911 research outputs found
Irreversible Quantum Baker Map
We propose a generalization of the model of classical baker map on the torus,
in which the images of two parts of the phase space do overlap. This
transformation is irreversible and cannot be quantized by means of a unitary
Floquet operator. A corresponding quantum system is constructed as a completely
positive map acting in the space of density matrices. We investigate spectral
properties of this super-operator and their link with the increase of the
entropy of initially pure states.Comment: 4 pages, 3 figures include
Filamentous green algae from the Early Devonian Rhynie chert
A relatively neglected element of the biota of the Lower Devonian Rhynie chert LagerstĂ€tte are filamentous green algae exceptionally preserved by silicification. Palynological processing of sediments associated with the cherts has yielded palynomorphs that we also interpret as the remains of filamentous green algae and one such taxon is described herein. Cells occur individually, in masses or joined end-to-end as an unbranched filament. The cells are characterised by end walls that form a âcollarâ structure and inner bodies interpreted as reproductive structures. Because of a lack of preserved characters taxonomic precision is limited, although we suggest the fossils are most likely either zygnematalean or oedogonialean algae that inhabited ponds or lakes and were either attached to substrates and/or free-floating
What is "system": the information-theoretic arguments
The problem of "what is 'system'?" is in the very foundations of modern
quantum mechanics. Here, we point out the interest in this topic in the
information-theoretic context. E.g., we point out the possibility to manipulate
a pair of mutually non-interacting, non-entangled systems to employ
entanglement of the newly defined '(sub)systems' consisting the one and the
same composite system. Given the different divisions of a composite system into
"subsystems", the Hamiltonian of the system may perform in general
non-equivalent quantum computations. Redefinition of "subsystems" of a
composite system may be regarded as a method for avoiding decoherence in the
quantum hardware. In principle, all the notions refer to a composite system as
simple as the hydrogen atom.Comment: 13 pages, no figure
Geochemical analysis of bulk marine sediment by Inductively Coupled PlasmaâAtomic Emission Spectroscopy on board the JOIDES Resolution
Geochemical analyses on board the JOIDES Resolution have been enhanced with the addition of a Jobin-Yvon Ultrace inductively coupled plasma-atomic emission spectrometer (ICP-AES) as an upgrade from the previous X-ray fluorescence facility. During Leg 199, we sought to both challenge and utilize the capabilities of the ICP-AES in order to provide an extensive bulk-sediment geochemical database during the cruise. These near real-time analyses were then used to help characterize the recovered sedimentary sequences, calculate mass accumulation rates of the different sedimentary components, and assist with cruise and postcruise sampling requests. The general procedures, sample preparation techniques, and basic protocol for ICP-AES analyses on board ship are outlined by Murray et al. (2000) in Ocean Drilling Program Tech Note, 29. We expand on those concepts and offer suggestions for ICP-AES methodology, calibration by standard reference materials, data reduction procedures, and challenges that are specific to the analysis of bulk-sediment samples. During Leg 199, we employed an extensive bulk-sediment analytical program of ~600 samples of varying lithologies, thereby providing several opportunities for refinement of techniques. We also discuss some difficulties and challenges that were faced and suggest how to alleviate such occurrences for sedimentary chemical analyses during future legs
Distribution modelling and statistical phylogeography: an integrative framework for generating and testing alternative biogeographical hypotheses
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73644/1/j.1365-2699.2007.01814.x.pd
Chaos in a double driven dissipative nonlinear oscillator
We propose an anharmonic oscillator driven by two periodic forces of
different frequencies as a new time-dependent model for investigating quantum
dissipative chaos. Our analysis is done in the frame of statistical ensemble of
quantum trajectories in quantum state diffusion approach. Quantum dynamical
manifestation of chaotic behavior, including the emergence of chaos, properties
of strange attractors, and quantum entanglement are studied by numerical
simulation of ensemble averaged Wigner function and von Neumann entropy.Comment: 9 pages, 18 figure
Do disinhibited eaters pay increased attention to food cues?
The Three Factors Eating Questionnaire's measure of disinhibited eating is a robust predictor of long-term weight gain. This experiment explored if disinhibited eaters display attentional bias to food cues. Participants (N = 45) completed a visual dot probe task which measured responses to food (energy dense and low energy foods) and neutral cues. Picture pairs were displayed either for a 100 ms or 2000 ms duration. All participants displayed attentional bias for energy dense food items. Indices of attentional bias were largest in disinhibited eaters. Attentional bias in disinhibited eaters appeared to be underpinned by facilitated attention
Conservative versus interventional treatment for spontaneous pneumothorax
BACKGROUND: Whether conservative management is an acceptable alternative to interventional management for uncomplicated, moderate-to-large primary spontaneous pneumothorax is unknown. METHODS: In this open-label, multicenter, noninferiority trial, we recruited patients 14 to 50 years of age with a first-known, unilateral, moderate-to-large primary spontaneous pneumothorax. Patients were randomly assigned to immediate interventional management of the pneumothorax (intervention group) or a conservative observational approach (conservative-management group) and were followed for 12 months. The primary outcome was lung reexpansion within 8 weeks. RESULTS: A total of 316 patients underwent randomization (154 patients to the intervention group and 162 to the conservative-management group). In the conservative-management group, 25 patients (15.4%) underwent interventions to manage the pneumothorax, for reasons prespecified in the protocol, and 137 (84.6%) did not undergo interventions. In a complete-case analysis in which data were not available for 23 patients in the intervention group and 37 in the conservative-management group, reexpansion within 8 weeks occurred in 129 of 131 patients (98.5%) with interventional management and in 118 of 125 (94.4%) with conservative management (risk difference, -4.1 percentage points; 95% confidence interval [CI], -8.6 to 0.5; Pâ=â0.02 for noninferiority); the lower boundary of the 95% confidence interval was within the prespecified noninferiority margin of -9 percentage points. In a sensitivity analysis in which all missing data after 56 days were imputed as treatment failure (with reexpansion in 129 of 138 patients [93.5%] in the intervention group and in 118 of 143 [82.5%] in the conservative-management group), the risk difference of -11.0 percentage points (95% CI, -18.4 to -3.5) was outside the prespecified noninferiority margin. Conservative management resulted in a lower risk of serious adverse events or pneumothorax recurrence than interventional management. CONCLUSIONS: Although the primary outcome was not statistically robust to conservative assumptions about missing data, the trial provides modest evidence that conservative management of primary spontaneous pneumothorax was noninferior to interventional management, with a lower risk of serious adverse events. (Funded by the Emergency Medicine Foundation and others; PSP Australian New Zealand Clinical Trials Registry number, ACTRN12611000184976.)
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