3,153 research outputs found
Pressure Shifts in High-Precision Hydrogen Spectroscopy: I. Long-Range Atom-Atom and Atom-Molecule Interactions
We study the theoretical foundations for the pressure shifts in
high-precision atomic beam spectrosopy of hydrogen, with a particular emphasis
on transitions involving higher excited P states. In particular, the long-range
interaction of an excited hydrogen atom in a 4P state with a ground-state and
metastable hydrogen atom is studied, with a full resolution of the hyperfine
structure. It is found that the full inclusion of the 4P_1/2 and 4P_3/2
manifolds becomes necessary in order to obtain reliable theoretical
predictions, because the 1S ground state hyperfine frequency is commensurate
with the 4P fine-structure splitting. An even more complex problem is
encountered in the case of the 4P-2S interaction, where the inclusion of
quasi-degenerate 4S-2P_1/2 state becomes necessary in view of the dipole
couplings induced by the van der Waals Hamiltonian. Matrices of dimension up to
40 have to be treated despite all efforts to reduce the problem to irreducible
submanifolds within the quasi-degenerate basis. We focus on the
phenomenologically important second-order van der Waals shifts, proportional to
1/R^6 where R is the interatomic distance, and obtain results with full
resolution of the hyperfine structure. The magnitude of van der Waals
coefficients for hydrogen atom-atom collisions involving excited P states is
drastically enhanced due to energetic quasi-degeneracy; we find no such
enhancement for atom-molecule collisions involving atomic nP states, even if
the complex molecular spectrum involving ro-vibrational levels requires a
deeper analysis.Comment: 32 pages; 2 figures; this is part 1 of a series of two papers; part 1
carries article number 075005, while part 2 carries article number 075006 in
the journal (online journal version has been rectified). arXiv admin note:
text overlap with arXiv:1711.1003
The Asian red seaweed Grateloupia turuturu (Rhodophyta) invades the Gulf of Maine
We report the invasion of the Gulf of Maine, in the northwest Atlantic Ocean, by the largest red seaweed in the world, the Asian Grateloupia turuturu. First detected in 1994 in Narragansett Bay, Rhode Island, south of Cape Cod, this alga had expanded its range in the following years only over to Long Island and into Long Island Sound. In July 2007 we found Grateloupia in the Cape Cod Canal and as far north (east) as Boston, Massachusetts, establishing its presence in the Gulf of Maine. Grateloupia can be invasive and may be capable of disrupting low intertidal and shallow subtidal seaweeds. The plant\u27s broad physiological tolerances suggest that it will be able to expand possibly as far north as the Bay of Fundy. We predict its continued spread in North America and around the world, noting that its arrival in the major international port of Boston may now launch G. turuturu on to new global shipping corridors
Southern expansion of the brown alga Colpomenia peregrina Sauvageau (Scytosiphonales) in the Northwest Atlantic Ocean
Blackler first recorded Colpomenia peregrina in the Northwest Atlantic based on collections from Nova Scotia, Canada. Five decades later we found large quantities of C. peregrina in Maine, USA, even though it was absent during earlier floristic studies in this region. Thus, C. peregrina has undergone a rapid southern expansion along the Northwest Atlantic coast. While the causes of such an expansion are unknown, it could have a major effect on both shellfish cultivation and native seaweeds within New England because of competitive interactions and increased drag
All-Optical Switching with Transverse Optical Patterns
We demonstrate an all-optical switch that operates at ultra-low-light levels
and exhibits several features necessary for use in optical switching networks.
An input switching beam, wavelength , with an energy density of
photons per optical cross section [] changes
the orientation of a two-spot pattern generated via parametric instability in
warm rubidium vapor. The instability is induced with less than 1 mW of total
pump power and generates several Ws of output light. The switch is
cascadable: the device output is capable of driving multiple inputs, and
exhibits transistor-like signal-level restoration with both saturated and
intermediate response regimes. Additionally, the system requires an input power
proportional to the inverse of the response time, which suggests thermal
dissipation does not necessarily limit the practicality of optical logic
devices
Quantum state tomography of slow and stored light
Quantum information can be transferred from a beam of light to a cloud of atoms and controllably released at a later time. These quantum memory devices are fundamental to applications in quantum information science, quantum computing, and quantum communication. We propose a technique for measuring the quantum state of light that has been stored and released from a quantum memory system. This technique does not require careful mode matching can in fact be used to optimize the measured field mode without a priori knowledge of the stored light
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Fargo: Seeing the significance of style in television poetics?
