2,080 research outputs found
A multi-sensor analysis of Nimbus 5 data on 22 January 1973
The Nimbus 5 meteorological satellite carried aloft a full complement of radiation sensors, the data from which were analyzed and intercompared during orbits 569-570 on 22 January 1973. The electrically scanning microwave radiometer (ESMR) which sensed passive microwave radiation in the 19.35 GHz region, delineated rain areas over the ocean off the U.S. east coast, in good agreement with WSR-57 and FPS-77 radar imagery and permitted the estimation of rainfall rates in this region. Residual ground water in the lower Mississippi Valley, which resulted from abnormal rainfall in previous months, was indicated under clear sky conditions by soil brightness temperature values in the Nimbus 5 ESMR and U.S. Air Force Data Acquisition and Processing Program (DAPP) IR data. The temperature-humidity infrared radiometer showed the height and spatial configuration of frontal clouds along the east coast and outlined the confluence of a polar jet stream with a broad sub-tropical jet stream along the U.S. Gulf Coast. Temperature profiles from three vertical temperature sounders, the infrared temperature profile radiometer (ITPR), the Nimbus E microwave spectrometer (NEMS) and the selective chopper radiometer (SCR) were found to be in good agreement with related radiosonde ascents along orbit 569 from the sub-tropics to the Arctic Circle
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Ontogenetic changes in cutaneous and branchial ionocytes and morphology in yellowfin tuna (Thunnus albacares) larvae.
The development of osmoregulatory and gas exchange organs was studied in larval yellowfin tuna (Thunnus albacares) from 2 to 25 days post-hatching (2.9-24.5 mm standard length, SL). Cutaneous and branchial ionocytes were identified using Na+/K+-ATPase immunostaining and scanning electron microscopy. Cutaneous ionocyte abundance significantly increased with SL, but a reduction in ionocyte size and density resulted in a significant decrease in relative ionocyte area. Cutaneous ionocytes in preflexion larvae had a wide apical opening with extended microvilli; however, microvilli retracted into an apical pit from flexion onward. Lamellae in the gill and pseudobranch were first detected ~ 3.3 mm SL. Ionocytes were always present on the gill arch, first appeared in the filaments and lamellae of the pseudobranch at 3.4 mm SL, and later in gill filaments at 4.2 mm SL, but were never observed in the gill lamellae. Unlike the cutaneous ionocytes, gill and pseudobranch ionocytes had a wide apical opening with extended microvilli throughout larval development. The interlamellar fusion, a specialized gill structure binding the lamellae of ram-ventilating fish, began forming by ~ 24.5 mm SL and contained ionocytes, a localization never before reported. Ionocytes were retained on the lamellar fusions and also found on the filament fusions of larger sub-adult yellowfin tuna; however, sub-adult gill ionocytes had apical pits. These results indicate a shift in gas exchange and NaCl secretion from the skin to branchial organs around the flexion stage, and reveal novel aspects of ionocyte localization and morphology in ram-ventilating fishes
A multisensor analysis of Nimbus-5 data recorded on 22 January 1973
The Nimbus 5 meteorological satellite has a full complement of radiation sensors. Data from these sensors were analyzed and intercompared for orbits 569 and 570. The electrically-scanning microwave radiometer (19.35-GHz region) delineated rain areas over the ocean off the U.S. east coast, in good agreement with radar imagery, and permitted the estimation of rainfall rates in this region. Residual ground water, from abnormal rainfall in the lower Mississippi Valley, was indicated under clear sky conditions by soil brightness temperature values in the Nimbus 5 electrically scanning microwave radiometer and U.S. Air Force Data Acquisition and Processing Program infrared data. The temperature-humidity infrared radiometer (6.7 micron and 11 micron) showed the height and spatial configuration of frontal clouds along the east coast and outlined the confluence of a polar jet stream with a broad subtropical jet stream along the U.S. Gulf Coast. Temperature profiles from three vertical temperature sounders are found to be in good agreement with related radiosonde ascents along orbit 569 from the subtropics to the Arctic Circle
Neutral Collective Excitations in Striped Hall States
In the striped Hall state, a magnetic translation in one direction is
spontaneously broken to the discrete translation. The spectrum of the neutral
collective excitation is obtained in the single mode approximation at
half-filled third and fourth Landau levels. The spectrum is anisotropic and has
a multiple line node structure. In one direction, the spectrum resembles the
liquid Helium spectrum with the phonon and roton minimum.Comment: 2 pages, 2 figures, LT23 Hiroshim
Hypernetted-chain study of broken rotational symmetry states for the = 1/3 fractional quantum Hall effect and other fractionally filled Landau levels
We investigate broken rotational symmetry (BRS) states for the fractional
quantum Hall effect (FQHE) at 1/3-filling of the valence Landau level (LL).
