353 research outputs found
Judging From Experience: Experienced Sequences are Predicted Better than Described Sequences
When attempting to predict future events, people commonly rely on historical data. Events in a time series can be experienced sequentially (dynamic mode), as in learning about decisions from experience (e.g., Kusev et al., in press, JEP:HPP), or, as with learning about decisions from descriptions, they can also be retrospectively viewed holistically (static mode) – not experienced individually in real time. In one experiment, we studied the influence of presentation mode (dynamic and static) on three sorts of judgments: (i) predictions of the next event (forecast), (ii) estimation of the average value of all the events in the presented series (average) and (iii) judged satisfaction of workers given that the series represented their monthly income (satisfaction). Relative to the static mode participants‘ responses in dynamic mode were anchored on more recent events for all three types of judgments but with different consequences – hence dynamic presentation improved prediction accuracy, but not estimation
Recommended from our members
Influence of regional-scale anthropogenic emissions on CO2 distributions over the western North Pacific
We report here airborne measurements of atmospheric CO2 over the western North Pacific during the March-April 2001 Transport and Chemical Evolution over the Pacific (TRACE-P) mission. The CO2 spatial distributions were notably influenced by cyclogenesis-triggered transport of regionally polluted continental air masses. Examination of the CO2 to C2H2/CO ratio indicated rapid outflow of combustion-related emissions in the free troposphere below 8 km. Although the highest CO2 mixing ratios were measured within the Pacific Rim region, enhancements were also observed further east over the open ocean at locations far removed from surface sources. Near the Asian continent, discrete plumes encountered within the planetary boundary layer contained up to 393 ppmv of CO2. Coincident enhancements in the mixing ratios of C2Cl4, C2H2, and C2H4 measured concurrently revealed combustion and industrial sources. To elucidate the source distributions of CO2, an emissions database for Asia was examined in conjunction with the chemistry and 5-day backward trajectories that revealed the WNW/W sector of northeast Asia was a major contributor to these pollution events. Comparisons of NOAA/CMDL and JMA surface data with measurements obtained aloft showed a strong latitudinal gradient that peaked between 35° and 40°N. We estimated a net CO2 flux from the Asian continent of approximately 13.93 Tg C day-1 for late winter/early spring with the majority of the export (79%) occurring in the lower free troposphere (2-8 km). The apportionment of the flux between anthropogenic and biospheric sources was estimated at 6.37 Tg C day-1 and 7.56 Tg C day-1, respectively
Recommended from our members
In situ measurements of HCN and CH3CN over the Pacific Ocean: Sources, sinks, and budgets
We report the first in situ measurements of hydrogen cyanide (HCN) and methyl cyanide (CH3CN, acetonitrile) from the Pacific troposphere (0-12 km) obtained during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) airborne mission (February-April 2001). Mean HCN and CH3CN mixing ratios of 243 ± 118 (median 218) ppt and 149 ± 56 (median 138) ppt, respectively, were measured. These in situ observations correspond to a mean tropospheric HCN column of 4.2 × 1015 molecules cm-2 and a CH3CN column of 2.5 × 1015 molecules cm-2. This is in good agreement with the 0-12 km HCN column of 4.4 (±0.6) × 1015 molecules cm-2 derived from infrared solar spectroscopic observations over Japan. Mixing ratios of HCN and CH3CN were greatly enhanced in pollution outflow from Asia and were well correlated with each other as well as with known tracers of biomass combustion (e.g., CH3Cl, CO). Volumetric enhancement (or emission) ratios (ERs) relative to CO in free tropospheric plumes, likely originating from fires, were 0.34% for HCN and 0.17% for CH3CN. ERs with respect to CH3Cl and CO in selected biomass burning (BB) plumes in the free troposphere and in boundary layer pollution episodes are used to estimate a global BB source of 0.8 ± 0.4 Tg (N) yr-1 for HCN and 0.4 ± 0.1 Tg (N) yr-1 for CH3CN. In comparison, emissions from industry and fossil fuel combustion are quite small (<0.05 Tg (N) yr-1). The vertical structure of HCN and CH3CN indicated reduced mixing ratios in the marine boundary layer (MBL). Using a simple box model, the observed gradients across the top of the MBL are used to derive an oceanic loss rate of 8.8 × 10-15 g (N) cm-2 s-1 for HCN and 3.4 × 10-15 g (N) cm-2 s-1 for CH3CN. An air-sea exchange model is used to conclude that this flux can be maintained if the oceans are undersaturated in HCN and CH3CN by 27% and 6%, respectively. These observations also correspond to an open ocean mean deposition velocity (vd) of 0.12 cm s-1 for HCN and 0.06 cm s-1 for CH3CN. It is inferred that oceanic loss is a dominant sink for these cyanides and that they deposit some 1.4 Tg (N) of nitrogen annually to the oceans. Assuming loss to the oceans and reaction with OH radicals as the major removal processes, a mean atmospheric residence time of 5.0 months for HCN and 6.6 months for CH3CN is calculated. A global budget analysis shows that the sources and sinks of HCN and CH3CN are roughly in balance but large uncertainties remain in part due to a lack of observational data from the atmosphere and the oceans. Pathways leading to the oceanic (and soil) degradation of these cyanides are poorly known but are expected to be biological in nature
Recommended from our members
Synoptic-scale transport of reactive nitrogen over the western Pacific in spring
Recommended from our members
