1,522 research outputs found
A Calibrated Time Domain Envelope Measurement System for the Behavioral Modeling of Power Amplifiers
This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power – 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects
Magnetic-dipole transition probabilities in B-like and Be-like ions
The magnetic-dipole transition probabilities between the fine-structure
levels (1s^2 2s^2 2p) ^2P_1/2 - ^2P_3/2 for B-like ions and (1s^2 2s 2p) ^3P_1
- ^3P_2 for Be-like ions are calculated. The configuration-interaction method
in the Dirac-Fock-Sturm basis is employed for the evaluation of the
interelectronic-interaction correction with negative-continuum spectrum being
taken into account. The 1/Z interelectronic-interaction contribution is derived
within a rigorous QED approach employing the two-time Green function method.
The one-electron QED correction is evaluated within framework of the anomalous
magnetic-moment approximation. A comparison with the theoretical results of
other authors and with available experimental data is presented
Isotope geochemistry and petrogenesis of peralkaline Middle Miocene ignimbrites from central Sonora: relationship with continental break-up and the birth of the Gulf of California
Middle Miocene peralkaline ignimbrites constitute a specific geodynamic marker of the early stage of opening of the Gulf of California, preserved either in central Sonora or the Puertecitos area, in Baja California. Very uniform ages (12-12.5 Ma) obtained on these rocks show that this volcanic episode corresponds to a specific stage in the tectonic evolution of the proto-gulf area. Field observations and slightly different Sr and Nd isotopic signatures support eruptions from several small volume magma batches rather than from a large-volume caldera forming event. Isotopic ratios help to constrain the petrogenesis of the peralkaline liquids by fractional crystallization of transitional basalts in a shallow reservoir, with slight contamination by Precambrian upper crustal material. Less differentiated glomeroporphyritic icelandites erupted at about 11 Ma, mark an increase in the magma production rate and highlight an easier access to the surface, illustrating an advanced stage in the weakening of the continental crust. The tilting of the Middle Tertiary sequences results from a major change in the tectonic regime, from E-W extension giving rise to N-S grabens, to NNW-SSE strike-slip motion that can be related to the transfer of Baja California from North America to the Pacific plate. The location of peralkaline volcanism coincides with the southern edge of the Precambrian crust and the southernmost extension of the California slab window at 12.5 Ma
First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
The first direct mass-measurement of He has been performed with the
TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the
mass of He was determined with improved precision over our previous
measurement. The obtained masses are (He) = 6.018 885 883(57) u and
(He) = 8.033 934 44(11) u. The He value shows a deviation from
the literature of 4. With these new mass values and the previously
measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and
1.959(16) fm for He and He respectively. We present a detailed
comparison to nuclear theory for He, including new hyperspherical harmonics
results. A correlation plot of the point-proton radius with the two-neutron
separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure
Human hypocretin and melanin-concentrating hormone levels are linked to emotion and social interaction.
The neurochemical changes underlying human emotions and social behaviour are largely unknown. Here we report on the changes in the levels of two hypothalamic neuropeptides, hypocretin-1 and melanin-concentrating hormone, measured in the human amygdala. We show that hypocretin-1 levels are maximal during positive emotion, social interaction and anger, behaviours that induce cataplexy in human narcoleptics. In contrast, melanin-concentrating hormone levels are minimal during social interaction, but are increased after eating. Both peptides are at minimal levels during periods of postoperative pain despite high levels of arousal. Melanin-concentrating hormone levels increase at sleep onset, consistent with a role in sleep induction, whereas hypocretin-1 levels increase at wake onset, consistent with a role in wake induction. Levels of these two peptides in humans are not simply linked to arousal, but rather to specific emotions and state transitions. Other arousal systems may be similarly emotionally specialized
Statistical real-time model for performance prediction of ship detection from microsatellite electro-optical imagers
For locating maritime vessels longer than 45 meters, such vessels are required to set up an Automatic Identification System (AIS) used by vessel traffic services. However, when a boat is shutting down its AIS, there are no means to detect it in open sea. In this paper, we use Electro-Optical (EO) imagers for noncooperative vessel detection when the AIS is not operational. As compared to radar sensors, EO sensors have lower cost, lower payload, and better computational processing load. EO sensors are mounted on LEO microsatellites. We propose a real-time statistical methodology to estimate sensor Receiver Operating Characteristic (ROC) curves. It does not require the computation of the entire image received at the sensor. We then illustrate the use of this methodology to design a simple simulator that can help sensor manufacturers in optimizing the design of EO sensors for maritime applications
Trapped-ion decay spectroscopy towards the determination of ground-state components of double-beta decay matrix elements
A new technique has been developed at TRIUMF's TITAN facility to perform
in-trap decay spectroscopy. The aim of this technique is to eventually measure
weak electron capture branching ratios (ECBRs) and by this to consequently
determine GT matrix elements of decaying nuclei. These branching
ratios provide important input to the theoretical description of these decays.
The feasibility and power of the technique is demonstrated by measuring the
ECBR of Cs.Comment: 9 pages, 9 figure
First Penning-trap mass measurement in the millisecond half-life range: the exotic halo nucleus 11Li
In this letter, we report a new mass for Li using the trapping
experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived
nuclide, , for which a mass measurement has ever been
performed with a Penning trap. Combined with our mass measurements of
Li we derive a new two-neutron separation energy of 369.15(65) keV: a
factor of seven more precise than the best previous value. This new value is a
critical ingredient for the determination of the halo charge radius from
isotope-shift measurements. We also report results from state-of-the-art
atomic-physics calculations using the new mass and extract a new charge radius
for Li. This result is a remarkable confluence of nuclear and atomic
physics.Comment: Formatted for submission to PR
GPM-DPR Observations on TGFs Producing Storms
Unique spaceborne measurements of the three-dimensional structure of convective
clouds producing terrestrial gamma ray flashes (TGFs) were performed using both active and passive
microwave sensors on board the Global Precipitation Measurement (GPM)-Core Observatory satellite,
finding coherent features for nine TGF-producing storms. The delineation of cloud structure using the
radar reflectivity factor shows convective cells with significant vertical development and thick layers with
high ice content. Compared to other cumulonimbus clouds in the tropics, the TGFs counterparts have
higher reflectivity values above 3 and 8 km altitude showing in all cases a cumulonimbus tower and the
TGFs locations are very close, or coincident, to these high Z columns, where reflectivity exceeds 50dBz.
Using the GPM Microwave Imager radiometer, most thunderstorms show a very strong depression of
polarization corrected temperature (PCT) at channel 89GHz, indicating a strong scattering signal by ice
in the upper cloud layers. At channel 166GHZ, the difference between vertical and horizontal brightness
temperature signal always returns positive values, from 0.2 up to 13.7K indicating a complex structure
with randomly/vertically oriented ice particles. The PCT was used to characterize the analyzed storms
in terms of hydrometeor types, confirming in 7/9 cases a high likelihood of hail/graupel presence. To
perform analysis on the TGFs parent flashes, radio atmospherics data from the Earth Networks Total
Lightning Network lightning network were used. Waveform data indicate that all cases are intra-cloud
events and TGFs typically take place during the peak of flash rate production. Finally, the analysis of the
most intense event is shown
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