Recent Monte Carlo calculations by Musaelian and Joynt [J. Phys.: Condens.\
Matter {\bf 8}, L105 (1996)] suggest that Laughlin's state becomes unstable to
a BRS state for some critical finite thickness value. We study in detail the
properties of such state by performing a hypernetted-chain calculation that
gives results in the thermodynamic limit, complementing other methods which are
limited to a finite number of particles. Our results indicate that while
Laughlin's state is stable in the lowest LL, in higher LLs a BRS instability
occurs, perhaps indicating the absence of FQHE at partial fillings of higher
LLs. Possible connections to the newly discovered liquid crystalline phases in
higher LLs are also discussed.Comment: 7 pages including 3 eps figure
Ballistic and Diffuse Electron Transport in Nanocontacts of Magnetics
The transition from the ballistic electron transport to the diffuse one is
experimentally observed in the study of the magnetic phase transition in Ni
nanocontacts with different sizes. It is shown that the voltage needed
for Joule heating of the near-contact region to the critical temperature does
not depend on the contact size only in the diffuse mode. For the ballistic
contact it increases with decrease in the nanocontact size. The reduction of
the transport electron mean free path due to heating of NCs may result in
change of the electron transport mode from ballistic to diffusive one.Comment: 7 pages, 2 figures accepted for the publication in JETPL
(http://www.jetpletters.ac.ru). Will be published on 25 april 201
The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
Since the discovery of superconductivity in the cuprates two decades ago, it
has been firmly established that the CuO_2 plane is consequential for high T_C
superconductivity and a host of other very unusual properties. A new family of
superconductors with the general composition of LaFeAsO_(1-x)F_x has recently
been discovered but with the conspicuous lacking of the CuO_2 planes, thus
raising the tantalizing questions of the different pairing mechanisms in these
oxypnictide superconductors. Intimately related to pairing in a superconductor
are the superconducting gap, its value, structure, and temperature dependence.
Here we report the observation of a single gap in the superconductor
SmFeAsO_0.85F_0.15 with T_C = 42 K as measured by Andreev spectroscopy. The gap
value of 2Delta = 13.34+/-0.3 meV gives 2Delta/k_BT_C = 3.68, close to the BCS
prediction of 3.53. The gap decreases with temperature and vanishes at T_C in a
manner consistent with the Bardeen-Cooper-Schrieffer (BCS) prediction but
dramatically different from that of the pseudogap behavior in the cuprate
superconductors. Our results clearly indicate a nodeless gap order parameter,
which is nearly isotropic in size across different sections of the Fermi
surface, and are not compatible with models involving antiferromagnetic
fluctuations, strong correlations, t-J model, and the like, originally designed
for cuprates.Comment: 8 pages, 3 figure
Atmospheric particulate matter characterization by Fourier transform infrared spectroscopy: a review of statistical calibration strategies for carbonaceous aerosol quantification in US measurement networks
Atmospheric particulate matter (PM) is a complex mixture of many different
substances and requires a suite of instruments for chemical
characterization. Fourier transform infrared (FT-IR) spectroscopy is a
technique that can provide quantification of multiple species provided that
accurate calibration models can be constructed to interpret the acquired
spectra. In this capacity, FT-IR spectroscopy has enjoyed a long history in monitoring
gas-phase constituents in the atmosphere and in stack emissions. However,
application to PM poses a different set of challenges as the condensed-phase
spectrum has broad, overlapping absorption peaks and contributions of
scattering to the mid-infrared spectrum. Past approaches have used laboratory
standards to build calibration models for prediction of inorganic substances
or organic functional groups and predict their concentration in
atmospheric PM mixtures by extrapolation.
