12,851 research outputs found
The formation of mixed germaniumâcobalt carbonyl clusters: an electrospray mass spectrometric study, and the structure of a high-nuclearity [GeâCoââ(CO)ââ]ÂČâ» anion
The reaction of [”â-Ge{Coâ(CO)â}â] with [Co(CO)â]â» has been monitored by electrospray mass spectrometry to detect the cluster anions generated. Conditions giving known mixed GeâCo carbonyl clusters were established, and a new high nuclearity cluster anion, [GeâCoââ(CO)ââ]ÂČâ» was detected. Conditions for its formation were optimised and it was subsequently isolated as its [EtâN]âș salt and characterised by single-crystal X-ray crystallography. The GeâCoââ cluster core has a novel geometry with the two germanium atoms in semi-encapsulated positions, forming seven formal GeâCo bonds. There are also eighteen formal CoâCo bonds. Corresponding reactions of [”â-Si{Coâ(CO)â}â] with [Co(CO)â]â» were also investigated
Ice Conditions in the Gulf of St.Lawrence and Cabot Strait (with particular reference to the Sydney Bight Area)
Les glaces qui, au printemps, se trouvent dans le dĂ©troit de Cabot et tout particuliĂšrement dans la rĂ©gion de la baie Sydney, gĂȘnent souvent les traversĂ©es des bateaux passeurs entre Port-aux-Basques, Terre-Neuve et North Sydney, Nouvelle-Ecosse. Des donnĂ©es sur les principaux relevĂ©s des glaces dans le golfe Saint-Laurent et le dĂ©troit de Cabot ont Ă©tĂ© recueillis et Ă©tudiĂ©es en tenant compte de ce problĂšme.Les relations qui existent entre les nuances de tempĂ©rature, les vents et l'Ă©tendue des glaces ont Ă©tĂ© Ă©tudiĂ©es Ă la lumiĂšre de la statistique. La somme des tempĂ©ratures de dĂ©cembre et janvier correspond assez bien aux principales Ă©tendues des glaces qui se trouvaient dans le golfe et le dĂ©troit durant ces deux mois. L'Ă©tude des vents indique un vĂ©ritable mouvement de la glace Ă partir du golfe en direction du dĂ©troit durant les annĂ©es oĂč des observations ont Ă©tĂ© faites. Si l'on additionne les tempĂ©ratures et les vents et les exprime en termes de glace de dĂ©rive, on dĂ©couvre que ces deux Ă©lĂ©ments sont trĂšs Ă©troitement liĂ©s l'un Ă l'autre
Towards gravitationally assisted negative refraction of light by vacuum
Propagation of electromagnetic plane waves in some directions in
gravitationally affected vacuum over limited ranges of spacetime can be such
that the phase velocity vector casts a negative projection on the time-averaged
Poynting vector. This conclusion suggests, inter alia, gravitationally assisted
negative refraction by vacuum.Comment: 6 page
Prediction of the Atomization Energy of Molecules Using Coulomb Matrix and Atomic Composition in a Bayesian Regularized Neural Networks
Exact calculation of electronic properties of molecules is a fundamental step
for intelligent and rational compounds and materials design. The intrinsically
graph-like and non-vectorial nature of molecular data generates a unique and
challenging machine learning problem. In this paper we embrace a learning from
scratch approach where the quantum mechanical electronic properties of
molecules are predicted directly from the raw molecular geometry, similar to
some recent works. But, unlike these previous endeavors, our study suggests a
benefit from combining molecular geometry embedded in the Coulomb matrix with
the atomic composition of molecules. Using the new combined features in a
Bayesian regularized neural networks, our results improve well-known results
from the literature on the QM7 dataset from a mean absolute error of 3.51
kcal/mol down to 3.0 kcal/mol.Comment: Under review ICANN 201
Electronic structure of periodic curved surfaces -- topological band structure
Electronic band structure for electrons bound on periodic minimal surfaces is
differential-geometrically formulated and numerically calculated. We focus on
minimal surfaces because they are not only mathematically elegant (with the
surface characterized completely in terms of "navels") but represent the
topology of real systems such as zeolites and negative-curvature fullerene. The
band structure turns out to be primarily determined by the topology of the
surface, i.e., how the wavefunction interferes on a multiply-connected surface,
so that the bands are little affected by the way in which we confine the
electrons on the surface (thin-slab limit or zero thickness from the outset).
