where the integration of multivariate analysis and machine learning modelling aids the selection of new incoming materials based on their manufacturability. The procedure was applied to an industrial representative database of thirty-four APIs and seven excipients where eight measurements relevant to flow properties for each of those forty-one materials were collected. The models identified four clusters of materials with different flow properties. These models can serve as a risk assessment tool for new API in early product development phases based on the nearest surrogate material which behave similarly, as well as to identify targeted and material sparring experiments to address key risks during secondary process selection
Lichens and animal camouflage: some observations from central Asian ecoregions
No full textCamouflage is a fitness-relevant trait that supports survival and fosters evolutionary adaptation by which animals match their body pattern to a background setting. Lichens are among the most common of these backgrounds that several animal species use for camouflage. Lichens are omnipresent and grow in wide arrays of colorations and compositions. Their composition and phenotypic diversity might facilitate cryptic coloration and habitat matching by various animal species. Here, we describe the role of lichens in providing camouflage to various animal species in central Asian and Caucasus mountain ecoregions, which are categorized as global biodiversity hotspots. Despite multiple ecological studies, no information is available on the role of this regions‘ lichen diversity in providing animal camouflage. Casual field observations of lichen camouflage are reported for four (one mammal and three reptile) species: the Persian Leopard’s Panthera pardus saxicolor body coat seems to closely match the colors and patterns of saxicolous lichens (Acarospora sp. and Circinaria sp.) in their habitat. A similar background matching pattern was observed in both morphs of the Caucasian Rock Agama Paralaudakia caucasia upon crustose lichens: Caloplaca spp., Circinaria spp., and the Radde’s Rock Lizard Darevskia raddei to the crustose lichens Acarospora sp. and Caloplaca sp. Likewise, the Horny-scaled Agama’s Trapelus ruderatus grey matches with the color of multiple lichens (Lecanora spp., Circinaria spp., Protoparmeliopsis spp., Rinodina spp., and Anaptychia spp.). Our observations preliminarily suggest that lichens play an important role for species of different trophic levels, ensuring adaptation and survival through camouflage. We call for more field-based empirical and experimental studies in various terrestrial ecosystems in other parts of the world to test the role of lichens in local adaption and evolutionary plasticity of regional species.Open-Access-Publikationsfonds 202
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