In this work, we review recent studies pursuing an alternate strategy, which
is to build statistical calibration models for mid-IR spectra of PM using
collocated ambient measurements. Focusing on calibrations with organic carbon
(OC) and elemental carbon (EC) reported from thermal–optical reflectance
(TOR), this synthesis serves to consolidate our knowledge for extending FT-IR
spectroscopy
to provide TOR-equivalent OC and EC measurements to new PM samples when TOR
measurements are not available. We summarize methods for model specification,
calibration sample selection, and model evaluation for these substances at
several sites in two US national monitoring networks: seven sites in the
Interagency Monitoring of Protected Visual Environments (IMPROVE) network for
the year 2011 and 10 sites in the Chemical Speciation Network (CSN) for the
year 2013. We then describe application of the model in an operational
context for the IMPROVE network for samples collected in 2013 at six of the
same sites as in 2011 and 11 additional sites. In addition to extending the
evaluation to samples from a different year and different sites, we describe
strategies for error anticipation due to precision and biases from the
calibration model to assess model applicability for new spectra a priori. We
conclude with a discussion regarding past work and future strategies for
recalibration. In addition to targeting numerical accuracy, we encourage
model interpretation to facilitate understanding of the underlying structural
composition related to operationally defined quantities of TOR OC and EC from
the vibrational modes in mid-IR deemed most informative for calibration. The
paper is structured such that the life cycle of a statistical calibration
model for FT-IR spectroscopy can be envisioned for any substance with IR-active
vibrational modes, and more generally for instruments requiring ambient
calibrations.</p
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Default perception of high-speed motion
When human observers are exposed to even slight motion signals followed by brief visual transients—stimuli containing no detectable coherent motion signals—they perceive large and salient illusory jumps. This novel effect, which we call “high phi”, challenges well-entrenched assumptions about the perception of motion, namely the minimal-motion principle and the breakdown of coherent motion perception with steps above an upper limit. Our experiments with transients such as texture randomization or contrast reversal show that the magnitude of the jump depends on spatial frequency and transient duration, but not on the speed of the inducing motion signals, and the direction of the jump depends on the duration of the inducer. Jump magnitude is robust across jump directions and different types of transient. In addition, when a texture is actually displaced by a large step beyond dmax, a breakdown of coherent motion perception is expected, but in the presence of an inducer observers again perceive coherent displacements at or just above dmax. In sum, across a large variety of stimuli, we find that when incoherent motion noise is preceded by a small bias, instead of perceiving little or no motion, as suggested by the minimal-motion principle, observers perceive jumps whose amplitude closely follows their own dmax limits
The Onset of Anisotropic Transport of Two-Dimensional Electrons in High Landau Levels: An Isotropic-to-Nematic Liquid Crystal Phase Transition?
The recently discovered anisotropy of the longitudinal resistance of
two-dimensional electrons near half filling of high Landau levels is found to
persist to much higher temperatures T when a large in-plane magnetic field B||
is applied. Under these conditions we find that the longitudinal resistivity
scales quasi-linearly with B||/T. These observations support the notion that
the onset of anisotropy at B||=0 does not reflect the spontaneous development
of charge density modulations but may instead signal an isotropic-to-nematic
liquid crystal phase transition.Comment: 5 pages, 4 figure
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