520,164 research outputs found
Solar Irradiance Variability is Caused by the Magnetic Activity on the Solar Surface
The variation in the radiative output of the Sun, described in terms of solar
irradiance, is important to climatology. A common assumption is that solar
irradiance variability is driven by its surface magnetism. Verifying this
assumption has, however, been hampered by the fact that models of solar
irradiance variability based on solar surface magnetism have to be calibrated
to observed variability. Making use of realistic three-dimensional
magnetohydrodynamic simulations of the solar atmosphere and state-of-the-art
solar magnetograms from the Solar Dynamics Observatory, we present a model of
total solar irradiance (TSI) that does not require any such calibration. In
doing so, the modeled irradiance variability is entirely independent of the
observational record. (The absolute level is calibrated to the TSI record from
the Total Irradiance Monitor.) The model replicates 95% of the observed
variability between April 2010 and July 2016, leaving little scope for
alternative drivers of solar irradiance variability at least over the time
scales examined (days to years).Comment: Supplementary Materials;
https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.119.091102/supplementary_material_170801.pd
The ecological impact of different mechanisms of chronic sub-lethal toxicity on feeding and respiratory physiology
Sub-lethal toxicity tests, such as the scope-for-growth test, reveal simple relationships between measures of contaminant concentration and effect on respiratory and feeding physiology. Simple models are presented to investigate the potential impact of different mechanisms of chronic sub-lethal toxicity on these physiological processes. Since environmental quality is variable, even in unimpacted environments, toxicants may have differentially greater impacts in poor compared to higher quality environments. The models illustrate the implications of different degrees and mechanisms of toxicity in response to variability in the quality of the feeding environment, and variability in standard metabolic rate. The models suggest that the relationships between measured degrees of toxic stress, and the maintenance ration required to maintain zero scope-for-growth, may be highly nonlinear. In addition it may be possible to define critical levels of sub-lethal toxic effect above which no environment is of sufficient quality to permit prolonged survival
Planning ahead: How recent experience with structures and words changes the scope of linguistic planning
The scope of linguistic planning, i.e., the amount of linguistic information that speakers prepare in advance for an utterance they are about to produce, is highly variable. Distinguishing between possible sources of this variability provides a way to discriminate between production accounts that assume structurally incremental and lexically incremental sentence planning. Two picture-naming experiments evaluated changes in speakers’ planning scope as a function of experience with message structure, sentence structure, and lexical items. On target trials participants produced sentences beginning with two semantically related or unrelated objects in the same complex noun phrase. To manipulate familiarity with sentence structure, target displays were preceded by prime displays that elicited the same or different sentence structures. To manipulate ease of lexical retrieval, target sentences began either with the higher-frequency or lower-frequency member of each semantic pair. The results show that repetition of sentence structure can extend speakers’ scope of planning from one to two words in a complex noun phrase, as indexed by the presence of semantic interference in structurally primed sentences beginning with easily retrievable words. Changes in planning scope tied to experience with phrasal structures favor production accounts assuming structural planning in early sentence formulation
The determinants of option adjusted delta credit spreads: A comparative analysis on US, UK and the Eurozone
We analyse the determinants of the variation of option adjusted credit spreads (OASs) on a unique database which enlarges the traditional scope of the analysis to more disaggregated indexes (combining industry, grade and maturity levels), new variables (volumes of sales and purchases of institutional investors) and a complete set of markets (beside US, UK and the Eurozone). With our extended set of regressors we explain almost half of the variability of OASs and we find evidence of the significant impact of institutional investors' purchases and sales on corporate bond risk. We also find that US business cycle indicators significantly affect the variability of OASs in the UK and in the Eurozone.
Quantify resilience enhancement of UTS through exploiting connect community and internet of everything emerging technologies
This work aims at investigating and quantifying the Urban Transport System
(UTS) resilience enhancement enabled by the adoption of emerging technology
such as Internet of Everything (IoE) and the new trend of the Connected
Community (CC). A conceptual extension of Functional Resonance Analysis Method
(FRAM) and its formalization have been proposed and used to model UTS
complexity. The scope is to identify the system functions and their
interdependencies with a particular focus on those that have a relation and
impact on people and communities. Network analysis techniques have been applied
to the FRAM model to identify and estimate the most critical community-related
functions. The notion of Variability Rate (VR) has been defined as the amount
of output variability generated by an upstream function that can be
tolerated/absorbed by a downstream function, without significantly increasing
of its subsequent output variability. A fuzzy based quantification of the VR on
expert judgment has been developed when quantitative data are not available.