Characteristics and influence of biosmoke on the fine-particle ionic composition measured in Asian outflow during the Transport and Chemical Evolution Over the Pacific (TRACE-P) experiment
2D vs 3D gamma analysis: Establishment of comparable clinical action limits
Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance; these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, because of the different search space available. We compared the results of 2D and 3D gamma analysis (where both datasets were generated the same way) for clinical treatment plans. Methods: 50 IMRT plans were selected from our database and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated”) and Monte Carlo-recalculated (“reference”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma and percentage of pixels passing gamma.Results: Average gamma and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. Average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a differences ranging from 0.8% to 1.5%. No appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs. 3D) were observed.Conclusion: We found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. Factors such as inherent dosimeter differences may be an important additional consideration to the extra dimension of available data that was evaluated in this study.------------------------------------Cite this article as: Pulliam KB, Huang JY, Bosca R, Followill D, Kry SF. 2D vs. 3D gamma analysis: Establishment of comparable clinical action limits. Int J Cancer Ther Oncol 2014; 2(2):020231. DOI: 10.14319/ijcto.0202.3
Exact Black Holes and Gravitational Shockwaves on Codimension-2 Branes
We derive exact gravitational fields of a black hole and a relativistic
particle stuck on a codimension-2 brane in dimensions when gravity is ruled
by the bulk -dimensional Einstein-Hilbert action. The black hole is locally
the higher-dimensional Schwarzschild solution, which is threaded by a tensional
brane yielding a deficit angle and includes the first explicit example of a
`small' black hole on a tensional 3-brane. The shockwaves allow us to study the
large distance limits of gravity on codimension-2 branes. In an infinite
locally flat bulk, they extinguish as , i.e. as on a 3-brane
in , manifestly displaying the full dimensionality of spacetime. We check
that when we compactify the bulk, this special case correctly reduces to the 4D
Aichelburg-Sexl solution at large distances. Our examples show that gravity
does not really obstruct having general matter stress-energy on codimension-2
branes, although its mathematical description may be more involved.Comment: 18 pages, LaTeX; v2: added references, version to appear in JHE
Brane cosmological solutions in six-dimensional warped flux compactifications
We study cosmology on a conical brane in the six-dimensional
Einstein-Maxwell-dilaton system, where the extra dimensions are compactified by
a magnetic flux. We systematically construct exact cosmological solutions using
the fact that the system is equivalently described by (6+n)-dimensional pure
Einstein-Maxwell theory via dimensional reduction. In particular, we find a
power-law inflationary solution for a general dilatonic coupling. When the
dilatonic coupling is given by that of Nishino-Sezgin chiral supergravity, this
reduces to the known solution which is not inflating. The power-law solution is
shown to be the late-time attractor. We also investigate cosmological tensor
perturbations in this model using the (6+n)-dimensional description. We obtain
the separable equation of motion and find that there always exist a zero mode,
while tachyonic modes are absent in the spectrum. The mass spectrum of
Kaluza-Klein modes is obtained numerically.Comment: 12 pages, 2 figures; v2: references added; v3: version published in
JCA
Charting the Landscape of Modified Gravity
We explore brane induced gravity on a 3-brane in six locally flat dimensions.
To regulate the short distance singularities in the brane core, we resolve the
thin brane by a cylindrical 4-brane, with the geometry of 4D Minkowski
a circle, which has an axion flux to cancel the vacuum pressure in the compact
direction. We discover a large diversity of possible solutions controlled by
the axion flux, as governed by its boundary conditions. Hence brane induced
gravity models really give rise to a {\it landscape} of vacua, at least
semiclassically. For sub-critical tensions, the crossover scale, below which
gravity may look 4D, and the effective 4D gravitational coupling are sensitive
to vacuum energy. This shows how the vacuum energy problem manifests in brane
induced gravity: instead of tuning the 4D curvature, generically one must tune
the crossover scale. On the other hand, in the near-critical limit, branes live
inside very deep throats which efficiently compactify the angular dimension. In
there, 4D gravity first changes to , and only later to . The crossover
scale saturates at the gravitational see-saw scale, independent of the tension.
Using the fields of static loops on a wrapped brane, we check the perturbative
description of long range gravity below the crossover scale. In sub-critical
cases the scalars are strongly coupled already at the crossover scale even in
the vacuum, because the brane bending is turned on by the axion flux. Near the
critical limit, linearized perturbation theory remains under control below the
crossover scale, and we find that linearized gravity around the vacuum looks
like a scalar-tensor theory.Comment: 47 LaTeX pages, 3 .eps figures, typos fixed to match the published
versio
Perturbations of Gauss-Bonnet Black Strings in Codimension-2 Braneworlds
We derive the Lichnerowicz equation in the presence of the Gauss-Bonnet term.
Using the modified Lichnerowicz equation we study the metric perturbations of
Gauss-Bonnet black strings in Codimension-2 Braneworlds.Comment: 26 pages, no figures, clarifying comments and one reference added, to
be published in JHE
- …