This article explores the adaptation of the original film to television and how a strain of art or independent cinema contributed to the development of the first series of Fargo (2014–present). By making this comparison, the transition to television of the storyworld established by the Coen brothers raises questions about who is talking in the TV drama – the Coens or makers of the series. At the same time, Fargo can be more easily explained and understood as a strategy by writers, directors and producers that further complicate ideas to do with Noah Hawley, as its showrunner and the show’s single-author status. In Fargo, fidelity to the Coen brothers as a testament to the memory of the original film is set against questions about the reliability of storytelling using complex imagery. By alternating between different levels of narration signified by its stylistic tonal qualities, Fargo succeeds in producing multiple meanings, representations and effects that call attention to textual pleasures in the complex television series
Spectroscopy and Dynamics of the Predissociated, Quasi-linear S2 State of Chlorocarbene
In this work, we report on the spectroscopy and dynamics of the quasi-linear S2 state of chlorocarbene, CHCl, and its deuterated isotopologue using optical-optical double resonance (OODR) spectroscopy through selected rovibronic levels of the S1 state. This study, which represents the first observation of the S2 state in CHCl, builds upon our recent examination of the corresponding state in CHF, where pronounced mode specificity was observed in the dynamics, with predissociation rates larger for levels containing bending excitation. In the present work, a total of 14 S2 state vibrational levels with angular momentum â„“ = 1 were observed for CHCl, and 34 levels for CDCl. The range of â„“ in this case was restricted by the pronounced Renner-Teller effect in the low-lying S1 levels, which severely reduces the fluorescence lifetime for levels with Ka \u3e 0. Nonetheless, by exploiting different intermediate S1 levels, we observed progressions involving all three fundamental vibrations. For levels with long predissociation lifetimes, rotational constants were determined by measuring spectra through different intermediate J levels of the S1 state. Plots of the predissociation linewidth (lifetime) vs. energy for various S2 levels show an abrupt onset, which lies near the calculated threshold for elimination to form C(3P) + HCl on the triplet surface. Our experimental results are compared with a series of high level ab initio calculations, which included the use of a dynamically weighted full-valence CASSCF procedure, focusing maximum weight on the state of interest (the singlet and triplet states were computed separately). This was used as the reference for subsequent Davidson-corrected MRCI(+Q) calculations. These calculations reveal the presence of multiple conical intersections in the singlet manifold
Autonomous decision-making against induced seismicity in deep fluid injections
The rise in the frequency of anthropogenic earthquakes due to deep fluid
injections is posing serious economic, societal, and legal challenges to
geo-energy and waste-disposal projects. We propose an actuarial approach to
mitigate this risk, first by defining an autonomous decision-making process
based on an adaptive traffic light system (ATLS) to stop risky injections, and
second by quantifying a "cost of public safety" based on the probability of an
injection-well being abandoned. The ATLS underlying statistical model is first
confirmed to be representative of injection-induced seismicity, with examples
taken from past reservoir stimulation experiments (mostly from Enhanced
Geothermal Systems, EGS). Then the decision strategy is formalized: Being
integrable, the model yields a closed-form ATLS solution that maps a risk-based
safety standard or norm to an earthquake magnitude not to exceed during
stimulation. Finally, the EGS levelized cost of electricity (LCOE) is
reformulated in terms of null expectation, with the cost of abandoned
injection-well implemented. We find that the price increase to mitigate the
increased seismic risk in populated areas can counterbalance the heat credit.
However this "public safety cost" disappears if buildings are based on
earthquake-resistant designs or if a more relaxed risk safety standard or norm
is chosen.Comment: 8 pages, 4 figures, conference (International Symposium on Energy
Geotechnics, 26-28 September 2018, Lausanne, Switzerland
Agent-based Social Psychology: from Neurocognitive Processes to Social Data
Moral Foundation Theory states that groups of different observers may rely on
partially dissimilar sets of moral foundations, thereby reaching different
moral valuations. The use of functional imaging techniques has revealed a
spectrum of cognitive styles with respect to the differential handling of novel
or corroborating information that is correlated to political affiliation. Here
we characterize the collective behavior of an agent-based model whose inter
individual interactions due to information exchange in the form of opinions are
in qualitative agreement with experimental neuroscience data. The main
conclusion derived connects the existence of diversity in the cognitive
strategies and statistics of the sets of moral foundations and suggests that
this connection arises from interactions between agents. Thus a simple
interacting agent model, whose interactions are in accord with empirical data
on conformity and learning processes, presents statistical signatures
consistent with moral judgment patterns of conservatives and liberals as
obtained by survey studies of social psychology.Comment: 11 pages, 4 figures, 2 C codes, to appear in Advances in Complex
System
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