Our approach has been applied to a critical scenario (water bomb/flash
flooding) considering two cases: when UTS has CC and IoE implemented or not.
The results show a remarkable VR enhancement if CC and IoE are deploye
Movement variability in stroke patients and controls performing two upper limb functional tasks: a new assessment methodology
Background: In the evaluation of upper limb impairment post stroke there remains a gap between detailed kinematic analyses with expensive motion capturing systems and common clinical assessment tests. In particular, although many clinical tests evaluate the performance of functional
tasks, metrics to characterise upper limb kinematics are generally not applicable to such tasks and very limited in scope. This paper reports on a novel, user-friendly methodology that allows for the assessment of both signal magnitude and timing variability in upper limb movement trajectories during functional task performance. In order to demonstrate the technique, we report on a study
in which the variability in timing and signal magnitude of data collected during the performance of two functional tasks is compared between a group of subjects with stroke and a group of individually matched control subjects.
Methods: We employ dynamic time warping for curve registration to quantify two aspects of movement variability: 1) variability of the timing of the accelerometer signals' characteristics and 2) variability of the signals' magnitude. Six stroke patients and six matched controls performed several trials of a unilateral ('drinking') and a bilateral ('moving a plate') functional task on two different days, approximately 1 month apart. Group differences for the two variability metrics were investigated on both days.
Results: For 'drinking from a glass' significant group differences were obtained on both days for
the timing variability of the acceleration signals' characteristics (p = 0.002 and p = 0.008 for test and
retest, respectively); all stroke patients showed increased signal timing variability as compared to
their corresponding control subject. 'Moving a plate' provided less distinct group differences.
Conclusion: This initial application establishes that movement variability metrics, as determined
by our methodology, appear different in stroke patients as compared to matched controls during unilateral task performance ('drinking'). Use of a user-friendly, inexpensive accelerometer makes this methodology feasible for routine clinical evaluations. We are encouraged to perform larger studies to further investigate the metrics' usefulness when quantifying levels of impairment
The determinants of option-adjusted delta credit spreads: a comparative analysis of the United States, the United Kingdom and the euro area
We analyse the determinants of the variation of option-adjusted credit spreads (OASs) on a unique database that enlarges the traditional scope of analysis to more disaggregated indexes (combining industry, grade and maturity levels), new variables (volumes of sales and purchases of institutional investors) and a complete set of markets (besides the United States, the United Kingdom and the euro area). With our extended set of regressors we explain almost half of the variability of OASs and find evidence of a significant impact of institutional investors’ purchases and sales on corporate bond risk. We also find that US business cycle indicators significantly affect the variability of OASs in the United Kingdom and the euro area.option-adjusted credit spreads; delta; corporate bond risk; institutional investors; business cycle indicators
Spectroscopic study of the O-type runaway supergiant HD 195592
The scope of this paper is to perform a detailed spectroscopic study of the
northern O-type supergiant HD 195592. We use a large sample of high quality
spectra in order to investigate its multiplicity, and to probe the line profile
variability. Our analysis reveals a clear spectroscopic binary signature in the
profile of the He {\sc i} 6678 line, pointing to a probable O + B
system. We report on low amplitude radial velocity variations in every strong
absorption line in the blue spectrum of HD 195592. These variations are ruled
by two time-scales respectively of 5.063 and about 20 days. The former is
firmly established, whilst the latter is poorly constrained. We report also on
a very significant line profile variability of the H line, with time
scales strongly related to those of the radial velocities. Our results provide
significant evidence that HD 195592 is a binary system, with a period that
might be the variability time-scale of about 5 days. The second time scale may
be the signature of an additional star moving along a wider orbit provided its
mass is low enough, even though direct evidence for the presence of a third
star is still lacking. Alternatively, the second time-scale may be the
signature of a variability intrinsic to the stellar wind of the primary,
potentially related to the stellar rotation.Comment: 9 pages, 5 postscript figures, accepted for publication in New
Astronom
On the Nature and Importance of Cultural Tightness-Looseness
Cross-cultural research is dominated by the use of values despite their mixed empirical support and their limited theoretical scope. This article expands the dominant paradigm in crosscultural research by developing a theory of cultural tightness-looseness, the strength of social norms and degree of sanctioning within societies, and advancing a multilevel research agenda for future research. Through an exploration of the top-down, bottom-up, and moderating impact that societal tightness-looseness has on individuals and organizations, as well as on variability across levels of analysis, the theory provides a new and complementary perspective to the values approach
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