128 research outputs found
North-South Distribution of Solar Flares during Cycle 23
In this paper, we investigate the spatial distribution of solar flares in the
northern and southern hemisphere of the Sun that occurred during the period
1996 to 2003. This period of investigation includes the ascending phase, the
maximum and part of descending phase of solar cycle 23. It is revealed that the
flare activity during this cycle is low compared to previous solar cycle,
indicating the violation of Gnevyshev-Ohl rule. The distribution of flares with
respect to heliographic latitudes shows a significant asymmetry between
northern and southern hemisphere which is maximum during the minimum phase of
the solar cycle. The present study indicates that the activity dominates the
northern hemisphere in general during the rising phase of the cycle
(1997-2000). The dominance of northern hemisphere is shifted towards the
southern hemisphere after the solar maximum in 2000 and remained there in the
successive years. Although the annual variations in the asymmetry time series
during cycle 23 are quite different from cycle 22, they are comparable to cycle
21.Comment: 6 pages, 2 figures, 1 table; Accepted for the publication in the
proceedings of international solar workshop held at ARIES, Nainital, India on
"Transient Phenomena on the Sun and Interplanetary Medium" in a special issue
of "Journal of Astrophysics and Astronomy (JAA)
VECSEL systems for quantum information processing with trapped beryllium ions
Two vertical-external-cavity surface-emitting laser (VECSEL) systems
producing ultraviolet (UV) radiation at 235 nm and 313 nm are demonstrated. The
systems are suitable for quantum information processing applications with
trapped beryllium ions. Each system consists of a compact, single-frequency,
continuous-wave VECSEL producing high-power near-infrared light, tunable over
tens of nanometers. One system generates 2.4 W at 940 nm, using a gain mirror
based on GaInAs/GaAs quantum wells, which is converted to 54 mW of 235 nm light
for photoionization of neutral beryllium atoms. The other system uses a novel
gain mirror based on GaInNAs/GaAs quantum-wells, enabling wavelength extension
with manageable strain in the GaAs lattice. This system generates 1.6 W at 1252
nm, which is converted to 41 mW of 313 nm light that is used to laser cool
trapped Be ions and to implement quantum state preparation and
detection. The 313 nm system is also suitable for implementing high-fidelity
quantum gates, and more broadly, our results extend the capabilities of VECSEL
systems for applications in atomic, molecular, and optical physics.Comment: 8 pages, 7 figure
Measurement of Muon Capture on the Proton to 1% Precision and Determination of the Pseudoscalar Coupling g_P
The MuCap experiment at the Paul Scherrer Institute has measured the rate L_S
of muon capture from the singlet state of the muonic hydrogen atom to a
precision of 1%. A muon beam was stopped in a time projection chamber filled
with 10-bar, ultra-pure hydrogen gas. Cylindrical wire chambers and a segmented
scintillator barrel detected electrons from muon decay. L_S is determined from
the difference between the mu- disappearance rate in hydrogen and the free muon
decay rate. The result is based on the analysis of 1.2 10^10 mu- decays, from
which we extract the capture rate L_S = (714.9 +- 5.4(stat) +- 5.1(syst)) s^-1
and derive the proton's pseudoscalar coupling g_P(q^2_0 = -0.88 m^2_mu) = 8.06
+- 0.55.Comment: Updated figure 1 and small changes in wording to match published
versio
Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling
The rate of nuclear muon capture by the proton has been measured using a new
experimental technique based on a time projection chamber operating in
ultra-clean, deuterium-depleted hydrogen gas at 1 MPa pressure. The capture
rate was obtained from the difference between the measured
disappearance rate in hydrogen and the world average for the decay
rate. The target's low gas density of 1% compared to liquid hydrogen is key to
avoiding uncertainties that arise from the formation of muonic molecules. The
capture rate from the hyperfine singlet ground state of the atom is
measured to be , from which the induced
pseudoscalar coupling of the nucleon, , is
extracted. This result is consistent with theoretical predictions for
that are based on the approximate chiral symmetry of QCD.Comment: submitted to Phys.Rev.Let
State of the Art in Building Façades
This chapter presents a portfolio of building materials suitable for facades. It describes the relationship between material type, building element, facade, and the entire building structure. Traditional facades based on static components, as well as adaptive concepts able to interact with changing environmental conditions, are briefly described and illustrated with pictures. Climatic design principles, biomimicry, and bioinspiration in architecture are introduced with the purpose of inspiring future developments
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