169 research outputs found
Contribution of forbidden orbits in the photoabsorption spectra of atoms and molecules in a magnetic field
In a previous work [Phys. Rev. A \textbf{66}, 0134XX (2002)] we noted a
partial disagreement between quantum R-matrix and semiclassical calculations of
photoabsorption spectra of molecules in a magnetic field. We show this
disagreement is due to a non-vanishing contribution of processes which are
forbidden according to the usual semiclassical formalism. Formulas to include
these processes are obtained by using a refined stationary phase approximation.
The resulting higher order in contributions also account for previously
unexplained ``recurrences without closed-orbits''. Quantum and semiclassical
photoabsorption spectra for Rydberg atoms and molecules in a magnetic field are
calculated and compared to assess the validity of the first-order forbidden
orbit contributions.Comment: 12 pages, 6 figure
Tourism income and economic growth in Greece: Empirical evidence from their cyclical components
This paper examines the relationship between the cyclical
components of Greek GDP and international tourism income for
Greece for the period 1976â2004. Using spectral analysis the authors
find that cyclical fluctuations of GDP have a length of about nine
years and that international tourism income has a cycle of about
seven years. The volatility of tourism income is more than eight
times the volatility of the Greek GDP cycle. VAR analysis shows that
the cyclical component of tourism income is significantly influencing
the cyclical component of GDP in Greece. The findings support the
tourism-led economic growth hypothesis and are of particular
interest and importance to policy makers, financial analysts and
investors dealing with the Greek tourism industry
Endoplasmic reticulum targeted GFP reveals ER organization in tobacco NT-1 cells during cell division
Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Plant Physiology and Biochemistry, doi:10.1016/j.plaphy.2006.03.003.The endoplasmic reticulum (ER) of plant cells undergoes a drastic reorganization
during cell division. In tobacco NT-1 cells that stably express a GFP construct targeted
to the ER, we have mapped the reorganization of ER that occurs during mitosis and
cytokinesis with confocal laser scanning microscopy. During division, the ER and
nuclear envelope do not vesiculate. Instead, tubules of ER accumulate around the
chromosomes after the nuclear envelope breaks down, with these tubules aligning parallel
to the microtubules of the mitotic spindle. In cytokinesis, the phragmoplast is
particularly rich in ER, and the transnuclear channels and invaginations present in many
interphase cells appear to develop from ER tubules trapped in the developing
phragmoplast. Drug studies, using oryzalin and latrunculin to disrupt the microtubules
and actin microfilaments respectively, demonstrate that during division, the arrangement
of ER is controlled by microtubules and not by actin, which is the reverse of the situation
in interphase cells.Funding for this project included NASA grant # NAGW-4984 to the North
Carolina NSCORT (NASA Specialized Center of Research and Training) (SLG, DAC,
NSA), NSF REU Site Grant #0243930 (NSA), a Sigma Xi Grant-in-Aid Award (SLG),
and Australian Research Council Discovery Grant no. DP0208806 (DAC)
TransmissĂŁo e a influĂȘncia do volume dos estoques pĂșblicos sobre o preço do arroz no Brasil
Cointegration analysis with state space models
Abstract: This paper presents and exemplifies results developed for cointegration analysis with state space models by Bauer and Wagner in a series of papers. Unit root processes, cointegration and polynomial cointegration are defined. Based upon these definitions the major part of the paper discusses how state space models, which are equivalent to VARMA models, can be fruitfully employed for cointegration analysis. By means of detailing the cases most relevant for empirical applications, the I(1), MFI(1) and I(2) cases, a canonical representation is developed and thereafter some available statistical results are briefly mentioned.
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
Assessing salivary C-reactive protein: Longitudinal associations with systemic inflammation and cardiovascular disease risk in women exposed to intimate partner violence.
This study evaluated individual differences in levels of C-reactive protein (CRP) measured in saliva, cross-sectionally and prospectively, in relation to systemic inflammation and risk for cardiovascular disease (CVD). Plasma and saliva samples, later assayed for CRP, were collected multiple times from an ethnically diverse group of women seeking help from domestic violence crisis shelters-agencies (N = 107; mean age at study start = 34 years). Plasma and saliva CRP levels were moderately associated cross-sectionally and across two years. There were indications that saliva CRP levels were, on average, higher in the morning than evening. Higher levels of saliva and plasma CRP were associated with a higher body mass index, but did not differ between women who did and did not smoke. Salivary CRP reliably discriminated between high and low levels of plasma CRP, using a clinically relevant cutoff point of 3 mg/L, recommended by the American Heart Association. Results build upon an emerging literature suggesting that under specific conditions levels of CRP in saliva may reflect low-grade inflammation and have the potential to serve as a screen for CVD risk status
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