Quantum molecular dynamics simulations for the nonmetal-to-metal transition in fluid helium

We have performed quantum molecular dynamics simulations for dense helium to study the nonmetal-to-metal transition at high pressures. We present new results for the equation of state and the Hugoniot curve in the warm dense matter region. The optical conductivity is calculated via the Kubo-Greenwood formula from which the dc conductivity is derived. The nonmetal-to-metal transition is identified at about 1 g/ccm. We compare with experimental results as well as with other theoretical approaches, especially with predictions of chemical models.Comment: 4 pages, 5 figure

X-Ray Computed Tomography: Semiautomated Volumetric Analysis of Late-Stage Lung Tumors as a Basis for Response Assessments

Background. This study presents a semiautomated approach for volumetric analysis of lung tumors and evaluates the feasibility of using volumes as an alternative to line lengths as a basis for response evaluation criteria in solid tumors (RECIST). The overall goal for the implementation was to accurately, precisely, and efficiently enable the analyses of lesions in the lung under the guidance of an operator. Methods. An anthropomorphic phantom with embedded model masses and 71 time points in 10 clinical cases with advanced lung cancer was analyzed using a semi-automated workflow. The implementation was done using the Cognition Network Technology. Results. Analysis of the phantom showed an average accuracy of 97%. The analyses of the clinical cases showed both intra- and interreader variabilities of approximately 5% on average with an upper 95% confidence interval of 14% and 19%, respectively. Compared to line lengths, the use of volumes clearly shows enhanced sensitivity with respect to determining response to therapy. Conclusions. It is feasible to perform volumetric analysis efficiently with high accuracy and low variability, even in patients with late-stage cancer who have complex lesions

Palaeoenvironmental significance of middle Oxfordian deep marine deposits from La Manga Formation, Neuquén Basin, Argentina

The Callovian-Oxfordian of the Neuquén Basin (Argentina) is characterized by an extensive marine carbonate system (La Manga Formation) with a predominance of shallow and middle ramp deposits, although locally in tectonically controlled settings, deeper deposits also formed. These middle Oxfordian deeper deposits consist of mudstone-wackestone carbonates alternating with black shales and show marked centimetre-scale rhythmicity, probably controlled by the Earth’s orbit parameters, mainly precession and eccentricity. The present study was designed to examine these deposits in terms of their sedimentology, geochemistry, and small-scale stratigraphy in Arroyo Los Blancos, southern Mendoza Province, where they are exceptionally well exposed and preserved. Results indicate that the sediments were deposited in an anoxic to dysoxic, relatively deep, sea-floor environment as revealed by the presence of: a) organic-rich shales, b) undisrupted lamination in most facies, c) pyrite framboids, and d) absence or scarcity of trace fossils and benthic fauna. Thin beds of graded wackestone-packstone and accumulations of thin shells of Bositra bivalves indicate sporadic reworking of the sea floor by weak currents. Organic petrology, Rock-Eval pyrolysis and thermal maturity indicators were used to characterize TOC and different types of organic matter. Low pyrolysis S yields along with low hydrogen indices suggest poor kerogen convertibility. Vitrinite reflectance (%Ro) ranged from 2.39 to 2.97 with an average of 2.70. The thermal alteration index (TAI) was 4+(5), indicating overmaturity. A tectono-sedimentary model is proposed for these deposits. According to this model, the relatively deep, organic-matter rich facies of La Manga Formation would have been deposited in the deepest zones of topographic lows controlled by tilting and differential subsidence of tectonic blocks bounded by normal faults.These faults were probably inherited from previous extensional tectonics of Late Triassic - Early Jurassic age.Facultad de Ciencias Naturales y Muse

Palaeoenvironmental significance of middle Oxfordian deep marine deposits from La Manga Formation, Neuquén Basin, Argentina

