8,004 research outputs found
Complex-mass scheme and perturbative unitarity
We derive cutting rules for loop integrals containing propagators with
complex masses. Using a field-theoretical model of a heavy vector boson
interacting with a light fermion, we demonstrate that the complex-mass scheme
respects unitarity order by order in a perturbative expansion provided that the
renormalized coupling constant remains real.Comment: Accepted for publication in International Journal of Modern Physics
Time-resolved spectroscopy of the excited electronic state of reaction centers of Rhodopseudomonas viridis
The spectral properties of the excited electronic state of the reaction centers of Rhodopseudomonas (Rps.) viridis are studied by dichroic transient absorption spectroscopy with sub-picosecond time resolution. The theoretical analysis of the experimental results allows the assignment of the transient absorption from two dimer bands of the special pair and show its excitonic coupling to other pigments
Fuel-cell performance of multiply-crosslinked polymer electrolyte membranes prepared by two-step radiation technique
A multiply-crosslinked polymer electrolyte membrane was
prepared by the radiation-induced co-grafting of styrene and a
bis(vinyl phenyl)ethane (BVPE) crosslinker into a
radiation-crosslinked polytetrafluoroethylene (cPTFE) film. We
then investigated its H2/O2 fuel-cell performance at 60 and 80ºC in
terms of the effect of radiation and chemical crosslinking. At 60ºC,
all the membranes initially exhibited similar performance, but only
the cPTFE-based membranes were durable at 80ºC, indicating the
necessity of radiation crosslinking in the PTFE main chains.
Importantly, cell performance of the multiply-crosslinked
membrane was found high enough to reach that of a Nafion112
membrane. This is probably because the BVPE crosslinks in the
graft component improved the membrane-electrode interface in
addition to membrane durability. After severe OCV hold tests at 80
and 95ºC, the performance deteriorated, while no significant
change was observed in ohmic resistivity. Accordingly, our
membranes seemed so chemically stable that an influence on
overall performance loss could be negligible
Maternal employment : enabling factors in context
Maternal employment is still below the overall EU recommended level of 60% in many European
countries. Understanding the individual, household and contextual circumstances under which
mothers of children of different ages are likely to be employed is crucial to develop strategies
capable of increasing maternal employment. This article takes a comparative approach to
investigating the characteristics associated with maternal employment in the presence of children
aged 0\u20132, 3\u20135, 6\u20139 and 10\u201312 years. We model the probability of being employed full-time, parttime
or being a homemaker using EU-SILC data (2004 to 2007) from Germany, Italy, Norway
and the United Kingdom \u2013 four countries belonging to different gender and welfare regimes. The
results indicate that individual and household characteristics are more relevant in determining
mothers\u2019 employment in countries where the state is less supportive towards maternal
employment: Italy and to a lesser extent Germany and the UK \u2013 for the period observed
Anatomic and Compression Topography of the Lesser Occipital Nerve.
BACKGROUND: The surgical treatment of occipital headaches focuses on the greater, lesser, and third occipital nerves. The lesser occipital nerve (LON) is usually transected with relatively limited available information regarding the compression topography thereof and how such knowledge may impact surgical treatment.
METHODS: Eight fresh frozen cadavers were dissected focusing on the LON in relation to 3 clinically relevant compression zones. The x axis was a line drawn through the occipital protuberance (OP) and the y axis, the posterior midline (PM). In addition, a prospectively collected cohort of 36 patients who underwent decompression of the LON is presented with their clinical results, including migraine headache index scores.
RESULTS: The LON was found in compression zone 1, with a mean of 7.8 cm caudal to the OP and 6.3 cm lateral to the PM. The LON was found at the midpoint of compression zone 2, with an average of 5.5 cm caudal to the OP and 6.2 cm lateral to the PM. At compression zone 3, the medial-most LON branch was located approximately 1 cm caudal to the OP and 5.35 cm lateral to the PM, whereas the lateral-most branch was identified 1 cm caudal to the OP and 6.5 cm lateral to the PM. Of the 36 decompression patients analyzed, only 5 (14%) required neurectomy as the remainder achieved statistically significant improvements in migraine headache index scores postoperatively.
CONCLUSION: The knowledge of LON anatomy can aid in nerve dissection and preservation, thereby leading to successful outcomes without requiring neurectomy
The Anomalous Decay eta -> pi pi gamma gamma
We investigate the rare radiative eta decay modes eta -> pi+ pi- gamma gamma
and eta -> pi0 pi0 gamma gamma within the framework of chiral lagrangians at
o(p^4) and present photon spectra for both processes.Comment: 5 pages, revtex preprint, PS figures in separate file, presented at
the International School of Nuclear Physics, Erice, Sicily, Italy, September
199
Hybrid-aligned nematic liquid-crystal modulators fabricated on VLSI circuits
A new method for fabricating analog light modulators on VLSI devices is described. The process is fully compatible with devices fabricated by commercial VLSI foundries, and the assembly of the modulator structures requires a small number of simple processing steps. The modulators are capable of analog amplitude or phase modulation and can operate at video rates and at low voltages (2.2 V). The modulation mechanism and the process yielding the modulator structures are described. Experimental data are presented
Topology and Evolution of Technology Innovation Networks
The web of relations linking technological innovation can be fairly described
in terms of patent citations. The resulting patent citation network provides a
picture of the large-scale organization of innovations and its time evolution.
Here we study the patterns of change of patents registered by the US Patent and
Trademark Office (USPTO). We show that the scaling behavior exhibited by this
network is consistent with a preferential attachment mechanism together with a
Weibull-shaped aging term. Such attachment kernel is shared by scientific
citation networks, thus indicating an universal type of mechanism linking ideas
and designs and their evolution. The implications for evolutionary theory of
innovation are discussed.Comment: 6 pages, 5 figures, submitted to Physical Review
Generalized polarizabilities and the spin-averaged amplitude in virtual Compton scattering off the nucleon
We discuss the low-energy behavior of the spin-averaged amplitude of virtual
Compton scattering (VCS) off a nucleon.
Based on gauge invariance, Lorentz invariance and the discrete symmetries, it
is shown that to first order in the frequency of the final real photon only two
generalized polarizabilities appear.
Different low-energy expansion schemes are discussed and put into
perspective.Comment: 13 pages, 1 postscript figure, Revtex using eps
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