Another curiosity is that different minimal surfaces connected by the Bonnet
transformation (such as Schwarz's P- and D-surfaces) possess one-to-one
correspondence in their band energies at Brillouin zone boundaries.Comment: 6 pages, 8 figures, eps files will be sent on request to
[email protected]
Those who left/are left behind : Schrödinger's refugee and the ethics of complementarity
âThose left behindâ was a recurring emphasis of media depictions of the emotions surrounding the departure of those who left Afghanistan. The relationship between âthose who leftâ and âthose left behind,â which is characteristic of any context of forced displacement, relates to potentials, compelled by life and death questions. A decision to leave or stay is on the surface a binary choice, defined by the physical impossibility of doing both. The purpose of this paper is to explore how the ethical questions change when placed in a framework of quantum complementarity, by which phenomena, defined by what they are not, are also, in important respects, that which they are not, that is, the polar opposite. The first section develops Schrödinger's thought experiment and problematizes his focus on life and death as physical states of the cat, and the separateness of the observer, as a misrepresentation of the Copenhagen School arguments from which the thought experiment arose, and complementarity in particular. The second section examines the relationship between âthose who left,â âthose left behind,â and external observers in terms of a duality of matter and consciousness, which is complementary and mutually constituted. The third section examines the liminality that arises from a series of nested âboxesâ and the various positions from which the forcefully displaced are observed within a holographic world. The final section then unpacks the ethical implications of quantum complementarity and ungrieved grief as they relate to forced displacement.Publisher PDFPeer reviewe
Experimental Extraction of Secure Correlations from a Noisy Private State
We report experimental generation of a noisy entangled four-photon state that
exhibits a separation between the secure key contents and distillable
entanglement, a hallmark feature of the recently established quantum theory of
private states. The privacy analysis, based on the full tomographic
reconstruction of the prepared state, is utilized in a proof-of-principle key
generation. The inferiority of distillation-based strategies to extract the key
is exposed by an implementation of an entanglement distillation protocol for
the produced state.Comment: 5 pages, 3 figures, final versio
Developing Interventions for Children's Exercise (DICE): a pilot evaluation of school-based exercise interventions for primary school children aged 7 to 8 years.
BACKGROUND: Developing Interventions for Children's Exercise (DICE) is an initiative aimed at determining effective school-based exercise programs. To assess feasibility, we conducted a pilot study of exercise sessions which varied in duration and frequency. METHODS: Exercise interventions were delivered to Year 3 pupils (age 7-8 years; n = 73) in primary schools within Yorkshire, UK. Evaluations were conducted using focus group sessions, questionnaires and observations. RESULTS: The study revealed positive aspects of all interventions, including favorable effects on children's concentration during lessons and identified the value of incorporation of the DICE concept into curriculum lessons. Children appeared enthused and reported well-being and enjoyment. Areas requiring attention were the need for appropriate timetabling of sessions and ensuring the availability of space. CONCLUSION: The concept and sessions were well-accepted by teachers who confirmed their full support of any future implementation There appears to be potential for the encouragement and empowerment of teachers to support physical activity and healthy school environments, and to take an interest in the health of their pupils. Ultimately, these findings should assist in the design of successful exercise interventions in the school setting
Doubled CO2 Experiments With the Global Change Research Center Two-Dimensional Statistical Dynamical Climate Model
The zonally averaged response of the Global Change Research Center two-dimensional statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton\u27s second law, and the first law of thermodynamics) for the prognostic variables: zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p=rhoRT, and an assumed hydrostatic atmosphere, Deltap=rhogDeltaz, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The model includes seasonal variations in solar intensity, including the effects of eccentricity, and has observed land and ocean fractions set for each zone. Seasonally varying values of cloud amounts, relative humidity profiles, ozone, and sea ice are all prescribed in the model. Equator to pole ocean heat transport is simulated in the model by turbulent diffusion
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