[EN] The Callovian-Oxfordian of the Neuquén Basin (Argentina) is characterized by an extensive marine carbonate system (La Manga Formation) with a predominance of shallow and middle ramp deposits, although locally in tectonically controlled settings, deeper deposits also formed. These middle Oxfordian deeper deposits consist of mudstone-wackestone carbonates alternating with black shales and show marked centimetre-scale rhythmicity, probably controlled by the Earth’s orbit parameters, mainly precession and eccentricity. The present study was designed to examine these deposits in terms of their sedimentology, geochemistry, and small-scale stratigraphy in Arroyo Los Blancos, southern Mendoza Province, where they are exceptionally well exposed and preserved. Results indicate that the sediments were deposited in an anoxic to dysoxic, relatively deep, sea-floor environment as revealed by the presence of: a) organic-rich shales, b) undisrupted lamination in most facies, c) pyrite framboids, and d) absence or scarcity of trace fossils and benthic fauna. Thin beds of graded wackestone-packstone and accumulations of thin shells of Bositra bivalves indicate sporadic reworking of the sea floor by weak currents. Organic petrology, Rock-Eval pyrolysis and thermal maturity indicators were used to characterize TOC and different types of organic matter. Low pyrolysis S yields along with low hydrogen indices suggest poor kerogen convertibility. Vitrinite reflectance (%Ro) ranged from 2.39 to 2.97 with an average of 2.70. The thermal alteration index (TAI) was 4+(5), indicating overmaturity. A tectono-sedimentary model is proposed for these deposits. According to this model, the relatively deep, organic-matter rich facies of La Manga Formation would have been deposited in the deepest zones of topographic lows controlled by tilting and differential subsidence of tectonic blocks bounded by normal faults.These faults were probably inherited from previous extensional tectonics of Late Triassic - Early Jurassic age.[ES] El Calloviense-Oxfordiense en el norte de la Cuenca Neuquina (Argentina) estuvo caracterizado por el desarrollo de un amplio sistema de rampa carbonatada (Formación La Manga) en el que predominaron los depósitos de rampa media y somera aunque localmente, y debido a control tectónico, pudieron acumularse depósitos más profundos. Estos depósitos, de edad Oxfordiense medio, están expuestos y preservados excepcionalmente en la zona de Arroyo Los Blancos, al sur de la provincia de Mendoza, y su estudio sedimentológico, geoquímico y estratigráfico representan el objetivo de este trabajo. Consisten en carbonatos (mudstone-wackestone) con acumulaciones de finas conchas de bivalvos de tipo Bositra que indican retrabajamientos esporádicos del sustrato marino debido a corrientes de baja intensidad. Se han caracterizado diferentes tipos de materia orgánica y TOC mediante petrología orgánica, Rock-Eval Pyrolisis e indicadores de madurez térmica. Los bajos valores en el campo del S unido al también bajo índice de H sugieren una baja convertibilidad de Kerógeno. La reflectancia de la vitrinita (%Ro) tiene un rango que oscila entre 2,39 y 2,97, con una media de 2,70, mientras que el índice de alteración térmico (TAI) es de 4+(5) indicando sobremaduración. Se propone también un modelo tectono-sedimentario para estos depósitos. En este modelo, estas facies relativamente profundas y ricas en materia orgánica de la Formación La Manga estarían depositadas en la parte más deprimida de bajos topográficos controlados por una subsidencia diferencial y de pulsos en bloques marcados por fallas normales heredadas probablemente de una tectónica extensional durante el Triásico Superior-Jurásico Inferior.Peer reviewe

Eye movements as a window to cognitive processes

Eye movement research is a highly active and productive research field. Here we focus on how the embodied nature of eye movements can act as a window to the brain and the mind. In particular, we discuss how conscious perception depends on the trajectory of fixated locations and consequently address how fixation locations are selected. Specifically, we argue that the selection of fixation points during visual exploration can be understood to a large degree based on retinotopically structured models. Yet, these models largely ignore spatiotemporal structure in eye-movement sequences. Explaining spatiotemporal structure in eye-movement trajectories requires an understanding of spatiotemporal properties of the visual sampling process. With this in mind, we discuss the availability of external information to internal inference about causes in the world. We demonstrate that visual foraging is a dynamic process that can be systematically modulated either towards exploration or exploitation. For an analysis at high temporal resolution, we suggest a new method: The renewal density allows the investigation of precise temporal relation of eye movements and other actions like a button press. We conclude with an outlook and propose that eye movement research has reached an appropriate stage and can easily be combined with other research methods to utilize this window to the brain and mind to its fullest

Interior structure models of GJ 436b

GJ 436b is the first extrasolar planet discovered that resembles Neptune in mass and radius. The particularly interesting property of Neptune-sized planets is that their mass Mp and radius Rp are close to theoretical M-R relations of water planets. Given Mp, Rp, and equilibrium temperature, however, various internal compositions are possible. A broad set of interior structure models is presented here that illustrates the dependence of internal composition and possible phases of water occurring in presumably water-rich planets, such as GJ 436b on the uncertainty in atmospheric temperature profile and mean density. We show how the set of solutions can be narrowed down if theoretical constraints from formation and model atmospheres are applied or potentially observational constraints for the atmospheric metallicity Z1 and the tidal Love number k2. We model the interior by assuming either three layers (hydrogen-helium envelope, water layer, rock core) or two layers (H/He/H2O envelope, rocky core). For water, we use the equation of state H2O-REOS based on FT-DFT-MD simulations. Some admixture of H/He appears mandatory for explaining the measured radius. For the warmest considered models, the H/He mass fraction can reduce to 10^-3, still extending over ~0.7 REarth. If water occurs, it will be essentially in the plasma phase or in the superionic phase, but not in an ice phase. Metal-free envelope models have 0.02<k2<0.2, and the core mass cannot be determined from a measurement of k2. In contrast, models with 0.3<k2<0.82 require high metallicities Z1<0.89 in the outer envelope. The uncertainty in core mass decreases to 0.4 Mp, if k2>0.3, and further to 0.2 Mp, if k2>0.5, and core mass and Z1 become sensitive functions of k2. To further narrow the set of solutions, a proper treatment of the atmosphere and the evolution is necessary.Comment: 9 pages, accepted to A&

Cold atmospheric pressure plasma for treatment of chronic wounds: drug or medical device?

Objective: The use of cold atmospheric pressure plasma (CAPP) as a new therapeutic option to aid the healing of chronic wounds appears promising. Currently, uncertainty exists regarding their classification as medical device or medical drug. Because the classification of CAPP has medical, legal, and economic consequences as well as implications for the level of preclinical and clinical testing, the correct classification is not an academic exercise, but an ethical need. Method: A multidisciplinary team of physicians, surgeons, pharmacists, physicists and lawyers has analysed the physical and technical characteristics as well as legal conditions of the biological action of CAPP. Results: It was concluded that the mode of action of the locally generated CAPP, with its main active components being different radicals, is pharmacological and not physical in nature. Conclusion: Depending on the intended use, CAPP should be classified as a drug, which is generated by use of a medical device directly at the point of therapeutic application

Spontaneous formation and stability of small GaP fullerenes

We report the spontaneous formation of a GaP fullerene cage in ab-initio Molecular Dynamics simulations starting from a bulk fragment. A systematic study of the geometric and electronic properties of neutral and ionized GaP clusters suggests the stability of hetero-fullerenes formed by a compound with zincblend bulk structure. We find that GaP fullerenes up to 28 atoms have high symmetry, closed electronic shells, large HOMO-LUMO energy gaps and do not dissociate when ionized. We compare our results for GaP with those obtained by other groups for the corresponding BN clusters.Comment: To appear on PRL, 4 pages, 1 figure, Late

Carbon clusters near the crossover to fullerene stability

The thermodynamic stability of structural isomers of $\mathrm{C}_{24}$, $\mathrm{C}_{26}$, $\mathrm{C}_{28}$ and $\mathrm{C}_{32}$, including fullerenes, is studied using density functional and quantum Monte Carlo methods. The energetic ordering of the different isomers depends sensitively on the treatment of electron correlation. Fixed-node diffusion quantum Monte Carlo calculations predict that a $\mathrm{C}_{24}$ isomer is the smallest stable graphitic fragment and that the smallest stable fullerenes are the $\mathrm{C}_{26}$ and $\mathrm{C}_{28}$ clusters with $\mathrm{C}_{2v}$ and $\mathrm{T}_{d}$ symmetry, respectively. These results support proposals that a $\mathrm{C}_{28}$ solid could be synthesized by cluster deposition.Comment: 4 pages, includes 4 figures. For additional graphics, online paper and related information see http://www.tcm.phy.cam.ac.uk/~prck